Steelworker Vol1

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DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

NONRESIDENT

TRAINING

COURSE November 1996

Steelworker, Volume 1NAVEDTRA 14250


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DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

Although the words he, him, andhis are used sparingly in this course toenhance communication, they are notintended to be gender driven or to affront ordiscriminate against anyone.


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C O N T E N T S

CHAPTER PAGE

1.

2.

3.

4.

5.

6.

7.

8.

Properties and Uses of Metal . . . . . . . . . . . . . . . . . . . . . 1-1

Basic Heat Treatment . . . . . . . . . . . . . . . . . . . . . 2-1

Introduction to Welding . . . . . . . . . . . . . . . . . . . . . . 3-1

Gas Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Gas Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

Soldering, Brazing, Braze Welding, and Wearfacing . . . . . . . . . 6-1

Shielded Metal-Arc Welding and Wearfacing . . . . . . . . . . . . 7-1

Gas Shielded-Arc Welding . . . . . . . . . . . . . . . . . . . 8-1

APPENDIX

I. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AI-1

II . References Used to Develop the TRAMAN . . . . . . . . . . . . . . . . AII-1

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .INDEX-1

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S U M M A RY O FS T E E LW O R K E R , V O L U M E I

T R A I N I N G M A N U A L S

VOLUME 1

S teelworker, Volum e 1, NAVEDTRA 14250, consists of chapters on thefollowing subjects: Properties and Uses of Metal; Basic Heat Treatment;

Introduction to Welding; Gas Cutting; Gas Welding; Soldering, Brazing, BrazeWelding, an d Wear facing; Shielded Metal-Arc Welding a nd Wearfacing; an d Ga sShielded-Arc Welding.

VOLUME 2

S teelworker, Volum e 2, NAVEDTRA 14251, consists of chapters on thefollowing subjects: Construction Administration and Support; Sheet Metal andFiber Glass Duct Layout and Fabrication; Structural Steel and Pipe Layout andFabrication; Fiber Line; Wire Rope; Rigging and Hoisting; Concrete Construction(Re in fo rc ing S t ee l ) ; P r e - eng inee red Bu i ld ings , Tower s , and An tennas ;Pre-engineered Storage Tanks; Pontoons; and SATS matting.

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C H A P T E R 1

P R O P E RT I E S A N D U S E S O F M E TA L

In the seabees, Steelworkers are the residentexperts on the properties and uses of metal. We layairfields, erect towers and storage tanks, assemblepontoon cau seways, and constr uct buildings. We useour expertise to repair metal items, resurface wornmachinery parts, and fabricate all types of metalobjects. To accomplish these tasks proficiently, onemu st possess a sound working k nowledge of var iousmetals and their properties. As we learn their differentproperties and characteristics, we can then select theright type of metal and use the proper method tocomplete the job. Steelworkers primarily work withiron and steel; however, we also must become familiarwith the nonferrous metals coming into use more andmore each day. As Steelworkers, we must be able toident i fy var ious meta ls and to associa te the i rindividual properties with their proper application oruse.

The primary objective of this chapter is to presenta detailed explanation of some of the properties of different metals and to provide instruction on usingsimple tests in establishing their identity.

M E TA L P R O P E RT I E S

Ther e is n o simple definition of metal; however,an y chemical element ha ving meta llic properties isclassed as a meta l. Metallic properties ar e definedas luster, good thermal and electrical conductivity, andthe capabi l i ty of be ing permanent ly shaped ordeformed at room temperature. Chemical elementslacking th ese properties a re classed as n onmeta ls. Afew elements, known as metalloids, sometimes behavelike a metal and at other times like a nonmetal. Someexamples of metalloids are as follows: carbon,phosphorus, silicon, and sulfur.

Although Steelworkers seldom work with puremetals, we must be knowledgeable of their propertiesbecau se th e alloys we work with ar e combina tions of pure metals. Some of the pure metals discussed in thischapter are the base metals in these alloys. This is trueof iron, aluminum, and magnesium. Other metalsdiscussed ar e th e alloying elements present in sma llquantities but important in their effect. Among these arechromium, molybdenum, titanium, and manganese.

An alloy is defined as a substance having metallicproperties that is composed of two or more elements.The elements used as alloying substances are usuallymetals or metalloids. The properties of an alloy differfrom the properties of the pure metals or metalloids thatmake up the alloy and this difference is what creates theusefulness of alloys. By combining metals and metal-loids, manufacturers can develop alloys that have theparticular properties required for a given use.

Table 1-1 is a list of various elements and theirsymbols that compose metallic materials.

Tab le 1-1.Symb ols of Base Meta ls and Alloying Elem ent s

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Figure 1-1.Stress applied to a materiaI .

Very ra rely do Steelworker s work with elementsin th eir pure st ate. We primarily work with alloys and h aveto understand their characteristics. The characteristicsof elements and alloys are explained in terms of phys i ca l , chemica l , e l ec t r i ca l , and mechan ica lproperties. Physical properties relate to color, density,weight, and heat conductivity. Chemical propertiesinvolve the behavior of the metal when placed incontact with the atmosphere, salt water, or other

substances. Electrical properties encompass theelectrical conductivity, resistance, and magneticqualities of the metal. The mechanical propertiesre la te to load-carry ing abi l i ty, wear res is tance ,har dness, and elasticity.

When selecting stock for a job, your mainconcern is the mechanical properties of the metal.The various properties of metals and alloys weredetermined in the laboratories of manufacturers andby var ious socie t ies in teres ted in meta l lurgica ldevelopment. Charts presenting the properties of aparticular metal or alloy are available in manycommerc i a l ly pub l i shed r e f e rence books . Thecharts provide information on the melting point,tensile strength, electrical conductivity, magneticproperties, and other properties of a particular metalor alloy. Simple tests can be condu cted to determ inesome of the properties of a metal; however, wenormal ly use a meta l tes t only as an a id foridentifying apiece of stock. Some of these methodsof testing are discussed later in this chapter.

MECHANICAL PROPERTIES

Strength, hardness, toughness, elasticity, plasticity,br i t t leness , and duct i l i ty and mal leabi l i ty aremechanical properties used as mea sur ement s of howmetals behave under a load. These properties aredescribed in t erms of th e types of force or st ress t ha tthe metal must withstand and how these are resisted.

Common types of stress are compression, tension,shea r, torsion, impact, 1-2 or a combinat ion of thesestresses, such as fatigue. (See fig. 1-1. )

Compression stresses develop within a materialwhen forces compress or crush the material. A columnthat supports an overhead beam is in compression, andthe internal stresses that develop within the column arecompression.

Tension (or tensile) stresses develop when amat erial is su bject to a pu lling load; for exam ple, whenusing a wire rope to lift a load or when u sing it as aguy to anchor an antenna. Tensile strength is definedas resistance to longitudinal stress or pull and can bemeasured in pounds per square inch of cross section.Shearing stresses occur within a material whenexternal forces are applied along parallel lines inopposite directions. Shearing forces can separatematerial by sliding part of it in one direction and therest in the opposite direction.

Some materials are equally strong in compression,tension, and shear. However, many materials showmarked differences; for example, cured concrete has amaximum strength of 2,000 psi in compression, butonly 400 psi in tension. Carbon steel has a maximumstrength of 56,000 psi in tension and compression buta maximum shear s t rength of only 42,000 ps i ;therefore, when dealing with maximum strength, youshould always state the type of loading.

A material that is stressed repeatedly usually failsat a point considerably below its maximum strength intension, compression, or shear. For example, a thinsteel rod can be broken by hand by bending it ba ck andforth several times in the same place; however, if thesame force is applied in a stea dy motion (not bent back and forth), the rod cannot be broken. The tendency of a ma terial to fail after r epeated bending at the sa mepoint is known as fatigue.

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Table 1-2.Mechanical Properties of Metals/Alloys

S t r e n g t h Rockwell C number. On nonferrous metals, that are

Strength is the property that enables a metal to resistdeformation under load. The ultimate strength is themaximum strain a material can withstand. Tensilestrength is a measu rement of the resistance to beingpulled apart when placed in a tension load.

Fat igue str ength is th e ability of mat erial to resistvarious kinds of rapidly changing stresses and is ex-pressed by the ma gnitude of alterna ting stress for aspecified number of cycles.

Impact str ength is t he abil ity of a m etal to resistsuddenly applied loads and is measured in foot-poundsof force.

H a r d n e s s

Hardness is the property of a material to resistpermanent indentation. Because th ere are several meth-ods of measuring hardness, the hardness of a material isalways specified in terms of the particular test that wasused to mea sur e th is propert y. Rockwell, Vickers, orBrinell are some of the meth ods of testing. Of these tests,Rockwell is the one most frequently used. The basicprinciple used in the Rockwell testis that a hard materialcan penetrate a softer one. We then m easure th e amountof penet ra tion an d compa re it t o a scale. For ferr ousmetals, which ar e usually harder t han nonferrous metals,a diamond tip is used and the hardness is indicated by a

softer, a metal ball is used and the hardness is indicatedby a Rockwell B number. To get an idea of theproperty of hardness, compare lead and steel. Lead canbe scratched with a pointed wooden stick but steelcannot because it is h arder than lead.

A full explanation of the various methods used todetermine th e har dness of a m ater ial is available incommercial books or books located in your base library.

Tou gh n ess

Toughness is the property that enables a material towithstand shock and to be deformed without rupturing.Toughness may be considered as a combination of strength a nd plastici ty . Table 1-2 shows the order of some of the more common materials for toughness aswell as other properties.

Elas t i c i ty

When a material has a load applied to it, the loadcauses the material to deform. Elasticity is the ability of a material to return to its original shape after the load isremoved. Theoretically, the elastic limit of a material isthe l imit t o which a mat erial can be loaded an d st i l lrecover its original shape after the load is removed.

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P last icity

Plasticity is the ability of a material to deformpermanent ly without breaking or ruptu ring. This prop-ert y is th e opposite of strengt h. By careful alloying of meta ls, the combination of plasticity an d str ength is u sedto manufacture large structural members. For example,should a m ember of a br idge stru cture become over-loaded, plasticity allows the overloaded member to flowallowing the distr ibution of the load t o other part s of the

bridge structure.

Bri t t len ess

Brittleness is the opposite of the property of plastic-ity. A brittle metal is one that breaks or shatters beforeit deforms. White cast iron and glass are good examplesof brittle material. Generally, brittle metals are high incompressive strength but low in tensile strength. As anexample, you would not choose cast iron for fabricatingsupport beams in a bridge.

Ducti l i ty and Malleabil i ty

Ductility is the property tha t ena bles a material t ostr etch, bend, or t wist without cracking or br eaking. Thisproperty mak es it possible for a mat erial to be drawn outinto a thin wire. In comparison, malleability is theproperty that enables a material to deform by compres-sive forces without developing defects. A malleablematerial is one that can be stamped, hammered, forged,pressed, or rolled into thin sheets.

CORROSION RESISTANCE

Corrosion resistance, although not a mechanicalproperty, is important in the discussion of metals. Cor-rosion resistance is the property of a metal that gives itthe ability to withstand attacks from atmospheric,chemical, or electrochemical conditions. Corrosion,sometimes called oxidation, is illustrated by the rustingof iron.

Table 1-2 lists four mechanical properties and thecorrosion resistance of various metals or alloys. The firstmetal or alloy in each column exhibits the best charac-teristics of that property. The last metal or alloy in eachcolumn exhibits the least. In the column labeled Tough-ness, note that iron is not as tough as copper or nickel;however, it is tougher than magnesium, zinc, and alumi-num. In the column labeled Ductility, iron exhibits areasonable a mount of ductility; however, in the columnslabeled Malleability and Brittleness, it is last.

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METAL TYP ES

The metals that Steelworkers work with are dividedinto two general classifications: ferrous and nonferrous.Ferr ous metals a re t hose composed prima rily of iron a ndiron alloys. Nonferrous metals are those composed pri-mar ily of some element or element s other t ha n iron.Nonferrous metals or alloys sometimes contain a smallamount of iron as a n alloying element or as an impurit y.

FER ROUS METALS

Ferrous metals include all forms of iron and steelalloys. A few examples include wrought iron, cast iron,carbon steels, alloy steels, and tool steels. Ferrous met-als a re ir on-base a lloys with small per centa ges of carbonand other elements added to achieve desirable proper-ties. Normally, ferrous metals are magnetic and nonfer-rous metals are nonmagnetic.

I ron

Pur e iron ra rely exists outside of the laborat ory. Ironis produced by reducing iron ore to pig iron through theuse of a blast furnace. From pig iron many other typesof iron and steel are produced by the addition or deletionof carbon and alloys. The following paragraphs discussthe different types of iron and steel that can be madefrom iron ore.

P IG IRON. Pig iron is composed of about 93%iron, from 3% to 5% carbon, and various a mount s of other elements. Pig iron is comparatively weak andbrittle; therefore, it has a limited use and approximatelyninety percent produced is refined to produce steel.Cast-iron pipe and some fittings and valves are manu-factu red from pig iron.

WROUGH T IRON. Wrought iron is made frompig iron with some slag mixed in during manufacture.Almost pur e iron, the presence of slag enables wroughtiron to r esist corr osion an d oxidat ion. The chemicalanalyses of wrought iron and mild steel are just aboutthe same. The difference comes from the propertiescontrolled during the manufacturing process. Wroughtiron can be gas and arc welded, machined, plated, andeasily formed; however, it ha s a low hardn ess an d a

low-fatigue strength.

CAST IRON. Cast iron is any iron cont aininggreater than 2% carbon alloy. Cast iron has a high-com-pressive strength and good wear resistance; however, itlacks ductility, malleability, and impact strength. Alloy-ing it with nickel, chromium, molybdenum, silicon, orvanadium improves toughness, tensile strength, a nd


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hardness. A malleable cast iron is produced through a easily as the low-carbon steels. They are used for craneprolonged annealing process. hooks, axles, shaft s, set screws, and so on.

INGOT IRON. Ingot iron is a commercially pureiron (99.85% iron) that is easily formed and possessesgood ductility an d corr osion resist an ce. The chem icalan alysis and pr operties of this iron and t he lowest carbonsteel are practically the same. The lowest carbon steel,known as dead-soft, has about 0.06% more carbon than

ingot iron. In iron the carbon content is considered animpur ity an d in steel it is consider ed an alloying ele-ment. The primary use for ingot iron is for galvanizedand enameled sheet.

Stee l

Of all the different metals and materials that we usein our trade, steel is by far the most important. Whensteel wa s developed, it revolutionized the American ironindustry. With it came skyscrapers, stronger and longer

bridges, and r ailroad t racks th at did not collapse. Steelis manufactured from pig iron by decreasing the amountof carbon and other impurities and adding specificamounts of alloying elements.

Do not confuse steel with the two general classes of iron: cast iron (greater than 2% carbon) and pure iron(less than 0.15% carbon). In steel manufacturing, con-trolled amounts of alloying elements are added duringth e molten s ta ge to produce the desir ed composition.The composition of a steel is determined by its applica-tion and the specifications that were developed by the

following: American Society for Testing and Materials(ASTM), the American Society of Mechanical Engi-neer s (ASME), th e Society of Aut omotive E ngineer s(SAE), and the American Iron an d Steel Inst itute (AISI).

Carbon steel is a term applied to a broad range of steel that falls between the commercially pure ingot ironand the cast irons. This ra nge of carbon steel ma y beclassified into four groups:

HIGH-CARBON STEEL/VERY HIGH-CAR-BON STEE L. Steel in these classes respond well toheat treat ment and can be welded. When welding, spe-cial electrodes must be used along with preheating andstress-relieving procedures to prevent cracks in the weldareas. These steels are used for dies, cutting tools, mill

tools, railroad car wheels, chisels, knives, and so on.

L O W- A L L O Y, H I G H - S T R E N G T H , T E M -P E R E D S T R U C T UR AL S T E E L . A special low-carbon steel, containing specific small amounts of alloying elements, that is quenched and tempered to geta yield strength of greater than 50,000 psi and tensilestr engths of 70,000 to 120,000 psi. Stru ctural membersmade from these high-strength steels may have smallercross-sectional areas tha n common st ructur al steelsand still have equal or greater strength. Additionally,these steels are normally more corrosion- and abrasion-

resista nt . High-str ength s teels ar e covered by ASTMspecifications.

N O T E : This type of steel is much tougher thanlow-carbon steels. Shea ring m achines for this t ype of steel must have twice the capacity than that required forlow-carbon steels.

STAINLESS STEE L. This type of steel is clas-sified by the American Iron and Steel Institute (AISI)into two general series named the 200-300 series and400 series. Each series includes several types of steelwith different characteristics.

The 200-300 series of stainless st eel is known asAUSTENITIC. This type of steel is very tough andductile in the as-welded condition; therefore, it is idealfor welding an d requires no ann ealing under norma latmospheric conditions. The most well-known types of steel in this series ar e the 302 an d 304. They are com-monly called 18-8 because th ey ar e composed of 18%chromium and 8% nickel. The chromium nickel steels

Low-Carbon Steel . . . . . . . . 0.05% to 0.30% carbon are the most widely used and are normally nonmagnetic.Medium -Carbon St eel . . . . . . 0.30% to 0.45% carbon The 400 s eries of steel is subdivided accordin g toHigh-Car bon St eel . . . . . . . . 0.45% to 0.75% carbon their crystalline structure into two general groups. One

Very High-Carbon Steel . . . . . 0.75% to 1.70% carbon group is kn own a s FE RRITIC CHROMIUM and t heother group as MARTENSITIC CHROMIUM.

LOW-CARBON ST EE L. Steel in t his classifi- F e r r i t ic C h r o m i u m . This type of steel containscation is tough an d ductile, easily ma chined, formed,

12% to 27% chromium and 0.08% to 0.20% carbon.and welded. It does not respond to any form of heat

These alloys are the straight chromium grades of stain-treating, except case hardening.

less steel since they contain no nickel. They are nonhar-MEDIUM-CARBON STEEL. These steels are denable by heat treatment and are normally used in the

strong an d har d but cann ot be welded or worked a s annealed or soft condition. Ferritic steels are magnetic

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and frequently used for decorative trim and equipmentsubjected to high pressures and temperatures.

M a r t e n s i t i c C h r o m i u m . These steels ar e mag-netic and are readily hardened by heat treatment. Theycontain 12% to 18% chromium, 0.15% to 1.2% carbon,an d up to 2.5% nickel. This group is used wher e highstr ength, corr osion resistan ce, and du ctility are r equired.

ALLOY STEELS. Steels that derive their prop-erties primarily from the presence of some alloyingelement other than carbon are called ALLOYS or AL-LOY STEELS. Note, however, that alloy steels alwayscontain traces of other elements. Among the more com-mon alloying elements are nickel, chromium, vana-dium, silicon, and tungsten. One or more of theseelements may be added to the steel during the manufac-tu ring process to produce th e desired cha ra cteristics.Alloy steels may be produced in structural sections,sheets, pla tes, a nd ba rs for u se in t he as-rolled condi-tion. Better physical properties are obtained with thesesteels than are possible with hot-rolled carbon steels.These alloys are used in structures where the strength of material is especially important. Bridge members, rail-road cars, dump bodies, dozer blades, and crane boomsare made from alloy steel. Some of the common alloysteels are briefly described in the paragraphs below.

Nicke l S t ee l s . These st eels contain from 3.5%nickel to 5% nickel. The nickel increases the strengthand toughness of these steels. Nickel steel containingmore than 5% nickel has an increased resistance tocorrosion and scale. Nickel steel is used in the manufac-ture of aircraft parts, such as propellers and airframe

support members.

C h r o m i u m S t e e l s. These steels have chromiumadded to improve hardening ability, wear resistance, andstrength. These steels contain between 0.20% to 0.75%chromium and 0.45% carbon or more. Some of thesesteels are so highly resistant to wear that they are usedfor t he ra ces and balls in an tifriction bearings. Chro-mium steels are highly resistant to corrosion and toscale.

C h r o m e Va n a d i u m S t e e l . This steel has t hemaximum amount of strength with the least amount of weight. Steels of this type contain from 0.15% to 0.25%van ad ium, 0.6% to 1.5% chromium , and 0.1% to 0.6%carbon. Common uses are for crankshafts, gears, axles,and other items that require high strength. This steel isalso used in the manufacture of high-quality hand tools,such as wrenches and sockets.

Tu n gst en Ste el. This is a special alloy that has theproperty of red hardness. This is the ability to continue

to cut after it becomes red-hot. A good grade of this steelcontains from 13% to 19% tungsten, 1% to 2% vana-dium , 3% to 5% chromiu m, a nd 0.6% to 0.8% carbon.Becau se th is alloy is expensive to produce, its u se islargely restricted to the m anu factur e of drills, lath e tools,milling cutters, and similar cutting tools.

Mo lybdenum. This is often used as an alloyingagent for steel in combination with chromium and

nickel. The molybdenum adds toughness to the steel. Itcan be used in place of tungst en to mak e the cheapergrades of high-speed steel and in carbon molybdenumhigh-pressure tubing.

Mangan ese S t ee l s. The amount of manganeseused depends upon the properties desired in the finishedproduct. Small amounts of manganese produce strong,free-machining steels. Larger amounts (between 2%and 10%) produce a somewhat brittle steel, while stilllarger amoun ts (11% to 14%) produce a st eel tha t istough an d very resistant t o wear after proper heat treat-ment .

NONFERR OUS METALS

Nonferr ous meta ls contain eith er no iron or onlyinsignificant amount s us ed as an alloy. Some of the morecommon nonferrous metals Steelworkers work with areas follows: copper, brass, bronze, copper-nickel alloys,lead, zinc, tin, aluminum, and Duralumin.

NOTE: These metals a re nonmagnetic.

Coppe r

This metal and its alloys have many desirable prop-erties. Among t he commer cial met als, it is one of themost popular. Copper is ductile, malleable, hard, tough,strong, wear resistant, machinable, weldable, and cor-rosion r esistant . It also has h igh-tensile strength , fatiguestrength, and thermal and electrical conductivity. Cop-per is one of the easier m etals t o work with but be carefulbecause it easily becomes work-hardened; however, this

condition can be remedied by heating it to a cherry redand then letting it cool. This process, called annealing,restores it to a softened condition. Annealing and sof-tening are the only heat-treating procedures that applyto copper. Seams in copper are joined by riveting, silverbrazing, bronze brazing, soft soldering, gas welding, orelectrical arc welding. Copper is frequently used to givea protective coating to sheets and rods and to make ballfloats, conta iners, and soldering coppers.

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Tr u e B r a s s sinks or pr otect bench t ops where a lar ge amount of acidis used. Lead-lined pipes are used in systems that carry

This is an alloy of copper and zinc. Additional corr osive chemicals. F requent ly, lead is u sed in alloyedelements, such as aluminum, lead, tin, iron, manganese, form to increase its low-tensile strength. Alloyed withor phosphorus, are added to give the alloy specific tin, lead produces a soft solder. When added to metalproperties. Naval rolled brass (Tobin bronze) contains alloys, lead improves their machinability.about 60% copper, 39% zinc, and 0.75% tin. This brassis highly corrosion-resistant and is practically impurityfree. CAUTION

Brass sheets and strips are available in severalgrades: soft, 1/4 har d, 1/2 har d, full har d, and spr ing When working with lead, you m ust takegrades . Hardness i s crea ted by the process of cold rol l- proper precaut ions because the dust , fumes, oring. All grades of bra ss can be softened by ann ealing at vapors from it are highly poisonous.a temperature of 550F to 600F then allowing it to coolby itself without quenching. Overheating can destroythe zinc in the alloy. Zinc

Bronze

Bronze is a combination of 84% copper and 16% tin

and was the best metal available before steel-makingtechniques were developed. Many complex bronze al-loys, containing such elements as zinc, lead, iron, alu-minum, silicon, and phosphorus, are now available.Today, the name bronze is applied to any copper-basedalloy that looks like bronze. In many cases, there is noreal distinction between the composition of bronze andthat of brass.

Copper-Nickel Alloys

Nickel is used in these alloys to make them strong,

tough, and resistant to wear and corrosion. Because of their high resistance to corrosion, copper nickel alloys,containing 70% copper and 30% nickel or 90% copperand 10% nickel, are used for saltwater piping systems.Small storage tanks and hot-water reservoirs are con-

You often see zinc used on iron or steel in the formof a protective coating called galvanizing. Zinc is alsoused in soldering fluxes, die castings, and as an alloy in

making brass a nd bronze.

T in

Tin has m any important uses as a n alloy. It can bealloyed with lea d to produce softer solders a nd withcopper to produce bronze. Tin-based alloys have a highresistance to corrosion, low-fatigue strength, and a com-pressive strength that accommodates light or mediumloads. Tin, like lead, has a good resistance to corrosionand has the added advantage of not being poisonous;however, when subjected to extremely low temper a-tures, it has a tendency to decompose.

Aluminum

str utt ed of a copper-nickel alloy tha t is available in sheet This metal is easy to work with and has a goodform. Copper-nickel alloys should be joined by metal- appearance. Aluminum is light in weight and has a higharc welding or by brazing.

strength per unit weight. A disadvantage is that the

L e a dtensile strength is only one third of that of iron and onefifth of that of annealed mild steel.

A heavy metal tha t weighs a bout 710 pounds per

cubic foot. In spite of its weight, lead is soft and malle-able and is a vailable in pig and sheet form . In sheet form ,it is rolled upon a rod so the user can unroll it and cutoff the desired amount. The surface of lead is grayish incolor; however, after scratching or scraping it, you cansee that the actual color of the metal is white. Becauseit is soft, lead is used as backing mat erial when pun chingholes with a hollow punch or when forming shapes byhammering copper sheets. Sheet lead is also used to line

Aluminum alloys usually contain at least 90% alu-

minu m. The addit ion of silicon, ma gnesium, copper,nickel, or manganese can raise the strength of the alloyto that of mild steel. Aluminum, in its pure state, is softand has a strong affinity for gases. The use of alloyingelements is used to overcome these disadvantages; how-ever, the alloys, unlike th e pur e alumin um , corrodesunless given a protective coating. Threaded parts madeof aluminum alloy should be coated with an antiseizecompound to prevent sticking caused by corrosion.

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Table 1-3.Sur face Colors of Some Comm on Meta ls

D u r a l u m i n Monel

One of the first of the strong structural aluminumalloys developed is called Duralumin. With the devel-opment of a variety of different wrought-aluminumalloys, a nu mbering system was a dopted. The digitsindicate the major alloying element and the cold-workedor heat-treated condition of the metal. The alloy, origi-nally called Duralumin, is now classified in the metalworking industries as 2017-T. The letter T indicates thatthe metal is heat-treated.

Alclad

This is a protective covering that consists of a thinsheet of pure a luminu m r olled ont o the sur face of analuminum alloy during manufacture. Zinc chromate isa pr otective covering tha t can be applied to an aluminu msurface as n eeded. Zinc chromate is also used as a primeron steel surfaces for a protective coating.

Monel is an alloy in which nickel is the majorelement. It contains from 64% to 68% nickel, about 30%copper, and small percentages of iron, manganese, andcobalt. Monel is har der an d str onger th an either nickelor copper a nd h as high ductility. It r esembles st ainlesssteel in appearance and has many of its qualities. Thestrength, combined with a high resistance to corrosion,make Monel an a cceptable substitut e for steel in systemswhere corr osion resistan ce is th e prima ry concern. Nuts,bolts, screws, and various fittings are made of Monel.This alloy can be worked cold and can be forged and

welded. If worked in t he temp erat ur e ran ge between1200F and 1600F, it becomes hot short or brittle.

K-Monel

This is a special type of alloy developed for greaterstrength a nd har dness than Monel. In strength, i t is

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comparable to heat-treated steel. K-monel is used forinstrument parts t hat must r esist corrosion.

I n c o n e l

This high-nickel alloy is often used in the exhaustsystems of aircraft engines. Inconel is composed of 78.5% nickel, 14% chromium, 6.5% iron, and 1% of

other elements. It offers good resistance to corrosion andretains its strength a t h igh-operating temperatures.

METAL IDENTIFICATION

Many methods are used to identify a piece of metal.Identification is necessary when selecting a metal foruse in fabrication or in determining its weldability.Some common methods used for field identification aresurface appearance, spark test, chip test, and the use of a magnet.

SURFACE APP EARANCE

Sometimes it is possible to identify metals by theirsurface appearance. Table 1-3 indicates the surface col-ors of some of th e more common met als. Referr ing tothe table, you can see that the outside appearance of ametal helps to identify and classify metal. Newly frac-tured or freshly filed surfaces offer additional clues.

A surface examination does not always provide

enough information for identification but should give usenough information to place the metal into a class. Thecolor of th e meta l and t he dist inctive mark s left frommanufacturing help in determining the identity of themetal. Cast iron and malleable iron usually show evi-dence of the sand mold. Low-carbon steel often showsforging marks, and high-carbon steel shows either forg-ing or rolling marks. Feeling the surface may provideanother clue. Stainless steel is slightly rough in theunfinished state, and the surfaces of wrought iron, cop-per, brass, bronze, nickel, and Monel are smooth. Leadalso is smooth but has a velvety appearance.

When the surface appearance of a metal does notgive en ough in form at ion to a llow positive identifica-tion, other identification tests become necessary. Someof these tests are complicated and require equipment wedo not usually have; however, other tests are fairlysimple and reliable when done by a skilled person. Threeof these tests areas follows: the spark test, the chip test,and t he magnetic tests.

Figure 1-2.Terms used in spark test ing.

SP ARK TEST

The spark test is m ade by holding a sam ple of thematerial against an abrasive wheel. By visually inspect-

ing the spark stream, an experienced metalworker canidentify the metals with considerable accuracy. This testis fast, economical, convenient, and easily accom-plished, and there is no requirement for special equip-ment . We can use t his test for ident ifying metal salvagedfrom scrap. Identification of scrap is particularly impor-tan t wh en selecting ma terial for cast iron or cast steelheat t rea tment .

When you h old a piece of iron or st eel in cont actwith a high-speed abrasive wheel, small particles of themeta l are t orn loose so rapidly tha t t hey become red-hot.As these glowing bits of meta l leave the wh eel, theyfollow a p at h (tr ajectory) called th e carr ier line. Thiscarrier line is easily followed with the eye, especial] ywhen observed against a dark background.

The spar ks given off, or t he lack of spar ks, aid in t heidentification of the metal. The length of the spark stream, the color, and the form of the sparks are featuresyou should look for. Figure 1-2 i llustrates the terms usedin referrin g to var ious ba sic spar k form s produced inspark testing.

Steels having the same carbon content but differing

alloying elements are difficult to identify because thealloying elements affect the carrier lines, the bursts, orthe forms of char acteristic bursts in th e spark pictur e,The effect of the alloying element may slow or acceler-ate t he carbon spar k or make t he carrier line lighter ordarker in color. Molybdenum, for example, appears asa detached, orange-colored spearhead on the end of thecarrier line. Nickel appears to suppress the effect of thecarbon burst ; however, the n ickel spar k can be identified

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by tiny blocks of brilliant white light. Silicon suppressesthe carbon burst even more than nickel. When silicon is

present, the carrier line usually ends abruptly in a whiteflash of light.

Spark testing may be done with either a portable orstationary grinder. In either case, the speed on the outerrim of the wheel should not be less than 4,500 feet perminu te. The abras ive wheel should be rat her coar se,very hard, and kept clean t o produce a true spa rk

To conduct a spark test on an abra sive wheel, hold

the piece of metal on the wheel in a position that allowsthe spa rk strea m t o cross your line of vision. By trial a nderror, you soon discover what pressure is needed to geta st ream of the pr oper length without r educing the speedof the grind er. Excessive pressur e increases t he tem -perature of the spark stream. This, in turn, increases thetemperature of the burst and gives the appearance of ahigher carbon content than actually is present. Whenmaking th e test , watch a point a bout one th ird of thedistance from the tail end of the spark stream. Watch

only those sparks that cross your line of vision and tryto forma m enta l image of the individual spar k. Fix thisspark image in your mind and then examine the wholespark picture.

While on the subject of abrasive wheels, it is a good

idea to discuss some of the safety precautions associatedwith this tool.

Never use an a brasive wheel that is cra cked orout of balance because the vibration causes the wheel toshatt er. When an abrasive wheel shatters, i t can be

disastrous for personnel standing in line with the wheel.

Always check the wheel for secure mounting andcracks before putting it to use. When you install a newwheel on a grinder, be sure t ha t it is t he corr ect size.Remember, as you increase th e wheel radius, the periph-eral speed at t he rim a lso increases, even though th e

driving motor rpm rema ins th e same. Thus, if you sh oulduse an oversized wheel, there is a distinct danger the

peripheral speed (and consequent centrifugal force) canbecome so great that the wheel may fly apart. Usewheels that are designed for a specific rpm. Guards areplaced on grinders as protection in case a wheel shouldshatter.

Never use a grinder when the guards have beenremoved. When tur ning the grinder on, you sh ould sta nd

to one side. This places you out of line with the wheelin case the wheel should burst.

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Never overload a grinder or put sideways pr es-sur e against t he wheel, unless it is expressly built towithstand such use.

Always wear appropriate safety goggles or a faceshield while using the grinder. Ensure that the tool rest(the device th at helps th e opera tor hold the work) isadjusted to the minimum clearance for the wheel. Movethe work a cross t he entir e face of the wh eel to eliminategrooving and to minimize wheel dressing. Doing this

prolongs the life of the wheel.

Keep your fingers clear of the abrasive surface,and do not allow rags or clothing to become entangledin the wheel.

Do not wear gloves while using an abrasivewheel.

Never hold metal with tongs while grinding.

Never grind nonferrous metals on a wheel in-tended for ferrous metals because such misuse clogs thepores of the abr asive mat erial. This buildup of meta lmay cause it t o become un balanced and fly apart.

Grinding wheels require frequent recondition-ing. Dressin g is the term used to describe the process of cleaning t he periphery. This cleaning br eaks a way dullabrasive grains and smooths the surface, removing allthe grooves. The wheel dresser shown in figure 1-3 isused for dressing grinding wheels on bench a nd pedestalgrinders. For more information on grinding wheels, youshould consult chapter 5 of NAVEDTRA 10085-B2(Tools an d Th eir Uses).

Referring now to figure 1-4, notice that in low-carbon steel (view A), the spark stream is about 70inches long and the volume is moderately large. Inhigh-carbon steel (view B), the stream is shorter (about55 inches) and th e volume larger. The few sparklers t hatmay occur at any place in low-carbon steel are forked,

Figure 1-3.Using a grinding wheel dresser.


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Figure 1-4.Spark pa t te rn s formed by common meta ls .

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Table 1-4.Metal Identification by Chip Test

and in high-carbon steel, they are small and repeating. these metals must be distinguished from each other byBoth metals produce a spark stream white in color.

Gray cast iron (view C) produces a stream of sparks

about 25 inches in length. The sparklers are small andrepeating, and their volume is rather small. Part of the

stream near the wheel is red, and the outer portion is

straw-colored.

Monel and nickel (view D) form almost identical

spark streams. The sparks are small in volume and

orange in color. The sparks form wavy streaks with no

sparklers. Because of the similarity of the spark picture,

some other method.

Sta inless steel (view E) produces a spar k str eam

about 50 inches in length, moderate volume, and withfew sparklers. The sparklers are forked. The stream nextto the wheel is straw-colored, and at the end, it is white.

The wrought -iron spa rk t est (view F) produces aspark str eam about 65 inches in length. The stream ha sa large volume with few sparklers. The sparks appearnear the end of the stream and a re forked. The streamnext t o the wheel is stra w-colored, and the out er end of the stream is a brighter r ed.

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One way to become proficient in spark testing fer-rous metals is to gather an assortment of samples of known metals and test them. Make all of the samplesabout the same size and shape so their identities are notrevealed simply by the size or shape. Number eachsample and prepare a list of names and correspondingnumbers. Then, without looking at the number of thesample, spark test one sam ple at a time, calling out itsname to someone assigned to check it against the namesand numbers on the list. Repeating this process givesyou some of the exper ience you need to become pr ofi-cient in identifying individual samples.

CHIP TEST

from small, broken fragments to a continuous strip. Thechip may have smooth, sharp edges; it maybe coarse-grained or fine-grained; or it may have sawlike edges.The size of the chip is importa nt in identifying the m etal.The ease with which the chipping can be accomplishedshould also be considered. The information given inta ble 1-4 can help you ident ify various meta ls by th echip test.

MAGNETIC TE ST

The use of a m agnet is an other meth od used to aidin the general identification of metals. Remember thatferrous met als, being iron-based alloys, norma lly ar e

Another simple test used to identify an unk nownpiece of metal is the chip test. The chip testis made byremoving a small amount of material from the test piecewith a sharp, cold chisel. The material removed varies

magnetic, and nonferrous metals are nonmagnetic. Thistest is not 100-percent accurate because some stainlesssteels are nonma gnetic. In th is instance, there is nosubstitute for experience.

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Table 2-1.Heat Colors for Steel

Table 2-2.Approximate Soaking Periods for Hardening, Annealing, and Normalizing Steel

metal and the properties desired. Some metals are F e r r o u s M e t a l

furnace-cooled, and others are cooled by burying themTo produce the maximum softness in steel, you heat

in ashes, lime, or other insulating materials. the metal to its proper temperature, soak it, and then letWelding produces areas that have molten metal next it cool very slowly. The cooling is done by burying the

to other a reas th at a re at room temperat ure. As the weld hot part in an insulating material or by shutting off the

cools, internal stresses occur along with hard spots and furnace and allowing the furnace and the part to cool

brittleness. Welding can actually weaken the metal.together. The soaking period depends on both the massof the par t a nd t he type of metal . The approximat e

Annealing is just one of the meth ods for corr ecting t hese soaking periods for annea ling steel are given in ta blcproblems. 2-2.

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Steel with an extremely low-carbon content re-quires the highest annealing temperature. As the carboncontent increases, the annealing temperatures decrease.

Nonfer rous Meta l

Copper becomes hard and brittle when mechani-

cally worked; however, it can be ma de soft again byannealing. The annealing temperature for copper is be-tween 700F and 900F. Copper maybe cooled rapidlyor slowly since the cooling rate has no effect on the heattreatment. The one drawback experienced in annealingcopper is th e ph enomenon called hot sh ortness . Atabout 900F, copper loses its tensile strength, and if notproperly supported, it could fracture.

Aluminum reacts similar to copper when heat treat-ing. It also has the characteristic of hot shortness. Anumber of aluminum alloys exist and each requiresspecial heat treatment to produce their best properties.

NORMALIZING

Normalizing is a type of heat treatment applicableto ferrous metals only. It differs from annealing in thatthe metal is heated to a higher temperature and thenremoved from the furnace for air cooling.

The pur pose of normalizing is to remove the int erna lstresses induced by heat tr eating, welding, casting, forg-ing, forming, or machining. Stress, if not controlled,leads to metal failure; therefore, before hardening steel,you should norma lize it first t o ensu re th e maximumdesired r esults. Usu ally, low-car bon steels do not r e-quire normalizing; however, if these steels are normal-ized, no harmful effects result. Castings are usuallyannealed, rather than normalized; however, some cast-ings require the normalizing treatment. Table 2-2 showsthe approximate soaking periods for normalizing steel.Note t hat the soaking time varies with t he th ickness of the metal .

Normalized steels are har der and st ronger tha n an -

nealed steels. In the normalized condition, steel is muchtougher than in any other structural condition. Partssubjected to impact and those that require maximumtoughness with resistance to external stress are usuallynormalized. In normalizing, the mass of metal has aninfluence on the cooling rate and on the resulting struc-ture. Thin pieces cool faster and are harder after normal-izing than thick ones. In annealing (furnace cooling), thehardness of the two are about the same.

HARDENING

The hardening treatment for most steels consists of heating the steel to a set temperature and then cooling it

ra pidly by plunging it int o oil, wat er, or brin e. Moststeels require rapid cooling (quenching) for hardeningbut a few can be air-cooled with the same results.Hardening increases the hardness and strength of thesteel, but m akes it less ductile. Generally, the h ar der th esteel, the more brittle it becomes. To remove some of the britt leness, you should temper t he steel after har d-ening.

Many nonferrous metals can be hardened and theirstrength increased by controlled heating and rapid cool-ing. In this case, the process is called heat treatment,rather than hardening.

To hard en st eel, you cool th e meta l rapidly afterthoroughly soaking it at a temperature slightly above itsupper critical point. The approximate soaking periods

for hardening steel are listed in table 2-2. The addit ionof alloys to steel decreases the cooling rate required toproduce hardness. A decrease in the cooling rate is anadvantage, since it lessens the danger of cracking andwarping.

Pure iron, wrought iron, and extremely low-carbonsteels have very little hardening properties and are dif-ficult to harden by heat treatment. Cast iron has limitedcapabilities for hardening. When you cool cast ironrapidly, it forms white iron, which is hard and brittle.And when you cool it slowly, it forms gray iron, which

is soft but brittle under impact.

In plain carbon steel, the maximum hardness ob-tained by heat treatment depends almost entirely on thecarbon content of the steel. As the carbon content in-creases, the hardening ability of the steel increases;however, this capability of hardening with an increasein carbon content continues only to a certain point. Inpractice, 0.80 percent carbon is required for maximumhardness. When you increase the carbon content beyond0.80 percent, there is no increase in hardness, but thereis an increase in wear resistance. This increase in wear

resistance is due to the formation of a substance calledhard cementite.

When you alloy steel to increase its hardness, thealloys ma ke t he car bon more effective in increasin ghardness and strength. Because of this, the carbon con-tent required to produce maximum hardness is lowertha n it is for plain carbon st eels. Usually, alloy steels ar esuperior to carbon steels.

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Carbon steels are usually quenched in brine orwater , and a lloy steels are gener ally quenched in oil.When har dening carbon steel, remember th at you m ustcool the steel to below 1000F in less than 1 second.When you add alloys to steel, the time limit for thetemperature to drop below 1000F increases above thel-second limit, and a slower quen ching medium canproduce the desired hardness.

Quenching produces extremely high internal

str esses in steel, and to relieve them, you can tem per th esteel jus t before it becomes cold. The pa rt is rem ovedfrom th e quenching bath at a tempera tur e of about 200Fan d allowed to air-cool. The tem pera tu re r an ge from200F down to room temperature is called the crackingrange and you do not want the steel to pass through it.

In the following paragraphs, we discuss the differ-ent methods of hardening that are commercially used.In the Seabees, we use a rapid surface hardening com-pound called Case th at can be order ed thr ough theNavy supply system. Information on the use of Caseis located in t he Welding Materials Handbook, P-433.

Case Hardening

Case hardening produces a hard, wear-resistant sur-face or case over a strong, tough core. The principalforms of casehardening are carburizing, cyaniding, andnitriding. Only ferrous metals are case-hardened.

Case hardening is ideal for par ts t hat require awear-resistant surface and must be tough enough inter-nally to withstand heavy loading. The steels best suitedfor case ha rden ing ar e th e low-carbon an d low-alloyseries. When high-carbon steels are case-hardened, thehardness penetr ates t he core an d causes brittleness. Incase hardening, you change the surface of the metalchemically by introducing a high carbide or nitridecontent. The core remains chemically unaffected. Whenheat-treated, the high-carbon surface responds to hard-ening, and the core toughens.

CARBURIZING. Carburizing is a case-harden-ing process by which carbon is added to the surface of low-carbon steel. This results in a carburized steel thatha s a h igh-carbon sur face an d a low-carbon interior.

When the carburized steel is heat-treated, the case be-comes hardened and the core remains soft and tough.

Two meth ods are u sed for carbu rizing steel. Onemethod consists of heating the steel in a furnace con-taining a carbon monoxide atmosphere. The othermethod has the steel placed in a container packed withcharcoal or some other carbon-rich material and then

heated in a furnace. To cool the parts, you can leave thecontainer in the furnace to cool or remove it and let itair cool. In both cases, th e par ts become a nnealed dur ingthe slow cooling. The depth of the carbon penetrationdepends on the length of the soaking period. With to-days methods, carburizing is almost exclusively doneby gas atmospheres.

CYANIDING. This process is a type of casehardening that is fast and efficient. Preheated steel is

dipped into a heated cyanide bath and allowed to soak.Upon removal, it is quenched and then rinsed to removeany residual cyanide. This process produces a thin, hardshell that is ha rder t han the one produced by carburizingand can be completed in 20 to 30 minutes vice severalhours. The major dr awback is th at cyanide salts a re adeadly poison.

NITRIDING. This case-hardening method pro-duces the h ardest sur face of an y of the ha rdening pr oc-esses. It differs from the other methods in that theindividual parts have been heat-treated and tempered

before nitriding. The parts are then heated in a furnacetha t h as an ammonia gas atm osphere. No quenching isrequir ed so th ere is no worry about war ping or othertypes of distortion. This process is used to case hardenitems, such a s gears, cylinder sleeves, camsh afts a ndother engine parts, that need to be wear resistant andoperate in high-heat areas.

F l a m e H a r d e n i n g

Flame har dening is another procedure tha t is used

to harden the surface of metal parts. When you use anoxyacetylene flame, a thin layer at the surface of the par tis rapidly heated t o its cri t ical temperat ure a nd t henimmediately quenched by a combination of a waterspray and the cold base metal. This process produces athin, hardened surface, and at the same time, the internalparts retain their original properties. Whether the proc-ess is manual or mechanical, a close watch must bemaintained, since the torches heat the metal rapidly andthe temperatures are usually determined visually.

Flame hardening may be either ma nual or automat-ic. Automatic equipment produces uniform results andis more desirable. Most automatic machines have vari-able tra vel speeds and can be a dapted t o parts of var ioussizes and shapes. The size and shape of the torch de-pends on the part. The torch consists of a mixing head,straight extension tube, 90-degree extension head, anadjustable yoke, and a water-cooled tip. Practically anyshape or size flame-hardening tip is available (fig. 2-1) .

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Figure 2-1.Progress ive h ardening torch t ip .

Tips are produced tha t can be used for h ardening flats,rounds, gears, cams, cylinders, and other regular orirregular shapes.

In hardening localized areas, you should heat themetal with a st anda rd ha nd-held welding torch. Adjustthe torch flame to neut ral (see chapter 4 ) for norma lheating; however, in corners and grooves, use a slightlyoxidizing flame to keep the torch from sputtering. Youalso should particularly guard against overheating incomers and grooves. If dark streaks appear on the metalsurface, this is a sign of overheating, and you need toincrease the distance between the flame and the metal.

For the best heating results, hold the torch with thetip of the inner cone about an eighth of an inch from thesurface and direct the flame at right angles to the metal.Sometimes it is necessary to change this angle to obtainbett er r esults ; however, you ra rely find a deviat ion of more than 30 degrees. Regulate the speed of torch travelaccording to the type of meta l, the ma ss an d sha pe of thepart, and the depth of hardness desired.

In addition, you must select the steel according tothe properties desired. Select carbon steel when surfacehar dness is the prima ry factor and a lloy steel when t hephysical propert ies of th e core a re a lso factors. Plaincarbon steels should contain more than 0.35% carbonfor good results inflame hardening. For water quench-ing, the effective carbon range is from 0.40% to 0.70%.

Par ts with a carbon content of more th an 0.70% arelikely to surface crack unless the heating and quenchingrate are carefully controlled.

The surface hardness of a flame-hardened section isequal to a section t hat was har dened by furna ce heatingand quenching. The decrease in hardness between thecase and the core is gradual. Since the core is notaffected by flame hardening, there is little danger of spalling or flaking while the pa rt is in use. Thus flame

Figure 2-2.Progressive hardening.

hardening produces a hard case that is highly resistantto wear and a core that retains its original properties.

Flame hardening can be divided into five generalmethods: stationary, circular band progressive, straight-line progressive, spiral band progressive, and circularband spinning.

STATIONARY METHOD. In this method thetorch a nd th e metal part are both held stationary.

CIRCULAR BAND P ROGRESSIVE METHOD.This method is used for hardening outside surfaces of round sections. Usually, the object is rotated in front of a stationary torch at a surface speed of from 3 to 12inches per minute. The heating and quenching are doneprogressively, as the part rotates; therefore, when thepart has completed one rotation, a hardened band encir-cles the par t. The width of the har dened band dependsupon th e width of the torch tip. To har den th e full lengthof a long section, you can move the torch and repeat theprocess over and over until the part is completely hard-

ened. Each pass or path of the torch should overlap theprevious one to prevent soft spots.

STRAIGHT-LINE PROGRESSIVE METHOD.With the straight-line progressive method, the torchtravels along the surface, treating a strip that is about thesame width as the torch tip. To harden wider areas, youmove the torch a nd repeat the pr ocess. Figure 2-2 is anexample of progressive hardening.

SP IRAL BAND P ROGRESSIVE METH OD.For this technique a cylindrical part is mounted betweenlathe centers, and a torch with an adjustable holder ismounted on the lathe carriage. As the part rotates, thetorch moves par allel to the surface of the par t. This tr avelis synchronized with the parts rotary motion to producea continu ous ban d of har dness. Heating an d quenchingoccur at the same time. The number of torches requireddepends on the diamet er of the pa rt, but seldom ar e morethan two torches used.

CIRCULAR BAND SPINNING METHOD.The circular band spinning meth od provides the best

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results for hardening cylindrical parts of small or me-dium diameters. The part is mounted between lathecenters an d turn ed at a high rat e of speed pasta st ation-ary t orch. Enough t orches a re placed side by side to heatthe entire part . The part can be quenched by waterflowing from the torch tips or in a separate operation.

When you perform heating a nd quenching as sepa-rate operations, the tips are water-cooled internally, butno water sprays onto the surface of the part.

In flame hardening, you should follow the samesafety precautions that apply to welding (see chapter 3) .In particular, guard against holding the flame too closeto the surface and overheating the metal. In judging thetemperature of the metal , remember that the flamemakes the metal appear colder than it actually is.

T E M P E R I N G

After the hardening treatment is applied, steel isoften har der th an needed and is t oo brit t le for mostpractical uses. Also, severe internal stresses are set upduring the rapid cooling from the hardening tempera-ture. To relieve the internal stresses and reduce brittle-ness, you should temper the steel after it is hardened.Tempering consists of heating the steel to a specifictemperature (below its hardening temperature), holdingit at that temperature for the required length of time, andthen cooling it, usually inst ill air. The resulta nt st rength ,hardness, and ductility depend on the temperature towhich the steel is heated during the tempering process.

The purpose of tempering is t o reduce the brittlenessimparted by hardening and to produce definite physicalproperties within the steel. Tempering always follows,never precedes, the hardening operation. Besides reduc-ing brittleness, tempering softens the steel. That is u n-avoidable, and the amount of hardness that is lostdepends on the temperature that the steel is heated toduring the tempering process. That is true of all steelsexcept high-speed steel. Tempering increases the hard-ness of high-speed steel.

Tempering is always conducted at temperatures be-low th e low-critical point of the s teel. In th is respect,tempering differs from annealing, normalizing, andhardening in which the temperatures are above the uppercritical point. When hardened steel is reheated, temper-ing begins at 212F and continues as the temperatureincreases toward the low-critical point. By selecting adefinite tempering temperature, you can predeterminethe resulting hardness and st rength. The minimum tem-perature time for tempering should be 1 hour. If the part

is more tha n 1 inch th ick, increase th e time by 1 hour foreach additional inch of thickness.

Norma lly, the r at e of cooling from t he t emperin gtemperature has no effect on the steel. Steel parts areusually cooled in still air after being removed from thetem pering furn ace; however, th ere ar e a few types of steel that must be quenched from the tempering tem-perature to prevent brittleness. These blue brittle steelscan become brit t le if heated in certain t emperat ureranges and allowed to cool slowly. Some of the nickelchromium steels are subject to this temper brittleness.

Steel may be tempered after being normalized, pro-viding there is any hardness to temper. Annealed steel isimpossible to temper . Tempering relieves quenchingstresses and reduces hardness and brittleness. Actually,the tensile strength of a hardened steel may increase asthe st eel is tempered u p to a tempera tur e of about 450F.Above this temperature it starts to decrease. Temperingincreases softness, ductility, malleability, and impact

resista nce. Again, high-speed st eel is an exception to therule. High-speed steel increases in hardness on temper-ing, provided it is tempered at a high temperature (about1550F). Remember, all steel should be removed fromthe qu enching bath and tempered before it is complete] ycold. Failure t o temper correctly results in a qu ick failureof the hardened part.

Permanent steel magnets are made of special alloysand a re heat-treated by hardening and tempering. Hard-ness and st ability are t he most importa nt pr operties inpermanent ma gnets. Magnets are t empered at the mini-

mum tempering tem peratu re of 212F by placing themin boiling water for 2 to 4 hours. Because of this low-tempering temperature, magnets are very hard.

Case-hardened parts should not be tempered at toohigh a tempera tur e or they ma y loose some of theirhardness. Usually, a temperature range from 212F to400F is high enough to relieve quenching stresses.Some metals require no tempering. The design of thepart helps determine the tempering temperature.

Color tempering is based on the oxide colors thatappear on the surface of steel, as it is heated. When youslowly heat a piece of polished hardened steel, you cansee the surface turn various colors as the temperaturechanges. These colors indicate structural changes areta king place with in th e meta l. Once the pr oper colorappears, the part is rapidly quenched to prevent furtherstructural change. In color tempering, the surface of thesteel must be smooth and free of oil. The part may beheated by a torch, in a furnace, over a hot plate, or byradiation.

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Tab le 2-3.0xide Colors for Temp erin g Steel

Cold chisels and similar tools must have hard cut- cutting edge. When you have completed the above de-ting edges and softer bodies and heads. The head mustbe tough enough to prevent shattering when struck withsham mer.The cutt ing edge must be more th an t wice ashard as the head, and the zone separating the two mustbe carefully blended to prevent a lineof demarcation. Amethod of color tempering frequently used for chiselsand s imilar tools is one in which the cutt ing end is heatedby the r esidual hea t of the opposite end of the same tool.To harden and tempera cold chisel by this method, youheat the tool to the proper hardening temperature and

then quench the cutting end only. Bob the chisel up anddown in the bath, always keeping the cutting edge belowth e sur face. This meth od air-cools th e head while rapidlyquenching the cutt ing edge. The result is a tough head,fully hardened cutting edge, and a properly blendedstructure.

When the cutting end has cooled, remove the chiselfrom t he bat h a nd quickly polish the cutt ing end with abuff stick (emery). Watch the polished surface, as theheat from the opposite end feeds back into the quenchedend. As the temperature of the hardened end increases,oxide colors a ppea r. Th ese oxide colors p rogres s frompale yellow, to a straw color, and end in blue colors. Assoon as the correct shade of blue appears, quench theentire chisel to prevent further softening of the cuttingedge. The metal is tempered as soon as the proper oxidecolor appears and quenching merely prevents furthertempering by freezing the process. This final quench hasno effect on the body and the head of the chisel, becausetheir temperature will have dropped below the criticalpoint by the time the proper oxide color appears on the

scribed process, the chisel will be har dened a nd t em-pered and only needs grinding.

During the tempering, the oxide color at which youquench the steel varies with the properties desired in thepart . Table 2- 3 lists the different colors and their corre-sponding temperatures. To see the colors clearly, youmust turn the part from side to side and have goodlighting. While hand tempering produces the same resultas furnace tempering, there is a greater possibility forerror. The slower the operation is performed, the more

accurat e are the r esults obtained.

QUENCHING MEDIA

The cooling rate of an object depends on manythings. The size, composition, and initial temperature of the part and final properties are the deciding factors inselecting the quenching medium. A quenching mediummust cool the metal at a rate rapid enough to producethe desired results.

Mass affects quenching in that as the mass in-

creases, the time required for complete cooling alsoincreases. Even though parts are the same size, thosecontaining holes or recesses cool more rapidly than solidobjects. The composition of th e meta l determ ines th emaximum cooling rate possible without the danger of cracking or warping. This critical cooling rate, in turn,influences the choice of the quenching medium.

The cooling rate of any quenching medium varieswith its temperat ure; therefore, to get uniform results,

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you must keep the temperature within prescribed limits.The absorption of heat by the quenching medium alsodepends, to a large extent, on the circulation of thequenching medium or the movement of the part. Agita-tion of the liquid or t he par t break s up th e gas tha t formsan insulating blanket between the part and the liquid.

Normally, hardening takes place when you quencha m etal. The composition of the met al usu ally deter-mines the type of quench to use to produce the desired

hardness. For example, shallow-hardened low-alloy andcarbon steels require severer quenching than deep-hard-ened alloy steels that contain large quantities of nickel,manganese, or other elements. Therefore, shallow-hard-ening steels are usually quenched in water or brine, andthe deep-hardening steels are quenched in oil. Some-times it is necessary to use a combination quench,starting with brine or water and finishing with oil. Inaddition to producing the desired hardness, the quenchmust keep cracking, warping, and soft spots to a mini-mum.

The volume of quen ching liquid sh ould be largeenough to absorb all the heat during a normal quenchingoperation without the use of additional cooling. As moremetals are quenched, the liquid absorbs the heat and thistemperature rise causes a decrease in the cooling rate.Since quenching liquids must be maintained withindefinite temperature ranges, mechanical means are usedto keep the tempera tur e at prescribed levels duringcontinuous operations.

LIQUID QUENCHING

The two methods used for liquid quenching arecalled still-bath and flush quenching.

Instill-bath quenching, you cool the metal in a tank of liquid. The only movement of the liquid is that causedby the movement of the hot metal, as it is beingquenched.

For flush quenching, the liquid is sprayed onto thesurface and into every cavity of the par t a t th e same t imeto ensure uniform cooling. Flush quenching is used forparts having recesses or cavities that would not be

properly quenched by ordinary methods. That assures athorough and uniform quench and reduces the possibili-ties of distortion.

Quenching liquids must be mainta ined at uniformtemperatures for satisfactory results. That is particularlytrue for oil. To keep the liquids at their proper tempera-ture, they are usually circulated through water-cooled

Figure 2-3.Por tab le quench tank .

coils. Self-contained coolers are integral parts of largequench tanks.

A typical portable quench tank is shown in figure2-3. This type can be moved as needed to various partsof the heat-treating shop. Some tanks may have one ormore compartments. If one compartment contains oiland the other water, the partition must be liquid-tight toprevent mixing. Each compart ment has a dra in plug, ascreen in t he bottom t o cat ch scale and oth er foreignmatter, and a mesh basket to hold the parts. A portableelectric pump can be attached to the rim of the tank tocirculate the liquid. This mechanical agitation aids inuniform cooling.

Water

Water can be used to quench some forms of steel,but does not produce good results with tool or other alloysteels. Water absorbs large quantities of atmosphericgases, and when a hot piece of metal is quenched, thesegases have a tendency to form bubbles on the surface of the metal. These bubbles tend to collect in holes orrecesses and can cause soft spots that later lead tocracking or warping.

The water in th e quench t ank should be chan geddaily or more often if required. The quench tank shouldbe large enough to hold the par t being treat ed and sh ould

have adequate circulation and temperature control. Thetemperature of the water should not exceed 65F.

When aluminum alloys and other nonferrous metalsrequire a liquid quench, you should quench them inclean wa ter. The volume of water in th e quench ta nk should be large enough to prevent a temperature rise of more th an 20F du ring a single quenching operation. For

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Table 2-4.Pr opert ies a nd Average Cooling Abili t ies of Quenching Media

heavy-sectioned parts, the temperature rise may exceed can cause cracking or stress in high-carbon or low-alloy20F, but should be kept as low as possible. For wrought steels that are uneven in cross section.products, the temperature of the water should be about

65F an d sh ould never exceed 100F before th e piece

Because of the corrosive action of salt on nonfer-

rous metals, these metals are not quenched in brine.enters the liquid.

Oil

Brine

Brine is the result of dissolving common rock saltin water. This mixture reduces the absorption of atmos-pheric gases th at, in tu rn, r educes the a mount of bubbles.As a r esult, brine wets t he met al sur face and cools itmore rapidly than water. In addition to rapid and uni-

form cooling, the brine r emoves a large per centage of any scale that may be present.

The brine solution should contain from 7% to 10%salt by weight or t hr ee-four th s pound of salt for ea chgallon of water . The correct temper at ur e ran ge for abrine solut ion is 65F to 100F.

Low-alloy and car bon steels can be quen ched inbrine solutions; however, the rapid cooling rate of brine

Oil is used to quench high-speed and oil-hardenedsteels and is preferred for all other steels provided thatthe required hardness can be obtained. Practically anytype of quenching oil is obtainable, including the vari-ous an imal oils, fish oils, vegetable oils, and minera loils. Oil is classed as an intermediate quench. It has aslower cooling rate than brine or water and a faster ratethan air. The quenching oil temperature should be keptwithin a ra nge of 80F t o 150F. The pr operties andaverage cooling powers of various quenching oils aregiven in ta ble 2-4.

Water usually collects in the bottom of oil tanks butis not harm ful in sma ll amounts. In large quant ities itcan interfere with the quenching operations; for exam-ple, the end of a long piece may extend int o the wat er a t

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C H A P T E R 3

I N T R O D U C T I O N TO W E L D I N G

In the Navy as well as private industry, welding iswidely used by metalworkers in the fabrication, main-

tenance, and repair of parts and structures. While thereare many methods for joining metals, welding is one of the most convenient and rapid methods available. Theterm welding refers to the process of joining metals byheating them to their melting temperat ure and causingth e molten met al t o flow together. These r an ge fromsimple steel brackets to nuclear reactors.

Welding, like any skilled trade, is broad in scope andyou cannot become a welder simply by reading a book.You need practice and experience as well as patience;however, much can be gained through study. For in-

stance, by learning the correct method or procedure foraccomplishing a job from a book, you may eliminatemany mistakes that otherwise would occur through trialand error.

This chapter is designed to equip you with a back-ground of basic information applicable to welding ingeneral. If you take t ime to study th is mat erial carefully,it will provide you with th e foun dat ion n eeded to be-come a skilled welder.

WELDING PROCESSES

Welding is not new. The earliest known form of welding, called forge welding, dat es back to th e year2000 B.C. Forge welding is a primitive process of

join in g met a ls by hea t ing and hammer ing unt il the met -als are fused (mixed) together. Although forge weldingstill exists, it is mainly limited to the blacksmith trade.

Today, there are many welding processes available.Figure 3-1 provides a list of processes used in modern

metal fabrication and repair. This list, published by theAmerican Welding Society (AWS), shows t he officialabbreviations for each process. For example, RSWstands for res i s tance spot weld ing . Shie lded meta l a r cw e l d i n g (SMAW) is an arc-welding process that fuses(melts) metal by heating it with an electric arc createdbetween a covered metal electrode and the metals being

join ed . Of t he weld in g proces se s list ed in figure 3-1,shielded metal arc welding, called stick welding, is the

most common welding process. The primary differ-ences between the var ious welding processes ar e the

methods by which heat is generated to melt the metal.Once you un derst an d th e th eory of welding, you canapply it to most welding processes.

The most common types of welding are oxyfuel gaswelding (OFW), arc welding (AW), and resistancewelding (RW). As a Steelworker, your primary concernis gas a nd a rc welding. The pr imar y difference betweenthese two processes is the method used to generate theheat.

GAS WELDING

One of the most popular welding meth ods uses a gasflame as a source of heat. In th e oxyfuel gas weldingproces s (fig. 3- 2), heat is produced by burning a com-bustible gas, such as MAPP (methylacetylene-propadi-ene) or acetylene, mixed with oxygen. Gas welding iswidely used in maintenance and repair work because of the ease in transporting oxygen and fuel cylinders. Onceyou learn the basics of gas welding, you will find theoxyfuel process adaptable to brazing, cutting, and heattreating all types of metals. You will learn more about

gas welding in chapter 5.

ARC WELDING

Arc welding is a pr ocess th at uses an electr ic arc to join the met a ls being welded. A d ist inct adva ntage of a rcwelding over gas welding is the concentration of heat.In gas welding the flame spreads over a large area,sometimes causing heat distortion. The concentration of heat, characteristic of arc welding, is an advantage be-cause less heat spread reduces buckling and warping.

This heat concentra tion also increases t he depth of pene-tration and speeds up the welding operation; therefore,you will find t hat ar c welding is often more pra ctical a ndeconomical than gas welding.

All arc-welding processes have three things in com-mon: a heat source, filler metal, and shielding. Thesource of heat in arc welding is produced by the arcingof an electrical current between two contacts. The power

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MASTER CH ART OF WELDING AND ALLlED P ROCE SSES

Figure 3-1.We1ding processes.

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Figure 3-2.0xyfuel ga s w elding (OFW).

source is called a welding machine or simply, a w e l d e r.This should not be confined with th e same t erm t hat isalso used to describe the person who is performing thewelding operation. The welder (welding machine) iseither electr ic- or m otor-powered. In th e Nava l Con-struction Force (NCF), there are two main types of ar c-welding processes with which you sh ould becomefamiliar. They are shielded metal arc welding and gasshielded arc welding.

Shie lded Meta l Arc Welding(SMAW)

Shielded metal arc welding (fig. 3-3) is performedby striking an arc between a coated-metal electrode andthe base metal. Once the arc has been established, themolten metal from the tip of the electrode flows togetherwith th e molten m etal from t he edges of the base meta lto forma sound joint. This process is known as f u s i o n .The coating from t he electr ode forms a covering overthe weld deposit, shielding it from contamination;

Figur e 3-3.Shielded met al ar c welding (SMAW).

therefore the process is called s h i e l d e d m e t a l a r cw e l d i n g . The main advantages of shielded metal arcwelding are that high-quality welds are made rapidly ata low cost. You will learn more about s hielded metal arcwelding in chapter 7.

Gas Shielded Arc Welding

The primary difference between shielded metal arc

welding and gas shielded arc welding is the type of shielding used. In gas shielded arc welding, both the arcand the molten puddle are covered by a shield of inertgas. The shield of inert gas prevents atmospheric con-tamination, thereby producing a better weld. The pri-mary gases used for this process are helium, argon, orcarbon dioxide. In some instances, a mixture of thesegases is used. The processes used in gas sh ielded arcwelding are known as g a s t u n g s t e n a r c w e l d i n g

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Figur e 3-4.Gas tu ngsten ar c welding (GTAW).

(GTAW) (fig. 3-4) and gas metal arc welding (GMAW)(fig. 3-5) . You will also hear these called TIG andMIG. Gas shielded arc welding is extremely usefulbecause it can be used to weld all types of ferrous andnonferrous metals of all thicknesses.

Now that we have discussed a few of the weldingprocesses available, which one should you choose?There are no hard-and-fast rules. In general, the control-ling factors are the types of metal you are joining, costinvolved, nat ure of the products you are fabricating, an dthe techniques you use to fabricate them. Because of itsflexibility and mobility, gas welding is widely used formaintenance and repair work in the field. On the otherha nd, you should probably choose gas sh ielded metal

arc welding to repair a critical piece of equipment madefrom aluminum or stainless steel.

No matter what welding process you use, there issome basic information you need to know. The remain-der of this chapter is devoted to this type of information.Study this information carefully because it allows youto follow welding inst ru ctions, read weldin g symbols,and weld various types of joints using the proper weld-ing techniques.

Figur e 3-5.Gas m etal a rc welding (GMAW).

WELDING TERMINOLOGY

To become a skilled welder, you first need to learnth e techn ical vocabu lar y (langua ge) of welding. Thesections in th is chapter intr oduce you t o some of th e

basic terms of the welding language. Once you under-stand the language of welding, you will be prepared tointerpret and communicate welding information accu-rately.

F ILLER METALS

When welding two pieces of metal together, youoften have to leave a space between the joint. Thematerial that you add to fill this space during the weldingprocess is known as the filler metal, or material. Twotypes of filler m eta ls commonly used in welding ar e

welding rods and welding electrodes.The term welding rod refers to a form of filler metal

that does not conduct an electric current during thewelding process. The only purpose of a welding rod isto supply filler metal to the joint. This type of filler metalis often used for gas welding.

In electr ic-arc welding, th e ter m electrode refers tothe component that conducts the current from the elec-trode holder to the metal being welded. Electrodes are

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classified into two groups: consumable and nonconsu-mable. Consumable electrodes not only provide a pathfor the current but they also supply fuller metal to the

join t . An exa mple is t h e elect rode u se d in sh ie ld edmetal-arc welding. Nonconsumable electrodes are onlyused as a conductor for the electrical current, such as ingas tungsten arc welding. The filler metal for gas tung-sten arc welding is a hand fed consumable welding rod.

Additional information about filler rods and elec-trodes is covered in other chapt ers of this TRAMAN t hatdeal with specific welding processes.

FLUXES

Before performing any welding process, you mustensure th e base metal is clean. No matter h ow much thebase metal is physically cleaned, it still contains impu-rities. These impurities, called oxides, result from oxy-gen combining with the metal and other contaminantsin the base metal. Unless these oxides are removed byusing a proper flux, a faulty weld may result. The term

fl ux refers to a material used to dissolve oxides andrelease trapped gases and slag (impurities) from the basemetal; thus the flux can be thought of as a cleaning agent.In p erform ing th is fun ction, th e flux a llows th e fillermetal and the base metal to be fused.

Different types of fluxes are used with differenttypes of metals; therefore, you should choose a fluxformulated for a specific base metal. Beyond that, youcan select a flux based on the expected soldering, braz-ing, or welding temperature; for example, when brazing,you should select a flux that becomes liquid at the

correct brazing temperature. When it melts, you willknow it is time t o add the filler met al. The ideal flux hasthe right fluidity at the welding temperature and thusblankets the molten metal from oxidation.

Fluxes are available in many different forms. Thereare fluxes for oxyfuel gas applications, such as brazingand soldering. These fluxes usually come in the form of a paste, powder, or liquid. Powders can be sprinkled onthe ba se meta l, or th e fuller rod can be heated a nd dippedinto the powder. Liquid and paste fluxes can be appliedto the filler r od and t o the base metal with a brush. Forshielded metal arc welding, the flux is on the electrode.

In t his case, the flux combines with impu rities in th ebase meta l, floating t hem a way in th e form of a heavyslag which shields the weld from the atmosphere.

You should realize that no single flux is satisfactoryfor universal use; however, there are a lot of goodgeneral-purpose fluxes for use with common metals. Ingeneral, a good flux has the following characteristics:

It is f luid an d active at t he melting point of thefuller m etal.

It remains stable and does not change to a vaporrapidly within the temperature range of the weld-ing procedure.

It dissolves all oxides an d removes them from t he join t su rfaces .

It adheres to the metal surfaces while they arebeing heated and does not ball up or blow away.

It does not cause a glare that makes it difficult tosee the progress of welding or brazing.

It is easy to remove after the joint is welded.

It is available in an easily applied form.

CAUTION

Near ly all fluxes give off fum es th at ma ybe toxic. Use ONLY in well-ventilated spaces.

It is also good to remember that AL L weldingoperations require adequate ventilation whethera flux is used or not.

WE L D J O I N T S

Th e weld joint is where two or more meta l parts a re join ed by we ld in g. Th e five ba sic t yp es of weld join t sar e the but t, corner , tee, lap, and edge, as shown in figure3-6.

Figure 3-6.Basic weld joints.

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Figure 3-9.Bevel angle, groove angle, groove radius, and root open ing of joints for welding.

A b u t t join t is used to join two mem bers align ed inthe same plane (fig. 3-6, view A). This joint is frequentlyused in plate, sheet metal, and pipe work. A joint of thistype may be either square or grooved. Some of thevariat ions of this joint a re discussed later in t his chapter .

C o r n e r and t e e join ts a re used to join two mem ber slocated at right angles to each other (fig. 3-6, views Band C). In cross section, the corner joint forms anL-shape, and t he tee joint h as t he shape of the letter T .Various joint designs of both types have uses in manytypes of metal structures.

A la p join t , as the name implies , is made by la pp ingone piece of metal over another (fig. 3-6, view D). Thisis one of the strongest types of joints available; however,for maximum joint efficiency, you should overlap themetals a minimum of three times the thickness of theth innest member you ar e joining. Lap joints a re com-monly used with torch brazing and spot welding appli-cations.

An e d g e join t is u sed to join t h e ed ges of two ormore members lying in the same plane. Inmost cases,one of the members is flanged, as shown in figure 3-6,view E. While this type of joint has some applicationsin platework, it is more fixquently used in sheet metalwork An edge joint should only be used for joiningmetals 1/4 inch or less in thickness that are not subjectedto heavy loads.

The above paragraphs discussed only the five basictypes of joints; however, there are many possible vari-ations. Later in this chapter, we discuss some of thesevariations.

PARTS OF J OINTS

While there are many variations of joints, the partsof the joint are described by standard terms. The roo t of a joint is t hat portion of the joint where t he meta ls areclosest t o each other . As sh own in figur e 3-7, th e rootmay be a point, a line, or an area, when viewed in crosssection. A g r o o v e (fig. 3-8 ) is an opening or spaceprovided between t he edges of the metal pa rts to bewelded. The groove face is that surface of a metal partincluded in the groove, as shown in figure 3-8, view A.

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