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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 1 of 12

    ABN 69 003 696 526

    QUESTION 1

    The following questions have multiple-choice answers and are worth 2 marks each.Only one answer is correct. Tick only one. If more than one box is ticked, no marks will be awarded.

    1.1 The basic reason for a bend test is:

    a. Measure the resistance to local penetration by a harder substance.b. To determine the soundness of weld metal and HAZ, and to give an

    indication of the ductility of welded joints.c. The resistance to bending under the application of a point load.d. None of the above.

    1.2 What would be the reason for using a nick break test?

    a. To test if the fillet weld is strong enough.b. To use as a substitute for a Charpy impact test.c. To find lack of root penetration.d. To expose porosity, lack of fusion, slag inclusions, and cold lap.

    1.3 What would be the approximate minimum chromium content be in a steel to be stainless?

    a. 11%b. 8%c. 20%d. None of the above

    1.4 The term t8

    /5 is used to describe:a. The time taken for a weld zone to cool from the post weld heat treatment

    temperature to room temperatureb. The time taken during cooling for a weld run and the HAZ to pass through the

    temperature range of 800

    C to 500

    Cc. The time taken during heating for the HAZ to pass through the temperature

    range of 500

    C to 800

    C.d. None of the above

    1.5 What problems could arise when welding a leaded brass alloy?

    a. There are no problems.b. Zinc and lead fume, cracking, and porosity.c. These structures are not normally welded.d. The cost of re-applying the galvanised layer.

    1.6 Galvanic corrosion can result if:

    a. Two dissimilar materials are joined in the presence of an electrolyteb. If similar materials are joined in the presence of an electrolytec. If carbon steel and stainless steel are joined together in chlorinated waterd. a and c above.

    1.7 When welding a 304L stainless steel to grade 250 carbon steel:

    a. An austenitic stainless steel weld metal should be used.b. A general purpose electrode should be used.c. A silicon bronze alloy weld metal should be used.d. Options b or c can be used.

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 2 of 12

    ABN 69 003 696 526

    1.8 When welding ferritic stainless steels, why must heat input be controlled?

    a. To avoid lack of fusion.b. To limit grain coarsening in the HAZc. In order to prevent excessive hardening of the weld metal.d. To ensure the correct welding parameters are used.

    1.9 Why is pickling and passivation of a weld joint important?

    a. To improve the aesthetic appearance of a welded structure.b. It is normally a client requirement.c. To restore the passive film on copper.d. To restore corrosion resistance to stainless steel in the weld zone.

    1.10 The weldability of quenched and tempered steel is mainly affected by:a. Its hardenability and the presence of hydrogenb. The presence of a passive film.c. The correct choice of welding consumable.d. The amperage used for welding.

    1.11 Which of the four following samples correspond to a steel:

    a. 0.2 % Cb. 2.4 % Cc. 6.4 % Cd. 12.0 % C

    1.12 A tensile test of parent material and weld metal enables:

    a. Determination of the tested materials resistance to impact stress.b. Determination of the tested materials creep strength.c. Determination of the tested materials hardness.d. Determination of the tested materials ultimate strength.

    1.13 Sulphur is known to have many bad effects on steel. Which of the following statements is not correctwith respect to Sulphur (S) in an unalloyed steel??

    a. Increases the risk of hot crackingb. Eases the process of turning and millingc. Decreases the risk of lamellar tearingd. Leads to poor weldability when present in significant amounts

    1.14 A steel of 0,2% C is heated over A3 temperature and is then cooled slowly. What constituents arepresent in the steel at room temperature?

    a. Ferriteb. Austenitec. Martensited. Ferrite and pearlite

    1.15 The t 8/5 cooling rate can be a significant parameter for welding:

    a. Quenched and tempered steels

    b. SAF 2205 type steels.c. Managing post weld heat treatments.d. Austenitic stainless steels.

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 3 of 12

    ABN 69 003 696 526

    1.16 Quenching is a heat treatment that tries to reach:

    a. Maximum hardness and strength.b. Maximum hardness and minimum strength.c. Minimum hardness and maximum strength.d. Minimum hardness and strength.

    1.17 When welding a mild steel, multi-pass welding allows:

    a. An improvement of the mechanical characteristics of the jointb. A saving of filler metal.c. An improvement of productivity.d. None of the above

    1.18 Which of the following microstructures will give the highest toughness values?

    a. Large grained, coarse martensite.b. Fine grained martensite.c. Large grained, coarse tempered martensite.d. Fine grained tempered martensite.

    1.19 Lamellar tearing of the parent plate can be countered by:

    a. Increase in yield strength of the weld metal.b. Improving through-thickness ductility of the parent plate.c. Increasing impact resistance of the weld metal.d. Reducing the nitrogen content in both parent plate and weld metal

    1.20 Which are the three necessary conditions for cold cracking to occur?

    a. Presence of hydrogen, tensile stresses, austenitic weld metalb. Presence of nitrogen, tensile stresses, susceptible microstructure.c. Presence of inclusions, tensile stresses, T-joints.d. Presence of hydrogen, susceptible microstructure, tensile stresses.

    1.21 What of the following is the most likely imperfection when welding quenched and tempered steel?

    a. Hot cracking.b. Cold cracking.c. Lamellar tearing.d. Lack of fusion.

    1.22 The basic property of steel required to successfully work in very low temperature is:

    a. Strength.b. Resistance to brittle crackingc. Hardness.d. Creep resistance.

    1.23 To be considered corrosion resistant, steels have to include minimally:

    a. 11 % of Cr.b. 18% of Crc. 6% of Cr.d. 3% Cr.

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 4 of 12

    ABN 69 003 696 526

    1.24 Generally speaking, aluminium alloys have wide solidification temperature ranges, and thereforethey are prone to:

    a. Hot crack.b. Cold crack.c. Form non-metallic inclusions.d. Form blowholes.

    1.25 What can be seen on macroetch sample?

    a. Microstructure .b. Carbides on grain boundaries.c. Appearance of weld metal and HAZ.

    d. Grain size.

    1.26 Describe what metallography is where it is used. 3 marks

    Metallography is a systematic method to examine the microstructure of materials. Important usesof metallography include process control and qualification of welds, examination of defects thatappear in finished or partly finished products and studies of parts that have failed in service.Investigations for these purposes usually require that the specimen be removed from a large massof material, and often involve more than one sectioning operation.

    1.27 Explain the term Carbon Equivalent 3 marks

    Different elements increase the hardenability of a steel to varying degrees. The Carbon Equivalent equates each elements hardenability against that of Carbon and by

    adding the effect of each element on hardenability together, one arrives at an equivalenthardenability to Carbon.

    The higher the carbon equivalent the greater is the difficulty in welding the steel.

    1.28 Find the Combined J oint Thickness for the joint given below assuming that the welds indicated inblack already exist. 4 marks

    All dimensions are in mm50 mm

    60 mm

    16 mm

    50 mm

    80 mm

    12 mm

    Weld here

    mmxxx

    T 9.4275

    6012

    75

    1650

    75

    165012 =+++=

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 5 of 12

    ABN 69 003 696 526

    QUESTION 2

    2.1 Explain the term Weldability 5 marks

    Weldability is a measure of how easy it is to:

    Obtain crack free welds Achieve adequate mechanical properties Produce welds resistant to service degradation.

    Weldability is not a fixed parameter for a given material, but will depend on joint details, servicerequirements, and welding processes and facilities available.

    OR :Metallic material is considered to be susceptible to welding to an established extent with given

    processes and for given purposes when welding provides metal integrity by a corresponding technologicalprocess for welded parts to meet technical requirements as to their own qualities as well as to their influenceon a structure they form

    2.2 What is stainless steel? List five basic groups of stainless steels used in welded fabrication.6 marks

    The term stainless steel is taken to mean any of a large number of steels i.e. iron-carbon alloy,containing a minimum of 11% chromium (Cr). Ferritic Austenitic Duplex Martensitic Precipitation hardening

    2.3 Explain the term sensitisation as applied to stainless steel. List one method of preventing it.4 marks

    Also known as chromium carbide precipitation, this condition primarily affects the heat affected zone(HAZ) and is dependent upon the level of carbon present in the material and the length of time thatthe material stays in the critical temperature range of 450C - 850C.

    The carbon in the steel combines with chromium to form chromium carbides. These carbides formalong the grain boundaries and result in the areas immediately adjacent to the precipitates being lowin chromium i.e. those areas are no longer stainless. Preferential corrosion attack occurs alongthese boundaries, resulting in intergranular corrosion or weld decay.

    PREVENTION

    Low carbon grades of stainless steel and filler material of less than 0.03% carbon should beused / use stabilised grades of austenitic stainless steel (321/347).

    Weld zones should be free of contamination.

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 6 of 12

    ABN 69 003 696 526

    2.4 With the aid of a sketch, what would the effect of grain size in a ferritic steel have on mechanicalproperties? 5 marks

    The finer the grain size, the lower the DBTT temperature, hence the greater the impact resistanceand ductility of the material, and the greater the yield strength.

    2.5 What are the common reasons for carrying out heat treatment on metals. 5 marks

    Common reasons for carrying out heat treatments are to:1. Remove internal (residual) stresses , incurred for example from such previous treatments as

    hardening, cold forming processes, welding and uneven cooling2. Refine the grain structure and size, leading to enhanced ductility3. Soften to permit further working operations e.g. rolling4. Improve mechanical properties , including hardness, improving wear resistance and

    machinability5. Improve uniformity in castings forgings and weldments.

    2.6 What is Stress Corrosion Cracking (SCC)? What factors contribute to its occurrence? How can it becontrolled? Give two examples of material-environment combination where SCC may occur.

    10 marks

    Stress corrosion cracking (SCC) requires three conditions, a susceptible alloy, tensile stresses, anda specific corrosive environment to occur simultaneously. The necessary tensile stress can beeither externally applied or existing in the material due to forming or welding. If one condition iseliminated, SCC will not occur. Some examples are caustic conditions for steel, ammonia for brass,various chloride solutions for certain stainless steel grades.

    Prevention can be achieved by:

    - Reducing the overall stress level and designing out stress concentrations- Selection of a suitable material not susceptible to the environment- Design to minimise thermal and residual stresses

    - Developing compressive stresses in the surface the material- Use of a suitable protective coating

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 7 of 12

    ABN 69 003 696 526

    QUESTION 3

    3.1 Discuss the weldability of medium carbon steels in relation to carbon content and risk mitigationtechniques to overcome weldability issues. 7 marks

    A pronounced change in the weldability of carbon steel takes place when the carbon content is in the 0.30 to0.50 % range . Steels containing about 0.30 % carbon and relatively low manganese content have goodweldability. As the carbon content is increased, the welding procedures must be designed to avoid theformation of large amounts of hard martensite in the heat-affected zone. For most applications, mediumcarbon steels should be preheated prior to welding. The preheat temperature depends upon the carbonequivalent of the steel, the joint thickness, and the welding procedure. A stress relief heat treatment isrecommended immediately after welding, especially with thick sections, high joint restraint, or serviceconditions involving impact or dynamic loading. If possible, the welded joint should be heated to the stressrelief temperature without intermediate cooling to ambient temperature.Low hydrogen welding procedures are mandatory with these steels. Selection of filler metal for arc weldingbecomes more critical as the carbon content increases. Pick-up of carbon will occur with steels of highercarbon content and this may produce a weld metal of high hardness, susceptibility to cracking and tendencyfor brittle failure. Dilution can be minimised by depositing small weld beads or using a welding procedurethat provides shallow penetration. Low heat input is generally recommended for the first few layers in amultipass weld to limit dilution.

    3.2 What are the three conditions required for the onset of brittle fracture in a welded steel structure?3 marks

    A defect. A tensile stress transverse to the defect. A microstructure which is susceptible at the temperature of interest.

    3.3 Explain briefly what is a TMCP steel and discuss its weldability? 5 marks

    Thermo-Mechanical Control Process (TMCP) steels achieve high strength by a combination of controlled rolling and controlled accelerated cooling. The microstructure is strengthened bymechanisms of precipitation hardening, grain refinement and work hardening, transformation andmicrostructure that allow for lower carbon contents than common steels. They have relatively goodweldability characterised by: Low hardenability (Carbon >0.1%) Even for thick sections and low temperatures preheat is hardly required

    3.4 Define the phenomenon of Creep of a material with the help of Strain/Elongation v/s Time diagram

    and explain the effect of the main variables. 10 marks

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 8 of 12

    ABN 69 003 696 526

    3.5 Discuss the weldability of duplex stainless steels and risk mitigation techniques to overcomeweldability issues. 5 marks

    Increased ferrite levels in both the base metal and weld metal can reduce joint toughness andcorrosion resistance.

    Control over ferrite level is possible through welding consumable selection and heat inputcontrol.

    Welding consumables for duplex stainless steels contain Nitrogen (a strong austenite stabiliser)as an alloying element.

    Generally heat input should be limited to between 0.5 - 2.5 kJ /mm.

    3.6 Comment in general on the weldability of copper and its alloys. 5 marks

    In terms of weldability, alloys have quite different welding characteristics. Due to the high thermal conductivity of copper substantial preheat is required to counteract the

    very high heat sink and avoid incomplete penetration. Copper is often cold worked. Welding softens the HAZ. Tendency for cracking. Precipitation hardened copper should be welded in the annealed condition and then heat

    treated. Be aware of alloying elements with low melting and boiling point. Welding free machining copper is not recommended.

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 9 of 12

    ABN 69 003 696 526

    3.7 Explain the mechanism and causes of reheat cracking with the aid of sketches. How would youavoid it and what materials are susceptible to it? 10 marks

    Reheat cracking may occur in low alloy steels containing alloying additions of chromium,vanadium and molybdenum when the welded component is subject to:

    Post weld heat treatment,Multiple welds orTo high temperature service (at 350 - 550 C).

    Cracks may occur in the coarse-grained region of the HAZ or sometimes in weld metalReheat cracking results from embrittlement of the grain boundaries caused by segregation of phosphorus, tin and arsenic

    Material susceptible to reheat cracking:Low alloy steels containing alloying additions of chromium, vanadium and molybdenum e.g. 5Cr1Mo, 0.5Cr 0.5Mo 0.25V

    How to avoid:Use appropriate welding procedureUse buttering techniqueControl heat iinputProduce the maximum refinement of the coarse grain HAZEliminating stress concentrations

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 10 of 12

    ABN 69 003 696 526

    QUESTION 4

    4.1 List two specific weld imperfections that may occur in each of the following:

    4.1.1 Nickel and Nickel Alloys 2 marks Porosity Oxide inclusions and lack of inter-run fusion Weld metal solidification cracking Microfissuring

    4.1.2 Heat treatable Aluminium Alloys 2 marks Excessive porosity if cleaning not performed correctly Over-aging of the heat affected zone

    4.1.3 Quenched and Tempered Steels 2 marks Cold cracking due to high Carbon Equivalent Excessive softening of the HAZ.

    4.1.4 Ferritic stainless steels for use catalytic convertors 2 marks Lower toughness due to excessive grain growth. Formation of brittle phases.

    4.2 What are the recommended steps for welding in planning welding of stainless steels to carbonsteels? 5 marks

    1. Selecting welding process and its parameter

    2. Determine dilution3. Pre-selection of the filler metal4. Determine the weld metal composition in the Schaeffler diagram5. Confirm filler metal, or select another one if the weld metal composition is outside of the safe

    area

    4.3 When joining cladded steels to each other, what are the areas of concern that should be addressedand how would a welding sequence be approached (use sketches)?

    In the weld joining of the clad steels it is essential to preserve the properties of the cladding at theweld. Otherwise, the desired corrosion resistance, abrasion resistance, or other properties of theclad surface are not continuous. At the same time, it is also essential that the properties of thebacking metal be maintained. These two requirements mean that special joint designs and welding

    procedures are required. In general, the procedure is to weld the backing metal portion of the jointfirst, followed by welding the clad side. This sequence prevents the formation of hard, brittle areasin the weld.

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 11 of 12

    ABN 69 003 696 526

    4.2 Discuss the weldability issues of martensitic stainless steels and how to overcome them?. 5 marks

    Martensitic stainless steels are difficult to weld successfully due to the formation of martensite inthe HAZ.

    To reduce the effects of martensite formation, adequate control over pre-heat, interpasstemperatures and heat input are essential.

    Depending on the carbon content, preheat temperatures of between 100 - 300C are commonlyrecommended to avoid cracking.

    Post Weld-Heat Treatment (tempering) my be required to improve mechanical properties andreduce welding stresses.

    4.3 Explain with the aid of sketches the phenomenon of lamellar cracking and how it may be mitigated. 12 marks

    A type of crack stretching parallel to rolling surfaces.If rolled products are stressed in the thickness direction, the deformation capacity is often lowerthan in the longitudinal and transversal direction.The reason for this is the arrangement of non-metallic inclusions in layers parallel to the surfaceduring rolling.Thus the danger of fractures parallel to the surface of the rolled products arises.

    There are three conditions that must be satisfied for lamellar tearing to occur:

    1. Transverse strain - the shrinkage strains on welding must act in the short direction of the platei.e. through the plate thickness

    2. Weld orientation - the fusion boundary will be roughly parallel to the plane of the inclusions3. Material susceptibility - the plate must have poor ductility in the through-thickness direction.

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    QUALIFICATI ON & CERTIFICATI ON BOARD Date of Issue: 23 May 2011Management System Manual IIW International Welding Specialist (IWS) Sample Questions and Anwers

    SA2 MATERIALS AND THEIR BEHAVIOUR DURING WELDINGPage 12 of 12

    ABN 69 003 696 526

    Specification of the use of steel tested in the z-direction.


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