ME310

Manufacturing Processes

Rahul Panat

School of Mechanical and Materials Engineering

Washington State University

1

RESEARCH TOPICS

• Thank you for submitting the topics

• Very interesting areas

• Presentations will be done by the end of April and May

• Why do a project? - An industry perspective

EXAM ON FRIDAY

• Same format as Exam #1

– Topics covered until last week ; Emphasize will be on questions after the exam #1, but there may be some questions from before the exam #1 as stated before in the class

– Three sets of questions –

– Set-1: Multiple choice

– Set-2: Short answers

– Set-3: Numerical problems

• Please study the text and class material (posted on Angel) with particular attention to

– Review questions in the class

– Problems discussed in the class

– HWs

• One A4 sheet (both sides) with your notes allowed for exam 2. You can bring the older sheet from exam 1 as well

• Exam date discussion!

JOINING PROCESSES- PART II

Week 9

4

OUTLINE

(Last Lecture)

• Joining and assembly

• Joining processes– Welding

– Fusion

(This Lecture)– Solid state

– Brazing and soldering

– Adhesive bonding

• Mechanical fastening

SOLID-STATE WELDING

• Joining without fusion, ie., no liquid (molten) phase in the joint

• Coalescence results from application of pressure alone or a combination of heat and pressure

• If heat is used, temperature is below melting point of metals being welded

• No filler metal is added in solid state welding

SOLID-STATE WELDING PROCESSES

Cold welding

Ultrasonic welding

Friction welding

Resistance welding

Explosion welding

Diffusion bonding

COLD WELDING (CW)

Pressure is applied to the mating faces by dies or rolls (roller bonding); Plastic deformation of one or both parts leads to welding

Interface can be precleaned using wire or power brush

Best bond strength happens between similar materials

Brittle intermetallic compounds may form between dissimilar metals leading to weak interface

Applied to small work pieces of soft, ductile metals, such as electrical connections, wire stock, sealing of heat sensitive containers

Schematic illustration of theroll-bonding, or cladding,process.

Movie

Adv Materials (2013) http://onlinelibrary.wiley.com/doi/10.1002/adma.201303400/pdf

Accumulative roll bonding (ARB) nano-layered compositesAdv Materials (2013) http://onlinelibrary.wiley.com/ doi/10.1002/adma.201303400/pdf

ULTRASONIC WELDING

● In USW, the faying faces are subjected to a static normal force + oscillating shear stress

● The shear stress is applied by the tip of a transducer, freq = 10-75 kHz

● Shearing stress cause small scale plastic deformation at the interface, breaking up oxide film and contaminants

Components of an ultrasonic welding machine for lapwelds.

• Temperatures well below Tm

• Extensively used in joining plastics in automotive and electronics industry

Movie

THERMOSONIC WIRE BONDING

IN MICROELECTRONICS

https://www.youtube.com/watch?v=fazeH4PHvpk

5 die stacked memory package(Molding compound removed –

isometric view)

https://www.youtube.com/watch?v=6-iuT_o8f00

FRICTION WELDING (FRW)

SSW process in which coalescence is achieved by frictional heat combined with pressure

When properly carried out, no melting occurs at faying surfaces

Can be used to join dissimilar metals

Widely used commercial process, amenable to automation and mass production

(1) Rotating part, no contact; (2) parts brought into contact to generate friction heat; (3) rotation stopped and axial pressure applied; and (4) weld created

Movie

FRICTION WELDING EXAMPLE

Cross section of butt joint of two steel tubes joined by friction welding (courtesy George E. Kane Manufacturing Technology Laboratory, Lehigh University)

APPLICATIONS AND LIMITATIONS

OF FRICTION WELDING

Applications:

Shafts and tubular parts

Industries: automotive, aircraft, farm equipment, petroleum and natural gas

Limitations:

At least one of the parts must be rotational

Flash must usually be removed (extra operation)

Upsetting reduces the part lengths (which must be taken into consideration in product design)

FRICTION STIR WELDING

Different from friction welding

A third body (small rotating pin) is rubbed against the two surfaces to be joined

The pin is plunged into the joint, causing frictional heating, leading to heating, mixing or stirring of the material in the joint

Most commonly used for butt joints of aluminum and titanium alloys in aerospace industry, now also in polymers and composites

The principle of the friction stir welding process.Aluminum-alloy plates up to 75 mm (3 in.) thickhave been welded by this process. Source: TWI,Cambridge, United Kingdom.

Friction stir welding animation

Friction Stir Welding of Steel

ADVANTAGES AND DISADVANTAGES OF

FRICTION STIR WELDING

Advantages

Superior weld strength

Little distortion or shrinkage

Good weld appearance

Disadvantages

An exit hole is produce when tool is withdrawn

Heavy duty clamping of parts is required

Incomplete welding at the bottom of the interface

Right Figure: 13 foot (4 meters) diameter Titanium nacelle lip skin (Boeing Frontiers/July 2010)

RESISTANCE WELDING (RW)

A group of welding processes that use a combination of heat and pressure to accomplish coalescence

Heat generated by electrical resistance to current flow at junction to be welded

V = 0.5-10V, I < 100,000A

Principal RW process is resistance spot welding (RSW)

Five basic method of RW

Spot (primary)

Seam

Projection

Flash

Upset

RESISTANCE SPOT WELDING

●Resistance welding process in which welding of faying surfaces of a lap joint is achieved at one location by opposing electrodes ● Used to join sheet metal parts

● Widely used in mass production of automobiles, metal furniture, appliances, and other products ● Typical car body has ~ 10,000 spot welds

● Annual production of automobiles in the world is measured in tens of millions of units

Animation

RESISTANCE SEAM WELDING (RSEW)

Uses rotating wheel electrodes to produce a series of overlapping spot welds along lap joint

Can produce air-tight joints

Applications:

Gasoline tanks

Automobile mufflers

Various sheet metal containers

RESISTANCE PROJECTION WELDING

Resistance welding process in which coalescence occurs at one or more small contact points on the parts

Contact points determined by design of parts to be joined

May consist of projections, embossments, or localized intersections of parts

ADVANTAGES AND DRAWBACKS

OF RESISTANCE WELDING

Advantages: High production rates possible

Lends itself to mechanization and automation

Lower operator skill level than for arc welding

Good repeatability and reliability

Disadvantages: High initial equipment cost

Limited to lap joints for most RW processes

EXPLOSION WELDING

Contact pressure is applied by detonating a layer of explosives place over one of the mating members

Kinetic energy of the flyer plate striking the mating member produces a turbulent, wavy interface, mechanically interlocking the two surfaces

Titanium on low carbon steel

1 Flyer (cladding)2 Welded interface3 Target (substrate). 4 Explosion. 5 Explosive powder. 6 Plasma jet.

Movie

ADVANTAGES AND DISADVANTAGES

Explosion welding can produce a bond between two metals that cannot necessarily be welded by conventional means.

Large areas can be bonded extremely quickly

Weld is very clean, due to the fact that the surface material of both metals is violently expelled during the reaction.

A major disadvantage of this method is that an expansive knowledge of explosives is needed before the procedure may be attempted.

Common applications:

Cladding plates and slabs with dissimilar metals in chemical industry

Resulting materials can be further rolled into thin section

Eg. tube and pipe jointed to the holes in header plates of boilers and tubular heat exchanges

DIFFUSION WELDING (DFW)

SSW process uses heat and pressure, usually in a controlled atmosphere, with sufficient time for diffusion and coalescence to occur

Temperatures 0.5 Tm

Plastic deformation at surfaces is minimal

Primary coalescence mechanism is solid state diffusion

Limitation: time required for diffusion can range from seconds to hours

Applications:

Joining of high-strength and refractory metals in aerospace and nuclear industries

Can be used to join either similar and dissimilar metals

For joining dissimilar metals, a filler layer of different metal is often sandwiched between base metals to promote diffusion

Illustration

DIFFUSION BONDING EXAMPLE

Sequence of operations in diffusion bonding andsuperplastic forming of a structure with three flatsheets. See also Fig. 7.46. Source: After D. Stephen andS.J. Swadling.

BRAZING AND SOLDERING

BRAZING

Brazing: a filler metal is placed at or between the faying surfaces to be joined, and the temperature is raised to melt the filler metal, but not the working pieces. The molten metal fills the gap by capillary action. Upon cooling and solidification of the filler metal, a strong joint is formed.

Filler metal for brazing melt above 450 ˚ C, but below Tm of

the workpieces

Heat source: torch, furnace, induction, resistance, laser or electron beam, etc

Optimal clearance in brazing is 0.025-0.2 mm

Good joint strength, principally used for maintenance and repair

SOLDERING

Filler metal (solder) melts below 450 ˚ C

Heat source: soldering iron, torches, or ovens

Solder joints has limited use in elevated temperature

Usually low strength, not for load bearing

Types of solders and their applications.

SUMMARY

Welding

Fusion welding (last time)

Oxyfuel gas, electric arc, high energy beam welding

Solid state welding

Cold, ultrasonic, friction, resistance, explosion and diffusion

Brazing and soldering

Adhesive bonding

Mechanical fastening