1. Chapter 31 Solid-State Welding Processes

2. THE WORK PIECE DOES NOT UNDERGO PHASE CHANGE

3. COLD WELDING -pressure is applied to the two parts -At least one of them is ductile -usually performed on non ferrous metals -Interface must be well cleaned

4. ROLL BONDING -used in manufacturing some US coin - can be performed on cold or hot temperatures -typical example is cladding as shown in following figure

5. FIGURE 31.1 Schematic illustration of the roll bonding, or cladding, process.

6. FIGURE (a) Components of an ultrasonic-welding machine for making lap welds; the lateral vibrations of the tool tip cause plastic deformation and bonding at the interface of the workpieces. (b) Ultrasonic seam welding, using a roller as the sonotrode.

7. FRICTION WELDING - ONLY ONE PART IS ROTATED -THE OTHER PART IS PRESSED AGAINST THE FIRST PART - A flash is developed by plastic deformation (upsetting)

8. FIGURE Sequence of operations in the friction-welding process: (1) The part on the left is rotated at high speed. (2) The part on the right is brought into contact with the part on the left under an axial force. (3) The axial force is increased, and the part on the left stops rotating; flash begins to form. (4) After a specified upset length or distance is achieved, the weld is completed. The upset length is the distance the two pieces move inward during welding after their initial contact; thus, the total length after welding is less than the sum of the lengths of the two pieces. The flash subsequently can be removed by machining or grinding.

9. THE SIZE AND SHAPE OF THE WELD JOINT DEPENDS UPON 1
THE SIZE AND SHAPE OF THE WELD JOINT DEPENDS UPON 1. Amount of heat generated 2. Thermal conductivity of the two materials 3. Mechanical properties of the two materials at elevated temperature 4. Rotational speed 5. Axial pressure applied

10. FIGURE Shape of the fusion zones in friction welding, as a function of the axial force applied and the rotational speed.

11. FIGURE 31. 5 The friction-stir-welding process
FIGURE The friction-stir-welding process. (a) Schematic illustration of friction stir welding; aluminum-alloy plates up to 75 mm (3 in.) thick have been welded by this process. (b) Multi-axis friction stir welding machine for large workpieces, such as aircraft wing and fuselage structures, that can develop 67 kN (15,000 lb) axial forces, is powered by a 15 kW (20 hp) spindle motor, and can achieve welding speeds up to 1.8 m/s. Source: (b) Courtesy of Manufacturing Technology, Inc.

12. RESISTANCE WELDING Heat required for welding is produced by means of electrical resistance across the two parts to be joined

13. FIGURE (a) Sequence of events in resistance spot welding of a lap joint. (b) Cross-section of a spot weld, showing the weld nugget and the indentation of the electrode on the sheet surfaces. This is one of the most commonly used processes in sheet-metal fabrication and in automotive-body assembly.

14. FIGURE 31.7 Two electrode designs for easy access to the components to be welded.

15. FIGURE 31. 8 Spot-welded (a) cookware and (b) muffler
FIGURE Spot-welded (a) cookware and (b) muffler. (c) A large automated spot-welding machine. The welding tip can move in three principal directions; sheets as large as 2.2 m × 0.55 m (88 in. × 22 in.) can be accommodated in this machine, with proper workpiece supports. (d) A spot welding machine. Source: (c) and (d) Courtesy of Taylor-Winfield Technologies, Inc.

16. TEST METHODS FOR SPOT WELDING 1. Tension-shear test 2
TEST METHODS FOR SPOT WELDING 1. Tension-shear test 2. Cross-tension test 3. Twist test 4. Peel test

17. FIGURE Test methods for spot welds: (a) tension-shear test, (b) cross-tension test, (c) twist test, and (d) peel test (see also Fig. 32.9).

18. RESISTANCE SEAM WELDING Electrodes are replaced by rollers

19. FIGURE (a) Seam-welding process in which rotating rolls act as electrodes; (b) overlapping spots in a seam weld; (c) roll spot welds; and (d) mash seam welding.

20. FIGURE 31.11 Two methods of high-frequency continuous butt welding of tubes.

21. FIGURE (a) Schematic illustration of resistance projection welding. (b) A welded bracket. (c) and (d) Projection welding of nuts or threaded bosses and studs. (e) Resistance-projection-welded grills.

22. FIGURE (a) Flash-welding process for end-to-end welding of solid rods or tubular parts. (b) and (c) Typical parts made by flash welding. (d) and (e) Some design guidelines for flash welding.

23. FIGURE The relative sizes of the weld beads obtained by tungsten-arc and by electron-beam or laser-beam welding.

24. FIGURE (a) Schematic illustration of the explosion-welding process. (b) Cross-section of explosion-welded joint: titanium (top) and low-carbon steel (bottom). (c) Iron–nickel alloy (top) and low-carbon steel (bottom).

25. DIFFUSION BONDING - used in joining dissimilar metals - Strength of the joints results from: 1. Diffusion: movement of atoms across the interface 2. plastic deformation at the interface

26. FIGURE 31.17 Aerospace diffusion-bonding applications.

27. FIGURE Sequence of operations in the fabrication of a structure by the diffusion bonding and superplastic forming of three originally flat sheets; see also Fig Source: (a) & (d) after D. Stephen and S.J. Swadling, (b) & (c) courtesy of Rockwell International Corp.

28. FIGURE 31. 19 The Monosteel piston
FIGURE The Monosteel piston. (a) Cutaway view of the piston, showing the oil gallery and the friction-welded sections; (b) detail of the friction welds before the external flash is removed and cylindrical grooves are machined. Produced by inertia friction welding