1. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-1 CHAPTER 29 The Metallurgy of Welding; Welding Design and Process Selection

2. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-2 Fusion Weld Zone Figure 29.1 Characteristics of a typical fusion weld zone in oxyfuel gas and arc welding. See also Figs. 27.16 and 28.14.

3. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-3 Grain Structure in Shallow and Deep Welds (a)(b) Figure 29.2 Grain structure in (a) a deep weld (b) a shallow weld. Note that the grains in the solidified weld metal are perpendicular to the surface of the base metal. In a good weld, the solidification line at the center in the deep weld shown in (a) has grain migration, which develops uniform strength in the weld bead.

4. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-4 Weld Beads Figure 29.3 (a) Weld bead (on a cold-rolled nickel strip) produced by a laser beam. (b) Microhardness profile across the weld bead. Note the lower hardness of the weld bead compared to the base metal. Source: IIT Research Institute. (a) (b)

5. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-5 Regions in a Fusion Weld Zone Figure 29.4 Schematic illustration of various regions in a fusion weld zone (and the corresponding phase diagram) for 0.30% carbon steel. Source: American Welding Society.

6. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-6 Corrosion Figure 29.5 Intergranular corrosion of a 310-stainless-steel welded tube after exposure to a caustic solution. The weld line is at the center of the photograph. Scanning electron micrograph at 20 X. Source: Courtesy of B. R. Jack, Allegheny Ludlum Steel Corp.

7. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-7 Incomplete Fusion Figure 29.6 Low-quality weld beads, the result of incomplete fusion. Source: American Welding Society.

8. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-8 Discontinuities in Fusion Welds Figure 29.7 Schematic illustration of various discontinuities in fusion welds. Source: American Welding Society.

9. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-9 Cracks in Welded Joints Figure 29.8 Types of cracks (in welded joints) caused by thermal stresses that develop during solidification and contraction of the weld bead and the surrounding structure. (a) Crater cracks. (b) Various types of cracks in butt and T joints.

10. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-10 Crack in a Weld Bead Figure 29.9 Crack in a weld bead, due to the fact that the two components were not allowed to contract after the weld was completed. Source: S. L. Meiley, Packer Engineering Associates, Inc.

11. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-11 Distortion After Welding Figure 29.10 Distortion of parts after welding: (a) butt joints; (b) fillet welds. Distortion is caused by differential thermal expansion and contraction of different parts of the welded assembly.

12. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-12 Residual Stresses Developed During Welding Figure 29.11 Residual stresses developed during welding of a butt joint. Source: American Welding Society.

13. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-13 Overview of Commercial Joining Processes

14. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-14 Overview of Commercial Joining Processes (cont.)

15. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-15 Overview of Commercial Joining Processes (cont.)

16. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-16 Destructive Techniques Figure 29.12 Two types of specimens for tension-shear testing of welded joints. Figure 29.13 (a) Wrap-around bend test method. (b) Three-point bending of welded specimens--see also Fig. 2.11.

17. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-17 Testing of Spot Welds Figure 29.14 (a) Tension- shear test for spot welds. (b) Cross-tension test. (c) Twist test. (d) Peel test; see also Fig. 30.8.

18. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-18 Welding Design Guidelines Figure 29.15 Design guidelines for welding. Source: J. G. Bralla (ed.), Handbook of Product Design for Manufacturing. Copyright ©1986, McGraw-Hill Publishing Company. Used with permission.

19. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-19 Standard Identification and Symbols for Welds Figure 29.16

20. Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 29-20 Weld Design Selection Figure 29.17