Projection Welding

1. Projection Welding

2. Projection Welding • Learning Activities • View Slides; • Read Notes, • Listen to lecture • Do on-line workbook • Lesson Objectives • When you finish this lesson you will understand: • The advantages and limitation of projection welding • Projection design for various thickness materials • Typical Applications of the process Keywords Projection Welding, Projection Design, Thin Material Projections, Thick Material Projections

3. Introduction to Projection Welding (a) (b) (c) (d) [Reference: Welding Handbook, Volume 2, p.566, AWS]

4. Examples of Various Projection Designs (a) (b) (c) (d) (e) [Reference: Welding Handbook, Volume 2, p.562, AWS]

5. Examples of Various Projection Designs (CONT.) (f) (g) (h) (i) (j) [Reference: Welding Handbook, Volume 2, p.562, AWS]

6. Considerations for Various Materials • Mild and HSLA Steels: • Both are considered readily projection weldable. • Both can adequately retain projection welding shape until adequate heating has occurred and are weldable using either embossed or solid projections. • The HSLA steels may, depending on the particular composition, suffer an array of metallurgical problems. • Galvanized Steels: • Projection welding can offer some major advantages in resistance welding galvanized steel. • The relatively low contact resistance is a major concern. • The use of a projection can put contact resistance back into the welding circuit directly at the faying surface. This, in turn, results in lower welding currents and possibly better electrode-life characteristics as compared to resistance spot welding.

7. Considerations for Various Materials (CONT.) • Aluminum and Aluminum Alloys: • They are considered not projection weldable. • Most aluminum alloys are of too low a strength to allow the projection to survive under the necessary welding forces. • The oxide formed appears to prevent the solid-state bond necessary to form the type of joint. • High Alloy Steels: • Projection welding is also quite readily applicable to the higher alloy steels. • The major concern here is material hardenability. Adequate precautions must be taken to prevent the development of brittle microstructures.

8. Considerations for Various Materials (CONT.) • Copper Alloys: • Projection welding has definite implied advantages for resistance welding copper and its alloys. Just as for the galvanized steels, the weld circuit resistance can be localized at the faying surface. • Effective projection welding is largely a function of the specific copper alloy used. • With respect to embossed projection welding, the suitability for welding appears to vary with the material strength level. • Higher-strength copper alloys are relatively projection weldable. However, lower-strength alloys appear to have difficulty retaining projection shape under the applied welding force. • Most copper alloys appear to be weldable with one or more forms of solid projection welding

9. Advantages of Projection Welding • Ease of obtaining satisfactory heat balance for welding difficult combinations • More uniform results in many applications • Increased output per machine because several welds are being made simultaneously • Longer electrode life

10. Advantages of Projection Welding (CONT.) • Welds may be placed more closely together • Parts are more easily welded in an assembly fixture • Finish, or surface appearance, is often improved • Parts may be projection welded that could not be otherwise resistance welded

11. Limitations of Projection Welding • Requires an additional operation to form projections • Requires accurate control of projection height and precise alignment of the welding dies with multiple welds • Requires thickness limitation for sheet metals • Requires higher capacity equipment than spot welding

12. Requirements for A Projection in Sheet Material • Rigid enough to support the initial weld force before current is applied. • Sufficient mass to raise a spot or weld nugget in the plane surface to welding temperature. If it is too small it will collapse before the other surface is heated. • Collapse without extruding between the parts. • Surfaces should be in intimate contact after welding. • Not be partially sheared. Such projections are weak, tear out easily and are of low shear strength. • Easy to form, so that the punch and die require little maintenance. • Cause minimal distortion of the part during forming.

13. Basic Projection Design in Steel Sheet Punch Die Spherical Radius A D 45° T H 15° Projection Wall Thickness Should Be at Least 70% of Sheet Thickness B D Point Radius “R” Projection Should Blend into Stock Surface without Shouldering [Reference: Welding Handbook, Volume 2, p.563, AWS]

14. Bubble - Button Type Projections (a) (c) (b) (d) <T [Reference: Resistance Welding Manual, p.3-3, RWMA]

15. Projections for 0.500-in & 0.250-in Stock 120° 60° 90° 0.52” 45° 0.15” 0.45” 0.094” 0.50” 0.25” When the thickness is greater than 0.125-in, the projection will not be completely forged back [Reference: Resistance Welding Manual, p.3-4, RWMA]

16. Embossed Annular Projection [Reference: Resistance Welding Manual, p.3-5, RWMA]

17. Punch & Die Dimensions for Spherical Dome Projections [Reference: Welding Handbook, Volume 2, p.563, AWS]

18. Projection Types for Sheet and Solid Applications Spherical Projections Elongated Projections [Reference: Metals Handbook, Volume 6 (Welding, Brazing and Soldering), p.503-524, ASM]

19. Projection Types for Sheet and Solid Applications (CONT.) Annular Projection on Pin-and-Tenon Joint Annular Projections Cross-Wire Weld Pyramidal Projections [Reference: Metals Handbook, Volume 6 (Welding, Brazing and Soldering), p.503-524, ASM]

20. Projection Welded Front Axle and Radiator Support for Tractors [Reference: Resistance Welding Manual, p.3-4, RWMA]