1. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Projection Welding: An Overview Chonghua (Cindy) Jiang AET Integration, Inc. 50388 Dennis Ct. Wixom, MI 48393 Cindy.jiang@aet-int.com

2. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Definition “Projection welding is an electric resistance welding process that produces welds by the heat obtained from the resistance to the flow of the welding current. The resulting welds are localized at predetermined points by projections, embossments, or intersections” (Welding Handbook, Vol. 3, Part 2, p50)

3. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Typical Projection Designs a. Embossedb. Stud-to-Platec. Annular

4. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Examples of Projection Design Examples of Various Projection Designs Before and After Welding (Welding Handbook, Vol. 3, Part 2, p56)

5. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Examples of Annular Projections (Welding Handbook, Vol. 3, Part 2, p58)

6. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Typical Commercially Available Fasteners Used in Projection Welding (Welding Handbook, Vol. 3, Part 2, p59)

7. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Medium Frequency (MFDC) Machine AC Machine Capacitor Discharge (CD) Machine Projection Welding Equipment

8. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Projection Welding Equipment (Cont’d)

9. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Design and location of the projection Thickness of the sections Thermal and electrical conductivity of the materials Heating rate Electrode geometry and alloy Tooling alignment Weld force Factors Affecting Heat Balance

10. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Welding Current –Welding current must be at least high enough to create fusion before the projection has completely collapsed Weld Time –Weld time is dependent on the welding current and projection rigidity –Depending on the type of base metal and its surface conditions, multiple pulses can be applied to yield the desired weld performance Electrode/Dies –Proper electrode design and alloy is a major factor in making projection welds Electrode Force –Electrode force is critical for proper projection collapse without expulsion and formation of a sound weld Key Process Variables

11. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Formation of Projection Welds Annular Projection Weld (solid state bonding develops) Embossed Projection Weld (fused nugget forms)

12. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Low carbon steel Hardenable steels Stainless steels-ferritic, martensitic, and austenitic types Nickel-base alloys Copper alloys Aluminum and magnesium alloys Titanium alloys Coated and plated steels Materials Suitable for Projection Welding (Welding Handbook, Vol. 3, Part 2, p63)

13. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Welding Trials on 1.6 mm Magnesium AZ31, AET Materials Suitable for Projection Welding-Example

14. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Example of Project Weld Property- Microhardness

15. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Parts preparation –Weld area clean of grease, rust, scale, dirt or shearing burrs –Less variance in part tolerance before welding Projection size and shape Materials Welding technique Heat balance Weld Quality

16. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Issue: Weld did not pass dye penetrant test and pull test Root Causes: – Tooling misalignment – Insufficient forging force at the faying surface Actions Taken: –Check tooling misalignment by using carbon imprints between faying surfaces –Increase applied forging force –Adjust welding parameters to get sufficient weld bonding area Projection Weld Performance Improvement: Example 1 Fracture surface No Bonding

17. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Projection Weld Performance Improvement: Example 2 Intergranular Fracture Mode of a Projection Weld Failed during Service

18. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Base Metal HAZ Broken part with Intergranular Fracture Non-broken Part The broken part with IG fracture shows primary ferrite along grain boundary. This generally results in low ductility and fracture toughness. The base metal microstructure of the broken part with IG fracture is a result of improper heat treatment of the base metal before it was welded. Projection Weld Performance Improvement: Example 2 (Cont’d)

19. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Advantages –Versatility –Speed –Ease of automation –Ability to make multiple welds simultaneously –Longer electrode/tooling life Limitations –The forming of projection may require an additional step of operation –Limitations on materials projection weldability Process Advantages and Limitations

20. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Tubular connections Projection Welding Applications

21. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Projection Welding Applications (Cont’d)

22. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Attaching nuts and stud Sheet metal assemblies Tank fittings and ferrules Fusites Projection Welding Applications (Cont’d)

23. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington Fabricate the metal sandwich plate of large area –Projection welding –Adhesive assisted projection welding (STS Shipbuilding, South Korea) (Welding in the World, v 53, n 7-8, p 5-11, 2009) Attach nuts and stud Potential Projection Welding Applications for Shipbuilding