Projection Welding: An Overview

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

Typical Projection Designs a. Embossed b. Stud-to-Plate c. Annular 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) Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

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

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

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

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

Factors Affecting Heat Balance • 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 Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

Key Process Variables • 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 Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

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

Materials Suitable for Projection Welding • 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 (Welding Handbook, Vol. 3, Part 2, p63) Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

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

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

Weld Quality • 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 Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

Fracture surface No Bonding Projection Weld Performance Improvement: Example 1 • 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 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 Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

Projection Weld Performance Improvement: Example 2 (Cont’d) Base Metal Base Metal HAZ HAZ Non-broken Part Broken part with Intergranular Fracture • 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. Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

Process Advantages and Limitations • 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 Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

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

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

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

Potential Projection Welding Applicationsfor Shipbuilding • 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 Welding in Shipbuilding May 10-11, 2011 Seattle, Washington

Projection Welding: An Overview