Welding Solutions for Advanced High- -

• Issues in RSW of AHSS
− Hot Stamped Boron Steel
• Case Study 1:
− Coating Effects
− Parameter Optimization Technique
• Case Study 2:
− Failure Behavior
− Initial Development of Criterion for Crash Simulation

• Destructive inspection
− Chisel test
− Peel test
• Modes of failure
• Implied cooling rates (1000s of  o C/s)
• Martensite formation

• In AHSS
applications,
the acceptable
strength can be
achieved with
PP or IF failure

• Presence of tensile stress
• Presence of liquid metals(low
melting alloy from coating)
• Susceptible
Microstructure(Austenite in
TRIP,TWIP Steels)

• Hot Stamped Boron Steel
−Coating Effects
−Parameter Optimization Technique
• C. Ji, M. Kimchi, Y. Kim and Y. Park, "The application of pulsed current
in resistance spot welding of zn-coated hot-stamped boron steels," in
Advances in Resistance Welding, Miami, FL, 2016.

• Comparison of heat generation pattern by 2 nd pulse

• Comparison of nugget diameter and contact diameter by 2 ndpulse

• Optimized welding conditions using three pulsed currentsteps

• Hot Stamped Boron Steel
−Failure Behavior
−Initial Development of Criterion for Crash
Simulation
• Andrea Peer, Ying Lu, Tim Abke, Menachem Kimchi, and Wei Zhang "Deformation Behaviors of Subcritical Heat
Affected Zone of Ultra-high Strength Steel Resistance Spot Welds." in 9th International Seminar & Conference on
Advances in Resistance Spot Welding. Miami, (3 2016). Paper No. 12
• Ying Lu, Andrea Peer, Tim Abke, Menachem Kimchi, and Wei Zhang "Heat-Affected Zone Microstructure and Local
Constitutive Behaviors of Resistance Spot Welded Hot-Stamped Steel." in Sheet Metal Welding Conference XVII.
Livonia, (10 2016).

• Objective: Develop an understanding of the deformation and failure behavior of resistance spot welds of ultra-high strength steels

• Incorporating softened
SCHAZ properties is essential
to predict the localized
deformation

• Three common problems associated with welding AHSS:
− Narrow Current Range:
− By implementing the proper welding schedule, the weldability window can be broadened.
− More complex welding schedules can allow for more control over heat generation and current
density, thus minimizing the possibility of expulsion to grow the nugget further.
− Hardness Values:
− The increased hardness values seen in AHSS weld nuggets can induce interfacial failure.
− Acceptable strengths can be achieved with interfacial failure.
− Nonhomogeneous Microstructures:
− The nonhomogeneous microstructures seen in AHSS welds cannot be universally classified as a
beneficial or detrimental effect of welding.
• Solutions need to be made on a case by case study and cannot be blanketed over all advanced high-strength
steels. Different solutions will need to be taken for different grades as well as different stack-up
configurations and sheet thicknesses.