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.