Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS)

Santella, M L; Hovanski, Yuri; Pan, Tsung-Yu

doi:10.4271/2012-01-0480

Title: Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS)

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Abstract

Friction stir spot welding (FSSW) is applied to join advanced high strength steels (AHSS): galvannealed dual phase 780 MPa steel (DP780GA), transformation induced plasticity 780 MPa steel (TRIP780), and hot-stamped boron steel (HSBS). A low-cost Si3N4 ceramic tool was developed and used for making welds in this study instead of polycrystalline cubic boron nitride (PCBN) material used in earlier studies. FSSW has the advantages of solid-state, low-temperature process, and the ability of joining dissimilar grade of steels and thicknesses. Two different tool shoulder geometries, concave with smooth surface and convex with spiral pattern, were used in the study. Welds were made by a 2-step displacement control process with weld time of 4, 6, and 10 seconds. Static tensile lap-shear strength achieved 16.4 kN for DP780GA-HSBS and 13.2kN for TRIP780-HSBS, above the spot weld strength requirements by AWS. Nugget pull-out was the failure mode of the joint. The joining mechanism was illustrated from the cross-section micrographs. Microhardness measurement showed hardening in the upper sheet steel (DP780GA or TRIP780) in the weld, but softening of HSBS in the heat-affect zone (HAZ). The study demonstrated the feasibility of making high-strength AHSS spot welds with low-cost tools.

Authors:: Santella, M L; Hovanski, Yuri; Pan, Tsung-Yu

Publication Date:: Mon Apr 16 00:00:00 EDT 2012

Research Org.:: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1051187

Report Number(s):: PNNL-SA-84858
VT0505000; TRN: US201218%%1292

DOE Contract Number:: AC05-76RL01830

Resource Type:: Journal Article

Journal Name:: SAE International Journal of Materials and Manufacturing

Additional Journal Information:: Journal Volume: 5; Journal Issue: 2

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; BORON; BORON NITRIDES; CERAMICS; FRICTION; HARDENING; MICROHARDNESS; PLASTICITY; STEELS; TRANSFORMATIONS; WELDED JOINTS; WELDING; FSSW; AHSS; friction stir

Citation Formats


                    Santella, M L, Hovanski, Yuri, and Pan, Tsung-Yu. Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS).  United States: N. p., 2012. 
        Web.  doi:10.4271/2012-01-0480.

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                    Santella, M L, Hovanski, Yuri, & Pan, Tsung-Yu. Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS).  United States.  https://doi.org/10.4271/2012-01-0480

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                    Santella, M L, Hovanski, Yuri, and Pan, Tsung-Yu. 2012.  
        "Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS)".  United States.  https://doi.org/10.4271/2012-01-0480.

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@article{osti_1051187,

  title        = {Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS)},

  author       = {Santella, M L and Hovanski, Yuri and Pan, Tsung-Yu},

  abstractNote = {Friction stir spot welding (FSSW) is applied to join advanced high strength steels (AHSS): galvannealed dual phase 780 MPa steel (DP780GA), transformation induced plasticity 780 MPa steel (TRIP780), and hot-stamped boron steel (HSBS). A low-cost Si3N4 ceramic tool was developed and used for making welds in this study instead of polycrystalline cubic boron nitride (PCBN) material used in earlier studies. FSSW has the advantages of solid-state, low-temperature process, and the ability of joining dissimilar grade of steels and thicknesses. Two different tool shoulder geometries, concave with smooth surface and convex with spiral pattern, were used in the study. Welds were made by a 2-step displacement control process with weld time of 4, 6, and 10 seconds. Static tensile lap-shear strength achieved 16.4 kN for DP780GA-HSBS and 13.2kN for TRIP780-HSBS, above the spot weld strength requirements by AWS. Nugget pull-out was the failure mode of the joint. The joining mechanism was illustrated from the cross-section micrographs. Microhardness measurement showed hardening in the upper sheet steel (DP780GA or TRIP780) in the weld, but softening of HSBS in the heat-affect zone (HAZ). The study demonstrated the feasibility of making high-strength AHSS spot welds with low-cost tools.},

  doi          = {10.4271/2012-01-0480},

  url          = {https://www.osti.gov/biblio/1051187},
  journal      = {SAE International Journal of Materials and Manufacturing},
number       = 2,

  volume       = 5,

  place        = {United States},

  year         = {Mon Apr 16 00:00:00 EDT 2012},

  month        = {Mon Apr 16 00:00:00 EDT 2012}

}

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