Processing-induced residual stresses in TWIP steel weld spots

ABSTRACT

The present study investigates the evolution of the residual stresses in TWIP steels induced by manufacturing chain for the production of automotive body-in-white. Two different manufacturing routes were considered. The first route encompassed a plastic deformation prior to the welding stage, whereas the second involved the spot welding followed by a baking treatment. A convergent approach was adopted to isolate the effects of the first and final manufacturing steps. The findings showed that the plastic deformation prior to the welding stage is not annihilated by the welding thermomechanical cycle. Abrupt hardness gradients along small material fractions are observed. The residual stresses state changes, although its profile is still defined by the welding stage. The post-weld bake treatment showed to promote slight residual stresses relaxation, but it is not effective in inducing the same post-weld residual stresses state for different RSW parameters set.

KEYWORDS:

• TWIP
• manufacturing
• chain
• residual
• stresses
• resistance
• spot
• welding
• RSW
• body-in-white
• advanced
• high
• strength
• steels
• AHSS
• XRD

Article Highlights

• The magnitude of the post-weld residual stresses has positive correlation to the degree of plastic deformation prior to the RSW process.

• The steep residual stresses gradients induced by the RSW are preserved after the post-weld bake treatment.

• Both prior stretching and post-weld baking treatment modify the residual stresses state, but the residual stresses profiles showed to be defined by the RSW stage.

Acknowledgments

Authors would like to acknowledge the Laboratório de Estruturas Leves (LEL) from the Instituto de Pesquisas Tecnológicas do Estado de São Paulo (IPT), especially in the person of Mario Batalha, for the support with the XRD measurements. The authors also thank the funding of the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) the Brazilian agency (CNPq) under grant 306193/2017-5.

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico [306193/2017-5].