Springback-free mechanism in hot stamping of ultra-high-strength steel parts and deformation behaviour and quenchability for thin sheet
- 132 Downloads
The springback-free mechanism in hot stamping of ultra-high-strength steel parts was clarified by the mechanical, thermal and transformation viewpoints. In hot stamping, the effects of elastic recovery during unloading and thermal shrinkage on the springback are comparatively small, but the effect of the phase transformation is critical. Volume expansion occurs primarily upon the start of the martensitic transformation, and plastic deformation is induced by the volume expansion during holding at the bottom dead centre, causing the springback including the post-stamping deformation to disappear. It was observed from well-organised experiments that holding at the bottom dead centre until the martensite finish temperature prevents the springback, and the springback-free mechanism in hot stamping of ultra-high-strength steel parts was clarified from the observation. The springback behaviour in hot stamping of a thin steel sheet with 0.6 mm thickness was explained from the above mechanism, and the deformation behaviour and quenchability for the thin sheet were examined. A sufficient holding time at the bottom dead centre was more closely associated with the prevention of springback rather than sufficient hardening. Additionally, local thinning around the bottom corner of a bent thin sheet was prevented by optimising the transfer time from the furnace.
KeywordsHot stamping Springback-free Thin sheet Local thinning
Unable to display preview. Download preview PDF.
This work was supported in part by the Grant-supported Researches in Amada Foundation (AF-2015001).
- 6.Kusumi K, Yamamoto S, Takeshita T, Abe M (2008) The effect of martensite transformation on shape fixability in the hot stamping process. Steel Res Int 79:71–76Google Scholar
- 7.Senuma T, Magome H, Tanabe A, Takemoto Y (2009) New hot stamping technology characterized by its high productivity. Proc of 2nd Int Conf on Hot Sheet Metal Forming of High-Performance Steel, Lulea, pp. 221–228Google Scholar
- 10.Bao J, Liu H, Xing Z, Song B, Yang Y (2013) Springback of hot stamping and die quenching with ultra-high-strength boron steel. Eng Rev 33(3):151–156Google Scholar
- 14.Nakagawa Y, Maeno T, Mori K (2015) Forming and quenching behaviours in hot stamping of thin quenchable sheets. MATEC Web Conf 21(05002):1–7Google Scholar
- 15.Georgiadis G, Tekkaya A E, Weigert P, Horneber S, Kuhnle P A (2017) Formability analysis of thin press hardening steel sheets under isothermal and non-isothermal conditions. Int J Mater Form In pressGoogle Scholar
- 18.Billur E, Porzner H, Lorenz D, Holecek M, Vrojlik M, Hoss M, Damenha B, Friberg J, Koroschetz C, Skrikerud M (2015) From part design to part production – virtual hot forming engineering illustrated – focus material modelling. Proc of 5th Int Conf on Hot Sheet Metal Forming of High-Performance Steel, Toronto, pp. 463–470Google Scholar