METHOD OF HOT FORMING A STEEL BLANK AND THE HOT FORMED PART

摘要

A method of hot forming a steel blank into an article the method including the following steps: d) cooling a heated steel blank to form an article during hot forming, starting at a starting temperature T2 above Ar3; to an interrupt temperature T3 in the range of 400-550° C. at a cooling rate V2 of at least 25° C./s; e) immediately further cooling the article from the interrupt temperature T3 to ambient temperature at a cooling rate V3 of 0.2-10° C./s, wherein the interrupt temperature T3 and cooling rate V3 are selected such that the article thus obtained has multiphase microstructure including by volume fraction: 55-90% of bainitic ferrite 5-15% of retained austenite 5-30% martensite.