Ultrahigh-strength thermal forming martensitic steel

Abstract

The invention belongs to the field of alloy steel, in particular to a high intensity hotforming martensite steel which is mainly applied to a thin part with the anti-tension intensity of 1.9 to 2.5GPa that is formed by hot punching. The main chemical components (weight percentage)of the steel are: 0.40 to 0.60 percent of C, 0.50 to 2.30 percent of Si, equal to or less than 0.25 percent of Mn, 0.50 to 1.50 percent of Cr, 0.80 to 3.00 percent of Ni, 0.15 to 0.40 percent of Mo, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, equal to or less than 0.003 percent of [O], 0.002 to 0.015 percent of [N] and the rest are Fe as well as other unavoidable impurities. Besides, any one of or two of 0.02 to 0.10 percent of Nb as well as 0.02 to 0.15 percent of V are added. Compared with the 22MnB5 steel of the existing hotforming martensite steel, the anti-tension intensity of the steel of the invention is improved from 1.0-1.5GPa to 1.9-2.5GPa; besides, the steel has excellent plasticity (percentage of elongtation is larger than 8 percent) and the sensitivity to hydrogen induced delayed fracture is reduced remarkably; thereby providing foundation for vehicle light weight and high safety performance.

Description

technical field [0001] The invention belongs to the field of alloy steel, and in particular relates to an ultra-high-strength hot-formed martensitic steel, which is mainly suitable for thin-thickness part steel with a tensile strength of 1.9-2.5 GPa and formed by hot stamping. Background technique [0002] With the improvement of automobile light weight and safety, the steel used for automobile structural parts is required to have higher and higher strength requirements under the premise of weight reduction. The strength levels of traditional ferritic steel, pearlitic steel and bainite steel are all lower than 1.2GPa, so only ultra-high strength martensitic steel can meet the requirements. Usually, martensitic steel is obtained by quenching and tempering heat treatment after processing and forming, and the quenching deformation of thin thickness parts is very serious; if heat treatment is used first and then cold stamping is used, it is difficult to deform and after deformat...

AI Technical Summary

Problems solved by technology

For hot-formed martensitic steels, which are generally not tempered after the hot-forming process, the problem of hydrogen-induced delayed fracture may be more prominent due to the high dislocation density in the steel

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