Method for producing hot rolling two-phase steel plate at 700MPa level of tensile strength

Abstract

The invention relates to a manufacture method for a thermal rolling double-phase steel plate with 700MPa of anti-tension intensity; the main chemical components of the invention calculated by weight percentage include: 0.03 to 0.08 percent of C, 0.50 to 0.70 percent of Si, 1.00 to 1.60 percent of Mn, 0 to 0.60 percent of Cr, 0 to 0.40 percent of Mo, and 0.02 to 0.05 percent of Nb, and the rest is Fe; the thickness specification of the invention is 3.0 to 4.0mm; the invention is provided with a polygonal ferrite and a martensite double-phase tissue; a few amount of grain bainites appear; wherein, the volume percent of the ferrite is 70 to 90 percent; the volume percent of the martensite is 30 to 10 percent; the average crystal grain dimension of the ferrite is 5Mum. The invention is rolled by a controlled rolling and controlled cooling technology; a beginning rolling temperature is controlled between 1250 to 1150 DEG C; the stopping rolling temperature is controlled between 800 to 850 DEG C; the cooling speed for a first section is controlled between 25 to 50 DEG C / s; after cooling the temperature is 680 to 750 DEG C; a second section controllable cooling is carried out after cooling the temperature between 670 to 700 DEG C by air; the cooling speed for a second section is controlled between 25 to 50 DEG C / s; the stopping cooling temperature, namely the coiling temperature is between 500 and 600 DEG C; then the steel plate is cooled to the room temperature by air.

Description

technical field [0001] The invention belongs to the field of metal materials, and is a low-alloy advanced high-strength steel (AHSS), in particular to a hot-rolled dual-phase steel plate with a tensile strength of 700MPa and a manufacturing method. Background technique [0002] Since the development of the automobile industry, energy saving and weight reduction, increased safety, and improved corrosion resistance of the car body have become the goals pursued by people. Therefore, the use of high-strength automotive steel plates is an inevitable trend in the development of automotive steel. [0003] Hot-rolled dual-phase steel is composed of ferrite and martensite, and is based on phase transformation strengthening. It has the characteristics of low yield ratio, high initial work hardening rate, and good strength and ductility. The development of high-strength hot-rolled steel sheets for automobiles has always been one of the hot spots in the research of materials work at hom...

AI Technical Summary

Problems solved by technology

Dual-phase steel for automobiles is divided into hot-rolled dual-phase steel and cold-rolled dual-phase steel. At present, cold-rolled dual-phase steel is relatively mature. The direct hot-rolled dual-phase steel that can be commercially produced adopts a complex alloying method. There are a lot of expensive alloy elements, so there is a problem of high cost, and due to the use of direct rolling, higher requirements are put forward for the production process in actual production, which is not conducive to promotion, and large-scale production is not yet possible in China

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