1400MPa-grade B micro-alloyed low-carbon hot-rolled dual-phase steel and preparation method thereof

Abstract

The invention relates to 1400MPa-grade B micro-alloyed low-carbon hot-rolled dual-phase steel and a preparation method of the 1400MPa-grade B micro-alloyed low-carbon hot-rolled dual-phase steel. According to the technical scheme, the low-carbon hot-rolled dual-phase steel comprises the chemical components of 0.17-0.22 wt% of C, 0.2-0.8 wt% of Si, 1.4-2.0 wt% of Mn, 0.03-0.06 wt% of Al, 0.03-0.06wt% of Nb, 0.001-0.004 wt% of B, not larger than 0.020 wt% of P, not larger than 0.005 wt% of S and the balance Fe and inevitable impurities. According to the preparation method, the chemical components are smelted, refining and blank casting are conducted, the blank is placed in a heating furnace, the charging temperature is 700-850 DEG C, and the temperature is kept at 1180-1230 DEG C for 1-2 h;large reduction is adopted during the first three passes, the reduction rate is 40%-60%, and the finish rolling temperature is 820-900 DEG C; after finish rolling, the rolled blank is rapidly cooledto 650-720 DEG C, air cooling relaxation is conducted for 2-7 s so as to separate out ferrite, then the obtained steel is water cooled to the indoor temperature, and therefore the 1400MPa-grade B micro-alloyed low-carbon hot-rolled dual-phase steel is obtained. The technology is simple, the production cost is low, the strength, plasticity and tenacity of the obtained product match well, and the formation performance is excellent.

Description

technical field [0001] The invention belongs to the technical field of low-carbon hot-rolled dual-phase steel. In particular, it relates to a 1400MPa grade B microalloyed low-carbon hot-rolled dual-phase steel and a preparation method thereof. Background technique [0002] In recent years, the number of cars in the world has been increasing day by day, and the problems of energy shortage and environmental pollution have become increasingly prominent. Energy saving, environmental protection, light weight, safety and low cost have become the pursuit goals of car manufacturers. The problem that the industry needs to solve urgently is that light alloys, plastics and fiber-reinforced materials driven by the lightweight of automobiles are constantly pouring into the automobile manufacturing industry. However, the high cost of light alloys and the low recycling rate of fiber-reinforced materials and plastics make steel Materials still occupy a dominant position in automotive mater...

AI Technical Summary

Problems solved by technology

[0004] At present, hot-rolled dual-phase steels for automobiles often need to add precious metal elements such as Cr, Mo and Ni to control the transformation of supercooled austenite, which significantly increases the production cost

Moreover, the existing high-strength steel for automobiles achieves high strength while obtaining poor plasticity and high yield-strength ratio, which is not conducive to stamping and forming of structural parts

"A boron microalloyed low-carbon dual-phase steel produced by hot continuous rolling process and its preparation method" (CN101302600A) patent technology, adding trace amounts of boron to the low-carbon dual-phase steel to improve the hardenability of the steel, through two stages After controlled cooling, the dual-phase steel plate is obtained. Although the process flow is short and the production efficiency is high, the strength level of the product is low at 540-700MPa; "a dual-phase steel with a tensile strength of 1000MPa and its production method" (CN105861926A) patent Although the composition is simple and has good hole expansion performance, the hot-rolled sheet needs to be cold-rolled and over-aged in the process. The technical process is complicated, time-consuming, and low in strength; / Low temperature bainite dual-phase steel and its preparation method” (CN106868398A) patented technology, although the strength level and strong plastic product are high, but in the process flow, the hot-rolled sheet needs to be further warm-rolled and cold-rolled, and then the cold-rolled sheet After being placed in the two-phase zone for 3-5 hours, it is quickly placed in a low-temperature salt bath for about 5 hours, which takes a long time and is difficult to apply to large-scale industrial production

Images