Holt-rolled bainite dual-phase steel with high reduction rate and high hole expansion rate and preparation method thereof

Abstract

The invention relates to holt-rolled bainite dual-phase steel with a high reduction rate and a high hole expansion rate and a preparation method thereof. According to the technical scheme, the chemical constituents of the holt-rolled bainite dual-phase steel with the high reduction rate and the high hole expansion rate comprise 0.05-0.09 wt% of C, 0.10-0.50wt% of Si, 1.40-1.80 wt% of Mn, 0.03-0.06wt% of Al, 0.03-0.05 wt% of Nb, 0.020 wt% or less of P, 0.005 wt% or less of S, 0.006 wt% or less of N, and the balance Fe and inevitable impurities. The chemical constituents are subjected to smelting, refining and casting or continuous casting so as to obtain a blank; the blank is put into a heating furnace with the charging temperature being 800-1000 DEG C, heated to 1180-1250 DEG C and subjected to heat preservation for 40-80 min; high reduction is carried out in first three passes, the reduction rate is 40-60%, and the finish rolling temperature is 840-900 DEG C; sectionally continuous laminar cooling and reeling are carried out; and the steel is naturally cooled to the room temperature. The process is simple and the production cost is low; and the prepared holt-rolled bainite dual-phase steel is good in strength and plasticity matching, excellent in welding performance and excellent in flange elongation.

Description

technical field [0001] The invention belongs to the technical field of hot-rolled bainite dual-phase steel. In particular, it relates to a hot-rolled bainitic dual-phase steel with high hole expansion rate under large pressure and a preparation method thereof. Background technique [0002] According to the development of the automobile market, there is a huge market demand for hot-rolled dual-phase steel. This type of steel is gradually replacing some cold-rolled plates to make automotive structural parts, such as body structural parts, frames, brake discs and wheels. The use of hot-rolled plates to make structural parts can not only avoid the work hardening of steel after cold rolling, reduce the wear and springback of the mold during the stamping process of parts, but also reduce the cold rolling, annealing, recoiling and other processes in the steel plate production process , so that the production cycle and cost are greatly reduced. Moreover, the use of high-strength ...

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Problems solved by technology

"A ferritic bainitic steel with a tensile strength of 450MPa and high hole expansion performance" (CN103469058A) patented technology, the production process is relatively simple and the hole expansion performance is good, but the C content is relatively high at 0.10-0.15%. It is beneficial to the welding performance of steel, and the strength level is low; "a ferritic bainite steel" (CN101033522A), the tensile strength is 700MPa ~ 900MPa, the production process is relatively simple, but the composition design contains high Al , the production is more difficult and the cost is higher; "a 580MPa grade ferritic bainite hot-rolled dual-phase steel and its preparation method" (CN102943205A), the laminar flow cooling adopts the segmental type of water cooling + air cooling + water cooling Discontinuous cooling method, its air-cooled waiting temperature reduces the production efficiency of the rolling line, and the content of Ti added in the composition is relatively high

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