A kind of 440mpa grade cold-rolled high-strength IF steel and production method thereof

Abstract

The invention discloses 440 MPa-level cold rolling high-strength IF steel. The 440 MPa-level cold rolling high-strength IF steel comprises chemical components which include, by weight percentage, 0.0015%-0.0035% of C, 0.40%-0.50% of Si, 0.75%-0.95% of Mn, 0.08%-0.10% of P, 0.02%-0.03% of Nb and 0.018%-0.035% of Ti. The production method includes the steps that after blast furnace molten iron is subjected to molten iron desulphurization, converter converting is conducted, high-phosphorus molten steel with the end point phosphorus accounting for 0.040 wt%-0.080 wt% is obtained, and a casting blank is poured; the tapping temperature of a hot rolling plate blank is divided according to the thickness specification, the heat insulation time is larger than or equal to 180 min, a rear section is cooled after finish rolling, and the coiling temperature ranges from 700 DEG C to 725 DEG C; the cold rolling reduction rate ranges from 60% to 75%, the continuous annealing soaking temperature ranges from 810 DEG C to 830 DEG C, the slow cooling temperature ranges from 640 DEG C to 660 DEG C, and the aging temperature ranges from 350 DEG C to 380 DEG C. The production cost of the type of steel is low, the texture is uniform, and the forming performance is good.

Description

technical field [0001] The invention relates to an IF steel and a production method thereof, in particular to a 440MPa grade cold-rolled high-strength IF steel with good formability and a production method thereof. Background technique [0002] With the development of the automobile industry, energy saving and emission reduction and the safety performance of automobiles have attracted much attention. Under this background, domestic and foreign iron and steel enterprises have begun to develop high-strength IF steels with high strength and excellent formability. Among them, the strength level is above 440MPa, High-strength IF steel with a plastic strain ratio (r value) greater than 1.8 is in great demand in the market, and has become an important direction for enterprises to promote structural adjustment in the field of high-strength IF steel. [0003] Generally speaking, as the strength of high-strength IF steel increases, the plasticity of the matrix decreases; especially fo...

AI Technical Summary

Problems solved by technology

In order to obtain good comprehensive mechanical properties, the above three patents adopted low phosphorus, high manganese, and relatively high content of carbon in combination with multi-element microalloying such as Nb, Ti, and Cr for composition design. The strength and plasticity of the product match, but the addition of a large number of alloying elements leads to high production costs, and the economics of industrial mass production are poor

In addition, in view of the high phosphorus content of high-strength IF steel, people have studied the control of phosphorus content in steel from the smelting process. The dephosphorization method adopts the method of leaving slag and secondary blowing to reduce the phosphorus content in high-phosphorus semi-steel from 0.25 to 0.80wt% to the range required by the steel type, and improve the utilization efficiency of high-phosphorus iron ore, but this method It is only suitable for the smelting of semi-steel with a phosphorus content of 0.25~0.80wt% after vanadium extraction; the patent with the publication number 104178682 and the application date is 8th 12th, 2014 discloses a process for preparing The method of IF steel containing phosphorus, silicon and manganese is not suitable for promotion and popularization in steel mills equipped with conventional reblowing converters, and there are still certain limitations in applicability

Images