Method for producing thin-gauge hot-rolled DP980 steel based on CSP process

Abstract

The invention discloses a method for producing thin-gauge hot-rolled DP980 steel based on a CSP process. The method comprises the following steps that (1) components of molten iron are regulated; (2)continuous casting of a thin slab is conducted, specifically, the thickness of the cast slab is controlled to be 55-60 mm, and the slab drawing speed is 3.6-3.9 m / min; (3) conventional soaking is conducted, specifically, the tapping temperature is controlled to be 1210-1230 DEG C, and the soaking time is 25-35 min; (4) high-pressure water descaling is conducted; (5) finish rolling is conducted forseven passes, specifically, the finished rolling temperature is 810-830 DEG C, and the rolling speed of a tail rack is 6.0-9.8 m / s; (6) two-stage type cooling and reeling are conducted, specifically,water cooling at the first stage is conducted till the temperature reaches 670-690 DEG C, then air cooling is conducted for 4.2-5.8 s, and water cooling at the second stage is conducted till the temperature reaches 100-200 DEG C; and (7) flattening is conducted. The manufacturing process is short, product performance is stable, the plate shape quality is good, and thickness precision is high; thecharacteristics of low cost, high strength, thin gauge and low yield ratio are achieved; and the quality requirement of cold-rolled products can be met, and the method has great significance for achieving the light weight of automobiles and promoting the progress of replacing cold rolling with hot rolling in the automobile industry.

Description

technical field [0001] The invention relates to a hot-rolled DP980 steel, in particular to a method for producing thin gauge hot-rolled DP980 steel based on a CSP process. Background technique [0002] With the depletion of energy and the deterioration of the ecological environment, the lightweight of automobiles has attracted more and more attention. The use of high-strength automotive steel is an effective means to reduce weight, save energy and improve safety. In the Ultra Light Steel Body-Advanced Concept Vehicle (ULSAB-AVC) program of the World Iron and Steel Institute, high-strength steel accounts for 97% of the materials used, of which advanced high-strength steel accounts for more than 80%. However, as the strength continues to increase, the formability of the material will become worse and worse, especially for high-strength steel above 980MPa, there are problems such as cracking, springback, and parts that cannot meet the precision requirements during the forming ...

AI Technical Summary

Problems solved by technology

However, in the process of producing thin-gauge hot-rolled DP980 steel (especially with a thickness below 1.5 mm), due to the short length of the laminar flow cooling zone and the fast rolling speed of the last stand, the short water cooling time and air cooling time make ferrite Insufficient body transformation, too high martensite content and even bainite and pearlite, the product has a high yield ratio

In addition, due to the low-temperature coiling, the thin-gauge hot-rolled DP980 steel has a poor shape and must be leveled, and the steel plate undergoes work hardening after leveling, resulting in a further increase in yield strength and yield ratio, resulting in the formation of hot-rolled DP980 steel. Poor performance, increased wear and springback on the die during part stamping

Therefore, under the existing thin slab continuous casting and rolling process conditions, it is difficult to achieve stable matching of chemical composition, process window, microstructure and shape quality for thin gauge hot-rolled DP980 steel, especially the thickness specification below 1.5mm

So far, there is no precedent for the production of hot-rolled dual-phase steel DP980 by thin slab continuous casting and rolling at home and abroad, which restricts the industrial production of this type of steel and the process of "replacing cold with heat" in the automotive industry

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