Process for producing high-strength interstitial-free (IF) steel with high plastic strain ratio (r) value

Abstract

The invention relates to the technical field of the auto sheet production process, and relates to a process for producing high-strength IF steel with a high r value. A P-Mn compound added 340 MPa high-strength IF steel is utilized, and the process comprises hot rolling, low-temperature finish rolling, direct online rapid annealing by using the rolled high temperature, rapid cooling till the temperature reaches the coiling temperature, and cold rolling and annealing to obtain a steel plate with 355 MPa extension strength and a 2.75 rolling direction r value. The temperature for hot rolling and finish rolling ranges from 550 DEG C to 850 DEG C, the finish rolling reduction rate is between 70% and 90%, the temperature of the finish rolling phase is below 650 DEG C, the finish rolling phase comprises more than two rolling passes, and the accumulated reduction rate is larger than 40%; the online annealing heating speed is between 30 DEG C / s and 50 DEG C / s, the annealing temperature is in a range of 800 DEG C to 820 DEGC, the heating time is between 10s and 20s, the coiling temperature is between 650 DEGC and 700 DEG C, the cold rolling reduction amount is in a range of 75% to 85%, the heating speed of the continuous annealing process is between 5 DEG C / s and 10 DEG C / s, the heat preservation temperature ranges from 810 DEG C to 830 DEG C, and the heat preservation time is between 100s and 180s.

Description

technical field [0001] The invention belongs to the technical field of automobile plate production technology, and relates to a technology for producing high-strength IF steel with high r value by means of hot rolling direct annealing plus cold rolling annealing. Background technique [0002] High-strength IF steel is the addition of certain strengthening elements to IF steel, which not only maintains the excellent stamping performance of ultra-deep drawing IF steel but also has high strength. After using high-strength IF steel instead of ordinary IF steel, it can reduce the weight of the car and reduce fuel consumption, so it is widely used in the automotive industry. From 1998 to 2000, FAW took the lead in using BIF340 and BH340 high-strength cold-rolled sheets to replace St13 and St14 on the CA1092 five-ton medium truck. After the dent resistance test of the steel plate, it was found that the 0.8mm thick BIF340 was 0.2mm thinner than the 1mm thick St14, and the former ha...

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Problems solved by technology

[0007] It can be seen from the above literature that the use of texture pretreatment can indeed improve the r value of ordinary IF steel and high-strength IF steel, but because of the addition of 2 to 3 processes compared with the conventional production process, the production cycle is prolonged and the energy efficiency is increased. consumption, high production cost, which limits its practical application

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