Understanding of high strength steel

Update:08 Sep 2018

High-strength steel is one of the development trends of […]

High-strength steel is one of the development trends of color coated steel coil products. Color-coated plates, color steel plates, color-coated rolls, and color steel coils are currently used in foreign countries with a yield strength of 350 grades. There are usually two kinds of processes for producing steel sheets of this type.

Another method is to reduce the annealing temperature of the hot-dip aluminum-zinc unit, so that the material is not completely annealed, and partially retain the rolling hardness to improve the strength. At present, most of the domestic aluminum-zinc and color coating factories adopt this process because they have not refined In the steel process, there is no corresponding high-strength steel grade for buying hard rolled coils or hot rolled sheets on the market.But if you do this, it will bring three kinds of harm:

1. Due to the lowering of the annealing temperature and the uneven temperature of the strip width, the annealing temperature is located near the recrystallization critical temperature of the steel sheet, which results in severe unevenness of the strip width in the width direction of the steel sheet, and it is difficult to obtain the plate shape after processing.

2. Reducing the annealing temperature inevitably results in poor cleaning performance because the fine oxidation of the surface is required to be reduced in the reducing gas at a high temperature, so that the adhesion of the hot-dip aluminum-zinc plating layer may be adversely affected.

3. The annealing temperature is lowered and the yield strength is increased, but the tensile strength is not increased correspondingly, which leads to an increase in the yield ratio of the material. The yield ratio has a considerable influence on the processing formability, earthquake resistance and fire resistance of the material.