Method for improving surface quality of medium-thick plates

Abstract

The invention provides a method for improving the surface quality of medium-thick plates. The method comprises the steps that a burner adopts pulse combustion control, a combustion control model is set, and the heating time of a slab is controlled within a set range; the air-fuel ratio is controlled to be not more than 2:1 according to the calorific value of coal gas; and it is ensured that the furnace pressure in a heating furnace is micro positive pressure, and the furnace pressure is controlled within 5-6 Pa. A high-pressure water descaling pump station adopts two kinds of system pressure of 25 MPa and 30 MPa, and switching is conducted according to the different steel grades during using; the 25 MPa system pressure is adopted for the ordinary steel grade; and the 30 MPa system pressureis adopted for high alloy steel. An intermediate blank cooling system is arranged on an intermediate blank holding roller way in front of a finishing mill, and an intermediate blank is subjected to water-cooling at the cooling speed of 3-5 DEG C/s. According to the method for improving the surface quality of the medium-thick plates, the oxidation combustion loss of the slab in the heating furnacecan be reduced, primary oxidized scales on the surface of the slab are effectively removed, the holding time of the intermediate blank during rolling is shortened, and producing of secondary oxidizedscales is inhibited.

Description

technical field [0001] The invention belongs to the technical field of steel rolling technology, and in particular relates to a method for improving the surface quality of a medium-thick plate by means of descaling optimization and the like. Background technique [0002] In the process of using the steel plate, it needs to have corresponding properties such as wear resistance and corrosion resistance, so it has corresponding requirements for the surface. At present, there are defects such as iron scale and foreign matter intrusion in the production process of medium and heavy plates, which affect the use of steel. [0003] The main causes of defects such as oxide scale and foreign matter intrusion: First, when the slab is heated in the heating furnace, the main reasons that affect the oxidation of the slab are heating temperature, heating time, air-fuel ratio, etc. When the heating temperature is too high, the time is too long, and the air-fuel ratio is too large, the iron ...

AI Technical Summary

Problems solved by technology

The warming time of the intermediate billet generally takes 5 to 10 minutes, and even more than 30 minutes for the intermediate billet with a thickness of more than 100 mm. Since the temperature of the intermediate billet is between 800 and 1000 ° C, the surface of the steel plate will continue to oxidize at this temperature. The longer the oxidation is, the more serious the oxidation will be, and the thickness of the secondary oxide scale will be greater, which will increase the difficulty of descaling the header of the rolling mill, and easily lead to surface quality defects such as pitting and pressing on the surface of the steel plate