Method for overcoming defect of pocks on surface of ultra-low carbon steel

Abstract

The invention belongs to the technical field of steel rolling and discloses a method for overcoming defect of pocks on the surface of ultra-low carbon steel. The method comprises the following steps that the tapping temperature of an ultra-low carbon steel blank is controlled, and the tapping temperature is controlled within the range of 1200 DEG C-1240 DEG C; the finish rolling steel throwing speed is increased and is controlled to range from 12 m / s to 15 m / s; the cooling water opening amounts of front three racks of finishing rolling work rolls are controlled to be 50%, 50% and 80% respectively; finish rolling second pass and third pass roll gap water is opened; the insertion depth of bending rolls and straightening rolls of a withdrawal and straightening machine is controlled, and the bending rolls and the straightening rolls are at the high-depth section. Due to the technological operation that the ultra-low carbon steel in the hot rolling and cold rolling technological sections is combined and adjusted, the ferric oxide skin layers are greatly prevented from being generated, and thus the defect of the pocks is overcome.

Description

technical field [0001] The invention relates to the technical field of steel rolling, in particular to a method for eliminating pitting defects on the surface of ultra-low carbon steel. Background technique [0002] Ultra-low carbon steel is characterized by ultra-low carbon, microalloying and pure steel. After adding Ti and Nb, carbon and nitrogen compounds are formed to fix interstitial atoms such as C and N. It is currently the best deep drawing performance and the highest level of stamping. Steel is widely used in automobile manufacturing, home appliance production and other industries, especially for making outer and inner panels of automobiles. [0003] In order to obtain comprehensive mechanical properties such as low yield strength and high elongation, IF steel usually adopts a hot rolling process of high-temperature final rolling and high-temperature coiling to obtain coarse precipitate particles such as TiC, thereby optimizing the properties of the steel coil. How...

AI Technical Summary

Problems solved by technology

However, high-temperature final rolling and high-temperature coiling will lead to the formation of a thick iron oxide layer on the surface of the hot coil, especially the four-time iron oxide layer after coiling, which makes it difficult to clean thoroughly during the pickling process. The residual iron oxide scale is crushed and pressed into the surface of the strip, and the broken iron oxide is reduced to sponge iron particles after continuous backing, which appears as gray-white pitting defects distributed in strips along the rolling direction macroscopically

Once pitting defects are formed, they cannot be eliminated in the subsequent process, which seriously affects the surface quality of IF steel products, especially restricting the application of IF steel in the field of automotive outer panels. Some serious pitting is a potential source of cracks. Afterwards, it is easy to further develop into cracking defects, causing heavy losses to both the steel producer and the user.