Method for improving defect of middle streaks of coated and galvanized plates

Abstract

The invention discloses a method for improving a defect of middle streaks of coated and galvanized plates. The method comprises annealing and coiling procedures, and is characterized in that: in the annealing procedure, the annealing temperature is improved and the yield strength of the coated and galvanized plates is reduced; and in the coiling procedure, tandem rolling is adopted and the coiling tension is reduced, wherein the annealing temperature is controlled to be between 660 and 680DEG C; the yield strength of the coated and galvanized plates is controlled to be between 280 and 300MPa;for an oiled coil, the coiling tension is reduced by 35-45 percent on the basis of the conventional coiling tension; and for unoiled coil, the coiling tension is reduced by 20-30 percent on the basisof the conventional coiling tension. By implementing the scheme for one year, rejection rates caused by the streaked plate shape defect are respectively reduced from 4.24 percent, 15.84 percent and 12.45 percent to 0.75 percent, 0.48 percent and 0.43 percent.

Description

technical field [0001] The invention belongs to the field of coating and plating of metal materials, in particular to the field of production of hot-dip galvanized sheets and color-coated sheets. Background technique [0002] There are two hot-dip galvanizing production lines in the CSP process of Masteel, and the process form adopts the United States Iron and Steel method. The main strip shape problem is the middle rib, which is manifested as a narrow wave after uncoiling in the middle of the strip, with a width of about 150mm, causing serious defects such as missing coating and color difference in the downstream color coating unit, affecting galvanizing and color coating Product market competitiveness. The "stringing" defect refers to the bulging phenomenon formed on the surface of the steel coil due to the accumulation of local characteristics such as local high points layer by layer during the coiling process. According to different degrees, the "reinforcement" of stri...

AI Technical Summary

Problems solved by technology

When the amount of "strength" is large, additional small waves will be generated after the steel coil is uncoiled, which will seriously affect the performance and appearance of the product, and cause the product to be degraded or scrapped

However, for this kind of shape defect, the shape control methods such as hydraulic bending, roll axis shifting, roll shape configuration and segmental cooling cannot be effectively controlled, which seriously affects the product quality.