In view of the high-frequency thickness fluctuations at the head and tail of DP590 cold rolled coils in a factory,the cau-ses were researched.The results indicate that the uneven property of the hot rolled coils along the longitudinal direction is a sig-nificant factor leading to process instability during cold rolling and thickness fluctuations of cold rolled coils.The fundamental reason for the uneven longitudinal property lies in the existence of mid-wave defects and residual cooling water during the pre-air cooling stage of hot rolled strip coiling.Therefore,it is proposed to control the shape of the strip,enhance the blow-off capabili-ty of the laminar cooling system,and adopt U-shaped cooling and other process optimization measures to ensure uniform cooling conditions along the longitudinal direction of the strip during the air cooling stage.The stability of thickness control during the cold rolling process can be significantly improved.The excessive thickness length of the cold rolled coils has been reduced from 41 meters to within 10 meters,and the first inspection failure rate has decreased from 31.8％to 1.6％.This effectively resolves the problem of thickness fluctuations at the head and tail of cold rolled coils,thereby improving the yield rate.
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