极薄板高速轧制热划伤缺陷控制技术

分析了4号机架热划伤为犁沟作用所致的金属堆积,属于轧辊和带钢剐蹭产生的热状态下的机械划伤。解决划伤的策略为降低4号机架轧制速度和压下率,增加乳化液温度和浓度,从而降低金属区的变形热。提出了一种以降低热划伤为原则的轧制策略,在保持5号机架出口速度不变的前提下,将4号机架压下率从34.1%降低至29.8%,将5号机架压下率从14.0%增加至29.3%,将4号机架轧制速度从1 615降低至1 272 m/min,从而降低了轧制区的温度。同时,提出了以乳化液浓缩变化为核心的润滑原则,通过将极薄规格镀锡基板的乳化液温度增加至55～60 ℃,乳化液S3箱质量分数提升至5.5%～7.0%,兼顾了轧制区内对油膜厚度和稳定润滑的要求以及轧制区外对轧辊和带钢强制冷却的要求。采取以上措施后,极薄板热划伤缺陷的发生率从12%降低至1%,带钢表面质量能够满足高端用户的需要。

Control technology of hot scratch defect in extremely thin plate high speed rolling

The hot scratch of No.4 rack is the metal accumulation caused by the ploughing ditch. It belongs to the mechanical scratch in hot state caused by the scratch of roll and strip steel. The strategy to solve scratches is to reduce the rolling speed and reduction rate of No.4 stand, increase the temperature and concentration of emulsion, and reduce the heat of deformation in the metal zone. A rolling strategy based on the principle of reducing hot scratch was proposed. The reduction rate of No.4 stand was reduced from 34.1% to 29.8%, the reduction rate of No.5 stand was increased from 14.0% to 29.3%, and the rolling speed of No.4 stand was reduced from 1 615 to 1 272 m/min under the premise of keeping the exit speed of No.5 stand unchanged. Thus, the temperature of the rolling zone was reduced. At the same time, the lubrication principle with the concentration change of emulsifier as the core was put forward. By increasing the temperature of emulsion to 55-60 ℃ and the concentration of S3 to 5.5%-7.0%, the requirement of oil film thickness and stable lubrication in the rolling area and the requirement of forced cooling of rolls and strips outside the rolling area were taken into account. After taking the above measures, the incidence of hot scratch defect of the ultra-thin plate was reduced from 12% to 1%, the surface quality of the strip could meet the needs of high-end users.