IF钢表面横纹缺陷分析

客户使用某钢厂 IF钢基料在冷轧、退火、冲压后出现横纹缺陷，严重影响使用。对该缺陷带钢和正常带钢化学成分及热轧工艺参数进行回查和分析，结果表明：热轧板卷出厂化学成分符合要求，热轧工艺参数正常，但缺陷试样组织存在表层细晶现象以及表面增碳现象，因此，试样在拉伸试验时存在屈服平台。经热轧 →冷轧→退火全流程产线检查，发现在退火过程中由于炉壁及炉腔中大量的油脂造成带钢表层增碳， C、N的质量分数之和高达 80×10－6，Ti元素无法将所有 C、N间隙原子转化为 Ti的碳氮化物，带钢出现屈服平台，最终导致冲压时表面横纹缺陷产生。通过对炉壁油污进行定期处理，对炉腔通入水蒸气等设备改造，消除了带钢的屈服平台和冲压横纹缺陷。

Analysis of cross striation on the surface of IFsteel

There were cross striation defects on IF steel after cold rolling，continuation annealing and pressing which seriously affected the use. After inquiry and analysis of the original chemical composition and the hot rolling process parameters of the normal and detected steel，the results showed that the chemical composition of the steel met there quirements and the hot rolling process parameters were normal. The surface fine-grains microstructure and surface carbonization were discovered on the defected sample，therefore there was a yield platform in the tensile test. Through the whole process inspection of hot rolling，cold rolling and annealing，it was found that the surface carburization was caused by a large amount of grease in the furnace wall andchamber during annealing，the sum of C and N content were as high as 80×10^－6，Ti element could not convert all the C and N interstitial atoms into Ti carbonitride，so the yield platform was appeared and reslute in cross striation on the surface of the steel during pressing. Through regular cleaning of grease on furnace wall and modification of equipment such as water vapor feeding into furnace chamber，the defects of yield platform and pressing cross striation were eliminated.