含硫量对超低碳钢热轧过程中氧化膜形成的影响

Effect of Sulfur Contents on Formation of Oxide Film on Ultra-low-carbon Steel during Hot Rolling

采用差热分析仪、扫描电镜和电子探针等试验设备检测了含0.010%、0.015%和0.020%S的超低碳钢在1000、950和900℃加热不同时间形成的氧化膜的表面和截面形貌、厚度、成分和钢的氧化速率,目的是揭示含硫量对超低碳钢热轧过程中氧化膜形成的影响。结果表明:不同含硫量的钢在950℃左右加热时的氧化增重速率最大;钢在950℃长时间加热,氧化膜易起泡,并形成贯穿裂纹。此外,硫会富集在氧化膜的表面,并在其与基体的界面形成熔融物并侵入基体,加剧了钢表面氧化铁皮的起泡。应合理控制超低碳钢的含硫量,防止精轧过程中铁皮压入基体和形成麻点等缺陷。

Surface and cross-section morphology,thickness and composition of oxide film developed on the ultra-low-carbon steels containing 0.010%,0.015%and 0.020%S,which were heated at 1000℃,950℃and 900℃for different times,as well as oxidizing rate of the steels were detected by means of differential thermal analyzer,scanning electron microscope and electron probe,to identify the effect of sulphur contents on the formation of oxide film on the ultra-low-carbon steel during hot rolling.The results indicated that the steels having different sulphur contents all exhibited the largest oxidation weight growth rate during heating at about 950℃,and the oxide film was prone to blister and to form through crack when the steels were heated at 950℃for a long time.In addition,sulphur will concentrate on the surface of oxide film,and fusant will form at the film-matrix interface and intrude into the matrix,thus intensifying bubble formation of scale on the steels.The sulphur content in the ultra-low-carbon steel should be reasonably controlled to prevent the scale from penetrating into the matrix and the pit or other defects from forming in the process of finish rolling.