高牌号3. 28 % Si钢冷轧板边裂机理分析和工艺改进

试验高牌号无取向硅钢（/%:0.006C,3.28Si,0.22Mn,0.030P,0.007S）的生产流程为180t BOF-真空精炼-230mm×（900~1750mm）板坯连铸-热轧成2.02mm板,冷轧成1.65mm板。从热轧基板的边部组织、力学性能、剪边以及断口显微形貌和成分等方面分析了冷轧高牌号硅钢中边裂的成因和机理。结果表明,高牌号硅钢冷轧板边部裂纹为解理断裂,热轧板料边部的存在混晶组织而导致塑性下降、圆盘切边引发撕裂带的裂纹和小凹坑是引发冷轧边裂主要因素;另外,边部断口处S和Mn的偏析也是引起边裂裂纹的重要因素;通过热轧过程减小边部与中部温差,热轧后圆盘剪刀片侧间隙由410μm减少到280μm,连铸过程电磁搅拌参数从380 A/3 Hz改进为350 A/6 Hz等工艺措施,使高牌号无取向硅钢冷轧板边裂发生率由原来的14%下降至4%。

Analysis on Mechanism of Edge Crack of High Grade 3.28% Si Steel Cold-Rolled Sheet and Process Improvement

The production flow sheet of tested high grade non-oriented silicon steel (/% : 0.006C, 3.28Si, 0.22Mn, 0.030P, 0.007S) is 180t BOF-vacuum refining-230mm x(900~1750)mm slab casing-hot rolled to 2.02mm plate-cold rolled to 1.65mm sheet. The causes and mechanism of edge cracks of cold rolled high grade silicon steel sheet are analyzed by testing edge composition and structure, mechanical properties, micro morphology of cutting side and fracture of hot rolled base plate. Results show that the edge crack of cold rolled sheet of high grade silicon steel is cleavage fracture, the mixed grain structure existing in edge of hot rolled plate led to decreasing plasticity and round saw cutting to cause crack and small pits in cutting band are main reason lo cause edge cracks in cold rolling process； besides the segregation of S and Mn at edge fracture is an important factor for the cracks initiation. With the measures including decreasing the temperature differential between edge and middle during hot rolling process, decreasing the side interval of round cutter to 280 μm from 410 μm after hot rolling, and improving the electromagnetic stirring parameters from 380 A/3 Hz to 350 A/6 Hz, the occurring rate of edge cracks of high grade silicon steel cold sheet decreases from original 14% to 4%.