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电力铁塔用18 mm厚160角钢Q420C(/%:≤0.20C,1.00~1.70Mn,≤0.55Si,≤0.035S,≤0.035P,0.02~0.20V,≥0.015Als)的冶金流程为80 t BOF-LF-CC-车制工艺。利用光学显微镜、SEM以及能谱分析仪对热轧角钢角部裂纹进行了分析,结果表明,裂纹周围存在脱碳层及铁素体膜,裂纹处发现S富集及在晶界析出的AlN破坏了钢基体的连续性;得出连铸振痕谷底的夹渣、成分偏析,热应力和弯曲矫直应力导致了角钢沿晶界开裂。通过降低[N]至0.008 0%,控制Als 0.017%~0.022%,Mn/S≥80,钢水过热度≥25℃,保护渣牯度0.73 Pa·s,矫直温度≥950℃等工艺措施,使连铸坯的优质品率由原25.78%提高至85%,有效地降低了角钢角部裂纹的发生。
Metallurgical processes for power towers with 18mm thick 160-angle Q420C (/%: ≤0.20C, 1.00-1.70Mn, ≤0.55Si, ≤0.035S, ≤0.035P, 0.02-0.20V, ≥0.015Als) are 80 t BOF -LF-CC-car technology. The angle cracks of hot-rolled angle steel were analyzed by optical microscope, SEM and EDS. The results show that there are decarburized layer and ferrite film around the crack, S enrichment and AlN damage at grain boundary are found The continuity of the steel substrate was obtained. The slag inclusions at the bottom of continuous casting vibration marks were obtained. The composition segregation, thermal stress and bending straightening stress caused the angle steel to crack along the grain boundaries. By reducing [N] to 0.008 0%, Als 0.017% -0.022%, Mn / S≥80, superheat of molten steel ≥25 ℃, protective slag 0. 0.73 Pa · s, straightening temperature 9950 ℃ and other technical measures, So that the quality of continuous casting billet from the original 25.78% to 85%, effectively reducing the corner crack angle.