Abstract: The forming cause and fracture mechanism of pen-tip shaped fracture of Φ12.5 mm SWRH82B steel (/%: 0. 80C, 0. 74Mn, 0. 22Si, 0. 013P, 0. 008S) wire rod is analyzed by optical microscope, scanning electron microscope and energy dispersive spectrometer etc. to get the main causes of formation of pen-tip shaped fracture are center carbon segregation and poor network cementite. With using optimum process measures including controlling 120 t converter end [C]30. 20%, controlling [C]0. 79% ~0. 81% in LF refining process, in 150 mm x 150 mm billet casting controlling liquid over heating extent ≤25 °C, casting speed 1.5 m/min, weak secondary cooling water ratio 0. 30 〜0. 45 L/kg, mold end electromagnetic stirring 3.5 Hz and 300 A, controlling and rolling temperature 900 〜930 ℃, wire rod exiting temperature 〜750 °C with cooling speed 〜5°C/min, the average carbon segregation index of casting billet decreases form original 1. 15 to 1.08, equiaxed ratio increases from 20% to 35%, sorbite ratio increases from 85% to 90%, rating of network cementite decreases to less than 2 and the percentage of pen-tip fracture decreases from original 20% to 3%.

摘要： 通过光学显微镜、扫描电镜-能谱仪等分析了Φ12.5 mm SWRH82B钢(/%:0.80C、0.74Mn、0.22Si、0.013P、0.008S)盘条笔尖状断口形成的原因和断裂机理,得出中心碳偏析和网状渗碳体是产生笔尖状断口的主要原因。通过控制120 t转炉终点[C]≥0.20%,LF精炼过程控制[C]0.79%～0.81%,150 mm×150 mm方坯连铸时控制钢水过热度≤25℃,拉坯速度1.5m/min,弱二冷比水量0.30～0.45 L/kg,结晶器末端电磁搅拌3.5 Hz,300 A,控制终轧温度900～930℃,吐丝温度～750℃,冷却速度～5℃/min,使铸坯平均碳偏析指数由原来1.15降至1.08,等轴晶由20%提高至35%,索氏体率由85%提高至90%,网状降到2级以下,笔尖状断口率由原来的20%降至3%。

关键词: SWRH82B盘条, 笔尖状断口, 网状碳化物, 中心碳偏析, 工艺改进