Abstract: The crack phenomenon of cold-drawn Φ12 mm bar of low-carbon high-sulphur free cutting steel (/% : 0.07 C, 1.24Mn, 0.06P, 0.39S) produced by 100t BOF-LF-165 mm x 165 mm casting billet -Φ14 mm hot-rolled bar-cold drawn to Φ12 mm rod process has been systematically analyzed to get the main cause of cold-drawn rod longitudinal crack is the billet inner defect formed in steelmaking and casting process by slag enclosure and oxidation etc factors. With the process measures including controlling mold cooling water rate in casting process, using weak secondary water cooling process with ratio water amount 0.83 L/kg, casting speed 1.5 m/min, non-oxidizing shielding casting and using viscosity 0.6 Pa·s at 1300℃ specialty mold powder, the occurrence of cold-drawn rod longitudinal crack is effectively avoided.

Key words: Low-Carbon High-Sulphur Free Cutting Steel, Cold-Drawn Rod, Longitudinal Crack

摘要： 对100t BOF-LF—165 mm×165 mm方坯连铸-热轧至Φ14 mm-冷拔至Φ12 mm的低碳高硫易切削钢(/%:0.07C,1.24Mn,0.06P,0.39S)冷拔材开裂现象进行系统分析,得出该钢在冶炼连铸过程中由于卷渣、氧化等原因造成钢坯内部缺陷是材料冷拔纵裂纹形成的主要原因。通过控制连铸过程结晶器冷却水量,二冷区采用弱冷工艺,比水量0.83 L/kg,拉速1.5 m/min,无氧化保护浇铸及采用1300℃粘度为0.6 Pa·s专用保护渣等工艺措施,有效避免冷拔纵裂纹的发生。

关键词: 低碳高硫易切削钢, 冷拔材, 纵裂纹