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.