PURPOSE: To obtain a free cutting steel excellent in machinability and cold workability and suitable, e.g. for frame material for cathode ray tube.
CONSTITUTION: The steel is an Fe-Cr alloy which has a composition containing, by weight, 0.04-0.15% S and also 11-13.5% Cr and containing, if necessary, 0.001-0.02% Ca and/or 0.02-0.20% Al and also has a structure regulated to a ferrite single phase structure of ≥No.7 grain size number specified by JIS G0552. This free cutting steel can be produced by subjecting a steel to hot rolling, to first-stage annealing at 950-1200°C, to second-stage annealing at 700-900°C, and then to slow cooling down to ≤600°C at (0.2-0.5)°C/min cooling rate. Because this steel has a ferrite single phase structure of grain size No.7 or above, a free cutting steel having superior cold workability while maintaining superior machinability owing to the addition of S can be formed.
YAMAZAKI KAZUNOBU
NOMA SABURO
