To provide a method for efficiently producing on-line a seamless steel pipe excellent in the performance, and also provide an on-line equipment therefor having apparatuses from casting to heat treatment.
This production method comprises continuously executing the below-mentioned (1)-(6) processes in order. (1) A round billet is produced with a continuous caster 1. (2) The billet once cooled to the Ar1 transformation pt. or lower is reheated in a heating furnace 3 and soaked. (3) The soaked billet is pierce-rolled with a piecer 5 at ≤200/sec strain speed to make a hollow base stock. (4) The hollow base stock is rolled with a rolling mill M adjacently arranging a mandrel mill 7 and a sizer 8 at ≥0.01/sec average strain speed, ≥40% reduction ratio and 800-1,050°C finishing temp. to produce the seamless steel pipe. (5) This seamless steel pipe is cooled with cooling device 9 to ≤Ar3 transformation pt. at ≥80°/min cooling speed. (6) After reheating the cooled seamless steel pipe at 850-1,000°C for 10sec-30min, quenching is executed and successively, tempering is executed.
OKADA YASUTAKA
TANIMOTO SEIJI
