抄録
Several investigations have been published on the bending and torsion creep strength of alloy steels. The present study was carried out to provide data for torsion and bending creep strength of 304 type stainless steel. Specimens were solution-treated by water quenching after heating at 1050°C for 40min. The torsional creep was measured at several temperatures from 200°C to 600°C of the solid cylindrical specimens of 5mm in diameter, and the bending creep at temperatures from 600°C to 650°C of the plate specimens of 5mm or 7mm in thickness and 10mm in width. The machines used for both the torsion and bending creep testing had been made in our laboratory. The results obtained are summarized as follows:
(1) The torsion creep limit for a mean creep rate of 1×10-4%/hr and 5×10-4%/hr during 200 to 300 hours were 6.5 and 10.8kg/mm2 for temperature of 500°C, and 4.5 and 8.9kg/mm2 for temperature of 600°C.
(2) on the torsional creep tests under a torsional stress of 11∼16kg/mm2 at 200°C∼400°C, a large initial transient creep was found, but at 200°C and 400°C the creeping did not proceed after about 200 hours, and at 300°C the creeping was continued even after 730 hours. The creep rate at 300 hours in the temperature of 300°C was 1.2×10-4%/hr for 11kg/mm2, 1.1×10-4%/hr for 13kg/mm2, and 1.6×10-5%/hr for 16kg/mm2.
(3) The relationship between the mean bending creep rate during 200 to 300 hours υ (near steady creep) and nominal bending stress σ was represented by following equations.
υ=1.8×10-8·σ3.7(%/hr) for 600°C
υ=4.6×10-9·σ4.9(%/hr) for 650°C
From this it was found that the bending creep limit for a creep rate of 1×10-4%/hr and 5×10-4 %/hr was 10.1kg/mm2 and 15.9kg/mm2 at the creep temperature of 600°C, and 7.5kg/mm2 and 10.4kg/mm2 at 650°C.
