Patent ID: 8105447

Claim:
An austenitic stainless hot-rolled steel material having a superior corrosion resistance, a proof stress, and a low-temperature toughness, wherein a content of intermetallic compounds contained in the steel material is at most about 0.5 mass %, about 0.2% proof stress at a room temperature is at least about 550 MPa, a Charpy impact value measured using a V-notch test piece at about −40° C. is at least about 100 J/cm 2 , a pitting potential measured in a deaerated aqueous solution of about 10% NaCl at about 50° C. (Vc′100) is at least about 500 mV as compared to a saturated solution of Ag/AgCl, and wherein the austenitic stainless hot-rolled steel material is produced by a process comprising: performing, at a temperature of 1200° C. to 1300° C. for at least about one hour, a homogenizing-heat treatment on a material which is at least one of a cast steel or a semi-finished product of the steel material which comprises: C: about 0.001 to 0.03 mass %, Si: about 0.1 to 1.5 mass %, Mn: about 0.1 to 3.0 mass %, P: about 0.005 to 0.05 mass %, S: about 0.0001 to 0.003 mass %, Ni: about 15.0 to 21.0 mass %; Cr: about 22.0 to 28.0 mass %, Mo: about 1.5 to 3.5 mass %, N: about 0.15 to 0.35 mass %, and O: about 0.0005 to 0.007 mass %, wherein a PI value expressed by the following formula ranges from about 35 to 40: PI=Cr+3.3(Mo+0.5W)+16N, and a δ cal value expressed by the following formula ranges from about −6 to +1: δ cal 2.9(Cr+0.3Si+Mo+0.5W)−2.6(Ni+0.3Mn+0.25Cu+35C+20N)−18, a remnant of the steel material comprising Fe and inevitable impurities, reheating the treated material at a temperature of about 1100° C. to 1300° C.; hot rolling the reheated material, wherein a temperature of at least about 850° C. is maintained, and the hot rolling includes a rough rolling stage, in which a total compaction is not less than about 50% at a temperature of not less than about 1050° C., and a final rolling stage, in which a total compaction is not less than about 10% at a temperature of about 1050° C. to 850° C., and after the rolling procedure is performed, cooling the rolled material from about 800° C. to 500° C. at an average cooling rate of at least about 150° C./min, without a solution treatment.