| 摘要 |
<p>A refractory steel material giving a welded joint having such excellent toughness that the welded joint has high high-temperature proof strength at 700-800‹C, which is a supposed fire temperature, and suffers no embrittlement even when exposed to the supposed fire temperature; and a process for producing the steel material. The refractory steel material is obtained by heating a steel billet to 1,150-1,300‹C, subsequently subjecting it to hot working or hot rolling in which the final temperature is 880‹C or higher, subjecting the worked or rolled steel material to accelerated cooling under such conditions that the cooling rate in a position where cooling is slowest is at least 2 ‹C/sec, stopping this accelerated cooling in a temperature region where the temperature of the surface of the steel material reaches 350-600‹C, and then allowing the steel material to cool. The refractory steel material has a composition which contains, in terms of mass%, 0.005-0.03%, excluding 0.03%, carbon, 0.01-0.50% silicon, 0.05-0.40% manganese, 1.50-5.00% chromium, 0.05-0.50% vanadium, and 0.001-0.005% nitrogen and is reduced in the contents of nickel, copper, molybdenum, boron, phosphorus, sulfur, and oxygen. ® KIPO & WIPO 2009</p> |
