PRODUCTION OF GAMMA-ALPHA DUPLEX STAINLESS STEEL SHEET HAVING COARSE GRAINING-PREVENTED WELD ZONE

摘要

PURPOSE:To produce a gamma-alpha duplex stainless steel sheet in which grain coarsening in a weld zone is prevented at a wide range of gamma/alpha by casting a molten gamma-alpha duplex stainless steel with a specific composition into a thin sheet and then carrying out specific rapid cooling and cooling treatments. CONSTITUTION:A molten gamma-alpha duplex stainless steel in which the value of deltaFecal defined by deltaFecal%=3(Cr+1.5Si+Mo+Nb)-2.8(Ni+0.5Cu+0.5Mn)-84(C+ N)-19.8% is regulated to 5-70% and which contains one or more kinds among 0.01-0.5% of Ce, La, Ti, Nb, Zr, and Al is cast to =10mm thickness by using a continuous casting machine in which the wall surface of mold is moved syn chronously with thin sheet. the resulting thin sheet is solidified and then cooled through a temp. range from a temp. as high as possible to 1200 deg.C at =10 deg.C/sec cooling rate, by which an alpha-phase is refined. Subsequently, the above thin sheet is cooled through a temp. range from 950 to 600 deg.C at =5 deg.C/sec cooling rate and coiled at =600 deg.C, by which the formation of alpha-phase is prevented. By this method, the gamma-alpha duplex stainless steel sheet capable of setting a wide range of gamma/alpha free from rolling crack and welding embrittlement can be obtained.