Abstract: Provided is a steel material for high heat input welding having excellent welding heat affected zone low-temperature toughness at ?55° C. in the case that the steel material is welded by high heat input welding with a heat input of more than 80 kJ/cm. The steel material may be used in low-temperature storage tanks, for example. The steel material for high heat input welding includes, in mass %, C: 0.04 to 0.09%, Si: 0.15 to 0.25%, Mn: 1.40 to 2.00%, P: 0.015% or less, S: 0.0005 to 0.0040%, Al: 0.030 to 0.080%, Ti: 0.005 to 0.025%, B: 0.0003 to 0.0020%, Ca: 0.0005 to 0.0030%, N: 0.0030 to 0.0060%, O: 0.0040% or less, Nb: 0.005% or less, and Mo: 0.005% or less, the balance being Fe and incidental impurities.

Abstract: Provided is a solid wire for gas metal arc welding, which has a small amount of fume during welding and is suitable as a welding material for high Mn steel materials. The wire has a chemical composition containing, in mass %, C: 0.2% to 0.8%, Si: 0.15% to 0.90%, Mn: 17.0% to 28.0%, P: 0.03% or less, S: 0.03% or less, Ni: 0.01% to 10.00%, Cr: 0.4% to 4.0%, Mo: 0.01% to 3.50%, B: less than 0.0010%, and N: 0.12% or less, with the balance consisting of Fe and inevitable impurities. It may contain at least one selected from V, Ti, Nb, Cu, Al, Ca and REM, if necessary. The wire has excellent manufacturability, can significantly suppress the amount of fume generated during gas metal arc welding, and can easily manufacture a weld joint having high strength and excellent impact toughness at cryogenic temperatures.

Abstract: Provided is a high-Mn steel which not only has high strength and excellent low-temperature toughness but also has excellent CTOD property at low temperatures. The high-Mn steel has a chemical composition containing, in mass %, C: 0.10-0.70%, Si: 0.05-0.50%, Mn: 20-30%, P: 0.030% or less, S: 0.0070% or less, Al: 0.01-0.07%, Cr: 0.5-7.0%, Ni: 0.01% or more and less than 0.1%, Ca: 0.0005-0.0050%, N: 0.0050-0.0500%, O: 0.0050% or less, Ti: less than 0.0050%, and Nb: less than 0.0050%, the balance consisting of Fe and inevitable impurities, and a microstructure having austenite as a base phase, where the austenite has a grain size of 1 ?m or more and a standard deviation of 9 ?m or less.

Abstract: Provided is a steel material for high heat input welding having excellent welding heat affected zone low-temperature toughness at ?55° C. in the case that the steel material is welded by high heat input welding with a heat input of more than 80 kJ/cm. The steel material may be used in low-temperature storage tanks, for example. The steel material for high heat input welding includes, in mass %, C: 0.04 to 0.09%, Si: 0.15 to 0.25%, Mn: 1.40 to 2.00%, P: 0.015% or less, S: 0.0005 to 0.0040%, Al: 0.030 to 0.080%, Ti: 0.005 to 0.025%, B: 0.0003 to 0.0020%, Ca: 0.0005 to 0.0030%, N: 0.0030 to 0.0060%, O: 0.0040% or less, Nb: 0.005% or less, and Mo: 0.005% or less, the balance being Fe and incidental impurities.