Long-life heat-resisting low alloy steel welded component and method of manufacturing the same

Abstract

The method of manufacturing a long-life heat-resisting low alloy steel welded component, with which creep damages do not easily occur in the heat affected zone. The manufacturing method includes the steps of subjecting a base metal containing, at % by weight, C: 0.15% or less, Si: 0.5% or less, Mn: 0.3 to 0.8%, Cr: 1.9 to 2.6%, Mo: 0.87 to 1.20%, and a balance of iron and unavoidable impurities, to a hot working, to a heat treatment, and then to a welding. In this method the base metal is normalized once or more times before the welding in addition to the hot working.

What is claimed is:  
     
         1 . A method of manufacturing a long-life heat-resisting low alloy steel welded component including the steps of subjecting a base metal containing, at % by weight, C: 0.15% or less, Si: 0.5% or less, Mn: 0.3 to 0.8%, Cr: 1.9 to 2.6%, Mo: 0.87 to 1.20%, and a balance of iron and unavoidable impurities, to a hot working, to a heat treatment, and then to a welding, wherein the base metal is normalized once or more times before the welding in addition to the hot working.  
     
     
         2 . The manufacturing method according to  claim 1 , wherein the base metal has been subjected to annealing or normalizing and tempering.  
     
     
         3 . The manufacturing method according to  claim 1 , wherein the base metal is subjected to the hot working in a normalizing temperature range, after the normalizing.  
     
     
         4 . The manufacturing method according to  claim 1 , wherein the base metal contains, at % by weight, Mn: 0.3 to 0.6% and Mo: 0.87 to 1.13%.  
     
     
         5 . The manufacturing method according to  claim 4 , wherein the normalizing of the base metal is carried out at least twice.  
     
     
         6 . A method of manufacturing a long-life heat-resisting low alloy steel welded component including the steps of subjecting a base metal containing, at % by weight, C: 0.04% to 0.10%, Si: 0.5% or less, Mn: 0.1 to 0.6%, Cr: 1.9 to 2.6%, Mo: 0.05 to 0.3%, V: 0.20 to 0.30%, Nb: 0.02 to 0.08%, W: 1.45 to 1.75%, B: 0.0005 to 0.006% and a balance of iron and unavoidable impurities, to a hot working, to a heat treatment, and then to a welding, wherein the base metal is normalized once or more times before the welding in addition to the hot working.  
     
     
         7 . The manufacturing method according to  claim 6 , wherein the base metal has been subjected to annealing or normalizing and tempering.  
     
     
         8 . The manufacturing method according to  claim 6 , wherein the base metal is subjected to the hot working in a normalizing temperature range, after the normalizing.  
     
     
         9 . A method of manufacturing a long-life heat-resisting low alloy steel welded component including the steps of subjecting a base metal containing, at % by weight, C: 0.2% or less, Si: 1.0% or less, Mn: 0.3 to 0.9%, Cr: 0.3 to 1.5%, Mo: 0.4 to 0.7%, and a balance of iron and unavoidable impurities, to a hot working, to a heat treatment, and then to a welding, wherein the base metal is normalized once or more times before the welding in addition to the hot working.  
     
     
         10 . The manufacturing method according to  claim 9 , wherein the base metal has been subjected to annealing or normalizing and tempering.  
     
     
         11 . The manufacturing method according to  claim 9 , wherein the base metal is subjected to the hot working in a normalizing temperature range, after the normalizing.  
     
     
         12 . The manufacturing method according to  claim 9 , wherein the base metal contains, at % by weight, Mn: 0.3 to 0.6%, Cr: 0.5 to 1.5% and Mo: 0.40 to 0.65%.  
     
     
         13 . The manufacturing method according to  claim 9 , wherein the base metal further contains, at % by weight, V: 0.22 to 0.50%.  
     
     
         14 . A long-life heat-resisting low alloy steel welded component manufactured by the steps of subjecting a base metal containing, at % by weight, C: 0.15% or less, Si: 0.5% or less, Mn: 0.3 to 0.8%, Cr: 1.9 to 2.6%, Mo: 0.87 to 1.20%, and a balance of iron and unavoidable impurities, to a hot working, to a heat treatment, and then to a welding, wherein the base metal is normalized once or more times before the welding in addition to the hot working.  
     
     
         15 . The heat-resisting low alloy steel welded component according to  claim 14 , wherein the base metal has been subjected to annealing or normalizing and tempering.  
     
     
         16 . The heat-resisting low alloy steel welded component according to  claim 14 , wherein the base metal is subjected to the hot working in a normalizing temperature range, after the normalizing.  
     
     
         17 . The heat-resisting low alloy steel welded component according to  claim 14 , wherein the welded component can be applied to at least one of longitudinal joint and circumferential joint of pipes, vessel, valve casing and branch pipes that are used under a high-temperature and high-pressure steam atmosphere at a temperature of 450° C. or higher.  
     
     
         18 . The heat-resisting low alloy steel welded component according to  claim 14 , wherein the base metal contains, at % by weight, Mn: 0.3 to 0.6% and Mo: 0.87 to 1.13%.  
     
     
         19 . The heat-resisting low alloy steel welded component according to  claim 18 , wherein the normalizing of the base metal is carried out at least twice.  
     
     
         20 . A long-life heat-resisting low alloy steel welded component manufactured by the steps of subjecting a base metal containing, at % by weight, C: 0.04% to 0.10%, Si: 0.5% or less, Mn: 0.1 to 0.6%, Cr: 1.9 to 2.6%, Mo: 0.05 to 0.3%, V: 0.20 to 0.30%, Nb: 0.02 to 0.08%, W: 1.45 to 1.75%, B: 0.0005 to 0.006% and a balance of iron and unavoidable impurities, to a hot working, to a heat treatment, and then to a welding, wherein the base metal is normalized once or more times before the welding in addition to the hot working.  
     
     
         21 . The heat-resisting low alloy steel welded component according to  claim 20 , wherein the base metal has been subjected to annealing or normalizing and tempering.  
     
     
         22 . The heat-resisting low alloy steel welded component according to  claim 20 , wherein the base metal is subjected to the hot working in a normalizing temperature range, after the normalizing.  
     
     
         23 . The heat-resisting low alloy steel welded component according to  claim 20 , wherein the welded component can be applied to at least one of longitudinal joint and circumferential joint of pipes, vessel, valve casing and branch pipes that are used under a high-temperature and high-pressure steam atmosphere at a temperature of 450° C. or higher.  
     
     
         24 . A long-life heat-resisting low alloy steel welded component manufactured by the steps of subjecting a base metal containing, at % by weight, C: 0.2% or less, Si: 1.0% or less, Mn: 0.3 to 0.9%, Cr: 0.3 to 1.5%, Mo: 0.4 to 0.7%, and a balance of iron and unavoidable impurities, to a hot working, to a heat treatment, and then to a welding, wherein the base metal is normalized once or more times before the welding in addition to the hot working.  
     
     
         25 . The heat-resisting low alloy steel welded component according to  claim 24 , wherein the base metal has been subjected to annealing or normalizing and tempering.  
     
     
         26 . The heat-resisting low alloy steel welded component according to  claim 24 , wherein the base metal is subjected to the hot working in a normalizing temperature range, after the normalizing.  
     
     
         27 . The heat-resisting low alloy steel welded component according to  claim 24 , wherein the welded component can be applied to at least one of longitudinal joint and circumferential joint of pipes, vessel, valve casing and branch pipes that are used under a high-temperature and high-pressure steam atmosphere at a temperature of 450° C. or higher.  
     
     
         28 . The heat-resisting low alloy steel welded component according to  claim 24 , wherein the base metal contains, at % by weight, Mn: 0.3 to 0.6%, Cr: 0.5 to 1.5% and Mo: 0.40 to 0.65%.  
     
     
         29 . The heat-resisting low alloy steel welded component according to  claim 24 , wherein the base metal further contains, at % by weight, V: 0.22 to 0.50%.