초록 ▼

A welding method and a welded joint for high strength, temperature resistant steels produce the same strength as the base metal in the welded joint, thereby resolving strength problems in the heat affected area by making a simple change to the welding method. Additionally, this advantage is extended

A welding method and a welded joint for high strength, temperature resistant steels produce the same strength as the base metal in the welded joint, thereby resolving strength problems in the heat affected area by making a simple change to the welding method. Additionally, this advantage is extended to high strength ferrite heat resistant steels by providing a multi-pass buildup welding method for such high strength ferrite heat resistant steels. A multi-layered cap 15a fusion area extends past the heat affected area 13 that lies outside groove 11, and the surface area of the foregoing extension that is required to impart the same level of creep strength as is inherent in the base metal is based on the relationship between the groove width and the base metal thickness shown as hatched area in FIG. 1(B).

대표청구항 ▼

1. A welded joint, comprising:an I-shaped joint groove in a base metal of high strength, heat resistant steel filled with multi-pass buildup welding, said I-shaped joint groove having a toe, a width X and a root, a weld face and a heat affected area formed by said welding; and a multi-layered weld c

1. A welded joint, comprising:an I-shaped joint groove in a base metal of high strength, heat resistant steel filled with multi-pass buildup welding, said I-shaped joint groove having a toe, a width X and a root, a weld face and a heat affected area formed by said welding; and a multi-layered weld cap atop the weld face that fuses at least a part of said heat affected area; wherein said high strength, heat-resistant steel is ferrite type heat resistant steel; wherein a toe of said I-shaped joint groove is formed into a tapered portion broadening upward with a slow grade; and wherein a fusion area on the heat affected area is formed by shifting a welding line from a toe of said joint groove and extending the welding line over an extended area having a width T′ that is slightly wider than a width T of the heat affected area on the surface of the base metal in order to form said multi-layered weld cap to cover said extended area, and said multi-layer weld cap extending over a width X+2T′ which is wider than the groove width X; and wherein the width X is constant along a majority of the distance of said I-shaped joint groove between a top surface and a bottom surface of said base metal. 2. The welded joint of claim 1, wherein said heat affected area has a level of creep strength that is at least the same as that inherent in the base metal and a surface area of said extended area required to impart the level of creep strength to said heat affected area is determined using a computation map based on a relationship between the width of said joint groove and the thickness of the base metal.3. The welded joint of claim 1, wherein said multi-layered weld cap over said extended area is formed by multi-pass buildup which gradually absorbs residual stress of said heat affected area on the surface of the base metal.4. A welding method for a welded joint in a base metal of high strength, heat resistant steel having an I-shaped joint groove with width X and a root filled by multi-pass buildup welding and subsequently covered with a multi-layered weld cap atop a weld face that fuses at least a part of a heat affected area, comprising:forming a fusion area in the heat affected area by beginning a welding line at a toe of the groove and successively extending the line to a width T′ over an extended area that is slightly wider than a width T of the heat affected area on the surface of the base metal and forming multi-pass buildup over the extended area; and subsequently forming excess metal atop the multi-pass buildup over the extended area; wherein the high strength, heat resistant steel is ferrite type heat resistant steel; wherein said heat affected area has a level of creep strength that is at least the same as that inherent in the base metal and a surface area of said extended area required to impart the level of creep strength to said heat affected area is determined using a computation map based on a relationship between the width of said joint groove and the thickness of the base metal; and wherein said toe of the groove is tapered and flattened, and said multi-layer weld cap extends over a width X+2T′ which is wider than groove width X; and wherein the width X is constant along a majority of the distance of the I-shaped joint groove between a top surface and a bottom surface of the base metal. 5. A welded joint, comprising:an I-shaped joint groove with width X and a root in a base metal of high strength, heat resistant steel filled with multi-pass buildup welding, said multi-pass welding having a heat affected area adjacent thereto in said base metal, and said heat affected area having a width T with respect to the surface of said base metal; an extended fusion area at a toe of said joint groove that extends to a width T′ that is slightly wider than said width T; and a multi-layered weld cap atop said extended fusion area, said multi-layered weld cap being wider than said width T; wherein said high strength, heat-resistant steel is high strength ferrite type heat resistant steel; and wherein said toe of the groove is tapered and flattened, and said multi-layer weld cap extends over a width X+2T′ which is wider than groove width X; and wherein the width X is constant along a majority of the distance of said I-shaped joint groove between a top surface and a bottom surface of said base metal. 6. The welded joint of claim 5, wherein said heat affected area has a level of creep strength that is at least the same as that inherent in the base metal and a surface area of said extended fusion area required to impart the level of creep strength to said heat affected area is determined using a computation map based on a relationship between the width of said joint groove and the thickness of the base metal.7. The welded joint of claim 5, wherein said multi-layered weld cap over said extended fusion area is formed by multi-pass buildup which gradually absorbs residual stress of said heat affected area on the surface of the base metal.8. A welding method comprising:filling an I-shaped joint groove of a base metal of high strength ferrite type heat resistant steel by multi-pass buildup welding, said joint groove having a width X and a root; subsequently forming excess weld to at least fuse over a part of a heat affected area of the base metal adjacent the joint groove; extending a fusion area in the heat affected area by beginning a welding line at a toe of the groove and successively extending the line to a width T′ over an extended fusion area that is slightly wider than a width T of the heat affected area on the surface of the base metal and forming multi-pass buildup over the extended fusion area; and subsequently forming excess metal atop the multi-pass buildup over the extended area; wherein said heat affected area has a level of creep strength that is at least the same as that inherent in the base metal and a surface area of said extended fusion area required to impart the level of creep strength to said heat affected area is determined using a computation map based on a relationship between the width of said joint groove and the thickness of the base metal; and wherein said toe of the groove is tapered and flattened, and said multi-layer weld cap extends over a width X+2T′ which is wider than groove width X; and wherein the width X is constant along a majority of the distance of the I-shaped joint groove between a top surface and a bottom surface of the base metal.