Abstract: A repair welding method according to at least one embodiment is for a member in which a first end and a second end of a parent material are connected by welding and includes: a step of removing a portion including at least a part of a first heat-affected zone of an existing welded portion of the member; and a step of performing repair welding after removing the portion. In a cross-section including the parent material and the existing welded portion, all intersection portions between the first heat-affected zone of the existing welded portion and a second heat-affected zone due to the repair welding have an intersection angle between the first heat-affected zone and the second heat-affected zone of 70° to 110°.

Abstract: In this cast austenitic stainless steel, in a cross section when heated at 1000° C., an average number Nc per unit area of carbides having an equivalent circle diameter of 500 nm or larger in a center portion of an austenite crystal grain is 6.0×10?2 particles/?m2 or more, and, when an average number per unit area of the carbides having an equivalent circle diameter of 500 nm or larger in a vicinity of a grain boundary in an austenite crystal grain is represented as Ngb, Ngb/Nc is 1.3 or less.

Abstract: A faulted condition determination method is designed to detect a chromium content and a nickel content in a predetermined boundary region proximate to a boundary between a high-strength ferrite steel and a weld material in a welded joint in which the high-strength ferrite steel and another steel are welded together using the weld material containing nickel and to thereby determine the faulted condition of the predetermined boundary region based on the chromium content and the nickel content. Accordingly, it is possible to appropriately determine the faulted condition of welding of a replacement part in which a high-strength ferrite steel and another steel are welded together using a nickel-based weld material.

Abstract: A learning model creation device includes, a verifying unit that verifies a learning model for predicting, from a predetermined manufacturing condition including at least one condition, a predetermined material property of a material manufactured under the manufacturing condition.

Abstract: A repair welding method according to at least one embodiment is for a member in which a first end and a second end of a parent material are connected by welding and includes: a step of removing a portion including at least a part of a first heat-affected zone of an existing welded portion of the member; and a step of performing repair welding after removing the portion. In a cross-section including the parent material and the existing welded portion, all intersection portions between the first heat-affected zone of the existing welded portion and a second heat-affected zone due to the repair welding have an intersection angle between the first heat-affected zone and the second heat-affected zone of 70° to 110°.

Abstract: A faulted condition determination method is designed to detect a chromium content and a nickel content in a predetermined boundary region proximate to a boundary between a high-strength ferrite steel and a weld material in a welded joint in which the high-strength ferrite steel and another steel are welded together using the weld material containing nickel and to thereby determine the faulted condition of the predetermined boundary region based on the chromium content and the nickel content. Accordingly, it is possible to appropriately determine the faulted condition of welding of a replacement part in which a high-strength ferrite steel and another steel are welded together using a nickel-based weld material.

Abstract: A first measured value of a specific physical quantity at a target portion is correlated with a damage evaluation index to calculate a damage degree corresponding to the first measured value. The specific physical quantity is measured at least once at a position corresponding to the first measurement position in another time period having a different usage elapsed time from that of the first measurement, and these second and subsequent measured values are correlated with damage degrees calculated based on temporal changes corresponding to the second and subsequent measurements. A new damage evaluation index is approximately calculated based on a relationship between the first, second, and subsequent measured values and the damage degrees corresponding to the first, second, and subsequent measured values.

Abstract: A first measured value of a specific physical quantity at a target portion is correlated with a damage evaluation index to calculate a damage degree corresponding to the first measured value. The specific physical quantity is measured at least once at a position corresponding to the first measurement position in another time period having a different usage elapsed time from that of the first measurement, and these second and subsequent measured values are correlated with damage degrees calculated based on temporal changes corresponding to the second and subsequent measurements. A new damage evaluation index is approximately calculated based on a relationship between the first, second, and subsequent measured values and the damage degrees corresponding to the first, second, and subsequent measured values.

Abstract: Deflection (bend) in the length direction due to a difference in the heat expansion between two plate-like members, between which rows of heat transfer tubes are sandwiched, is reduced, and deflection (bend) of rows of heat transfer tubes is prevented. Two long plate-like members, in which a plurality of cutouts along the longitudinal direction are provided in one side the widthwise direction, are provided, and each of the cutouts includes two rectilinear sections that extend in a direction perpendicular to the longitudinal direction axis of the plate-like members, and a semicircular section that links one end of the rectilinear sections together. The distance between the two rectilinear sections along the lengthwise direction axis of the plate-like members and the diameter of the semicircular section is set so as to be greater than the diameter of the heat transfer tubes that are contained within the cutouts.

Abstract: In order to provide a welding structure of a tube header and tube stubs which successfully improves the durability thereof against creep and fatigue damage of the tube stubs without interposing a component of a different material between the tube header and the tube stubs, i.e. requiring additional components, a welding structure of the present invention comprises: a tube header (2) being made of ferritic heat resisting steel; a plurality of tube stubs (4) which are welded onto an outer surface of the tube header, each of the tube stubs having a bended section, in which the plurality of tube stubs (4) are made of austenite stainless steel, and welded to the tube header (2) by using nickel base alloy as a welding material.

Abstract: A high-precision method for evaluating creep damage of high tension heat resistant steel used in high temperature exposed apparatuses involves comparing particle size behavior varying with creep damage progress of crystal grains having a crystal orientation difference of about 2 degrees or more, preferably 3 degrees or more at an evaluated part on the basis of a working curve or a working map prepared in advance by looking for the relation of grain sizes to creep damage extent. A high-precision apparatus evaluates the creep damage of high tension heat resistant steel used in high temperature exposed apparatuses.

Abstract: 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).

Abstract: The present invention provides a high-precision method for evaluating creep damage of high tension heat resistant steel used in high temperature exposing apparatuses comprising comparing particle size behavior varying with creep damage progress of crystal grains having a crystal orientation difference of about 2 degrees or more, preferably 3 degrees or more at an evaluated part on the basis of a working curve or a working map prepared in advance by looking for the relation of grain sizes to creep damage extents, and also provides a high-precision apparatus for evaluating creep damage of high tension heat resistant steel used in high temperature exposing apparatuses comprising a measuring means for measuring particle size variation behavior of crystal grains or sub grains having a crystal orientation difference of about 2 degrees or more with regard to a specimen at the evaluated part of high tension heat resistant steel and a working curve or a working map prepared in advance by looking for the relation of th

Abstract: This invention provides a welding method and a welded joint for high strength, temperature resistant steels that produces the same strength as the base metal in the welded joint, thereby resolving the strength problems in the heat affected area by making a simple change to the welding method, and additionally, to extend this advantage to high strength ferrite heat resistant steels by providing a multi-pass buildup welding method for such high strength ferrite heat resistant steels. The 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).

Abstract: A high strength, low alloy, heat resistant steel having excellent weldability has an average crystal grain diameter of at most 110 &mgr;m and consists essentially of, by mass %: C: 0.03-0.15%, Si: at most 1%, Mn: at most 2%, P: at most 0.03%, S: at most 0.03%, Ni: at most 0.5%, Cu: at most 0.5%, Cr: 1.8-2.8%, V: 0.1-0.3%, Nb: 0.01-0.08%, Mo: 0.05-0.35%, W: 1.2-1.8%, Ti: 0.001-0.05%, B: 0-0.02%, Al: at most 0.1%, O: at most 0.1%, N: in an amount satisfying the formula [%N]≦[%Ti]+5[%B]+0.004, and a remainder of unavoidable impurities.

Abstract: This invention provides a welding material for low chromium (Cr) ferritic heat-resisting steel having high toughness, wherein the chemical composition of welding metal comprises, in weight %, carbon (c) 0.04-0.1%, silicon (Si) 0.1-0.6%, manganese (Mn) 0.1-0.6%, phosphorus (P) 0.0005-0.03%, sulfur (S) 0.0005-0.015%, chromium (Cr) 1.75-2.5%, nickel (Ni) 0.01-0.8%, molybdenum (Mo) 0.05-1.5%, vanadium (V)0.01-0.5%, tungsten (W) 0.05-2%, niobium (Nb) 0.01-0.2%, tantalum (Ta) 0.01-0.5%, aluminum (Al) 0.003-0.05%, boron (B) 0.0001-0.01%, nitrogen (N) 0.003-0.03%, and the remainder comprises iron and inevitable impurities. The welding material satisfies the following formula: C+Cr/20+Mo/15+V/10+W/7+5B.ltoreq.0.8%. According to this invention, the welding material is suitable for welding low Cr ferritic heat-resisting steels having high strength such as those used in steam generators and heat exchangers of boilers, etc.

Abstract: This invention provides low-Cr ferritic steels and low-Cr ferritic cast steels having excellent high-temperature strength and weldability. These low-Cr ferritic steels and low-Cr ferritic cast steels consist essentially of, on a weight percentage basis, 0.03 to 0.12% C, 0.05 to 0.7% Si, 0.05 to 1% Mn, 0.002 to 0.025% P, 0.001 to 0.015% S, 0.3 to 3% Cr, 0.01 to 1% Ni, 0.05 to 3% Mo, 0.01 to 0.5% V, 0.1 to 3% W, 0.01 to 0.2% Nb, 0.02 to 1.5% Re, 0.003 to 0.05% Al, 0.0001 to 0.01% B, 0.003 to 0.03% N, and the balance being Fe and incidental impurities, and have excellent high-temperature strength and weldability.

Abstract: A low Mn-low Cr ferritic heat resistant steel consisting essentially of, in weight %: 0.02-0.20% C, up to 0.7% Si, less than 0.1% Mn, up to 0.8% Ni, 0.8-3.5% Cr, 0.01-3.0% W, 0.1-0.5% V, 0.01-0.20% Nb, 0.001-0.05% Al, 0.0005-0.05% Mg, 0.0005-0.01% B, less than 0.05% N, up to 0.03% P, up to 0.015% S, 0.001-0.05% Ti and the balance Fe and incidental impurities, wherein the B content is defined so as to satisfy the following formula (14/11)B>N-N(V/51)/{(C/12)+(N/14)}-N(Nb/93)/{(C/12)+(N/14)}-N(Ti/48)/{C/12 )+(N/14)}. The steel can further contain optionally 0.01-1.5% Mo, and/or one or more elements selected from the group consisting of 0.01-0.2% La, 0.01-0.2% Ce, 0.01-0.2% Y, 0.01-0.2% Ca, 0.01-0.2% Ta and 0.01-0.2% Zr. The steel can be used in place of the austenitic steels or high Cr ferritic steels, since it has remarkably improved toughness, workability and weldability, and excellent creep properties at elevated temperatures.