A method of manufacturing a joining apparatus includes: providing a first metal member including an opening and a joint structure; providing a second metal member including an outer circumferential wall capable of contacting an inner circumferential wall that surrounds the opening and a joined structure, to which the joint structure is joined; causing the first metal member and the second metal member to move relative to each other, bringing one of a first joining section, which is configured by the inner circumferential wall and the outer circumferential wall, and a second joining section, which is configured by the joint structure and the joined structure, into contact, and separating the other joining section; starting energization between the first and the second metal members; bringing components of the other joining section into contact with each other; and joining the first and second joining sections by the relative movement and the energization.

A method of manufacturing a joining apparatus includes: providing a first metal member including an opening and a joint structure; providing a second metal member including an outer circumferential wall capable of contacting an inner circumferential wall that surrounds the opening and a joined structure, to which the joint structure is joined; causing the first metal member and the second metal member to move relative to each other, bringing one of a first joining section, which is configured by the inner circumferential wall and the outer circumferential wall, and a second joining section, which is configured by the joint structure and the joined structure, into contact, and separating the other joining section; starting energization between the first and the second metal members; bringing components of the other joining section into contact with each other; and joining the first and second joining sections by the relative movement and the energization.

Provided are a dissimilar metal welded body and a method of manufacturing the same, capable of preventing galvanic corrosion in a connection portion between dissimilar metals in the dissimilar metal welded body and of sufficient insulation coating being applied even when the insulation coating is applied to the dissimilar metal welded body. The dissimilar metal welded body includes a first member made of a metal containing aluminum as a main component, a second member made of a metal containing copper as a main component, a welded portion formed by pressure-welding an end face of the first member and an end face of the second member to each other, and a metal film that continuously covers a substantially entire part of the first member and at least a part of the second member. The metal film is a film made of a metal containing copper as a main component.

Provided are a dissimilar metal welded body and a method of manufacturing the same, capable of preventing galvanic corrosion in a connection portion between dissimilar metals in the dissimilar metal welded body and of sufficient insulation coating being applied even when the insulation coating is applied to the dissimilar metal welded body. The dissimilar metal welded body includes a first member made of a metal containing aluminum as a main component, a second member made of a metal containing copper as a main component, a welded portion formed by pressure-welding an end face of the first member and an end face of the second member to each other, and a metal film that continuously covers a substantially entire part of the first member and at least a part of the second member. The metal film is a film made of a metal containing copper as a main component.

Provided are a hot-rolled steel sheet for an electric resistance welded steel pipe and a method for manufacturing the same, an electric resistance welded steel pipe and a method for manufacturing the same, a line pipe, and a building structure. The hot-rolled steel sheet has a chemical composition containing, by mass %, C: 0.030% or more and 0.20% or less, Si: 0.02% or more and 1.0% or less, Mn: 0.40% or more and 3.0% or less, P: 0.050% or less, S: 0.020% or less, N: 0.0070% or more and 0.10% or less, and Al: 0.005% or more and 0.080% or less, the balance being Fe and incidental impurities, in which N dissolved in steel is contained in an amount of 0.0010% or more and 0.090% or less, and letting a sheet thickness be t, a steel microstructure at a ½t position has an average grain size of 20.0 μm or less.

To provide a method and apparatus for manufacturing a joined member that inhibit occurrence of cracks in a joined member even when the joined portion is quenched when members are welded together. The method includes placing the first member D and the second member E with a joint target portion Df and a joint target portion Ef being in contact with each other, welding the joint target portions by heating, subjecting the first member D after the welding to a process for inhibiting occurrence of cracks, and tempering a portion where the first and second members have been welded to each other by electromagnetic heating. The apparatus includes a first electrode 11 to contact with the first member D; a second electrode 12 to contact with the second member E; and an induction heating coil 23 for performing induction heating of a portion where a joint target portions Df and Ef have been contacted and joined to each other, and the induction heating coil 23 is placed between the two electrodes 11 and 12 when the induction heating is performed.

To provide a method and apparatus for manufacturing a joined member that inhibit occurrence of cracks in a joined member even when the joined portion is quenched when members are welded together. The method includes placing the first member D and the second member E with a joint target portion Df and a joint target portion Ef being in contact with each other, welding the joint target portions by heating, subjecting the first member D after the welding to a process for inhibiting occurrence of cracks, and tempering a portion where the first and second members have been welded to each other by electromagnetic heating. The apparatus includes a first electrode 11 to contact with the first member D; a second electrode 12 to contact with the second member E; and an induction heating coil 23 for performing induction heating of a portion where a joint target portions Df and Ef have been contacted and joined to each other, and the induction heating coil 23 is placed between the two electrodes 11 and 12 when the induction heating is performed.

To provide a fitting member, an annular member, a joined member and a method of manufacturing the joined member, which prevent occurrence of a not-joined portion. A fitting member 10 has a fitting protrusion 10p which is protruded outward on an outside face 10s. An annular member 20 contains a space 20h in which the fitting member 10 is to be fitted. An annular member 20 has an annular protrusion 20p on an inside face 20f. When the fitting member 10 is fitted into the space 20h at a predetermined depth, the fitting protrusion 10p and the annular protrusion 20p fill not-joined portions which may be generated assuming that they are not provided. A joined member 30 is produced by fitting the fitting member 10 into the space 20h at the predetermined depth, so that a contact portion between the fitting member 10 and the annular member 20 is joined in solid phase.

To provide a fitting member, an annular member, a joined member and a method of manufacturing the joined member, which prevent occurrence of a not-joined portion. A fitting member 10 has a fitting protrusion 10p which is protruded outward on an outside face 10s. An annular member 20 contains a space 20h in which the fitting member 10 is to be fitted. An annular member 20 has an annular protrusion 20p on an inside face 20f. When the fitting member 10 is fitted into the space 20h at a predetermined depth, the fitting protrusion 10p and the annular protrusion 20p fill not-joined portions which may be generated assuming that they are not provided. A joined member 30 is produced by fitting the fitting member 10 into the space 20h at the predetermined depth, so that a contact portion between the fitting member 10 and the annular member 20 is joined in solid phase.

A welding apparatus includes a welding rod; a temperature measuring jig to measure a temperature of the welding rod; and a welding rod cooler to cool the welding rod.