A method of single-sided resistance welding includes providing a first workpiece and a second workpiece. The first workpiece is positioned so that at least a portion of the first workpiece is in contact with at least a portion of the second workpiece. A weld electrode is positioned in contact with the first workpiece, and a ground electrode is positioned in contact with the second workpiece. A determination is made as to whether a gap or other high resistance condition is present between the first workpiece and the second workpiece. If a gap or other high resistance condition is determined to be present between the first workpiece and the second workpiece, the gap or other high resistance condition is reduced, and the first workpiece and the second workpiece are joined through welding.

A method of single-sided resistance welding includes providing a first workpiece and a second workpiece. The first workpiece is positioned so that at least a portion of the first workpiece is in contact with at least a portion of the second workpiece. A weld electrode is positioned in contact with the first workpiece, and a ground electrode is positioned in contact with the second workpiece. A determination is made as to whether a gap or other high resistance condition is present between the first workpiece and the second workpiece. If a gap or other high resistance condition is determined to be present between the first workpiece and the second workpiece, the gap or other high resistance condition is reduced, and the first workpiece and the second workpiece are joined through welding.

A piston main body in a piston assembly of a fluid pressure cylinder includes a first piston member and a second piston member including a plate-shaped member. The first piston member and the second piston member are joined in a state overlapping in the axial direction of a piston rod. The second piston member is not provided with a hole that passes through in the plate thickness direction.

A piston main body in a piston assembly of a fluid pressure cylinder includes a first piston member and a second piston member including a plate-shaped member. The first piston member and the second piston member are joined in a state overlapping in the axial direction of a piston rod. The second piston member is not provided with a hole that passes through in the plate thickness direction.

A low-yield ratio high-strength electric resistance welded steel pipe has a yield ratio of 80% or less and a TS of 655 MPa or more. A steel material has a composition containing 0.38% to 0.45% C, 0.1% to 0.3% Si, 1.0% to 1.8% Mn, 0.03% or less P, 0.03% or less S, 0.01% to 0.07% sol. Al, and 0.01% or less N on a mass basis.

A low-yield ratio high-strength electric resistance welded steel pipe has a yield ratio of 80% or less and a TS of 655 MPa or more. A steel material has a composition containing 0.38% to 0.45% C, 0.1% to 0.3% Si, 1.0% to 1.8% Mn, 0.03% or less P, 0.03% or less S, 0.01% to 0.07% sol. Al, and 0.01% or less N on a mass basis.

A system for spot welding two metal sheets together includes a plurality of conductive particles placed in an interface between the two metal sheets, a first electrode, and a second electrode. The first electrode and the second electrode are arranged to clamp the two metal sheets together such that the conductive particles become embedded into the metal sheets at the interface between the metal sheets. A conductive path is formed from the first electrode to the second electrode through the metal sheets and the plurality of metallic particles.

This application relates to a resistance spot weld, a resistance spot welding method, a resistance spot welded joint, and a method for manufacturing the resistance spot welded joint. In the resistance spot weld, at least one of steel sheets is a high-strength steel sheet having a prescribed chemical composition. In at least one of a nugget edge region corresponding to a faying interface, the nugget edge region has a metal microstructure including tempered martensite as a main phase. The hardness Hv of the nugget edge region and the hardness Hmw of martensite in the nugget as a whole satisfy formula (4). In at least one of a strong HAZ region corresponding to the faying interface, the hardness Hh of the strong HAZ region and the hardness Hmh of martensite in a prescribed steel sheet satisfy formula (8).

[00001]$\begin{array}{cc}\mathrm{Hv}\le \mathrm{Hmw}-40& \left(4\right)\\ \mathrm{Hh}<\mathrm{Hmh}-25& \left(8\right)\end{array}$

A joint structure, includes: a first member including a high tensile strength steel; a second member including a high tensile strength steel and superposed on the first member; a surface soft layer formed on at least one of a superposition surface of the first member, on which the second member is superposed, and a superposition surface of the second member, on which the first member is superposed; a molten-solidified portion formed by melting and solidifying the first member and the second member; and a heat affected zone formed around the molten-solidified portion, in which the surface soft layer has a total thickness of 5 μm to 200 μm, and the molten-solidified portion has a carbon amount of 0.21 mass % or more, and a maximum Vickers hardness of the surface soft layer in the heat affected zone is 100 Hv to 500 Hv.

A joint structure includes a first metallic material having a first projection, a second metallic material similar to and weldable to the first metallic material, and a different material having a first penetrating part and sandwiched between the first and second metallic materials, the different material being difficult to weld to the first and second metallic materials. The first projection is smaller than the first penetrating part and is spaced from the rim of the first penetrating part. The first projection is positioned in the first penetrating part and spaced from the second metallic material by a gap. The gap has a size of a predetermined percentage of the thickness of the first projection to which arc welding is applied. The first and second metallic materials are melted and joined together inside the first penetrating part to compress and fix the different material, so all three are fixed together.