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.

A welding method for joining a first plate made of a material other than steel and a second plate made of steel includes a step of making a hole through each of the first plate and the second plate, a press-fitting step, an overlapping step, and a filling and welding step. A shaft portion of a joining assist member being solid, being made of steel, and having an outer shape with step having the shaft portion and a flange portion is press-fitted in the hole of the first plate. The first plate and the second plate is overlapped such that the shaft portion faces the hole of the second plate. The hole of the second plate is filled with a weld metal and the second plate and the joining assist member are welded.

A welding method for joining a first plate made of a material other than steel and a second plate made of steel includes a step of making a hole through each of the first plate and the second plate, a press-fitting step, an overlapping step, and a filling and welding step. A shaft portion of a joining assist member being solid, being made of steel, and having an outer shape with step having the shaft portion and a flange portion is press-fitted in the hole of the first plate. The first plate and the second plate is overlapped such that the shaft portion faces the hole of the second plate. The hole of the second plate is filled with a weld metal and the second plate and the joining assist member are welded.

A TIG-type method for tack welding two metal sheets or parts, such as tubes. The method includes, for each zone/point of tack welding of the metal sheets or of the tubes, a tack welding cycle including successively applying at least one smooth or pulsed direct current DC, and then at least one smooth or pulsed alternating current AC.

To solve the problem about the difference in temperature increasing rate between an overlapped part and a one-sheet part so as to further improve the corrosion resistance of plating after hot stamping. An overlapped blank for hot stamping includes: a first steel sheet; and at least one second steel sheet connected to a surface of the first steel sheet via a welding point and smaller in area than the first steel sheet, wherein: the first steel sheet is a plated steel sheet having an aluminum-based plated layer on both faces of the first steel sheet, and the second steel sheet is a plated steel sheet having an aluminum-based plated layer on both faces of the second steel sheet; a coating weight of the aluminum-based plated layer on the first steel sheet is W1 (g/m.sup.2) in terms of an average coating weight on both the faces; a coating weight of the aluminum-based plated layer on a surface on a side not in contact with the first steel sheet in the second steel sheet is W2 (g/m.sup.2); and each of the W1 and the W2 is within a range of 20 g/m.sup.2 or more and 120 g/m.sup.2 or less, and satisfies relationships of Expression (1) and Expression (2).

A second member has a through-portion penetrating toward a first member. An overlapped surface of the second member with the first member includes a recess. The recess is recessed so as to surround an entire periphery of the through-portion. The recess is provided with a sealing material. The sealing material closes a gap between overlapped surfaces of the first member and the second member.

A second member has a through-portion penetrating toward a first member. An overlapped surface of the second member with the first member includes a recess. The recess is recessed so as to surround an entire periphery of the through-portion. The recess is provided with a sealing material. The sealing material closes a gap between overlapped surfaces of the first member and the second member.

A second member has a through-portion penetrating toward a first member. An overlapped surface of the second member with the first member includes a recess. The recess is recessed so as to surround an entire periphery of the through-portion. A sealing material is injected into the recess from an injection hole to close a gap between overlapped surfaces of the first member and the second member.

A second member has a through-portion penetrating toward a first member. An overlapped surface of the second member with the first member includes a recess. The recess is recessed so as to surround an entire periphery of the through-portion. A sealing material is injected into the recess from an injection hole to close a gap between overlapped surfaces of the first member and the second member.

A stable welding process for a welding method in which at least one welding device is used for welding. During the welding process carried out using the welding device, synchronization information is transmitted to the at least one welding device from at least one other electric device, in which a device current that changes over time flows in a device current circuit at least at one point in time, and the at least one welding device is designed to use the obtained synchronization information in order to ignore measurement values detected at the point in time for the measurement variable.