Abstract: This spot welding method for an aluminum material comprises: a processing step in which, in a plan view, a circular emboss expanded in a direction of superposition on a second aluminum plate side is formed at a position-to-be-welded of a first aluminum plate; an arrangement step in which positions-to-be-welded are superimposed while the expansion side of the emboss faces the second aluminum plate, and the positions-to-be-welded are arranged between a pair of electrodes; a pressing step in which the superimposed aluminum plates are pinched between the electrodes, and a central side excluding a peripheral edge of the emboss is pressed; and an electrification step of performing pressing and electrification. An electrode having a tip diameter larger than the diameter of a root part of the expansion part of the emboss is used.

Abstract: A method for manufacturing a different material joined member comprises: a step of punching a shaft portion of a steel rivet into a light alloy material provided with a solid resin layer on at least one surface thereof; a step of causing a shaft portion tip of the rivet to protrude from the solid resin layer on the light alloy material; a step of laying a steel material over the surface of the light alloy material on the side where the shaft portion tip of the rivet protrudes, with the solid resin layer therebetween; and a step of welding the shaft portion of the rivet with the steel material. Instead of punching the rivet, a hole may be drilled in the light alloy material provided with the solid resin layer together with the solid resin layer, the steel material may be laid over via the solid resin layer, and the shaft portion of the steel rivet may be inserted into the hole.

Abstract: A joint structure including a first member, a second member superposed on the first member, a steel insertion member, and a welded part formed on an insertion tip of the insertion member. Each of the first member and the second member includes a high tensile strength steel. The steel insertion member is held by the second member in a state of having been inserted toward a superposition surface between the first member and the second member from a surface of the second member opposite the superposition surface. A carbon equivalent Ceq of the insertion member is lower than a carbon equivalent Ceq of the second member, where Ceq=C+Si/30+Mn/20+2P+4S.

Abstract: An outer panel of a different-material panel structure has a hem part in which a peripheral edge part of an inner panel is held via a resin layer on a folded part formed in the peripheral edge part. A rivet has a shaft part passing through the outer panel, and a rivet shaft recess is formed in the tip of the shaft part. An inner protrusion is provided in the inner panel, and the inner protrusion is disposed in the rivet shaft recess. A fused nugget is formed in the location where the rivet shaft recess and the tip of the inner protrusion come into contact, and a first heat-insulating part including at least the resin layer is formed in the gap formed with the resin layer in between the inner protrusion and the outer panel.

Abstract: A different-material joining structure includes a plurality of different types of plate materials stacked on one other and secured by means of a rivet. The plate materials include a first member and a second member of which end surfaces at one end of each overlap each other, and a third member arranged overlapping the surface of the first member on the opposite side to the second member. The rivet has a shank part penetrating through the first member and the third member and joined to the second member at a tip end thereof, and a head part not inserted into the third member and remaining on the surface of the third member. A joining part for joining the first member and the third member together is formed in at least a part of an overlapping region of the first member and the third member, on the side toward the other end of the second member relative to the position at which the rivet penetrates.

Abstract: A forged rivet for joining dissimilar materials includes a disc-shaped head and a shank. The shank includes: a first shank portion extending from the head; a ring-shaped protruding portion that protrudes outward at the lip of the first shank portion; and a second shank portion, the cross-sectional area of which is smaller than the first shank portion and which extends further in the direction of the tip from the protruding portion. On the surfaces of the shank and the head, surfaces that contact a light alloy material when the rivet is driven into the light alloy material, a coating film with a higher electrical resistance than steel is formed.

Abstract: Provided is a different materials panel structure having reduced occurrence of displacement or warping of a joining section and having excellent external appearance of an outer panel (2). The different materials panel structure has: an outer panel comprising a first metal material; an inner panel (3) arranged on the lower surface side of the outer panel and comprising a second metal material having a higher fusion point than the first metal material; and a rivet (6) comprising the same material as the second metal material and comprising a head section and a shaft section. An outer panel comprises a hemmed section formed by folding a rim section and which supports the inner panel via an adhesive layer (9). The head section of the rivet remains on the outer panel surface. The shaft section of the rivet penetrates from the lower surface side of the hemmed section of the outer panel towards the inner panel.

Abstract: Provided is a different materials panel structure having reduced occurrence of displacement or warping of a joining section and having excellent external appearance of an outer panel (2). The different materials panel structure has: an outer panel comprising a first metal material; an inner panel (3) arranged on the lower surface side of the outer panel and comprising a second metal material having a higher fusion point than the first metal material; and a rivet (6) comprising the same material as the second metal material and comprising a head section and a shaft section. An outer panel comprises a hemmed section formed by folding a rim section and which supports the inner panel via an adhesive layer (9). The head section of the rivet remains on the outer panel surface. The shaft section of the rivet penetrates from the lower surface side of the hemmed section of the outer panel towards the inner panel.

Abstract: A rivet for connecting different materials, including: a shaft part, inserted into a first material to be joined, with a tip welded to a second material to be joined of different material type than the first material; a plate-shaped head part provided at the base end on the opposite side from the tip of the shaft part in the axial direction. A first chamfered part, located at the outer edge of the surface in contact with the first material, an annular groove, located around the shaft part in the surface in contact with the first material, and a flat part, located between the first chamfered surface and the annular groove on the surface in contact with the first material, are formed on the head part. The rivet is formed of same type of material as the second material.

Abstract: A steel/aluminum welded structure comprises a hot-dip Al-coated steel sheet 1 spot welded with an aluminum or aluminum alloy sheet 2. The steel sheet 1 is coated with a coating layer 4 containing, by mass, 3-12% of Si and 0.5-5% of Fe. An area ratio of an Al—Fe binary alloy layer, formed at the joint boundary, is controlled to 90% or less. An unalloyed region 9 exists between an Al—Fe—Si ternary alloy layer 6 at an interface of a steel substrate 5 with the coating layer 4 interface and the Al—Fe binary alloy layer at the joint boundary. A steel substrate 5 preferably contains 0.002-0.020% of N for formation of a N-enriched surface layer in contact with the coating layer 4. The N-enriched layer impedes propagation of the brittle Al—Fe binary alloy layer to the whole of the joint boundary and raises joint strength of the steel/aluminum welded structure.

Abstract: There is provided method for joining dissimilar metals of a steel product and a light metal product with each other, wherein the light metal product and a rivet made of an iron-base metal are connected with each other beforehand in a previous process preceding spot welding, and subsequently, the rivet and the steel product are spot welded with each other. Then, a cavity for use in clinching the light metal product is formed, and upon the stem of the rivet is embedded into the light metal product to penetrate therethrough, light metal is caused to undergo plastic flow into the cavity of the rivet, for clinching the light metal product to be thereby clinched with the rivet whereupon spot welding for forming a weld nugget only within the scope of an interface between the stem of the rivet, and the steel product is carried out.

Abstract: A joined part of an aluminum-coated steel sheet and an aluminum sheet is composed of an intermetallic compound layer which exists in a region in which a part of a coated layer exists before the joining and an aluminum melted and solidified part which also exists on the side of the aluminum sheet to enclose the intermetallic compound layer. The atoms existing on the surface of the aluminum melted and solidified part are intermetallic-bonded with atoms which exist on the surface of the steel sheet except in the region in which the intermetallic compound layer exists seen in the plan view. Further, the area of the intermetallic compound layer is limited to 60% or less of the total area of the joined part at the interface between the aluminum-coated steel sheet and the aluminum sheet. Thus, the area of the aluminum melted and solidified part exceeds 40% of the total area of the joined part. The strong joining having a high fracture energy can be provided at a high efficiency.

Abstract: A steel/aluminum welded structure comprises a hot-dip Al-coated steel sheet 1 spot welded with an aluminum or aluminum alloy sheet 2. The steel sheet 1 is coated with a coating layer 4 containing, by mass, 3-12% of Si and 0.5-5% of Fe. An area ratio of an Al—Fe binary alloy layer, formed at the joint boundary, is controlled to 90% or less. An unalloyed region 9 exists between an Al—Fe—Si ternary alloy layer 6 at an interface of a steel substrate 5 with the coating layer 4 interface and the Al—Fe binary alloy layer at the joint boundary. A steel substrate 5 preferably contains 0.002-0.020% of N for formation of a N-enriched surface layer in contact with the coating layer 4. The N-enriched layer impedes propagation of the brittle Al—Fe binary alloy layer to the whole of the joint boundary and raises joint strength of the steel/aluminum welded structure.

Abstract: A joined part of an aluminum-coated steel sheet and an aluminum sheet is composed of an intermetallic compound layer which exists in a region in which a part of a coated layer exists before the joining and an aluminum melted and solidified part which also exists on the side of the aluminum sheet to enclose the intermetallic compound layer. The atoms existing on the surface of the aluminum melted and solidified part are intermetallic-bonded with atoms which exist on the surface of the steel sheet except in the region in which the intermetallic compound layer exists seen in the plan view. Further, the area of the intermetallic compound layer is limited to 60% or less of the total area of the joined part at the interface between the aluminum-coated steel sheet and the aluminum sheet. Thus, the area of the aluminum melted and solidified part exceeds 40% of the total area of the joined part. The strong joining having a high fracture energy can be provided at a high efficiency.

Abstract: A self-piercing rivet comprises a flange with a large diameter and a shank with a hollow cavity extending from the flange inward. The rivet is made of aluminum or an aluminum alloy. The shank is a straight cylinder with outer diameter D1, and the hollow cavity in the shank has conical section tapered from the shank end and converging towards the flange at angle &agr; and a straight cylinder section with inner diameter D2 extending from the conical section to the end on the flange side. The shank has a substantially flat ring-shaped end with outer diameter D1 and radial length T1. The angle &agr; of the conical section ranges between 70° and 110°.