An aluminum alloy brazing sheet may include a sacrificial material having a function of a brazing material on at least one surface of a core material, wherein the sacrificial material has a composition containing: in a mass %, 2% to 5% of Si; 3% to 5% of Zn; and an Al balance with inevitable impurities the core material is made of an Al—Mn-based alloy, an in the core material before brazing, Al—Mn based secondary particles having an equivalent circle diameter of 100 to 400 nm are distributed with a number density of 0.3 to 5 particles/μm.sup.2.

A strip intended for the manufacture of brazed heat exchangers, having a core made of an alloy with the composition (weight %):

Si: 0.10-0.30%, preferably 0.15-0.25%
Fe<0.25%, preferably 0.1-0.2%
Cu: 0.85-1.1%, preferably 0.9-1.0%
Mn: 1.2-1.7%, preferably 1.2-1.4%
Mg: 0.1-0.3%, preferably 0.1-0.21%
Zn<0.1%
Ti 0.05-0.20%, preferably 0.06-0.15%, more preferably 0.06-0.1%
optionally up to 0.15% of Bi and/or Y
other elements <0.05% each and <0.15% in total,
remainder aluminium.

A brazing sheet (1) includes a core material (11) composed of an Al alloy that contains 0.20-3.0 mass % of Mg; and a filler material (12) layered on the core material and composed of an Al alloy that contains Mg, 6.0-13.0 mass % of Si, and more than 0.050 mass % and 1.0 mass % or less of Bi. The Mg concentration of the filler material becomes continuously lower in a direction from a boundary (122) with the core material to an outermost surface (121). The Mg concentration of the filler material is 0.150 mass % or less at a first depth from the outermost surface that is ⅛ of a thickness (t.sub.f) of the filler material and is 5-90% of the amount of Mg in the core material at a second depth from the outermost surface that is ⅞ of the thickness of the filler material.

A brazing sheet (1) includes a core material (11) composed of an Al alloy that contains 0.20-3.0 mass % of Mg; and a filler material (12) layered on the core material and composed of an Al alloy that contains Mg, 6.0-13.0 mass % of Si, and more than 0.050 mass % and 1.0 mass % or less of Bi. The Mg concentration of the filler material becomes continuously lower in a direction from a boundary (122) with the core material to an outermost surface (121). The Mg concentration of the filler material is 0.150 mass % or less at a first depth from the outermost surface that is ⅛ of a thickness (t.sub.f) of the filler material and is 5-90% of the amount of Mg in the core material at a second depth from the outermost surface that is ⅞ of the thickness of the filler material.

A brazing, monolayer, aluminum-alloy material has a chemical composition composed of Si: 1.5 mass % or more and 3.5 mass % or less, Fe: 0.05 mass % or more and 2.00 mass % or less, Mn: 0.1 mass % or more and 2.0 mass % or less, Mg: 0.005 mass % or more and 0.500 mass % or less, and Bi: 0.010 mass % or more and 0.500 mass % or less, the remainder being Al and unavoidable impurities; and has a metallographic structure in which Mg—Bi-series compounds are dispersed in an Al matrix. The surface-area ratio of the above-mentioned Mg—Bi-series compounds in any arbitrary cross section is 0.05% or more.

A vehicle body upper structure includes: roof side rails provided at end portions in a vehicle width direction of a vehicle body upper portion; side outer panels covering vehicle outer side surfaces of the roof side rails; and a roof panel made of a material different from a martial of the roof side rails and provided at a center portion in the vehicle width direction of the vehicle body upper portion, and the roof panel and the paired side outer panels are fixed to one another by braze joining. Outer end portions in the vehicle width direction of the side outer panels are joined to outer end portions in the vehicle width direction of the roof side rails. Inner end portions in the vehicle width direction of the side outer panels are not joined to inner end portions in the vehicle width direction of the roof side rails.

Methods for joining a first blank and a second blank, at least one of the first and second blanks comprising at least a layer of aluminum or of an aluminum alloy or a layer of zinc or of a zinc alloy. The method comprises selecting a first portion of the first blank to be joined to the second blank, and selecting a second portion of the second blank to be joined to the first portion, and welding the first portion to the second portion. The welding comprises using a filler metal laser beam and a welding laser beam, and displacing both laser beams in a welding direction to melt and mix a filler wire material with the melted portions of the two blanks. The present disclosure further relates to blanks obtained by any of these methods and to products obtained from such blanks.

Provided are: an aluminum alloy filler material which is less likely to cause welding cracks and from which a joint portion having excellent strength and toughness is formed, in high-speed joining of an aluminum alloy; an aluminum alloy welded structure manufactured using the aluminum alloy filler material; and a method for joining an aluminum material using the aluminum alloy filler material. The aluminum alloy filler material for high-speed joining according to the present invention is characterized by comprising aluminum including a surface-active element that lowers the surface tension of molten aluminum, wherein the surface-active element is at least one among Ca, Sr, and Ba, and the content of the surface-active element is 0.05-0.50 mass %.

A brazing sheet (1) includes a core material (11) composed of an Al alloy containing 0.40-2.50 mass % Mg; and a filler material (12) composed of an Al alloy containing Mg, 6.0-13.0 mass % Si, and 0.010-0.050 mass % Bi. The filler material is layered on a side of the core material and is exposed at an outermost surface (121). The Mg concentration in the filler material continuously decreases in a direction from a boundary (122) with the core material toward the outermost surface. The Mg concentration (c.sub.1/8) is 0.080 mass % or less at a depth (position P.sub.1/8) from the outermost surface that is ⅛ of the thickness t.sub.f of the filler material (12). The Mg concentration (c.sub.7/8) is 15-45% of the amount of Mg in the core material at a depth (position P.sub.7/8) from the outermost surface that is ⅞ of the thickness t.sub.f of the filler material.

A novel spot welding method for steel sheets and an aluminum alloy sheet, includes stacked sheet materials from a pair of opposing electrodes to join the sheet materials by resistance heating. The pair of opposing electrodes are in pressure contact with both outer surfaces of the sheet sets. The sheet sets include at least a first and second steel sheet, and an aluminum alloy sheet stacked in this order. A first energization step forms a molten pool between facing surfaces of the first and second steel sheets without melting the aluminum alloy sheet. A second energization step causes a melting reaction between facing surfaces of the second steel sheet and the aluminum alloy sheet. The first and second steel sheets are joined via a first nugget. The second steel sheet and the aluminum alloy sheet are joined via a second nugget including an intermetallic compound generated by the melting reaction.