This disclosure relates to weldability of steel alloys that provide weld joints which retain hardness values in a heat affected zone adjacent to a fusion zone and which also have improved resistance to liquid metal embrittlement due to the presence of zinc coatings.

Provided is an Al—Fe-alloy plated steel sheet for hot forming, having excellent TWB welding characteristics since excellent hardness uniformity of a TWB weld zone after hot forming is obtained by suitably controlling a batch annealing condition, after plating Al, such that an Al—Fe-alloy layer is formed; a hot forming member; and manufacturing methods therefor.

A method for producing a welded blank (1) includes providing two precoated sheets (2), butt welding the precoated sheets (2) using a filler wire. The precoating (5) entirely covers at least one face (4) of each sheet (2) at the time of butt welding. The filler wire (20) has a carbon content between 0.01 wt. % and 0.45 wt. %. The composition of the filler wire (20) and the proportion of filler wire (20) added to the weld pool is chosen such that the weld joint (22) has (a) a quenching factor FT.sub.WJ: FT.sub.WJ−0.9FT.sub.BM≥0, where FT.sub.BM is a quenching factor of the least hardenable substrate (3), and FT.sub.WJ and FT.sub.BM are determined: FT=128+1553×C+55×Mn+267×Si+49×Ni+5×Cr−79×Al−2×Ni.sup.2−1532×C.sup.2−5×Mn.sup.2−127×Si.sup.2−40×C×Ni−4×Ni×Mn, and (b) a carbon content C.sub.WJ<0.15 wt. % or, if C.sub.WJ≥0.15 wt. %, a softening factor FA.sub.WJ such that FA.sub.WJ>5000, where FA=10291+4384.1×Mo+3676.9Si−522.64×Al−2221.2×Cr−118.11×Ni−1565.1×C−246.67×Mn.

A method for welding at least one hanger to a fork. A friction welding process may be used to create a weld between the hanger and the fork, after which the heat-affected zone (HAZ) may be allowed to cool. Preferably the cooling occurs until martensite is formed, after which a post-tempering current is applied to the HAZ.

A method for producing a precoated steel sheet (1) includes providing a precoated steel strip comprising a steel substrate carrying, on at least one of its faces, a precoating. The precoating includes an intermetallic alloy layer and a metallic alloy layer extending atop the intermetallic alloy layer. The metallic alloy layer is a layer of aluminum, a layer of aluminum alloy or a layer of aluminum-based alloy. The method also includes laser cutting the precoated steel strip so as to obtain at least one precoated steel sheet (1). The precoated steel sheet (1) includes at least one cut edge surface (13). The cut edge surface (13) includes a substrate region (14) and a precoating region (15) and the thickness of the precoated steel sheet (1) being comprised between 1 mm and 5 mm. The laser cutting is carried out such that it results directly in a reduced-aluminum zone (20), extending over the entire height (h) of the cut edge surface (13) and over a length smaller than or equal to the length thereof. The surface fraction of aluminum on the substrate region (14) of the reduced-aluminum zone (20) directly results from the laser cutting operation being comprised between 0.3% and 6%.

A weld joint manufacturing method of the present disclosure includes performing current-passing through an aluminum-plated steel sheet provided with an aluminum plating layer while moving a pair of wheel electrodes relative to the aluminum-plated steel sheet by sandwiching the aluminum-plated steel sheet between the pair of wheel electrodes and rotating the pair of wheel electrodes in a circumferential direction; and welding a part of the aluminum-plated steel sheet, where the current-passing has been performed, and another steel sheet, in an overlapped state of the aluminum plating layer with the other steel sheet.

A method of processing a joint, including forming an actively brazed joint in a vacuum furnace, wherein the actively brazed joint is formed from at least two components coupled together by a volume of a joining metal alloy having a solidus temperature and a liquidus temperature, wherein the joining metal alloy is heated to a first temperature that is higher than the liquidus temperature in the vacuum furnace. The method also includes cooling the actively brazed joint to a second temperature lower than the solidus temperature, and maintaining the second temperature within the vacuum furnace for a predefined duration to form at least one region of segregated crystallization within the volume of the joining metal alloy, the at least one region of segregated crystallization is configured to increase the liquidus temperature of a layer of brazed metal, formed from the joining metal alloy, between the at least two components.

The invention relates principally to a welded steel part with a very high mechanical strength characteristics obtained by heating followed by hot forming, then cooling of at least one welded blank obtained by butt welding of at least one first and one second sheet consisting at least in part of a steel substrate and a pre-coating which is constituted by an intermetallic alloy layer in contact with the steel substrate, topped by a metal alloy layer of aluminum or aluminum-based alloy. This welded steel part claimed by the invention is essentially characterized in that the metal alloy layer (19, 20) has been removed from the edges (36) in direct proximity to the weld metal zone (35), while the intermetallic alloy layer (17, 18) has been left in place, and in that over at least a portion of the length of the weld metal zone (35), the ratio between the carbon content of the weld metal zone (35) and the carbon content of the substrate (25, 26) of either the first or the second sheet (11, 12) having the higher carbon content (Cmax) is between 1.27 and 1.59. The invention likewise relates to a method for the fabrication of a welded steel part as well as the use of this welded steel part for the fabrication of structural or safety parts for automotive vehicles.

This disclosure relates to weldability of steel alloys that provide weld joints which retain hardness values in a heat affected zone adjacent to a fusion zone and which also have improved resistance to liquid metal embrittlement due to the presence of zinc coatings.

The invention relates to a method for producing components from sheet metal, wherein at least one patch sheet (2) is placed on a base sheet (1) to form a material doubling and is positionally securely fixed, the component unit thus formed, comprising base sheet (1) and patch sheet (2), is heated to a temperature suitable for hot forming and is then hot-formed to form the component and, preferably subsequently or simultaneously, is subjected to partial or total cooling or quenching for the purpose of a specific structure conversion, wherein, for the purpose of improved corrosion protection, the base of sheet (1) in the contact region of the patch sheet (2), or the patch sheet (2) on the side thereof facing the base sheet (1), or both base sheet (1) and patch sheet (2) in the corresponding area are coated with an anti-corrosion coating (6) that is resistant to the temperatures occurring during the hot forming, before the patch sheet (2) is placed on the base sheet (1).