A method for producing a zinc or zinc-alloy coated steel sheet with a tensile strength higher than 900 MPa, for the fabrication of resistance spot welds containing in average not more than two Liquid Metal Embrittlement cracks per weld having a depth of 100 m or more, with steps of providing a cold-rolled steel sheet, heating cold-rolled steel sheet up to a temperature T1 between 550 C. and Ac1+50 C. in a furnace zone with an atmosphere (A1) containing from 2 to 15% hydrogen by volume, so that the iron is not oxidized, then adding in the furnace atmosphere, water steam or oxygen with an injection flow rate Q higher than (0.07%/h), being equal to 1 if said element is water steam or equal to 0.52 if said element is oxygen, at a temperature TT1, so to obtain an atmosphere (A2) with a dew point DP2 between 15 C. and the temperature Te of the iron/iron oxide equilibrium dew point, then heating the sheet from temperature T.sub.1 up to a temperature T.sub.2 between 720 C. and 1000 C. in a furnace zone under an atmosphere (A2) of nitrogen containing from 2 to 15% hydrogen and more than 0.1% CO by volume, with an oxygen partial pressure higher than 10.sup.21 atm., wherein the duration t.sub.D of heating of the sheet from temperature T.sub.1 up to the end of soaking at temperature T.sub.2 is between 100 and 500s., soaking the sheet at T.sub.2, then cooling the sheet at a rate between 10 and 400 C./s, then coating the sheet with zinc or zinc-alloy coating.

A steel sheet for the manufacture of a press hardened part is provided, having a composition of: 0.15%C%0.22%, 3.5%Mn<4.2%, 0.001%Si%1.5%, 0.020%Al0.9%, 0.001%Cr1%, 0.001%Mo0.3%, 0.001%Ti0.040%, 0.0003%B0.004%, 0.001%Nb0.060%, 0.001%N0.009%, 0.0005%S0.003%, 0.001%P0.020%. A microstructure has less than 50% ferrite, 1% to 20% retained austenite, cementite, such that the surface density of cementite particles larger than 60 nm is lower than 107/mm.sup.2, and a complement of bainite and/or martensite, the retained austenite having an average Mn content of at least 1.1*Mn %. Press-hardened steel part obtained by hot forming the steel sheet, and manufacturing methods thereof.

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.

A method for welding a stack of sheets having a plurality of sheets of different materials is provided. In an aspect, the stack of sheets includes an aluminum sheet and a galvanneal steel sheet. In an aspect, the method includes resistively spot welding the galvanneal sheet to a hot-stamped steel sheet placed between the aluminum sheet and the galvanneal sheet, the sheet of hot-stamped steel including stress relief sections. The method further includes placing a metal foil on the aluminum sheet and vaporizing the metal foil to project portions of the aluminum sheet through the stress relief sections of the hot-stamped steel sheet to weld the portions of the aluminum sheet to the galvanized steel sheet. In another aspect, the method includes placing the metal foil on a raised portion of the aluminum sheet and projecting the raised portion of the aluminum onto the galvanneal steel sheet.

Provided is a method for resistance spot-welding at least two overlapping steel sheets. When an electrode force F after an electric current supply is started changes from an initial electrode force Fi to an electrode force F.sub.h.sup.(1) while a lapse from the start of the electric current supply is between 20 ms and 80 ms inclusive, a suspension of the electric current supply of from 20 ms to 60 ms inclusive is started. Then the electric current supply is resumed when the electrode force F reaches an electrode force F.sub.c.sup.(1).

A method for fusing an electrical conductor to a film pad circuit including the steps of: providing an electrically inert substrate having a first surface and an opposing second surface; applying an electrically conductive film to the second surface of the electrically inert substrate; applying an electrically conductive member to the electrically conductive film; placing an electrical conductor on the first surface of the electrically inert substrate; and fusing the electrical conductor to the conductive member.

Methods are provided for manufacturing an orthopedic prosthesis by resistance welding a porous metal layer of the orthopedic prosthesis onto an underlying metal substrate of the orthopedic prosthesis. The resistance welding process involves directing an electrical current through the porous layer and the substrate, which dissipates as heat to cause softening and/or melting of the materials, especially along the interface between the porous layer and the substrate. The softened and/or melted materials undergo metallurgical bonding at points of contact between the porous layer and the substrate to fixedly secure the porous layer onto the substrate.

A method to mitigate liquid metal embrittlement cracking in resistance welding of galvanized steels includes modifying at least one face of a steel member to create a first workpiece by: applying a zinc containing material in a first layer to the at least one face of the steel member; and spraying a second layer of a copper containing material onto the first layer of the zinc containing material. The at least one face of the first workpiece is abutted to a second workpiece of a steel material. A resistance welding operation is performed to join the first workpiece to the second workpiece. A temperature of the resistance welding operation locally melts the zinc containing material and the copper containing material to create a brass alloy of the zinc containing material and the copper containing material.

A method for joining of at least two materials, non-weldable directly to each other with thermal joining processes in a lap joint configuration includes a two step sequence including a first step to apply a thermomechanical or mechanical surface protection layer on the surface of a (stainless) steel substrate and a second step where, a thermal joining process is used to weld the sprayed layer with an applied aluminum sheet without having brittle intermetallic phases in the whole material configuration.

The present disclosure inhibits liquid metal embrittlement (LME) cracking and improves corrosion resistance in a welded joint obtained by spot welding a first steel sheet and a second steel sheet. In the welded joint of the present disclosure, a first plating layer is provided on a surface of the first steel sheet facing the second steel sheet, no plating layer is present on or a second plating layer is provided on a surface of the second steel sheet facing the first steel sheet, and a boundary plating layer is provided between the first steel sheet and the second steel sheet in a range of 0.5 mm from an end part of the corona bond toward an outside of the spot welded part. A higher tensile strength of a tensile strength of the first steel sheet and a tensile strength of the second steel sheet is 780 MPa or more, an area ratio of a MgZn.sub.2 phase at the cross-section of the boundary plating layer is 10% or more, and the first plating layer and the second plating layer satisfy a predetermined Relation I.