The present invention provides a resistance spot welding method. A resistance spot welding method according to the present invention in which a sheet combination of two or more overlapping steel sheets is sandwiched between a pair of electrodes and joined together by applying current while applying pressure, the method including a main current application step in which current application is performed with a current I.sub.w (kA), and subsequently, a post-tempering heat treatment step in which after cooling is performed for a cooling time t.sub.ct (ms) shown in formula (1) below, current application is performed with a current I.sub.t (kA) shown in formula (2) below for a current application time t.sub.t (ms) shown in formula (3) below: 800≤t.sub.ct . . . formula (1), 0.5×I.sub.w≤I.sub.t≤I.sub.w . . . formula (2), and 500≤t.sub.t . . . formula (3).

The present invention provides a resistance spot welding method. A resistance spot welding method according to the present invention in which a sheet combination of two or more overlapping steel sheets is sandwiched between a pair of electrodes and joined together by applying current while applying pressure, the method including a main current application step in which current application is performed with a current I.sub.w (kA), and subsequently, a post-tempering heat treatment step in which after cooling is performed for a cooling time t.sub.ct (ms) shown in formula (1) below, current application is performed with a current I.sub.t (kA) shown in formula (2) below for a current application time t.sub.t (ms) shown in formula (3) below: 800≤t.sub.ct . . . formula (1), 0.5×I.sub.w≤I.sub.t≤I.sub.w . . . formula (2), and 500≤t.sub.t . . . formula (3).

An ultrasonic resistance welding apparatus 10 contains a resistance spot welding apparatus 15, a first electrode 16 and a vibrable second electrode 18, the vibrable second electrode 18 in operable communication with an ultrasonic transducer 12, whereby the ultrasonic transducer 12 selectively imparts vibratory energy to the vibrable second electrode 18 based on signals from a controller 32. The vibrable second electrode 18 may be tuned or designed to resonate within 2.5% of an operating frequency of the ultrasonic transducer 12. During operation of the welding apparatus 10, a tip 19 of the second vibrable electrode 18 may be positioned at an anti-nodal point 38 of the vibratory energy and the vibrable second electrode 18 may be attached to the resistance spot welding apparatus 15 at a nodal plane 36 of the vibratory energy. A process for employing the apparatus 10 is also presented.

A welded assembly includes a first object or substrate, an interlayer, and a subsequent layer deposited on the interlayer. The interlayer is an ESD coating deposited on the first object, and the subsequent layer is deposited by ESD on the interlayer. The subsequent layer is made of a different materials from the substrate. Both the interlayer and the subsequent layer are subject to peening. In one case the interlayer has a lower either a lower thermal conductivity or a lower electrical conductivity than the substrate and the subsequent layer. In another example, the subsequent layer has a cermet content of greater than 40% by wt.

A welded assembly includes a first object or substrate, an interlayer, and a subsequent layer deposited on the interlayer. The interlayer is an ESD coating deposited on the first object, and the subsequent layer is deposited by ESD on the interlayer. The subsequent layer is made of a different materials from the substrate. Both the interlayer and the subsequent layer are subject to peening. In one case the interlayer has a lower either a lower thermal conductivity or a lower electrical conductivity than the substrate and the subsequent layer. In another example, the subsequent layer has a cermet content of greater than 40% by wt.

A resistance spot welding method of galvanized high-strength steel with good joint performance, in which three welding pulses are used within one spot welding schedule. The method includes applying a first welding pulse and a second welding pulse which are used for generating a nugget and suppressing the generation of liquid metal embrittlement (LME) cracks, respectively. The first welding pulse generates a nugget having a diameter of 3.75T.sup.1/2-4.25T.sup.1/2 in which T represents a plate thickness. The second welding pulse causes the nugget to grow at a rate less than a rate of growth during the first welding pulse. A third welding pulse, which is a tempering pulse, is applied for improving plasticity of a welding spot.

A method of controlling highly regulated power and frequency from a high frequency power supply system to provide a highly regulated power and frequency to a workpiece load where the highly regulated power and frequency can be independent of the workpiece load characteristics by inverter switching control and an inverter output impedance adjusting and frequency control network that can include precision variable reactor pairs with a geometrically-shaped moveable insert core section and a stationary split-bus section with a complementary geometrically-shaped split bus section and a split electric terminal bus section where the insert core section can be moved relative to the stationary split-bus section to vary the inductance of the variable reactors.

A metallic member bonding device includes a pressurizing unit, a current supply unit, and a deformation suppressing unit. The pressurizing unit pressurizes a first metallic member toward a hole portion of a second metallic member to press the first metallic member therein. The current supply unit supplies a welding current between the first metallic member and the second metallic member. The deformation suppressing unit suppresses deformation of one of the first metallic member and the second metallic member, the one member having a constituent metallic material with at least one of a proof stress and a melting temperature lower than that of the other member, the deformation being in a direction of a cross section crossing a direction of the press-in. Then, the deformation suppressing unit is provided in a region covering at least a plastic flow range in the press-in direction.

A spot welding method including: a main energization step of energizing a pair of opposing electrodes in pressure contact with both outer surfaces of a set of sheets where multiple sheet materials are stacked, thereby to cause melting between facing surfaces of the sheet materials; and a pressing variation step of, prior to the main energization step, causing a pulsation of pressing force applied to the set of sheets from the electrodes. A resin material such as an adhesive or a sealant may be interposed between the facing surfaces of at least a pair of the sheet materials. The period of the pulsation is 0.01 to 0.7 seconds. The amplitude of the pulsation is 10% to 90% with respect to a reference value of the pressing force. The set of sheets may include a first and a second steel sheet, and an aluminum alloy sheet that are stacked in order.

A spot welding method including: a main energization step of energizing a pair of opposing electrodes in pressure contact with both outer surfaces of a set of sheets where multiple sheet materials are stacked, thereby to cause melting between facing surfaces of the sheet materials; and a pressing variation step of, prior to the main energization step, causing a pulsation of pressing force applied to the set of sheets from the electrodes. A resin material such as an adhesive or a sealant may be interposed between the facing surfaces of at least a pair of the sheet materials. The period of the pulsation is 0.01 to 0.7 seconds. The amplitude of the pulsation is 10% to 90% with respect to a reference value of the pressing force. The set of sheets may include a first and a second steel sheet, and an aluminum alloy sheet that are stacked in order.