A method for resistance welding includes performing a plurality of resistance welding processes during which welding electrodes are pressed against respective welding spots of respective workpieces. The welding electrodes are energized with a respective welding current for each of the plurality of resistance welding processes, and for each of the plurality of resistance welding processes, a respective at least one characteristic value that characterizes a quality of the welding is determined. A statistical analysis of the determined at least one characteristic value for each of the plurality of resistance welding processes is performed, and based upon the analysis, an adaptation of the prescribed welding parameters is determined.

A resistance spot welding device that joins predetermined parts to be welded includes: a storage configured to store a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume in test welding that precedes actual welding; and an adaptive controller and an electrode force controller configured to, in the case where the time variation of the instantaneous amount of heat generated per unit volume in the actual welding differs from a time variation curve stored as the target value, respectively control the current or a voltage during current passage and the electrode force to the parts to be welded to compensate for the difference within a remaining welding time so that the cumulative amount of heat generated per unit volume in the actual welding matches the cumulative amount of heat generated per unit volume stored in the storage.

A joining device for connecting a metal member and a resign member with a metal fastener including a penetrating tip comprises: a cylindrical nosepiece; a high frequency electromagnetic induction coil around the nosepiece; an electrode punch for pressing the fastener into the resign member; a electronic chopper for producing a high frequency current; a high frequency power supply for supplying an induction current to the induction coil; a welding power supply for supplying a welding current between the electrode punch and the metal member; a contact detector for sensing when the fastener tip touches the metal member; and a switching unit for automatically switching from the induction current to the welding current when the contact detector senses that the tip has contacted the metal member.

Provided is a setting assistance device capable of informing that which welding condition should be corrected with a value as the limit in order to achieve the target quality.

In a setting assistance device (40) of a welding condition which is a condition in welding, an input receiving unit (42) accepts designation of the target quality in welding, and a welding condition information output unit (44) outputs an item of a welding condition to be corrected to achieve the target quality, and limit information indicating a limit of a value which can be taken by the item of the welding condition to achieve the target quality, in accordance with the acceptance of the designation of the target quality by the input receiving unit (42).

A method and an apparatus for determining the temporal curve of the voltage (u.sub.e(t)) at the electrodes (3) of a spot welding gun (1) during a spot welding process as an indicator of the welding quality, wherein the electrodes (3) are fastened to gun arms (2) that can be moved relative to each other are provided. The apparatus includes a device (9) for measuring a measuring voltage (u.sub.m(t)) between the electrodes (3), that measuring device (9) being connected to measuring leads (6) extending along the gun arms (2), and further includes a compensating coil (7) for measuring a compensating voltage (u.sub.k(t)) for compensating measuring errors within measuring leads. In order to determine the temporal curve of the voltage (u.sub.e(t)) at the electrodes (3) of the spot welding gun (1) during a spot welding process as precisely as possible, the device (9) for measuring the measuring voltage (u.sub.m(t)) and the device (10) for measuring the compensating voltage (u.sub.k(t)) are designed as separate units for separate detection and are connected to a device (11) for processing the detected values.

A resistance welding apparatus includes a welding tool with a welding electrode configured to contact a component. A welding transformer is configured to feed an electric current to the welding tool and a control device is configured to control a polarity of welding transformer by transmitting polarity information to the welding transformer such that a polarity of the welding transformer is switchable. A circuit including two transistors is operably connected in series between the welding tool and an output of the welding transformer and a polarity one of the transistors is rotated relative to the other transistor, such that a polarity of a welding voltage at the welding electrode is switchable with the switching of the polarity of the welding transformer, and such that a polarity of a welding current at the welding transformer is switchable with the switching of the polarity of the welding transformer.

A resistance spot welding device that joins predetermined parts to be welded includes: a storage configured to store a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume in test welding that precedes actual welding; and an adaptive controller and an electrode force controller configured to, in the case where the time variation of the instantaneous amount of heat generated per unit volume in the actual welding differs from a time variation curve stored as the target value, respectively control the current or a voltage during current passage and the electrode force to the parts to be welded to compensate for the difference within a remaining welding time so that the cumulative amount of heat generated per unit volume in the actual welding matches the cumulative amount of heat generated per unit volume stored in the storage.

The present application provides a method for weld quality detection comprising: applying a detection voltage to a weld during a cooling phase after the cut-off of the metal material welding current; detecting a detection current corresponding to the detection voltage applied to the weld; calculating continuous values of resistance of the weld during the cooling phase based on the detection voltage and the detection current; and determining whether a welding defect exists at the weld based on an initial value, an intermediate value, and an end value of the resistance. By measuring and analyzing the resistance variation in the melting core cooling phase and using the relationship between the resistivity of metal material and temperature to indirectly characterize the heat stored in weld nugget, the detection and evaluation of the quality of resistance spot welding can be realized.