A multi-tiered weld program that is effective in resistance spot welding of dissimilar materials is disclosed. The process is repeatable across a multitude of grades/thicknesses, and number of sheets of conductive materials, and is possible to perform with traditional weld tooling and electrodes. Different size/different material/different contact face geometries weld surfaces are used to balance thermal properties of the materials, and the process is designed to create a small, consistent Intermetallic Compound (IMC) that is effective in holding two different conductive materials together with a high level of strength that is suitable for industrial mass production. The multi-tiered resistance spot weld process uniformly preheats, welds, and cools the samples to control the formation of the IMC that is formed therein.

A resistance welding control system includes an electrode displacement detector, a temperature estimation information acquiring unit, and a temperature estimation unit. The electrode displacement detector detects a positional displacement between opposite electrodes while the electrodes are supplying electricity between the electrodes to perform resistance welding of welding members held between the electrodes. At least one of the electrodes is movable toward or apart from the other electrode. The temperature estimation information acquiring unit acquires at least an interelectrode voltage, a current density in the welding members, and a physical property value of the welding members as temperature estimation information to be used to estimate a temperature of a welding portion between the welding members. The temperature estimation unit estimates the temperature of the welding portion based on the temperature estimation information and the positional displacement while at least either one of the positional displacement and the interelectrode voltage is stabilized.

A resistance spot welding method includes sandwiching metal plates put on top of one another between a pair of electrodes and performing resistance spot welding sequentially on a plurality of welding points close to each other on the metal plates by performing a current application between the electrodes so as to join the metal plates to each other. A welding current value to form a welding nugget at a welding point to be subjected to the resistance spot welding second or later among the welding points is set to be higher than a first welding current value to form a first welding nugget at a first welding point to be subjected to the resistance spot welding first among the welding points.

A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in subsequent current passage in the test welding, current passage is performed by constant current control under a condition: 0.5≤Vtp/Vtm≤2.0 when tc<800 ms; 0.5−0.3×(tc−800)/800≤Vtp/Vtm≤2.0−0.5×(tc−800)/800 when 800 ms≤tc<1600 ms; and 0.2≤Vtp/Vtm≤1.5 when tc≥1600 ms, where Vtm is an average value of a voltage between the electrodes in main current passage in the test welding, and Vtp is an average value of a voltage between the electrodes in the subsequent current passage in the test welding, and wherein in main current passage in the actual welding, adaptive control welding is performed, and in subsequent current passage in the actual welding, current passage is performed by constant current control under a condition: 0.8×Itp≤Imp≤1.2×Itp, where Itp is a current in the subsequent current passage in the test welding, and Imp is a current in the subsequent current passage in the actual welding.

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.

A resistance spot welded joint of an aluminum material is obtained by joining a stack of a plurality of aluminum materials by spot welding. A nugget formed by the spot welding includes a solidified part of the aluminum materials and a shell having a different solidification structure from the solidified part. The shell is formed annularly in a cross-section of the nugget in a stacking direction of the aluminum materials. The solidified part and the shell are alternately arranged from an outer edge of the nugget toward a nugget central part.

A resistance spot welded joint of an aluminum material is obtained by joining a stack of a plurality of aluminum materials by spot welding. A nugget formed by the spot welding includes a solidified part of the aluminum materials and a shell having a different solidification structure from the solidified part. The shell is formed annularly in a cross-section of the nugget in a stacking direction of the aluminum materials. The solidified part and the shell are alternately arranged from an outer edge of the nugget toward a nugget central part.

A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in the test welding, 0.2≤Vtp/Vtm≤1.5 is satisfied where Vtm is an average value of a voltage between the electrodes in main current passage in the test welding and Vtp is an average value of a voltage between the electrodes in subsequent current passage in the test welding, and in each of main current passage and subsequent current passage in the actual welding, a time variation curve of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are stored in a corresponding one of the main current passage and the subsequent current passage in the test welding are set as a target, and adaptive control welding is performed to control a current passage amount according to the target.

The present disclosure generally relates to a welding machine adapted for performing a spot welding process on a workpiece, wherein the welding machine is specifically adapted for automatically applying pre-conditioning a welding pulse portion to the workpiece prior to performing the spot welding process. The present disclosure also relates to a corresponding method and computer program product.

The present disclosure generally relates to a welding machine adapted for performing a spot welding process on a workpiece, wherein the welding machine is specifically adapted for automatically applying pre-conditioning a welding pulse portion to the workpiece prior to performing the spot welding process. The present disclosure also relates to a corresponding method and computer program product.