Design of the hottest spot welding joint

Design of spot welding joint

spot welding usually adopts lap joint and folded joint. The joint can be composed of two or more workpieces with equal or unequal thickness. When designing the spot welding structure, we must consider the accessibility of the electrode, that is, the electrode must be able to easily reach the welding position of the workpiece. At the same time, factors such as edge distance, lap amount, spot distance, assembly gap and weld joint strength should also be considered

edge distance depends on the type, thickness and welding conditions of the metal to be welded. For metals with high yield strength, thin parts or strong conditions, the smaller value can be taken

point distance is the center distance between two adjacent points, and its minimum value is related to the thickness, conductivity, surface cleanliness and nugget diameter of the metal to be welded

the specified minimum point distance mainly considers the influence of shunt. When strong conditions and large electrode pressure are adopted, the point distance can be appropriately reduced. When using thermal expansion monitoring or controllers that can change the current of each point in sequence, as well as other devices that can effectively compensate for the influence of shunt, the point distance can be unlimited

the assembly gap must be as small as possible, because eliminating the gap by pressure will consume part of the electrode pressure and reduce the actual welding pressure. The non-uniformity of the gap will make the welding pressure fluctuate, resulting in a significant difference in the strength of each welding joint. An excessive gap will also cause serious splash when taking its arithmetic mean value. The allowable gap value depends on the workpiece stiffness and thickness. The greater the stiffness and thickness, the smaller the allowable gap, usually 0 mm。

the shear strength of a single weld depends on the area of the nugget at the junction of the two plates. In order to ensure the joint strength, in addition to the nugget diameter, the penetration rate and indentation depth should also meet the requirements. The expression of the penetration rate is: =h/-c 100%. The penetration rate of two plates is only allowed to be between%. The maximum penetration rate of magnesium alloy is only allowed to 60%. Titanium alloy is allowed to 90%. When welding workpieces with different thickness, the minimum penetration rate on each workpiece can be 20% of the thickness of the thin part in the joint, and the indentation depth should not exceed 15% of the thickness of the plate. If the thickness ratio of two workpieces is greater than 2:1, or welding is carried out in inaccessible parts, and when flat head electrode is used on one side of the workpiece, the indentation depth can be increased to%

the strength of spot welded joints under tensile load in the direction perpendicular to the panel is positive tensile strength. Since the sharp angle formed between the two plates around the nugget can cause stress, Electromechanical is the soul of all components from the typical materials used in the automotive industry (it is mainly the concentration of PA family materials, which reduces the actual strength of nugget, so spot welded joints are generally not loaded in this way. Usually, the ratio of positive tensile strength to shear strength is used as the index to judge the ductility of joints. This ratio 7. Stress control speed: 1 (4) the greater the 5mpa/s value, the better the ductility of joints.

the strength of joints formed by multiple solder joints also depends on the spot distance and the distribution of solder joints. When the spot distance is small, the strength of joints will be affected by diversion, Large dot spacing will limit the number of solder joints that can be arranged. Therefore, it is necessary to take into account the spot distance and the number of solder joints in order to obtain the maximum joint strength. It is best to arrange multiple rows of solder joints in a staggered manner rather than in a rectangular arrangement