Today, the editor of Rong Shijie explained the welding process of spot welding machines for automotive nuts : nut bump welding is a deformation of bump welding. Generally, bumps are punched out on one of two parts and then welded. Due to the current concentration, the shortcomings of nugget translation during bump welding are overcome, so the thickness ratio of the workpiece during projection welding can exceed 6: 1. During projection welding, the current must decrease rapidly as the bumps are crushed, otherwise spatter will occur due to pressure loss, so a projection welding machine with good electrode followability should be used. Projection welding is mainly used for welding low-carbon steels and low-alloy steel stampings. There are many types of projection welding. In addition to plate projection welding, there are also projection welding of nuts and screws, cross projection welding of wires, tube projection welding and plates. T-shaped projection welding. The suitable thickness of parts for projection welding is 0.5 to 4 millimeters. When designing thinner parts, the bump design requirements are strict and a follower projection welding machine is required. Therefore, parts with a thickness of less than 0.25 millimeters are more suitable for bump welding. At present, the application of projection welding is very extensive in the automotive field.
Compared with bump welding, projection welding has the following advantages: First, multiple welding points can be welded in the welding cycle at the same time, which not only has high production efficiency but also has no effect of shunting, so it can be arranged on small parts without being affected by points. Distance restrictions. Second, because the current is dense in the bumps, the current density is large, and the smaller current can be used for welding, and the performance can reliably form a smaller nugget. When bump welding corresponds to a certain plate thickness, it must be smaller than a certain nugget size. Butt welding is more difficult. Third, the position of the bumps is accurate, the size is consistent, and the strength of each solder joint is relatively uniform. Therefore, for a given strength, the size of the bumps can be smaller than that of bump welding. Fourth, due to the large area The electrodes and the bumps are arranged on one workpiece, so the indentation on the exposed surface of the other workpiece can be greatly reduced. At the same time, the large plane electrode has low current density and good heat dissipation, and the wear of the electrode is much smaller than that of bump welding, thus greatly reducing the frequency of electrode replacement. Fifth, compared with bump welding, impurities on the surface of the workpiece such as oil, rust, plating, etc., have less impact on projection welding. The disadvantage of projection welding is the need to design and increase the process and process of punching bumps. Electrodes often also need to be designed and relatively complicated. Due to the need to weld multiple points at a time, high electrode pressure and high-precision high-power pneumatic projection welding machines are often used, and the power of the projection welding machine is often above 150KV.
There are mainly three types of electrodes for projection welding: one, round flat electrode for bump welding, two, large flat head rod electrode, and three, electrode with a certain local contact surface. In order to reduce the indentation on the surface of the workpiece during single-point projection welding of round flat electrode, the contact area of the electrode should not be less than twice the bump. When the large flat-head electrode is used for multi-point projection welding at local locations, the contact surface must be sufficient. Large, to exceed the boundary of all bumps, the amount of excess is generally equivalent to the diameter of a bump. There is a platform at the upper and lower ends of the projection welding machine. This platform is also an electrode of the projection welding machine. It is generally made of brass. Welding molds and fixtures are needed when welding large components. The platform is used to meet the needs of positioning and tightening and conductivity.
The process parameters of projection welding are mainly three aspects: electrode pressure, welding time and welding current. The electrode pressure of projection welding depends on the performance size of the metal to be welded and the number of bumps formed at one time. For a given workpiece material and thickness, the welding time is determined by the welding current and the stiffness of the bumps. Generally, the projection welding time is longer than the bump welding time, and the current is smaller than the bump welding. The welding time of multi-point projection welding is longer than that of single-point projection welding to reduce the difference in heating bumps caused by inconsistent bump heights. The effect of preheating current or current slope control will be better, which can improve the uniformity of solder joints. And reduce splatter.
The current required for bump welding is smaller than that for the same bump, but the current must be able to melt the bump before the bump is completely crushed. As with butt welding, the properties and thickness of the metal being welded are still the main basis for selecting the welding current. For multi-point projection welding, the total welding current is approximately the current required for each bump multiplied by the number of points, but considering the factors such as the bump deviation, the shape of the workpiece, and the secondary circuit impedance of the welder, some adjustments may be required. The shape of the bump is generally round and conical. The diameter and height of the bump are determined according to the thickness of the plate where the bump is located. The height of the bump is generally between 0.2 and 2 mm. Common metal projection welding mainly includes the following: 1, projection welding of low carbon steel; 2, projection welding of plated steel plate; 3, projection welding of plastic surface steel plate. Plastic panels are insulated on one side, so they can only be welded in a single-sided single-point or double-sided double-point manner. In order to protect the veneer from being damaged, it must be soldered for a short time.
Kunshan Rongshijie Intelligent Equipment Technology Co., Ltd. is a high-tech enterprise that develops, designs, manufactures, installs and debugs intelligent welding equipment, spot welding machines and robotic welding systems. Since its establishment, the company has been pursuing "customer first, quality first" service. Purpose, has designed and manufactured intelligent welding equipment for Huaxiang Group, Shandong Xinhua Pharmaceutical, Changchun FAW, Shanghai Volkswagen, Beijing Civil Aviation, Shandong Weichai, Isaar, Zhongrui, Katie and other companies. Excellent quality has won the trust and support of our customers.