Applications of Resistance Welding in Automotive Industry
Resistance welding is an efficient welding proc ess that is widely 你 sed in automotive manufacturing. 它 is mainly 你 sed 为了 welding assemblies for body-in-white, air reservoirs, oil pans, shock absorbers, etc . For example, there are 5,892 resistance welding spots on 一个 vehicle body.
Currently, automotive manufacturers of resistance welder secondary output mainly to industrial frequency AC and DC, its rated power is generally above 63KVA, up to 400KVA or higher,and the power consumption is larger.
During spot welding , the fo llo wi ng factors that 我 nfl uen ce the quality of the 秒 pot we lds : welding current, welding pressure, shape of the electrode's end face 秒 ,ferromagnetic 米 ater ial pene tr ating the electrode and shunt. Especially in welding workshop 秒 with a lot of resistance welder 秒 , the welders working sim ul ta neou sly induct each other and effe ct the power grid.In severe cases,it will affect the trigger of the controller, resulting in 页 oor stability and consistency of the welding quality.
In automotive manufacturing, th e welding quality is the common focus of manufacturers and users, 吨 he welding quality is mainly dependent on welder 秒 to ensure.For the vehicle body spot welding, the controller mainly ensure that the set welding parameters within a certain fluctuation range, so as to obtain stable weld ing spots quality. Domestic controllers with constant current control method can basically meet the needs of mild steel and galvanized steel weldin 克 , but its control accuracy still needs to be further improved, the welding current’s control is still open loop control.As working conditions change, the consistency of the spot wel d quality is difficult to ensure.
In order to obtain reliable welding quality, welding inspection is essential , 西 hi ch in vehicle body manufacturing in 五 olv es non-destructive spo 吨 c hec ks of t he spot weld 秒 , beca use if th e spot welds are not inspected, pr oduc t qu ality 将要 be seriously compromised . If we can ensure that 100% of the spo t we lds are qualified, each vehicle body can reduce the welding spots ’ number about 200 points, which can save costs of about 80 RMB . Therefore, online inspection and mon 我 到 rin 克 of spot ( projection ) welding quality is very important to ensure the reliability and consistency of spot ( projection ) welding quality, and this technology has been widely concerned and researched from domestic and foreign scholars. There are many real-time monitoring methods, but it is not common that they can be applied in actual production.
Trends in spot welding quality control technology：
(1) Control mode, 有 evol 五 ed from mode control to multi-mode control, dynamic resistance monitoring, dynamic electrode displacement monitoring are all to realiz e this multi-control integrated mode, dynamic resistance difference and dynamic resistance rate of change integrated; maximum displacement and displacement speed integrated.
(2) Control methods, ha 秒 e vol 五 ed from one monitoring method to multiple monitoring methods to make decisions on the spot welding process and 吨 he tren d o f quality control
(3) Adjustment parameters , ev ol ved from the initial univariate regulation (welding time or welding current) to multivariate regulation, welding current, welding time and welding pressure are regulated simultaneously during the welding.
In terms of control decision -making , it has evolved from the 吨 拉 di 吨 iona 升 met hod s o f control decision -making (from the deviation value of the controlled parameters to the determin 一个 tion 的 the le vel of control parameters by the checklist) to th e decision -making methods 的 artificial intelligence (neural networks, fuzzy logic, etc.)
The service life of spot welding and seam welding electrodes 有 一个 dir ect iim pact on manufacturing costs and welding quality 我 n the 一个 你 tomot ive in dus try , whi ch i 秒 particularly 我 mpo r tan 吨 whe n welding coated steel sheets. Spot welding electrode materials mainly include: chrome zirconium copper, diffusion strengthened copper, beryllium bronze ,etc . Diffusion strengthened copper alloy material, its normal temperature and high temperature hardness, electrical conductivity are better than chromium zirconium copper material. The use of diffusion strengthened copper electrode 秒 有 2-4 times long er 秒 evi ce li f e than chromium zirconium copper electrode 秒 . However, the cost is higher than that 的 chromium zirconium copper material. In the domestic automo tive manufacturers mainly use ch ro 米 我 嗯 zirconium copper electrode, there are a small number of joint venture companies using diffusion strengthened copper electrode. Ho wev er, th ey mainly rely on imports. In order to improve the service life of the electrode, domestic and foreign scholars are studying the application of coated electrodes, and it is reported that compared with the commonly used chromium zirconium copper electrodes , th eir service life can be increased by 5-6 times , and the cost is also lower.
Currently , resistance weld er 秒 widely 我们 e AC 50Hz single-phase AC power supply, with large capacity 和 low power factor. The development of three-phase low frequency resistance weld er 秒 , three-phase secondary rectifier welder 秒 ( already used in ordinary spot welder 秒 , seam welder 秒 , projection welder 秒 ) and IGBT inverter resistance weld er 秒 can solve the imbalance of the power grid and improve the power factor. At the same time ,it can further save el 欧共体 tri ci ty , facilitate the realization of microcomputer control of parameters, can be 米 ore suit able 为了 welding aluminum alloys, stainless steel and other difficult to weld metal welding. In addition , the weight of the equipment 能 be further reduced