Energy saving and control technology for resistance welding

Energy saving and control technology for resistance welding

1. Energy saving and control technology of resistance welding

(1) Joint-mounted spot welding machine The most widely used in the automotive industry is the hanging spot welding machine. One workshop is often dozens or hundreds of units, and its capacity is mostly above 100kVA. It has been widely used in the welding of automobile sheets. Applications.

(2) Resistance welding machine At present, the resistance welding machine uses a large amount of AC 50Hz single-phase AC power, which has large capacity and low power factor. Development of three-phase low-frequency resistance welding machine, three-phase secondary rectification contact welding machine (already applied in ordinary spot welding machine, seam welding machine, projection welding machine) and IGBT inverter resistance welding machine can solve grid imbalance and improve Power factor (up to 0? 9 or higher). At the same time, it can further save energy, which is beneficial to realize the microcomputer control of parameters, and can be better applied to the welding of welded aluminum alloy, stainless steel and other difficult-to-weld metals. In addition, the weight of the device can be further reduced.

(3) Control of resistance welding Southwest Jiaotong University developed a rim welding PLC (programmable controller) intelligent controller for the welding of aluminum alloy rims in a factory, and modified the original machine to solve the welding of aluminum alloy rims. Quality issues have improved welding productivity. Later, the same factory developed the PLC seam welding controller, which solved the seam welding problem for the general cleaning requirements. Through the development of these two controllers, it is proved that PLC has stronger anti-interference ability than single-chip microcomputer controller, and it has high flexibility. Compared with industrial computer controller, it is small in size and low in cost. It uses universal single-phase power frequency AC resistance welding machine. Completed difficult butt welding and seam welding work.

2. Gas protection welding technology

(1) The key to the waveform control method of surface tension transition is to complete one droplet transfer with two current pulses, the first current pulse forms a droplet and grows until the droplet is short-circuited with the workpiece; the second The current pulse is a short-time narrow pulse and continuously detects its di/dt, and simultaneously controls the current pulse value to generate an appropriate electromagnetic contraction force to make the droplet neck shrink and thin. Finally, the surface tension of the molten pool is broken and completed. 1 droplet transfer without splashing.

(2) Inverter power supply waveform control Utilizes the good dynamic characteristics and flexible controllability of the inverter power supply, adopts waveform control, and suppresses the current rise at the initial stage of the short circuit to reduce the electromagnetic force hindering the droplet transition when the bridge is formed. And bursting, reducing the splash of large particles, and facilitating the spread of the droplets in the molten pool; when the droplets are spread out in the molten pool, the current is rapidly increased to accelerate the formation of the necking, and then slowly rise to a lower peak. To reduce the splash when the bridge breaks.

(3) New technology of argon arc welding TIG welding has two types of non-melting poles (TIG) and melting poles (MIG), which are used in the welding of non-ferrous metals and high-alloy steels in the automotive industry. In order to improve the formation of CO2 gas shielded welding and reduce splashing, a mixed gas protective weld with 80% or 20% Ar is added.

3. High energy beam heat source welding and processing technology

High-energy beam heat source refers to heat sources (electron beam, ion beam and laser) with energy density greater than 5×108 W/m2. It is used in the automotive industry. The new technologies developed abroad are:

(1) Laser and arc composite heating welding Laser welding can weld narrow and deep welds, and arc welding can weld wide and shallow welds; the former has large investment and the latter has low cost, and the combination of the two characteristics will greatly improve Welding efficiency. The design of the torch for laser and arc composite heating welding is particularly important. The angle between the two heat sources should be as small as possible, and the torch is also designed as a laser + double arc power supply.

This method has been used in steel structures of 4 to 8 mm thick and is intended for use in thinner automotive parts production and aluminum alloy welding. In addition to its application in welding and precision cutting, lasers also form oil-repellent fine patterns or remelted composite layers on the friction surface to improve wear resistance.

(2) Plasma application Plasma welding of argon gas protection has been used in various industries, mainly for alloy steel and non-ferrous metal processing. At present, air plasma cutting has been widely used in the cutting of general steel and non-ferrous metals. The domestic railway passenger car factory has introduced underwater plasma cutting to reduce deformation and improve precision. The engine valve body has long been plasma-welded with a fill ring. In the past ten years, powder plasma surfacing has been greatly developed, and it is possible to carry out fine surfacing of thin layers of small fusion ratio and to weld various special alloy surfaces.