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1. Resistance welding energy saving and control technology
(1) Conjoined hanging spot welding machine The most widely used in the automotive industry is the hanging type spot welding machine. A workshop is often tens or hundreds of units, and its capacity is mostly above 100 kVA. It has been widely used in the welding of automotive sheet metal. Applications.
(2) Resistance welding machine At present, the resistance welding machine uses a large number of single-phase AC power sources with AC 50Hz, which has large capacity and low power factor. Development of three-phase low-frequency resistance welding machine, three-phase secondary rectification contact welding machine (which has been applied in ordinary spot welding machines, seam welding machines, and projection welding machines) and IGBT inverter resistance welding machine, which can solve grid imbalance and increase Power factor (up to 0?9) problem. At the same time, it can further save energy, which is conducive to the realization of the parameters of the computer control, can be better applied to the welding of aluminum alloys, stainless steel and other welding difficult welding. In addition, the equipment weight can be further reduced.
(3) Control of resistance welding Southwest Jiaotong University developed a rim washer PLC (programmable controller) intelligent controller for welding aluminum alloy rims in a factory. The original machine was modified to solve the welding of aluminum alloy rims. Quality issues increase welding productivity. Afterwards, a PLC seam welding controller was developed at the same factory to solve the problem of seam welding for general cleaning requirements. Through the development of these two controllers, it is proved that PLC has stronger anti-interference ability than monolithic microcomputer controllers and can be used for high performance; it is smaller in size and lower in cost than the IPC controller, and it uses a 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 the surface tension transition is to complete a droplet transfer with 2 current pulses. The first current pulse forms a droplet and grows until the droplet short-circuits with the workpiece; The current pulse is a short-term, short pulse and constantly detects its di/dt, and at the same time controls the current pulse value to generate an appropriate electromagnetic contraction force, so that the neck of the droplet shrinks, and finally the surface tension of the molten pool is pulled off, completing One droplet transition without splashing.
(2) Inverter power waveform control utilizes good dynamic characteristics and flexible controllability of the inverter power supply. Waveform control is used to suppress the current increase in the initial stage of the short circuit phase to reduce the impediment of the droplet transfer when the electromagnetic force is just forming a small bridge. And breaking, reducing large particles splashing, and conducive to the droplets spread in the pool; when the droplets spread in the pool, the current is increased rapidly to accelerate the formation of necking, and then slowly rise to a lower peak Causes the splash to decrease when the bridge breaks.
(3) Argon arc welding There are two types of non-melting (TIG) and melting (MIG) argon arc welding. They are used in the welding of nonferrous metals and high alloy steels in the automotive industry. In order to improve the formation of CO2 gas shielded arc welding and reduce spattering, a mixed gas shielded arc welded with 80% or 20% Ar is used.
3. High energy beam heat source welding and processing technology
The high-energy beam heat source refers to a heat source (electron beam, ion beam, and laser) with an energy density of more than 5×10 8 W/m 2 , and is used in the automotive industry. New technologies developed abroad are:
(1) Laser and arc combined heat welding Laser welding can weld narrow and deep welds, and arc welding can weld wide and shallow welds; the former has a large investment, the latter has a low cost, and the combination of the two will greatly improve Welding efficiency. The design of the welding torch for laser and arc combined heat welding is particularly important. The angle between the two heat sources should be as small as possible. The torch is also designed as a laser + double arc power source.
This method has been used in 4-8mm thick steel structures and is intended for use in thinner automotive parts production and aluminum alloy welding. In addition to the application of lasers in welding and precision cutting, it also forms oil-retaining patterns or remelted composite layers on the friction surface to improve wear resistance.
(2) Application of plasma Plasma-arc cutting with argon protection has long been applied in various industries, and is mainly used for the processing of alloy steel and non-ferrous metals. At present, air plasma cutting has been generally applied to the cutting of general steel and non-ferrous metals. The domestic railway passenger car plant has introduced underwater plasma cutting to reduce distortion and improve accuracy. The valve body of the engine has already been filled with plasma-filled rings. In the past decade, the development of powder plasma surfacing has made great progress. It is possible to carry out fine surfacing of thin layer materials with a small fusion ratio, and it can deposit various special alloy surfaces.
Venous cannula is also a deep venous puncture catheter. The method is to select the appropriate puncture site and insert the needle under the skin, and insert the needle with negative pressure until the dark red blood is absorbed, indicating that the needle has entered the vein, and the guide wire is inserted. Withdraw the puncture needle to leave the guide wire in the blood vessel, and then insert the venous catheter that needs to be indwelled along the guide wire, then exit the guide wire, inject diluted heparin saline and fix the catheter, the deep venous catheterization is completed. The veins for puncture and catheterization are usually selected clinically, including the subclavian vein, internal jugular vein, and femoral vein. After the puncture catheter is indwelled, attention must be paid to the care of the puncture site to avoid infection with thrombus or catheter falling off.
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