A simple and rapid grinding method for tungsten rod
Among many welding methods, TIG and plasma arc welding are developing rapidly. In pressure vessel, boiler and chemical equipment manufacturing industry, the former is widely used in the welding of thin-walled pipe, thick wall pipe and nozzle back weld, stainless steel pipe fittings and forming parts, and the latter is used in aerospace, nuclear energy, electronics, shipbuilding and other industrial sectors. Tungsten electrode is one of their main parts. Due to the high maximum power density (up to 1010w / cm2) and temperature up to 10000 ~ 24000 ° K, the electrode is often burned in the process of use. According to our statistics of tungsten electrode burning in inner hole argon arc welding, one ground tungsten electrode can only weld 50 pipe joints at most. Therefore, welders often encounter the problem of tungsten rod grinding.
At present, our factory and many other factories and mines mainly use grinding wheel to grind tungsten rod by hand. However, this method takes a long time, the shape of tungsten electrode wheat surface is poor, the service life is short, and the workers are injured by dust.
According to the introduction of relevant data, the method of using sodium nitrite to repair and grind tungsten rod is comprehensively developed. Add a small amount of water to sodium nitrite to make it viscous. Then, use gas cutting gun to burn the end of the tungsten rod red, screw the tungsten rod back and forth by fingers, and immerse it into the viscous sodium nitrite. When the end of the tungsten rod is in circular drop shape, the tungsten rod can be lifted up to obtain the round conical tungsten pole with regular shape. If there is a small drill, the tungsten rod can be clamped on the drill chuck, the end of the red tungsten rod can be burned, the drill machine can be started, and the feed handle of the drill bit is pressed down to immerse the tungsten rod into sodium nitrite, so that the effect of grinding the tungsten rod is better.
The tungsten electrode polished by sodium nitrite has good shaping and small eccentricity, which can make the cathode glow point stable and the arc stable combustion, thus prolonging the service life of tungsten electrode. For plasma arc welding, which requires that the electrodes must be completely concentric, it also helps to avoid the generation of double arcs. It only takes about 10 seconds to prepare a tungsten electrode, which reduces a lot of working hours and does not need special equipment.
In addition, the cone angle of tungsten electrode can be adjusted by the length of tungsten rod immersed in sodium nitrite and the lifting speed of tungsten electrode from sodium nitrite. The longer the immersion length, the smaller the cone angle. Because of the reaction of tungsten with sodium nitrite and the droplet shape of tungsten rod end in sodium nitrite, the droplet is pulled when lifting the tungsten rod, so that the tungsten rod has a certain cone angle. The slower the lifting speed is, the longer the pulling time is, the smaller the cone angle is, and vice versa. In this way, the tungsten rod end can be ground into a sharp angle (about 20 ° in low current welding), and the arc is easy to ignite and stabilize. In the case of high current welding, the tungsten rod can be ground into a large cone angle (greater than 90 ° to stabilize the arc and centralize the heating). In addition, in order to prolong the service life of tungsten electrode, the tungsten electrode can be ground into a flat bottom cone.
The tungsten electrode cone made by this method has good shaping and high quality, stable arc, concentrated heat source and good weld quality. Compared with grinding wheel, the processing time of a tungsten electrode with the same diameter can be reduced by about 50 times. Moreover, the dust pollution is reduced and the working conditions of workers are improved.
