Pulsed Argon Arc Welding in Stainless Steel Sheet
Application of stainless steel pulsed tungsten electrode argon arc welding The welding process of pulsed tungsten arc welding is as follows: Pulsed tungsten electrode argon arc welding is a new welding process developed on the basis of common tungsten electrode argon arc welding. the principle is to maintain a ionization channel of the arc with a smaller base value current, on which a homopolar peak pulsed main arc is periodically added to melt the metal and control the droplet transition. Pulse welding power supply is generally composed of DC power supply plus a thyristor DC switchgear. In stainless steel welding, dc pulsed tungsten electrode argon arc welding process is usually used, when welding austenitic stainless steel foil and metal hose tube billet with thickness less than 1mm, the welding current required is only several amps or ten amps if the welding current is uniform. Although the diameter of the selected tungsten wire electrode can be reduced accordingly, the current density will still become too small, which will cause the local polar spot of the tungsten wire to drift, resulting in the arc instability; if the welding current is adjusted more, it will cause the soldered thin parts to overheat and burn through. In order to overcome the above shortcomings and ensure continuous welding, a process-gas-protected pulse arc welding is developed. Its advantages include: 1) It can precisely control the heat input of the weld to be welded, and overcome the collapse of the weld caused by insufficient tension on the surface of the deposited metal to support the molten pool, thus improving the ability of the weld to resist burning, especially for the thin plate (up to 0.1 m) butt weld. It can achieve single-sided welding double-sided forming without pad and small amount of welding deformation. 2) The heat input and weld retention time can be adjusted under the condition of guaranteed penetration, so it is suitable for welding of various materials with poor weldability, which can reduce the tendency of hot crack, hardening and cold cracking. 3) It is not sensitive to the fluctuation of welding process and welding parameters, and has strong adaptability to all kinds of welding positions, and is suitable for welding in all positions. 4) The weld shape is beautiful, the quality is stable, and the mechanical properties of the welded joints are higher than that of ordinary tungsten arc welding. 5) Depending on the thickness of the welding piece, you can choose whether to fill the welding wire or use helium as a protective gas. According to the pulse frequency, it can be divided into low frequency, intermediate frequency and high frequency pulse argon arc welding. 1。 Low frequency pulsed tungsten arc welding The basic principle of low-frequency pulsed tungsten arc welding is that the size of welding current (the effective amount of DC or AC) varies periodically, and the frequency of the pulse is close to one to several times per second, not more than a dozen times, and the current pulse is supplied by low-frequency pulse. low frequency pulse tungsten electrode argon arc welding is used more in production, for example, welding parameters of austenitic stainless steel sheet butt weld and pipe butt weld with mechanical operation of tungsten pole pulse argon arc welding, see figure 1 and figure 2(for non-filled wire tungsten pole pulse argon arc welding). The DC positive power supply is used for welding. 2。 Intermediate frequency pulsed tungsten electrode argon arc welding intermediate frequency pulse tungsten arc welding is superimposed on dc with 200-500 hz intermediate frequency pulse current, which can increase the arc stiffness, increase the penetration depth to a certain extent, and promote the molten pool metal grain refinement, which can improve the toughness of weld metal. This process is used for welding important components of aerospace engineering. 3。 High frequency pulsed tungsten arc welding technology The difference between high-frequency pulsed tungsten arc welding and low-frequency and medium-frequency pulsed argon arc welding is that the welding current varies at a very high frequency of thousands or even tens of thousands of times per second. Such a high-frequency pulse current makes the magnetic collection effect of the arc relatively strong, so that the conical arc becomes a cylindrical arc, and the compression of the arc is more intense, and the stiffness of the arc is enhanced. not only increases the energy density of the arc but also enhances the penetration of the arc. at the same effective current, it can achieve a larger penetration depth or increase the welding speed at the same penetration. at the same time, the molten pool can be stirred well and the metallurgical properties of the weld are improved, especially suitable for the welding of aluminum and aluminum alloy. the pressure generated by the high-frequency pulse arc also leads to ultrasonic vibration, which can enhance the fluidity of the molten metal. These are beneficial to refine the grain, reduce the weld porosity, but also make the weld shape beautiful. In the case of equal average welding current, high frequency pulsed tungsten arc welding! n connection speed can be doubled than that of ordinary tungsten pole argon arc welding, which will inevitably shorten the residence time of weld metal at high temperature, which is beneficial to improve the corrosion resistance of austenitic stainless steel. However, this kind of welding method has the noise of piercing ear during the welding process, which has certain influence on human health. At the same time, this kind of arc welding machine power supply is expensive, resulting in a small range of applications, in stainless steel high-speed welded pipe production line sometimes adopt this process. There are also hot wire pulsed tungsten electrode argon arc welding, double arc and multi-arc pulsed tungsten electrode argon arc welding.
