High-tech argon welding
A lot of products used in everyday life and inindustry, is made of metals and their alloys. To obtain a durable and high-quality all-in-one connection of metal products, the best way is to weld by melting. Among the methods that are comparatively cheap and which make it possible to obtain a decent quality of the welded joint, argon welding can be called. This is one of the types of electric arc welding. It is carried out by an arc burning between non-consumable (more often - tungsten) electrode and a metal workpiece. The electrode is fixed in the burner, and the filler material supplied to the melting zone from the outside is not part of the electrical circuit. The edges of the base metal and the filler material are melted by the arc plasma and form a seam. An inert argon gas is fed to the welding bath through the burner nozzle in an automatic mode. It practically does not enter into chemical interaction with the molten metal and gases formed in the arc zone. Due to the fact that Ar is 38% heavier than air, it descends downward, displacing atmospheric gases from the weld zone, thereby protecting it and preventing the occurrence of defects in the welded joint. To reduce the porosity of the seam, 3-5% of oxygen can be added to the argon, then the protection of the metal is more active.
Argon arc welding provides the formation of a seamby large-drop or jet transfer of metal. The large-drop transfer results in a large spray and does not allow achieving a stable welding process. The technological characteristics of the weld obtained in this case are worse than in semiautomatic welding in CO2. The jet metal transfer provides argonwelding at welding currents above I sv = 260A. The welding process becomes stable, the quality of the seam increases. But the use of such a high current strength often does not meet the technological requirements for the process (for example, it unnecessarily heats the workpiece and alters the properties of alloyed metals). Therefore, it is advisable to use impulse power sources. This allows us to proceed to the jet transfer of the metal already at currents close to I s = 100 A.
If a direct current is applied, at the cathode andan uneven release of heat occurs (about 70% - at the anode). Therefore, for steels, titanium alloys and other metals, except for aluminum, the polarity is used straight to maximize the melting of the billet. Welding of Al is performed on alternating current, which allows to destroy the oxide film without overheating the product.
For welding parts made of stainless steels,aluminum and its alloys, argon-arc welding with a consumable electrode can also be used. But the field of its application is much narrower than with tungsten electrodes.
It finds application both manually andautomatic argon welding. Its advantages include the ability to join small products without filler materials, work with one-way access to the surfaces to be treated. The method is excellent for welding non-rotating pipe joints from metal. The weld being formed has good technological parameters. Arc argon welding is the technology most suitable for joining alloy steels, titanium alloys, aluminum.
Because of the relative simplicity of the process, argonself-welding is available not only to professional welders. In this case, due to the small amount of work performed, the low productivity of the process is not so important, which limits its use in large-scale production.
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