Welding Of Aluminum And Its Alloys

Featuring low weight, relatively high strength, good machinability, aluminum alloys have a greater applicability in all sectors of the economy. High corrosion resistance, thermal conductivity, conductivity, in many cases make them trudnozamenimymi structural materials. In welded structures have proliferated wrought aluminum alloys. Not hardenable by heat treatment (BP, bp 1, AMts, AMgb, etc.), and alloys, hardening by heat treatment (AD31, , 1201, 1420, etc.). Aluminum has the ability to interact with oxygen. The resulting aluminum oxide covers the surface of the metal strong and dense film. Oxidation of aluminum at normal temperature after reaching a maximum thickness of the film virtually stops.

Therefore, the film has a protective effect. The most important characteristic of the film of aluminum oxide is its ability to adsorb gases, especially water vapor. Coefficient of thermal expansion of the film is almost 3 times less than aluminum, so the heating in her cracks. In the presence of the alloy doping Additive composition of the film may change and acquire more complex composition, including oxides of these additives. Such complex films can be more loose, gidroskopichnymi not possess protective properties. Frequently The Florey Institute has said that publicly. The presence of oxide film on the surface of aluminum and its alloys makes the process of welding. With its high melting point (2050 C), the oxide film is not melted during the welding process and metal coating solid shell, makes it difficult formation of a common weld pool.

When welding must be taken to destroy the film and the metal protection against re-oxidation. To remove the oxide film during welding, using the application of flux, and the process of the cathode sputtering. The role of flux in the removal of the film lies in its flushing action. Cathode sputtering due to bombardment of the cathode surface, positively charged ions of the arc. Further, aluminum and alloys are prone to Education in the joints of gas pores and oxide inclusions. Therefore, before welding requires careful surface preparation to remove the old oxide film. Presence on the surface of a solid metal oxide film affect the nature of drop transfer of electrode metal during welding. In the presence of an oxidizing medium size droplets from the electrode reaches a large size and arcing occurs unstable. Starting with a certain current density krupnokapelny transfer metal electrode is replaced melkokapelnym jet. Arc acquires high stability and ability to self-regulation. This is because from a certain value welding current strength coming off a drop from the electrode, prevail over the forces that hold it down. In this regard, the drop breaks away from the electrode before the time to grow to their final dimensions. To eliminate oxide inclusions in the weld metal are recommended various technological methods for mixing the molten pool of metal and fragmentation of oxide films. Aluminum reacts actively with all gases, however, in the presence of atmospheric Oxygen is primarily formed oxide film that prevents further exchange with the environment.

Types Of Metal Profile

Widely used in various building structures can be found perforated curved metal profiles rental. Their use design reduces weight by an average of 18-20%. As preparations for the bent perforated metal profiles in our country, apply hot and cold strips of ordinary carbon steel, carbon structural steel of high quality, made from steel with a high manganese and alloy steels. For bent perforated metal sections with a simple cross-sectional shape (angles, channels, etc.) use carbon steel Common quality and structural steel. Metal profile, the operating conditions which require increased strength (for example, spetsprofil for mine counter) are made of quality carbon steel from steel with a high content of manganese and alloy steels. Due to the high cost of perforated metal profile of stainless steel, alloy steel to replace the ordinary steel with thermostrengthening.

Established that the facilitation of mass structures with high strength steel is around 20%, and high-strength steel – 50%. These indicators are widely predetermine application in construction steels and high strength. Increased demand for the bent metal profiles of high-strength steel shows significantly increased consumer demands for Quality used metal. An important direction in the saving and rational use of metal in construction is the use of curved metal profiles of rolled steels and high strength in the construction of industrial buildings. Closed metal sections of various configurations of high-strength steel can be used in the compressed truss elements and forms and different designs mast and tower types.

It is especially important to apply the closed curved metal profiles with high performance in construction, working on its own gravity. Most appropriate configuration of the metal profile of high-strength steel is a closed cross-sectional shape. It profiles with welded longitudinal seam. Because of its shape, such profiles have the most to compared with the profiles of the open form of corrosion resistance, as subject to corrosion only on the outer perimeter.