Welding and welders

Welding is the main one-piece metal compound in a modern building, with approximately 80-85% of all welds is performed using manual metal arc welding stick electrode and semi-automatic welding in shielding gas on them and described in this article. Manual arc welding stick electrode is highly versatile and great mobility. It provides an opportunity without the substitution of welding tools and equipment to carry out the seams of different configurations, to weld in any position, including remote locations, allows you to perform work under virtually any weather conditions. It is used in the manufacture and installation of building and technological metal structures; mortgages parts and components, performing installation of compounds of elements of reinforcement concrete structures, welding butt joints of pipes connecting parts and components technology, thermal engineering and pipelines; the manufacture of electrical and plumbing and etc. In the process of manual electric arc welding of the main part of the heat needed for heating and melting the metal is produced by arc discharge, which occurs between the welded metal and the electrode, the energy required for the formation and maintenance of the arc comes from the power source AC or DC . Welding is carried out by the so-called single-piece electrode coated, which are based on a metal wire in the form of rods, for which the method is applied by dipping or molding plaster. The composition of coating includes a variety of substances, from which mainly depends on the formation and weld quality. Manual arc welding is performed single-phase transformers, single and three phase rectifiers or autonomous units. The best quality weld is achieved in the case of three-phase DC (from three-phase rectifiers and generators), while decreasing the metal spatter, improves ignition of the arc, increasing productivity. Electric arc dc burns more stable than the ac, so the quality of the weld obtained by the rectifier is higher than a similar quality weld made from the transformer. This is especially important when welding responsible building designs. However, it should be noted that the welding transformers and rectifiers, for all their diversity of design and technical features include a power transformer having a significant size and weight, which, in turn, significantly increases the weight of the entire apparatus as a whole. Therefore, the most promising trend in the development of modern welding technology, and to a large extent - the equipment for MMA welding - is used in power supplies for arc welding of elements of high-frequency equipment. These welders are called inverters. Compared with those in power transformers and rectifiers, inverters have a much smaller mass, and the best welding properties. Inverters provide a good ignition arc welding process differs little splash. Due to the high stability of the welding current the electrode can be used with virtually no residue, increases the efficiency of the welder. In addition, all inverter sources have stepless welding current in a wide range, which is very important when the ceiling and vertical joints. All these properties make the inverters are technologically efficient and cost-effective in carrying out construction works, welding at height and in confined spaces. Inverter welders are technically complex products, whose production is associated with the solution of a complex technical and organizational problems. Unfortunately, their cost is higher than that of similar power rectifiers (25-50%) and transformers (about half), in addition, transformers and rectifiers to this point in time a bit more reliable. Nevertheless, the obvious technical advantages of the inverters and the trend toward lower costs allow to predict a gradual increase in their share in total electric appliances. Semi-automatic welding in protective gases - a relatively new type of welding, is actively developing in the last 20-25 years. The most common semi-automatic welding in carbon dioxide. With the help of weld metal thickness of 25-30 mm, made of low carbon, alloy and heat-resistant steels. The essence of this type of welding is that the electrode wire with a high content of silicon and manganese is supplied with a constant velocity in the weld area and simultaneously in the same area goes carbon dioxide, which protects the molten or heated by the electrode and base metal from the harmful effects of ambient air. Shielding gas (carbon dioxide) at the same time served from the cylinder through a reducer. Because the shielding is provided by a gaseous medium, rather than molten substance coating the electrode, as with the piece of electrode, a welder can observe and control the entire process of forming the joint. Besides the fact that semi-automatic welding provides high quality seam much easier ignition of the arc, dramatically increases the convenience and speed (ie, efficiency) of work - a welder spared the necessity of changing the electrodes and the stripper joints from the slag. However, the use of gas shielding does not allow for welding work in the wind and drafts, ie, under conditions where the flow of air can blow away the gas shield. This circumstance, as well as "binding" to the gas cylinder somewhat narrowed the scope of semi-automatic welding in CO2 in the building, but in stationary conditions this type of welding to compete with any other type of welding can not. For example, a semi-automatic welding extremely effective in the manufacture of structures with many joints of small length - bars, railings, doors, gates, fences, barriers, etc. In this case, the transition from MMA welding to a semi-automatic welding productivity increases of 2-4 times.