Here we shall talk about tubes welding and pipe systems welding with small wall thicknesses and not very big sizes of the cross section. Indeed, many industries do not need very long tubes ( cross section of which may be round,oval,square,etc.).Such tubes are usually may be formed from metal strip (with thickness up to 3 mm) that are followed by performing a butt or a flange weld without filler material usage and post cleaning.This process is rather flexible depending on change of tube diameter or cross section configuration. There also may be used many more base materials, sometimes hardly deformed or problematic in over heating, - for which, for example, drawing and hot rolling are impossible or very difficult.In these cases we propose the usage of our technologies and equipment, but their user has to solve problems of cutting metal into strip, of forming it into tube with the corresponding configuration and of moving it under fixed plasma torch (please, see the picture 2 - WELDING OF SHORT TUBES - from our

We have successfully solved another problem - how to weld the received intermediate product.If it is made from low carbon steel, CO2 may be used as a shielding gas.This gas usage, besides of fall in the price (because of argon substitution), provides a speed up to 200 m/h - for a butt weld. Using the same shielding gas, the unique technology has been developed still for flange seams. It permits welding without a filler material and post cleaning low carbon stells but with speeds 3 times less than for the above mentioned butt seam - for material 1,2 mm thick. In both cases only small amounts of argon are used as a plasma forming gas. The walls thickness of welded tubes has usually been of 0,8 - 2 mm.

One of Urals plants used butt welding of such tubes with diameters 90-160mm and lenghts up to 180 mm. We had built for them the simplistic equipment (which is described in our blocked plasma set), and then this plant ordered the additional such sets.The cycle of production of one tube was nearly 5 sec.There were produced large amount of such tubes, saving a lot of money. Appointed Ural's plant used as a prototype a short tube of one of leading Germany company.This tube was welded with a filler material and cleaned after welding. Such welding technology may be claimed by many similar plants in Russia and other countries.For example, plasma equipment and technology may be used for automobile silencers production, which needs short tubes with diameters 30-40 mm and even up to 180 mm.

Model of capillary tube end welding.

Up to now microplasma welding is successfully used for production of very thin-walled small diameter pipes (including capillary tubes) of copper alloys, stainless steel, titanium, zirconium alloys,etc. The technological process consists in coiling 3-40 mm dia pipes from a 0,15-0,5 mm thick strip in a die assembly with their simultaneous welding.The speed of microplasma welding of pipes constitutes 26 - 400m/h. Welded pipes are 10 times cheaper than seamless pipes and display a higher quality due to the absence of differences in thickness of a wall and the corresponding weld. It was known that 2-3 plama torches simutaneous usage permits to increase welding speed more than to 400m/h.

The ends of the above mentioned capillary tubes have to be welded with very high quality. Based on analityc model of such weld, we have found the best way of how to weld these ends without a filler material usage (40), (45).

Our equipment may be also used for welding of single wall stainless steel chimneys and chimneys repair.

Steinless steel chimnays.
[Picture has been taken from ]

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