In High Frequency Welded (HFW) pipe production process, hot rolled steel coils are fed with a high capacity accumulator in order to achieve continuous welding. Coil edges are milled using carbide cutters in order to assure a high quality weld. Coils are then formed by cold forming method using a set of cage rolls and fin passes, and then joined using high frequency currents using induction or alternatively conduction methods.
The coil edges, which reach welding temperature through the resistance shown by steel to the applied electrical current, are butted together and welded. This method does not use any filler material for the weld to take place. Immediately subsequent to welding, internal and external burrs are removed in order to achieve a uniform surface.
Post weld heat treatment facilities are used in order to temper martensitic structure created by the welding process. As a result of applied controlled normalization process, the weld area achieves a fine grain structure with required ductility.
The pipe string is brought to the exact required and precise outside diameter and straightness by passing through a set of sizing rolls. The pipe string is finally cut-to-length by a flying cut-off operating at the same speed as the pipe. Following beveling, hydrostatic testing, non-destructive testing, the pipes are subject to final inspection for the compliance to customer requirements.
Starting from incoming control up to the final inspection stage; entire process is monitored and supported by computerized system. Traceability is achieved by input controls and barcodes through entire production lines.
HFW welded steel pipes are widely preferred in Oil, Natural Gas, Water and other liquids transportation and distribution lines, heating, cooling, ventilation piping and steel structures for construction and other general purposes by means of precise production tolerances and high capacity manufacturing method.
Besides standard API diameters, Umran also manufactures 325 mm., 377 mm. and 426 mm. outside diameters specified in Russian standards.
Umran is able to manufacture and supply high frequency welded pipes up to 16 m. in unit length.