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Representative office of VRTZ is opened in Riga, Latvia.

Manufacturing Method

At the beginning of the production cycle rolled steel enters the slitter and is cut into strips. The slitter design allows cutting of hot-rolled steels from 15 to 36 tons, width from 1000 to 1800 mm, and wall thickness of a strip from 2,0 to 10,0 mm.
One of the important conditions of high quality and pipe output increase is the continuous welding process and required strip edges preparation. The main technological operations are as follows: straightening of strips and strip edges welding in a butt-welder, the use of a modern strip spiral accumulator.
Pipe is formed from a strip on the forming stand and welded with high- frequency current. Alternative high- frequency current conducted through circular inductor instantly heats a narrow area along the strip edges to a melting point. Edges of the strip regularly heated approximately to melting temperature are pressed with rolls and welded without flux.

All the relevant parameters of welding: temperature, speed, current power and voltage are constantly automatically measured and optimized, providing high quality welding seam. Outside and inside flash is removed by flash trimmers. Right after welding, the weld area is normalized through pipe heating up to a required processing temperature, and cooling it within a water and air cooling line. This process stabilizes mechanical properties, the weld area and the base metal structure.
On a sizing stand the continuous pipe is accurately shaped, and its body is straightened. Then, at a certain distance, the pipe is marked with the lot number, strip number, shift, grade, etc. Program-controlled continuous pipe cutting machine moves together with the pipe and cuts it into definite lengths from 6 to 11,8 meters each depending on the purchaser order requirements.

After cutting, inside surface of the pipes . During that process, remnants of inner flash (bead), metal shavings and chips are washed out of the chamber with a jet of highly compressed liquid. The next stage is an additional straightening in a cross roll straighter. Two optional modes (bending or flattening) may be combined, thus increasing the level of straightening. Pipe ends finishing (with or without beveling) is done automatically with the help of an end-cutting machine.
At the end of the production cycle, after a number of quality control procedures (water pressure control at 850Atm., ultrasonic control of pipe ends and magnetic flow control of pipe body), pipes are weighed, measured, marked at buyer's request and tied in hexagonal bundles (ranging from 3 to 6 tons in weight). At buyer's request, the outer surface of pipes may be temporally protected from corrosion with special coating.

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