SU1611486A1 - Method of producing welded tubes - Google Patents

Abstract

The invention relates to the processing of metals by pressure, in particular to the technology for the production of welded reduced pipes. The purpose of the invention is to improve the quality of pipes with a ratio of wall thickness of pipes to a diameter of 0.01-0.015, and expansion of the range by manufacturing pipes from high carbon and low alloy steels. When unwinding, the rolls are butt-welded to form a continuous strip. The strip strip forming is carried out in two stages. At the first stage, the strip is formed in a cold state up to the forming angle of 180-270 °. Forming a profile to 180-270 ° ensures its rigidity and stability when moving in a heating furnace. The profile’s non-closure allows torch jets to be directed both to the inside of the profile and to the outside, which increases the heating efficiency. In the furnace, the open profile is heated to 850-950 ° C, and then deform and weld the edges. The minimum temperature difference between the edges and the rest of the pipe body contributes to improving the quality of the finished pipes and the weld, and reducing the energy consumption for heating the tube stock. Reducing heat loss allows pipes to be reduced with virtually no additional heating. 1 ill., 1 tab.

Description

The invention relates to the processing of metals by pressure, in particular to the technology for the production of welded reduced pipes.

The purpose of the invention is to improve the quality of pipes with a ratio of the wall thickness of pipes to a diameter of 0.01-0.015 and the expansion of the range by manufacturing pipes from high carbon and low alloy steels.

The drawing shows the sequence of operations for implementing the method for producing welded pipes.

The diagram shows the uncoiler 1 rolls, the device 2 butt welding of the ends of the rolls, continuous strip 3. Stand 4 of forming an open profile in a cold state, open profile 5 formed through an angle of 180-270 °. heating furnace 6, burner 7 of jet-torch heating, stand 8 for profile reforming in a hot condition, unit 9 for welding the edges of a molded closed profile, induction furnace 10 for preheating before reduction, mill 11 for reducing a welded pipe, vol saw 12 dl

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cutting the pipe to the measured length and the pipe 13 measuring length,

The essence of the method is as follows.

The operation of forming the strip into a pipe billet is divided into two stages. At the first step, the strip is formed in a cold state in cells with open calibers with a uniformity angle of 180-270 °. Then the resulting open profile is transported through a gas heating furnace, where they heat it up.

The formation of an open profile to 180–270 ° angles ensures its sufficient rigidity and stability of movement in the heating furnace. The range of the forming angle of the open profile 180-270 ° provides the stiffness of the profile without loss of stability and stable movement through the furnace for a range of thin-walled pipes with a ratio of pipe wall thickness to diameter equal to 0.01-0.015. A larger angle of moldedness refers to a smaller ratio.

The profile inviolability allows, during jet-torch heating in gas curing, to direct the jet of the jet to the inside of the profile and to carry out its direct heating both from the inside and from the outside. Compared with the heating of the closed profile of the pipe, the heating efficiency increases, which allows to increase the speed of movement of the profile through the heating furnace or to reduce the number of burners and gas consumption,

Compared to strip heating, an unclosed profile is moved in a furnace without hesitation in height, which also makes it possible to increase the efficiency of jet-torch heating. In addition, an unclosed profile is more rational from the point of view of heat accumulation than a relocatable strip strip.

After the heating furnace, an open profile is formed into a pipe billet and its edges are welded with high-frequency iTO-cells. Since the re-shaping of an open profile is carried out in the minimum number of stands (for example, one), then the heat loss during the conversion is also minimal. Since the profile already formed by 180–270 ° arrives at the additional forming, during the additional forming, a small convergence angle is ensured, which is necessary to obtain a high-quality weld. The welding temperature is 1350-1450 ° С.

The table shows the rationale for the range of angles of formation of an unclosed profile.

The minimum temperature difference between the edges between the edges at a welding temperature of 1350-1450 ° C and the rest of the pipe body also contributes to an increase in the quality of the weld, and consequently, the quality of the finished pipes.

Thus, the proposed method provides a favorable molding pattern and minimal temperature difference between the edges and the rest of the pipe, which, in turn, allows high-carbon and low-alloyed steels to be welded, improve the quality of the weld and finished pipes and reduce energy consumption for heating tubular billet.

Reducing the heat loss (temperature) during molding and welding allows for the reduction of pipes either with no additional heating at all, or with less power.

Example. The pipes with the size 57 X2.8. Mm are made of the strip with the size 315Х 3 mm. The rolls 1 of the strip on the butt-welding machine 2 are joined into a continuous strip 3. The first stage (stage) of forming the strip into a tubular billet is carried out in three cells 4 with open gauges in the cold state. The angle of formation of an unlocked profile is 270 ° C. The unclosed profile 5 enters the heating gas passage sectional furnace 6, equipped with burners 7 of jet-torch heating. When passing through the stump 6, the open profile 5 is heated to 850-950 ° C. The torch jets of the burners are directed both inside the unclosed profile and on its outer surface. Such a heating scheme ensures its high efficiency with minimal fuel (gas) consumption.

At the exit of the furnace, an open profile is formed into a round closed one molding stand 8 with a vertical arrangement of the rolls. The edges of the billet are welded by high frequency currents. The welded pipe is then heated in an induction furnace 10 and reduced with tension in the reduction mill 11,

The presence of tension in the pipe between the reduction mill and the welding stand favorably affects the welding process and the quality of the weld. At the outlet of the reduction mill, the continuous pipe is cut by a flying saw 12 into pipes of 13 dimensional length.

For the initial filling of an open profile, a section of pipe that passes through the furnace, a closed molding gauge is welded to it in front of the heating furnace, is fed into the welding cage, transported through it to a reduction mill. The welding head is turned on at the moment of entering the open profile for re-shaping into the closed caliber of the forming stand.

Claims (1)

Invention Formula Method for the production of welded pipes, butt-welding of individual coils into a continuous strip, forming a strip into a pipe billet using flare heating and subsequent welding of its edges, characterized in that, with the aim of improving the quality of pipes with a ratio of wall thickness of pipes to a diameter of 0.01-0.015, and expanding the range by producing pipes from high carbon and low alloy steels, forming a strip into pipe the preform is carried out in two stages, at the same time, in the first stage, the preform is molded in a cold state up to the forming angle of the tube 180-270 °, after which the heating is carried out, while it is heated to 850-950 ° and carried out closed profile with the subsequent welding of edges. eleven 12