RU2586177C1 - Unit for production of seamless tubes - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: unit comprises at least two rotary piercing mills installed in process sequence and connected by transport facilities. Enlarging dimensional row of tubular billets, possibility of tubes manufacturing, including from hard-to-deform materials using various process layouts is ensured by fact that unit includes annular furnace, blank end centering device connected by transporting roller conveyor, and installed before piercing mills, one of which is made in form of two-roll helical rolling mill, and other is in form of three-roll helical rolling mill with thrust-regulating device, water descaling unit installed before two-roll helical rolling mill, and arranged behind piercing mills continuous rolling and stripper-sizing mills, heating furnace, continuous reducing-stretching mill, refrigerator and manufactured pipes finishing equipment.

EFFECT: invention can be used in production of seamless hot-rolled pipes, including from difficult-to-form steels and alloys at pipe rolling units, mainly with longitudinal rolling reeling machines of continuous type.

1 cl, 1 dwg

Description

The invention relates to the processing of metals by pressure, namely to pipe production, and can be used in the production of hot-rolled seamless pipes, including from hardly deformable steels and alloys, on tube-rolling units, mainly with continuous rolling mills.

A well-known group of tube rolling units, for example, TPA "24.5-127", installed at the factory "Wendsfild steel tube" (Great Britain), in which for piercing a tube billet, piercing mills of helical rolling with three-roll stands are used (Zimovets V.G. Modern production of steel pipes. - Volzhsky: Polygraph Plant, 1998. - S. 180). The drawing coefficient on these mills is less than on piercing mills of helical rolling with double roll stands. The advantage of piercing mills of helical rolling with three-roll stands is a more favorable stress-strain state of the metal in the deformation zone, which makes it possible to flash difficult to deform steels and alloys.

The disadvantages of using piercing mills of helical rolling with three-roll stands are the inability to obtain thin-walled sleeves (with a ratio of diameter to wall thickness of more than 12) and increased axial force on the mandrel. Studies have established that, unlike flashing a workpiece on a helical rolling mill with a two-roll stand, when flashing on a mill with a three-roll stand, self-centering of the mandrel on the axis of the mill does not occur. Therefore, the proportion of the eccentric component that remains on the finished pipes is high in the transverse difference of the stitched sleeves. In this regard, helical rolling mills with three-roll stands have found limited use, mainly for flashing relatively thick-walled sleeves.

A known tube-rolling unit having a piercing mill for screw rolling with a double roll stand, which, to expand technological capabilities, is equipped with a three-roll stand for screw rolling, which allows reduction (reduction with reduction in diameter) of a continuous cross-section of a tube billet (RF patent No. 2361689, B21B 19/04, publ. 07/20/2009).

The described tube rolling unit has technological capabilities that allow working with one profiling of the working tool of a two-roll stand of a piercing mill of screw rolling with different diameters of the tube billet due to its preliminary compression in a three-roll stand. The main disadvantage of this tube rolling unit is its limited technological capabilities in the manufacture of pipes from hardly deformable materials, for example, 13Cr steels, the manufacturing technology of which requires the installation of several piercing stands. In this invention, the three-roll stand is structurally not piercing, which is an obstacle to the so-called "double" firmware blanks on this unit despite the presence of two screw rolling stands in its composition.

Another well-known technical solution of the rolling unit involves the use of a rolling mill with a three-roll stand, which, due to the installation of an additional piercing mechanism, can operate both in the reduction mode (with the mandrel bar retracted to the inoperative position) and in the firmware mode (RF patent No. 2274503, B21B 1/18, B21B 23/00, published on 04/20/2006). In the specified unit, after the helical rolling mill with a three-roll stand, a continuous longitudinal rolling mill is installed, which extends the technological capabilities of the known devices, providing simultaneous production of various products on the same rolling unit: rods, wire and seamless pipes.

However, the universalization of the mill with a three-roll stand does not provide the possibility of continuous “double” flashing of the tube stock, which significantly narrows the technological capabilities of the considered tube rolling unit.

The closest technical solution chosen as a prototype is a tube rolling unit with a continuous rolling mill, which contains at least two piercing mills of helical rolling, installed in series and having the same design of two-roll stands with different profiling of the working tool (RF patent No. 2441722, V21V 19 / 00, published February 10, 2012), while the first mill is actually piercing, and the second serves as an elongator mill.

The described pipe rolling unit for the manufacture of seamless pipes allows for multi-stage (“double”) flashing of the billet, but has a significant drawback - limited technological capabilities, consisting in a narrow range of section sizes of the tube billet. When switching to a larger cross-sectional size, a replacement of the working tool is required, which reduces the performance of the unit and increases the cost of the technological tool.

The technical problem solved by the invention is to expand the technological capabilities of the pipe rolling unit by increasing the size range of the pipe billet and the options for implementing technological schemes.

The problem is solved due to the fact that in the unit for the manufacture of seamless pipes containing at least two screw rolling piercing mills installed in a technological sequence and connected by vehicles and a rolling mill located behind them, mainly continuous longitudinal rolling, according to the invention, one of piercing mills made with a three-roll stand.

The use of one of the piercing mills of screw rolling made with a three-roll stand in the unit for the manufacture of pipes expands the technological capabilities of the unit, allows reducing the workpiece while maintaining the possibility of manufacturing pipes from difficult to deform materials using the “double” firmware technology. At the same time, various variants of technological schemes for manufacturing pipes are realized, the size range of the used pipe billet is significantly expanded, the fleet of the working tool for firmware is reduced, the time lost for its replacement is reduced, which ensures an increase in the productivity of the tube rolling unit.

The proposed technical solution is illustrated in the drawing, which shows a simplified arrangement of the equipment of the unit for the manufacture of seamless pipes.

The unit for the manufacture of seamless pipes contains an annular furnace 1, a scale descaling unit 2, a conveyor roller conveyor 3, a device for centering the end face of a workpiece 4, a piercing two-roll screw rolling mill 5, a piercing three-roll screw rolling mill 6 with a stop-adjusting mechanism 7, continuous rolling 8 and extracting calibration 9 mills, a heating furnace 10, a continuous reduction and stretching mill 11, a refrigerator 12 and pipe finishing equipment 13.

The proposed unit for the manufacture of seamless pipes works, in particular, according to four technological schemes that differ in operations and equipment at the stage of flashing the pipe billet.

In the basic technological scheme I, a pipe billet of a typical cross-sectional size (according to the technological documentation of the unit) after heating in the furnace 1 is moved along the rolling table 3, the centering of the end face on the corresponding device 4 is carried out, the mill scale is passed through the hydraulic sinter unit 2, which is installed in front of the mill with a two-roll stand 5, and then carry out the firmware on the mentioned mill. Next, operations with the sleeve of the same type are carried out for all technological schemes, namely: the obtained sleeve is subjected to deoxidation, successively rolled in continuous rolling 8 and extraction-calibration 9 mills, the resulting pipe is heated in furnace 10, rolled on a continuous reduction and expansion mill 11 to obtain a given cross-sectional size, after which the finished pipe is cooled in the refrigerator 12 and subjected to decoration on the equipment 13.

According to the technological scheme II, the tube billet of an increased cross-sectional size after heating in the furnace 1 is passed through the scale descaling unit 2, it is moved along the rolling table 3 towards the screw rolling mill 6 with a three-roll stand with the thrust-adjusting mechanism 7 withdrawn to the inoperative position and the workpiece is reduced to typical section size. After that, the workpiece is passed through a scale descaling unit 2 and flashing is carried out on a screw rolling mill 5 with a two-roll stand. Then, the above-described cycle of operations of rolling the sleeve, extracting the mandrel, heating, reducing the pipe, cooling and finishing it is repeated.

According to the technological scheme III, a pipe billet from a hardly deformable material after heating in the furnace 1 is passed through a scale descaling unit 2, moved along the roller table 3, the end face is centered on the corresponding device 4 and flashing is carried out on the helical rolling mill 6 with a three-roll stand when it is fixed in the working position -regulating mechanism 7. Then, the obtained thick-walled sleeve is passed through a scale descaling unit 2 and re-flashed on a screw rolling mill 5 with a two-roll stand th. Then, the above-described cycle of operations of rolling the sleeve, extracting the mandrel, heating, reducing the pipe, cooling and finishing it is repeated.

Technological scheme IV is implemented mainly in the case of a long stop (breakdown or major overhaul) of the piercing mill of helical rolling 5 with a two-roll stand. After heating the pipe billet in the furnace 1, it is passed through a scale descaling unit 2, moved along the roller table 3, the centering of the end face is carried out using the device 4, and piercing is carried out on the helical rolling mill 6 with a three-roll stand with the thrust-adjusting mechanism 7 installed. After that the resulting sleeve is subjected to a standard cycle of rolling the sleeve, removing the mandrel, heating, reducing the pipe, its cooling and finishing.

It should be noted that when implementing technological schemes I and II, a piercing mill with a two-roll stand acts as the main piercing mill. In the implementation of technological scheme III, a hole is pierced in a billet with a three-roll stand to produce a thick-walled sleeve, which is finally stitched in a helical rolling mill with a two-roll stand, and the mill acts as an elongator. In the technological scheme IV, a piercing mill with a three-roll stand is used as the main piercing mill. When working according to schemes III and IV, the working tool of both mills has a profiling different from its profiling when working according to technological schemes I and II.

The technical solution described can be implemented in the conditions of SinTZ OJSC. According to the developed concept, pipes for the following purposes can be produced on the unit - tubing, oil and gas, drill, boiler, casing, bearing, general purpose pipes (outer diameter from 60 to 187 mm and wall thickness from 3.5 to 30 mm) coupling sleeve made of steel of grades: 10, 15, 20, 30, 35, 45, 20X, 40X, 09G2S, 10G2, 12GB, 15XM, 30HGSA, 17GS, 12X1MF, 26KHMFA, 32G2, 38G2SF, ShKh15, 15Kh5M, 20X13, 08Kh14MF and their modifications.

The basic technological scheme I involves the use of two nominal sizes of pipe billets: with a diameter of 210 and 156 mm. The first is focused on the manufacture of pipes in the size range of the outer diameter of the finished pipe from 102 to 187 mm, and the second from 60 to 102 mm.

When using a workpiece with a diameter of 210 mm on a piercing mill for rolling with a double roll stand, a sleeve with an external diameter of 239 mm is made with a minimum wall thickness of 14.3 mm (maximum drawing ratio is 3.43), then it is rolled sequentially on a rolling and extraction-calibration continuous mills to pipes with an outer diameter of 208 mm with a minimum wall thickness of 5 mm (maximum total drawing coefficient is 3.17), are heated, rolled in a reduction-stretching mill into a pipe of a finished size, cooled and subjected to dissolved finishing.

When using a billet with a diameter of 156 mm on a piercing mill for rolling with a double roll stand, a sleeve with an outer diameter of 146 mm and a minimum wall thickness of 10 mm is made (maximum drawing ratio is 4.47), then it is rolled sequentially on a rolling and extraction-calibration continuous mills to the outer pipe with a diameter of 111.6 mm with a minimum wall thickness of 3.5 mm (maximum total drawing coefficient - 3.59), which is heated and rolled in a reduction-stretching mill into a pipe of a finished size, after which the resulting pipe is cooled and subjected to finishing.

When implementing technological scheme II, it is assumed to use a blank of a larger cross section, for example, with a diameter of 250 mm. In this case, the billet is initially heated and rolled on a helical rolling mill with a three-roll stand to a circular size of 210 mm in diameter with a drawing coefficient of 1.42, after which the above-described cycle of operations for manufacturing a hot-rolled pipe in the range of outer diameter sizes from 102 to 187 mm is repeated . In the absence of a pipe billet of the required nominal size (156 mm) in the case of pipe manufacturing in the range of outer diameter sizes from 60 to 102 mm, flow chart II provides the desired billet cross section by reducing a larger tube billet, for example 210 mm, in a helical rolling mill with a three-roll stand .

In the manufacture of pipes with an outer diameter from 102 to 187 mm from hard-deformed steel grades, for example 20X13, technological scheme III is used, which provides for rolling a heated tube billet with a diameter of 215 mm in a thick-walled sleeve with an outer diameter of 215 mm and a wall thickness of 50 ÷ with a three-roll stand 60 mm (drawing ratio 1.40 ÷ 1.24). Next, this sleeve is elongated on a helical rolling mill with a two-roll stand into a sleeve with an external diameter of 239 mm and a wall thickness of 14.3 mm (drawing coefficient 2.57 ÷ 2.89), then rolled sequentially on a rolling, extraction-calibration and reduction-extension continuous mills into a pipe of a finished size.

When implementing technological scheme IV, a preheated billet with a diameter of 240 mm is flashed on a helical rolling mill with a three-roll stand in a sleeve with a diameter of 239 mm and a wall thickness of 23 mm (drawing ratio 2.9), after carrying out the above cycle of hot rolling operations on a rolling, extracting gauge and reduction-extension continuous mills receive a pipe of finished size, for example, an outer diameter of 114 mm and a wall thickness of 10 mm When using technological scheme IV, any repair and maintenance work can be carried out on a helical rolling mill with a two-roll stand, and when implementing technological scheme I, it is possible to carry out any repair work on a helical rolling mill with a three-roll stand, which virtually eliminates mill downtime at the stage of flashing the pipe billet.

The proposed design of the unit for the manufacture of seamless pipes allows you to flexibly design various process options and, while maintaining high productivity, provides the expansion of technological capabilities of the equipment by increasing the size range of the pipe billet, as well as the possibility of manufacturing pipes from difficult to deform materials.

Claims (1)

A unit for the manufacture of seamless pipes, containing at least two piercing mills of screw rolling, characterized in that it contains an annular furnace connected by a conveyor roller conveyor, a device for centering the end face of the workpiece, installed in front of the piercing mills, one of which is made in the form of a two-roll screw rolling mill, and the other - in the form of a three-roll helical rolling mill with a stop-adjusting mechanism, a descaling unit installed in front of the two-roll helical rolling mill, and placed Behind the piercing mills there are continuous rolling and extracting and calibration mills, a heating furnace, a continuous reduction and extension mill, a refrigerator and equipment for finishing manufactured pipes.

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