RU2351422C1 - Method of production of steel seamless pipes of major diameter - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metal deformation process field. Particularly it relates to manufacturing technique of steel seamless pipes. Method includes heating of solid round, its and extrusion toolage coating by grease lubricant on the basis of glass, blank stitching and pipes pressing, separating of received pipe from butt-end and its disposal from matrix. Stitching and pressing are implemented on vertical hydraulic trumpet extruding-press in one operating cycle of the press. Blank is stitched in container by press mandrel with preliminary premolding of the blank. Pipe is pressed by direct method with metal outflow under a force of compression ram with pressure pad through the matrix down with elongation ratio no less than 1.4. Grease lubricant contains graphite in volume ratio with glass (1:4)…(1:5).

EFFECT: invention provides operations unification of blank stitching and pipe pressing, design simplification, downsizing and mass reduction of the press, process productivity improvement of pipes pressing and waste metal reduction while stitching and pressing.

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Description

The invention relates to the field of metal forming, and in particular to a technology for the production of seamless steel pipes.

The most effective processes for the manufacture of large-diameter seamless steel pipes are those based on the use of hot pressing (extrusion). Compared with other well-known methods (forging and machining, flashing and broaching), it provides higher accuracy of the size and shape of the pipes obtained, the possibility of manufacturing long pipes, pipes of medium and high alloy steels, bimetallic pipes, including with a clad inner layer from stainless steel; higher process performance and less metal waste.

One of the analogues of the claimed invention can be a technological process for the production of steel pipes with a diameter of up to 1200 mm on vertical hydraulic extruding presses with an effort of 30,000 tf and 35,000 tf manufactured by Cameron (Avery D. How Cameron vertically extrudes seamless pipe. // Metal Progress, 1977, v. 3, No. 2, pp. 52-57). Another analogue is the production of pipes with a diameter of up to 1400 mm on a vertical extruding press with a force of 45,000 tf according to a later project developed in the USSR in 1980-90 (Starikov BC et al. Technology and tool for the production of large diameter steel pipes by extrusion. / / Forging and stamping. 1988, No. 10, p.14-17).

The manufacture of pipes according to the above analogous methods is characterized by the use of the direct pressing method with the pipe flowing up and separating it from the pressure switch using a die cutter. During the pressing process, the press stamp installed on the press table remains stationary, and the container with the die is pushed down from above. In contrast to the technology implemented on Cameron presses and involving the use of graphite-based technological lubricants, pressing on a press of 45,000 tf can be carried out with highly efficient glass-based lubricants, which provide a higher surface quality of the pipes and increase the durability of the pressing tool. This was achieved as a result of the development of a new design of a pressing tool with a free (not fixed on the press stamp) press washer (USSR Author's Certificate No. 1274889 for the invention of “Pipe Pressing Tool”).

The most serious drawback of these analogues is the need to use only hollow billets for extrusion press pressing. This drawback necessitates the inclusion of additional large equipment (forging or piercing press) for the preliminary preparation of such blanks in the composition of the tubing complex. This in turn leads to a significant increase in the cost of both the creation of the complex and its subsequent operation.

As a prototype of the present invention, a method for manufacturing seamless steel pipes according to the patent of the Russian Federation No. 2166394 is selected. The main advantage of the prototype over the mentioned analogues is that it provides the possibility of using solid blanks. It is achieved by flashing the workpiece directly on the extruding press, and the flashing operation is combined with the subsequent operation of pressing the pipe into one working cycle of the press. Thus, a combined process of flashing and pressing is carried out.

The prototype method includes heating a workpiece, applying technological grease to it and a tool and flashing the workpiece sequentially on a vertical hydraulic extruding press with a press needle (mandrel) with prepressing the workpiece in the container with a stamp, pressing by direct method with the pipe flowing through the die downwards, carried out by a movable press stamp and a free (not fixed on it) press washer with the container and die stationary, and separating the pipes obtained from the press Atka by cutting device specifically provided in the press.

In the production of pipes of the usual, most widespread assortment, the prototype method provides a significant reduction in capital costs when creating pipe production, labor and operational costs (electricity, tools, equipment maintenance, etc.) in the manufacture of pipes, contributes to an increase in the share of pipes obtained by hot pressing, in general volume of production of steel seamless pipes, creates favorable conditions for the construction of metallurgical mini-plants, as well as for the organization of machinery roitelnyh enterprises in their procurement departments, its own production of pipes.

However, in relation to special steel seamless pipes of large diameter (400-500 mm and above - up to 1400 mm), including pipes with increased wall thickness (up to 100 mm), some of the significant features of the prototype method cause serious shortcomings in the production of these pipes in this way.

So, for the manufacture of pipes according to the prototype method, an extruding press is necessary, which, in addition to the main drive for pressing the pipe with the press stroke of the press stamp, also has a sufficiently powerful independent drive for the working stroke of the mandrel when it is pierced with the original billet, as well as a bulky device for cutting the pipe from the press balance. All this leads to an additional increase in the dimensions and mass of the press, and consequently, the costs for its creation. This fact becomes the main disadvantage of the method of the prototype upon receipt of large diameter pipes by this method. It will be appropriate to note here that even a press with a force of 45,000 tf, designed for the production of pipes with a diameter of up to 1400 mm from a hollow billet according to one of the above methods, which is analogous and does not have a powerful piercing system and a cutting device, nevertheless already has overall dimensions (length × width × height) 31.1 × 14.9 × 52.7 meters. In this case, the mass of the entire press unit reaches 20 thousand tons. Other disadvantages of the prototype method in relation to large-diameter pipes are the need to separate the pipe from the press residue directly on the press and flashing the workpiece with its support on the press matrix. This entails a corresponding increase in the length of the pipe manufacturing cycle on the press and an increase in the volume of metal waste (“otter”) obtained by cutting through the mandrel of the bottom of the stitched blank. It should be noted that in the production of pipes with a diameter of 1400 mm and a wall thickness of 100 mm on a press of 45,000 tf, the mass of the initial hollow billet reaches 18 tons.

Noting these disadvantages of the prototype method, it should be especially noted that the creation of a tube-pressing complex for the manufacture of hot-pressed large-diameter pipes and the operation of such a complex are associated with very significant financial and material costs. Therefore, the indicators of profitability and competitiveness of the created pipe production are becoming especially important, of paramount importance.

The main objective of the present invention is to provide a method for manufacturing large-diameter seamless steel pipes, based on the combination of billet piercing and pipe pressing operations in one working cycle of an extruding press and providing reduction in capital costs during the construction of the press complex and operating costs during its operation due to simplification of the design, reducing the size and weight of the press, increasing the productivity of the pipe pressing process and reducing metal waste during flashing and pressing . Thus, the invention is intended to eliminate the largest disadvantages of all known analogues and prototype.

Achieving the stated objective of the claimed invention is achieved by the fact that the proposed method for manufacturing large-diameter steel seamless pipes involves heating a continuous cylindrical billet, applying glass lubricant to it and onto a pressing tool, successively carried out on a vertical hydraulic extruding press in one operating cycle of the flashing operation workpieces in a container with a pressing mandrel with preliminary prepressing of the workpiece and pressing the pipe by a direct method with the expiration metal under the action of a stamp with a press washer through the die down, as well as separating the resulting pipe from the press residue and releasing it from the die. At the same time, graphite is introduced into the technological lubricant in a volume ratio with glass (1: 4) ... (1: 5). The preform is pressed with a press mandrel and the preform is pierced with a drawing ratio of at least 1.4. During the flashing process, the workpiece rests on a continuous stand, and the press stamp moves continuously upward as the workpiece height increases. For flashing and pressing, a press washer rigidly mounted on the press stamp is used. The pipe is released from the matrix after the matrix is transferred to the product removal position by moving the pipe with the pressure switch up, and the pressure switch is separated outside the press.

The advantages of the proposed method are as follows.

- The introduction of graphite, which has high antifriction properties, into the technological lubricant facilitates the movement of the pressed pipe through the die when the pipe is removed and the press residue is displaced from the container, and also eliminates the risk of jamming of the press stamp with the press washer in the container during reverse travel stamps after extruding the pipe.

- Flashing a workpiece with a high degree of deformation allows pressing the workpiece in the container before flashing, not with a stamp, but with a mandrel and reduces (by reducing the wall thickness of the stitched workpiece) the fraction of deformation attributable to subsequent pressing, and therefore the value of the nominal force of the main drive press. All this makes it possible to carry out both firmware and pressing from this drive alone and eliminates the need for an independent powerful mandrel drive.

- The support of the workpiece when it is flashed onto a monolithic stand (and not onto a matrix with an internal working channel) provides a reduction in the thickness of the remaining unbroken bottom of the workpiece, and, consequently, a decrease in the volume of metal waste in the form of the so-called “otter” during subsequent cutting through the mandrel of the workpiece bottom .

- Continuous lifting of the stamp with the press washer when flashing the workpiece compared with its preliminary one-time lifting by the final increase in the height of the workpiece provides the best conditions for centering the mandrel with the press washer during the flashing process.

- The use of a press washer permanently fixed on the press stamp eliminates the need to feed it into the container in each pressing cycle and the presence of an additional device for separating the press washer from the press residue.

- Removing the pipe from the matrix by moving it up without first separating the pipe from the press residue on the press itself with a special cutting mechanism included in it, simplifies the design of the press and shortens the working cycle of the pipe on it. Performing this operation in a position offset from the axis of the press simplifies the reception of pipes from the press and their storage.

Due to the above advantages of the invention, it is achieved the achievement of the above-mentioned ultimate goals.

The invention is illustrated by the drawings: FIG. 1 (“a” to “c”), FIG. 2 (“a” to “g”) and FIG. 3 (“a” to “c”), which schematically illustrates the process manufacture of pipes according to the new method on a vertical hydraulic press according to the application No. 2007134334 with a priority of September 17, 2007.

This press has a movable bed with upper and lower crossbars, a container-containing drive located between them and a fixed crosshead. The guide columns of the bed are fixed on it in the corners, a movable table is installed on top, and the main drive is located below, which includes a group of working cylinders with housings mounted on a fixed crossarm and plungers connected with the lower cross member. The technological tool of the press consists of a container, a mandrel, a stamp, and a die. The mandrel is mounted on the upper cross member of the movable bed. The stamp is installed in an additional cross-member located between this cross member and the container, equipped with an auxiliary drive for moving the stamp relative to the mandrel. The technological tool kit also contains a stand (plug) for firmware. The pressing matrix and the plug for firmware are located on two positions of the press table. An emphasis is placed on the lower cross member of the movable bed to push the pressed pipe out of the matrix, and a vertical groove is made in the stationary cross-beam to allow the pipe to move from the press axis to the removal position.

Figure 1 shows the technological transitions of the billet firmware (“a” - installation of the billet in the container, “b” - the end of the compression of the billet, “c” - the end of the firmware), figure 2 - the technological transitions of pressing the pipe (“a” - movement matrixes on the axis of the press, “b” is the cut-through of the bottom of the stitched blank, “c” is the beginning of the pressing of the pipe, “d” is the end of the pressing of the pipe), Fig. 3 shows the technological transitions for removing the pipe from the matrix and from the press (“a” - release of the press residue from the container, “b” - moving the matrix with the pipe to the pipe removal position , “C” - release of the pipe from the matrix and its removal from the press).

The manufacture of pipes according to the method of the invention is as follows.

In the initial state, the mandrel 1, connected with the upper cross member 2 of the press frame, and the container 3 are in the highest position, and the press stamp 4 mounted on the additional cross member 5 of the press, with the press washer 6 fixed to it, in the position in which the bottom end of the press washer is located at the exit of the working cavity of the container. Stand 7 for firmware, placed on the table 8, occupies a position on the axis of the press. The heated continuous billet 9 with technological glass-graphite lubricant deposited on its side surface is fed to the axis of the press in the space between the container and the stand (Fig. 1, item “a”) and mounted on this stand. A portion of the same lubricant is placed on the upper end of the workpiece in the form of a disk 10 with a diameter corresponding to the diameter of the mandrel. Then the container is lowered down to the stop in the stand, while the workpiece is inside the container.

Flashing of the workpiece begins. Previously, under the action of an auxiliary drive (not shown), the press stamp is lowered. Then, under the action of the main drive of the press (not shown), the working course of the bed with the mandrel begins. First, the mandrel upsets (presses) the workpiece until the gaps between its side surface and the container disappear. In the process of precipitation, the workpiece is shortened. The press stamp moves downward, still leaning on the workpiece with the end face of the press washer. After unpressing the workpiece (Fig. 1, pos. “B”), the mandrel, continuing its downward movement, is embedded in the blank and flashing it, forming an inner cylindrical cavity in it (Fig. 1, pos. “C”). At the same time, the workpiece metal displaced during the firmware moves upward, towards the movement of the mandrel. At the same time, using the auxiliary drive, the stamp also moves upwards, making room for an elongated workpiece. At the end of the firmware in the workpiece, at its lower end, there remains a partition (bottom) of small thickness.

Following the flashing of the workpiece, the pipe is pressed. To do this, first the container, the mandrel and the stamp are displaced a small distance up. The table feeds to the axis of the press the matrix 11 installed in it with technological glass-graphite grease placed on its upper end in the form of a washer 12 with an opening (Fig. 2, item “a”). The container is lowered onto the matrix. Next, in a short stroke of the needle, the bottom of the stitched workpiece is cut through with the formation of the metal waste of the workpiece in the form of an otter 13 (Fig. 2, pos. “B”). After that, the upper cross member of the bed, carrying the mandrel, and the additional cross member with a press stamp fixed to it, are closed. Follows the working course of pressing. Under the action of the main drive of the press, the mandrel and the stamp with the press washer move down. Under pressure from the side of the stamp, the metal of the hollow billet is extruded in the form of a pipe 14 into the annular gap between the matrix and the mandrel (Fig. 2, pos. “C”). Pressing ends when a part of the under-pressed blank of small thickness 15 (pressostat) remains in the container near the matrix, and a small distance equal to this thickness remains between the cross of the press stamp and the upper end of the container (Fig. 2, item “g”).

After pressing, the resulting pipe is removed from the press. The mandrel moves up and out of the press balance. The container with the press residue in it is lifted to the stop against the cross of the press stamp. In this case, the press residue, supported from above by a stationary press stamp, is displaced from the container (Fig. 3, item “a”). Then the matrix with the pipe in it is moved by the table to the pipe removal position, and on the axis of the press there is a stand for firmware. At the same time, the press stamp and the mandrel are moved up to their original position, the container rises above the table to install the next workpiece (Fig. 3, pos. “B”). Following this, the press frame begins its movement to its highest position. During this movement, the stop 16 mounted on the lower cross member of the bed (not shown) acts on the lower end of the pressed pipe, pushing it through the matrix upward on the size of the bed travel. Following this, with the help of an overhead crane 17, the pipe for the press residue is finally removed from the matrix (Fig. 2, item “c”). This completes the pipe manufacturing cycle on the press. The separation of the press residue from the pressed pipe is carried out outside the press using a special cutting device.

The use of this invention will significantly improve the technical and economic indicators of the production of seamless steel pipes of large diameter, consumed by the basic sectors of the economy, including thick-walled pipes used in many industrial facilities of the new generation with increased pressure and temperature parameters inside the pipe, for example, in modern nuclear and thermal power plants.

Claims (1)

A method of manufacturing large-diameter steel seamless pipes, including heating a continuous cylindrical billet, applying glass lubricant to it and to a pressing tool, successively carried out on a vertical hydraulic extruding press in one working cycle of the process of flashing the workpiece in the container with a pressing mandrel with pre-pressing the workpiece and pressing the pipe by the direct method with the expiration of the metal under the action of a press stamp with a press washer through the die down, as well as the separation of the obtained pipe from the press residue and its release from the matrix, characterized in that they use technological lubricant containing graphite in volumetric ratio with glass (1: 4) ... (1: 5), the preform is pressed with a press mandrel, and the billet is pierced with a draw ratio of at least 1.4, and during the flashing process, the workpiece is supported on a continuous stand, and the stamp is continuously moved upward as the workpiece height increases; for flashing and pressing, a press washer rigidly fixed to ss-stamp, the release of the tube from the die of the matrix is carried out after transfer to the removal position by moving the product pipe from the press residue up and separation is pressostatka produce press.

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