WO2009067045A1 - Method for producing seamless large-diameter pipes - Google Patents

Abstract

The invention relates to metal-forming processing, namely to producing seamless steel pipes. The inventive method involves heating a solid cylindrical billet, applying a glass-based working lubricant on said billet and an extrusion tool, carrying out the billet piecing, extruding a pipe, separating the thus produced pipe from extrusion discard and releasing the pipe from the die. The piercing and pressing operations are carried out on a vertical hydraulic pipe-extrusion press at one operational cycle thereof. The billet piecing operation is carried out by means of a press mandrel in a container and is preceded by the billet prepressing. The pipe is extruded by a direct pressing method when a metal flows through a die downwards under the action of an extrusion stem provided with a pressing disc with an elongation ratio equal to or greater than 1.4. The working lubricant contains graphite taken in a graphite/glass volume ratio of (1:4)...(1:5). The invention makes it possible to combine the billet piercing and pipe extrusion operations, to simplify the structural design for the press and to reduce the size and the mass thereof, to improve the performance of the pipe pressing process and to reduce metal waste during piercing and extrusion.

Description

 PREPARATION METHOD

STEEL SEAMLESS PIPES OF LARGE DIAMETER

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 in the size and shape of the pipes obtained, the ability to produce pipes of long length, pipes from medium and high alloy steels, bimetallic pipes, including clad inner a layer of stainless steel; higher process performance and less metal waste.

One of the analogues of the claimed invention can serve as 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 (Avero D. NoCameroopertulés séméless pére // Metal Prégres, 1977 v. 3, Ns, 2, p. 52-57). Another analogue is the production of pipes with a diameter of up to 1400 mm on a vertical extrusion press with a force of 45,000 tf according to a later project developed in the USSR in 1980-90. (Starikov V.S. et al. Technology and tools for the production of large-diameter steel pipes by pressing // Forging and stamping. 1988, JChk 10, p. 14-17).

The manufacture of pipes according to the above methods - analogues is characterized by the use of the direct method of pressing with the pipe flowing up and separating it from the pressure switch using a notch. In the process of pressing, a press stamp mounted on the table of the press remains stationary, and the container with the matrix is pushed down on it. In contrast to the technology implemented on Kameron 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 achieved as a result of the development of a new design of a pressing tool with a free (not fixed on the stamp) press washer (USSR Author's Certificate N ° 1274889 on the image ix "Inctpyment for pressing tp.yb") ..

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, the method of manufacturing steel seamless pipes according to the patent of the Russian Federation Ns 2166394 was selected. The main advantage of the prototype over the aforementioned analogues is that it provides the possibility of using solid billets. 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 method is a prototype, which includes heating a workpiece, applying technological glass grease to it and a tool, and sequentially using a vertical hydraulic extruding press to flush the workpiece with a press needle (mandrel) with a preliminary pressing the workpiece in the container with a stamp, pressing by direct method with the pipe flowing out through the die downward by a movable stamp and a free (not fixed on it) press washer with the container and die stationary, and separating the pipes obtained from the pressure switch by means of pieces specially designed on 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 costs and operating 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 production of seamless steel tubes, creates favorable conditions for the construction of steel mini-mills, as well as for the organization ^'on vehicles construction 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 defects 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 ram stroke, also has a sufficiently powerful independent drive for the working stroke of the mandrel when it is flashing the original billet, as well as a bulky device for cutting the pipe from the pressure switch . All this leads to an additional increase in the dimensions and mass of the press, and, consequently, the costs for its creation. This circumstance becomes the main disadvantage of the method - 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 tons intended for the production of pipes with a diameter of up to 1400 mm from a hollow billet according to one of the above methods is analogous and does not have a powerful piercing system and a cutting device, however, it already has overall dimensions (length x width x height) 31.1 x 14.9 x 52.7 meters. In this case, the mass of the entire press unit reaches 20 thousand tons. Other disadvantages of the prototype method with respect to large diameter pipes are the need to separate the pipe from the pressostat 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 the manufacture of large-diameter seamless steel pipes, based on the combination of billet piercing and tube pressing operations in one working cycle of an extruding press and providing a reduction in capital costs during the construction of the press complex and operating costs during its operation due to simplification of the design, size and weight reduction 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 prepressing the workpieces and pressing the pipe by 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 pressure switch and releasing it from the die. At the same time, trafit 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 postmark moves continuously upward as the workpiece height increases. For flashing and pressing, a press washer is used, which is rigidly fixed to the press post. Releasing pipe from the matrix after the matrix is performed on the translation product removal position displacement ^'pipe pressostatkom up and separation is pressostatka produce 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 pressure of the pressure container is displaced, and also eliminates the risk of “jamming” a stamp with a fixed washer in the container during the reverse stroke of the stamp 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 blank) the proportion of deformation attributable to subsequent pressing, and therefore. and the value of the nominal effort of the main drive of the press. All this makes it possible to carry out both firmware and pressing from this drive alone and eliminates the need for

- 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 not stitched bottom of the workpiece, and, consequently, a decrease in the volume of waste metal in the workpiece in the form of the so-called otter during subsequent cutting through the mandrel bottom of the workpiece.

• Continuous lifting of the stamp with the press washer when flashing the workpiece as 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 attached to the press stamp eliminates the need to feed it into the container during 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 pressostat on the press itself by a special cutting mechanism included in its composition 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 in FIG. 1 ("a" -

“C”), FIG. 2 (“a” - “g”) and FIG. 3 (“a” - “c”), on. which schematically demonstrates the technological process of manufacturing pipes according to the new method on a vertical hydraulic press according to application Na 2007134334 with a priority of September 17, 2007.

This press has a movable bed with upper and lower crossbars, a container holder with a 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. A kit of a technological tool 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 for pushing 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.

In FIG. 1 shows the technological transitions of the workpiece firmware (“a” - installation of the workpiece in the container, “6” - end of the workpiece unpressing, “c” - end of the firmware), FIG. 2 - technological transitions pipe pressing (“a” - moving the die onto the axis of the press,

“6” is the cut-through of the bottom of the stitched blank, “c” is the beginning of pipe pressing, “g” is the end of pipe pressing), in FIG. 3 - technological, transitions of removing the pipe from the matrix and from the press (“a” - release the pressure switch from the container, “6” - moving the matrix with the pipe to the pipe removal position, “c” - releasing the pipe from the matrix and removing it from the press).

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

In the initial state, the mandrel 1, connected with the upper cross member 2 of the press bed, 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 washer 6 fixed to it, in the position in which the lower 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. I, pos. “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 ram 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 ram moves downward, still leaning on the workpiece with the end face of the press washer. After pressing the workpiece (Fig. 1, pos. "6"), the mandrel, continuing its downward movement, is introduced into the workpiece 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, with the help of an 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 shifted a small distance up. The table feeds to the press axis the matrix 11 installed in it with technological glass-graphite grease placed on its upper end in the form of a washer 12 with a hole (Fig. 2, item “a”). The container is lowered onto the matrix. Next, a short stroke of the needle prosekayut bottom stitched preform to form a metal preform departing ^'otter form 13 (Fig. 2, Pos. "B"). After that, the upper cross member of the bed, bearing the mandrel, and the additional cross member with the stamp attached to it, are closed. Follows the working course of pressing. Under the action of the main drive of the press, the mandrel and the ram 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 die 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 • at the die, and a small distance is kept between the stamp cross-piece and the top end of the container - equal to this thickness (Fig. 2, item “g”).

After pressing, the resulting pipe is removed from the press. The mandrel moves up and out of the pressure switch. The container with the pressure switch in it is lifted up to the stop against the cross member of the stamp. - In this case, the pressure switch, supported from above fixed stamp, it is forced out of the container (Fig. 3, pos. "a"). Then the matrix with the pipe located in it moves the table to the ^“ pipe removal position ^” , and a stand for firmware appears on the press axis. At the same time, the stamp and the mandrel move up to the initial 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 fixed on the lower cross member of the frame (not shown) acts on the lower end of the pressed pipe, Alkylating it through the matrix upwards by the stroke of the bed .. Following this, with the help of an overhead crane 17, the pipe for the pressure switch is finally removed from the matrix (Fig. 2, pos. “c”). This completes the pipe production cycle on the press. the pressed pipe is produced 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

CLAIM 1. A method of manufacturing a seamless steel pipe of large diameter, including heating. a continuous cylindrical billet, applying glass lubricant to it and to a pressing tool, sequentially performed on a vertical, hydraulic extrusion press in one working cycle of the operation of piercing the billet in the container with a press mandrel with preliminary pre-pressing of the billet and pressing the pipe by a direct method with metal flow under the action of a stamp with a press washer through the die down, as well as separating the resulting pipe from the pressure switch and releasing it from the die, different I mean that 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, and in the process the firmware rests on a solid stand, and the stamp continuously moves upward as the workpiece height increases; for flashing and pressing, use a washer • rigidly fixed to the stamp, the pipe is released from the matrix after the matrix is transferred to position, product removal by moving the pipe with the pressure switch up, and the separation of the pressure switch is performed outside the press.