RU2166394C1 - Method for making seamless steel tubes - Google Patents

Abstract

FIELD: manufacture of steel seamless tubes. SUBSTANCE: method of making tube of solid blank by hot piercing and extrusion for one working cycle of press comprises steps of heating blank, lubricating it, successively piercing blank, extruding tube and separating tube from remainder of blank. Tube is made in vertical hydraulic tube extrusion press having apparatus for cutting off remainder of blank at using pressure pad non-coupled with extrusion ram and technological lubricant of glass material. Lubricant is applied onto lateral surface of heated blank at rolling the last on glass powder and it is applied also onto die and upper end of blank in the form of preliminarily compacted discs at using turned blank having recess for glass disc on its one end and radially rounded edge on its opposite end. Before piercing blank is upset in container by means of extrusion ram , the last is then lifted over blank in order to create free space for increased height of blank at piercing. It is possible to use blank with preliminarily drilled central opening having cone flared portion near its upper end and with reduced outer diameter providing increased annular gap between blank and wall of container cavity. Such blank is pierced by expanding method with use of needle having special expanding tip without preliminary upsetting of blank by extrusion ram and without lifting extrusion ram over blank. EFFECT: lowered investment for building tube production plant, reduced labor consumption, operational cost of making tubes, favorable conditions for building metallurgical mini-shops and organization of tube manufacture process in storage shops of machine engineering plants, enhanced quality of tubes, significantly improved ecological characteristics of tube manufacture process. 2 cl

Description

 The invention relates to metallurgy, and more specifically to the manufacture of seamless steel pipes, and can be used in the shops of metallurgical and engineering enterprises producing such pipes by hot pressing.

 A significant number of developments has been devoted to the production of seamless steel pipes, since these products are used in large volumes and are widely used to create various objects and assemblies, including pipe fittings for water, air, gas, liquid fuel and other materials, and are also widely used as blanks tubular parts in most engineering industries. Moreover, hot pressing after rolling is the most common method of manufacturing seamless steel pipes (Manegin Yu. V., Pritomanov A.E. et al. "Hot pressing of pipes and profiles" - M .: Metallurgy, 1980). So, back in 1976, in the world as a whole, there were 91 press plants in operation for the production of hot-rolled steel products in more than 30 plants (ibid., P. 9, table 1). A significant progress in the production of steel hot-pressed pipes was obtaining a hollow billet for pressing the hot flashing method instead of machining (drilling and boring).

 As an analogue of the claimed invention, one should take the most common technological scheme for the production of hot-pressed steel seamless pipes, according to which the hollow billet (sleeve) is sequentially obtained at the tube press complex by flashing a continuous cylindrical initial billet on a piercing press and subsequent pressing from the resulting pipe sleeve on a pipe extruding press (see, for example, Schloemann's brochure "Kombinierte Pre β- und Walzanlagen fur Stahlrore"). To ensure the required temperature regime of flashing and pressing and protecting the forming tool from wear and tear on modern tube press complexes with separate flashing and pressing, effective technological lubricants based on glass are used, which have high heat-insulating and antifriction properties. The use of such a lubricant ensures a high surface quality of pressed pipes.

 The main disadvantages of this analogue are the large capital costs necessary to create a pipe-press complex, and increased operating costs during its operation. This is due to the use of two units of press equipment - a piercing press and a tube extruding press and two units of heating equipment - respectively in front of each of the presses. Due to these drawbacks, the use of the analogue method is economically justified only for large-scale production of seamless steel pipes in metallurgical plants with a full technological cycle - from casting steel billets to finishing operations for hot or cold rolling of pressed pipes.

 At the same time, there is currently a tendency in world practice to create the production of steel pipes in mini-metallurgical plants, as well as in the procurement workshops of machine-building plants that use pipe blanks to create their products. Obviously, in these cases, a less laborious and cheaper method of manufacturing hot-pressed pipes is required than the analogue method described above. This way is a process in which the firmware and pressing operations are combined on the same press and carried out in one working cycle.

 The closest analogue (prototype) of the claimed invention is a method developed by Mannesmann-Meer "Meer-Bericht. Mechanische Strangpressen zur Herstellung von Stahlroren"). The manufacture of pipes according to the prototype method is as follows. The heated continuous, non-turned blank is placed in a press container. The pressing beam supporting the stamp and the piercing beam with the needle attached to it move down so that the stamp and the needle reach the upper end of the workpiece. Under the influence of the weight of the pressing beam, a blank (pre-pressing) of the workpiece occurs. Then the needle resumes the downward movement, in which it flashes the workpiece, forming a through central hole in it. During the flashing process, due to the displacement of the workpiece metal by the needle, there is a slight increase in the workpiece height and the lifting of the press stamp. After flashing the workpiece, the needle continues to move down together with the stamp. In this case, under the influence of the latter, the metal of the workpiece is forced into the annular gap between the matrix and the needle, being formed into a pipe. Pressing ends when the press residue of the minimum allowable size remains in the container. After that, the stamp and the needle return to their original upper position. A device is installed in the container for separating the pressed pipe from the press residue, and with it, the press residue is cut. The separated pipe enters the gutter located under the press. The tool with the remaining press residue left is removed from the container.

 All interconnected movements of the press stamp and needle during the pressing process are carried out using a press crank drive on which the piercing beam is fixed, and a cam mechanism with a linkage system connecting the piercing beam to the pressing. Technological lubricant during pressing is graphite-oil mixture. A portion of this mixture is placed on the upper end of the workpiece after loading the latter into the container.

 Thus, combining the firmware and pressing operations in one working cycle, carried out on one press, the prototype method eliminates the main disadvantages of the first analogue described above.

 However, the described prototype method, developed in time earlier than the analogue method with separate firmware and pressing on individual presses, did not receive widespread further industrial use. This is due to its main drawback - the impossibility of using modern high-performance glass lubricants in the production of hot-pressed pipes by this method.

 Features of the operation of glass lubricant are that this lubricant, applied to a heated billet and a pressing tool in its original solid state, forms a thin uniform molten layer with high heat-insulating and antifriction properties at the contact of the billet with the tool. In solid form, glass causes very high friction on contact surfaces. Therefore, an absolute requirement when using glass as a technological lubricant for pressing is work with the use of a press stamp with its front part separately made, facing the billet - a press washer. Otherwise, namely when working with a press stamp with an integral head acting as a press washer (as in the prototype), on the contact surface of the press stamp and the inner wall of the container covered with a crust of frozen glass, during the return stroke of the stamp occurs so significant friction that frequent cases of jamming of the press stamp in the container are possible due to insufficient effort of the return cylinders of the press or even breakage of the head of the stamp. In turn, the use of an independent press washer requires special additional movements of the press yoke to eject the press washer and press residue from the container after the product is pressed and separated from the press residue. For the implementation of such movements of the traverse, the most suitable are presses with a hydraulic drive, and not with a rigid mechanical drive (as in the prototype). In addition, when working with a press washer, it is impossible to separate the pipe from the press residue by a notch, since the press washer after pressing remains in the container, on the press residue, and it is naturally impossible to feed through its hole with a diameter corresponding to the diameter of the needle to the press residue, a notch with a diameter of the working part close to the diameter of the matrix. Therefore, presses designed for pressing glass-lubricated pipes are equipped with special devices for separating the pipe with a saw.

 From the foregoing, it is clear that the manufacture of steel pipes by the prototype method (on mechanical presses with a press stamp having an integral head and a device for separating the pipe by a notch) using glass grease is not possible. As noted above, in the operation of such presses, a graphite-oil mixture is used as a lubricant. Such a lubricant does not have sufficient heat-insulating properties and does not provide the creation of a thin continuous uniform lubricating layer on the contact surfaces. Because of this, the manufacture of pipes according to the prototype method is characterized by low resistance of the pressing tool and low surface quality of the pressed pipes. In addition, the use of graphite lubricant is also impractical for environmental reasons, as it is associated with significant pollution of industrial premises with graphite dust and oil vapors with graphite particles.

 The prototype method also has some other serious disadvantages. Thus, the kinematic characteristic of the crank drive of mechanical presses (maximum speed at the beginning of the stroke and minimum at the end) does not provide the required temperature and temperature conditions for pressing pipes from high alloy steels and steels with reduced ductility. The lack of high-quality draft of the workpiece in the container before flashing (carried out according to the prototype under the influence of only the weight of the moving parts of the press) often leads to a decrease in the concentricity and straightness of the holes flashed in the workpieces and, as a result, to an increase in the difference between the pressed pipes. The heightened condition of the workpiece during flashing (the press stamp lies on the blank) is the reason for the increased volume of waste during flashing (otter).

 Due to the above disadvantages, the prototype method, despite the combination of flashing and pressing operations on one press, is used today in the manufacture of hot-pressed steel pipes on a very limited scale - mainly in the production of thick-walled pipes from carbon and low alloy high-ductility steels with relatively low requirements for dimensional accuracy and surface quality. As a rule, such pipes are then processed by rolling on a reduction mill, usually located directly behind the press.

 The present invention eliminates the aforementioned disadvantages of the analogue and prototype by the fact that in the production of seamless steel pipes from a continuous billet by hot flashing and pressing in one working cycle of the press, including heating the workpiece, applying technological lubricant, sequential operations of flashing the workpiece in the press container with a needle, pressing the pipe with a stamp through the die and separating the pipe from the press residue, the pipe is manufactured on a vertical hydraulic pipe extruding press, equipped with Hinnom device for cutting press residue using not secured to the press ram press washer and technological lubricant from the glass material applied to the side surface of a heated blank by running last in glass powder and placed in a die and the upper end of the blank as pre-compacted washers. In this case, a turned workpiece with a central recess made under the glass washer at the end facing the press stamp during pressing and a radial rounding of the edge at the opposite end. Before flashing the workpiece, it is settled in the container with a press stamp under the influence of the press beam of the press, followed by lifting the stamp over the workpiece to create free space for increasing the height of the workpiece during flashing.

 The present invention also includes the possibility of using a workpiece with a diameter of 0.2-0.3 from the diameter of the needle, with a conical extension at the upper end and with a reduced outer diameter, providing an increased annular gap between the workpiece and pre-made in it by drilling through the center hole of the diameter. the wall of the cavity of the container with a cross-sectional area of 0.9-1.0 of the cross-sectional area of the needle. In this case, the workpiece is flashed using the expansion method using a needle equipped with a special expanding tip, without preliminary precipitation of the workpiece with a press stamp and subsequent lifting of the press stamp over the workpiece.

The implementation of the "Method for manufacturing seamless steel pipes" is illustrated by the drawings in FIG. 1, 2 and 3, which show:
FIG. 1 - initial billet and lubricating glass washers for flashing and pressing;
FIG. 2 - a sequence of technological transitions in the manufacture of pipes by piercing and pressing;
FIG. 3 - initial billet, lubricating glass washer and needle for pressing with expansion.

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

 The initial blanks are obtained by cutting cast or deformed (forged, rolled, pressed) round rods. Billet 1 (Fig. 1) is grinded along the outer diameter. At one of its ends, a recess is made with a diameter corresponding to the diameter of the needle, and the annular edge at the opposite end is rounded with a radius transition.

 The billet for pressing is heated to a predetermined temperature in an induction, gas or electric resistance furnace. Before loading the workpiece into a container, glass lubricant is applied to its side surface by rolling on a special table covered with a layer of glass powder. This grease is designed to contact the workpiece with the container. Then, on the end face of the workpiece, a lubricating washer 2 is mounted in the central recess, which is compacted on the basis of glass powder and designed to contact the workpiece with the needle (Fig. 1). Before pressing on the end face of the matrix, another lubricating washer 3 is placed, intended for contact of the workpiece with the matrix (Fig. 1). In this case, the shape of the radial rounding at the end of the workpiece should correspond to the surface shape of this washer facing the workpiece during pressing.

 The sequence of technological transitions when pressing the pipe according to the claimed method is as follows (Fig. 2).

 The heated preform with glass lubricant applied to its side surface and with a glass washer installed on the upper end is fed into the press and loaded into container 4 (Fig. 2, a). Following this, the press washer 5 is fed into the press and is also loaded into the container on the workpiece located there (Fig. 2, b). In this case, the grease washer is in the hole of the press washer. The pressing crosshead of the press 6 with the press stamp 7 fixed thereon moves down until the press stamp contacts the press washer. With the further course of the pressing beam, the press stamp settles the workpiece in the container (Fig. 2, c). Then, using the return cylinders of the press, the stamp makes a small stroke upward, rising above the workpiece. Using the press piercing cylinder (not shown in the drawing), the needle 8 is moved down and, making a working stroke, carries out the flashing of the workpiece (Fig. 2, d). The firmware ends by displacing into the matrix 9 the departure of the firmware - otter 10 and introducing a needle into the working channel of the matrix. In the course of the firmware, due to the displacement of the workpiece metal by the needle, the workpiece increases in height, filling the free space under the stamp. The lubricating glass washer installed on the upper end of the workpiece is first forced out of the press washer into the workpiece when flashing, then, with the further introduction of the needle into the workpiece, a thin uniform molten layer is distributed on the contact surface between them. Next, the pressing of the pipe begins. In this case, the stamp and the needle jointly move downward, and the metal of the workpiece, under the influence of the stamp, is forced into the annular gap formed by the matrix and the needle, forming a pipe 11 (Fig. 2, e). In the process of pressing, a lubricating glass washer placed previously on the end face of the matrix is gradually melted at the contact with the workpiece and is continuously replaced at the contact of the extruded pipe with the surface of the working channel of the matrix, covering the outer surface of the pipe with a thin uniform layer. Pressing is completed by leaving the remainder 12 of the minimum allowable height in the container of the press. Then the stamp with the needle make a slight upward movement. The container with the press washer and press remain in it rises above the die. A saw 13 is introduced into the space formed between the container and the matrix, with the help of which a piece of pressed pipe is produced from the press residue (Fig. 2, e). Then the needle returns to its original position. The container is lowered onto the die, while the press remainder in it pushes the pressed tube out of the die working channel with its tube part (Fig. 2, g). The pipe falls down into the receiving chute of a press (not shown). The container rises again above the matrix. Instead of a matrix, a receiver 14 is installed on the press axis. The container is lowered onto the receiver, and after this stroke of the press stamp, the press residue and press washer are displaced from the container to the receiver (Fig. 2, h). The receiver moves to its original position, removing them from the press zone. A matrix with a new glass washer placed on it is again mounted on the axis of the press. The container is pressed against the matrix. The container and needle rise to their original position. Thus, the pressing tool returns to its original state (Fig. 2, a).

 In the implementation of the proposed "Method of manufacturing seamless steel pipes" it is also possible implementation of the firmware blanks expansion method. Moreover, in the workpiece 15 (Fig. 3), a central through hole with a diameter of 0.2-0.3 of the diameter of the needle is preliminarily performed by drilling. At the end face of the workpiece facing the press stamp during pressing, the hole ends with a conical extension (funnel). After heating the workpiece, a lubricating glass washer 16 (Fig. 3), also having a conical shape, is placed in this funnel. The front end of the needle 17 is equipped with a conical expanding tip (Fig. 3). The outer diameter of the extrusion billet is smaller than the extrusion billet with piercing. It is selected so that the area of the annular gap between the workpiece placed in the container and the container is 0.9-1.0 of the needle cross-sectional area. The exact value of the outer diameter of the workpiece is calculated from the condition that the volumes of the metal of the workpiece displaced by the needle during expansion are equal, and the initial clearance between the workpiece and the container.

 The sequence of technological transitions in the manufacture of pipes according to the variant with expansion is close to that described above with respect to the variant with firmware (Fig. 2). The differences are that the operation of upsetting the workpiece is excluded (Fig. 2, c), and the formation of a hollow sleeve is carried out by expanding the hole in the original workpiece to the diameter of the needle with an expanding needle tip when introducing the latter into the workpiece. In this case, the flow of the workpiece metal occurs only in the radial (transverse) direction until the initial radial gap between the workpiece and the container is filled. The flow of metal upward and, accordingly, friction along the container during expansion are absent. An increase in the height of the workpiece does not occur, as a result, there is no need for a preliminary lifting of the stamp over the workpiece.

 Compared to clean firmware, expansion is characterized by less technological effort and lower needle loads, which increases the accuracy (concentricity) of the hole obtained in the workpiece, and also reduces the amount of waste (otter).

 The use of expansion is most appropriate when obtaining relatively thin-walled pipes - with the ratio of the outer diameter of the pipe to the thickness of its wall exceeding 25-28, as well as with the ratio of the height of the stitched workpiece and its internal diameter exceeding 7-8.

 From the above descriptions of the invention “Method for the production of seamless steel pipes”, its analogue and prototype, it follows that the invention allows the production of pipes on hydraulic presses using high-performance glass-based lubricants to combine the operations of piercing the billet and pressing the pipe into one working cycle of one extrusion -press, ensure optimal temperature and speed conditions of the process and reduce the load on the pressing tool, increase the service life of this tool one to improve the accuracy and reduce the sewn blanks metal waste during piercing.

 As a result, a significant reduction in capital costs is ensured in the creation of pipe production, labor and operational costs (electricity, tools, equipment maintenance, etc.) in the manufacture of pipes, favorable conditions are created for the construction of mini-metallurgical plants and the organization of pipe production in the procurement workshops of machine-building plants, expansion of the range of hot-pressed steel pipes in terms of steel sizes and grades and an increase in the total volume of manufactured x pipes the proportion of pressed pipes, including those that do not require subsequent redistribution on rolling equipment, increases the accuracy of the dimensions of such pipes and the quality of their surface, significantly improves the environmental performance of pipe production.

Claims (2)

 1. A method of manufacturing seamless steel pipes from a continuous billet by hot flashing and pressing for one press working cycle, which includes heating the billet, applying technological grease, sequential batch flashing operations in the press container with a needle, pressing the pipe with a stamp via a die and separating the pipe from the press -residue, characterized in that the manufacture of the pipe is carried out on a vertical hydraulic tube extruding press equipped with a device for cutting the press residue, using a press washer fastened with a press stamp and technological glass grease applied to the side surface of the heated billet by rolling the latter over the glass powder and placed on the matrix and the upper end of the billet in the form of pre-compacted washers, using a turned billet with a central recess made under the glass washer at the end facing the press stamp during pressing, and with a radial rounding of the edge at the opposite end, and before flashing the workpiece, it is upset the teiner with a press stamp under the influence of the press traverse of the press with the subsequent lifting of the press stamp over the workpiece using the return cylinders of the press to create free space for increasing the height of the workpiece during firmware.  2. A method of manufacturing a seamless steel pipe according to claim 1, characterized in that a preform is used with a hole pre-made in it by drilling through a central hole with a diameter of 0.2-0.3 of the diameter of the needle, with a conical extension at the upper end and reduced outer diameter, providing an increased annular gap between the workpiece and the wall of the container cavity with a cross-sectional area of 0.9 - 1.0 from the cross-sectional area of the needle, and the workpiece is flashed using the expansion method using and ly provided with a special tip ekspandiruyuschim without prior precipitation preform ram and the subsequent lifting of the slide over the workpiece.

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