RU2493929C1 - Device and method of forming by zone extrusion - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metal forming and may be used in, for example, production of nuclear reactor containments. Proposed device comprises forming female die 6 and male die 9. Male die 9 is arranged in lengthwise direction to enter into blind cavity 61 or female die 6 to extrude the billet. Male die 9 consists of extrusion shaft 8 and forming head 93 coupled therewith. Cross-section area of forming head 93 perpendicular to female die lengthwise axis is smaller than that of extrusion shaft 92 arranged perpendicular to lengthwise axis of female die 6. Male die 9 can turn about lengthwise axis of female die 6. Note here that sequential deformation of billet by forming head 93 is performed in appropriate zones. Forming head center has recess to generate 3D compression strains in billet material.

EFFECT: uniform wall thickness, high reliability and strength, ruled out cracks and flaws.

18 cl, 15 dwg

Description

Technical field

The invention relates to the field of material processing, in particular to a device and method for forming metals by zone extrusion.

Prior level

The development of nuclear energy has become one of the strategic goals and objectives of national development, and for the manufacture of shells for nuclear reactors a domestic manufacturer is urgently required. The shells for the Qinshan and Day Bei nuclear power plants are imported to China, which is very expensive by Alstom, France and Nippon Steel Corporation. To develop clean energy and reduce carbon dioxide emissions, China plans to add 80 million kW of installed nuclear power by 2020, which will require about eighty shells for nuclear reactors with a capacity of 1 million kW each. The total cost of eighty shells for nuclear reactors with a capacity of 0.4 million kW is 40 to 48 billion yuan. In China, the own production of shells for nuclear reactors requires urgent and rapid development, which is a complex engineering and technical task.

Shells for nuclear reactors are usually made by rolling on a mandrel, drilling hollow ingots, drawing thick plates and encircling welding, etc. After the Chernobyl nuclear accident in the Soviet Union, welding with longitudinal welds in the manufacture of shells for nuclear reactors was prohibited. Now the shells of nuclear reactors are mainly made by rolling on a mandrel as shown in Figure 1. First, as shown in FIG. 1, five rings 100 'are made, then they are welded to form a cylindrical shell body. Further, as shown in FIGS. 2-3, a bottom 200 'or 200 ”is made by pressing or drawing from a thick plate. The cylindrical body and the bottom are welded, processed thermally and mechanically, resulting in a shell 300 'for a nuclear reactor, shown in Fig.4. However, this process is complex, multi-stage, has low efficiency and insufficient reliability. The latter is due to the fact that both in the manufacture of the ring 100 'and in the manufacture of the bottom 200' by pressing or drawing, molding is not in a state of three-dimensional compressive stresses, and in the molding processes in the presence of local tensile stresses there is a high risk of closing and renewal of cracks and defects .

In addition, at present, in many processes of heavy-duty forging for nuclear power, changing the shape of the anvil, pressing and feeding operations, etc., which are carried out under a pressing force of 10,000 to 20,000 tons, may also not create sufficient compression stresses in three directions and also may not reduce or eliminate tensile stresses. In addition, the amount of deformation during the process is difficult to maintain uniform. Figure 5 schematically shows a conventional rotary extrusion press. As shown in FIG. 5, the rounded billet 103 ”is forged, starting with raising the punch 101” to a certain height, turning the punch 101 ”by a certain angle, and then lowering the punch 101” into the lower die 102 ”. However, experiments showed that during free forging due to the application of force acting on the material in only one direction, as shown in Fig. 5, the spherical stress tensor reaches only about 80 MPa, and it is still difficult to eliminate cracks and defects in deformable materials.

SUMMARY OF THE INVENTION

The present invention is directed to solving at least one of the existing problems. Accordingly, a method for zone extrusion in a forming die is proposed, with which a shell for a nuclear reactor can be molded having a uniform wall thickness, high reliability and strength, with cracks and defects completely eliminated. A device for implementing such a method is also provided.

One object of the invention is a stamp extrusion device. The device may include a forming matrix and a punch located longitudinally with the ability to enter the cavity of the forming matrix to extrude the workpiece. The punch consists of an extrusion shaft and a forming head connected to the extrusion shaft and located under it. The cross-sectional area of the forming head in a plane perpendicular to the longitudinal axis of the forming matrix is less than the cross-sectional area of the extrusion shaft. The punch is made with the possibility of rotation around the longitudinal axis of the forming matrix so that the workpiece is successively and in zones extruded by the head of the punch into the through cavity of the forming matrix.

In the device for forming by zone extrusion according to the invention, by sequentially extruding the preform into zones of the forming matrix, the metal can flow radially, forming the bottom of the shell, and can rise along the forming shell, forming its cylindrical part. That is, one-stage molding of the cylindrical body and the bottom of the shell of a nuclear reactor is possible without the use of encircling welding. Therefore, such a process can be performed simpler and faster, with fewer operations and more efficiently. In addition, since the metal is extruded by the punch into the forming matrix, the workpiece is mainly deformed in a state with compressive loads in three directions. Tensile stresses during deformation can be minimized or even eliminated, so that the shell can have a uniform wall thickness with high strength and high reliability, and cracks and defects can be completely eliminated.

According to the invention, the extrusion shaft and the forming head can be made as a single part.

In one of the constructive variants of the invention, the extrusion shaft comprises a cylindrical section and a flange section molded between the bottom of the cylindrical shaft section and the forming head, the cross-sectional area of the forming head in the plane perpendicular to the longitudinal axis of the forming matrix being smaller than that of the flange section.

According to one of the constructive variants of the invention, the forming matrix is pre-stressed, and the inner diameter of the forming cavity of the prestressed matrix is larger than the maximum diameter of the extrusion shaft and the forming head.

According to one of the structural variants of the invention, the cross section of the forming head in the plane perpendicular to the longitudinal axis of the forming matrix has a rectangular shape, the long side of the rectangle being equal to the diameter of the extrusion shaft, and the ratio of the length of the short side of the rectangle to its long side is from 0.05 to 0.95.

According to one of the structural variants of the invention, the ratio of the cross-sectional area of the forming head to the cross-sectional area of the extruding shaft is in the range from 0.1 to 0.9. Therefore, the workpiece can be sequentially deformed by zones using a forming head.

According to one of the structural variants of the invention, in the extrusion process, the extruding force applied to the punch is distributed over the width of the forming head and the diameter of the extrusion shaft.

According to one of the constructive variants of the invention, the extrusion force is from about 1000 to 1500 meganewtons.

According to one of the structural variants of the invention, a recess is made in the central part of the forming head.

Another object of the invention is a zone extrusion molding method. A zone extrusion molding method may include: (1) placing a preform with a central recess of a predetermined depth in the forming matrix and heating the preform to a temperature suitable for extrusion molding and (2) sequentially extruding the preform into the forming matrix using a punch that is rotated around a longitudinal axis the forming matrix, the punch consists of: an extrusion shaft and a forming head connected to it, located under the extrusion shaft. The cross-sectional area of the forming head in a plane perpendicular to the longitudinal axis of the forming matrix is less than that of the extruding shaft.

In the method according to the invention, when a workpiece is successively extruded into zones of the forming matrix using a punch, the metal can flow radially to form the bottom of the shell and can rise along the forming shell to form the cylindrical part of the vessel, so that the cylindrical part can be formed in one step and the bottom of the shell of a nuclear reactor without the use of sheath welding. That is, this process can reduce the number and complexity of operations performed, shorten production time and increase productivity. In addition, since the metal is extruded by the punch into the forming matrix, the workpiece is mainly deformed in a state with compressive loads in three directions, tensile stresses during deformation can be minimized or even eliminated, so that the shell can have a uniform wall thickness with great strength and high reliability, and cracks and defects can be completely eliminated.

According to one embodiment of the invention, step (2) includes: (2.1) extruding the workpiece in a central recess with a predetermined force; (2.2) raising the punch for reinstallation; (2.3) the rotation of the punch relative to the longitudinal axis of the forming matrix by a given angle and (2.4) the repetition of stages (2.1), (2.2) and (2.3).

According to one of the structural variants of the invention, a recess is made in the central part of the forming head.

According to one embodiment of the invention, in step (2), an extruding force applied to the punch is distributed over the width of the forming head and the diameter of the extrusion shaft.

According to one of the structural variants of the invention, the extrusion shaft includes: a cylindrical section and a flange section, molded between the bottom of the cylindrical section of the shaft and the forming head, and the cross-sectional area of the forming head in the plane perpendicular to the longitudinal axis of the forming matrix is less than the cross-section of the flange section.

According to one embodiment of the invention, the extrusion force is from about 1000 to 1500 meganewtons.

According to one embodiment, the method for imparting uniform thickness to the walls of the preform extruded in step (2) further includes: (3) finishing the inner surface of the central recess of the preform using a finishing extruder shaft.

In one embodiment of the invention, steps (2) and (3) are alternately performed to extrude the workpiece.

According to the invention, the predetermined rotation angle is from 10 to 120 degrees.

According to one embodiment of the invention, the step (2) for imparting uniform thickness to the walls of the workpiece further includes lapping the inner surface along the central recess sequentially and along the zones of the extruded workpiece using a finishing extruder shaft.

According to one embodiment of the invention in step (2), the extrusion displacement is from 2 mm to 2000 mm.

According to one embodiment of the invention, the extrusion movement in stage (3) each time exceeds the movement in stage (2) by 0.01-0 .5 times.

According to the invention, the immersion speed of the forming head in the workpiece is in the range from 5 mm / s to 90 mm / s if the workpiece is made of iron alloys or from 20 mm / s to 300 mm / s if the workpiece is made of non-iron alloys.

According to one of the constructive variants of the invention, the forming matrix is pre-stressed, and the inner diameter of the forming cavity of the prestressed matrix is larger than the maximum diameter of the extrusion shaft and the forming head.

According to one embodiment of the invention, a central recess of a predetermined depth is obtained by upsetting, stamping, and hot-pressing the workpiece into a forming matrix, respectively.

According to one of the structural variants of the invention, the extrusion shaft and the forming head are made in the form of a single part.

According to one of the constructive variants of the invention, the cross section of the forming head has a rectangular shape, the long side of the rectangle being equal to the diameter of the extruding shaft, and the ratio of the length of the short side of the rectangle to its long side is from 0.05 to 0.95.

According to one constructive embodiment of the invention, the ratio of the cross-sectional area of the forming head to the cross-sectional area of the extruder shaft is from about 0.1 to 0.9.

The zone extrusion molding method according to the invention can also be used to mold vessels operating under high and ultrahigh pressure and requiring high reliability, such as a nuclear reactor steam generator, hydrogenation reactor or large volume vessels for storing natural gas under high pressure.

Other features and advantages of the structural variants of the invention will be partially given in the further description, and will be visible from the description or may be established during the implementation of the invention.

Brief Description of the Drawings

Already described and other features and advantages of the invention will be better visible and understandable from the following description with the application of the drawings, in which:

Figure 1 - manufacturing of a straight cylindrical section of a vessel operating under pressure, isometric view;

Figure 2 is a cross section of the extruded bottom of a conventional pressure vessel;

Figure 3 is a cross section of a conventional pressure vessel made by pulling the bottom;

4 is a schematic illustration of a typical shell of a nuclear reactor;

5 is a schematic illustration of a typical rotary extrusion press;

6 is a General view of a device for forming a zone extrusion according to one of the structural variants of the invention;

7 is a front view of the punch in the device for forming a zone extrusion according to one of the structural variants of the invention;

Fig. 8 is a left side view of a punch in a zone extrusion molding apparatus according to one of the structural variants of the invention;

Fig.9 is one stage of zone extrusion according to one embodiment of the invention;

Figure 10 - stage debugging in the method of forming zone extrusion according to one of the embodiments of the invention;

11 is a schematic depiction of the initial preform in a zone extrusion molding method according to the invention;

Fig. 12 shows the planting of a preform in a zone extrusion molding method to one embodiment of the invention;

13 shows stamping a workpiece in a zone extrusion molding method to one of the embodiments of the invention;

Fig. 14 shows hot pressing of a preform in a zone extrusion molding method to one embodiment of the invention; and

Fig. 15 shows a preform deployed after the hot-pressing operation shown in Fig. 14.

Detailed description of the invention

The invention will be described in detail below, the structural variants of which are visible in the accompanying drawings, in which the same or the same elements and elements having the same or similar functions are denoted by the same digital position throughout the description. The structural options described below with reference to the accompanying drawings are used only for a general understanding and illustration of the invention. Design options should not be construed as limiting the invention.

The inventive concept of the present invention is that due to a significant increase in extrusion force and while limiting deformation by a stamp, the zone extrusion method is used to increase three-dimensional compressive stresses, reduce and eliminate tensile stresses, increase the magnitude and uniformity of deformation, which smooth cracks and defects and increase reliability and strength of the vessel. In addition, in the method and device according to the variants of the present invention, optimal conditions for the flow of metal can be created, and the possibility of delamination is eliminated.

It should be noted that the term "zone extrusion" as used in this description means that the material is sequentially extruded into the chamber or cavity, section after section, adjacent or non-adjacent. As a result, the material is successively deformed by a variety of regional or local deformations.

In the process of material deformation, the spherical stress tensor O is usually used as a quantitative indicator of the probability of crack closure and / or cleavage after deformation of the material.

In particular, in a deformed material, the stress tensor σ _ij at any point can be represented as the sum of two tensors, namely, the spherical stress tensor σ _m and the deviator of the stress tensor S _ij .

The stress tensor σ _{ij is} described by the formula:

σ _ij = σ _m δ _ij + S _ij

$$\left[\begin{array}{ccc}{\sigma }_x& {\tau }_{xy}& {\tau }_{xz}\\ {\tau }_{yx}& {\sigma }_y& {\tau }_{yz}\\ {\tau }_{zx}& {\tau }_{zy}& {\sigma }_z\end{array}\right]=\left[\begin{array}{ccc}{\sigma }_m& 0& 0\\ 0& {\sigma }_m& 0\\ {\sigma }_m& 0& 0\end{array}\right]+\left[\begin{array}{ccc}{\sigma }_x-{\sigma }_m& {\tau }_{xy}& {\tau }_{xz}\\ {\tau }_{yx}& {\sigma }_y-{\sigma }_m& {\tau }_{yz}\\ {\tau }_{zx}& {\tau }_{zy}& {\sigma }_z-{\sigma }_m\end{array}\right]$$

According to one embodiment of the invention, successive extrusion of the preform into zones of the forming matrix by zones, a large and uniform spherical stress tensor dm can be ensured, which guarantees the elimination of microscopic defects and cracks. In this case, optimal cleavage conditions are achieved and the best conditions for thermomechanical coupling are created.

Below, a zone extrusion molding apparatus and a zone extrusion molding method according to the invention are described in detail with reference to the drawings, in which Fig. 6 shows a general view of a zone extrusion molding apparatus 100 according to one of the structural variants of the invention; 7 is a front view of the punch in the device for forming a zone extrusion according to one of the structural variants of the invention; and FIG. 8 is a left side view of a punch in a zone extrusion molding apparatus.

According to one embodiment of the invention, the zone extrusion molding apparatus 100 may include: a forming matrix 6 and a punch 9 arranged in a longitudinal direction and configured to enter a non-through cavity 61 of the forming matrix 6 for extruding the workpiece. The punch 9 may include an extrusion shaft 92 and a forming head 93 connected to the extruding shaft 92 and located under the extruding shaft 92. The cross-sectional area of the forming head 93 in a plane perpendicular to the longitudinal axis of the forming matrix 6 is less than the cross-sectional area of the extruding shaft 92. The punch 9 made with the possibility of rotation around the longitudinal axis of the forming matrix 6 so that the workpiece is sequentially and in zones deformed by the forming head 93 into a through cavity 61 oobrazuyuschey 6 matrix.

In the device 100 for forming by zone extrusion according to the invention, by sequentially extruding the preform 9 into the forming matrix 6 over the zones, the metal can flow radially, forming the bottom of the shell, and can rise along the forming shell, forming its cylindrical part. Therefore, such a process can be performed easier and faster, with fewer operations and more efficiently.

In addition, since the metal is extruded by the punch 9 into the forming matrix 6, the workpiece is mainly deformed in a state with compressive loads in three directions, and tensile stresses during deformation can be minimized or even eliminated, so that the shell can have a uniform wall thickness at great strength and high reliability, and cracks and defects can be completely eliminated.

According to one of the structural variants of the invention, the extrusion shaft 92 and the forming head 93 can be made as a single part. It is also possible to separate the extrusion shaft 92 and the forming head 93 so that the forming head 93 can be conveniently replaced, which reduces the cost of manufacturing the punch 9. As shown in Fig. 8, the extrusion shaft 92 may include: a cylindrical section 921 and a flange section 922, molded between the bottom of the cylindrical section 921 and the forming head 93, and the cross-sectional area of the forming head 93 in the plane perpendicular to the longitudinal axis of the forming matrix 6 is less than the cross-section of the flange Single 922. Therefore, in the molding process only the flange portion 922 may contact the inner surface of the extruded preform, thereby reducing the deformation resistance of the metal.

According to one of the structural variants of the invention, the forming matrix 6 may be prestressed, which increases the safety of the extrusion process. The internal diameter of the non-through cavity 61 of the prestressed matrix is larger than the maximum radial size of the extrusion shaft 92 and the forming head 93. The difference in size can be determined and designed based on the requirements for the product obtained.

According to one of the structural variants of the invention, the cross section of the forming head 93 in the plane perpendicular to the longitudinal axis of the forming matrix 6 has a rectangular shape, the long side of the rectangle being equal to the diameter of the extrusion shaft 92, and the ratio of the length of the short side of the rectangle to its long side is from 0.05 to 0 95 and can be selected based on practical needs.

According to one of the structural variants of the invention, the ratio of the cross-sectional area of the forming head 93 to the cross-sectional area of the extrusion shaft 92 is from about 0.1 to 0.9. Thus, the workpiece can be sequentially and in zones extruded using the forming head 93.

According to one embodiment of the invention, during the molding process, the extruding force applied to the punch 9 is distributed over the width of the forming head 93 and the diameter of the extrusion shaft 92.

According to the invention, the extruding force is from about 1000 to 1500 meganewtons, which differs from the extruding force in the range from 100 to 200 used in known methods. The extrusion force in combination with the aforementioned zone extrusion molding apparatus provides high extrusion loads on the workpiece so as to eliminate microscopic defects of the crystal lattice during deformation during extrusion.

According to one structural embodiment of the invention, a recess 94 is made in the central part of the forming head 93. Thus, during extrusion by the punch 9, three-dimensional compressive stresses are created in the material entering the recess 94, as shown in FIG. 9. Therefore, tensile stresses during molding can be minimized or completely eliminated, so that the shell can have a uniform wall thickness with great strength and high reliability, and cracks and defects can be completely eliminated.

According to one of the structural variants of the invention, the non-through cavity 61 of the forming matrix 6 can be round, rectangular or elliptical, and the cross section of at least part of the extrusion shaft 92 can be rectangular, polygonal or elliptical.

During operation of the zone extrusion apparatus 100, due to the fact that the cross-sectional area of the forming head 93 is smaller than that of the extruding shaft 92, the extruding force can be markedly reduced, the extrusion efficiency can be increased, and the ratio of the cross-sectional area of the forming head 93 to the area The cross section of the extrusion shaft 92 may depend on extrusion forces. As described above, the cross section of the forming head 93 has a rectangular shape, the long side of the rectangle being equal to the diameter of the extruding shaft 92, and the ratio of the short side, that is, the width of the rectangle, to the diameter of the extruding shaft 92 depends on the extruding force. The forming matrix 6, the extruding shaft 92 and the forming head 93 are located coaxially. The forming matrix 6 may be of a cylindrical shape with a top hole having an inner diameter larger than the outer extrusion shaft 92 and the forming head 93. In practice, the upper end of the extrusion shaft 92 is detachably fixed to the extrusion press device (not shown), and the lower side of the forming matrix 6 are detachably fixed to the extrusion press desktop. Since the metal is successively and in zones extruded by the extruding shaft 92 and the forming head 93 into the non-through cavity 61 of the forming matrix 6 under very high three-dimensional compressive loads, the metal can flow in the radial direction, forming the bottom of the shell, and can rise along the forming shell, forming its cylindrical part as shown in Fig.9, which provides a one-stage process of forming the shell of a nuclear reactor. Moreover, the metal is squeezed out under the action of three-dimensional compressive stresses, which increases the strength of the resulting shell 1.

Below, a method of forming zone extrusion according to one of the structural variants of the invention will be described with reference to the drawings.

A zone extrusion molding method according to an embodiment of the invention may include: (1) placing a preform with a central recess of a predetermined depth in the forming matrix 6 and heating the preform to a temperature suitable for extrusion molding; and (2) sequentially extruding the preform into sections of the forming matrix 6 using a punch 9, which is rotated around the longitudinal axis of the forming matrix 6, while the punch 9 consists of an extruding shaft 92 and a forming head 93 connected thereto, located under the extruding shaft 92. The cross-sectional area of the forming head 93 in a plane perpendicular to the longitudinal axis of the forming matrix 6 is smaller than that of the extruding shaft 92. The punch 9 mentioned here can be any of the punch 9 described above.

In the method of zone extrusion molding according to one embodiment of the invention, as a result of successive extrusion of the preform into the forming matrix 6 by means of a punch 9, the metal can flow radially, forming the bottom 11 of the shell, and can rise along the forming shell, forming its cylindrical part 12, which provides a one-step process of forming the shell of a nuclear reactor without the use of sheath welding. Therefore, such a process can be performed easier and faster, with fewer operations and more efficiently. In addition, since the metal is extruded by the punch 9 into the forming matrix 6, the workpiece is mainly deformed in a state with three-dimensional compressive loads, and tensile stresses during deformation can be minimized or even eliminated, so that the shell can have a uniform wall thickness with great strength and high reliability, and cracks and defects can be completely eliminated.

A preform molded with a central hole of a predetermined depth will be described below with reference to the drawings, in which Fig. 11 shows a schematic illustration of a preform 1 in a zone extrusion molding method according to the invention; 12 shows the planting of a preform 1 in a zone extrusion molding method to one embodiment of the invention; Fig. 13 shows the stamping of a preform 1 in a zone extrusion molding method to one of the embodiments of the invention; Fig. 14 shows hot pressing of a preform 1 in a zone extrusion molding method to one embodiment of the invention; and FIG. 15 shows a preform deployed after the hot-pressing operation shown in FIG. 14.

First, the cleaned preform 1 is heated to a temperature suitable for extrusion molding, for example, to a temperature of the order of 1050 ° C-1250 ° C. Then, according to the technical conditions, the blank 2 of the workpiece is removed by cutting in an oxygen-acetylene flame or by another method. Sometimes it is necessary to remove both the head 2 of the blank 1 and the bottom section of the blank 1. However, whether it is necessary to cut the bottom section of the blank 1 depends on the quality of the previous cleaning of the bottom section.

Then the preform 1 is planted, as shown in Fig.12. 12, the bottom of the preform 1 is molded with a centering protrusion 3. The preform 1 is placed in the upsetting matrix 4, while the arcuate growth 11 at the bottom of the preform 1 is just placed in the centering recess 41 of the upsetting matrix 4, then applied to the upper part of the preform 1 force to upset the workpiece. Thus, the correct centering protrusion 3 is formed from an arcuate outgrowth 11 at the bottom of the workpiece 1 during its upsetting. The workpiece 1 can be planted in open or closed stamp, respectively.

Next, the planted blank 1 can be subjected to stamping, as shown in Fig.13. The workpiece 1 is first centered using a centering protrusion 3. Then, the upper part 13 of the workpiece 1 is stamped with a central punch 5 with a guide device to form a central recess 12 of a given depth and a given diameter.

Then, the preform 1 with the molded central recess 12 is subjected to hot flashing. That is, the preform 1 with the molded central recess 12 is installed in the forming matrix 6. The first piercing 7 is lowered, extruding the preform 1 as the center of the first piercing 7 moves along the central depression 12 on the upper surface 13 of the preform 1, so that the depth and diameter of the central recesses 12 were increased to predetermined values.

Then the workpiece 1 is subjected to extrusion sequentially in zones. As shown in FIG. 6, the preform 1 is placed in the forming matrix 6 and set using the centering protrusion 3 at the bottom of the preform 1, the centering protrusion 3 down. The metal is extruded by the extruding shaft 92 and the forming head 93 along the central hole 12 of the workpiece 1 under the action of an extruding force of 1000 - 1,500 meganewtons so that the metal can flow in the radial direction, forming the bottom 11 of the shell and can rise along the forming shell, forming its cylindrical part. Then the forming head 93 is raised for reinstallation along with the extrusion shaft 92 and with it rotate by a predetermined angle a. After that, the metal is again extruded by the extrusion shaft 92 and the forming head 93 along the central recess 12 of the workpiece 1, and these steps are repeated until the upper edge of the extruded workpiece 1 becomes flat. At each stage of the process, the forming head 93 is rotated by a predetermined angle and together with the extrusion shaft 92.

The process is carried out as follows. The blank 1 is placed in the forming matrix 6 and successively, over and over, extruded into zones by the extruding shaft 92 and the forming head 93. As a result of extrusion by the forming head 93, the metal flows essentially radially in the direction from the forming head 93. According to the law of least resistance to metal flow, formulated by the Soviet scientist Ivan Gubkin, metal flows most rapidly in the position when the distance between the forming head 93 and the inner wall of the central recess 12 of the workpiece 1 is maximum. Thus, when the central recess 12 of the workpiece 1 is extruded by the forming head 93, the flowing metal penetrates into the gap between the forming matrix 6 and the extrusion shaft 92 and flows upward along the forming shell, so that the height of the section on the cylindrical part of the shell at the place where the metal flows faster , becomes greater than the height of other sections on the cylindrical part of the shell. Since the forming head 93 is rotated sequentially and in one direction in the central recess 12 of the workpiece 1, and the forming head 93 is rotated by a predetermined angle a after each extrusion step in a separate zone, the upper edge of the shell extruded from the workpiece 1 at the end becomes flat. Obviously, the smaller the predetermined angle a, by which the forming head 93 is rotated, the smaller the height difference at the upper edge of the shell extruded from the workpiece 1. Many extrusion steps in individual zones comprise one zone extrusion stage. That is, one stage of zone extrusion consists of many extrusion steps in a separate zone. The number of extrusion steps in individual zones is determined by dividing 360 by the value of the specified angle a.

After the zone extrusion stage described above, the preform 1 is respectively adjusted as shown in FIG. 10. The entire inner surface of the extruded preform obtained from the initial preform 1 passes along the central recess 12 of the preform 1 with a finishing extruding shaft 10 so that the inner cavity of the extruded preform 1 has a flat surface and the extruded preform has a uniform wall thickness. After lifting and proper rotation of the finishing extruder shaft 10, extrusion finishing is repeated in order to eliminate the influence of the eccentricity of the extrusion extrusion shaft 10 and to improve the accuracy of finishing.

It should be noted that the zone extrusion stage and the finishing stage described above can be carried out alternately until the height, thickness, and relief of the upper edge of the extruded workpiece reach the required predetermined values.

According to one embodiment of the invention, when the preform 1 is subjected to zone extrusion, the speed at which the preform 1 is extruded by the forming head 93 along the central recess 12 of the preform 1 is related to the type of material of the preform 1. For example, the immersion speed of the forming head in the preform can be maintained in the range of 5 mm / s to 90 mm / s, if the workpiece is made of iron alloys with a high melting point or stainless steel. In another example, the lowering speed of the forming head 93 during extrusion can be maintained in the range from 20 mm / s to 300 mm / s if the workpiece is made of non-iron-based alloys, for example, aluminum or copper alloys.

According to the invention, when the forming head 93 is not in contact with the metal, both the lifting speed and lowering speed of the forming head 93 can be from 90 mm / s to 300 mm / s.

When the workpiece 1 is subjected to zone extrusion, the rotation angle a is from 10 to 120 degrees.

According to the invention, the displacement at the zone extrusion stage is from 2 mm to 2000 mm.

The pressing speed of the finishing extruding shaft 10, the lifting speed and lowering speed of the finishing extruding shaft 10, when it is not in contact with the metal at the finishing stage, can be the same as the pressing speed of the forming head 93, as well as the lifting speed and lowering speed of the forming head 93, when forming the head 93 does not come into contact with the metal in the zone of extrusion, respectively, but the extrusion movement each time in the finishing stage exceeds the movement in the extrusion stage by 0.01-0 .5 times.

According to one embodiment of the invention, after the hot flashing step, a hot flashing step can be carried out. That is, the central recess 12 of the workpiece 1 is deployed using a second firmware 8, the diameter of which is larger than that of the first firmware 7, thereby contributing to further deformation of the workpiece, as shown in FIG. It should be noted that both the hot flashing stage and the hot rolling stage can occur in the forming matrix 6.

The zone extrusion molding method according to the invention can also be used to mold vessels operating under high and ultrahigh pressure and requiring high reliability, such as a nuclear reactor steam generator, a hydrogenation reactor or large volume vessels for storing natural gas under high pressure, for example, the bottom of a water tank steam generator of a nuclear reactor.

In general, in the device and method for forming by zone extrusion according to an embodiment of the invention, due to the large generated extrusion force from 1000 to 1500 meganewtons, the coupling reaction is significantly improved, the best conditions for deformation of the metal are created (with intensive extrusion and through / through piercing / piercing) and can be achieved high and uniform spherical stress tensor σ _m (typically reaches 300 to 400 MPa), which provides optimum conditions for removal of microscopic defects and cracks on Zagot ke 1 and creates the best conditions for thermomechanical coupling. In addition, when using the device and method of forming by zone extrusion according to the invention, productivity can be significantly increased, the percentage of rejects can be reduced and, accordingly, the degree of useful use of the material can be increased.

The terms throughout the description "embodiment", "options for implementation", "one constructive option", "example", "separate example", or "some examples" mean that individual features, structures, materials or parameters given for example or constructive options relate to at least one of the options or examples of the invention. Verbal expressions, such as “in some structural options”, “According to one of the constructive variants of the invention”, “in a constructive variant”, “example”, “separate example”, or “some examples” in different places of the description do not necessarily mean sending only to one specific example embodiment of the invention. Moreover, individual features, structures, materials or parameters may be combined in any suitable way in one or more design options or examples.

Although explanatory examples have been presented and described, one skilled in the art will appreciate that changes, variations and modifications may be present in constructive variations without departing from the spirit and meaning of the invention. All such changes, variations and modifications fall within the scope of the claims in the claims and their equivalents.

Claims (18)

1. A device for forming a zone extrusion, containing:
shape matrix and
a punch located in the longitudinal direction and configured to enter into the forming cavity of the forming matrix for extruding the workpiece,
moreover, the punch consists of an extrusion shaft and a forming head connected to the extruding shaft and located under it, while the cross-sectional area of the forming head in the plane perpendicular to the longitudinal axis of the forming matrix is less than the cross-sectional area of the extruding shaft, while in the central part of the forming head is made a recess for creating three-dimensional compressive stresses in the workpiece material,
and the punch is made with the possibility of rotation around the longitudinal axis of the forming matrix for successive zones of deformation of the workpiece by the forming head inside the cavity through the cavity of the forming matrix. 2. The device according to claim 1, characterized in that the extrusion shaft includes:
cylindrical section and
a flange portion molded between the bottom of the cylindrical shaft portion and the forming head, wherein the cross-sectional area of the forming head in a plane perpendicular to the longitudinal axis of the forming matrix is smaller than the cross-sectional area of the flange portion. 3. The device according to claim 1, characterized in that the extrusion shaft and the forming head are made as a single part, and the forming matrix is pre-stressed, and the inner diameter of the forming cavity of the prestressed forming matrix is larger than the maximum diameter of the extruding shaft and forming head. 4. The device according to claim 1, characterized in that the cross section of the forming head in a plane perpendicular to the longitudinal axis of the forming matrix has a rectangular shape, the long side of the rectangle being equal to the diameter of the extruding shaft, and the ratio of the length of the short side of the rectangle to its long side is from 0.05 to 0.95. 5. The device according to claim 1, characterized in that the ratio of the cross-sectional area of the forming head to the cross-sectional area of the extruding shaft is from about 0.1 to 0.9. 6. A method of forming by zone extrusion, including:
(1) placing the preform with a central recess of a predetermined depth in the forming matrix and heating the preform to a temperature suitable for extrusion molding,
(2) sequentially extruding the preform into zones of the forming matrix with the help of a punch that is rotated around the longitudinal axis of the forming matrix, the punch consisting of an extrusion shaft and a forming head connected to it, located under the extrusion shaft and having a recess in the central part, providing in the workpiece material three-dimensional compressive stresses, and the cross-sectional area of the forming head in the plane perpendicular to the longitudinal axis of the forming matrix is less ie cross-sectional area of the shaft extrusion. 7. The method according to claim 6, characterized in that stage (2) includes:
(2.1) extruding the workpiece in a central recess with a predetermined force,
(2.2) raising the punch for reinstallation,
(2.3) the rotation of the punch relative to the longitudinal axis of the forming matrix by a given angle and
(2.4) repetition of stages (2.1), (2.2) and (2.3). 8. The method according to claim 6, characterized in that the extrusion shaft includes:
cylindrical section and
a flange portion molded between the bottom of the cylindrical shaft portion and the forming head, wherein the cross-sectional area of the forming head in a plane perpendicular to the longitudinal axis of the forming matrix is smaller than the cross-sectional area of the flange portion. 9. The method according to claim 6, characterized in that at the stage (2) the extruding force applied to the punch is distributed along the width of the forming head and the diameter of the extruding shaft, and the extruding force is from about 1000 to 1500 MN. 10. The method according to claim 6, characterized in that it further includes:
(3) fine-tuning the inner surface of the preform extruded in step (2) along its central recess with a finishing extruding shaft to impart a uniform thickness to the walls of the preform. 11. The method according to claim 10, characterized in that stages (2) and (3) are alternately performed to extrude the workpiece. 12. The method according to claim 7, characterized in that the predetermined angle of rotation of the punch is from 10 to 120 °. 13. The method according to claim 7, characterized in that stage (2) further includes:
fine-tuning the inner surface of the extruded workpiece along its central recess with a finishing extruding shaft to give a uniform thickness to the walls of the workpiece. 14. The method according to claim 10, characterized in that at the stage (2) the movement during extrusion is from 2 mm to 2000 mm, and the extrusion movement at the stage (3) each time exceeds the movement at the stage (2) by 0.01- 0.5 times. 15. The method according to claim 6, characterized in that the immersion speed of the forming head in the workpiece is in the range from 5 mm / s to 90 mm / s, if the workpiece is made of iron alloys, or from 20 mm / s to 300 mm / s if the workpiece is made of non-iron based alloys. 16. The method according to claim 6, characterized in that the forming matrix is pre-stressed, and the inner diameter of the through cavity of the prestressed matrix is larger than the maximum diameter of the extruding shaft and the forming head. 17. The method according to claim 6, characterized in that the Central recess of a given depth is molded through the endless landing, stamping and hot piercing of the workpiece in the forming matrix, respectively, and the extruding shaft and the forming head are made as a single part. 18. The method according to claim 6, characterized in that the cross-section of the forming head has a rectangular shape, and the long side of the rectangle is equal to the diameter of the extrusion shaft, and the ratio of the length of the short side of the rectangle to its long side is from 0.05 to 0.95 or the ratio the cross-sectional area of the forming head to the cross-sectional area of the extrusion shaft is from about 0.1 to 0.9.

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