An ellipsoidal head of a large steam generator and a forming method thereof

Abstract

The present invention relates to the technical field of nuclear power equipment. Specifically, it relates to a large steam generator ellipsoidal head and a forming method thereof. The method includes: preparing a blank, the blank including a columnar main body; placing the blank in a first mold, upsetting the columnar main body of the blank to obtain a first intermediate blank; assembling a second mold at the upper end of the first mold to expand the first mold cavity to form a second mold cavity, using a semi-ellipsoidal punch to punch a semi-ellipsoidal blind hole on the upper end surface of the first intermediate blank to obtain a second intermediate blank; simultaneously turning the second intermediate blank, the second mold, the first mold, and the semi-ellipsoidal punch downward by 180°, removing the mold, and using a shaping hammer head to perform spin forming on the second intermediate blank to obtain an ellipsoidal head. The present invention can not only effectively avoid the punch from being locked during the punching process, but also avoid the appearance of scale pits at the spherical bottom of the head after the head is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power equipment, and more particularly, to a large steam generator ellipsoidal head and a forming method thereof. Background Art

[0002] A nuclear power steam generator is one of the three major equipment in a nuclear island. As the power of nuclear power units gradually increases, the diameter of the main equipment also increases accordingly. The steam generator is a container with a forged and welded structure, and its upper part is an ellipsoidal head with a straight section. At present, the diameter of the ellipsoidal head of the third-generation nuclear power AP1000 exceeds 5 meters, and the diameter of the ellipsoidal head of the third-generation nuclear power CAP1400 reaches 6.4 meters. The ellipsoidal heads of traditional second-generation plus nuclear power evaporators are relatively small. Generally, such heads are forged circular blanks, and then machined and finally formed on a hydraulic press. However, if the diameter of the head is extremely large, the diameter of the required blank will also be extremely large. After calculation, if the blank forming process is adopted, the diameter of the circular blank required for the AP1000 ellipsoidal head reaches 7.5 meters, and the blank of the CAP1400 ellipsoidal head exceeds 8 meters. Due to the extremely large diameter of the blank, the manufacturing of the blank is restricted by the column spacing of the press. In addition, since the diameter of the blank exceeds the column spacing of the hydraulic press, the forming cannot be completed between the columns of the press. Therefore, the traditional manufacturing method cannot be used to manufacture super-large ellipsoidal heads. The super-large head forgings are generally formed by the method of die forging. First, a cylindrical blank is forged, and then it is first placed in a mold and upset within the mold with a cover plate, and then a sector-shaped hammer head is used for rotary forging to form. However, this method has the following problems:

[0003] First of all, the situation of the hammer head being locked is likely to occur. Similar to the special-shaped head forgings such as the ellipsoidal heads of the AP1000 and CAP1400 evaporators and the water chamber heads, the die cavity depth is relatively deep, and there is a straight section with a certain height in the inner cavity. Generally, the design of the strip-shaped hammer head will have a certain draft angle to avoid being locked with the blank during the spinning process. However, in order to reduce the machining allowance of the inner cavity, the draft angle of the hammer head cannot be enlarged too much. Therefore, after spinning for a period of time, the deformation resistance of the material increases, and the situation where the hammer head is locked with the blank may still occur. At this time, forging cannot continue. On the one hand, the design of the hammer head with a certain draft angle increases the forging allowance to a certain extent, and on the other hand, the limitation of its pressing depth further leads to an increase in the allowance at each position of the inner cavity.

[0004] In addition, scale pits are likely to appear at the bottom of the sealing head ball. After the forming in the tyre mold, deep scale pits are caused by the accumulation of scale from multiple heating processes at the bottom of the sealing head ball. During the forming process, the scale in the spherical cavity cannot be cleaned, and the scale always accumulates towards the bottom of the ball during each forging process. Subsequently, the scale is pressed into the matrix during the spinning process. For the forged parts of special-shaped sealing heads formed by multi-pass spinning, the depth of the scale pit at the center of the bottom of the ball can reach 200 - 300 mm. Therefore, in order to avoid scrapping the workpiece due to the relatively deep scale pit, it is necessary to increase the forging allowance at the bottom of the ball. Summary of the Invention

[0005] The technical problems solved by the present invention are at least one of the following problems: during the forging of an extra-large ellipsoidal sealing head using the existing tyre forming method, the hammer head is likely to be locked; during the forging of an extra-large ellipsoidal sealing head using the existing tyre forming method, scale pits are likely to appear at the bottom of the sealing head ball after the forming of the sealing head.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A forming method for an ellipsoidal sealing head of a large steam generator, comprising:

[0008] Step S1, preparing a blank, the blank including a columnar main body;

[0009] Step S2, placing the blank in a first mold, upsetting the columnar main body of the blank to obtain a first intermediate blank; wherein, the inner cavity of the first mold includes a first mold cavity with an upward opening;

[0010] Step S3, assembling a second mold at the upper end of the first mold to expand the first mold cavity to form a second mold cavity, and punching a semi-ellipsoidal blind hole on the upper end surface of the first intermediate blank using a semi-ellipsoidal punch to obtain a second intermediate blank; wherein, the second mold cavity is semi-ellipsoidal;

[0011] Step S4, turning the second intermediate blank, the second mold, the first mold and the semi-ellipsoidal punch downward by 180° simultaneously, removing the second mold and the first mold, and performing spinning forming on the second intermediate blank using a shaping hammer head to obtain an ellipsoidal sealing head.

[0012] Optionally, in the step S1, the blank further includes a convex platform, and the convex platform is connected to the middle area of the lower end surface of the columnar main body.

[0013] Optionally, in the step S2, the inner cavity of the first mold further includes a positioning cavity, the positioning cavity and the first mold cavity are distributed in sequence from bottom to top to form the inner cavity, and the convex platform is stuck in the positioning cavity.

[0014] Optionally, in the step S3, the first mold cavity is equivalent to the bottom of the second mold cavity.

[0015] Optionally, the second mold is a cylindrical structure with openings at both the upper and lower ends, the first mold is a cylindrical structure with an opening at the top, a circular protrusion is formed at the lower end of the second mold, and a circular notch matching the circular protrusion is formed at the upper end of the first mold.

[0016] Optionally, the shaping hammer head is a double-sector hammer head. The double-sector hammer head includes a cross beam and two sector hammer heads. The two sector hammer heads are respectively fixed to the lower sides of both ends of the cross beam. The two sector hammer heads and the cross beam enclose to form an insertion opening therebetween. When the shaping hammer head performs spin forming on the second intermediate blank, the boss of the second intermediate blank is located within the insertion opening.

[0017] Optionally, the sector hammer head is fixed to the cross beam by inclined ribs.

[0018] Optionally, after the step S4, there is further included a step S5, and the step S5 includes: assembling the first mold and the second mold into an integral mold, sleeving the integral mold downward on the ellipsoidal head, and applying pressure to the ellipsoidal head so that a straight section is formed at the lower part of the ellipsoidal head.

[0019] The present invention also provides a large steam generator ellipsoidal head, which is obtained by using the forming method of the large steam generator ellipsoidal head as described above.

[0020] Optionally, the major axis diameter of the large steam generator ellipsoidal head is greater than 5 m.

[0021] Compared with the prior art, in the present invention, an integral semi-ellipsoidal punch is used in cooperation with a die to punch a spherical blind hole on the upper end face of a blank, so as to achieve the purpose of shaping the inner contour of the head. Since the punching depth is small, the problem of punch seizure will not occur. Moreover, an integral semi-ellipsoidal punch is used instead of a strip hammer head for spinning to shape the inner contour of the head. During the punching process, the entire upper end face of the punch and the blank always remain in contact, and the scale is always clamped between the blank and the hammer head and cannot move relatively. This can effectively prevent the scale from accumulating at the bottom of the head during the punching process, thereby avoiding the appearance of scale pits at the spherical bottom of the head after the head is formed; after the inner contour of the head is shaped, the second intermediate blank is integrally flipped 180° for spinning forming, so as to thin the wall thickness of the second intermediate blank while broadening the diameter of the second intermediate blank and pressing down the edge of the second intermediate blank to form a spherical blank. During this process, since the opening of the second intermediate blank is downward and the punch always remains in contact with the inner wall of the second intermediate blank throughout the process, the scale cannot transfer to the spherical bottom of the head during this process, thus further avoiding the appearance of scale pits at the spherical bottom of the head after the head is formed. In summary, the present invention can not only effectively prevent the punch from seizing during the punching process, but also avoid the appearance of scale pits at the spherical bottom of the head after the head is formed, can realize the near-net forming of the ellipsoidal head of a large steam generator, reduce the machining allowance, and also avoid the generation of waste products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic process flow diagram of the ellipsoidal head of a large steam generator in an embodiment of the present invention;

[0023] Figure 2 is a schematic diagram after placing the blank in the first die in step S2;

[0024] Figure 3 is a schematic diagram after upsetting the blank in step S2;

[0025] Figure 4 is a schematic diagram after assembling the second die on the upper end of the first die in step S3;

[0026] Figure 5 is a schematic diagram after punching a semi-ellipsoidal blind hole on the upper end face of the first intermediate blank in step S3;

[0027] Figure 6 is a schematic diagram after the second intermediate blank is turned downward by 180° and the die is removed in step S4;

[0028] Figure 7 is a schematic diagram after the straight section of the ellipsoidal head of a large steam generator is formed in step S5;

[0029] Figure 8 is a schematic structural diagram of a strip hammer head in the prior art;

[0030] Figure 9 This is a schematic structural view of the first mold in the embodiments of the present invention;

[0031] Figure 10 This is a schematic view when the first mold and the second mold in the embodiments of the present invention are assembled together;

[0032] Figure 11 This is a schematic structural view of the sizing hammer head in the embodiments of the present invention.

[0033] Description of the reference numerals:

[0034] 1. Blank, 101. Columnar main body, 102. Boss, 2. First mold, 201. First mold cavity, 202. Positioning cavity, 3. First intermediate blank, 4. Second mold, 5. Second mold cavity, 6. Semi-ellipsoidal punch, 7. Second intermediate blank, 8. Sizing hammer head, 801. Cross beam, 802. Sector-shaped hammer head, 803. Oblique rib, 9. Strip-shaped hammer head. Detailed implementation manners

[0035] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings.

[0036] It should be noted that, without conflict, the features in the embodiments of the present invention can be combined with each other. The meanings of the terms "comprising", "including", "containing", "having" are non-restrictive, that is, other steps and other components that do not affect the result can be added. The above terms cover the terms "consisting of" and "consisting essentially of". At the same time, it should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. Unless otherwise specified, the materials, equipment, and reagents are all commercially available.

[0037] In addition, it should be noted that the ellipsoidal head of the large steam generator in the present invention refers to the ellipsoidal head of the steam generator with a major axis diameter exceeding 5 meters

[0038] As Figures 1-6 shown, the embodiments of the present invention provide a forming method for the ellipsoidal head of a large steam generator, including:

[0039] Step S1, prepare the blank 1, as Figure 2 shown, the blank 1 includes a columnar main body 101. Exemplarily, the columnar main body 101 is cylindrical;

[0040] Step S2, as Figure 2 and Figure 3As shown, place the blank 1 in the first mold 2, upset the columnar main body 101 of the blank 1 to obtain the first intermediate blank 3. Figure 2 As shown; among which, as Figure 9 shown, the inner cavity of the first mold 2 includes a first mold cavity 201 with an upward opening.

[0041] Step S3: As Figure 4 and Figure 5 shown, assemble the second mold 4 at the upper end of the first mold 2 to expand the first mold cavity 201 to form a second mold cavity 5, and use a semi-ellipsoidal punch 6 to punch a semi-ellipsoidal blind hole on the upper end face of the first intermediate blank 3 to obtain a second intermediate blank 7; among which, as Figure 5 and Figure 10 shown, the second mold cavity 5 is semi-ellipsoidal, and during the process of punching the blind hole, the outer contour of the first intermediate blank 3 is shaped according to the inner contour of the second mold cavity 5.

[0042] Step S4: As Figure 6 shown, turn the second intermediate blank 7, the second mold 4, the first mold 2 and the semi-ellipsoidal punch 6 downward by 180° simultaneously, remove the second mold 4 and the first mold 2, and use a sizing hammer head 8 to perform spin forming on the second intermediate blank 7 to obtain an ellipsoidal head.

[0043] It should be noted that in steps S2, S3 and S4, before upsetting, punching the blind hole and spin forming the blank 1, the first intermediate blank 3 and the second intermediate blank 7, they need to be heated to the forging temperature first, and the forging temperature is 1200 - 1240°C.

[0044] In the prior art, when shaping the inner contour of the head, generally, the spin forming method with a strip-shaped hammer head 9 as Figure 8 shown is adopted. During the spin forming process, since the strip-shaped hammer head 9 is in a partial contact state with the upper end face of the blank, the scale will continuously gather towards the bottom of the blank due to the action of gravity during the punching process, so there will be scale pits at the spherical bottom of the head after the head is formed.

[0045] Compared with the prior art, in the present invention, by using the integral semi-ellipsoidal punch 6 in cooperation with the die to punch a spherical blind hole on the upper end face of the blank, the purpose of shaping the inner contour of the head is achieved. Since the punching depth is small, the problem of the punch being locked will not occur. Moreover, by using the integral semi-ellipsoidal punch 6 instead of the strip hammer head for spinning to shape the inner contour of the head, during the punching process, the entire upper end face of the punch and the blank always remain in contact, and the scale is always clamped between the blank and the hammer head and cannot move relatively, which can effectively prevent the scale from accumulating at the bottom of the head during the punching process, thereby avoiding the appearance of scale pits at the bottom of the spherical head after the head is formed; after the inner contour of the head is shaped, the second intermediate blank 7 is integrally flipped 180° for spinning forming, so as to thin the wall thickness of the second intermediate blank 7 while widening the diameter of the second intermediate blank, and pressing down the edge of the second intermediate blank 7 to form a spherical blank. During this process, since the opening of the second intermediate blank 7 is downward and the punch always remains in contact with the inner wall of the second intermediate blank 7 throughout the process, the scale cannot transfer to the bottom of the spherical head of the head during this process, thus further avoiding the appearance of scale pits at the bottom of the spherical head of the head after the head is formed. In summary, the present invention can not only effectively prevent the punch from being locked during the punching process, but also avoid the appearance of scale pits at the bottom of the spherical head of the head after the head is formed, can realize the near-net forming of the ellipsoidal head of the large steam generator, reduce the machining allowance, and also avoid the generation of waste products.

[0046] In some embodiments of the present invention, such as Figure 2 shown, in the step S1, the blank 1 further includes a boss 102, and the boss 102 is connected to the middle area of the lower end face of the columnar body 101. The setting of the boss 102 is beneficial to the centering of the blank during upsetting in the first die 2 and is also beneficial to the filling of the blank during upsetting. Exemplarily, the boss 102 is generally cylindrical and is arranged at the exact middle position of the lower end face of the columnar body 101.

[0047] In some embodiments of the present invention, such as Figure 2 and Figure 9 shown, in the step S2, the inner cavity of the first die 2 further includes a positioning cavity 202. The positioning cavity 202 and the first die cavity 201 are distributed in sequence from bottom to top to form the inner cavity. The shape of the positioning cavity 202 matches the shape of the boss 102. When the blank 1 is installed in the first die, the boss 102 is stuck in the positioning cavity 202, thereby realizing the positioning of the blank 1.

[0048] In some embodiments of the present invention, in the step S3, such as Figure 4 and Figure 10 shown, the first die cavity 201 is equivalent to the bottom of the second die cavity 5.

[0049] In some embodiments of the present invention, such as Figure 4and Figure 5 As shown, the second mold 4 is a cylindrical structure with openings at both the upper and lower ends, and the first mold 2 is a cylindrical structure with an opening at the top. An annular protrusion is formed at the lower end of the second mold 4, and an annular notch matching the annular protrusion is formed at the upper end of the first mold 2. They can be fixed by bolts, which facilitates the assembly and disassembly of the first mold 2 and the second mold 4. The area of the upper opening of the second mold 4 is larger than that of the lower opening, and the area of the lower opening of the second mold 4 matches the area of the upper opening of the first mold 2. The upper opening of the second mold 4 serves as the opening of the second mold cavity 5 formed after expansion, which is larger than the opening of the first mold cavity 201. The second mold cavity 5 is formed by expanding from the first mold cavity 201, realizing the expansion of the cavity accommodation volume and the inner surface.

[0050] In some embodiments of the present invention, as Figure 11 shown, the shaping hammer head 8 is a double-sector hammer head. The double-sector hammer head includes a cross beam 801 and two sector hammer heads 802. The two sector hammer heads 802 are respectively fixed to the lower sides of both ends of the cross beam 801. The two sector hammer heads 802 and the cross beam 801 enclose to form an insertion opening therebetween. When the shaping hammer head 8 performs spin forming on the second intermediate blank 7, the boss of the second intermediate blank 7 is located within the insertion opening. Exemplarily, the sector hammer head 802 is fixed to the cross beam 801 through an inclined rib 803. When using the shaping hammer head 8 to perform spin forming on the second intermediate blank 7, the sector surface of the sector hammer head 802 contacts the second intermediate blank 7.

[0051] In some embodiments of the present invention, as Figure 7 shown, after the step S4, there is further included a step S5. The step S5 includes: assembling the first mold 2 and the second mold 4 into an integral mold, sleeving the integral mold downward on the ellipsoidal head, and applying pressure to the ellipsoidal head so that a straight section is formed at the lower part of the ellipsoidal head. In the existing method, the straight section of the head with a straight section is formed during the forming process of the inner contour of the head, so the punching depth is relatively deep, and the situation of the punch being locked is likely to occur. The present invention is more applicable to the forming of large-sized ellipsoidal heads of steam generators with straight sections. In the present invention, since the straight section of the head is formed by pressing downward with the integral mold after the semi-ellipsoidal section of the head is formed, the punching depth of the punch during the plastic forming process of the inner contour of the head can be reduced, thus effectively avoiding the occurrence of the situation of the punch being locked.

[0052] An embodiment of the present invention also provides a large-sized ellipsoidal head of a steam generator, which is obtained by using the forming method of the large-sized ellipsoidal head of a steam generator as described above.

[0053] In some embodiments of the present invention, the major axis diameter of the ellipsoidal head of the large steam generator is greater than 5 m.

[0054] In addition, it should be noted that although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Without departing from the spirit and scope of the present invention, those skilled in the art can make various changes and modifications, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A forming method for an ellipsoidal head of a large steam generator, characterized in that, Including: Step S1: Prepare a blank (1), the blank (1) includes a columnar main body (101); Step S2: Place the blank (1) in a first mold (2), upset the columnar main body (101) of the blank (1) to obtain a first intermediate blank (3); wherein, the inner cavity of the first mold (2) includes a first mold cavity (201) with an upward opening; Step S3: Assemble a second mold (4) at the upper end of the first mold (2) to expand the first mold cavity (201) to form a second mold cavity (5), use a semi-ellipsoidal punch (6) to punch a semi-ellipsoidal blind hole on the upper end face of the first intermediate blank (3) to obtain a second intermediate blank (7); wherein, the second mold cavity (5) is semi-ellipsoidal; Step S4: Simultaneously turn the second intermediate blank (7), the second mold (4), the first mold (2) and the semi-ellipsoidal punch (6) downward by 180°, remove the second mold (4) and the first mold (2), and use a shaping hammer head (8) to perform spin forming on the second intermediate blank (7) to obtain an ellipsoidal head.

2. The forming method of the ellipsoidal head of a large steam generator according to claim 1, characterized in that, In the step S1, the blank (1) further includes a boss (102), and the boss (102) is connected to the middle area of the lower end face of the columnar main body (101).

3. The forming method of the ellipsoidal head of a large steam generator according to claim 2, characterized in that, In the step S2, the inner cavity of the first mold (2) further includes a positioning cavity (202), and the positioning cavity (202) and the first mold cavity (201) are distributed from bottom to top in sequence to form the inner cavity, and the boss (102) is stuck in the positioning cavity (202).

4. The forming method of the ellipsoidal head of a large steam generator according to claim 3, characterized in that, In the step S3, the first mold cavity (201) is equivalent to the bottom of the second mold cavity (5).

5. The forming method of the ellipsoidal head of a large steam generator according to claim 4, characterized in that The second mold (4) is a cylindrical structure with openings at both the upper end and the lower end, the first mold (2) is a cylindrical structure with an opening at the top, a circular protrusion is formed at the lower end of the second mold (4), and a circular notch matching the circular protrusion is formed at the upper end of the first mold (2).

6. The forming method of the ellipsoidal head of a large steam generator according to claim 2, characterized in that, The shaping hammer head (8) is a double-sector hammer head, the double-sector hammer head includes a cross beam (801) and two sector hammer heads (802), the two sector hammer heads (802) are respectively fixed to the lower sides of both ends of the cross beam (801), and the two sector hammer heads (802) and the cross beam (801) surround each other to form an insertion opening therebetween. When the shaping hammer head (8) performs spin forming on the second intermediate blank (7), the boss of the second intermediate blank (7) is located in the insertion opening.

7. The forming method of the ellipsoidal head of a large steam generator according to claim 6, characterized in that, The sector hammer head (802) is fixed to the cross beam (801) through an inclined rib (803).

8. The forming method of the ellipsoidal head of a large steam generator according to claim 1, characterized in that, After the step S4, there is further a step S5, and the step S5 includes: Assemble the first mold (2) and the second mold (4) into an integral mold, sleevethe integral mold downward on the ellipsoidal head, and apply pressure to the ellipsoidal head so that a straight section is formed at the lower part of the ellipsoidal head.

9. An ellipsoidal head of a large steam generator, characterized in that, It is obtained by using the forming method of the ellipsoidal head of a large steam generator as described in any one of claims 1-8.

10. The ellipsoidal head of the large steam generator according to claim 9, characterized in that, The major axis diameter of the ellipsoidal head of the large steam generator is greater than 5 m.

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