CN107695163B

CN107695163B - Nuclear island evaporator end socket integral stamping forming device and stamping forming method

Info

Publication number: CN107695163B
Application number: CN201710933267.XA
Authority: CN
Inventors: 张乐福; 夏爽; 陈芙甜; 许丽娇; 周怡君; 马武江
Original assignee: SHANGHAI XINMIN (DONGTAI) HEAVY FORGING CO Ltd
Current assignee: SHANGHAI XINMIN (DONGTAI) HEAVY FORGING CO Ltd
Priority date: 2017-10-10
Filing date: 2017-10-10
Publication date: 2023-06-16
Anticipated expiration: 2037-10-10
Also published as: CN107695163A

Abstract

The invention discloses an integral stamping forming device for a seal head of a nuclear island evaporator, which comprises a forming punch and a forming ring anvil corresponding to the forming punch, wherein a punch body of the forming punch consists of a punch forming section and a punch crown, a generatrix of the punch forming section is an involute, and a circle center of a forming involute base circle of the involute generatrix is positioned on the bottom surface of the punch body; the top crown of the punch head is a spherical crown; the inner hole surface of the forming ring anvil is a ring anvil forming surface, and the ring anvil forming surface is an involute curved surface. The stamping forming method comprises the following steps: (1) heating and blanking; (2) forging stock upsetting and drawing; (3) slab forming; (4) integrally molding; (5) heat treatment of the forging; and (6) processing a finished product. The invention has higher stamping forming efficiency, uniform and compact forging structure, complete metal streamline, more consistent forging fiber structure and appearance, and uniform head microstructure and mechanical property.

Description

Nuclear island evaporator end socket integral stamping forming device and stamping forming method

Technical Field

The invention relates to a large structural member for nuclear power facilities, in particular to an impact forming device capable of integrally forging a nuclear power island steam generator lower end socket blank. The invention also relates to a method for forging the integral lower end socket of the steam generator by using the stamping forming device.

Background

The pressurized water reactor nuclear power station mainly comprises a nuclear island and a conventional island, and four parts of the pressurized water reactor nuclear power station nuclear island are a steam generator, a voltage stabilizer, a main pump and a reactor core. The nuclear island steam generator is the most critical main equipment of the nuclear power station, is connected with a reactor pressure vessel, is a component with the largest pressure difference, plays a role in sealing and isolating the primary and secondary loop coolants, also plays a role in collecting the chamber before or after the primary loop side coolants flow through the tube bundle, directly influences the power and the efficiency of the power station, plays a role in blocking the radioactive heat carrier when carrying out heat exchange, and is critical to the safety of the nuclear power station.

The lower end socket of the steam generator structurally comprises a main body sphere, an outlet and an inlet connecting pipe of a loop coolant and two manhole seats, wherein the diameter of a tube plate of the lower end socket can reach 7-8 meters, the weight of a single finished product part is more than tens of tons, the lower end socket belongs to a complex nuclear primary forging with large volume, large section, complex curved surface and multiple diameters, and the forging difficulty is very high. Due to the complex structural shape and the limitation of the self-hardenability of the material (SA 508 Gr.3 Cl.2 steel), various production links such as smelting, forging, heat treatment and the like must be comprehensively arranged to obtain uniform microstructure and mechanical properties, thereby achieving the purposes of controlling and controlling so as to improve the reliability and safety of the integrally forged lower seal head.

The existing steam generator bottom head is mostly manufactured by splicing through a welding method, although the performance of welding materials is greatly improved along with the development of material science, a new welding process is also endlessly developed, a spliced structure can not always form a complete metal streamline through welding, and the nuclear power steam generator is in a severe running environment with high temperature and high pressure for a long time and bears pressure mutation formed by alternating load and pipeline vortex, so that uneven stress distribution and concentrated stress are easily caused, and fatigue, creep and damage are easily generated. The welding manufacturing method is complex in process, long in welding period, poor in quality stability of complex stress areas, low in yield and high in manufacturing cost. The applicant firstly performs trial production of integral stamping forming of the lower seal head of the steam generator in China, and realizes integral forging forming of the seal head on a large-tonnage hydraulic press by means of an annular lower anvil and a spherical crown forming punch head. Firstly, as the curvature radius of each stamping point of the spherical crown punch is always fixed, and the deformation of each section of the head forging stock is larger and larger along with the continuous undershoot of the punch in the actual stamping process, namely the axial deformation and the radial deformation are not fixed, the spherical crown punch cannot adapt to the change, so that the stamping deformation gradient of each forging section of the head is overlarge, and obvious differences of microstructures and mechanical properties of different parts of the forging are caused, so that the microstructure and the mechanical property uniformity of the head forging integrally forged are deteriorated, and the reliability and the safety of the head product are affected. Moreover, the stamping forming resistance directions of the spherical crown punch are all directed to the spherical center position of the spherical crown, the radial forming resistance and the axial forming resistance are almost equal, and the radial forming resistance on two sides of the center line of the punch are opposite in direction, so that the radial forming resistance is not a direct factor for forming the working resistance of the hydraulic machine, and the axial forming resistance is required to be overcome by the hydraulic machine, so that the forming resistance of the spherical crown punch is larger, the working resistance of the hydraulic machine is increased, and the stamping working efficiency of the hydraulic machine is lowered. Therefore, the optimal design of the forming punch and the punching lower anvil is an important way for obtaining the end socket product with uniform structure and mechanical property and has higher punching efficiency.

Disclosure of Invention

Aiming at the defects existing in the prior art, the technical problem to be solved by the invention is to provide the integral stamping forming device of the nuclear island steam generator, which not only can effectively improve the uniformity of the microstructure and mechanical property of the sealing head, but also has higher stamping forming efficiency. The invention further aims to solve the technical problem of a method for forging the whole lower end socket of the steam generator by using the stamping forming device.

In order to solve the technical problems, the integral stamping forming device for the seal head of the nuclear island evaporator comprises a forming punch and a forming ring anvil corresponding to the forming punch, wherein a punch body of the forming punch consists of a punch forming section and a punch crown, the punch crown is positioned at the lower end of the punch forming section, a bus of the punch forming section is an involute, the circle center of a forming involute base circle of the involute bus is positioned on the bottom surface of a punch body of the punch body, and the radius of the bottom surface of the punch body is equal to the radius of the forming involute base circle; the top crown of the punch head is a spherical crown, and the radius of the sphere where the spherical crown is positioned is equal to the radius of the forming involute base circle; the forming ring anvil is of a ring structure, an inner hole surface of the forming ring anvil is a ring anvil forming surface, the ring anvil forming surface is an involute curved surface, and the circle center of an involute base circle of the ring anvil forming surface is positioned on the bottom surface of the forming ring anvil.

Preferably, the forming punch is composed of a punch body and a punch holder, and the punch body is fixedly mounted on the punch holder.

Preferably, the punch holder is of a short circular tube structure, and a punch holder hole is formed in the center of the punch holder.

Preferably, the radius of the forming involute base circle of the punch forming section is R, and the distance between the center of the forming involute base circle and the sphere center of the sphere where the punch crown is located is a= (1/3-1/2) R.

Preferably, the involute bus base radius R of the annular anvil molding surface is smaller than the molding involute base radius R of the punch molding section.

Preferably, the involute bus base radius r= (2/5-3/5) R of the annular anvil molding surface.

The invention relates to a method for carrying out integral stamping forming by using an integral stamping forming device, which is characterized in that: the press forming method comprises the following steps:

(1) Heating and blanking: heating the steel ingot to 1210-1240 ℃ step by step in a heating furnace, preserving heat for one hour, taking out the chopped heads and tails from the heating furnace, and removing an oxide layer to form a forging stock;

(2) Forging stock upsetting and pulling: upsetting the forging stock, wherein the forging-to-forging ratio is 3.0-3.5; after forging, the forging stock is drawn into a cylinder shape, and the drawing ratio is 3.0-3.5; the forging stock upsetting temperature is controlled within the range of 800-1240 ℃;

(3) And (3) plate blank forming: upsetting the forging stock which is drawn into a cylindrical shape into a head plate blank, wherein the head plate blank is of a circular plate-shaped structure, and the thickness of the central part of the head plate blank is thicker than the thickness of the periphery;

(4) And (3) integrally forming: the head plate blank is moved to a forming ring anvil, a forming punch is used for forming the head forging by next stamping along the center line of the circular plate-shaped head plate blank at a constant speed, and the stamping speed of the forming punch is 18 mm/s-22 mm/s;

(5) And (3) heat treatment of the forging: heating the end socket forging to 905-925 ℃, preserving heat for 6-8 hours, air-cooling to 300-400 ℃, preserving heat for 4-6 hours, heating to 640-660 ℃ at a heating speed of 45-50 ℃/h, preserving heat for 12-14 hours, and discharging from the furnace for air cooling when the furnace is cooled to 180 ℃ to form an end socket crude product;

(6) And (3) processing a finished product: sampling the end socket crude product subjected to the performance heat treatment, performing physical and chemical tests on the sample, and machining the end socket crude product reaching the technical conditions of the physical and chemical tests to obtain a qualified end socket product.

Preferably, the forming punch presses downwards along the center line of the circular plate head plate blank, and the pressing stroke of the forming punch is the hemispherical concave depth of the head plate blank.

Preferably, the downward stamping speed of the forming punch along the center line of the circular plate head plate blank is 20 mm/s.

Preferably, the end socket preform has a machining allowance.

In the invention, the punch body of the forming punch consists of the punch forming section and the punch crown, and the generatrix of the punch forming section is an involute, as any point on the involute is farther from the base circle, the corresponding curvature radius is larger, namely, the cylindrical surface of the forming section of the forming punch is flatter and straighter as the front end of the forming section of the forming punch is closer to the base circle, the curvature radius is smaller, the bending degree of the forming cylindrical surface is larger, so that the deformation of the plate blank caused by stamping is changed along with the change of the stamping stroke, the deformation of the plate blank corresponding to the front end to the rear end of the punch is gradually increased, the deformation of the plate blank corresponding to the front end of the punch is reduced, and the deformation of the plate blank corresponding to the cylindrical surface of the forming section of the punch is gradually increased as the deformation gradient of the plate blank on each section is reduced, the deformation of the end socket is relatively gentle, the uniformity of the variable between the sections of the end socket ensures the uniformity of microstructures and mechanical properties of different parts of the end socket forging, and the reliability and the safety of the end socket product are effectively ensured. And because the annular anvil forming surface for forming the annular anvil inner hole surface also adopts an involute curve, the involute curve and the involute column surface of the punch forming section are in mutual coordination, so that the stamping deformation of the end socket blank becomes more uniform and gentle, and the uniformity of the mechanical property of the whole forging is ensured. The involute cylindrical surface is adopted in the punch forming section, the normal line of the involute at any point on the involute is the tangent line of the base circle, and the stamping forming force is along the normal line direction, so that the stamping forming resistance direction of the punch is changed, the radial component of the stamping forming resistance is increased, the axial component of the stamping forming resistance is reduced, the axial stamping forming resistance component is reduced, the work load of the hydraulic press is reduced, and the work efficiency of the hydraulic press can be effectively improved; meanwhile, the smaller axial component generates a larger radial component, so that a boosting effect is realized, and the stamping forming efficiency is obviously improved.

The invention also adopts the optimized stamping speed of the forming punch to ensure the gradual and balanced change of the microstructure of the forging piece, so as to avoid the formation of metal structure defects such as cracks and the like in the forging piece in the stamping forming process, ensure the integrity of a metal streamline and solve the problem of anisotropy of the forging piece caused by overlarge one-time forming deformation of a large forging piece. The special forging heat treatment specifications are adopted at different processing stages, so that the large-volume and large-section forging can be uniformly heated, the heating temperatures of the forging core and each area of the surface are consistent, and the cracking of forging steel ingots caused by temperature stress generated by section temperature difference is avoided; the forging starting and final forging temperature and the heating speed enable the forging to be formed in a good plastic state, so that overheating is effectively prevented, and the recrystallization of the forging is guaranteed to be sufficient; according to different technological processes of the forging, different heat treatment specifications are determined, so that not only is forging stress effectively eliminated and structure improved, but also grains are effectively refined and segregation is eliminated, the structure and performance of steel are more uniform, and the comprehensive mechanical property of the finished forging is stabilized and improved.

Drawings

The invention is further described below with reference to the drawings and the detailed description.

FIG. 1 is a schematic view of the working positions of a forming punch and forming anvil in an embodiment of the present invention;

FIG. 2 is a schematic view of the primary cross-sectional structure of the forming punch of the embodiment of FIG. 1;

FIG. 3 is a schematic top view of FIG. 2;

FIG. 4 is a schematic view of the primary cross-sectional structure of the forming ring anvil of the embodiment of FIG. 1;

fig. 5 is a schematic top view of fig. 4.

In the figure, a 1-forming punch, an 11-punch seat, a 12-punch seat hole, a 13-forming involute base circle, a 14-punch body, a 15-punch forming section, a 16-punch crown, a 17-involute generating line and an 18-punch body bottom surface are shown; 2-forming ring anvil, 21-forming surface of ring anvil, 22-ring anvil body, 23-forming surface base circle and 24-ring anvil bottom surface.

Detailed Description

The integral stamping forming device of the nuclear island steam generator seal head as shown in fig. 1 comprises a forming punch head 1 and a forming ring anvil 2 which are arranged correspondingly, wherein the forming punch head 1 is positioned above the forming ring anvil 2, and the center line of the forming punch head 1 and the center line of the forming ring anvil 2 are positioned on the same straight line.

As shown in fig. 2 and 3, the forming punch 1 is composed of a punch body 14 at the lower end and a punch holder 11 at the upper end, the punch body 14 is fixedly connected to the punch holder 11, and the punch body 14 and the punch holder 11 are mutually fixedly connected with each other by a step surface, so that the forming punch 1 has high connection strength and positioning performance. In order to reduce the material consumption and the dead weight, the punch holder 11 is in a short round tube structure, namely, a punch holder hole 2 is arranged at the center of the punch holder 11.

The punch body 14 is composed of a punch forming section 15 and a punch crown 16, the punch crown 16 being located at the lower end of the punch forming section 15. The surface shape of the punch forming section 15 is an involute rotary curved surface, a generatrix of the involute rotary curved surface is an involute, a base circle of the involute is a forming involute base circle 13, a radius R of the forming involute base circle 13, a circle center of the forming involute base circle 13 is located on a punch body bottom surface 18 of the punch body 14, the punch body bottom surface 18 is a circular surface with the radius R, and the radius of the punch body bottom surface 18 is equal to that of the forming involute base circle 13. Also included in fig. 2 is the involute generating line 17 of the punch forming section 15. The punch crown 16 is a spherical crown connected with the punch forming section 15, and the spherical radius of the spherical crown is equal to the base radius R of the involute generatrix. The distance a=1/3R, preferably a= (1/3-1/2) R, between the center of the formed involute base circle 13 and the center of the spherical crown where the punch crown 16 is located is selected and determined.

As shown in fig. 4 and 5, the forming ring anvil 2 has a ring structure, the inner hole surface of the forming ring anvil 2 is a ring anvil forming surface 21, the ring anvil forming surface 21 is also an involute curved surface, and the involute base circle center of the ring anvil forming surface 21 is positioned on the ring anvil bottom surface 24 of the forming ring anvil 2. The radius R of the involute base circle of the annular anvil molding surface 21 is smaller than the radius R of the molding involute base circle 13 of the punch molding section 15. In this embodiment, the involute base circle radius of the annular anvil molding surface 21 is R, and the radius of the molded involute base circle 13 is R, r=3/5R. Preferably r= (2/5-3/5) R.

The integral stamping forming method comprises the following steps: firstly, selecting an eight-prism-shaped steel ingot, heating the steel ingot in a sectional manner, firstly, putting the steel ingot into a heating furnace for heating to improve metal plasticity, enabling the steel ingot to be easy to flow and form and obtain good forged tissues, and selecting a proper heating temperature interval to enable a metal blank to be formed in a state with good plasticity; since the steel ingot belongs to a large block, the steel ingot should be heated uniformly to raise the temperature in order to reduce the temperature stress caused by the temperature difference of the section. The invention adopts sectional heating and temperature rising standard, firstly, steel ingots are sent into a heating furnace to be heated to 580 ℃, the temperature is kept for 3 hours, the second heating section is heated to 830 ℃ at the heating speed of 55 ℃/h, the temperature is kept for 4 hours, the third heating section is heated to 1130 ℃ at the heating speed of 78 ℃/h, when the temperature of the steel ingots is higher than 800 ℃, the steel ingots have certain plasticity, the heating section adopts relatively quick heating speed, the fourth section is heated to 1240 ℃ at the heating speed of 78 ℃/h, and the steel ingots are kept for 1 hour at the temperature to form forging heating blanks.

Heating and blanking: the steel ingot heated to 1240 ℃ is taken out of the heating furnace and sent to a large hydraulic press, a chopper is taken as an upper anvil to chop the heated steel ingot into a head and a tail, so as to ensure the quality of useful middle section materials, and the left steel ingot middle section is knocked by a steel hammer to remove an oxide skin layer on the periphery of the steel ingot, so that a forging stock for forging is obtained.

Forging stock upsetting and pulling: the forging stock is axially pressed down to be upset, and the upset adopts a large upset ratio so as to enable the internal pores of the forging stock to be fully pressed, the cast dendrite is smashed, the upset ratio of the upset is 3.0, and the upset pressing rate of each time of the upsetting of the forging stock is controlled within the range of 24% -30%. Drawing after upsetting, and drawing after upsetting, wherein the drawing ratio of drawing is 3.0, the rolling reduction of each drawing is controlled within 24% -30%, and finally the forging stock is drawn into a nearly cylindrical forging stock. By the upsetting and drawing, the closure of pore defects such as shrinkage porosity and shrinkage cavity in the forging can be ensured, and a better forging structure is obtained. The forging stock upsetting temperature should be controlled between 800 ℃ and 1240 ℃, namely the forging stock temperature is reduced to 800 ℃ in the forging process, and the forging stock is required to be reheated, so that the forging stock temperature is always kept within the range of 800 ℃ to 1240 ℃.

And (3) plate blank forming: moving the forging stock which is drawn into a cylindrical shape onto a widening anvil, and upsetting to form a disc-shaped head plate blank, wherein the front surface of the head plate blank is upsetted to form an outer convex table surface with a large cone angle; the thickness of the central part of the head plate blank is thicker than that of the periphery of the head plate blank. The forging temperature of upsetting and drawing should be controlled between 800 ℃ and 1240 ℃.

And (3) integrally forming: and mounting a forming ring anvil on a hydraulic press, then moving the head plate blank onto the forming ring anvil with the forming surface of the ring anvil, moving a forming punch onto the head plate blank, enabling the center line of the forming punch to be positioned at the center line of the circular plate-shaped head plate blank and the forming ring anvil, starting the hydraulic press and acting on the forming punch, and punching downwards at the speed of 20mm/s by the forming punch until the head plate blank is punched into the head forging. The speed of the forming punch should be controlled within the range of 18 mm/s-22 mm/s to obtain uniform crystalline phase structure and mechanical properties.

And (3) heat treatment of the forging: performing heat treatment on the end socket forging again; firstly, heating the stamped end socket forging to 905-925 ℃, preserving heat for 6-8 hours in Wen Luzhong, then air-cooling to 300-400 ℃, then transferring to a heat preservation furnace, preserving heat for 4-6 hours, heating to 640-660 ℃ at a heating speed of 45-50 ℃/h, preserving heat in a heating furnace for 12-14 hours, cooling to 180 ℃ along with the furnace, discharging and air-cooling to room temperature.

And (3) processing a finished product: sampling at the sampling reserved position of the end socket crude product subjected to the performance heat treatment, performing physical and chemical tests on a specified item, and performing mechanical finish machining on the end socket crude product which is qualified by the physical and chemical tests and reaches the technical conditions of the physical and chemical tests so as to meet the size and shape requirements of the qualified end socket, thereby completing forging, machining and heat treatment of the end socket to form an end socket finished product.

Claims

1. The utility model provides a nuclear island evaporator head whole stamping forming device, includes shaping drift (1) and shaping ring anvil (2) that corresponds with it, its characterized in that: the punch body (14) of the forming punch (1) consists of a punch forming section (15) and a punch crown (16), the punch crown (16) is positioned at the lower end of the punch forming section (15), a generatrix of the punch forming section (15) is an involute, the circle center of a forming involute base circle (13) of the involute generatrix is positioned on the punch body bottom surface (18) of the punch body (14), and the radius of the punch body bottom surface (18) is equal to the radius of the forming involute base circle (13); the punch top crown (16) is a spherical crown, and the spherical radius of the spherical crown is equal to the radius of the forming involute base circle (13); the forming ring anvil (2) is of a ring structure, an inner hole surface of the forming ring anvil (2) is a ring anvil forming surface (21), the ring anvil forming surface (21) is an involute curved surface, and the involute bus base circle center of the ring anvil forming surface (21) is positioned on a ring anvil bottom surface (24) of the forming ring anvil (2).

2. The nuclear island evaporator head integral stamping forming device of claim 1, wherein: the forming punch (1) is composed of a punch body (14) and a punch seat (11), and the punch body (14) is fixedly arranged on the punch seat (11).

3. The nuclear island evaporator head integral stamping forming device of claim 2, wherein: the punch holder (11) is of a short round tube structure, and a punch holder hole (12) is formed in the center of the punch holder (11).

4. The nuclear island evaporator head integral stamping forming device of claim 1, wherein: the radius of the forming involute base circle (13) of the punch forming section (15) is R, and the distance between the center of the forming involute base circle (13) and the sphere center of the sphere where the punch crown (16) is positioned is a= (1/3-1/2) R.

5. The nuclear island evaporator head integral stamping forming device of claim 1, wherein: the radius R of the involute base circle of the annular anvil molding surface (21) is smaller than the radius R of the molding involute base circle (13) of the punch molding section (15).

6. The nuclear island evaporator head integral stamping forming device of claim 5, wherein: involute bus base radius r= (2/5-3/5) R of the annular anvil molding surface (21).

7. A method for stamping and forming an integral lower head by using the integral stamping and forming device as claimed in claim 1, which is characterized in that: the press forming method comprises the following steps:

8. The integral press forming method as claimed in claim 7, wherein: the forming punch presses downwards along the center line of the circular plate head plate blank, and the pressing stroke of the forming punch is the hemispherical concave depth of the head plate blank.

9. The integral press forming method as claimed in claim 7, wherein: the downward stamping speed of the forming punch along the center line of the circular plate head plate blank is 20 mm/s.

10. The integral press forming method as claimed in claim 7, wherein: and the end socket coarse product is provided with machining allowance.