A near-net-shape forging method for nuclear power plant water chamber head forgings

Abstract

This invention discloses a near-net-shape forging method for nuclear power plant water chamber head forgings, belonging to the field of material forming. Addressing the problems of low conformity and operational difficulties in existing nuclear power plant water chamber head forging methods, this invention provides a near-net-shape forging method for nuclear power plant water chamber head forgings. It includes: pre-forming a cylindrical billet; upsetting the cylindrical billet to pre-form the irregular nozzle area; using a first die upside down on top of the cylindrical billet to upset the cylindrical billet, pre-forming the irregular nozzle area within the cylindrical billet; and rolling the upset cylindrical billet to obtain the nuclear power plant water chamber head forging. This invention employs a "full-process conformity die forging" method, which ensures sufficient material flowability and maximizes the conformity to the complex contour of the water chamber head. The overall method has low forming risk, high operational efficiency, and can reduce the steel ingot weight from 300 tons to 230 tons, increasing material utilization by nearly 30%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal material forming, more specifically, relates to a near-net forming forging method for a nuclear power water chamber head forging. BACKGROUND

[0002] Nuclear power, as a stable and efficient clean energy, has ushered in a new historical opportunity for development. Hualong No. 1, as a self-developed advanced million-kilowatt pressurized water reactor in China, is the main brand of China's nuclear power "going out", and will certainly develop in the direction of higher quality, higher efficiency and higher utilization rate in the future. The Hualong No. 1 steam generator water chamber head (such as Figure 1 ) is also called primary side head and lower head of steam generator, which is the most complex and most difficult to manufacture key component among the forgings for steam generator. The Hualong No. 1 pressurized water reactor steam generator water chamber head is a special-shaped head forging with two side nozzles, has many branch nozzles, and is complex in shape. The near-net shape forging is difficult, the water chamber head has a side nozzle and a "bowl" shaped part with low height, which limits the possibility of its stamping forming. The traditional forging forming scheme mostly adopts rolling forming, that is, first forging the steel ingot into a cylindrical blank, then putting the blank into a lower die with low degree of profiling, and rolling forming with an upper rotating anvil, which has low degree of profiling, large weight of steel ingot, needs multiple steel water pouring, increases the segregation degree of steel ingot itself and other metallurgical risks, and has large processing amount and long cycle in cold working stage, high cost of forgings and low market competitiveness.

[0003] Corresponding improvements have been made for the above problems, such as Chinese patent application No. CN201811345763.4, published on March 26, 2019, which discloses an extrusion forming method for a nuclear power water chamber head, which adopts the mode of first pressing the ingot head, and then cutting the T shoulder to remove the defects at the ingot body head end; the blank is heated to a suitable temperature range and is subjected to heat preservation, and through the combined operation of large forging ratio upsetting, "WHF" forging method strong pressure elongation and "JTS" forging method center compaction, the internal performance quality of the blank is greatly improved, and then the blank head and bottom deposition area defects are cut off, the blank shape is upset and trimmed, so that the blank diameter is adapted to the extrusion die; the blank is put into a special die for extrusion forming. The deficiency of the patent is that the steps are complicated and the processing cycle is long.

[0004] For example, Chinese patent application No. CN201410524841.2, published on January 7, 2015, discloses a large nuclear reactor water chamber head forging whole forming forging device and method in the technical field of nuclear power infrastructure, which comprises: a spherical upper punch, a forming lower die with a plurality of whole water nozzle forming cavities, and a positioning ring arranged on the forming lower die for bearing the blank; the whole water nozzle forming cavity is arranged on the bottom surface of the spherical cavity of the forming lower die and is connected with the external device of the forming lower die. The blank is hot stamped into a whole head with a water nozzle by the forming of the preform blank under the load of a heavy hydraulic press. The patent has the disadvantages of high cost and complex structure. SUMMARY

[0005] 1. Problem to be solved

[0006] In view of the problems of low forging simulation degree and difficult operation of the existing nuclear power water chamber head forging, the present application provides a near-net forming forging method for nuclear power water chamber head forgings. The present application adopts the method of "forming the whole process of profiled die forging", which can ensure sufficient material flowability and maximum simulation of the complex profile of the water chamber head. The whole method has low forming risk, high operation efficiency, and can reduce the steel ingot from 300 tons to 230 tons, and the material utilization rate is increased by nearly 30%.

[0007] 2. Technical scheme

[0008] To solve the above problems, the present application adopts the following technical scheme.

[0009] A near-net forming forging method for nuclear power water chamber head forgings, comprising the following steps:

[0010] S1: Preparing a cylindrical blank;

[0011] S2: Upsetting and preforming the cylindrical blank in the shaped nozzle area: using a first die to upset the cylindrical blank above the cylindrical blank; the first die has a shaped nozzle profiling area inside, which is used to preform the shaped nozzle area in the cylindrical blank during upsetting;

[0012] S3: Rolling and forming the cylindrical blank after upsetting and preforming to obtain a nuclear power water chamber head forging: placing the cylindrical blank after upsetting and preforming in a profiled die, and using a rotary anvil to roll and form the top of the cylindrical blank to obtain a nuclear power water chamber head forging.

[0013] Further, the first die comprises a die body, the die body has a shaped nozzle profiling area and a positioning area inside, the positioning area is located at the middle end of the die body inside, and the shaped nozzle profiling area is located at the lower end of the die body inside.

[0014] Further, the positioning area is a positioning ring, and the size of the positioning ring is matched with the size of the cylindrical blank, so that the cylindrical blank is centered with the positioning ring.

[0015] Further, the method for centering the cylindrical blank with the positioning ring comprises: directly placing the blank in the positioning ring, and the blank is in surface contact with the mold, the surface is horizontal and has the same diameter size as the blank, without positioning measurement, the horizontal placement and axis centering of the blank can be ensured. Without the positioning ring, the blank is placed in the inner cavity of the mold, and is in line contact with the inner cavity of the mold, which causes difficulty in horizontal positioning of the blank, and the upsetting process is prone to instability of the blank. After the centering is completed, the upsetting is performed.

[0016] Further, the profiling mold comprises a first mold and a second mold which is detachably connected with the first mold, and the second mold is in the shape of a ring, and the hollow area of the ring is used for placing the cylindrical blank.

[0017] Further, the inside of the second mold is provided with a draft angle, and the angle of the draft angle is 6°-8°.

[0018] Further, the rotating anvil is a strip-shaped anvil which is wide at the top and narrow at the bottom, the upper part is connected with a hydraulic rotating device, the length direction draft angle θ1 is 19°-25°, the width direction draft angle θ2 is 3°-5°, the total length of the top X2 is 3100-3300 mm, the thickness Y2 is 800-1000 mm, the length of the bottom X1 is 2000-2200 mm, and the thickness Y1 is 700-900 mm. In the rotating rolling process, the rolling frequency of each circle can be controlled to be 6-8 times, so that the folding defects in the inner cavity of the forged piece caused by excessive rolling frequency can be effectively avoided. The design of being wide at the top and narrow at the bottom can ensure the best deformation effect under the same pressure. The water chamber head forged piece is formed by rolling and forming the inner cavity of the top of the cylindrical blank by the rotating anvil, so as to obtain the nuclear power water chamber head forged piece.

[0019] 3. Beneficial effects

[0020] Compared with the prior art, the beneficial effects of the present application are:

[0021] (1) The application changes the traditional single rolling forming method, adopts a "molding full process profiling die forging" mode, that is, first adopts a first die to upset the pre-forming of the special-shaped nozzle area of the cylindrical blank, then passes through the profiling die and the rotary anvil to obtain the nuclear power water chamber head forging by rolling forming; the full process profiling forging can ensure sufficient material fluidity, profile the special-shaped complex contour of the water chamber head to the maximum extent, finally realize the near-net forming forging of the Hualong No. 1 steam generator water chamber head, significantly improve the product utilization rate, the processing cycle, and reduce the quality risk caused by the excessive weight of the ingot; the overall method has low forming risk, high operation efficiency, and can reduce the ingot from 300 tons to 230 tons, and the material utilization rate is increased by nearly 30%;

[0022] (2) The application adopts the first die to upset the pre-forming of the special-shaped nozzle area of the cylindrical blank, the special-shaped nozzle profiling area in the die body is the same as the shape of the special-shaped nozzle of the final nuclear power water chamber head forging, and is used for filling the special-shaped nozzle area in the whole forging process; the positioning area is used for positioning and centering the cylindrical blank before upsetting, and maintaining the stability of the cylindrical blank in the die body; and the positioning ring is used as the positioning area, which has simple structure and is easy to manufacture, and can easily and simply realize the shape matching with the cylindrical blank, and can realize multi-directional positioning of the cylindrical blank, thereby improving the stability;

[0023] (3) The profiling die in the application is formed by combining the first die and the second die to form a combined die, and the first die and the second die are detachably connected, which is convenient for use in different stages, so that one profiling die has multiple use purposes, which saves cost and improves material fluidity and effectively fills the special-shaped area of the forging; at the same time, the combined die is used to profile the shape of the nozzle to the maximum extent under the condition of limited pressure, so that the forging of the water chamber head has sufficient allowance, and sufficient space for deviation is reserved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a delivery structure schematic diagram of Hualong No. 1 water chamber head;

[0025] Figure 2 It is a size schematic diagram of the cylindrical blank;

[0026] Figure 3 It is a structure schematic diagram of the first die;

[0027] Figure 4 It is a model schematic diagram of the first die;

[0028] Figure 5 It is a schematic diagram of the blank placed in the positioning ring;

[0029] Figure 6 It is a structure schematic diagram of the second die;

[0030] Figure 7 This is a schematic diagram of the upsetting preforming process;

[0031] Figure 8 This is a schematic diagram of the rotating anvil.

[0032] Figure 9 This is a schematic diagram of the rotation of the rotating anvil;

[0033] Figure 10 This is a schematic diagram of the working process of the rotating anvil;

[0034] Figure 11 This is the final structural drawing of the forging;

[0035] Figure 12 This is a diagram showing the allowance analysis for forgings. Detailed Implementation

[0036] The present invention will now be further described with reference to specific embodiments and accompanying drawings.

[0037] Example 1

[0038] A near-net-shape forging method for a nuclear power plant water chamber head forging includes the following steps:

[0039] S1: Precast cylindrical blank;

[0040] Specifically, in step S1, after the steel ingot undergoes multiple overall upsetting processes (generally three overall upsetting processes) and WHF drawing, the shrinkage cavities and porosity inside the large steel ingot are effectively welded together, achieving a good forging compaction effect. This produces a pre-formed cylindrical billet with a height-to-diameter ratio ranging from 1.0 to 1.5. Through continuous simulation experiments, the inventors concluded that an excessively large height-to-diameter ratio increases the risk of upsetting misalignment, while an excessively small ratio results in a small upsetting reduction, leading to poor filling effects in the subsequent irregular nozzle area. The pre-formed cylindrical billet, as shown... Figure 2 As shown, its height is H0 and its diameter is D0;

[0041] S2: As Figure 7 As shown, the cylindrical blank is pre-formed by upsetting the irregular nozzle area: a first mold is used to upset the cylindrical blank by inverting it above the blank; the interior of the first mold has an irregular nozzle contouring area, which is used to pre-form the irregular nozzle area in the cylindrical blank during the upsetting process; the heights of the cylindrical blank before and after upsetting are H0 and H1, and the diameters are D0 and D1, respectively;

[0042] Specifically, in step S2, the first mold is as follows: Figure 3 , 4As shown, it comprises a mold body, the mold body is in the shape of a circular truncated cone, the outer diameter is D1, the total height is Z1, the first mold upper surface outer circle exists a step, the step inner circle diameter is D2, the depth is Z2, used for combination with the second mold, the mold body inside is provided with a special-shaped nozzle profiling area and a positioning area, the body inside diameter is D3, the depth is Z3, the nozzle profiling area and the mold axis direction included angle is θ2, the positioning area and the mold axis direction included angle is θ1. The positioning area is located in the middle end of the mold body inside, and the special-shaped nozzle profiling area is located in the lower end of the mold body inside; the special-shaped nozzle profiling area is to preform the special-shaped nozzle area of the cylindrical blank, so the shape of the special-shaped nozzle profiling area is the same as the shape of the special-shaped nozzle in the water chamber head forging; the positioning area is to position and limit the cylindrical blank during the upsetting process, to ensure the stable forming of the cylindrical blank during the upsetting process.

[0043] In one specific embodiment, the special-shaped nozzle profiling area can be a boss arranged at the lower end of the mold body inside, the position of the boss corresponds to the nozzle position of the water chamber head forging, to extrude the cylindrical blank at the boss to form the nozzle of the water chamber head forging during the upsetting process; the positioning area can be a positioning ring arranged at the terminal end of the mold body inside, and the size of the positioning ring is matched with the size of the cylindrical blank, so that the cylindrical blank is centered with the positioning ring. In this embodiment, a method for centering the cylindrical blank with the positioning ring is given, which comprises: directly placing the cylindrical blank in the positioning ring, the size of the surface of the cylindrical blank in contact with the positioning ring is the same as the size of the cylindrical blank. Figure 5 As shown, the existence of the positioning ring enables the blank to be directly placed in the positioning ring, the blank is in surface contact with the mold, the surface is horizontal and has the same diameter size as the blank, so that the blank can be ensured to be placed horizontally and the axis to be centered without measurement positioning. Without the positioning ring, the blank is placed in the mold inner cavity and is in line contact with the mold inner cavity, which causes the blank to be difficult to be positioned horizontally and the blank to be unstable during the upsetting process.

[0044] S3: rolling forming the cylindrical blank after the upsetting preforming to obtain the nuclear power water chamber head forging: placing the cylindrical blank after the upsetting preforming in the profiling mold, and rolling forming the top of the cylindrical blank by using the rotary anvil to obtain the nuclear power water chamber head forging. The nuclear power water chamber head forging is as shown in the figure. Figure 10 As shown, further near-net forming needs to be further carried out to finally obtain the nuclear power water chamber head, but the process is not a forging process, so the final forming nuclear power water chamber head is completed after step S3 of the present application, and the operation is simple.

[0045] Specifically, in step S3, the profiling die comprises a first die, a second die detachably connected with the first die, the second die is in the shape of a circular ring, and a hollow region of the circular ring is used for placing a cylindrical blank. An inside of the second die is provided with a draft angle, and an angle of the draft angle is 6-8 degrees. The provision of the draft angle makes the demolding process smoother and less likely to cause adhesion, thereby ensuring the quality of the blank.

[0046] The profiling die is formed by combining the first die and the second die to form a combined die, and the first die and the second die are detachably connected, facilitating use in different stages, so that one profiling die is used for multiple purposes, thereby saving cost and improving material flowability, and effectively filling the special-shaped region of the forging; at the same time, the combined die is used to profile the shape of the nozzle to the maximum extent under the condition of limited pressure, so that the forging forming water chamber head has sufficient allowance, and sufficient space for deflection is reserved.

[0047] Further, as shown in Figures 8 to 10 The rotating anvil is a strip-shaped anvil with a wide upper part and a narrow lower part, the upper part of the rotating anvil is connected with a hydraulic rotating device, the length of the rotating anvil changes from the top to the bottom, the length changes from the top X2=3200mm to the bottom X1=2100mm, the length direction draft angle θ1 is 22°, the width of the rotating anvil changes from the top to the bottom, the width changes from the top Y2=900mm to the bottom Y1=800mm, the width direction draft angle θ2 is 4°, and the height of the rotating anvil is Z1=2750mm. In the rotating and rolling process, the rolling frequency of each circle can be controlled to be 6-8 times, so that the folding defect of the inner cavity of the forging caused by excessive rolling frequency can be effectively avoided; the design of the wide upper part and the narrow lower part can ensure the best deformation effect under the same pressure. The water chamber head forging is formed by rolling and forming the inner cavity of the top of the cylindrical blank by the rotating anvil, so as to obtain the nuclear power water chamber head forging.

[0048] The present application changes the traditional single rolling forming method, adopts a "profiling die forging in the whole forming process" mode, that is, first, the cylindrical blank is subjected to profiled nozzle region upsetting preforming by the first die, and then the nuclear power water chamber head forging is obtained by rolling and forming through the profiling die and the rotating anvil; the whole process profiling forging can ensure sufficient material flowability, and the water chamber head special-shaped complex profile is profiled to the maximum extent, so that the near-net forming forging of the Hualong No.1 steam generator water chamber head is finally realized, the product utilization rate and the processing cycle are significantly improved, and the quality risk caused by the excessive weight of the ingot is reduced; the whole method has low forming risk and high operation efficiency, and the ingot can be reduced from 300 tons to 230 tons, and the material utilization rate is increased by nearly 30%.

[0049] Example 2

[0050] The near-net shape forging method of the nuclear power water chamber head forging with a specific size is basically the same as that of the example 1, which comprises the following steps:

[0051] S1: Preparing a cylindrical blank: After three times of upsetting and three times of elongation, the steel ingot obtains a good forging compaction effect, and a cylindrical blank with a proper height-diameter ratio is prepared. The diameter D0 of the cylindrical blank is 2700 mm, the height H0 is 3230 mm, and the weight is about 145 tons. The positioning ring in the first die can accommodate the blank with a diameter range of 2550-2770 mm. The size of the cylindrical blank needs to match the positioning ring of the first die to ensure the centering and stability of the blank, and finally obtain a better filling effect;

[0052] S2: Upsetting preforming of the cylindrical blank in the special-shaped nozzle area: Place the cylindrical blank on the lower plate, use the first die as the upsetting anvil, and place it upside down above the blank. The blank matches the positioning ring in the first die, and the blank is placed directly in the positioning ring. The surface contact between the blank and the positioning ring is horizontal and has the same diameter as the blank, so there is no need to measure the positioning, which can ensure that the blank is placed horizontally and the axis is centered. The blank is "hat upsetting", and the height of the blank is increased from H0=3230 mm to H1=2150 mm, so that the side nozzle area of the cylindrical blank is preformed. Through simulation analysis and test verification, the hat upsetting method has better forming effect than directly upsetting in the die, because the force first acts on the nozzle area which needs to be deformed most, so that it is effectively filled. After the upsetting stage, the size of the cylindrical blank is D1=3300 mm and H1=2150 mm;

[0053] S3: Rolling forming of the cylindrical blank after preforming to obtain the nuclear power water chamber head forging: After the hat upsetting is completed, the first die and the second die are combined into one to form a profiling die. The preformed blank is placed in the profiling die, and the centering is performed according to the horizontal condition of the upper surface of the blank, the distance between the upper surface of the blank and the upper surface of the profiling die, and the positioning ring. The rotating anvil is used, and the bottom length X1 of the rotating anvil is 2000 mm, the top length X2 is 3170 mm, the bottom thickness Y1 is 700 mm, the top thickness Y2 is 900 mm, the height Z is 1800 mm, the front view θ1 is 20°, and the side view θ2 is 3.7°. The rotation angle θ is 25° each time, the reduction δ1 is 150 mm, and the reduction δ2 is 100 mm. The total rotation N=N1+N2 is 7 turns, and the total reduction S=δ1×N1+δ2×N2 is 1000 mm. The final forging is shown in Figure 11 , and Figure 12As shown, by using three-dimensional scanning software, the water chamber head formed by the method is three-dimensionally scanned, and is introduced into a tolerance analysis software for comparative analysis. In the figure, the blank area is the delivery drawing size, the color area is the forged piece formed by the method, the left drawing is the water chamber head nozzle section, the forged piece drawing and the delivery drawing tolerance analysis, and the right drawing is the water chamber head non-nozzle section, the forged piece drawing and the delivery drawing tolerance analysis. The simulation and test results both show that by using the forging method of the forming profiling die, the water chamber head formed by forging has sufficient tolerance, and sufficient space for deviation is reserved.

[0054] The examples described in the present application are merely used to describe the preferred embodiments of the present application, and are not used to limit the concept and scope of the present application. Without departing from the design idea of the present application, various modifications and improvements of the technical solutions of the present application made by the engineers and technicians in the field should all fall within the protection scope of the present application.

Claims

1. A near-net shape forging method of a nuclear power water room head forging, characterized by: The method comprises the following steps: S1: preparing a cylindrical blank; the cylindrical blank has a height-diameter ratio ranging from 1.0 to 1.5; S2: performing upsetting preforming on the cylindrical blank to form a special-shaped nozzle area; a first die is inverted on the cylindrical blank to perform upsetting on the cylindrical blank; the first die has a special-shaped nozzle profiling area inside, which is used to preform a special-shaped nozzle area in the cylindrical blank during the upsetting; S3: performing rolling forming on the cylindrical blank after the upsetting preforming to obtain a nuclear power water chamber head forging; the cylindrical blank after the upsetting preforming is placed in a profiling die, and a rotary anvil is used to perform rolling forming on the top of the cylindrical blank to obtain a nuclear power water chamber head forging. The first die comprises a die body, and the die body is internally provided with a special-shaped nozzle profiling area and a positioning area; the positioning area is located at the middle end inside the die body, and the special-shaped nozzle profiling area is located at the lower end inside the die body.

2. A near net shape forging method of a nuclear power water chamber head forging according to claim 1, characterized in that: The positioning area is a positioning ring, and the size of the positioning ring is matched with the size of the cylindrical blank, so that the cylindrical blank is centered with the positioning ring.

3. A near net shape forging method of a nuclear power water chamber head forging according to claim 2, characterized in that: The method for centering the cylindrical blank with the positioning ring comprises the following steps: the cylindrical blank is directly placed in the positioning ring, and the size of the surface of the cylindrical blank in contact with the positioning ring is the same as the size of the cylindrical blank.

4. A near net shape forging method of a nuclear power water chamber head forging according to claim 1, characterized in that: The profiling die comprises a first die and a second die which is detachably connected with the first die; the second die is in the shape of a circular ring, and the hollow area of the circular ring is used to place the cylindrical blank.

5. A near net shape forging method of a nuclear power water chamber head forging according to claim 4, characterized in that: The second die is internally provided with a draft angle, and the angle of the draft angle is 6°-8°.

6. A near net shape forging method of a nuclear power water chamber head forging according to claim 1, characterized by: The rotary anvil is a strip-shaped anvil which is wide at the top and narrow at the bottom; the upper part of the rotary anvil is connected with a hydraulic rotating device; the length direction draft angle θ1 is 19°-25°, the width direction draft angle θ2 is 3°-5°, the total length of the top X2 is 3100-3300 mm, the thickness Y2 is 800-1000 mm; the length of the bottom X1 is 2000-2200 mm, and the thickness Y1 is 700-900 mm.

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