A forging process for improving mutual tearing in the metal hot forming process of a nuclear power pump shell

Abstract

This invention relates to the field of nuclear power pump casing technology, specifically to a forging process that improves the tearing between materials during the hot forming process of nuclear power pump casings. The forging process includes: S1, raw material inspection, selecting qualified raw materials; S2, forging; S3, post-forging heat treatment; S4, rough machining, followed by UT self-inspection; S5, performance heat treatment; S6, sampling and physicochemical testing; S7, further rough machining and UT inspection; S8, dimensional inspection, and labeling and packaging after passing inspection. Addressing the issue that existing technologies often produce defective pump casings due to loose centers and coarse grains, resulting in unusable products after flaw detection, this solution, considering the company's existing press operating conditions and tooling ratios, focuses on the forging process and adds optimized forging steps; improves the forging heating process, further improving pump casing product quality and increasing the yield rate.

Description

Technical Field

[0001] This invention relates to the field of nuclear power pump casing technology, and more specifically, to a forging process that improves the tearing between metals during the hot forming process of nuclear power pump casings. Background Technology

[0002] Various types of pumps operate in all systems of a nuclear power plant. In the primary loop system of the nuclear island, the pump used to drive the circulation of coolant within the RCP (Reactor Coolant System) is called the main pump. The main pump is the only rotating piece of equipment in the main equipment of the nuclear island of a pressurized water reactor nuclear power plant, and it is of paramount importance. Located in the heart of the nuclear island, the main pump is used to pump hot water into the evaporator to convert it into heat energy. It is the key to controlling the water circulation in the operation of the nuclear power plant and belongs to the first-level equipment of the nuclear power plant. Each steam generator has one main pump.

[0003] The main pump carries the heat generated inside the nuclear island out and exchanges heat with the secondary side of the steam generator to drive the steam turbine generator set to generate electricity. At the same time, it also plays a role in cooling the nuclear island. This requires it to have higher reliability than other non-rotating equipment. It is like the heart of the nuclear island. Once it fails, the damage will be enormous.

[0004] Currently, most major forging suppliers at home and abroad use free forging and unidirectional die forging processes to forge the pump casing of nuclear power main pumps. Due to the inherent limitations of unidirectional forging equipment, the yield rate of traditional free forging and unidirectional die forging processes has always been low, and the losses caused by scrap are significant.

[0005] In recent years, the production tasks and requirements for pump casing forgings have increased significantly, and pump casing production has become increasingly large-scale. However, the previous pump casing forging process is still not perfect. The overall yield rate cannot meet requirements during batch and large-scale production. The reasons for defective pump casing forgings are mainly as follows: First, insufficient forging penetration, resulting in defects such as central porosity and coarse grains. Second, uneven deformation in different parts of the forging during the forging process, leading to tearing of the metal and mixed grains. Different causes of defects naturally require different countermeasures.

[0006] Therefore, it is imperative to improve and change the existing forging process to further improve the quality of pump casing forgings produced in batches and on a large scale. Summary of the Invention

[0007] The purpose of this invention is to provide a forging process that improves the tearing between metals during the hot forming process of nuclear power pump casings, thereby improving the overall yield and quality when mass-producing nuclear power pump casings.

[0008] This invention is achieved through the following technical solution:

[0009] A forging process to improve the tearing between metals during the hot forming process of nuclear power plant pump casings, the forging process comprising:

[0010] S1. Raw material inspection: Select raw materials that meet the requirements;

[0011] S2, forging;

[0012] S3. Post-forging heat treatment;

[0013] S4. Rough machining, followed by UT self-inspection;

[0014] S5, Performance Heat Treatment;

[0015] S6. Physicochemical testing after sampling;

[0016] S7. UT inspection after rough machining;

[0017] S8. Dimension inspection, label and package after passing inspection.

[0018] The above technical solutions address the issue that existing scrap products are mostly due to loose centers and coarse grains in the pump casing, resulting in unqualified flaw detection and rendering them unusable. This solution, combined with the company's existing press operating conditions and tooling ratios, focuses on the forging process and adds optimized forging steps; improves the forging heating process, and further mitigates the tearing between metals during hot forming, thereby improving the quality and yield of pump casing products.

[0019] To better realize the present invention, further, in S1, the weight percentage of each component in the raw materials selected to meet the requirements is as follows: C: 0-0.08%, Si: 0-1%, Mn: 0-2%, Ti: 5xC%-0.7%, Cr: 17-19%, P: 0-0.045%, S: 0-0.03%, Ni: 9-12%, Co: 0-0.05%.

[0020] By using the above technical solutions, raw materials that meet product requirements are selected, product quality is improved, and subsequent forging processes are more precisely controlled, thereby improving the quality of pump casing products.

[0021] To better realize the present invention, further, in S1, the weight percentage of each component in the raw materials selected to meet the requirements is as follows: C: 0.04-0.055%, Si: 0.35-0.55%, Mn: 0.9-1.8%, Ti: 0.2-0.5%, Cr: 17-19%, P: 0.015-0.02%, S: 0.001-0.005%, Ni: 9-11%, Co: 0.035-0.045%.

[0022] By employing the above technical solutions, we can select high-quality raw materials, improve product quality, further enhance the precision of subsequent process control, reduce the difficulty of process operation, and save on raw material consumption.

[0023] To better realize the present invention, further, the S2 forging includes hot delivery at a temperature of 650°C; preheating to 850-950°C and holding for 5 hours; then heating the material to 1150-1200°C and holding for 10 hours by medium frequency heating; and finally heating to 1320°C and holding for 18 hours.

[0024] Through the above technical solutions, medium-frequency heating can achieve assembly line heating, allowing the workpiece to move and be heated in the medium-frequency heating furnace, rationalizing the heating temperature, time and stage heating steps, improving the mutual tearing of nuclear power pump shell metal in the hot forming process, avoiding crystal mixing of forgings, and improving the yield of pump shells.

[0025] To better realize the present invention, furthermore, the forging is performed by a hydraulic press. The mold of the hydraulic press is divided into an upper mold and a lower mold. The upper mold includes an upper mold base and a mold core installed in the upper mold base by fasteners. The mold core includes a flat mold, a punch, and a die. The upper mold is combined to complete the pressing and forming. The lower mold is a mold for the outer dimensions of the forging. The upper mold is used in the following order: first use the flat mold, then the die, then the flat mold, then the punch, and finally the flat mold is used to complete the die forging and pressing. The final forging temperature of the forging is controlled at 1150-1280℃.

[0026] The above technical solutions aim to fill the mold cavity, generate large deformation to promote grain refinement, improve grain size, and maintain consistent deformation in all parts, thereby improving the yield of pump casings.

[0027] To better realize the present invention, a forging ratio of 2.5-2.8, a total drawing ratio of >5, and a total upsetting ratio of >5 are adopted. A 1200mm wide flat anvil is used for drawing, with a corner radius of 120mm and a length of 2800mm. After 8 drawing passes, the forging is directly drawn to the size of the forging product.

[0028] Through the above technical solutions, a large forging ratio improves the internal quality of steel, eliminates the as-cast structure, makes the internal structure of the forging uniform, improves or eliminates porosity and segregation, and can effectively forge internal inclusions into smaller or broken pieces, solving defects such as insufficient forging penetration, central porosity, and coarse grains in forgings, thereby improving the yield of pump casings.

[0029] To better realize the present invention, further, the S3 post-forging heat treatment includes air cooling the forging after forging to a temperature ≤700℃, immediately loading the forging into a heat treatment furnace for normalizing treatment at a temperature of 980-1100℃, and holding the forging at that temperature for 24-27 hours during the normalizing process; after holding, removing the forging from the furnace and quenching it; during the quenching process, immersing the forging in flowing water for cooling; after quenching, the water temperature is ≤65℃, and after quenching, the forging is placed in a furnace for tempering treatment at a temperature of 730-890℃, holding the tempering for 35-40 hours, and then air cooling the forging.

[0030] Through the above technical solutions, in the post-forging heat treatment process, normalizing ensures more uniform and refined grains in the forgings, while controlling the immersion time and cooling water temperature during quenching ensures the quenching effect of the forgings. Sufficient tempering holding time ensures better elimination of internal stress in the forgings, improving the yield of pump casings.

[0031] To better realize the present invention, the performance heat treatment further includes stress relief heat treatment of the forging, wherein the forging is subjected to stress relief heat treatment at a temperature below 400°C.

[0032] The above technical solutions aim to eliminate the stress caused by machining and hydrostatic testing, stabilize dimensions, and ensure the corrosion resistance of the pump casing.

[0033] The beneficial effects of this invention are:

[0034] 1. This invention starts with the forging process and improves the forging ratio and adds forging steps. At the same time, this invention improves the forging heating process, rationalizes the heating temperature, time and stage heating steps, and solves the two reasons why existing pump casing forgings become defective. Thus, in the mass production of nuclear power pump casings, it improves the tearing of metal during hot forming and improves the yield and quality of pump casing forging products.

[0035] 2. Based on the existing working conditions of the company's press and the tooling ratio, this invention improves the process, designs a reasonable forging ratio, adjusts heating parameters, and changes forging steps, effectively improving product performance and quality, reducing energy waste, increasing yield, and shortening the processing cycle. Attached Figure Description

[0036] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the present invention will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0037] Figure 1To improve upon the existing pump casing flaw detection results and the actual results of metallographic analysis;

[0038] Figure 2 The results of the pump casing flaw detection and metallographic analysis are as follows:

[0039] Figure 3 This is a schematic diagram of the cross-sectional dimensions of the existing pump casing forging before the improvement.

[0040] Figure 4 This is a schematic diagram of the cross-sectional dimensions of the pump casing forging after the process improvement of this invention;

[0041] Figure 5 This is a comparison diagram of the longitudinal mechanical properties of the pump casing forging at room temperature before and after the process improvement of this invention;

[0042] Figure 6 This is a comparison diagram of the tangential mechanical properties of the pump casing forging at room temperature before and after the process improvement of this invention;

[0043] Figure 7 This is a comparison diagram of the tangential mechanical properties of the pump casing forgings at room temperature before and after the process improvement of this invention;

[0044] Figure 8 This is a comparison diagram of the tangential mechanical properties of the pump casing forging at 350℃ before and after the process improvement of this invention;

[0045] Figure 9 This is a comparison diagram of the tangential mechanical properties of the pump casing forging at 350°C before and after the process improvement of this invention. Detailed Implementation

[0046] The technical solutions of the present invention will now be described with reference to the accompanying drawings.

[0047] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0048] A forging process to improve the tearing between metals during the hot forming process of nuclear power pump casings includes raw material inspection → forging → post-forging heat treatment → rough machining 1 → UT self-inspection (internal control) → performance heat treatment → sampling → physical and chemical testing → rough machining 2 → UT inspection → dimensional inspection → marking and packaging → completion and shipment. Example 1

[0049] A forging process to improve the tearing between metals during the hot forming process of nuclear power pump casings

[0050] S1 Raw Material Inspection: The raw material is selected from 06Cr18Ni11Ti stainless steel. Impurities and oxide shells are removed from the surface of the raw material to ensure that the weighed mass is close to the designed mass, thereby guaranteeing the quality of the forged workpiece, including uniformity and overall quality. The composition of the raw material is also inspected to ensure that each component fully meets the requirements. The weight percentage of each component in the compliant raw material is as follows: C: 0.045%, Si: 0.4%, Mn: 0.97%, Ti: 0.26%, Cr: 17.58%, P: 0.018%, S: 0.001%, Ni: 9.72%, Co: 0.04%.

[0051] S2 forging, the forging cross-section size is 1180*1080mm, the hot delivery temperature is 650℃; the preheating temperature is 850℃ and held for 5 hours, and then medium frequency heating can realize the assembly line heating, so that the workpiece can be moved and heated in the medium frequency heating furnace. The material is heated to 1150℃ and held for 10 hours using medium frequency heating, and finally heated to 1320℃ and held for 18 hours. It is then forged using a hydraulic press. The hydraulic press mold is divided into upper mold and lower mold. The upper mold includes an upper mold base and a mold core installed in the upper mold base by fasteners. The mold core includes a flat mold, a punch, and a die. The upper mold is used in the following order: first use the flat mold, then the die, then the flat mold, then the punch, and finally the flat mold is used to complete the die forging and forming, to fill the mold cavity, generate large deformation to promote grain refinement, and combine the upper mold to complete the forming. The lower mold is the mold for the shape and size of the forging. The final forging temperature of the forging is controlled at 1200℃.

[0052] The forging process adopts a forging ratio of 2.5, with a total drawing ratio > 5 and a total upsetting ratio > 5. A 1200mm wide flat anvil is used for drawing. The corner radius of the wide flat anvil is 120mm and the length is 2800mm. After 8 drawing passes, the forging product with a cross-sectional size of 1180*1080mm is directly drawn.

[0053] The obtained forgings were subjected to ultrasonic testing and met the requirements of SEP 1921E / e. The hardness of the obtained modular forgings was tested, and the test results were: the hardness of the ingot riser was 35.5~37 HBC and the hardness of the ingot nozzle was 34~36 HBC.

[0054] S3 Forging Post-Forging Heat Treatment: After forging and air cooling, if the forging temperature is ≤700℃, immediately place the forging in a heat treatment furnace for normalizing at 980℃. Hold the forging at this temperature for 24 hours during normalizing. After holding, remove the forging from the furnace and quench it. During quenching, immerse the forging in running water for cooling. After quenching, if the water temperature is ≤65℃, place the forging in a furnace for tempering at 730℃ for 35 hours, followed by air cooling.

[0055] S4 performs rough machining on the forging, followed by UT self-inspection, and ultrasonic testing is conducted on the forging to detect defects.

[0056] S5 performance heat treatment, which involves heat treatment of forgings, can include stress relief heat treatment. Specifically, stress relief heat treatment is performed on forgings at a temperature below 400°C to eliminate stress caused by machining and hydrostatic testing, stabilize dimensions, and ensure the corrosion resistance of the pump casing. By performing stress relief heat treatment on the blank material after solution treatment, the mechanical properties and corrosion resistance of the pump casing can be further improved.

[0057] S6 samples were taken from the forgings for physicochemical testing, mainly focusing on: 1. Longitudinal mechanical properties of the inner hole at room temperature: tensile strength: ≥515MPa, yield strength: ≥205MPa, elongation: ≥40%, reduction of area: ≥50%, impact energy: 80J; 2. Longitudinal mechanical properties of the inner hole at room temperature: tensile strength: ≥490MPa, yield strength: ≥195MPa, elongation: ≥30%, reduction of area: ≥40%, impact energy: 60J; 3. Tangential mechanical properties of the outer circle at room temperature: tensile strength... 4. Tangential mechanical properties of the inner hole at 350℃: Tensile strength: ≥343MPa, Yield strength: ≥157MPa, Elongation: ≥32%, Reduction of area: ≥44%; 5. Tangential mechanical properties of the outer circle at 350℃: Tensile strength: ≥343MPa, Yield strength: ≥157MPa, Elongation: ≥32%, Reduction of area: ≥44%.

[0058] After S7 physicochemical testing, it undergoes further rough processing and UT inspection.

[0059] S8 final size inspection, labeling, packaging, completion, and shipment. Example 2

[0060] A forging process to improve the tearing between metals during the hot forming process of nuclear power pump casings

[0061] S1 Raw Material Inspection: The raw material is selected from 06Cr18Ni11Ti stainless steel. Impurities and oxide shells are removed from the surface of the raw material to ensure that the weighed mass is close to the designed mass, thereby guaranteeing the quality of the forged workpiece, including uniformity and overall quality. The composition of the raw material is also inspected to ensure that each component fully meets the requirements. The weight percentage of each component in the compliant raw material is as follows: C: 0.053%, Si: 0.41%, Mn: 1.74%, Ti: 0.49%, Cr: 17.9%, P: 0.019%, S: 0.004%, Ni: 9.5%, Co: 0.038%.

[0062] S2 forging, the forging cross-section size is 1180*1080mm, the hot delivery temperature is 650℃; the preheating temperature is 900℃ and held for 5 hours, and then medium frequency heating can realize the assembly line heating, so that the workpiece can be moved and heated in the medium frequency heating furnace. The material is heated to 1180℃ and held for 10 hours using medium frequency heating, and finally heated to 1320℃ and held for 18 hours. It is then forged using a hydraulic press. The hydraulic press mold is divided into upper mold and lower mold. The upper mold includes an upper mold base and a mold core installed in the upper mold base by fasteners. The mold core includes a flat mold, a punch, and a die. The upper mold is used in the following order: first use the flat mold, then the die, then the flat mold, then the punch, and finally use the flat mold to complete the die forging and forming, to fill the mold cavity, generate large deformation to promote grain refinement, and combine the upper mold to complete the forming. The lower mold is the mold for the shape and size of the forging. The final forging temperature of the forging is controlled at 1280℃.

[0063] The forging process adopts a forging ratio of 2.7, with a total drawing ratio > 5 and a total upsetting ratio > 5. A 1200mm wide flat anvil is used for drawing. The corner radius of the wide flat anvil is 120mm and the length is 2800mm. After 8 drawing passes, the forging product with a cross-sectional size of 1180*1080mm is directly drawn.

[0064] The obtained forgings were subjected to ultrasonic testing and met the requirements of SEP 1921E / e. The hardness of the obtained modular forgings was tested, and the test results were: the hardness of the ingot riser was 36.5~38 HBC and the hardness of the ingot nozzle was 35~38 HBC.

[0065] After S3 forging, the forging temperature is ≤700℃. Immediately after forging, the forging is placed in a heat treatment furnace for normalizing at 1050℃. The forging is held at this temperature for 26 hours during normalizing. After holding, the forging is removed from the furnace and quenched. During quenching, the forging is cooled in flowing water. After quenching, the water temperature is ≤65℃. After quenching, the forging is placed in a furnace for tempering at 800℃ for 38 hours, followed by air cooling.

[0066] S4 performs rough machining on the forging, followed by UT self-inspection, and ultrasonic testing is conducted on the forging to detect defects.

[0067] S5 performance heat treatment, which involves heat treatment of forgings, can include stress relief heat treatment. Specifically, stress relief heat treatment is performed on forgings at a temperature below 400°C to eliminate stress caused by machining and hydrostatic testing, stabilize dimensions, and ensure the corrosion resistance of the pump casing. By performing stress relief heat treatment on the blank material after solution treatment, the mechanical properties and corrosion resistance of the pump casing can be further improved.

[0068] S6 samples were taken from the forgings for physicochemical testing, mainly focusing on: 1. Longitudinal mechanical properties of the inner hole at room temperature: tensile strength: ≥515MPa, yield strength: ≥205MPa, elongation: ≥40%, reduction of area: ≥50%, impact energy: 80J; 2. Longitudinal mechanical properties of the inner hole at room temperature: tensile strength: ≥490MPa, yield strength: ≥195MPa, elongation: ≥30%, reduction of area: ≥40%, impact energy: 60J; 3. Tangential mechanical properties of the outer circle at room temperature: tensile strength... 4. Tangential mechanical properties of the inner hole at 350℃: Tensile strength: ≥343MPa, Yield strength: ≥157MPa, Elongation: ≥32%, Reduction of area: ≥44%; 5. Tangential mechanical properties of the outer circle at 350℃: Tensile strength: ≥343MPa, Yield strength: ≥157MPa, Elongation: ≥32%, Reduction of area: ≥44%.

[0069] After S7 physicochemical testing, it undergoes further rough processing and UT inspection.

[0070] S8 final size inspection, labeling, packaging, completion, and shipment. Example 3

[0071] A forging process to improve the tearing between metals during the hot forming process of nuclear power pump casings

[0072] S1 Raw Material Inspection: The raw material is selected from 06Cr18Ni11Ti stainless steel. Impurities and oxide shells are removed from the surface of the raw material to ensure that the weighed mass is close to the designed mass, thereby guaranteeing the quality of the forged workpiece, including uniformity and overall quality. The composition of the raw material is also inspected to ensure that each component fully meets the requirements. The weight percentage of each component in the compliant raw material is as follows: C: 0.049%, Si: 0.54%, Mn: 1.21%, Ti: 0.39%, Cr: 18.36%, P: 0.019%, S: 0.001%, Ni: 10.1%, Co: 0.037%.

[0073] S2 forging, the forging cross-section size is 1180*1080mm, the hot delivery temperature is 650℃; the preheating temperature is 950℃ and held for 5 hours, and then medium frequency heating can realize the assembly line heating, so that the workpiece can be moved and heated in the medium frequency heating furnace. The material is heated to 1200℃ and held for 10 hours using medium frequency heating, and finally heated to 1320℃ and held for 18 hours. It is then forged using a hydraulic press. The hydraulic press mold is divided into upper mold and lower mold. The upper mold includes an upper mold base and a mold core installed in the upper mold base by fasteners. The mold core includes a flat mold, a punch, and a die. The upper mold is used in the following order: first use the flat mold, then the die, then the flat mold, then the punch, and finally the flat mold is used to complete the die forging and forming, to fill the mold cavity, generate large deformation to promote grain refinement, and combine the upper mold to complete the forming. The lower mold is the mold for the shape and size of the forging. The final forging temperature of the forging is controlled at 1280℃.

[0074] The forging process adopts a forging ratio of 2.8, with a total drawing ratio > 5 and a total upsetting ratio > 5. A 1200mm wide flat anvil is used for drawing. The corner radius of the wide flat anvil is 120mm and the length is 2800mm. After 8 drawing passes, the forging product with a cross-sectional size of 1180*1080mm is directly drawn.

[0075] The obtained forgings were subjected to ultrasonic testing and met the requirements of SEP 1921E / e. The hardness of the obtained modular forgings was tested, and the test results were: the hardness of the ingot riser was 34.5~36 HBC and the hardness of the ingot nozzle was 35~38 HBC.

[0076] S3 Forging Post-Forging Heat Treatment: After forging and air cooling, if the forging temperature is ≤700℃, immediately place the forging in a heat treatment furnace for normalizing at 1100℃. Hold the forging at this temperature for 27 hours during normalizing. After holding, remove the forging from the furnace and quench it. During quenching, immerse the forging in running water for cooling. After quenching, if the water temperature is ≤65℃, place the forging in a furnace for tempering at 890℃ for 40 hours, followed by air cooling.

[0077] S4 performs rough machining on the forging, followed by UT self-inspection, and ultrasonic testing is conducted on the forging to detect defects.

[0078] S5 performance heat treatment, which involves heat treatment of forgings, can include stress relief heat treatment. Specifically, stress relief heat treatment is performed on forgings at a temperature below 400°C to eliminate stress caused by machining and hydrostatic testing, stabilize dimensions, and ensure the corrosion resistance of the pump casing. By performing stress relief heat treatment on the blank material after solution treatment, the mechanical properties and corrosion resistance of the pump casing can be further improved.

[0079] S6 samples were taken from the forgings for physicochemical testing, mainly focusing on: 1. Longitudinal mechanical properties of the inner hole at room temperature: tensile strength: ≥515MPa, yield strength: ≥205MPa, elongation: ≥40%, reduction of area: ≥50%, impact energy: 80J; 2. Longitudinal mechanical properties of the inner hole at room temperature: tensile strength: ≥490MPa, yield strength: ≥195MPa, elongation: ≥30%, reduction of area: ≥40%, impact energy: 60J; 3. Tangential mechanical properties of the outer circle at room temperature: tensile strength... 4. Tangential mechanical properties of the inner hole at 350℃: Tensile strength: ≥343MPa, Yield strength: ≥157MPa, Elongation: ≥32%, Reduction of area: ≥44%; 5. Tangential mechanical properties of the outer circle at 350℃: Tensile strength: ≥343MPa, Yield strength: ≥157MPa, Elongation: ≥32%, Reduction of area: ≥44%.

[0080] After S7 physicochemical testing, it undergoes further rough processing and UT inspection.

[0081] S8 final size inspection, labeling, packaging, completion, and shipment.

[0082] Table 1 compares the chemical composition of the raw materials used in Examples 1-3.

[0083]

[0084] Figure 1 This is based on the actual results of pump casing flaw detection and metallographic analysis in the prior art.

[0085] Figure 2 The results of flaw detection and metallographic analysis of the pump casing after process improvement are the actual results of the present invention.

[0086] Figure 3 Before the improvement, the forging material used was 10.8T, the forging was a 1180*1080*900 square block with a center punch, the machining allowance was large, and the machining cycle was long.

[0087] Figure 4 After the process improvement of this invention, the forging material consumption is 7.8T. This process saves raw material costs by (10.8-7.8) / 10.8*100%=28%. After the process improvement, the shape of the forging is infinitely close to the product size, which ensures the continuous fiber of the product, greatly improves the product performance, saves the processing cycle, and greatly reduces the waste of raw materials.

[0088] Figure 5-9 The results are from the physicochemical testing of the sample. Figure 5 For the longitudinal mechanical properties of the inner hole at room temperature, Figure 6The mechanical properties of the inner bore at room temperature are as follows: Figure 7 The mechanical properties of the outer tangential section at room temperature are as follows: Figure 8 The internal tangential mechanical properties at 350℃ Figure 9 Tangential mechanical properties of the outer circle at 350℃;

[0089] in, Figure 5-9 Data 1-4 represent the test data before the improvement, while data 5 and 6 represent the test data of Examples 1 and 2 after the process improvement of this invention.

[0090] Regarding the two reasons mentioned in the background art for pump casing forgings becoming defective after forging, this invention applies different countermeasures for the different causes of defects. For the first cause of defects, this invention starts with the forging process and improves it by changing the forging ratio, adding forging steps, etc. For the second cause of defects, this invention improves the forging heating process, rationalizes the heating temperature, time, and stage heating steps, etc. Based on the company's existing press operation and tooling ratio, through the process improvement of this invention, a reasonable forging ratio is designed, heating parameters are adjusted, and forging steps are changed, which effectively improves product performance and quality, reduces energy waste, increases yield, and shortens the processing cycle.

[0091] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A forging process to improve the tearing between metal parts during the hot forming process of nuclear power plant pump casings, characterized in that, Forging processes include: S1. Raw material inspection: Select raw materials that meet the requirements. The raw materials selected are stainless steel 06Cr18Ni11Ti. S2. Forging, including hot feeding at 650℃; preheating to 850-950℃ and holding for 5 hours, then heating the material to 1150-1200℃ and holding for 10 hours via medium frequency heating, and finally heating to 1320℃ and holding for 18 hours. Forging is performed using a hydraulic press. The hydraulic press mold is divided into an upper mold and a lower mold. The upper mold includes an upper mold base and a mold core installed in the upper mold base by fasteners. The mold core includes a flat mold, a punch, and a die. The lower mold is a mold for the shape and dimensions of the forging. The order of use of the upper mold is: first use the flat mold, then the die, then the flat mold, then the punch, and finally use the flat mold to complete the die forging. The final forging temperature of the forging is controlled at 1150-1280℃. S3. Post-forging heat treatment, including air cooling of forgings with a temperature ≤700℃, immediately placing the forgings in a heat treatment furnace for normalizing at a temperature of 980-1100℃, holding the forgings at that temperature for 24-27 hours; after holding, removing the forgings from the furnace and quenching them; during quenching, immersing the forgings in flowing water for cooling; after quenching, the water temperature ≤65℃, and then placing the forgings in a furnace for tempering at a temperature of 730-890℃, holding the tempering for 35-40 hours, followed by air cooling of the forgings; S4. Rough machining, followed by UT self-inspection; S5, Performance Heat Treatment; S6. Physicochemical testing after sampling; S7. UT inspection after rough machining; S8. Dimension inspection, label and package after passing inspection.

2. The forging process for improving the tearing between metal parts during the hot forming process of nuclear power plant pump casings according to claim 1, characterized in that, Performance heat treatment includes stress relief heat treatment of forgings, which is performed at a temperature below 400°C.

Images