A method for closing forming of an extra-large thick-walled cylinder with a taper

Abstract

The present application relates to the field of forging forming method, especially to a closing forming method of super large thick-walled cylinder with taper, that is, using multi-step closing forging process to manufacture super large thick-walled cylinder with taper. The thick-walled cylinder with taper is closed by multi-pass free forging, and the closing forming of the thick-walled cylinder with taper is completed. The closing forming method of the super large thick-walled cylinder with taper can complete the integrated forming manufacturing of the super large thick-walled cylinder with taper under the condition of the existing forming equipment. Compared with the traditional welding method of cylinder and taper section, the strength of the forging is greatly improved, which can better serve in harsh environment and ensure the safety performance during equipment use.

Description

Technical Field

[0001] This invention relates to the field of forging forming methods, and in particular to a method for forming an ultra-large thick-walled cylindrical body with a tapered opening. Background Technology

[0002] With the development of nuclear power energy, the operating conditions of main nuclear power equipment are becoming increasingly demanding. The nuclear power pressure vessel is the most important main equipment in the nuclear island, operating in the harshest environment. Due to long-term neutron radiation, it must possess extremely high stability. Currently, nuclear power pressure vessels are welded from ultra-large forgings. The quality of the nuclear power forgings, as well as the quality and quantity of the welds, are qualitatively significant to the reliability of the pressure vessel. Regular in-service inspections of the welds of in-service pressure vessels are essential to ensure stable operation. In recent years, with increasing emphasis on nuclear safety and the continuous development of smelting and forging technologies, major large equipment in nuclear island plants no longer uses welded structures but instead employs integrated large forging assemblies. Therefore, to further promote the development of nuclear power energy in my country, mastering the key manufacturing technologies of large forgings and improving the manufacturing level of heavy and large-scale key equipment is imperative.

[0003] The challenge in forming ultra-large, thick-walled cylindrical bodies with tapered vents lies in the enormous size of the forgings, the high demands on the forming equipment, and the inability to create the tapered shape using conventional reaming methods. Therefore, alternative forming processes must be considered. Forging with tapered vents is a forging process that reduces the diameter of hollow forgings such as cylindrical parts. This process suits the forming characteristics of such thick-walled cylindrical bodies with tapered vents, where the diameter of the tapered portion is smaller than that of the cylindrical body. Forging with tapered vents often uses flat anvils, V-shaped anvils, conical anvils, or arc-shaped anvils, employing one or more heating passes. The general steps for forging with tapered vents are: original steel ingot – cylindrical billet – upsetting – punching – reaming – forging with tapered vents. For the integrated forming of such thick-walled cylindrical bodies with tapered vents, it is necessary to consider whether the final forging can completely enclose the required parts and whether it meets the shape and size requirements of the parts in all areas. Furthermore, the forming equipment requirements must be compatible with the manufacturing capabilities of existing forming equipment. Summary of the Invention

[0004] The integrated forming and manufacturing of thick-walled cylindrical bodies with tapered vents is a problem that needs to be solved in the manufacturing of ultra-large forgings for nuclear power plants. To address this problem, the present invention aims to provide a method for forming ultra-large thick-walled cylindrical bodies with tapered vents, specifically utilizing a multi-step tapering forging process to manufacture such bodies. The method involves performing multiple passes of free forging to achieve the tapering and forming of the thick-walled cylindrical body; this method enables the integrated forming and manufacturing of ultra-large thick-walled cylindrical bodies with tapered vents under existing forming equipment conditions.

[0005] The objective of this invention can be achieved through the following technical solutions: This invention provides a method for forming an ultra-large thick-walled cylindrical body with a tapered opening, which involves performing multiple free forging passes on the thick-walled cylindrical body with a tapered opening to complete the forming of the thick-walled cylindrical body with a tapered opening. The specific method includes the following steps: (1) Based on the ratio of the reduction in diameter of the tapered part of the ultra-large thick-walled cylindrical part to the diameter of the cylindrical part, design the target size for each forging pass; (2) The design of the forging reduction amount for each pass is optimized multiple times based on finite element numerical simulation. In conjunction with the forging of the subsequent passes, the reduction amount for each pass is designed under the condition of considering the load of the existing forming equipment and whether the billet is unstable during the forming process. (3) Compare the shape and dimensions of the forging results of the multi-pass forging with those of the part. If the forging meets the requirements, provide the above process plan; if the forging does not meet the requirements, redesign the process plan. (4) Based on the results of multi-pass forging, give the specific forming scheme of this process.

[0006] In one embodiment of the present invention, any pass of free forging at the end of the billet must take into account the load of the existing forming equipment and whether the billet is unstable during the forming process.

[0007] In one embodiment of the present invention, the thick-walled cylindrical body with a tapered opening is reheated in the furnace after any one of the forging processes to reach the initial forging temperature, and then the next forging process begins.

[0008] In one embodiment of the present invention, the reheating temperature is the initial forging temperature, and the temperature is held for a period of time to ensure uniform temperature distribution; wherein the temperature is maintained at the initial forging temperature to ensure the material's deformability.

[0009] In one embodiment of the present invention, the initial forging temperature is 1200°C.

[0010] In one embodiment of the present invention, the method for preparing a thick-walled cylindrical body with a tapered opening specifically includes the following steps: (S1) Preparation of prefabricated thick-walled cylinder with tapered opening: The billet is subjected to upsetting and punching, mandrel drawing, reaming and machining in sequence to obtain the prefabricated thick-walled cylinder with tapered opening; (S2) Preparation of the thick-walled cylinder with tapered opening: The prefabricated thick-walled cylinder with tapered opening prepared in step (S1) is heated in the furnace to obtain the thick-walled cylinder with tapered opening.

[0011] In one embodiment of the present invention, in step (S1), the blank is a blank based on a thick-walled cylindrical part with a tapered opening, which has undergone size and shape design; when designing the shape and size of the blank, the shape of the blank is improved and optimized by finite element numerical simulation based on the shape and size of the thick-walled cylindrical part with a tapered opening and in conjunction with the forging process; the specific design process is as follows: (a1) Based on the outline and size requirements of the ultra-large thick-walled cylindrical part with a tapered opening, and in combination with the machining allowance requirements of the part, the shape and size of the blank are initially designed; (b1) Import the billet design results obtained in step (a1) into the finite element software to simulate the forging process of the tapered forging. Determine whether the shape of the forging in the simulation results meets the outline, size and subsequent machining requirements of the thick-walled cylindrical body with tapered opening. If the shape of the forging meets the requirements, extract the overall strain and temperature distribution of the forging during the tapering forging process. If the shape of the forging does not meet the requirements, repeat S101 and redesign the billet shape. (c1) Based on the simulation and optimization results, the billet shape is given.

[0012] In one embodiment of the present invention, based on a thick-walled cylindrical part with a tapered opening, the shapes of the upper and lower dies for each pass are designed. When designing the shape and dimensions of the upper and lower dies, the shapes of the upper and lower dies are improved and optimized using finite element numerical simulation, based on the shape and dimensions of the thick-walled cylindrical part with a tapered opening and in conjunction with the forging process. The specific design process is as follows: (a2) Based on the outline and size requirements of the ultra-large thick-walled cylindrical part with a tapered opening, and in combination with the machining allowance requirements of the part, the shapes of the upper mold and the lower mold for the third, second, and first passes are designed in sequence. (b2) Import the upper and lower die design results obtained in step (a2) into the finite element software to simulate the forging process of the tapered forging. Determine whether the shape of the forging in the simulation results meets the outline, size and subsequent machining requirements of the thick-walled cylindrical body with tapered opening. If the shape of the forging meets the requirements, extract the overall strain and temperature distribution of the forging during the tapering forging process. If the shape of the forging does not meet the requirements, repeat S201 and redesign the shape of the upper and lower dies. (c2) Based on the simulation and optimization results, give the shapes of the upper and lower molds.

[0013] In one embodiment of the present invention, the method for preparing a prefabricated thick-walled cylinder with a tapered opening specifically includes the following steps: (S101) Upsetting and punching: After upsetting the billet, a hole is punched in the center to form a through hole; (S102) Mandrel drawing: After step (S101) is completed, the mandrel is inserted into the through hole of the billet for drawing and forging. (S103) Hole enlargement of the mandrel: After step (S102) is completed, the hole enlargement mandrel is inserted into the through hole to enlarge the hole evenly, and then upsetting is performed to form a cylindrical blank with flat end faces; (S104) Machining: After step (S102) is completed, the outer side of the cylindrical blank is machined to reduce the thickness of the cylinder in some areas, and a prefabricated thick-walled cylinder with a tapered opening is obtained.

[0014] In one embodiment of the present invention, the reheating temperature is the initial forging temperature.

[0015] In one embodiment of the present invention, the initial forging temperature is 1200°C.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention can achieve the integrated forming of ultra-large thick-walled cylinder with tapered opening through multi-step forging process. Compared with the traditional method of welding cylinder and tapered opening, it greatly improves the strength of forging, enabling it to better serve in harsh environments and ensuring the safety performance of equipment during use.

[0017] (2) The present invention adopts a multi-pass forging process to form the billet in as few passes as possible, which can reduce the number of times the billet is reheated during the forging process, greatly improve production efficiency, and reduce the consumption of human and material resources caused by reheating.

[0018] (3) Through continuous optimization and improvement, the present invention can effectively control the forming load in each forming process, so that it fully meets the forging level of existing free forging forming equipment. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of a method for forming an ultra-large thick-walled cylindrical body with a tapered opening, as described in Example 1. Figure 2 This is a cross-sectional view of the upper die in the third pass of free forging for a method for forming an ultra-large thick-walled cylindrical body with a tapered opening, as described in Example 1. Figure 3 This is a cross-sectional view of the upper die in the second pass of free forging in a method for forming an ultra-large thick-walled cylindrical body with a tapered opening, as described in Example 1. Figure 4 This is a cross-sectional view of the upper die in the first pass of free forging in the forming method of a super-large thick-walled cylindrical body with a tapered opening, as described in Example 1. Figure 5 This is a process flow diagram of the prefabrication process of a prefabricated thick-walled cylindrical body with a tapered opening in the necking and forming method of an ultra-large thick-walled cylindrical body with a tapered opening in Example 1; Figure 6This is a schematic diagram illustrating the structural changes during the preparation of the prefabricated thick-walled cylinder with a tapered opening and the preparation of the thick-walled cylinder with a tapered opening in the necking forming method of an ultra-large thick-walled cylinder with a tapered opening in Example 1. Figure 7 This is a cross-sectional view of the forged ultra-large thick-walled cylindrical body with tapered opening prepared in Example 1; Figure 8 This is a schematic diagram of the shape envelope of the ultra-large thick-walled cylindrical body with a tapered opening in Example 1; The numbers in the drawing are: 1. Extra-large thick-walled cylindrical part with tapered opening; 2. Forged part with tapered opening and tapered opening. Detailed Implementation

[0020] This invention provides a method for forming an ultra-large thick-walled cylindrical body with a tapered opening, which involves performing multiple free forging passes on the thick-walled cylindrical body with a tapered opening to complete the forming of the thick-walled cylindrical body with a tapered opening. The specific method includes the following steps: (1) Based on the ratio of the reduction in diameter of the tapered part of the ultra-large thick-walled cylindrical part to the diameter of the cylindrical part, design the target size for each forging pass; (2) The design of the forging reduction amount for each pass is optimized multiple times based on finite element numerical simulation. In conjunction with the forging of the subsequent passes, the reduction amount for each pass is designed under the condition of considering the load of the existing forming equipment and whether the billet is unstable during the forming process. (3) Compare the shape and dimensions of the forging results of the multi-pass forging with those of the part. If the forging meets the requirements, provide the above process plan; if the forging does not meet the requirements, redesign the process plan. (4) Based on the results of multi-pass forging, give the specific forming scheme of this process.

[0021] In one embodiment of the present invention, any pass of free forging at the end of the billet must take into account the load of the existing forming equipment and whether the billet is unstable during the forming process.

[0022] In one embodiment of the present invention, the thick-walled cylindrical body with a tapered opening is reheated in the furnace after any one of the forging processes to reach the initial forging temperature, and then the next forging process begins.

[0023] In one embodiment of the present invention, the reheating temperature is the initial forging temperature, and the temperature is held for a period of time to ensure uniform temperature distribution; wherein the temperature is maintained at the initial forging temperature to ensure the material's deformability.

[0024] In one embodiment of the present invention, the initial forging temperature is 1200°C.

[0025] In one embodiment of the present invention, the method for preparing a thick-walled cylindrical body with a tapered opening specifically includes the following steps: (S1) Preparation of prefabricated thick-walled cylinder with tapered opening: The billet is subjected to upsetting and punching, mandrel drawing, reaming and machining in sequence to obtain the prefabricated thick-walled cylinder with tapered opening; (S2) Preparation of the thick-walled cylinder with tapered opening: The prefabricated thick-walled cylinder with tapered opening prepared in step (S1) is heated in the furnace to obtain the thick-walled cylinder with tapered opening.

[0026] In one embodiment of the present invention, in step (S1), the blank is a blank based on a thick-walled cylindrical part with a tapered opening, which has undergone size and shape design; when designing the shape and size of the blank, the shape of the blank is improved and optimized by finite element numerical simulation based on the shape and size of the thick-walled cylindrical part with a tapered opening and in conjunction with the forging process; the specific design process is as follows: (a1) Based on the outline and size requirements of the ultra-large thick-walled cylindrical part with a tapered opening, and in combination with the machining allowance requirements of the part, the shape and size of the blank are initially designed; (b1) Import the billet design results obtained in step (a1) into the finite element software to simulate the forging process of the tapered forging. Determine whether the shape of the forging in the simulation results meets the outline, size and subsequent machining requirements of the thick-walled cylindrical body with tapered opening. If the shape of the forging meets the requirements, extract the overall strain and temperature distribution of the forging during the tapering forging process. If the shape of the forging does not meet the requirements, repeat S101 and redesign the billet shape. (c1) Based on the simulation and optimization results, the billet shape is given.

[0027] In one embodiment of the present invention, based on a thick-walled cylindrical part with a tapered opening, the shapes of the upper and lower dies for each pass are designed. When designing the shape and dimensions of the upper and lower dies, the shapes of the upper and lower dies are improved and optimized using finite element numerical simulation, based on the shape and dimensions of the thick-walled cylindrical part with a tapered opening and in conjunction with the forging process. The specific design process is as follows: (a2) Based on the outline and size requirements of the ultra-large thick-walled cylindrical part with a tapered opening, and in combination with the machining allowance requirements of the part, the shapes of the upper mold and the lower mold for the third, second, and first passes are designed in sequence. (b2) Import the upper and lower die design results obtained in step (a2) into the finite element software to simulate the forging process of the tapered forging. Determine whether the shape of the forging in the simulation results meets the outline, size and subsequent machining requirements of the thick-walled cylindrical body with tapered opening. If the shape of the forging meets the requirements, extract the overall strain and temperature distribution of the forging during the tapering forging process. If the shape of the forging does not meet the requirements, repeat S201 and redesign the shape of the upper and lower dies. (c2) Based on the simulation and optimization results, give the shapes of the upper and lower molds.

[0028] In one embodiment of the present invention, the method for preparing a prefabricated thick-walled cylinder with a tapered opening specifically includes the following steps: (S101) Upsetting and punching: After upsetting the billet, a hole is punched in the center to form a through hole; (S102) Mandrel drawing: After step (S101) is completed, the mandrel is inserted into the through hole of the billet for drawing and forging. (S103) Hole enlargement of the mandrel: After step (S102) is completed, the hole enlargement mandrel is inserted into the through hole to enlarge the hole evenly, and then upsetting is performed to form a cylindrical blank with flat end faces; (S104) Machining: After step (S102) is completed, the outer side of the cylindrical blank is machined to reduce the thickness of the cylinder in some areas, and a prefabricated thick-walled cylinder with a tapered opening is obtained.

[0029] In one embodiment of the present invention, the reheating temperature is the initial forging temperature.

[0030] In one embodiment of the present invention, the initial forging temperature is 1200°C.

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] In the following embodiments, unless otherwise specified, the functional components or structures are conventional components or structures used in the art to achieve the corresponding functions; unless otherwise specified, the processing techniques are also conventional processing techniques used in the art.

[0033] Example 1 This embodiment provides a necking forming technology for an ultra-large thick-walled cylindrical body with a tapered opening made of SA508 Gr.3 steel. The process is as follows: Figure 1 As shown, it includes the following steps: (S1) Blank Design: When designing the blank shape and dimensions, based on the shape and dimensions of the ultra-large thick-walled cylindrical part with a tapered opening, and in conjunction with the forging process, finite element numerical simulation is used to improve and optimize the blank shape; specifically, the design process is as follows: (S101): Based on the outline and size requirements of the ultra-large thick-walled cylindrical part with a tapered opening, and in combination with the machining allowance requirements of the part, the shape and size of the blank are initially designed.

[0034] (S102): Import the billet design results obtained in step (S101) into the finite element software to simulate the forging process of the tapered opening. Determine whether the shape of the forging in the simulation results meets the outline, size and subsequent machining requirements of the thick-walled cylindrical body with tapered opening. If the shape of the forging meets the requirements, extract the overall strain and temperature distribution of the forging during the tapering process. If the shape of the forging does not meet the requirements, repeat step (S101) and redesign the billet shape.

[0035] (S103): Based on the simulation and optimization results, the billet shape is given.

[0036] (S2) Design of upper and lower dies: When designing the shape and dimensions of the upper and lower dies, based on the shape and dimensions of the ultra-large thick-walled cylindrical part with a tapered opening, and in conjunction with the forging process, finite element numerical simulation is used to improve and optimize the shape of the upper and lower dies; specifically, the design process is as follows: (S201): Based on the outline and dimensional requirements of the ultra-large thick-walled cylindrical part with a tapered opening, and considering the machining allowance requirements of the part, design the shapes of the upper molds for the third, second, and first passes respectively (e.g., Figure 2-4 (as shown) and the shape of the lower mold.

[0037] (S202): Import the upper and lower die design results obtained in step (S201) into the finite element software to simulate the forging process of the tapered forging. Determine whether the shape of the forging in the simulation results meets the outline, size and subsequent machining requirements of the thick-walled cylindrical body with tapered opening. If the shape of the forging meets the requirements, extract the overall strain and temperature distribution of the forging during the tapering forging process. If the shape of the forging does not meet the requirements, repeat step (S201) and redesign the shape of the upper and lower dies. (S203): Based on the simulation and optimization results, give the shapes of the upper and lower molds.

[0038] (S3) Blank preparation (preparation method of prefabricated thick-walled cylinder with tapered opening, such as...) Figure 5-6 (as shown) (S301) Upsetting and punching: After upsetting the billet, a hole is punched in the center to form a through hole; (S302) Mandrel drawing: The mandrel is inserted into the through hole of the punched billet for drawing and forging. (S303) Hole enlargement by mandrel: insert the mandrel into the through hole to enlarge the hole evenly, and then upset to form a cylindrical blank with flat end faces; (S304) Machining: Based on the completed blank shape, the blank after hole expansion is machined on the outside to reduce the thickness of the cylinder in some areas, and a prefabricated thick-walled cylinder with tapered opening is obtained. (S4) Billet heating and heat preservation (preparation method of thick-walled cylinder with tapered opening): The prefabricated thick-walled cylinder with tapered opening is placed in a heating furnace and heated to the initial forging temperature of 1200℃. It is kept at the temperature for a certain time to make the temperature distribution uniform, and the thick-walled cylinder with tapered opening is obtained. (S5) Three-pass free forging for the tapered thick-walled cylinder: The tapered thick-walled cylinder is forged in three passes to form the tapered cylinder. Specifically, the thick-walled cylindrical body with a tapered opening undergoes a first-pass forging (reduction of 1700mm), after which it is placed in a heating furnace and heated to the initial forging temperature of 1200℃; then, a second-pass forging (reduction of 210mm) is performed, after which it is placed in a heating furnace and heated to the initial forging temperature of 1200℃; finally, a third-pass forging (reduction of 1350mm) is performed to complete the forging of the ultra-large thick-walled cylindrical body with a tapered opening, resulting in a forged ultra-large thick-walled cylindrical body with a tapered opening (e.g., Figure 7 (As shown).

[0039] In this example, the shape envelope results of the ultra-large thick-walled cylinder with a tapered opening obtained from numerical simulation are as follows: Figure 8 As shown (extra-large thick-walled cylindrical part 1 with a tapered opening and an extra-large thick-walled cylindrical part 2 with a tapered opening). The extra-large thick-walled cylindrical part 1 with a tapered opening is completely enclosed by the extra-large thick-walled cylindrical part 1, achieving its shape and size requirements.

[0040] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A method for forming the opening of an ultra-large thick-walled cylindrical body with a tapered opening, characterized in that, The specific method includes the following steps: Multi-pass free forging of thick-walled cylindrical bodies with tapered openings effectively controls the forming load during each forming process, thus completing the tapering forming of the thick-walled cylindrical bodies with tapered openings. After any rounding forging, the thick-walled cylindrical body with a tapered rim is reheated in the furnace to reach the initial forging temperature before the next rounding forging begins. Among them, based on the thick-walled cylindrical part with a tapered opening, the shape of the upper mold and the shape of the lower mold for each pass are designed; when designing the shape and size of the upper and lower molds, the shape of the upper and lower molds is improved and optimized by finite element numerical simulation based on the shape and size of the thick-walled cylindrical part with a tapered opening and in combination with the forging process. Based on finite element numerical simulation optimization, and in conjunction with subsequent forging passes, the reduction amount for each pass is designed, taking into account the load of existing forming equipment and whether the billet forming process is unstable.

2. The method for forming the opening of an ultra-large thick-walled cylindrical body with a tapered opening according to claim 1, characterized in that, The preparation method of the thick-walled cylinder with a tapered opening specifically includes the following steps: (S1) Preparation of prefabricated thick-walled cylinder with tapered opening: The billet is subjected to upsetting and punching, mandrel drawing, reaming and machining in sequence to obtain the prefabricated thick-walled cylinder with tapered opening; (S2) Preparation of the thick-walled cylinder with tapered opening: The prefabricated thick-walled cylinder with tapered opening prepared in step (S1) is heated in the furnace to obtain the thick-walled cylinder with tapered opening.

3. The method for forming the opening of an ultra-large thick-walled cylindrical body with a tapered opening according to claim 2, characterized in that, In step (S1), the blank is a blank designed in terms of size and shape based on a thick-walled cylindrical part with a tapered opening.

4. The method for forming the opening of an ultra-large thick-walled cylindrical body with a tapered opening according to claim 2, characterized in that, The preparation method of prefabricated thick-walled cylinders with tapered openings specifically includes the following steps: (S101) Upsetting and punching: After upsetting the billet, a hole is punched in the center to form a through hole; (S102) Mandrel drawing: After step (S101) is completed, the mandrel is inserted into the through hole of the billet for drawing and forging. (S103) Hole enlargement of the mandrel: After step (S102) is completed, the hole enlargement mandrel is inserted into the through hole to enlarge the hole evenly, and then upsetting is performed to form a cylindrical blank with flat end faces; (S104) Machining: After step (S102) is completed, the outer side of the cylindrical blank is machined to reduce the thickness of the cylinder in some areas, and a prefabricated thick-walled cylinder with a tapered opening is obtained.

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