A special-shaped head and a preparation tool and method thereof

Abstract

The application discloses a special-shaped head and a preparation tool and a preparation method thereof, and the special-shaped head is integrally formed without a welding seam by adopting a hot forming process step by step. The special-shaped head is integrally formed without a welding seam by adopting a hot forming process step by step, through local heating by a medium-frequency induction and cooperation with a special tooling die, sequentially completing processes such as a reducing forming, a large-head punching, a head forming and a straight section flanging, and realizing the integrally formed special-shaped head without a welding seam. In the forming process, most of the metal is deformed as a shrinkage deformation, effectively solving the safety risks existing in the current cold forming with a welding seam technology, the local thinning cracking and material waste caused by the repeated stamping technology without a welding seam and other problems, and being suitable for various metal materials such as carbon steel, alloy steel, stainless steel, high-temperature alloy, nickel-based alloy and the like. The application can meet the process test requirements of the hot forming or the combination of the hot forming and the cold forming, and is especially suitable for a high-level waste glass solidification container and other scenes with high requirements for safety and material performance.

Description

Technical Field

[0001] This invention relates to the field of metal irregular part forming technology, specifically to an irregular end cap and its preparation tooling and preparation method. Background Technology

[0002] Currently, due to their complex structure, the forming technology for thin-walled metal irregular-shaped heads is mainly divided into two categories: Cold forming technology with weld seams: Using steel plates as raw materials, irregularly shaped heads are disassembled into two parts at the "neck" point. These parts are then formed separately by cold stamping or spinning, and finally welded together. While this technology enables product manufacturing, the presence of weld seams severely affects the high-temperature strength and impact toughness of the material, reducing the container's service life. For critical equipment such as containers for high-level radioactive waste vitrification, weld seam cracking could lead to radioactive material leakage, posing a significant safety risk.

[0003] Seamless repeated stamping technology: It also uses steel plate as raw material and achieves a seamless structure by repeated stamping. However, the local tensile deformation rate of the metal is high during the forming process, which can easily lead to serious thinning or even cracking. In addition, thicker steel plates are required as raw materials, and excess waste needs to be removed after forming, resulting in high production costs.

[0004] Existing technologies cannot simultaneously meet the requirements of "seamless safety", "low forming risk", "low cost" and "wide material applicability" for irregularly shaped heads. Therefore, a new forming technology and supporting tooling are urgently needed to solve this problem. Summary of the Invention

[0005] Purpose of the Invention: The purpose of this invention is to provide an irregularly shaped end cap, its preparation tooling, and preparation method, suitable for the mass production of thin-walled metal irregularly shaped end caps, especially suitable for the manufacture of special containers (such as containers for vitrified high-level radioactive waste) with stringent requirements for structural integrity, high-temperature strength, and impact toughness. During the manufacturing process, most of the metal deformation is shrinkage deformation, which solves the problem of severe local deformation or even cracking caused by large metal deformation and stretching, and also solves the problem of insufficient metal volume for the upper end flange, necessitating a weld seam, while reducing material waste during production.

[0006] Technical solution: The irregular-shaped end cap of the present invention is integrally made of seamless tube by thermoforming process. Its structure includes end cap body and upper port part formed by flange, and there are no splicing welds in the whole.

[0007] Preferably, the material of the irregularly shaped end cap is carbon steel, alloy steel, stainless steel, high-temperature alloy or nickel-based alloy.

[0008] The tooling for preparing the irregular-shaped head of the present invention includes: a set of large and small head molds for multi-pass diameter reduction forming, a punch mold for punching, an upper head mold and a lower head mold for final forming, and a punching mold for flanging forming. More preferably, the supporting tooling includes: large and small head molds (including lower mold 1 and lower mold 2), punch molds (including punch 1 and punch 2), an upper head mold, a lower head mold, and a punching mold. Each tooling mold is individually designed according to the specifications and dimensions of the irregular-shaped head, the wall thickness of the raw material, and the forming process requirements to ensure forming accuracy and structural adaptability.

[0009] Preferably, the reducing mold assembly includes multiple sets of molds with gradually changing sizes, used to gradually reduce the diameter of the heating section of the steel pipe blank to a predetermined size.

[0010] The method for preparing irregularly shaped heads using the aforementioned tooling of the present invention includes the following steps: S1: Provide seamless tube as blank; locally heat the predetermined deformation section of the blank, and use the reducer die set to perform 1 to 3 passes of diameter reduction forming to obtain a primary reducer workpiece with a straight section; S2: Repeat step S1 multiple times to gradually reduce the diameter of the heating section of the primary large and small head workpiece until the diameter of the small head and the straight section size meet the requirements of the flange volume, and obtain the final large and small head workpiece. S3: Locally heat the straight section of the large end of the final large and small head workpiece, and use a punch die and matching lower die to punch it 1 to 3 times, so that its port diameter is close to the target head diameter; S4: Heat the punched workpiece as a whole and shape it using the upper die and lower die to obtain a blank of the head with a straight section; S5: The straight section of the head blank with straight section is locally heated, and the blank is formed by 1 to 3 passes of flanging using a punching die and upper and lower dies of the head to obtain the finished blank of the irregular head.

[0011] Preferably, the local heating in steps S1, S2 and S5 is performed using medium-frequency induction heating, with a heating temperature of 1000°C to 1050°C.

[0012] Preferably, the overall heating temperature in step S4 is 1000°C to 1050°C.

[0013] Preferably, in step S5, the flanging process is replaced by a spinning process instead of a stamping process.

[0014] Preferably, the preparation method is suitable for process testing combining thermoforming and cold forming.

[0015] Preferably, the large and small head molds, punch molds, and end cap molds are designed individually according to the product specifications and the wall thickness of the material.

[0016] Preferably, the method for preparing irregular end caps uses seamless tubes as blanks and adopts a step-by-step thermoforming process. The specific steps are as follows: (1) Diameter reduction forming (first time): Select seamless tubes as raw materials and use medium frequency induction to locally heat the deformation length section of the blank. The heating temperature is controlled at 1000~1050℃. Use the large and small end mold (1~3 passes) to reduce the diameter of the heated section and form a large and small end workpiece with a straight section. (2) Multiple diameter reduction optimization: Repeat step (1) 2~4 times. By gradually reducing the diameter, the small end diameter and the straight section length of the large and small end meet the metal volume requirements of the subsequent flanging process. (3) Large end punching: Use medium frequency induction to locally heat the large end straight section of the large and small end to 1000~1050℃. With the punch mold (1~3 passes) and the small and small end lower mold 2, punch the large end to be consistent with the diameter of the target end cap. (4) Head forming: The large and small heads that have been punched are heated to 1000~1050℃. After being taken out of the furnace, they are quickly placed into the upper and lower molds of the head and pressed into a semi-finished head with a straight section. (5) Straight section flanging: The straight section of the head is deformed by medium frequency induction heating (temperature 1000~1050℃). The straight section is flanged and formed by using punching molds (1~3 passes) and upper and lower molds of the head to obtain the final irregular head product.

[0017] The key technical points of this invention are: (1) seamless tubes are selected as raw materials to avoid the introduction of weld seams from the source; (2) local heating with medium frequency induction at 1000~1050℃ is adopted, combined with step-by-step diameter reduction, punching and flanging processes, so that the metal is mainly deformed by shrinkage, the wall thickness is increased, and the tendency to crack is reduced; (3) special tooling molds and step-by-step processes work together to ensure the forming accuracy of each process and meet the metal volume requirements for flanging; (4) support process tests of hot forming or hot forming and cold forming combined, and adapt to a variety of metal materials.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. Achieve a seamless, one-piece molding structure for irregularly shaped heads, eliminating safety hazards caused by welds (such as the risk of leakage from high-level radioactive waste containers), ensuring the product's high-temperature strength and impact toughness, and guaranteeing the product's service life.

[0019] 2. During the manufacturing process, metal deformation is mainly shrinkage with no large tensile deformation, which effectively solves the problem of local thinning or even cracking caused by large metal deformation and stretching. This improves the product forming quality, wall thickness uniformity and structural integrity, and the metal deformation rate can be reduced to less than 15%. In contrast, traditional repeated stamping technology is prone to severe metal deformation and work hardening, especially for high-strength alloys such as high-temperature alloys and nickel-based alloys, where the metal deformation rate can reach 30% or even more than 50%. Improper control can even lead to cracking and scrapping.

[0020] 3. It solves the problem of insufficient metal volume for the upper edge of the product, which necessitates the inclusion of welds. At the same time, it reduces material waste during the production process (eliminating the need to use thick plates or cut off large amounts of waste to make up for the volume), lowers production costs, and increases material utilization by more than 10%.

[0021] 4. It is applicable to a variety of metal materials such as carbon steel, alloy steel, stainless steel, high-temperature alloys, and nickel-based alloys, especially valuable high-temperature alloy materials; at the same time, this technical solution is applicable to both hot forming process tests (overall or partial heating) and forming tests through cold forming, making it highly adaptable. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the raw material, steel pipe.

[0023] Figure 2 This is a schematic diagram of the lower mold 1.

[0024] Figure 3 This is a schematic diagram of the formed workpiece with straight sections and different sizes.

[0025] Figure 4 This is a schematic diagram of the final product (with straight sections and different sizes) after molding.

[0026] Figure 5 This is a schematic diagram of a punch die.

[0027] Figure 6 This is a schematic diagram of the lower mold 2 for the reducer.

[0028] Figure 7 This is a schematic diagram of the shape after the large-head punch is punched.

[0029] Figure 8 This is a schematic diagram of the mold on the head.

[0030] Figure 9 This is a schematic diagram of the lower mold for the head.

[0031] Figure 10 This is a schematic diagram of a head with a straight section.

[0032] Figure 11 This is a schematic diagram of punch 1.

[0033] Figure 12 This is a schematic diagram of punch 2.

[0034] Figure 13 This is a schematic diagram showing the placement of the workpiece before it is formed.

[0035] Figure 14 This is a schematic diagram of the finished blank after flanging. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Example 1

[0038] This embodiment takes the fabrication of an irregularly shaped head with a designed wall thickness of 5mm as an example. The specific parameters are as follows: Raw materials: Seamless tubes with a wall thickness of 6.5mm; Heating process: medium frequency induction local heating, heating temperature is controlled at 1000~1050℃, and the heating length is the length of each billet deformation section; Die pass count: 2 passes for diameter reduction forming, 2 passes for large end punching, and 1 pass for straight section flanging; This invention uses steel pipe as raw material and employs a thermoforming method, implementing the process in steps. During the forming process, most of the deformation is shrinkage deformation, resulting in increased wall thickness, which greatly reduces the material's tendency to crack and is beneficial to ensuring the material's performance. 1. Using steel pipe as the billet, medium-frequency induction local heating is applied at a temperature of 1000~1050℃. The heating length is the deformation length of the billet. A reducing mold (1~3 passes) is used to reduce the diameter of the heated section, forming a reducer with a straight section. Figures 1-3 .

[0039] 2. Repeat step 1 multiple times (usually 2-4 times) to gradually reduce the diameter of the heating section of the billet, making it a shape where both the smaller end diameter and the straight section meet the flanging requirements (volume requirements). Figure 4 .

[0040] 3. Using medium-frequency induction local heating, the straight section of the larger end of the reducer is locally heated to 1000~1050℃. Using a punch die (1~3 passes) and the lower reducer die 2, the larger end of the reducer is punched to approximately equal to the diameter of the end cap. Figures 5-7 .

[0041] 4. Heat the entire reducer to 1000~1050℃. After removing it from the furnace, use the upper and lower molds to shape it into a head with a straight section, such as... Figures 8-10 .

[0042] 5. The straight section of the end cap is heated locally at 1000~1050℃ using medium-frequency induction heating, with the heating length being the deformed portion of the straight section. Using punching dies (1~3 passes) and upper and lower dies on the end cap, the straight section is flanged and formed into the final product. Figures 11-14 .

[0043] The above embodiment illustrates a non-circular end cap with a wall thickness of 5mm, using a seamless tube with a wall thickness of 6.5mm as the raw material. This invention can also be applied to non-circular end caps with other wall thicknesses. Step 5 can also be spun instead of stamping. This invention is applicable to various carbon steel, alloy steel, stainless steel, high-temperature alloys, nickel-based alloys, and other metal materials. In practical applications, the upper die, lower die, and punch can be designed individually according to product specifications and material wall thickness. This invention is suitable for hot forming process experiments, and for process experiments involving overall or partial heating or a combination of hot forming and cold forming.

[0044] Example 2

[0045] This embodiment takes the fabrication of an irregularly shaped head with a designed wall thickness of 5mm as an example. The specific parameters are as follows: Raw materials: Seamless tubes with a wall thickness of 6.5mm; Heating process: Combination of overall heating and cold forming, with heating temperature controlled at 1000℃; Die pass count: 3 passes for diameter reduction forming, 1 pass for large end punching, and 1 pass for straight section flanging; This invention uses steel pipe as raw material and employs a thermoforming method, implementing the process in steps. During the forming process, most of the deformation is shrinkage deformation, resulting in increased wall thickness, which greatly reduces the material's tendency to crack and is beneficial to ensuring the material's performance. 1. Using steel pipes as raw materials, cold forming is employed. A reducing mold (2-3 passes) is used to reduce the diameter of the deformed section, creating a reducer with a straight section. Figures 1-3 .

[0046] 2. Repeat step 1 multiple times (usually 2-3 times) to gradually reduce the diameter of the deformed section of the billet, making it a large-end shape where both the smaller end diameter and the straight section meet the flanging requirements (volume requirements), such as... Figure 4 .

[0047] 3. The workpiece is heated as a whole to a temperature of 1000℃. Using a punch die (one pass) and a reducer die 2, the large end of the reducer is punched to approximately equal to the diameter of the end cap. Figures 5-7 .

[0048] 4. Heat the entire reducer to 1000℃. After removing it from the furnace, use the upper and lower molds to shape it into a head with a straight section, such as... Figures 8-10 .

[0049] 5. The straight section of the end cap is spun into the mold core using a spinning process. The heating length is the deformed portion of the straight section. The spinning machine spindle drives the straight section of the end cap to rotate synchronously with the mold core (speed range 800~1000rpm). The spinning wheel applies continuous pressure (pressure range 100~300kN) to the rotating straight section along a preset trajectory until the straight section of the end cap is in contact with the mold core, thus spinning and flanging the straight section into the final product. Figures 11-14 .

Claims

1. An irregularly shaped end cap, characterized in that, The irregularly shaped end cap is integrally formed from a seamless tube through a thermoforming process. Its structure includes the end cap body and the upper port portion formed by the flange, and there are no splicing welds on the whole.

2. The irregular-shaped end cap according to claim 1, characterized in that, The material of the irregularly shaped end cap is carbon steel, alloy steel, stainless steel, high-temperature alloy or nickel-based alloy.

3. A tooling for preparing the irregularly shaped head according to claim 1 or 2, characterized in that, include: Die sets for multi-pass diameter reduction forming, punch dies for punching, upper and lower end cap dies for final forming, and punch dies for flanging forming.

4. The preparation tooling according to claim 3, characterized in that, The reducing and increasing mold set includes multiple sets of molds with gradually changing sizes, used to gradually reduce the diameter of the heating section of the steel pipe billet to a predetermined size.

5. A method for preparing irregularly shaped heads using the tooling described in claim 3 or 4, characterized in that, Includes the following steps: S1: Provide seamless tube as blank; locally heat the predetermined deformation section of the blank, and use the reducer die set to perform 1 to 3 passes of diameter reduction forming to obtain a primary reducer workpiece with a straight section; S2: Repeat step S1 multiple times to gradually reduce the diameter of the heating section of the primary large and small head workpiece until the diameter of the small head and the straight section size meet the requirements of the flange volume, and obtain the final large and small head workpiece. S3: Locally heat the straight section of the large end of the final large and small head workpiece, and use a punch die and matching lower die to punch it 1 to 3 times, so that its port diameter is close to the target head diameter; S4: Heat the punched workpiece as a whole and shape it using the upper die and lower die to obtain a blank of the head with a straight section; S5: The straight section of the head blank with straight section is locally heated, and the blank is formed by 1 to 3 passes of flanging using a punching die and upper and lower dies of the head to obtain the finished blank of the irregular head.

6. The method according to claim 5, characterized in that, The local heating in steps S1, S2 and S5 uses medium-frequency induction heating, with a heating temperature of 1000℃ to 1050℃.

7. The method according to claim 5, characterized in that, The overall heating temperature in step S4 is 1000℃ to 1050℃.

8. The method according to claim 5, characterized in that, The flanging process in step S5 is performed using either stamping or spinning.

9. The method according to claim 5, characterized in that, The preparation method is applicable to process experiments combining thermoforming and cold forming.

10. The method according to claim 5, characterized in that, The large and small head molds, punch molds, and end cap molds are designed individually according to product specifications and material wall thickness.

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