Hammer hot deep drawing forming die and forming method for thin-wall deep-cavity structure part

Abstract

This invention discloses a hammer-operated hot drawing die and forming method for thin-walled deep-cavity structural parts, aiming to solve the problems of wall thickness reduction and uneven wall thickness distribution in traditional sheet metal plastic forming processes, which cannot meet the requirements of subsequent processing. The hammer-operated hot drawing die for thin-walled deep-cavity structural parts includes an upper die, a lower die, an underpressure ring, and a closing ring. When the raw material of the part is a 15mm-30mm titanium alloy sheet, the hot drawing process uses a 3-pass forming method, with a heating temperature of 700℃-800℃ and a die drop height of 50mm-60mm per pass. When the raw material of the part is a 15mm-30mm stainless steel sheet, the hot drawing process uses a 3-pass forming method, with a heating temperature of 950℃-1050℃ and a die drop height of 50mm-60mm per pass. As shown in Figure 1, the thin-walled deep-cavity structural parts produced by this invention have uniform wall thickness distribution, high forming efficiency, and are suitable for mass production.

Description

Technical Field

[0001] This application relates to the technical field of rocket engines, and in particular to a hot drawing die and forming method for a thin-walled deep cavity structure part. Background Technology

[0002] Thin-walled deep-cavity structural parts are key components in liquid rocket engine propellant tanks, and they have extremely high requirements for overall performance and dimensions. Thin-walled deep-cavity structural parts formed using traditional press cold drawing processes suffer from severe springback and localized thinning, resulting in uneven wall thickness distribution after forming. Furthermore, cold drawing requires multiple sets of transition forming dies, leading to high costs and long processing cycles, which seriously affect the production schedule and delivery requirements of the parts. Summary of the Invention

[0003] This invention addresses the problems of springback, severe local thinning, and uneven wall thickness distribution that occur during the cold deep drawing process of thin-walled deep cavity structural parts using traditional presses. It provides a hot deep drawing die and forming method for thin-walled deep cavity structural parts using a hammer.

[0004] In a first aspect, a hot drawing die for a thin-walled deep cavity structure part is provided, including an upper die and a lower die. The lower die has an annular cavity around the opening of the forming deep cavity. The die also includes a closing ring, which is disposed in the annular cavity. The inner surface of the closing ring mates with the outer surface of the upper die.

[0005] During the forming process of the mold, the deep cavity portion of the sheet metal extends into the forming deep cavity through the upper mold and the closing ring, and is drawn into the sheet metal by the lower mold. The portion of the sheet metal located outside the deep cavity is sandwiched between the closing ring and the lower mold.

[0006] The sealing ring is used to reduce the fillet radius at the opening of the part. Sealing ring 2 also serves a positioning function. During the forming process, the upper die moves downwards, and the gap between it and the sealing ring gradually decreases, improving positioning accuracy. Additionally, due to heat conduction during part forming, the upper die's temperature gradually increases and it expands, posing a risk of jamming between the upper die and the sealing ring. Using a beveled fit can easily solve the problem of the upper die and the sealing ring jamming.

[0007] In conjunction with the first aspect, in some implementations of the first aspect, the closing ring protrudes from the opening of the annular cavity.

[0008] In conjunction with the first aspect, in some implementations of the first aspect, the height of the closing ring protruding from the annular cavity is 30-40 mm.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the side of the closing ring facing the upper mold is provided with an inclined step, the inclined step being used to insert a pry bar.

[0010] Due to the pre-cooling shrinkage during the part forming process, it often gets stuck in the upper mold, preventing the part from being demolded. The inclined step on the upper end of the sealing ring is used to insert a pry bar to demold the part when it is stuck in the mold.

[0011] In conjunction with the first aspect, in certain implementations of the first aspect, the closing ring satisfies at least one of the following:

[0012] The reserved gap between the outer contour of the sealing ring and the inner surface of the lower mold is 6-8mm;

[0013] The reserved gap between the inner surface of the closing ring and the outer contour of the upper mold is 2-3mm.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the mold further includes an underpressure ring, which surrounds the periphery of the sheet metal and is located within the annular cavity. The underpressure ring is used to engage with the outer periphery of the sheet metal. During the mold forming process, the underpressure ring is clamped between the lower mold and the closing ring.

[0015] The underpressure ring serves two purposes: first, it provides positioning. Its inner diameter is slightly larger than the outer diameter of the sheet metal, allowing it to position the sheet metal before forming and prevent misalignment. Second, it provides a limiting function. Since the part is formed using a free forging hammer, the hammer's stroke cannot be precisely controlled. During forming, once the lower end face of the closing ring contacts the underpressure ring, the upper die will not move downwards, preventing the formed part from experiencing flash or thinning.

[0016] In conjunction with the first aspect, in certain implementations of the first aspect, the undervoltage ring satisfies at least one of the following:

[0017] The reserved gap between the outer contour of the underpressure ring and the inner surface of the lower mold is 2-3mm;

[0018] The reserved gap between the inner surface of the underpressure ring and the outer contour of the upper mold is 2-3mm;

[0019] The thickness of the undervoltage ring is the same as the thickness of the sheet metal.

[0020] Secondly, a method for hot drawing of thin-walled deep-cavity structural parts on a hammer is provided, the method using a mold as described in the last two implementations of the first aspect above, the method comprising:

[0021] The first heat is used to heat the sheet metal to the hot drawing temperature and hold it at that temperature. The sheet metal is then removed and placed in the lower die. The upper die is used to press and form the sheet metal, and the descent height of the upper die is controlled to be the first descent height. After forming, the sheet metal is returned to the furnace for heating.

[0022] The second heat is used to heat the sheet to the hot drawing temperature and hold it at that temperature. The sheet is then removed and placed in the lower die. The upper die is used to press and form the sheet. The lowering height of the upper die is controlled to be the second lowering height. After forming, the sheet is returned to the furnace for heating. The second lowering height is greater than the first lowering height.

[0023] The third heat is used to heat the sheet metal to the hot drawing forming temperature and hold it at that temperature. The sheet metal is then removed and placed in the lower die. The underpressure ring is placed in the center of the upper end face of the lower die, and the closing ring is placed in the center of the upper end face of the underpressure ring. The upper die is used for pressing and forming. The lowering height of the upper die is controlled to be a third lowering height, which is greater than the second lowering height and is sufficient for the closing ring to contact the underpressure ring.

[0024] In conjunction with the second aspect, in some implementations of the second aspect, the sheet material is a 15mm-30mm stainless steel sheet, and the method satisfies at least one of the following:

[0025] The hot drawing temperature is 700℃-800℃;

[0026] The heat preservation time is 20-40 minutes;

[0027] The first descent height is 50-60mm;

[0028] The second descent height is 60-90mm;

[0029] The third descent height is 180-190mm.

[0030] In conjunction with the second aspect, in some implementations of the second aspect, the sheet material is a 15mm-30mm stainless steel sheet, and the method satisfies at least one of the following:

[0031] The hot drawing temperature is 950℃-1050℃;

[0032] The heat preservation time is 30-50 minutes;

[0033] The first descent height is 50-60mm;

[0034] The second descent height is 60-90mm;

[0035] The third descent height is 180-190mm.

[0036] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0037] I. Thin-walled deep cavity structural parts formed by hammer hot drawing forming die and forming method have low springback and uniform wall thickness distribution.

[0038] Second, the mold has a reasonable structure and strong versatility, and is suitable for forming titanium alloy and stainless steel parts.

[0039] Third, the hot drawing forming method for thin-walled deep cavity structural parts is reasonable, requires fewer forming passes, and can greatly improve production efficiency and reduce mold costs. Attached Figure Description

[0040] Figure 1 This is a drawing of a forming mold for a thin-walled, deep-cavity structural part;

[0041] Figure 2 This is a top view of the closure ring;

[0042] Figure 3 This is a schematic diagram of the raw material sheet for thin-walled deep cavity structural parts. Detailed Implementation

[0043] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0044] Figure 1 This is a schematic diagram of a hot drawing die for a thin-walled deep cavity structure part provided in an embodiment of this application. Figure 3 This is a schematic diagram of the raw material sheet for a thin-walled deep-cavity structural part.

[0045] A hot-drawing die for thin-walled deep-cavity structural parts may include an upper die 1, a closing ring 2, an underpressure ring 3, and a lower die 4. The lower die 4 forms a deep cavity for forming the raw material sheet. Around the opening of the deep cavity, the lower die 4 also has an annular cavity for accommodating the closing ring 2 and the underpressure ring 3. The underpressure ring 3 is placed within the annular cavity and is positioned at the center of the upper end face of the lower die 4. The closing ring 2 is positioned at the center of the upper end face of the underpressure ring 3. The outer diameters of the closing ring 2 and the underpressure ring 3 are Φ580–Φ600 mm × 90 mm and Φ580–Φ600 mm × 15 mm, respectively.

[0046] The reducing ring 2 is used to reduce the fillet radius at the opening of the part. When the reducing ring 2 is placed into the lower mold 4, it can extend beyond the opening of the lower mold 4 by 30-40mm. The outer contour of the reducing ring 2 is designed according to the surface dimensions of the lower mold 4, with a clearance of 6-8mm. The inner surface dimensions are designed according to the surface dimensions of the upper mold 1, with a clearance of 2-3mm. Figure 2 A top view of the sealing ring 2 is shown. Due to the pre-cooling shrinkage during the part forming process, it often gets stuck in the upper mold, preventing the part from being demolded. The inclined step on the upper surface of the sealing ring 2 is used to insert a pry bar to demold the part when it is stuck in the mold.

[0047] The retaining ring 2 also serves a positioning function. During the part forming process, as the upper mold 1 moves downwards, the gap between it and the retaining ring 2 gradually decreases, improving positioning accuracy. Additionally, due to heat conduction during part forming, the upper mold 1 gradually heats up and expands, posing a risk of jamming between it and the retaining ring 2. The use of a beveled fit effectively addresses this jamming issue.

[0048] The inner diameter of the underpressure ring 3 is designed based on the outer diameter of the formed sheet metal, with a reserved gap of 2-3mm. The outer diameter is designed based on the inner diameter of the platform of the lower mold 4, with a reserved gap of 2-3mm. The height is designed based on the flash size of the part.

[0049] The underpressure ring 3 serves two purposes: first, it provides positioning. The inner diameter of the underpressure ring is slightly larger than the outer diameter of the sheet metal, allowing it to position the sheet metal before forming and prevent misalignment. Second, it provides a limiting function. Since the part is formed using a free forging hammer, the hammer's stroke cannot be precisely controlled. During the forming process, once the lower end face of the closing ring 2 contacts the underpressure ring 3, the upper die 1 will no longer move downwards, preventing the formed part from experiencing flash or thinning.

[0050] This application also provides a method for hot drawing of thin-walled deep cavity structural parts on a hammer.

[0051] In some embodiments, when the raw material for the thin-walled deep cavity structure part is a 15mm-30mm (e.g., 25mm) titanium alloy plate, the following steps are performed.

[0052] The first heat is used to heat the sheet metal 5 to 700℃-800℃ (e.g., 780℃) and hold it for 20-40 minutes (e.g., 30 minutes). The sheet metal 5 is then removed and placed in the lower mold 4. The upper mold 1 is used to press and form the sheet metal, and the descent height of the upper mold 1 is controlled to be 50-60mm (e.g., 60mm). After forming, the sheet metal is returned to the furnace for heating.

[0053] The second heat is used to heat the sheet to 700℃-800℃ (e.g., 780℃) and hold it for 20-40 minutes (e.g., 30 minutes). The sheet 5 is then removed and placed in the lower mold 4. The upper mold 1 is used to press and form the sheet, and the descent height of the upper mold 1 is controlled to be 80-90mm (e.g., 90mm). After forming, the sheet is returned to the furnace for heating.

[0054] The third heat is used to heat the sheet metal 5 to 700℃-800℃ (e.g., 780℃) and hold it for 20-40 minutes (e.g., 30 minutes). The sheet metal 5 is then removed and placed in the lower mold 4. The underpressure ring 3 is placed in the center of the upper end face of the lower mold 4, and the closing ring 2 is placed in the center of the upper end face of the underpressure ring 3. The upper mold 1 is used to press down and form the sheet metal, controlling the descent height of the upper mold 1 to be 180-190mm (e.g., 190mm). The forming is completed when the closing ring 2 contacts the underpressure ring 3.

[0055] In other embodiments, when the raw material for the thin-walled deep cavity structure part is a 15mm-30mm (e.g., 25mm) stainless steel plate, the following steps are performed.

[0056] The first heat is used to heat the sheet metal 5 to 950℃-1050℃ (e.g., 1000℃) and hold it for 30-50 minutes (e.g., 40 minutes). The sheet metal 5 is then removed and placed in the lower mold 4. The upper mold 1 is used to press and form the sheet metal, and the descent height of the upper mold 1 is controlled to be 50-60mm (e.g., 60mm). After forming, the sheet metal is returned to the furnace for heating.

[0057] The second heat is used to heat the sheet material 5 to 950℃-1050℃ (e.g., 1000℃) and hold it for 30-50 minutes (e.g., 40 minutes). The sheet material 5 is then removed and placed in the lower mold 4. The upper mold 1 is used to press and form the sheet material, and the descent height of the upper mold 1 is controlled to be 80-90mm (e.g., 90mm). After forming, the sheet material is returned to the furnace for heating.

[0058] The third heat is used to heat the sheet metal 5 to 950℃-1050℃ (e.g., 1000℃) and hold it for 30-50 minutes (e.g., 40 minutes). The sheet metal 5 is then removed and placed in the lower mold 4. The underpressure ring 3 is placed in the center of the upper end face of the lower mold 4, and the closing ring 2 is placed in the center of the upper end face of the underpressure ring 3. The upper mold 1 is used to press down and form the sheet metal, controlling the descent height of the upper mold 1 to be 180-190mm (e.g., 190mm). The forming is completed when the closing ring 2 contacts the underpressure ring 3.

[0059] Thin-walled deep-cavity structural parts produced by the above-mentioned forming molds and forming processes exhibit less springback and more uniform wall thickness distribution.

[0060] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for hot drawing of thin-walled deep-cavity structural parts on a hammer, characterized in that, The method uses a hot-drawing forming die for thin-walled deep-cavity structural parts. The hot-drawing forming die for thin-walled deep-cavity structural parts includes an upper die (1) and a lower die (4). The lower die (4) has an annular cavity around the opening of the forming deep cavity. The die also includes a closing ring (2), which is located inside the annular cavity. The inner surface of the closing ring (2) matches the outer surface of the upper die (1). The closing ring (2) protrudes from the opening of the annular cavity, and the height of the closing ring (2) protruding from the annular cavity is 30~40mm. During the forming process of the mold, the deep cavity portion of the sheet metal (5) extends into the forming deep cavity through the upper mold (1) and the closing ring (2), and is drawn into the sheet metal (5) by the lower mold (4). The portion of the sheet metal (5) located outside the deep cavity is sandwiched between the closing ring (2) and the lower mold (4). The mold also includes an underpressure ring (3), which surrounds the outer periphery of the sheet metal (5) and is located in the annular cavity. The underpressure ring (3) is used to cooperate with the outer periphery of the sheet metal (5). During the forming process of the mold, the underpressure ring (3) is sandwiched between the lower mold (4) and the closing ring (2). The method includes: The first heat is used to heat the sheet (5) to the hot drawing temperature and hold it at that temperature. The sheet (5) is then removed and placed in the lower die (4). The upper die (1) is used to press and form the sheet. The lowering height of the upper die (1) is controlled to be the first lowering height. After forming, the sheet is returned to the furnace for heating. The second heat is used to heat the sheet (5) to the hot drawing temperature and keep it warm. The sheet (5) is then taken out and placed in the lower die (4). The upper die (1) is used for pressing and forming. The lowering height of the upper die (1) is controlled to be the second lowering height. After forming, the sheet is returned to the furnace for heating. The second lowering height is greater than the first lowering height. The third heat is used to heat the sheet metal (5) to the hot drawing temperature and keep it warm. The sheet metal (5) is taken out and placed in the lower die (4). The underpressure ring (3) is placed in the center of the upper end face of the lower die (4). The closing ring (2) is placed in the center of the upper end face of the underpressure ring (3). The upper die (1) is used for pressing and forming. The lowering height of the upper die (1) is controlled to be the third lowering height. The third lowering height is greater than the second lowering height, and the third lowering height satisfies the contact between the closing ring (2) and the underpressure ring (3). The sheet material (5) is a 15mm-30mm stainless steel sheet, and the method satisfies: The hot drawing temperature is 700℃-800℃; The heat preservation time is 20-40 minutes; The first descent height is 50-60mm; The second descent height is 60-90mm; The third descent height is 180-190mm; The undervoltage ring (3) satisfies at least one of the following: The reserved gap between the outer contour of the underpressure ring (3) and the inner surface of the lower mold (4) is 2-3mm; The reserved gap between the inner surface of the undervoltage ring (3) and the outer contour of the upper mold (1) is 2-3mm; The thickness of the undervoltage ring (3) is the same as the thickness of the sheet metal (5).

2. The method according to claim 1, characterized in that, The closing ring (2) has an inclined step on the side facing the upper mold (1), and the inclined step is used to insert a pry bar.

3. The method according to claim 1, characterized in that, The closing ring (2) satisfies at least one of the following: The reserved gap between the outer contour of the closing ring (2) and the inner surface of the lower mold (4) is 6-8mm; The reserved gap between the inner surface of the closing ring (2) and the outer contour of the upper mold (1) is 2-3mm.

4. A method for hot drawing of thin-walled deep-cavity structural parts on a hammer, characterized in that, The method uses a hot-drawing forming die for thin-walled deep-cavity structural parts. The hot-drawing forming die for thin-walled deep-cavity structural parts includes an upper die (1) and a lower die (4). The lower die (4) has an annular cavity around the opening of the forming deep cavity. The die also includes a closing ring (2), which is located inside the annular cavity. The inner surface of the closing ring (2) matches the outer surface of the upper die (1). The closing ring (2) protrudes from the opening of the annular cavity, and the height of the closing ring (2) protruding from the annular cavity is 30~40mm. During the forming process of the mold, the deep cavity portion of the sheet metal (5) extends into the forming deep cavity through the upper mold (1) and the closing ring (2), and is drawn into the sheet metal (5) by the lower mold (4). The portion of the sheet metal (5) located outside the deep cavity is sandwiched between the closing ring (2) and the lower mold (4). The mold also includes an underpressure ring (3), which surrounds the outer periphery of the sheet metal (5) and is located in the annular cavity. The underpressure ring (3) is used to cooperate with the outer periphery of the sheet metal (5). During the forming process of the mold, the underpressure ring (3) is sandwiched between the lower mold (4) and the closing ring (2). The method includes: The first heat is used to heat the sheet (5) to the hot drawing temperature and hold it at that temperature. The sheet (5) is then removed and placed in the lower die (4). The upper die (1) is used to press and form the sheet. The lowering height of the upper die (1) is controlled to be the first lowering height. After forming, the sheet is returned to the furnace for heating. The second heat is used to heat the sheet (5) to the hot drawing temperature and keep it warm. The sheet (5) is then taken out and placed in the lower die (4). The upper die (1) is used for pressing and forming. The lowering height of the upper die (1) is controlled to be the second lowering height. After forming, the sheet is returned to the furnace for heating. The second lowering height is greater than the first lowering height. The third heat is used to heat the sheet metal (5) to the hot drawing temperature and keep it warm. The sheet metal (5) is taken out and placed in the lower die (4). The underpressure ring (3) is placed in the center of the upper end face of the lower die (4). The closing ring (2) is placed in the center of the upper end face of the underpressure ring (3). The upper die (1) is used for pressing and forming. The lowering height of the upper die (1) is controlled to be the third lowering height. The third lowering height is greater than the second lowering height, and the third lowering height satisfies the contact between the closing ring (2) and the underpressure ring (3). The sheet material (5) is a 15mm-30mm stainless steel sheet, and the method satisfies: The hot drawing temperature is 950℃-1050℃; The heat preservation time is 30-50 minutes; The first descent height is 50-60mm; The second descent height is 60-90mm; The third descent height is 180-190mm; The undervoltage ring (3) satisfies at least one of the following: The reserved gap between the outer contour of the underpressure ring (3) and the inner surface of the lower mold (4) is 2-3mm; The reserved gap between the inner surface of the undervoltage ring (3) and the outer contour of the upper mold (1) is 2-3mm; The thickness of the undervoltage ring (3) is the same as the thickness of the sheet metal (5).

5. The method according to claim 4, characterized in that, The closing ring (2) has an inclined step on the side facing the upper mold (1), and the inclined step is used to insert a pry bar.

6. The method according to claim 4, characterized in that, The closing ring (2) satisfies at least one of the following: The reserved gap between the outer contour of the closing ring (2) and the inner surface of the lower mold (4) is 6-8mm; The reserved gap between the inner surface of the closing ring (2) and the outer contour of the upper mold (1) is 2-3mm.

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