Heat treatment method and heat treatment fixture for large-diameter spinning box bottom containing ultra-long straight sections

Abstract

This invention discloses a heat treatment method and fixture for large-diameter spinning box bottoms containing ultra-long straight sections, comprising the following steps: S1: The large-diameter spinning box bottom containing ultra-long straight sections to be heat-treated is placed on the heat treatment fixture with the larger end facing down, and preheated together; S2: A constraint steel strip assembly is placed on the outer surface of the large-diameter spinning box bottom containing ultra-long straight sections to be heat-treated, and the constraint steel strip assembly is connected to the heat treatment fixture to obtain the assembled heat treatment fixture; S3: The assembled heat treatment fixture and the large-diameter spinning box bottom containing ultra-long straight sections to be heat-treated are subjected to a first heating and a second heating. After the heating is completed, the box bottom is vertically immersed in water for quenching, and after aging treatment, the heat treatment of the spinning box bottom is completed. This invention meets the low ellipticity heat treatment requirements of large-diameter spinning box bottoms with ultra-long straight sections, and the diameter of the spinning box bottom can reach 4-5 meters, significantly improving the degree of deformation during heat treatment while ensuring the mechanical properties of the parts.

Description

Technical Field

[0001] This invention belongs to the field of box bottom processing technology, and in particular relates to a heat treatment method and heat treatment tooling for large-diameter spun box bottoms containing ultra-long straight sections. Background Technology

[0002] The tank bottom is a key component of the rocket fuel storage tank. In traditional manufacturing processes, the tank bottom is "welded" together from multiple parts such as segments and forked rings, resulting in numerous welds and lower reliability and yield rates. Furthermore, each segment requires more than ten processes before "welding," including material preparation, quenching, liquid filling / deep drawing, finishing, and aging, leading to a long production cycle. Integrated spinning forming of the tank bottom can reduce production steps by 35% and increase production efficiency by more than 30%, representing the future trend in tank bottom manufacturing.

[0003] The tank bottom mainly consists of two parts: a circular ring and a fork-shaped ring. Unlike smaller diameter tank bottoms such as 3.35 meters and 3.8 meters, the straight section of the fork-shaped ring at the large opening of the 5-meter diameter tank bottom is relatively long, reaching 140-180mm. Furthermore, the 5-meter tank bottom is a low-rigidity component with a large diameter-to-thickness ratio, and the fork-shaped ring is also quite thick (maximum thickness in the range of 28-30mm). If the parameters are not properly controlled during heat treatment, the roundness of the large opening of the tank bottom can easily exceed tolerances, resulting in insufficient machining allowance for the fork-shaped ring. The fork-shaped ring is a single forging, resulting in high raw material costs. Therefore, accurately controlling the amount of heat treatment deformation while ensuring the mechanical properties of the component, and meeting the dimensional requirements for integrated machining of the tank bottom with the fork-shaped ring, is of great significance.

[0004] Problems existing in the prior art:

[0005] (1) The raw material and machining cost of a 5-meter fork ring exceeds RMB 700,000. The traditional spinning box bottom heat treatment method cannot meet the machining size allowance requirements of the integrated ring and fork ring due to the large deformation, resulting in poor economic benefits.

[0006] (2) In the existing technology, the spinning of circular rings and fork-shaped rings involves separate forming, machining, heat treatment, and finally welding, resulting in low production efficiency. By optimizing the heat treatment process to achieve integrated processing of circular rings and fork-shaped rings, the production efficiency can be increased by more than 40%. Summary of the Invention

[0007] In view of this, the present invention aims to provide a heat treatment method and heat treatment fixture for the bottom of a large-diameter spinning box containing an ultra-long straight section, so as to solve at least one technical problem in the background art.

[0008] This invention enables heat treatment with low deformation of the spinning box bottom with an ultra-long straight section, meeting the machining allowance requirements of the integrated fork ring and circular ring after heat treatment.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0010] The heat treatment method for the bottom of a large-diameter spinning box containing an ultra-long straight section includes the following steps:

[0011] S1: After the top opening of the large-diameter spinning box bottom containing the ultra-long straight section to be heat-treated is completed, place it on the heat treatment fixture with the large opening end facing down, and preheat the large-diameter spinning box bottom containing the ultra-long straight section to be heat-treated and the heat treatment fixture together.

[0012] S2: The constraint steel strip assembly is placed on the outer surface of the bottom of the large-diameter spinning box containing an ultra-long straight section to be heat-treated. The constraint steel strip assembly is connected to the heat treatment fixture to obtain the assembled heat treatment fixture.

[0013] S3: The heat treatment fixture assembled in step S2 and the large-diameter spinning box bottom containing the ultra-long straight section to be heat-treated are subjected to the first heating and the second heating. After the heating is completed, the assembled heat treatment fixture and the large-diameter spinning box bottom containing the ultra-long straight section are vertically immersed in water for quenching and then subjected to aging treatment. The large-diameter spinning box bottom containing the ultra-long straight section after aging treatment is separated from the heat treatment fixture to obtain the heat-treated large-diameter spinning box bottom containing the ultra-long straight section.

[0014] The constraint steel strip assembly described in step S2 includes a steel strip connecting ring and several steel strips. The several steel strips are connected to the steel strip connecting ring by a second steel wire rope, and the other end of the steel strip is connected to the heat treatment fixture by a first steel wire rope.

[0015] Furthermore, in step S1, the top opening is circular in shape, and the diameter of the top opening is 800-900mm;

[0016] In step S1, the diameter of the large-diameter spinning box bottom containing the ultra-long straight section is 4-5 meters.

[0017] The preheating temperature in step S1 is 380-420℃, the holding time is 1.8-2.2h, and the heating rate is 5-10℃ / min.

[0018] In step S2, the outer diameter of the steel strip connecting ring is smaller than the inner diameter of the top opening of the large-diameter spinning box bottom containing the ultra-long straight section to be heat-treated.

[0019] Furthermore, in step S3, the temperature of the first heating is 380-420℃, the holding time is 1.8-2.2h, and the heating rate is 5-10℃ / min;

[0020] In step S3, the temperature of the second heating is 530-540℃, the holding time is 4-5h, and the heating rate is 5-10℃ / min;

[0021] In step S3, the quenching transfer time shall not exceed 15s. During quenching, the assembled heat treatment fixture and the bottom of the large-diameter spinning box containing the ultra-long straight section shall be vertically immersed in water (completely submerging the workpiece), with an immersion rate of 0.5-0.8m / s, and the water temperature before immersion shall not exceed 25℃;

[0022] In step S3, the aging treatment temperature is 170-175℃, and the holding time is 20-22h;

[0023] In step S3, after the aging treatment is completed, the large-diameter spinning box bottom containing the ultra-long straight section and the heat treatment fixture are separated within 20 minutes.

[0024] Furthermore, in step S1, the wall thickness of the large-diameter spinning box bottom containing the ultra-long straight section to be heat-treated is 40-60mm;

[0025] Furthermore, the large-diameter spun box bottom with ultra-long straight sections obtained in step S3 has a tensile strength ≥410MPa, a yield strength ≥300MPa, and an elongation after fracture ≥8%.

[0026] The heat treatment fixture used in the above-mentioned heat treatment method for the bottom of a large-diameter spinning box containing an ultra-long straight section includes a lower support assembly and an upper support assembly, with the upper support assembly fixedly installed above the lower support assembly.

[0027] The lower support assembly is equipped with a hoisting assembly and a connecting assembly for installing steel straps;

[0028] The hoisting components and connecting components are alternately and evenly arranged on the lower support components;

[0029] The number of hoisting components must be at least 6;

[0030] The number of connecting components must be at least 6.

[0031] Furthermore, the upper support assembly includes an upper inner ring, an upper outer ring, double support tubes, an upper support column, and support lugs;

[0032] The upper inner ring and the upper outer ring are connected by several double support tubes, and the upper inner ring and the upper outer ring are set at the same center.

[0033] Several supporting lugs are vertically and evenly arranged between the upper outer ring and the lower supporting assembly;

[0034] Several upper support columns are vertically and evenly arranged between the upper inner ring and the lower support components.

[0035] Furthermore, it also includes a support brace, one end of which is connected to the lower support assembly and the other end of which is connected to the upper support column;

[0036] The supporting ear piece has a smooth transition section, a diagonal section, and a straight section from top to bottom on one side. The smooth transition section of the supporting ear piece is located on the side away from the upper inner ring.

[0037] The outer diameter of the straight segment of several circumferentially arranged support lugs is 3-5 mm smaller than the inner diameter of the large-diameter spinning box bottom containing the extra-long straight segment to be heat-treated;

[0038] The number of dual support tubes is the same as the number of support ear pieces, and the number of support ear pieces is at least 48.

[0039] The number of upper support columns should be at least 8.

[0040] Furthermore, the lower support assembly includes a first lower outer ring, a second lower outer ring, a lower support column, a lower inner ring, and a lower connecting column;

[0041] Several lower support columns are evenly and vertically arranged between the first lower outer ring and the second lower outer ring, and the lower part of the support lug is fixed to the upper surface of the first lower outer ring through a connecting ring;

[0042] Several lower inner rings are connected to the second lower outer ring through several lower connecting posts;

[0043] The supporting diagonal brace is installed on the second lower outer ring;

[0044] The first lower outer ring, the second lower outer ring, and the lower inner ring are set at the same center.

[0045] The number of lower support columns and lower connecting columns is at least 8.

[0046] Furthermore, the lifting assembly includes a lifting plate, which is evenly arranged around the outside of the first lower outer ring, and the lifting plate is provided with lifting rings;

[0047] The connecting assembly includes a first connecting plate, a first vertical plate, a second vertical plate, and a rotating shaft; the first connecting plates are evenly arranged around the outside of the first lower outer ring; the position of the hoisting assembly corresponds to the position of the first connecting plate;

[0048] The first vertical plate and the second vertical plate are vertically arranged between the first lower outer ring and the second lower outer ring;

[0049] The rotating shaft is positioned between the first vertical plate and the second vertical plate;

[0050] A first steel wire rope for connecting the constraint steel belt assembly is provided on the rotating shaft. One end of the first steel wire rope is fixedly wound on the rotating shaft, and the other end is connected to the constraint steel belt assembly.

[0051] The first connecting plate is provided with a through hole that allows the first steel wire rope to pass through;

[0052] A rotating gear is provided on the side of the rotating shaft near the first vertical plate. A locking element is rotatably provided on the first vertical plate. The locking element cooperates with the rotating gear to form a one-way rotation mechanism, so that the gear can only rotate in one direction.

[0053] Compared with existing technologies, the heat treatment method and heat treatment fixture for large-diameter spinning box bottoms containing ultra-long straight sections described in this invention have the following advantages:

[0054] (1) The steel strip and the tooling of the present invention are connected by steel wire rope instead of bolts. During the heating and heat preservation process, the steel wire rope can be stretched within a certain range under the tension of the steel strip and its own softening effect, realizing flexible clamping between the parts and the tooling, which can prevent the steel strip itself from being broken by the expanding parts and improve the safety of heat treatment.

[0055] (2) By reasonably setting the heat treatment tooling structure, the present invention can meet the actual production needs such as lightweight tooling structure, assembly of parts with tooling before heat treatment, and separation of parts from tooling after heat treatment, while increasing the internal support and shape preservation effect of tooling on parts.

[0056] (3) The diameter of the tooling in this invention is close to the diameter of the bottom part of the box, which makes it impossible for the part to fall completely into the heat treatment tooling before heat treatment. By preheating at 400°C, and taking into account the difference in the coefficient of thermal expansion between the part and the heat treatment tooling, the bottom of the spinning box and the heat treatment tooling can be clamped together.

[0057] (4) In view of the characteristics of large diameter and large thickness of 5-meter spinning box bottom, the present invention adopts reasonable quenching and aging heat treatment process parameters, and combined with the product water immersion rate control method after exiting the furnace, to meet the low ellipticity heat treatment requirements of large diameter spinning box bottom with ultra-long straight section. Under the premise of ensuring the mechanical properties of the parts, the degree of heat treatment deformation is significantly improved, and a solid foundation is provided for the integrated machining of rings and fork rings. Attached Figure Description

[0058] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0059] Figure 1 This is a schematic diagram of the assembled heat treatment fixture and the bottom of the large-diameter spinning box containing an ultra-long straight section, as proposed in this invention.

[0060] Figure 2 This is a schematic diagram of the assembled heat treatment fixture and the bottom of the large-diameter spinning box containing an ultra-long straight section to be heat treated, as proposed in this invention.

[0061] Figure 3 For the present invention Figure 2 Enlarged view of point A;

[0062] Figure 4 For the present invention Figure 2 Enlarged view of point B;

[0063] Figure 5 This is a top view of the assembled heat treatment fixture and the bottom of the large-diameter spinning box containing an ultra-long straight section, as proposed in this invention.

[0064] Figure 6 This is a schematic diagram of the supporting ear piece proposed in this invention;

[0065] Figure 7 This is a schematic diagram of the heat treatment fixture proposed in this invention;

[0066] Figure 8 This is a cross-sectional schematic diagram of the bottom of the large-diameter spinning box containing an ultra-long straight section, as proposed in this invention.

[0067] Figure 9 This is a top view schematic diagram of the bottom of the large-diameter spinning box containing an ultra-long straight section proposed in this invention.

[0068] Explanation of reference numerals in the attached figures:

[0069] 1. Upper support assembly; 101. Upper inner ring; 102. Upper outer ring; 103. Double support tube; 104. Upper support column; 105. Support lug; 1051. Smooth transition section; 1052. Diagonal section; 1053. Straight section; 106. Support diagonal rod; 2. Lower support assembly; 201. First lower outer ring; 202. Second lower outer ring; 203. Lower support column; 204. Lower inner ring; 205. Lower connecting column; 3. Hanging plate; 4. Hanging ring; 5. Connecting assembly; 501. First connecting plate; 502. First vertical plate; 503. Second vertical plate; 504. Rotating shaft; 505. Rotating gear; 506. Locking component; 507. First steel wire rope; 6. Steel strip connecting ring; 7. Steel strip; 8. Second steel wire rope; 9. Large-diameter spinning box bottom with ultra-long straight section to be heat treated. Detailed Implementation

[0070] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0071] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0072] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0073] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0074] Example 1

[0075] like Figures 1-2 As shown, the heat treatment fixture includes a lower support assembly 2 and an upper support assembly 1. The upper support assembly 1 is fixedly installed above the lower support assembly 2. The lower support assembly 2 is provided with a lifting assembly and a connecting assembly 5 for installing the steel strip 7. The lifting assembly and the connecting assembly 5 are alternately and evenly arranged on the lower support assembly 2. The number of lifting assemblies is at least 6. The number of connecting assemblies 5 is at least 6.

[0076] like Figure 7 As shown, the upper support assembly 1 includes an upper inner ring 101, an upper outer ring 102, double support tubes 103, upper support columns 104, and support lugs 105; the upper inner ring 101 and the upper outer ring 102 are connected by a number of double support tubes 103, and the upper inner ring 101 and the upper outer ring 102 are arranged concentrically; a number of support lugs 105 are vertically and evenly arranged between the upper outer ring 102 and the lower support assembly 2; a number of upper support columns 104 are vertically and evenly arranged between the upper inner ring 101 and the lower support assembly 2.

[0077] It also includes a support diagonal rod 106, one end of which is connected to the lower support assembly 2, and the other end is connected to the upper support column 104;

[0078] like Figure 6 As shown, one side of the support lug 105 is provided with a smooth transition section 1051, a diagonal section 1052, and a straight section 1053 from top to bottom. The smooth transition section 1051 of the support lug 105 is located on the side away from the upper inner ring 101. The number of double support tubes 103 is the same as the number of support lugs 105, and the number of support lugs 105 is at least 48. The number of upper support columns 104 is at least 8. The use of support lugs 105 avoids the contact between the large end area of ​​the part and the heat treatment tooling surface, which can improve the cooling rate of the part during quenching, thereby improving the heat treatment effect.

[0079] The lower support assembly 2 includes a first lower outer ring 201, a second lower outer ring 202, a lower support column 203, a lower inner ring 204, and a lower connecting column 205; several lower support columns 203 are evenly and vertically arranged between the first lower outer ring 201 and the second lower outer ring 202, and the lower part of the support lug 105 is fixed to the upper surface of the first lower outer ring 201 through a connecting ring; several lower inner rings 204 are connected to the second lower outer ring 202 through several lower connecting columns 205; a support diagonal rod 106 is arranged on the second lower outer ring 202; the first lower outer ring 201, the second lower outer ring 202, and the lower inner ring 204 are arranged concentrically; the number of lower support columns 203 and lower connecting columns 205 is at least 8.

[0080] The hoisting assembly includes a hoisting plate 3, which is evenly arranged around the outside of the first lower outer ring 201, and a hoisting ring 4 is provided on the hoisting plate 3.

[0081] like Figures 3-4As shown, the connecting assembly 5 includes a first connecting plate 501, a first vertical plate 502, a second vertical plate 503, and a rotating shaft 504; the first connecting plate 501 is evenly arranged around the outside of the first lower outer ring 201; the position of the hoisting assembly corresponds to the position of the first connecting plate 501, and the first vertical plate 502 and the second vertical plate 503 are vertically arranged between the first lower outer ring 201 and the second lower outer ring 202; the rotating shaft 504 is arranged between the first vertical plate 502 and the second vertical plate 503; the rotating shaft 504 is provided with a useful... A first steel wire rope 507 is connected to the constraint steel strip 7 assembly. One end of the first steel wire rope 507 is fixedly wound around the rotating shaft 504, and the other end is connected to the constraint steel strip 7 assembly. A through hole is provided on the first connecting plate 501 to allow the first steel wire rope 507 to pass through. A rotating gear 505 is provided on the side of the rotating shaft 504 near the first vertical plate 502. A locking member 506 is rotatably provided on the first vertical plate 502. The locking member 506 cooperates with the rotating gear 505 to form a one-way rotation mechanism, so that the gear can only rotate in one direction. This mechanism allows the rotating shaft to rotate in one direction to tighten the steel strip and can automatically lock to prevent loosening. This system provides a crucial radial constraint force for the ultra-long straight section of the workpiece to suppress its bulging or unstable deformation during heating and quenching.

[0082] like Figure 5 As shown, the constrained steel strip assembly includes a steel strip connecting ring 6 and several steel strips 7. The steel strips 7 are connected to the steel strip connecting ring 6 via a second steel wire rope 8. The other end of each steel strip 7 is connected to a rotating shaft 504 via a first steel wire rope 507. The diameter of the steel strip connecting ring 6 corresponds to the diameter of the top opening of the workpiece to be heat-treated. To prevent the part from detaching from the fixture during water quenching, at least six steel strips 7 are used to fix the part to the fixture. The steel strips 7 are connected to the steel strip connecting ring 6 (which is a steel ring) at the top of the part and to the heat treatment fixture at the larger end of the part via steel wire ropes.

[0083] This invention relates to a heat treatment process for large thin-walled components used in aerospace and other fields, particularly suitable for the heat treatment of large-diameter spinning box bottoms (hereinafter referred to as workpieces) containing ultra-long straight sections. The purpose of this method is to effectively control the deformation of the workpiece during heat treatment through a dedicated heat treatment fixture (hereinafter referred to as the fixture) and a specific thermal cycling process, thereby achieving uniform and excellent mechanical properties. It is confirmed that the wall thickness of the workpiece after spinning is within the range of 40-60 mm, and that the dimensions meet design requirements. The inner and outer surfaces of the workpiece and all components of the fixture are cleaned to ensure they are free of oil and impurities.

[0084] Inspect the tooling to ensure that all connecting parts (such as support braces, locking parts, etc.) are secure and reliable, and that moving parts (such as rotating shafts) operate flexibly.

[0085] Step 1: Clamping and positioning. With the large end of the workpiece facing down, carefully lift and place it onto the pre-positioned fixture. The support surface of the upper support component 1 of the fixture (composed of the upper outer ring 102, double support tubes 103, etc.) needs to be precision machined. The outer diameter of the straight section of several circumferentially arranged support lugs is 3-5mm smaller than the inner diameter of the large-diameter spinning box bottom containing the extra-long straight section to be heat-treated. This design ensures that after quenching shrinkage, the workpiece can achieve optimal fit and support with the fixture.

[0086] Step 2: Place the workpiece and tooling together as a single unit into the heat treatment furnace for preheating. This eliminates assembly stress and minimizes temperature gradients between the workpiece and tooling, as well as between different parts of the workpiece itself, laying a uniform thermal foundation for subsequent high-temperature treatment. Increase the temperature to 380-420℃ at a rate of 5-10℃ / min and hold at this temperature for 1.8-2.2 hours. At the end of the holding period, ensure that the large end of the workpiece is completely flush with the tooling support platform.

[0087] Step 3: Install the steel strip system: Wrap the constraint steel strip assembly (consisting of steel strip connecting ring 6, multiple steel strips 7, and a second steel wire rope 8) around the outer surface of the workpiece. Then, pass the first steel wire rope 507 at the lower end of the steel strip 7 through the through hole on the first connecting plate 501 of the connecting assembly 5, and fix it to the rotating shaft 504.

[0088] The steel strip tightening system is achieved through a unidirectional rotation mechanism consisting of a rotating gear 505 at one end of the rotating shaft 504 and a locking element 506. This mechanism allows the rotating shaft to rotate in one direction to tighten the steel strip and can automatically lock to prevent loosening. This system provides crucial radial constraint force for the extra-long straight sections of the workpiece to suppress bulging or unstable deformation during heating and quenching.

[0089] Step 4: First Heating (Low-Temperature Homogenization): The assembled assembly (workpiece + tooling + steel strip system) continues to be heated in the furnace. The parameters for this stage are the same as the preheating stage (380-420℃, holding for 1.8-2.2 hours). The purpose is to fully release and equalize any new thermal stress that may be introduced after adding the steel strip system. The second heating (solution treatment) is the crucial heat treatment strengthening stage. This fully dissolves the alloy strengthening phase into the matrix, preparing for subsequent age hardening. Continue heating at a rate of 5-10℃ / min to 530-540℃, and hold at this temperature for 4-5 hours to ensure that all parts of the workpiece reach the target temperature and complete the full solution treatment process.

[0090] After vertical quenching and solution treatment, the entire assembly is quickly removed from the heating furnace.

[0091] The hoisting process is carried out smoothly and quickly using at least six hoisting components (lifting plates 3 and lifting rings 4) evenly arranged on the lower support assembly 2 of the tooling. The quenching transfer time shall not exceed 15 seconds to prevent the decomposition of the supersaturated solid solution during the transfer process.

[0092] Maintaining the assembly in a strictly vertical position, immerse it smoothly and rapidly into the quenching water bath at a speed of 0.5-0.8 m / s. Before immersion, the temperature of the quenching water should not exceed 25℃ to ensure sufficient cooling intensity. This rapidly "freezes" the microstructure at high temperature to room temperature, obtaining a supersaturated solid solution.

[0093] Step 5: After quenching, a significant temperature difference and stress exist between the workpiece and the tooling. Aging treatment is then performed to induce the precipitation of fine, uniform strengthening phases from the supersaturated solid solution, thereby significantly improving the workpiece's strength and hardness. This process requires holding at 170-175℃ for 20-22 hours. The workpiece and tooling must be separated from their hot state within 20 minutes after aging treatment. Use jacks to separate the workpiece and tooling.

[0094] The mechanical properties of the workpiece treated by this method can stably reach the following indicators: tensile strength (Rm) ≥ 410 MPa; yield strength (Rp0.2) ≥ 300 MPa; elongation after fracture (A) ≥ 8%. These performance indicators fully demonstrate the effectiveness of this heat treatment method and can meet the high standard requirements for the use of large-diameter box bottom components with complex structures containing ultra-long straight sections.

[0095] Example 2

[0096] The 2219 aluminum alloy box bottom is in an annealed state before spinning, exhibiting good plasticity but relatively low strength. To improve the mechanical properties of the box bottom after spinning, quenching and aging treatments are required. To meet the venting requirements of the box bottom parts during immersion quenching, an opening is made at the top of the spun box bottom before heat treatment. The selection of the opening size is crucial: an opening that is too small cannot meet the venting speed requirements; an opening that is too large will reduce the overall rigidity of the parts and increase the degree of deformation during machining. Based on the overall contour characteristics of the 5-meter spherical bottom, the opening size before heat treatment is determined to be a circular hole with a diameter of 800-900 mm. Figures 8-9 As shown.

[0097] To improve the shape retention effect during quenching, a heat treatment shape-retaining fixture is required. This invention employs an internal support shape-retaining fixture, with the diameter of the fixture's support surface being 3-5mm smaller than the average diameter of the inner surface of the spinning box bottom to be heat-treated. The fixture diameter is slightly smaller than the part size, facilitating clamping between the fixture and the part. Additionally, the part at the bottom of the box shrinks after quenching, allowing it to fit snugly against the fixture, achieving a good shape-retaining effect. (If the fixture diameter is too large, it cannot clamp the part at the bottom of the box; if the diameter is too small, the part at the bottom of the box cannot "hold tightly" to the fixture after quenching, resulting in a poor fit and ineffective shape retention.) The fixture is made of high-temperature resistant 309S stainless steel, primarily constructed using hollow-structure profiles welded together, offering advantages such as lightweight structure and high overall rigidity. The bottom layer of the fixture features a double-layer design, with a jack placed in the middle for lifting the part after heat treatment, allowing the part to detach from the fixture.

[0098] The fixture consists of 48 vertically mounted support lugs 105, with the support surface of the lugs matching the internal surface structure of the bottom of the chamber, providing internal support during the quenching and cooling stage. The use of support lugs 105 prevents the large end area of ​​the part from contacting the surface of the heat treatment fixture, thereby increasing the cooling rate of the part during quenching and improving the heat treatment effect.

[0099] To prevent the parts from detaching from the fixture during water quenching, six steel straps 7 are used to secure the parts to the fixture. The steel straps 7 are connected to the steel strap connecting rings 6 (which are steel rings) at the top of the parts, and are connected to the heat treatment fixture at the large end of the parts by steel wire ropes.

[0100] Step 1: Place the spinning box bottom. First, place the 5-meter-class box bottom part (workpiece) with its large opening facing down on the heat treatment fixture. Since the diameter of the fixture's support surface is designed to be 3-5mm smaller than the average diameter of the workpiece's inner surface, the workpiece and fixture will initially have a clearance fit. Through preheating, utilizing the fact that aluminum alloy has a higher coefficient of thermal expansion than stainless steel, the workpiece expands outwards, thus allowing its large opening to fully fit and clamp with the fixture's support platform.

[0101] Step 2: Preheat the parts. The heat treatment fixture and workpiece are hoisted into the furnace together. The furnace is then heated to 400℃ at a rate of 5-10℃ / min and held for 2 hours. The coefficient of thermal expansion of aluminum alloy is higher than that of the stainless steel used in the fixture. Therefore, during heating, the parts will expand outwards relative to the fixture, increasing the gap between them. Preheating ensures that the large end of the bottom part fits perfectly against the fixture support platform, achieving fixture mounting.

[0102] Step 3: Fix the part. Place 6 steel strips 7 on the outer surface of the workpiece and use the first steel wire rope 507 to connect the large end of the steel strips 7 to the heat treatment fixture to achieve binding and fixing between the part and the fixture.

[0103] Step 4: Furnace heating. The pre-assembled heat treatment fixture and workpiece are hoisted into the furnace. The temperature is increased to 400℃ at a rate of 5-10℃ / min and held for 1 hour. Then, the temperature is increased to 530-540℃ at a rate of 5-10℃ / min and held for 4-5 hours. Through preheating at 400℃, slow heating, and prolonged holding at solution temperature, the strengthening phase in the large-diameter spinning furnace bottom is fully dissolved during the heat treatment process.

[0104] Step 5: After the workpiece is removed from the furnace and quenched, the bottom workpiece and the heat treatment fixture are vertically immersed in water for quenching. The quenching transfer time shall not exceed 15 seconds, the vertical immersion rate in water shall be 0.5-0.8 m / s, and the water temperature before immersion shall not exceed 25℃.

[0105] While controlling the quenching transfer time and water temperature to ensure the mechanical properties of the workpiece, appropriately reducing the immersion rate during quenching is crucial for maintaining dimensional accuracy. This is because the bottom of a 5-meter diameter spinning furnace is relatively large; if it were to be immersed in water in a free-fall manner after exiting the furnace, the impact of the water flow on the workpiece at the bottom would be significant, easily leading to uneven cooling and poor ellipticity of the furnace bottom. By controlling the quenching rate of vertical immersion in water to 0.5-0.8 m / s, the cooling uniformity and roundness of the furnace bottom are greatly improved while ensuring the quenching cooling effect of the workpiece at the bottom. Using this method, the roundness of the large end area does not exceed 7 mm, while the roundness of the large end area of ​​the workpiece at the bottom of the furnace exceeds 20 mm during free-fall quenching. By reasonably adjusting parameters such as quenching transfer time, immersion rate, and water temperature, both the mechanical properties and dimensional accuracy of the workpiece are effectively balanced.

[0106] Step 6, Artificial Aging: Immediately send the bottom workpiece of the box that has completed thermal separation into the aging furnace and keep it at 170-175℃ for 20-22 hours.

[0107] Step 7, Tooling Separation: Complete the thermal separation of the workpiece and the heat treatment tooling within 20 minutes after aging treatment. Due to the shrinkage of the workpiece circumference after aging treatment, the large end of the workpiece will be in contact with the support surface of the heat treatment tooling. It is necessary to use a jack to lift the workpiece and complete the tooling disassembly.

[0108] The spinning box bottom mentioned in step 7 is a large-size spinning box bottom with an ultra-long straight section and a diameter of 5 meters, and the wall thickness after spinning is 40-60mm.

[0109] After the heat treatment fixture and the workpiece at the bottom of the box are properly installed in step 2, six steel straps 7 are used to fix them together to prevent the workpiece at the bottom of the box from floating up and detaching from the heat treatment fixture during quenching.

[0110] After quenching and artificial aging treatment, the performance of the 2219 alloy spinning box bottom body fully meets the requirements, with a tensile strength of 419MPa, a yield strength of 312MPa, and an elongation after fracture of 11%.

[0111] The overall structure of the heat treatment fixture offers advantages such as lightweight design and good shape retention. The connection method between the fixture and the steel strip 7 ensures both workpiece fixation and heat treatment safety. During quenching, the bottom of the chamber and the workpiece are immersed in water at a controlled rate, rather than in free fall, which reduces the impact of cooling water on the bottom of the chamber during rapid quenching and improves the uniformity of cooling during heat treatment. After heat treatment using this method, the roundness of the large-mouth area of ​​the chamber bottom does not exceed 7mm, providing sufficient dimensional allowance for the integrated machining of the fork-shaped ring and the circular ring. After quenching, the workpiece and the heat treatment fixture are in close contact. The bottom parts of the chamber exhibit significant quenching internal stress. Under this condition, the workpiece and the heat treatment fixture undergo aging treatment together. During this process, the quenching stress of the workpiece is released to a certain extent, further stabilizing the workpiece's dimensions and improving the roundness of the bottom workpiece. With appropriate heat treatment process parameters, the heat treatment fixture enables the machining of a 5-meter diameter spinning chamber bottom with a fork-shaped ring, achieving significant cost reduction and efficiency improvement. The tooling diameter is only 3-5mm smaller than the bottom diameter of the 5-meter class box, which is conducive to a tight fit between the bottom workpiece and the heat treatment tooling after heat treatment, resulting in good shape preservation during heat treatment.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of heat treatment of a large diameter spinning box bottom containing an ultra-long straight section, characterized in that: The method comprises the following steps: S1: after the top opening of the large-diameter spinning box bottom with an ultra-long straight section to be heat treated is opened, the large-diameter spinning box bottom with an ultra-long straight section to be heat treated is placed on a heat treatment tool in a manner that the large opening end faces downward, and the large-diameter spinning box bottom with an ultra-long straight section to be heat treated and the heat treatment tool are collectively preheated; S2: a constraint steel belt assembly is placed on the outer surface of the large-diameter spinning box bottom with an ultra-long straight section to be heat treated, the constraint steel belt assembly is connected with the heat treatment tool to obtain an assembled heat treatment tool; S3: the assembled heat treatment tool and the large-diameter spinning box bottom with an ultra-long straight section to be heat treated in step S2 are collectively subjected to first heating and second heating, after which the assembled heat treatment tool and the large-diameter spinning box bottom with an ultra-long straight section are vertically immersed in water for quenching, and then are subjected to aging treatment, the large-diameter spinning box bottom with an ultra-long straight section after the aging treatment is separated from the heat treatment tool, and a large-diameter spinning box bottom with an ultra-long straight section after heat treatment is obtained; The constraint steel belt assembly in step S2 comprises a steel belt connecting ring and a plurality of steel belts, the plurality of steel belts are connected with the steel belt connecting ring through a second steel wire rope, and the other end of the steel belt is connected with the heat treatment tool through a first steel wire rope; The diameter of the supporting surface of the heat treatment tool in step S1 is 3-5 mm smaller than the average diameter of the inner profile surface of the large-diameter spinning box bottom with an ultra-long straight section to be heat treated; The preheating temperature in step S1 is 380-420℃, the holding time is 1.8-2.2 h, and the heating speed is 5-10℃ / min; The heat treatment tool used in the method for heat treating the large-diameter spinning box bottom with an ultra-long straight section comprises a lower supporting assembly and an upper supporting assembly, and the upper supporting assembly is fixedly arranged above the lower supporting assembly; The lower supporting assembly is provided with a lifting assembly and a connecting assembly for mounting a steel belt; The lifting assembly and the connecting assembly are alternately and uniformly arranged on the lower supporting assembly; The connecting assembly comprises a first connecting plate, a first vertical plate, a second vertical plate and a rotating shaft, the first connecting plate is uniformly arranged on the outside of the first lower outer ring along the circumference, and the position of the lifting assembly corresponds to the position of the first connecting plate; The first vertical plate and the second vertical plate are vertically arranged between the first lower outer ring and the second lower outer ring; The rotating shaft is arranged between the first vertical plate and the second vertical plate; The rotating shaft is provided with a first steel wire rope for connecting the constraint steel belt assembly, one end of the first steel wire rope is fixedly wound on the rotating shaft, and the other end is connected with the constraint steel belt assembly; the first connecting plate is provided with a through hole through which the first steel wire rope passes; The side of the rotating shaft close to the first vertical plate is provided with a rotating gear, and the first vertical plate is rotatably provided with a locking piece, the locking piece cooperates with the rotating gear to form a one-way rotating mechanism, so that the gear can only rotate in one direction; After the workpiece is treated by the method, the mechanical properties thereof can stably reach the following indexes: tensile strength (Rm) ≥ 410 MPa, yield strength (Rp0.2) ≥ 300 MPa, and elongation after fracture (A) ≥ 8%.

2. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 1, characterized in that: The shape of the top opening of the large-diameter spinning box bottom with an ultra-long straight section to be heat treated in step S1 is circular, and the diameter of the top opening is 800-900 mm. The large-end diameter of the large-diameter spinning box bottom with super-long straight section to be heat treated in step S1 is 4-5 meters; The outer diameter of the steel band connecting ring in step S2 is smaller than the inner diameter of the top opening of the large-diameter spinning box bottom with super-long straight section to be heat treated.

3. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 1, characterized in that: In step S3, the temperature of the first heating is 380-420℃, the holding time is 1.8-2.2h, and the heating rate is 5-10℃ / min; in step S3, the temperature of the second heating is 530-540℃, the holding time is 4-5h, and the heating rate is 5-10℃ / min; In step S3, the quenching transfer time is not more than 15s; during quenching, the assembled heat treatment tooling is vertically immersed in water with the large-diameter spinning box bottom with super-long straight section, the immersion rate is 0.5-0.8m / s, and the water temperature before immersion is not higher than 25℃; in step S3, the temperature of the aging treatment is 170-175℃, and the holding time is 20-22h; In step S3, after the aging treatment is completed, the large-diameter spinning box bottom with super-long straight section and the heat treatment tooling are separated within 20min.

4. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 1, characterized in that: The wall thickness of the large-diameter spinning box bottom with super-long straight section to be heat treated in step S1 is 40-60mm. The number of the lifting assemblies is at least 6; 5. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 1, characterized in that: The number of the connecting assemblies is at least 6. The upper support assembly comprises an upper inner ring, an upper outer ring, double support pipes, upper support columns, and support lugs.

6. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 1, characterized in that: The upper inner ring and the upper outer ring are connected by the double support pipes, and are arranged with the same center. The support lugs are vertically and uniformly arranged between the upper outer ring and the lower support assembly. The upper support columns are vertically and uniformly arranged between the upper inner ring and the lower support assembly. The support assembly further comprises support inclined rods, one end of each support inclined rod is connected to the lower support assembly, and the other end is connected to the upper support column.

7. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 1, characterized in that: One side of the support lug is sequentially provided with a smooth transition section, an inclined section, and a straight section from top to bottom, and the smooth transition section is arranged on the side away from the upper inner ring. The outer diameter of the straight section of each support lug arranged along the circumference is 3-5mm smaller than the inner diameter of the large-diameter spinning box bottom with super-long straight section to be heat treated. The number of the double support pipes is the same as the number of the support lugs, and the number of the support lugs is at least 48. The number of the upper support columns is at least 8. The lower support assembly comprises a first lower outer ring, a second lower outer ring, lower support columns, a lower inner ring, and a lower connecting column.

8. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 1, characterized in that: The lower support columns are vertically and uniformly arranged between the first lower outer ring and the second lower outer ring, and the lower part of the support lug is fixed to the upper surface of the first lower outer ring through the connecting ring. The lower inner ring is connected to the second lower outer ring through the lower connecting column, and the support inclined rod is arranged on the second lower outer ring; the first lower outer ring, the second lower outer ring, and the lower inner ring are arranged with the same center; and the number of the lower support columns and the lower connecting columns is at least 8. The lifting assembly comprises a lifting plate, the lifting plate is uniformly arranged along the circumference on the outside of the first lower outer ring, and the lifting plate is provided with a lifting ring.

9. The method of heat treatment of a large diameter spinning box with an ultra-long straight section according to claim 8, characterized in that: ​

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