Hard stainless steel rocket tank barrel section and barrel manufacturing method
By using variable thickness slab design and elastic pad roll forming technology, the problem of weakened welding strength of hard stainless steel rocket tank sections was solved, achieving low-cost and high-efficiency manufacturing. The strength redundancy in the welding area offsets the welding softening, avoiding weight increase and secondary weak areas, and meeting the requirements of rapid response in commercial aerospace.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN GONGDA HAIZHUO INTELLIGENT FORMING TECH CO LTD
- Filing Date
- 2026-05-25
- Publication Date
- 2026-07-21
AI Technical Summary
During the welding process of hard stainless steel rocket propellant tank sections, the high-temperature thermal cycle during welding leads to microstructural transformation and grain coarsening in the weld zone and heat-affected zone, resulting in a significant weakening of the weld joint strength, which becomes a weak link in the propellant tank structure. Existing reinforcement methods increase ineffective mass and cannot completely solve the strength problem.
By adopting a variable thickness slab design, a first thick zone, a thin zone, and a second thick zone are set on the slab, and an elastic pad is used to form an integral roll-bending shape to form an arc-shaped cylindrical sheet. After welding, the load-bearing capacity of the thick zone joint is the same as that of the thin zone base material, and no additional reinforcement structure is required, thus avoiding the strength loss of the weld heat-affected zone.
It has achieved low-cost and high-efficiency manufacturing of hard stainless steel rocket propellant tank sections. The strength redundancy of the welded area offsets the softening during welding, avoids the risk of weight increase and secondary weak areas, shortens the manufacturing cycle, and meets the rapid response requirements of commercial aerospace.
Smart Images
Figure CN122425450A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rocket manufacturing technology, and in particular to a method for manufacturing a rigid stainless steel rocket propellant tank section and body. Background Technology
[0002] With the rapid development of the commercial space industry, reducing launch costs and improving payload efficiency have become important goals in the development of launch vehicles. The payload coefficient (the ratio of effective payload mass to takeoff mass) is a key indicator for measuring rocket performance, and one of the core ways to improve this indicator is through lightweighting and increasing the strength of the rocket body structure.
[0003] As the main structure of a launch vehicle, the propellant tank accounts for a large proportion of the rocket's dry weight, and the choice of its manufacturing materials directly determines the rocket's structural efficiency. Currently, rockets with a diameter of less than 5m in service are mostly made of aluminum alloy. However, for heavy-lift launch vehicles with a diameter greater than 5m or even 10m, stainless steel plates have become an ideal material due to their advantages such as low cost, good heat and corrosion resistance, and ease of repeated maintenance.
[0004] In the manufacturing process of rocket propellant tank sections, welding is an indispensable process for connecting curved sections and ultimately forming the tank section. However, welding hardened high-strength stainless steel plates presents the following technical challenges: the high-temperature thermal cycling during welding causes microstructural transformation, grain coarsening, and dissolution of strengthening phases in the weld zone and heat-affected zone, resulting in a significant weakening of the mechanical properties of this area, known as "weld joint softening." Even using higher-strength special welding wires for filling cannot prevent strength loss in the heat-affected zone. Ultimately, the strength of the weld joint is far lower than that of the hardened base material, becoming a weak point in the entire propellant tank structure and failing to meet the load-bearing requirements of the rocket body under extreme operating conditions.
[0005] To address the aforementioned issue of localized strength weakening caused by welding, conventional techniques involve reinforcing the welded joint area, such as by adding reinforcing structures. However, while this reinforcement method improves the load-bearing capacity of the joint to some extent, it introduces new technical drawbacks: First, the reinforcing structure directly increases the ineffective mass of the rocket body, contradicting the initial goal of improving the load-bearing capacity; second, reinforcing the existing weld or heat-affected zone can cause a new heat-affected zone to form at the connection between the reinforcing structure and the base material, creating a new "weak zone" and failing to fundamentally solve the problem of low localized strength. Summary of the Invention
[0006] The purpose of this invention is to provide a method for manufacturing a rigid stainless steel rocket propellant tank section and body, in order to solve the problems existing in the prior art, directly form a propellant tank section with near-equal load-bearing capacity, without the need for post-processing of the weld, and achieve low-cost and high-efficiency manufacturing of rocket propellant tanks.
[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for manufacturing a rigid stainless steel rocket propellant tank section, comprising the following steps: S1. Prepare a variable thickness slab and an elastic pad; the variable thickness slab includes a first thick region, a thin region, and a second thick region distributed sequentially along the length of the slab, the thickness of the first thick region is the same as the thickness of the second thick region and is greater than the thickness of the thin region, and both the first thick region and the second thick region protrude towards the first side of the variable thickness slab relative to the thin region; the area of the elastic pad is the same as the area of the variable thickness slab, one side of the elastic pad is a concave-convex side and the other side is a planar side, and the concave-convex side of the elastic pad can match the first side of the variable thickness slab; S2. The elastic pad is placed on the first side of the variable thickness slab, such that the edge of the elastic pad is aligned with the edge of the thin area, and the elastic pad is attached to the thin area to obtain a composite slab of equal thickness. S3. The equal-thickness composite plate blank is integrally rolled and bent to make the equal-thickness composite plate blank bend in the length direction, and then the elastic pad in the equal-thickness composite plate is removed to obtain a cylindrical sheet with an arc surface. S4. Prepare several cylindrical segments with the same radius, and the sum of the radii of all the cylindrical segments is 2π. Arrange all the cylindrical segments in sequence along the circumferential direction, and weld the ends of adjacent cylindrical segments to obtain a single hardened stainless steel rocket tank segment.
[0008] Preferably, the method for determining the thickness ratio of the first thick region to the thin region in the same variable thickness slab includes the following steps: S101. Determine the minimum thickness of the thin zone based on the design parameters of the rocket propellant tank; S102. Roll out a hardened slab of equal thickness with the same thickness as the minimum thickness of the thin region; S103. Along the rolling direction of the uniformly thick hardened slab, bone-shaped specimens are cut according to standard and subjected to uniaxial tensile testing to obtain the yield strength of the uniformly thick hardened slab base material. ; S104. Two sample plates are cut from the uniform-thickness hardened slab, each sample plate having the same thickness as the uniform-thickness hardened slab. The two sample plates are welded together to obtain a welded plate. Bone-shaped specimens are cut along the rolling direction of the welded plate and subjected to uniaxial tension. During the tensioning process, digital image correlation technology is used to measure the local strain in the weld area in real time to obtain the tensile stress at yield in the weld area of the hardened slab. According to formula (1) Calculate the yield strength of the weld region of the hardened slab, where, The yield strength of the weld region of the hardened slab. The stress state coefficient is a factor that takes values ranging from 1 to 1.22. S105. Calculate the thickness ratio and the thicknesses of the first and second thickness regions in the variable thickness slab according to the following formula: ; (2) in, The minimum thickness of the thin region. The thicknesses of the first thick region and the second thick region are, The thickness ratio is... The yield strength of the uniformly thick hardened slab base material. The stress state coefficient, The tensile stress is the stress at which the weld region of the hardened slab yields.
[0009] Preferably, in step S1, the length of a single variable thickness slab is calculated based on the diameter of the hard stainless steel rocket propellant tank section and the number of plates included in the hard stainless steel rocket propellant tank section, so that in step S4, the sum of the radian angles of all the plates is 2π; after determining the length of the variable thickness slab, the lengths of the first thick region, the thin region, and the second thick region are determined.
[0010] Preferably, the elastic pad is made of polyurethane, nylon, or rubber.
[0011] Preferably, in step S3, a four-roll CNC roll bending machine is used to perform the integral roll bending forming, and during the roll bending forming process, the elastic pad and the variable thickness stainless steel slab are partially or completely constrained.
[0012] Preferably, in step S4, laser welding, argon arc welding, or plasma welding is used to weld the ends of adjacent cylindrical sections.
[0013] The present invention also provides a method for manufacturing a rigid stainless steel rocket propellant tank body: multiple rigid stainless steel rocket propellant tank sections with the same diameter are obtained by using the above-mentioned method for manufacturing rigid stainless steel rocket propellant tank sections; the weld ends of each rigid stainless steel rocket propellant tank section are treated with equal thickness, and finally the multiple rigid stainless steel rocket propellant tank sections are arranged sequentially along the axial direction and welded together to form the entire rigid stainless steel rocket propellant tank body.
[0014] Preferably, when performing the equal thickness treatment, milling or grinding is used to chamfer the thick areas at both ends of the weld, so that the thickness of the edge of the thick area is consistent with the thickness of the middle thin area.
[0015] Preferably, the longitudinal welds of any two adjacent hardened stainless steel rocket tank sections are staggered circumferentially, and the stagger distance is >200mm.
[0016] Preferably, the longitudinal weld of the hardened stainless steel rocket propellant tank section is aligned with the center of the thin area in the adjacent hardened stainless steel rocket propellant tank section.
[0017] The present invention achieves the following technical effects compared to the prior art: The present invention relates to a method for manufacturing hard stainless steel rocket propellant tank sections and bodies. This method utilizes pre-reserved strength redundancy in the thicker areas to offset weld softening, cleverly avoiding the material science bottleneck of unavoidable softening in the heat-affected zone of hard stainless steel welding. It is applicable to the manufacturing of sections with different diameters and numbers of segments, possessing good engineering applicability and promotional value. Based on the strength relationship between the welded area and the base material, the present invention designs a variable-thickness slab, ensuring that the load-bearing capacity of the thicker joint after welding is the same as that of the thinner base material, eliminating the need for additional reinforcement structures. This avoids weight gain and eliminates the risk of secondary welding forming new weak areas. It eliminates the need for post-weld heat treatment or mechanical reinforcement, reducing material consumption and welding workload, significantly shortening the manufacturing cycle and lowering manufacturing costs, meeting the rapid response requirements of commercial aerospace. The use of periodic variable-thickness rolling to manufacture variable-thickness slabs, combined with a composite roll bending technology with elastic pads, achieves integrated and precise shape control of the variable-thickness slab, ensuring the geometric accuracy and material microstructure continuity of the sections. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of butt welding of variable thickness slabs in this invention; Figure 2 This is a schematic diagram of the structure of the variable thickness slab in this invention; Figure 3 for Figure 2 Sectional view of section AA; Figure 4 This is a schematic diagram of the combination of variable thickness slab and elastic pad into a uniform thickness slab in this invention; Figure 5 This is a schematic diagram of the integral roll bending forming of the medium-thickness composite slab of the present invention; Figure 6 This is a schematic diagram of the arc-shaped cylindrical plate in this invention; Figure 7A schematic diagram of a single hardened stainless steel rocket propellant tank section formed by welding multiple cylindrical sections; Figure 8 This is a flowchart of the method for manufacturing a rigid stainless steel rocket propellant tank body according to the present invention; Figure 9 A schematic diagram showing the formation of a hardened stainless steel rocket propellant tank body by circumferential welding of multiple hardened stainless steel rocket propellant tank sections. In the figure: 3. Variable thickness slab; 301. First thick zone; 302. Thin zone; 303. Second thick zone; 304. Weld area; 4. Elastic pad; 5. Tube. Detailed Implementation
[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] The purpose of this invention is to provide a method for manufacturing a rigid stainless steel rocket propellant tank section, which solves the problems existing in the prior art, directly forming a propellant tank section with near-equal load-bearing capacity, without the need for post-processing of the weld, and realizing low-cost and high-efficiency manufacturing of rocket propellant tanks.
[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0023] Example 1 like Figures 1 to 7 As shown, this embodiment provides a method for manufacturing a rigid stainless steel rocket propellant tank section, including the following steps: S1. Prepare a variable thickness slab 3 and an elastic pad 4. The variable thickness slab 3 includes a first thick region 301, a thin region 302, and a second thick region 303 distributed sequentially along the length of the variable thickness slab 3. The thickness of the first thick region 301 is the same as the thickness of the second thick region 303 and is greater than the thickness of the thin region 302. Both the first thick region 301 and the second thick region 303 protrude relative to the thin region 302 toward the first side of the variable thickness slab 3. The area of the elastic pad 4 is the same as the area of the variable thickness slab 3. One side of the elastic pad 4 is a concave-convex side and the other side is a flat side. The concave-convex side of the elastic pad 4 can match the first side of the variable thickness slab 3. In this embodiment, the variable thickness slab 3 is a 301, 304(L) or other grade stainless steel slab in H1 / 2, H3 / 4 or H state.
[0024] S2. Place the elastic pad 4 on the first side of the variable thickness slab 3, so that the edge of the elastic pad 4 is aligned with the edge of the thin area 302, and the elastic pad 4 is in contact with the thin area 302 to obtain a composite slab of equal thickness. S3. The equal-thickness composite slab blank is integrally rolled and formed, so that the equal-thickness composite slab blank is bent in the length direction. Then the elastic pad 4 in the equal-thickness composite slab is removed to obtain the arc-shaped cylindrical sheet 5. S4. Prepare several cylindrical segments 5 with the same radius, and the sum of the radii of all cylindrical segments 5 is 2π. Arrange all cylindrical segments 5 in sequence along the circumferential direction, and weld the ends of adjacent cylindrical segments 5 to obtain a single hardened stainless steel rocket tank segment. Due to the thickness compensation effect of the first thick area 301 and the second thick area 303, the load-bearing capacity of the weld area 304 after welding is basically equal to the load-bearing capacity of the base material of the thin area 302 in the middle of the cylindrical segment 5, and no reinforcement treatment is required.
[0025] This embodiment increases the thickness of the end of the cylindrical plate 5 that needs to be welded, reserving strength redundancy for the welding area. This offsets the softening caused by welding, transforming the welding metallurgy problem into a structural mechanics problem. Precise thickness compensation compensates for the strength loss caused by welding, ultimately achieving the manufacturing goal of "no post-weld reinforcement required, structural load-bearing capacity," cleverly avoiding the material science bottleneck of unavoidable softening in the heat-affected zone of hard stainless steel welding. After the variable-thickness slab 3 is bonded to the elastic pad 4, the upper and lower surfaces of the resulting uniform-thickness composite slab become planar. During the bending process, the force of the bending roller is transmitted to the variable-thickness slab 3 below through the elastic pad 4. Since the elastic pad 4 is an elastic body, its compression is greater at the thinner region 302 of the strain-thickness slab 3, and smaller at the corresponding first thicker region 301 and second thicker region 303, thus converting the concentrated rigid pressure into a uniformly distributed flexible pressure acting on the variable-thickness slab 3. This makes the bending deformation of the variable-thickness slab 3 more uniform, ultimately obtaining a curved cylindrical plate 5 with consistent curvature and no distortion.
[0026] In an optional embodiment, a preferred method for determining the thickness ratio of the first thick region 301 to the thin region 302 in the same variable thickness slab 3 includes the following steps: S101. Determine the minimum thickness of thin zone 302 based on the design parameters of the rocket propellant tank; S102, Roll out a hardened slab of equal thickness with the minimum thickness of thin zone 302; S103. Bone-shaped specimens are cut according to standard measurements along the rolling direction of the uniformly thick hardened slab and subjected to uniaxial tensile testing to obtain the yield strength of the uniformly thick hardened slab base material. ; S104. Two sample plates are cut from a hardened slab of equal thickness, each with the same thickness as the slab. The two sample plates are then welded together to obtain a welded plate. Bone-shaped specimens are cut along the rolling direction of the welded plate and subjected to uniaxial tensile testing. Before the tensile test, black and white speckle patterns are sprayed onto the gauge length area of the specimen (including the weld area). During the tensile test, digital image correlation (DIC) technology is used to measure the strain in the weld area in real time to obtain the tensile stress at yield in the weld area of the hardened slab. ; It is important to note that when a specimen containing a weld is subjected to uniaxial tension, because the strength of the weld and heat-affected zone (HAZ) is lower than that of the base metal, plastic deformation will be highly concentrated in this narrow area of the weld and HAZ. This deformation is constrained by the high-strength base metal on both sides, causing the stress state in the weld zone to change from uniaxial tension to a near-plane strain state. Therefore, tensile stress cannot be simply used as the basis for stress determination. To represent the yield strength of the weld region material; in reality, during a uniaxial tensile test, the weld region material may exhibit some anisotropy, causing it to deviate from isotropy. In this case, the yield strength of the weld region material can be expressed as... , where k is the stress state coefficient, which ranges from 1 to 1.22. Therefore, when calculating thickness compensation, the tensile stress measured from the single tensile test of the welded specimen must be multiplied by the coefficient k to obtain the yield strength of the weld area; According to formula (1) Calculate the yield strength of the weld region in the hardened slab, where, The yield strength of the weld region in the hardened slab. The stress state coefficient ranges from 1 to 1.22. S105. Calculate the thickness ratio and the thickness of the first thickest region 301 and the second thickest region 303 in the variable thickness slab 3 according to the following formula: ; (2) in, This represents the minimum thickness of thin region 302. The thicknesses of the first thick region 301 and the second thick region 303 are... For thickness ratio, The yield strength of a hardened slab base material of uniform thickness. The stress state coefficient, This refers to the tensile stress at which the weld zone of the hardened slab yields.
[0027] In the optional scheme of this embodiment, a preferred approach is that, in step S1, the length of a single variable-thickness slab 3 is calculated based on the diameter of the hard stainless steel rocket propellant tank section and the number of cylindrical plates 5 included in the hard stainless steel rocket propellant tank section, so that in step S4, the sum of the radian angles of all cylindrical plates 5 is 2π; after determining the length of the variable-thickness slab 3, the lengths of the first thick region 301, the thin region 302, and the second thick region 303 are determined; the width of a single variable-thickness slab 3 is w0, the length of a single variable-thickness slab 3 is L+2l, the length of the thin region 302 is L, and the lengths of the first thick region 301 and the second thick region 303 are both l. The diameter of the hard stainless steel rocket propellant tank section is generally D=3m~12m, and the number of cylindrical plates 5 included in the hard stainless steel rocket propellant tank section is generally n=1~8 pieces. Based on the diameter of the cylindrical plate 5 included in the hard stainless steel rocket propellant tank section, the circumferential unfolded length L0 of the cylindrical plate 5 included in the hard stainless steel rocket propellant tank section can be obtained after unfolding according to the neutral layer, where L0 = n(L + 2l). In this embodiment, the lengths of the first thick region 301 and the second thick region 303 in the variable thickness slab 3 are both less than 100mm.
[0028] In this embodiment, a variable thickness slab 3 is produced by continuous periodic (thick-thin-thick) rolling process; that is, after rolling, it can be cut along the middle position of the thick section to obtain multiple variable thickness slabs 3 for forming the single cylindrical piece 5. Alternatively, a single variable thickness slab 3 can be produced by reciprocating rolling using a single-stand rolling mill, and the edge process section can be cut off to obtain the variable thickness slab 3 for forming the single cylindrical piece 5.
[0029] In the optional solutions of this embodiment, the elastic pad 4 is preferably made of polyurethane, nylon, or rubber. The cross-sectional shape of the elastic pad 4 needs to be precisely designed according to the longitudinal cross-sectional shape of the variable thickness slab 3 to ensure the uniform thickness of the composite slab. The thickness of the uniform thickness composite slab can be flexibly adjusted by changing the thickness of the elastic pad 4 according to the actual rolling bending process. During the rolling bending process, the elastic pad 4 and the variable thickness slab 3 can be partially or fully constrained. Roll bending is generally carried out using a four-roll CNC rolling bending machine, which can monitor and adjust the curvature radius of the slab online in real time to achieve the curvature radius required by the curved cylindrical sheet 5; the elastic pad 4 can be reused. This cleverly avoids the problems of uneven curvature, wrinkling, or even cracking caused by sudden changes in stiffness when directly rolling bending variable thickness plates.
[0030] In the optional schemes of this embodiment, it is more preferred that, in step S4, laser welding, argon arc welding or plasma welding is used to weld the ends of adjacent cylindrical plates 5.
[0031] Example 2 Reference Figure 8 and Figure 9This embodiment provides a method for manufacturing a hardened stainless steel rocket propellant tank body: Multiple hardened stainless steel rocket propellant tank sections of the same diameter are produced using the manufacturing method of the hardened stainless steel rocket propellant tank section in Embodiment 1. The specific number of hardened stainless steel rocket propellant tank sections is determined according to actual usage requirements. The weld ends of each hardened stainless steel rocket propellant tank section are individually treated to achieve equal thickness, making its thickness consistent with the thin middle region 302, to facilitate subsequent circumferential butt welding between sections. Finally, the multiple hardened stainless steel rocket propellant tank sections are arranged sequentially along the axial direction and welded together to form the entire hardened stainless steel rocket propellant tank body.
[0032] In the optional solutions of this embodiment, a preferred method is to chamfer the thick areas at both ends of the weld by milling or grinding during the equal thickness treatment, so that the thickness of the edge of the thick area is consistent with that of the thin area 302 in the middle. The aforementioned equal thickness treatment is crucial for the high-quality assembly of the final cylinder. Since the welds at both ends of the cylinder section are thickened areas, directly performing circumferential butt welding would lead to problems such as stress concentration at the joint and uneven weld penetration due to the thickness difference. Therefore, by milling or grinding the thickness of the weld end within a certain width to match the thin area 302, a uniform thickness can be created for the circumferential weld, ensuring the welding quality of the circumferential weld. It is worth noting that although the thickness of the weld end is reduced by milling or grinding, making the thickness of the circumferential weld between two adjacent cylinder sections smaller than the thickness of the longitudinal weld on the cylinder section (i.e., the weld between cylinder segments within the same cylinder section), in actual use, the longitudinal weld on the cylinder section (i.e., the weld between cylinder segments within the same cylinder section) needs to bear a greater load, while the circumferential weld between two adjacent cylinder sections needs to bear a smaller load. That is, the cylinder mainly needs to bear a larger radial load and a smaller axial load. Therefore, the thinner circumferential weld between two adjacent cylinder sections can meet the requirements of the cylinder to bear the axial load and will not affect the overall performance of the cylinder.
[0033] In the optional embodiments of this example, a preferred approach is that the longitudinal welds of any two adjacent hardened stainless steel rocket propellant tank sections are staggered circumferentially, with a stagger distance >200mm. Requiring the longitudinal welds of adjacent sections to be staggered by a certain distance (e.g., greater than 200mm) is to distribute structural stress and prevent multiple welds from converging circumferentially to form a cross weld, thereby improving the overall structural integrity and fatigue life of the propellant tank.
[0034] In an optional embodiment, it is more preferred that the longitudinal weld of the hardened stainless steel rocket propellant tank section is aligned with the center of a thin region 302 in an adjacent hardened stainless steel rocket propellant tank section.
[0035] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.
Claims
1. A method for manufacturing a rigid stainless steel rocket propellant tank section, characterized in that, Includes the following steps: S1. Prepare a variable thickness slab and an elastic pad; the variable thickness slab includes a first thick region, a thin region, and a second thick region distributed sequentially along the length of the slab, the thickness of the first thick region is the same as the thickness of the second thick region and is greater than the thickness of the thin region, and both the first thick region and the second thick region protrude towards the first side of the variable thickness slab relative to the thin region; the area of the elastic pad is the same as the area of the variable thickness slab, one side of the elastic pad is a concave-convex side and the other side is a planar side, and the concave-convex side of the elastic pad can match the first side of the variable thickness slab; S2. The elastic pad is placed on the first side of the variable thickness slab, such that the edge of the elastic pad is aligned with the edge of the thin area, and the elastic pad is attached to the thin area to obtain a composite slab of equal thickness. S3. The equal-thickness composite plate blank is integrally rolled and bent to make the equal-thickness composite plate blank bend in the length direction, and then the elastic pad in the equal-thickness composite plate is removed to obtain a cylindrical sheet with an arc surface. S4. Prepare several cylindrical segments with the same radius, and the sum of the radii of all the cylindrical segments is 2π. Arrange all the cylindrical segments in sequence along the circumferential direction, and weld the ends of adjacent cylindrical segments to obtain a single hardened stainless steel rocket tank segment.
2. The method for manufacturing a hardened stainless steel rocket propellant tank section according to claim 1, characterized in that, The method for determining the thickness ratio of the first thick region to the thin region in the same variable thickness slab includes the following steps: S101. Determine the minimum thickness of the thin zone based on the design parameters of the rocket propellant tank; S102. Roll out a hardened slab of equal thickness with the same thickness as the minimum thickness of the thin region; S103. Along the rolling direction of the uniformly thick hardened slab, bone-shaped specimens are cut according to standard and subjected to uniaxial tensile testing to obtain the yield strength of the uniformly thick hardened slab base material. ; S104. Two sample plates are cut from the uniform-thickness hardened slab, each sample plate having the same thickness as the uniform-thickness hardened slab. The two sample plates are welded together to obtain a welded plate. Bone-shaped specimens are cut along the rolling direction of the welded plate and subjected to uniaxial tension. During the tensioning process, digital image correlation technology is used to measure the local strain in the weld area in real time to obtain the tensile stress at yield in the weld area of the hardened slab. According to formula (1) Calculate the yield strength of the weld region of the hardened slab, where, The yield strength of the weld region of the hardened slab. The stress state coefficient is a factor that takes values ranging from 1 to 1.
22. S105. Calculate the thickness ratio and the thicknesses of the first and second thickness regions in the variable thickness slab according to the following formula: ； （2） in, The minimum thickness of the thin region. The thicknesses of the first thick region and the second thick region are, The thickness ratio is... The yield strength of the uniformly thick hardened slab base material. The stress state coefficient, The tensile stress is the stress at which the weld region of the hardened slab yields.
3. The method for manufacturing a hardened stainless steel rocket propellant tank section according to claim 1, characterized in that: In step S1, the length of a single variable thickness slab is calculated based on the diameter of the hard stainless steel rocket propellant tank section and the number of tubes included in the hard stainless steel rocket propellant tank section, so that in step S4, the sum of the radian angles of all the tubes is 2π; after determining the length of the variable thickness slab, the lengths of the first thick region, the thin region, and the second thick region are determined.
4. The method for manufacturing a hardened stainless steel rocket propellant tank section according to claim 1, characterized in that: The elastic pad is made of polyurethane, nylon, or rubber.
5. The method for manufacturing a hardened stainless steel rocket propellant tank section according to claim 1, characterized in that: In step S3, a four-roll CNC roll bending machine is used to perform the integral roll bending forming, and during the roll bending forming process, the elastic pad and the variable thickness stainless steel slab are partially or completely constrained.
6. The method for manufacturing a hardened stainless steel rocket propellant tank section according to claim 1, characterized in that: In step S4, laser welding, argon arc welding, or plasma welding is used to weld the ends of adjacent cylindrical sections.
7. A method for manufacturing a rigid stainless steel rocket propellant tank, characterized in that: Multiple hard stainless steel rocket propellant tank sections with the same diameter are obtained by using the manufacturing method of any one of claims 1-6; the weld ends of each hard stainless steel rocket propellant tank section are treated with equal thickness, and finally the multiple hard stainless steel rocket propellant tank sections are arranged in sequence along the axial direction and welded together to form the entire hard stainless steel rocket propellant tank body.
8. The method for manufacturing a hardened stainless steel rocket propellant tank according to claim 7, characterized in that: When performing the equal thickness treatment, milling or grinding is used to chamfer the thick areas at both ends of the weld so that the thickness of the edge of the thick area is consistent with the thickness of the thin area in the middle.
9. The method for manufacturing a hardened stainless steel rocket propellant tank according to claim 7, characterized in that: The longitudinal welds of any two adjacent hardened stainless steel rocket tank sections are staggered circumferentially, with a stagger distance >200mm.
10. The method for manufacturing a hardened stainless steel rocket propellant tank according to claim 9, characterized in that: The longitudinal weld of the hardened stainless steel rocket propellant tank section is aligned with the center of the thin section in the adjacent hardened stainless steel rocket propellant tank section.