Manufacturing method of dissimilar material maraging steel solid rocket engine combustion chamber shell

Abstract

The invention discloses a manufacturing method of a dissimilar material maraging steel solid rocket engine combustion chamber shell, and belongs to the technical field of manufacturing of solid rocket engine combustion chamber shells. The method comprises the following steps: selecting materials for parts: selecting maraging steel T250 or C250 for a front sealing head, a rear sealing head and a cylinder body, and selecting T200 or C200 for a front skirt, a rear skirt and a mounting seat; selecting materials of welding wires: selecting HT250 welding wires when a welding substrate is maraging steel T250; when the welding matrix is maraging steel C250, an HC250 welding wire is selected; solution treatment is conducted, specifically, all parts of the combustion chamber shell are subjected to solution treatment; aging treatment: carrying out aging treatment on the front skirt, the rear skirt and the mounting seat; all the parts are welded into a solid rocket engine combustion chamber shell blank according to requirements; aging treatment is conducted, specifically, the whole welded combustion chamber shell blank is subjected to aging treatment; and machining and forming the combustion chamber shell. The toughness of the shell is improved, the machining efficiency is improved, machining deformation is reduced, the quality of the shell is improved, and the qualification rate of the shell is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of manufacturing a combustion chamber casing of a solid rocket engine, and in particular relates to a method for manufacturing a combustion chamber casing of a solid rocket engine made of a dissimilar material, martensitic aging steel. Background Art

[0002] Maraging steel is a special type of ultra-high strength steel. Different from traditional ultra-high strength steel, it is strengthened by the precipitation of certain intermetallic compounds on an ultra-low carbon iron-nickel martensitic matrix. Therefore, it has excellent strength and toughness combination, high dimensional stability and good weldability. It is widely used in solid rocket engine combustion chamber casings and other aspects.

[0003] Solid rocket engine combustion chamber shells are usually made of T250 and C250 maraging steel. The typical structure diagram of the combustion chamber shell is shown in Figure 1 , mainly welded by front connector, rear connector, cylinder and mounting seat, while the front connector is welded by front skirt and front head, and the rear connector is welded by rear skirt and rear head. Before welding, the front skirt, front head, rear skirt, rear head, mounting seat and cylinder are subjected to solid solution heat treatment, and then each part is processed and formed, welded, heat treated and machined. The current mature process flow of the maraging steel combustion chamber shell is: welding of front connector, rear connector, mounting seat and cylinder → aging → machining of front and rear connectors and mounting seat. Since the cylinder, front head and rear head have to withstand the instantaneous high temperature and high pressure thrust, the mechanical properties are required to be above 1760MPa; while the front skirt, rear skirt and mounting seat are only for connection, the mechanical properties are required to be above 1080MPa, so the mechanical properties of the mounting seat are required to be lower. Since the combustion chamber shell is generally composed of various parts and components of the same material, it is convenient for subsequent welding and heat treatment. This leads to high mechanical properties of all parts and components of the maraging steel T250 and C250 combustion chamber shell after solid solution and aging, with a hardness of up to 52HRC. This leads to low processing efficiency and rapid tool wear when turning and drilling the front skirt and rear skirt, and the high hardness of the mounting seat during milling and drilling, which leads to processing difficulties, large deformation of the combustion chamber shell and rapid tool wear. The front skirt, rear skirt and mounting seat have high processing precision and high assembly requirements, resulting in low processing efficiency of the combustion chamber shell and low product qualification rate. Therefore, dissimilar materials are often used in production to reduce processing difficulty. Due to the large difference in thermal physical properties of dissimilar materials, the residual stress of the joint after welding is large and easy to deform, and the two are metallurgically incompatible, so it is very easy to form a brittle phase at the weld interface, which significantly reduces the performance of the joint.

[0004] There are many problems in the design and manufacturing process of the solid rocket engine combustion chamber shell. For example, if the same material is used, the hardness of the front skirt, rear skirt and mounting seat will be high after heat treatment, the tool will wear quickly, the production efficiency will be low, and the qualified rate will not be high. If different materials are used for welding, there will be problems such as the matching of welding wire and the two materials, whether the metallurgical incompatibility of different materials will bring brittle phase to the weld, resulting in the decline of mechanical properties of the weld, and other unstable factors, which will bring great hidden dangers to the quality of the combustion chamber shell. Therefore, it is imperative to seek a high-efficiency, low-cost, reliable quality and stable mechanical properties maraging steel combustion chamber shell manufacturing method. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a method for manufacturing a combustion chamber shell of a solid rocket engine made of maraging steel of different materials, which not only solves the problems of high hardness, fast tool wear, low production efficiency, and low qualified rate after welding heat treatment of the same material, but also avoids the problem of brittle intermetallic compounds generated in the weld joint area caused by welding of different materials, which reduces the strength of the weld. In addition, by adjusting the aging temperature and time, the heat treatment of parts with different strength requirements can be met, the hardness is reduced, and the overall aging method after welding is used to improve the toughness of the shell, improve the processing efficiency, reduce processing deformation, and improve the shell quality and qualified rate.

[0007] The technical solution of the present invention is: a method for manufacturing a combustion chamber shell of a solid rocket engine made of a dissimilar material maraging steel, wherein the combustion chamber shell of the solid rocket engine comprises a front head, a front skirt, a rear head, a rear skirt, a cylinder, and a mounting seat; the specific steps are as follows:

[0008] Parts material selection: The front head, rear head and cylinder are made of maraging steel T250 or C250, and the front skirt, rear skirt and mounting seat are made of T200 or C200;

[0009] Welding wire selection: When the welding substrate is maraging steel T250, use HT250 welding wire; when the welding substrate is maraging steel C250, use HC250 welding wire;

[0010] Solution treatment: All parts of the combustion chamber casing are subjected to solution treatment;

[0011] Aging treatment: Perform aging treatment on the front skirt, rear skirt and mounting seat;

[0012] Welding: Weld the parts into the solid rocket engine combustion chamber shell blank as required;

[0013] Aging treatment: The welded combustion chamber shell blank is subjected to aging treatment as a whole;

[0014] The combustion chamber casing is machined and formed.

[0015] A further technical solution of the present invention is that the tensile strength of the parts made of T250 and C250 maraging steel materials after solution treatment and aging treatment is not less than 1760 MPa; the tensile strength of the parts made of T200 and C200 maraging steel materials after solution treatment and primary aging treatment is not less than 1450 MPa.

[0016] A further technical solution of the present invention is that the process parameters of the solution treatment are: heating to 820° C. to 840° C., keeping the temperature for 90 min to 120 min, and then taking the furnace out of the furnace and air cooling to room temperature after the end of the keeping temperature.

[0017] A further technical solution of the present invention is: the process parameters of the mechanical energy aging treatment of the front skirt, rear skirt and mounting seat are as follows: the aging temperature range is between 480°C and 600°C, the aging insulation time is between 180min and 360min, and after the insulation is completed, they are taken out of the furnace and air-cooled to room temperature.

[0018] A further technical solution of the present invention is that the process parameters for the aging treatment of the combustion chamber shell as a whole are: heating to 480°C to 520°C, keeping warm for 180min to 240min, and air cooling after the insulation is completed.

[0019] Beneficial Effects

[0020] The beneficial effects of the present invention are:

[0021] 1) Same heat treatment parameters: For the front head, rear head and cylinder with high mechanical performance requirements such as instantaneous high temperature and high pressure thrust, higher strength T250 or C250 maraging steel is used for solid solution treatment; for the front skirt, rear skirt, mounting seat, etc. with lower mechanical performance requirements, lower strength dissimilar materials T200 or C200 maraging steel is used, and solid solution treatment or solid solution + over-aging treatment is performed. Since the heat treatment parameters of T250, C250, T200 and C200 maraging steel are the same, the solid solution temperature is 820℃~840℃, and the aging temperature is 480℃~520℃, there is no need to worry about the choice of solid solution temperature causing another dissimilar material to be overburned or insufficiently dissolved, or the choice of aging temperature affects the precipitation hardening reaction, thereby affecting the mechanical properties of the shell.

[0022] 2) Similarity of chemical composition: T200 and T250 have similar chemical compositions, and only the Ti content is adjusted to reduce the strength; C200 and C250 maraging steels have similar chemical compositions, and only the Mo and Ti contents are adjusted to reduce the strength; T200 and T250 maraging steels are based on C200 and C250, but do not contain Co, increase the Ti content and reduce the Mo content, and keep other elements unchanged, while the mechanical properties are similar to those of C200 and C250 maraging steels; Due to the similarity of chemical compositions of T200, T250, C200 and C250 (see Table 1 Chemical Composition), there is no problem of brittle intermetallic compounds generated in the weld when dissimilar materials are welded due to metallurgical incompatibility.

[0023] 3) Consistent welding parameters: When welding maraging steels T200 and T250, C200 and C250, when high-strength HT250 welding wire and HC250 welding wire are used, the weld strength is equivalent to that of T250 or C250 welding with the same materials, that is, when welding T200 and T250, when welding C200 and C250, the welding parameters are consistent with those of T250 or C250 with the same materials, that is, when dissimilar materials are welded and after overall aging, the weld strength can be guaranteed to be consistent with the weld strength of the same material T250 or C250, and the strength of dissimilar material T200 or C200 front skirt, rear skirt, mounting seat and other parts after solid solution + aging or solid solution + over-aging can be maintained.

[0024] 4) The strength of the front skirt, rear skirt and mounting seat is adjustable: Because the front head, rear head and cylinder need to withstand instantaneous high temperature and high pressure thrust, T250 or C250 maraging steel with higher strength after solid solution + aging is used to ensure that the tensile strength is not less than 1760MPa and the hardness is not less than HRC50.5; while the strength requirements of the front skirt, rear skirt and mounting seat are relatively low, so T200 or C200 maraging steel after solid solution + aging can be used to ensure that the tensile strength is not less than 1450MPa (up to 1600MPa) and the hardness is not less than HRC50.5. The tensile strength of the front skirt, rear skirt and mounting seat can be no less than HRC44.5 (up to HRC47.5), and the hardness can be no less than HRC36 by solid solution + over-aging heat treatment method. That is, the strength of the front skirt, rear skirt and mounting seat can be adjusted between 1080MPa and 1600MPa or the hardness between HRC36 and HRC47.5 according to design requirements, which ensures the high strength requirements of the high temperature and high pressure parts and meets the low strength and easy processing requirements of the non-pressure parts.

[0025] 5) High processing efficiency, small shell deformation, high pass rate and good economic benefits: Since the strength of the front skirt, rear skirt and mounting seat is lower than that of the same material, the processing efficiency is high, the tool wear is small, the shell deformation is small during processing, the pass rate is high, and the overall economic benefits are higher.

[0026] Table 1 Chemical composition of four materials (mass fraction, %)

[0027]

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the combustion chamber casing structure.

[0030] Explanation of the accompanying drawings: 1. front skirt, 2. first ring weld, 3. front head, 4. second ring weld, 5. mounting seat, 6. third ring weld, 7. rear head, 8. fourth ring weld, 9. rear skirt. DETAILED DESCRIPTION

[0031] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0032] The traditional manufacturing method of the combustion chamber shell of T250 and C250 maraging steel is as follows: all parts of the combustion chamber shell are made of the same material, and all parts are solution treated at 820℃~840℃, machined, welded, aged at 480℃~520℃, and machined after heat treatment. Since the hardness of the front skirt, rear skirt, mounting seat, etc. is very high after solution aging, this leads to difficult machining, fast tool wear, low machining efficiency, large deformation of the combustion chamber shell, and low product qualification rate.

[0033] Based on the above problems, the present invention provides a method for manufacturing a combustion chamber casing of a solid rocket engine made of a dissimilar material maraging steel, comprising the following steps:

[0034] Step 1: Material selection: The front head, rear head and cylinder are made of maraging steel T250 or C250. The solid solution + aging tensile strength of T250 and C250 maraging steel is not less than 1760MPa. The front skirt, rear skirt, mounting seat, etc. are made of T200 and C200. The solid solution + aging tensile strength of T200 and C200 maraging steel is not less than 1450MPa.

[0035] Step 2: Selection of welding wire: When the front head, rear head and cylinder are made of maraging steel T250 or C250, the front skirt, rear skirt, mounting seat, etc. can be made of T200 or C200. When welding, the base T250 can be made of HT250 welding wire, and the base C250 can be made of HC250 welding wire;

[0036] Step 3: Solution treatment of parts: Solution treatment of the combustion chamber shell parts, heating to 820℃~840℃, keeping warm for 90min~120min, and then taking out of the furnace and air cooling to room temperature after the end of the heat preservation;

[0037] Step 4: Aging: Aging the front skirt, rear skirt, mounting seat and other parts. The aging temperature and aging time are selected according to the strength of the parts. The aging temperature range is between 480℃ and 600℃, and the aging insulation time is between 180min and 360min. After the insulation is completed, take the parts out of the furnace and air cool them to room temperature.

[0038] Step 5: Welding: Weld the components into the combustion chamber shell;

[0039] Step 6: Aging: The welded combustion chamber shell is subjected to aging treatment as a whole, heated to 480℃~520℃, kept warm for 180min~240min, and then taken out of the furnace and air-cooled after the insulation is completed.

[0040] Step 7: Machining of the combustion chamber housing.

[0041] The manufacturing method of the present invention has a simple process, which not only solves the problems of large deformation of the shell during processing due to high hardness, low processing efficiency, fast tool wear, etc., but also improves production efficiency, product quality and qualified rate.

[0042] The above technical solution is further explained below with reference to examples:

[0043] Embodiment 1:

[0044] The manufacturing method of a dissimilar martensitic aging steel solid rocket engine combustion chamber shell described in this embodiment is specifically carried out according to the following steps: the front head, rear head and barrel are made of T250 material, the front skirt, rear skirt and mounting seat are made of dissimilar material T200, and the solid solution treatment is carried out, and the heat treatment parameters are kept at 820℃ for 90min to 120min, and then air-cooled to room temperature; then the blanks such as the front skirt, rear skirt and mounting seat after solid solution are subjected to aging treatment, and the heat treatment parameters are kept at 600℃ for 180min, and then air-cooled to room temperature. Then the blanks are processed into shape, the front head and the front skirt are welded into the front connecting piece with HT250 welding wire, the rear head and the rear skirt are welded into the rear connecting piece with HT250 welding wire, and then the front connecting piece, the barrel and the mounting seat are welded into the combustion chamber shell with HT250 welding wire, and the combustion chamber shell is subjected to aging treatment after welding, and the heat treatment parameters are kept at 500℃ for 180min, and then air-cooled to room temperature. Then the front skirt, rear skirt and mounting seat are machined and formed. The wear amount of tool, processing time, deformation before and after processing and qualified rate of single-engine housing are shown in Table 1.

[0045] In Example 1, the tensile strength of the cylinder, front head and rear head is distributed between 1830MPa and 1900MPa, the elongation after fracture is between 6.8% and 7.9%, and the hardness is distributed between 51.0 and 52.5HRC; the tensile strength of the front skirt, rear skirt and mounting seat is distributed between 1210MPa and 1250MPa, the elongation after fracture is between 10.8% and 12.5%, and the hardness is between 37.2 and 39.5HRC; the tensile strength of the weld strength is distributed between 1180MPa and 1290MPa.

[0046] Comparative experiment 1:

[0047] The parts used in the combustion chamber shell are all made of the same material, T250 martensitic aging steel. The front head, rear head, cylinder, front skirt, rear skirt, and mounting seat are solid solution treated. The heat treatment parameters are 820℃ for 90min~120min, and air cooling to room temperature. Then the blanks are processed and formed. The front head and front skirt are welded into the front connecting parts with HT250 welding wire, and the rear head and rear skirt are welded into the rear connecting parts with HT250 welding wire. Then the front connecting parts, cylinder and mounting seat are welded into the combustion chamber shell with HT250 welding wire. After welding, the combustion chamber shell is aged. The heat treatment parameters are 500℃ for 180min, and air cooling to room temperature. Then the front skirt, rear skirt, and mounting seat are machined and formed. The number of tool wear, processing time and qualified rate of single shell are shown in Table 2.

[0048] In comparative example 1, after heat treatment, the tensile strength of the cylinder, front head, rear head, front skirt, rear skirt and mounting seat is distributed between 1860MPa and 1940MPa, the elongation after fracture is between 6.1% and 6.5%, the tensile strength of the weld strength is distributed between 1840MPa and 1870MPa, and the hardness is between 51.3 and 52.8HRC.

[0049] Table 2

[0050]

[0051] Analysis of the implementation effect of the present invention:

[0052] Compared with the comparative experiment 1, after the heat treatment of the dissimilar maraging steel in the embodiment 1, the tensile strength of the front head, rear head and cylinder of the combustion chamber shell at the pressure position meets the technical requirements of not less than 1760MPa and the strength of the welds of the front and rear connectors and the mounting seat is not less than 1080MPa. The hardness of the front skirt, rear skirt and mounting seat is between 37.2 and 39.5HRC. The wear of the tool on the single shell is small, the processing time is shorter, the deformation is small, the product qualification rate is high, and the heat treatment process is suitable for the production of front skirts, rear skirts and mounting seats of different strengths. While the mechanical properties of the maraging steel of the same material in the comparative experiment meet the requirements, but the hardness of the front skirt, rear skirt and mounting seat is high, the processing is difficult, the tool is wasteful and time-consuming, the processing efficiency is low, and the shell qualification rate is not high.

[0053] It can be seen that the maraging steel solid rocket engine combustion chamber casing heat-treated by the method of the present invention has mechanical properties that meet the requirements, moderate hardness, less tool wear on a single casing, shorter processing time, less deformation, and a high product qualification rate. The heat treatment process is suitable for the production of parts with different strengths and can be widely used in the production of maraging steel solid rocket engine combustion chamber casings.

[0054] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for manufacturing a combustion chamber shell of a solid rocket engine made of a dissimilar material maraging steel, wherein the combustion chamber shell of the solid rocket engine comprises a front head, a front skirt, a rear head, a rear skirt, a barrel, and a mounting seat; characterized in that The specific steps are as follows: Parts material selection: The front head, rear head and cylinder are made of maraging steel T250 or C250, and the front skirt, rear skirt and mounting seat are made of T200 or C200; Welding wire selection: When the welding substrate is maraging steel T250, use HT250 welding wire; when the welding substrate is maraging steel C250, use HC250 welding wire; Solution treatment: subject all parts of the combustion chamber casing to solution treatment; Aging treatment: Perform aging treatment on the front skirt, rear skirt and mounting seat; Welding: Weld the parts into the solid rocket engine combustion chamber shell blank as required; Aging treatment: The welded combustion chamber shell blank is subjected to aging treatment as a whole; The combustion chamber casing is machined and formed.

2. The method for manufacturing a combustion chamber casing of a solid rocket engine made of a dissimilar material maraging steel according to claim 1, characterized in that: The tensile strength of the parts made of the T250 and C250 maraging steel materials after solution treatment and aging treatment is not less than 1760 MPa; the tensile strength of the parts made of the T200 and C200 maraging steel materials after solution treatment and primary aging treatment is not less than 1450 MPa.

3. The method for manufacturing a combustion chamber casing of a solid rocket engine made of a dissimilar material maraging steel according to claim 1, characterized in that: The process parameters of the solution treatment are: heating to 820° C. to 840° C., keeping the temperature for 90 min to 120 min, and then taking the furnace out of the furnace and air cooling to room temperature.

4. The method for manufacturing a combustion chamber casing of a solid rocket engine made of a dissimilar material maraging steel according to claim 3, characterized in that: The process parameters of the mechanical energy aging treatment of the front skirt, the rear skirt and the mounting seat are as follows: the aging temperature range is between 480° C. and 600° C., the aging insulation time is between 180 min and 360 min, and after the insulation is completed, the product is taken out of the furnace and air-cooled to room temperature.

5. The method for manufacturing a combustion chamber casing of a solid rocket engine made of a dissimilar material maraging steel according to claim 4, characterized in that: The process parameters for the aging treatment of the combustion chamber shell as a whole are: heating to 480° C. to 520° C., keeping warm for 180 min to 240 min, and taking out of the furnace and air cooling after the end of the keeping warm.

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