Tailor-welding machining forming method for large-size copper inner wall of liquid rocket engine

Abstract

The invention discloses a tailor-welding machining forming method for a large-size copper inner wall of a liquid rocket engine. The tailor-welding machining forming method comprises the steps that thickening treatment is conducted on a large-size copper inner wall model; the thickened large-size copper inner wall model is divided into multiple sections of models in the axial direction; process design allowance is increased for each section of model in the axial direction, and a part drawing of each section is formed; according to the drawing of each section of part, processing to form each section of copper inner wall and a plurality of welding test plates; carrying out pre-welding preparation on each section of copper inner wall and various welding test plates; vacuum electron beam welding tests with different welding parameters are conducted respectively; preferably selecting welding parameters of each section of welding seam; vacuum electron beam welding is conducted on butt welding seams of the inner walls of all the sections; and performing post-welding surface inspection and X-ray inspection on the welded copper inner wall, and analyzing a welding inspection result. By means of the method, development and production of the large-size copper inner wall of the liquid rocket engine can be effectively achieved, the using amount of raw materials is reduced, the development cost is reduced, and meanwhile the mechanical property and the welding requirement of part materials are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical manufacturing, and particularly relates to a method for welding and processing the large-sized copper inner wall of a liquid rocket engine to form a shape. Background Art

[0002] For a staged combustion cycle liquid rocket engine, due to the relatively large heat flux density, copper-based alloy materials with excellent thermal conductivity are often used for the inner wall of the thrust chamber part. With the development of large-thrust liquid rocket engines, the processing of large-sized copper inner walls has become a difficult problem. On the one hand, it is difficult to directly forge the blank of the large-sized copper inner wall, and forging defects often occur. On the other hand, the mechanical properties of the large-sized copper inner wall blank after forging are poor and cannot meet the use requirements.

[0003] Therefore, a method for welding and processing the large-sized copper inner wall of a liquid rocket engine to form a shape is needed. The large-sized copper inner wall is segmented, and the blanks are respectively forged and processed. Then, the blanks of each section are welded by vacuum electron beam welding to realize the forming of the forged blank of the large-sized copper inner wall, ensuring the processing of the large-sized copper inner wall. Summary of the Invention

[0004] The technical problem solved by the present invention: Overcoming the deficiencies of the prior art, a method for welding and processing the large-sized copper inner wall of a liquid rocket engine to form a shape is provided, reducing the consumption of forging raw materials and at the same time ensuring the mechanical properties of the inner wall parts.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The present invention discloses a method for welding and processing the large-sized copper inner wall of a liquid rocket engine to form a shape, including:

[0007] S1. Referring to the design drawings, thicken the large-sized copper inner wall model;

[0008] S2. Axially divide the thickened large-sized copper inner wall model into multiple sections of models;

[0009] S3. Add process design margins axially to each section of the model to form the part drawings of each section;

[0010] S4. According to the part drawings of each section, process each section of the copper inner wall and a variety of welding test plates;

[0011] S5. Conduct pre-welding preparations for each section of the copper inner wall and a variety of welding test plates;

[0012] S6. Using the welding test plates, simulate the butt welds of each section of the inner wall, and respectively conduct vacuum electron beam welding tests with different welding parameters;

[0013] S7. Inspect the welds of different welding test plates, and according to the test results, optimize the welding parameters of each section of the weld;

[0014] S8. Using the preferred welding parameters for each section, vacuum electron beam welding is carried out on the butt welds of the inner walls of each section respectively to form the copper inner wall after welding.

[0015] S9. Conduct post-weld surface inspection and X-ray inspection on the copper inner wall after welding, and analyze the welding inspection results.

[0016] S10. If the welding inspection results meet the requirements, continue to process the copper inner wall after welding according to the design drawing to form a large-size copper inner wall; otherwise, optimize the welding parameters and return to step S6.

[0017] Further, in the above method, the large end diameter of the large-size copper inner wall exceeds 900 mm, and the height dimension exceeds 600 mm; the material of the copper inner wall is copper or copper-based alloy material.

[0018] Further, in the above method, the thickening treatment of the large-size copper inner wall model is specifically as follows:

[0019] Starting from the small end of the outer surface of the inner wall, the outer surface of the inner wall is widened outward, and the widened outer surface is within a range of 1 - 5 mm from the original outer surface in the direction perpendicular to the generatrix.

[0020] Starting from the small end of the inner surface of the inner wall, the inner surface of the inner wall is widened inward, and the widened inner surface is within a range of 1 - 5 mm from the original inner surface in the direction perpendicular to the generatrix.

[0021] The inner and outer surfaces of the cross-section passing through the central axis of the thickened inner wall remain parallel.

[0022] The maximum wall thickness of each thickened section of the inner wall does not exceed 20 mm in the direction perpendicular to the generatrix.

[0023] Further, in the above method, the division of the thickened large-size copper inner wall model into multiple sections along the axial direction is specifically as follows: It is determined comprehensively according to the large end diameter size and height size of the copper inner wall. The division surface is perpendicular to the generatrix of the model surface, and the thickened large-size copper inner wall model is divided into 2 - 4 sections along the axial direction.

[0024] Further, in the above method, the process design allowance includes axial welding shrinkage allowance and axial machining allowance; the axial welding shrinkage allowance is the axial shrinkage of the product during vacuum electron beam welding, and the calculation formula is: ΔW = β·W·ΔT, where ΔW is the axial shrinkage; β is the axial shrinkage coefficient; W is the weld width; ΔT is the temperature difference between the welding temperature and the room temperature; the axial machining allowance is to extend along the outer surface at the small ends and large ends of the first and last sections respectively, and the extended axial distance is 5 - 10 mm.

[0025] Further, in the above method, the types of welding test plates are the same as the number of welds; the materials and thicknesses of various welding test plates are the same as those of the materials and wall thicknesses at the butt welds of each section of the inner wall; the shapes of various welding test plates are square, and the side length of the square is 200 - 300 mm; 4 - 6 pieces of each type of welding test plate are processed.

[0026] Further, in the above method, the pre - welding preparations for each section of the copper inner wall and various welding test plates are specifically as follows:

[0027] Pickle each section of the copper inner wall and multiple groups of welding test plates;

[0028] Wipe the surface of the base metal at the weld with white silk cloth and clean gasoline until metallic luster is seen;

[0029] Assemble each section of the copper inner wall and the welding test plates, and the gap and misalignment of the butt welds are not more than 0.2 mm.

[0030] Further, in the above method, the welding parameters include: electron beam current, focusing current, welding speed, accelerating voltage, vacuum degree of the welding gun, and vacuum degree of the welding chamber, specifically as follows:

[0031] The electron beam current is controlled at 130 - 260 mA;

[0032] The focusing current is controlled at 1.5 - 2.5 A;

[0033] The welding speed is controlled at 0.3 - 1.0 m / min;

[0034] The accelerating voltage is greater than 50 KV;

[0035] The vacuum degree of the welding gun is less than 3×10 -3 Pa;

[0036] The vacuum degree of the welding chamber is less than 3×10 -2 Pa.

[0037] Furthermore, in the above method, the inspection of welds of different welding test plates includes: surface inspection, X-ray inspection, dimensional inspection, bending performance test, tensile mechanical properties test and metallographic analysis; the surface inspection is to check whether there are cracks, pores, undercuts or depressions on the weld surface; the X-ray inspection is to check whether the internal quality of the weld meets the Level I requirements of GJB1718A-2005 "Electron Beam Welding"; the dimensional inspection is to check whether the front weld width, back weld width and weld excess height of the weld meet the requirements; the bending performance test is to bend the welding test plate 180° along the weld to check whether there are defects on the weld surface; the tensile mechanical properties test is to perform a tensile test on the welding test plate to detect whether the tensile strength and yield strength of the weld meet the requirements; the metallographic analysis is to section the weld, make a metallographic specimen, and check the macroscopic and microscopic morphology of the weld.

[0038] Furthermore, in the above method, the welding parameters of each weld section are preferably as follows: based on the inspection results of the weld of the welding test plate, the welding quality of the weld is evaluated, and the welding parameters of the weld with the best quality are selected as the welding parameters of the butt weld corresponding to each section of the inner wall.

[0039] Furthermore, in the above method, the copper inner wall is processed and welded according to the design drawing to form a large-sized copper inner wall, and the specific method is:

[0040] Turning the inner surface of the copper inner wall after welding to form the first prototype;

[0041] Processing to form a support tire, wherein the outer profile of the support tire has the same size as the inner profile of the first prototype;

[0042] The first prototype is mounted on the support tire, and the outer surface is machined according to the upper tolerance value of the wall thickness dimension to form the second prototype;

[0043] Milling grooves on the inner wall of the second preliminary sample to obtain a third preliminary sample;

[0044] According to the middle tolerance value of the wall thickness, the outer surface of the third prototype is machined to form a large-sized copper inner wall.

[0045] The beneficial effects of the present invention are:

[0046] (1) The present invention is used for the first time in the field of liquid rocket engines, solving the problem of processing and forming large-size copper inner walls of high-performance, high-thrust liquid rocket engines.

[0047] (2) The present invention proposes for the first time a vacuum electron beam welding method for butt welds of large-sized and thick-walled copper inner wall blanks, thereby obtaining large-sized and thick-walled copper inner wall blanks that meet the use requirements.

[0048] (3) By segmenting the processing of the large-sized copper inner wall, the present invention reduces the usage amount of forging raw materials, lowers the raw material cost, and at the same time ensures the forging mechanical properties of the blank of each section of the copper inner wall, which is beneficial to ensuring the final performance of the product.

[0049] (4) By adopting the process method of machining the outer profile surface once before and after milling the groove for the large-sized copper inner wall, the present invention ensures the accuracy of the final outer profile surface size of the large-sized inner wall parts formed by the copper-based soft metal material, which is beneficial to the subsequent welding of the inner and outer walls.

[0050] (5) The large-sized copper inner wall developed by the present invention has been applied in a liquid rocket engine with a thrust of 1200 KN level, and the continuous working time of the engine exceeds 100 s.

[0051] (6) The present invention can effectively realize the research and production of the large-sized copper inner wall of the liquid rocket engine, reduce the usage amount of raw materials, lower the research and development cost, and at the same time ensure the mechanical properties and welding requirements of the part materials. Description of the Drawings

[0052] Figure 1 is a flowchart of the method for forming the large-sized copper inner wall by butt welding and processing of the present invention; Detailed Embodiments

[0053] As Figure 1 shown, the present invention designs a method for forming the large-sized copper inner wall of the liquid rocket engine by butt welding and processing. By this method, the usage amount of forging raw materials can be reduced, and at the same time, the mechanical properties of the inner wall parts can be ensured.

[0054] The present invention discloses a method for forming the large-sized copper inner wall of the liquid rocket engine by butt welding and processing, including:

[0055] S1. Referring to the design drawing, thicken the large-sized copper inner wall model;

[0056] S2. Axially divide the thickened large-sized copper inner wall model into multiple sections of models;

[0057] S3. Add process design allowances to each section of the model axially to form the part drawings of each section;

[0058] S4. According to the part drawings of each section, process and form each section of the copper inner wall and a variety of welding test plates;

[0059] S5. Make preparations before welding for each section of the copper inner wall and a variety of welding test plates;

[0060] S6. Use the welding test plates to simulate the butt welds of each section of the inner wall, and respectively conduct vacuum electron beam welding tests with different welding parameters;

[0061] S7. Inspect the welds of different welding test plates, and optimize the welding parameters for each section of the weld according to the test results.

[0062] S8. Use the optimized welding parameters for each section to perform vacuum electron beam welding on the butt welds of the inner walls of each section to form the copper inner wall after welding.

[0063] S9. Conduct post-weld surface inspection and X-ray inspection on the copper inner wall after welding, and analyze the welding inspection results.

[0064] S10. If the welding inspection results meet the requirements, continue to process the copper inner wall after welding according to the design drawing; otherwise, optimize the welding parameters and return to step S6.

[0065] Preferably, in step S1, the large end diameter of the large-sized copper inner wall exceeds 900 mm, and the height dimension exceeds 600 mm; the material of the copper inner wall is not limited to pure copper, including other copper-based alloy materials; the large-sized copper inner wall model is thickened. Specifically: starting from the small end of the inner wall outer profile surface, the outer profile surface of the inner wall is widened outward, and the widened outer profile surface is within a range of 1 - 5 mm from the original outer profile surface in the direction perpendicular to the generatrix; then starting from the small end of the inner wall inner profile surface, the inner profile surface of the inner wall is widened inward, and the widened inner profile surface is within a range of 1 - 5 mm from the original inner profile surface in the direction perpendicular to the generatrix. For the convenience of processing, the inner and outer profile surfaces of the cross-section passing through the center axis of the thickened inner wall are kept parallel; to ensure the welding quality, the maximum wall thickness of each section of the thickened inner wall in the direction perpendicular to the generatrix does not exceed 20 mm.

[0066] Preferably, in step S2, the thickened large-sized copper inner wall model is axially divided into multiple sections of models. Specifically: divided into 2 - 4 sections, which needs to be comprehensively determined according to the large end diameter size and height dimension of the copper inner wall, and the dividing surface is perpendicular to the generatrix of the model profile surface. Division principle: the number of divided sections should be as few as possible to reduce the number of welds; the processing difficulty of each section after division is small, and each section can be forged into a blank with qualified performance alone; the total demand for forging raw materials of each section after division should be as small as possible to reduce costs.

[0067] Preferably, in step S3, the process design allowances include axial welding shrinkage allowance and axial machining allowance; the axial welding shrinkage allowance is the axial shrinkage amount of the product during vacuum electron beam welding, and the calculation formula is: ΔW = β·W·ΔT, where ΔW is the axial shrinkage amount; β is the axial shrinkage coefficient; W is the weld width; ΔT is the temperature difference between the welding temperature and the room temperature; the axial machining allowance is to extend along the outer profile surface at the small ends and large ends of the first and last sections respectively, and the extended axial distance is 5 - 10 mm.

[0068] Preferably, in step S4, the types of welding test plates are the same as the number of welds; the materials and thicknesses of various welding test plates are the same as the materials and wall thicknesses at the butt welds of each section of the inner wall; the shapes of various welding test plates are generally square, and the side length of the square is 200 - 300 mm; generally, 4 - 6 pieces of each welding test plate are processed.

[0069] Preferably, in step S5, the pre - welding preparations include: first, pickling the test plates or each section; then wiping the surface of the base metal at the weld with white silk cloth and clean gasoline, and it is required that the metal luster can be seen after wiping; finally, assembling the test plates or each section, and it is required that the gap and misalignment of the butt welds are not more than 0.2 mm.

[0070] Preferably, in step S6, the main welding parameters of vacuum electron beam welding include: electron beam current, focusing current, welding speed, accelerating voltage, vacuum degree of the welding gun, and vacuum degree of the welding chamber, etc. Specifically:

[0071] The electron beam current is generally controlled within 130 - 260 mA;

[0072] The focusing current is generally controlled within 1.5 - 2.5 A;

[0073] The welding speed is generally controlled within 0.3 - 1.0 m / min;

[0074] The accelerating voltage is greater than 50 KV;

[0075] The vacuum degree of the welding gun is less than 3×10 -3 Pa;

[0076] The vacuum degree of the welding chamber is less than 3×10 -2 Pa.

[0077] Preferably, in step S6, the welding test is as follows: Assemble two identical welding test plates in place, fix them by spot welding, adjust the focusing current to focus on the surface of the butt weld of the test plate, and adjust the accelerating voltage, vacuum degree of the welding gun, and vacuum degree of the welding chamber within the required range. Select two parameters from the above - mentioned ranges of electron beam current and welding speed parameters to form four groups of welding parameter combinations, use each group of welding parameters to weld 1 weld on the welding test plate, and make marks.

[0078] Preferably, the inspection of welds of different welding test plates in step S7 includes: surface inspection, X-ray inspection, dimensional inspection, bending performance test, tensile mechanical properties test and metallographic analysis; the surface inspection is to check whether there are cracks, pores, undercuts or depressions on the weld surface; the X-ray inspection is to check whether the internal quality of the weld meets the Level I requirements of GJB1718A-2005 "Electron Beam Welding"; the dimensional inspection is to check whether the front weld width, back weld width and weld excess height of the weld meet the requirements; the bending performance test is to bend the welding test plate 180° along the weld to check whether there are defects on the weld surface; the tensile mechanical properties test is to perform a tensile test on the welding test plate to detect whether the tensile strength and yield strength of the weld meet the requirements; the metallographic analysis is to section the weld, make a metallographic specimen, and check the macroscopic and microscopic morphology of the weld.

[0079] Preferably, the preferred welding parameters of each weld section in step S7 are: based on the inspection results of the welds of the welding test plates, the welding quality of the welds is evaluated, and the welding parameters of the welds with the best quality are selected as the welding parameters of the butt welds corresponding to the inner walls of each section.

[0080] Preferably, the welding parameters for vacuum electron beam welding of each section of the copper inner wall in step S8 are optimal vacuum electron beam welding parameters comprehensively selected from the test plate welding test.

[0081] Preferably, the processing method of processing the large-sized copper inner wall according to the pattern in step S10 is:

[0082] Turning the inner surface of the copper inner wall after welding to form the first prototype;

[0083] Processing to form a support tire, wherein the outer profile of the support tire has the same size as the inner profile of the first prototype;

[0084] The first prototype is mounted on the support tire, and the outer surface is machined according to the upper tolerance value of the wall thickness dimension to form the second prototype;

[0085] Milling grooves on the inner wall of the second preliminary sample to obtain a third preliminary sample;

[0086] According to the middle tolerance value of the wall thickness, the outer surface of the third prototype is machined to form a large-sized copper inner wall.

[0087] Example 1

[0088] (1) Process as follows Figure 1 As shown in the figure, the inner wall thickness of the thrust chamber of a liquid rocket engine made of QCr0.8 is The large end diameter is 1000 mm, the height is 700 mm. Referring to the design drawing, the inner wall is thickened. The inner surface of the inner wall is thickened by 4 mm in the direction perpendicular to the generatrix, and the forming surface of the inner wall is thickened by 4 mm in the direction perpendicular to the generatrix. The wall thickness of the thickened copper inner wall is 15 mm.

[0089] (2) The thickened large-sized copper inner wall is axially divided into two sections, namely the small section and the large section. The dividing position is 250 mm away from the large end. After division, each section can be separately forged into a blank with qualified performance.

[0090] (3) Using the formula to calculate, the axial welding shrinkage allowance is obtained as 3 mm, and the axial machining allowance is 5 mm. After compensating for the two sections, two part drawings are formed. That is, the axial length of the small end of the small section is extended by 5 mm along the forming surface, and the axial length of the large end of the small section is extended by 1.5 mm; the axial length of the small end of the large section is extended by 1.5 mm, and the axial length of the large end of the large section is extended by 5 mm along the forming surface.

[0091] (4) Using forgings as blanks, the small section and the large section of the copper inner wall are respectively machined according to the part drawings of the two sections. The processing material is a welding test plate of QCr0.8 with a specification of 200 mm × 200 mm × 15 mm, 6 pieces.

[0092] (5) The test plates and the two sections of the copper inner wall are pickled; then the surface of the base metal at the weld is wiped with white silk cloth and clean gasoline, and it is required to show metallic luster after wiping; finally, the test plates and the two sections of the copper inner wall are assembled respectively, and it is required that the gap and misalignment of the butt welds are not greater than 0.2 mm.

[0093] (6) Vacuum electron beam welding tests are carried out on the test plates. Welding parameters: electron beam current 180, 200 mA, focusing current 2.0 A, welding speed 0.7, 0.8 m / min, accelerating voltage 50 KV, vacuum degree of the welding gun 2×10 -3 Pa, vacuum degree of the welding chamber 2×10 - 2 Pa, forming four groups of welding parameter combinations. One weld is welded on the welding test plate using each group of welding parameters and marked.

[0094] (7) Inspect the welds of different welding test plates, including: surface inspection, X-ray inspection, shape and size inspection, bending property test, tensile mechanical property test, metallographic analysis, etc. According to the inspection results of the welds of the welding test plates, evaluate the welding quality of the welds, and select the welding parameters of the weld with the best quality as the welding parameters for the butt welds of each section of the inner wall.

[0095] (8) Carry out vacuum electron beam welding of each section of the copper inner wall according to the best vacuum electron beam welding parameters.

[0096] (9) Inspect the copper inner wall after welding, including: surface inspection, X-ray inspection.

[0097] (10) The qualified copper inner wall of the weld is machined according to the design drawing. First, the inner surface of the inner wall is turned, and then it is installed on the support tire. The outer surface is turned according to the wall thickness dimension of 7.1 mm. After turning, the inner wall is milled, and finally the outer surface is turned according to the wall thickness dimension of 7 mm to machine a qualified large-size copper inner wall.

[0098] Example 2

[0099] (1) The process is as Figure 1 shown. The wall thickness of the inner wall of a liquid rocket engine thrust chamber made of a certain material QBe2 is The large end diameter is 900 mm and the height is 600 mm. Referring to the design drawing, the inner wall is thickened. The inner surface of the inner wall is thickened by 5 mm along the direction perpendicular to the busbar, and the outer surface of the inner wall is thickened by 5 mm along the direction perpendicular to the busbar. The thickened copper inner wall has a wall thickness of 18 mm.

[0100] (2) The thickened large-size copper inner wall is axially divided into two sections, namely a small section and a large section. The dividing position is 200 mm away from the large end. After division, each section can be separately forged into a qualified blank.

[0101] (3) Use the formula to calculate and obtain the axial welding shrinkage allowance of 4 mm and the axial machining allowance of 6 mm. After compensating the two sections, two part drawings are formed. That is, the small end of the small section is axially extended by 6 mm along the surface, and the large end of the small section is axially extended by 2 mm; the small end of the large section is axially extended by 2 mm, and the large end of the large section is axially extended by 6 mm along the surface.

[0102] (4) Use forgings as blanks to machine the two sections of copper inner walls respectively according to the part drawings of the two sections. The processing material is 5 welding test plates of QBe2 with a specification of 250 mm × 250 mm × 18 mm.

[0103] (5) Pickle the test plates and the two sections of copper inner walls; then use white silk cloth and clean gasoline to wipe the surface of the base metal at the weld. It is required to see the metallic luster after wiping; finally, assemble the test plates and the two sections of copper inner walls respectively. It is required that the gap and misalignment of the butt welds are not greater than 0.2 mm.

[0104] (6) Vacuum electron beam welding is carried out on the two sections of copper inner walls. Welding parameters: electron beam current 220, 240 mA, focusing current 2.1 A, welding speed 0.4, 0.5 m / min, accelerating voltage 60 KV, vacuum degree of the electron gun 2 × 10 -3 Pa, vacuum degree of the welding chamber 2 × 10 - 2 Pa, forming four groups of welding parameter combinations. Use each group of welding parameters to weld 1 weld on the welding test plate and mark it.

[0105] (7) Inspect the test plate after welding, including: surface inspection, X-ray inspection, dimensional inspection, bend test, tensile mechanical property test, metallographic analysis, etc. Evaluate the welding quality of the weld according to the inspection results of the weld of the welding test plate, and select the welding parameters of the weld with the best quality as the welding parameters for the butt welds of each section of the inner wall.

[0106] (8) Perform vacuum electron beam welding on each section of the copper inner wall according to the optimal vacuum electron beam welding parameters.

[0107] (9) Inspect the copper inner wall after welding, including: surface inspection, X-ray inspection.

[0108] (10) Machine the copper inner wall with qualified welds according to the design drawings. First, machine the inner surface of the inner wall, then install it on the support fixture, machine the outer surface according to the wall thickness dimension of 8.1 mm, mill the groove on the inner wall after machining, and finally machine the outer surface according to the wall thickness dimension of 8 mm to machine a qualified large-size copper inner wall.

[0109] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention shall be defined by the appended claims.

[0110] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A method for welding and forming a large-size copper inner wall of a liquid rocket engine, characterized in that: include: S1. Refer to the design drawings to thicken the large-sized copper inner wall model; S2, dividing the thickened large-size copper inner wall model into multiple segment models along the axial direction; S3, adding process design margins to each segment model along the axial direction to form a part drawing of each segment; S4. According to the parts drawings of each section, process and form the copper inner wall of each section and various welding test plates; S5. Prepare each section of the copper inner wall and various welding test plates before welding; S6. Use welding test plates to simulate the butt welds of the inner walls of each section and conduct vacuum electron beam welding tests with different welding parameters; S7. Inspect the welds of different welding test plates and optimize the welding parameters of each weld according to the inspection results; S8, using the preferred welding parameters for each section, respectively performing vacuum electron beam welding on the butt welds of the inner wall of each section to form a copper inner wall after welding; S9. Conduct post-weld surface inspection and X-ray inspection on the inner wall of the copper after welding, and analyze the welding inspection results; S10. If the welding inspection result meets the requirements, continue to process the copper inner wall after welding according to the design drawing to form a large-sized copper inner wall; otherwise, optimize the welding parameters and return to step S6.

2. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The large end diameter of the large-size copper inner wall exceeds 900 mm, and the height exceeds 600 mm; the material of the copper inner wall is copper or copper-based alloy material.

3. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The thickening treatment of the large-sized copper inner wall model is specifically as follows: Starting from the small end of the inner wall outer profile, the inner wall outer profile is widened outwards, and the distance between the widened outer profile and the original outer profile in the direction perpendicular to the generatrix is ​​within the range of 1-5mm; Starting from the small end of the inner surface of the inner wall, the inner surface of the inner wall is widened inwards, and the distance between the widened inner surface and the original inner surface in the direction perpendicular to the generatrix is ​​within the range of 1-5mm; The inner and outer surfaces of the center axis section of the thickened inner wall remain parallel; The maximum wall thickness of each thickened inner wall section in the direction perpendicular to the generatrix shall not exceed 20 mm.

4. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The thickened large-size copper inner wall model is divided into multiple models along the axial direction, specifically: according to the comprehensive determination of the large end diameter size and height size of the copper inner wall, the dividing surface is perpendicular to the generatrix of the model profile, and the thickened large-size copper inner wall model is divided into 2-4 sections along the axial direction.

5. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The process design allowance includes axial welding shrinkage allowance and axial machining allowance; the axial welding shrinkage allowance is the axial shrinkage of the product when vacuum electron beam welding is adopted, and the calculation formula is: ΔW=β·W·ΔT, wherein ΔW is the axial shrinkage; β is the axial shrinkage coefficient; W is the weld width; ΔT is the temperature difference between the welding temperature and the room temperature; the axial machining allowance is extended along the outer surface at the small end and the large end of the first and the last sections respectively, and the extended axial distance is 5-10mm.

6. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The above-mentioned preparations before welding of each section of the copper inner wall and various welding test plates are specifically as follows: Carry out pickling treatment on the inner wall of each section of copper and multiple groups of welding test plates; Use white silk cloth and clean gasoline to wipe the surface of the base material at the weld until the metallic luster is visible; Assemble each section of the copper inner wall and the welding test plate, and the gap and misalignment of the butt weld should not exceed 0.2mm.

7. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The welding parameters include: electron beam current, focusing current, welding speed, acceleration voltage, welding gun vacuum degree and welding chamber vacuum degree, specifically: The electron beam current is controlled at 130-260mA; The focusing current is controlled at 1.5-2.5A; The welding speed is controlled at 0.3-1.0m / min; The accelerating voltage is greater than 50KV; The vacuum degree of welding gun is less than 3×10 -3 Pa; The vacuum degree of welding chamber is less than 3×10 -2 Pa.

8. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The inspection of welds of different welding test plates includes: surface inspection, X-ray inspection, dimensional inspection, bending performance test, tensile mechanical performance test and metallographic analysis; the surface inspection is to check whether there are cracks, pores, undercuts or depressions on the weld surface; the X-ray inspection is to check whether the internal quality of the weld meets the Grade I requirements of GJB1718A-2005 "Electron Beam Welding"; the dimensional inspection is to check whether the front weld width, back weld width and weld excess height of the weld meet the requirements; the bending performance test is to bend the welding test plate 180° along the weld to check whether there are defects on the weld surface; the tensile mechanical performance test is to perform a tensile test on the welding test plate to detect whether the tensile strength and yield strength of the weld meet the requirements; the metallographic analysis is to section the weld, make a metallographic specimen, and check the macroscopic and microscopic morphology of the weld.

9. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The preferred welding parameters of each weld section are: based on the inspection results of the weld of the welding test plate, the welding quality of the weld is evaluated, and the welding parameters of the weld with the best quality are selected as the welding parameters of the butt weld corresponding to each section of the inner wall.

10. The method for welding and forming a large-size copper inner wall of a liquid rocket engine according to claim 1, characterized in that: The copper inner wall is processed and welded according to the design drawing to form a large-sized copper inner wall. The specific method is: Turning the inner surface of the copper inner wall after welding to form the first prototype; Processing to form a support tire, wherein the outer profile of the support tire has the same size as the inner profile of the first prototype; The first prototype is mounted on the support tire, and the outer surface is machined according to the upper tolerance value of the wall thickness dimension to form the second prototype; Milling grooves on the inner wall of the second preliminary sample to obtain a third preliminary sample; According to the middle tolerance value of the wall thickness, the outer surface of the third prototype is machined to form a large-sized copper inner wall.

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