A kind of guide body for vacuum high pressure gas quenching and its design and gas quenching method

Abstract

A guide body for vacuum high-pressure gas quenching and its design and gas quenching method, through the vacuum medium guide body, the lateral airflow facing the thin-walled shell is converged through the vacuum medium guide body, so that the gas circulates along the guide body into the workpiece area facing away from the air hole, reducing the difference in gas flow rate between the thin-walled shell facing the air outlet and the thin-walled shell facing away from the air outlet, thereby reducing deformation. The simulation shows that the gas flow rate of the thin-walled shell facing the air outlet is equivalent to the gas flow rate of the thin-walled shell facing away from the air outlet, and the difference is small. When the curvature radius of the guide body is 2000mm, it can play a role in reducing the difference in gas flow rate between the thin-walled shell facing the air outlet and the thin-walled shell facing away from the air outlet. In the present invention, due to the addition of the guide body, the gas flow rate measured away from the air outlet is increased, so the gas pressure during gas quenching is reduced by 0.5-1 bar, the deformation of the shell is reduced, and the average straightness change of the three-piece 30Cr3 steel thin-walled shell before and after vacuum high-pressure gas quenching in the furnace is reduced from 1.56 mm / m to 0.49 mm / m, and the average roundness change is reduced from 2.45 mm to 0.35 mm.

Description

Technical Field

[0001] The invention relates to the technical field of metal heat treatment, in particular to a body guide for vacuum high-pressure gas quenching of a furnace with multiple thin-wall shells and a design method, as well as a method for vacuum high-pressure gas quenching using the body guide. Background Art

[0002] In order to achieve non-oxidative heat treatment of thin-walled metal shells of solid rocket engines and improve the performance stability of tempered products, my country currently uses vacuum high-pressure gas quenching furnaces for shell tempering. So far, the difficulty in putting equipment into stable production lies in the deformation of workpieces caused by vacuum high-pressure gas quenching when multiple thin-walled shells are loaded into the furnace for vacuum high-pressure gas quenching. The design of the air cooling device of the vacuum high-pressure gas quenching furnace mostly adopts a circular arrangement of high-speed fluid nozzles around the effective heating area of ​​the furnace body and a large-size air outlet at the bottom of the furnace body. Due to the uneven flow field caused by the nozzle arrangement method, a fast cooling area directly facing the nozzle and a slow cooling area not directly facing the nozzle will inevitably be formed on the workpiece. As a result, a temperature difference is formed at different positions of the shell during the cooling process, that is, the yin-yang surface phenomenon. When the temperature difference between the fast cooling and slow cooling areas is so large that the thermal stress generated during the material cooling process exceeds the yield strength of the material, irreversible plastic deformation will occur. This phenomenon is bound to occur when multiple thin-walled shells are loaded into the furnace for gas quenching.

[0003] In response to the above problems, since the overall structure and air duct design of the equipment cannot be changed, it is necessary to transform and optimize the tooling to improve the uniformity of the flow field during gas quenching, reduce the deformation of the product after gas quenching, meet the needs of post-process processing, avoid shape correction, and improve production efficiency. Summary of the invention

[0004] In order to overcome the problem of shell deformation caused by cooling positive and negative surfaces during vacuum high-pressure gas quenching in the prior art when multiple thin-walled shells are loaded into a furnace, the present invention proposes a method for vacuum high-pressure gas quenching of multiple thin-walled shells and a fluid guide.

[0005] The guide body for vacuum high-pressure gas quenching proposed by the present invention includes a plurality of guide plates; the axial length of each guide plate is the same as the axial length of the inner cavity in the gas quenching tool. The number of the guide plates is the same as the number of the thin-walled shells to be gas quenched, which is 3 to 5. Each of the guide plates is an arc plate, and the long sides of each guide plate are welded and fixed respectively to obtain a guide body with a cross-section of an equilateral triangle, a square or a pentagon.

[0006] When the number of the guide plates is 3, the cross-section of the guide body is an equilateral triangle; when the number of the guide plates is 4, the cross-section of the guide body is a square; when the number of the guide plates is 5, the cross-section of the guide body is a pentagon.

[0007] The concave arc surface of each guide plate is the outer surface of the guide body, and the curvature radius of the concave arc surface of each guide plate is matched with the curvature radius of the outer surface of the thin-wall shell to be gas quenched.

[0008] The specific process of determining the curvature radius of the concave arc surface of the guide plate proposed by the present invention is:

[0009] Step 1, set the initial curvature radius of the guide plate:

[0010] The curvature radius of the guide plate is determined according to the curvature radius of the outer surface of the thin-walled shell to which the guide body is adapted.

[0011] When determining the curvature radius of the guide plate, an initial curvature radius is set first.

[0012] The initial curvature radius is set to:

[0013] When the outer diameter D of the shell is 100>D≤300mm, the initial curvature radius is set to 500mm; when the outer diameter of the shell is 300>D≤500mm, the initial curvature radius is set to 800mm; when the outer diameter of the shell is 500>D≤800mm, the initial curvature radius is set to 1200mm.

[0014] Step 2, determine the radius of curvature of the guide plate:

[0015] By using the flow field simulation software COMSOL, the flow field distribution cloud maps of the initial curvature radii corresponding to the different shell outer diameters are obtained respectively; the flow field distribution cloud maps obtained are analyzed. If the initial curvature radii corresponding to the different shell outer diameters fail to meet the design objectives, the initial curvature radius of the guide plate used for the shells with different outer diameters is adjusted, and the simulation calculation is performed again until the desired effect is achieved.

[0016] The determined curvature radius of the guide plate is: when the outer diameter D of the shell is 100<D≤300mm, the curvature radius r of the guide plate is 1000<r≤1500mm; when the outer diameter D of the shell is 300<D≤500mm, the curvature radius r of the guide plate is 1500>r≤3000mm; when the outer diameter of the shell is 500<D≤800mm, the curvature radius of the guide plate is 3000>r≤4000mm.

[0017] The curvature radius of the deflector is determined to be:

[0018] Ⅰ When the outer diameter of the shell is 100-300 mm, the curvature radius of the guide plate is determined to be 500 mm.

[0019] i Obtain the flow field distribution cloud diagram of the initial curvature radius of the guide plate:

[0020] The flow field distribution cloud diagram obtained by the flow field simulation software COMSOL. According to the gas flow rate on both sides of the thin-walled shell in the flow field distribution cloud diagram, it is determined whether the set initial curvature radius can reduce the flow rate difference between the gas flow rate 5 of the thin-walled shell facing the air outlet and the gas flow rate 4 of the thin-walled shell facing away from the air outlet.

[0021] If the obtained flow field distribution cloud diagram shows that the gas flow rate of the thin-walled shell on the side facing away from the air outlet is greater than 0.8 m / s within 200-400 mm, the initial curvature radius meets the design target and is determined as the curvature radius of the guide plate.

[0022] If the gas flow rate of the thin-walled shell on the side facing away from the air outlet is ≤0.8 m / s within 200-400 mm, it is judged that the set initial curvature radius cannot meet the design target, and the initial curvature radius of the guide plate needs to be adjusted, and a new flow field distribution cloud map is obtained again through the flow field simulation software COMSOL.

[0023] The design target is that the difference between the gas flow velocity 5 of the thin-walled shell facing the air outlet and the gas flow velocity 4 of the thin-walled shell facing away from the air outlet is ≤0.1 m / s.

[0024] ⅱ Adjust the initial curvature radius of the guide plate

[0025] When the set initial curvature radius cannot meet the design target, the initial curvature radius is increased in steps of 500mm to obtain a new initial curvature radius. The obtained new initial curvature radius is input into the flow field simulation software COMSOL, and the flow field distribution cloud map of the initial curvature radius corresponding to the different shell outer diameters is obtained again; the obtained flow field distribution cloud maps are analyzed; if the initial curvature radius corresponding to the different shell outer diameters still fails to meet the design target, the initial curvature radius is continued to be increased and the simulation is continued until the set initial curvature radius can meet the design target; the initial curvature radius is determined as the curvature radius of the guide plate for gas quenching with a shell outer diameter of 100 to 300mm.

[0026] Ⅱ When the outer diameter of the shell is 300~<500mm, the curvature radius of the guide plate is determined to be 1000mm.

[0027] The process of obtaining the flow field distribution cloud diagram of the initial curvature radius of the guide plate when the outer diameter of the shell is 100-300 mm and adjusting the initial curvature radius of the guide plate is repeated to determine the curvature radius of the guide plate adapted to the outer diameter of the shell of 300-<500 mm.

[0028] Ⅲ When the outer diameter of the shell is 500-800mm, the curvature radius of the guide plate is determined to be 1500mm.

[0029] The process of obtaining the flow field distribution cloud diagram of the initial curvature radius of the guide plate when the outer diameter of the shell is 100-300 mm and adjusting the initial curvature radius of the guide plate is repeated to determine the curvature radius of the guide plate adapted to the outer diameter of the shell of 500-800 mm.

[0030] Step 3: Make the guide body;

[0031] At this point, the curvature radius of the concave arc surface of the guide plate is obtained and the guide body is manufactured.

[0032] The specific process of using the flow guide body to perform vacuum high-pressure gas quenching of multiple thin-walled shells is as follows:

[0033] Step 1: Assembly of the guide body and gas quenching tooling:

[0034] The guide body is placed in the inner cavity of the gas quenching tool, and the center of the space circle formed by the outer edge of the guide body is coaxial with the center of the gas quenching tool. The guide body and the gas quenching tool are fixed by welding to complete the assembly.

[0035] Step 2: Install the thin-walled shell

[0036] According to the structural shape of the guide body, a plurality of thin-walled shells are placed around the guide body, and the distance between the vertex of the outer circumferential surface of each thin-walled shell and the lowest point of the concave surface of each guide plate is 70 mm.

[0037] When installing thin-walled housings:

[0038] When there are three thin-walled shells for gas quenching, the three thin-walled shells are respectively placed on the concave surface of each guide plate in the guide body with a triangular cross section;

[0039] When there are four thin-walled shells for gas quenching, the four thin-walled shells are respectively placed on the concave surface of each guide plate in the guide body with a square cross section;

[0040] When there are five thin-wall shells for gas quenching, the five thin-wall shells are respectively arranged at the concave surface of each guide plate in the guide body with a pentagonal cross section.

[0041] Step 3, vacuum high pressure gas quenching of thin wall shell:

[0042] i. The device equipped with a flow guide and multiple thin-walled shells is placed in the effective heating zone of a vacuum high-pressure gas quenching furnace.

[0043] ⅱ Preheating treatment: The preheating temperature of the thin-walled shell is 500-700°C, and the preheating time is 60-120 minutes.

[0044] ⅲ Gas quenching. During gas quenching, heat the vacuum high-pressure gas quenching furnace to a quenching temperature of 880℃~980℃ at a rate of 5~20℃ / min and keep it warm for 1~3h. After the insulation is completed, nitrogen is introduced into the furnace for cooling; nitrogen is introduced during the cooling process until the temperature of the vacuum high-pressure gas quenching furnace drops to 50℃. The gas pressure introduced is 6~12bar.

[0045] At this point, the gas quenching of multiple thin-walled shells is completed.

[0046] The invention relates to a vacuum medium guide body installed on an existing tooling before gas quenching, and a heat treatment process method for reducing the existing gas quenching pressure to perform vacuum high-pressure gas quenching.

[0047] The technical core point of the present invention is to converge the lateral airflow at the shell cylinder section at the vacuum medium guide body, so that the gas circulates along the guide body, narrowing the difference in gas flow field between the workpiece facing the air inlet and the workpiece facing away from the air inlet, and at the same time reducing the gas quenching pressure, thereby reducing deformation.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention adds a vacuum medium guide body to the tooling, and converges the lateral airflow facing the thin-walled shell through the vacuum medium guide body, so that the gas circulates along the guide body into the workpiece area facing away from the air hole, narrowing the difference in gas flow rate between the thin-walled shell facing the air outlet and the thin-walled shell facing away from the air outlet, thereby reducing deformation. Figure 5 The middle horizontal axis is the distance that the shell is in the horizontal position, the left vertical axis is the distance that the shell is in the vertical position, and the right vertical axis is the gas flow rate in the furnace. The darker the color, the greater the gas flow rate. Figure 5 In a, the color of the side facing away from the air outlet is lighter, and the color of the side facing the air outlet is darker, indicating that the gas flow rate of the thin-walled shell facing the air outlet is much greater than the gas flow rate of the thin-walled shell facing away from the air outlet. The difference is large. When the curvature radius of the guide body is 1500mm, it fails to reduce the difference in gas flow rate between the thin-walled shell facing the air outlet and the thin-walled shell facing away from the air outlet. Then the curvature radius of the guide body is increased by 500mm to 2000mm for simulation calculation. Figure 5 b, Figure 5 In b, the color of the side facing away from the air outlet is darker, and the color of the side facing the air outlet is also darker, indicating that the gas flow rate of the thin-walled shell facing the air outlet is similar to that of the thin-walled shell facing away from the air outlet, and the difference is small. When the curvature radius of the guide body is 2000mm, it can play a role in narrowing the difference in gas flow rate between the thin-walled shell facing the air outlet and the thin-walled shell facing away from the air outlet. Then increase the curvature radius of the guide body by 500mm to 2500mm for simulation calculation to obtain Figure 5 c, Figure 5In c, the color of the side facing away from the air outlet is lighter, and the color of the side facing the air outlet is darker, indicating that the gas flow rate of the thin-walled shell facing the air outlet is greater than the gas flow rate of the thin-walled shell facing away from the air outlet, and the difference is large. When the curvature radius of the guide body is 2500mm, it fails to play the role of narrowing the difference in gas flow rate between the thin-walled shell facing the air outlet and the thin-walled shell facing away from the air outlet. At the same time, due to the addition of the guide body, the gas flow rate measured away from the air outlet is increased, so the gas pressure during gas quenching can be reduced from the existing technology by (0.5~1) bar, further reducing the deformation of the shell. Through the use of the present invention, the average straightness change of the three-piece 30Cr3 steel thin-walled shell in this embodiment before and after vacuum high-pressure gas quenching is reduced from the original 1.56mm / m to 0.49mm / m, and the average roundness change is reduced from 2.45mm in the existing technology to 0.35mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the structure of the vacuum medium guide body in the present invention. Figure 1 a is the main view, Figure 1 b is a top view.

[0051] Figure 2a It is a schematic diagram of the coordination between the tooling and the vacuum medium guide body of the present invention.

[0052] Figure 2b yes Figure 2a Top view of the .

[0053] Figure 3 It is a schematic diagram of the structure of a thin-walled shell.

[0054] Figure 4 It is a schematic diagram of the hanging method of three thin-walled shells in the existing tooling and the embodiment of the present invention.

[0055] Figure 5 : is a flow field distribution cloud diagram of adding vacuum medium guide bodies with different curvature radii in the embodiment of the present invention; wherein, Figure 5 a is the flow field distribution cloud diagram when the curvature radius of the vacuum medium guide body is 1200mm; Figure 5 b is the flow field distribution cloud diagram when the curvature radius of the vacuum medium guide body is 1700 mm; Figure 5 c is the flow field distribution cloud diagram when the curvature radius of the vacuum medium guide body is 2200mm.

[0056] Figure 6 is a schematic diagram of the structure of the vacuum medium guide body in an embodiment of the present invention; wherein, Figure 6 a is the front view; Figure 6 b is a top view.

[0057] Figure 7Schematic diagram of the coordination between the existing tooling, the thin-walled shell and the vacuum medium guide body in the embodiment of the present invention; wherein, Figure 7 a is the main view, Figure 7 b is a schematic diagram of the position of the thin-walled shell in the vacuum medium flow guide.

[0058] Figure 8 are the roundness measurement results of different cross sections of three thin-walled shells before and after heat treatment in the embodiment of the present invention; wherein, Figure 8 a is a schematic diagram of the measurement results of the first thin-walled shell. Figure 8 b is a schematic diagram of the measurement results of the second thin-walled shell. Figure 8 c is a schematic diagram of the measurement results of the third thin-walled shell.

[0059] Fig. 9 is the straightness measurement result of three thin-walled shells before and after heat treatment in the embodiment of the present invention; wherein, Fig. 9 a is a schematic diagram of the measurement results of the first thin-walled shell. Fig. 9 b is a schematic diagram of the measurement results of the second thin-walled shell. Fig. 9 c is a schematic diagram of the measurement results of the third thin-walled shell.

[0060] In the figure: 1. tooling; 2. vacuum medium guide body; 3. thin-walled shell; 4. gas flow rate of the thin-walled shell on the side facing away from the air outlet; 5. gas flow rate of the thin-walled shell on the side facing the air outlet; 6. roundness before gas quenching; 7. roundness after gas quenching; 8. straightness before gas quenching; 9. straightness after gas quenching. DETAILED DESCRIPTION

[0061] This embodiment is a flow guide body for vacuum high-pressure gas quenching of multiple thin-walled shells in a furnace. By adding the vacuum medium flow guide body to the tooling, the difference in gas flow rate between the thin-walled shell facing the air outlet and the thin-walled shell facing away from the air outlet is reduced, thereby reducing the deformation of the thin-walled shell.

[0062] In this embodiment, the air outlet mode of vacuum high-pressure gas quenching adopts conventional circumferential blowing plus bottom blowing; the number of thin-walled shells to be processed is three. The structure of the thin-walled shell is as follows Figure 3 As shown, the material is 30Cr3 steel, the length is 1900mm, the diameter is 350mm, and the shell wall thickness is 2.1mm. Figure 4 It is a schematic diagram of the hanging method of the existing tooling and three thin-walled shells. The column height of the existing tooling is 2500mm.

[0063] The guide body is used in conjunction with the existing gas quenching tooling, and includes a plurality of guide plates; the axial length of each guide plate is the same as the axial length of the inner cavity in the gas quenching tooling. The number of the guide plates is the same as the number of the thin-walled shells to be gas quenched, which is 3 to 5.

[0064] When the number of the guide plates is 3, the cross-section of the guide body is an equilateral triangle; when the number of the guide plates is 4, the cross-section of the guide body is a square; when the number of the guide plates is 5, the cross-section of the guide body is a pentagon.

[0065] Each of the guide plates is an arc plate, and the long sides of each guide plate are welded and fixed to obtain a guide body with a cross section of an equilateral triangle, square or pentagon. When welding each guide plate, the concave arc surface of each guide plate is the outer surface of the guide body. The curvature radius of the concave arc surface of each guide plate is adapted to the curvature radius of the outer surface of the thin-walled shell to be gas quenched.

[0066] This embodiment also proposes a method for determining the curvature radius of the concave arc surface of the guide plate, and the specific process is:

[0067] Step 1: Set the initial curvature radius of the guide plate

[0068] The curvature radius of the guide plate is determined according to the curvature radius of the outer surface of the thin-walled shell to which the guide body is adapted.

[0069] When determining the curvature radius of the guide plate, the initial curvature radius is set first. The set initial curvature radius is:

[0070] When the outer diameter D of the shell is 100>D≤300mm, the initial curvature radius is set to 500mm; when the outer diameter of the shell is 300>D≤500mm, the initial curvature radius is set to 800mm; when the outer diameter of the shell is 500>D≤800mm, the initial curvature radius is set to 1200mm.

[0071] Step 2: Determine the curvature radius of the guide plate

[0072] The flow field simulation software COMSOL is used to obtain the flow field distribution cloud diagrams of the initial curvature radius corresponding to the different shell outer diameters; if the initial curvature radius corresponding to the different shell outer diameters fails to meet the design target, the initial curvature radius of the guide plate used for the shell with different outer diameters is adjusted, and the simulation calculation is performed again until the desired effect is achieved. Specifically:

[0073] Ⅰ When the outer diameter of the shell is 100-300 mm, the curvature radius of the guide plate is determined to be 500 mm.

[0074] i Obtain the flow field distribution cloud diagram of the initial curvature radius of the guide plate:

[0075] The flow field distribution cloud diagram obtained by the flow field simulation software COMSOL. According to the gas flow rate on both sides of the thin-walled shell in the flow field distribution cloud diagram, it is determined whether the set initial curvature radius can reduce the flow rate difference between the gas flow rate 5 of the thin-walled shell facing the air outlet and the gas flow rate 4 of the thin-walled shell facing away from the air outlet.

[0076] If the obtained flow field distribution cloud diagram shows that the gas flow rate of the thin-walled shell on the side facing away from the air outlet is greater than 0.8 m / s within 200-400 mm, the initial curvature radius meets the design target and is determined as the curvature radius of the guide plate.

[0077] If the gas flow rate of the thin-walled shell on the side facing away from the air outlet is ≤0.8 m / s within 200-400 mm, it is judged that the set initial curvature radius cannot meet the design target, and the initial curvature radius of the guide plate needs to be adjusted, and a new flow field distribution cloud map is obtained again through the flow field simulation software COMSOL.

[0078] The design target is that the difference between the gas flow velocity 5 of the thin-walled shell facing the air outlet and the gas flow velocity 4 of the thin-walled shell facing away from the air outlet is ≤0.1 m / s.

[0079] ⅱ Adjust the initial curvature radius of the guide plate

[0080] When the set initial curvature radius cannot meet the design target, the initial curvature radius is increased in steps of 500mm to obtain a new initial curvature radius. The obtained new initial curvature radius is input into the flow field simulation software COMSOL, and the flow field distribution cloud map of the initial curvature radius corresponding to the different shell outer diameters is obtained again; the obtained flow field distribution cloud maps are analyzed; if the initial curvature radius corresponding to the different shell outer diameters still fails to meet the design target, the initial curvature radius is continued to be increased and the simulation is continued until the set initial curvature radius can meet the design target; the initial curvature radius is determined as the curvature radius of the guide plate for gas quenching with a shell outer diameter of 100 to 300mm.

[0081] Ⅱ When the outer diameter of the shell is 300~<500mm, the curvature radius of the guide plate is determined to be 1000mm.

[0082] The process of obtaining the flow field distribution cloud diagram of the initial curvature radius of the guide plate when the outer diameter of the shell is 100-300 mm and adjusting the initial curvature radius of the guide plate is repeated to determine the curvature radius of the guide plate adapted to the outer diameter of the shell of 300-<500 mm.

[0083] Ⅲ When the outer diameter of the shell is 500-800mm, the curvature radius of the guide plate is determined to be 1500mm.

[0084] The process of obtaining the flow field distribution cloud diagram of the initial curvature radius of the guide plate when the outer diameter of the shell is 100-300 mm and adjusting the initial curvature radius of the guide plate is repeated to determine the curvature radius of the guide plate adapted to the outer diameter of the shell of 500-800 mm.

[0085] At this point, the determined curvature radius of the guide plate is: when the outer diameter D of the shell is 100<D≤300mm, the curvature radius r of the guide plate is 1000<r≤1500mm; when the outer diameter D of the shell is 300<D≤500mm, the curvature radius r of the guide plate is 1500>r≤3000mm; when the outer diameter of the shell is 500<D≤800mm, the curvature radius of the guide plate is 3000>r≤4000mm.

[0086] The guide body in this embodiment is triangular, and the diameter of the thin-walled shell is 350 mm, so the curvature radius of the vacuum medium guide body is 1500-3000 mm. The flow field simulation software COMSOL is used to calculate and analyze the influence of the curvature radius of the vacuum medium guide body on the gas flow rate on both sides of the thin-walled shell.

[0087] Step 3: Make the deflector:

[0088] The guide body is made of heat-resistant stainless steel and is welded from 3 to 5 guide plates with arc surfaces. The curvature radius of each guide plate is determined by step 2.

[0089] In this embodiment, the guide body is formed by welding three guide plates; each guide plate has a curvature radius of 2000 mm, a height of 2500 mm, and a thickness of 10 mm.

[0090] The present invention also proposes a method for vacuum high-pressure gas quenching of multiple thin-walled shells, the specific process of which is:

[0091] Step 1: Assembly of the guide body and gas quenching tooling:

[0092] The guide body is placed in the inner cavity of the gas quenching tool, and the center of the space circle formed by the outer edge of the guide body is coaxial with the center of the gas quenching tool. The guide body and the gas quenching tool are fixed by welding to complete the assembly.

[0093] Step 2: Install the thin-walled shell

[0094] According to the structural shape of the guide body, a plurality of thin-walled shells are placed around the guide body, specifically:

[0095] When there are three thin-walled shells for gas quenching, the three thin-walled shells are respectively placed on the concave surface of each guide plate in the guide body with a triangular cross-section; when there are four thin-walled shells for gas quenching, the four thin-walled shells are respectively placed on the concave surface of each guide plate in the guide body with a square cross-section; when there are five thin-walled shells for gas quenching, the five thin-walled shells are respectively placed on the concave surface of each guide plate in the guide body with a pentagonal cross-section.

[0096] The distance between the vertex of the outer circumferential surface of each thin-walled shell and the lowest point of the concave surface of each guide plate is 70 mm.

[0097] Step 3, vacuum high pressure gas quenching of thin wall shell:

[0098] i. The device equipped with a flow guide and multiple thin-walled shells is placed in the effective heating zone of a vacuum high-pressure gas quenching furnace.

[0099] ⅱ Preheating treatment: The preheating temperature is 500-700°C and the preheating time is 60-120 minutes.

[0100] ⅲ Gas quenching. Heat the vacuum high-pressure gas quenching furnace to a quenching temperature of 880℃~980℃ at a rate of 5~20℃ / min and keep it at that temperature for 1~3h. After the insulation is completed, nitrogen is introduced into the furnace for cooling; nitrogen is introduced during the cooling process until the temperature of the vacuum high-pressure gas quenching furnace drops to 50℃. The introduced gas pressure is 6~12bar.

[0101] In this embodiment, the preheating temperature of the three thin-walled shells is 630±10℃, and the preheating time is 60±10min. The heating rate is 10℃ / min, the quenching temperature is 880±10℃, and the quenching holding time is 60±10℃. The gas pressure is generally 8bar in the prior art, but the addition of the guide in the present invention greatly increases the gas flow rate at the side facing away from the air outlet, which can ensure the hardenability of the shell on the side facing away from the air outlet, and can reduce the gas quenching pressure by 0.5~1bar. In this embodiment, the gas quenching pressure is reduced from 8bar to 7bar through a series of experimental results, which can further reduce the deformation of the thin-walled cylindrical parts.

[0102] At this point, the gas quenching of multiple thin-walled shells is completed.

[0103] In order to verify the effect of the present invention, the roundness and straightness of the thin-walled shell after gas quenching were measured.

[0104] Take the gas quenching of three thin-walled shells as an example. The roundness measurement results are as follows: Figure 8 shown. Figure 8 The horizontal axis represents the 8 measurement sections of the thin-walled shell, and the vertical axis represents the roundness measurement values ​​of the 8 measurement sections of the thin-walled long cylindrical parts before and after gas quenching. Figure 8 a is a schematic diagram of the measurement results of the first thin-walled shell. Figure 8 b is a schematic diagram of the measurement results of the second thin-walled shell. Figure 8 c is a schematic diagram of the measurement results of the third thin-walled shell. The average roundness change of the three thin-walled shells before and after gas quenching is 0.35mm.

[0105] Straightness measurement results are as follows: Fig. 9 As shown, Fig. 9 a is a schematic diagram of the measurement results of the first thin-walled shell. Fig. 9 b is a schematic diagram of the measurement results of the second thin-walled shell. Fig. 9 c is a schematic diagram of the measurement results of the third thin-walled shell; Fig. 9 The horizontal axis represents the four measuring quadrants of the thin-walled long cylindrical parts, and the vertical axis represents the straightness measurement values ​​of the four measuring quadrants of the thin-walled long cylindrical parts before and after gas quenching. The average straightness change of the three thin-walled parts before and after gas quenching is 0.49 mm / m.

Claims

1. A vacuum high pressure gas quenching body, characterized in that: It comprises a plurality of guide plates; the axial length of each guide plate is the same as the axial length of the inner cavity in the gas quenching tooling; the number of the guide plates is the same as the number of the thin-walled shells to be gas quenched, which is 3 to 5; each of the guide plates is an arc plate, and the long sides of each guide plate are welded and fixed respectively to obtain a guide body with a cross section of an equilateral triangle, square or pentagon.

2. The vacuum high pressure gas quenching body according to claim 1, characterized in that: When the number of the guide plates is 3, the cross-section of the guide body is an equilateral triangle; when the number of the guide plates is 4, the cross-section of the guide body is a square; when the number of the guide plates is 5, the cross-section of the guide body is a pentagon.

3. The vacuum high pressure gas quenching body according to claim 1, characterized in that: The concave arc surface of each guide plate is the outer surface of the guide body; the curvature radius of the concave arc surface of each guide plate is matched with the curvature radius of the outer surface of the thin-wall shell to be gas quenched.

4. A method for determining the curvature radius of the concave surface of the guide plate according to claim 1, characterized in that: The specific process is: Step 1, set the initial curvature radius of the guide plate: The curvature radius of the guide plate is determined according to the curvature radius of the outer surface of the thin-walled shell to which the guide body is adapted; When determining the curvature radius of the guide plate, an initial curvature radius is first set; Step 2, determine the radius of curvature of the guide plate: By using the flow field simulation software COMSOL, the flow field distribution cloud diagrams of the initial curvature radii corresponding to the different shell outer diameters are obtained respectively; if the initial curvature radii corresponding to the different shell outer diameters fail to meet the design target, the initial curvature radii of the guide plates used for the shells with different outer diameters are adjusted, and the simulation calculation is performed again until the desired effect is achieved; The curvature radius of the guide plate is determined as follows: when the outer diameter D of the shell is 100<D≤300mm, the curvature radius r of the guide plate is 1000<r≤1500mm; when the outer diameter D of the shell is 300<D≤500mm, the curvature radius r of the guide plate is 1500>r≤3000mm; when the outer diameter D of the shell is 500<D≤800mm, the curvature radius of the guide plate is 3000>r≤4000mm; Step 3: Make the guide body; At this point, the curvature radius of the concave arc surface of the guide plate is obtained and the guide body is manufactured.

5. The method for determining the curvature radius of the concave surface of the guide plate according to claim 4, characterized in that: The initial curvature radius set in step 1 is: When the outer diameter D of the shell is 100>D≤300mm, the initial curvature radius is set to 500mm; when the outer diameter of the shell is 300>D≤500mm, the initial curvature radius is set to 800mm; when the outer diameter of the shell is 500>D≤800mm, the initial curvature radius is set to 1200mm.

6. The method for determining the curvature radius of the concave surface of the guide plate according to claim 4, characterized in that: The curvature radius of the guide plate determined in step 2 is specifically: Ⅰ When the outer diameter of the shell is 100-300 mm, the curvature radius of the guide plate is determined to be 500 mm; i Obtain the flow field distribution cloud diagram of the initial curvature radius of the guide plate: The flow field distribution cloud map obtained by the flow field simulation software COMSOL; according to the gas flow rate on both sides of the thin-walled shell in the flow field distribution cloud map, determine whether the set initial curvature radius can reduce the flow rate difference between the gas flow rate 5 of the thin-walled shell facing the air outlet side and the gas flow rate 4 of the thin-walled shell facing away from the air outlet side; If the obtained flow field distribution cloud map shows that the gas flow rate of the thin-walled shell on the side facing away from the air outlet is greater than 0.8 m / s within 200 to 400 mm, the initial curvature radius meets the design target and is determined as the curvature radius of the guide plate; if the gas flow rate of the thin-walled shell on the side facing away from the air outlet is less than 0.8 m / s within 200 to 400 mm, it is determined that the set initial curvature radius cannot meet the design target, and the initial curvature radius of the guide plate needs to be adjusted, and a new flow field distribution cloud map is obtained again through the flow field simulation software COMSOL; The design goal is that the difference between the gas flow velocity 5 of the thin-walled shell facing the air outlet and the gas flow velocity 4 of the thin-walled shell facing away from the air outlet is ≤0.1 m / s; ⅱ Adjust the initial curvature radius of the guide plate When the set initial curvature radius cannot meet the design target, the initial curvature radius is increased in steps of 500 mm to obtain a new initial curvature radius; the obtained new initial curvature radius is input into the flow field simulation software COMSOL, and the flow field distribution cloud map of the initial curvature radius corresponding to the different shell outer diameters is obtained again; the obtained flow field distribution cloud maps are analyzed; if the initial curvature radius corresponding to the different shell outer diameters still cannot meet the design target, the initial curvature radius is continued to be increased and the simulation is continued until the set initial curvature radius can meet the design target; the initial curvature radius is determined as the curvature radius of the guide plate for gas quenching with a shell outer diameter of 100 to 300 mm; Ⅱ When the outer diameter of the shell is 300~<500mm, the curvature radius of the guide plate is determined to be 1000mm; Repeat the process of obtaining the flow field distribution cloud map of the initial curvature radius of the guide plate when the outer diameter of the shell is 100 to 300 mm and adjusting the initial curvature radius of the guide plate to determine the curvature radius of the guide plate adapted to the outer diameter of the shell of 300 to <500 mm; Ⅲ When the outer diameter of the shell is 500-800 mm, the curvature radius of the guide plate is determined to be 1500 mm; The process of obtaining the flow field distribution cloud diagram of the initial curvature radius of the guide plate when the outer diameter of the shell is 100-300 mm and adjusting the initial curvature radius of the guide plate is repeated to determine the curvature radius of the guide plate adapted to the outer diameter of the shell of 500-800 mm.

7. A method for vacuum high-pressure gas quenching of multiple thin-walled shells using the body guide as claimed in claim 1, characterized in that: The specific process is: Step 1: Assembly of the guide body and gas quenching tooling: The guide body is placed in the inner cavity of the gas quenching tool, and the center of the space circle formed by the outer edge of the guide body is coaxial with the center of the gas quenching tool; and the guide body and the gas quenching tool are fixed by welding to complete the assembly; Step 2, install the thin-walled shell: According to the structural shape of the guide body, a plurality of thin-walled shells are placed around the guide body; and the distance between the vertex of the outer circumferential surface of each thin-walled shell and the lowest point of the concave surface of each guide plate is 70 mm; Step 3, vacuum high pressure gas quenching of thin wall shell: i. Place the device equipped with the guide body and multiple thin-walled shells in the effective heating zone of the vacuum high-pressure gas quenching furnace; ⅱPreheating treatment; ⅲGas quenching; At this point, the gas quenching of multiple thin-walled shells is completed.

8. The method for vacuum high-pressure gas quenching of multiple thin-walled shells using a flow-conducting body as claimed in claim 7, characterized in that: When installing a thin-walled housing in step 2: When there are three thin-walled shells for gas quenching, the three thin-walled shells are respectively placed on the concave surface of each guide plate in the guide body with a triangular cross section; When there are four thin-walled shells for gas quenching, the four thin-walled shells are respectively placed on the concave surface of each guide plate in the guide body with a square cross section; When there are five thin-wall shells for gas quenching, the five thin-wall shells are respectively arranged at the concave surface of each guide plate in the guide body with a pentagonal cross section.

9. The method for vacuum high-pressure gas quenching of multiple thin-walled shells using a flow-conducting body as claimed in claim 7, characterized in that: In step 3, the preheating temperature of the thin-walled shell is 500-700° C., and the preheating time is 60-120 min.

10. The method for vacuum high-pressure gas quenching of multiple thin-walled shells using a flow-conducting body as claimed in claim 7, characterized in that: When the thin-walled shell is gas quenched in step 3, the vacuum high-pressure gas quenching furnace is heated to a quenching temperature of 880°C to 980°C at a rate of 5 to 20°C / min and kept warm for 1 to 3 hours; after the insulation is completed, nitrogen is introduced into the furnace for cooling; during the cooling process, nitrogen is introduced until the temperature of the vacuum high-pressure gas quenching furnace drops to 50°C; the introduced gas pressure is 6 to 12 bar.

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