A heat-resistant steel thin-walled multi-port ferrule joint hot gas expansion forming device and method

Abstract

This invention discloses a hot gas expansion forming apparatus and method for heat-resistant steel thin-walled multi-port ferrule joints, relating to the field of metal forming and manufacturing technology. It includes a die-clamping press, a warm drawing die, a gas expansion forming die, a heating system, and a gas expansion forming-rapid gas quenching system. The die-clamping press includes a press and a punch; the press includes a lower table, an upper table, and a slider. The warm drawing die includes a lower heat insulation plate, a lower die, a segmented die, and a warm drawing upper die. The gas expansion forming die includes a lower heat insulation plate, a lower die, a segmented die, an upper heat insulation plate, and a hot gas expansion forming upper die. The heating system is used to heat and control the temperatures required for the shared die, blank, and cylinder during the warm drawing and gas expansion forming processes. The gas expansion forming-rapid gas quenching system includes a compressed air source and a gas source control cabinet; the compressed air source is connected to a gas channel through the gas source control cabinet. This invention can significantly shorten the process cycle, reduce the oxidation degree of heat-resistant steel cylinders, and ensure the microstructure, properties, and dimensional accuracy of the parts after hot gas expansion forming.

Description

Technical Field

[0001] This invention relates to the field of metal forming and manufacturing technology, and in particular to a heat-resistant steel thin-walled multi-port ferrule joint hot gas expansion forming apparatus and method. Background Technology

[0002] Thin-walled multi-port compression fittings are key components in high-end equipment fields such as aerospace. Among them, heat-resistant steel compression fittings are used in jet engine connectors and aircraft piping joints. The commonly used raw material is martensitic precipitation-hardening heat-resistant steel, which has poor room temperature plasticity but high corrosion resistance and stress resistance. After heat treatment, it has high tensile strength.

[0003] Thin-walled multi-port ferrule fittings have thin walls and multiple channels in the circumferential direction of the cylinder wall. Each channel has a different diameter and has complex and irregular overall structural features. Heat-resistant steel has poor room temperature plasticity, and the amount of deformation in a single operation should not be too large. The deformation resistance and springback are relatively large during forming. It is difficult to form thin-walled multi-port ferrule fittings in one operation using traditional stamping dies.

[0004] Existing processes typically employ multi-pass stamping; however, this method results in significant thinning of the material's edge wall after flanging, leading to cracking and poor process stability. To address room temperature cracking and improve the plasticity and microstructure of parts, forming under heating conditions is necessary. For heat-resistant steel, increasing the heating temperature enhances plasticity, and hot forming presents several potential and feasible applications. However, no single hot forming technique can achieve the desired results.

[0005] Hot stamping technology heats steel sheets above the austenitic temperature, altering their crystal structure and increasing their ductility, enabling the formation of complex parts. However, heat-resistant steel requires high forming temperatures and is prone to oxidation during stamping. The accumulation of oxide scale affects die friction and the quality of subsequent parts. Direct hot gas expansion of sheet metal can form metals that are difficult to deform at room temperature, but subsequent heat treatment is required to improve strength. This process is prone to shape distortion, precision deviations, and other drawbacks, requiring multiple steps and a long production cycle. Superplastic forming utilizes the high plasticity, strong activity, and diffusion capabilities of metallic materials under specific conditions, allowing for one-piece forming and suitable for small-batch production of complex-shaped parts. However, the superplastic properties of heat-resistant steel are highly sensitive to deformation temperature, strain rate, and microstructure, making superplastic forming conditions demanding. Therefore, a new method for forming compression fittings is urgently needed. Summary of the Invention

[0006] The purpose of this invention is to provide a hot gas expansion forming device and method for heat-resistant steel thin-walled multi-port ferrule joints to solve the problems existing in the prior art. It can significantly shorten the process cycle, reduce the oxidation degree of heat-resistant steel cylinder parts, and at the same time ensure the microstructure and dimensional accuracy of the parts after hot gas expansion forming.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a hot air expansion forming device for a heat-resistant steel thin-walled multi-port ferrule joint, including a mold clamping press, a warm drawing forming mold, an air expansion forming mold, a heating system, and an air expansion forming-rapid air quenching system;

[0009] The mold-closing press includes a press and a punch. The press includes a lower table and an upper table and a slider that independently control the loading force and pressing speed. The punch is fixedly mounted on the slider to form a temperature-stretched cylindrical part.

[0010] The warm drawing forming die includes a lower heat insulation plate, a lower die, a segmented die, and a warm drawing upper die. The air expansion forming die includes the lower heat insulation plate, the lower die, the segmented die, the upper heat insulation plate, and a hot air expansion forming upper die. The lower heat insulation plate is fixedly disposed on the lower platform. The lower die is disposed on the lower heat insulation plate. The segmented die is disposed on the lower die and forms a common concave die with the lower die for warm drawing of the cylindrical blank and air expansion forming of the cylindrical part. The warm drawing upper die cooperates with the segmented die and is fixedly disposed on the upper platform to provide blank holder force during warm drawing. The upper heat insulation plate is fixedly disposed on the slider. The hot air expansion forming upper die cooperates with the segmented die and is fixedly disposed on the upper heat insulation plate to provide blank holder force during air expansion forming. The hot air expansion forming upper die is provided with a gas channel communicating with the inner cavity of the common concave die.

[0011] The heating system is used to heat and control the required temperatures of the common die, blank, and cylinder during the warm stretching and air-expansion forming processes.

[0012] The air expansion forming-rapid air quenching system includes a compressed air source and an air source control cabinet. The compressed air source is connected to the gas channel through the air source control cabinet. The air source control cabinet is used to control the injection of compressed gas into the cylinder during hot air expansion forming and to perform rapid exchange of hot and cold gas in the cylinder after hot air expansion forming.

[0013] Preferably, it further includes a temperature and displacement measurement system, which is used to measure the temperature signal inside the common die cavity and the bulging displacement of the inner cylindrical part of the common die cavity.

[0014] Preferably, the temperature and displacement measurement system includes a thermocouple, a quartz rod, a displacement sensor, and a multi-channel touch data logger. The thermocouple is disposed on the segmented mold and is used to measure the temperature signal inside the common concave mold. The quartz rod and the displacement sensor are both disposed on the segmented mold. One end of the quartz rod contacts the outer wall of the inner cylinder of the common concave mold, and the other end contacts the displacement sensor, for transmitting the bulging displacement change of the cylinder to the displacement sensor. Both the thermocouple and the displacement sensor are electrically connected to the multi-channel touch data logger.

[0015] Preferably, the heating system includes an induction heating coil and a high-frequency induction heater. The induction heating coil is sleeved on the outside of the common concave cavity, and the high-frequency induction heater is electrically connected to the induction heating coil to control the output power of the induction heating coil.

[0016] This invention also provides a method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint, based on the above-described hot gas expansion forming device for a heat-resistant steel thin-walled multi-port ferrule joint, comprising the following steps:

[0017] (1) The heat-resistant steel plate is installed in the warm drawing forming mold. After the mold is closed, the heat-resistant steel plate and the common die are heated to the warm drawing forming temperature by the heating system. The heat-resistant steel plate is warmly drawn by the punch pressing down at a constant speed to form a warm drawing cylinder.

[0018] (2) The cylindrical part is placed in the gas forming mold. After the mold is closed, the heating system is used to heat the cylindrical part and the common cavity mold to the hot gas forming temperature, so that the microstructure of the cylindrical part is austenitized.

[0019] (3) High-pressure inert gas is introduced into the cylinder through the gas expansion forming-rapid gas quenching system to perform hot gas expansion forming and obtain the target shape forming component;

[0020] (4) Quickly discharge the gas inside the formed component, and introduce high-pressure low-temperature inert gas into the formed component through the gas expansion forming-rapid gas quenching system to exchange hot and cold gases, and perform rapid gas quenching on the formed component to transform the structure of the formed component into martensite;

[0021] (5) Discharge the compressed gas inside the forming component, remove the forming component, and cut off the excess at each interface to obtain a multi-port ferrule connector.

[0022] Preferably, when the heat-resistant steel plate is martensitic heat-resistant steel, the warm stretching forming temperature in step (1) is 600℃~0.6T. m Melting point temperature T mThe temperature range is 1400–1440℃, the heating rate is 25–30℃ / s, and the speed at which the punch presses down uniformly is 100–200 mm / s.

[0023] Preferably, when the heat-resistant steel plate is martensitic heat-resistant steel, in step (2), the hot gas expansion forming temperature is 1000~1100℃ and the heating rate is 40~50℃ / s.

[0024] Preferably, in step (3), the pressure of the high-pressure inert gas introduced is 15-20 MPa and the pressurization rate is 0.5-1 MPa / s; in step (4), the pressure of the high-pressure low-temperature inert gas introduced is 15-20 MPa and the cooling rate is 5-10 °C / s; in steps (3) and (4), the inert gas is nitrogen, helium or argon.

[0025] Preferably, in step (4), a constant pressure environment is maintained inside the formed component throughout the gas quenching process.

[0026] Preferably, when the heat-resistant steel plate is a martensitic precipitation hardening heat-resistant steel, the warm stretching forming temperature is 600-700℃, and the hot gas expansion forming temperature is 1020-1060℃.

[0027] The heat-resistant steel thin-walled multi-port ferrule joint hot gas expansion forming device and method provided by the present invention achieves the following technical advantages compared with the prior art:

[0028] 1) Steel-flexible composite forming: In the medium temperature range, the steel mold utilizes the matching of material strain hardening, strain rate hardening and plasticity enhancement to obtain a cylindrical part with a large displacement depth without cracking.

[0029] 2) Hot gas expansion forming of multi-pass structures with unequal diameters, and modification during expansion forming. It utilizes the martensitic phase transformation characteristics of heat-resistant steel after high-temperature hot forming and rapid cooling, isolates air to reduce oxidation, and ensures the microstructure and dimensional accuracy. The forming speed is fast and the efficiency is high.

[0030] 3) The cylindrical parts are equipped with an inert gas quenching device. Compared with air cooling or water cooling, which can cause performance degradation and shape distortion, gas quenching can effectively improve the microstructure and achieve dimensional accuracy control.

[0031] 4) The adiabatic pressure reduction cooling effect of rapidly releasing gas after hot gas expansion and molding can remove some of the heat from the mold and effectively reduce the cooling intensity of the mold. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the hot gas expansion forming process in this invention;

[0034] Figure 2 This is a schematic diagram of the hot gas expansion forming process in this invention;

[0035] Figure 3 This is a flowchart of the hot gas expansion forming process in this invention;

[0036] Figure 4 This is a structural diagram of the initial state of the hot drawing forming apparatus in this invention;

[0037] Figure 5 This is a structural diagram of the forming state of the temperature deep drawing forming apparatus in this invention;

[0038] Figure 6 This is a structural diagram of the hot gas expansion forming device in this invention;

[0039] Figure 7 This is a top view cross-sectional structural diagram of the hot gas expansion forming device in this invention;

[0040] Figure 8 The figures show the room temperature and high temperature unidirectional mechanical property curves of the heat-resistant stainless steel in this invention.

[0041] In the diagram: 1-punch, 2-lower table, 3-upper table, 4-slider, 5-lower heat insulation plate, 6-lower die, 7-segmented die, 8-warm stretching upper die, 9-upper heat insulation plate, 10-hot gas expansion forming upper die, 11-common cavity die, 12-gas channel, 13-compressed air source, 14-air source control cabinet, 15-thermocouple, 16-displacement sensor, 17-induction heating coil, 18-heat insulation plate, 19-warm stretching cavity die, 20-induction coil, 21-heating element, 22-punch, 23-hot gas expansion cavity die. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The purpose of this invention is to provide a hot gas expansion forming device and method for heat-resistant steel thin-walled multi-port ferrule joints to solve the problems existing in the prior art. It can realize rapid gas quenching and cooling after hot gas expansion forming in the mold, and ensure the microstructure and dimensional accuracy of the parts after hot gas expansion forming.

[0044] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figures 1-8 As shown, this embodiment provides a hot air expansion forming device for a heat-resistant steel thin-walled multi-port ferrule joint, including a mold clamping press, a warm drawing forming mold, an air expansion forming mold, a heating system, and an air expansion forming-rapid air quenching system;

[0046] The mold press includes a press and a punch 1. The press includes a lower table 2, an upper table 3 and a slide 4 that independently control the loading force and pressing speed. The punch 1 is fixedly set on the slide 4 to form a temperature-stretched cylindrical part.

[0047] The warm drawing die includes a lower heat insulation plate 5, a lower die 6, a segmented die 7, and a warm drawing upper die 8. The air expansion die includes a lower heat insulation plate 5, a lower die 6, a segmented die 7, an upper heat insulation plate 9, and a hot air expansion upper die 10. The lower heat insulation plate 5 is fixedly mounted on the lower platform 2. The lower die 6 is mounted on the lower heat insulation plate 5. The segmented die 7 is mounted on the lower die 6 and forms a common concave die 11 with the lower die 6 for warm drawing of the cylindrical blank and air expansion forming of the cylindrical part. The warm drawing upper die 8 cooperates with the segmented die 7 and is fixedly mounted on the upper platform 3 to provide blank holder force during warm drawing. The upper heat insulation plate 9 is fixedly mounted on the slider 4. The hot air expansion upper die 10 cooperates with the segmented die 7 and is fixedly mounted on the upper heat insulation plate 9 to provide blank holder force during air expansion forming. The hot air expansion upper die 10 is provided with a gas channel 12 that communicates with the inner cavity of the common concave die 11.

[0048] The heating system is used to heat and control the required temperatures of the shared die 11, the blank, and the cylinder during the stretch forming and air-expansion forming processes.

[0049] The air expansion forming-rapid air quenching system includes a compressed air source 13 and an air source control cabinet 14. The compressed air source 13 is connected to the gas channel 12 through the air source control cabinet 14. The air source control cabinet 14 is used to control the injection of compressed gas into the cylinder during hot air expansion forming and to perform rapid exchange of hot and cold gas in the cylinder after hot air expansion forming.

[0050] The mold-closing press can be a traditional hydraulic press or a dedicated mold-closing device built with a pneumatic-hydraulic booster cylinder. The mold-closing press features dual-action controllable speed loading. The warm-stretching upper mold 8 is fixed to the upper table 3 of the press, with a blank holder force of 20-40 KN. Mold materials can be selected from commonly used mold materials for hot gas expansion forming, such as low-carbon steel, stainless steel, Ni7N, etc. The lower heat insulation plate 5 and upper heat insulation plate 9 isolate the heat emitted by the mold during warm stretching and hot gas expansion forming. The split mold 7 is used to form the circumferential interface, facilitating the removal of the part after expansion. The compressed air source 13 emits gas, and the gas flow rate and pressure are regulated by the air source control cabinet 14. The quenching speed within the mold is controlled by the internal air pressure and temperature of the cylinder.

[0051] It also includes a temperature and displacement measurement system, which is used to measure the temperature signal inside the common die 11 and the bulging displacement of the inner cylinder of the common die 11.

[0052] The temperature and displacement measurement system includes a thermocouple 15, a quartz rod, a displacement sensor 16, and a multi-channel touch data logger. The thermocouple 15 is mounted on the segmented mold 7 and is used to measure the temperature signal inside the common concave mold 11. The quartz rod and the displacement sensor 16 are both mounted on the segmented mold 7. One end of the quartz rod contacts the outer wall of the inner cylinder of the common concave mold 11, and the other end contacts the displacement sensor 16, which is used to transmit the bulging displacement change of the cylinder to the displacement sensor 16. Both the thermocouple 15 and the displacement sensor 16 are electrically connected to the multi-channel touch data logger. The thermocouple 15 is positioned 30mm from the outer side of the common concave mold 11 at its tip. The temperature measurement range of the thermocouple 15 is 0–1200℃. The displacement sensor 16 has a resolution of 5μm, a measurement range of 0–125mm, and an optional output DC current range of 4–20mA. It operates at temperatures from -50℃ to 120℃ and is not resistant to high temperatures. Therefore, a quartz rod is required to insulate the heat of the cylinder while transmitting the expansion displacement of the cylinder. The input signals of the multi-channel touch data logger include five types: DC current, DC voltage, resistance temperature detector (RTD), thermocouple, and remote pressure gauge. The range of DC current signals it accepts is 0–20mA, and the range of thermocouple temperatures it accepts is -200–1800℃.

[0053] The heating system includes an induction heating coil 17 and a high-frequency induction heater. The induction heating coil 17 is sleeved on the outer side of the inner cavity of the common concave mold 11. The high-frequency induction heater is electrically connected to the induction heating coil 17 and is used to control the output power of the induction heating coil 17. An insulation layer is attached to the outer side of the molds (lower mold 6, segmented mold 7, warm stretching upper mold 8, and hot air expansion forming upper mold 10), which both prevents the induction heating coil 17 from directly contacting the molds and provides insulation. The use of induction heating instead of an ambient heating furnace for the cylindrical component allows for rapid heating, significantly improving the heating rate.

[0054] A method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint, based on the aforementioned hot gas expansion forming device for a heat-resistant steel thin-walled multi-port ferrule joint, includes the following steps:

[0055] (1) The heat-resistant steel plate is installed in the warm drawing forming mold. After the mold is closed, the heat-resistant steel plate and the common concave mold 11 are heated to the warm drawing forming temperature by the heating system. The heat-resistant steel plate is drawn by the punch 1 at a uniform speed to form a warm drawing cylindrical part. During heating, the power current output of the high-frequency induction heater is adjusted. The induction heating coil 17 is used to heat the mold and the cylindrical part at a controllable heating rate. The temperature information is monitored and fed back by the thermocouple 15 in real time to adjust the current power to ensure a uniform temperature field of the cylindrical part. The rated output voltage of the power supply is 380V and the rated output current is 50A. The heating range of the cylindrical part is usually 600~700℃.

[0056] (2) Place the cylindrical part in the gas expansion forming mold. After the mold is closed, use the heating system to heat the cylindrical part and the common cavity mold 11 to the hot gas expansion forming temperature so that the cylindrical part is austenitized. During heating, adjust the power current output of the high frequency induction heater and use the induction heating coil 17 to rapidly heat the mold and the cylindrical part at a controllable heating rate.

[0057] (3) High pressure inert gas is introduced into the cylinder through the gas expansion forming-rapid gas quenching system to perform hot gas expansion forming and obtain the target shape forming component; when the high pressure inert gas is introduced, the pressure and pressurization rate of the high pressure inert gas are adjusted by adjusting the gas source control cabinet 14, and the displacement of the outer side of the cylinder wall convex is measured by the displacement sensor 16 until the cylinder undergoes plastic deformation and fits the mold.

[0058] (4) Quickly discharge the gas inside the formed component, and introduce high-pressure low-temperature inert gas into the formed component through the gas expansion forming-rapid gas quenching system to exchange hot and cold gases and perform rapid gas quenching on the formed component, so that the structure of the formed component is transformed into martensite; when introducing high-pressure low-temperature inert gas, the pressure and pressurization rate of the high-pressure low-temperature inert gas are adjusted by adjusting the gas source control cabinet 14 to control the cooling behavior, effectively improve the microstructure and achieve dimensional accuracy control.

[0059] (5) Discharge the compressed gas inside the forming component, remove the forming component, and cut off the excess at each interface to obtain a multi-port ferrule connector.

[0060] Figure 1 This is a schematic diagram illustrating the principle of the hot gas expansion forming process of the present invention, wherein, Figure 1Figure (a) shows the initial state after mold assembly; Figure (b) shows the warm stretching stage of the steel mold, where the punch presses down to form the cylindrical blank; Figure (c) shows the flexible gas hot expansion stage, where inert gas is introduced into the cylindrical blank located in the hot expansion mold to form the part features; Figure (d) shows the cold gas rapid quenching stage, where hot and cold gases are exchanged for rapid gas quenching. In Figures (a) and (b), the warm stretching die 19 is placed on the heat insulation plate 18, and the warm stretching die 19 is heated by the induction coil 20. The blank is heated by the heating element 21, and the punch 22 cooperates with the warm stretching die 19 to perform warm stretching forming. In Figures (c) and (d), the hot gas expansion die 23 is placed on the heat insulation plate 18, and the hot gas expansion die 23 is heated by the induction coil 20, followed by hot gas expansion forming and cold gas rapid quenching.

[0061] Figure 2 This is a schematic diagram of the hot gas expansion forming process in this invention. The curves represent the temperature changes from room temperature to the warm drawing stage, then to the hot gas expansion forming stage, and finally rapid gas quenching. Schematic diagrams of the microstructure transformation at each stage are shown below the curves. RT represents room temperature, and T... a T is the austenitic phase transformation temperature. b T is the martensitic phase transformation temperature. m It is the melting point temperature, <0.6T m This is the upper limit of the temperature in the medium-temperature forming zone.

[0062] Figure 3 This is a flowchart of the hot gas expansion forming process in this invention, which summarizes the method for obtaining a multi-port ferrule connector by hot gas expansion forming in this invention.

[0063] Figure 8 The figures show the room temperature and high temperature unidirectional mechanical property curves of the heat-resistant stainless steel in this invention. They are the room temperature (25℃), high temperature (950℃), and high temperature (1000℃) unidirectional mechanical property curves, respectively. The heat-resistant stainless steel has extremely poor room temperature plasticity and good high temperature plasticity.

[0064] The warm-drawn cylindrical blank is a circular steel plate with a diameter of 120mm; the outer diameter of the cylinder is 82mm; and the wall thickness of the cylinder is 1mm.

[0065] The material of the deep drawing die is 3Cr24Ni7N, and the operating temperature range is 25~1100℃.

[0066] When the heat-resistant steel plate is martensitic heat-resistant steel, in step (1), the warm stretching forming temperature is 600℃~0.6T. m Melting point temperature T m The temperature range is 1400~1440℃, the heating rate is 25~30℃ / s, and the speed at which the punch 1 presses down uniformly is 100~200mm / s.

[0067] When the heat-resistant steel plate is martensitic heat-resistant steel, in step (2), the hot gas expansion forming temperature is 1000~1100℃, and the heating rate is 40~50℃ / s. During the hot gas expansion forming process, the blank holder force of the gas expansion mold is 30~50KN, and the forming force is 20~50KN. The gas pressure of the cylinder is 0.1~20MPa.

[0068] In step (3), the pressure of the high-pressure inert gas introduced is 15-20 MPa and the pressurization rate is 0.5-1 MPa / s; in step (4), the pressure of the high-pressure low-temperature inert gas introduced is 15-20 MPa and the cooling rate is 5-10 °C / s; in steps (3) and (4), the inert gas is nitrogen, helium or argon.

[0069] In step (4), a constant pressure environment is maintained inside the formed component during the gas quenching process. It is preferable to use room temperature high-pressure nitrogen for gas quenching to avoid pressure changes caused by elastic deformation of the formed component.

[0070] When the billet material is martensitic precipitation hardening heat-resistant steel, the warm drawing temperature is 600-700℃, and the hot gas expansion forming temperature is 1020-1060℃.

[0071] The microstructure of martensitic precipitation-hardening heat-resistant steel is formed by the complete solution treatment of stainless steel to create supersaturated quenched martensite, a metastable structure. After high-temperature solution treatment, carbides dissolve, alloying elements homogenize, and the heat-resistant steel undergoes an austenitic transformation. Following rapid cooling, the heat-resistant steel undergoes a martensitic transformation, and alloying elements in the supersaturated martensite precipitate as carbides and intermetallic compounds as second-phase particles, forming dispersed particles. This hinders dislocation movement within the crystals, strengthening the material and increasing its strength and hardness, while slightly decreasing its plasticity and toughness. Therefore, introducing integrated forming and heat treatment technology into the forming process of thin-walled multi-port compression fittings ensures the microstructure, properties, and precision of the formed parts.

[0072] The following describes the forming method of the heat-resistant steel thin-walled multi-port ferrule joint of the present invention, taking 0Cr17Ni4Cu4Nb heat-resistant steel as an example, including the following steps:

[0073] Step 1: Install the heat-resistant steel plate in the warm drawing mold. After the mold is closed, energize the induction heating coil 17. Use the induction heating system to adjust the power current output to control the heating power. Heat the heat-resistant steel plate and the mold to 650℃ at a heating rate of 30℃ / s and keep it at that temperature for 5 minutes to make the temperature uniform.

[0074] Step 2: Press the punch 1 down at a constant speed of 200 mm / s to form a warm-drawn cylindrical part;

[0075] Step 3: Place the cylinder in the air-expansion forming mold, close the mold and energize the induction heating coil 17. Use the induction heating system to adjust the power current output to control the heating power and rapidly heat the cylinder to 1050℃ at a heating rate of 50℃ / s. Hold the temperature for 5 minutes to make the temperature uniform and reduce the oxidation of the cylinder surface caused by open heating.

[0076] Step 4: After the cylinder is heated, argon gas is introduced through the gas source control cabinet 14. The gas pressure is 20MPa and the pressurization rate is 1MPa / s. During the expansion process, the temperature and pressure inside the cylinder are maintained. After the cylinder undergoes elastic deformation, it adheres to the mold and forms a circumferential multi-channel convex shape.

[0077] Step 5: Adjust the argon gas filling through the gas source control cabinet 14 to perform hot and cold gas conversion. By controlling the filling gas temperature and rate, the mold is cooled at a rate of 5℃ / s for quenching.

[0078] Step 6: Open the exhaust valve to release the compressed gas inside the sealed parts;

[0079] Step 7: Mold opening. By splitting the segmented mold 7, the bulging part is removed, and the excess at each interface is cut off to obtain the multi-port ferrule connector.

[0080] The heat-resistant steel plate material in step one is 0Cr17Ni4Cu4Nb, with the following chemical composition: C≤0.07%, Si≤1.00%, Mn≤1.00%, Mo≤0.50%, P≤0.035%, S≤0.025%, Ni: 3.00%~5.00%, Cr: 15.0%~17.5%, Cu: 3.00%~5.00%, Nb+Ta: 0.15%~0.45%.

[0081] The heat-resistant steel thin-walled multi-port ferrule joint hot gas expansion forming device and method provided by the present invention can greatly improve heating efficiency and shorten the experimental cycle by heating with an external induction coil. The integrated process of hot forming and rapid gas quenching can significantly shorten the process cycle while ensuring the microstructure and dimensional accuracy of the cylinder.

[0082] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint, characterized in that, The process is carried out using a heat-resistant steel thin-walled multi-port ferrule hot air expansion forming device, which includes a mold clamping press, a warm drawing forming mold, an air expansion forming mold, a heating system, and an air expansion forming-rapid air quenching system. The mold-closing press includes a press and a punch. The press includes a lower table and an upper table and a slider that independently control the loading force and pressing speed. The punch is fixedly mounted on the slider to form a temperature-stretched cylindrical part. The warm drawing forming die includes a lower heat insulation plate, a lower die, a segmented die, and a warm drawing upper die. The air expansion forming die includes the lower heat insulation plate, the lower die, the segmented die, the upper heat insulation plate, and a hot air expansion forming upper die. The lower heat insulation plate is fixedly disposed on the lower platform. The lower die is disposed on the lower heat insulation plate. The segmented die is disposed on the lower die and forms a common concave die with the lower die for warm drawing of the cylindrical blank and air expansion forming of the cylindrical part. The warm drawing upper die cooperates with the segmented die and is fixedly disposed on the upper platform to provide blank holder force during warm drawing. The upper heat insulation plate is fixedly disposed on the slider. The hot air expansion forming upper die cooperates with the segmented die and is fixedly disposed on the upper heat insulation plate to provide blank holder force during air expansion forming. The hot air expansion forming upper die is provided with a gas channel communicating with the inner cavity of the common concave die. The heating system is used to heat and control the required temperatures of the common die, blank, and cylinder during the warm stretching and air-expansion forming processes. The air expansion forming-rapid air quenching system includes a compressed air source and an air source control cabinet. The compressed air source is connected to the gas channel through the air source control cabinet. The air source control cabinet is used to control the injection of compressed gas into the cylinder during hot air expansion forming and to perform rapid exchange of hot and cold gas in the cylinder after hot air expansion forming. Includes the following steps: (1) The heat-resistant steel plate is installed in the warm drawing forming mold. After the mold is closed, the heat-resistant steel plate and the common die are heated to the warm drawing forming temperature by the heating system. The heat-resistant steel plate is warmly drawn by the punch pressing down at a constant speed to form a warm drawing cylinder. (2) The cylindrical part is placed in the gas forming mold. After the mold is closed, the heating system is used to heat the cylindrical part and the common cavity mold to the hot gas forming temperature, so that the microstructure of the cylindrical part is austenitized. (3) High-pressure inert gas is introduced into the cylinder through the gas expansion forming-rapid gas quenching system to perform hot gas expansion forming and obtain the target shape forming component; (4) Quickly discharge the gas inside the formed component, and introduce high-pressure low-temperature inert gas into the formed component through the gas expansion forming-rapid gas quenching system to exchange hot and cold gases, and perform rapid gas quenching on the formed component to transform the structure of the formed component into martensite; (5) Discharge the compressed gas inside the forming component, remove the forming component, and cut off the excess at each interface to obtain a multi-port ferrule connector.

2. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 1, characterized in that: When the heat-resistant steel plate is martensitic heat-resistant steel, in step (1), the warm stretching forming temperature is 600℃~0.6T. m Melting point temperature T m The temperature range is 1400–1440℃, the heating rate is 25–30℃ / s, and the speed at which the punch presses down uniformly is 100–200 mm / s.

3. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 2, characterized in that: In step (2), the hot gas expansion forming temperature is 1000-1100℃ and the heating rate is 40-50℃ / s.

4. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 1, characterized in that: In step (3), the pressure of the high-pressure inert gas introduced is 15-20 MPa and the pressurization rate is 0.5-1 MPa / s; in step (4), the pressure of the high-pressure low-temperature inert gas introduced is 15-20 MPa and the cooling rate is 5-10 °C / s; in steps (3) and (4), the inert gas is nitrogen, helium or argon.

5. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 1, characterized in that: In step (4), a constant pressure environment is maintained inside the formed component throughout the gas quenching process.

6. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 3, characterized in that: When the heat-resistant steel plate is a martensitic precipitation hardening type heat-resistant steel, the warm stretching forming temperature is 600-700℃, and the hot gas expansion forming temperature is 1020-1060℃.

7. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 1, characterized in that: The heat-resistant steel thin-walled multi-port ferrule hot gas expansion forming device also includes a temperature and displacement measurement system, which is used to measure the temperature signal inside the common die and the expansion displacement of the inner cylinder of the common die.

8. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 7, characterized in that: The temperature and displacement measurement system includes a thermocouple, a quartz rod, a displacement sensor, and a multi-channel touch data logger. The thermocouple is mounted on the segmented mold and is used to measure the temperature signal inside the common concave mold. The quartz rod and the displacement sensor are both mounted on the segmented mold. One end of the quartz rod contacts the outer wall of the inner cylinder of the common concave mold, and the other end contacts the displacement sensor, for transmitting the bulging displacement change of the cylinder to the displacement sensor. Both the thermocouple and the displacement sensor are electrically connected to the multi-channel touch data logger.

9. The method for hot gas expansion forming of a heat-resistant steel thin-walled multi-port ferrule joint according to claim 1, characterized in that: The heating system includes an induction heating coil and a high-frequency induction heater. The induction heating coil is sleeved on the outside of the common concave cavity, and the high-frequency induction heater is electrically connected to the induction heating coil to control the output power of the induction heating coil.

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