Preparation method of multi-principal alloy high-pressure oil pipe

Abstract

The invention discloses a preparation method of a multi-principal alloy high-pressure oil pipe, and the method comprises the following steps: S1: mechanical grinding, mixing Fe powder, Co powder, Cr powder, Cu powder and Si powder and grinding to obtain a mixed powder; the atomic percentages of Fe powder, Co powder, Cr powder, Cu powder and Si powder are 65-x:20:10:5:x, and the range of x is 1-5; S2: green billet molding, pouring the mixed powder into a molding mold and pressing to form a FeCoCrCuSi metal green billet; S3: microwave sintering, sintering the FeCoCrCuSi metal green billet obtained in step S2 into a FeCoCrCuSi multi-principal alloy ingot by microwave heating; S4: tempering heat treatment, performing tempering heat treatment on the FeCoCrCuSi multi-principal alloy ingot; S5: cryogenic treatment, machining a center hole on the FeCoCrCuSi multi-principal alloy ingot and then placing it in liquid nitrogen for cryogenic treatment; S6: cold extrusion, performing cold extrusion on the FeCoCrCuSi multi-principal alloy ingot to make a pipe fitting. The present invention can improve the fatigue strength of the pipe fittings, so that the pipe fittings can be suitable for a working pressure of 200 MPa, and can also improve the wear resistance of the pipe fittings, reduce wear and tear, and extend the service life.

Description

Technical Field

[0001] The invention relates to a method for preparing a multi-principal-element alloy high-pressure oil pipe. Background Art

[0002] At present, my country's green, low-carbon, circular economic system and clean, low-carbon, safe and efficient energy system have been fully established, and green environmental protection has become a key technology in the engine industry. New engines must use high-pressure common rail technology to improve fuel economy and reduce emissions. In the common rail fuel system, the working pressure of the injection system can reach up to 200MPa, which is 3 times higher than that of traditional diesel engines. Among them, the high-pressure oil pipe needs to withstand the high-frequency and high-pressure pulse impact of the fuel, and fatigue cracks often occur, causing engine failure. Moreover, the high-pressure oil pipe is susceptible to friction between the piston and the oil, and is easily worn, which affects the service life of the high-pressure oil pipe.

[0003] At present, the domestic steel grades 16Mn and 16MnV are mainly used to make high-pressure oil pipes. The fatigue strength of high-pressure oil pipes made of 16Mn and 16MnV steels is not high enough, and they can only be used for working pressures below 160MPa, and cannot meet the 200MPa working pressure requirements of the common rail fuel system. In addition, 16Mn and 16MnV steels cannot meet the wear resistance requirements of high-pressure oil pipes, and are easily worn during use, which will affect the service life.

[0004] A Chinese patent with publication number CN101474641 discloses a production process for high-pressure oil pipes, in which the tube blanks are subjected to multiple pickling, phosphating, lubrication, cold drawing and intermediate heat treatment processes, and finally oxygen-free heat treatment. However, the fatigue strength and wear resistance of the high-pressure oil pipes produced by this process are not high enough, and they cannot be used for the working pressure of 200MPa in the common rail fuel system, nor can they meet the wear resistance requirements. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for preparing a multi-principal alloy high-pressure oil pipe, which can improve the fatigue strength of the pipe fittings, make the pipe fittings suitable for a working pressure of 200MPa, and can also improve the wear resistance of the pipe fittings, reduce wear and extend the service life.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a method for preparing a multi-principal alloy high-pressure oil pipe, the method comprising the following steps:

[0007] S1: mechanical grinding, mixing Fe powder, Co powder, Cr powder, Cu powder and Si powder and obtaining a mixed powder by mechanical grinding; wherein the atomic percentage of Fe powder, Co powder, Cr powder, Cu powder and Si powder is 65-x:20:10:5:x, and the range of x is 1 to 5;

[0008] S2: green body forming, pouring the mixed powder in step S1 into a forming mold and pressing to form a FeCoCrCuSi metal green body;

[0009] S3: microwave sintering, sintering the FeCoCrCuSi metal green body obtained in step S2 into a FeCoCrCuSi multi-principal alloy ingot by microwave heating;

[0010] S4: tempering heat treatment, using supersonic flame to temper the FeCoCrCuSi multi-principal alloy ingot obtained in step S3 under the protection of inert gas;

[0011] S5: cryogenic treatment, machining a center hole on the FeCoCrCuSi multi-principal alloy ingot after tempering heat treatment, and then placing it in liquid nitrogen for cryogenic treatment;

[0012] S6: cold extrusion, cold extruding the FeCoCrCuSi multi-principal alloy ingot after deep cryogenic treatment to make a pipe fitting.

[0013] Furthermore, in step S1, Fe powder, Co powder, Cr powder, Cu powder and Si powder are all single powders with a purity of 99.99% and a particle size of 200-400 μm, and the particle size of the mixed powder obtained after grinding is 35-80 μm.

[0014] A specific operation of step S2 is further provided. The specific operation of step S2 is: first, a molding die for molding is installed on a tablet press, and then a lubricating liquid is sprayed into the inner cavity of the molding die. After the lubricating liquid is naturally air-dried, the mixed powder is poured into the molding die and molded to obtain a cylindrical FeCoCrCuSi metal green body.

[0015] Furthermore, the lubricating liquid sprayed into the molding die is an aqueous emulsion of molybdenum disulfide particles and graphite particles.

[0016] A specific operation of step S3 is further provided. The specific operation of step S3 is: placing the obtained FeCoCrCuSi metal green body in a ceramic mold and sintering the FeCoCrCuSi metal green body into a FeCoCrCuSi multi-principal alloy ingot using a microwave melting device.

[0017] Furthermore, the ceramic mold is made of a wave-transmitting composite material, which contains 80% SiO2 and 20% MgO;

[0018] The microwave heating power in the microwave smelting equipment is 20 kW, the frequency is 300 MHz, the vacuum degree is less than 0.01 Pa, and the process temperature is 1400-1500°C.

[0019] Further, in step S4, the inert gas is argon with a purity of 99.99%, the distance between the center of the supersonic flame and the FeCoCrCuSi multi-principal alloy ingot is 10-20 mm, the moving speed of the supersonic flame is 0.5 m / min, the rotation speed of the FeCoCrCuSi multi-principal alloy ingot is 2-3 r / s, and the raw materials of the supersonic flame are 60% aviation kerosene and 40% oxygen.

[0020] Further, in step S5, the FeCoCrCuSi multi-principal alloy ingot is cryogenically treated in liquid nitrogen for 12 hours.

[0021] Further, in step S6, the FeCoCrCuSi multi-principal alloy ingot is placed in an extruder for cold extrusion after deep cryogenic treatment to form a pipe fitting, the extrusion method is double-action reverse extrusion, the extrusion speed is 2 to 5 mm / s, and the extrusion temperature range is -196 to -60°C.

[0022] Furthermore, the wall thickness of the pipe formed by cold extrusion in step S6 is 0.8-1.5 mm.

[0023] After adopting the above technical solution, the pipe fittings made by the method of the present invention can be used as high-pressure oil pipes. The material of the pipe fittings is a multi-principal alloy. The composition of the pipe fittings is designed by the multi-principal theory, and the stacking fault energy of the alloy is controlled to be 10-18 J / cm by adjusting the atomic percentage of Fe and Si. 2 . Firstly, a cryogenic treatment is performed and then a thin-walled pipe is made by a cold extrusion process. The material is subjected to cold plastic deformation by low-temperature cold extrusion to activate intracrystalline deformation twins, so that a large number of high-density gradient nano twins are contained inside the grains of the pipe. The size of the high-density gradient nano twins is 2 to 10 nanometers. The nano twins have an inhibitory effect on the extension of fatigue crack tips, thereby improving the fatigue strength and fatigue life of the pipe, making the pipe suitable for a working pressure of 200MPa in a common rail fuel system, and solving the problem of multiple deformation mechanisms such as the inability to activate deformation twins during the cold deformation of existing steel pipes.

[0024] In addition, in the structure of the pipe fittings prepared by the method of the present invention, the Si element with a small atomic radius is dissolved in the large atomic gaps, and the lattice distortion improves the hardness of the pipe fittings, improves the wear resistance of the pipe fittings, reduces wear during use, and extends the service life of the pipe fittings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a TEM image of the microstructure of the pipe prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a multi-principal alloy high-pressure oil pipe. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It should be particularly pointed out that all similar replacements and modifications are obvious to those skilled in the art, and they all fall within the scope of protection of the present invention. The method of the present invention has been described through a preferred embodiment, and relevant personnel can obviously modify or appropriately change and combine the method of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0027] The present invention provides a method for preparing a multi-principal alloy high-pressure oil pipe, the method comprising the following steps:

[0028] S1: mechanical grinding, mixing Fe powder, Co powder, Cr powder, Cu powder and Si powder and obtaining a mixed powder by mechanical grinding; wherein the atomic percentage of Fe powder, Co powder, Cr powder, Cu powder and Si powder is 65-x:20:10:5:x, and the range of x is 1 to 5;

[0029] S2: green body forming, pouring the mixed powder in step S1 into a forming mold and pressing to form a FeCoCrCuSi metal green body;

[0030] S3: microwave sintering, sintering the FeCoCrCuSi metal green body obtained in step S2 into a FeCoCrCuSi multi-principal alloy ingot by microwave heating;

[0031] S4: tempering heat treatment, using supersonic flame to temper the FeCoCrCuSi multi-principal alloy ingot obtained in step S3 under the protection of inert gas;

[0032] S5: cryogenic treatment, machining a center hole on the FeCoCrCuSi multi-principal alloy ingot after tempering heat treatment, and then placing it in liquid nitrogen for cryogenic treatment;

[0033] S6: cold extrusion, cold extruding the FeCoCrCuSi multi-principal alloy ingot after deep cryogenic treatment to make a pipe fitting.

[0034] Specifically, the pipe fittings prepared by the method of the present invention can be used as high-pressure oil pipes. The material of the pipe fittings is a multi-principal alloy. The composition of the pipe fittings is designed by the multi-principal element theory, and the stacking fault energy of the alloy is controlled to be 10-18 J / cm by adjusting the atomic percentage of Fe and Si. 2 Firstly, the thin-walled pipe is made by deep cryogenic treatment and then cold extrusion. The material is cold-plastically deformed by low-temperature cold extrusion to activate intracrystalline deformation twins, so that the grains of the pipe contain a large number of high-density gradient nano twins, such as Figure 1As shown, the size of the high-density gradient nano twins is 2 to 10 nanometers, and the nano twins have an inhibitory effect on the extension of the fatigue crack tip, which can improve the fatigue strength and fatigue life of the pipe fittings, so that the pipe fittings can be suitable for the working pressure of 200MPa in the common rail fuel system, and solve the problem that the deformation twins and other deformation mechanisms cannot be activated during the cold deformation of the existing steel pipes. In addition, in the structure of the pipe fittings prepared by the method of the present invention, the Si element with a small atomic radius is dissolved into the large atomic gap, and the lattice distortion improves the hardness of the pipe fittings, the wear resistance is better, the wear resistance of the pipe fittings is improved, the wear during use is reduced, and the service life of the pipe fittings is extended.

[0035] More specifically, the pipe fittings produced by the molding process in step S2 and the microwave sintering process in step S3 have high dimensional accuracy and high production efficiency, solving the problem of complex current high-pressure oil pipe drawing process.

[0036] Furthermore, in step S1, Fe powder, Co powder, Cr powder, Cu powder and Si powder are all single powders with a purity of 99.99% and a particle size of 200-400 μm, and the particle size of the mixed powder obtained after grinding is 35-80 μm.

[0037] Further, the specific operation of step S2 is: first, the molding die for molding is installed on the tablet press, and then the lubricating liquid is sprayed into the inner cavity of the molding die, and after the lubricating liquid is naturally air-dried, the mixed powder is poured into the molding die and molded to obtain a cylindrical FeCoCrCuSi metal green body. Among them, the inner diameter of the molding die is φ80mm, the outer diameter is φ85mm, the inner cavity depth is 800mm, the size of the cylindrical FeCoCrCuSi metal green body obtained by molding is φ80×700mm, the molding pressure of the tablet press is 30KN, and the tablet press is an existing device, and its specific structure is not repeated in this embodiment.

[0038] Furthermore, the lubricating liquid sprayed into the molding die is an aqueous emulsion of molybdenum disulfide particles and graphite particles.

[0039] Further, the specific operation of step S3 is: placing the obtained FeCoCrCuSi metal green body in a ceramic mold and sintering the FeCoCrCuSi metal green body into a FeCoCrCuSi multi-principal alloy ingot using a microwave smelting device. The ceramic mold is made of a wave-transmitting composite material, which contains 80% SiO2 and 20% MgO; the microwave heating power in the microwave smelting device is 20kW, the frequency is 300MHz, the vacuum degree is less than 0.01Pa, and the process temperature is 1400-1500℃.

[0040] Further, in step S4, the inert gas is argon with a purity of 99.99%, the distance between the center of the supersonic flame and the FeCoCrCuSi multi-principal alloy ingot is 10-20 mm, the moving speed of the supersonic flame is 0.5 m / min, the rotation speed of the FeCoCrCuSi multi-principal alloy ingot is 2-3 r / s, and the raw materials of the supersonic flame are 60% aviation kerosene and 40% oxygen.

[0041] Further, in step S5, the diameter of the central hole machined on the FeCoCrCuSi multi-principal alloy ingot is φ10 mm, and the FeCoCrCuSi multi-principal alloy ingot is cryogenically treated in liquid nitrogen for 12 hours.

[0042] Further, in step S6, the FeCoCrCuSi multi-principal alloy ingot is placed in an extruder for cold extrusion after deep cryogenic treatment to form a pipe fitting, the extrusion method is double-action reverse extrusion, the extrusion speed is 2 to 5 mm / s, and the extrusion temperature range is -196 to -60°C.

[0043] Furthermore, the wall thickness of the pipe made by cold extrusion in step S6 is 0.8-1.5 mm, and the thin wall thickness of the pipe can meet the requirements of lightweight design. After testing, the fatigue strength of the pipe made by the method of the present invention can reach more than 620 MPa, the hardness can reach more than 6.5 GPa, and the wear rate is less than 6.33×10 -4 mm 3 / (N·mm), using the pipe fitting as a high-pressure oil pipe can reduce fatigue damage and cracking of the high-pressure oil pipe, and can be applied to the working pressure of 200MPa in the common rail fuel system, which has broad application prospects.

[0044] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments.

[0045] Example 1

[0046] A method for preparing a multi-principal alloy high-pressure oil pipe, the method comprising the following steps:

[0047] S1: Mechanical grinding, mixing Fe powder, Co powder, Cr powder, Cu powder and Si powder according to the atomic percentage of 64:20:10:5:1 and obtaining a mixed powder with a particle size of 35 to 80 μm by mechanical grinding; wherein the Fe powder, Co powder, Cr powder, Cu powder and Si powder are all single substance powders with a purity of 99.99% and a particle size of 200 to 400 μm;

[0048] S2: green body molding, taking a molding die with an inner diameter of φ80 mm, an outer diameter of φ85 mm, and an inner cavity depth of 800 mm, installing the molding die on a tablet press, spraying a lubricating liquid into the inner cavity of the molding die, and pouring the mixed powder in step S1 into the molding die after the lubricating liquid is naturally air-dried, and then molding at a molding pressure of 30 KN to obtain a cylindrical FeCoCrCuSi metal green body of φ80×700 mm; wherein the lubricating liquid is an aqueous emulsion of molybdenum disulfide particles and graphite particles;

[0049] S3: Microwave sintering, placing the obtained FeCoCrCuSi metal green body in a ceramic mold, and using a microwave melting device to sinter the FeCoCrCuSi metal green body obtained in step S2 into a FeCoCrCuSi multi-principal alloy ingot by microwave heating; wherein the material of the ceramic mold is a wave-transmitting composite material containing 80% SiO2 and 20% MgO, the microwave heating power in the microwave melting device is 20kW, the frequency is 300MHz, the vacuum degree is less than 0.01Pa, and the process temperature is 1400°C;

[0050] S4: tempering heat treatment, using a supersonic flame to temper the FeCoCrCuSi multi-principal alloy ingot obtained in step S3 under the protection of argon gas with a purity of 99.99%; wherein the distance between the center of the supersonic flame and the FeCoCrCuSi multi-principal alloy ingot is 10 mm, the moving speed of the supersonic flame is 0.5 m / min, the rotation speed of the FeCoCrCuSi multi-principal alloy ingot is 2 r / s, and the raw materials of the supersonic flame are 60% aviation kerosene and 40% oxygen;

[0051] S5: cryogenic treatment, machining a central hole with a diameter of φ10 mm on the FeCoCrCuSi multi-principal alloy ingot after tempering heat treatment, and then placing it in liquid nitrogen for cryogenic treatment for 12 hours;

[0052] S6: cold extrusion, placing the FeCoCrCuSi multi-principal alloy ingot after deep cryogenic treatment into an extruder for cold extrusion to form a pipe fitting with a wall thickness of 1.5 mm; wherein the extrusion method is double-action reverse extrusion, the extrusion speed is 2 mm / s, and the extrusion temperature range is -196 to -60°C.

[0053] It has been detected that the size of the high-density gradient nano twins in the pipe prepared in this embodiment is 2 to 10 nanometers.

[0054] The pipe fittings prepared in this embodiment were tested using the following test methods and the measured fatigue strength, wear rate and hardness are listed in Table 1. The specific method is as follows:

[0055] Fatigue strength test method: The prepared pipe fittings were cut into 300 mm lengths and installed on fatigue test equipment for fatigue testing, and the measured fatigue strengths are listed in Table 1. The high-frequency pulse power source in the fatigue test equipment provides sufficiently high fuel pressure to the pipe fittings, and the opening pressure of the pressure relief device in the fatigue test equipment is set to 100 bar. The high-frequency pulse power source parameters and the opening and closing of the pressure relief device are controlled to provide the pipe fittings with high-frequency and high-amplitude fluctuating oil pressure.

[0056] Wear rate test method: Take a sample with a size of 20mm*20mm from the prepared pipe fitting, use a friction and wear tester to perform a wear resistance test on the sample to measure the wear rate, and the test results are listed in Table 1.

[0057] Hardness test method: A nano indenter was used to test the hardness of the pipe, and the test results are listed in Table 1.

[0058] Example 2

[0059] The preparation method of this embodiment is basically the same as the preparation method of the multi-principal alloy high-pressure oil pipe in Example 1, and the only difference from Example 1 is that in step S1 of this embodiment, Fe powder, Co powder, Cr powder, Cu powder and Si powder are mixed in an atomic percentage of 63:20:10:5:2 and mechanically ground to obtain a mixed powder with a particle size of 35 to 80 μm.

[0060] It has been detected that the size of the high-density gradient nano twins in the pipe prepared in this embodiment is 2 to 10 nanometers.

[0061] The pipe fittings prepared in this example were tested using the test method described in Example 1 and the measured fatigue strength, wear rate and hardness are listed in Table 1.

[0062] Example 3

[0063] The preparation method of this embodiment is basically the same as the preparation method of the multi-principal alloy high-pressure oil pipe in Example 1, and the only difference from Example 1 is that in step S1 of this embodiment, Fe powder, Co powder, Cr powder, Cu powder and Si powder are mixed in an atomic percentage of 62:20:10:5:3 and mechanically ground to obtain a mixed powder with a particle size of 35 to 80 μm.

[0064] It has been detected that the size of the high-density gradient nano twins in the pipe prepared in this embodiment is 2 to 10 nanometers.

[0065] The pipe fittings prepared in this example were tested using the test method described in Example 1 and the measured fatigue strength, wear rate and hardness are listed in Table 1.

[0066] Example 4

[0067] The preparation method of this embodiment is basically the same as the preparation method of the multi-principal alloy high-pressure oil pipe in Example 1, and the only difference from Example 1 is that in step S1 of this embodiment, Fe powder, Co powder, Cr powder, Cu powder and Si powder are mixed in an atomic percentage of 61:20:10:5:4 and mechanically ground to obtain a mixed powder with a particle size of 35 to 80 μm.

[0068] It has been detected that the size of the high-density gradient nano twins in the pipe prepared in this embodiment is 2 to 10 nanometers.

[0069] The pipe fittings prepared in this example were tested using the test method described in Example 1 and the measured fatigue strength, wear rate and hardness are listed in Table 1.

[0070] Example 5

[0071] The preparation method of this embodiment is basically the same as the preparation method of the multi-principal alloy high-pressure oil pipe in Example 1, and the only difference from Example 1 is that in step S1 of this embodiment, Fe powder, Co powder, Cr powder, Cu powder and Si powder are mixed in an atomic percentage of 60:20:10:5:5 and mechanically ground to obtain a mixed powder with a particle size of 35 to 80 μm.

[0072] It has been detected that the size of the high-density gradient nano twins in the pipe prepared in this embodiment is 2 to 10 nanometers.

[0073] The pipe fittings prepared in this example were tested using the test method described in Example 1 and the measured fatigue strength, wear rate and hardness are listed in Table 1.

[0074] Example 6

[0075] The preparation method of this embodiment is basically the same as the preparation method of the multi-principal component alloy high-pressure oil pipe in Example 1, and the only difference from Example 1 is that: the process temperature in step S3 is 1500°C, the distance between the supersonic flame center and the FeCoCrCuSi multi-principal component alloy ingot in step S4 is 20mm, the rotation speed of the FeCoCrCuSi multi-principal component alloy ingot is 3r / s, and the FeCoCrCuSi multi-principal component alloy ingot after deep freezing treatment in step S6 is placed in an extruder for cold extrusion to form a pipe fitting with a wall thickness of 0.8mm; wherein, the extrusion speed is 5mm / s.

[0076] It has been detected that the size of the high-density gradient nano twins in the pipe prepared in this embodiment is 2 to 10 nanometers.

[0077] The pipe fittings prepared in this example were tested using the test method described in Example 1 and the measured fatigue strength, wear rate and hardness are listed in Table 1.

[0078] Example 7

[0079] The preparation method of this embodiment is basically the same as the preparation method of the multi-principal component alloy high-pressure oil pipe in Example 1, and the only difference from Example 1 is that: the process temperature in step S3 is 1450°C, the distance between the supersonic flame center and the FeCoCrCuSi multi-principal component alloy ingot in step S4 is 15mm, the rotation speed of the FeCoCrCuSi multi-principal component alloy ingot is 2.5r / s, and the FeCoCrCuSi multi-principal component alloy ingot after deep freezing treatment in step S6 is placed in an extruder for cold extrusion to form a pipe fitting with a wall thickness of 1.1mm; wherein, the extrusion speed is 3.5mm / s.

[0080] It has been detected that the size of the high-density gradient nano twins in the pipe prepared in this embodiment is 2 to 10 nanometers.

[0081] The pipe fittings prepared in this example were tested using the test method described in Example 1 and the measured fatigue strength, wear rate and hardness are listed in Table 1.

[0082] Comparative Example 1

[0083] The preparation method of this comparative example is basically the same as the preparation method of the multi-principal alloy high-pressure oil pipe in Example 1, and the only difference from Example 1 is that in step S1 of this comparative example, Fe powder, Co powder, Cr powder, Cu powder and Si powder are mixed in an atomic percentage of 55:20:10:5:10 and mechanically ground to obtain a mixed powder with a particle size of 35 to 80 μm.

[0084] The size of the high-density gradient nano twins in the pipe prepared in this comparative example was tested to be 80 to 120 nanometers.

[0085] The pipe fittings prepared in this comparative example were tested using the test method described in Example 1 and the measured fatigue strength, wear rate and hardness are listed in Table 1.

[0086] Comparative Example 2

[0087] A high-pressure oil pipe made of 16Mn steel was purchased from the market, and the purchased high-pressure oil pipe was tested using the test method described in Example 1. The measured fatigue strength, wear rate and hardness are listed in Table 1.

[0088] Table 1

[0089]

[0090] As can be seen from the above table, Examples 1 to 7 use the atomic percentages of chemical elements specified in the technical solution of the present invention and are produced according to the preparation method provided by the present invention. The fatigue strength of the pipes prepared in Examples 1 to 7 can reach above 620 MPa, the hardness can reach above 6.5 GPa, and the wear rate is less than 6.33×10 -4 mm 3 / (N·mm), using the pipe fittings as high-pressure oil pipes can reduce fatigue damage and cracking of high-pressure oil pipes, can be suitable for a working pressure of 200MPa in a common rail fuel system, can also improve the wear resistance of the pipe fittings, reduce wear, and extend service life, and has broad application prospects.

[0091] The specific embodiments described above further illustrate the technical problems, technical solutions and beneficial effects solved by the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a multi-principal alloy high-pressure oil pipe, characterized in that: The steps of the method include: S1: mechanical grinding, mixing Fe powder, Co powder, Cr powder, Cu powder and Si powder and obtaining a mixed powder by mechanical grinding; wherein the atomic percentage of Fe powder, Co powder, Cr powder, Cu powder and Si powder is 65-x:20:10:5:x, and the range of x is 1-5; S2: green body forming, pouring the mixed powder in step S1 into a forming mold and pressing to form a FeCoCrCuSi metal green body; S3: microwave sintering, sintering the FeCoCrCuSi metal green body obtained in step S2 into a FeCoCrCuSi multi-principal alloy ingot by microwave heating; S4: tempering heat treatment, using supersonic flame to temper the FeCoCrCuSi multi-principal alloy ingot obtained in step S3 under the protection of inert gas; S5: cryogenic treatment, machining a center hole on the FeCoCrCuSi multi-principal alloy ingot after tempering heat treatment, and then placing it in liquid nitrogen for cryogenic treatment; S6: cold extrusion, cold extruding the FeCoCrCuSi multi-principal alloy ingot after deep cryogenic treatment to form a pipe fitting; Wherein, in step S1, Fe powder, Co powder, Cr powder, Cu powder and Si powder are all single powders with a purity of 99.99% and a particle size of 200-400 μm, and the particle size of the mixed powder obtained after grinding is 35-80 μm; The specific operation of step S2 is as follows: firstly, the molding die for molding is installed on the tablet press, and then the lubricating liquid is sprayed into the inner cavity of the molding die, and after the lubricating liquid is naturally air-dried, the mixed powder is poured into the molding die and molded to obtain a cylindrical FeCoCrCuSi metal green body.

2. The method for preparing a multi-principal alloy high-pressure oil pipe according to claim 1, characterized in that: The lubricating liquid sprayed into the forming die is an aqueous emulsion of molybdenum disulfide particles and graphite particles.

3. The method for preparing a multi-principal alloy high-pressure oil pipe according to claim 1, characterized in that: The specific operation of step S3 is: placing the obtained FeCoCrCuSi metal green body in a ceramic mold and sintering the FeCoCrCuSi metal green body into a FeCoCrCuSi multi-principal alloy ingot using a microwave melting device.

4. The method for preparing a multi-principal alloy high-pressure oil pipe according to claim 3, characterized in that: The ceramic mold is made of a wave-transmitting composite material, which contains 80% SiO2 and 20% MgO; The microwave heating power in the microwave smelting equipment is 20 kW, the frequency is 300 MHz, the vacuum degree is less than 0.01 Pa, and the process temperature is 1400-1500°C.

5. The method for preparing a multi-principal alloy high-pressure oil pipe according to claim 1, characterized in that: In step S4, the inert gas is argon with a purity of 99.99%, the distance between the center of the supersonic flame and the FeCoCrCuSi multi-principal alloy ingot is 10~20mm, the moving speed of the supersonic flame is 0.5m / min, the rotation speed of the FeCoCrCuSi multi-principal alloy ingot is 2~3r / s, and the raw materials of the supersonic flame are 60% aviation kerosene and 40% oxygen.

6. The method for preparing a multi-principal alloy high-pressure oil pipe according to claim 1, characterized in that: In step S5, the FeCoCrCuSi multi-principal alloy ingot is cryogenically treated in liquid nitrogen for 12 hours.

7. The method for preparing a multi-principal alloy high-pressure oil pipe according to claim 1, characterized in that: In step S6, the FeCoCrCuSi multi-principal alloy ingot is placed in an extruder for cold extrusion after deep cryogenic treatment to form a pipe fitting. The extrusion method is double-action reverse extrusion, the extrusion speed is 2-5 mm / s, and the extrusion temperature range is -196--60°C.

8. The method for preparing a multi-principal alloy high-pressure oil pipe according to claim 1, characterized in that: The wall thickness of the pipe formed by cold extrusion in step S6 is 0.8-1.5 mm.

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