Oxide dispersion strengthened maraging steel and method of making same

Abstract

The present application belongs to the field of metallic structural materials, and particularly relates to an oxide dispersion strengthened maraging steel and a preparation method thereof. The alloying components of the steel are as follows in terms of percentage by weight: Ni: 18.0-21.0%, Mo: 2.5-3.5%, Ti: 1.0-1.8%, 0.05≤Y2O3≤0.5, C≤0.01%, Si≤0.10%, Mn≤0.10%, S≤0.008%, P≤0.008%, and Fe in the rest. Y2O3 is uniformly distributed in the matrix in the form of supersaturated solid solution or amorphous state by mechanical alloying; firstly, a number density of 10 21 ~10 23 / m 3 of nanometer oxides is precipitated in the process of thermal solidification forming; then a large number of nanometer Ni3Ti is precipitated again after solid solution and aging treatment; finally, a high-density composite strengthening phase of nanometer oxides and Ni3Ti is formed, and the average grain size is ≤300 nm, so that a maraging steel with super-high strength and good high-temperature thermal stability is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metallic structural materials, and particularly relates to an oxide dispersion strengthened maraging steel and a preparation method thereof. BACKGROUND

[0002] The ultra-high strength steel is widely used in the fields of aerospace and military, such as rocket engine shell, missile shell, binding belt, missile gyroscope inner and outer flexible joint, rotating cylinder of centrifugal separator for uranium enrichment, helicopter landing gear, hydrofoil strut, high-pressure container, torsion rotating shaft, high-strength gear for airplane, bearing, high-pressure sensor, fastener, spring, aluminum alloy extrusion die and pressing die, precision die, cold punching die, and the like, and becomes a front topic and research focus in the field of material science.

[0003] The traditional ultra-high strength alloy steel can be classified into low-alloy ultra-high strength steel with low-temperature tempered martensite structure or lower bainite structure, ultra-high strength steel with high-temperature tempered alloy carbide and secondary hardening structure, and maraging steel with intermetallic compound precipitated from low-C martensite matrix for strengthening. Among them, the maraging steel breaks the tradition of taking C as the main strengthening element and taking Ni as the main alloying element, forms a flexible Fe-Ni martensite matrix, and realizes the strengthening and toughening of the material by precipitating and forming intermetallic compounds from the supersaturated solid solution of Mo, Ti, Al and other elements in the alloy during aging. It is the highest in strength and toughness among existing materials. However, as the strength of the maraging steel increases, the plasticity and toughness tend to decrease, so how to improve the strength while ensuring the plasticity and toughness is a key problem to be solved in the development of the maraging steel.

[0004] To solve the problem of matching the strength and toughness of the maraging steel, the existing research schemes include: 1) adjusting the content of alloying elements in the steel to fully play the interaction between the elements to optimize the performance of the maraging steel; and 2) improving the preparation process of the material, controlling the purity of the material during smelting, and adjusting the microstructure of the steel, refining the grain size, and the like to improve the performance of the material. The methods for refining the grain size include cold deformation (such as rolling, spinning, equal channel angular pressing ECAP) and cyclic phase transformation (multiple reverse transformation of austenite recrystallization), but the grain size will reach a limit after being refined, and the refined grain size is generally 5-10 μm. SUMMARY

[0005] The present application aims to provide an oxide dispersion strengthened maraging steel and a preparation method thereof, which is strengthened by nano-oxides and nano-Ni3Ti, and has ultra-high strength and good high-temperature thermal stability.

[0006] The technical scheme of the present application is:

[0007] An oxide dispersion strengthened maraging steel, the alloying components of which are as follows in percentage by weight: Ni: 18.0-21.0%, Mo: 2.5-3.5%, Ti: 1.0-1.8%, 0.05≤Y2O3≤0.5, C≤0.01%, Si≤0.10%, Mn≤0.10%, S≤0.008%, P≤0.008%, Fe balance; Y2O3 is uniformly distributed in the matrix in the form of supersaturated solid solution or amorphous by mechanical alloying.

[0008] The preparation method of the oxide dispersion strengthened maraging steel, comprising the following steps:

[0009] (1) master alloy smelting;

[0010] (2) gas atomization powder spraying;

[0011] (3) high-energy ball milling;

[0012] (4) packaging and air extraction;

[0013] (5) hot isostatic pressing solidification forming;

[0014] (6) forging;

[0015] (7) hot rolling;

[0016] (8) solid solution + aging heat treatment;

[0017] First, a large number of nanometer oxides with a density of 10 21 ~10 23 / m 3 are precipitated in the hot solidification forming process; then a large number of dispersed nanoscale Ni3Ti are precipitated again after solid solution and aging treatment; finally, a high-density composite strengthening phase of nanometer oxides and Ni3Ti is formed.

[0018] In the preparation method of the oxide dispersion strengthened maraging steel, the components obtained by smelting the master alloy in steps (1) and (2) are as follows in percentage by weight: Ni: 18.0-21.0%, Mo: 2.5-3.5%, Ti: 1.0-1.8%, C≤0.01%, Si≤0.10%, Mn≤0.10%, S≤0.008%, P≤0.008%, Fe balance; the master alloy is subjected to gas atomization powder spraying, the powder particle size is <75 μm, the atomization gas pressure is ≥3.5 MPa, the superheat is ≥200℃, and the protective atmosphere is argon with a volume purity of ≥99.99%.

[0019] The preparation method of the oxide dispersion strengthened maraging steel, in step (3), in order to make the nanometer oxide dispersedly distributed in the material, the Y2O3 with a weight percentage of 0.05≤Y2O3≤0.5 is high-energy ball milled with the master alloy atomized powder, the particle size of Y2O3 is 50-100 nm, and the process parameters of the high-energy ball milling are controlled as follows: the ball milling atmosphere is argon with a volume purity of more than 99.99%, the ball-to-material mass ratio is (8-15):1, the ball milling time is 50-100 h, and the rotating speed is 250-450 r / min.

[0020] The preparation method of the oxide dispersion strengthened maraging steel, in step (4), in order to remove the gas adsorbed on the surface of the powder particles and reduce the porosity, the powder with a particle size of <200 μm is loaded into a capsule; the capsule is pumped to a vacuum atmosphere with a pressure of ≤10 -2 Pa and a temperature of 150-450 ℃ for 3-8 h.

[0021] The preparation method of the oxide dispersion strengthened maraging steel, in step (5), the hot isostatic pressing solidification forming process of the capsule is as follows: the pressure is 100-180 MPa, the temperature is 1000-1200 ℃, and the holding time is 3-8 h.

[0022] The preparation method of the oxide dispersion strengthened maraging steel, in steps (6) and (7), in order to further improve the density and mechanical properties of the maraging steel after solidification forming, first, the forging process is as follows: the open forging temperature is 1100-1200 ℃, and the finish forging temperature is 850-950 ℃; then, the hot rolling process of the forged blank is as follows: the open rolling temperature is 1100-1200 ℃, the finish rolling temperature is 900-950 ℃, the rolling pass is 3-10 times, the deformation amount of each pass is 10-30%, and the total deformation amount is 50-70%.

[0023] The preparation method of the oxide dispersion strengthened maraging steel, in step (8), the heat treatment process is as follows: the solid solution process parameters are 800-950 ℃ for 60-90 min of heat preservation followed by water cooling, and the aging process parameters are 450-550 ℃ for 3-6 h of heat preservation followed by air cooling.

[0024] The preparation method of the oxide dispersion strengthened maraging steel, the microstructure of the maraging steel is martensite and a small amount of reversed austenite, the average grain size is ≤300 nm, a large amount of nanometer Ni3Ti and Y-Ti-O precipitated phases are dispersedly distributed in the matrix; the Ni3Ti is short rod-shaped with an average length of 2-5 nm; the diameter of the Y-Ti-O particles is 3-30 nm, and the number density is 10 21 -10 23 / m 3 .

[0025] The preparation method of the oxide dispersion strengthened maraging steel has the room temperature yield strength of more than or equal to 1950 MPa, the tensile strength of more than or equal to 2000 MPa, and the elongation of more than or equal to 6%; the yield strength of more than or equal to 900 MPa, the tensile strength of more than or equal to 1200 MPa, and the elongation of more than or equal to 20% at 500 DEG C; and the yield strength of more than or equal to 350 MPa, the tensile strength of more than or equal to 650 MPa, and the elongation of more than or equal to 20% at 600 DEG C.

[0026] The design idea of the present application is:

[0027] 1. The present application adopts the ultra-high strength maraging steel as a matrix, breaks the coarse grain mode of the maraging steel prepared by traditional smelting by using the high-energy ball milling process, obtains the sub-micron ultra-fine grain, and makes the average grain size of the material less than or equal to 300 nm. By the way of grain refinement, not only the ultra-high strength can be obtained, but also the material can have good plasticity.

[0028] 2. The oxide dispersion strengthened maraging steel prepared by the present application has the nanometer Y-Ti-O dispersedly distributed in the matrix, and the oxides can play the role of dispersion strengthening for the material and improve the strength of the material. Meanwhile, the nanometer Y-Ti-O has good high-temperature stability, and improves the high-temperature mechanical properties of the material.

[0029] 3. The oxide dispersion strengthened maraging steel prepared by the present application has a large amount of short rod-shaped Ni3Ti precipitated phase with the average length of 2-5 nm and a large amount of nanometer Y-Ti-O phase after solid solution + aging heat treatment, the diameter of the Y-Ti-O particles is 3-30 nm, the number density is 10 21 ~10 23 / m 3 The two kinds of strengthening phases jointly play the effect of composite strengthening, and can greatly improve the room temperature strength of the material.

[0030] The present application has the following advantages and beneficial effects:

[0031] 1. The present application is prepared by the powder metallurgy method, on the one hand, the sub-micron level grain can be obtained, the grain refinement not only improves the strength but also improves the plasticity and toughness, and can be used as an effective measure to break through the problem of matching strength and toughness. On the other hand, a large amount of nanometer oxide dispersion strengthening phase is introduced to pin the dislocation and grain boundary in the matrix, reduces the sliding of the grain boundary, and plays the role of strengthening. In addition, the dispersedly distributed oxide particles have excellent thermal stability at high temperature, and improve the high-temperature strength of the material by hindering the sliding of the grain boundary.

[0032] 2、The present application solves the problem of mismatch between ultra-high strength and plasticity by component and preparation process design and organization control, and improves the high temperature mechanical properties of the material. The room temperature yield strength is ≥1950MPa, the tensile strength is ≥2000MPa, and the elongation is ≥6%; the yield strength at 500℃ is ≥900MPa, the tensile strength is ≥1200MPa, and the elongation is ≥20%; the yield strength at 600℃ is ≥350MPa, the tensile strength is ≥650MPa, and the elongation is ≥20%. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 EBSD inverse pole figure of the oxide dispersion martensite and aging steel example 1 prepared by the present application.

[0034] Figure 2 Grain size distribution diagram of the oxide dispersion martensite and aging example 1 prepared by the present application. In the diagram, the horizontal coordinate Grain size is particle size (μm), and the vertical coordinate Frequency is frequency of occurrence (%).

[0035] Figure 3 EBSD phase distribution diagram of the oxide dispersion martensite and aging steel example 1 prepared by the present application.

[0036] Figure 4 Distribution diagram of oxides in the oxide dispersion martensite and aging steel example 1 prepared by the present application.

[0037] Figure 5 Distribution diagram of Ni3Ti in the oxide dispersion martensite and aging steel example 1 prepared by the present application.

[0038] Figure 6 Element distribution diagram of the oxide dispersion martensite and aging steel example 1 prepared by the present application. The upper row from left to right is the morphology diagram, Fe element, Ni element, Fe element, Mo element, and the lower row from left to right is Ti element, Y element, O element. DETAILED DESCRIPTION

[0039] In the following, the technical solutions of the present application will be further described in combination with specific examples.

[0040] Example 1

[0041] In this embodiment, the preparation method of the oxide dispersion strengthened martensite and aging steel is as follows:

[0042] (1) Preparation of master alloy powder

[0043] The master alloy is prepared by vacuum induction melting furnace, and the components of the master alloy are as follows in percentage by weight: Ni: 18.3%, Mo: 2.93%, Ti: 1.72%, C: 0.0078%, Si: 0.009%, Mn: 0.005%, S: 0.0058%, P: 0.006%, and Fe: balance. The master alloy powder is subjected to gas atomization powder spraying, and the requirements are as follows: powder particle size < 75 μm, atomization gas pressure 4.0 MPa, superheat 200°C, and protective atmosphere argon with purity of more than 99.99% by volume.

[0044] (2) High-energy ball milling

[0045] In order to disperse the nanometer oxides in the material, 0.5% of Y2O3 by weight is high-energy ball milled with the atomized powder of the master alloy, the particle size of Y2O3 is 50-100 nm, and the process parameters of high-energy ball milling are controlled as follows: ball milling atmosphere is argon with purity of more than 99.99% by volume, ball-to-material mass ratio is 9:1, ball milling time is 60 h, and rotating speed is 300 r / min.

[0046] (3) Powder loading and jacket evacuation

[0047] In order to remove the gas adsorbed on the surface of powder particles and reduce the porosity, the powder after ball milling in the jacket has a particle size < 200 μm. The evacuation process of the jacket is as follows: vacuum pressure is 10 -2 Pa, temperature is 400°C, and time is 8 h.

[0048] (4) Hot isostatic pressing forming

[0049] The hot isostatic pressing solidification forming process of the jacket is as follows: pressure is 170 MPa, temperature is 1150°C, and holding time is 4 h.

[0050] (5) Forging and hot rolling

[0051] In order to further improve the density and mechanical properties of the maraging steel after solidification forming, the material is forged into a plate, and the forging process is controlled as follows: open forging temperature is 1150°C, and final forging temperature is 850°C. The forged plate is subjected to hot rolling, and the hot rolling process is controlled as follows: open rolling temperature is 1150°C, final rolling temperature is 900°C, rolling passes are 4, deformation amount of each pass is 12%, 13%, 15%, and 15% respectively, and total deformation amount is 55%.

[0052] (6) The heat treatment process of the maraging steel is as follows: solid solution process parameters are 850°C for 60 min, water cooling to room temperature, and aging process parameters are 480°C for 5 h, air cooling to room temperature.

[0053] Example 2

[0054] In this embodiment, a preparation method of oxide dispersion strengthened maraging steel is as follows:

[0055] (1) Preparation of master alloy powder

[0056] The master alloy is prepared by a vacuum induction melting furnace, and the composition of the master alloy is, in percentage by weight, Ni: 18.3%, Mo: 2.93%, Ti: 1.72%, C: 0.0078%, Si: 0.009%, Mn: 0.005%, S: 0.0058%, P: 0.006%, and Fe: balance. The master alloy powder is subjected to gas atomization spraying, and the requirements are as follows: powder particle size < 75 μm, atomization gas pressure 4.0 MPa, superheat 200°C, and protective atmosphere argon with a volume purity of more than 99.99%.

[0057] (2) High-energy ball milling

[0058] In order to disperse the nanometer oxide in the material, 0.5% of Y2O3 by weight is high-energy ball milled with the atomized powder of the master alloy, the particle size of Y2O3 is 50-100 nm, and the process parameters of high-energy ball milling are controlled as follows: ball milling atmosphere is argon with a volume purity of more than 99.99%, ball-to-material mass ratio is 9:1, ball milling time is 60 h, and rotation speed is 350 r / min.

[0059] (3) Powder loading and canister degassing

[0060] In order to remove the gas adsorbed on the surface of the powder particles and reduce the porosity, the powder particle size after ball milling in the canister is < 200 μm. The degassing process of the canister is as follows: vacuum air pressure is 10 -2 Pa, temperature is 400°C, and time is 8 h.

[0061] (4) Hot isostatic pressing forming

[0062] The hot isostatic pressing solidification forming process of the canister is as follows: pressure is 170 MPa, temperature is 1150°C, and holding time is 4 h.

[0063] (5) Forging and hot rolling

[0064] In order to further improve the density and mechanical properties of the maraging steel after solidification forming, the material is forged into a plate, and the forging process is controlled as follows: open forging temperature is 1150°C, and final forging temperature is 850°C. The forged plate is subjected to hot rolling, and the hot rolling process is controlled as follows: open rolling temperature is 1150°C, final rolling temperature is 900°C, rolling passes are 4, and the deformation amount of each pass is 12%, 13%, 15%, and 15% respectively, and the total deformation amount is 55%.

[0065] (6) The heat treatment process of the maraging steel is as follows: the solid solution process parameters are 850℃ for 60min, then water cooling to room temperature, and the aging process parameters are 480℃ for 5h, then air cooling to room temperature.

[0066] Example 3

[0067] In this embodiment, the preparation method of the oxide dispersion strengthened maraging steel is as follows:

[0068] (1) Preparation of master alloy powder

[0069] The master alloy is prepared by a vacuum induction melting furnace, and the composition of the master alloy is, in terms of weight percentage, Ni: 18.3%, Mo: 2.93%, Ti: 1.72%, C: 0.0078%, Si: 0.009%, Mn: 0.005%, S: 0.0058%, P: 0.006%, and Fe: balance. The master alloy powder is subjected to gas atomization spraying, with the following requirements: powder particle size < 75μm, atomization gas pressure 4.0MPa, superheat 200℃, and protective atmosphere argon with a volume purity of more than 99.99%.

[0070] (2) High-energy ball milling

[0071] In order to disperse the nanometer oxides in the material, 0.5% of Y2O3 by weight is high-energy ball milled with the master alloy atomized powder, and the particle size of Y2O3 is 50-100nm. The process parameters of high-energy ball milling are controlled as follows: the ball milling atmosphere is argon with a volume purity of more than 99.99%, the ball-to-material mass ratio is 9:1, the ball milling time is 60h, and the rotation speed is 300r / min.

[0072] (3) Powder loading and canister degassing

[0073] In order to remove the gas adsorbed on the surface of the powder particles and reduce the porosity, the powder particle size after ball milling in the canister is < 200μm. The degassing process of the canister is as follows: vacuum air pressure 10 -2 Pa, temperature 400℃, and time 8h.

[0074] (4) Hot isostatic pressing forming

[0075] The hot isostatic pressing solidification forming process of the canister is as follows: pressure 120MPa, temperature 1150℃, and holding time 4h.

[0076] (5) Forging and hot rolling

[0077] In order to further improve the density and mechanical properties of the maraging steel after solidification forming, the material is forged into a plate, and the forging process is controlled as follows: the open forging temperature is 1150℃, and the final forging temperature is 850℃. The forged plate is hot-rolled, and the hot-rolling process is controlled as follows: the open rolling temperature is 1150℃, the final rolling temperature is 900℃, the rolling passes are 4, and the deformation amount of each pass is 12%, 13%, 15% and 15% respectively, and the total deformation amount is 55%.

[0078] (6) The heat treatment process of the maraging steel is as follows: the solid solution process parameters are 850℃ for 60min, and then water cooling to room temperature, and the aging process parameters are 480℃ for 5h, and then air cooling to room temperature.

[0079] Example 4

[0080] In this embodiment, a preparation method of an oxide dispersion strengthened maraging steel is as follows:

[0081] (1) Preparation of master alloy powder: The master alloy is prepared by using a vacuum induction melting furnace, and the composition of the master alloy is as follows in terms of weight percentage: Ni: 18.3%, Mo: 2.93%, Ti: 1.72%, C: 0.0078%, Si: 0.009%, Mn: 0.005%, S: 0.0058%, P: 0.006%, and Fe: balance. The master alloy powder is subjected to gas atomization spraying, and the requirements are as follows: powder particle size <75μm, atomization gas pressure 4.0MPa, superheat 200℃, and protective atmosphere is argon with a volume purity of more than 99.99%.

[0082] (2) High-energy ball milling

[0083] In order to disperse the nanometer oxides in the material, 0.5% of Y2O3 by weight is high-energy ball milled with the master alloy atomized powder, and the particle size of Y2O3 is 50-100nm, and the process parameters of high-energy ball milling are controlled as follows: the ball milling atmosphere is argon with a volume purity of more than 99.99%, the ball-to-material mass ratio is 9:1, the ball milling time is 60h, and the rotation speed is 300r / min.

[0084] (3) Powder loading and canister evacuation

[0085] In order to remove the gas adsorbed on the surface of the powder particles and reduce the porosity, the powder particle size after ball milling in the canister is <200μm. The evacuation process of the canister is as follows: vacuum air pressure is 10 -2 Pa, temperature is 400℃, and time is 8h.

[0086] (4) Hot isostatic pressing forming

[0087] The hot isostatic pressing solidification forming process of the canister is as follows: pressure is 170MPa, temperature is 1150℃, and holding time is 4h.

[0088] (5) Forging and hot rolling

[0089] In order to further improve the density and mechanical properties of the maraging steel after solidification molding, the material is forged into a plate, and the forging process is controlled as follows: the open forging temperature is 1150°C, and the final forging temperature is 850°C. The forged plate is hot rolled, and the hot rolling process is controlled as follows: the open rolling temperature is 1150°C, the final rolling temperature is 900°C, the rolling pass is 4, and the deformation amount of each pass is 12%, 13%, 15%, and 15% respectively, and the total deformation amount is 55%.

[0090] (6) The heat treatment process of the maraging steel is as follows: the solution process parameters are 800°C for 60min, and then water cooled to room temperature, and the aging process parameters are 500°C for 5h, and then air cooled to room temperature.

[0091] Comparative Example 1

[0092] In this comparative example, the preparation method of a maraging steel is as follows:

[0093] (1) Prepared by vacuum induction melting furnace, the composition of the alloy is, by weight percentage, Ni: 17.9%, Mo: 2.98%, Ti: 1.42%, C: 0.001%, Si: 0.010%, Mn: 0.010%, S: 0.004%, P: 0.005%, Fe balance.

[0094] (2) The forging process is controlled as follows: the open forging temperature is 1150°C, and the final forging temperature is 850°C.

[0095] (3) The heat treatment process of the maraging steel is as follows: the solution process parameters are 850°C for 60min, and then water cooled to room temperature, and the aging process parameters are 480°C for 5h, and then air cooled to room temperature.

[0096] Comparative Example 2

[0097] In this comparative example, the preparation method of a maraging steel is as follows:

[0098] (1) Prepared by vacuum induction melting furnace, the composition of the alloy is, by weight percentage, Ni: 17.9%, Mo: 2.98%, Ti: 1.42%, C: 0.001%, Si: 0.010%, Mn: 0.010%, S: 0.004%, P: 0.005%, Fe balance.

[0099] (2) The forging process is controlled as follows: the open forging temperature is 1150°C, and the final forging temperature is 850°C.

[0100] (3) The heat treatment process of the martensitic aging steel is as follows: the solution treatment process parameters are 800℃ for 60 min and then water cooling to room temperature, and the aging process parameters are 500℃ for 5 h and then air cooling to room temperature.

[0101] Table 1 Mechanical properties of each embodiment and comparative example at different temperatures.

[0102]

[0103] The results of Example 1 show that the oxide dispersion-strengthened martensitic aging steel obtained by the present invention has a relatively uniform grain size, no obvious texture orientation, and the martensite does not have obvious lath characteristics. The average effective grain size is 0.235 μm, breaking the limitations of traditional processes on grain size and refining the grain size to the submicron level. Figure 1 and Figure 2 As shown in the phase distribution diagram, the blue area represents the martensite phase with a BCC structure, ensuring the material's high strength, while the red area represents the austenite phase with an FCC structure, with a volume percentage of 6.62%, ensuring the ductility and toughness of the martensitic aging steel and achieving a good strength-toughness balance. Figure 3 As shown, a large number of spherical oxides are dispersed in the matrix, with sizes ranging from 3 nm to 30 nm, and most of the oxides having sizes from 5 to 15 nm. The number density of the oxides is 10. 22 / m 3 ,like Figure 4 As shown. After aging treatment, a large number of dispersed short rod-shaped precipitates of Ni3Ti were formed in the matrix, with a length of 2-5 nm, as shown. Figure 5 As shown in the figure, the spherical phase is clearly enriched with Y, Ti, and O, representing Y-Ti-O nano-oxides. The short rod-shaped phase is clearly enriched with Ni and Ti, representing Ni3Ti precipitates. Figure 6 As shown.

[0104] Preferably, the oxide dispersion strengthened martensitic aging steel of the present invention can achieve a room temperature yield strength of not less than 1950 MPa, a tensile strength of not less than 2000 MPa, and an elongation of not less than 6%; a yield strength of not less than 900 MPa, a tensile strength of not less than 1200 MPa, and an elongation of not less than 20% at 500°C; and a yield strength of not less than 350 MPa, a tensile strength of not less than 650 MPa, and an elongation of not less than 20% at 600°C.

[0105] The ball milling speed of Example 2 is higher than that of Example 1, but the strength of the material is reduced. The strength of the material does not increase with the increase of the ball milling speed. The appropriate ball milling speed can ensure that the powder crushing and welding effects are balanced, so that the material performance is more excellent. The hot isostatic pressing pressure of Example 3 is lower than that of Example 1, and the strength of the material is reduced. The higher the hot isostatic pressing pressure, the higher the density of the material, and the more excellent the performance. The solid solution and aging temperature of Example 4 is changed compared with Example 1, and the strength of the material is reduced. The optimal heat treatment process is 850℃ solid solution for 1h and water cooling + 480℃ aging for 5h and air cooling.

[0106] Comparative Example 1 is compared with Example 1. The material is prepared by a traditional smelting method, and Y2O3 is not added. The sub-micron size grain cannot be obtained, and the dispersed oxides are not distributed in the matrix. The room temperature yield strength and tensile strength of the material are 1736MPa and 1803MPa, respectively. The yield strength at 500℃ is 837MPa, and the tensile strength is 1150MPa. The yield strength at 600℃ is 332MPa, and the tensile strength is 596MPa. The room temperature and high temperature mechanical properties are greatly different from those of the examples of the application. The heat treatment process of the material in Comparative Example 2 is adjusted. Compared with Comparative Example 1, the room temperature mechanical properties and high temperature mechanical properties of the material are reduced. The room temperature yield strength and tensile strength of the material are 1706MPa and 1794MPa, respectively. The yield strength at 500℃ is 824MPa, and the tensile strength is 1132MPa. The yield strength at 600℃ is 324MPa, and the tensile strength is 588MPa.

[0107] The implementation results show that the oxide dispersion strengthened maraging steel obtained by the application solves the problem of mismatching between ultra-high strength and plasticity. By adding nano-oxides and mechanical alloying ball milling, the grain size of the material is refined to less than 300nm. Through the effect of fine grain strengthening, the material has certain plasticity while the strength level is improved. The dispersed nano-oxides and the Ni3Ti precipitated by aging form a composite strengthening effect, which further improves the strength of the material. The dispersed nano-oxides have good high temperature stability, which significantly improves the high temperature mechanical properties of the material.

[0108] The above examples only illustrate the technical concept and characteristics of the application, and cannot limit the protection scope of the application. Any equivalent changes or modifications made according to the spirit and essence of the application should be covered within the protection scope of the application.

Claims

1. A method for producing an oxide dispersion strengthened maraging steel, characterized in that, The alloying components of the maraging steel are as follows in percentage by weight: Ni: 18.0-21.0% and greater than 18.0%, Mo: 2.5-3.5%, Ti: 1.0-1.8%, 0.05≤Y2O3≤0.5, C≤0.01%, Si≤0.10%, Mn≤0.10%, S≤0.008%, P≤0.008%, Fe balance; Y2O3 is uniformly distributed in the matrix in the form of supersaturated solid solution or amorphous by mechanical alloying method; The preparation method of the oxide dispersion strengthened maraging steel comprises the following steps: (1) master alloy smelting; (2) gas atomization powder spraying; (3) high-energy ball milling; (4) packaging and air extraction; (5) hot isostatic pressing solidification molding; (6) forging; (7) hot rolling; (8) solid solution + aging heat treatment; Firstly, nano-oxides with a number density of 10 21 ~ 10 23 / m 3 are precipitated during the hot consolidation process; then a large amount of dispersed nano-sized Ni3Ti is precipitated again after the solution and aging treatment; finally, a high-density composite strengthening phase of nano-oxides and Ni3Ti is formed; In step (8), the heat treatment process is as follows: the solid solution process parameters are 800-950℃ for 60-90min and then water cooling, and the aging process parameters are 450-550℃ for 3-6h and then air cooling; The microstructure of the martensite-aging steel is martensite and a small amount of reversed austenite, the average grain size is less than or equal to 300 nm, and a large number of nanoscale Ni3Ti and Y-Ti-O precipitates are dispersedly distributed in the matrix; wherein the Ni3Ti is short rod-shaped, and the average length is 2-5 nm; the diameter of the Y-Ti-O particles is 3-30 nm, and the number density is 10 21 -10 23 / m 3 . The maraging steel has the following properties: the yield strength at room temperature is ≥1950MPa, the tensile strength is ≥2000MPa, and the elongation is ≥6%; the yield strength at 500℃ is ≥900MPa, the tensile strength is ≥1200MPa, and the elongation is ≥20%; the yield strength at 600℃ is ≥350MPa, the tensile strength is ≥650MPa, and the elongation is ≥20%.

2. The method of producing an oxide dispersion strengthened maraging steel according to claim 1, characterized in that, In steps (1) and (2), the components obtained by smelting the master alloy are as follows in percentage by weight: Ni: 18.0-21.0%, Mo: 2.5-3.5%, Ti: 1.0-1.8%, C≤0.01%, Si≤0.10%, Mn≤0.10%, S≤0.008%, P≤0.008%, Fe balance; the master alloy is subjected to gas atomization powder spraying, the powder particle size is <75μm, the atomization gas pressure is ≥3.5MPa, the superheat degree is ≥200℃, and the protective atmosphere is argon with a volume purity of more than 99.99%.

3. The method of producing an oxide dispersion strengthened maraging steel according to claim 1, characterized in that, In step (3), in order to make the nanometer oxide dispersedly distributed in the material, the high-energy ball milling is performed on the master alloy atomized powder with 0.05≤Y2O3≤0.5 in percentage by weight, the particle size of Y2O3 is 50-100nm, and the process parameters of the high-energy ball milling are controlled as follows: the ball milling atmosphere is argon with a volume purity of more than 99.99%, the ball-to-material mass ratio is (8-15):1, the ball milling time is 50-100h, and the rotating speed is 250-450r / min.

4. The method of producing an oxide dispersion strengthened maraging steel according to claim 1, characterized in that, In step (4), in order to remove the gas adsorbed on the surface of the powder particles and reduce the porosity, the size of the powder in the capsule is < 200 μm; the parameters of the gas extraction of the capsule are as follows: the vacuum air pressure is ≤ 10 -2 Pa, the temperature is 150-450 °C, and the time is 3-8 h.

5. The method of producing an oxide dispersion strengthened maraging steel according to claim 1, characterized in that, In step (5), the hot isostatic pressing solidification molding process of the package is as follows: the pressure is 100-180MPa, the temperature is 1000-1200℃, and the holding time is 3-8h.

6. The method of producing an oxide dispersion strengthened maraging steel according to claim 1, characterized in that, In steps (6) and (7), in order to further improve the density and mechanical properties of the maraging steel after solidification molding, the forging process is as follows: the open forging temperature is 1100-1200℃, and the finish forging temperature is 850-950℃; then the forged blank is subjected to the hot rolling process as follows: the open rolling temperature is 1100-1200℃, the finish rolling temperature is 900-950℃, the rolling passes are 3-10, the deformation amount of each pass is 10-30%, and the total deformation amount is 50-70%.

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