Copper-containing maraging ultrahigh-strength steel and preparation method thereof

Abstract

The invention discloses copper-containing maraging ultrahigh-strength steel and a preparation method thereof, and belongs to the field of steel and iron materials. The copper-containing maraging ultrahigh-strength steel is prepared from the following chemical components in percentage by mass: 14.5 to 16.0 percent of Co, 17.0 to 18.0 percent of Ni, 6.0 to 8.0 percent of Mo, 1.0 to 1.5 percent of Ti, 0.5 to 1.0 percent of Cu, 0.5 to 1.0 percent of Al and the balance of Fe and inevitable impurities. The preparation method comprises the steps of vacuum smelting, high-temperature homogenization, forging cogging, thermal deformation and thermal treatment. According to the copper-containing maraging ultrahigh-strength steel prepared through the preparation method, under the condition that the grain size is larger than or equal to 8.0, the tensile strength of the material reaches 2800 MPa or above, meanwhile, the elongation of 7% or above is kept, and the application requirements of different fields for the ultrahigh-strength steel with the tensile strength of 2800 MPa or above can be met.

Description

Technical Field

[0001] The present invention belongs to the field of steel materials, and relates to the composition design and preparation method of ultra-high strength steel above 2800MPa, and specifically to a copper-containing martensitic aging ultra-high strength steel and a preparation method thereof. Background Art

[0002] Maraging steel has been widely used in aerospace and communications due to its ultra-high strength and excellent plasticity. With the increasing requirements for lightweight in these fields, steel, as a high-density structural material, faces more stringent performance requirements. Therefore, the development of maraging steel with ultra-high strength and high plasticity is of great significance to promoting the development of my country's aerospace and communication technology. The external dimensions of the material (such as bars, wires, and plates) have a significant impact on its performance, and the requirements for the external dimensions of the material vary greatly in different application scenarios. Therefore, it has become a top priority to develop maraging steels that can adapt to a variety of external dimensions and meet the requirements of ultra-high strength and high plasticity.

[0003] CN119392114A discloses a high-strength and plastic 3GPa-grade martensitic aging steel and a preparation method thereof. According to weight percentage, the element composition of the high-strength and plastic 3GPa-grade martensitic aging steel is: Ni: 15-20%, Al: 0.1-2%, Mo: 3-7%, Ti: 1.0-2.0%, Co: 12-16%, and the balance is Fe and unavoidable impurities. By reasonably adding elements and their proportions, and combining the forging ratio and forging temperature to reasonably control the forging process, a martensitic aging type ultra-high strength steel with ultra-high strength and excellent plasticity with a tensile strength of more than 3GPa is obtained. The forging process includes: heating temperature of 1180-1250℃ for billet forging, holding time of 3-15h, and billeting after no less than three times of upsetting and drawing; reheating after billet forging, heating temperature of 980-1100℃, holding time of 3-10h, upsetting and drawing times of no less than three times, forging ratio of 2-6; heating at 850-1050℃, holding time of 3-10h, and one-time forging for the final bar, forging ratio ≥6. This method involves the preparation of maraging steel bars, which is limited by its external dimensions and its application scenarios; the forging process is strictly restricted in this method, and the processing is difficult; at the same time, the tensile strength of the maraging steel bars produced by this method is 3008-3035MPa, but the elongation after fracture is only 5%-5.5%, and its plasticity needs to be further improved.

[0004] CN115786813A discloses a method for preparing a maraging steel plate, which comprises the following steps: smelting an alloy ingot by adopting a vacuum induction and vacuum consumable dual process; subjecting the alloy ingot to peeling, hot rolling and homogenization to obtain a slab; hot rolling and finish rolling the slab to obtain a hot-rolled plate; peeling and cold rolling the hot-rolled plate to obtain a plate; and subjecting the cold-rolled plate to multiple aging processes to obtain a finished maraging steel plate. The chemical composition ratio of the maraging steel plate is: Ni: 10.0-13.0; Co: 11.0-14.0; Mo: 10.0-13.0; Ti: 0.2-1.0; Al: 1.5-2.5; Zr: 0.005-0.015; Ce: 0.01-0.03; C < 0.005; N < 0.001; O < 0.001; P < 0.01; S < 0.01; the balance is Fe. The average grain size is 6.0 μm-10.0 μm, the grain size grade is 9.5-11.5, the tensile strength is ≥ 3000 MPa, and the elongation is ≥ 10%. This method is mainly used to prepare maraging steel plates. Although it has high strength and elongation, its application scenarios are limited due to size restrictions. At the same time, its chemical composition uses rare earth elements, and the preparation method uses cold rolling and involves multiple aging passes. The preparation process is complicated, and the raw material cost and production cost are high. Summary of the invention

[0005] The technical problem to be solved by the present invention is that traditional maraging steel cannot adapt to a variety of external dimensions and cannot simultaneously meet the requirements of ultra-high strength and high plasticity. The purpose of the present invention is to provide a copper-containing maraging ultra-high strength steel and a preparation method thereof to meet the application requirements of ultra-high strength steel above 2800MPa in different fields.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present invention provides a copper-containing martensitic aged ultra-high strength steel, whose chemical composition, by mass percentage, is: Co 14.5-16.0%, Ni 17.0-18.0%, Mo 6.0-8.0%, Ti 1.0-1.5%, Cu 0.5-1.0%, Al 0.5-1.0%, and the balance is Fe and unavoidable impurities.

[0008] In the chemical composition of the above copper-containing maraging ultra-high strength steel, the unavoidable impurities are: C≤0.008%, Si≤0.1%, Mn≤0.1%, P≤0.005%, S≤0.005%, N≤0.0015%, O≤0.0015%.

[0009] The tensile strength Rm of the copper-containing martensitic aging ultra-high strength steel is ≥2800MPa, the yield strength Rp0.2 is ≥2700MPa, and the elongation A is ≥7%.

[0010] The grain size of the above copper-containing martensitic aging ultra-high strength steel is ≥ grade 8.0.

[0011] In a second aspect, the present invention provides a method for preparing the above copper-containing martensitic aging ultra-high strength steel, which specifically comprises the following steps:

[0012] S1 adopts vacuum induction and vacuum consumable dual process to smelt ingots, and then performs skinning treatment on the ingots;

[0013] After the S2 heating furnace is preheated, the peeled ingot is placed into the heating furnace for high-temperature homogenization treatment as the furnace heats up. After completion, it is taken out of the furnace and cooled to the forging temperature for forging and blanking.

[0014] After S3 blanking, the forged material is returned to the furnace for heating, and after being taken out of the furnace, it is fine forged or rolled to the final size, and then heat treated to obtain copper-containing martensitic aged ultra-high strength steel.

[0015] In the above step S2, the heating furnace is preheated to a furnace temperature of 1000°C ± 10°C.

[0016] In the above step S2, the temperature of the high temperature homogenization treatment is 1250°C to 1260°C, and the insulation time is 36h to 48h.

[0017] In the above step S2, the forging process adopts "three upsetting and three drawing", the starting forging temperature is 1180℃~1200℃, the final forging temperature is ≥1000℃, the downsetting amount of each time is ≥50%, and the drawing rate is ≥200%.

[0018] Furthermore, during the forging process, when the temperature is lower than 1050°C, the steel is returned to the furnace and heated at 1150°C±10°C for 2h±10min before continuing the upsetting; during the final forging process, when the temperature is lower than 1000°C, the steel is returned to the furnace and heated at 1100°C±10°C for 2h±10min before continuing the upsetting.

[0019] In the above step S3, the furnace heating is to raise the temperature to 1150°C ± 10°C and keep it for 2h ± 10min; the single pass reduction of the fine forging or rolling is ≤ 35%, and the final forging or final rolling temperature is ≥ 950°C.

[0020] In the above step S3, the heat treatment is specifically as follows: keeping at 850℃~860℃ for 1h~2h, and then immediately oil cooling to room temperature; keeping at 820℃~830℃ for 1h~1.5h, and then immediately oil cooling to room temperature, repeated twice; deep freezing treatment at -70℃~-80℃ for 1h~2h within 4 hours, and then naturally warming up in the air; aging treatment at 480℃~500℃ for 5h~8h within 8 hours.

[0021] The beneficial effects of the present invention are:

[0022] Compared with the prior art, the preparation method of the copper-containing martensitic aged ultra-high strength steel provided by the present invention directly obtains the final size by optimizing the forging process (such as "three-upsetting and three-drawing" blanking combined with fine forging / hot rolling), avoiding the problem of high alloy steel being prone to cracking during cold rolling. This not only shortens the production cycle, but also significantly reduces equipment requirements and processing costs, and is more conducive to large-scale production. The preparation method of the present invention has the advantages of simplified process and high industrial feasibility.

[0023] The copper-containing martensitic aging ultra-high strength steel prepared by the preparation method of the present invention has a tensile strength of more than 2800MPa under the condition of grain size ≥8.0, while maintaining an elongation of more than 7%, breaking through the contradiction between strength and plasticity of traditional high-strength steel. The composition and process of the present invention are coordinated and regulated, and there are no special restrictions on the external dimensions of the finished product (such as rods, wires, and plates), which can meet the diversified needs of complex components in the aerospace field. The copper-containing martensitic aging ultra-high strength steel prepared by the present invention has excellent comprehensive performance and strong adaptability, and can be promoted and applied in the aerospace and 3C electronics fields. The material design method can be extended to the design of martensitic aging steels with other personalized mechanical performance requirements, and has broad application prospects. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear, the present application is further described in detail below in combination with the implementation methods. Unless otherwise defined, all scientific and technological terms used herein have the same meanings as understood by ordinary technicians in the field.

[0025] A copper-containing martensitic aging ultra-high strength steel, the chemical composition of which is as follows by mass percentage: Co 14.5-16.0%, Ni 17.0-18.0%, Mo 6.0-8.0%, Ti 1.0-1.5%, Cu 0.5-1.0%, Al 0.5-1.0%, and the balance is Fe and inevitable impurities.

[0026] In one embodiment of the present invention, the copper-containing martensitic aging ultra-high strength steel has the following chemical compositions by mass percentage: Co 14.5-16.0%, Ni 17.0-18.0%, Mo 6.0-8.0%, Ti 1.0-1.5%, Cu0.5-1.0%, Al0.5-1.0%, C≤0.008%, Si≤0.1%, Mn≤0.1%, P≤0.005%, S≤0.005%, N≤0.0015%, O≤0.0015%, and the balance is Fe.

[0027] Compared with the prior art, the present invention achieves a balance between high strength and plasticity through the synergistic effect of the following components.

[0028] By controlling the Cu content (0.5-1.0%) and the Ti content (1.0-1.5%), Cu nanoclusters can be generated while retaining a certain amount of nanoscale Ni3Ti precipitation phase, avoiding the increase in brittleness caused by excessive amounts of both. The introduction of a certain number of Cu nanoclusters can greatly improve the strength without deteriorating the plasticity and toughness, while Ti directly participates in the formation of the Ni3Ti phase, and the two synergistically enhance the precipitation strengthening effect.

[0029] By adding Al (0.5-1.0%), nano-scale NiAl intermetallic compounds are generated during the aging process, which together with Ni3Ti form a multiphase precipitation system. The high content of Ni (17.0-18.0%) not only provides sufficient matrix Ni elements for the precipitation phase, but also improves the matrix toughness through solid solution strengthening, balancing the brittle tendency caused by precipitation strengthening.

[0030] The amount of Ni3Mo precipitates is significantly increased by increasing the Mo content (6.0-8.0%), while the grain coarsening is inhibited together with Co (14.5-16.0%). Co promotes the precipitation of fine Ni3Mo by reducing the solubility of Mo in the matrix, and accelerates the uniform distribution of Mo-Ti composite precipitates in combination with the severe deformation of the "three upsetting and three drawing" process. The two work together to strengthen the grain boundaries and improve the tensile strength of the material.

[0031] By controlling impurities such as C≤0.008%, N≤0.0015%, the formation of brittle phases such as TiC, TiN, and AlN is reduced, and interference with the uniform precipitation of the main strengthening phases (Ni3Ti, Ni3Al) is avoided, the purity of the matrix is ​​guaranteed, and a basis for high plasticity is provided.

[0032] Through the above-mentioned component design, the present invention complements each other in precipitation strengthening, solid solution strengthening, grain boundary regulation and other aspects. Through the precipitation phase strengthening of nano-sized Ni3Mo and Ni3Ti, the second phase strengthening of Cu nanoclusters, the aging strengthening of Al-Ni, and the refinement of Mo-Co organization and stabilization of grain boundaries, the comprehensive performance of tensile strength ≥2800MPa and elongation ≥7% at a grain size ≥8.0 is finally achieved, while avoiding reliance on difficult processing procedures such as cold rolling.

[0033] The method for preparing the above copper-containing martensitic aging ultra-high strength steel comprises the following steps.

[0034] (1) Vacuum smelting: vacuum induction and vacuum consumable dual process are used to smelt martensitic aging steel ingots, strictly controlling impurities such as C, N, and O (e.g., C ≤ 0.008%) to avoid the formation of brittle phases (e.g., TiC, TiN, and AlN), and providing a high-purity matrix for subsequent forging and precipitation phase regulation; the ingots are peeled to remove the oxide layer and defects on the surface of the ingots to ensure that there is no interference from inclusions during the hot working process.

[0035] (2) High temperature homogenization: The temperature of the homogenization treatment is 1250℃~1260℃, and the holding time is 36h~48h. In view of the segregation tendency of high alloy components, Mo, Ti and other elements are evenly distributed through long-term high-temperature diffusion to avoid local stress concentration during subsequent forging; after the holding period is completed, the forging is carried out after the furnace is taken out and cooled to the forging temperature.

[0036] (3) Forging and blanking: "Three upsetting and three drawing" is adopted to completely break the coarse cast structure through multi-directional repeated deformation, eliminate banded segregation, and refine the grain to ≥8.0 level. Therefore, the forging temperature is controlled to be 1180~1200℃, the upsetting reduction is ≥50%, and the drawing rate is ≥200%. At the same time, the work hardening cracking is prevented by low-temperature furnace return to ensure the plastic deformation capacity of high Mo and high Co steel. Therefore, during the forging and blanking process, when the temperature is lower than 1050℃, the furnace is returned to heat at 1150℃±10℃ for 2h±10min and then the upsetting is continued. The final forging temperature is controlled to be ≥1000℃. When the temperature is lower than 1000℃, the furnace is returned to heat at 1100℃±10℃ for 2h±10min and then the upsetting is continued.

[0037] (4) Hot deformation: After the “three upsetting and three drawing” process, the forged material is returned to the furnace and heated to 1150℃±10℃, and kept at this temperature for 2h±10min to restore the hot processing plasticity, and then fine forging or rolling is performed to the final size. The single pass reduction of fine forging or rolling is ≤35%, and the final forging or final rolling temperature is ≥950℃. Control of the single pass reduction and the final forging temperature can avoid grain boundary damage caused by severe deformation of high-alloy steel; the final size of bars, wires or plates can be directly obtained through hot deformation without the need for cold rolling, thus avoiding the risk of cold rolling cracking of high-strength steel.

[0038] (5) Heat treatment:

[0039] Keep at 850-860℃ for 1-2h, then immediately oil cool to room temperature, and form lath martensite with high dislocation density through the first high-temperature quenching; keep at 820-830℃ for 1-1.5h, then immediately oil cool to room temperature, repeat twice, and further refine the martensite substructure through the second low-temperature quenching to provide a uniform matrix for subsequent precipitation.

[0040] Place it in a cryogenic device at a temperature of -70 to -80°C for 1 to 2 hours within 4 hours to induce the transformation of retained austenite to martensite through ultra-low temperature, reduce the residual soft phase, increase the lattice distortion, and enhance the driving force for the nucleation of the precipitation phase; then take it out of the cryogenic device and naturally return to temperature in the air.

[0041] The material that has stabilized to room temperature is aged within 8 hours at a temperature of 480-500°C for 5-8 hours. The aging treatment precisely matches the diffusion capacity of Cu, Ti, and Al in the composition, promotes the synergistic strengthening of multi-scale precipitation phases such as Ni3Ti (Cu doping), NiAl, and Ni3Mo, and avoids brittleness caused by over-aging.

[0042] Specific examples will be listed below to explain the scheme of the present invention. It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the examples, the techniques or conditions described in the literature in this area or the product instructions are used. Reagents or instruments used that do not indicate manufacturers are all conventional products that can be obtained commercially.

[0043] The present invention provides an embodiment of preparing copper-containing maraging ultra-high strength steel and a comparative example of preparing maraging steel, the main chemical components of which are shown in Table 1 (the balance is Fe).

[0044] Table 1 Chemical composition (by mass percentage, %)

[0045] Co Ni Mo Ti Cu Al C Si Mn P S N O Example 1 15.5 17.7 7.12 1.45 0.5 0.5 0.003 0.01 0.01 0.0018 0.0010 0.0010 0.0012 Example 1 16.0 18.0 7.80 1.10 0.7 0.7 0.002 0.02 0.01 0.0015 0.0012 0.0007 0.0010 Comparative Example 1 12.0 18.2 4.53 1.43 / 0.12 0.0011 0.009 0.01 0.0013 0.0016 0.0011 0.0008 Comparative Example 2 11.96 18.18 4.46 1.39 / 0.14 0.0027 0.014 0.012 0.0013 0.0016 0.0005 0.0006

[0046] Example 1 Copper-containing martensitic aging ultra-high strength steel and preparation method thereof, the specific steps are as follows:

[0047] (1) A vacuum induction and vacuum consumable dual process is used to smelt a maraging steel ingot, the chemical composition of which is shown in Table 1; and the ingot is subjected to a peeling treatment.

[0048] (2) placing the maraging steel ingot after the peeling treatment into a heating furnace at a furnace temperature of 1000° C. and performing high-temperature homogenization treatment as the furnace is heated; the homogenization treatment conditions include: a holding temperature of 1250° C. and a holding time of 48 h. After the holding is completed, the ingot is taken out of the furnace and cooled to a forging temperature of 1200° C. before forging and blanking.

[0049] (3) Forging blanks adopt "three upsetting and three drawing", the forging temperature is 1200℃, the first upsetting reduction is 55%, the drawing rate is 250%; the second upsetting reduction is 55%, the drawing rate is 250%; the third upsetting reduction is 50%, the drawing rate is 200%; the blanks are opened into diameters Round rod.

[0050] (4) The round bar forging material after the above-mentioned "three upsetting and three drawing" blanking is returned to the furnace and heated to 1150°C, and kept at this temperature for 2 hours; then it is taken out of the furnace for fine forging, with the first pass of fine forging reducing by 30%, and the subsequent passes reducing by 10%, and finally the diameter is obtained. The round bar has a final forging temperature of 960℃.

[0051] (5) Keep at 860℃ for 1 hour, then immediately cool to room temperature with oil; keep at 820℃ for 1 hour, then immediately cool to room temperature with oil, repeat twice; cool in a -73℃ deep freezer for 1.5 hours within 4 hours, then take out of the deep freezer and allow to warm up naturally in the air; age the material that has been stabilized to room temperature within 8 hours at 485℃ for 5 hours.

[0052] Example 2 Copper-containing martensitic aging ultra-high strength steel and preparation method thereof, the specific steps are as follows:

[0053] (1) A vacuum induction and vacuum consumable dual process is used to smelt a maraging steel ingot, the chemical composition of which is shown in Table 1; and the ingot is subjected to a peeling treatment.

[0054] (2) The maraging steel ingot after the peeling treatment is placed in a heating furnace at a furnace temperature of 1000° C. and subjected to high-temperature homogenization treatment. The homogenization treatment conditions include: a holding temperature of 1260° C. and a holding time of 36 h. After the holding is completed, the ingot is taken out of the furnace and cooled to a forging temperature of 1200° C. before forging and blanking.

[0055] (3) Forging blanks adopt "three upsetting and three drawing", the forging temperature is 1200℃, the first upsetting reduction is 60%, the drawing rate is 300%; the second upsetting reduction is 55%, the drawing rate is 250%; the third upsetting reduction is 50%, the drawing rate is 200%. The blanks are 3000mm in length, 1000mm in width, and 500mm in height.

[0056] (4) The slab forging material after the above “three upsetting and three drawing” is returned to the furnace and heated to 1150°C, and kept at this temperature for 2 hours. Then it is rolled out of the furnace, with the first rolling pass reducing by 20%, and the subsequent rolling passes reducing by 10%, and finally a plate with a thickness of 20 mm is obtained, and the final rolling temperature is 950°C.

[0057] (5) Keep at 850℃ for 2 hours, then immediately cool to room temperature with oil; keep at 820℃ for 1 hour, then immediately cool to room temperature with oil, repeat twice; cool in a -73℃ deep freezer for 2 hours within 4 hours, then take out of the deep freezer and allow to warm up naturally in the air; age the material that has been stabilized to room temperature within 8 hours, with an aging temperature of 480℃ and a time of 7 hours.

[0058] Comparative Example 1: The difference from Example 1 is that the chemical composition of the maraging steel ingot in step (1) is as shown in Table 1; the rest of the process is consistent with Example 1.

[0059] Comparative Example 2: The difference from Example 2 is that the chemical composition of the maraging steel ingot in step (1) is as shown in Table 1, and the aging temperature in step (5) is 510° C. and the time is 3 hours; the rest of the process is the same as Example 1.

[0060] The mechanical properties of the maraging steels obtained in the examples and comparative examples after aging are shown in Table 2.

[0061] Table 2 Mechanical properties

[0062] Mechanical properties Tensile strength Rm(MPa) Yield strength Rp0.2(MPa) Elongation A(%) Example 1 2835 2781 7.2 Example 2 2874 2816 7.8 Comparative Example 1 2412 2358 12.5 Comparative Example 2 2418 2364 12.5

[0063] As shown in Table 2, the mechanical properties of the copper-containing martensitic aging ultra-high strength steel obtained by the method of the present invention are significantly better than those of the comparative examples. Among them, the mechanical properties of comparative examples 1 and 2 are significantly lower than those of embodiments 1 and 2, mainly due to the influence of composition differences on precipitation strengthening, solid solution strengthening and organizational uniformity; due to the insufficient content of key elements (Co, Mo, Cu, Al) and excessive Ni, the precipitation strengthening and solid solution strengthening effects are significantly reduced, and the grain boundary stability is reduced. The elongation of comparative examples 1 and 2 is relatively high, which is due to the small number of precipitated phases, small resistance to dislocation movement, and easier deformation, but accompanied by a significant decrease in strength. This high plasticity lacks application value in actual engineering and cannot meet the application requirements of ultra-high strength steel. At the same time, over-aging in comparative example 2 leads to coarsening of the precipitated phase: high temperature accelerates the coarsening of the precipitated phase, reduces its pinning ability to dislocations, and leads to a decrease in strength; and 3 hours is not enough to complete the full diffusion of Cu nanoclusters and the complete precipitation of NiAl and Ni3Mo phases, resulting in insufficient volume fraction of the precipitated phase. In contrast, Examples 1 and 2 achieve a highly efficient balance between strength and plasticity through precise composition control (Cu-Ti-Al-Mo-Co synergy) combined with process optimization.

Claims

1. A copper-containing martensitic aging ultra-high strength steel, characterized in that: Its chemical composition is calculated by mass percentage as follows: Co 14.5-16.0%, Ni 17.0-18.0%, Mo 6.0-8.0%, Ti 1.0-1.5%, Cu 0.5-1.0%, Al 0.5-1.0%, and the balance is Fe and inevitable impurities.

2. The copper-containing maraging ultra-high strength steel according to claim 1, characterized in that: In its chemical composition, the unavoidable impurities are C≤0.008%, Si≤0.1%, Mn≤0.1%, P≤0.005%, S≤0.005%, N≤0.0015%, and O≤0.0015%.

3. The copper-containing maraging ultra-high strength steel according to claim 1, characterized in that: Its grain size is ≥8.0 grade, tensile strength Rm ≥2800MPa, yield strength Rp0.2 ≥2700MPa, and elongation A ≥7%.

4. The method for preparing the copper-containing maraging ultra-high strength steel according to any one of claims 1 to 3, characterized in that: The specific steps include: S1 adopts vacuum induction and vacuum consumable dual process to smelt ingots, and then performs skinning treatment on the ingots; After the S2 heating furnace is preheated, the peeled ingot is placed into the heating furnace for high-temperature homogenization treatment as the furnace heats up. After completion, it is taken out of the furnace and cooled to the forging temperature for forging and blanking. After S3 blanking, the forged material is returned to the furnace for heating, and after being taken out of the furnace, it is fine forged or rolled to the final size, and then heat treated to obtain copper-containing martensitic aged ultra-high strength steel.

5. The method for preparing copper-containing maraging ultra-high strength steel according to claim 4, characterized in that: In step S2, the heating furnace is preheated to a furnace temperature of 1000°C ± 10°C.

6. The method for preparing copper-containing maraging ultra-high strength steel according to claim 4, characterized in that: In step S2, the temperature of the high temperature homogenization treatment is 1250°C to 1260°C, and the insulation time is 36h to 48h.

7. The method for preparing copper-containing maraging ultra-high strength steel according to claim 4, characterized in that: In step S2, the forging process adopts "three upsetting and three drawing", the starting forging temperature is 1180°C to 1200°C, the final forging temperature is ≥1000°C, the downsetting amount of each time is ≥50%, and the drawing rate is ≥200%.

8. The method for preparing copper-containing maraging ultra-high strength steel according to claim 7, characterized in that: During the forging process, when the temperature is lower than 1050℃, return to the furnace and heat at 1150℃±10℃ for 2h±10min before continuing the roughing; during the final forging process, when the temperature is lower than 1000℃, return to the furnace and heat at 1100℃±10℃ for 2h±10min before continuing the upsetting.

9. The method for preparing copper-containing maraging ultra-high strength steel according to claim 4, characterized in that: In step S3, the furnace heating is to raise the temperature to 1150°C±10°C and keep it for 2h±10min; the single pass reduction of the fine forging or rolling is ≤35%, and the final forging or final rolling temperature is ≥950°C.

10. The method for preparing copper-containing maraging ultra-high strength steel according to claim 4, characterized in that: In step S3, the heat treatment is specifically as follows: keeping at 850°C to 860°C for 1h to 2h, and then immediately oil cooling to room temperature; keeping at 820°C to 830°C for 1h to 1.5h, and then immediately oil cooling to room temperature, repeated twice; deep freezing treatment at -70°C to -80°C for 1h to 2h within 4 hours, and then naturally warming up in the air; aging treatment at 480°C to 500°C for 5h to 8h within 8 hours.