High plasticity 3gpa grade medium-low alloy steel and its preparation method

Abstract

The application belongs to the technical field of metallurgy, and more particularly relates to a high-plasticity 3GPa-grade medium-low alloy steel and a preparation method thereof. The high-plasticity 3GPa-grade medium-low alloy steel is prepared by the following steps: after austenitizing treatment of the medium-low alloy steel, high-temperature hot deformation treatment is performed, then the medium-low alloy steel is cooled to a first preset temperature at a first cooling speed, continuous warm deformation is performed between the first preset temperature and a second preset temperature, the medium-low alloy steel is cooled to room temperature, and then low-temperature tempering treatment is performed. The high-plasticity 3GPa-grade medium-low alloy steel has excellent work hardening capacity, solves the problem of low plasticity of the existing super-high-strength steel, enables the material to have excellent plasticity under the condition of super-high strength, and significantly reduces the total amount of expensive metal elements such as Mo and Ni, reduces the material composition segregation of the material, and improves the service stability of the parts prepared from the material.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and more specifically relates to a high-ductility 3GPa grade medium-low alloy steel and its preparation method. Background Technology

[0002] Ultra-high strength steel is not only the most important material used in key load-bearing components of high-end equipment in fields such as aviation, energy, transportation, and weaponry, such as aircraft landing gear and protective armor, but also a key structural material that is essential in major projects such as "deep earth, deep sea, and deep space" as well as in key high-end equipment for future interstellar exploration and comprehensive resource utilization.

[0003] The inverse relationship between strength and ductility in traditional materials results in very low ductility in ultra-high-strength steel. Currently, only maraging steel or cold-drawn pearlitic steel wire can achieve the 3GPa level of ultra-high-strength steel. However, both of these materials have very low ductility, <5%, and the ductility of cold-drawn steel wire is even lower, <2%, leading to brittle fracture.

[0004] Furthermore, maraging steels contain large amounts of expensive metallic elements such as Co, Mo, and Ni, with the total alloy content typically exceeding 40%. This not only significantly increases the cost of steel materials but also leads to poor fluidity and severe material composition segregation due to the addition of numerous alloying elements, easily causing instability in the service performance of critical components.

[0005] Therefore, developing technologies for preparing medium-alloy or low-alloy steels to achieve ultra-high strengths of 3GPa is at the forefront of current research in the field of steel materials and is also a challenge in the field of high-end steel materials. Summary of the Invention

[0006] The purpose of this invention is to provide a high-ductility 3GPa grade medium-low alloy steel and its preparation method, so as to solve the problems existing in the prior art and realize the preparation of high-ductility 3GPa grade medium-low alloy steel.

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

[0008] One of the technical solutions of this invention is to provide a method for preparing high-ductility 3GPa grade medium-low alloy steel, the steps of which include:

[0009] After austenitizing treatment, medium and low alloy steel is subjected to high-temperature hot deformation treatment, cooled to a first preset temperature at a first cooling rate, continuously warm deformed between the first preset temperature and the second preset temperature, cooled, and then subjected to low-temperature tempering treatment to obtain the high-plasticity 3GPa grade medium and low alloy steel.

[0010] This invention involves austenitizing medium and low alloy steel using conventional heating methods or rapid heating methods such as induction heating, thereby forming an austenitic structure. Then, high-temperature hot deformation treatment effectively refines the austenitic grains. Subsequently, by controlling the initial cooling rate, the supercooled austenite does not undergo ferrite or pearlite phase transformation during cooling. Following continuous warm deformation treatment, the supercooled austenite undergoes warm deformation and precipitates a nano-second phase. Finally, tempering treatment after cooling effectively eliminates quenching stress.

[0011] Furthermore, the high-temperature heat deformation treatment is performed at a temperature of 850-1250℃, with a deformation amount >30%.

[0012] Furthermore, the first cooling rate is 1-100℃ / s.

[0013] Furthermore, the first preset temperature is 500-700℃.

[0014] Furthermore, the second preset temperature is 100-500℃.

[0015] Furthermore, the continuous temperature deformation has ≥2 deformation passes and a total deformation amount ≥50%.

[0016] Furthermore, the cooling rate after continuous temperature deformation is >2℃ / s.

[0017] Furthermore, the low-temperature tempering treatment is performed at a temperature of 100-300℃ for a time of 0.1-5 hours.

[0018] Furthermore, by mass percentage, the composition of the medium-low alloy steel includes: C 0.40-0.65%, Mn+Cr 1.0-3.5%, Al+Si 1.0-2.0%, Mo+Ni<2.0%, V+Nb+Ti 0-0.3%, P<0.02%, S<0.02%, O<0.0015%, N<0.008%, and H<0.0001%, with the balance being Fe and unavoidable impurities.

[0019] Furthermore, the high-plasticity 3GPa grade medium-low alloy steel includes martensite and retained austenite, wherein the content of retained austenite is <20%.

[0020] Optionally, the high-plasticity 3GPa grade medium-low alloy steel may also include bainite and / or nano-second phases.

[0021] The second technical solution of the present invention provides a high-plasticity 3GPa grade medium-low alloy steel, wherein the high-plasticity 3GPa grade medium-low alloy steel is prepared by the above-mentioned preparation method.

[0022] The third technical solution of the present invention provides an application of the above-mentioned high-plasticity 3GPa grade medium and low alloy steel in the preparation of load-bearing components.

[0023] Fourth technical solution of the present invention: A method for improving the strength and plasticity of medium and low alloy steel, comprising the following steps:

[0024] After austenitizing treatment, medium and low alloy steel is subjected to high-temperature hot deformation treatment, then cooled to a first preset temperature at a first cooling rate, and then subjected to continuous warm deformation between the first preset temperature and the second preset temperature. After cooling to room temperature, it is subjected to low-temperature tempering treatment to obtain high-plasticity 3GPa grade medium and low alloy steel.

[0025] Furthermore, the high-temperature heat deformation treatment is performed at a temperature of 850-1250℃, with a deformation amount >30%.

[0026] Furthermore, the first cooling rate is 1-100℃ / s.

[0027] Furthermore, the first preset temperature is 500-700℃.

[0028] Furthermore, the second preset temperature is 100-500℃.

[0029] Furthermore, the continuous temperature deformation has ≥2 deformation passes and a total deformation amount ≥50%.

[0030] Furthermore, the cooling rate to room temperature is >2°C / s.

[0031] Furthermore, the low-temperature tempering treatment is performed at a temperature of 100-300℃ for a time of 0.1-5 hours.

[0032] Furthermore, by mass percentage, the composition of the medium-low alloy steel includes: C 0.40-0.65%, Mn+Cr 1.0-3.5%, Al+Si 1.0-2.0%, Mo+Ni<2.0%, V+Nb+Ti 0-0.3%, P<0.02%, S<0.02%, O<0.0015%, N<0.008%, and H<0.0001%, with the balance being Fe and unavoidable impurities.

[0033] Furthermore, the high-plasticity 3GPa grade medium-low alloy steel includes martensite and retained austenite, wherein the content of retained austenite is <20%.

[0034] Optionally, the high-plasticity 3GPa grade medium-low alloy steel may also include bainite and / or nano-second phases.

[0035] The present invention discloses the following technical effects:

[0036] This invention utilizes mechanical metallurgical processes to produce ultra-high strength steel with a tensile strength ≥3GPa and an elongation ≥5% from medium and low alloy steel. It exhibits excellent work hardening capabilities and solves the problem of low plasticity in existing ultra-high strength steels. This allows the material to possess excellent plasticity while maintaining ultra-high strength. At the same time, the total amount of expensive metal elements such as Mo and Ni is significantly reduced, which reduces material composition segregation and improves the service stability of components made from it. Attached Figure Description

[0037] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0038] Figure 1 The image shows a TEM image of the high-ductility 3GPa grade medium-low alloy steel prepared in Example 1.

[0039] Figure 2 The image shows a TEM image of the high-ductility 3GPa grade medium-low alloy steel prepared in Example 2. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0046] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0047] Example 1

[0048] The preparation steps for high-ductility 3GPa grade medium-low alloy steel include:

[0049] Raw material preparation: By mass percentage, the composition of medium and low alloy steel includes: C 0.47%, Al+Si 1.35%, Mn+Cr 3.0%, Mo+Ni 0.70%, V+Nb+Ti 0.17%, O 0.0011%, H 0.00005%, N 0.005%, P 0.01%, and S 0.01%, with the balance being iron and unavoidable impurities.

[0050] The above-mentioned medium and low alloy steel was subjected to austenitization treatment. The heating temperature was 1150℃, and the temperature was held for 5 minutes to austenitize the steel. High-temperature hot deformation (1150℃) was then performed with a deformation amount of 60%. The steel was then cooled to 650℃ at a cooling rate of 10℃ / s. The steel was then continuously deformed in 5 passes, with deformation amounts of 15%, 12%, 11%, 12%, and 15% for each pass, respectively. After the deformation was completed, the temperature was 380℃. The steel was then cooled to room temperature at a cooling rate of 5℃ / s. Finally, the steel was tempered at 170℃ for 2 hours to obtain high-plasticity 3GPa grade medium and low alloy steel.

[0051] After processing according to Example 1, the high-plasticity 3GPa grade medium-low alloy steel obtained has a residual austenite content of 12.5%, a yield strength of 1950MPa, a tensile strength of 3025MPa, a uniform elongation of 5.8%, and a total elongation of 7.2%.

[0052] Figure 1 The image shows a TEM image of the high-ductility 3GPa grade medium-low alloy steel prepared in Example 1.

[0053] Example 2

[0054] The preparation steps for high-ductility 3GPa grade medium-low alloy steel include:

[0055] Raw material preparation: By mass percentage, the composition of medium and low alloy steel includes: C 0.57%, Al+Si 1.80%, Mn+Cr 2.5%, Mo+Ni 0.52%, V+Nb+Ti 0.28%, O 0.0010%, H 0.00007%, N 0.004%, P 0.01%, and S 0.01%, with the balance being iron and unavoidable impurities.

[0056] The above-mentioned medium and low alloy steel was subjected to austenitization treatment, heated to 1000℃ and held for 5 minutes, followed by high-temperature hot deformation (1000℃) with a deformation amount of 45%. It was then cooled to 550℃ at a cooling rate of 30℃ / s, and then deformed continuously for 3 passes, with deformation amounts of 20%, 15%, and 28% in each pass, respectively. After deformation, the temperature was 350℃, and then cooled to room temperature at a rate of 8℃ / s. Finally, it was tempered at 220℃ and held for 0.5 hours to obtain high-plasticity 3GPa grade medium and low alloy steel.

[0057] After processing according to Example 2, the high-plasticity 3GPa grade medium-low alloy steel obtained has a residual austenite content of 11.0%, a yield strength of 1760MPa, a tensile strength of 3083MPa, a uniform elongation of 6.4%, and a total elongation of 6.8%.

[0058] Figure 2 The image shows a TEM image of the high-ductility 3GPa grade medium-low alloy steel prepared in Example 2.

[0059] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0060] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-ductility 3GPa grade medium-low alloy steel, characterized in that the steps include... include: After austenitizing treatment, medium and low alloy steel is subjected to high-temperature hot deformation treatment, cooled to a first preset temperature at a first cooling rate, subjected to continuous warm deformation between the first preset temperature and the second preset temperature, cooled, and then subjected to low-temperature tempering treatment to obtain the high plasticity 3GPa grade medium and low alloy steel. Among them, by controlling the first cooling rate, the supercooled austenite does not undergo ferrite or pearlite phase transformation during the cooling process; The composition of the medium-low alloy steel, by mass percentage, includes: C 0.40-0.65%, Mn+Cr 1.0-3.5%, Al+Si 1.0-2.0%, Mo+Ni <2.0%, V+Nb+Ti 0-0.3%, P <0.02%, S <0.02%, O <0.0015%, N <0.008%, and H <0.0001%, with the balance being Fe and unavoidable impurities; The high-temperature heat deformation treatment is performed at a temperature of 850-1250℃, with a deformation amount >30%. The first preset temperature is 500-700℃; The second preset temperature is 100-500℃; The continuous temperature deformation has ≥2 deformation passes and a total deformation amount ≥50%.

2. The preparation method according to claim 1, characterized in that, The first cooling rate is 1-100℃ / s.

3. The preparation method according to claim 1, characterized in that, The cooling rate after continuous warm deformation is >2℃ / s; and / or the temperature of the low-temperature tempering treatment is 100-300℃ and the time is 0.1-5h.

4. A high-ductility 3GPa grade medium-low alloy steel, characterized in that, The high-plasticity 3GPa grade medium-low alloy steel is prepared by the preparation method described in any one of claims 1-3.

5. The application of the high-ductility 3GPa grade medium-low alloy steel as described in claim 4 in the preparation of load-bearing components.

Images