Preparation method of fracture-controllable lightweight steel material based on three-phase structure regulation and control

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a preparation method of fracture-controllable light steel based on three-phase structure regulation and control. The structure of the light steel material is composed of ferrite, M / A island and kappa carbide, heat preservation treatment is conducted on light steel to be treated in a ferrite and austenite two-phase region, then hot rolling is conducted, then cooling is conducted to a first preset temperature at a first cooling speed, heat preservation is conducted, cooling is conducted to a second preset temperature at a second cooling speed, and heat preservation is conducted. And finally, cooling at a third cooling rate to prepare the steel plate, the volume percent of the ferrite is 70-76%, the volume percent of the M / A island is 15-20%, and the volume percent of the kappa carbide is 4-15%. Through alloy element regulation and control and structural design of controllable fragmentation performance, M / A island and kappa carbides of the prepared lightweight steel are distributed in ferrite grain boundaries, the impact energy is lower than 20 J, and the ductility is lower than 2%.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and more specifically relates to a method for preparing a controllable fracture lightweight steel material based on three-phase structure regulation. Background Art

[0002] Controllable fracture steels have unique application value in many fields. They are often used in scenarios where automatic fracture under specific conditions is required for safety, protection, self-destruction, or energy release. The design and application of controlled fracture steels require a comprehensive consideration of factors such as the material's fracture properties, environmental adaptability, and cost-effectiveness. These materials require not only high strength but also low manufacturing costs and lightweight requirements. Therefore, lightweight controlled fracture steels have become a research hotspot.

[0003] Many R&D units have improved and developed the composition and process of lightweight steel, which are introduced as follows:

[0004] Chinese patent publication CN 116426836 A proposes a Fe-Mn-Al-C-Nb-V austenitic lightweight steel and its preparation method. The chemical composition of the Fe-Mn-Al-C-Nb-V austenitic lightweight steel, measured by mass, includes: C 0.95-1.15%, Mn 27.00-29.00%, Al 17.00-8.50%, Mo 0.55-0.65%, Nb 0.15-1.50%, V 0.15-1.20%, with the remainder being Fe and unavoidable impurities. This invention achieves a fine-grained austenitic structure through a solutionizing, hot rolling, and aging process. The steel exhibits an upper tensile strength exceeding 900 MPa and an elongation exceeding 50%.

[0005] Chinese patent publication CN 104674109 A proposes a low-density Fe-Mn-Al-C cold-rolled automotive steel sheet and its preparation method. The chemical composition of the automotive steel sheet is as follows: 0.65% to 0.75% C, 14.0% to 19.0% Mn, 7.0% to 10.5% Al, P < 0.003%, S < 0.002%, with the balance being Fe and unavoidable impurities. The preparation process includes smelting, forging, hot rolling, solution treatment, and annealing. The steel has an austenite + ferrite dual-phase structure, which reduces density while maintaining excellent overall mechanical properties, resulting in significant weight reduction. Its strength-ductility product can reach 40 GPa·%.

[0006] Chinese patent publication CN 118441223 A proposes a lightweight, high-strength ferritic steel plate with integrated structure and function, and its manufacturing method. The steel plate's chemical element weight percentages are: C: ≤ 0.003%, Si: ≤ 0.05%, Cu: 0.3% to 0.8%, Al: 5% to 8%, S: ≤ 0.01%, P ≤ 0.018%, and N ≤ 0.005%, with the remainder being Fe and unavoidable impurities. The steel plate has a yield strength of ≥ 400 MPa, a tensile strength of ≥ 550 MPa, and an elongation (A50) of ≥ 20%, reducing equipment weight by more than 5%.

[0007] Chinese patent publication CN117327994 A proposes a ferrite-based lightweight steel and a method for preparing the same. The steel comprises, by mass, 0.04% to 0.12% C, 25.0% to 36.0% Mn, 8.0% to 10.0% Al, <0.02% P, <0.01% S, 0.05% to 1.0% Nb, 0.05% to 1.0% V, 0.5% to 1.5% Mo, and 0.5% to 1.5% W, with the remainder being Fe and unavoidable trace impurities. The steel structure comprises 20% to 35% austenite by volume and 65% to 80% ferrite by volume. The steel has a room temperature tensile strength of 740 MPa or greater and an impact energy of 130 J or greater.

[0008] The lightweight steels mentioned in the aforementioned invention patents all possess high elemental content and good ductility and toughness. However, the high cost of raw materials limits their application in disposable devices and shock-absorbing structural components. Against this backdrop, there is an urgent need to develop lightweight, controlled-fracture steels that can meet the needs of specific applications. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for preparing a controllable fracture lightweight steel material based on three-phase microstructure regulation to solve the problems existing in the above-mentioned prior art.

[0010] To achieve the above object, the present invention provides the following solutions:

[0011] One of the technical solutions of the present invention is to provide a controlled fracture lightweight steel based on three-phase microstructure regulation, wherein the microstructure of the lightweight steel material is composed of ferrite, M / A islands and kappa carbide;

[0012] The ferrite content is 70-76%;

[0013] The content of the M / A island is 15-20%;

[0014] The content of the kappa carbide is 4-15%.

[0015] Furthermore, the grain size of the ferrite is 5-9 μm.

[0016] Furthermore, the size of the M / A island is 2-5 μm.

[0017] Furthermore, the size of the κ carbide is 1-2 μm.

[0018] The second technical solution of the present invention is to provide a method for preparing the above-mentioned controlled fracture lightweight steel based on three-phase microstructure regulation, comprising the following steps:

[0019] The lightweight steel to be treated is heat-treated in the ferrite and austenite two-phase region, followed by hot rolling, and then cooled to a first preset temperature at a first cooling rate and kept warm, then cooled to a second preset temperature at a second cooling rate and kept warm, and finally cooled at a third cooling rate to obtain the controllable fracture lightweight steel based on three-phase structure regulation.

[0020] Furthermore, in terms of mass percentage, in addition to Fe, the components of the lightweight steel to be treated include: C 0.7%-0.8%, Si 1.0%-1.5%, Mn 1.2%-1.8%, Al 7.0%-8.5% and Cr 0%-0.48%, as well as inevitable impurities.

[0021] Optionally, the mass percentage ratio of C, Si, Al, Cr and Mn in the components of the lightweight steel to be treated meets 0.70≤η≤1.67, η=ln(Al-2Mn)-[1.5Si+Cr 1 / 2 -1.2C] / 4.

[0022] Based on the role and content control of each alloying element, the present invention designs the alloy components of lightweight steel: C, Si, Cr, Al and Mn. Based on the reasonable control of the chemical composition range of each element in the steel, and through the element content regulation relationship: 0.70≤η≤1.67, η=ln(Al-2Mn)-[1.5Si+Cr 1 / 2 -1.2C] / 4, regulating the ratio of C, Si, Cr, Al, and Mn alloying elements facilitates the precise determination of the content of each element, which is crucial for the elemental control of the controlled fracture lightweight steel based on three-phase microstructure regulation of the present invention. The η value is controlled between 0.7 and 1.67. Excessively high η values ​​result in high alloying element content in the controlled fracture lightweight steel based on three-phase microstructure regulation, leading to excessively high production costs and segregation, further complicating the subsequent production process and other adverse effects. Excessively low η values ​​increase plastic toughness and reduce efficient fragmentation characteristics.

[0023] Furthermore, the temperature of the heat preservation treatment in the ferrite and austenite two-phase region is 1050-1200° C., and the time is 40-90 minutes.

[0024] Furthermore, the hot rolling temperature is 1050-1200° C., the rolling passes are 2-4 times, and the deformation amount is 40%-60%.

[0025] Furthermore, the cooling rate of the first cooling rate is 0.1-10°C / s.

[0026] Furthermore, the first preset temperature is 890-1000°C.

[0027] Furthermore, the cooling to the first preset temperature and keeping warm takes place for 60-90 minutes.

[0028] The present invention hot-rolls a lightweight steel that is heat-insulated in the austenite and ferrite two-phase regions, and cools it to a first preset temperature at a first cooling rate to obtain a deformed ferrite + austenite complex phase structure. During the first cooling rate cooling to the preset temperature, recrystallization may occur, increasing the grain boundary area to ensure that nucleation sites for κ carbide are provided during the heat-insulation process at the first preset temperature, thereby promoting the growth of κ carbide.

[0029] Furthermore, the cooling rate of the second cooling rate is 1-5°C / s.

[0030] Furthermore, the second preset temperature is 800-850°C.

[0031] Furthermore, the cooling to the second preset temperature and keeping warm takes place for 60-120 minutes.

[0032] Furthermore, the cooling rate of the third cooling rate is 5-30°C / s.

[0033] Furthermore, the temperature after cooling at the third cooling rate is 18-22°C.

[0034] During the third cooling process, austenite is transformed into M / A islands, which can achieve high hardness and strength properties, and finally a lightweight steel with a structure with controllable fragmentation properties is obtained, with ferrite as the matrix, M / A islands and κ carbides distributed at the ferrite grain boundaries.

[0035] The controlled fracture lightweight steel based on three-phase microstructure regulation prepared by the present invention has ferrite as the matrix, and M / A islands and kappa carbides are distributed at the ferrite grain boundaries, forming a structure with controllable fragmentation performance.

[0036] The present invention discloses the following technical effects:

[0037] The present invention, while maintaining a relatively low alloying element content, produces a lightweight steel with a ferrite matrix containing M / A islands and kappa carbides through simple heat treatment and controlled thermal processing parameters. This controlled fracture structure imparts excellent, efficient fracture characteristics to the lightweight steel. Through alloying element control and the design of a controlled fracture structure, the lightweight steel's M / A islands and kappa carbides are distributed at ferrite grain boundaries, resulting in an impact energy below 20 J, an elongation below 2%, and excellent ductile fracture behavior under high-speed impact loads.

[0038] The lightweight steel alloy component system of the present invention is reasonably regulated, the preparation process is simple and easy, it is conducive to industrial production, and the preparation efficiency is high.

[0039] The controlled fracture lightweight steel based on three-phase microstructure regulation provided by the present invention has a hardness of 430-520 HV, a tensile strength of 1000-1020 MPa, an elongation of 0.5-1.5%, and an impact energy of 10-18 J. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0041] Figure 1 This is the SEM image of the controlled fracture lightweight steel based on three-phase structure regulation prepared in Example 1.

[0042] Figure 2 This is the SEM image of the controlled fracture lightweight steel based on three-phase structure regulation prepared in Example 2.

[0043] Figure 3 This is the SEM image of the controlled fracture lightweight steel based on three-phase structure regulation prepared in Example 3. DETAILED DESCRIPTION

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0045] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0046] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0047] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0048] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0049] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0050] Unless otherwise specified, the "room temperature" and "normal temperature" involved in the specific embodiments of the present invention refer to 20-30°C.

[0051] The raw materials used in the present invention are all commercially available products, and the purchase channels do not affect the realization of the technical effects.

[0052] Example 1

[0053] The preparation steps of controlled fracture lightweight steel based on three-phase microstructure regulation include:

[0054] S1. Prepare a lightweight steel to be processed (original smelted steel), wherein the composition of the lightweight steel to be processed is, by mass percentage, 0.72% C, 1.10% Si, 7.20% Al, 1.20% Mn, and 0.10% Cr, with the balance being Fe and unavoidable impurities; η = 1.29;

[0055] S2, holding the to-be-treated lightweight steel at 1050°C for 60 minutes for ferrite and austenite two-phase heat treatment, then heating to 1200°C for 30 minutes before rolling, with four rolling passes and a deformation of 60%;

[0056] S3. After rolling, the steel is cooled to 980°C at a cooling rate of 10°C / s and kept warm for 60 minutes. Then, the steel is cooled to 800°C at a cooling rate of 1°C / s and kept warm for 60 minutes. Finally, the steel is cooled to 18°C ​​at a cooling rate of 15°C / s to obtain a lightweight steel with controllable fracture based on three-phase microstructure regulation.

[0057] Figure 1 This is the SEM image of the controlled fracture lightweight steel based on three-phase structure regulation prepared in Example 1.

[0058] Testing revealed that the lightweight steel material produced in Example 1 consisted of ferrite, M / A islands, and kappa carbide, with contents of 72%, 20%, and 8%, respectively. The ferrite grain size was 6 μm, the M / A islands were 3 μm, and the kappa carbide was 1.2 μm. This lightweight steel material exhibited a hardness of 435 HV, a tensile strength of 1000 MPa, an elongation of 1.4%, and an impact energy of 18 J.

[0059] Example 2

[0060] The preparation steps of controlled fracture lightweight steel based on three-phase microstructure regulation include:

[0061] S1. Prepare a lightweight steel to be processed, wherein the composition of the lightweight steel to be processed is, by mass percentage, C 0.76%, Si 1.30%, Al 7.80%, Mn 1.50%, and Cr 0.32%, with the balance being Fe and unavoidable impurities; η = 1.17;

[0062] S2, heat-treating the light steel to be treated at 1100°C for 90 minutes to perform heat-treating treatment in the ferrite and austenite two-phase region, then cooling to 1050°C for 30 minutes before rolling, with two rolling passes and a deformation of 40%;

[0063] S3. After rolling, the steel is cooled to 950°C at a cooling rate of 2°C / s and kept warm for 75 minutes. Then, it is cooled to 820°C at a cooling rate of 3°C / s and kept warm for 90 minutes. Finally, it is cooled to 20°C at a cooling rate of 25°C / s to obtain a controlled fracture lightweight steel based on three-phase microstructure regulation.

[0064] Figure 2 This is the SEM image of the controlled fracture lightweight steel based on three-phase structure regulation prepared in Example 2.

[0065] Testing revealed that the lightweight steel material produced in Example 2 consisted of ferrite, M / A islands, and kappa carbide, with contents of 74%, 16%, and 10%, respectively. The ferrite grain size was 7.2 μm, the M / A island size was 3.8 μm, and the kappa carbide size was 1.4 μm. This lightweight steel material exhibited a hardness of 487 HV, a tensile strength of 1008 MPa, an elongation of 0.9%, and an impact energy of 12 J.

[0066] Example 3

[0067] The preparation steps of controlled fracture lightweight steel based on three-phase microstructure regulation include:

[0068] S1. Prepare a lightweight steel to be processed, wherein the composition of the lightweight steel to be processed is, by mass percentage, C 0.80%, Si 1.50%, Al 8.40%, Mn 1.70%, and Cr 0.46%, with the balance being Fe and unavoidable impurities; η = 1.12;

[0069] S2, the light steel to be treated is kept at 1200°C for 40 minutes for a ferrite and austenite two-phase insulation treatment, then cooled to 1100°C for 30 minutes before rolling, with three rolling passes and a deformation of 50%;

[0070] S3. After rolling, the steel is cooled to 900°C at a cooling rate of 0.2°C / s and kept warm for 90 minutes. Then, it is cooled to 850°C at a cooling rate of 5°C / s and kept warm for 120 minutes. Finally, it is cooled to 22°C at a cooling rate of 10°C / s to obtain a controlled fracture lightweight steel based on three-phase microstructure regulation.

[0071] Figure 3 This is the SEM image of the controlled fracture lightweight steel based on three-phase structure regulation prepared in Example 3.

[0072] Testing revealed that the lightweight steel material produced in Example 3 consisted of ferrite, M / A islands, and kappa carbide, with contents of 75%, 15%, and 10%, respectively. The ferrite grain size was 4.7 μm, the M / A islands were 5 μm, and the kappa carbide was 1.8 μm. This lightweight steel material exhibited a hardness of 515 HV, a tensile strength of 1020 MPa, an elongation of 0.6%, and an impact energy of 11 J.

[0073] Comparative Example 1

[0074] The preparation steps of lightweight steel include:

[0075] S1. Prepare a lightweight steel to be processed, wherein the composition of the lightweight steel to be processed is, by mass percentage, C 0.72%, Si 1.10%, Al 7.20%, Mn 1.20%, and Cr 0.10%, with the balance being Fe and unavoidable impurities; η = 1.29;

[0076] S2, holding the to-be-treated lightweight steel at 1050°C for 60 minutes for ferrite and austenite two-phase heat treatment, then heating to 1200°C for 30 minutes before rolling, with four rolling passes and a deformation of 60%;

[0077] S3. After rolling, the steel is cooled to 1100°C at a cooling rate of 10°C / s and kept warm for 60 minutes. Then, the steel is cooled to 750°C at a cooling rate of 10°C / s and kept warm for 60 minutes. Finally, the steel is cooled to 18°C ​​at a cooling rate of 1°C / s to obtain lightweight steel.

[0078] Testing revealed that the lightweight steel material (lightweight steel) prepared in Comparative Example 1 exhibited a microstructure consisting of ferrite, M / A islands, and kappa carbide, with contents of 71%, 22%, and 7%, respectively. The ferrite grain size was 8.2 μm, the M / A island size was 4.1 μm, and the kappa carbide size was 1.4 μm. This lightweight steel material exhibited a hardness of 421 HV, a tensile strength of 978 MPa, an elongation of 3.2%, and an impact energy of 21 J.

[0079] Comparative Example 2

[0080] The preparation steps of lightweight steel include:

[0081] S1. Prepare a lightweight steel to be processed, wherein the composition of the lightweight steel to be processed is, by mass percentage, C 0.76%, Si 1.30%, Al 7.80%, Mn 1.50%, and Cr 0.32%, with the balance being Fe and unavoidable impurities; η = 1.17;

[0082] S2, heat-treating the light steel to be treated at 1100°C for 90 minutes to perform heat-treating treatment in the ferrite and austenite two-phase region, then cooling to 1050°C for 30 minutes before rolling, with two rolling passes and a deformation of 40%;

[0083] S3. After rolling, the steel is cooled to 860°C at a cooling rate of 2°C / s and kept at this temperature for 75 minutes. Then, the steel is cooled to 650°C at a cooling rate of 0.3°C / s and kept at this temperature for 90 minutes. Finally, the steel is cooled to 20°C at a cooling rate of 35°C / s to obtain lightweight steel.

[0084] Testing revealed that the lightweight steel material (lightweight steel) prepared in Comparative Example 2 exhibited a microstructure consisting of ferrite, M / A islands, and kappa carbide, with contents of 81%, 6%, and 5%, respectively. The ferrite grain size was 6.1 μm, the M / A island size was 2.8 μm, and the kappa carbide size was 1.1 μm. This lightweight steel material exhibited a hardness of 412 HV, a tensile strength of 962 MPa, an elongation of 6.9%, and an impact energy of 28 J.

[0085] Comparative Examples 1 and 2 are based on Examples 1 and 2, respectively, and the parameter settings of step S3 are changed. The content of the tissue finally obtained is no longer within the range limited by the present invention, and the hardness and tensile strength are significantly reduced; the elongation and toughness are increased, which is not conducive to the application of lightweight controlled fracture steel in special fields such as disposable devices and building shock-absorbing structural parts.

[0086] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0087] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one 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 present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A controlled fracture lightweight steel based on three-phase microstructure regulation, characterized in that: The structure of the lightweight steel material consists of ferrite, M / A islands and kappa carbide; The ferrite content is 70-76%; The content of the M / A island is 15-20%; The content of the kappa carbide is 4-15%.

2. The controlled fracture lightweight steel based on three-phase microstructure regulation according to claim 1, characterized in that: The grain size of the ferrite is 5-9 μm; and / or the size of the M / A island is 2-5 μm; and / or the size of the κ carbide is 1-2 μm.

3. A method for preparing controlled fracture lightweight steel based on three-phase structure regulation according to claim 1 or 2, characterized in that the steps include: The lightweight steel to be treated is heat-treated in the ferrite and austenite two-phase region, followed by hot rolling, and then cooled to a first preset temperature at a first cooling rate and kept warm, then cooled to a second preset temperature at a second cooling rate and kept warm, and finally cooled at a third cooling rate to obtain the controllable fracture lightweight steel based on three-phase microstructure regulation; In terms of mass percentage, in addition to Fe, the components of the lightweight steel to be treated include: C 0.7%-0.8%, Si 1.0%-1.5%, Mn 1.2%-1.8%, Al 7.0%-8.5% and Cr 0%-0.48%, as well as inevitable impurities.

4. The preparation method according to claim 3, wherein The mass percentage ratio of C, Si, Al, Cr and Mn in the components of the light steel to be treated meets the requirement of 0.70≤η≤1.67, η=ln(Al-2Mn)-[1.5Si+Cr 1 / 2 -1.2C] / 4.

5. The preparation method according to claim 3, wherein The temperature of the heat preservation treatment in the ferrite and austenite two-phase region is 1050-1200° C., and the time is 40-90 minutes.

6. The preparation method according to claim 3, wherein The hot rolling temperature is 1050-1200° C., the rolling passes are 2-4 times, and the deformation amount is 40%-60%.

7. The preparation method according to claim 3, wherein The cooling rate of the first cooling rate is 0.1-10°C / s; and / or, the first preset temperature is 890-1000°C; and / or, the holding time for cooling to the first preset temperature and holding the temperature is 60-90 minutes.

8. The preparation method according to claim 3, wherein The cooling rate of the second cooling rate is 1-5°C / s; and / or, the second preset temperature is 800-850°C; and / or, the holding time for cooling to the second preset temperature and holding the temperature is 60-120 minutes.

9. The preparation method according to claim 3, wherein The cooling rate of the third cooling rate is 5-30°C / s.

10. The preparation method according to claim 3, wherein The temperature after cooling at the third cooling rate is 18-22°C.

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