CN113528981B - 2000 MPa-level steel plate for protection and preparation method thereof - Google Patents
2000 MPa-level steel plate for protection and preparation method thereof Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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Abstract
The invention discloses a 2000 MPa-level steel plate for protection and a preparation method thereof, wherein the preparation method comprises the following steps: step S100: smelting and refining molten steel in a converter, and then continuously casting to obtain a casting blank; step S200: putting the casting blank into a heating furnace for heating, and controlling the heating temperature and the heat preservation time; step S300: putting the heated casting blank into a rolling mill for rough rolling, finish rolling and continuous rolling to obtain a hot rolled plate; step S400: carrying out laminar cooling on the hot rolled plate by adopting a back-end cooling mode, and coiling the cooled hot rolled plate to obtain a hot rolled coil; step S500: flattening the hot rolled coil, and then straightening and transversely cutting to obtain a first steel plate; step S600: quenching and heating the first steel plate, and performing water quenching to room temperature to obtain a second steel plate; step S700: tempering and heating the second steel plate, and air-cooling to room temperature to obtain a target steel plate; the strength level of the steel plate is more than 2000MPa, the plasticity, toughness and cold formability of the steel plate are improved, and the technical effect of large-scale production of the size is easy to realize.
Description
Technical Field
The invention relates to the technical field of steel plate production, in particular to a 2000 MPa-level steel plate for protection and a preparation method thereof.
Background
With the increasing demand of the fields of protective vehicles and protective instruments on the bulletproof performance of protective steel, the strength grade of the thin-specification bulletproof plate is also increased continuously, and the 2000MPa protective steel plate in the prior art is reported.
However, in the process of implementing the technical solution in the embodiment of the present application, the inventor of the present application finds that the above prior art has at least the following technical problems:
(1) the strength level is low, and the problem of overweight exists when the protective vehicle or the appliance is manufactured. (2) The steel plate has poor plasticity and toughness, brittle fracture is easy to occur in the bullet striking process, and the plastic deformation capability is insufficient. (3) Steel sheets are poor in cold formability and are prone to cracking when members to be bent or press-formed are produced. (4) The steel plate prepared by the on-line quenching and pressure quenching processes is thin, and full-size large-scale production is difficult to realize.
Disclosure of Invention
The invention provides a 2000 MPa-level steel plate for protection and a preparation method thereof, solves the technical problems that the steel plate in the prior art is low in strength level, poor in plasticity and toughness and poor in cold forming and is difficult to realize full-size large-scale production, achieves the technical effects that the strength level of the steel plate is larger than 2000MPa, the plasticity, toughness and cold forming property of the steel plate are improved, and the size large-scale production is easy to realize.
In order to solve the above problem, in one aspect, an embodiment of the present application provides a method for manufacturing a 2000 MPa-grade steel plate for protection, where the method includes: step S100: smelting and refining molten steel in a converter, and then continuously casting to obtain a casting blank; the casting blank comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%, silicon: 2.20% -2.60%, manganese: 0.10% -0.18%, aluminum: 0.020% -0.060%, nickel: 2.7% -3.3%, chromium: 1.10% -1.50%, niobium: 0.045% -0.065%, boron: 0.0025% -0.0035%, phosphorus: less than or equal to 0.012 percent, sulfur: less than or equal to 0.004%, hydrogen: less than or equal to 0.0002 percent, oxygen: less than or equal to 0.002%, nitrogen: less than or equal to 0.004 percent, and the balance of iron and inevitable impurities; step S200: putting the casting blank into a heating furnace for heating, and controlling the heating temperature and the heat preservation time; step S300: putting the heated casting blank into a rolling mill for rough rolling, finish rolling and continuous rolling to obtain a hot rolled plate; step S400: carrying out laminar cooling on the hot rolled plate by adopting a back-end cooling mode, and coiling the cooled hot rolled plate to obtain a hot rolled coil; step S500: flattening the hot rolled coil, and then straightening and transversely cutting to obtain a first steel plate; step S600: quenching and heating the first steel plate, and performing water quenching to room temperature to obtain a second steel plate; step S700: tempering and heating the second steel plate, and air-cooling to room temperature to obtain a target steel plate; wherein the thickness of the target steel plate is 3mm-12mm, the tensile strength is more than 2000MPa, the Rockwell hardness HRC is more than 54, and the steel plate does not crack when being cold-bent at 180 degrees D-3 a; the impact energy is more than or equal to 18J at minus 40 ℃.
Preferably, in step S200, the heating temperature of the heating furnace is 1260-1290 ℃, and the heat preservation time is 210-240 min.
Preferably, in step S300, the rolling finishing temperature is 820 ℃ to 870 ℃.
Preferably, in step S400, the back-end cooling mode specifically includes: after the hot rolled plate is finish rolled, firstly performing air cooling on a laminar flow roller way, and opening laminar flow cooling water from the last group to the front; the coiling temperature of coiling is 700-750 ℃.
Preferably, in step S600, the quenching and heating specifically includes: high-frequency induction heating is adopted, the heating rate is more than 90 ℃/s, the heating temperature is 900-950 ℃, and the heat preservation time is 12-14 min.
Preferably, in step S700, the heating temperature of the tempering heating is 140-170 ℃, and the holding time is 240-300 min.
Preferably, the metallographic structure of the target steel plate consists of tempered martensite and retained austenite, wherein the retained austenite proportion is 8.2-9.7%.
On the other hand, the embodiment of the application provides a 2000 MPa-level steel plate for protection, the steel plate is prepared by the preparation method, and the steel plate comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%, silicon: 2.20% -2.60%, manganese: 0.10% -0.18%, aluminum: 0.020% -0.060%, nickel: 2.7% -3.3%, chromium: 1.10% -1.50%, niobium: 0.045% -0.065%, boron: 0.0025% -0.0035%, phosphorus: less than or equal to 0.012 percent, sulfur: less than or equal to 0.004%, hydrogen: less than or equal to 0.0002 percent, oxygen: less than or equal to 0.002%, nitrogen: less than or equal to 0.004 percent, and the balance of iron and inevitable impurities.
One or more technical solutions in the embodiments of the present invention at least have one or more of the following technical effects:
1. according to the embodiment of the invention, the casting blank adopts the design of high carbon, high silicon and low manganese in chemical components, and the manganese content is reduced to be below 0.2, so that the steel plate has good weldability. In the aspect of alloy, high nickel and high chromium are added and strengthened in a composite mode, and in addition, the toughness and the fatigue performance of a steel plate welding joint and the protective performance of a steel plate are improved by adding high-content niobium. Molybdenum element and copper element are not added, and 25-35ppm of boron element is added to improve the hardenability of the steel plate.
2. In the embodiment of the invention, the heating temperature of the heating furnace is 1260-1290 ℃, and the heat preservation time is 210-240 min. On one hand, the high content nickel and chromium elements in the casting blank are fully dissolved; in the second aspect, segregation of elements such as C, Si in the middle of the cast slab is reduced, and in the third aspect, the high temperature of the cast slab is advantageous for smooth proceeding of the subsequent rolling process.
2. According to the embodiment of the invention, induction heating is adopted, so that the heating stage time is greatly shortened, the generated cementite is not easy to aggregate and grow up, and the quenching structure is refined, so that the toughness, plasticity and cold forming performance of the target steel plate are improved, and the protective performance is greatly improved. The heat preservation time of quenching heating is strictly controlled, the phenomenon that austenite grains are large in size due to long-time high-temperature heating is avoided, and the strength, plasticity and impact toughness of the first steel plate are improved.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
FIG. 1 is a flow chart of a method for manufacturing a 2000 MPa-grade steel plate for protection in an embodiment of the invention;
FIG. 2 is a 1000-fold metallographic structure photograph of a 2000 MPa-grade protective steel plate according to an embodiment of the present invention;
FIG. 3 is a scanning electron micrograph of 5000 times of a 2000MPa protective steel plate in an embodiment of the invention.
Detailed Description
The embodiment of the invention provides a 2000 MPa-level steel plate for protection and a preparation method thereof, solves the technical problems that the steel plate in the prior art is low in strength level, poor in plasticity and toughness and poor in cold forming and is difficult to realize full-size large-scale production, achieves the technical effects that the strength level of the steel plate is greater than 2000MPa, the plasticity, toughness and cold forming property of the steel plate are improved, and the size large-scale production is easy to realize.
The technical scheme in the embodiment of the invention has the following overall structure:
a preparation method of a 2000 MPa-level steel plate for protection comprises the following steps: step S100: smelting and refining molten steel in a converter, and then continuously casting to obtain a casting blank; the casting blank comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%, silicon: 2.20% -2.60%, manganese: 0.10% -0.18%, aluminum: 0.020% -0.060%, nickel: 2.7% -3.3%, chromium: 1.10% -1.50%, niobium: 0.045% -0.065%, boron: 0.0025% -0.0035%, phosphorus: less than or equal to 0.012 percent, sulfur: less than or equal to 0.004%, hydrogen: less than or equal to 0.0002 percent, oxygen: less than or equal to 0.002%, nitrogen: less than or equal to 0.004 percent, and the balance of iron and inevitable impurities; step S200: putting the casting blank into a heating furnace for heating, and controlling the heating temperature and the heat preservation time; step S300: putting the heated casting blank into a rolling mill for rough rolling, finish rolling and continuous rolling to obtain a hot rolled plate; step S400: carrying out laminar cooling on the hot rolled plate by adopting a back-end cooling mode, and coiling the cooled hot rolled plate to obtain a hot rolled coil; step S500: flattening the hot rolled coil, and then straightening and transversely cutting to obtain a first steel plate; step S600: quenching and heating the first steel plate, and performing water quenching to room temperature to obtain a second steel plate; step S700: tempering and heating the second steel plate, and air-cooling to room temperature to obtain a target steel plate; wherein the thickness of the target steel plate is 3mm-12mm, the tensile strength is more than 2000MPa, the Rockwell hardness HRC is more than 54, and the steel plate does not crack when being cold-bent at 180 degrees D-3 a; the impact energy is more than or equal to 18J at minus 40 ℃. The preparation method solves the technical problems that the steel plate in the prior art is low in strength level, poor in plasticity and toughness and poor in cold forming and is difficult to realize full-size large-scale production, achieves the technical effects that the strength level of the steel plate is larger than 2000MPa, the plasticity, toughness and cold forming property of the steel plate are improved, and the size large-scale production is easy to realize.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
The embodiment of the invention provides a preparation method of a 2000 MPa-level protective steel plate, please refer to fig. 1-3, and the preparation method comprises the following steps:
step S100: smelting and refining molten steel in a converter, and then continuously casting to obtain a casting blank; the casting blank comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%, silicon: 2.20% -2.60%, manganese: 0.10% -0.18%, aluminum: 0.020% -0.060%, nickel: 2.7% -3.3%, chromium: 1.10% -1.50%, niobium: 0.045% -0.065%, boron: 0.0025% -0.0035%, phosphorus: less than or equal to 0.012 percent, sulfur: less than or equal to 0.004%, hydrogen: less than or equal to 0.0002 percent, oxygen: less than or equal to 0.002%, nitrogen: less than or equal to 0.004 percent, and the balance of iron and inevitable impurities;
specifically, carbon is the most economical element for improving the strength of heat-treated high-strength steel, but too high an addition thereof adversely affects the toughness, cold formability and weldability of a cast slab. The addition of carbon is increased to more than 0.5%, the size, shape and distribution of carbide in a final product are controlled through a full-flow production process, the adverse effects of high carbon on indexes such as toughness and the like are reduced while high strength and hardness are obtained, and the carbon content in the casting blank adopted by the invention is 0.51-0.56%.
The addition of high-content silicon (Si) is an important core technology of the invention, a sufficient proportion of residual austenite structure is obtained after heat treatment by adding high-content silicon, the residual austenite structure has beneficial effects on improving the plasticity and cold formability of the steel plate, the plastic deformation capacity of the steel plate can be improved when a bullet strikes by a certain proportion of the residual austenite structure, more energy of the bullet is absorbed by relying on more plastic deformation, and the residual austenite structure can be converted into a martensite structure with higher hardness in the plastic deformation process, so that the protective performance of the steel plate is further improved, and the silicon content in the casting blank is 2.20-2.60%.
Manganese (Mn) improves the strength of steel products by solid solution strengthening and also improves the hardenability of steel products. However, the manganese element affects the welding performance of the material, and the addition amount of the manganese content needs to be controlled under the condition that higher carbon and silicon contents are added so as to obtain good weldability and toughness. Therefore, the content of the added manganese is 0.1-0.18%.
The aluminum is a deoxidizing element in the smelting process and has a certain grain refining effect. In order to obtain the low enough oxygen content, the invention limits the aluminum content in the casting blank to be 0.02-0.06%.
The nickel (Ni) is an important alloy element, and the toughness of the steel plate, the toughness of a welding seam, the fatigue property of the welding seam and the protective property are improved by adding high-content nickel. The addition of high-content nickel is beneficial to avoiding the generation of copper brittleness and boron-containing steel casting blank cracks. The corrosion resistance of the steel plate is greatly improved by high-content nickel, and the service life of the steel plate can be greatly prolonged. Therefore, the nickel content in the casting blank is 2.7-3.3%.
The addition of high-content niobium (Nb) is an important core technology of the invention, and the addition of the high-content Nb can refine the structure and improve the toughness of the steel plate, thereby improving the protective performance of the steel plate. On the other hand, niobium can obviously improve the toughness of a welding heat affected zone, refine the structure of the heat affected zone and improve the overall fatigue performance of the welding seam. The niobium content in the casting blank is 0.045% -0.06%.
The high-chromium (Cr) content is added to improve the hardenability and strength of the material, and the acid medium corrosion resistance of the steel plate is greatly improved. Without the addition of molybdenum (Mo), chromium replaces the effect of molybdenum, so that a steel sheet obtains a sufficient proportion of a refined quenched martensite or bainite structure during quenching. However, the high chromium content is not favorable for controlling the toughness of the steel plate, so that the chromium content in the casting blank is 1.1-1.50%.
The invention adds the boron (B) with higher content, improves the hardenability of the material, replaces the action of molybdenum, enlarges the quenching cooling speed window and ensures that a high-hardness quenching structure is obtained. In order to avoid the adverse effect of boron on the toughness and cold formability, the content of boron added into the casting blank is limited to 0.0025-0.0035 percent.
In the invention, sulfur and phosphorus are harmful elements, and the toughness and plasticity of the material are adversely affected by too high content of the sulfur and phosphorus. Therefore, the content of sulfur and phosphorus in the smelting process is required to be strictly controlled, the invention limits that the content of sulfur in the casting blank is controlled within 0.004%, and the content of phosphorus is controlled within 0.012%.
Oxygen is a harmful gas element in the invention, and influences the toughness and the protective performance of the material. The invention strictly limits oxygen, and requires that the oxygen content in the casting blank is strictly controlled to be less than or equal to 20ppm in the smelting and refining process.
The hydrogen is a harmful gas element in the invention, the hydrogen is easy to cause hydrogen-induced crack and crack, the service cycle of the steel plate is influenced, and meanwhile, the protective performance of the steel plate is reduced due to the over-high hydrogen content. The invention limits the hydrogen content in the casting blank to be less than or equal to 2ppm, and strictly controls the hydrogen content in the casting blank in the smelting process.
Nitrogen influences the toughness of the steel plate, and the grain boundary segregation of the free nitrogen element reduces the protective performance of the steel plate, so that the content of nitrogen in the casting blank is limited to be less than or equal to 40 ppm.
The casting blank disclosed by the invention adopts the design of high carbon (C), high silicon (si), high nickel (Ni), high chromium (Cr), high niobium (Nb), low manganese (Mn) and no addition of molybdenum (Mo) and copper (Cu) as chemical components, and the manganese content is reduced to be below 0.2, so that the steel plate has good weldability. In the aspect of alloy, high nickel and high chromium are added and strengthened in a composite mode, and in addition, the toughness and the fatigue performance of a steel plate welding joint and the protective performance of a steel plate are improved by adding high-content niobium. Molybdenum element and copper element are not added, and 25-35ppm of boron element is added to improve the hardenability of the material. The smelting process strictly controls the content of harmful elements such as phosphorus, sulfur, oxygen, hydrogen and nitrogen, and ensures the purity of the casting blank.
Step S200: putting the casting blank into a heating furnace for heating, and controlling the heating temperature and the heat preservation time;
further, in step S200, the heating temperature of the heating furnace is 1260 ℃ to 1290 ℃, and the heat preservation time is 210-240 min.
Specifically, when the casting blank is heated in a heating furnace, the higher heating time and the longer heat preservation time are adopted, so that on one hand, the high-content nickel and chromium elements in the casting blank are fully dissolved; in the second aspect, segregation of elements such as C, Si in the middle of the cast slab is reduced, and in the third aspect, the high temperature of the cast slab is advantageous for smooth proceeding of the subsequent rolling process.
Step S300: putting the heated casting blank into a rolling mill for rough rolling, finish rolling and continuous rolling to obtain a hot rolled plate;
further, in step S300, the finishing temperature of the rolling is 820 ℃ to 870 ℃.
Specifically, a rough rolling and finish rolling continuous rolling process is adopted to roll the heated casting blank, and the finish rolling temperature is in a middle-low temperature range of 820-870 ℃, so that the accumulated reduction of an austenite non-recrystallization region in the hot rolling process is increased, refined flattened austenite grains are obtained, a large number of deformation zones are formed in the refined flattened austenite grains, the nucleation in the subsequent cooling phase transformation process is promoted, and the final finished material structure after heat treatment is refined by refining the original hot rolling state structure. The thickness of the hot-rolled coil is the same as that of the target steel plate and is 3-12 mm.
Step S400: carrying out laminar cooling on the hot rolled plate by adopting a back-end cooling mode, and coiling the cooled hot rolled plate to obtain a hot rolled coil;
further, in step S400, the rear-stage cooling mode specifically includes: after the hot rolled plate is finish rolled, firstly performing air cooling on a laminar flow roller way, and opening laminar flow cooling water from the last group to the front; the coiling temperature of coiling is 700-750 ℃.
Specifically, traditional hot continuous rolling laminar cooling all adopts anterior segment cooling mode, and laminar cooling last two sets of accurate water of adjusting that are of, and it is stable to control the temperature of rolling up through surveying the accurate water yield of adjusting of temperature feedback before rolling up. However, the front-stage cooling mode has a disadvantage in producing thin steel plate products, that is, the air cooling section between two sections of cooling water is easy to undergo medium-high temperature phase transformation, such as pearlite phase transformation, which causes the performance of final products to be reduced. This drawback can be avoided to back end cooling mode in this application, improves product quality.
In the embodiment of the invention, after the hot rolled plate is subjected to finish rolling, air cooling is carried out firstly, and then laminar cooling is carried out by adopting a back-end cooling mode, namely laminar cooling water is started from the last group forward, the final coiling temperature is controlled to be 700-750 ℃, and coiling is carried out in the temperature range, so that the formation of coarse pearlite can be avoided, and the influence on plate shape quality caused by transformation into low-temperature transformation tissues such as bainite and the like can also be avoided; meanwhile, the higher coiling temperature can not only ensure that the plate shape reduces the subsequent flattening and straightening difficulty, but also promote the precipitation of Nb element, thereby providing a foundation for refining the quenching structure.
Step S500: flattening the hot rolled coil, and then straightening and transversely cutting to obtain a first steel plate;
step S600: quenching and heating the first steel plate, and performing water quenching to room temperature to obtain a second steel plate;
further, in step S600, the quenching and heating specifically includes: high-frequency induction heating is adopted, the heating rate is more than 90 ℃/s, the heating temperature is 900-950 ℃, and the heat preservation time is 12-14 min.
Specifically, the first steel sheet is obtained by straightening and crosscutting the hot-rolled coil. Carrying out quenching heating on the first steel plate in an off-line heat treatment mode, wherein the quenching heating specifically comprises the following steps: and (3) heating the first steel plate by adopting high-frequency induction, wherein the heating rate is more than 90 ℃/s, the heating temperature is 900-950 ℃, and the heat preservation time is 12-14 min. The aim of adopting high-frequency induction heating is to ensure that the key method for obtaining the fine cementite and martensite lath spacing after adding high C greatly shortens the heating stage time by adopting induction heating, the generated cementite is not ready for aggregation and growth, and the quenching structure is refined, thereby improving the toughness, plasticity and cold forming performance of the target steel plate and greatly improving the protective performance.
And (3) preserving the heat of the first steel plate after the high-frequency induction heating for 12-14 min. The invention strictly controls the heat preservation time of quenching heating, and avoids the problem of large austenite grain size caused by long-time high-temperature heating. The quenching heat preservation time is not too short, the austenitizing process needs to be fully completed, but the growth of the austenitizing process needs to be controlled, so the upper limit of the heat preservation time needs to be controlled.
After the first steel plate is quenched and heated, water quenching is adopted, the temperature of the first steel plate is directly adjusted to room temperature, and fine and uniform quenching structures, mainly lath martensite and lath bainite structures, are obtained after quenching, so that the strength, plasticity and impact toughness of the first steel plate are improved.
Since the high-frequency induction heating has a high heating rate, the thin-gauge steel plate can be rapidly heated to a target temperature, and therefore division of different thicknesses and different heat preservation times is not required.
Step S700: tempering and heating the second steel plate, and air-cooling to room temperature to obtain a target steel plate;
further, in step S700, the heating temperature of the tempering heating is 140-170 ℃, and the heat preservation time is 240-300 min.
Specifically, the tempering heating is performed by conventional heating due to a low temperature, but the heating temperature range needs to be strictly controlled. The heat preservation time of tempering and heating is 240-300min, and the technical effect of improving the plasticity and toughness of the steel plate under the condition of less strength reduction is achieved through long-time low-temperature tempering. The long-time tempering and heat preservation also improve the cold forming performance of the steel plate, the insufficient tempering time can cause the toughness and the brittleness of the steel plate to be increased, and the steel plate is broken in a large block in the target shooting process. The low-temperature tempering temperature and the long-time heat preservation process adopted by the invention must cooperate with each other, so that the comprehensive mechanical property and the protective property of the steel plate can be improved.
The metallographic structure of the target steel plate consists of tempered martensite and residual austenite, and the proportion of the residual austenite structure is 8.2-9.7%.
Specifically, in one aspect of the invention, tempered martensite with high hardness is obtained by long-time low-temperature tempering heating at 170 ℃ or below; on the other hand, 8.2 to 9.7 percent of retained austenite is obtained as an important tissue component through special chemical composition design and preparation process. The cold forming performance of the steel plate is improved by relying on the easy deformation characteristic of austenite, and the plastic deformation capacity of the steel plate in the process of penetrating the steel plate by bullets is improved by utilizing the deformation hardening characteristic of austenite, so that the energy absorption effect of the steel plate is improved by relying on the plastic deformation, and the protective performance of the steel plate is improved.
In the embodiment of the invention, the target steel plate comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%; silicon: 2.20% -2.60%; manganese: 0.10% -0.18%; aluminum: 0.020-0.060%; nickel: 2.7-3.3%; chromium: 1.10% -1.50%; niobium: 0.045-0.065%, boron: 0.0025 to 0.0035%, phosphorus: less than or equal to 0.012 percent; sulfur: less than or equal to 0.004 percent; hydrogen: less than or equal to 0.0002 percent; oxygen: less than or equal to 0.002 percent; nitrogen: less than or equal to 0.004 percent; the balance of iron and inevitable impurities.
The thickness of the target steel plate is 3mm-12mm, the tensile strength is more than 2000MPa, the Rockwell hardness HRC is more than 54, and the steel plate does not crack when being subjected to cold bending at 180 degrees D-3 a; the impact energy is more than or equal to 18J at minus 40 ℃, and the steel plate has good strength, toughness, welding performance and plate shape quality. The target steel plate has excellent comprehensive mechanical properties and ultrahigh protective performance, is suitable for standards of about 4569 in North, 1522 in European Union and the like, and is beneficial to improving the protective performance of a protective vehicle and reducing the overall vehicle weight.
Example two
The embodiment of the invention provides a 2000 MPa-level steel plate for protection, which is prepared by the preparation method of the embodiment I, and comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%; silicon: 2.20% -2.60%; manganese: 0.10% -0.18%; aluminum: 0.020-0.060%; nickel: 2.7-3.3%; chromium: 1.10% -1.50%; niobium: 0.045-0.065%, boron: 0.0025 to 0.0035%, phosphorus: less than or equal to 0.012 percent; sulfur: less than or equal to 0.004 percent; hydrogen: less than or equal to 0.0002 percent; oxygen: less than or equal to 0.002 percent; nitrogen: less than or equal to 0.004 percent; the balance of iron and inevitable impurities.
Various changes and specific examples of the preparation method of the 2000MPa grade steel plate in the first embodiment of fig. 1 are also applicable to the 2000MPa grade steel plate in the present embodiment, and the implementation method of the 2000MPa grade steel plate in the present embodiment is clear to those skilled in the art from the foregoing detailed description of the preparation method of the 2000MPa grade steel plate, so for the brevity of the description, detailed description is omitted here.
EXAMPLE III
The embodiment of the invention provides a preparation method of a 2000 MPa-level protective steel plate, which refers to the accompanying drawings 1-3 and comprises the following steps:
s1: smelting and refining molten steel in a converter, and then continuously casting to obtain a casting blank; the content of harmful elements P, S, O, N, H is strictly controlled in the smelting process. The casting blank comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%; silicon: 2.20% -2.60%; manganese: 0.10% -0.18%; aluminum: 0.020% -0.060%; nickel: 2.7% -3.3%; chromium: 1.10% -1.50%; niobium: 0.045% -0.065%, boron: 0.0025% -0.0035%, phosphorus: less than or equal to 0.012 percent; sulfur: less than or equal to 0.004 percent; hydrogen: less than or equal to 0.0002 percent; oxygen: less than or equal to 0.002 percent; nitrogen: less than or equal to 0.004 percent; the balance of iron and inevitable impurities.
8 examples are carried out in the examples of the application, and the smelting chemical components of the specific examples are shown in Table 1:
chemical composition of specific examples of protective steel sheet in Table 12000 MPa
S2: and (3) heating the casting blank in a heating furnace, and controlling the heating temperature and the heat preservation time.
S3: and (3) putting the heated casting blank into a rolling mill for rolling, and controlling the finish rolling temperature to obtain the hot rolled plate.
S4: cooling the hot rolled plate, carrying out laminar cooling by adopting a back-end cooling mode, and coiling the cooled hot rolled plate to obtain a hot rolled coil;
s5: and flattening the hot-rolled coil, straightening and transversely cutting to obtain a first steel plate.
S6: and carrying out quenching induction heating and heat preservation on the first steel plate, and then carrying out water quenching to room temperature to obtain a second steel plate.
S7: and after tempering and heating and heat preservation are carried out on the second steel plate, air cooling is carried out to room temperature.
The specific production process of examples No. 1 to No. 8 is shown in Table 2:
production process of specific embodiment of steel plate for protection at 22000 MPa
The ratio of the retained austenite is determined by an XRD method; mechanical property tests are carried out on the samples 1 to 8, and the mechanical properties of the bulletproof plates obtained after the test methods are carried out in GB/T228.1, GB/T232, GB/T229 and GB/T231.1 and the samples 1 to 8 are subjected to heat treatment are shown in Table 3:
performance of specific examples of protective Steel sheets of grade 32000 MPa
The examples were tested for targeting, the specific targeting pattern and results are shown in table 4:
| serial number | Thickness of | Shooting distance (rice) | Bullet speed (meter/second) | Bullet/gun | Whether or not to break down |
| 1 | 3 | 5 | 515 | 7.62 x 25mm steel core projectile, 79 miniature submachine gun, 9Bullet | Not breakdown |
| 2 | 4 | 5 | 730 | 7.62 x 39mm steel core projectile, 56 semi-automatic rifle, 6 projectiles | Not breakdown |
| 3 | 4.5 | 30 | 710 | 7.62 × 54mm steel core projectile, AK47 rifle, 5 projectiles | Not breakdown |
| 4 | 5.5 | 10 | 910 | SS109, M16 rifle, 3 bullets | Not breakdown |
| 5 | 6 | 10 | 830 | M80 NATO, M14, 3 bullet | Not breakdown |
| 6 | 8 | 30 | 710 | 7.62 × 39mm API BZ, AK rifle, 5 shots | Not breakdown |
| 7 | 10 | 30 | 710 | 7.62 × 39mm API BZ, AK rifle, 5 shots | Not breakdown |
| 8 | 12 | 30 | 710 | 7.62 × 54mm armor piercing combustion bomb, AK rifle, 5 bombs | Not breakdown |
Table 32000 MPa protection steel plate specific example targeting experiment result
The 2000 MPa-level steel plate for protection provided by the invention has the advantages that through special chemical components and production process design, the finally obtained steel plate finished product has good strength, toughness, welding performance and plate shape quality. The material has excellent comprehensive mechanical properties and ultrahigh protective performance, and is suitable for the standards of about 4569 in the north, 1522 in the European Union and the like.
One or more technical solutions in the embodiments of the present invention at least have one or more of the following technical effects:
1. according to the embodiment of the invention, the casting blank adopts the design of high carbon, high silicon and low manganese in chemical components, and the manganese content is reduced to be below 0.2, so that the steel plate has good weldability. In the aspect of alloy, high nickel and high chromium are added and strengthened in a composite mode, and in addition, the toughness and the fatigue performance of a steel plate welding joint and the protective performance of a steel plate are improved by adding high-content niobium. Molybdenum element and copper element are not added, and 25-35ppm of boron element is added to improve the hardenability of the steel plate.
2. In the embodiment of the invention, the heating temperature of the heating furnace is 1260-1290 ℃, and the heat preservation time is 210-240 min. On one hand, the high content nickel and chromium elements in the casting blank are fully dissolved; in the second aspect, segregation of elements such as C, Si in the middle of the cast slab is reduced, and in the third aspect, the high temperature of the cast slab is advantageous for smooth proceeding of the subsequent rolling process.
3. According to the embodiment of the invention, induction heating is adopted, so that the heating stage time is greatly shortened, the generated cementite is not easy to aggregate and grow up, and the quenching structure is refined, so that the toughness, plasticity and cold forming performance of the target steel plate are improved, and the protective performance is greatly improved. The heat preservation time of quenching heating is strictly controlled, the phenomenon that austenite grains are large in size due to long-time high-temperature heating is avoided, and the strength, plasticity and impact toughness of the first steel plate are improved.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.
Claims (6)
1. A preparation method of a 2000 MPa-level steel plate for protection is characterized by comprising the following steps:
step S100: smelting and refining molten steel in a converter, and then continuously casting to obtain a casting blank; the casting blank comprises the following chemical components in percentage by weight: carbon: 0.51% -0.56%, silicon: 2.20% -2.60%, manganese: 0.10% -0.18%, aluminum: 0.020% -0.060%, nickel: 2.7% -3.3%, chromium: 1.10% -1.50%, niobium: 0.045% -0.065%, boron: 0.0025% -0.0035%, phosphorus: less than or equal to 0.012 percent, sulfur: less than or equal to 0.004%, hydrogen: less than or equal to 0.0002 percent, oxygen: less than or equal to 0.002%, nitrogen: less than or equal to 0.004 percent, and the balance of iron and inevitable impurities;
step S200: putting the casting blank into a heating furnace for heating, and controlling the heating temperature and the heat preservation time;
step S300: putting the heated casting blank into a rolling mill for rough rolling, finish rolling and continuous rolling to obtain a hot rolled plate;
step S400: carrying out laminar cooling on the hot rolled plate by adopting a back-end cooling mode, and coiling the cooled hot rolled plate to obtain a hot rolled coil;
step S500: flattening the hot rolled coil, and then straightening and transversely cutting to obtain a first steel plate;
step S600: quenching and heating the first steel plate, and performing water quenching to room temperature to obtain a second steel plate, wherein the quenching and heating specifically comprises the steps of adopting high-frequency induction heating, heating at the rate of more than 90 ℃/s, heating at the temperature of 900-950 ℃, and keeping the temperature for 12-14 min;
step S700: tempering and heating the second steel plate, and air-cooling to room temperature to obtain a target steel plate, wherein the tempering and heating temperature is 140-170 ℃, and the heat preservation time is 240-300 min;
wherein the thickness of the target steel plate is 3mm-12mm, the tensile strength is more than 2000MPa, the Rockwell hardness HRC is more than 54, and the steel plate does not crack when being cold-bent at 180 degrees D-3 a; the impact energy is more than or equal to 18J at minus 40 ℃.
2. The method as claimed in claim 1, wherein in step S200, the heating temperature of the heating furnace is 1260-1290 ℃ and the holding time is 210-240 min.
3. The method of claim 1, wherein in step S300, the final rolling temperature of the rolling is 820 ℃ to 870 ℃.
4. The method according to claim 1, wherein in step S400, the back-end cooling mode is specifically: after the hot rolled plate is finish rolled, firstly performing air cooling on a laminar flow roller way, and opening laminar flow cooling water from the last group to the front;
the coiling temperature of coiling is 700-750 ℃.
5. The production method according to claim 1, wherein the metallographic structure of the target steel sheet consists of tempered martensite and retained austenite, and wherein the retained austenite proportion is 8.2% to 9.7%.
6. A2000 MPa-level steel plate for protection, which is prepared by the preparation method of any one of claims 1-5, and is characterized by comprising the following chemical components in percentage by weight: carbon: 0.51% -0.56%, silicon: 2.20% -2.60%, manganese: 0.10% -0.18%, aluminum: 0.020% -0.060%, nickel: 2.7% -3.3%, chromium: 1.10% -1.50%, niobium: 0.045% -0.065%, boron: 0.0025% -0.0035%, phosphorus: less than or equal to 0.012 percent, sulfur: less than or equal to 0.004%, hydrogen: less than or equal to 0.0002 percent, oxygen: less than or equal to 0.002%, nitrogen: less than or equal to 0.004 percent, and the balance of iron and inevitable impurities.
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