CN114686762B - Production method of high-strength high-toughness hot continuous rolling thin steel plate with Brinell hardness of 500HBW - Google Patents
Production method of high-strength high-toughness hot continuous rolling thin steel plate with Brinell hardness of 500HBW Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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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- 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
- C21D1/34—Methods of heating
- C21D1/42—Induction 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C21—METALLURGY OF IRON
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention relates to a production method of a Brinell hardness 500HBW steel plate, in particular to a production method of a Brinell hardness 500HBW high-strength high-toughness hot continuous rolling thin steel plate. The thickness is less than or equal to 10mm, and the coating consists of the following chemical elements in percentage by weight: c:0.21 to 0.26 percent, si:0.60 to 0.80 percent, mn:0.90 to 1.30 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.003 percent, al:0.10 to 0.13 percent, cr:0.70-0.90%, B:0.0010 to 0.0025 percent, N is less than or equal to 0.0040 percent, H is less than or equal to 0.00020 percent, and Nb:0.020 to 0.040 percent, ti:0.020 to 0.050 percent, mo:0.20 to 0.50 percent, and satisfies Ti/N more than or equal to 5, ceq less than or equal to 0.68, wherein Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Cu+Ni)/15, and the balance of Fe and unavoidable impurities. The invention adopts an economic C-Mn component design, is assisted with a small amount of Nb, ti and MO microalloy elements, does not need to add noble alloying elements such as Ni, adopts intermediate frequency rapid heating in the quenching heating temperature rising process, further reduces the addition of the microalloy elements, realizes high strength and high hardness of steel, good low-temperature impact toughness and cold bending processability, and has excellent plate shape.
Description
Technical Field
The invention relates to a production method of a Brinell hardness 500HBW steel plate, in particular to a production method of a Brinell hardness 500HBW high-strength high-toughness hot continuous rolling thin steel plate.
Background
Under the large background of green manufacturing, low carbon and environmental protection, industries such as domestic engineering machinery, commercial vehicles and the like pay more attention to product structure upgrading in the direction of high strength, weight reduction, green service life, and high requirements of higher strength, more wear resistance, more corrosion resistance and the like are provided for steel materials.
In recent years, the development and production of high-strength steel in China are obvious, and engineering machinery users begin to adopt super-high-strength structural steel with yield of over 960MPa to manufacture crane boom and pump truck distributing rod. The dumper users begin to use steel plates with yield strength of 700Mpa or even more than 1000Mpa to replace 345 Mpa-level products. However, in the fields of metallurgy, mines, building materials, transportation and the like, a plurality of workpieces and equipment are rapidly failed due to abrasion, so that huge waste of materials and energy sources is caused, and the steel plate is required to have high hardness and high abrasion resistance, so that the abrasion of the steel plate is reduced, and the service life of the steel plate is prolonged.
CN102943212A discloses a NM500 high-strength wear-resistant steel plate and a heat treatment process thereof, wherein the chemical components comprise 0.25-0.28% of C, 0.80-1.20% of Mn, 0.20-0.40% of Si, less than or equal to 0.010% of S, less than or equal to 0.020% of P, 0.45-0.70% of Cr, 0.10-0.30% of Mo, 0.010-0.030% of Ti, 0.0010-0.0030% of B, 0.015-0.045% of Als, 0.015-0.050% of Nb, and the balance of Fe and unavoidable impurities. The quenching temperature is low, which can affect the hardenability of the steel plate and the hardness of the product.
CN105385951A discloses a NM500 wear-resistant steel plate with high hardness and high toughness and a production method thereof, wherein the chemical components of the wear-resistant steel plate are C0.25-0.30%, si0.10-0.30%, mn0.10-0.60%, P less than or equal to 0.015%, S less than or equal to 0.005%, als0.020-0.035%, ti0.010-0.020%, cr0.5-1.0%, mo0.2-0.5%, ni0.3-0.5%, and the balance of Fe and unavoidable impurities; the heat treatment comprises quenching and tempering, wherein the quenching temperature is 880-910 ℃, the quenching heat preservation time is 15-25 minutes, the tempering temperature is 220-290 ℃, and the tempering heat preservation time is 25-40 minutes; the technology adds noble alloy elements such as Ni and the like, and has higher cost.
CN102943212A discloses a NM500 high-strength wear-resistant steel plate and a heat treatment process thereof, wherein the chemical components comprise 0.25-0.28% of C, 0.80-1.20% of Mn, 0.20-0.40% of Si, less than or equal to 0.010% of S, less than or equal to 0.020% of P, 0.45-0.70% of Cr, 0.10-0.30% of Mo, 0.010-0.030% of Ti, 0.0010-0.0030% of B, 0.015-0.045% of Als, 0.015-0.050% of Nb, and the balance of Fe and unavoidable impurities. The quenching temperature is low, which can affect the hardenability of the steel plate and the hardness of the product.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a production method of a high-strength and high-toughness hot continuous rolling thin steel plate with the Brinell hardness of 500HBW, and the product produced according to the chemical components and the production process requirements of the steel has the advantages of high strength, high toughness, low cost, and the Brinell hardness of 500HBW, and simultaneously has good wear resistance.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
a high-strength high-toughness hot continuous rolling thin steel plate with Brinell hardness of 500HBW, the thickness of which is less than or equal to 10mm, comprises the following chemical elements in percentage by weight:
c:0.21% -0.26%, si:0.60 to 0.80 percent, mn:0.90 to 1.30 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.003 percent, al:0.10 to 0.13 percent, cr:0.70% -0.90%, B:0.0010 to 0.0025 percent, N is less than or equal to 0.0040 percent, H is less than or equal to 0.00020 percent, and Nb:0.020% -0.040%, ti:0.020 to 0.050 percent, mo:0.20 to 0.50 percent, and satisfies Ti/N more than or equal to 5, ceq less than or equal to 0.68, wherein Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Cu+Ni)/15, and the balance of Fe and unavoidable impurities.
A production method of a high-strength high-toughness hot continuous rolling thin steel plate with Brinell hardness of 500HBW specifically comprises the following steps:
1) Smelting and casting
Smelting and casting into blanks according to the components;
2) Slab reheating
The plate blank is hot-charged into a furnace, the charging temperature is more than or equal to 500 ℃, the heating temperature is 1220-1270 ℃, the heat preservation time is 2.5-4 h, and the soaking heat preservation time is not less than 45min;
3) Controlled rolling
The rolling is divided into a rough rolling stage and a finish rolling stage, the rough rolling stage adopts large reduction rolling, the pass reduction is controlled to be more than 20% or more than 45mm, meanwhile, the thickness ratio of an intermediate blank to a finished product is required to be more than or equal to 5, and the reduction of the last pass of the finish rolling is controlled to be not less than 12%; the final rolling temperature is controlled between 900 and 950 ℃;
4) Coiling
The coiling temperature is controlled between 700 ℃ and 750 ℃;
5) The heat treatment adopts a whole-coil continuous heat treatment mode, and comprises quenching, tempering, straightening and cutting;
quenching: the heating temperature is controlled to be 55-100 ℃ above the Ac3 point of the steel grade, and the heating temperature is controlled to be 900-930 ℃; firstly, heating the steel strip to 650-700 ℃ by adopting medium frequency induction at a frequency of 5-20 Hz, heating to a quenching temperature by adopting a resistance furnace after heating, and preserving heat; the quenching heat preservation time is T1, T1 = steel plate thickness x (3.0-3.5) min, the steel plate thickness unit is mm, and the T1 unit is min; directly water-quenching to room temperature after taking out of the furnace to form a martensitic structure, wherein the cooling speed is more than or equal to 40 ℃/s;
tempering: quenching the steel strip, then entering a tempering furnace, tempering at 190-230 ℃ and preserving heat; tempering and heat preserving time is T2, wherein T2 = thickness of the steel plate is x (5.0-5.5) min, the thickness unit of the steel plate is mm, and the unit of T2 is min;
straightening: straightening the steel plate by adopting a strong straightening machine after tempering, so as to ensure the shape and the unevenness of the steel plate, wherein the unevenness of the steel plate is controlled to be less than or equal to 4mm/m;
cutting: the diagonal line of the steel plate is not more than 10mm.
Compared with the prior art, the invention has the beneficial effects that:
the method can realize the production of the high-hardness high-wear-resistance steel plate with the thickness of less than or equal to 10mm, the yield strength is more than 1250MPa, the tensile strength is more than 1450MPa, the elongation is more than or equal to 8 percent, the hardness is 500+/-20 HBW, and the impact power value at minus 40 ℃ is more than 20J.
The invention adopts an economic C-Mn component design, is assisted with a small amount of Nb, ti and MO microalloy elements, does not need to add noble alloying elements such as Ni, adopts intermediate frequency rapid heating in the quenching heating temperature rising process, further reduces the addition of the microalloy elements, realizes high strength and high hardness of steel, good low-temperature impact toughness and cold bending processability, and has excellent plate shape.
Detailed Description
The invention discloses a production method of a high-strength high-toughness hot continuous rolling thin steel plate with Brinell hardness of 500 HBW. Those skilled in the art can, with the benefit of this disclosure, suitably modify the process parameters to achieve this. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included in the present invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the relevant art that variations and modifications can be made in the methods and applications described herein, and in the practice and application of the techniques of this invention, without departing from the spirit or scope of the invention.
A high-strength high-toughness hot continuous rolling thin steel plate with Brinell hardness of 500HBW, the thickness of which is less than or equal to 10mm, comprises the following chemical elements in percentage by weight:
c:0.21% -0.26%, si:0.60 to 0.80 percent, mn:0.90 to 1.30 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.003 percent, al:0.10 to 0.13 percent, cr:0.70% -0.90%, B:0.0010 to 0.0025 percent, N is less than or equal to 0.0040 percent, H is less than or equal to 0.00020 percent, and Nb:0.020% -0.040%, ti:0.020 to 0.050 percent, mo:0.20 to 0.50 percent, and satisfies Ti/N more than or equal to 5, ceq less than or equal to 0.68, wherein Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Cu+Ni)/15, and the balance of Fe and unavoidable impurities.
In the composition design of the steel of the invention:
c:0.21-0.26%. The carbon can improve the hardenability of the steel plate, has strong solid solution strengthening effect, and obviously improves the strength and hardness of the martensitic wear-resistant steel plate with high wear resistance; the appropriate amount of carbon combines with titanium to form TiC particles, which can significantly improve wear resistance. The content of C in percentage by weight is too high, the volume fraction of TiC particles formed is too high, the elongation and impact performance of the martensitic wear-resistant steel plate with high wear resistance are reduced, and the welding performance is poor.
Si:0.60-0.80%. Si plays a role in solid solution strengthening in the steel grade, and the strength and hardness of the material can be obviously improved by adding Si element into the metal material. Si also improves the tempering resistance of the material, thus allowing the material to be used at higher temperatures.
Mn:0.90-1.30%. The addition of Mn element to the metal material can play a role of enlarging an austenite region, and besides, the element can also remarkably improve the hardenability of the steel, so that more martensite structures can be obtained at the same cooling rate. The increased Mn content aggravates the high temperature temper brittleness and heat sensitivity of the steel.
P: less than or equal to 0.015 percent, and less than or equal to 0.003 percent of S. Sulfur combines with manganese and the like in steel to form manganese sulfide, a plastic inclusion, which is disadvantageous in particular in terms of transverse plasticity and toughness of steel, so that the sulfur content should be as low as possible. Phosphorus is also a harmful element in steel, seriously impairing the plasticity and toughness of steel sheets. For the present invention, both sulfur and phosphorus are unavoidable impurity elements, and the lower should be the better.
Cr:0.70-0.90%. The austenite phase region can be reduced. Since the binding ability of chromium atoms to carbon atoms is prominent, different carbides can be formed with carbon in steel. At the same time, chromium may sometimes replace some of the iron atoms in cementite, thereby forming cementite containing chromium atoms. Cr can also improve the hardenability of the steel because the amount of this element in cementite is greater than in solid solution, so Cr will necessarily diffuse from cementite into solid solution when transformation occurs, however, because the inter-austenitic gaps are small, diffusion is difficult, and Cr will combine with C atoms during diffusion, which will slow down the diffusion rate of C element and eventually delay the austenite decomposition time.
Al:0.10-0.13%. The Al is added into steel as deoxidizer in steelmaking process, and the trace Al is favorable for refining grains and improving the toughness of steel. However, too high Al will increase the ferritic brittleness in the steel and result in a decrease in toughness of the steel.
B:0.0010 to 0.0025 percent. The segregation of B in solid solution in the steel to the austenitic grain boundary reduces the interfacial energy and hinders the formation of ferrite crystal nucleus, so that the incubation period of transformation of proeutectoid ferrite and upper bainite is prolonged, and the transformation of lower bainite and martensite is basically not affected, therefore, the main function of B in the low alloy wear-resistant steel is to greatly improve the hardenability of the steel. Meanwhile, a trace amount of B is used for replacing part of noble alloy elements such as Ni, cr, mo and the like, thereby being beneficial to saving the alloy cost. When the B content is too high, excessive solid solution B and C on the austenite grain boundary are combined, the hardenability and impact toughness of the steel are reduced, and the fracture mode of the steel is gradually changed from cleavage fracture to along-grain fracture.
Ti:0.020-0.050% and Ti/N is more than or equal to 5. Is a very active metal element and has extremely strong affinity with O, N, C and other elements. In the smelting process, ti can be preferentially combined with N to form TiN, so that the formation of BN can be inhibited, and the B element is ensured to be dissolved in the matrix in a solid manner. In addition, in the solidification process, the separated TiN can be used as a heterogeneous nucleation core of a primary phase & -ferrite, can reduce the peritectic reaction rate of transformation of the ferrite and liquid phase-to-austenite, and prevent subsequent growth of austenite dendrites, so that solidification structures are obviously refined.
Nb:0.020-0.040%. Is a strong carbonitride forming element, has similar effect to Ti in steel, and mainly plays a role in inhibiting grain growth at high temperature and strengthening micro-alloying at low temperature by forming tiny and stable MX type precipitated phases. Especially when combined with thermal deformation technologies such as controlled rolling and controlled cooling, the Nb microalloying has more obvious effect. In addition, in the low-temperature tempering process, nb can delay the precipitation of carbide and the decomposition of residual austenite, so that the stability of a tempered structure is improved.
Mo:0.20-0.50%. Mo promotes the separation of pearlite and bainite transformation line, and obviously moves the transformation line of eutectoid ferrite and pearlite to the right, has little influence on the transformation line of bainite, is beneficial to the acquisition of bainitic structure and improves the hardenability of the bainite. Mo is added, so that the structure can be thinned, the toughness is improved, and the toughness matching of the steel is promoted. In order to greatly improve the hardenability of the steel plate.
A production method of a high-strength high-toughness continuous rolling thin steel plate with Brinell hardness of 500HBW comprises the following steps:
1) Smelting and casting
Smelting and casting into blanks according to the components;
2) Slab reheating
The slab is required to be hot-charged into a furnace, the charging temperature is more than or equal to 500 ℃, the heating temperature is 1220-1270 ℃, and the heat preservation time is 2.5-4 hours, wherein the soaking heat preservation time is not less than 45min;
3) Controlled rolling
The rolling is divided into a rough rolling stage and a finish rolling stage, the rough rolling stage adopts large reduction rolling, the pass reduction is controlled to be more than 20% or more than 45mm, meanwhile, the thickness ratio of an intermediate blank to a finished product is required to be more than or equal to 5, and the reduction of the last pass of the finish rolling is controlled to be not less than 12%; the final rolling temperature is controlled between 900 and 950 ℃;
4) Coiling
The coiling temperature is controlled between 700 ℃ and 750 ℃;
5) The heat treatment adopts a whole-coil continuous heat treatment mode, and comprises quenching, tempering, straightening and cutting.
Quenching, wherein the heating temperature is controlled to be 55-100 ℃ above the Ac3 point of the steel grade, and the heating temperature is controlled to be 900-930 ℃; the steel belt is first heated to 650-700 deg.c fast in the frequency of 10Hz via medium frequency induction, heated to quenching temperature in a resistance furnace and maintained. The heat preservation time T1, min=the thickness of the steel plate is x (3.0-3.5) min, the steel strip is directly quenched to room temperature after being discharged from the furnace, a martensitic structure is formed, and the cooling speed is required to be more than or equal to 40 ℃/s;
tempering, namely, after the steel strip is quenched, the steel strip enters a tempering furnace, tempering treatment is carried out at 190-230 ℃, and the tempering heat preservation time and the heat preservation time are T1, and min=the thickness of the steel plate is x (5.0-5.5) min. The tempered steel plate matrix is a tempered martensite structure, has proper hardness and good low-temperature impact toughness, and improves cold bending performance.
And straightening the steel plate by using a strong straightening machine after tempering, ensuring the shape and the unevenness of the steel plate, controlling the unevenness of the steel plate to be 4mm/m, and finally cutting the steel plate, wherein the diagonal cutting slope of the steel plate is required to be not more than 10mm.
In the production method of the steel sheet of the present invention:
the maximum addition amount of the carbon equivalent elements such as C, mn is controlled so that the maximum carbon equivalent is limited to be within 0.68, and the steel plate has certain weldability.
The slab needs to be hot-charged into a furnace, the charging temperature is more than or equal to 500 ℃, the tendency of cracking is greatly increased after the casting blank is cooled to normal temperature, the production safety is threatened, and the energy consumption can be reduced. The heating temperature is 1220-1270 ℃ and the heat preservation time is 2-4 h, wherein the soaking heat preservation time is not less than 45min, so that the casting blank is ensured to burn thoroughly, powerful conditions are provided for rolling, and the decarburization phenomenon is not caused by the condition of overburning. The rolling is divided into two stages of rough rolling and finish rolling, in order to obtain the fine original austenite grain size, the casting blank is rolled by adopting large reduction in the rough rolling stage, and the pass reduction rate is controlled to be more than 20% or more than 45 mm. In order to obtain fine grain size and good plate shape, the thickness ratio of the intermediate blank to the finished product is more than or equal to 5, and the reduction rate of the last pass of finish rolling is controlled to be not lower than 12 percent so as to ensure that the deformation exceeds the critical deformation amount, thereby obtaining good plate shape and uniform matrix structure.
The invention adopts off-line heat treatment after rolling the steel, and has no special requirement on the rolling temperature of casting blanks. However, in order to reduce the rolling load, a high finish rolling temperature is used, and a high coiling temperature is also used to reduce the coiler load and ensure a good coil shape.
The heat treatment adopts a whole-coil continuous heat treatment mode, has the advantage of high treatment efficiency, and in the heat treatment process, the steel belt always runs in a unit under tension, so that the steel plate can be effectively ensured to have good original plate shape in the heat treatment process and after heat treatment. The steel plate is heated rapidly at medium frequency, so that the temperature rising speed of the steel plate can be improved, and the growth of crystal grains can be effectively avoided, so that the grain size of the original austenite is fine, the quenching thickness intensity and the quenching hardness of the steel plate are effectively improved, and the alloy saving effect is achieved.
The quenching heating temperature directly influences the granularity of a follow-up martensitic structure, thereby influencing the toughness of the steel plate. The austenite grains are easily coarsened due to the over high heating temperature, the martensite structure is coarse after quenching, and the toughness is deteriorated; the lower heating temperature leads to insufficient austenitization, complete martensitic structure cannot be obtained after quenching, and the problem that the quenching temperature cannot be ensured due to the fact that the temperature of the steel sheet is quickly reduced before the steel sheet enters a quenching machine after exiting a holding furnace is avoided. The heat preservation time has a similar rule on quenching performance, the grains are easy to be coarse due to overlong time, meanwhile, the energy consumption is increased, the cost is increased, austenitization is insufficient due to overlong time, and the hardness and strength after quenching cannot meet the requirements. Quenching, wherein the heating temperature is controlled to be 55-100 ℃ above the Ac3 point of the steel grade, and the heating temperature is controlled to be 880-930 ℃; the steel belt is first heated to 650-700 deg.c fast in the frequency of 10Hz via medium frequency induction, heated to quenching temperature in a resistance furnace and maintained. The heat preservation time T1, min=the thickness of the steel plate is mm× (3.0-3.5) min, the steel belt is directly quenched to room temperature after being discharged from the furnace, a martensitic structure is formed, and the cooling speed is required to be more than or equal to 40 ℃/s;
tempering mainly slows down and eliminates quenching stress, improves toughness and toughness. The higher tempering temperature easily reduces the strength and hardness of the steel plate too much to meet the design requirements, and meanwhile, the cost is increased. The tempering process parameters of the steel sheet should be limited. In the invention, the steel plate is tempered at 190-230 ℃ for a tempering and heat preserving time T1, min=the thickness of the steel plate is mm min. And (3) carrying out cold straightening on the quenched and tempered steel plate, ensuring the shape and the unevenness of the steel plate, controlling the unevenness of the steel plate to be 4mm/m, and finally cutting the steel plate, wherein the diagonal cutting cooperation of the steel plate is required to be not more than 10mm.
The method can realize the production of the high-hardness high-wear-resistance steel plate with the thickness of less than or equal to 10mm, the yield strength is more than 1250MPa, the tensile strength is more than 1450MPa, the elongation is more than or equal to 8 percent, the hardness is 500+/-20 HBW, and the impact power value at minus 40 ℃ is more than 20J.
Examples:
the chemical compositions of the examples of the invention are shown in Table 1; the rolling process of the corresponding example is shown in table 2; the heat treatment process of the corresponding example is shown in table 3; the mechanical properties and steel plate irregularities of the corresponding examples are shown in Table 4.
TABLE 1 chemical composition wt% of the examples of the invention
TABLE 2 Rolling Process according to an embodiment of the invention
TABLE 3 Heat treatment Process according to an embodiment of the invention
TABLE 4 mechanical Properties and Steel plate irregularities of the examples of the invention
The invention adopts an economic C-Mn component design, is assisted with a small amount of Nb, ti and MO microalloy elements, does not need to add noble alloying elements such as Ni, adopts intermediate frequency rapid heating in the quenching heating temperature rising process, further reduces the addition of the microalloy elements, realizes high strength and high hardness of steel, good low-temperature impact toughness and cold bending processability, and has excellent plate shape.
The method can realize the production of the high-hardness high-wear-resistance steel plate with the thickness of less than or equal to 10mm, the yield strength is more than 1250MPa, the tensile strength is more than 1450MPa, the elongation is more than or equal to 8 percent, the hardness is 500+/-20 HBW, and the impact power value at minus 40 ℃ is more than 20J.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (1)
1. A production method of a high-strength high-toughness hot continuous rolling thin steel plate with Brinell hardness of 500HBW is characterized in that the thickness of the steel plate is less than or equal to 2mm and less than or equal to 10mm, and the steel plate consists of the following chemical elements in percentage by weight:
c:0.24 to 0.26 percent, si: 0.74-0.80%, mn:0.90 to 1.30 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.003 percent, al:0.10 to 0.13 percent, cr: 0.73-0.90%, B:0.0010 to 0.0025 percent, N is less than or equal to 0.0040 percent, H is less than or equal to 0.00020 percent, and Nb:0.020% -0.040%, ti:0.020 to 0.050 percent, mo:0.22 to 0.50 percent, and satisfies Ti/N more than or equal to 5, ceq less than or equal to 0.68, wherein Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Cu+Ni)/15, and the balance of Fe and unavoidable impurities;
the method specifically comprises the following steps:
1) Smelting and casting
Smelting and casting into blanks according to the components;
2) Slab reheating
The plate blank is hot-charged into a furnace, the charging temperature is more than or equal to 500 ℃, the heating temperature is 1220-1270 ℃, the heat preservation time is 2.5-4 h, and the soaking heat preservation time is not less than 45min;
3) Controlled rolling
The rolling is divided into a rough rolling stage and a finish rolling stage, the rough rolling stage adopts large reduction rolling, the pass reduction is controlled to be more than 20% or more than 45mm, meanwhile, the thickness ratio of an intermediate blank to a finished product is required to be more than or equal to 5, and the reduction of the last pass of the finish rolling is controlled to be not less than 12%; the final rolling temperature is controlled between 900 and 950 ℃;
4) Coiling
The coiling temperature is controlled between 700 ℃ and 750 ℃;
5) The heat treatment adopts a whole-coil continuous heat treatment mode, and comprises quenching, tempering, straightening and cutting;
quenching: the heating temperature is controlled to be 55-100 ℃ above the Ac3 point of the steel grade, and the heating temperature is controlled to be 900-930 ℃; firstly, heating the steel strip to 650-700 ℃ by adopting medium frequency induction at a frequency of 5-20 Hz, and then heating to a quenching temperature by adopting a resistance furnace and preserving heat; directly water quenching the steel strip to room temperature after discharging the steel strip from the furnace to form a martensitic structure, wherein the cooling rate is more than or equal to 40 ℃/s;
tempering: quenching the steel strip, then entering a tempering furnace, tempering at 190-230 ℃ and preserving heat;
straightening: the unevenness of the steel plate is controlled to be less than or equal to 4mm/m;
cutting: the diagonal cutting of the steel plate is not more than 10mm;
the quenching heat preservation time is T1, T1 = steel plate thickness x (3.0-3.5) min, the steel plate thickness unit is mm, and the T1 unit is min;
tempering and heat preserving time is T2, wherein T2 = steel plate thickness x (5.0-5.5) min, the steel plate thickness unit is mm, and the T2 unit is min.
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