High-strength hot rolled steel, preparation method and application thereof and structural member

Abstract

The invention relates to high-strength hot rolled steel, a preparation method and application thereof and a structural member, and the high-strength hot rolled steel comprises the following components in percentage by mass: 0.14%-0.16% of C, 0.05%-0.15% of Si, 1.2%-1.8% of Mn, less than or equal to 0.015% of P, less than or equal to 0.002% of S, 0.01%-0.03% of Ti, 0.11%-0.2% of Mo, 0.4%-0.6% of Cr, 0.01%-0.03% of Nb, 0.01%-0.02% of V, less than or equal to 0.005% of N, 0.0005%-0.0015% of B and the balance of Fe and inevitable impurity elements. The steel has high strength, good ductility and excellent toughness at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of alloys, and in particular to a high-strength hot-rolled steel and a preparation method and application thereof, and a structural part thereof. Background Art

[0002] Steel is one of the most widely used materials in industry. Large mechanical structural parts are all made of steel. For example, steel is one of the important structural materials for automobiles. Some structural parts as precision parts require high strength, good elongation and excellent toughness. In traditional technology, the comprehensive mechanical properties of steel are often improved by increasing the addition of precious metal elements such as molybdenum (Mo) and vanadium (V). However, the increase in the addition of molybdenum (Mo) and vanadium (V) will lead to a significant increase in alloy costs, which is not conducive to large-scale applications. How to obtain steel with high strength, good elongation and excellent toughness while reducing costs is still a difficult problem to be overcome.

[0003] Therefore, the existing technology still needs to be improved. Summary of the invention

[0004] Based on this, the present invention provides a high-strength hot-rolled steel with high strength, good elongation and excellent toughness, and its preparation method and application, structural parts, and can reduce the addition amount of molybdenum (Mo) element and vanadium (V) element.

[0005] One aspect of the present invention provides a high-strength hot-rolled steel, which comprises the following components in terms of mass percentage:

[0006] C: 0.14% ~ 0.16%, Si: 0.05% ~ 0.15%, Mn: 1.2% ~ 1.8%, P ≤ 0.015%, S ≤ 0.002%, Ti: 0.01% ~ 0.03%, Mo: 0.11% ~ 0.2%, Cr: 0.4% ~ 0.6%, Nb: 0.01% ~ 0.03%, V: 0.01% ~ 0.02%, N ≤ 0.005%, B: 0.0005% ~ 0.0015% and the balance Fe and unavoidable impurity elements.

[0007] The yield strength of the high-strength hot-rolled steel is ≥800MPa, the tensile strength is ≥850MPa, the elongation after fracture is ≥12%, and the impact toughness KV2 at -40°C is ≥40J.

[0008] In the conventional technology, if the yield strength of the steel is to reach 800 MPa, it is necessary to add about 0.20-0.30 wt% of molybdenum (Mo) element and 0.03-0.05 wt% of vanadium (V) element. The technical solution of the present application greatly reduces the addition amount of molybdenum (Mo) element and vanadium (V) element, thereby reducing the cost while ensuring excellent comprehensive mechanical properties.

[0009] In some embodiments, the high-strength hot-rolled steel has a thickness of 7.8 mm to 11.8 mm.

[0010] Another aspect of the present invention provides a method for preparing high-strength hot-rolled steel, comprising the following steps:

[0011] Providing raw materials according to the stoichiometric ratio of the components of the high-strength hot-rolled steel, and subjecting the raw materials to smelting and casting treatments in sequence to prepare alloy slabs;

[0012] The alloy slab is subjected to heating treatment, rolling treatment, cooling treatment, coiling treatment and slow cooling treatment in sequence to obtain high-strength hot-rolled steel.

[0013] In some embodiments, the rolling process includes rough rolling and finish rolling performed sequentially;

[0014] The rough rolling conditions include: 5 to 7 rolling passes, the first rolling reduction ratio is ≥20%, the last rolling reduction ratio is ≥30%, the start rolling temperature is 1150°C to 1210°C, and the final cooling temperature is 1040°C to 1120°C;

[0015] The finishing rolling process conditions include: using 7-stand continuous rolling, the descaling pressure at the finishing rolling entrance is ≥18MPa, the entrance temperature of the first rolling is ≤980℃, the last pass reduction rate is ≥10%, and the final cooling temperature is 840℃-900℃.

[0016] The rolling conditions are further adjusted to break up the coarse cast structure, refine the original austenite grains, and improve the low-temperature impact toughness of the rolled steel plate.

[0017] In some embodiments, the cooling treatment includes ultrafast cooling treatment and layer cooling treatment performed sequentially, the cooling rate of the ultrafast cooling treatment is 80℃ / s-200℃ / s, the cooling rate of the layer cooling treatment is ≥15℃ / s, and the terminal temperature of the cooling treatment is 560℃~640℃.

[0018] In some of the embodiments, the target coiling temperature of the coiling process is 560°C to 640°C, and during the coiling process, the coiling temperatures of the head area and the tail area formed by extending 10m from both ends of the steel to the middle of the steel are controlled to be 40°C to 60°C higher than the target coiling temperature.

[0019] The coiling temperature of the head area and the tail area is controlled to be higher than the target coiling temperature during coiling, thereby reducing the Nb and Ti precipitation strengthening effect caused by the excessively fast cooling rate in the head area and the tail area during the subsequent slow cooling process, thereby ensuring that the overall performance of the steel is uniform and stable.

[0020] In some embodiments, the slow cooling treatment is performed by centralized stack cooling in an insulated box.

[0021] In some embodiments, the heating treatment is carried out in a heating furnace, the insulation temperature of the heating furnace is 1230℃-1300℃, the insulation time is 20min-100min, the total furnace time of the alloy slab is 170min-400min, and the furnace outlet temperature is 1180℃-1300℃.

[0022] In some embodiments, the casting process is performed by continuous casting.

[0023] In another aspect of the present invention, there is provided a structural member, comprising the high-strength hot-rolled steel as described above or the high-strength hot-rolled steel produced by the method for producing the high-strength hot-rolled steel as described above. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below. Preferred embodiments of the present invention are provided in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0026] the term

[0027] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0028] The terms "and / or", "or / and", and "and / or" used in this article include any one of two or more related listed items, and also include any and all combinations of related listed items, and the arbitrary and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, the technical solution undoubtedly includes technical solutions that are all connected by "logical and", and undoubtedly includes technical solutions that are all connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B and the combination of A and B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution that is all connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, the combination of any two or any three of A, B, C, and D, and also includes the combination of four of A, B, C, and D (that is, the technical solution that is all connected by "logical AND").

[0029] In the present invention, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel solutions of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0030] In the present invention, in the "first aspect", "second aspect", "third aspect", "fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0031] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0032] In the present invention, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0033] The temperature parameters in the present invention, if not specifically limited, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0034] In the present invention, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of the present invention, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of the present invention, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0035] The mass or weight of the relevant components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also indicate the proportional relationship of the mass or weight between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the description of the embodiments of the present invention, it is within the scope disclosed in the description of the embodiments of the present invention. Specifically, the mass or weight described in the description of the embodiments of the present invention may be units known in the chemical industry such as μg, mg, g, and kg.

[0036] An embodiment of the present invention provides a high-strength hot-rolled steel. The high-strength hot-rolled steel comprises the following components in terms of mass percentage:

[0037] C: 0.14% ~ 0.16%, Si: 0.05% ~ 0.15%, Mn: 1.2% ~ 1.8%, P ≤ 0.015%, S ≤ 0.002%, Ti: 0.01% ~ 0.03%, Mo: 0.11% ~ 0.2%, Cr: 0.4% ~ 0.6%, Nb: 0.01% ~ 0.03%, V: 0.01% ~ 0.02%, N ≤ 0.005%, B: 0.0005% ~ 0.0015% and the balance Fe and unavoidable impurity elements.

[0038] The study found that: each specific element has its own advantages and disadvantages on the various properties of steel. Among them, carbon is an element that affects strength. Too high or too low carbon content will affect the toughness of steel and have an adverse effect. Silicon plays a role of solid solution strengthening in steel. A specific amount of Si can effectively improve the strength of steel, but silicon is also easy to form Fe2SiO4 and form a eutectic product with FeO on the surface of the billet, making FeO difficult to remove, which is not good for the comprehensive performance of steel. A specific amount of manganese is an effective element for improving strength and toughness. It can expand the austenite phase region, reduce the critical quenching rate of steel, stabilize austenite, refine grains, and effectively delay pearlite transformation. Too high or too low content cannot simultaneously have high strength and toughness. Phosphorus is prone to central segregation, affecting the forming performance. Sulfur and nitrogen are easy to combine with Ti in steel, affecting the strengthening effect of Ti, and at the same time greatly affecting the plasticity of steel. Due to unfavorable impurity factors, the amount needs to be strictly controlled; titanium has certain fine grain strengthening and precipitation strengthening effects, and is an element with the greatest cost-effectiveness for strength increment; chromium is a carbide-forming element, and has a strong affinity with carbon, which can hinder the diffusion of carbon atoms. Coupled with the comprehensive effect of manganese, the transformation of pearlite and bainite is significantly delayed; niobium has a strong fine grain and precipitation strengthening effect, and a specific content of niobium contributes greatly to the strength; molybdenum can improve the hardenability and thermal strength in steel and prevent temper brittleness. In quenched and tempered steel, it can make the steel harden deeply and harden thoroughly, and improve the tempering resistance or tempering stability of steel; the main role of vanadium in steel is to refine the organization and grain of steel, reduce the strength and toughness of steel, and when dissolved into solid solution at high temperature, it increases hardenability, which can improve the strength and yield ratio after normalizing and low-temperature characteristics; the main role of boron in steel is to increase the hardenability of steel, thereby saving other more expensive and rare metals. Therefore, the iron element and other specific components are combined in a specific ratio to produce a steel material with high strength, good elongation and excellent toughness.

[0039] In some of the embodiments, 0≤N≤0.005%, 0≤P≤0.015%, 0≤S≤0.002%.

[0040] The yield strength of the high-strength hot-rolled steel is ≥800MPa, the tensile strength is ≥850MPa, the elongation after fracture is ≥12%, and the impact toughness KV2 at -40°C is ≥40J.

[0041] In the conventional technology, if the yield strength of the steel is to reach 800 MPa, it is necessary to add about 0.20-0.30 wt% of molybdenum (Mo) element and 0.03-0.05 wt% of vanadium (V) element. The technical solution of the present application greatly reduces the addition amount of molybdenum (Mo) element and vanadium (V) element, thereby reducing the cost while ensuring excellent comprehensive mechanical properties.

[0042] Optionally, the mass percentage of carbon includes: 0.14%, 0.15%, 0.16%, and each value between the minimum and maximum values, or a range consisting of any two values.

[0043] The mass percentage of silicon mentioned above includes: 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.13%, 0.14%, 0.15%, and every value between the minimum and maximum values, or a range consisting of any two values.

[0044] The mass percentage of manganese includes: 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, and any value between the minimum and maximum values, or a range consisting of any two values.

[0045] The mass percentage of titanium mentioned above includes: 0.01%, 0.013%, 0.014%, 0.015%, 0.02%, 0.025%, 0.03%, and any value between the minimum and maximum values, or a range consisting of any two values.

[0046] The mass percentage of Mo mentioned above includes: 0.11%, 0.12%, 0.125%, 0.13%, 0.135%, 0.14%, 0.145%, 0.15%, 0.155%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, and each value between the minimum and maximum values, or the range consisting of any two values.

[0047] The mass percentage of Cr mentioned above includes: 0.4%, 0.435%, 0.5%, 0.545%, 0.6%; and any value between the minimum and maximum values, or a range consisting of any two values.

[0048] The mass percentage of Nb mentioned above includes: 0.01%, 0.02%, 0.03%; and any value between the minimum value and the maximum value, or a range consisting of any two values.

[0049] The mass percentage of V mentioned above includes: 0.01%, 0.015%, 0.02%; and any value between the minimum and maximum values, or a range consisting of any two values.

[0050] The mass percentage of B mentioned above includes: 0.0015%, 0.001%, 0.0009%, 0.0008%, 0.0007%, 0.0006%, 0.0005%; and every value between the minimum and maximum values, or a range consisting of any two values.

[0051] It can be understood that unavoidable impurity elements are impurities that are inevitably introduced into the smelting process due to the limitations of raw materials or process conditions, and their content is at a level that is well known in the art and does not affect the properties of the alloy.

[0052] In some of the embodiments, the high strength hot rolled steel has a thickness of 7.8 mm to 11.8 mm.

[0053] Another aspect of the present invention provides a method for preparing high-strength hot-rolled steel, comprising the following steps S10 to S20.

[0054] S10, providing raw materials according to the stoichiometric ratio of the components of the high-strength hot-rolled steel, and subjecting the raw materials to smelting and casting treatments in sequence to prepare alloy slabs.

[0055] It should be noted that the raw materials can be adjusted according to the composition of high-strength hot-rolled steel. The ratio of each element in the raw materials can meet the composition of high-strength hot-rolled steel. There is no special requirement for the specific type. It can be a metal element or an alloy.

[0056] In some of the embodiments, the casting process is performed by continuous casting.

[0057] In some of the embodiments, the thickness of the alloy slab is 230 mm-240 mm.

[0058] S20, subjecting the alloy slab to heating treatment, rolling treatment, cooling treatment, coiling treatment and slow cooling treatment in sequence to obtain high-strength hot-rolled steel.

[0059] In the preparation method of the above-mentioned high-strength hot-rolled steel, the preparation raw materials according to the stoichiometric ratio of the above-mentioned high-strength hot-rolled steel are smelted and cast to form alloy slabs, and then processed through specific steps to ensure the overall stability of the steel, thereby obtaining steel with high strength, good elongation and excellent toughness.

[0060] In some of the embodiments, the rolling process includes rough rolling and finish rolling performed sequentially.

[0061] Among them, the rough rolling step conditions include: 5 to 7 rolling passes, the rolling reduction rate of the first pass is ≥20%, the rolling reduction rate of the last pass is ≥30%, the starting rolling temperature is 1150℃~1210℃, and the final cooling temperature is 1040℃-1120℃.

[0062] In some of the embodiments, the rolling reduction ratio of the first pass is 20% to 30%, and the rolling reduction ratio of the last pass is 30% to 45%.

[0063] The conditions of the finishing rolling steps include: using 7-stand continuous rolling, the descaling pressure at the finishing rolling entrance is ≥18MPa, the entrance temperature of the first rolling is ≤980℃, the last pass reduction rate is ≥10%, and the final cooling temperature is 840℃-900℃.

[0064] The rolling conditions are further adjusted to break up the coarse cast structure, refine the original austenite grains, and improve the low-temperature impact toughness of the rolled steel plate.

[0065] In some of the embodiments, the descaling pressure at the entrance of the finishing rolling is 18 MPa to 30 MPa, the entrance temperature of the first rolling is 800° C. to 980° C., and the final reduction rate is 10% to 25%.

[0066] In some of the embodiments, before the rough rolling step, the step of dephosphorizing the slab after the heating treatment is further included.

[0067] In some embodiments, the cooling treatment includes ultra-fast cooling treatment and layer cooling treatment performed sequentially, the cooling rate of the ultra-fast cooling treatment is 80°C / s-200°C / s, the cooling rate of the layer cooling treatment is ≥15°C / s, and the terminal temperature of the cooling treatment is 560°C~640°C.

[0068] Specifically, the time ratio of the ultrafast cooling treatment and the layer cooling treatment is 1:(0.5-1).

[0069] In some of the embodiments, the target coiling temperature of the coiling process is 560°C to 640°C, and during the coiling process, the coiling temperatures of the head area and the tail area formed by extending 10m from both ends of the steel to the middle of the steel are controlled to be 40°C to 60°C higher than the target coiling temperature.

[0070] In some of the embodiments, the coiling temperatures of the head region and the tail region during coiling are controlled to be higher than the target coiling temperature, thereby reducing the precipitation strengthening effect of Nb and Ti in the head region and the tail region due to excessively fast cooling during the subsequent slow cooling process, thereby ensuring that the overall performance of the steel is uniform and stable throughout the steel.

[0071] In some of the embodiments, the slow cooling treatment is performed by centralized stack cooling in an insulated box.

[0072] In some embodiments, the heating treatment is carried out in a heating furnace, the insulation temperature of the heating furnace is 1230℃-1300℃, the insulation time is 20min-100min, the total furnace time of the alloy slab is 170min-400min, and the furnace outlet temperature is 1180℃-1300℃.

[0073] In some of the embodiments, the casting process is performed by continuous casting.

[0074] Another embodiment of the present invention further provides a structural member, the structural member comprising the high-strength hot-rolled steel as described above or the high-strength hot-rolled steel prepared by the method for preparing the high-strength hot-rolled steel as described above.

[0075] Structural parts include but are not limited to: large machinery and equipment parts, automobile parts, etc.

[0076] The present invention will be described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present invention. Under the guidance of the concept of the present invention, those skilled in the art should realize that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention. Specific embodiments

[0078] The following are specific embodiments.

[0079] Example 1

[0080] (1) The mass percentage of each element of high-strength hot-rolled steel is shown in Table 1, and the corresponding preparation raw materials are provided.

[0081] (2) The raw materials are melted into molten iron and continuously cast into alloy slabs, the thickness of the alloy slabs being 230 mm.

[0082] (3) The alloy slab is fed into a heating furnace of a conventional hot rolling line for heating. The holding temperature of the heating furnace is 1230°C, the holding time is 60 min, the total time the slab is in the furnace is 300 min, and the temperature out of the furnace is 1180-1300°C.

[0083] (4) The slab is descaled and then rough rolled. The rough rolling is performed in 7 passes to obtain an intermediate slab. The starting rolling temperature of the rough rolling is 1210°C, the first rolling reduction is 20%, the final rolling reduction is 30%, and the final cooling temperature of the rough rolling is 1040-1120°C. Then, the slab is finished by 7-stand continuous rolling: the descaling pressure at the finishing entrance is 18 MPa, the starting rolling entrance temperature is 980°C, the final rolling reduction is 10%, and the final cooling temperature of the finishing is 880°C to obtain a steel strip.

[0084] (5) After the strip leaves the finishing mill, ultra-fast cooling + layer cooling is adopted. The first stage adopts ultra-fast cooling with a cooling rate of 100°C / s. The second stage adopts layer cooling with a cooling rate of 15°C / s. The strip is coiled after cooling to the target coiling temperature of 640°C. The coiling temperature at 10m at both ends of the strip is 60°C higher than the target coiling temperature to obtain the steel coil. The steel coil is concentratedly piled and cooled in the insulation box off the line for slow cooling. The steel coil is slowly cooled to a temperature below 150°C before leaving the box to obtain the high-strength steel hot-rolled coil. The thickness is shown in Table 2.

[0085] (6) The mechanical properties of the high-strength steel hot-rolled coil were tested using industry standard tests. The results are shown in Table 2. The high-strength steel hot-rolled coil was flattened and mechanical properties were tested at its head, middle and tail. The results are shown in Table 3.

[0086] Embodiments 2 to 4

[0087] Examples 2 to 4 are substantially the same as Example 1, except that the mass percentage of each element in the high-strength hot-rolled steel in step (1) is different from that in Example 1. For details, please see Table 1.

[0088] The performance test results of Examples 2 to 4 are shown in Table 2 and Table 3, respectively.

[0089] The compositions of the high-strength hot-rolled steels of Examples 1 to 4 are shown in Table 1.

[0090] Table 1

[0091]

[0092] The thickness and mechanical properties of the high-strength steel hot-rolled coils obtained in Examples 1 to 4 are specifically shown in Table 2.

[0093] Table 2

[0094] Example Thickness / mm Yield strength / MPa Tensile strength / MPa Elongation after break / % -40℃ impact energy / J 1 11.8 863 924 15.5 94 / 107 / 110 2 9.8 874 935 16 90 / 99 / 93 3 8.8 879 941 15.5 105 / 102 / 115 4 7.8 891 953 16.5 108 / 105 / 116

[0095] The mechanical properties of the high-strength steel hot-rolled coils obtained in Examples 1 to 4 at different sampling positions after flattening are specifically shown in Table 3.

[0096] Table 3

[0097]

[0098] It can be seen from the data in Tables 2 to 3 that the high-strength hot-rolled steel material of the present application has high strength, good elongation and excellent low-temperature toughness, and has small isotropy difference and uniform and stable performance everywhere.

[0099] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high-strength hot-rolled steel, characterized in that: The high-strength hot-rolled steel comprises the following components in terms of mass percentage: C: 0.14% ~ 0.16%, Si: 0.05% ~ 0.15%, Mn: 1.2% ~ 1.8%, P ≤ 0.015%, S ≤ 0.002%, Ti: 0.01% ~ 0.03%, Mo: 0.11% ~ 0.2%, Cr: 0.4% ~ 0.6%, Nb: 0.01% ~ 0.03%, V: 0.01% ~ 0.02%, N ≤ 0.005%, B: 0.0005% ~ 0.0015% and the balance Fe and unavoidable impurity elements.

2. The high-strength hot-rolled steel according to claim 1, characterized in that: The thickness of the high-strength hot-rolled steel is 7.8 mm to 11.8 mm.

3. A method for preparing high-strength hot-rolled steel, characterized in that: The steps include: Providing a raw material according to the stoichiometric ratio of the components of the high-strength hot-rolled steel according to any one of claims 1 to 2, and subjecting the raw material to smelting treatment and casting treatment in sequence to prepare an alloy slab; The alloy slab is subjected to heating treatment, rolling treatment, cooling treatment, coiling treatment and slow cooling treatment in sequence to obtain high-strength hot-rolled steel.

4. The method for preparing high-strength hot-rolled steel according to claim 3, characterized in that: The rolling process includes rough rolling and finish rolling performed sequentially; The rough rolling conditions include: 5 to 7 rolling passes, the first rolling reduction ratio is ≥20%, the last rolling reduction ratio is ≥30%, the start rolling temperature is 1150°C to 1210°C, and the final cooling temperature is 1040°C to 1120°C; The finishing rolling process conditions include: using 7-stand continuous rolling, the descaling pressure at the finishing rolling entrance is ≥18MPa, the entrance temperature of the first rolling is ≤980℃, the last pass reduction rate is ≥10%, and the final cooling temperature is 840℃-900℃.

5. The method for preparing high-strength hot-rolled steel according to claim 3, characterized in that: The cooling treatment includes ultrafast cooling treatment and layer cooling treatment performed in sequence, the cooling rate of the ultrafast cooling treatment is 80°C / s-200°C / s, the cooling rate of the layer cooling treatment is ≥15°C / s, and the terminal temperature of the cooling treatment is 560°C-640°C.

6. The method for preparing high-strength hot-rolled steel according to any one of claims 3 to 5, characterized in that: The target coiling temperature of the coiling process is 560°C to 640°C, and during the coiling process, the coiling temperatures of the head area and the tail area formed by extending 10m from both ends of the steel to the middle of the steel are controlled to be 40°C to 60°C higher than the target coiling temperature.

7. The method for preparing high-strength hot-rolled steel according to any one of claims 3 to 5, characterized in that: The slow cooling treatment is carried out in a concentrated stack cooling manner in an insulated box.

8. The method for preparing high-strength hot-rolled steel according to any one of claims 4 to 5, characterized in that: The heating treatment is carried out in a heating furnace, the insulation temperature of the heating furnace is 1230°C-1300°C, the insulation time is 20min-100min, the total furnace time of the alloy slab is 170min-400min, and the furnace outlet temperature is 1180°C-1300°C.

9. The method for preparing high-strength hot-rolled steel according to any one of claims 4 to 5, characterized in that: The casting process adopts a continuous casting method.

10. A structural member, characterized in that: The structural member comprises the high-strength hot-rolled steel as claimed in any one of claims 1 to 2 or the high-strength hot-rolled steel produced by the method for producing high-strength hot-rolled steel as claimed in any one of claims 3 to 9.

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