CN115537682A

CN115537682A - Thin-gauge hot-rolled 1200MPa steel and preparation method thereof

Info

Publication number: CN115537682A
Application number: CN202211186215.8A
Authority: CN
Inventors: 肖宝亮; 朱国森; 李晓林; 徐海卫; 田志红; 杨春政; 于孟; 林绍峰; 李继新; 徐永先; 缪成亮; 董占奎; 文杰; 刘朋; 梁江涛; 吕博; 季晨曦; 王永强; 张明生; 张大伟
Original assignee: Shougang Group Co Ltd
Current assignee: Shougang Group Co Ltd
Priority date: 2022-09-27
Filing date: 2022-09-27
Publication date: 2022-12-30

Abstract

The invention particularly relates to thin-gauge hot-rolled 1200MPa steel and a preparation method thereof, belonging to the technical field of steel preparation. A thin gauge hot rolled 1200MPa steel comprises the following chemical components in percentage by mass: c:0.20-0.30%, si: less than or equal to 0.05 percent, mn:2.5-3.0%, al:0.02-0.35%, P: less than or equal to 0.010 percent, S: less than or equal to 0.005 percent, nb:0.01-0.10%, ti:0.010-0.030%, cr:0.5-1.0%, N: less than or equal to 0.004%, B:0.0020 to 0.0040 percent, and the balance of Fe and inevitable impurities. The steel is designed by chemical components, a C-Si-Mn-Nb-Ti-Cr-B component system is adopted, the hardenability of the material is improved by adding a proper amount of B element, a martensite structure is obtained, the strength of the material is ensured by solid solution strengthening of C, mn and Cr, fine grain strengthening of Nb and structure strengthening, the yield strength of the obtained steel is more than 1050MPa, the tensile strength is more than 1200MPa, the elongation is more than 7%, transverse cold bending D =4a and 180 degrees are qualified, the thickness of a hot rolled steel plate can reach 0.8-4.0mm, and the technical problems that the thin-specification hot rolled 1200MPa steel plate type is poor in quality and large in strength fluctuation in the prior art can be effectively solved.

Description

Thin-gauge hot-rolled 1200MPa steel and preparation method thereof

Technical Field

The invention belongs to the technical field of steel preparation, and particularly relates to thin-gauge hot-rolled 1200MPa steel and a preparation method thereof.

Background

In recent years, driven by the factors of 'replacing cold with heat', reducing cost, saving energy, reducing emission, shortening flow, improving efficiency and the like, the endless rolling technology gradually improves the production proportion of ultrathin specification strip steel products, and with the increasing market demand on high-performance thin/ultrathin specification hot rolled strip steel, a plurality of thin slab continuous casting and rolling (ESP) production lines are put into production in China, so that common low-carbon ultrathin sheet and high-strength ultrathin hot rolled sheet products can be stably, reliably and accurately produced. The difference between the multi-mode thin slab continuous casting and rolling production line and the conventional ESP production line is that: the thickness of the plate blank is increased by 20-30mm compared with that of an ESP production line, a roller hearth type tunnel furnace is additionally arranged between the outlet of a continuous casting machine and rough rolling, the tunnel furnace comprises a fixed section and a movable section, the plate blank offline function is realized, single-blank, semi-endless and full-endless multi-mode rolling can be realized, and the product thickness range is expanded.

The high-strength steel can meet the safety and use requirements and achieve the purposes of weight reduction, energy conservation and emission reduction, so that the high-strength steel becomes a new-generation environment-friendly material, is widely applied to the fields of engineering machinery, automobile manufacturing, container manufacturing and the like, and has increasingly expanded demand and good market prospect. 1200 MPa-level high-strength steel is widely applied to the fields of automobile girders, automobile frames, carriages, crane booms and container carriage plates in the engineering machinery industry and the like, replaces low-strength-level products, and realizes reduction production. However, the conventional hot continuous rolling line for producing thin 1200MPa high-strength steel has the problems of poor plate shape, large strength fluctuation, poor dimensional precision control and the like.

Disclosure of Invention

The application aims to provide thin-gauge hot-rolled 1200MPa steel and a preparation method thereof, and aims to solve the technical problems that the plate type quality of the thin-gauge hot-rolled 1200MPa steel is poor and the strength fluctuation is large in the prior art.

The embodiment of the invention provides thin-gauge hot-rolled 1200MPa steel, which comprises the following chemical components in percentage by mass:

c:0.20-0.30%, si: less than or equal to 0.05 percent, mn:2.5-3.0%, al:0.02-0.35%, P: less than or equal to 0.010 percent, S: less than or equal to 0.005 percent, nb:0.01-0.10%, ti:0.010-0.030%, cr:0.5-1.0%, N: less than or equal to 0.004%, B:0.0020 to 0.0040 percent, and the balance of Fe and inevitable impurities.

Optionally, the metallographic structure of the thin gauge hot rolled 1200MPa steel is martensite.

Based on the same inventive concept, the embodiment of the invention also provides a preparation method of the thin-gauge hot-rolled 1200MPa steel, which comprises the following steps:

performing KR desulfurization, converter smelting, LF refining and VD refining to obtain molten steel according with the chemical components;

continuously casting the molten steel to obtain a plate blank;

preheating the plate blank, roughly removing phosphorus, roughly rolling, inductively heating, finely removing phosphorus, finely rolling, carrying out laminar cooling, coiling and air cooling to obtain the thin-specification hot-rolled 1200MPa steel;

wherein:

the finish rolling is any one of single billet rolling, semi-endless rolling and full endless rolling;

the fine descaling is single-row dephosphorization or double-row dephosphorization;

when the finish rolling is single-billet mode rolling, the finish descaling is double-row descaling;

and when the finish rolling is in a semi-endless mode rolling or a full endless mode rolling, the finish phosphorus removal is single-row phosphorus removal.

Optionally, the pre-heating end point temperature is 1150-1200 ℃.

Optionally, the drawing speed of the continuous casting is 4.0-6.5m/min, and the thickness of the continuously cast slab is 110-123mm.

Optionally, the pressure of the coarse phosphorus removal is more than or equal to 30MPa, the pressure of the fine phosphorus removal is more than or equal to 30MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 60-110mm.

Optionally, the inlet temperature of rough rolling is more than or equal to 1150 ℃, the outlet temperature of rough rolling is 930-1000 ℃, and the number of rough rolling passes is 3.

Optionally, the end temperature of the induction heating is 1050-1150 ℃.

Optionally, the accumulated deformation of the finish rolling is 70-80%, the finish rolling temperature of the finish rolling is 800-860 ℃, and the number of passes of the finish rolling is 5.

Optionally, the cooling speed of laminar cooling is more than or equal to 40 ℃, and the coiling temperature is 250-400 ℃.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

according to the thin hot rolled 1200MPa steel provided by the embodiment of the invention, through chemical composition design, a C-Si-Mn-Nb-Ti-Cr-B component system is adopted, the hardenability of the material is improved by adding a proper amount of B element, a martensite structure is obtained, the strength of the material is ensured by means of solid solution strengthening of C, mn and Cr, fine grain strengthening of Nb and structure strengthening, the yield strength of the obtained steel is more than 1050MPa, the tensile strength is more than 1200MPa, the elongation is more than 7%, transverse cold bending D =4a, 180 degrees are qualified, the thickness of a hot rolled steel plate can reach 0.8-4.0mm, and the technical problems of poor quality and large strength fluctuation of a thin hot rolled 1200MPa steel plate in the prior art can be effectively solved.

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

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a flow chart of a method provided by an embodiment of the present invention;

FIG. 2 is a metallographic structure diagram of thin gauge hot rolled 1200MPa steel according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. For example, room temperature may refer to a temperature in the interval of 10 to 35 ℃.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

according to an exemplary embodiment of the present invention, there is provided a thin gauge hot rolled 1200MPa steel having a chemical composition comprising, in mass percent:

According to the thin hot-rolled 1200MPa steel provided by the embodiment of the invention, through chemical composition design, a C-Si-Mn-Nb-Ti-Cr-Mo-V-B component system is adopted, the hardenability of the material is improved by adding a proper amount of Mo and B elements, a martensite structure is obtained, the strength of the material is ensured by means of solid solution strengthening of C, mn and Cr, fine grain strengthening of Nb and structure strengthening, the yield strength of the obtained steel is more than 1200MPa, the tensile strength is more than 1400MPa, the elongation is more than 7%, transverse cold bending D =4a and 180 degrees are qualified, the thickness of a hot-rolled steel plate can reach 0.8-4.0mm, and the technical problems that the thin hot-rolled 1200MPa steel plate in the prior art is poor in quality and large in strength fluctuation can be effectively solved.

The actions and the limited ranges of the main alloy elements are explained in detail as follows:

c: c is the most important alloy element in steel and is one of the most economical elements for improving the strength, C atoms are limitedly and fixedly dissolved in gamma-Fe, a gamma phase region is enlarged, the influence on the structure and the performance is great, the strength and the hardness are mainly controlled, and the C atoms and micro alloy elements can form carbonitrides to adjust the performance of the steel in a large range. When the C is more than 0.30 percent, a banded structure is easily formed in the slab smelting and rolling processes, the severe banded structure has adverse effects on the cold forming performance and the fatigue performance of the steel plate, and when the C is more than 0.30 percent, the welding performance is not facilitated; when the C content is less than 0.20%, the smelting difficulty is increased. Therefore, the content of C is controlled to be 0.20-0.30%.

Si: si mainly influences the surface quality of hot-rolled strip steel, pickled steel plates and hot-dip galvanized strip steel, and according to the Sandlin effect, when the Si content is controlled to be below 0.05 percent, the coating structure is basically not influenced by silicon, and a bright coating with normal thickness can be obtained, so that the Si content is controlled to be less than or equal to 0.05 percent.

Mn: mn and Fe can be mutually replaced, and are replaced solute atoms in an iron-based solid solution, so that the iron-based solid solution has good solid solution strengthening performance; manganese can also refine grains and improve strength, and is an austenite stabilizing element to enlarge a single austenite phase region; manganese can obviously lower the temperature of gamma → alpha transition, so the A1 point can be lowered; in order to reduce the energy consumption of induction heating, the finish rolling end point temperature is generally controlled at 800-860 ℃, if the Mn content is lower, the strip steel is subjected to finish rolling in the temperature range, the strip steel easily enters a two-phase region, partial austenite is converted into a ferrite structure, and the strength of the strip steel is reduced, so that the Mn content is added to be more than 2.0 percent in order to obtain a whole martensite structure, the strip steel is ensured to be still in a complete austenite region during the finish rolling at 800-860 ℃, and the formation of the ferrite structure is avoided; when the Mn content is more than 3.0%, the production cost of the test steel is increased, and therefore, the Mn content is controlled to be 2.5 to 3.0%.

Al: al is one of effective deoxidizing elements, and can form nitrides to refine grains. Al content > 0.35% will impair the toughness of the steel and the toughness of the weld heat affected zone will also deteriorate.

P, S and N: p, S and N elements are too high, which can generate adverse effects on the plasticity, toughness and fatigue property of the material, and the N content is too high, which is easy to combine with B elements, BN precipitate is formed at a high temperature stage, part of B elements are consumed, thereby the hardenability of the strip steel is reduced, all martensite structures cannot be obtained, and the strength of the strip steel is reduced, so that the P content is controlled to be less than or equal to 0.010 percent, the S content is controlled to be less than or equal to 0.005 percent, and the N content is controlled to be less than or equal to 0.004 percent.

Nb: nb is one of key strengthening elements in the HSLA steel, has various strengthening mechanisms such as solid solution strengthening and precipitation in the thermomechanical process, and can obviously improve the dynamic recrystallization temperature of the steel by solid solution Nb, so that the generation of deformation induced precipitation is promoted by rolling in a non-recrystallization zone; the dispersed precipitates of Nb can strengthen the matrix through the dragging effect on dislocation and also refine grains through the pinning effect on grain boundaries, thereby improving the strength and the toughness and the plasticity of the steel; in addition, nb can also ensure the refinement of weld structures, improve the strength after welding, and consider the cost factor, and the excessively high Nb content causes the increase of the production cost of the material, so the Nb content is controlled to be 0.01-0.10%.

Ti: ti is a strong carbonitride forming element, and is firstly combined with N to form a TiN precipitated phase at a high temperature stage, so that the N element can be consumed, the content of solid solution N is reduced, and the cleanliness of molten steel is improved; on the other hand, the TiN precipitated phase is formed earlier than BN, so that the combination of B and N is avoided, the consumption of N to solid solution B elements is reduced, and the hardenability with the sense is ensured; fine TiN particles are precipitated after the molten steel is solidified, and the fine TiN particles are very stable and can effectively prevent austenite grains from growing to refine the structure; in the welding process, the second phase particles containing Ti can prevent the growth of a coarse crystal area in the welding process, so that crystal grains are refined, and the welding performance of steel is improved; the high Ti content, ti and C combine to form TiC or Ti (C, N), consumes part of C elements, and the low solid solution C content can reduce the strength of the strip steel, so the Ti content is controlled to be 0.010-0.030%.

Cr: cr is an element with strong hardenability, plays a role in solid solution strengthening in a matrix, and is added with a proper amount in order to obtain finer ferrite grains, so that the hardenability of the material is improved, and the grains are refined. However, since excessive Cr causes deterioration of weldability of the material, the Cr content is controlled to be 0.5 to 1.0%.

B: the B element is a strong hardenability element, the content of the B element in the steel is very small (not more than 50 ppm), the main function of the B element is to increase the hardenability of the steel, the influence effect of the B element is much larger than that of Cr, mn and other alloy elements, and a large amount of alloy elements can be saved by applying a small amount of B. However, B is very active chemically and has a strong affinity to N, O and C also forms B ₄ C; only B present in a solid solution state has a beneficial effect on the hardenability of steel, while B present as a compound has no effect on the hardenability of steel, and thus the B content is controlled to be 0.0020 to 0.0040%.

As an alternative embodiment, the metallographic structure of the thin gauge hot rolled 1200MPa steel is martensitic.

The reason why the metallographic structure is controlled to be martensite is as follows: in order to satisfy the mechanical properties, the material strength strengthening mechanism is structure strengthening, and martensite is a low-temperature phase transformation structure and has excellent strength, so the structure is controlled to be a martensite structure.

According to another exemplary embodiment of the present invention, there is provided a method of manufacturing the thin gauge hot rolled 1200MPa steel provided above, including the steps of:

s1, performing KR desulfurization, converter smelting, LF refining and VD refining to obtain molten steel according with the chemical components.

And S2, continuously casting the molten steel to obtain a plate blank.

And S3, preheating the plate blank, roughly removing phosphorus, roughly rolling, inductively heating, finely removing phosphorus, finely rolling, carrying out laminar cooling, coiling and air cooling to obtain the thin-gauge hot-rolled 1200MPa steel.

Wherein:

the finish rolling is any one of single billet mode rolling, semi-endless mode rolling and full endless mode rolling;

and when the finish rolling is in a semi-endless mode rolling or a full endless mode rolling, the finish rolling is in single-row dephosphorization.

The steps are as follows: dephosphorization is carried out twice before rough rolling and finish rolling to ensure the surface quality of the strip steel, and the intermediate billet is inductively heated before finish rolling to ensure that carbo-nitrides of Nb and Ti formed in the rough rolling are redissolved, nb is separated out again in the finish rolling stage, austenite grains are refined, and further the size of martensite grains is refined; the proper amount of Mo and V elements are added, mo has the effect of promoting bainite formation, and after the steel plate is welded, a bainite structure is formed in the cooling process of a heat affected zone, so that the hardness of heat affected is increased, and welding softening is avoided. The V is very easy to combine with C, N element to form fine V (C, N), and the V (C, N) separated out in the heat affected zone in the cooling process after welding can increase the hardness of the heat affected zone and avoid welding softening; after rolling, laminar cooling is adopted, the cooling speed and the coiling temperature are adjusted according to different strip steel thicknesses, 1000MPa hot rolled strip steel with uniform performance is obtained, and the strip steel is good in shape, high in size precision and small in strength fluctuation.

It should be noted that the single-slab mode rolling, the semi-endless mode rolling, and the full endless mode rolling respectively refer to: the three rolling modes are a definition of whether the casting blank is cut into ends or not in the rolling process, the single-blank rolling mode refers to that the casting blank needs to be cut into ends and one steel coil is produced after one casting blank is rolled, and the semi-endless rolling mode refers to that the casting blank needs to be cut into ends and ends, but the casting blank is longer in length and can produce a plurality of steel coils generally. The full endless mode rolling means that the casting blank does not need to be cut to the end and the tail in the whole rolling process, and only the strip steel is split coiled after being coiled.

The single-row phosphorus removal or the double-row phosphorus removal respectively means: the number of rows of the descaling header is referred to, the header is arranged in one row and is called single-row descaling, and the header is arranged in two rows and is called double-row descaling.

The reason for selecting the fine descaling mode through the fine rolling mode is as follows: the dephosphorization mode before finish rolling is selected according to the rolling mode, and double rows of descaling are selected because the rolling speed is high during single-billet rolling, and the entry temperature of finish rolling is low and the viscosity of iron scales is large and is not easy to remove completely during single-billet rolling; semi-endless and full endless rolling, the rolling speed is slow, the slab needs to be subjected to induction heating before finish rolling, the temperature of the slab is increased, the viscosity of iron scales is reduced after the temperature is increased, and the iron scales are easy to remove, so that single-row descaling is selected.

As an alternative embodiment, the end temperature of the preheating is 1150-1200 ℃.

The reason for controlling the end temperature of preheating is: the temperature range can ensure the temperature of the plate blank entering the rolling mill, so that the plate blank is excessively uniform; when the temperature is higher than 1200 ℃, energy is wasted, and when the temperature is lower than 1150 ℃, rolling instability is caused.

As an alternative embodiment, the drawing speed of the continuous casting is 4.0-6.5m/min, and the thickness of the continuously cast slab is 110-123mm.

The reason for controlling the continuous casting drawing speed is as follows: the continuous casting matched endless rolling production mode can be ensured by controlling the drawing speed of the continuous casting to be 4.0-6.5 m/min; when the pulling speed is more than 6.5m/min, the adverse effect is that 6.5m/min is the equipment operation limit, equipment needs to be replaced when the pulling speed is too high, the cost is increased, and when the value of the pulling speed is less than the minimum value of the end point of the range, the adverse effect is that the pulling speed is too low, and the matching of continuous casting and rolling production cannot be ensured.

As an optional embodiment, the pressure of the coarse phosphorus removal is more than or equal to 30MPa, the pressure of the fine phosphorus removal is more than or equal to 30MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 60-110mm.

The reason for controlling the pressure of the crude phosphorus removal is that: in the pressure range, the scale on the surface of the strip steel can be fully removed; when the value of the descaling pressure is less than the minimum value of the end point of the range, the adverse effect is that iron oxide scale remains on the surface of the strip steel, so that the surface quality of the strip steel is affected.

The reason for controlling the pressure of fine phosphorus removal is that: in the pressure range, the scale on the surface of the strip steel can be fully removed; when the value of the descaling pressure is less than the minimum value of the end point of the range, the adverse effect is that the scale on the surface of the strip steel is remained, and the surface quality of the strip steel is affected.

The reason for controlling the distance of the nozzle from the slab is: the distance between the fine descaling nozzle and the continuously cast slab is controlled to be 60-110mm, so that the descaling effect of the strip steel can be ensured; when the value of the distance is larger than the maximum value of the end point of the range, the adverse effect is that the distance is too large, the effect of the descaling nozzle is poor, and an over-descaling area exists.

As an optional embodiment, the inlet temperature of rough rolling is more than or equal to 1150 ℃, the outlet temperature of rough rolling is 930-1000 ℃, and the number of passes of rough rolling is 3.

The reason for controlling the above parameters is that: in the temperature range, the temperature of the plate blank entering the rolling mill can be ensured; when the temperature is greater than the maximum value of the end point of the range, the temperature is too high, energy waste is caused, and when the temperature is less than the minimum value of the end point of the range, the temperature is too low, and rolling instability is caused.

The reason for controlling the roughing outlet temperature is: in the temperature range, the temperature of the plate blank entering the rolling mill can be ensured; when the value of the temperature is larger than the maximum value of the end point of the range, the adverse effect is that the temperature is too high, energy waste is caused, and when the value of the temperature is smaller than the minimum value of the end point of the range, the adverse effect is that the temperature is too low, and rolling instability is caused.

As an alternative embodiment, the end temperature of the induction heating is 1050-1150 ℃.

The reason why the end temperature of the induction heating is controlled is that: the finish rolling adopts 5 stands for rolling, the temperature drop in the finish rolling process is large, and the finish rolling temperature is 820-880 ℃ for ensuring, so that the plate blank has high temperature before entering a finish rolling machine, and the requirement of the finish rolling temperature is met after the finish rolling of the plate blank is finished. When the semi-endless or full endless mode rolling is adopted, the required finish rolling inlet temperature (induction heating end point temperature) is higher due to the slow rolling speed and the large temperature drop in the finish rolling process, and when the single-billet rolling is adopted, the required finish rolling inlet temperature is lower due to the fast finish rolling speed and the finish rolling process Wen Jiangshao which is relative to the semi-endless and full endless rolling, but the finish rolling inlet temperature is more than 1050 ℃.

As an optional embodiment, the accumulated deformation amount of the finish rolling is 70-80%, the finish rolling temperature of the finish rolling is 800-860 ℃, and the number of passes of the finish rolling is 5.

The reason why the integrated deformation amount is controlled is that: within the deformation range, the grain structure can be refined, and the strength and the toughness of the product are improved; when the value of the accumulated deformation is larger than the maximum value of the end point of the range, the deformation is too large, the strength of the product is higher, and when the value of the accumulated deformation is smaller than the minimum value of the end point of the range, the deformation is too low, and the strength of the product is insufficient.

The reason why the finish rolling temperature of the finish rolling is controlled is that: within the temperature range, the final structure of the product can be ensured to be uniform; when the value of the temperature is larger than the maximum value of the end point of the range, the adverse effect is that the temperature is too large, so that the rolling is unstable, and when the value of the temperature is smaller than the minimum value of the end point of the range, the adverse effect is that the temperature is too low, so that the finish rolling is rolled in a two-phase region, and the obtained microstructure is not uniform.

As an alternative embodiment, the cooling speed of laminar cooling is more than or equal to 40 ℃, and the coiling temperature is 250-400 ℃.

The reason for controlling the cooling rate of the laminar cooling is that: within the cooling speed range, the required metallographic structure and mechanical property can be obtained; when the value of the cooling rate is larger than the maximum value of the end point of the range, the adverse effect caused is that the cooling rate is too high, different structures are obtained, the performance of the final finished product is influenced, and when the value of the cooling rate is smaller than the minimum value of the end point of the range, the adverse effect caused is that the cooling rate is too low, different structures are obtained, and the performance of the final finished product is influenced.

The reason for controlling the temperature of the coiling is that: within the temperature range, the final tissue uniformity of the product can be ensured; when the value of the temperature is greater than the maximum value of the end point of the range, the adverse effect caused by overhigh temperature can obtain different structures and influence the performance of the final finished product, and when the value of the temperature is less than the minimum value of the end point of the range, the adverse effect caused by overlow temperature can obtain different structures and influence the performance of the final finished product.

The present application will be described in detail below with reference to examples, comparative examples, and experimental data.

Example 1

A thin gauge hot rolled 1200MPa steel, the chemical composition of which comprises, in mass percent:

c:0.25%, si:0.021%, mn:2.56%, al:0.031%, P:0.005%, S:0.0015%, nb:0.033%, ti:0.015%, cr:0.60%, N:0.0028%, B:0.0020%, and the balance of Fe and inevitable impurities.

The metallographic structure of the thin gauge hot rolled 1200MPa steel is martensite.

The thickness of the thin gauge hot rolled 1200MPa steel is 0.8mm.

The preparation method of the thin gauge hot-rolled 1200MPa steel comprises the following steps:

s1, performing KR desulfurization, converter smelting, LF refining and VD refining to obtain molten steel according with chemical components.

And S2, continuously casting the molten steel to obtain a plate blank.

And S3, preheating the plate blank, roughly removing phosphorus, roughly rolling, inductively heating, finely removing phosphorus, finely rolling, carrying out laminar cooling, coiling and air cooling to obtain the thin-specification hot-rolled 1200MPa steel.

Wherein:

the finish rolling is full endless rolling;

fine descaling is single-row dephosphorization;

the end temperature of preheating is 1200 ℃;

the drawing speed of continuous casting is 4.9m/min, and the thickness of a continuously cast plate blank is 110mm;

the pressure of the rough phosphorus removal is 35MPa, the pressure of the fine phosphorus removal is 37MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 60mm;

the inlet temperature of rough rolling is 1150 ℃, the outlet temperature of rough rolling is 930 ℃, and the number of rough rolling passes is 3;

the end point temperature of induction heating is 1100 ℃;

the accumulated deformation of the finish rolling is 80 percent, the finish rolling temperature of the finish rolling is 840 ℃, and the pass of the finish rolling is 5 passes;

the cooling rate of laminar cooling was 35 ℃ and the coiling temperature was 320 ℃.

Example 2

c:0.22%, si:0.033%, mn:2.66%, al:0.025%, P:0.006%, S:0.0040%, nb:0.025%, ti:0.025%, cr:0.75%, N:0.0032%, B:0.0034%, and the balance of Fe and inevitable impurities.

The thickness of the thin gauge hot rolled 1200MPa steel is 1.0mm.

And S2, continuously casting the molten steel to obtain a plate blank.

Wherein:

the finish rolling is full endless rolling;

fine descaling is single-row dephosphorization;

the end temperature of preheating is 1200 ℃;

the pressure of the rough phosphorus removal is 35MPa, the pressure of the fine phosphorus removal is 37MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 63mm;

the inlet temperature of rough rolling is 1150 ℃, the outlet temperature of rough rolling is 940 ℃, and the number of rough rolling passes is 3;

the end point temperature of induction heating is 1100 ℃;

the cooling rate of laminar cooling was 37 ℃/s, and the coiling temperature was 300 ℃.

Example 3

c:0.26%, si:0.031%, mn:2.75%, al:0.040%, P:0.007%, S:0.0030%, nb:0.030%, ti:0.019%, cr:0.88%, N:0.0030%, B:0.0022%, and the balance of Fe and inevitable impurities.

The thickness of the thin gauge hot rolled 1200MPa steel is 1.2mm.

And S2, continuously casting the molten steel to obtain a plate blank.

Wherein:

the finish rolling is full endless rolling;

fine descaling is single-row dephosphorization;

the end temperature of preheating is 1200 ℃;

the drawing speed of continuous casting is 5.0m/min, and the thickness of a continuously cast plate blank is 110mm;

the pressure of the rough phosphorus removal is 35MPa, the pressure of the fine phosphorus removal is 37MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 67mm;

the inlet temperature of rough rolling is 1160 ℃, the outlet temperature of rough rolling is 940 ℃, and the number of rough rolling passes is 3;

the end point temperature of induction heating is 1120 ℃;

the accumulated deformation of the finish rolling is 78 percent, the finish rolling temperature of the finish rolling is 840 ℃, and the pass of the finish rolling is 5 passes;

the cooling rate of laminar cooling was 40 ℃/s, and the coiling temperature was 300 ℃.

Example 4

A thin gauge hot rolled 1200MPa steel, the chemical composition of the steel in percentage by mass comprising:

c:0.21%, si:0.035%, mn:2.80%, al:0.032%, P:0.009%, S:0.0050%, nb:0.028%, ti:0.023%, cr:0.62%, N:0.0029%, B:0.0028%, and the balance of Fe and inevitable impurities.

The thickness of the thin gauge hot rolled 1200MPa steel is 1.5mm.

And S2, continuously casting the molten steel to obtain a plate blank.

Wherein:

the finish rolling is full endless rolling;

fine descaling is single-row dephosphorization;

the end temperature of preheating is 1200 ℃;

the drawing speed of continuous casting is 5.2m/min, and the thickness of a continuously cast plate blank is 110mm;

the pressure of the rough phosphorus removal is 35MPa, the pressure of the fine phosphorus removal is 37MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 70mm;

the inlet temperature of rough rolling is 1170 ℃, the outlet temperature of rough rolling is 935 ℃, and the number of rough rolling passes is 3;

the end point temperature of induction heating is 1120 ℃;

the accumulated deformation of the finish rolling is 75%, the finish rolling temperature of the finish rolling is 820 ℃, and the pass of the finish rolling is 5;

the cooling rate of laminar cooling was 43 ℃/s, and the coiling temperature was 300 ℃.

Example 5

c:0.27%, si:0.038%, mn:2.83%, al:0.043%, P:0.005%, S:0.0020%, nb:0.013%, ti:0.028%, cr:0.78%, N:0.0022%, B:0.0030%, and the balance of Fe and inevitable impurities.

The thickness of the thin gauge hot rolled 1200MPa steel is 2.0mm.

And S2, continuously casting the molten steel to obtain a plate blank.

Wherein:

the finish rolling is full endless rolling;

fine descaling is single-row dephosphorization;

the end temperature of the preheating is 1180 ℃;

the drawing speed of continuous casting is 5.5m/min, and the thickness of a continuously cast plate blank is 110mm;

the pressure of the rough phosphorus removal is 35MPa, the pressure of the fine phosphorus removal is 38MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 75mm;

the inlet temperature of rough rolling is 1140 ℃, the outlet temperature of rough rolling is 942 ℃, and the number of rough rolling passes is 3;

the end point temperature of induction heating is 1140 ℃;

the cooling rate of laminar cooling was 47 ℃/s, and the coiling temperature was 260 ℃.

Example 6

c:0.24%, si:0.042%, mn:2.83%, al:0.034%, P:0.009%, S:0.0050%, nb:0.038%, ti:0.013%, cr:0.93%, N:0.0025%, B:0.0025%, and the balance of Fe and inevitable impurities.

The thickness of the thin gauge hot rolled 1200MPa steel is 3.0mm.

And S2, continuously casting the molten steel to obtain a plate blank.

And S3, preheating the plate blank, carrying out coarse dephosphorization, carrying out coarse rolling, carrying out induction heating, carrying out fine dephosphorization, carrying out finish rolling, carrying out laminar cooling, coiling and carrying out air cooling to obtain the thin hot-rolled 1200MPa steel.

Wherein:

the finish rolling is full endless rolling;

fine descaling is single-row dephosphorization;

the end temperature of the preheating is 1180 ℃;

the drawing speed of continuous casting is 6.0m/min, and the thickness of a continuously cast plate blank is 110mm;

the pressure of the rough phosphorus removal is 36MPa, the pressure of the fine phosphorus removal is 38MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 78mm;

the inlet temperature of rough rolling is 1150 ℃, the outlet temperature of rough rolling is 933 ℃, and the number of rough rolling passes is 3;

the end point temperature of induction heating is 1140 ℃;

the accumulated deformation of the finish rolling is 73 percent, the finish rolling temperature of the finish rolling is 800 ℃, and the pass of the finish rolling is 5 passes;

the cooling rate of laminar cooling was 47 ℃/s and the coiling temperature was 280 ℃.

Example 7

c:0.23%, si:0.021%, mn:2.45%, al:0.024%, P:0.006%, S:0.0019%, nb:0.028%, ti:0.027%, cr:0.85%, N:0.0030%, B:0.0035%, and the balance of Fe and inevitable impurities.

The thickness of the thin gauge hot rolled 1200MPa steel is 4.0mm.

And S2, continuously casting the molten steel to obtain a plate blank.

Wherein:

the finish rolling is semi-endless rolling;

fine descaling is single-row dephosphorization;

the end temperature of preheating is 1150 ℃;

the drawing speed of continuous casting is 4.5m/min, and the thickness of a continuously cast plate blank is 110mm;

the pressure of the rough phosphorus removal is 36MPa, the pressure of the fine phosphorus removal is 37MPa, and the distance between a nozzle of the fine phosphorus removal and the plate blank is 80mm;

the inlet temperature of rough rolling is 1100 ℃, the outlet temperature of rough rolling is 970 ℃, and the number of rough rolling passes is 3;

the end point temperature of induction heating is 1060 ℃;

the accumulated deformation of the finish rolling is 73 percent, the finish rolling temperature of the finish rolling is 860 ℃, and the pass of the finish rolling is 5 passes;

the cooling rate of laminar cooling was 50 ℃ and the coiling temperature was 280 ℃.

Comparative example 1

A thin gauge hot rolled steel, the chemical composition of the steel comprises by mass percent:

c:0.12%, si:0.3%, mn:1.8%, al:0.024%, P:0.006%, S:0.0019%, nb:0.018%, cr:0.3%, N:0.0034%, B:0.0018%, and the balance of Fe and inevitable impurities.

The metallographic structure of the thin hot rolled steel is martensite.

The thickness of the thin hot rolled steel is 3.0mm.

The preparation method of the thin hot rolled steel comprises the following steps:

s1, performing KR desulfurization, converter smelting and LF refining to obtain molten steel according with chemical components.

And S2, continuously casting the molten steel to obtain a plate blank.

And S3, preheating the plate blank, roughly descaling, roughly rolling, finely descaling, finely rolling, carrying out laminar cooling, coiling and air cooling to obtain the thin hot rolled steel.

Wherein:

the finish rolling is semi-endless rolling;

the fine descaling is single-row descaling;

the end point temperature of the preheating is 1230 ℃;

the drawing speed of continuous casting is 0.7m/min, and the thickness of a continuously cast plate blank is 240mm;

the pressure of rough descaling is 36MPa, the pressure of fine descaling is 37MPa, and the distance between a nozzle of the fine descaling and the plate blank is 100mm;

the inlet temperature of rough rolling is 1120 ℃, the outlet temperature of the rough rolling is 1020 ℃, and the number of rough rolling passes is 3;

the inlet temperature of finish rolling is 1090 ℃;

the accumulated deformation of the finish rolling is 80 percent, the finish rolling temperature of the finish rolling is 880 ℃, and the pass of the finish rolling is 7 passes;

the cooling rate of laminar cooling was 30 ℃/s and the coiling temperature was 380 ℃.

Comparative example 2

c:0.15%, si:0.4%, mn:1.45%, al:0.024%, P:0.006%, S:0.0019%, nb:0.068%, ti:0.037%, cr:1.1%, N:0.0030%, and the balance of Fe and inevitable impurities.

The metallographic structure of the thin hot rolled steel is martensite.

The thickness of the thin hot rolled steel is 4.0mm.

And S2, continuously casting the molten steel to obtain a plate blank.

Wherein:

the finish rolling is semi-endless rolling;

the fine descaling is single-row descaling;

the end point temperature of the preheating is 1230 ℃;

the drawing speed of continuous casting is 0.8m/min, and the thickness of a continuously cast plate blank is 240mm;

the inlet temperature of rough rolling is 1130 ℃, the outlet temperature of rough rolling is 970 ℃, and the number of rough rolling passes is 3;

the inlet temperature of finish rolling is 1080 ℃;

the accumulated deformation of the finish rolling is 73 percent, the finish rolling temperature of the finish rolling is 870 ℃, and the pass of the finish rolling is 7 passes;

the cooling rate of laminar cooling was 35 ℃/s and the coiling temperature was 410 ℃.

Comparative example 3

c:0.18%, si:0.021%, mn:1.8%, al:0.024%, P:0.006%, S:0.0019%, ti:0.015%, cr:0.3%, N:0.0030%, B:0.0025%, and the balance of Fe and inevitable impurities.

The metallographic structure of the thin hot rolled steel is bainite.

The thickness of the thin gauge hot rolled steel is 4.5mm.

And S2, continuously casting the molten steel to obtain a plate blank.

Wherein:

the finish rolling is semi-endless rolling;

the fine descaling is single-row descaling;

the end temperature of preheating is 1200 ℃;

the inlet temperature of rough rolling is 1130 ℃, the outlet temperature of rough rolling is 1020 ℃, and the number of rough rolling passes is 3;

the inlet temperature of finish rolling is 1050 ℃;

the accumulated deformation of the finish rolling is 75 percent, the finish rolling temperature of the finish rolling is 860 ℃, and the pass of the finish rolling is 7 passes;

the cooling rate of laminar cooling was 40 ℃/s and the coiling temperature was 480 ℃.

Examples of the experiments

The thin gauge hot rolled 1200MPa steels provided in examples 1 to 7 and comparative examples 1 to 3 were subjected to property tests, and the specific results are shown in Table 1.

The processing method comprises the following steps:

yield strength: according to GB/T228.1-2010 Metal Material tensile test part 1: room temperature test method;

tensile strength: according to GB/T228.1-2010 Metal Material tensile test part 1: room temperature test method;

elongation percentage: according to GB/T228.1-2010 Metal Material tensile test part 1: room temperature test method;

transverse cold bending: according to GB/T228.1-2010 Metal Material tensile test part 1: room temperature test method.

TABLE 1

	Yield strength (MPa)	Tensile strength (MPa)	Elongation (%)	Transverse cold bending
					Example 1	1084	1251	9.5	Qualified
Example 2	1071	1310	10.5	Qualified
					Example 3	1091	1293	11.5	Qualified
Example 4	1075	1326	9.5	Qualified
					Example 5	1103	1306	10.0	Qualified
Example 6	1113	1273	12.5	Qualified
					Example 7	1067	1293	11.5	Qualified
Comparative example 1	901	1075	13.5	Qualified
					Comparative example 2	739	1027	15.5	Qualified
Comparative example 3	803	1003	17.0	Qualified

Table 1 specific analysis:

the yield strength is the yield limit of the steel when the yield phenomenon occurs, namely the stress resisting micro plastic deformation, and when the yield strength is higher, the yield limit of the steel when the yield phenomenon occurs is higher.

The tensile strength is the maximum stress value of the steel before breaking, and the higher the tensile strength is, the higher the maximum stress value of the filament is.

The elongation is the percentage of the ratio of the total deformation delta L of the gauge length section after the steel is stretched and broken to the original gauge length L, and the higher the elongation is, the stronger the tensile resistance of the steel is.

The transverse cold bending refers to the bending degree which can be borne by the steel at normal temperature, and the larger the transverse cold bending is, the larger the bending degree which can be borne by the steel is.

From the data of examples 1-7, it can be seen that:

the multi-mode sheet billet continuous casting and rolling production line is adopted, the yield strength of the obtained steel is more than 1050MPa, the tensile strength is more than 1200MPa, the elongation is more than 8 percent, the transverse cold bending D =2a and 180 degrees are qualified by adjusting the chemical components of the steel and improving the continuous casting and rolling processes, the steel plate is good in plate shape, high in size precision and small in strength fluctuation, and the thickness of the steel plate can be controlled to be 0.8-4.0mm.

The drawings illustrate:

FIG. 2 is a metallographic structure diagram of a thin gauge hot-rolled 1200MPa steel according to an example of the present application, and it can be seen from FIG. 2 that the structure is controlled to martensite.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

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 changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations 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 include such modifications and variations.

Claims

1. A thin gauge hot rolled 1200MPa steel, characterized in that the chemical composition of the steel comprises, in mass%:

2. The thin gauge hot rolled 1200MPa steel according to claim 1, wherein the metallographic structure of the thin gauge hot rolled 1200MPa steel is martensitic.

3. A method of producing a thin gauge hot rolled 1200MPa steel according to claim 1 or 2, comprising the steps of:

continuously casting the molten steel to obtain a plate blank;

preheating the plate blank, roughly removing phosphorus, roughly rolling, inductively heating, finely removing phosphorus, finely rolling, carrying out laminar cooling, coiling and air cooling to obtain the thin hot-rolled 1200MPa steel;

wherein:

4. The method of producing a thin gauge hot rolled 1200MPa steel according to claim 3, characterized in that the end point temperature of the preheating is 1150-1200 ℃.

5. The method of manufacturing thin gauge hot rolled 1200MPa steel according to claim 3, wherein the continuous casting is performed at a casting speed of 4.0-6.5m/min and the thickness of the continuously cast slab is 110-123mm.

6. The method for preparing the thin gauge hot rolled 1200MPa steel according to claim 3, wherein the pressure of the crude phosphorus removal is greater than or equal to 30MPa, the pressure of the fine phosphorus removal is greater than or equal to 30MPa, and the distance between a nozzle of the fine phosphorus removal and the slab is 60-110mm.

7. The method for preparing the thin gauge hot rolled 1200MPa steel according to claim 3, wherein the inlet temperature of the rough rolling is greater than or equal to 1150 ℃, the outlet temperature of the rough rolling is 930-1000 ℃, and the number of passes of the rough rolling is 3.

8. The method of producing a thin gauge hot rolled 1200MPa steel according to claim 3, characterized in that the end point temperature of the induction heating is 1050-1150 ℃.

9. The method of manufacturing a thin gauge hot rolled 1200MPa steel according to claim 3, wherein the cumulative deformation of the finish rolling is 70-80%, the finish rolling temperature of the finish rolling is 800-860 ℃, and the number of passes of the finish rolling is 5.

10. The method for preparing the thin gauge hot rolled 1200MPa steel according to claim 3, wherein the cooling rate of the laminar cooling is not less than 40 ℃ and the coiling temperature is 250-400 ℃.