CN115232938A - Hot rolled steel strip for 700 MPa-level high-strength engineering machinery and production method thereof - Google Patents
Hot rolled steel strip for 700 MPa-level high-strength engineering machinery and production method thereof Download PDFInfo
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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
- C21D8/0205—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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- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C22C38/04—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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- 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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Abstract
The invention provides a hot-rolled steel strip for 700 MPa-level high-strength engineering machinery and a production method thereof, wherein the production method comprises the following steps: smelting and continuously casting molten iron to obtain a steel billet; (2) Feeding the steel billet into a heating furnace, wherein the charging temperature is less than 400 ℃, the discharging temperature is 1220-1260 ℃, and the furnace time is 200-300min; (3) Sending the reheated steel billet into a rough rolling mill for multi-pass rough rolling, wherein the single-pass rolling deformation is more than or equal to 20%; (4) The steel plate after rough rolling is sent into a finishing mill to be subjected to multi-pass finish rolling, the initial rolling temperature is less than or equal to 980 ℃, and the outlet temperature is 850-900 ℃; (5) Carrying out laminar cooling on the finish-rolled steel plate, cooling the steel plate to the final cooling temperature of less than or equal to 650 ℃ at the speed of 10-20 ℃/s, and then air-cooling to 550-600 ℃ for coiling; the steel strip is an Nb-Ti-Cr composite micro-alloying component system with the thickness of more than or equal to 8mm and less than 10mm, or an Nb-V-Ti-Mo composite micro-alloying component system with the thickness of 10-16 mm. The invention solves the problems of high cost, unstable performance and the like in the production of hot rolled steel strips in the prior art.
Description
Technical Field
The invention relates to the technical field of steel for engineering machinery, in particular to a 700 MPa-grade high-strength hot-rolled steel strip for engineering machinery and a production method thereof.
Background
At present, the engineering machinery is developing towards large-scale, high-power and high-parameter. The high-strength steel for the engineering machinery can improve the specific strength of the machinery, improve the performance parameters of the engineering machinery or realize light weight under the same parameter condition, and accords with the development direction of the steel for the engineering machinery. The steel for the high-strength engineering machinery is low-alloy high-strength steel which is prepared by adding micro-alloy elements such as Mo, nb, V, ti and the like into C-Mn steel. At present, high-strength steel plates are widely applied to the engineering machinery industry and the coal mine machinery industry, the required thickness is 4-80mm, wherein the steel plates with the thickness of less than 20mm are mainly plate-rolled flat products, and most of the steel plates are applied to the engineering machinery industry and are used for manufacturing crane booms, frames and the like; the steel plate with the thickness of more than 20mm is mainly a medium plate product, and is mostly applied to the coal mine machinery industry. Because the hot rolled plate coil does not have a strong cooling control means like a medium plate, more alloy elements are often required to be added, the cost is increased, the plate coil needs to be opened and flattened in the using process, the residual stress has great influence on the plate shape, and in order to reduce or eliminate the influence of the residual stress, the plate coil is mostly subjected to flattening straightening and heat treatment processes in the production process.
Patent CN107119238A discloses a method for producing 700MPa grade steel plate for thin and wide engineering machinery by using wide and thick plate rolling mill, the added amount of C and Cr elements in the steel plate is high, which brings large rolling load in the high temperature rolling process, is not suitable for hot continuous rolling production line, and only provides a method for producing wide steel plate with thickness of 6.0-6.5mm, which does not relate to the production method of thick specification finished product, and has limited application scene.
The patent CN109136724A discloses a steel plate for a low yield ratio Q690F engineering machine and a manufacturing method thereof, and provides a manufacturing method of a steel plate for a hot rolling engineering machine, wherein the steel plate has the yield strength of not less than 690MPa, the tensile strength of not less than 740MPa, the yield ratio of 0.75 +/-0.05, the elongation after fracture of not less than 16%, and the impact power at minus 60 ℃ of not less than 150J.
Disclosure of Invention
The invention provides a hot rolled steel strip for 700 MPa-level high-strength engineering machinery and a production method thereof, aiming at the technical problems of high cost, unstable performance and the like in the production of the hot rolled steel strip in the prior art.
The technical means adopted by the invention are as follows:
a production method of a hot rolled steel strip for 700 MPa-grade high-strength engineering machinery comprises the following steps:
(1) Smelting and continuously casting molten iron to obtain a steel billet;
(2) Feeding the steel billet into a heating furnace, wherein the charging temperature is less than 400 ℃, the discharging temperature is 1220-1260 ℃, and the furnace time is 200-300min;
(3) Sending the reheated steel billet into a rough rolling mill for multi-pass rough rolling, wherein the single-pass rolling deformation is more than or equal to 20%;
(4) The steel plate after rough rolling is sent into a finishing mill for multi-pass finish rolling, the finish rolling initial rolling temperature is less than or equal to 980 ℃, and the outlet temperature is 850-900 ℃;
(5) And carrying out laminar cooling on the finish-rolled steel plate, cooling the steel plate to the final cooling temperature of less than or equal to 650 ℃ at the speed of 10-20 ℃/s, and then air-cooling to 550-600 ℃ for coiling.
Further, the smelting in the step (1) comprises molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining and calcium treatment.
Further, the thickness of the steel billet obtained by continuous casting is 200-230mm.
Further, in the step (3), the rough rolling adopts 6-pass rolling, and the thickness of the intermediate blank obtained after the rough rolling is 50-60mm.
Further, in the step (4), the finish rolling is performed by 6 passes.
The invention also provides a 700 MPa-level high-strength hot rolled steel strip for engineering machinery, which is produced by adopting the method, and the hot rolled steel strip is an Nb-Ti-Cr composite microalloying component system, and comprises the following chemical components in percentage by mass: c:0.05-0.09%, si:0.05-0.35%, mn:1.60-1.90%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, als:0.02 to 0.05%, nb:0.03 to 0.06%, ti:0.10-0.15%, cr:0.10-0.30%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities; the thickness of the hot rolled steel strip is more than or equal to 8mm and less than 10mm.
The invention also provides a hot rolled steel strip for 700 MPa-level high-strength engineering machinery, which is produced by adopting the method, the hot rolled steel strip is an Nb-V-Ti-Mo composite micro-alloying component system, and the chemical components comprise the following components in percentage by mass: c:0.06-0.10%, si:0.05 to 0.35%, mn:1.60-1.90%, P: less than or equal to 0.015 percent, S: less than or equal to 0.005%, als:0.02 to 0.05%, nb:0.03-0.06%, V:0.06-0.10%, ti:0.07 to 0.10%, mo:0.10-0.20%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities; the thickness of the hot rolled steel strip is 10-16 mm.
Compared with the prior art, the invention has the following advantages:
compared with the traditional production mode of rolling, heating and tempering heat treatment, the production method of the hot rolled steel strip for the 700 MPa-level high-strength engineering machinery provided by the invention has the characteristics of short process, high efficiency and low cost, can adjust the toughness matching in a large range by adjusting the controlled rolling and cooling process parameters, has a large process control window during large-scale production, and has stable performance.
The 700 MPa-level high-strength hot-rolled steel strip for the engineering machinery comprises two sets of component systems, the cooling uniformity difference required by steel strips with different thickness specifications on a conventional hot continuous rolling production line is fully considered, and different alloy proportions are designed so as to achieve the purpose of reducing alloy waste while meeting the performance; the microstructure of the steel strip provided by the invention is quasi-polygonal ferrite, trace pearlite and precipitated phases with different scales, and the steel strip can keep good plasticity and toughness while improving the strength.
Based on the reason, the method can be widely popularized in the production field of the hot rolled steel strip for the high-strength engineering machinery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a microstructure of a steel strip according to example 2 of the present invention.
FIG. 2 is a microstructure of a steel strip according to example 4 of the present invention.
FIG. 3 is a microstructure of a steel strip according to example 3 of the present invention.
FIG. 4 is a transmission electron micrograph of a precipitated phase of a steel strip according to example 3 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a production method of a hot rolled steel strip for 700 MPa-level high-strength engineering machinery, which comprises the following steps:
(1) Smelting and continuously casting molten iron to obtain a steel billet; smelting comprises molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining and calcium treatment;
(2) Feeding the steel billet into a heating furnace, wherein the charging temperature is less than 400 ℃, the discharging temperature is 1220-1260 ℃, and the furnace time is 200-300min;
(3) Feeding the reheated steel billet into a rough rolling mill for 6-pass rough rolling, wherein the single-pass rolling deformation is more than or equal to 20%, and the thickness of an intermediate billet obtained after rough rolling is 50-60mm;
(4) Sending the roughly rolled steel plate into a finishing mill for 6 times of finish rolling, wherein the finish rolling start temperature is less than or equal to 980 ℃, and the outlet temperature is 850-900 ℃;
(5) And carrying out laminar cooling on the finish-rolled steel plate, cooling the steel plate to the final cooling temperature of less than or equal to 650 ℃ at the speed of 10-20 ℃/s, and then air-cooling to 550-600 ℃ for coiling.
Further, the thickness of the steel billet obtained by continuous casting is 200-230mm.
The invention provides a production method of a hot rolled steel strip for 700 MPa-level high-strength engineering machinery, which comprises the following steps:
the main effect of reheating the steel billet is to make alloy elements solid-dissolve and make the alloy concentration uniform, if the heating temperature of the steel billet is lower, the alloy elements such as niobium, vanadium, titanium and the like in the finished steel can not form effective solid solution, so that precipitation is influenced, crystal grains can not be effectively refined, and the obdurability is reduced; if the heating temperature of the steel billet is too high or the temperature of the steel billet in the furnace is too high, the microstructure of the finished steel is coarse, and the toughness of the finished steel is reduced, so the reheating temperature is controlled to be 1220-1260 ℃;
the rough rolling has the main functions of refining grains through austenite dynamic recrystallization and simultaneously pinning austenite grain boundaries by utilizing precipitated phases in austenite so as to refine the grains; the larger single-pass deformation of rough rolling can promote precipitation, reduce the size of recrystallized austenite, and the deformation required by dynamic recrystallization exceeds the critical deformation, so the single-pass deformation of rough rolling is controlled to be more than or equal to 20 percent;
the former stage of finish rolling is still in an austenite recrystallization zone, and the grain size is controlled through dynamic recrystallization; the finish rolling rear section is positioned in an austenite non-recrystallization region, and aims to fully deform recrystallized austenite to provide nucleation energy and nucleation particles for subsequent ferrite phase change, and the pass rolling reduction of a plurality of rear stands can be improved by adopting six-stand rolling, so that the deformation of unrecrystallized austenite is increased;
meanwhile, the initial rolling temperature of finish rolling is set to be less than or equal to 980 ℃, the growth of recrystallized austenite can be prevented, otherwise, mixed crystal structure is easy to cause, and the precipitation process can be considered;
setting the outlet temperature of finish rolling to 860-900 ℃, avoiding austenite-ferrite two-phase region to avoid mixed crystal structure, and simultaneously reducing the outlet temperature of finish rolling as much as possible to prevent crystal grains from growing after phase transformation;
in the laminar cooling process, ferrite phase change and supersaturated precipitation in ferrite can occur, and in order to improve the strength of finished steel and improve the precipitation proportion of a nano-scale precipitated phase, the coiling temperature is set to 550-600 ℃ to promote precipitation; meanwhile, because the pearlite phase transformation can seriously influence carbide precipitation, the invention adopts higher cooling rate of 10-20 ℃/s during the first stage of laminar cooling to avoid a pearlite phase transformation area, thereby improving the proportion of precipitated phases and enhancing the strengthening effect.
The invention also provides a 700 MPa-level high-strength hot rolled steel strip for engineering machinery, which is produced by adopting the method, and the hot rolled steel strip is an Nb-Ti-Cr composite microalloying component system, and comprises the following chemical components in percentage by mass: c:0.05 to 0.09%, si:0.05 to 0.35%, mn:1.60-1.90%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, als:0.02 to 0.05%, nb:0.03 to 0.06%, ti:0.10-0.15%, cr:0.10-0.30%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities; the thickness of the hot rolled steel strip is more than or equal to 8mm and less than 10mm.
The invention also provides a hot rolled steel strip for 700 MPa-level high-strength engineering machinery, which is produced by adopting the method, the hot rolled steel strip is an Nb-V-Ti-Mo composite micro-alloying component system, and the chemical components comprise the following components in percentage by mass: c:0.06-0.10%, si:0.05-0.35%, mn:1.60-1.90%, P: less than or equal to 0.015%, S: less than or equal to 0.005%, als:0.02 to 0.05%, nb:0.03-0.06%, V:0.06-0.10%, ti:0.07 to 0.10%, mo:0.10-0.20%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities; the thickness of the hot rolled steel strip is 10-16 mm.
TABLE 1 composition of steel strips of different thickness specifications
| Thickness of | C | Si | Mn | P | S | Als |
| 8～<10mm | 0.05-0.09 | 0.10-0.35 | 1.60-1.90 | ≤0.015 | ≤0.005 | 0.02-0.05 |
| 10～16mm | 0.06-0.10 | 0.10-0.35 | 1.60-1.90 | ≤0.015 | ≤0.005 | 0.02-0.05 |
| Nb | V | Ti | Mo | Cr | N | |
| 8～<10mm | 0.03-0.06 | / | 0.10-0.15 | / | 0.10-0.30 | ≤0.005 |
| 10～16mm | 0.03-0.06 | 0.06-0.10 | 0.07-0.10 | 0.10-0.20 | / | ≤0.005 |
The steel strip provided by the invention has the following design principles:
carbon (C): carbon is used as a main solid solution strengthening element, can improve the strength, can form carbide with micro alloy elements such as niobium, molybdenum, vanadium, titanium and the like, prevents abnormal growth of crystal grains in each stage of heating and rolling of the plate blank and has a certain precipitation strengthening effect; but the toughness and the plasticity of the steel can be reduced and the performance of a welding area can be influenced if the carbon content is too high, and the carbon content is controlled within 0.10 percent in the invention;
silicon (Si): silicon is used as a reducing agent and a deoxidizing agent in the smelting process, the plasticity, the toughness and the welding performance of steel can be reduced due to excessively high silicon content, and the silicon content is controlled not to exceed 0.40 percent;
manganese (Mn): the main function of manganese is to replace solid solution strengthening to compensate for the strength reduction caused by low carbon content. Meanwhile, manganese can reduce the austenite phase transition temperature, stabilize the austenite phase, refine the phase transition structure and reduce the ductile-brittle transition temperature. The strength of the steel can be reduced due to low manganese content, the center segregation and dendritic crystal segregation can be easily caused due to high manganese content, the impact toughness of the steel is reduced, and the anisotropy of mechanical properties is caused, wherein the manganese content is controlled to be 1.60-1.90%;
niobium (Nb), vanadium (V), titanium (Ti): niobium, vanadium and titanium are main microalloy elements, and carbonitride is precipitated in different stages of heating and hot rolling of a plate blank to play roles in refining grains and strengthening precipitation; niobium mainly has the functions of precipitating in austenite, pinning austenite grain boundaries, expanding an austenite non-recrystallization region and increasing the deformation of non-recrystallized austenite so as to refine grains; in addition, niobium carbonitride can pin austenite crystal boundaries to refine the crystal grains, so that the uniformity of the structure in the thickness direction is improved; vanadium can be precipitated at high temperature in the finish rolling stage to play a role in increasing ferrite core particles and refining ferrite grains; the carbonitride of titanium precipitated in the heating stage of the plate blank can prevent austenite grains from growing abnormally; pinning austenite grain boundaries at the recrystallization rolling stage, and refining recrystallized austenite; supersaturation precipitation of nano-scale carbide from ferrite in the subsequent cooling and coiling processes, and dispersion strengthening effect is achieved; considering the precipitation effect and the alloy cost comprehensively, the invention controls the niobium content to be 0.03-0.06%, the vanadium content to be 0.06-0.10% and the titanium content to be 0.07-0.15%; in order to reduce the influence of nitrogen on titanium precipitation, the nitrogen content is limited within 0.005%;
chromium (Cr), molybdenum (Mo): the main functions of the chromium and the molybdenum are to improve the hardenability of the steel, improve the uniformity of the surface and the core structure of the thick steel, inhibit the transformation of proeutectoid ferrite, promote the transformation of acicular ferrite or low-carbon bainite, improve the dislocation density in a microstructure and improve the impact energy of the steel; the chromium has a slightly weak effect of improving hardenability but has low cost, and the molybdenum can promote the second phase of vanadium and titanium to be separated out and finely dispersed, so that the strength and toughness of the steel are improved; the invention controls the molybdenum content of thick (more than 10 mm) products at 0.10-0.20%, does not add chromium; the chromium content of thin (10 mm or less) product is controlled at 0.10-0.30%, and molybdenum is not added.
The invention provides a hot rolled steel strip for 700 MPa-level engineering machinery and a production method thereof, wherein the steel strip adopts a low-carbon composite microalloyed component system and combines a controlled rolling and controlled cooling process to obtain a finished product with the tensile strength of 760-950MPa, the yield strength of more than 685MPa, the elongation of more than 15 percent, the pass of 180-degree cold bending test d =2a and the average value of impact work at-20 ℃ of more than 40J.
The steel strip and the production method thereof according to the present invention will be described in detail with reference to examples 1 to 4, wherein the steel strip components and the corresponding process parameters are shown in tables 2 to 3, wherein examples 1 to 2 are products with a thickness less than 10mm, a Nb-Ti-Cr composite micro-alloying component system is adopted, examples 3 to 4 are products with a thickness of 10 to 16mm, and a Nb-Ti-V-Mo composite micro-alloying component system is adopted, and the corresponding finished steel sheets are respectively prepared by sequentially performing hot continuous rolling and laminar cooling in a preceding stage rapid cooling manner by using the production method provided by the present invention.
Table 2 chemical compositions corresponding to steel strips according to examples 1-4
Table 3 process parameters of the corresponding production methods for the steel strips described in examples 1 to 4
As shown in fig. 1 to 3, which respectively show the microstructures of the steel strips of examples 2 to 4, it can be seen that the steel strips all include ferrite and a small amount of pearlite, and fig. 4 is a transmission electron micrograph of precipitated phases of the steel strip of example 3 of the present invention, and it can be seen that many nano-sized precipitated phases exist inside the grains; table 4 lists the corresponding mechanical property indexes of the steel strips of examples 1-4, which shows that the steel strips and the production method thereof provided by the invention can improve the strength of the steel strips and maintain good plasticity and toughness.
Table 4 mechanical properties of the steel strips of examples 1 to 4
| Performance index | Yield strength/MPa | Tensile strength/MPa | Elongation/percent | Impact work at-20 ℃ J | 180 degree cold bending | Yield ratio |
| Example 1 | 723 | 808 | 21.8 | 103 | 2a | 0.89 |
| Example 2 | 726 | 828 | 21.8 | 83.3 | 2a | 0.88 |
| Example 3 | 703 | 801 | 19.0 | 105.3 | 2a | 0.88 |
| Example 4 | 721 | 845 | 18.5 | 78.6 | 2a | 0.86 |
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. A production method of a hot rolled steel strip for 700 MPa-grade high-strength engineering machinery is characterized by comprising the following steps:
(1) Smelting and continuously casting molten iron to obtain a steel billet;
(2) Feeding the steel billet into a heating furnace, wherein the charging temperature is less than 400 ℃, the discharging temperature is 1220-1260 ℃, and the furnace time is 200-300min;
(3) Sending the reheated steel billet into a rough rolling mill for multi-pass rough rolling, wherein the single-pass rolling deformation is more than or equal to 20%;
(4) The steel plate after rough rolling is sent into a finishing mill for multi-pass finish rolling, the finish rolling initial rolling temperature is less than or equal to 980 ℃, and the outlet temperature is 850-900 ℃;
(5) And carrying out laminar cooling on the finish-rolled steel plate, cooling the steel plate to the final cooling temperature of less than or equal to 650 ℃ at the speed of 10-20 ℃/s, and then air-cooling to 550-600 ℃ for coiling.
2. The method for improving the low-temperature toughness of the steel for the thick-gauge high-strength engineering machinery according to claim 1, wherein the smelting in the step (1) comprises molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining and calcium treatment.
3. The method for improving the low-temperature toughness of the steel for the thick-gauge high-strength engineering machinery as claimed in claim 1, wherein the thickness of the billet obtained through continuous casting is 200-230mm.
4. The method for improving the low-temperature toughness of the steel for the thick gauge high strength engineering machinery according to claim 1, wherein in the step (3), the rough rolling adopts 6-pass rolling, and the thickness of an intermediate billet obtained after the rough rolling is 50-60mm.
5. The method for improving the low-temperature toughness of the steel for the thick-gauge high-strength engineering machinery as claimed in claim 1, wherein in the step (4), the finish rolling is performed by 6 passes.
6. A hot-rolled steel strip for high-strength engineering machinery at 700MPa, which is produced by the method of any one of claims 1 to 5 and comprises the following chemical components in percentage by mass: c:0.05 to 0.09%, si:0.05-0.35%, mn:1.60-1.90%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, als:0.02 to 0.05%, nb:0.03-0.06%, ti:0.10-0.15%, cr:0.10-0.30%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities; the thickness of the hot rolled steel strip is more than or equal to 8mm and less than 10mm.
7. A hot-rolled steel strip for high-strength engineering machinery at 700MPa level, which is produced by the method of any one of claims 1 to 5 and comprises the following chemical components in percentage by mass: c:0.06-0.10%, si:0.05 to 0.35%, mn:1.60-1.90%, P: less than or equal to 0.015 percent, S: less than or equal to 0.005 percent, als:0.02 to 0.05%, nb:0.03-0.06%, V:0.06-0.10%, ti:0.07 to 0.10%, mo:0.10-0.20%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities; the thickness of the hot rolled steel strip is 10-16 mm.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116445818A (en) * | 2023-04-13 | 2023-07-18 | 山东钢铁集团日照有限公司 | Thick high-toughness hot rolled strip steel with yield strength of 600MPa and production method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101899616A (en) * | 2010-07-22 | 2010-12-01 | 河北省首钢迁安钢铁有限责任公司 | Steel for 600MPa-grade high-strength engineering machines and production method thereof |
| CN103160746A (en) * | 2011-12-14 | 2013-06-19 | 鞍钢股份有限公司 | Steel for high-strength thick-wall water delivery pipe and manufacturing method thereof |
| CN104561486A (en) * | 2015-01-22 | 2015-04-29 | 首钢总公司 | Thick hot continuous rolling steel strip with excellent ultralow temperature CTOD (China railway high speed) performance and production method thereof |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101899616A (en) * | 2010-07-22 | 2010-12-01 | 河北省首钢迁安钢铁有限责任公司 | Steel for 600MPa-grade high-strength engineering machines and production method thereof |
| CN103160746A (en) * | 2011-12-14 | 2013-06-19 | 鞍钢股份有限公司 | Steel for high-strength thick-wall water delivery pipe and manufacturing method thereof |
| CN104561486A (en) * | 2015-01-22 | 2015-04-29 | 首钢总公司 | Thick hot continuous rolling steel strip with excellent ultralow temperature CTOD (China railway high speed) performance and production method thereof |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116445818A (en) * | 2023-04-13 | 2023-07-18 | 山东钢铁集团日照有限公司 | Thick high-toughness hot rolled strip steel with yield strength of 600MPa and production method thereof |
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