CN114231837A - 600 MPa-grade dual-phase steel for wheel spoke and production method thereof - Google Patents
600 MPa-grade dual-phase steel for wheel spoke and production method thereof Download PDFInfo
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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
- 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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- 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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- C22C33/04—Making ferrous alloys by melting
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
The invention discloses 600 MPa-grade dual-phase steel for wheel spokes and a production method thereof, belonging to the technical field of metallurgy. The dual-phase steel comprises the following chemical components in percentage by mass: c: 0.07-0.10%, Si is less than or equal to 0.05%, Mn: 1.10% -1.40%, Cr: 0.4-0.7%, P is less than or equal to 0.018%, S is less than or equal to 0.008%, Als: 0.02 to 0.04 percent, and the balance of Fe and inevitable impurities. The production method comprises the working procedures of continuous casting, heating, rolling, cooling and coiling. The steel plate manufactured by the invention eliminates the addition of Mo and Nb alloy elements, realizes low-cost production through reasonable component and process system design, and the manufactured product has the characteristics of high strength and low yield ratio, has excellent surface quality, provides excellent material for manufacturing wheel spoke assemblies of passenger cars, and is suitable for large-batch industrial production.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to 600 MPa-grade dual-phase steel for wheel spokes and a production method thereof.
Background
With the development requirement of light weight in the automobile industry, at present, each large host machine factory generally selects high-strength steel plates to manufacture wheels so as to realize the effects of thinning and reducing weight, but the deformation is difficult due to high material selection strength and low elongation, and particularly when complex wheel parts are manufactured, the problems of cracking, wrinkling and the like are easily caused due to low material elongation and narrow plastic forming range. The thin 3-8mm wheel spoke is processed and formed more complicated by adopting a punch forming process, requires good strong plasticity matching of materials, and solves the problems of difficult deformation, center hole flanging cracking and the like in the spoke forming process.
The traditional high-strength steel for wheels mainly adopts ferrite and pearlite structure materials which are compounded with Nb, V, Ti and other microalloy elements, the content of the added alloy elements is continuously increased along with the improvement of the strength, the cost is increased, the strong plasticity of the produced material is poor, the forming performance is reduced, particularly, when the tensile strength is more than 600Mpa, the yield ratio of the material reaches more than 0.8, the forming is difficult, the cracking proportion of a stamping part is high, and the requirement of mass production of a host factory is difficult to meet.
The dual-phase steel which takes ferrite-martensite as a main structure and contains 15-28% of dispersed and uniformly distributed martensite structure has good strong plasticity, low yield ratio, high initial work hardening rate and baking hardening performance, the good strong plasticity and low yield ratio are favorable for smooth stamping forming, the high initial work hardening rate and baking hardening performance ensure that the final steel plate has the advantages of high strength, fatigue resistance and the like, the weight of an automobile can be reduced by more than 3%, the development theme of light weight, high performance, safety, environmental protection and energy conservation of automobile materials is met, the comprehensive requirement of high strength, high formability and high fatigue performance of wheel spokes is well met, and the dual-phase steel is one of the preferred steel types of the automobile steel.
The thin-specification dual-phase steel is mainly characterized in that the composition ratio of ferrite and martensite is controlled through chemical components and processes, the control of the mechanical property of the dual-phase steel is finally realized, the control of the volume fraction of the martensite is the key for obtaining the ideal mechanical property, and the selection of the chemical components and the fluctuation of the rolling process are the biggest difficulties in the production of the hot-rolled dual-phase steel. The technical solutions disclosed in the prior art relating to 600Mpa grade hot rolled dual phase steel and the manufacturing method thereof have the following problems: the addition of Mo and Nb elements increases the cost, and the addition of Si elements of more than 0.25 percent causes the surface of the steel plate to have serious red rust defects, thus the high surface quality requirement of wheels can not be met, and the requirements of the automobile industry on energy conservation and consumption reduction can not be met.
Disclosure of Invention
The invention aims to solve the technical problem of providing 600MPa grade dual-phase steel for wheel spokes and a production method thereof, the method has low cost, the produced steel plate has excellent mechanical property, the microstructure is ferrite and martensite which are dispersed and uniformly distributed, the steel plate has good forming property and deformation uniformity, and the technical problems of low strength grade, poor surface quality and thin spoke punch forming cracking in the prior art are solved. Realizes the stable production of the low-temperature controlled rolling and cooling process, thereby obtaining a dual-phase structure.
In order to solve the technical problems, the invention adopts the technical scheme that: the 600 MPa-grade dual-phase steel for the wheel spoke comprises the following chemical components in percentage by mass: c: 0.07-0.10%, Si is less than or equal to 0.05%, Mn: 1.10% -1.40%, Cr: 0.4-0.7%, P is less than or equal to 0.018%, S is less than or equal to 0.008%, Als: 0.02 to 0.04 percent, and the balance of Fe and inevitable impurities.
Further, the dual-phase steel structure is a ferrite and martensite dual-phase structure, wherein the volume fraction of ferrite is 72-85%, the volume fraction of martensite is 15-28%, and the average grain size of ferrite is 1.3-4.7 μm.
Further, the thickness of the dual-phase steel plate is 3.0-8.0mm, the yield strength is 365-441 MPa, the tensile strength is 613-665 MPa, the elongation is 26.5-38%, and the yield ratio is 0.57-0.72.
According to the invention, the high-valence Mo and Nb alloy elements are replaced by increasing Mn, Cr and other elements of the alloy and improving the rolling process through effective control and component optimized proportioning in the production process and considering the production cost. Based on the fact that Si element is easy to oxidize to generate a hercynite phase and deteriorate the surface (red rust or pressing in) of the dual-phase steel, a component control strategy of micro Si (not intentionally added) and Cr is developed in the project, the difficulty of phase change control caused by the fact that a soft phase region is narrowed due to reduction of the Si element is reduced, the defect of red rust on the surface of a steel plate is fundamentally overcome, and the surface quality of the hot-rolled dual-phase steel for the wheel is improved. The steel sheet chemical composition according to the invention has the following composition:
c: 0.07-0.10 wt% to ensure the subsequent martensite to fully transform and achieve the required strength;
si: the content of Si is less than or equal to 0.05wt%, the silicon olivine can be pinned on a substrate due to higher Si content, and the oxide scale is easy to remove, so that the red oxide scale defect appears on the surface of the steel coil, and in order to avoid the red oxide scale defect, the purpose of the invention is realized by adding aluminum alloy and controlling the temperature in the rolling process by adopting a Si-free component system;
mn: 1.10-1.40 wt%, improving the strength of steel through solid solution strengthening, simultaneously considering enlarging a rolling process window to improve stability, and comprehensively considering two factors, firstly, Mn element can enlarge an austenite phase region, reduce the transformation temperature of a supercooled austenite phase, and is beneficial to refining a phase change structure, the content improvement also creates conditions for replacing high-valence alloy Nb, secondly, the rolling mill load in the rolling process of strip steel is reduced, the rolling stability is ensured, the strip steel shape quality is ensured, the strengthening mode mainly takes the phase change strengthening in the cooling process after rolling as the main mode, and the content of Mn element is determined based on the reasons;
p is less than or equal to 0.018wt%, S is less than or equal to 0.008wt%, and the low content of phosphorus and sulfur can ensure that the steel has good toughness, cold formability and weldability;
cr: 0.40-0.70 wt%, effectively improves the hardenability of the steel plate in the cooling process, simultaneously considers enlarging the rolling process window to improve the stability and replace high-price alloy Mo alloy elements, ensures that the martensite structure is fully transformed, and ensures that the martensite structures of the cross sections of the steel plate at different positions are in dispersed and uniform distribution so as to obtain good plate shape quality.
And Als: 0.02-0.04 wt%, Al is a common deoxidizer in steel, and a small amount of aluminum is added into the steel, so that crystal grains can be refined, and the impact toughness can be improved. Al also has oxidation resistance and corrosion resistance, and aluminum and silicon are combined, so that the high-temperature non-peeling performance and the high-temperature corrosion resistance of the steel can be obviously improved. However, if Al exceeds a certain amount, the hot workability, weldability, and machinability of the steel are impaired.
The invention also provides a production method of the 600 MPa-grade dual-phase steel for the wheel spoke, which comprises the working procedures of continuous casting, heating, rolling, cooling and coiling; the rolling procedure comprises two stages of rough rolling and finish rolling, wherein the initial rolling temperature of the rough rolling is 1180-1200 ℃, and the single-pass reduction rate of the rough rolling is 26.2-53.6%; the initial rolling temperature of finish rolling is 980-1030 ℃, constant-speed rolling is adopted in the finish rolling stage, the rolling speed is 5.5-8.5 m/s, the single-pass reduction rate is 6.5-45.8%, and the final rolling temperature is 850-880 ℃; the selection of the process parameters creates conditions for subsequent phase change, also considers the surface quality of the steel plate, improves the scale structure, reduces the proportion of FeO, increases the compactness and prevents the scale from loosening and falling.
Further, in the continuous casting process, dynamic soft reduction is adopted in a fan-shaped section in the slab casting process, the reduction of 1.5-2.0 mm is adopted in the solidification tail end position of a slab liquid core in the fan-shaped section, the length of the soft reduction is 8-10 m, and the total reduction is 6-8 mm; the gas N, H and O in the slab sampling inspection steel are less than or equal to 60ppm, less than or equal to 1.5ppm and less than or equal to 20 ppm; the pure molten steel obtained by smelting is subjected to continuous casting sector section dynamic soft reduction technology, so that the looseness and component segregation caused by the bridging of central dendrites are reduced, the inclusions are uniformly distributed, and a defect-free casting blank is obtained.
Further, in the continuous casting process, the thickness of the slab is 237-240mm, and the chemical components and the mass percentage thereof are as follows: c: 0.07-0.10%, Si is less than or equal to 0.05%, Mn: 1.10% -1.40%, Cr: 0.4-0.7%, P is less than or equal to 0.018%, S is less than or equal to 0.008%, Als: 0.02 to 0.04 percent, and the balance of Fe and inevitable impurities.
Further, in the heating procedure, the plate blank is placed in a stepping heating furnace to be heated, the charging temperature is 300-600 ℃, the plate blank is heated to 1230-1270 ℃, the temperature is kept for 180-250 min, alloy elements are fully dissolved and separated out, and finally steel plate grains are refined and uniform; in order to avoid final rolling temperature fluctuation caused by large tail temperature drop in the finish rolling stage, tail compensation is adopted for heating the casting blank, and the temperature is 20-40 ℃ higher than that of the head.
Further, in the rolling procedure, the heated plate blank is subjected to rough rolling for 6-8 times, the descaling pressure of the rough rolling is guaranteed to be more than or equal to 190bar, and the thickness of the intermediate blank after the rough rolling is 45-55 mm; and performing finish rolling for 6-7 times to obtain a 3-8mm steel plate.
Further, the cooling procedure comprises the steps of carrying out water cooling-air cooling-water cooling three-stage cooling on the finish-rolled steel plate, cooling at a cooling speed of 17-25 ℃/s to be intensively cooled to 650-685 ℃, then carrying out air cooling for 4-9 s, and finally carrying out conventional cooling at a cooling speed of 60-85 ℃/s to 50-200 ℃ to carry out coiling. The temperature of the laminar cooling water is 28-33 ℃. And a three-section cooling mode is adopted. Three-section cooling, namely front section concentrated cooling, air cooling and rear section conventional cooling. The temperature of the laminar cooling water is 28-33 ℃, different cooling speeds, intercooling temperatures and air cooling times have important influences on the size of ferrite grains and the form, distribution and content of martensite, and the mechanical property and the process property of the dual-phase steel are directly influenced.
Adopt above-mentioned technical scheme's beneficial effect to lie in:
1. the invention realizes low-cost production through reasonable components and process design. The produced steel plate with the thickness of 3.0-8.0mm has excellent performance, the characteristics of low yield ratio and high plasticity, the problems of difficult deformation, cracking and the like in the wheel processing process are effectively eliminated, the excellent surface quality meets the appearance quality requirement of the wheel, and an excellent material is provided for manufacturing the wheel steel.
2. The invention does not add Mo, Nb and other alloy elements, thereby greatly reducing the alloy smelting cost. Si exists as a residual element and is not added intentionally, so that the risk of the red oxide scale defect on the surface of the steel plate is effectively avoided.
3. According to the invention, by adjusting key process parameters of each procedure, temperature compensation formulation of the tail part of the plate blank, constant-speed rolling of a finish rolling section and the like are adopted, so that the process temperature is stable, and ferrite-martensite structure phase transformation is uniform and stable. The hot-rolled dual-phase steel plate with good tissue form and proportion is obtained, the processing and forming performance is excellent, and the fatigue times of the lightweight wheel prepared by the material are far higher than the standard requirements.
4. The yield strength of the steel plate produced by the method is 365-441 MPa, the tensile strength is 613-665 MPa, the elongation is 26.5-38%, the yield ratio is 0.57-0.72, the structure of the steel plate is mainly composed of ferrite and 15-28% martensite which are uniformly dispersed, the steel plate is used for stamping and accurately forming wheel spokes, and a high-quality material is provided for manufacturing wheel spoke assemblies of passenger cars.
Drawings
FIG. 1 is a metallographic structure diagram of a steel sheet produced in example 1;
FIG. 2 is a metallographic structure diagram of a steel sheet produced in example 2;
FIG. 3 is a metallographic structure chart of a steel sheet produced in example 3;
FIG. 4 is a metallographic structure chart of a steel sheet produced in example 4;
FIG. 5 is a metallographic structure chart of a steel sheet produced in example 5;
FIG. 6 is a metallographic structure chart of a steel sheet produced in example 6.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
The production method of 600 MPa-grade dual-phase steel comprises the working procedures of continuous casting, heating, rolling, cooling and coiling, and comprises the following specific process steps:
(1) and (3) continuous casting process: and (3) adopting a dynamic soft reduction technology at the position of a liquid core at the solidification tail end of the continuous casting fan-shaped section, wherein the dynamic soft reduction adopts a reduction amount of 1.5-2.0 mm, the soft reduction length is 8-10 m, and the total reduction amount is 6-8 mm, so that the looseness and component segregation caused by bridging of central dendrites are reduced, inclusions are uniformly distributed, and a defect-free casting blank is obtained.
The thickness of the casting blank is 237-240mm, and the chemical components and the mass percentage content thereof are as follows: 0.07 to 0.10 percent of C, less than or equal to 0.05 percent of Si, 1.10 to 1.40 percent of Mn, 0.4 to 0.7 percent of Cr, less than or equal to 0.018 percent of P, less than or equal to 0.008 percent of S, 0.02 to 0.04 percent of Als, and the balance of Fe and inevitable impurities.
The gas N, H and O in the casting blank sampling inspection steel are less than or equal to 60ppm, less than or equal to 1.5ppm and less than or equal to 20 ppm;
(2) and a heating procedure, namely, the charging temperature of the casting blank is 300-600 ℃, the casting blank is heated to 1230-1270 ℃, the temperature is kept for 180-250 min, the alloy elements are fully dissolved and separated out, and finally the crystal grains of the steel plate are refined and uniform. In order to avoid final rolling temperature fluctuation caused by large tail temperature drop in the finish rolling stage, tail compensation is adopted for heating the casting blank, and the temperature is 20-40 ℃ higher than that of the head.
(3) A rolling procedure, wherein the heated plate blank is subjected to 6-8 times of rough rolling, the initial rolling temperature of the rough rolling is 1180-1200 ℃, the single-pass reduction rate of the rough rolling is 26.2-53.6%, the thickness of an intermediate blank after the rough rolling is 45-55 mm, the initial rolling temperature of the finish rolling is 980-1030 ℃, constant-speed rolling is adopted in the finish rolling stage, the rolling speed is 5.5-8.5 m/s, 6-7 times of finish rolling are carried out, the single-pass reduction rate is 6.5-45.8%, and the final rolling temperature is 850-880 ℃, so that a 3-8mm steel plate is obtained;
the selection of the process parameters creates conditions for subsequent phase change, also considers the surface quality of the steel plate, improves the scale structure, reduces the proportion of FeO, increases the compactness and prevents the scale from loosening and falling. The rough rolling descaling pressure is ensured to be more than or equal to 190 bar.
(4) A cooling and coiling process: the cooling adopts a three-section type cooling mode, namely front section concentrated cooling, air cooling and rear section conventional cooling. The first section is cooled to 650-685 ℃ by adopting concentrated cooling at the cooling speed of 17-25 ℃/s, then air cooling is carried out for 4-9 s, and then the second section is cooled in a concentrated manner at the cooling speed of 60-85 ℃/s and the coiling temperature of 50-200 ℃;
the temperature of the laminar cooling water is 28-33 ℃, different cooling speeds, intercooling temperatures and air cooling times have important influences on the size of ferrite grains and the form, distribution and content of martensite, and the mechanical property and the process property of the dual-phase steel are directly influenced.
The chemical composition and the mass percentage of the slab in examples 1 to 6 are as shown in Table 1:
table 1 examples 1-6 slab chemical composition and mass percentage (%)
The balance of the ingredients in table 1 is Fe and unavoidable impurities.
Example 1
The thickness of the 600 MPa-grade dual-phase steel for the wheel spoke is 3.0mm, the chemical component composition and the mass percentage content of the steel are shown in table 1, the production method comprises the working procedures of slab continuous casting, slab heating, controlled rolling, cooling and coiling, and the specific process steps are as follows:
(1) and a slab continuous casting process: the pure molten steel obtained by smelting adopts a fan-shaped section dynamic soft reduction technology in the casting process, the reduction of 1.5mm is adopted at the solidification tail end of the liquid core, the soft reduction length is 9m, the total reduction is 6mm, the looseness and component segregation caused by central dendritic crystal bridging are avoided, inclusions are uniformly distributed, and a defect-free plate blank is obtained, wherein the chemical components and the mass percentage of the plate blank are as shown in the table 1;
(2) a slab heating process: hot charging the plate blank, heating the plate blank to 1253 ℃ at the charging temperature of 600 ℃, preserving heat for 192 min, and adopting a tail temperature compensation measure which is 20 ℃ higher than that of the head;
(3) and (3) controlling a rolling process: and 4, carrying out rough rolling on the two frames for 8 times, ensuring the descaling pressure of the rough rolling to be 195bar, and descaling the rough rolling for 7 times, wherein the initial rolling temperature of the rough rolling is 1181 ℃, and the thickness of the rough rolling intermediate blank is 47 mm. The initial rolling temperature of finish rolling is 983 ℃, the final rolling temperature is 853 ℃, and the rolling speed is 5.5 m/s;
(4) strip steel cooling and coiling: adopting front section concentrated cooling, air cooling and rear section conventional cooling, firstly cooling to 675 ℃ at a cooling rate of 21 ℃/s, then air cooling for 7s, then carrying out third section conventional cooling at a cooling rate of 75 ℃/s, wherein the coiling temperature is 100 ℃, and the coil of coil which is off-line is stacked in the warehouse at room temperature.
The mechanical properties of the 600MPa grade dual-phase steel for the wheel spoke obtained in the embodiment are shown in Table 2, the metallographic microstructure after being corroded by 4% nitric acid alcohol is shown in figure 1, and the microstructure mainly comprises the following components: ferrite and martensite are uniformly dispersed and distributed, and the proportion of the martensite is 15%. Ferrite ensures that the steel has good plasticity, and martensite ensures that the steel has high strength. The wheel spoke has good forming in the processing process, has no cracking problem, and meets the processing and use requirements of the wheel.
Example 2
The thickness of the 600 MPa-grade dual-phase steel for the wheel spoke is 4.2mm, the chemical component composition and the mass percentage content of the steel are shown in Table 1, the production method comprises the working procedures of slab continuous casting, slab heating, controlled rolling, cooling and coiling, and the specific process steps are as follows:
(1) and a slab continuous casting process: the pure molten steel obtained by smelting adopts a fan-shaped section dynamic soft reduction technology in the casting process, the reduction of 1.5mm is adopted at the solidification tail end of the liquid core, the soft reduction length is 10m, the total reduction is 8mm, the looseness and component segregation caused by central dendritic crystal bridging are avoided, inclusions are uniformly distributed, and a defect-free plate blank is obtained, wherein the chemical components and the mass percentage of the plate blank are as shown in the table 1;
(2) a slab heating process: hot charging the plate blank, heating the plate blank to 1237 ℃ at the charging temperature of 300 ℃, preserving heat for 187 min, and adopting a tail temperature compensation measure which is 27 ℃ higher than that of the head;
(3) and (3) controlling a rolling process: and (3) carrying out rough rolling for 6 passes by using a two-stand, wherein the rough rolling descaling pressure is ensured to be 197bar, the 5-pass descaling is carried out, the rough rolling starting temperature is 1185 ℃, and the thickness of a rough rolling intermediate blank is 45 mm. The initial rolling temperature of finish rolling is 980 ℃, the final rolling temperature is 875 ℃, and the rolling speed is 7.5 m/s;
(4) strip steel cooling and coiling: adopting front section concentrated cooling, air cooling and rear section conventional cooling, firstly cooling to 650 ℃ at a cooling speed of 25 ℃/s, then carrying out air cooling for 9s, then carrying out third section conventional cooling at a cooling speed of 85 ℃/s, wherein the coiling temperature is 50 ℃, and the coil of coil which is off-line is stacked in the warehouse at room temperature.
The mechanical properties of the 600MPa grade dual-phase steel for the wheel spoke obtained in the embodiment are shown in Table 2, the metallographic microstructure after being corroded by 4% nitric acid alcohol is shown in FIG. 2, and the microstructure mainly comprises the following components: ferrite and martensite are uniformly dispersed and distributed, the proportion of the martensite is 20%, the ferrite ensures that the ferrite has good plasticity, and the martensite ensures that the martensite has high strength. The wheel spoke has good forming in the processing process, has no cracking problem, and meets the processing and use requirements of the wheel.
Example 3
The thickness of the 600 MPa-grade dual-phase steel for the wheel spoke is 5.5mm, the chemical component composition and the mass percentage content of the steel are shown in table 1, the production method comprises the working procedures of slab continuous casting, slab heating, controlled rolling, cooling and coiling, and the specific process steps are as follows:
(1) and a slab continuous casting process: the pure molten steel obtained by smelting adopts a fan-shaped section dynamic soft reduction technology in the casting process, the reduction of 2.0mm is adopted at the solidification tail end of the liquid core, the soft reduction length is 8m, the total reduction is 8mm, the looseness and component segregation caused by central dendritic crystal bridging are avoided, inclusions are uniformly distributed, and a defect-free plate blank is obtained, wherein the chemical components and the mass percentage of the plate blank are as shown in the table 1;
(2) a slab heating process: hot charging the plate blank, heating the plate blank to 1270 ℃ at the charging temperature of 327 ℃, preserving heat for 250min, and adopting a tail temperature compensation measure which is 31 ℃ higher than that of the head;
(3) and (3) controlling a rolling process: and 4, carrying out rough rolling on the two frames for 8 times, ensuring the descaling pressure of the rough rolling to be 195bar, and descaling the rough rolling for 6 times, wherein the initial rolling temperature of the rough rolling is 1180 ℃, and the thickness of the rough rolling intermediate blank is 52 mm. The initial rolling temperature of finish rolling is 1030 ℃, the final rolling temperature is 850 ℃, and the rolling speed is 6.3 m/s;
(4) strip steel cooling and coiling: adopting front section concentrated cooling, air cooling and rear section conventional cooling, cooling to 660 ℃ at the speed of 17 ℃/s, then carrying out air cooling for 8s, then entering second section conventional cooling, wherein the cooling speed is 65 ℃/s, the coiling temperature is 150 ℃, and the coil of coil which is off-line is stacked in the warehouse at room temperature.
The mechanical properties of the 600MPa grade dual-phase steel for the wheel spoke obtained in the embodiment are shown in Table 2, the metallographic microstructure after being corroded by 4% nitric acid alcohol is shown in figure 3, and the microstructure mainly comprises the following components: ferrite and martensite are uniformly dispersed and distributed, the proportion of the martensite is 25%, the ferrite ensures that the ferrite has good plasticity, and the martensite ensures that the martensite has high strength. The wheel spoke has good forming in the processing process, has no cracking problem, and meets the processing and use requirements of the wheel.
Example 4
The thickness of the 600 MPa-grade dual-phase steel for the wheel spoke is 6.3mm, the chemical component composition and the mass percentage content of the steel are shown in table 1, the production method comprises the working procedures of slab continuous casting, slab heating, controlled rolling, cooling and coiling, and the specific process steps are as follows:
(1) and a slab continuous casting process: the pure molten steel obtained by smelting adopts a fan-shaped section dynamic soft reduction technology in the casting process, the reduction of 2.0mm is adopted at the solidification tail end of the liquid core, the soft reduction length is 10m, the total reduction is 6mm, the looseness and component segregation caused by central dendritic crystal bridging are avoided, inclusions are uniformly distributed, and a defect-free plate blank is obtained, wherein the chemical components and the mass percentage of the plate blank are as shown in the table 1;
(2) a slab heating process: hot charging the plate blank, wherein the charging temperature of the plate blank is 381 ℃, the plate blank is heated to 1230 ℃, the temperature is kept for 205 min, and the temperature is compensated by adopting a tail temperature compensation measure and is 34 ℃ higher than the head;
(3) and (3) controlling a rolling process: and (3) carrying out rough rolling for 6 times by using a two-stand frame, ensuring the descaling pressure of the rough rolling to be 202bar, descaling for 5 times, and carrying out rough rolling at the beginning temperature of 1200 ℃ to obtain a rough-rolled intermediate blank with the thickness of 55 mm. The initial rolling temperature of finish rolling is 1000 ℃, the final rolling temperature is 865 ℃, and the rolling speed is 8.5 m/s;
(4) strip steel cooling and coiling: adopting front section concentrated cooling, air cooling and rear section conventional cooling, cooling to 685 ℃ at 19 ℃/s, then carrying out air cooling for 6s, then entering a second section conventional cooling, wherein the cooling speed is 79 ℃/s, the coiling temperature is 70 ℃, and the coil of coil which is off-line is stacked in the warehouse at room temperature.
The mechanical properties of the 600MPa grade dual-phase steel for the wheel spoke obtained in the embodiment are shown in Table 2, the metallographic microstructure after being corroded by 4% nitric acid alcohol is shown in FIG. 4, and the microstructure mainly comprises the following components: ferrite and martensite are dispersed and uniformly distributed, the proportion of the martensite is 18%, the ferrite ensures that the ferrite has good plasticity, and the martensite ensures that the martensite has high strength. The wheel spoke has good forming in the processing process, has no cracking problem, and meets the processing and use requirements of the wheel.
Example 5
The thickness of the 600 MPa-grade dual-phase steel for the wheel spoke is 7.1mm, the chemical component composition and the mass percentage content of the steel are shown in Table 1, the production method comprises the working procedures of slab continuous casting, slab heating, controlled rolling, cooling and coiling, and the specific process steps are as follows:
(1) and a slab continuous casting process: the pure molten steel obtained by smelting adopts a fan-shaped section dynamic soft reduction technology in the casting process, the reduction of 2.0mm is adopted at the solidification tail end of the liquid core, the soft reduction length is 8m, the total reduction is 4mm, the looseness and component segregation caused by central dendritic crystal bridging are avoided, inclusions are uniformly distributed, and a defect-free plate blank is obtained, wherein the chemical components and the mass percentage of the plate blank are as shown in the table 1;
(2) a slab heating process: hot charging the plate blank, wherein the charging temperature of the plate blank is 462 ℃, the plate blank is heated to 1265 ℃, the temperature is kept for 236 min, and a tail temperature compensation measure is adopted and is 40 ℃ higher than the head;
(3) and (3) controlling a rolling process: and 4, carrying out rough rolling on the two frames for 8 times, ensuring the descaling pressure of the rough rolling to be 210bar, and descaling the rough rolling for 6 times, wherein the rough rolling start temperature is 1195 ℃, and the thickness of the rough rolling intermediate blank is 53 mm. The initial rolling temperature of finish rolling is 1025 ℃, the finishing temperature is 871 ℃, and the rolling speed is 6.5 m/s;
(4) strip steel cooling and coiling: adopting front section concentrated cooling, air cooling and rear section conventional cooling, cooling to 680 ℃ at 23 ℃/s, then carrying out air cooling for 5s, then entering second section conventional cooling, wherein the cooling speed is 72 ℃/s, the coiling temperature is 200 ℃, and the coil of coil which is off-line is stacked in the warehouse at room temperature.
The mechanical properties of the 600MPa grade dual-phase steel for the wheel spoke obtained in the embodiment are shown in Table 2, the metallographic microstructure after being corroded by 4% nitric acid alcohol is shown in figure 5, and the microstructure mainly comprises the following components: ferrite and martensite are uniformly dispersed and distributed, the proportion of the martensite is 23%, the ferrite ensures that the ferrite has good plasticity, and the martensite ensures that the martensite has high strength. The wheel spoke has good forming in the processing process, has no cracking problem, and meets the processing and use requirements of the wheel.
Example 6
The 600MPa grade dual-phase steel for the wheel spoke has the thickness of 8.0mm, the chemical component composition and the mass percentage content thereof are shown in Table 1, the production method comprises the working procedures of slab continuous casting, slab heating, controlled rolling, cooling and coiling, and the specific process steps are as follows:
(1) and a slab continuous casting process: the pure molten steel obtained by smelting adopts a fan-shaped section dynamic soft reduction technology in the casting process, the reduction of 1.5mm is adopted at the solidification tail end of the liquid core, the soft reduction length is 8m, the total reduction is 8mm, the looseness and component segregation caused by central dendritic crystal bridging are avoided, inclusions are uniformly distributed, and a defect-free plate blank is obtained, wherein the chemical components and the mass percentage of the plate blank are as shown in the table 1;
(2) a slab heating process: hot charging the plate blank, wherein the charging temperature of the plate blank is 523 ℃, the plate blank is heated to 1243 ℃, the temperature is kept for 180 min, and the tail temperature compensation measure is adopted and is 23 ℃ higher than the head temperature;
(3) and (3) controlling a rolling process: and (3) carrying out rough rolling for 6 passes by using a two-stand, wherein the rough rolling descaling pressure is ensured to be 197bar, the rough rolling descaling pressure is ensured to be 5 passes, the rough rolling starting temperature is 1189 ℃, and the thickness of a rough rolling intermediate blank is 50 mm. The initial rolling temperature of finish rolling is 1015 ℃, the final rolling temperature is 880 ℃, and the rolling speed is 8.1 m/s;
(4) strip steel cooling and coiling: adopting front section concentrated cooling, air cooling and rear section conventional cooling, cooling to 662 ℃ at 24 ℃/s, then carrying out air cooling for 4s, then entering second section conventional cooling, wherein the cooling speed is 60 ℃/s, the coiling temperature is 160 ℃, and the coil of coil which is off-line is stacked in the warehouse at room temperature.
The mechanical properties of the 600MPa grade dual-phase steel for the wheel spoke obtained in the embodiment are shown in Table 2, the metallographic microstructure after being corroded by 4% nitric acid alcohol is shown in figure 6, and the microstructure mainly comprises the following components: ferrite and martensite are uniformly dispersed and distributed, the percentage of the martensite is 28%, the ferrite ensures that the ferrite has good plasticity, and the martensite ensures that the martensite has high strength. The wheel spoke has good forming in the processing process, has no cracking problem, and meets the processing and use requirements of the wheel.
Table 2 mechanical properties of 600MPa grade dual phase steels for wheel spokes of examples 1-6
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and it is intended to cover in the claims the invention as defined in the appended claims.
Claims (9)
1. The 600 MPa-grade dual-phase steel for the wheel spoke is characterized by comprising the following chemical components in percentage by mass: c: 0.07-0.10%, Si is less than or equal to 0.05%, Mn: 1.10% -1.40%, Cr: 0.4-0.7%, P is less than or equal to 0.018%, S is less than or equal to 0.008%, Als: 0.02 to 0.04 percent, and the balance of Fe and inevitable impurities.
2. The 600MPa grade dual-phase steel for the wheel spoke according to claim 1, wherein the dual-phase steel structure is a ferrite and martensite dual-phase structure, the ferrite volume fraction is 72-85%, the martensite volume fraction is 15-28%, and the ferrite average grain size is 1.3-4.7 μm.
3. The 600MPa grade dual-phase steel for the wheel spoke according to claim 1, wherein the thickness of the dual-phase steel plate is 3.0-8.0mm, the yield strength is 365-441 MPa, the tensile strength is 613-665 MPa, the elongation is 26.5-38%, and the yield ratio is 0.57-0.72.
4. A production method of 600MPa grade dual phase steel for a wheel spoke according to any one of claims 1 to 3, which comprises the procedures of continuous casting, heating, rolling, cooling and coiling; the rolling procedure comprises two stages of rough rolling and finish rolling, wherein the initial rolling temperature of the rough rolling is 1180-1200 ℃, and the single-pass reduction rate of the rough rolling is 26.2-53.6%; the initial rolling temperature of finish rolling is 980-1030 ℃, constant-speed rolling is adopted in the finish rolling stage, the rolling speed is 5.5-8.5 m/s, the single-pass reduction rate is 6.5-45.8%, and the final rolling temperature is 850-880 ℃.
5. The production method of the 600MPa grade dual-phase steel for the wheel spoke according to the claim 4 is characterized in that in the continuous casting process, dynamic soft reduction is adopted in a fan-shaped section in the slab casting process, the reduction of 1.5-2.0 mm is adopted in the solidification tail end position of a slab liquid core in the fan-shaped section, the length of the soft reduction is 8-10 m, and the total reduction is 6-8 mm; the gas N, H and O in the slab sampling inspection steel are less than or equal to 60ppm, less than or equal to 1.5ppm and less than or equal to 20 ppm.
6. The production method of the 600MPa grade dual phase steel for the wheel spoke as claimed in claim 4, wherein the continuous casting process has a slab thickness of 237- & 240mm, and comprises the following chemical components in percentage by mass: c: 0.07-0.10%, Si is less than or equal to 0.05%, Mn: 1.10% -1.40%, Cr: 0.4-0.7%, P is less than or equal to 0.018%, S is less than or equal to 0.008%, Als: 0.02 to 0.04 percent, and the balance of Fe and inevitable impurities.
7. The production method of the 600MPa grade dual-phase steel for the wheel spoke according to any one of the claims 4 to 6, characterized in that the heating procedure comprises the steps of placing a plate blank in a stepping heating furnace for heating, wherein the feeding temperature is 300-600 ℃, the plate blank is heated to 1230-1270 ℃, and the temperature is kept for 180-250 min; the casting blank is heated by adopting tail compensation and is higher than the head by 20-40 ℃.
8. The production method of the 600MPa grade dual-phase steel for the wheel spoke according to any one of claims 4 to 6, characterized in that in the rolling procedure, the heated plate blank is subjected to 6-8 times of rough rolling, the rough rolling descaling pressure is ensured to be more than or equal to 190bar, and the thickness of the intermediate blank after rough rolling is 45-55 mm; and performing finish rolling for 6-7 times to obtain a 3-8mm steel plate.
9. The method for producing 600MPa grade dual phase steel for wheel spokes according to any one of claims 4 to 6, wherein the cooling step is to cool the finish rolled steel plate in three stages of water cooling-air cooling-water cooling, wherein the steel plate is cooled intensively to 650 to 685 ℃ at a cooling rate of 17 to 25 ℃/s, then air cooled for 4 to 9s, and finally cooled to 50 to 200 ℃ at a cooling rate of 60 to 85 ℃/s, and the temperature of the laminar cooling water is 28 to 33 ℃.
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| JP2010001531A (en) * | 2008-06-20 | 2010-01-07 | Nippon Steel Corp | Method for manufacturing low-yield-ratio type high-strength galvannealed steel sheet |
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| CN110184535A (en) * | 2019-05-21 | 2019-08-30 | 邯郸钢铁集团有限责任公司 | 600L steel for automobile crossbeam band and production method with good processability |
| CN110863151A (en) * | 2019-10-24 | 2020-03-06 | 邯郸钢铁集团有限责任公司 | One-steel multi-stage multi-thickness hot-rolled dual-phase steel and production method thereof |
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| JP2010001531A (en) * | 2008-06-20 | 2010-01-07 | Nippon Steel Corp | Method for manufacturing low-yield-ratio type high-strength galvannealed steel sheet |
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