CN115198206B - High mechanical property hot-rolled complex phase steel and preparation method thereof - Google Patents
High mechanical property hot-rolled complex phase steel and preparation 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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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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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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- 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
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C21D2211/001—Austenite
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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
- C21D2211/002—Bainite
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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 application relates to the technical field of steel smelting, in particular to hot-rolled complex phase steel with high mechanical property and a preparation method thereof; the high-strength reaming steel comprises the following chemical components in percentage by mass: c, si, mn, cr, P, S, nb, ti, mo, N, RE, and the balance of Fe and unavoidable impurity elements; the method comprises the following steps: obtaining molten steel after smelting; pretreating the molten steel after smelting, and then carrying out converter smelting, external refining and continuous casting to obtain a plate blank; heating the slab, and then performing rough rolling and finish rolling to obtain a hot rolled plate; cooling, coiling and flattening the hot rolled plate to obtain hot rolled complex phase steel with high mechanical property; the strength, hardness, extensibility, hole expansion rate and the like of the steel can be comprehensively improved by limiting the content of C, nb, ti, mo, mn, S and rare earth RE, so that the hot-rolled complex phase steel with high mechanical properties is obtained.
Description
Technical Field
The application relates to the technical field of steel smelting, in particular to hot-rolled complex phase steel with high mechanical properties and a preparation method thereof.
Background
The complex phase steel is used as one steel grade in advanced high-strength steel, compared with the traditional martensitic double phase steel, the complex phase steel has good combination of strength and extending flange property, is more suitable for manufacturing parts with thicker requirements such as automobile chassis and the like and good flanging property, can realize the weight reduction of automobiles and simultaneously ensure the safety of the automobiles, so the complex phase steel is a trend of developing a new high-strength material complex phase steel with good formability, and has development prospect and economic benefit potential.
The existing complex phase steel after hot rolling can well give consideration to contradiction and balance of strength and ductility, and has excellent stretch flange property, but the existing complex phase steel is generally low in mechanical property and cannot be effectively applied to other fields of automobile industry, so that how to improve the mechanical property of the complex phase steel is a technical problem to be solved at present.
Disclosure of Invention
The application provides high-performance hot-rolled complex phase steel and a preparation method thereof, which aim to solve the technical problem of lower mechanical property of complex phase steel in the prior art.
In a first aspect, the application provides a high mechanical property hot-rolled complex phase steel, which comprises the following chemical components in percentage by mass: 0.05 to 0.16 percent of C, 0.1 to 0.5 percent of Si, 1.0 to 2.0 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.003 percent of S, 0.01 to 0.06 percent of Nb, 0.05 to 0.15 percent of Ti, 0.1 to 0.3 percent of Mo, 0.003 to 0.008 percent of N, 0.001 to 0.015 percent of RE, and the balance of Fe and unavoidable impurity elements.
Optionally, the metallographic structure of the hot-rolled complex phase steel comprises, in terms of volume fraction: bainite: 80% -90%, residual austenite: 5% -10% of martensite: 5 to 10 percent.
In a second aspect, the present application provides a method for preparing the hot rolled complex phase steel according to the first aspect, the method comprising:
obtaining molten steel after smelting;
pretreating the molten steel after smelting, and then carrying out converter smelting, external refining and continuous casting to obtain a plate blank;
heating the slab, and then performing rough rolling and finish rolling to obtain a hot rolled plate;
and cooling, coiling and flattening the hot rolled plate to obtain the hot rolled complex phase steel with high mechanical property.
Optionally, the end point temperature of the heating is 1180 ℃ to 1230 ℃.
Optionally, the finishing temperature of the rough rolling is 1030-1080 ℃, and the thickness of the rough rolled intermediate billet is less than or equal to 38mm.
Optionally, the finish rolling temperature of the finish rolling is 860-900 ℃, the rolling speed of the finish rolling is 5-10 m/s, and the thickness of the hot rolled plate is 1.8-5 mm.
Optionally, the finish rolling temperature of the finish rolling is 880-900 ℃.
Optionally, the cooling comprises first cooling and air cooling, wherein the end temperature of the first cooling is 430-480 ℃, and the cooling rate of the first cooling is more than or equal to 80 ℃/s.
Optionally, the coiling temperature is 400-450 ℃.
Optionally, the flat elongation is 3% -4%.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
according to the high mechanical property hot rolled multi-phase steel provided by the embodiment of the application, C content, nb content, ti content and Mo content are limited, C and N are utilized to form carbonitride with microalloy Nb and Ti elements and form carbonitride with Mo elements in the heat treatment process, crystal grains can be refined and ferrite can be reinforced, the strength of the multi-phase steel is improved, S and Mn can be prevented from being combined to generate MnS by limiting Mn content and S content, so that the material property is deteriorated, the elongation of the steel is further ensured, finally rare earth element RE is added to optimize inclusion formation in the steel, and because the rare earth element and S form spherical rare earth sulfide, the rare earth sulfide can keep tiny spherical or spinned conical shape, can be more uniformly distributed in the steel, part of MnS precipitates are eliminated, the hole expansion rate of the steel can be improved, and the hot rolled multi-phase steel with high mechanical property can be obtained.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.
In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic flow chart of a method according to an embodiment of the present application;
fig. 2 is a schematic diagram of a metallographic structure of a hot-rolled complex phase steel according to an embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In one embodiment of the application, a high mechanical property hot rolled complex phase steel is provided, and the chemical components of the hot rolled complex phase steel comprise, in mass fraction: 0.05 to 0.16 percent of C, 0.1 to 0.5 percent of Si, 1.0 to 2.0 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.003 percent of S, 0.01 to 0.06 percent of Nb, 0.05 to 0.15 percent of Ti, 0.1 to 0.3 percent of Mo, 0.003 to 0.008 percent of N, 0.001 to 0.015 percent of RE, and the balance of Fe and unavoidable impurity elements.
In the embodiment of the application, the positive effect that the mass fraction of C is 0.05-0.16% is that in the mass fraction range, because the C element is the most important solid solution strengthening element in the steel and the element for ensuring the hardenability of austenite, the proper C content can ensure that the steel obtains enough martensite in the cooling process so as to ensure the strength of the steel, and meanwhile, C can form carbonitride with microalloy Nb and Ti elements in the heat treatment process, refine grains and strengthen ferrite, thereby improving the mechanical property of the steel; when the value of the mass fraction is larger than the maximum value of the end point of the range, the content of C is too high, the strength of the steel is too hard, the flexibility of the steel is affected, and when the value of the mass fraction is smaller than the minimum value of the end point of the range, the content of C is too low, and the strength of the steel cannot be ensured.
The positive effect of the Si with the mass fraction of 0.1-0.5% is that in the mass fraction range, because Si is a solid solution strengthening element of the steel, si can promote the enrichment of C element to austenite, improve the hardenability of the austenite, purify ferrite phase and improve the elongation of the steel; when the value of the mass fraction is larger than the end maximum value of the range, the austenite hardenability of the steel is insufficient, and when the value of the mass fraction is smaller than the end minimum value of the range, the Si content is too low, and the austenite hardenability cannot be improved.
The mass fraction of Mn is 1.0% -2.0%, and in the range of the mass fraction, mn is an important element for solid solution strengthening and austenite stabilization, so that the Mn plays an important role in strengthening the mechanical properties of the steel; when the value of the mass fraction is larger than the maximum value of the end point of the range, the Mn content is too high, the tissue segregation is easily caused, the steel is cracked in the forming process, the mechanical property of the steel is deteriorated, meanwhile, the segregated precipitate is enriched to the surface in the annealing process, the steel surface is cracked, and when the value of the mass fraction is smaller than the minimum value of the end point of the range, the Mn content is insufficient, and the effects of solid solution strengthening and austenite stabilization cannot be effectively achieved.
The positive effect of P being less than or equal to 0.02 percent is that in the mass fraction range, the P can inhibit the formation of carbide, and the carbon equivalent of the whole steel can be ensured to be in a proper range; when the mass fraction is larger than the end maximum value of the range, segregation of carbide at the grain boundary is caused, and the grain boundary strength is lowered to deteriorate the mechanical properties of the material.
The positive effect of S being less than or equal to 0.003 percent is that in the mass fraction range, S is a harmful element and can be combined with Mn to generate MnS, so that the mechanical property of the steel is deteriorated; when the mass fraction is larger than the end point maximum value of the range, the S content is excessive, on one hand, the Ti consumption is required to be increased, on the other hand, the mechanical property of the steel is weaker, and the expanding property of reaming is affected.
The mass fraction of Nb is 0.01% -0.06%, and the positive effects are that in the mass fraction range, nb and C or N can be combined to form nano precipitated phases, thereby playing roles in refining grains and precipitation strengthening, having remarkable roles in improving tissue morphology and increasing yield strength, refining austenite grain size in the heating process, finally obtaining hard phase diffusion, and having positive effects in improving reaming performance; when the value of the mass fraction is larger than the end point maximum value of the range, the elongation of the steel is reduced, and when the value of the mass fraction is smaller than the end point minimum value of the range, enough nano precipitated phases cannot be formed due to insufficient Nb content, and the effects of grain melting and precipitation strengthening cannot be achieved.
The positive effect of Ti with the mass fraction of 0.05-0.15% is that in the mass fraction range, ti and C or N can be combined to form nano precipitated phase, thereby playing roles in refining grains and precipitation strengthening, having remarkable roles in improving tissue morphology and increasing yield strength, refining austenite grain size in the heating process, finally obtaining hard phase diffusion, and having positive effects in improving reaming performance; when the value of the mass fraction is larger than the end maximum value of the range, the elongation of the steel is reduced, and when the value of the mass fraction is smaller than the end minimum value of the range, enough nano precipitated phases cannot be formed due to insufficient Ti content, and the effects of grain crystallization and precipitation strengthening cannot be achieved.
The positive effect that the mass fraction of Mo is 0.1-0.3% is that the steel hardenability is improved within the mass fraction range; when the mass fraction is larger than the end point maximum value of the range, adverse effects are caused by the fact that Mo is relatively expensive, excessive Mo is added to increase the cost of the steel, and when the mass fraction is smaller than the end point minimum value of the range, adverse effects are caused by insufficient content of Mo, and insufficient hardenability of the steel is caused.
The positive effect of the mass fraction of N being 0.003% -0.008% is that in the mass fraction range, as N can form nano precipitated phases with Ti and Nb, the effects of grain refinement and precipitation strengthening can be achieved, and therefore the strength of steel can be improved; when the value of the mass fraction is larger than the maximum value of the end point of the range, the N content is excessive, the educts are increased, the performance of the steel is affected, and when the value of the mass fraction is smaller than the minimum value of the end point of the range, the N content is insufficient, and the number of the educts in the nano educt phase cannot be ensured.
The RE has the positive effects that in the mass fraction range, the rare earth element and S form spherical rare earth sulfide, and the rare earth sulfide can keep a tiny spherical shape or spinning cone shape, can be uniformly distributed in the steel, eliminates part of MnS precipitate, further can improve the hole expansion rate of the steel, and ensures excellent mechanical property of the steel; when the mass fraction is larger than the end point maximum value of the range, the cost of the steel will be increased, and when the mass fraction is smaller than the end point minimum value of the range, the elimination of part of MnS precipitates will not be effective.
In some alternative embodiments, the metallographic structure of the high strength, expanded steel comprises, in volume fractions: bainite: 80% -90%, residual austenite: 5% -10% of martensite: 5 to 10 percent.
In the embodiment of the application, the volume fraction of the bainite is 80% -90%, and the positive effects of the volume fraction of the bainite are that the whole hardness and toughness of the steel can be ensured to be good within the range of the mass fraction, so that the comprehensive capability of the steel is ensured to be good; when the volume fraction is larger or smaller than the end value of the range, the hardness and toughness of the steel are unstable, and the mechanical properties of the steel are affected.
The volume fraction of martensite is 5% -10%, and the positive effect is that the strength of the steel can be ensured to be in a proper range within the volume fraction range; when the volume fraction is larger or smaller than the end value of the range, the strength of the steel is unstable, and the mechanical property of the steel is unstable.
In one embodiment of the present application, as shown in fig. 1, there is provided a method for preparing a high mechanical property hot rolled complex phase steel, the method comprising:
s1, obtaining molten steel after smelting;
s2, pretreating the molten steel after smelting, and then carrying out converter smelting, external refining and continuous casting to obtain a plate blank;
s3, heating the slab, and then performing rough rolling and finish rolling to obtain a hot rolled plate;
s4, cooling, coiling and flattening the hot rolled plate to obtain the hot rolled complex phase steel with high mechanical property.
In some alternative embodiments, the end point temperature of the heating is 1180 ℃ to 1230 ℃.
In the embodiment of the application, the heating terminal temperature is 1180-1230 ℃, and the positive effect is that the alloy element of the steel can be ensured to be fully dissolved in the temperature range; when the temperature is higher or lower than the end value of the range, the prior austenite is coarse or the solid solution of the alloy element is insufficient.
In some alternative embodiments, the finishing temperature of the rough rolling is 1030 ℃ to 1080 ℃, and the thickness of the rough rolled intermediate billet is less than or equal to 38mm.
In the embodiment of the application, the end temperature of rough rolling is 1030-1080 ℃, and the positive effects are that in the temperature range, the microstructure of the steel plate after rough rolling is ensured to be uniformly distributed, and the mechanical property of the steel plate is ensured; when the temperature is higher or lower than the end value of the range, the microstructure of the steel plate is disturbed, and a uniform microstructure cannot be effectively formed.
The thickness of the rough rolled intermediate billet is less than or equal to 38mm, and the positive effect is that the distribution of the microstructure of the rolled steel is uniform within the thickness range, so that the excellent mechanical property of the steel plate is ensured; when the thickness is larger than the end value of the range, the microstructure of the steel is distributed irregularly, which is not beneficial to the improvement of the mechanical property of the steel.
In some alternative embodiments, the finish rolling temperature of the finish rolling is 860 ℃ to 900 ℃, the rolling speed of the finish rolling is 5m/s to 10m/s, and the thickness of the hot rolled plate is 1.8mm to 5mm.
In the embodiment of the application, the finish rolling temperature of finish rolling is 860-900 ℃, and the positive effects are that in the temperature range, the microstructure of the steel plate can be ensured to be uniformly distributed, and the mechanical property of the steel plate is ensured; when the temperature is higher or lower than the end value of the range, uneven structure distribution of the steel plate is caused, and meanwhile, the too low rolling temperature leads to increased deformation resistance of the hot rolled plate, and edge cracking is easy to occur, so that good structure performance is not facilitated.
The rolling speed of finish rolling is 5 m/s-10 m/s, and the positive effects are that the high-efficiency rolling of steel can be realized within the range of the rolling speed; when the speed is greater or less than the end of the range, the adverse effect is unstable rolling or low rolling efficiency.
In some alternative embodiments, the finish rolling has a finish rolling temperature of 880 ℃ to 900 ℃.
The finish rolling temperature of the finish rolling is 880-900 ℃, and the positive effects are that in the temperature range, the microstructure of the steel plate can be ensured to be uniformly distributed, and the mechanical property of the steel plate can be ensured; when the temperature is higher or lower than the end value of the range, uneven structure distribution of the steel plate is caused, and meanwhile, the too low rolling temperature leads to increased deformation resistance of the hot rolled plate, and edge cracking is easy to occur, so that good structure performance is not facilitated.
In some alternative embodiments, the cooling includes a first cooling and an air cooling, the first cooling having an end temperature of 430 ℃ to 480 ℃, the first cooling having a cooling rate of greater than or equal to 80 ℃/s.
In the embodiment of the application, the end temperature of the first cooling is 430-480 ℃, and the positive effect is that a small amount of residual austenite can be regulated and separated out in the temperature range, so that the strength of the steel is ensured, and the excellent mechanical property of the steel is further ensured; when the temperature is higher or lower than the end point value of the range, the amount of ferrite precipitation cannot be controlled effectively, and the strength of the steel cannot be ensured.
The positive effect of the cooling rate of the first cooling is that the content of the precipitated residual austenite is ensured to be sufficient within the range of the cooling rate, so that the strength of the steel is ensured; when the cooling rate is smaller than the end value of the range, the adverse effect is that too slow cooling rate will cause the residual austenite to be unable to separate out, and the uniformity of microstructure distribution is affected.
In some alternative embodiments, the temperature of the coiling is 400 ℃ to 450 ℃.
In the embodiment of the application, the coiling temperature is 400-450 ℃, and the positive effects are that in the temperature range, uniform hot rolling structure can be ensured, and the hot rolling structure comprises fully transformed bainite and residual austenite, so that the structure can be ensured to be uniformly distributed in the plate width direction, and the mechanical property of the steel plate in the plate width direction is ensured to be uniform; when the temperature is less than the end of the range, an adverse effect is that too slow a cooling rate will result in incomplete transformation of bainite, affecting the uniformity of the microstructure distribution.
In some alternative embodiments, the flat extension is 3% to 4%.
In the embodiment of the application, the flat elongation is 3-4%, and the positive effects are that in the temperature range, the steel plate product with better surface quality can be obtained finally, the yield strength of the steel plate can be adjusted, and the reaming performance of the steel plate is improved.
Example 1
The hot-rolled complex phase steel with high mechanical property comprises the following chemical components in percentage by mass: 0.07% of C, 0.3% of Si, 1.6% of Mn, 0.018% of P, 0.003% of S, 0.05% of Nb, 0.09% of Ti, 0.25% of Mo, 0.004% of N, 0.007% of RE, and the balance of Fe and unavoidable impurity elements.
A preparation method of hot-rolled complex phase steel with high mechanical properties comprises the following steps:
s1, obtaining molten steel after smelting;
s2, pretreating molten steel after smelting, and then carrying out converter smelting, external refining and continuous casting to obtain a plate blank;
s3, heating the slab, and then performing rough rolling and finish rolling to obtain a hot rolled plate;
s4, cooling, coiling and flattening the hot rolled plate to obtain the hot rolled complex phase steel with high mechanical property and the metallographic structure shown in figure 2.
The end temperature of the heating was 1200 ℃.
The end temperature of the rough rolling was 1050 ℃, and the thickness of the rough rolled intermediate billet was 36mm.
The rolling speed of the finish rolling was 8m/s, and the thickness of the hot rolled sheet was 3mm.
The finish rolling temperature of the finish rolling was 880 ℃.
The cooling includes a first cooling and an air cooling, the end temperature of the first cooling is 470 ℃, and the cooling rate of the first cooling is 100 ℃/s.
The temperature of the winding was 440 ℃.
The elongation at flattening was 3.5%.
Example 2
Example 2 and example 1 were compared, and the difference between example 2 and example 1 is that:
the hot-rolled complex phase steel with high mechanical property comprises the following chemical components in percentage by mass: 0.11% of C, 0.5% of Si, 1.7% of Mn, 0.015% of P, 0.002% of S, 0.03% of Nb, 0.13% of Ti, 0.2% of Mo, 0.005% of N, 0.011% of RE, and the balance of Fe and unavoidable impurity elements.
The end temperature of the heating was 1230 ℃.
The end temperature of the rough rolling was 1060 ℃, and the thickness of the rough rolled intermediate billet was 34mm.
The rolling speed of the finish rolling was 6m/s, and the thickness of the hot rolled sheet was 4mm.
The finish rolling temperature of the finish rolling was 860 ℃.
The cooling includes a first cooling and an air cooling, the end temperature of the first cooling is 450 ℃, and the cooling rate of the first cooling is 110 ℃/s.
The temperature of the winding was 420 ℃.
The elongation at flattening was 4%.
Example 3
Example 3 was compared with example 1, and the difference between example 3 and example 1 was:
the end temperature of the heating was 1180 ℃.
The end temperature of the rough rolling was 1030 ℃.
The rolling speed of the finish rolling was 10m/s, and the thickness of the hot rolled sheet was 5mm.
The finish rolling temperature of the finish rolling was 900 ℃.
The cooling includes a first cooling and an air cooling, the end temperature of the first cooling being 430 ℃.
The temperature of the winding was 400 ℃.
The elongation at flattening was 3%.
Comparative example 1
Comparative example 1 was compared with example 1, and the difference between comparative example 1 and example 1 was that:
RE element is not added into the chemical components of the hot rolled complex phase steel.
Comparative example 2
Comparative example 2 and example 1 were compared, and the comparative example 2 and example 1 differ in that:
the end temperature of the heating was 1100 ℃.
The finishing temperature of the rough rolling was 1000℃and the finishing temperature of the rough rolling was 850 ℃.
The rolling speed of the finish rolling is 3m/s, and the thickness of the hot rolled plate is 1.8 mm-5 mm.
The finish rolling temperature of the finish rolling was 850 ℃.
The cooling includes a first cooling and an air cooling, the end temperature of the first cooling being 400 ℃.
The temperature of the winding was 350 ℃.
Comparative example 3
Comparative example 3 was compared with example 1, and the difference between comparative example 3 and example 1 was that:
the end temperature of the heating was 1250 ℃.
The finishing temperature of the rough rolling was 1100℃and the finishing temperature of the rough rolling was 950 ℃.
The rolling speed of the finish rolling was 15m/s, and the thickness of the hot rolled sheet was 6mm.
The finish rolling temperature of the finish rolling was 950 ℃.
The cooling includes a first cooling and an air cooling, the end temperature of the first cooling being 500 ℃.
The temperature of the winding was 500 ℃.
Related experiments:
the steel products obtained in examples 1-3 and comparative examples 1-3 were collected, respectively, and subjected to performance test, and the results are shown in Table 1.
Test method of related experiment:
tensile strength: the test was carried out in a Z1200 electronic tensile universal tester from ZWICK, germany, using the standard GBT 228.1-2021 Metal materials tensile test part 1: room temperature test method.
Hole expansion rate lambda: the test was carried out in a BUP400 sheet forming tester from ZWICK, germany, using the reaming test method of Standard ISO 16630-2003 Metal Material.
Elongation a80: the test was carried out in a Z1200 electronic tensile universal tester from ZWICK, germany, using the standard GBT 228.1-2021 Metal materials tensile test part 1: room temperature test method.
Bake hardening value: the test was carried out in a Z1200 electronic tensile universal tester from ZWICK company, germany, using the standard GBT 24174-2009 Steel bake hardening value (BH 2) determination method.
TABLE 1
| Group of | Tensile strength (MPa) | Hole expansion ratio lambda (%) | Elongation A80 (%) | Bake hardening value (MPa) |
| Example 1 | 805 | 65 | 13 | 75 |
| Example 2 | 812 | 71 | 12 | 68 |
| Example 3 | 835 | 75 | 14 | 75 |
| Comparative example 1 | 865 | 45 | 13 | 50 |
| Comparative example 2 | 765 | 60 | 13 | 50 |
| Comparative example 3 | 815 | 38 | 16 | 45 |
Specific analysis of table 1:
the tensile strength refers to the maximum stress value born by the material before breaking, and the larger the tensile strength is, the larger the maximum stress value born by the steel is, and further the mechanical property of the steel is good.
The hole expansion rate is an examination index of the flanging forming performance of the part, and the larger the hole expansion rate is, the better the flanging forming of the part is, and further the good mechanical property of the steel is shown.
The elongation is the percentage of the ratio of the total deformation of the gauge length after the tensile fracture of the sample to the original gauge length, and the larger the elongation is, the stronger the toughness of the metal is, namely the good mechanical property of the steel is.
The bake-hardening value is an index of the bake-hardening characteristics of the steel sheet, and is essentially an improvement value of the yield strength of the steel sheet after being deformed and baked, and the larger the bake-hardening value is, the more excellent the mechanical properties of the steel sheet under the high-temperature condition are.
From the data of examples 1-3, it can be seen that:
if the complex phase steel and the preparation method are adopted, the strength, the hardness, the extensibility, the hole expansibility and the like of the steel can be comprehensively improved by limiting the content of C, the content of Nb, the content of Ti, the content of Mo, the content of Mn, the content of S and the content of rare earth elements RE, so that the hot rolled complex phase steel with high mechanical property is obtained.
One or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:
(1) According to the hot-rolled complex phase steel provided by the embodiment of the application, the strength, hardness, extensibility, hole expansibility and the like of the steel can be comprehensively improved by limiting the content of C, the content of Nb, the content of Ti, the content of Mo, the content of Mn, the content of S and the content of rare earth elements RE, so that the hot-rolled complex phase steel with high mechanical property is obtained.
(2) The tensile strength of the hot-rolled complex phase steel provided by the embodiment of the application is more than or equal to 780MPa, the reaming ratio lambda is more than or equal to 55%, the elongation A80 is more than or equal to 12%, and the bake hardening value is more than or equal to 50MPa.
(3) According to the method provided by the embodiment of the application, the microstructure containing 'bainite + retained austenite + martensite' can be obtained by limiting the technological parameter conditions of rough rolling, finish rolling, cooling and coiling, so that the mechanical properties of the hot-rolled complex phase steel can be effectively improved.
It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, 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. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. The hot-rolled complex phase steel with high mechanical property is characterized by comprising the following chemical components in percentage by mass: 0.05 to 0.16 percent of C, 0.1 to 0.5 percent of Si, 1.0 to 2.0 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.003 percent of S, 0.01 to 0.06 percent of Nb, 0.05 to 0.15 percent of Ti, 0.1 to 0.3 percent of Mo, 0.003 to 0.008 percent of N, 0.001 to 0.015 percent of RE, and the balance of Fe and unavoidable impurity elements;
the metallographic structure of the hot-rolled complex phase steel comprises: 80-90% of bainite, 5-10% of residual austenite and 5-10% of martensite.
2. A method of producing hot rolled complex phase steel according to claim 1, characterized in that the method comprises:
obtaining molten steel after smelting;
pretreating the molten steel after smelting, and then carrying out converter smelting, external refining and continuous casting to obtain a plate blank;
heating the slab, and then performing rough rolling and finish rolling to obtain a hot rolled plate;
cooling, coiling and flattening the hot rolled plate to obtain hot rolled complex phase steel with high mechanical property;
the end temperature of the heating is 1180-1230 ℃;
the elongation of the leveling is 3% -4%.
3. The method of claim 2, wherein the rough rolling is terminated at a temperature of 1030 ℃ to 1080 ℃ and the rough rolled intermediate billet has a thickness of 38mm or less.
4. The method according to claim 2, wherein the finish rolling temperature of the finish rolling is 860 ℃ to 900 ℃, the rolling speed of the finish rolling is 5m/s to 10m/s, and the thickness of the hot rolled sheet is 1.8mm to 5mm.
5. The method according to claim 2, wherein the finish rolling has a finishing temperature of 880-900 ℃.
6. A method according to claim 3, wherein the cooling comprises a first cooling and an air cooling, the end temperature of the first cooling being 430 ℃ to 480 ℃, the cooling rate of the first cooling being greater than or equal to 80 ℃/s.
7. A method according to claim 3, wherein the temperature of the coiling is between 400 ℃ and 450 ℃.
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| CN103108971A (en) * | 2010-09-17 | 2013-05-15 | 杰富意钢铁株式会社 | High-strength hot-rolled steel sheet having superior fatigue resistance properties and method for producing same |
| CN103496294A (en) * | 2013-09-29 | 2014-01-08 | 首钢总公司 | Wheel rim for heavy-load truck and forming technology thereof |
| US20150000797A1 (en) * | 2012-07-10 | 2015-01-01 | Thyssenkrupp Steel Europe Ag | Cold-Rolled Flat Steel Product and Method for its Production |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103108971A (en) * | 2010-09-17 | 2013-05-15 | 杰富意钢铁株式会社 | High-strength hot-rolled steel sheet having superior fatigue resistance properties and method for producing same |
| US20150000797A1 (en) * | 2012-07-10 | 2015-01-01 | Thyssenkrupp Steel Europe Ag | Cold-Rolled Flat Steel Product and Method for its Production |
| CN103496294A (en) * | 2013-09-29 | 2014-01-08 | 首钢总公司 | Wheel rim for heavy-load truck and forming technology thereof |
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