CN114086080B - Dual-phase-isomerism light high-strength steel and preparation method thereof - Google Patents

Dual-phase-isomerism light high-strength steel and preparation method thereof Download PDF

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CN114086080B
CN114086080B CN202111369497.0A CN202111369497A CN114086080B CN 114086080 B CN114086080 B CN 114086080B CN 202111369497 A CN202111369497 A CN 202111369497A CN 114086080 B CN114086080 B CN 114086080B
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CN114086080A (en
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刘帅
刘焕优
***
冯运莉
钱立和
张福成
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North China University of Science and Technology
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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
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • 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
    • 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
    • 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
    • C21D8/0236—Cold rolling
    • 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
    • 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
    • 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
    • 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
    • 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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Abstract

The invention discloses dual-phase-isomerism light high-strength steel and a preparation method thereof, and belongs to the technical field of light high-strength automobile steel. The chemical components are as follows: 0.1-0.3wt.% of C, 10-14wt.% of Mn, 6-8wt.% of Al, 0.5-0.7wt.% of Si, less than or equal to 0.01wt.% of P, less than or equal to 0.005wt.% of S, and the balance of Fe and inevitable impurities. The cast structure of the dual-phase isomerism lightweight high-strength steel is a complex phase structure containing coarse fishbone delta ferrite and coarse granular austenite, and the structure of the prepared finished product dual-phase isomerism lightweight high-strength steel plate is strip delta ferrite and fine equiaxed austenite. The finished product of the dual-phase heterogeneous light high-strength steel plate has the yield strength of 388-807MPa, the tensile strength of 656-945MPa, the elongation of 33-55 percent, the product of strength and elongation of 31-38GPa percent, and the density of 6.9-7.1g/cm 3 。

Description

Dual-phase-isomerism light high-strength steel and preparation method thereof
Technical Field
The invention belongs to the technical field of light-weight high-strength automobile steel, and relates to dual-phase-structure light-weight high-strength steel and a preparation method thereof.
Background
In recent decades, the automobile industry has been rapidly developed and the automobile has been kept in an increasing state. But the problems of fuel shortage, automobile environmental pollution and the like are increasingly serious, and energy conservation and environmental protection become a new direction for the development of the automobile industry.
The light weight design of the automobile can reduce the self weight of the automobile body on the premise of ensuring the safety of the automobile, improve the fuel economy of the automobile and reduce the carbon emission, and is an effective way for solving the problems.
Currently, there are two main approaches to achieving light weight: firstly, the strength of the automobile steel is further improved, and the steel consumption is reduced while the mechanical property requirement of parts is ensured; another approach is to use lightweight materials such as low density aluminum, magnesium alloys, engineering plastics or carbon fiber composites, etc. However, the aforementioned materials often have the disadvantages of low strength, high preparation cost, poor thermal stability, etc., which limits the application and development of these light materials in the automobile industry.
Researches find that a certain amount of light Al element is added into steel, and the developed Fe-Mn-Al-C series low-density steel has higher strength and toughness and good fatigue resistance and oxidation resistance, and is novel automobile steel with great potential. However, the low-density steel of Fe-Mn-Al-C series developed at present often has the problems of low product of strength and elongation, high cost, complex processing and preparation process and the like, and can not meet the application requirements of light high-strength steel for automobiles.
For example: chinese patent CN113278896A discloses Fe-Mn-Al-C series high-strength low-density steel and a preparation method thereof. The patent focuses on that the chemical components of the steel are as follows: 1.0 to 2.0 percent of C, 20 to 40 percent of Mn, 10 to 14 percent of Al, more than or equal to 2 percent and less than or equal to 15 percent of Ni and Cr, and the balance of Fe, an austenite structure containing a large amount of DO3 precipitated phase is obtained through forging and hot rolling treatment, and under the second phase strengthening action, although relatively superior mechanical properties can be obtained, the defects are that the production cost is higher due to the large addition of Cr and Ni elements, and the welding performance of steel is poor due to the C content exceeding 1.0 percent. And the product of strength and elongation of the prepared high-strength low-density steel can be seen from the table 2, and the maximum product of strength and elongation is 19.5GPa%, which is far smaller than the requirement of light-weight high-strength steel for automobiles.
Chinese patent CN111235484A discloses high-strength high-hardness low-density steel and a preparation method and application thereof. The patent focuses on improving the strength and hardness of steel materials through smelting, hot forging, water toughening, hot rolling, solid solution, cold rolling, aging, nitriding and nitrogen annealing treatment processes in sequence, but does not improve the product of strength and elongation and reduce the content of C, and the steel becomes brittle and hard due to the over-high content of manganese, and the rust resistance and weldability of the steel are reduced. In addition, the prepared high-strength high-hardness low-density steel has the defects that the whole process is complex, and the nitriding and denitrating processes have high requirements on production equipment and are not favorable for production.
In summary, although more technical achievements are achieved in the technical field of high-strength lightweight steel, the high-strength lightweight steel developed at present still has the technical problems that the cost is high due to the addition of a large amount of alloy, the welding performance of the steel is poor due to the high C equivalent, the rust resistance and the weldability are reduced due to the embrittlement and hardening of the steel due to the high manganese content, the preparation process is complicated, and the industrial large-scale production and popularization are not facilitated.
Disclosure of Invention
The invention solves the technical problems that in the prior art, the addition cost of alloy elements in the light high-strength steel for the automobile is high, the preparation process is complex, the operation difficulty is high, the added alloy elements can deteriorate the strength and toughness, the weldability, the density and the rust resistance of the light high-strength steel for the automobile, and the industrial production is not facilitated.
In order to solve the technical problems, the invention provides the following technical scheme:
the dual-phase isomeric light high-strength steel comprises the following chemical components in percentage by mass: 0.1-0.3wt.% of C, 10-14wt.% of Mn, 6-8wt.% of Al, 0.5-0.7wt.% of Si, less than or equal to 0.01wt.% of P, less than or equal to 0.005wt.% of S, and the balance of Fe and inevitable impurities.
Preferably, the as-cast structure of the dual-phase heterogeneous lightweight high-strength steel is a complex phase structure comprising coarse fishbone-shaped delta ferrite and coarse granular austenite, and the structure of the finished dual-phase heterogeneous lightweight high-strength steel plate is strip-shaped delta ferrite and fine equiaxed austenite.
Preferably, the yield strength of the finished product of the dual-phase heterogeneous light high-strength steel plate is 388-807MPa, the tensile strength is 656-945MPa, the elongation is 33-55%, the product of strength and elongation is 31-38GPa%, and the density is 6.9-7.1g/cm 3 。
The preparation method of the dual-phase heterogeneous light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum melting under the protection of argon, and then casting the molten steel into ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, and then hot forging the homogenized cast ingot into a square billet;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature, performing multi-pass rolling by using a rolling mill to obtain a hot rolled steel plate with the thickness of 5-7mm, and air-cooling to room temperature after hot rolling;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out multi-pass rolling and 1-pass flat rolling by using a cold rolling mill to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), quickly quenching the cold-rolled steel plate into water after annealing, and cooling to room temperature to obtain the finished product of the dual-phase-structure light-weight high-strength steel plate.
Preferably, the temperature of the homogenization treatment in the step S2 is 1200 +/-30 ℃, the heat preservation time is 3-5h, and the forging temperature is 900-1150 ℃.
Preferably, the hot rolling temperature in the step S3 is 1200 +/-30 ℃, and the heat preservation time is 0.3-0.7h; the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃.
Preferably, the multi-pass rolling in the step S3 is 4-6 passes, and the rolling reduction is 55-65%.
Preferably, the multi-pass rolling in the step S4 is 8-10 passes, and the rolling reduction is 45-55%.
Preferably, the annealing temperature in the step S5 is 660-1000 ℃, and the heat preservation time is 25-35min.
Preferably, the cold rolling mill in step S4 is a four-roll cold rolling mill.
The technical scheme provided by the embodiment of the invention at least has the following beneficial effects:
in the scheme, compared with the high-strength light steel in the prior art: from the aspect of components, the content of the C element is greatly reduced, and the weldability of the material is improved; the addition of a proper amount of Si element plays roles in solid solution strengthening and carbide precipitation inhibition; the addition of a large amount of Al element not only plays a role in reducing the density of steel, but also plays a role in improving corrosion resistance and simultaneously promoting the preservation of high-temperature delta ferrite to a room-temperature structure.
According to the invention, less Mn element and more Al element are added in the component design of the dual-phase isomerization light-weight high-strength steel ingot, the formation of high-temperature delta ferrite is promoted and the high-temperature delta ferrite is kept to the room temperature, the as-cast structure contains a complex phase structure of coarse fishbone delta ferrite and coarse granular austenite, and then the homogenization treatment, hot forging, hot rolling, cold rolling and annealing treatment are carried out to obtain the finished steel with strip delta ferrite and fine equiaxed austenite structure, so that the density of the steel can be effectively reduced, the product of strength and elongation can be improved, and the light weight can be realized.
In the process of tensile test, the finished steel product of the invention promotes the transfer of strain in two phases due to the existence of two isomeric structures with different forms and performances, forms a strain hardening effect induced by metamorphism, delays the occurrence of plastic instability, and ensures that the yield strength of the novel high-strength light steel is 388-807MPa, the tensile strength is 656-945MPa, the elongation is 33-55%, the product of strength and elongation is 31-38GPa%, and the density is 6.9-7.1g/cm 3 The steel meets the performance requirements of third-generation automobile steel, and has higher practical application value than common third-generation automobile steel.
The preparation process of the finished steel product is simple and economical, and large-scale industrial production can be realized by depending on the existing production line. The research, development and application of the finished steel product have important economic value and social significance for promoting the lightweight design of automobiles, reducing energy consumption and reducing greenhouse gas emission.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a metallographic picture of a dual phase structure light weight high strength steel according to example 1 of the present invention;
FIG. 2 is a metallographic picture of a dual phase isomeric light weight high strength steel according to example 2 of the present invention;
FIG. 3 is an EBSD map of a dual phase isomeric light weight high strength steel of example 2 of the present invention;
FIG. 4 is a metallographic picture of a dual-phase isomeric light high strength steel according to example 3 of the present invention;
fig. 5 is an engineering stress-strain curve of the bi-phase-structure light weight high strength steel of examples 1 to 6 of the present invention, which is uniaxially stretched at room temperature, wherein: mark 1 is the tensile curve of the finished dual phase isomerized light weight and high strength steel sheet of example 1, mark 2 is the tensile curve of the finished dual phase isomerized light weight and high strength steel sheet of example 2, mark 3 is the tensile curve of the finished dual phase isomerized light weight and high strength steel sheet of example 3, mark 4 is the tensile curve of the finished dual phase isomerized light weight and high strength steel sheet of example 4, mark 5 is the tensile curve of the finished dual phase isomerized light weight and high strength steel sheet of example 5, and mark 6 is the tensile curve of the finished dual phase isomerized light weight and high strength steel sheet of example 6.
Detailed Description
To make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
Example 1
The dual-phase isomeric light high-strength steel comprises the following chemical components in percentage by mass: c0.14 wt.%, mn 13.9wt.%, al 6.1wt.%, si 0.68wt.%, P ≦ 0.01wt.%, S ≦ 0.005wt.%, and the balance Fe and unavoidable impurities.
The preparation method of the dual-phase isomeric light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum smelting under the protection of argon, and then casting the smelted molten steel into cast ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, wherein the temperature of the homogenizing treatment is 1200 +/-30 ℃, and the heat preservation time is 3-5h; then hot forging the homogenized cast ingot into a square billet at the forging temperature of 900-1150 ℃;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature of 1200 +/-30 ℃ and keeping the temperature for 0.3-0.7h; rolling by a rolling mill for 4-6 times with rolling amount of 55-65% to obtain a hot rolled steel plate with thickness of 5-7mm, air-cooling to room temperature after hot rolling, wherein the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out 8-10-pass rolling and 1-pass flat rolling by using a cold rolling mill, wherein the rolling reduction is 45-55%, so as to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), wherein the annealing temperature is 660 ℃, the heat preservation time is 25min, and the cold-rolled steel plate is quickly quenched into water after annealing and cooled to room temperature to obtain the finished product of the dual-phase heterogeneous light high-strength steel plate.
As shown in fig. 1, the structure of the finished dual-phase heterogeneous lightweight high-strength steel sheet is strip-shaped δ ferrite and fine equiaxed austenite.
The tensile properties of the dual-phase heterogeneous lightweight high-strength steel prepared in this example were tested. According to GBT228-2002 and a metal material room temperature tensile test method, the finished product of the dual-phase heterogeneous light high-strength steel plate is processed into a standard tensile sample, and the tensile rate is 0.05mm/s. The tensile properties thus measured are shown in Table 1, and the engineering stress strain curve is shown in FIG. 5. The high-strength lightweight steel prepared in example 1 had a yield strength of 807MPa, a tensile strength of 945MPa, a total elongation of 32.5%, a product of strength and elongation of 30.6GPa%, and a density of 7.08g/cm 3 And the strength and elongation product level of the current advanced high-strength automobile steel is achieved.
Example 2
The dual-phase heterogeneous light high-strength steel comprises the following chemical components in percentage by mass: 0.22wt.% of C, 12.1wt.% of Mn, 7.2wt.% of Al, 0.63wt.% of Si, less than or equal to 0.01wt.% of P, less than or equal to 0.005wt.% of S, and the balance of Fe and inevitable impurities.
The preparation method of the dual-phase isomeric light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum smelting under the protection of argon, and then casting the smelted molten steel into cast ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, wherein the temperature of the homogenizing treatment is 1200 +/-30 ℃, and the heat preservation time is 3-5h; then hot forging the cast ingot subjected to the homogenization treatment into a square billet at the forging temperature of 900-1150 ℃;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature of 1200 +/-30 ℃ and keeping the temperature for 0.3-0.7h; rolling by a rolling mill for 4-6 times with rolling amount of 55-65% to obtain a hot rolled steel plate with thickness of 5-7mm, air-cooling to room temperature after hot rolling, wherein the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out 8-10-pass rolling and 1-pass flat rolling by using a cold rolling mill, wherein the rolling amount is 45-55%, so as to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), wherein the annealing temperature is 800 ℃, the heat preservation time is 30min, and the cold-rolled steel plate is quickly quenched into water after annealing and cooled to room temperature to obtain the finished product of the dual-phase heterogeneous light high-strength steel plate.
As shown in fig. 2 and 3, the structure of the finished dual-phase heterogeneous lightweight high-strength steel sheet is strip-shaped δ ferrite and fine equiaxed austenite, and the strip-shaped δ ferrite and the fine equiaxed austenite are greatly different in phase morphology and size.
The tensile properties of the dual-phase heterogeneous lightweight high-strength steel prepared in this example were tested. According to GBT228-2002 and a metal material room temperature tensile test method, the finished product of the dual-phase heterogeneous light high-strength steel plate is processed into a standard tensile sample, and the tensile rate is 0.05mm/s. The tensile properties thus measured are shown in Table 1, and the engineering stress strain curve is shown in FIG. 5. Is composed of a fruitThe high-strength light steel prepared in example 1 has a yield strength of 449MPa, a tensile strength of 720MPa, a total elongation of 52.3%, a product of strength and elongation of 37.6GPa%, and a density of 6.97g/cm 3 And the strength and elongation product level of the current advanced high-strength automobile steel is achieved.
Example 3
The dual-phase heterogeneous light high-strength steel comprises the following chemical components in percentage by mass: 0.28wt.% of C, 10.1wt.% of Mn, 8.1wt.% of Al, 0.55wt.% of Si, less than or equal to 0.01wt.% of P, less than or equal to 0.005wt.% of S, and the balance of Fe and inevitable impurities.
The preparation method of the dual-phase isomeric light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum melting under the protection of argon, and then casting the molten steel into ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, wherein the temperature of the homogenizing treatment is 1200 +/-30 ℃, and the heat preservation time is 3-5h; then hot forging the homogenized cast ingot into a square billet at the forging temperature of 900-1150 ℃;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature of 1200 +/-30 ℃ and keeping the temperature for 0.3-0.7h; rolling by a rolling mill for 4-6 times, wherein the rolling amount is 55-65%, so as to obtain a hot rolled steel plate with the thickness of 5-7mm, air-cooling to room temperature after hot rolling, wherein the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out 8-10-pass rolling and 1-pass flat rolling by using a cold rolling mill, wherein the rolling reduction is 45-55%, so as to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), wherein the annealing temperature is 1000 ℃, the heat preservation time is 35min, and the cold-rolled steel plate is quickly quenched into water after annealing and cooled to room temperature to obtain the finished product of the dual-phase heterogeneous light high-strength steel plate.
As shown in fig. 4, the microstructure of the finished dual-phase heterogeneous lightweight high-strength steel plate is strip-shaped delta ferrite and fine equiaxed austenite; and, as compared with examples 1 and 2, it is understood that the ferrite and austenite sizes are gradually increased as the annealing temperature is increased, but the structure of the dual phase structure is maintained.
The tensile properties of the dual-phase heterogeneous lightweight high-strength steel prepared in this example were tested. According to GBT228-2002 and a metal material room temperature tensile test method, the finished product of the dual-phase heterogeneous light high-strength steel plate is processed into a standard tensile sample, and the tensile rate is 0.05mm/s. The tensile properties thus measured are shown in Table 1, and the engineering stress strain curve is shown in FIG. 5. The high-strength lightweight steel prepared in example 1 had a yield strength of 388MPa, a tensile strength of 656MPa, a total elongation of 54.6%, a product of strength and elongation of 35.6GPa%, and a density of 6.9g/cm 3 And the product level of strength and elongation of the current advanced high-strength automobile steel is achieved.
Example 4
The dual-phase heterogeneous light high-strength steel comprises the following chemical components in percentage by mass: c0.12 wt.%, mn 13.5wt.%, al 6.1wt.%, si 0.69wt.%, P ≤ 0.01wt.%, S ≤ 0.005wt.%, and the balance Fe and inevitable impurities.
The preparation method of the dual-phase heterogeneous light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum melting under the protection of argon, and then casting the molten steel into ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, wherein the temperature of the homogenizing treatment is 1200 +/-30 ℃, and the heat preservation time is 3-5h; then hot forging the homogenized cast ingot into a square billet at the forging temperature of 900-1150 ℃;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature of 1200 +/-30 ℃, and keeping the temperature for 0.3-0.7h; rolling by a rolling mill for 4-6 times with rolling amount of 55-65% to obtain a hot rolled steel plate with thickness of 5-7mm, air-cooling to room temperature after hot rolling, wherein the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out 8-10-pass rolling and 1-pass flat rolling by using a cold rolling mill, wherein the rolling amount is 45-55%, so as to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), wherein the annealing temperature is 700 ℃, the heat preservation time is 25min, and the cold-rolled steel plate is quickly quenched into water after annealing and cooled to room temperature to obtain a finished product of the dual-phase heterogeneous light high-strength steel plate.
The tissue structure of the finished product of the dual-phase heterogeneous light high-strength steel plate is strip delta ferrite and fine equiaxed austenite.
The tensile properties of the dual-phase heterogeneous lightweight high-strength steel prepared in this example were tested. According to GBT228-2002 and a metal material room temperature tensile test method, the finished product of the dual-phase heterogeneous light high-strength steel plate is processed into a standard tensile sample, and the tensile rate is 0.05mm/s. The tensile properties thus measured are shown in Table 1, and the engineering stress-strain curves are shown in FIG. 5. The high-strength lightweight steel prepared in example 4 had a tensile strength of 857MPa, an elongation of 35.7%, a product of strength and elongation of 30.6GPa%, and a density of 7.08g/cm 3 And the product level of strength and elongation of the current advanced high-strength automobile steel is achieved.
Example 5
The dual-phase heterogeneous light high-strength steel comprises the following chemical components in percentage by mass: 0.24wt.% of C, 12.7wt.% of Mn, 6.8wt.% of Al, 0.61wt.% of Si, less than or equal to 0.01wt.% of P, less than or equal to 0.005wt.% of S, and the balance of Fe and inevitable impurities.
The preparation method of the dual-phase heterogeneous light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum melting under the protection of argon, and then casting the molten steel into ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, wherein the temperature of the homogenizing treatment is 1200 +/-30 ℃, and the heat preservation time is 3-5h; then hot forging the homogenized cast ingot into a square billet at the forging temperature of 900-1150 ℃;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature of 1200 +/-30 ℃ and keeping the temperature for 0.3-0.7h; rolling by a rolling mill for 4-6 times with rolling amount of 55-65% to obtain a hot rolled steel plate with thickness of 5-7mm, air-cooling to room temperature after hot rolling, wherein the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out 8-10-pass rolling and 1-pass flat rolling by using a cold rolling mill, wherein the rolling amount is 45-55%, so as to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), wherein the annealing temperature is 750 ℃, the heat preservation time is 30min, and the cold-rolled steel plate is quickly quenched into water after annealing and cooled to room temperature to obtain a finished product of the dual-phase heterogeneous light high-strength steel plate.
The tissue structure of the finished product of the dual-phase heterogeneous light high-strength steel plate is strip-shaped delta ferrite and fine equiaxed austenite.
The tensile properties of the dual-phase heterogeneous lightweight high-strength steel prepared in this example were tested. According to GBT228-2002 and a metal material room temperature tensile test method, the finished product of the dual-phase heterogeneous light high-strength steel plate is processed into a standard tensile sample, and the tensile rate is 0.05mm/s. The tensile properties thus measured are shown in Table 1, and the engineering stress strain curve is shown in FIG. 5. The high-strength lightweight steel prepared in example 5 had a tensile strength of 771MPa, an elongation of 45.6%, a product of strength and elongation of 35.1GPa%, and a density of 7g/cm 3 And the strength and elongation product level of the current advanced high-strength automobile steel is achieved.
Example 6
The dual-phase heterogeneous light high-strength steel comprises the following chemical components in percentage by mass: c0.26 wt.%, mn 11.1wt.%, al 7.8wt.%, si 0.51wt.%, P ≦ 0.01wt.%, S ≦ 0.005wt.%, and the balance Fe and unavoidable impurities.
The preparation method of the dual-phase heterogeneous light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum melting under the protection of argon, and then casting the molten steel into ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, wherein the temperature of the homogenizing treatment is 1200 +/-30 ℃, and the heat preservation time is 3-5h; then hot forging the homogenized cast ingot into a square billet at the forging temperature of 900-1150 ℃;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature of 1200 +/-30 ℃, and keeping the temperature for 0.3-0.7h; rolling by a rolling mill for 4-6 times with rolling amount of 55-65% to obtain a hot rolled steel plate with thickness of 5-7mm, air-cooling to room temperature after hot rolling, wherein the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out 8-10-pass rolling and 1-pass flat rolling by using a cold rolling mill, wherein the rolling reduction is 45-55%, so as to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), wherein the annealing temperature is 900 ℃, the heat preservation time is 35min, and the cold-rolled steel plate is quickly quenched into water after annealing and cooled to room temperature to obtain the finished product of the dual-phase heterogeneous light high-strength steel plate.
The tissue structure of the finished product of the dual-phase heterogeneous light high-strength steel plate is strip-shaped delta ferrite and fine equiaxed austenite.
The tensile properties of the dual-phase heterogeneous lightweight high-strength steel prepared in this example were tested. According to GBT228-2002, a metal material room temperature tensile test method processes a finished product dual-phase heterogeneous light high-strength steel plate into a standardThe specimen was quasi-drawn at a drawing rate of 0.05mm/s. The tensile properties thus measured are shown in Table 1, and the engineering stress-strain curves are shown in FIG. 5. The high-strength lightweight steel prepared in example 6 had a tensile strength of 682MPa, an elongation of 51.9%, a product of strength and elongation of 35.4GPa, and a density of 6.9g/cm 3 And the product level of strength and elongation of the current advanced high-strength automobile steel is achieved.
Table 1 mechanical property data of the finished steel sheets obtained in each example
Figure BDA0003355658140000111
In the above scheme, compared with the high-strength light steel in the prior art: from the aspect of components, the content of the element C is greatly reduced, and the weldability of the material is improved; the addition of a proper amount of Si element plays a role in solid solution strengthening and carbide precipitation inhibition; the addition of a large amount of Al element not only plays a role in reducing the density of steel, but also plays a role in improving corrosion resistance and simultaneously promoting the preservation of high-temperature delta ferrite to a room-temperature structure.
The dual-phase isomeric light high-strength steel ingot is added with less Mn element and more Al element in the composition design, the formation of high-temperature delta ferrite is promoted and the high-temperature delta ferrite is kept to room temperature, the as-cast structure comprises a complex phase structure of coarse fishbone delta ferrite and coarse granular austenite, and then the complex phase structure is subjected to homogenization treatment, hot forging, hot rolling, cold rolling and annealing treatment to obtain a finished product steel with strip delta ferrite and fine equiaxed austenite structure, so that the density of the steel can be effectively reduced, the product of strength and elongation is improved, and the light weight is realized.
In the process of tensile test, the finished steel product of the invention promotes the transfer of strain in two phases due to the existence of two isomeric structures with different forms and performances, forms a strain hardening effect induced by metamorphism, delays the appearance of plastic instability, and ensures that the yield strength of the novel high-strength light steel is 388-807MPa, the tensile strength is 656-945MPa, the elongation is 33-55%, the product of strength and elongation is 31-38GPa%, and the density is 6.9-7.2g/cm 3 Meets the performance requirements of third-generation automobile steel, and has higher practical application value than common third-generation automobile steel。
The preparation process of the finished steel product is simple and economic, and large-scale industrial production can be realized by depending on the existing production line. The research, development and application of the finished steel product have important economic value and social significance for promoting the lightweight design of automobiles, reducing energy consumption and reducing greenhouse gas emission.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (6)

1. The dual-phase-structure light-weight high-strength steel is characterized by comprising the following chemical components in percentage by mass: 0.1-0.3wt.% of C, 12.1-14wt.% of Mn, 7.2-8wt.% of Al, 0.5-0.7wt.% of Si, less than or equal to 0.01wt.% of P, less than or equal to 0.005wt.% of S, and the balance of Fe and inevitable impurities;
the preparation method of the dual-phase heterogeneous light high-strength steel comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum smelting under the protection of argon, and then casting the smelted molten steel into cast ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, and then hot forging the homogenized cast ingot into a square billet;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature, performing multi-pass rolling by using a rolling mill to obtain a hot rolled steel plate with the thickness of 5-7mm, and air-cooling to room temperature after hot rolling;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out multi-pass rolling and 1-pass flat rolling by using a cold rolling mill to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: annealing the cold-rolled steel plate obtained in the step S4, quickly quenching the cold-rolled steel plate into water after annealing, and cooling to room temperature to obtain a finished dual-phase heterogeneous light high-strength steel plate;
the multi-pass rolling in the step S3 is 4-6 passes of rolling, and the rolling reduction is 55-65%;
the multi-pass rolling in the step S4 is 8-10 passes of rolling, and the rolling reduction is 45-55%;
the cast structure of the dual-phase heterogeneous light high-strength steel is a complex phase structure containing coarse fishbone delta ferrite and coarse granular austenite, and the structure of the prepared finished dual-phase heterogeneous light high-strength steel plate is strip delta ferrite and fine equiaxed austenite;
the finished product of the dual-phase heterogeneous light high-strength steel plate has the yield strength of 388-807MPa, the tensile strength of 656-945MPa, the elongation of 33-55 percent, the product of strength and elongation of 31-38GPa percent, and the density of 6.9-7.1g/cm 3 。
2. The method for preparing the dual-phase-structure light-weight high-strength steel according to claim 1, wherein the method comprises the following steps:
s1, selecting raw materials: weighing Fe, mn, C, al and Si powder with the purity of more than or equal to 99.9 percent as alloy raw materials according to the chemical component proportion of the dual-phase heterogeneous light high-strength steel, putting the alloy raw materials into an electromagnetic induction furnace, carrying out vacuum melting under the protection of argon, and then casting the molten steel into ingots;
s2, hot forging after homogenization treatment: homogenizing the cast ingot in the step S1, and then hot forging the homogenized cast ingot into a square billet;
s3, hot rolling: reheating the square billet in the step S2 to a hot rolling temperature, performing multi-pass rolling by using a rolling mill to obtain a hot rolled steel plate with the thickness of 5-7mm, and air-cooling to room temperature after hot rolling;
s4, cold rolling after acid pickling: pickling the hot rolled steel plate obtained in the step S3, and then carrying out multi-pass rolling and 1-pass flat rolling by using a cold rolling mill to obtain a cold rolled steel plate with the thickness of 3-4 mm;
s5, annealing treatment: and (5) annealing the cold-rolled steel plate obtained in the step (S4), quickly quenching the cold-rolled steel plate into water after annealing, and cooling to room temperature to obtain the finished product of the dual-phase-structure light-weight high-strength steel plate.
3. The method for preparing dual-phase-structure light-weight high-strength steel according to claim 2, wherein the homogenization treatment in the step S2 is carried out at 1200 +/-30 ℃, the holding time is 3-5h, and the forging temperature is 900-1150 ℃.
4. The method for preparing the dual-phase-structure light-weight high-strength steel according to claim 2, wherein the hot rolling temperature in the step S3 is 1200 +/-30 ℃, and the holding time is 0.3-0.7h; the initial rolling temperature is 1150 +/-20 ℃, and the final rolling temperature is higher than 900 ℃.
5. The method for preparing the dual-phase heterogeneous light weight and high strength steel according to claim 2, wherein the annealing temperature in the step S5 is 660-1000 ℃, and the holding time is 25-35min.
6. The method for preparing the dual-phase heterogeneous light weight and high strength steel according to claim 2, wherein the cold rolling mill in the step S4 is a four-roll cold rolling mill.
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