CN115612928B - High-strength steel based on CSP process and manufacturing method thereof - Google Patents
High-strength steel based on CSP process and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 59
- 239000010959 steel Substances 0.000 title claims abstract description 59
- 230000008569 process Effects 0.000 title claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 238000003672 processing method Methods 0.000 title description 3
- 238000001816 cooling Methods 0.000 claims abstract description 36
- 238000005096 rolling process Methods 0.000 claims abstract description 35
- 238000000034 method Methods 0.000 claims abstract description 33
- 238000009749 continuous casting Methods 0.000 claims abstract description 16
- 238000005266 casting Methods 0.000 claims abstract description 15
- 238000002791 soaking Methods 0.000 claims abstract description 7
- 239000000126 substance Substances 0.000 claims abstract description 5
- 238000003723 Smelting Methods 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 238000007670 refining Methods 0.000 claims abstract description 4
- 229910001566 austenite Inorganic materials 0.000 claims description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims description 18
- 229910001563 bainite Inorganic materials 0.000 claims description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 3
- 230000009467 reduction Effects 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- 238000005516 engineering process Methods 0.000 abstract description 6
- 238000005098 hot rolling Methods 0.000 abstract description 6
- 229910000885 Dual-phase steel Inorganic materials 0.000 abstract description 5
- 238000005097 cold rolling Methods 0.000 abstract description 5
- 238000005336 cracking Methods 0.000 abstract description 3
- 238000004080 punching Methods 0.000 abstract 1
- 239000000463 material Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 11
- 239000011572 manganese Substances 0.000 description 8
- 229910000734 martensite Inorganic materials 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 6
- 229910052748 manganese Inorganic materials 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000000717 retained effect Effects 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 229910001208 Crucible steel Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
Classifications
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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
-
- 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
-
- 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
- C21D8/0247—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
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
The invention discloses a high-strength steel based on CSP technology and a manufacturing method thereof, wherein the high-strength steel comprises the following chemical components in percentage by mass: 0.14 to 0.18 percent, si:0.7 to 0.9 percent, mn:2.0 to 2.5 percent, als is 0.02 to 0.05 percent, P: less than or equal to 0.02 percent, S: less than or equal to 0.008 percent, N: less than or equal to 0.008 percent, and the balance of Fe and other unavoidable impurities. The yield strength of the high-strength steel is 450-540 Mpa, the tensile strength is 780-880 Mpa, the reaming ratio is more than or equal to 32%, and the elongation is more than or equal to 20%. The manufacturing method comprises the following steps: smelting, refining, continuous casting of sheet billet, soaking of casting blank, rolling, laminar cooling, coiling and flattening. The reaming performance and the elongation of the high-strength steel are superior to those of the dual-phase steel with the same level, and the punching cracking is effectively reduced. The CSP process is adopted in the manufacturing process, and compared with the conventional hot rolling and cold rolling, the production cost is reduced.
Description
Technical Field
The invention relates to the field of steel material high-strength steel production, in particular to a CSP (cast steel plate) process-based high-strength steel and a manufacturing method thereof.
Background
In recent years, development of the automotive industry requires weight saving and high reinforcement of automotive materials. High-strength steel is widely used for automobile structural members, in which dual-phase steel is widely used, but as strength increases, plasticity and workability of dual-phase steel deteriorate, and particularly flange flanging property, bending property and the like are impaired due to local elongation. In order to solve the problem, high-strength steel reinforced by adopting a transformation induced plasticity effect attracts wide attention, the retained austenite in the steel induces martensite transformation under plastic deformation, and a transformation strengthening and plasticity growth mechanism is introduced, so that better unification of strength and plasticity is realized.
In recent decades, the sheet bar continuous casting and rolling technology has made great progress and has been widely popularized and applied. The sheet bar continuous casting and rolling process can directly roll and produce the sheet steel with the thickness of 0.8-2.0 mm, and some high-strength steel which is originally produced by using the conventional hot rolling and cold rolling processes can be replaced by the sheet steel directly rolled by the continuous casting and rolling process. Compared with cold rolling and conventional hot rolling, the sheet billet continuous casting and rolling process effectively shortens the process flow and greatly reduces the energy consumption. At present, thin slab continuous casting and rolling technologies which are put into industrial production comprise CSP technology, TFSR technology, ISP technology and the like.
Chinese patent CN107829027B discloses 780 Mpa-level dual-phase steel based on CSP process and processing method thereof, comprising the following chemical elements in weight percentage: 0.05 to 0.08 percent of C, 0.60 to 1.00 percent of Si, 1.40 to 1.80 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.004 percent of S, 0.30 to 0.70 percent of Cr, 0.020 to 0.060 percent of Als, and the balance of iron and unavoidable impurities. The structure is composed of 60-70% ferrite and 30-40% martensite. Because of the large difference between the structure and the mechanical properties of ferrite and martensite, the risk of cracking during stamping is large compared with the high-strength steel with a bainite matrix.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide high-strength steel for automobile structural parts, which has low cost, the yield strength of 450MPa or more and the tensile strength of 780MPa or more, and a manufacturing method thereof. The CSP process is adopted in the manufacturing process, and compared with the conventional hot rolling and cold rolling, the production cost is reduced.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
on one hand, the invention provides high-strength steel based on a CSP process, wherein the high-strength steel comprises the following chemical components in percentage by mass: 0.14 to 0.18 percent, si:0.7 to 0.9 percent, mn:2.0 to 2.5 percent, als is 0.02 to 0.05 percent, P: less than or equal to 0.02 percent, S: less than or equal to 0.008 percent, N: less than or equal to 0.008 percent, and the balance of Fe and other unavoidable impurities.
Preferably, the yield strength of the high-strength steel is 450-540 Mpa, the tensile strength is 780-880 Mpa, the reaming ratio is more than or equal to 32%, and the elongation is more than or equal to 20%.
Preferably, the structure of the high-strength steel includes: ferrite with the content of 0-10%, residual austenite with the content of 5-8%, and carbide-free bainite with the rest.
In another aspect, the present invention provides a method of preparing high strength steel comprising: smelting, refining, continuous casting of sheet billet, soaking of casting blank, rolling, laminar cooling, coiling and flattening.
Preferably, in the sheet bar continuous casting step, the superheat degree of the ladle molten steel is 15-30 ℃; the thickness of the casting blank is 70-75 mm, and the pulling speed is 4.0-4.8 m/s.
Preferably, the cast blank of the thin slab continuous casting is subjected to descaling treatment before being put into the furnace, and the descaling pressure is 15-30 bar.
Preferably, in the casting blank soaking step, the casting blank is fed into the furnace at a temperature of 820-1050 ℃ and is discharged at a temperature of 1190-1240 ℃.
Preferably, in the rolling step, the rolling pass reduction is distributed as: 50-60% of the first pass, 40-50% of the second pass and 8-12% of the last pass; controlling the rolling speed to be 7-12 m/s; the final rolling temperature is 840-880 ℃; the descaling process in the rolling process adopts high-pressure water to remove scales before entering the rolling mill, and the descaling water pressure is 200-380 bar.
Preferably, the laminar cooling includes two cooling modes, one of which is: the strip steel is directly and rapidly cooled to a target coiling temperature after being discharged from a rolling mill, and the cooling rate of rapid cooling is not less than 40 ℃/s; the second mode is as follows: after the strip steel leaves the rolling mill, air cooling is carried out for no more than 3s, the temperature is reduced to a two-phase region, a small amount of ferrite is generated, then the strip steel is rapidly cooled to a target coiling temperature, and the cooling rate of the rapid cooling is not less than 40 ℃/s.
Preferably, the coiling temperature is 420-460 ℃; flattening the steel coil after the temperature of the steel coil is reduced to below 50 ℃, wherein the flattening force is controlled to be 160-200 tons; removing iron oxide scale by acid washing; the thickness of the obtained product is 1.0-2.0 mm.
Compared with the prior art, the invention has the following advantages:
the composition design of the invention adopts low alloy and low cost design, and the content of main alloy elements is controlled as follows:
action of C: carbon is the most basic strengthening element in steel and also an austenite stabilizing element; the higher carbon content in the austenite is beneficial to improving the quantity and stability of the residual austenite, thereby improving the mechanical property of the material; higher carbon content reduces the weldability of the steel; therefore, the invention controls the carbon content to be 0.14-0.18%.
Action of Si: the solubility of silicon in carbide is extremely small, so that the generation of the carbide can be effectively inhibited or delayed, carbon-rich austenite can be formed in the distribution process, and the stability of the residual austenite is improved; higher silicon content is beneficial to obtaining more residual austenite, but excessive silicon content can reduce high-temperature plasticity of the material and increase defect occurrence rate in steelmaking, continuous casting and hot rolling processes; therefore, the silicon content is controlled to be 0.7-0.9 percent.
Action of Mn: manganese is an austenite stabilizing element; manganese can reduce the temperature of the martensite generation starting point, so that the content of the residual austenite is increased, and the stability of the residual austenite is improved; manganese also plays a solid solution strengthening role in steel; too high manganese content can cause too high hardenability of the steel, which is not beneficial to control of material structure; therefore, the manganese content is controlled to be 2.0-2.5 percent.
The key process points are controlled as follows:
finishing temperature: the finishing temperature is above 840 ℃, the structure before cooling is ensured to be completely austenite, and excessive ferrite generated in a two-phase region is avoided, so that the strength of the material is greatly reduced; the finishing temperature is set in the range 840 to 880 ℃.
Laminar cooling: the laminar cooling process is divided into two types, wherein one type is that the strip steel is directly and quickly cooled to the coiling temperature after exiting the rolling mill, and the cooling rate is not less than 40 ℃/s. The generated structure is carbide-free bainite and residual austenite, and ferrite is absent; too low a cooling rate will lead to precipitation of pearlite, degrading the properties of the material. The other is to slowly cool to ferrite and austenite two-phase region and then to the target coiling temperature, and to introduce a small amount of ferrite to improve the plasticity of the material through the slow cooling process; the specific control is as follows: after the strip steel is discharged from the rolling mill, air cooling is carried out for no more than 3s, the temperature is reduced to a two-phase region (ferrite and austenite), a small amount of ferrite is generated, and then the strip steel is rapidly cooled to a target coiling temperature, wherein the cooling rate is not less than 40 ℃/s; the process needs to avoid air cooling for too long, and excessive ferrite is prevented from being generated, so that the strength of the material is greatly reduced.
Coiling temperature: the coiling temperature must be higher than the martensite generation starting temperature and be in the bainite generation temperature range; too low a coiling temperature will result in formation of a martensitic matrix and a partially retained austenitic structure, and the plasticity of the material will be greatly reduced; too high a coiling temperature will reduce the strength of the material; therefore, the coiling temperature is set to 420-460 ℃.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention provides high-strength steel for an automobile structural member, which has the yield strength of 450-540 Mpa, the tensile strength of 780-880 Mpa, the hole expansion rate of more than or equal to 32% and the elongation rate of more than or equal to 20%. Compared with dual-phase steel, the matrix is carbide-free bainite, the difference of the microstructure and the mechanical properties of the bainite and ferrite is smaller than that of the ferrite and the martensite, the hole expansion rate is improved, and the occurrence of stamping cracking can be reduced.
(2) The manufacturing process adopts CSP process, the process scheme is feasible, and compared with the conventional hot rolling and cold rolling, the CSP product has short manufacturing flow and reduces the production cost.
(3) During manufacture, a small amount of ferrite can be introduced by adjusting laminar cooling, so that the strength and the elongation of the material can be adjusted to meet different material requirements.
Detailed Description
In order that those skilled in the art will better understand the technical solution of the present invention, preferred embodiments of the present invention will be described below with reference to specific examples, but should not be construed as limiting the present patent.
The test methods or test methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, are obtained from conventional commercial sources or prepared in conventional manner.
Table 1 shows the values of the chemical components and the contents of examples 1 to 8 and comparative examples 9 to 12 according to the present invention.
Table 2 shows some of the process parameters and sample properties of inventive examples 1-8 and comparative examples 9-12. In Table 2, the numbers 1 to 8 are examples, and the numbers 9 to 12 are comparative examples.
The invention provides a manufacturing method of high-strength steel for automobile structural parts, which has low cost, yield strength of more than 450MPa and tensile strength of more than 780MPa, wherein the CSP process flow is as follows: smelting, refining, sheet billet continuous casting, casting blank soaking, rolling, laminar cooling, coiling and flattening, and the method comprises the following steps of:
in the thin slab continuous casting step, the superheat degree of the ladle molten steel is 15-30 ℃; the thickness of the casting blank is 70-75 mm, and the pulling speed is 4.0-4.8 m/s. The casting blank of the thin slab continuous casting is subjected to descaling treatment before being put into the furnace, and the descaling pressure is 15-30 bar.
In the casting blank soaking step, the casting blank is fed into a furnace at a temperature of 820-1050 ℃ and is discharged at a temperature of 1190-1240 ℃.
In the rolling step, the rolling pass reduction is distributed as follows: 50-60% of the first pass, 40-50% of the second pass and 8-12% of the last pass; controlling the rolling speed to be 7-12 m/s; the final rolling temperature is 840-880 ℃; the descaling process in the rolling process adopts high-pressure water to remove scales before entering the rolling mill, and the descaling water pressure is 200-380 bar.
Laminar cooling includes two cooling modes, one is: the strip steel is directly and rapidly cooled to a target coiling temperature after being discharged from a rolling mill, and the cooling rate of rapid cooling is not less than 40 ℃/s; the second mode is as follows: after the strip steel leaves the rolling mill, air cooling is carried out for no more than 3s, the temperature is reduced to a two-phase region, a small amount of ferrite is generated, then the strip steel is rapidly cooled to a target coiling temperature, and the cooling rate of the rapid cooling is not less than 40 ℃/s.
The coiling temperature is 420-460 ℃; flattening the steel coil after the temperature of the steel coil is reduced to below 50 ℃, wherein the flattening force is controlled to be 160-200 tons; removing iron oxide scale by acid washing; the thickness of the obtained product is 1.0-2.0 mm.
Table 1 chemical composition (wt.%) of steel material
| Composition of the components | Category(s) | C | Si | Mn | Als | P | S | N |
| A | Examples | 0.14 | 0.7 | 2.0 | 0.028 | 0.007 | 0.004 | 0.005 |
| B | Examples | 0.18 | 0.8 | 2.3 | 0.021 | 0.009 | 0.004 | 0.003 |
| C | Examples | 0.16 | 0.9 | 2.5 | 0.029 | 0.009 | 0.006 | 0.004 |
| D | Comparative example | 0.10 | 0.9 | 2.0 | 0.032 | 0.007 | 0.005 | 0.006 |
Table 2 example and comparative examples part of the process parameters and sample tensile properties
As can be seen from tables 1 and 2, the yield strength of the high-strength steel prepared in examples 1 to 8 of the invention reaches more than 450MPa, the tensile strength reaches more than 780MPa, the hole expansion ratio is more than or equal to 32%, and the elongation is more than or equal to 20%, so as to meet different material requirements.
In comparative examples 1 to 8 and comparative example 9, when the C content is too low, sufficient retained austenite cannot be formed, and the properties of the material are lowered. In comparative examples 3 and 10, when the finishing temperature exceeds 880 ℃, the final structure is not as fine as that of the sample at the lower finishing temperature due to coarsening of austenite grains, and the performance is lowered. In comparative examples 1 to 3 and comparative example 11, when the coiling temperature was decreased to 420 ℃ or lower, martensite was formed, and the strength was greatly increased, but the molding was poor. In comparative examples 4 and 12, when the air-cooling time was 5s, excessive ferrite was generated during cooling, and the yield strength was reduced to 450Mpa or less.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-mentioned preferred embodiment should not be construed as limiting the invention, and the scope of the invention should be defined by the appended claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (9)
1. The high-strength steel based on the CSP process is characterized by comprising the following chemical components in percentage by mass: 0.14 to 0.18 percent, si:0.7 to 0.9 percent, mn:2.0 to 2.5 percent, als is 0.02 to 0.05 percent, P: less than or equal to 0.02 percent, S: less than or equal to 0.008 percent, N: less than or equal to 0.008 percent, and the balance of Fe and other unavoidable impurities;
the method for the high-strength steel comprises the following steps: smelting, refining, sheet billet continuous casting, casting blank soaking, rolling, laminar cooling, coiling and flattening; the final rolling temperature is 840-880 ℃, and the coiling temperature is 420-460 ℃;
laminar cooling includes two cooling modes, one is: the strip steel is directly and rapidly cooled to a target coiling temperature after being discharged from a rolling mill, and the cooling rate of rapid cooling is not less than 40 ℃/s; the second mode is as follows: after the strip steel leaves the rolling mill, air cooling is carried out for no more than 3s, the temperature is reduced to a two-phase region, ferrite is generated, then the strip steel is rapidly cooled to a target coiling temperature, and the cooling rate of the rapid cooling is not less than 40 ℃/s.
2. The high-strength steel based on the CSP process according to claim 1, wherein the yield strength of the high-strength steel is 450-540 MPa, the tensile strength is 780-880 MPa, the hole expansion ratio is more than or equal to 32%, and the elongation is more than or equal to 20%.
3. The CSP process-based high strength steel of claim 1, wherein the structure of the high strength steel includes: ferrite with the content of 0-10%, residual austenite with the content of 5-8%, and carbide-free bainite with the rest.
4. A method for producing a high-strength steel, characterized in that the method is used for producing a CSP-process-based high-strength steel as claimed in any one of claims 1 to 3.
5. The method according to claim 4, wherein in the thin slab continuous casting step, the superheat degree of the ladle molten steel is 15-30 ℃; the thickness of the casting blank is 70-75 mm, and the pulling speed is 4.0-4.8 m/s.
6. The method according to claim 4, wherein the thin slab continuous casting slab is subjected to descaling before being charged, and the descaling pressure is 15-30 bar.
7. The method according to claim 4, wherein in the step of soaking the casting blank, the temperature of the casting blank in the furnace is 820-1050 ℃ and the temperature of the casting blank out of the furnace is 1190-1240 ℃.
8. The method of claim 4, wherein in the rolling step, the rolling pass reduction is assigned as: 50-60% of the first pass, 40-50% of the second pass and 8-12% of the last pass; controlling the rolling speed to be 7-12 m/s; the descaling process in the rolling process adopts high-pressure water to remove scales before entering the rolling mill, and the descaling water pressure is 200-380 bar.
9. The method of claim 4, wherein the steel coil is leveled after the temperature of the steel coil is reduced to below 50 ℃, and the leveling force is controlled to be 160-200 tons; removing iron oxide scale by acid washing; the thickness of the obtained product is 1.0-2.0 mm.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211183801.7A CN115612928B (en) | 2022-09-27 | 2022-09-27 | High-strength steel based on CSP process and manufacturing method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2004225105A (en) * | 2003-01-23 | 2004-08-12 | Nippon Steel Corp | Thin steel sheet for working having excellent deep drawability, and production method therefor |
| CN102965569A (en) * | 2012-11-26 | 2013-03-13 | 宝山钢铁股份有限公司 | Hot rolling phase change inducing plastic steel plate and manufacturing method thereof |
| CN111684084A (en) * | 2018-02-07 | 2020-09-18 | 塔塔钢铁荷兰科技有限责任公司 | High-strength hot-rolled or cold-rolled and annealed steel and method for the production thereof |
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| JP4410741B2 (en) * | 2005-09-05 | 2010-02-03 | 新日本製鐵株式会社 | High strength thin steel sheet with excellent formability and method for producing the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004225105A (en) * | 2003-01-23 | 2004-08-12 | Nippon Steel Corp | Thin steel sheet for working having excellent deep drawability, and production method therefor |
| CN102965569A (en) * | 2012-11-26 | 2013-03-13 | 宝山钢铁股份有限公司 | Hot rolling phase change inducing plastic steel plate and manufacturing method thereof |
| CN111684084A (en) * | 2018-02-07 | 2020-09-18 | 塔塔钢铁荷兰科技有限责任公司 | High-strength hot-rolled or cold-rolled and annealed steel and method for the production thereof |
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| Title |
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| 杨光辉等编著.薄板坯连铸连轧和薄带连铸关键工艺技术.冶金工业出版社,2016,第135-136页. * |
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