CN113862580A - Hot-rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel and production method thereof - Google Patents
Hot-rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel and production method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 112
- 239000010959 steel Substances 0.000 title claims abstract description 112
- 229910000885 Dual-phase steel Inorganic materials 0.000 title claims abstract description 41
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 27
- 238000005096 rolling process Methods 0.000 claims abstract description 100
- 238000000034 method Methods 0.000 claims abstract description 96
- 238000010438 heat treatment Methods 0.000 claims abstract description 73
- 238000001816 cooling Methods 0.000 claims abstract description 60
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000009749 continuous casting Methods 0.000 claims abstract description 23
- 238000010583 slow cooling Methods 0.000 claims abstract description 22
- 239000000126 substance Substances 0.000 claims abstract description 22
- 229910052742 iron Inorganic materials 0.000 claims abstract description 15
- 238000003723 Smelting Methods 0.000 claims abstract description 12
- 238000007670 refining Methods 0.000 claims abstract description 12
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 6
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 4
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 3
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 3
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 3
- 238000005266 casting Methods 0.000 claims description 54
- 238000002791 soaking Methods 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- 238000004321 preservation Methods 0.000 claims description 20
- 238000005204 segregation Methods 0.000 description 9
- 230000000087 stabilizing effect Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 2
- 238000004134 energy conservation Methods 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- QFGIVKNKFPCKAW-UHFFFAOYSA-N [Mn].[C] Chemical compound [Mn].[C] QFGIVKNKFPCKAW-UHFFFAOYSA-N 0.000 description 1
- UWTVDIWVFAQDFS-UHFFFAOYSA-N [Mn].[Cr].[C] Chemical compound [Mn].[Cr].[C] UWTVDIWVFAQDFS-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000011573 trace mineral Substances 0.000 description 1
- 235000013619 trace mineral Nutrition 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
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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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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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
- C21D2211/005—Ferrite
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Abstract
A hot rolled steel strip for 590 MPa-grade cold rolled dual-phase steel and a production method thereof are disclosed, wherein the steel strip comprises the following chemical components in percentage by mass: 0.08-0.12%, Mn: 1.40-1.70%, S is less than or equal to 0.008%, P is less than or equal to 0.015%, Si: 0.20-0.30%, Als: 0.02-0.06%, Cr + Mo: 0.50-0.80%, Mo is less than or equal to 0.30%, N is less than or equal to 0.005%, Nb + V + Ti is less than or equal to 0.05%, and the balance is iron and inevitable impurities. The production method comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling. The hot rolled steel strip obtained by the invention has the structure of ferrite and bainite, the band structure level is less than or equal to 1.5, ReL: 440-560 MPa, Rm: 540-660 MPa, and the elongation A after fracture is more than or equal to 19 percent.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a hot-rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel and a production method thereof.
Background
With the explosive increase of automobile output, the environmental and energy crisis is increasingly aggravated, and energy conservation and emission reduction become important problems in the automobile manufacturing industry. On the premise of ensuring the performances such as safety and the like, the goals of energy conservation, emission reduction and consumption reduction through the weight reduction of the automobile become common recognition, and the automobile lightweight technology becomes the development trend of the current automobile industry. In order to achieve the obvious effects of reducing weight and weight of automobiles, the cold-rolled steel plate needs to be thinner and have higher strength and cold-forming performance. At present, cold-rolled dual-phase steel is widely used in China, the cold-rolled dual-phase steel mostly adopts carbon-manganese components, and if the process is improperly controlled, the banded structure of a hot-rolled product is serious, so that the forming property and the plasticity of the cold-rolled product are influenced, and the product is seriously cracked. Meanwhile, the conventional process is adopted to produce the hot-rolled dual-phase steel product, the problem of flat rolling is easy to occur after the hot-rolled steel strip is rolled off line, the production efficiency and the yield are influenced, and although the problem of flat rolling can be solved by adopting a lower rolling temperature, the strength of the hot-rolled steel strip is greatly increased, and the performance of a cold-rolled finished product and the subsequent use effect are influenced.
Disclosure of Invention
The invention provides a hot rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel and a production method thereof, wherein the obtained hot rolled steel strip is composed of ferrite and bainite, and the grade of a banded structure is less than or equal to 1.5. The invention improves the fatigue property of the cold-rolled finished product by improving the banded structure of the hot-rolled steel strip. And a proper low-temperature coiling process is adopted, so that the technical problem that the hot-rolled dual-phase steel is easy to coil flatly in coiling is solved.
In order to realize the purpose of the invention, the invention adopts the technical scheme that:
a hot rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel comprises the following chemical components in percentage by mass: 0.08-0.12% of C, Mn: 1.40-1.70%, S is less than or equal to 0.008%, P is less than or equal to 0.015%, Si: 0.20-0.30%, Als: 0.020 to 0.060%, Cr + Mo: 0.50-0.80%, Mo is less than or equal to 0.30%, N is less than or equal to 0.0050%, Nb + V + Ti is less than or equal to 0.05%, and the balance of iron and inevitable impurities.
The thickness of the steel strip is 2.3-6.0 mm; the steel strip structure is ferrite and bainite, the grain size is more than or equal to grade 12, and the band structure is less than or equal to grade 1.5.
The yield strength ReL of the hot rolled steel strip is as follows: 440-560 MPa, tensile strength Rm: 540-660 MPa, and the elongation A after fracture is more than or equal to 19 percent.
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and stacking cooling.
In the continuous casting process, when the width of a casting blank is less than or equal to 1300mm, the pulling speed v is as follows: v is more than 1.40 and less than or equal to 1.50 m/min; when the width of the casting blank is more than 1300mm, the pulling speed v is as follows: v is more than or equal to 1.30 and less than or equal to 1.40 m/min; and continuously casting to obtain a billet with the thickness of 180-230 mm.
And in the casting blank slow cooling process, the casting blank is put into a heat preservation pit after being off-line, and is taken out of the pit after being naturally cooled for more than or equal to 60 hours.
The heating procedure is carried out by heating in a stepping heating furnace, the total in-furnace time is 150-200 min, the heating temperature of the soaking section is 1250-1300 ℃, and the soaking time is 35-45 min.
In the rough rolling procedure, single-stand reciprocating type 5-pass rough rolling is carried out, single-pass high-pressure water descaling is carried out, the dephosphorization water pressure is 20-25 MPa, the thickness of the obtained intermediate blank is 32-36 mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box.
In the finish rolling procedure, a steel strip with the thickness of 2.3-6.0 mm is rolled by 7 times of finish rolling, the inlet temperature of the finish rolling is 1030-1060 ℃, and the finishing temperature is 820-860 ℃.
And the cooling step is to cool the steel plate to a coiling temperature of 520-560 ℃ by adopting a laminar cooling mode.
And in the heap cooling process, the heap cooling time is 36-48 h.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: 1. the invention adopts the design of carbon-manganese-chromium/molybdenum system components, and the obtained hot rolled steel strip structure is ferrite and bainite with the zonal structure grade less than or equal to 1.5 grade by adjusting alloy components, controlling the content of trace elements, controlling a cooling path and adopting a proper low-temperature coiling process. Practice proves that the yield strength ReL of the hot-rolled steel strip is as follows: 440-560 MPa, tensile strength Rm: 540-660 MPa, and the elongation A after fracture is more than or equal to 19 percent. The galvanized finished product produced by using the hot rolled steel strip has higher tensile strength, excellent cold stamping forming performance and fatigue performance, the tensile strain hardening index n value of the galvanized finished product is more than or equal to 0.14, and the fatigue limit is more than or equal to 217 MPa. 2. The invention adopts a proper low-temperature coiling process, the obtained hot-rolled steel strip structure is ferrite and bainite, a pearlite transformation interval is avoided, the technical problem of flat coiling caused by volume change caused by phase change of a hot-rolled dual-phase steel product after coiling is effectively solved, and the production efficiency and the yield are improved.
Drawings
FIG. 1 is a metallographic structure diagram of a hot-rolled steel strip according to example 1;
FIG. 2 is a metallographic structure diagram of a hot rolled steel strip according to example 2;
FIG. 3 is a metallographic structure diagram of a hot rolled steel strip according to example 3;
FIG. 4 is a metallographic structure diagram of a hot rolled steel strip according to example 4;
FIG. 5 is a metallographic structure diagram of a hot rolled steel strip according to example 5;
FIG. 6 is a metallographic structure chart of a hot rolled steel strip according to example 6;
FIG. 7 is a metallographic structure chart of a hot rolled steel strip according to example 7;
FIG. 8 is a metallographic structure diagram of a hot rolled steel strip according to example 8;
FIG. 9 is a metallographic structure chart of a hot-rolled steel strip according to example 9.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example 1
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.40m/min, and continuously casting to obtain a billet with the thickness of 180mm and the width of 1280mm, and the chemical components and the mass percentage of the billet are shown in table 1;
(2) a casting blank slow cooling process: after the casting blank is off line, the casting blank is put into a heat preservation pit and is naturally cooled for 60 hours in the heat preservation pit;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 160min, the heating temperature of a soaking section of the heating furnace is 1260 ℃, and the soaking time is 35 min;
(4) rough rolling procedure: the single-stand reciprocating type 5-pass rough rolling is carried out, the single-pass high-pressure water descaling is carried out, the dephosphorization water pressure is 22MPa, the thickness of the obtained intermediate blank is 34mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 4.0mm by 7-pass finish rolling, wherein the inlet temperature of the finish rolling is 1040 ℃, and the finish rolling temperature is 860 ℃;
(6) a cooling process: cooling the steel strip to a coiling temperature of 560 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 48 hours.
The chemical components and the mass percentage content of the hot rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel produced by the embodiment are shown in a table 1, and the specification, the metallographic structure, the rating and the mechanical property of the steel strip are shown in a table 2; the metallographic structure of the steel strip is shown in figure 1.
Example 2
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.40m/min, and continuously casting to obtain a billet with the thickness of 230mm and the width of 1240mm, and the chemical components and the mass percentage of the billet are shown in table 1;
(2) a casting blank slow cooling process: after the casting blank is off-line, the casting blank is put into a heat preservation pit, and the slab is naturally cooled for 61 hours in the heat preservation pit;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 190min, the heating temperature of a soaking section of the heating furnace is 1290 ℃, and the soaking time is 40 min;
(4) rough rolling procedure: the single-stand reciprocating type 5-pass rough rolling is carried out, the single-pass high-pressure water descaling is carried out, the dephosphorization water pressure is 22MPa, the thickness of the obtained intermediate blank is 36mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 6.0mm by 7-pass finish rolling, wherein the finish rolling inlet temperature is 1030 ℃ and the finish rolling temperature is 840 ℃;
(6) a cooling process: cooling the steel strip to a coiling temperature of 540 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 36 h.
The chemical components and the mass percentage content of the hot rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel produced by the embodiment are shown in a table 1, and the specification, the metallographic structure, the rating and the mechanical property of the steel strip are shown in a table 2; the metallographic structure of the steel strip is shown in FIG. 2.
Example 3
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.50m/min, and continuously casting to obtain a steel billet with the thickness of 200mm and the width of 1250mm, and the chemical components and the mass percentage content of the steel billet are shown in table 1;
(2) a casting blank slow cooling process: after the casting blank is off-line, the casting blank is put into a heat preservation pit, and the slab is naturally cooled for 61 hours in the heat preservation pit;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 200min, the heating temperature of a soaking section of the heating furnace is 1300 ℃, and the soaking time is 44 min;
(4) rough rolling procedure: the single-stand reciprocating type 5-pass rough rolling is carried out, the single-pass high-pressure water descaling is carried out, the dephosphorization water pressure is 22MPa, the thickness of the obtained intermediate blank is 36mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 6.0mm by 7-pass finish rolling, wherein the inlet temperature of the finish rolling is 1030 ℃, and the finish rolling temperature is 860 ℃;
(6) a cooling process: cooling the steel strip to the coiling temperature of 530 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 42 h.
The chemical components and the mass percentage content of the hot rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel produced by the embodiment are shown in a table 1, and the specification, the metallographic structure, the rating and the mechanical property of the steel strip are shown in a table 2; the metallographic structure of the steel strip is shown in FIG. 3.
Example 4
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.30m/min, and continuously casting to obtain a steel billet with the thickness of 200mm and the width of 1320mm, wherein the chemical components and the mass percentage of the steel billet are shown in a table 1;
(2) a casting blank slow cooling process: the casting blank is put into a heat preservation pit after being off line, and the slab is naturally cooled in the heat preservation pit for 60.5 hours;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 180min, the heating temperature of a soaking section of the heating furnace is 1280 ℃, and the soaking time is 38 min;
(4) rough rolling procedure: the single-stand reciprocating type 5-pass rough rolling is carried out, the single-pass high-pressure water descaling is carried out, the dephosphorization water pressure is 23MPa, the thickness of the obtained intermediate blank is 32mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 2.3mm by 7 times of finish rolling, wherein the inlet temperature of the finish rolling is 1060 ℃, and the finish rolling temperature is 850 ℃;
(6) a cooling process: cooling the steel strip to a coiling temperature of 535 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 39.5 h.
The chemical components and the mass percentage content of the hot rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel produced by the embodiment are shown in a table 1, and the specification, the metallographic structure, the rating and the mechanical property of the steel strip are shown in a table 2; the metallographic structure of the steel strip is shown in FIG. 4.
Example 5
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.40m/min, and continuously casting to obtain a billet with the thickness of 230mm and the width of 1270mm, and the chemical components and the mass percentage of the billet are shown in table 1;
(2) a casting blank slow cooling process: the casting blank is put into a heat preservation pit after being off line, and the slab is naturally cooled in the heat preservation pit for 60.8 hours;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 165min, the heating temperature of a soaking section of the heating furnace is 1275 ℃, and the soaking time is 37 min;
(4) rough rolling procedure: carrying out single-stand reciprocating 5-pass rough rolling, carrying out single-pass high-pressure water descaling, wherein the dephosphorization water pressure is 22.5MPa, the thickness of the obtained intermediate blank is 34mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 3.0mm by 7-pass finish rolling, wherein the finish rolling inlet temperature is 1045 ℃, and the finish rolling temperature is 820 ℃;
(6) a cooling process: cooling the steel strip to the coiling temperature of 530 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 41 h.
The chemical components and the mass percentage content of the hot rolled steel strip for 590 MPa-grade cold-rolled dual-phase steel produced by the embodiment are shown in a table 1, and the specification, the metallographic structure, the rating and the mechanical property of the steel strip are shown in a table 2; the metallographic structure of the steel strip is shown in FIG. 5.
Example 6
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.35m/min, and continuously casting to obtain a billet with the thickness of 225mm and the width of 1350mm, wherein the chemical components and the mass percentage of the billet are shown in table 1;
(2) a casting blank slow cooling process: the casting blank is put into a heat preservation pit after being off line, and the slab is naturally cooled in the heat preservation pit for 62 hours;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 157min, the heating temperature of a soaking section of the heating furnace is 1258 ℃, and the soaking time is 35.5 min;
(4) rough rolling procedure: carrying out single-stand reciprocating 5-pass rough rolling, carrying out single-pass high-pressure water descaling, wherein the dephosphorization water pressure is 20MPa, the thickness of the obtained intermediate blank is 33.5mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 3.5mm by 7-pass finish rolling, wherein the inlet temperature of the finish rolling is 1060 ℃, and the finish rolling temperature is 825 ℃;
(6) a cooling process: cooling the steel strip to the coiling temperature of 553 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is curled and then intensively piled and cooled for 37 h.
The chemical components and mass percentage contents of the hot rolled steel strip for 590MPa grade cold rolled dual phase steel produced by the embodiment are shown in table 1, and the specification, metallographic structure, rating and mechanical properties of the steel strip are shown in table 2.
Example 7
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.45m/min, and continuously casting to obtain a billet with the thickness of 190mm and the width of 1220mm, wherein the chemical components and the mass percentage of the billet are shown in table 1;
(2) a casting blank slow cooling process: after the casting blank is off line, the casting blank is put into a heat preservation pit and is naturally cooled for 61.5 hours in the heat preservation pit;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 150min, the heating temperature of a soaking section of the heating furnace is 1266 ℃, and the soaking time is 41 min;
(4) rough rolling procedure: the single-stand reciprocating type 5-pass rough rolling is carried out, the single-pass high-pressure water descaling is carried out, the dephosphorization water pressure is 25MPa, the thickness of the obtained intermediate blank is 33mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 4.5mm by 7 times of finish rolling, wherein the finish rolling inlet temperature is 1055 ℃, and the finish rolling temperature is 858 ℃;
(6) a cooling process: cooling the steel strip to a coiling temperature of 535 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 47 h.
The chemical components and mass percentage contents of the hot rolled steel strip for 590MPa grade cold rolled dual phase steel produced by the embodiment are shown in table 1, and the specification, metallographic structure, rating and mechanical properties of the steel strip are shown in table 2.
Example 8
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.35m/min, and continuously casting to obtain a billet with the thickness of 220mm and the width of 1360mm, and the chemical components and the mass percentage of the billet are shown in table 1;
(2) a casting blank slow cooling process: after the casting blank is off line, the casting blank is put into a heat preservation pit and is naturally cooled for 60 hours in the heat preservation pit;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 195min, the heating temperature of a soaking section of the heating furnace is 1294 ℃, and the soaking time is 45 min;
(4) rough rolling procedure: carrying out single-stand reciprocating 5-pass rough rolling, carrying out single-pass high-pressure water descaling, wherein the dephosphorization water pressure is 21MPa, the thickness of the obtained intermediate blank is 32.5mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 5.0mm by 7-pass finish rolling, wherein the inlet temperature of the finish rolling is 1047 ℃, and the final rolling temperature is 848 ℃;
(6) a cooling process: cooling the steel strip to the coiling temperature of 520 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 48 hours.
The chemical components and mass percentage contents of the hot rolled steel strip for 590MPa grade cold rolled dual phase steel produced by the embodiment are shown in table 1, and the specification, metallographic structure, rating and mechanical properties of the steel strip are shown in table 2.
Example 9
The production method of the hot rolled steel strip for the 590 MPa-grade cold rolled dual-phase steel comprises the working procedures of molten iron pretreatment, converter smelting, secondary refining, continuous casting, casting blank slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling, and comprises the following specific process steps:
(1) and (3) continuous casting process: controlling component segregation by stabilizing the drawing speed, wherein the drawing speed is 1.45m/min, continuously casting to obtain a billet with the thickness of 185mm and the width of 1300mm, and the chemical components and the mass percentage content of the billet are shown in table 1;
(2) a casting blank slow cooling process: after the casting blank is off line, the casting blank is put into a heat preservation pit and is naturally cooled for 62.5 hours in the heat preservation pit;
(3) a heating procedure: heating by a stepping heating furnace, wherein the total standing time of the heating furnace is 174min, the heating temperature of a soaking section of the heating furnace is 1250 ℃, and the soaking time is 42.5 min;
(4) rough rolling procedure: carrying out single-stand reciprocating 5-pass rough rolling, carrying out single-pass high-pressure water descaling, wherein the dephosphorization water pressure is 24MPa, the thickness of the obtained intermediate blank is 35mm, and the head and the tail of the intermediate blank are reversed after being coiled by a hot coil box;
(5) a finish rolling procedure: rolling the steel strip into a steel strip with the thickness of 5.5mm by 7 times of finish rolling, wherein the inlet temperature of the finish rolling is 1036 ℃, and the finish rolling temperature is 830 ℃;
(6) a cooling process: cooling the steel strip to the coiling temperature of 550 ℃ by laminar flow;
(7) a heap cooling process: the hot coil is coiled and then intensively cooled for 44 h.
The chemical components and mass percentage contents of the hot rolled steel strip for 590MPa grade cold rolled dual phase steel produced by the embodiment are shown in table 1, and the specification, metallographic structure, rating and mechanical properties of the steel strip are shown in table 2.
The galvanized finished products produced by using the hot rolled steel strips of the examples 1 to 9 have higher tensile strength and excellent cold stamping forming performance and fatigue performance, and specific performance indexes are shown in a table 3.
TABLE 1 chemical composition and content (wt%) of hot rolled steel strip for 590MPa grade cold rolled dual phase steel of each example
TABLE 2 specification, metallographic structure, rating and mechanical properties of the steel strips of the examples
TABLE 3 Process parameters and product Properties of the galvanized product produced from the hot rolled strip of each example
Note: the fatigue limit is: maximum stress at 10^7 cycles without fracture, the fatigue limit is used by the invention to evaluate fatigue performance.
Claims (10)
1. A hot rolled steel strip for 590 MPa-grade cold rolled dual-phase steel is characterized by comprising the following chemical components in percentage by mass: c: 0.08-0.12%, Mn: 1.40-1.70%, S is less than or equal to 0.008%, P is less than or equal to 0.015%, Si: 0.20-0.30%, Als: 0.020 to 0.060%, Cr + Mo: 0.50-0.80%, Mo is less than or equal to 0.30%, N is less than or equal to 0.0050%, Nb + V + Ti is less than or equal to 0.05%, and the balance of iron and inevitable impurities.
2. The hot-rolled steel strip for 590MPa grade cold-rolled dual phase steel according to claim 1, wherein the steel strip has a thickness of 2.3 to 6.0 mm; the steel strip structure is ferrite and bainite, the grain size is more than or equal to grade 12, and the band structure is less than or equal to grade 1.5.
3. The hot-rolled steel strip for 590MPa grade cold-rolled dual phase steel according to claim 1 or 2, characterized in that the steel strip yield strength ReL: 440-560 MPa, tensile strength Rm: 540-660 MPa, and the elongation A after fracture is more than or equal to 19 percent.
4. The method for producing the hot-rolled steel strip for the 590MPa grade cold-rolled dual-phase steel according to any one of claims 1 to 3, wherein the production method comprises the steps of molten iron pretreatment, converter smelting, secondary refining, continuous casting, slab slow cooling, heating, rough rolling, finish rolling, cooling, coiling and heap cooling; and the cooling step is to cool the steel plate to a coiling temperature of 520-560 ℃ by adopting a laminar cooling mode.
5. The method for producing a hot-rolled steel strip for 590MPa grade cold-rolled dual-phase steel according to claim 4, wherein in the continuous casting step, when the width of the cast slab is not more than 1300mm, the casting speed v is: v is more than 1.40 and less than or equal to 1.50 m/min; when the width of the casting blank is more than 1300mm, the pulling speed v is as follows: v is more than or equal to 1.30 and less than or equal to 1.40 m/min; and continuously casting to obtain a billet with the thickness of 180-230 mm.
6. The method for producing the hot rolled steel strip for 590MPa grade cold rolled dual phase steel according to claim 4, wherein the casting blank is slowly cooled, the casting blank is put into a heat preservation pit after being taken off line, and the casting blank is taken out of the pit after being naturally cooled for more than or equal to 60 hours.
7. The method for producing a hot-rolled steel strip for 590MPa grade cold-rolled dual-phase steel according to claim 4, wherein the heating step is performed by a step-type heating furnace, the total in-furnace time is 150-200 min, the heating temperature of the soaking section is 1250-1300 ℃, and the soaking time is 35-45 min.
8. The method for producing the hot-rolled steel strip for 590MPa grade cold-rolled dual-phase steel according to claim 4, wherein the rough rolling process comprises single-stand reciprocating 5-pass rough rolling, single-pass high-pressure water descaling, dephosphorization water pressure of 20-25 MPa, thickness of the obtained intermediate blank of 32-36 mm, and head and tail reversal through coiling of a hot coil box.
9. The method for producing a hot-rolled steel strip for 590MPa grade cold-rolled dual-phase steel according to claim 4, wherein the finish rolling step comprises 7-pass finish rolling to obtain a steel strip with a thickness of 2.3 to 6.0mm, wherein the inlet temperature of the finish rolling is 1030 to 1060 ℃, and the finishing temperature is 820 to 860 ℃.
10. The method for producing a hot-rolled steel strip for 590MPa grade cold-rolled dual-phase steel according to any one of claims 4 to 9, wherein the heap cooling process is performed for a heap cooling time of 36 to 48 hours.
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