CN113684419A - Low-cost 400 MPa-grade cold-rolled continuous annealing steel strip and production method thereof - Google Patents
Low-cost 400 MPa-grade cold-rolled continuous annealing steel strip and production method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 70
- 239000010959 steel Substances 0.000 title claims abstract description 70
- 238000000137 annealing Methods 0.000 title claims abstract description 33
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- 238000005096 rolling process Methods 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 18
- 238000009749 continuous casting Methods 0.000 claims abstract description 14
- 239000002253 acid Substances 0.000 claims abstract description 11
- 239000000126 substance Substances 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 6
- 238000009628 steelmaking Methods 0.000 claims abstract description 4
- 238000005097 cold rolling Methods 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 11
- 238000003723 Smelting Methods 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 3
- 239000010960 cold rolled steel Substances 0.000 claims description 3
- 238000010079 rubber tapping Methods 0.000 claims description 3
- 238000010583 slow cooling Methods 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 abstract description 4
- 239000000956 alloy Substances 0.000 abstract description 4
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 239000011572 manganese Substances 0.000 description 7
- 238000005098 hot rolling Methods 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000011574 phosphorus Substances 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- QFGIVKNKFPCKAW-UHFFFAOYSA-N [Mn].[C] Chemical compound [Mn].[C] QFGIVKNKFPCKAW-UHFFFAOYSA-N 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
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- 238000011161 development Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
- B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- 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
- 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
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials 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 low-cost 400 MPa-grade cold-rolled continuous annealing steel strip and a production method thereof, wherein the steel strip comprises the following chemical components in percentage by mass: c: 0.12-0.18%, Si is less than or equal to 0.040%, and Mn: 0.25-0.45%, P: 0.015-0.020%, S is less than or equal to 0.020%, Als: 0.020-0.060% of Fe and the balance of inevitable impurities; the manufacturing method comprises the working procedures of steel making, continuous casting, hot continuous rolling, acid continuous rolling and continuous annealing; the invention adopts the steps of adding no noble alloy element, reducing Mn element and collectingThe system is designed by using a small amount of P element components, and finally the yield strength is more than or equal to 250MPa, the tensile strength is more than or equal to 400MPa, and the elongation A is achieved50The mechanical property index is more than or equal to 35 percent, the use requirements of structural reinforcements of automobiles, buildings and the like are met, and the method has the characteristics of low production cost, high efficiency and the like and is very wide in application.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to a low-cost 400 MPa-grade cold-rolled continuous-annealed steel strip and a production method thereof.
Background
With the rapid development of industry, light weight and high strength are becoming the trend, the steel for the cold rolling high strength structure of 400Mpa grade still dominates, and by virtue of good obdurability and surface quality and low cost advantage, the steel is widely applied to parts such as automobile structural parts, automobile bodies, automobile chassis and the like, household appliances, building structures and the like. At present, the alloy cost adopted by the cold-rolled continuous annealing steel strip is high, the requirement on smelting control is higher, and the research on how to control the smelting components and the production process becomes the key for acquiring the competitive advantage of domestic steel enterprises under the situation of intense competition in the steel industry at present.
CN103509996A discloses a high-strength carbon-manganese structural steel with 400MPa of tensile strength and a manufacturing method thereof, wherein the steel comprises the following chemical components in percentage by weight: carbon: 0.10-0.20%, silicon is less than or equal to 0.30%, manganese is less than or equal to 0.40%, and aluminum: 0.010-0.030 percent of phosphorus, less than or equal to 0.02 percent of sulfur, less than or equal to 0.015 percent of sulfur, and the balance of Fe and inevitable impurity elements. Compared with the method, the CN103509996A adopts cover annealing, the production mode of the method is completely different from continuous annealing, and the mechanical property, the plate shape and the surface quality of the product are different.
CN102758071A discloses a continuous annealing production method of 280 MPa-grade steel for automobile structures. The technical scheme comprises the working procedures of smelting, hot rolling and cold rolling continuous annealing, and the final chemical components in percentage by mass are as follows: c: 0.145-0.185%, 0.05-0.15% of Si, 0.55-0.65% of Mn, less than or equal to 0.025% of P, less than or equal to 0.015% of S, 0.013-0.023% of Als, less than or equal to 0.004% of N, and the balance of Fe. Compared with the invention, the CN102758071A does not add the strong solid solution strengthening element P, the Mn content is relatively high, the relative production cost is relatively high, in addition, the annealing soaking temperature is only about 710 ℃, the low temperature annealing is easy to cause the steel strip deflection, and the production control difficulty is relatively large.
CN103509997A discloses a 440 MPa-grade cold-rolled high-strength automobile structural steel and a manufacturing method thereof, and the steel comprises the following main chemical components in percentage by mass: carbon: 0.06-0.12%, less than or equal to 0.25% of silicon, 1.0-1.4% of manganese, aluminum: 0.015-0.060 percent, less than or equal to 0.02 percent of phosphorus, less than or equal to 0.01 percent of sulfur, and the balance of Fe and inevitable impurity elements. Compared with the invention, the CN103509997A adopts the component design of low carbon and high manganese and no strong solid solution strengthening element P, and the relative production cost is higher.
Therefore, a low-cost 400 MPa-grade cold-rolled continuous annealing steel strip and a production method thereof need to be designed to solve the problems of high alloy cost and high smelting control requirement in the existing smelting process of the cold-rolled continuous annealing steel strip.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a low-cost 400 MPa-grade cold-rolled continuous-annealed steel strip and a production method thereof.
The technical scheme adopted by the invention for solving the technical problems is as follows: a low-cost 400 MPa-grade cold-rolled continuous-annealing steel strip comprises the following chemical components in percentage by mass: c: 0.12-0.18%, Si is less than or equal to 0.040%, and Mn: 0.25-0.45%, P: 0.015-0.020%, S is less than or equal to 0.020%, Als: 0.020 to 0.060% and the balance Fe and inevitable impurities.
Specifically, the thickness specification of the steel strip is 0.4-2.5 mm, and the width specification is 1000-1800 mm.
Specifically, the mechanical properties of the steel strip are as follows: the yield strength is more than or equal to 250MPa, the tensile strength is more than or equal to 400MPa, and the elongation percentage A50≥35％。
A production method of a low-cost 400 MPa-grade cold-rolled continuous-annealed steel strip comprises the following steps:
1) steel making, namely smelting molten steel;
2) continuous casting, namely continuously casting the mixture into a continuous casting slab;
3) hot continuous rolling, namely performing hot continuous rolling on the continuous casting plate blank to obtain a hot rolled steel strip;
4) acid continuous rolling, namely continuously acid washing and cold continuous rolling the hot rolled steel strip to obtain a cold hard steel strip;
5) and continuously annealing, namely continuously annealing the cold-hard steel strip to obtain the cold-rolled steel strip.
Specifically, the thickness of the continuously cast slab in the continuous casting step in the step 2) is 230 mm.
In the hot continuous rolling procedure in the step 3), the temperature of the soaking section of the slab heating furnace is 1250 +/-15 ℃, and the in-furnace time is 170-260 min; the finishing temperature is 880 +/-15 ℃; adopting front-section laminar cooling, wherein the coiling temperature is 640 +/-15 ℃.
Specifically, in the acid continuous rolling process in the step 4), five-frame six-roller CVC (continuous variable crown) is adopted+And in the continuous cold rolling mill, the total cold rolling reduction rate is 58.3-82.6%.
In the continuous annealing process in the step 5), a vertical full radiant tube is adopted to heat the continuous annealing furnace, the soaking temperature is 770 +/-10 ℃, the slow cooling temperature is 670 +/-10 ℃, the fast cooling temperature is 450 +/-10 ℃, the overaging temperature is 370 +/-10 ℃, the final cooling tapping temperature is less than or equal to 155 ℃, and the elongation of the temper mill is 0.6-1.4%.
The invention has the following beneficial effects:
the invention designs a low-cost 400 MPa-grade cold-rolled continuous annealing steel strip and a production method thereof
1) The method adopts a component system without adding noble alloy elements, replaces expensive metal by increasing the content of carbon and the content of partial strong solid solution strengthening element-phosphorus, reduces the production cost, combines with the optimization control of the process, leads the carbon and the Fe to form fine and dispersed carbide which is uniformly distributed in the ferrite, and ensures that the steel strip has the characteristic of high strength;
2) the hot rolling finishing temperature, the cooling mode and the coiling temperature have larger influence on the ferrite grain size and carbide precipitation, and the fine ferrite structure can be obtained by adopting lower finishing and coiling temperatures and front-stage concentrated laminar cooling, so that the strength of a steel matrix is improved;
3) adopt shallow slot turbulent flow hydrochloric acid to wash and five frame tandem CVC+The rolling machine has high rolling load capacity, and can realize the control of cold rolling large-range reduction rate and plate shape quality;
4) the vertical full radiant tube is adopted to heat the continuous annealing furnace, the annealing temperature and process curve precision is higher, and the precise control of the microstructure and the mechanical property of the steel strip can be realized; through complete recrystallization annealing at about 770 ℃, fine and uniform equiaxed crystal structures are obtained; through the treatment of the annealing overaging section, the content of C in the steel grade gradually forms FeC precipitates, and the reduction of solid solution C is beneficial to improving the toughness of the steel. The six-roller CVC wet type temper mill is adopted, the design rolling load is high, the control of the flattening elongation of the steel strip in a large range can be realized, and the plate type guaranteeing capability is good;
5) the yield strength of the cold-rolled continuous annealing steel strip is more than or equal to 250MPa, the tensile strength is more than or equal to 400MPa, and the elongation percentage A after fracture50Not less than 35 percent, ensures high strength and good processing performance and surface quality on the premise of low production cost, and can meet the use requirements of structural reinforcements of automobiles, buildings and the like.
Drawings
FIG. 1 is a typical metallographic structure of a low-cost 400MPa grade cold rolled continuous annealed steel strip provided in example 1.
Detailed Description
The technical solutions in the embodiments of the present invention will be described in further detail in the following clearly and completely with reference to the accompanying drawings in the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A low-cost 400 MPa-grade cold-rolled continuous-annealing steel strip comprises the following chemical components in percentage by mass: c: 0.12-0.18%, Si is less than or equal to 0.040%, and Mn: 0.25-0.45%, P: 0.015-0.020%, S is less than or equal to 0.020%, Als: 0.020 to 0.060% and the balance Fe and inevitable impurities.
The thickness specification of the steel strip is 0.4-2.5 mm, and the width specification is 1000-1800 mm; the mechanical property of the steel strip is as follows: the yield strength is more than or equal to 250MPa, the tensile strength is more than or equal to 400MPa, and the elongation A50 is more than or equal to 35 percent.
A production method of a low-cost 400 MPa-grade cold-rolled continuous-annealed steel strip comprises the following steps:
1) steel making, namely smelting molten steel;
2) continuously casting the steel plate into a continuously cast plate blank, wherein the thickness of the continuously cast plate blank is 230 mm;
3) hot continuous rolling, namely carrying out hot continuous rolling on a continuous casting slab, wherein the temperature of a soaking section of a slab heating furnace is 1250 +/-15 ℃, and the in-furnace time is 170-260 min; the finishing temperature is 880 +/-15 ℃; adopting front-section laminar cooling, wherein the coiling temperature is 640 +/-15 ℃, and obtaining a hot-rolled steel strip;
4) performing acid continuous rolling, namely performing continuous acid washing and cold continuous rolling on the hot rolled steel strip, and obtaining a cold-hard steel strip by adopting a five-rack six-roller CVC + continuous cold rolling mill with a cold rolling total reduction rate of 58.3-82.6%;
5) and (3) continuously annealing, namely continuously annealing the cold-hard steel strip, heating the continuous annealing furnace by adopting a vertical full radiant tube, wherein the soaking temperature is 770 +/-10 ℃, the slow cooling temperature is 670 +/-10 ℃, the fast cooling temperature is 450 +/-10 ℃, the overaging temperature is 370 +/-10 ℃, the final cooling tapping temperature is less than or equal to 155 ℃, and the elongation of a temper mill is 0.6-1.4%, so that the cold-rolled steel strip is obtained.
Table 1 shows the chemical composition (in weight%) of the steel of examples of the present invention, with the balance being Fe and other unavoidable impurities.
Table 1 chemical composition of the steels of the examples of the invention, in units: weight percent (%)
| Chemical elements | C | Si | Mn | P | S | Als |
| The invention | 0.12～0.18 | ≤0.040 | 0.25～0.45 | 0.015～0.020 | ≤0.020 | 0.020～0.060 |
| Example 1 | 0.15 | 0.032 | 0.29 | 0.020 | 0.020 | 0.052 |
| Example 2 | 0.18 | 0.018 | 0.35 | 0.018 | 0.011 | 0.025 |
| Example 3 | 0.15 | 0.022 | 0.27 | 0.015 | 0.003 | 0.032 |
| Example 4 | 0.12 | 0.029 | 0.45 | 0.018 | 0.008 | 0.060 |
| Example 5 | 0.16 | 0.040 | 0.25 | 0.016 | 0.005 | 0.020 |
Molten steel meeting the chemical composition requirement is obtained through KR desulfurization of molten iron and smelting in a converter, the molten steel is subjected to slab continuous casting after LF refining to obtain a qualified continuous casting billet, the continuous casting billet is sent to a hot rolling heating furnace to be reheated, and phosphorus is removed after discharge and then sent to a hot continuous rolling mill set to be rolled; the steel is rolled by a rough rolling unit and a fine continuous rolling unit, and is coiled after being cooled by front-section laminar flow, and the control parameters of the hot rolling process are shown in a table 2.
TABLE 2 Hot Rolling Process parameters of steels of examples of the invention
| Hot rolling parameters | Heating temperature/. degree.C | Heating time/min | Final Rolling temperature/. degree.C | Coiling temperature/. degree.C |
| The invention | 1250±15 | 170～260 | 880±15 | 640±15 |
| Example 1 | 1235 | 260 | 870 | 630 |
| Example 2 | 1255 | 210 | 872 | 643 |
| Example 3 | 1245 | 202 | 865 | 625 |
| Example 4 | 1265 | 170 | 895 | 652 |
| Example 5 | 1260 | 178 | 886 | 655 |
The hot rolled steel strip is subjected to continuous acid pickling in an ascending way in a cold rolling acid continuous rolling unit and is subjected to cold continuous rolling in five racks, and the control parameters of the cold rolling process are shown in a table 3.
TABLE 3 Cold Rolling Process parameters of steels of examples of the invention
The low-cost 400 MPa-grade cold-rolled continuous-annealed steel strip obtained by the method is stretched according to a metal material tensile test method (GB/T228.1), and the mechanical property values are shown in Table 4.
TABLE 4 mechanical Properties of steels of examples of the invention
| Thickness of steel strip (mm) | Yield strength (MPa) | Tensile strength (MPa) | Elongation after fracture A50(％) | |
| The invention | 0.4～2.5 | ≥250 | ≥400 | ≥35 |
| Example 1 | 0.4 | 285 | 423 | 35 |
| Example 2 | 1.0 | 263 | 410 | 40 |
| Example 3 | 1.4 | 278 | 411 | 38 |
| Example 4 | 1.5 | 252 | 403 | 39 |
| Example 5 | 2.5 | 265 | 409 | 37 |
The present invention is not limited to the above embodiments, and any structural changes made under the teaching of the present invention shall fall within the scope of the present invention, which is similar or similar to the technical solutions of the present invention.
The techniques, shapes, and configurations not described in detail in the present invention are all known techniques.
Claims (8)
1. The low-cost 400 MPa-grade cold-rolled continuous annealing steel strip is characterized by comprising the following chemical components in percentage by mass: c: 0.12-0.18%, Si is less than or equal to 0.040%, and Mn: 0.25-0.45%, P: 0.015-0.020%, S is less than or equal to 0.020%, Als: 0.020 to 0.060% and the balance Fe and inevitable impurities.
2. The low-cost 400MPa grade cold-rolled continuous-annealed steel strip according to claim 1, wherein the thickness specification of the steel strip is 0.4-2.5 mm, and the width specification is 1000-1800 mm.
3. The low-cost 400MPa grade cold rolled continuous annealed steel strip according to claim 1, characterized by the following mechanical properties: the yield strength is more than or equal to 250MPa, the tensile strength is more than or equal to 400MPa, and the elongation percentage A50≥35％。
4. A method for producing a low-cost 400MPa grade cold rolled continuous annealed steel strip according to any of claims 1 to 3, characterized by comprising the steps of:
1) steel making, namely smelting molten steel;
2) continuous casting, namely continuously casting the mixture into a continuous casting slab;
3) hot continuous rolling, namely performing hot continuous rolling on the continuous casting plate blank to obtain a hot rolled steel strip;
4) acid continuous rolling, namely continuously acid washing and cold continuous rolling the hot rolled steel strip to obtain a cold hard steel strip;
5) and continuously annealing, namely continuously annealing the cold-hard steel strip to obtain the cold-rolled steel strip.
5. The method for producing a low-cost 400MPa grade cold rolled continuous annealed steel strip according to claim 4, characterized in that the thickness of the continuous casting slab of the continuous casting process in the step 2) is 230 mm.
6. The production method of the low-cost 400 MPa-grade cold-rolled continuous-annealed steel strip according to claim 4, characterized in that in the hot continuous rolling process in the step 3), the temperature of a soaking section of a slab heating furnace is 1250 +/-15 ℃, and the in-furnace time is 170-260 min; the finishing temperature is 880 +/-15 ℃; adopting front-section laminar cooling, wherein the coiling temperature is 640 +/-15 ℃.
7. The method for producing the low-cost 400MPa cold-rolled and continuously-annealed steel strip as claimed in claim 4, wherein the acid continuous rolling process in the step 4) adopts a five-stand six-roller CVC+And in the continuous cold rolling mill, the total cold rolling reduction rate is 58.3-82.6%.
8. The production method of the low-cost 400 MPa-grade cold-rolled continuous-annealed steel strip according to claim 4, characterized in that the continuous annealing process in the step 5) adopts a vertical full radiant tube heating continuous annealing furnace, the soaking temperature is 770 +/-10 ℃, the slow cooling temperature is 670 +/-10 ℃, the fast cooling temperature is 450 +/-10 ℃, the overaging temperature is 370 +/-10 ℃, the final cooling tapping temperature is less than or equal to 155 ℃, and the elongation of a temper mill is 0.6-1.4%.
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