CN116815050B - A 450MPa grade cold-rolled steel plate based on hood annealing, preparation method and application thereof - Google Patents
A 450MPa grade cold-rolled steel plate based on hood annealing, preparation method and application thereof Download PDFInfo
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- 239000010960 cold rolled steel Substances 0.000 title claims abstract description 135
- 238000000137 annealing Methods 0.000 title claims abstract description 70
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000004519 manufacturing process Methods 0.000 claims abstract description 22
- 229910000831 Steel Inorganic materials 0.000 claims description 35
- 239000010959 steel Substances 0.000 claims description 35
- 238000001816 cooling Methods 0.000 claims description 24
- 238000005096 rolling process Methods 0.000 claims description 20
- 238000005097 cold rolling Methods 0.000 claims description 17
- 238000010438 heat treatment Methods 0.000 claims description 14
- 238000005098 hot rolling Methods 0.000 claims description 14
- 238000005266 casting Methods 0.000 claims description 13
- 229910000859 α-Fe Inorganic materials 0.000 claims description 13
- 239000002253 acid Substances 0.000 claims description 12
- 229910001567 cementite Inorganic materials 0.000 claims description 12
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 claims description 12
- 229910001562 pearlite Inorganic materials 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 8
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 239000003963 antioxidant agent Substances 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- 230000003064 anti-oxidating effect Effects 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 5
- 239000003973 paint Substances 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 238000000034 method Methods 0.000 abstract description 19
- 230000000052 comparative effect Effects 0.000 description 22
- 239000000126 substance Substances 0.000 description 10
- 239000000203 mixture Substances 0.000 description 9
- 230000009286 beneficial effect Effects 0.000 description 5
- 238000011161 development Methods 0.000 description 5
- 230000003078 antioxidant effect Effects 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000011056 performance test Methods 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011534 incubation Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005246 galvanizing Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000002905 metal composite material Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- 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
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Abstract
本发明提供了一种基于罩式退火的450MPa级冷轧钢板、制备方法及应用。通过本发明的制备方法制得了一种低成本、屈服强度以及抗拉强度较好且屈强比较低的450MPa级冷轧钢板用于制造汽车部件，解决了相关工艺生产的用于制造汽车部件的冷轧钢板成本高、性能波动大，屈强比高的问题。The present invention provides a 450MPa cold-rolled steel sheet based on hood annealing, a preparation method and an application thereof. The preparation method of the present invention is used to prepare a low-cost 450MPa cold-rolled steel sheet with good yield strength and tensile strength and low yield strength ratio for manufacturing automobile parts, which solves the problems of high cost, large performance fluctuation and high yield strength ratio of cold-rolled steel sheets for manufacturing automobile parts produced by related processes.
Description
Technical Field
The invention relates to the technical field of steel heat treatment, in particular to a 450 MPa-level cold-rolled steel plate based on hood-type annealing, a preparation method and application.
Background
With the increasing demands of application fields such as the automobile industry, development of high-strength cold-rolled steel sheets and research of production industry have become hot spots. Since the deformation resistance itself has been great at the time of cold rolling of steel sheets, control of the shape and dimensional accuracy thereof has been difficult, and the requirements of the automotive industry for the welding performance of steel sheets have also required that the chemical composition of high strength steel sheets be maintained at a low carbon equivalent level. Therefore, the development of modern cold-rolled high-strength steel is mainly focused on the development of annealing/hot-dip galvanizing processes after cold rolling, i.e., not only the strength of steel is controlled by controlling chemical element components, but also the strength grade of steel sheet is required to be improved by the annealing process after cold rolling.
The cold-rolled high-strength steel mainly comprises C, mn and Si, and is designed by adding a microalloying component of metal composite such as Nb, ti and the like and a low-carbon component, and realizes the high strength of the plate and strip through fine grain, precipitation strengthening and other approaches. However, the steel plate obtained by the existing preparation method has higher cost, large performance fluctuation and high yield ratio. In the annealing process, continuous annealing has become the main annealing process in recent years, and although continuous annealing is easier to obtain a target annealing structure so as to enable the steel plate to achieve the target mechanical property, due to higher equipment cost of continuous annealing, some manufacturers do not have the capability of implementing continuous annealing, and need other annealing modes for heat treatment, such as traditional hood annealing, however, the performance of the steel plate obtained by the hood annealing in the related art is lower than that of the steel plate obtained by continuous annealing, so that the steel plate does not meet the market demand.
In view of the foregoing, there is a need for a 450MPa grade cold rolled steel sheet based on cap annealing, a method for preparing the same, and applications thereof to solve the above problems.
Disclosure of Invention
The invention mainly aims to provide a 450 MPa-level cold-rolled steel plate based on hood-type annealing, a preparation method and application thereof, so as to solve the technical problems of high cost, large performance fluctuation and high yield ratio of the steel plate obtained by the prior art.
In order to achieve the aim, the invention provides a 450MPa grade cold-rolled steel plate based on hood annealing, which comprises, by mass, 0.07-0.09% of C, 0.75-0.85% of Si, 1.80-2.00% of Mn, 0.012% of P, 0.008% of S, 0.02-0.05% of Al, 0.4-0.5% of Cr, and the balance of Fe and unavoidable impurities, wherein the 450MPa grade cold-rolled steel plate comprises.
Wherein the thickness of the cold-rolled steel plate is 0.7-1.5mm, and further preferably the thickness of the cold-rolled steel plate is 1.2-1.3mm.
The yield strength of the cold-rolled steel plate is 251MPa-286MPa, the tensile strength is 450MPa-471MPa, the yield ratio is 0.55-0.61, and the elongation is more than 25%.
The beneficial effects of the invention are as follows:
(1) The components of the 450 MPa-level cold-rolled steel sheet provided by the invention are removed from the commonly used microalloying components of Nb, ti and other metals in the related technology, and Cr is adopted as the microalloying component. By using proper components and corresponding proportions, more pearlite with better plasticity, ferrite with higher strength and cementite are formed inside the cold-rolled steel plate, so that the yield strength and tensile strength of the cold-rolled steel plate are maintained, and the yield ratio is reduced. In addition, cr is cheaper than Nb and Ti, so that the cost of the 450MPa grade cold-rolled steel plate is reduced.
(2) The 450 MPa-grade cold-rolled steel sheet provided by the invention has the advantages that the yield strength of the cold-rolled steel sheet can be kept between 251MPa and 286MPa, and the tensile strength is kept between 450MPa and 471MPa by controlling the thickness of the steel sheet, so that the provided cold-rolled steel sheet has better service performance.
The invention also provides a preparation method for preparing the 450 MPa-grade cold-rolled steel plate, which comprises the following steps:
Carrying out hot rolling and cold rolling on casting blanks of the components corresponding to the 450 MPa-level cold-rolled steel plate in sequence to obtain cold-rolled steel;
And (3) performing cover annealing on the cold-rolled steel, cooling to 250-350 ℃ along with a furnace after annealing, and then air-cooling to room temperature to obtain the 450 MPa-grade cold-rolled steel plate, wherein the annealing temperature is 690-730 ℃, and the heat preservation time is 4-5h.
Preferably, the hot rolling comprises the steps of heating the casting blank, then sequentially carrying out rough rolling, finish rolling, laminar cooling and coiling to obtain hot rolled steel, wherein the thickness of the casting blank after rough rolling is 25-40mm, and the thickness of the hot rolled steel is 3.0-6.0mm.
Preferably, the target temperature for heating in the hot rolling step is 1180-1220 ℃, the heating time is 110-130min, the finish rolling temperature is 870-940 ℃, the cooling speed of laminar cooling is 5-15 ℃ per second, and the coiling temperature is 600-650 ℃.
Preferably, the method further comprises the step of removing an oxide layer on the surface of the hot rolled steel before the step of cold rolling, wherein the rolling reduction rate is 70-77%, and the thickness of the cold rolled steel is 0.7-1.5mm.
Preferably, the oxide layer on the surface of the hot rolled steel is removed by acid washing, and the acid used for acid washing comprises one or more of sulfuric acid, hydrochloric acid and hydrofluoric acid.
Preferably, the method further comprises the step of coating an antioxidant on the surface of the cold rolled steel before the step of carrying out the hood annealing, wherein the antioxidant comprises an anti-oxidation paint.
The beneficial effects of the invention are as follows:
(1) The cold-rolled steel plate prepared by the preparation method provided by the invention has good comprehensive performance, the yield strength can be kept between 251MPa and 286MPa, the tensile strength is kept between 450MPa and 471MPa, the cold-rolled steel plate with ferrite, cementite and pearlite is obtained by selecting proper components and casting blanks with corresponding proportions, performing hot rolling and cold rolling and then performing cover annealing, the yield strength of the cold-rolled steel plate obtained by the method is between 251MPa and 286MPa, the tensile strength is between 450MPa and 471MPa, the yield ratio is between 0.55 and 0.61, and the elongation is more than 25%.
(2) According to the invention, the contents of ferrite, cementite and pearlite in the cold-rolled steel plate are effectively improved by controlling the parameters of the hood annealing, when the hood annealing is carried out at 690 ℃, the cementite cannot be discretely separated out, the strip-shaped distribution is shown in steel, the crystal grains are fine, the yield strength of the cold-rolled steel plate reaches about 380MPa, when the temperature is further increased, the crystal grains grow up, when the heat preservation time reaches 4 hours, a large amount of ferrite and carbide are separated out, a large amount of ferrite and carbide are generated in the cold-rolled steel plate, the yield strength is further improved, and when the temperature reaches 710 ℃, the pearlite is formed, the plasticity of the cold-rolled steel plate is improved, and the tensile strength of the cold-rolled steel plate is further improved.
(3) Compared with the existing continuous annealing process, the annealing process adopted by the invention is hood annealing, has low equipment cost, and for some factories without continuous annealing conditions, the cold-rolled steel sheet prepared by the preparation method provided by the invention has the same performance as the cold-rolled steel sheet obtained by continuous quenching, ensures the performance of the product while reducing the cost and the production condition, and is beneficial to promoting the industry development of the steel industry.
The invention also provides an application of the 450MPa grade cold-rolled steel plate or the 450MPa grade cold-rolled steel plate prepared by the preparation method in the manufacture of automobile parts.
The invention has the beneficial effects that the cold-rolled steel plate with low cost, good yield strength and tensile strength and low yield ratio is used for manufacturing automobile parts, and the problems of high cost, large performance fluctuation and high yield ratio of the existing cold-rolled steel plate for manufacturing automobile parts are solved.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
It should be noted that all directional indicators (such as upper and lower..times.) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a certain specific posture, and if the specific posture is changed, the directional indicator is changed accordingly.
Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.
Moreover, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the embodiments, and when the technical solutions are contradictory or cannot be implemented, it should be considered that the combination of the technical solutions does not exist, and is not within the scope of protection claimed by the present invention.
The invention provides a 450MPa grade cold-rolled steel sheet based on hood annealing, which comprises, by mass, 0.07-0.09% of C, 0.75-0.85% of Si, 1.80-2.00% of Mn, 0.012% of P, 0.008% of S, 0.02-0.05% of Al, 0.4-0.5% of Cr, and the balance of Fe and unavoidable impurities, wherein the crystal form of the 450MPa grade cold-rolled steel sheet steel comprises ferrite, cementite and pearlite. The components of 450MPa grade cold-rolled steel plates are removed from the microalloying components of Nb, ti and other metals commonly used in the related technology, and Cr is adopted as the microalloying component. By using proper components and corresponding proportions, more pearlite with better plasticity, ferrite with higher strength and cementite are formed inside the cold-rolled steel plate, so that the yield strength and tensile strength of the cold-rolled steel plate are maintained, and the yield ratio is reduced. In addition, cr is cheaper than Nb and Ti, so that the cost of the 450MPa grade cold-rolled steel plate is reduced.
In the present invention, the thickness of the cold-rolled steel sheet is 0.7 to 1.5mm, and more preferably, the thickness of the cold-rolled steel sheet is 1.2 to 1.3mm. The thickness of the steel plate is controlled, so that the yield strength of the cold-rolled steel plate can be kept between 251MPa and 286MPa, and the tensile strength of the cold-rolled steel plate can be kept between 450MPa and 471MPa, and the cold-rolled steel plate has good service performance.
In the invention, the yield strength of the cold-rolled steel plate is 251MPa-286MPa, the tensile strength is 450MPa-471MPa, the yield ratio is 0.55-0.61, and the elongation is more than 25%.
The invention also provides a preparation method for preparing the 450 MPa-grade cold-rolled steel plate, which comprises the following steps:
The cold rolled steel is obtained by sequentially carrying out hot rolling and cold rolling on casting blanks of the components corresponding to the 450 MPa-level cold rolled steel plate, and the cold rolled steel plate with ferrite, cementite and pearlite is obtained by carrying out cover annealing after selecting proper components and casting blanks with corresponding proportions, wherein the yield strength of the cold rolled steel plate obtained by the method is 251MPa-286MPa, the tensile strength is 450MPa-471MPa, the yield ratio is 0.55-0.61, and the elongation is more than 25%.
And (3) performing cover annealing on the cold-rolled steel, cooling to 250-350 ℃ along with a furnace after annealing, and then performing air cooling to room temperature to obtain the 450 MPa-grade cold-rolled steel plate, wherein the annealing temperature is 690-730 ℃, and the heat preservation time is 4-5h. The method has the advantages that the content of ferrite, cementite and pearlite in the cold-rolled steel plate is effectively improved by controlling the parameters of the hood annealing, when the hood annealing is carried out at 690 ℃, the cementite cannot be discretely precipitated, the steel is in banded distribution, the grains are fine, the yield strength of the cold-rolled steel plate reaches about 380MPa, when the temperature is further increased, the grains grow up, when the heat preservation time reaches 4 hours, the cementite is precipitated, a large amount of ferrite and carbide are generated in the cold-rolled steel plate, the yield strength is further improved, when the temperature reaches 710 ℃, the pearlite is formed, the plasticity of the cold-rolled steel plate is improved, and the tensile strength of the cold-rolled steel plate is further improved.
And because the annealing process adopted by the invention is hood annealing, compared with the existing continuous annealing process, the equipment cost is low, and for some factories without continuous annealing conditions, the cold-rolled steel sheet prepared by the preparation method provided by the invention has the performance equivalent to that of the cold-rolled steel sheet obtained by continuous quenching, and the invention ensures the performance of the product while reducing the cost and the production condition, thereby being beneficial to promoting the industry development of the steel industry.
The hot rolling comprises the steps of heating the casting blank, then sequentially carrying out rough rolling, finish rolling, laminar cooling and coiling to obtain hot rolled steel, wherein the thickness of the casting blank after rough rolling is 25-40mm, and the thickness of the hot rolled steel is 3.0-6.0mm. The hot rolling production is carried out within the thickness specification range, the refining effect of the recrystallization structure is good, and the product with uniform mechanical property is obtained.
The target temperature for heating in the hot rolling step is 1180-1220 ℃, the heating time is 110-130min, the finish rolling temperature is 870-940 ℃, the cooling speed of laminar cooling is 5-15 ℃ per second, the austenitic rolling is realized under the condition of lower energy consumption by controlling the hot rolling temperature, the condition of dynamic recrystallization is realized, the coiling temperature is 600-650 ℃, and the coiling temperature range influences the content of ferrite, cementite and pearlite in the finished product.
And removing an oxide layer on the surface of the hot rolled steel before the cold rolling.
In the cold rolling step, the rolling reduction is 70-77%, the thickness of the cold rolled steel is 0.7-1.5mm, the cold rolled steel with the thickness similar to that of the finished cold rolled steel sheet is obtained through cold rolling, and the finished cold rolled steel sheet with excellent performance can be obtained through subsequent cover annealing.
And acid washing is adopted to remove the oxide layer on the surface of the hot rolled steel, and the acid used for acid washing comprises one or more of sulfuric acid, hydrochloric acid and hydrofluoric acid.
The method further comprises the step of coating an antioxidant on the surface of the cold rolled steel before the hood-type annealing, wherein the antioxidant comprises an anti-oxidation paint.
The 450MPa grade cold-rolled steel sheet or the 450MPa grade cold-rolled steel sheet prepared by the preparation method is applied to the manufacture of automobile parts. The cold-rolled steel plate with low cost, good yield strength and tensile strength and low yield ratio is used for manufacturing automobile parts, and the problems of high cost, large performance fluctuation and high yield ratio of the existing cold-rolled steel plate for manufacturing automobile parts are solved.
For a further understanding of the present invention, an illustration is now given:
according to the chemical compositions and proportions set in Table 1, different casting blanks are prepared according to the following process flows, and the chemical compositions C, si, mn, cr, al, the balance of Fe and unavoidable impurities are used as raw materials to perform converter smelting, refining, continuous casting, and direct heating or soaking of the casting blanks.
TABLE 1 chemical composition (unit: wt%, balance Fe and unavoidable impurities)
| Project | C | Si | Mn | P | S | Al | Cr |
| Proportion 1 | 0.08 | 0.78 | 1.90 | 0.0055 | 0.0024 | 0.03 | 0.45 |
| Proportion 2 | 0.09 | 0.85 | 2.00 | 0.012 | 0.008 | 0.05 | 0.40 |
| Proportion 3 | 0.07 | 0.75 | 1.80 | 0.0050 | 0.0020 | 0.02 | 0.50 |
| Proportion 4 | 0.09 | 0.85 | 2.00 | 0.012 | 0.008 | 0.05 | 0.30 |
| Proportion 5 | 0.07 | 0.75 | 1.70 | 0.0050 | 0.0020 | 0.02 | 0.60 |
Example 1 preparation of 450MPa grade cold rolled steel sheet based on hood annealing comprising the steps of taking a cast slab (thickness of the cast slab is 210 mm) of the chemical composition as described in the ratio 1 in Table 1, and carrying out hot rolling specifically:
Heating to 1220 ℃ in a heating furnace for 118 minutes, performing 7-pass rolling in a rough rolling process, performing 7-pass rolling in a finish rolling process, performing hot rolling at 870 ℃ and then performing laminar cooling, wherein the cooling speed of the laminar cooling is 5-15 ℃ per second, cooling to 30 ℃ in a coiling temperature, and coiling to obtain the hot rolled steel with the thickness of 5.5mm.
And then cold rolling, specifically, the hot rolled steel is subjected to acid washing (the acid adopted by the acid washing is hydrochloric acid) to remove oxide skin, and then cold rolling is performed on a cold rolling mill, wherein the reduction rate is 76%, and the target thickness is 1.3mm (namely, the thickness of the cold rolled steel sheet).
Finally, performing cover annealing, namely coating anti-oxidation paint (QY 600 type anti-oxidation paint) on the surface of cold rolled steel, performing cover annealing, wherein nitrogen protection is adopted during annealing, the annealing temperature is 730 ℃, the heat preservation time is 4 hours, cooling to 250-350 ℃ along with a furnace under the acceleration of cooling water after annealing, then carrying out air cooling to about 90 ℃ with a cover, discharging from the furnace, cooling to room temperature, cooling to 300 ℃ along with the furnace after annealing, and then cooling to room temperature.
Example 2 differs from example 1 in that the annealing temperature is 710 ℃ and the incubation time is 5h.
Example 3 differs from example 1 in that the annealing temperature is 690℃and the incubation time is 5h.
Example 4 the difference from example 1 is that a cast slab having the chemical composition shown in the formula 2 in Table 1 was obtained.
Example 5 the difference from example 1 is that a cast slab having the chemical composition shown in the formula 3 in Table 1 was obtained.
Example 6 the difference from example 1 is that the cold rolled steel sheet has a thickness of 1.2mm.
Example 7 the difference from example 1 is that the cold rolled steel sheet has a thickness of 0.7mm.
Example 8 the difference from example 1 is that the cold rolled steel sheet has a thickness of 1.5mm.
Comparative example 1 the difference from example 1 is that the annealing temperature was 800℃and the holding time was 6 hours.
Comparative example 2 the difference from example 1 is that the annealing temperature was 600℃and the soak time was 3 hours.
Comparative example 3A cast slab having the chemical composition shown in the formula 4 in Table 1 was obtained, unlike example 1.
Comparative example 4A cast slab having the chemical composition shown in the formula 5 in Table 1 was obtained, unlike example 1.
Comparative example 5 the difference from example 1 is that the cold rolled steel sheet has a thickness of 0.5mm.
Comparative example 6 the difference from example 1 is that the cold rolled steel sheet has a thickness of 1.7mm.
Comparative example 7 the difference from example 1 is that Cr in the ratio 1 in Table 1 is replaced with Nb.
Comparative example 8 the difference from example 1 is that Cr in the ratio 1 in Table 1 is replaced with Ti.
Comparative example 9 the difference from example 1 is that the cap annealing was replaced with continuous annealing in the related art.
The cold rolled steel sheets obtained in examples 1 to 8 and comparative examples 1 to 9 were subjected to a yield strength test and a tensile strength test performance test according to the test method prescribed in GB/T228.1-2020, and the results are shown in Table 2:
Table 2 results of performance tests for examples 1-8 and comparative examples 1-9
As is clear from examples 1 to 8, the cold-rolled steel sheet produced by the present invention has a yield strength of 251MPa to 286MPa, a tensile strength of 450MPa to 471MPa, a yield ratio of 0.55 to 0.61, and an elongation of >25%.
As is clear from examples 1 to 3 and comparative examples 1 to 2, when the hood-type annealing temperature is controlled to 690 ℃ to 730 ℃, the yield strength of the cold-rolled steel sheet is 253 MPa to 261MPa, the tensile strength is 455 MPa to 468MPa, and the yield ratio is 0.55 to 0.56.
When the annealing temperature is higher than 730 ℃, the pearlite generated in the cold-rolled steel sheet is more due to the higher temperature, and the relative content of ferrite and carburized body is reduced, so that the yield strength and the tensile strength of the obtained cold-rolled steel sheet are reduced, for example, as shown by the performance effect of comparative example 1, the yield strength is 232MPa, the tensile strength is 442MPa, and the yield ratio is 0.52, which is far lower than those of examples 1-3.
When the annealing temperature is lower than 690 ℃, for example, comparative example 2, although it is superior in yield strength and tensile strength, the previously formed crystal grains are broken due to the early cold rolling and the later temperature is low, so that the cold rolled steel sheet cannot be recrystallized, resulting in non-uniform product properties obtained at the temperature, incomplete annealing, failing to meet the factory requirements, and since the cold rolled steel sheet in comparative example 2 is too high in yield strength, it is difficult to process and shape and use for manufacturing automobile parts.
As is apparent from examples 1, 4,5 and comparative examples 3 to 4, the ratio of each chemical component of the cold-rolled steel sheet of the present invention is very important, and particularly, by controlling the content of Cr in the whole cold-rolled steel sheet, a cold-rolled steel sheet having a yield strength of 253MPa to 286MPa, a tensile strength of 455MPa to 471MPa and a yield ratio of 0.55 to 0.61 can be obtained.
When the Cr content in the cold-rolled steel sheet was too high, for example, the cold-rolled steel sheet obtained in comparative example 4 had a yield strength of 245MPa and a tensile strength of 434MPa in the performance test, which was lower than those provided in examples 1, 4 and 5, due to the excessive plasticity of the cold-rolled steel sheet.
When the Cr content in the cold-rolled steel sheet is too low, for example, the cold-rolled steel sheet obtained in comparative example 3, although it is excellent in yield strength and tensile strength due to the too low Cr content, the obtained cold-rolled steel sheet is liable to rust, and the yield strength is too high, resulting in difficulty in forming and use for manufacturing automobile parts.
From examples 1, examples 6 to 8 and comparative examples 5 to 6, it is understood that the control of the appropriate thickness of the cold rolled steel sheet can effectively control the yield strength and tensile strength so that the cold rolled steel sheet can be used for manufacturing automobile parts well, that when the cold rolled steel sheet is too thin, the yield strength and tensile strength are low, and that the performance requirements of the 450MPa grade cold rolled steel sheet cannot be satisfied, and that when the cold rolled steel sheet is too thick, the yield strength and tensile strength are greatly increased, resulting in difficulty in processing, difficulty in processing and forming, and use for manufacturing automobile parts.
As is clear from examples 1 and 7, the substitution of Cr for Nb in the cold-rolled steel sheet according to the present application increases the yield strength, but the reduction in tensile strength is large and the yield ratio is large, and the cold-rolled steel sheet obtained in example 1 is more plastic than comparative example 7, and is preferably suitable for use in manufacturing automobile parts, indicating that the present application uses Cr as a microalloying ingredient for cold-rolled steel sheets, and can ensure the performance of cold-rolled steel sheets while reducing the production cost.
As is apparent from example 1 and comparative example 8, substitution of Cr for Ti in the cold-rolled steel sheet according to the present application greatly improves both yield strength and tensile strength, and substitution of Cr for Ti reduces the production cost of the cold-rolled steel sheet.
As is apparent from example 1 and comparative example 9, the cold-rolled steel sheet obtained by the cap annealing according to the present application has a lower yield strength than the cold-rolled steel sheet obtained by the continuous annealing according to the related art, but has a relatively close tensile strength, and the cold-rolled steel sheet obtained by the cap annealing according to the present application has a lower yield ratio than the cold-rolled steel sheet obtained by the continuous annealing according to the related art, has a better plasticity, can be formed by a better process, and can be used for manufacturing automobile parts.
In the above technical solution of the present invention, the above is only a preferred embodiment of the present invention, and therefore, the patent scope of the present invention is not limited thereto, and all the equivalent structural changes made by the content of the present invention under the technical concept of the present invention, or the direct/indirect application in other related technical fields are included in the patent protection scope of the present invention.
Claims (8)
1. The 450MPa grade cold-rolled steel sheet based on hood annealing is characterized by comprising, by mass, 0.07-0.09% of C, 0.75-0.85% of Si, 1.80-2.00% of Mn, 0.012% of P, 0.008% of S, 0.02-0.05% of Al, 0.4-0.5% of Cr, and the balance of Fe and unavoidable impurities, wherein the crystal form of the 450MPa grade cold-rolled steel sheet comprises ferrite, cementite and pearlite;
Wherein the thickness of the cold-rolled steel plate is 0.7-1.5mm;
the preparation method of the 450 MPa-grade cold-rolled steel plate comprises the following steps:
carrying out hot rolling and cold rolling on casting blanks of the components corresponding to the 450 MPa-level cold-rolled steel plate in sequence to obtain cold-rolled steel;
and (3) performing cover annealing on the cold-rolled steel, cooling to 250-350 ℃ along with a furnace after annealing, and then air-cooling to room temperature to obtain the 450 MPa-grade cold-rolled steel plate, wherein the annealing temperature is 690-730 ℃, and the heat preservation time is 4-5h.
2. The 450MPa grade cold rolled steel sheet according to claim 1, wherein the cold rolled steel sheet has a yield strength of 251MPa-286MPa, a tensile strength of 450MPa-471MPa, a yield ratio of 0.55-0.61 and an elongation >25%.
3. The 450 MPa-grade cold-rolled steel sheet according to claim 1, wherein the hot rolling comprises the steps of heating the casting blank, performing rough rolling, finish rolling, laminar cooling and coiling in sequence to obtain hot rolled steel, and the thickness of the casting blank after rough rolling is 25-40mm and the thickness of the hot rolled steel is 3.0-6.0mm.
4. The 450MPa grade cold rolled steel sheet as claimed in claim 3, wherein the target temperature of heating in the hot rolling step is 1180-1220 ℃, the heating time is 110-130min, the finish rolling temperature is 870-940 ℃, the cooling rate of laminar cooling is 5-15 ℃ per second, and the coiling temperature is 600-650 ℃.
5. The 450MPa grade cold rolled steel sheet according to claim 1, further comprising removing an oxide layer of the hot rolled steel surface before the cold rolling;
in the cold rolling step, the rolling reduction is 70-77%, and the thickness of the cold rolled steel is 0.7-1.5mm.
6. The 450MPa grade cold rolled steel sheet as claimed in claim 5, wherein the oxide layer on the hot rolled steel surface is removed by acid washing, and the acid used for acid washing comprises one or more of sulfuric acid, hydrochloric acid and hydrofluoric acid.
7. The 450 MPa-grade cold-rolled steel sheet according to claim 1, wherein the method for producing the 450 MPa-grade cold-rolled steel sheet further comprises coating an antioxidant agent on the surface of the cold-rolled steel sheet before the cap annealing, wherein the antioxidant agent comprises an anti-oxidation paint.
8. Use of a 450 MPa-grade cold-rolled steel sheet according to any one of claims 1-7 in the manufacture of automotive parts.
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| CN103469089A (en) * | 2013-09-11 | 2013-12-25 | 马鞍山市安工大工业技术研究院有限公司 | Cake-shaped crystal grain deep-draw double-phase steel plate and preparation method thereof |
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| DE102008056844A1 (en) * | 2008-11-12 | 2010-06-02 | Voestalpine Stahl Gmbh | Manganese steel strip and method of making the same |
| KR101353634B1 (en) * | 2011-11-18 | 2014-01-21 | 주식회사 포스코 | Low alloy cold rolled steel sheet having excellent weldability and strength and method for manufacturing the same |
| CN102925817B (en) * | 2012-11-27 | 2014-10-08 | 莱芜钢铁集团有限公司 | Cold-rolled steel sheet with yield strength of 980 MPa grade and manufacturing method thereof |
| CN103305762A (en) * | 2013-06-21 | 2013-09-18 | 安徽工业大学 | Cold-rolled dual-phase sheet steel with 400MPa-level tensile strength and preparation method thereof |
| CN103509997B (en) * | 2013-09-25 | 2016-02-10 | 马钢(集团)控股有限公司 | A kind of 440MPa level cold-rolled high-strength automobile structural steel and manufacture method thereof |
| CN103938101B (en) * | 2014-04-10 | 2016-08-31 | 马钢(集团)控股有限公司 | A kind of steel plate and preparation method thereof |
| CN106011643B (en) * | 2016-07-11 | 2018-05-01 | 攀钢集团攀枝花钢铁研究院有限公司 | A kind of tensile strength 590MPa grades of cold-rolled biphase steels and preparation method thereof |
| CN110230000A (en) * | 2019-07-10 | 2019-09-13 | 马鞍山钢铁股份有限公司 | A kind of 500MPa grades of galvanizing by dipping high-strength steel and preparation method thereof |
| CN111979489B (en) * | 2020-09-07 | 2021-11-16 | 鞍钢股份有限公司 | A kind of 780MPa grade high plasticity cold-rolled DH steel and preparation method thereof |
| CN113403549B (en) * | 2021-05-21 | 2022-08-16 | 鞍钢股份有限公司 | 1.2 GPa-grade fatigue-resistant high-formability ultrahigh-strength automobile steel and preparation method thereof |
| CN115948692B (en) * | 2022-09-22 | 2024-06-14 | 马鞍山钢铁股份有限公司 | Cold-rolled hood-type annealed high-strength steel with tensile strength of 450MPa for automobile and manufacturing method thereof |
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