CN117344241A - High-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness and manufacturing method thereof - Google Patents
High-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness and manufacturing method thereof Download PDFInfo
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- CN117344241A CN117344241A CN202210734605.8A CN202210734605A CN117344241A CN 117344241 A CN117344241 A CN 117344241A CN 202210734605 A CN202210734605 A CN 202210734605A CN 117344241 A CN117344241 A CN 117344241A
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- 229910001335 Galvanized steel Inorganic materials 0.000 title claims abstract description 86
- 239000008397 galvanized steel Substances 0.000 title claims abstract description 86
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 31
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 171
- 239000010959 steel Substances 0.000 claims abstract description 171
- 239000000758 substrate Substances 0.000 claims abstract description 138
- 230000007704 transition Effects 0.000 claims abstract description 44
- 229910000765 intermetallic Inorganic materials 0.000 claims abstract description 34
- 238000005246 galvanizing Methods 0.000 claims abstract description 29
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000013078 crystal Substances 0.000 claims abstract description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000000137 annealing Methods 0.000 claims abstract description 14
- 239000012535 impurity Substances 0.000 claims abstract description 12
- 229910052729 chemical element Inorganic materials 0.000 claims abstract description 8
- 238000007747 plating Methods 0.000 claims description 79
- 239000011701 zinc Substances 0.000 claims description 61
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 55
- 229910052725 zinc Inorganic materials 0.000 claims description 55
- 238000000034 method Methods 0.000 claims description 19
- 239000011248 coating agent Substances 0.000 claims description 16
- 238000000576 coating method Methods 0.000 claims description 16
- 238000010438 heat treatment Methods 0.000 claims description 15
- 238000001816 cooling Methods 0.000 claims description 11
- 238000002791 soaking Methods 0.000 claims description 8
- KCZFLPPCFOHPNI-UHFFFAOYSA-N alumane;iron Chemical compound [AlH3].[Fe] KCZFLPPCFOHPNI-UHFFFAOYSA-N 0.000 claims description 5
- 238000005097 cold rolling Methods 0.000 claims description 5
- 238000007654 immersion Methods 0.000 claims description 4
- 230000008901 benefit Effects 0.000 abstract description 5
- 238000002310 reflectometry Methods 0.000 abstract description 5
- 239000010410 layer Substances 0.000 description 103
- 239000000243 solution Substances 0.000 description 55
- 230000000052 comparative effect Effects 0.000 description 26
- 230000007547 defect Effects 0.000 description 13
- 230000008569 process Effects 0.000 description 13
- 238000013461 design Methods 0.000 description 11
- 239000011247 coating layer Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 9
- 230000007797 corrosion Effects 0.000 description 8
- 238000005260 corrosion Methods 0.000 description 8
- 238000004321 preservation Methods 0.000 description 8
- 239000011572 manganese Substances 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000002893 slag Substances 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- 239000003112 inhibitor Substances 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 238000005482 strain hardening Methods 0.000 description 2
- OUCSEDFVYPBLLF-KAYWLYCHSA-N 5-(4-fluorophenyl)-1-[2-[(2r,4r)-4-hydroxy-6-oxooxan-2-yl]ethyl]-n,4-diphenyl-2-propan-2-ylpyrrole-3-carboxamide Chemical compound C=1C=CC=CC=1C1=C(C=2C=CC(F)=CC=2)N(CC[C@H]2OC(=O)C[C@H](O)C2)C(C(C)C)=C1C(=O)NC1=CC=CC=C1 OUCSEDFVYPBLLF-KAYWLYCHSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- -1 iron-aluminum compound Chemical class 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- 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
-
- 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
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—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
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Coating With Molten Metal (AREA)
Abstract
The invention discloses a high-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness, which comprises a steel substrate, a hot-dip galvanized layer and a transition layer positioned between the steel substrate and the hot-dip galvanized layer, wherein the transition layer comprises zinc-iron intermetallic compounds, and the average thickness of the transition layer is 2-30% of the thickness of the hot-dip galvanized layer; the crystal grains in the hot dip galvanizing layer are in equiaxed crystal morphology, and the average crystal grain size is less than 30% of the thickness of the hot dip galvanizing layer; the steel substrate contains Fe and unavoidable impurities, and further contains the following chemical elements in percentage by mass: c:0.09-0.25%, mn:2.3-3.0%, si:0.3-2.0%, cr:0-0.7%, nb:0-0.03%, ti:0-0.03%. Correspondingly, the invention also discloses a manufacturing method of the high-strength cold-rolled hot-dip galvanized steel sheet, which comprises the following steps: (1) preparing a steel substrate; (2) continuous annealing; (3) hot dip galvanization. The cold-rolled hot-dip galvanized steel sheet prepared by the invention has excellent performance, and has the advantages of high surface reflectivity, high formability, low cost and the like.
Description
Technical Field
The present invention relates to a steel sheet and a method for manufacturing the same, and more particularly, to a cold-rolled hot-dip galvanized steel sheet and a method for manufacturing the same.
Background
In recent years, with rapid development of industrial production, cold-rolled hot-dip galvanized steel sheets have come into wide use in the fields of construction materials, automobiles, home appliances, and the like, and the application fields of cold-rolled hot-dip galvanized steel sheets have become more and more.
One of the characteristics of the hot dip galvanized steel sheet is that it has a good corrosion resistance. In the currently obtained hot-dip galvanized steel sheet, a zinc plating layer on the surface of the hot-dip galvanized steel sheet insulates the steel substrate from the external corrosive environment, and a primary cell can be formed between the zinc plating layer and the steel substrate, which can realize the improvement of the corrosion resistance of the steel substrate by the principle of sacrificial anode protection.
In the actual production of hot-dip galvanized steel sheets, hot-dip galvanized steel sheets are generally produced by continuously annealing a cold rolled steel substrate. The preparation method has higher production efficiency and can effectively reduce the production cost. In addition, in the manufacturing process, the technicians in the field can also adjust the mechanical properties of the steel substrate in a wider range by adjusting the technological parameters such as the temperature, the cooling speed and the like of the strip steel in the continuous annealing process and changing the components of the steel substrate so as to meet the requirements of users on the strength, the elongation and the like of the steel substrate.
However, there are few prior art solutions for the appearance characteristics of hot dip galvanized steel sheets, especially how to solve the surface gloss. Two patent documents with publication number CN106795612a, publication date 2017, 5 month 31, entitled "high-strength hot-dip galvanized steel sheet" and publication number CN107075653a, publication date 2017, 8 month 18, entitled "high-strength hot-dip galvanized steel sheet" disclose two high-strength hot-dip galvanized steel sheets with different surface gloss.
Disclosure of Invention
One of the objects of the present invention is to provide a high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss, which can obtain the advantage of high surface light reflection performance without post-treatment by optimally designing a self steel substrate, a hot-dip zinc layer and a transition layer between the steel substrate and the hot-dip zinc layer, and which has an attractive appearance, less surface defects and low cost, and which can simultaneously obtain excellent formability, high strength and high corrosion resistance.
In order to achieve the above object, the present invention provides a high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss, comprising a steel substrate, a hot-dip galvanized layer, and a transition layer between the steel substrate and the hot-dip galvanized layer:
the transition layer comprises zinc-iron intermetallic compound, and the average thickness of the transition layer is 2-30% of the thickness of the hot galvanizing layer;
the crystal grains in the hot dip galvanizing layer are in equiaxed crystal morphology, and the average crystal grain size is less than 30% of the thickness of the hot dip galvanizing layer;
the steel substrate contains Fe and unavoidable impurities, and further contains the following chemical elements in percentage by mass: c:0.09-0.25%, mn:2.3-3.0%, si:0.3-2.0%, cr:0-0.7%, nb:0-0.03%, ti:0-0.03%.
In the prior art, the surface glossiness of a hot dip galvanized layer of a conventional hot dip galvanized steel sheet is low, and the reason is that microscopic fluctuation exists on the surface of the hot dip galvanized layer, so that the reflectivity of light is affected. In addition, the grain size of the hot dip zinc coating layer of conventional hot dip zinc coated steel sheets is large, and the grain size in a plane parallel to the surface of the steel substrate is generally larger than the coating thickness.
Therefore, in order to solve the problem in the prior art, the inventor finds through a great deal of research and practice that when the microstructure of the hot dip galvanizing layer is changed, namely, the grain size of the hot dip galvanizing layer is reduced, the grains in the hot dip galvanizing layer can be in an equiaxed crystal morphology, and the microscopic fluctuation of the surface of the hot dip galvanizing layer can be obviously reduced, so that the design can effectively increase the glossiness of the surface of the hot dip galvanizing layer.
The inventor researches and discovers that the key of changing the microstructure and the surface microscopic fluctuation degree of the hot dip galvanizing layer is as follows: by adjusting the hot dip galvanizing process, a layer of transition layer with proper thickness and containing zinc-iron intermetallic compound is formed at the interface of the zinc liquid and the steel substrate before the surface of the steel substrate is solidified, thereby effectively increasing nucleation points during solidification of the zinc liquid and finally reducing the grain size of the hot dip galvanizing layer.
In the invention, the high-strength cold-rolled hot-dip galvanized steel sheet designed by the inventor consists of three layers of a hot-dip galvanized layer, a transition layer and a steel substrate, wherein the transition layer comprises zinc-iron intermetallic compounds, and when the thickness of the transition layer is less than 2% of the thickness of the hot-dip galvanized layer, the transition layer has no obvious influence on the microstructure of the hot-dip galvanized layer; and when the thickness of the transition layer is greater than 30% of the thickness of the hot galvanizing layer, the transition layer can influence the flow of liquid zinc on the surface of the steel substrate when the steel substrate is purged by the air knife, so that the local thickness of the hot galvanizing layer is uneven, and the surface quality and glossiness of the hot galvanizing layer are reduced. Thus, in the present invention, the average thickness of the transition layer is specifically controlled to be 2-30% of the thickness of the hot dip zinc coating.
Accordingly, based on this design of the present invention, the grains in the hot dip galvannealed layer of the steel sheet may be of equiaxed morphology, and it is necessary to specifically control the average grain size in the hot dip galvannealed layer to be less than 30% of the thickness of the hot dip galvannealed layer. This is because: when the average grain size in the hot dip zinc coating is greater than 30% of the thickness of the hot dip zinc coating, the effect of microscopic relief on the surface of the hot dip zinc coating is poor.
In addition, in the above technical solution of the present invention, the inventors have further designed the composition of the chemical elements of the steel substrate, and the purpose of the composition design is to obtain a steel substrate with better formability and lower cost while achieving a tensile strength higher than 980MPa.
Specifically, in the steel substrate of the high-strength cold-rolled hot-dip galvanized steel sheet, the design principle of each chemical element is as follows:
c: in the steel substrate of the high-strength cold-rolled hot-dip galvanized steel sheet, the content of the C element directly influences the strength and plasticity of the steel substrate. When the content of the C element in the steel is too low, a steel substrate with tensile strength higher than 980MPa is difficult to obtain, the effect of stabilizing austenite can be achieved by properly increasing the content of the C element, residual austenite can be formed at room temperature, and the work hardening rate and the elongation rate of the steel substrate are improved; when the content of C element in steel is too high, toughness and plasticity of steel are reduced. Therefore, in consideration of the influence of the C element on the steel properties, in the present invention, the mass percentage of the C element is controlled to be between 0.09 and 0.25%.
Mn: in the steel substrate of the high-strength cold-rolled hot-dip galvanized steel sheet, mn is one of main solid solution strengthening elements in the steel substrate, so that the strength of the steel substrate can be increased, and the hardenability of the steel substrate can be improved. When the content of Mn element in steel is too low, the strengthening effect of Mn is weakened; when the content of Mn element in steel is too high, however, the platability of the steel substrate is adversely affected. Based on this, considering the influence of the content of Mn element on the performance of the steel, it is necessary to strictly control the content of Mn element, and in the present invention, the mass percentage content of Mn element is controlled to be between 2.3 and 3.0%.
Si: in the steel substrate of the high-strength cold-rolled hot-dip galvanized steel sheet, si is also one of solid solution strengthening elements in the steel substrate, and can effectively improve the strength of the steel substrate. Meanwhile, the Si can inhibit carbide precipitation, promote C atoms to be enriched into austenite, and improve the stability of the austenite, so that the work hardening rate of the steel substrate is improved. When the content of Si element in steel is too low, the effect of improving the ductility of the steel substrate is poor; when the content of Si element in steel is too high, red iron sheet defects are easily formed on the hot rolled plate, the surface quality of the cold rolled plate and finished products is affected, and the manufacturing difficulty of strip steel is increased. Therefore, in order to exert the beneficial effect of the Si element, in the present invention, the mass percentage of the Si element is controlled to be between 0.3 and 2.0%.
Cr: in the steel substrate of the high-strength cold-rolled hot-dip galvanized steel sheet, the hardenability of the steel substrate can be effectively improved, the critical cooling speed of quenching is reduced, and the strength of the steel substrate is improved by adding a proper amount of Cr element. However, it should be noted that the Cr element content in the steel is not too high, and when the Cr element content in the steel is too high, the ductility of the steel substrate is reduced, the Cr element price is high, and the production cost is also significantly increased. Therefore, in the present invention, the mass percentage of Cr element is controlled to be 0-0.7%.
Nb: in the steel substrate of the high-strength cold-rolled hot-dip galvanized steel sheet, nb (C, N) is formed by combining with C, N, so that coarsening of grains in a hot working process can be effectively inhibited, ferrite grains are refined, and the strength and toughness of the steel substrate are improved. It should be noted, however, that the Nb element content in the steel is not too high, and that excessive Nb increases the recrystallization temperature and increases the cost of the steel substrate. Therefore, in the present invention, the mass percentage of Nb is controlled to be between 0 and 0.03%.
Ti: in the steel substrate of the high-strength cold-rolled hot-dip galvanized steel sheet according to the invention, ti element is Ti (C, N) formed by bonding to C, N, so that the structure of the steel substrate can be effectively refined. However, excessive Ti increases the size of the above-mentioned precipitates, thereby reducing ductility of the steel substrate and increasing production costs. Therefore, in order to exert the beneficial effects of the Ti element, in the present invention, the mass percentage of the Ti element is controlled to be between 0 and 0.03%.
Further, in the high-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness, the zinc-iron intermetallic compound accounts for more than 70% of the volume of the transition layer.
Further, in the high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to the invention, the transition layer further comprises an iron-aluminum intermetallic compound.
In the high-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness, the transition layer can be specifically composed of zinc-iron intermetallic compounds and iron-aluminum intermetallic compounds, wherein the zinc-iron intermetallic compounds influence the nucleation and solidification of zinc liquid and the microstructure of the zinc coating layer, so that the proportion of the zinc-iron intermetallic compounds in the transition layer is more than 70 percent. In addition, the iron-aluminum intermetallic compound is formed due to the reaction of the steel substrate with Al element in the plating solution, and the formation thereof cannot be completely avoided.
Further, in the high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to the invention, the thickness of the hot-dip galvanized layer is 5-25 μm.
In the cold-rolled hot-dip galvanized steel sheet designed by the invention, when the thickness of a hot-dip galvanized layer is less than 5 mu m, the steel sheet cannot achieve an excellent corrosion-resistant effect; when the thickness of the hot dip zinc coating is greater than 25 μm, the uniformity of the thickness of the coating at the edges and the middle of the steel substrate in the width direction is not easy to control, and the cost is too high. Therefore, in the present invention, the hot dip zinc coating thickness can be preferably controlled to be between 5 and 25 μm.
Further, in the high-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness, the steel substrate comprises the following chemical elements in percentage by mass: c:0.09-0.25%, mn:2.3-3.0%, si:0.3-2.0%, cr:0-0.7%, nb:0-0.03%, ti:0-0.03%, and the balance being Fe and unavoidable impurities.
Further, in the high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss, the hot-dip galvanized layer comprises the following components in percentage by mass: al:0.1-0.5%, and the balance Zn and unavoidable impurities.
In the technical scheme, the inventor can further ensure that the formed hot dip galvanizing layer contains 0.1-0.5% of Al element by mass percent and the balance of Zn and unavoidable impurities by designing the plating solution. In this design, since a small amount of Al element is added to the plating solution, al element is inevitably contained in the hot dip zinc coating.
When the content of Al element in the formed hot dip zinc coating layer is too high, al element is enriched on the surface of the hot dip zinc coating layer and forms an aluminum oxide film, thereby reducing the surface gloss, and therefore, the mass percentage of Al in the hot dip zinc coating layer of the present invention is preferably controlled to be 0.1 to 0.5%.
Further, in the high-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness, the average glossiness value of the surface is more than 400 gloss units, and the tensile strength is more than 980MPa.
Accordingly, another object of the present invention is to provide a method for manufacturing the high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss, which is provided by the present invention, wherein the manufacturing process is optimally designed, and the high-strength cold-rolled hot-dip galvanized steel sheet obtained by the manufacturing method has the advantages of low cost, high strength, good formability, and high corrosion resistance while having the advantages of high surface light reflection performance and less surface defects.
In order to achieve the above object, the present invention provides a method for producing the high-strength cold-rolled hot-dip galvanized steel sheet having high surface gloss, comprising the steps of:
(1) Preparing a steel substrate;
(2) Continuous annealing: heating the strip steel to the soaking temperature of 750-900 ℃ and then preserving heat for 30-180s;
(3) Hot dip galvanization: wherein the mass percentage of Al element in the plating solution is 0.10-0.25%; the total immersion time of the steel substrate in the plating solution is 1-5s; cooling the steel substrate to less than or equal to 250 ℃ at a cooling rate of more than 20 ℃/s after the steel substrate is taken out of the zinc pot.
In the technical scheme designed by the invention, the inventor does not limit the manufacturing process of the steel substrate in particular, and a person skilled in the art can adopt conventional technical means to correspondingly prepare the plate according to the chemical composition design of the designed steel substrate. Wherein in certain embodiments, one skilled in the art can perform smelting according to the chemical composition designed in the present invention, and specifically heat the cast slab at 1150-1250 deg.c for 0.5-3 hours, hot rolling at 850-950 deg.c, then coiling at 500-600 deg.c, then pickling and cold rolling the hot rolled coil, and controlling the final cold rolling reduction to be between 30-90% to produce the desired steel substrate.
In the continuous annealing process of the step (2), the soaking temperature is controlled to be 750-900 ℃ according to the selection of the soaking temperature and the heat preservation time, and the heat preservation is controlled to be 30-180 seconds mainly for obtaining proper mechanical properties and excellent surface platability of the steel substrate. When the soaking temperature is lower than 750 ℃ and the heat preservation time is lower than 30 seconds, the austenite content formed in the steel substrate in the soaking process is lower, so that the proportion of a strengthening phase formed after cooling is lower, and the tensile strength higher than 980MPa is difficult to realize; when the soaking temperature is higher than 900 ℃, and the heat preservation time is longer than 180 seconds, coarsening of crystal grains in the steel substrate can occur, the strength and toughness of the steel substrate are reduced, alloy elements in the steel substrate can be promoted to diffuse to the surface by high-temperature long-time annealing, the oxide thickness of the surface of the steel substrate is increased, and the platability of the surface of the steel substrate is not good.
In addition, in the hot dip galvanization process of step (3) of the present invention, the mass percentage of effective Al in the plating solution may be specifically controlled to be 0.10 to 0.25%. This is because, when the effective Al content in the plating solution is too low, less than 0.10%, the chemical reaction rate between the steel substrate and the zinc solution (plating solution) is too high, and the thickness of the zinc-iron intermetallic compound formed at the interface between the steel substrate and the zinc solution is not easily controlled, thereby reducing the uniformity of the thickness of the plating layer and the surface gloss of the plating layer. In addition, when the Al content in the plating solution is too low, fe element dissolved in the plating solution in the steel substrate easily forms bottom slag in the plating solution, eventually increasing the incidence of surface defects of the plating layer. When the Al content in the plating solution is too high and is higher than 0.25%, a thicker and compact Fe-Al intermetallic compound layer is formed between the steel substrate and Al element in the plating solution after the steel substrate enters the plating solution, so that the formation of Zn-Fe intermetallic compounds is inhibited, and the effect of improving the surface reflectivity of the plating layer cannot be realized.
In addition, in the step (3), it is also necessary to specifically control the immersion time of the steel substrate in the plating solution to be 1 to 5 seconds. If the immersion time of the steel substrate in the plating solution is too short, the thickness of the zinc-iron intermetallic compound transition layer is too thin or the proportion of the zinc-iron intermetallic compound in the transition layer is too low, so that the effect of improving the reflectivity cannot be achieved. If the steel substrate is immersed in the plating solution for too long, the amount of the Fe-Al intermetallic compound formed between the steel substrate and the plating solution increases, and the Fe-Al intermetallic compound inhibits the growth of the Zn-Fe intermetallic compound, thereby causing uneven thickness of the Fe-Zn intermetallic compound and thickness of the plating layer and finally reducing the surface glossiness of the plating layer.
Accordingly, in the hot dip galvanization process designed by the present invention, it is also necessary to control the steel substrate to be cooled to less than or equal to 250 ℃ at a cooling rate of more than 20 ℃/s after it is taken out of the zinc pot. This is because: when the cooling rate is too slow, a martensitic structure cannot be formed, resulting in a steel sheet having a tensile strength of 980MPa or more.
Further, in the production method according to the present invention, in the step (2), the atmosphere in the heating section and the heat-retaining section is N 2 、H 2 And H 2 Mixed gas of O, wherein H 2 The volume content is 1-20%, and the dew point is-30-20deg.C.
In the manufacturing method designed by the invention, N can be adopted in the heating section and the heat preservation section 2 、H 2 And H 2 O mixed gas as atmosphere, wherein H 2 The volume content is controlled and the dew point is selected to obtain better platability of the steel substrate. Wherein when H is designed 2 When the volume content is less than 1%, the residual ferric oxide film on the surface of the cold rolled steel substrate cannot be effectively reduced, so that the plating solution is not easy to infiltrate into the surface of the steel substrate; and when H 2 When the volume content is more than 20%, potential safety hazards and cost are increased.
In addition, gas impurity H cannot be completely avoided in the annealing furnace 2 The presence of O and H in the annealing atmosphere 2 Can be combined with unavoidable gas impurity O in the furnace 2 React to form H 2 O, so the dew point in the annealing furnace is difficult to ensure below-50 ℃; when the dew point is between-50 and-30 ℃, the steel substrate tends to be oxidized outwards, which is unfavorable for chemical bond combination between the steel substrate and the plating solution, thereby causing plating defects such as plating leakage, uneven plating thickness and the like, and affecting the appearance and corrosion resistance of the product; when the dew point is higher than 20 ℃, the Fe element in the steel substrate and H can be mixed 2 O reacts to form ferric oxide, so that the wettability between the steel substrate and the plating solution and the coating adhesion are reduced. Thus, in the technical proposal designed by the invention, the device can be retractedThe dew point in the fire atmosphere is defined between-30 and 20 ℃.
Further, in the manufacturing method according to the present invention, in the step (2), when the Si mass percentage content in the steel substrate is more than 0.7%, the atmosphere dew point in the heating section and the heat retaining section is controlled to be more than-10 ℃.
In the technical scheme of the invention, when the Si mass percent content in the steel substrate is more than 0.7%, the reason for further controlling the atmosphere dew point in the heating section and the heat preservation section to be more than-10 ℃ is that: when the Si content in the steel substrate is high and the dew point of the annealing atmosphere is low, si element in the steel substrate tends to be biased on the surface of the steel substrate and reacts with H in the atmosphere 2 O reacts to form a Si-containing oxide film on the surface of the steel substrate, so that the wettability and adhesive force of the plating solution on the surface of the steel substrate are reduced; when the dew point of the annealing atmosphere is higher, the diffusion flux of the O element to the inside of the steel substrate is increased, the Si element is combined with the O element in the steel substrate to form an oxide precipitation phase, and the segregation amount of the Si element on the surface of the steel substrate is reduced, so that the thickness of Si-containing oxide formed on the surface of the steel substrate in the annealing process is reduced.
Therefore, in order to suppress segregation of Si element on the surface of the steel substrate and its adverse effect on the platability of the steel substrate, when the Si mass percentage content in the steel substrate is more than 0.7%, the atmosphere dew point in the heating section and the heat-retaining section can be preferably controlled to-10 ℃ or higher.
Further, in the manufacturing method of the invention, in the step (3), the temperature of the plating solution is controlled to be 450-470 ℃, and the difference between the temperature of the steel substrate and the temperature of the plating solution when the steel substrate is put into a zinc pot is less than 10 ℃.
In the technical scheme of the invention, the temperature of the plating solution can be controlled to be 450-470 ℃, because: when the temperature of the plating solution is too low, the fluidity of the plating solution is poor, and the thickness uniformity of the plating layer is not easy to control; when the temperature of the plating solution is too high, the evaporation rate of the zinc solution is increased, zinc ash is easily generated in the furnace nose, and thus the plating defects such as exposed iron and the like are increased; in addition, the high plating solution temperature leads to the increase of heating energy consumption of the zinc pot, which is unfavorable for reducing the production cost. Thus, preferably, the plating bath temperature can be controlled between 450-470 ℃.
In addition, when the difference between the temperature of the steel substrate and the temperature of the plating solution is large during the process of entering the zinc pot, the heat balance management difficulty of the zinc pot is increased, and the formation of zinc slag is promoted, so that the plating defect is brought, and the surface quality of a finished product is affected. Therefore, the difference between the temperature of the steel substrate and the temperature of the plating solution when entering the zinc pot can be preferably controlled within 10 ℃.
Further, in the manufacturing method of the present invention, in the step (3), when the Si mass percentage content in the steel substrate is not less than 0.7%, the Al mass percentage content in the plating solution is controlled to be 0.10 to 0.14%.
In the technical scheme, when the mass percentage content of Si in the steel substrate is more than or equal to 0.7%, the mass percentage content of Al element in the plating solution can be further controlled to be 0.10-0.14%. This is because: when the mass percentage of Al element in the plating solution is more than 0.14%, the reaction rate of the surface of the steel substrate and the Al in the plating solution is higher, a compact Fe-Al intermetallic compound layer is easy to form, the formation of Zn-Fe intermetallic compounds is hindered, and the surface glossiness of the plating layer is reduced.
Further, in the manufacturing method of the present invention, in the step (3), when the Si mass percentage content in the steel substrate is < 0.7%, the Al element mass percentage content in the plating solution is controlled to be 0.16 to 0.25%.
In the technical scheme, when the mass percentage of Si in the steel substrate is less than 0.7%, the proportion of manganese oxide in the annealed steel substrate surface oxide in the atmosphere with the dew point of more than minus 30 ℃ is larger, the chemical activity of the manganese oxide is higher, and the reaction speed with Al in the plating solution is higher, so that the Al element in the plating solution near the surface of the steel substrate is easily consumed rapidly, and the reaction of the steel substrate and Zn in the plating solution is accelerated to form zinc-iron intermetallic compounds. Therefore, when the effective Al content in the plating solution is low, the formation rate of zinc-iron intermetallic compounds is high, the thickness of the transition layer is easy to be thick, the thickness uniformity of the transition layer is difficult to control, the thickness uniformity of the plating layer is further influenced, and finally the surface reflectivity of the plating layer of the finished product is reduced. For this reason, preferably, when the Si mass percentage in the steel substrate is less than 0.7%, the mass percentage content of Al element in the plating bath may be controlled to be 0.16 to 0.25%.
Compared with the prior art, the high-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness and the manufacturing method thereof have the following advantages:
the high-strength cold-rolled hot-dip galvanized steel sheet with high surface glossiness can obtain high surface light reflection performance without subsequent treatment by the optimized design and reasonable control of the self steel substrate, the hot-dip galvanized layer and the transition layer between the steel substrate and the hot-dip galvanized layer, has fewer defects and lower cost of the hot-dip galvanized layer on the surface, and has high formability and high corrosion resistance while having higher strength.
Unlike conventional hot dip galvanized steel sheet designed in the prior art, the high strength cold rolled hot dip galvanized steel sheet designed by the invention has tensile strength greater than 980MPa, and the glossiness value of the surface of the high strength cold rolled hot dip galvanized steel sheet is greater than 400 gloss units (the polished black glass with refractive index of 1.567 is set to 100 gloss units under the geometric angle of 60 degrees), so that the high strength cold rolled hot dip galvanized steel sheet has very wide popularization and application prospect and use value.
Drawings
Fig. 1 schematically shows a structural schematic view of a high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to the invention.
Fig. 2 is a metallographic scanning electron microscope back-scattered electron image of an actual cross section of a high-strength cold-rolled hot-dip galvanized steel sheet of example 1 with high surface gloss.
Fig. 3 is a secondary electron image of a transition layer surface scanning electron microscope after removing a hot dip zinc coating from the high-strength cold rolled hot dip zinc coated steel sheet of example 1.
Detailed Description
The high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss and the method for manufacturing the same according to the present invention will be further explained and illustrated with reference to specific examples and drawings, but the explanation and illustration do not unduly limit the technical scheme of the present invention.
Examples 1 to 6 and comparative examples 1 to 10
In the present invention, the steel substrates corresponding to the high-strength cold-rolled hot-dip galvanized steel sheets of examples 1 to 6 and the comparative hot-dip galvanized steel sheets of comparative examples 1 to 10 were each designed with the chemical element composition shown in the following table 1.
Table 1 (wt.%), the balance being Fe and unavoidable impurity elements other than impurity P
The high-strength cold-rolled hot-dip galvanized steel sheets of examples 1 to 6 and the comparative hot-dip galvanized steel sheets of comparative examples 1 to 10 according to the invention were prepared by the following steps:
(1) The steel substrate is manufactured by adopting the prior art: smelting according to chemical compositions shown in Table 1, heating a casting blank at 1150-1250 ℃, controlling the heat preservation time to be 0.5-3h, hot rolling the final rolling temperature to be 850-950 ℃, coiling at 500-600 ℃, pickling and cold rolling the hot rolled coil, and controlling the final cold rolling reduction to be 30-90%.
(2) Continuously annealing the steel substrate: heating to 750-900 ℃ at an average heating rate of 10 ℃/s, and then preserving heat for 30-180s, wherein the atmosphere of the heating section and the preserving heat section adopts N 2 、H 2 And H 2 O mixed gas, and H 2 The volume content of the catalyst is fixed at 1-20%, and the atmosphere dew point is-30-20 ℃. When the mass percentage content of Si in the steel substrate is more than 0.7%, the atmosphere dew point in the heating section and the heat preservation section is specifically controlled to be more than-10 ℃.
(3) Hot dip galvanization: the annealed strip steel is at 40 ℃/s in N 2 10% by volume of H 2 And H 2 And (3) cooling the mixed gas of O to the temperature of entering the zinc pot with the strip steel, and carrying out hot dip plating on the strip steel entering the plating solution in the zinc pot after preserving heat for 15s at the temperature of entering the zinc pot. Wherein the temperature of the plating solution is kept between 450 and 470 ℃, and the temperature of the zinc pot and the temperature of the plating solution are keptThe difference of the alloy is not more than 10 ℃, the mass percentage of Al element in the plating solution is 0.10-0.25%, and the balance is Zn and unavoidable impurities. The soaking time of the steel substrate in the plating solution is controlled to be 1-5s, the steel substrate is quickly purged by an air knife after leaving the plating solution to control the thickness of a hot galvanizing layer to be 5-25 microns, and then the strip steel is cooled to 250 ℃ or below at an average cooling speed higher than 20 ℃/s;
wherein, in the hot dip galvanization, when the Si mass percent content in the steel substrate is more than or equal to 0.7%, the Al element mass percent content in the plating solution is specifically controlled to be 0.10-0.14%; when the mass percentage content of Si in the steel substrate is less than 0.7%, the mass percentage content of Al element in the plating solution is specifically controlled to be 0.16-0.25%.
In the invention, the hot dip galvanizing layer can be effectively formed on the surface of the steel substrate through the hot dip galvanizing process in the step (3), and a transition layer containing zinc-ferrum intermetallic compounds and ferrum-aluminum intermetallic compounds is also formed between the hot dip galvanizing layer and the steel substrate.
The chemical composition design and the related process of the high-strength cold-rolled hot-dip galvanized steel sheets of examples 1 to 6 all meet the specification requirements designed by the present invention. While the steps used for the comparative hot-dip galvanized steel sheets of comparative examples 1 to 10 were also prepared in the above steps (1) to (3), there were parameters which did not satisfy the design requirements of the present invention in the specific processes used for the comparative hot-dip galvanized steel sheets of comparative examples 1 to 10.
Specific process parameters for the high strength cold rolled hot dip galvanized steel sheets of examples 1-6 and the comparative hot dip galvanized steel sheets of comparative examples 1-10 are set forth in tables 2-1 and 2-2.
Table 2-1.
Table 2-2.
The high-strength cold-rolled hot-dip galvanized steel sheets of the finished examples 1 to 6 and the comparative hot-dip galvanized steel sheets of the comparative examples 1 to 10, which were obtained through the above-mentioned process steps, were sampled respectively, and the galvanized steel sheets of each example and comparative example were observed and analyzed to accurately analyze the characteristics of the prepared galvanized steel sheets.
In the present invention, the inventors judged the plating appearance by visual observation of the hot dip galvanized steel sheets of each of examples 1 to 6 and comparative examples 1 to 10, and judged that the plating was uniform, the number of spot leaks was small, and the number of spot slag defects was small as "good", namely, the appearance "OK"; the appearance defect such as uneven plating, large area of the missed plating area, and large number of spot slag defects was determined as "defective", that is, appearance "NG". The results of the correlation determination observations are listed in table 3 below.
Further, the inventors measured 60-degree specular gloss on the surface of a hot-dip galvanized steel sheet using a BYK4561 micro-gloss meter based on ASTM D523 standard to obtain average gloss values for the surfaces of the steel sheets of each example and comparative example. Wherein the specular gloss value of the polished black glass having a refractive index of 1.567 at a geometric angle of 60 degrees was set to 100 gloss units.
Accordingly, in the detection of the sample steel sheets of each example and comparative example, a tensile test was specifically performed, and the tensile strength of the galvanized steel sheets of each example and comparative example was measured by stretching under room temperature conditions according to the GB/T228.1 standard.
In the invention, the average thickness of the transition layer is also measured by shooting a scanning electron microscope back-scattered electron image of a corresponding hot dip galvanized steel sheet section metallographic phase and measuring. The thickness of the transition layer, especially the thickness of the zinc-iron compound, is measured by firstly corroding a metallographic specimen of a section for 5s by using 0.5% nitric alcohol solution, then shooting a scanning electron microscope back scattering electron image, and finally analyzing the obtained image by using image analysis software to obtain the average thickness of the transition layer. The results of the relevant tests are shown in Table 3 below.
Accordingly, quantification of the thickness of the iron-aluminum compound in the transition layer of the zinc-coated steel sheets of each of examples and comparative examples can be performed by measuring the depth profile of the Al element by means of a glow discharge spectrometer in particular, to integrate the Al element enrichment peak observed at the interface position of the hot dip zinc-coated layer and the steel substrate, and to obtain Fe as 2 Al 5 The atomic ratio in the chemical formula converts the integrated area into thickness.
In addition, regarding the observation of the morphology of the crystal grains in the hot dip zinc coating and the measurement of the average crystal grain size, the crystal grains in the hot dip zinc coating of each example were observed to have an equiaxed morphology and the average crystal grain size was less than 30% of the thickness of the hot dip zinc coating.
The Al content in the hot dip zinc coating layer can be quantified by peeling off the hot dip zinc coating layer with dilute hydrochloric acid containing an inhibitor and then by ICP emission spectrometry.
Table 3 shows the results of observation and analysis for the high strength cold rolled hot dip galvanized steel sheets of examples 1 to 6 and the comparative hot dip galvanized steel sheets of comparative examples 1 to 10.
Table 3.
It should be noted that the measured Al content in the hot dip zinc coating layer shown in Table 3 is higher than the effective Al content in the plating solution shown in tables 2 to 2 because Al is inevitably carried into the transition layer when the Al content in the hot dip zinc coating layer is measured.
As can be seen from the above Table 3, the high strength cold-rolled hot-dip galvanized steel sheets according to examples 1 to 6 have more excellent combination properties than comparative examples 1 to 10, and the cold-rolled hot-dip galvanized steel sheets according to examples 1 to 6 have a surface appearance of "OK", i.e., they are uniformly plated, have fewer spot defects, and have less spot defects. In comparative examples 1 to 10, the surface appearance quality was poor.
Further, it was found by observation and analysis that in the present invention, the transition layers of the high-strength cold-rolled hot-dip galvanized steel sheets of examples 1 to 6 each include zinc-iron intermetallic compounds, and the volume ratio of the zinc-iron intermetallic compounds in the transition layers is more than 70%, and specifically between 95 and 99%. In addition, in the high-strength cold-rolled hot-dip galvanized steel sheet of the embodiment 1-6 designed by the invention, the thickness of the hot-dip galvanized layer is specifically between 9.1 and 22.3 mu m, the average thickness of the transition layer is 8 to 18 percent of the thickness of the hot-dip galvanized layer, the grains in the corresponding hot-dip galvanized layer are in equiaxed morphology, and the average grain size of the hot-dip galvanized layer is less than 30 percent of the thickness of the hot-dip galvanized layer.
Accordingly, it is not difficult to find out through research and analysis that in the present invention, the high strength cold rolled hot dip galvanized steel sheets of examples 1 to 6 have higher strength, the tensile strength is between 983 and 1085MPa, the content of Al element in the hot dip galvanized layer is between 0.17 and 0.45%, the hot dip galvanized layer has very excellent surface glossiness, and the average glossiness value of the surface is greater than 400 gloss units, and in particular, is between 473 and 502 GU.
In the comparative examples 1 to 10, the parameters which do not meet the design requirements of the present invention are present in the design, so that the average surface gloss value of the comparative hot dip galvanized steel sheets of the comparative examples 1 to 10 finally prepared are less than 400 gloss units, the surface quality of the steel sheets is NG, the tensile strength of the steel sheets is insufficient, etc.
Fig. 1 schematically shows a structural schematic view of a high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to the invention.
As can be seen from fig. 1, in the present invention, the high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to the present invention may specifically include: the steel substrate 1 and the hot dip galvanizing layer 3, wherein the hot dip galvanizing layer 3 is positioned on the surface of the steel plate, and a transition layer 2 is arranged between the steel substrate 1 and the hot dip galvanizing layer 3. Wherein the transition layer 2 is composed of zinc-iron intermetallic compound and iron-aluminum intermetallic compound.
Fig. 2 is a metallographic scanning electron microscope back-scattered electron image of an actual cross section of a high-strength cold-rolled hot-dip galvanized steel sheet of example 1 with high surface gloss.
As shown in fig. 2, the high-strength cold-rolled hot-dip galvanized steel sheet of example 1 still has a three-layer structure, namely, a steel substrate C, a hot-dip galvanized layer a, and a transition layer B between the steel substrate C and the hot-dip galvanized layer a, as shown in fig. 2, under a scanning electron microscope.
Fig. 3 is a secondary electron image of a transition layer surface scanning electron microscope after removing a hot dip zinc coating from the high-strength cold rolled hot dip zinc coated steel sheet of example 1.
As shown in fig. 3, in this example embodiment, the high-strength cold-rolled hot-dip galvanized steel sheet of example 1 was subjected to removal of the surface hot-dip zinc layer in dilute hydrochloric acid to which a corrosion inhibitor was added, and after removal of the surface hot-dip zinc layer, a transition layer mainly composed of zinc-iron intermetallic compounds was observed.
It should be noted that the combination of the technical features in the present invention is not limited to the combination described in the claims or the combination described in the specific embodiments, and all the technical features described in the present invention may be freely combined or combined in any manner unless contradiction occurs between them.
It should also be noted that the above-recited embodiments are merely specific examples of the present invention. It is apparent that the present invention is not limited to the above embodiments, and similar changes or modifications will be apparent to those skilled in the art from the present disclosure, and it is intended to be within the scope of the present invention.
Claims (13)
1. The utility model provides a high strength cold rolling hot dip galvanized steel sheet of high surface gloss, its includes steel base plate, hot dip galvanizing layer and is located the transition layer between steel base plate and the hot dip galvanizing layer, its characterized in that:
the transition layer comprises zinc-iron intermetallic compound, and the average thickness of the transition layer is 2-30% of the thickness of the hot galvanizing layer;
the crystal grains in the hot dip galvanizing layer are in equiaxed crystal morphology, and the average crystal grain size is less than 30% of the thickness of the hot dip galvanizing layer;
the steel substrate contains Fe and unavoidable impurities, and further contains the following chemical elements in percentage by mass: c:0.09-0.25%, mn:2.3-3.0%, si:0.3-2.0%, cr:0-0.7%, nb:0-0.03%, ti:0-0.03%.
2. The high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to claim 1, characterized in that the zinc-iron intermetallic compound is present in the transition layer in a volume ratio of more than 70%.
3. The high surface gloss high strength cold rolled hot dip galvanized steel sheet according to claim 1, characterized in that the transition layer further comprises an iron aluminum intermetallic compound.
4. The high-strength cold-rolled hot-dip galvanized steel sheet having a high surface gloss according to claim 1, characterized in that the hot-dip zinc coating thickness is 5 to 25 μm.
5. The high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to claim 1, wherein the steel substrate comprises the following chemical elements in percentage by mass: c:0.09-0.25%, mn:2.3-3.0%, si:0.3-2.0%, cr:0-0.7%, nb:0-0.03%, ti:0-0.03%, and the balance being Fe and unavoidable impurities.
6. The high-strength cold-rolled hot-dip galvanized steel sheet with high surface gloss according to claim 1, characterized in that the hot-dip galvanized layer comprises the following components in percentage by mass: al:0.1-0.5%, and the balance Zn and unavoidable impurities.
7. The high-strength cold-rolled hot-dip galvanized steel sheet having a high surface gloss as claimed in any one of claims 1 to 6, characterized in that the average gloss value of the surface is more than 400 gloss units and the tensile strength is > 980MPa.
8. The method for producing a high-strength cold-rolled hot-dip galvanized steel sheet having a high surface gloss according to any one of claims 1 to 7, comprising the steps of:
(1) Preparing a steel substrate;
(2) Continuous annealing: heating the strip steel to the soaking temperature of 750-900 ℃ and then preserving heat for 30-180s;
(3) Hot dip galvanization: wherein the mass percentage of Al element in the plating solution is 0.10-0.25%; the total immersion time of the steel substrate in the plating solution is 1-5s; cooling the steel substrate to less than or equal to 250 ℃ at a cooling rate of more than 20 ℃/s after the steel substrate is taken out of the zinc pot.
9. The method according to claim 8, wherein in the step (2), the atmosphere in the heating section and the heat-retaining section is N 2 、H 2 And H 2 Mixed gas of O, wherein H 2 The volume content is 1-20%, and the dew point is-30-20deg.C.
10. The manufacturing method according to claim 9, wherein in the step (2), when the Si mass percentage content in the steel substrate is more than 0.7%, the atmosphere dew point in the heating section and the heat retaining section is controlled to be more than-10 ℃.
11. The manufacturing method according to claim 8, wherein in the step (3), the plating solution temperature is controlled to be 450-470 ℃, and the difference between the temperature of the steel substrate and the temperature of the plating solution when the steel substrate is put into the zinc pot is less than 10 ℃.
12. The manufacturing method according to claim 8, wherein in the step (3), when the content of Si in the steel substrate is not less than 0.7% by mass, the content of Al element in the plating solution is controlled to be 0.10 to 0.14% by mass.
13. The manufacturing method according to claim 8, wherein in the step (3), when the Si mass percentage content in the steel substrate is < 0.7%, the Al element mass percentage content in the plating solution is controlled to be 0.16 to 0.25%.
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