CN116987862A - 22MnB5 steel hot forming process with high-quality zinc-based coating - Google Patents

22MnB5 steel hot forming process with high-quality zinc-based coating Download PDF

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Publication number
CN116987862A
CN116987862A CN202310980808.XA CN202310980808A CN116987862A CN 116987862 A CN116987862 A CN 116987862A CN 202310980808 A CN202310980808 A CN 202310980808A CN 116987862 A CN116987862 A CN 116987862A
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hot
temperature
steel plate
22mnb5
steel
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郑士建
沈春光
齐建军
熊自柳
张玲玲
苗斌
梁健
刘宏强
董伊康
赵景轩
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Hebei University of Technology
HBIS Co Ltd
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Hebei University of Technology
HBIS Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0257—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C18/00—Alloys based on zinc
    • C22C18/04—Alloys based on zinc with aluminium as the next major constituent
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • 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
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/10—Oxidising

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Abstract

The application relates to a 22MnB5 steel hot forming process with a high-quality zinc-based coating. The process comprises the following steps: and (3) placing the hot dip galvanized 22MnB5 hot formed steel plate in a heating furnace at 900-910 ℃ to quickly raise the temperature to an austenitizing temperature range (namely 900-910 ℃) at a heating rate of 20-50 ℃/min, preserving the heat for 5-7 minutes, taking the steel plate out of the furnace after heat treatment, transferring the steel plate to a hot forming die within 2-5 seconds, and quenching the steel plate to room temperature in a water-cooling mode in the die to complete the hot forming process. The application can shorten the heat treatment process period, improve the production efficiency, reduce the energy consumption, and improve the corrosion resistance and the service life of the steel plate.

Description

22MnB5 steel hot forming process with high-quality zinc-based coating
Technical Field
The application relates to a 22MnB5 steel hot forming process with a high-quality zinc-based coating, and belongs to the technical field of hot dip galvanized hot forming steel production.
Background
With the continuous improvement of the requirements on the light weight and the safety performance of automobiles, the ultra-high strength steel is widely applied and is also the main development trend of the steel structural materials for the current automobiles. The strength of the 22MnB5 hot forming steel is above 1500MPa, and the hot forming steel is widely applied to key safety structural members such as car doors, anti-collision beams and the like. To improve the corrosion resistance of the component, hot-formed steel components are typically prepared from hot-dip galvanized hot-formed steel substrates by a hot-forming process.
The hot forming processing needs to carry out austenitizing heat treatment on the steel plate, and zinc layer melting and surface oxidation can not occur on the hot dip galvanized hot formed steel substrate, so that the structure and quality of the surface galvanization are affected, and the performances of subsequent galvanization and the like are finally affected. Therefore, the optimized heat treatment process system needs to be proposed to reduce the surface oxidation degree and ensure the quality of the galvanized layer.
The document of Chinese patent application No. 202211267789.8 discloses a hot forming process for reducing the surface chromatic aberration of hot dip galvanized hot formed steel, which comprises the steps of carrying out austenitizing heat treatment on a hot dip galvanized steel sheet at 870-890 ℃, preserving heat for 2-10 minutes, and cooling the galvanized steel sheet to room temperature by adopting air cooling. Although the hot forming process reported in this document is effective in reducing the surface color difference of hot dip galvanized hot formed steel sheet, it does not involve the fine microstructure treatment of the galvanized layer after the heat treatment. Because the plating microstructure directly determines the corrosion resistance of the steel plate, development of a heat treatment process capable of preparing a plating structure with excellent performance is significant in improving the surface quality of the hot dip galvanized steel plate and the practical application effect thereof.
Disclosure of Invention
The application aims to provide a 22MnB5 steel hot forming process with a high-quality zinc-based coating, aiming at the defects in the prior art. The process obtains the zinc layer with the optimal thickness by providing a heat treatment process system of rapid heating and high-temperature austenitizing treatment, and forms continuous and compact Al on the surface 2 O 3 And the protective layer reduces the volatilization of zinc in the plating layer, prevents oxidation of the galvanized layer, and simultaneously effectively avoids the generation of large-size harmful oxides. The application provides a process system of rapid heating and high-temperature austenitizing treatment, which can shorten the heat treatment process period, improve the production efficiency and reduce the energy consumption. Preparing zinc layer and Al 2 O 3 High-quality zinc coating structure of protective layer, and obviously improves the protection of zinc-based coating to 22MnB5 steel plateThe corrosion resistance of the steel plate is improved, and the service life of the steel plate is prolonged.
The technical scheme of the application is as follows:
a 22MnB5 steel hot forming process with a high quality zinc-based coating, the process comprising the steps of:
(1) Heating furnace temperature is raised to austenitizing temperature in advance, namely 900-910 ℃, and heat preservation is carried out for 5-10 minutes, so that temperature distribution in the furnace is uniform;
(2) Placing the hot dip galvanized 22MnB5 hot formed steel plate in a heating furnace, quickly raising the hot dip galvanized 22MnB5 hot formed steel plate to an austenitizing temperature range (namely 900-910 ℃) at a heating rate of 20-50 ℃/min, and preserving the heat for 5-7 minutes to ensure that the microstructure is completely transformed into austenite;
(3) And taking the steel plate after heat treatment out of the furnace, transferring the steel plate to a hot forming die within 2-5 seconds, and quenching the steel plate to room temperature in a water cooling mode in the die to complete the hot forming process.
The surface of the finally obtained hot dip galvanized 22MnB5 steel plate is provided with Al 2 O 3 The thickness of the oxide layer is 3-4 mu m.
The 22MnB5 steel contains the following chemical elements in percentage by weight: c:0.10 to 0.30wt.%, si:0 to 0.3wt.%, mn:1.00 to 1.50wt.%, al:0.02 to 0.04wt.%, ti:0.03 to 0.05wt.%, ni:0.01 to 0.03wt.%, B:0.002 to 0.004wt.%, P <0.02wt.%, S <0.002wt.%, the balance being Fe and unavoidable impurities;
the zinc liquid for hot galvanizing contains the following chemical elements in percentage by weight: al:0.15 to 0.18wt.%, fe:0.03 to 0.05 weight percent, and the balance of Zn and unavoidable impurities;
the preparation method of the hot dip galvanized 22MnB5 hot formed steel plate comprises the following steps: smelting to obtain a 22MnB5 steel casting blank meeting the chemical component requirements, heating the casting blank to 1150-1250 ℃, preserving heat for 1-2 h, wherein the initial rolling temperature is 1100-1150 ℃, the final rolling temperature is not lower than 900 ℃, the hot rolling reduction is not lower than 75%, and the coiling temperature is 600-750 ℃;
the hot-rolled sheet is subjected to cold rolling after pickling, the cold rolling reduction is not less than 70%, and the sheet thickness after cold rolling is 1-2 mm. Then continuous annealing treatment is carried out, the annealing temperature is 750-800 ℃, and the heat preservation time is 5-8 minutes;
the annealed steel plate is then hot galvanized, the temperature of the zinc pot is 450-470 ℃, and the hot dip plating time is 2-5 seconds;
through the process flow, the hot dip galvanized 22MnB5 steel plate with the galvanized layer thickness of about 20-30 mu m is finally prepared;
the application has the substantial characteristics that:
in the prior art, the heating rate of heat treatment in the conventional hot forming process is slower, the time of a workpiece in a furnace is prolonged, and the oxide content of the surface of a steel plate coating is increased; in addition, the heating temperature is low (850-890 ℃), which is unfavorable for the diffusion of alloy elements such as Al and the like, and restricts the formation of Al on the surface of the coating 2 O 3 The compactness and continuity of the protective layer; based on the defects, the heating rate (20-50 ℃/min) and austenitizing temperature (900-910 ℃) of the heat treatment are improved, the heating rate is high, the time of the steel plate in a furnace can be reduced, the high-temperature oxidation time is shortened, and the formation of harmful oxides on the surface is further reduced; the adoption of the high austenitizing temperature can increase the diffusion capacity of the alloy element by increasing the temperature, is beneficial to the formation of the Fe-Zn alloy layer and is also beneficial to the formation of Al on the surface of the Fe-Zn alloy layer by the diffusion of the Al element through the Zn layer 2 O 3 And the layer plays a role in protecting the zinc layer.
The beneficial effects of the application are as follows:
by implementing the 22MnB5 steel hot forming process through the technical scheme, the heating rate and the austenitizing temperature are reasonably increased, the furnace time of the steel plate is effectively reduced, the alloy element diffusion capacity in the heat treatment process is improved, and the 22MnB5 steel with a high-quality zinc-based coating is prepared, wherein the fine structure of the coating is as follows:
(1) The zinc layer mainly consists of alpha-Fe (Zn) phase and a small amount of Fe 3 Zn 10 Phase composition, thickness 20-30 μm;
(2) Forming continuous compact Al on the surface of the zinc layer 2 O 3 The film thickness is 3-4 μm, and large-size Mn oxide and zinc layer internal oxide are not generated;
the excellent coating structure can effectively prevent the steel plate substrate from contacting with media such as airThe corrosion resistance is improved, and the service life is greatly prolonged. In addition, compared with the traditional process (austenitizing temperature is 2-10 minutes), the method adopts rapid heating and short-time (5-7 minutes) high-temperature austenitizing heat treatment, can shorten the period of the thermoforming process, reduces the energy consumption and the manufacturing cost, and is convenient for industrial production. Compared with the hot forming process for reducing the surface chromatic aberration of hot dip galvanized hot formed steel disclosed in the document of Chinese patent application No. 202211267789.8, the hot forming process provided by the application prepares Al with the thickness of 3-4 mu m and better compactness 2 O 3 The oxide layer, mn oxide particles are not found in the structure, so that the microstructure of the coating is optimized.
Drawings
FIG. 1 is a schematic view of a heat treatment process according to the present application;
FIG. 2 is the calculation result of the complete austenitizing temperature of the hot formed steel of example 1;
FIG. 3 is an SEM-EDS diagram of a hot dip zinc coating obtained in example 1;
FIG. 4 is a TEM-EDS diagram of the zinc layer and the surface oxide layer obtained in example 1;
FIG. 5 is a TEM-EDS plot of the zinc layer location obtained in example 1 and its diffraction calibration;
FIG. 6 is a SEM-EDS of a hot dip zinc coating of an Olympic series product as described in example 1;
FIG. 7 is an SEM-EDS image of the hot dip zinc coating obtained in example 2;
FIG. 8 is an SEM-EDS image of the hot dip zinc coating obtained in example 3;
Detailed Description
The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application.
The thermoforming process according to the present application will be described in detail with reference to examples.
22MnB5 hot forming steel chemical elements and the content thereof are as follows: c:0.10 to 0.30wt.%, si:0.1 to 0.3wt.%, mn:1.00 to 1.50wt.%, al:0.02 to 0.04wt.%, ti:0.03 to 0.05wt.%, ni:0.01 to 0.03wt.%, B:0.002 to 0.004wt.%, P <0.02wt.%, S <0.002wt.%, the balance being Fe and unavoidable impurities.
The element C is a main strengthening element in the steel, the strength and the hardness are increased along with the increase of the content of the element C, but the plasticity and the welding performance of the steel are deteriorated due to the excessively high content of the element C, so that the design principle of the content of the element C is to adopt an ultralow carbon design principle as much as possible on the premise of ensuring the strength, and the content of the element C is selected to be 0.10-0.30 wt%;
the Si element can effectively inhibit carbide formation and promote hardenability, and can reduce volume expansion in the martensitic transformation process and prevent crack formation, wherein the Si content is selected to be 0.10-0.30 wt.%;
mn element is effective austenite stabilizing element, can promote the enrichment of C element into austenite, increase the content of residual austenite, the Mn content is selected to be 1.00-1.50 wt.%;
the Ti element is a high-melting-point alloy element, can be used as a microalloying element in steel and can be combined with C, N and other elements to form carbide, so that austenite grains are prevented from growing up, and the Ti content is selected to be 0.03-0.05 wt.%;
the B element can obviously improve the hardenability of the material in the steel, stabilize the size and the morphology of the martensite lath and strengthen the grain boundary, and the B content is selected to be 0.002-0.004 wt%.
Example 1
Smelting to obtain a 22MnB5 steel casting blank meeting the chemical component requirements, heating the casting blank to 1200 ℃, preserving heat for 1h, wherein the initial rolling temperature is 1100 ℃, the final rolling temperature is 950 ℃, the hot rolling reduction is 80%, and the coiling temperature is 650 ℃;
the hot-rolled sheet was subjected to cold rolling after pickling, the reduction of the cold rolling was 70%, and the sheet thickness after cold rolling was 1.5mm. Then continuous annealing treatment is carried out, the annealing temperature is 750 ℃, and the heat preservation time is 5 minutes;
the annealed steel plate is subjected to hot galvanizing treatment immediately, the temperature of a zinc pot is 465 ℃, the hot galvanizing time is 5 seconds, the Al content in zinc liquid is 0.15wt%, the Fe content is 0.03wt%, and the rest is Zn element;
through the process flow, the hot dip galvanized 22MnB5 steel plate is prepared.
Raising the temperature of the heating furnace to 900 ℃ of austenitizing temperature, and preserving the temperature for 10 minutes to ensure that the temperature distribution in the furnace is uniform;
the hot dip galvanized 22MnB5 hot formed steel plate is placed in a heating furnace, the hot dip galvanized 22MnB5 hot formed steel plate is quickly heated to an austenitizing temperature range at a heating rate of 30 ℃/min, the heat preservation time is 6 minutes, and the critical temperature of the alloy for complete austenitizing is 813 ℃ as shown in the figure 2 through thermodynamic calculation, so that when the hot formed steel plate is heated to 900 ℃, the microstructure is completely transformed into austenite;
after heat treatment, the steel plate is taken out of the furnace, takes 3 seconds to transfer the steel plate to a hot forming die, is stamped into a part with a fixed geometric shape, and is quenched to room temperature in a water cooling mode in the die, so that the hot forming process is completed.
A metallographic sample is cut out from a hot dip galvanized thermoforming plate, and after grinding and polishing, the section of the sample is observed by using an SEM-EDS function in a TESCAN GAIA Ga ion double beam scanning electron microscope, and a galvanized layer and a surface oxide are concerned, as shown in figure 3. The SE graph is a secondary electron imaging result, the other alloy element graphs are quantitative analysis results of the alloy elements at scanning positions of the SE graph, and the whiter the color is, the higher the content of the alloy elements is. As seen from the Zn element profile, the thickness of the zinc layer was 30.4. Mu.m; from the Al element distribution diagram, al 2 O 3 The layer is continuous and compact, and the thickness is about 3.8 mu m; as can be seen from the Mn element distribution diagram, the galvanized layer does not contain Mn oxide and internal oxide; the transmission sample was cut out in a thermoformed plate, ground, ion thinned, and then observed for cross section using TEM-EDS, as shown in figure 4. The HADDF graph shows the TEM morphology of the zinc layer and the surface oxide, and the other alloy element graphs show the distribution results of the alloy elements at the position. As can be seen from the distribution diagram of Al and Zn elements, the continuous Al and Zn-rich oxide layer on the surface of the plating layer is Al 2 O 3 A layer and a ZnO layer. The application adopts a rapid heating means, so that the furnace time of the hot forming steel is reduced, on one hand, the oxidation degree is reduced, the formation and the quantity of Mn oxide are effectively prevented, on the other hand, the volatilization of zinc element is reduced, and the thickness of a zinc layer is ensured; meanwhile, the application also adopts a high-temperature austenitizing means, thereby effectively improving alloy elements, in particularThe diffusion capacity of Al element, so that a compact and continuous oxide layer is formed on the surface of the galvanized layer;
the cross section of the coating was observed using a JEM-2100F high resolution transmission electron microscope and diffraction spots were used to calibrate the phase crystal structure as shown in FIG. 5. The HADDF graph is the TEM morphology of the zinc layer and the surface oxide, the other alloy element graphs are the distribution results of the alloy elements at the positions, and the graphs (a-b) are the diffraction patterns and the calibration results of the corresponding positions in the HADDF graph. From the calibration results, the zinc layer is mainly composed of alpha-Fe (Zn) phase and Fe 3 Zn 10 Phase composition. This is because Fe element in the hot-formed steel matrix diffuses into the zinc layer during the heat treatment and then chemically reacts with Zn element to form various kinds of Fe-Zn compounds;
the zinc layer on the surface of the hot dip galvanized steel sheet prepared by adopting the hot forming parameters is proper in thickness, and a layer of continuous and compact Al is formed on the surface 2 O 3 Layers, no surface oxide and no internal oxide of Mn were found at the same time, indicating Al 2 O 3 The zinc layer can be effectively blocked from contacting with air, and the protection effect is achieved. The fine structure of the zinc layer is mainly composed of an alpha-Fe (Zn) phase and contains only a small amount of brittle Fe 3 Zn 10 And the zinc layer can be ensured to have better plasticity and toughness, the risk of cracking in the deformation process is reduced, and as shown in a SE chart in figure 3, no cracks are found in the zinc layer.
FIG. 6 is a SEM-EDS result of a hot dip galvanized hot formed steel coating of Olympic company, which has excellent corrosion resistance. The hot dip galvanized hot forming steel and the Olympic product obtained by the application have the thickness of a galvanized layer close to each other (the thickness of the zinc layer in the embodiment is 30.4 mu m, and the Olympic product is 31.1 mu m), and simultaneously, both the hot dip galvanized hot forming steel and the Olympic product form Al on the surface of a plating layer 2 O 3 The thickness of the oxide layer in this example was 3.8. Mu.m, and the Oldham product was 2.1. Mu.m. In conclusion, the plating structure of the embodiment is very similar to that of an Olympic-steel-linked product, but because the embodiment adopts a high-temperature austenitizing process, the capability of expanding Al element in a zinc layer is improved, and Al with the thickness of 3.8 mu m and better compactness is obtained 2 O 3 The oxide layer effectively prevents corrosive media such as air and the like from contacting the plating layer, and can greatlyGreatly improves the service life and the corrosion resistance.
Example 2
The embodiment provides the coating structure analysis of hot dip galvanized hot forming steel under the low heating rate (heating along with the furnace) process, which is convenient for comparison with the rapid heating process of the application;
smelting to obtain a 22MnB5 steel casting blank meeting the chemical component requirements, heating the casting blank to 1200 ℃, preserving heat for 1h, wherein the initial rolling temperature is 1100 ℃, the final rolling temperature is 950 ℃, the hot rolling reduction is 80%, and the coiling temperature is 650 ℃;
the hot-rolled sheet was subjected to cold rolling after pickling, the reduction of the cold rolling was 70%, and the sheet thickness after cold rolling was 1.5mm. Then continuous annealing treatment is carried out, the annealing temperature is 750 ℃, and the heat preservation time is 5 minutes;
the annealed steel plate is subjected to hot galvanizing treatment immediately, the temperature of a zinc pot is 465 ℃, the hot galvanizing time is 5 seconds, the Al content in zinc liquid is 0.15wt%, the Fe content is 0.03wt%, and the rest is Zn element;
through the process flow, a hot dip galvanized 22MnB5 steel plate is prepared;
placing the 22MnB5 steel plate in a heating furnace, heating to an austenitizing temperature of 900 ℃ along with the furnace, and preserving the heat for 400 seconds to enable the microstructure to be completely transformed into austenite;
after heat treatment, the steel plate is taken out of the furnace, takes 3 seconds to transfer to a hot forming die, and is quenched to room temperature in a water cooling mode in the die, so that the hot forming process is completed.
Metallographic samples are cut out from the hot forming plate, and after grinding and polishing, SEM-EDS is adopted to observe the cross section of the samples, and a galvanized layer and surface oxide are focused on, as shown in figure 7. The SE graph is a secondary electron imaging result, the other alloy element graphs are quantitative analysis results of the alloy elements at scanning positions of the SE graph, and the whiter the color is, the higher the content of the alloy elements is. From the Zn element profile, the thickness of the zinc layer is about 24 μm; as is clear from the Al element distribution diagram, no obvious Al is found on the surface of the coating 2 O 3 A protective layer; as is clear from the distribution pattern of Mn and Zn, mn oxide and internal oxide are not found, but zinc oxide layer with thickness of 19 μm is formed on the surface of zinc layer, on one hand, the formation of zinc oxide layerThe Zn element in the zinc layer is consumed, and the thickness of the zinc layer is reduced; on the other hand, the thick zinc layer is very easy to crack and fall off in the deformation process, so that the zinc layer is exposed and the protection effect is lost.
Compared with the rapid heating and high-temperature austenitizing treatment method provided by the application, when the heating along with the furnace (low heating rate) is adopted, the zinc layer fully reacts with air to form a thick zinc oxide layer due to long placement time of the steel plate in the heating furnace. The presence of zinc oxide layer also hinders Al 2 O 3 The layer is formed on the surface, and finally, the zinc layer surface does not form continuous and compact Al 2 O 3 A layer.
Example 3
The embodiment provides the coating structure analysis of hot dip galvanized hot forming steel under low temperature austenitizing treatment, which is convenient for comparison with the high temperature austenitizing process of the application;
smelting to obtain a 22MnB5 steel casting blank meeting the chemical component requirements, heating the casting blank to 1200 ℃, preserving heat for 1h, wherein the initial rolling temperature is 1100 ℃, the final rolling temperature is 950 ℃, the hot rolling reduction is 80%, and the coiling temperature is 650 ℃;
the hot-rolled sheet was subjected to cold rolling after pickling, the reduction of the cold rolling was 70%, and the sheet thickness after cold rolling was 1.5mm. Then continuous annealing treatment is carried out, the annealing temperature is 750 ℃, and the heat preservation time is 5 minutes;
the annealed steel plate is subjected to hot galvanizing treatment immediately, the temperature of a zinc pot is 465 ℃, the hot galvanizing time is 5 seconds, the Al content in zinc liquid is 0.15wt%, the Fe content is 0.03wt%, and the rest is Zn element;
through the process flow, a hot dip galvanized 22MnB5 steel plate is prepared;
raising the temperature of the heating furnace to the austenitizing temperature of 870 ℃, and preserving the temperature for 10 minutes to ensure that the temperature distribution in the furnace is uniform;
placing the hot dip galvanized 22MnB5 hot formed steel plate in a heating furnace, quickly raising the temperature to an austenitizing temperature range, and keeping the temperature for 400 seconds to ensure that the microstructure is completely transformed into austenite;
and taking the steel plate out of the furnace after heat treatment, rapidly transferring the steel plate to a hot forming die, and quenching the steel plate to room temperature in a water cooling mode in the die to complete the hot forming process.
Metallographic samples are cut out from the hot forming plate, and after grinding and polishing, SEM-EDS is adopted to observe the cross section of the samples, and a galvanized layer and surface oxide are focused on, as shown in figure 8. The SE graph is a secondary electron imaging result, the other alloy element graphs are quantitative analysis results of the alloy elements at scanning positions of the SE graph, and the whiter the color is, the higher the content of the alloy elements is. From the Zn element profile, the thickness of the zinc layer is about 30 μm; as is clear from the distribution diagram of Mn and Al, no Mn oxide or internal oxide is found, and no Al is found on the surface of the coating 2 O 3 And (3) a protective layer.
Compared with the rapid heating and high-temperature austenitizing treatment method provided by the application, when the austenitizing temperature is lower (870 ℃), the diffusion capability of the alloy element is relatively reduced, so that the Al element in the matrix is difficult to diffuse through the zinc layer, and finally, continuous and compact Al is not obtained on the surface 2 O 3 The protective layer cannot effectively protect the zinc layer.
According to the characterization and comparison analysis, the surface of the steel plate prepared by the hot forming process provided by the application has a continuous and compact Al oxide layer, does not have large-size Mn oxide, and has a good protection effect on a steel substrate; the zinc layer consisted mainly of an alpha-Fe (Zn) phase and was found to be a small amount of brittle Fe 3 Zn 10 In summary, the application prepares the 22MnB5 steel plate with high quality zinc-based coating.
While embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.
The application is not a matter of the known technology.

Claims (4)

1. A22 MnB5 steel hot forming process with a high quality zinc-based coating is characterized by comprising the following steps:
(1) Heating furnace temperature is raised to austenitizing temperature in advance, namely 900-910 ℃, and heat preservation is carried out for 5-10 minutes, so that temperature distribution in the furnace is uniform;
(2) Placing the hot dip galvanized 22MnB5 hot formed steel plate in a heating furnace, quickly raising the hot dip galvanized 22MnB5 hot formed steel plate to an austenitizing temperature range (namely 900-910 ℃) at a heating rate of 20-50 ℃/min, and preserving the heat for 5-7 minutes;
(3) And taking the steel plate after heat treatment out of the furnace, transferring the steel plate to a hot forming die within 2-5 seconds, and quenching the steel plate to room temperature in a water cooling mode in the die to complete the hot forming process.
2. The hot forming process of 22MnB5 steel with high quality zinc based coating as claimed in claim 1, wherein the surface of the finally obtained hot dip galvanized 22MnB5 steel sheet has Al 2 O 3 The thickness of the oxide layer is 3-4 mu m.
3. The hot forming process for 22MnB5 steel with high quality zinc-based coating according to claim 1, wherein the 22MnB5 steel contains the following chemical elements and contents: c:0.10 to 0.30wt.%, si:0 to 0.3wt.%, mn:1.00 to 1.50wt.%, al:0.02 to 0.04wt.%, ti:0.03 to 0.05wt.%, ni:0.01 to 0.03wt.%, B:0.002 to 0.004wt.%, P <0.02wt.%, S <0.002wt.%, the balance being Fe and unavoidable impurities;
the zinc liquid for hot galvanizing contains the following chemical elements in percentage by weight: al:0.15 to 0.18wt.%, fe:0.03 to 0.05 weight percent, and the balance of Zn and unavoidable impurities.
4. The hot forming process of 22MnB5 steel with high quality zinc-based coating as claimed in claim 1, wherein the preparation of hot dip galvanized 22MnB5 hot formed steel sheet comprises the steps of:
smelting to obtain a 22MnB5 steel casting blank meeting the chemical component requirements, heating the casting blank to 1150-1250 ℃, preserving heat for 1-2 h, wherein the initial rolling temperature is 1100-1150 ℃, the final rolling temperature is not lower than 900 ℃, the hot rolling reduction is not lower than 75%, and the coiling temperature is 600-750 ℃;
the hot rolled plate is subjected to cold rolling after pickling, the cold rolling reduction is not less than 70%, the plate thickness is 1-2 mm after cold rolling, then continuous annealing treatment is carried out, the annealing temperature is 750-800 ℃, and the heat preservation time is 5-8 minutes;
the annealed steel plate is then hot galvanized, the temperature of the zinc pot is 450-470 ℃, and the hot dip plating time is 2-5 seconds;
through the process flow, the hot dip galvanized 22MnB5 steel plate with the galvanized layer thickness of about 20-30 mu m is finally prepared.
CN202310980808.XA 2023-08-07 2023-08-07 22MnB5 steel hot forming process with high-quality zinc-based coating Pending CN116987862A (en)

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