CN118007024A - Low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel plate and preparation method thereof - Google Patents

Low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel plate and preparation method thereof Download PDF

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CN118007024A
CN118007024A CN202410306178.2A CN202410306178A CN118007024A CN 118007024 A CN118007024 A CN 118007024A CN 202410306178 A CN202410306178 A CN 202410306178A CN 118007024 A CN118007024 A CN 118007024A
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hot
temperature
mpa
performance
dip galvanized
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刘万春
侯晓英
李洪翠
陈庆军
尹翠兰
郝亮
梁亚
张同同
文雄
宇凡
吕明鹏
李雨晴
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SD Steel Rizhao Co Ltd
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SD Steel Rizhao Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • 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
    • 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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel

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  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
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  • Crystallography & Structural Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Coating With Molten Metal (AREA)

Abstract

The invention belongs to the technical field of cold-rolled automobile steel, and particularly relates to a low-cost high-reaming-performance 500 MPa-grade hot-dip galvanized dual-phase steel plate and a preparation method thereof. High-valence alloy elements such as Mo, nb and the like are not added, so that the manufacturing cost of the product is reduced. By adopting key parameters such as LF+RH twice refining, lower superheat degree, reasonable hot rolling temperature, annealing temperature and the like, the product is ensured to have uniform structure, fine grains, no banded structure and no inclusion segregation with larger size, and the structure proportion is reasonable, so that the product is ensured to have higher reaming performance, and the application scene is greatly increased. On the other hand, in the annealing process, the furnace atmosphere and the dew point are controlled, so that the substrate has good wettability, and a Fe2Al5 inhibition layer is formed on the surface of the steel during galvanization, so that the galvanization adhesiveness is improved, and better surface quality is obtained.

Description

Low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel plate and preparation method thereof
Technical Field
The invention belongs to the technical field of cold-rolled automobile steel, and particularly relates to a low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel plate and a preparation method thereof.
Background
With the increasing demands of countries and markets for automobile weight reduction, galvanized dual-phase steel is widely applied to automobile structural parts due to its high strength, low yield ratio, good formability and excellent corrosion resistance. The galvanized dual-phase steel which is most widely applied in the prior automobile structural parts and reinforcing parts is 600MPa grade dual-phase steel and 800MPa grade dual-phase steel, and the hot dip galvanized dual-phase steel below 600MPa grade is less applied in the automobile structural parts. The low alloy high strength steel and the high strength IF steel have lower price than the dual phase steel, and the forming performance can meet the requirements of general vehicle body structural members, so that most of the low alloy high strength steel and the high strength IF steel are born in the scene of the requirements of the hot dip galvanized steel with the strength below 600 MPa.
However, in recent years, as the requirements of the vehicle body structural members on the comprehensive properties of materials become more and more stringent, the hot dip galvanized dual-phase steel gradually occupies the market of the hot dip galvanized steel with the strength below 600MPa level due to the remarkable advantages of low yield ratio, continuous yield, high ductility, high tensile strain hardening index, no obvious timeliness and the like.
The invention discloses a 500 MPa-grade high work hardening rate hot dip galvanized dual phase steel plate and a preparation method thereof, wherein the steel plate comprises the following chemical components in percentage by weight ：C：0.02～0.05％,Si：0.10～0.20％,Mn：0.80～1.20％,Cr：0.15～0.30％,Mo：0.30～0.50％,Nb：0.025～0.040％,Als：0.02～0.04％,P≤0.020％,S≤0.0030％,, and the balance of Fe and unavoidable residual impurity elements. Mo alloy is high in price, the Mo content is 0.30-0.50% according to the price of 2022-2023 years ferromolybdenum alloy, the cost of ferromolybdenum alloy required by ton steel is up to 1200-2000 yuan, and the industrialized production and popularization difficulties are high. The hot rolling coiling temperature is 700-730 ℃, belongs to high-temperature coiling, but is not matched with U-shaped coiling, so that the heat dissipation of the head and the tail in the slow cooling process of the hot coil is quick, the temperature is low, the difference between the tissue performance and the coil is large, the difference between the tissue performance and the coil is inherited to the finished coil, the whole coil performance is large, and the stamping use of a client is influenced.
The invention discloses a galvanized dual-phase steel for 500 MPa-level sedan and a production method thereof, wherein the galvanized dual-phase steel comprises the following components in percentage by weight: 0.04 to 0.09 percent, si: less than or equal to 0.01 percent, mn:1.0 to 2.0 percent, P: less than or equal to 0.015 percent, S: less than or equal to 0.010%, als:0.01 to 0.08 percent, mo:0.01 to 0.30 percent or Cr:0.02 to 0.9 percent, nb:0.001 to 0.03 percent, N: less than or equal to 0.005 percent, and the balance of iron and other unavoidable impurities. In order to ensure the good surface of the hot dip galvanized steel strip, the extremely low Si content is adopted, and Mo or Cr element is properly added, but the Mo or Cr element alloy has higher cost, and is not beneficial to industrialized production and popularization. Meanwhile, the flanging reaming performance of the 500MPa galvanized dual-phase steel is not mentioned in the invention, but the requirements of middle-high-end passenger cars on the complex forming performance of flanging reaming are increasingly improved at present.
Disclosure of Invention
Based on the defects in the prior art, the invention aims to provide a low-cost high-reaming-performance 500 MPa-level hot dip galvanized dual-phase steel plate and a preparation method thereof.
The technical scheme adopted for solving the technical problems is as follows: the hot dip galvanized dual phase steel plate with low cost and high reaming performance and 500MPa grade comprises the following chemical components in percentage by mass of ：C：0.05％～0.08％,Si：0.20～0.40％,Mn：1.20％～1.60％,Cr：0.2％～0.4％,P≤0.020％,S≤0.007％,Alt：0.035％～0.065％,N≤0.0050％,, wherein the other elements are Fe and unavoidable impurities; the microstructure comprises the following components in percentage by volume: 85-90% of ferrite, 7-12% of martensite and 3-5% of bainite.
The basic principle of the design of the content of each alloy element in the invention is as follows:
C: c is the most economical and effective strengthening element, and plays a role in phase transformation strengthening in the dual-phase steel, and the content of martensite and the strength of strip steel in the final dual-phase steel are controlled; to ensure good welding performance, the strip steel requires lower carbon content; therefore, the invention controls the content of C within the range of 0.05-0.08%.
Si: si is ferrite forming element, and can effectively promote C to diffuse into austenite when the two-phase region is insulated and cooled slowly, so that remarkable purifying effect is achieved on ferrite, the purity of ferrite in the dual-phase steel is improved, and good drawing performance of the strip steel is ensured; along with the improvement of the pre-oxidation reduction capability of a galvanization production line, the galvanization dual-phase steel with the strength of more than 600MPa grade gradually changes the traditional thought of replacing silicon with aluminum, and the surface quality of a galvanization product is not affected by adding a proper amount of silicon; the Si content is controlled to be in the range of 0.20 to 0.40%.
Mn: mn is a common solid solution strengthening element, is an element which is helpful for expanding an austenite region in the dual-phase steel, and delays the transformation of pearlite and bainite in the austenite cooling process, thereby improving the hardenability of the steel. In order to ensure good strength, the Mn content is controlled within the range of 1.20-1.60%.
Cr: the quenching degree of the steel can be improved as Mn element, and the quenching degree of the steel can be greatly improved when Mn element is added into the steel, so that the transformation between pearlite and bainite is delayed; meanwhile, the moderate addition of Cr can reduce the yield ratio of the dual-phase steel, improve the distribution of martensite and further improve the elongation; however, too high a Cr content deteriorates the weldability. Therefore, the Cr content is controlled to be in the range of 0.20-0.40%.
P, S, N: the impurity elements in steel deteriorate the plasticity and toughness of steel, and generally need to be controlled at a low level. The invention controls P to be less than or equal to 0.020 percent, S to be less than or equal to 0.007 percent and N to be less than or equal to 0.0050 percent by combining the performance requirements of actual products.
Alt: the main function of aluminum in steel is to refine grains and fix N in steel, thereby improving the impact toughness of steel and reducing the tendency of cold embrittlement and aging. So the Alt is controlled to be 0.035% -0.065%.
Further, the yield strength of the steel plate is 310-350 MPa, the tensile strength is 500-540 MPa, and the elongation after break A80: 24-28%, tensile strain hardening index n0:0.15 to 0.19, and the hole expansion ratio lambda: 70-90%.
Further, the thickness of the steel plate is 0.6-2.5 mm, the hot dip galvanized steel plate has no plating leakage, no bending dezincification, and the inhibition layer is continuous and compact, and the surface quality is good.
The preparation method of the low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel plate comprises the following steps of:
(1) Steelmaking and continuous casting processes:
1) LF refining and RH refining are adopted;
2) The superheat degree of molten steel is 15-30 ℃;
3) Optionally red-feeding the continuous casting blank to a hot rolling heating furnace;
(2) Hot rolling:
The soaking temperature of the slab is 1190-1230 ℃, the hot-feeding heating time of the casting blank is 160-200 min, the cold-feeding heating time of the casting blank is 200-240 min, and the tapping temperature is 1180-1220 ℃; the laminar cooling adopts front-stage sparse cooling, and adopts coiling temperature of 540-570 ℃; after hot rolling, stacking and slowly cooling for 72 hours in a hot rolling warehouse;
(3) Pickling and cold continuous rolling:
the total rolling reduction rate of the cold rolling is 52-70%, and the reflectivity of the strip steel after pickling and continuous rolling is more than or equal to 70%;
(4) Continuous hot galvanizing process:
Soaking temperature of continuous annealing: 790-810 ℃; slow cooling end temperature: 670-690 ℃; rapid cooling end temperature: 440-460 ℃; tapping temperature: t is more than or equal to 0.6 and less than 1.0mm, and the temperature is 450-470 ℃; t is more than or equal to 1.0 and less than 1.80mm, and the temperature is 445-465 ℃; t is more than or equal to 1.80 and less than or equal to 2.50mm, and the temperature is 440-460 ℃; the cooling speed after plating is more than or equal to 18 ℃/s, the belt speed is 90-130 m/min, the temperature of the pre-oxidation chamber is 600-680 ℃, the compressed air injected into the oxidation chamber is preheated to be more than 300 ℃, the oxygen content in the oxidation chamber is 1.0-2.0%, the dew point is-15-0 ℃, and the finishing elongation is set to be 0.6-1.2%.
Influence of key manufacturing process on the product of the invention:
In the steelmaking process, LF refining and RH refining are adopted, so that the impurity elements such as P, S, N and the like can be ensured to be controlled at a lower level, and the alloy components and the molten steel temperature can be ensured to be controlled uniformly. When the content of Mn element is higher, the continuous casting billet is easy to generate segregation, and strip-shaped tissues are easy to generate in the finished strip steel after inheritance, so that the reaming performance and the forming performance of the strip steel are deteriorated. The superheat degree of the molten steel is 15-30 ℃, and the lower superheat degree can reduce the segregation degree of the continuous casting billet and ensure the reaming performance and the forming performance of the strip steel. The continuous casting billet can be optionally sent to a hot rolling heating furnace, and the continuous casting billet is preferably sent to the hot rolling heating furnace for saving energy, protecting environment and improving the production rhythm.
Hot rolling, namely soaking the slab at 1190-1230 ℃, heating the casting blank for 160-200 min, cooling the casting blank for 200-240 min, and discharging at 1180-1220 ℃; the heating time and the heating temperature of the casting blank need to ensure that the hot material or the cool material of the casting blank is heated uniformly, and the lower tapping temperature of 1180-1220 ℃ avoids that the oxidized iron scales are too thick and difficult to remove and are transmitted to the subsequent pass. The laminar cooling adopts front stage sparse cooling and adopts coiling temperature of 540-570 ℃. The low-temperature coiling is adopted, so that the influence on the surface quality of galvanized products caused by difficult removal of scale scales generated four times after coiling is avoided. After hot rolling, stacking and slow cooling are carried out for 72 hours in a hot rolling warehouse, and the cooling speed of the whole coil tends to be consistent through stacking and slow cooling, so that the uniformity of the whole coil performance tissue is ensured, and the fluctuation of the thickness of the acid rolled coil and poor plate shape are avoided.
And (3) an acid pickling cold continuous rolling process, wherein the total rolling reduction rate is 52-70%. The reflectivity of the strip steel after pickling and cold continuous rolling is more than or equal to 70 percent. The total reduction rate within a reasonable range can refine grains and provide recrystallization deformation energy, and meanwhile, the load of the acid rolling mill is controlled within a reasonable range, so that the total reduction rate of the cold rolling is set to be 52-70%. The reflectivity of the strip steel after pickling and cold continuous rolling is more than or equal to 70%, the reflectivity of the surface of the chilled coil is higher, the higher surface cleanliness is easier to ensure after the cleaning in the galvanization process, and good wettability is provided.
Continuous hot galvanizing process, continuous annealing soaking temperature: 790-810 ℃; slow cooling end temperature: 670-690 ℃; rapid cooling end temperature: 440-460 ℃; tapping temperature: t is more than or equal to 0.6 and less than 1.0mm, and the temperature is 450-470 ℃; t is more than or equal to 1.0 and less than 1.80mm, and the temperature is 445-465 ℃; t is more than or equal to 1.80 and less than or equal to 2.50mm, and the temperature is 440-460 ℃. The cooling speed after plating is more than or equal to 18 ℃/s. The belt speed is 90-130 m/min. The annealing soaking temperature and the belt speed control the austenitizing degree, and influence the ferrite, the austenite proportion and the austenite stability; the slow cooling end temperature, the fast cooling end temperature and the tapping temperature influence the content of newly generated ferrite and pre-plating bainite; the cooling speed after plating, namely the cooling speed of the strip steel out of the zinc pot, is controlled to be more than 18 ℃/s, mainly controls the content of martensite in a finished product structure, and ensures enough strength. The microstructure comprises the following components in percentage by volume: 85-90% of ferrite, 7-12% of martensite and 3-5% of bainite.
The temperature of the pre-oxidation chamber is 600-680 ℃, the compressed air injected into the oxidation chamber is preheated to more than 300 ℃, the oxygen content in the oxidation chamber ranges from 1.0 to 2.0%, and the dew point is-15-0 ℃. Reasonable pre-oxidation-reduction parameters are set, so that a large amount of silicon and manganese oxides are prevented from being formed on the surface of a substrate to influence wettability, a good inhibition layer is ensured to be formed on the surface of the substrate, and the requirements of no dezincification and no plating leakage during bending are met. The finishing elongation is set to be 0.6-1.2%, the surface roughness of the hot dip galvanized product is controlled, and the stamping use requirement of customers is met. The larger finishing elongation is not set, and the drawing performance of the finished product is prevented from being influenced.
The invention has the following beneficial effects: the invention adopts an alloy component system of C-Si-Mn-Cr, C is the most basic strengthening element, and a proper amount of Si element can 'purify' a ferrite matrix, so that the drawing performance is ensured, and meanwhile, a proper amount of Mn and Cr elements are added, so that the hardenability of steel is improved, and a proper amount of martensitic structure is generated. High-valence alloy elements such as Mo, nb and the like are not added, so that the manufacturing cost of the product is reduced. By adopting key parameters such as LF+RH twice refining, lower superheat degree, reasonable hot rolling temperature, annealing temperature and the like, the product is ensured to have uniform structure, fine grains, no banded structure and no inclusion segregation with larger size, and the structure proportion is reasonable, so that the product is ensured to have higher reaming performance, and the application scene is greatly increased. On the other hand, in the annealing process, the furnace atmosphere and the dew point are controlled, so that the substrate has good wettability, and a Fe2Al5 inhibition layer is formed on the surface of the steel during galvanization, so that the galvanization adhesiveness is improved, and better surface quality is obtained.
Drawings
FIG. 1 is a drawing showing the structure of a hot-dip galvanized steel sheet in example 1.
FIG. 2 is a surface topography of the hot galvanized steel strip of example 1.
Detailed Description
The following are specific examples of the present invention, and the technical solutions of the present invention are further described, but the scope of the present invention is not limited to these examples. All changes and equivalents that do not depart from the gist of the invention are intended to be within the scope of the invention.
The present invention is described in further detail below by way of specific examples 1 to 5:
In the steelmaking process, LF refining and RH refining are adopted; the superheat degree of molten steel is 15-30 ℃; the continuous casting blank can be selectively sent to a hot-rolling heating furnace in red, when the quality of the slab is qualified, the slab is preferably sent to the hot-rolling heating furnace in red, when the slab needs to be finished, the slab is slowly cooled and finished, and then is sent to the hot-rolling heating furnace in cold.
The chemical composition of the continuous casting slab used for the 500 MPa-grade hot dip galvanized dual phase steel in the specific examples 1 to 5 is shown in Table 1, and the technological parameters of the steelmaking process are shown in Table 2.
TABLE 1 chemical composition (wt%)
Examples C Si P S N Mn Alt Cr
1 0.065 0.25 0.001 0.007 0.0040 1.42 0.035 0.20
2 0.050 0.27 0.002 0.005 0.0050 1.20 0.035 0.21
3 0.061 0.40 0.001 0.004 0.0040 1.51 0.052 0.31
4 0.080 0.32 0.002 0.007 0.0030 1.60 0.065 0.40
5 0.071 0.20 0.001 0.006 0.0035 1.39 0.046 0.20
TABLE 2 key process parameters for steelmaking process
Examples Refining process route Degree of superheat of molten steel Continuous casting billet rolling mode
1 LF refining+RH refining 17 Red conveyer
2 LF refining+RH refining 20 Red conveyer
3 LF refining+RH refining 22 Red conveyer
4 LF refining+RH refining 15 Red conveyer
5 LF refining+RH refining 30 Cold feed
In a hot rolling heating furnace, the soaking temperature of a slab is 1190-1230 ℃, the heating time of a casting blank hot material is 160-200 min, the cooling heating time of the casting blank is 200-240 min, and the tapping temperature is 1180-1220 ℃; the laminar cooling adopts front-stage sparse cooling, and adopts coiling temperature of 540-570 ℃; after hot rolling, the hot rolled stock was stacked and slowly cooled for 72 hours. Specific parameters of the hot rolling process example are shown in Table 3.
TABLE 3 Hot Rolling Process parameters
Examples Kinds of blanks Soaking temperature/. Degree.C Heating time/min Tapping temperature/DEGC Coiling temperature/. Degree.C Stacking slow cooling time length/h of hot rolled coil
1 Hot material 1220 200 1220 550 72
2 Hot material 1220 180 1200 570 72
3 Hot material 1190 190 1180 555 72
4 Hot material 1210 160 1210 560 72
5 Cool material 1230 230 1220 540 72
The total rolling reduction rate is 52-70%. The reflectivity of the strip steel after pickling and cold continuous rolling is more than or equal to 70 percent. The hot rolled coil is changed into a chilled coil through an acid pickling cold continuous rolling process, and specific parameters of the acid pickling cold continuous rolling process are shown in table 4.
Table 4 pickling cold tandem rolling process parameters
Examples Cold rolling total reduction/% Reflectivity of strip steel
1 52 70
2 55 73
3 62 72
4 55 71
5 70 73
Continuous hot galvanizing process, continuous annealing soaking temperature: 790-810 ℃; slow cooling end temperature: 670-690 ℃; rapid cooling end temperature: 440-460 ℃; tapping temperature: t is more than or equal to 0.6 and less than 1.0mm, and the temperature is 450-470 ℃; t is more than or equal to 1.0 and less than 1.80mm, and the temperature is 445-465 ℃; t is more than or equal to 1.80 and less than or equal to 2.50mm, and the temperature is 440-460 ℃. The cooling speed after plating is more than or equal to 18 ℃/s. The belt speed is 90-130 m/min. The temperature of the pre-oxidation chamber is 600-680 ℃, the compressed air injected into the oxidation chamber is preheated to more than 300 ℃, the oxygen content in the oxidation chamber ranges from 1.0 to 2.0%, and the dew point is-15-0 ℃. The finishing elongation is set to 0.6-1.2%. The chilled rolls were subjected to a continuous hot dip galvanizing process to obtain finished products, and specific parameters of examples of the continuous hot dip galvanizing process are shown in tables 5 and 6.
TABLE 5 Process parameters for continuous Hot galvanizing Process
TABLE 6 preoxidation reduction process parameters
Examples Pre-oxidation chamber temperature/°c Compressed air preheating temperature/°c Oxygen content in oxidation chamber/% Dew point/. Degree.C
1 650 310 1.0 -15
2 600 340 1.5 -5
3 680 330 2.0 0
4 669 325 1.2 -12
5 640 336 1.3 -10
The microstructure of the hot dip galvanized steel sheet comprises the following components in percentage by volume: the microstructure comprises the following components in percentage by volume: 85-90% of ferrite, 7-12% of martensite and 3-5% of bainite.
The yield strength of the hot dip galvanized steel sheet is 310-350 MPa, the tensile strength is 500-540 MPa, and the elongation after break A80: 24-28%, tensile strain hardening index n0:0.15 to 0.19, and the hole expansion ratio lambda: 70-90%. The mechanical properties of the hot-dip galvanized steel sheets of examples 1 to 5 are shown in Table 7.
TABLE 7 mechanical Properties of hot dip galvanized Steel sheet
Examples Yield strength/MPa Tensile strength/MPa Elongation after break A80/% Tensile strain hardening index n0 Expansion ratio lambda/%
1 312 510 28 0.19 75
2 345 538 26 0.18 79
3 337 529 27 0.18 70
4 328 526 26 0.17 85
5 339 533 27 0.18 86
The present invention is not limited to the above embodiments, and any person who can learn the structural changes made under the teaching of the present invention can fall within the scope of the present invention if the present invention has the same or similar technical solutions.
The technology, shape, and construction parts of the present invention, which are not described in detail, are known in the art.

Claims (4)

1. A low-cost high-reaming-performance 500 MPa-grade hot-dip galvanized dual-phase steel plate is characterized in that the chemical components comprise ：C：0.05％～0.08％,Si：0.20～0.40％,Mn：1.20％～1.60％,Cr：0.2％～0.4％,P≤0.020％,S≤0.007％,Alt：0.035％～0.065％,N≤0.0050％, mass percent of Fe and unavoidable impurities as the rest elements; the microstructure comprises the following components in percentage by volume: 85-90% of ferrite, 7-12% of martensite and 3-5% of bainite.
2. The low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel sheet according to claim 1, wherein the steel sheet has a yield strength of 310-350 MPa, a tensile strength of 500-540 MPa and a post-fracture elongation a80: 24-28%, tensile strain hardening index n0:0.15 to 0.19, and the hole expansion ratio lambda: 70-90%.
3. The low-cost high-reaming-performance 500 MPa-grade hot-dip galvanized dual-phase steel plate according to claim 1, wherein the thickness of the steel plate is 0.6-2.5 mm, the hot-dip galvanized steel plate has no plating leakage, no bending dezincification, continuous and compact inhibition layer and good surface quality.
4. The method for preparing the low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel sheet according to any one of claims 1 to 3, comprising the following steps:
(1) Steelmaking and continuous casting processes:
1) LF refining and RH refining are adopted;
2) The superheat degree of molten steel is 15-30 ℃;
3) Optionally red-feeding the continuous casting blank to a hot rolling heating furnace;
(2) Hot rolling:
The soaking temperature of the slab is 1190-1230 ℃, the hot-feeding heating time of the casting blank is 160-200 min, the cold-feeding heating time of the casting blank is 200-240 min, and the tapping temperature is 1180-1220 ℃; the laminar cooling adopts front-stage sparse cooling, and adopts coiling temperature of 540-570 ℃; after hot rolling, stacking and slowly cooling for 72 hours in a hot rolling warehouse;
(3) Pickling and cold continuous rolling:
the total rolling reduction rate of the cold rolling is 52-70%, and the reflectivity of the strip steel after pickling and continuous rolling is more than or equal to 70%;
(4) Continuous hot galvanizing process:
Soaking temperature of continuous annealing: 790-810 ℃; slow cooling end temperature: 670-690 ℃; rapid cooling end temperature: 440-460 ℃; tapping temperature: t is more than or equal to 0.6 and less than 1.0mm, and the temperature is 450-470 ℃; t is more than or equal to 1.0 and less than 1.80mm, and the temperature is 445-465 ℃; t is more than or equal to 1.80 and less than or equal to 2.50mm, and the temperature is 440-460 ℃; the cooling speed after plating is more than or equal to 18 ℃/s, the belt speed is 90-130 m/min, the temperature of the pre-oxidation chamber is 600-680 ℃, the compressed air injected into the oxidation chamber is preheated to be more than 300 ℃, the oxygen content in the oxidation chamber is 1.0-2.0%, the dew point is-15-0 ℃, and the finishing elongation is set to be 0.6-1.2%.
CN202410306178.2A 2024-03-18 2024-03-18 Low-cost high-reaming-performance 500 MPa-level hot-dip galvanized dual-phase steel plate and preparation method thereof Pending CN118007024A (en)

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