CN113061812B - 980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel and preparation method thereof - Google Patents
980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel and preparation method thereof Download PDFInfo
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- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- 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
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- 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
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Abstract
The invention relates to 980MPa grade cold-rolled alloyed galvanized quenching distribution steel and a preparation method thereof, wherein the steel comprises the following chemical components in percentage by weight: 0.1% -0.17%, Si: 0.60-1.0%, Mn: 1.50 to 2.50 percent of the total weight of the alloy, less than or equal to 0.05 percent of P, less than or equal to 0.05 percent of S and less than or equal to 0.05 percent of Als; one of Nb, Ti and V, wherein Nb is less than or equal to 0.02 percent, Ti is less than or equal to 0.02 percent, and V is less than or equal to 0.05 percent; the balance of Fe and inevitable impurities; simultaneously, the following requirements are met: c + Si/4 is less than or equal to 0.4 percent; the metallographic structure is a ferrite structure, a tempered martensite structure and a residual austenite structure, and the austenitizing temperature of the steel is less than or equal to 840 ℃. The production process comprises the following steps: smelting, hot continuous rolling, acid pickling and cold rolling, and alloying galvanization. The invention realizes the hole expansion rate of more than 60 percent by the alloy and the process design with lower alloy cost, and the product has more market competitiveness.
Description
Technical Field
The invention relates to the technical field of automobile steel manufacturing, in particular to 980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel and a preparation method thereof.
Background
With the development of the automotive industry, the proportion of automotive high-strength steel applied to body-in-white (referring to a welded assembly of body structural members and panels, and including front wings, doors, hoods, trunk lids, but not including unpainted bodies of accessories and trim parts) is gradually increasing, and the level of strength is also gradually increasing. For example, the application proportion of the strength steel plate of 980MPa or above on a domestic vehicle is increased from 3% in 2014 to about 10% at present. Meanwhile, the application proportion of the hot-dip galvanized steel sheet and the alloyed galvanized steel sheet is continuously increased.
Up to now, high strength steels of 980MPa class include DP steel (dual phase steel), TRIP steel (strain induced plasticity steel), QP steel (quench split steel), TWIP steel (twin induced plasticity steel), medium manganese steel, and the like. Among them, TWIP steel and TRIP steel have not been marketed in a wide range because of their high alloy cost and because of their industrial stability. Therefore, 980 MPa-grade automotive high-strength steel with large market consumption and high user acceptance mainly comprises DP steel and QP steel.
It is worth noting that when the strength of the steel plate reaches 980MPa or above, the automotive application performance of the steel plate is gradually reduced, such as key performance indexes of ductility, hole expanding rate, cold bending, forming limit, welding and the like. Wherein, the reaming performance marks whether the steel plate can be used for manufacturing automobile parts with higher flanging performance requirements. However, in the case of high-strength steels of 980MPa class or higher, the hole expansion ratio is only marginally about 30% (for example, DP700/980 steel and QP700/980 steel) even in high hole expansion type products.
The good hole expansion performance is caused by the fact that the steel plate has high yield ratio and good structure uniformity, the structure of the existing 980 MPa-level product basically comprises more than 30% of ferrite phase and more than 50% of martensite or tempered martensite phase, the difference between the hardness and the softness of the structure is large, cracks are easily generated at the phase boundary, and the hole expansion performance is poor. Compared with a cold-rolled product with a simple process, the production difficulty of a high-reaming galvanized product with better surface quality is higher, the fixed zinc pot temperature and the limited galvanized section length are not beneficial to regulation and control of the structure, and the production difficulty is increased.
Chinese invention patent with publication number CN 102586688B discloses 'a dual-phase steel plate and a manufacturing method thereof', relating to 980MPa cold-rolled dual-phase steel,the main chemical components are as follows: c: 0.07-0.098, Si: 0.1 to 0.4, Mn: 1.95-2.2, Cr: 0.3-0.6, P is less than or equal to 0.015, S is less than or equal to 0.004, N is less than or equal to 0.005, and Nb: 0.015 to 0.04, Ti: 0.015 to 0.04, Al: 0.015-0.045, B: 0.002-0.004, Mo: 0.2-0.4, and the balance of Fe and inevitable impurities. The product is a cold-rolled annealed steel plate, and the yield strength of the product is as follows: 595-700 MPa, tensile strength not less than 980MPa, elongation A50: 13% -17%, hole expansion ratio: 35 to 55 percent. According to the technical scheme, the steel plate has high yield strength and hole expansion rate, the hardenability of the steel is improved through Cr, Mo and other elements by mainly depending on high proportion of noble metals such as Cr, Mo and the like and adding micro alloy elements such as Nb, Ti and the like, and the proportion of martensite is improved; the prior austenite grain boundary is separated and refined through microalloy such as Nb, Ti and the like, and a ferrite phase is dispersed and strengthened, so that the ferrite strength is improved, the hardness difference of a soft phase and a hard phase is reduced, and the hole expanding performance is improved. However, the idea of relying on the alloy alone significantly increases the alloy cost of the steel plate, and it is difficult to ensure that the product has market competitiveness.
The Chinese patent with publication number CN108913991B discloses '980 MPa grade cold-rolled complex phase steel with good hole expansion performance and a preparation method thereof', which comprises the following main chemical components: c: 0.15% -0.20%, Si: 0.3% -0.8%, Mn: 1.7-2.3%, P is less than or equal to 0.015%, S is less than or equal to 0.008%, Als is less than or equal to 0.08%, Nb: 0.02-0.08%, Cr: 0.4-0.8%, Ti: 0.02 to 0.06 percent, and the balance of Fe and inevitable impurities. The technical scheme adopts a process idea of reducing the hardness difference of the soft and hard phases by bainite to obtain the mechanical properties of yield strength of more than 700MPa, tensile strength of more than 980MPa, elongation after fracture of more than 12 percent and hole expansion rate of 25-32 percent; however, the alloy cost is obviously increased by greatly increasing the proportion of microalloying, and meanwhile, the nonuniformity of the bainite phase structure is not favorable for the uniform distribution of strain in a hole expanding stage. Therefore, under the condition of greatly improving the alloy proportion, the hole expansion ratio is only about 30 percent.
Disclosure of Invention
The invention provides 980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel and a preparation method thereof, and the hole expansion rate of more than 60% is realized by alloy and process design with lower alloy cost, so that the product has more market competitiveness.
In order to achieve the purpose, the invention adopts the following technical scheme:
the 980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel comprises the following chemical components in percentage by weight: 0.1-0.17%, Si: 0.60-1.0%, Mn: 1.50-2.50%, P is less than or equal to 0.05%, S is less than or equal to 0.05%, and Als is less than or equal to 0.05%; one of Nb, Ti and V, wherein Nb is less than or equal to 0.02 percent, Ti is less than or equal to 0.02 percent, and V is less than or equal to 0.05 percent; the balance of Fe and inevitable impurities; simultaneously, the following requirements are met: c + Si/4 is less than or equal to 0.4 percent; the metallographic structure is a ferrite structure, a tempered martensite structure and a residual austenite structure, and the austenitizing temperature of the steel is less than or equal to 840 ℃.
The tensile strength of the steel is more than or equal to 980MPa, the yield strength is more than or equal to 800MPa, the yield ratio is more than or equal to 0.75, the elongation A80 is more than or equal to 12%, and the hole expansion rate is more than or equal to 60%.
A preparation method of 980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel comprises the following steps: smelting, hot continuous rolling, acid pickling and cold rolling, and alloying and galvanizing; wherein:
1) smelting:
smelting in a converter to obtain molten steel meeting the requirements of chemical components; the temperature of the molten steel is 1550-1650 ℃;
2) hot continuous rolling:
the heating temperature is 1250-1300 ℃; two-stage controlled rolling is adopted, namely recrystallization zone rolling and non-recrystallization zone rolling, the recrystallization rolling temperature is above 1050 ℃, and the accumulated deformation is above 50%; the rolling temperature of the non-recrystallization zone is more than 900 ℃, and the accumulated deformation is more than 70%; rolling and then coiling when the temperature is 600-650 ℃;
3) acid pickling and cold rolling:
removing the iron oxide scale on the surface of the steel coil by acid liquor before cold rolling, wherein the cold rolling reduction rate is 50-75%;
4) alloying and galvanizing:
(1) the annealing temperature is A3+ (5-15) DEG C, and the annealing time is 35-60 s;
(2) the slow cooling speed is less than or equal to 5 ℃/s, and the slow cooling temperature is 650-700 ℃;
(3) the rapid cooling speed is more than or equal to 20 ℃/s, and the rapid cooling temperature is 220-240 ℃;
(4) the tempering temperature is 440-460 ℃, the temperature is adjusted to 440-460 ℃, and the temperature of the zinc pot is the same as the adjusted temperature of the steel; the galvanizing time is 1-3 s, and the total time of temperature adjustment and galvanizing before the zinc pot is put into the zinc pot is 25-30 s;
(5) the alloying galvanization temperature is 460-520 ℃, and the time is 15-20 s; then cooling to room temperature, and finishing the elongation of 0.1-0.4%.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, only C, Mn and Si are added into the steel as main elements, and a small amount of Nb, V or Ti is added as micro-alloy elements, so that the prepared 980MPa grade steel has lower alloy cost and better welding performance;
(2) the steel adopts the production process of smelting, continuous casting and continuous rolling, acid pickling and cold rolling, alloying and annealing, has wide process window and simple process flow, and can adapt to domestic mainstream galvanizing production lines; has the advantages of low production cost, no need of adding new production equipment and stable production process.
(3) The final structure of the steel is a ferrite structure, a tempered martensite structure and a residual austenite structure, the structure uniformity is high, the force performance representation of high yield is realized, and the user requirements for manufacturing a high-reaming anti-flanging automobile body structural part are met.
Drawings
FIG. 1 is a heating profile of the alloying galvanization process according to the invention.
FIG. 2 is a metallographic structure photograph of 980MPa grade cold rolled alloyed galvanized quenching distribution steel.
Detailed Description
The invention relates to 980MPa grade cold-rolled alloyed galvanized quenching distribution steel, which comprises the following chemical components in percentage by weight: 0.1-0.17%, Si: 0.60-1.0%, Mn: 1.50-2.50%, P is less than or equal to 0.05%, S is less than or equal to 0.05%, and Als is less than or equal to 0.05%; one of Nb, Ti and V, wherein Nb is less than or equal to 0.02 percent, Ti is less than or equal to 0.02 percent, and V is less than or equal to 0.05 percent; the balance of Fe and inevitable impurities; simultaneously, the following requirements are met: c + Si/4 is less than or equal to 0.4 percent; the metallographic structure is a ferrite structure, a tempered martensite structure and a residual austenite structure, and the austenitizing temperature of the steel is less than or equal to 840 ℃.
The tensile strength of the steel is more than or equal to 980MPa, the yield strength is more than or equal to 800MPa, the yield ratio is more than or equal to 0.75, the elongation A80 is more than or equal to 12%, and the hole expansion rate is more than or equal to 60%.
A preparation method of 980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel comprises the following steps: smelting, hot continuous rolling, acid pickling and cold rolling, and alloying and galvanizing; wherein:
1) smelting:
smelting in a converter to obtain molten steel meeting the requirements of chemical components; the temperature of the molten steel is 1550-1650 ℃;
2) hot continuous rolling:
the heating temperature is 1250-1300 ℃; two-stage controlled rolling is adopted, namely recrystallization zone rolling and non-recrystallization zone rolling, the recrystallization rolling temperature is above 1050 ℃, and the accumulated deformation is above 50%; the rolling temperature of the non-recrystallization zone is more than 900 ℃, and the accumulated deformation is more than 70%; rolling, and then coiling when the temperature is 600-650 ℃;
3) acid pickling and cold rolling:
removing the iron oxide scale on the surface of the steel coil by acid liquor before cold rolling, wherein the cold rolling reduction rate is 50-75%;
4) alloying and galvanizing:
(1) the annealing temperature is A3+ (5-15) DEG C, and the annealing time is 35-60 s;
(2) the slow cooling speed is less than or equal to 5 ℃/s, and the slow cooling temperature is 650-700 ℃;
(3) the rapid cooling speed is more than or equal to 20 ℃/s, and the rapid cooling temperature is 220-240 ℃;
(4) the tempering temperature is 440-460 ℃, the temperature is adjusted to 440-460 ℃, and the temperature of the zinc pot is the same as the adjusted temperature of the steel; the galvanizing time is 1-3 s, and the total time of temperature adjustment and galvanizing before the zinc pot is put into the zinc pot is 25-30 s;
(5) the alloying galvanization temperature is 460-520 ℃, and the time is 15-20 s; then cooling to room temperature, and finishing the elongation of 0.1-0.4%.
Although the traditional cold-rolled high-hole-expansion steel with the pressure of 980MPa or above realizes higher hole expansion performance, the main means is to add a large amount of precious alloy elements, so that the product has no market competitiveness, and the application performance of the steel plate in the aspects of welding and the like is necessarily deteriorated by adding high alloy.
The chemical composition design reason of 980MPa grade cold-rolled alloyed galvanized quenching distribution steel is as follows:
c: c is one of the important elements of the steel of the present invention. The role of C in the steel according to the invention is as follows: (1) the Mn element is added to determine key transformation points such as an A3 point (austenitizing temperature), an Ms point (starting temperature of austenite-martensite transformation) and an Mf point (finishing temperature of austenite-martensite transformation) of the steel sheet; (2) precipitates related to Nb/V/Ti microalloy elements are formed in the stages of continuous casting, hot rolling and continuous annealing, and the functions of refining original austenite grains and strengthening a second phase are achieved; (3) the addition of the element C determines the content and stability of the retained austenite in the steel according to the invention. Based on the three points, the content of C in the steel is not suitable to be less than 0.1 percent. Meanwhile, the common addition of C and Si elements is comprehensively considered in the steel, namely C + Si/4 is less than or equal to 0.4, the welding performance of the steel plate is deteriorated by excessively high addition of the C element, and the strength of the steel plate is ensured by adding enough Si, so that the C content is not higher than 0.17 percent.
Mn: mn is one of the important elements in the steel of the present invention. The role of Mn in the present invention is as follows: (1) adding the element C in a matching manner to determine key phase transformation points such as an A3 point, an Ms point, an Mf point and the like of the steel plate; (2) the Mn element determines the content and stability of the retained austenite in the steel of the present invention. Based on the two points, the content of Mn element in the steel is not lower than 1.5%; too high Mn content easily causes C/Mn segregation in the continuous casting stage, causes heat cracking of the continuous casting billet and is not beneficial to improving the production efficiency; and secondly, the higher Mn content can improve the carbon equivalent of the steel plate and seriously affect the welding performance. Therefore, the Mn content in the present invention cannot be higher than 2.5%.
Si: si is one of the important elements in the steel according to the present invention. Si itself promotes ferrite formation, and dissolves in ferrite to increase the ferrite strength. The effect of Si in the steel according to the invention is as follows: (1) adjusting a ferrite/austenite phase region to adapt to a process window of a heat preservation section in a galvanizing stage; (2) the carbide precipitation is inhibited in the galvanizing and alloying galvanizing stages, and the martensite tempering resistance is improved. Based on the two points, the Si content is not lower than 0.6% in the invention; however, too high Si addition will lower the surface dew point temperature, affecting the quality of the zinc layer in the hot galvanizing and galvannealing stages. Therefore, the content of Si element in the present invention is not preferably higher than 1.0%
Nb: the main effect of adding Nb is in the rolling stage of a hot rolling recrystallization zone, NbC precipitation is formed with C atoms in a strain-induced precipitation mode, and the effect of refining original grains is achieved. Of course, too high an addition of Nb not only increases the cost of the alloy, but more importantly, Nb will occupy a greater content of C atoms, hindering the obtainment of residual austenite during the quenching stage. Therefore, in the present invention, the content of the Nb element is controlled to 0.02% or less.
Ti: TiN can be separated out in the solidification process, and plays a role in pinning the prior austenite crystal boundary and refining the prior austenite crystal grain; meanwhile, a small amount of Ti is precipitated in the continuous annealing stage, and can play a role in strengthening ferrite and tempered martensite; however, excessive Ti precipitation occupies the C atoms necessary for retained austenite. Therefore, in the present invention, the content of Ti element is controlled to 0.02% or less.
V: VC is precipitated from the matrix in the hot rolling and coiling stage, is reserved to the galvanizing and alloying galvanizing stages, and can play a role in strengthening the tempered martensite matrix; however, higher V additions will occupy more C atoms, which is detrimental to the retention of the final retained austenite. Therefore, in the present invention, the content of V element is controlled to 0.05% or less.
P: the P element is a harmful element in steel, and the lower the content, the better. In the invention, the content of the P element is controlled to be less than or equal to 0.05 percent in consideration of the cost.
S: the S element is a harmful element in steel, and the lower the content, the better. In the invention, the content of the S element is controlled to be less than or equal to 0.05 percent in consideration of the cost.
The invention relates to a technological design principle of 980MPa grade cold-rolled alloyed galvanized quenching distribution steel, which comprises the following steps:
1) hot continuous rolling: the heating temperature is 1250-1300 ℃, two-stage controlled rolling is adopted, namely, rolling in a recrystallization zone and rolling in a non-recrystallization zone, the recrystallization rolling temperature is above 1050 ℃, and the accumulated deformation is above 50%; the rolling temperature of the non-recrystallization zone is above 950 ℃, and the accumulated deformation is above 70%; and then coiling the steel when the temperature is 600-650 ℃.
The design reason is as follows: the heating temperature of 1250-1300 ℃ ensures the precipitation behavior of TiN or Ti (C, N) at high temperature, and plays the roles of pinning original austenite grain boundaries and refining grains; in addition, the higher heating temperature (over 1250 ℃) can improve the dragging effect of Nb atoms and promote the refinement of original austenite grains; the rolling heating temperature of the recrystallization zone is more than 1050 ℃, the accumulated deformation exceeds 50 percent, the rolling deformation of the recrystallization zone can be fully promoted, the recrystallization activation energy is improved, and the recrystallization behavior of austenite grains is promoted; the coiling temperature is set to be 600-650 ℃, in the temperature range, the hot rolling coiling composition phase is ferrite + pearlite, the yield strength is 480-500 MPa, the tensile strength is 650-700 MPa, the elongation is more than 25%, and the performance ensures the smooth cold rolling; a bainite or martensite structure appears in a structure at an excessively high coiling temperature, so that the strength of the steel plate is improved, and coiling and cold rolling are not facilitated.
2) Acid pickling and cold rolling: removing the iron oxide scales on the surface of the steel coil by acid liquor before cold rolling, wherein the cold rolling reduction rate is 50-75 percent
The design reason is as follows: the rolling reduction is too high, so that the deformation resistance is too high, and the rolling is difficult to reach the target thickness; the reduction ratio is too low, resulting in a decrease in the elongation of the cold-rolled steel sheet.
3) An alloying galvanization process comprises the following steps:
(1) the annealing temperature is A3+ (5-15) DEG C, and the annealing time is 35-60 s;
the design reason is as follows: the invention adopts the full austenitizing annealing to obtain a tempered martensite structure with high proportion, so the temperature is selected to be higher than the A3 temperature point; however, too high an annealing temperature will promote excessive austenite grain growth, so the austenitizing temperature should not be too high.
(2) Slowly cooling at the speed of 5 ℃/s and the temperature of 650-700 ℃;
the design reason is as follows: in order to obtain higher hole expansion performance, the ferrite phase introduced by the method is attached to the grain boundary of tempered martensite so as to obtain uniform tissue distribution; ferrite attached to tempered martensite is oriented epiphytic ferrite obtained in a cooling stage and needs to be realized through migration of austenite grain boundaries in a slow cooling stage, so that the slow cooling temperature is not low; meanwhile, the cooling speed is not high enough to influence the migration rate of the grain boundary.
(3) The rapid cooling speed is more than or equal to 20 ℃/s, and the rapid cooling temperature is 220-240 ℃;
the design reason is as follows: in the rapid cooling stage, the steel is cooled at a cooling speed of more than 20 ℃/s, so that the formation of a martensite phase in the quenching process is ensured, and ferrite and bainite tissues formed due to too slow cooling speed are prevented; and (3) rapidly cooling to 220-240 ℃, so that sufficient martensite is formed and 4-8% of residual austenite structure is reserved in the structure.
(4) Tempering temperature is 440-460 ℃, the temperature is adjusted to 450-460 ℃, and the temperature of the zinc pot is the same as the adjusted temperature of the steel; the galvanizing time is 1-3 s, and the total time of temperature adjustment and galvanizing before the zinc pot is put into the zinc pot is 25-30 s;
the design reason is as follows: and (3) after quenching, raising the tempering temperature to not less than 440 ℃, so that the temperature of the plate is adjusted to a target temperature in a zinc pot, adjusting the strip speed, controlling and adjusting the galvanizing time to 25-30 s, tempering martensite at the stage, and diffusing supersaturated C atoms into the retained austenite to ensure the austenite stability.
(5) The alloying galvanization temperature is 460-520 ℃, the time is 15-20 s, then the temperature is cooled to the room temperature, and the finishing elongation is 0.1% -0.4%.
The heating curve of the alloying galvanization process is shown in figure 1.
The steel obtained by the process has tensile strength of over 980MPa, yield strength of over 800MPa, yield ratio of over 0.75, elongation A80 of over 12 percent and hole expansion rate of over 60 percent, and has good flanging resistance. The metallographic structure photograph of 980MPa grade cold-rolled alloyed galvanized quenching distribution steel is shown in figure 2.
The following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.
[ examples ] A method for producing a compound
In the examples, the chemical composition of the steel is shown in Table 1, the process parameters of continuous casting and hot rolling of the steel are shown in Table 2, the process parameters of cold rolling and alloying galvanization of the steel are shown in Table 3, and the mechanical properties of the steel are shown in Table 4.
TABLE 1 chemical composition of the steel,% by weight
TABLE 2 continuous casting and Hot Rolling Process parameters of the steels
TABLE 3 Cold-Rolling and galvannealing Process parameters of the steels
TABLE 4 mechanical Properties of the steels
| Examples | Rp0.2/MPa | Rm/MPa | A50/％ | λ/％ | RA/vol.％ |
| 1 | 805 | 1010 | 12.3 | 65 | 7 |
| 2 | 812 | 1008 | 13.5 | 60 | 8 |
| 3 | 803 | 1020 | 12.5 | 71 | 6 |
| 4 | 820 | 1022 | 12.1 | 65 | 7 |
| 5 | 811 | 1005 | 13.2 | 62 | 5 |
| 6 | 807 | 1015 | 12.9 | 63 | 6 |
| 7 | 809 | 1016 | 13.2 | 65 | 7 |
| 8 | 802 | 1022 | 12.4 | 66 | 5 |
In Table 4, Rp02 yield strength, Rm tensile strength, A50In the case of elongation, λ is the hole expansion ratio, and RA is the residual austenite content.
The embodiment proves that the high-hole-expansion alloyed galvanized steel plate with the tensile strength of over 980MPa, the yield strength of over 800MPa, the yield ratio of over 0.75, the elongation A80 of over 12 percent and the hole expansion ratio of over 60 percent is prepared by adopting the chemical component design of the invention and combining the rolling and alloying galvanization processes.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (1)
1. The 980 MPa-grade cold-rolled alloyed galvanized quenching distribution steel is characterized by comprising the following chemical components in percentage by weight: 0.1% -0.17%, Si: 0.60-1.0%, Mn: 1.50-2.50%, P is less than or equal to 0.05%, S is less than or equal to 0.05%, and Als is less than or equal to 0.05%; one of Nb, Ti and V, wherein Nb is less than or equal to 0.02 percent, Ti is less than or equal to 0.02 percent, and V is less than or equal to 0.05 percent; the balance of Fe and inevitable impurities; simultaneously, the following requirements are met: c + Si/4 is less than or equal to 0.4 percent; the metallographic structure is an oriented periphytic ferrite structure, a tempered martensite structure and a residual austenite structure, the content of the residual austenite is 4-8%, and the austenitizing temperature of the steel is less than or equal to 840 ℃; the tensile strength of the steel is more than or equal to 980MPa, the yield strength is more than or equal to 800MPa, the yield ratio is more than or equal to 0.75, the elongation A80 is more than or equal to 12%, and the hole expansion rate is more than or equal to 60%;
the preparation method of 980MPa grade cold-rolled alloyed galvanized quenching distribution steel comprises the following steps: smelting, hot continuous rolling, acid pickling and cold rolling, and alloying and galvanizing; wherein:
1) smelting:
smelting in a converter to obtain molten steel meeting the requirements of chemical components; the temperature of the molten steel is 1550-1650 ℃;
2) hot continuous rolling:
the heating temperature is 1290-1300 ℃; two-stage controlled rolling is adopted, namely recrystallization zone rolling and non-recrystallization zone rolling, the recrystallization rolling temperature is above 1050 ℃, and the accumulated deformation is above 50%; the rolling temperature of the non-recrystallization zone is more than 900 ℃, and the accumulated deformation is more than 70%; rolling and then coiling when the temperature is 600-650 ℃;
3) acid pickling and cold rolling:
removing the iron oxide scale on the surface of the steel coil by acid liquor before cold rolling, wherein the cold rolling reduction rate is 50-75%;
4) alloying and galvanizing:
(1) the annealing temperature is A3+ (5-15) DEG C, and the annealing time is 35-60 s;
(2) the slow cooling speed is less than or equal to 5 ℃/s, and the slow cooling temperature is 650-700 ℃;
(3) the rapid cooling speed is more than or equal to 20 ℃/s, and the rapid cooling temperature is 220-240 ℃;
(4) the tempering temperature is 440-460 ℃, the temperature is adjusted to 440-460 ℃, and the temperature of the zinc pot is the same as the adjusted temperature of the steel; the galvanizing time is 1-3 s, and the total time of temperature adjustment and galvanizing before the zinc pot is put into the zinc pot is 25-29 s;
(5) the alloying galvanization temperature is 460-520 ℃, and the time is 15-20 s; then cooling to room temperature, and finishing the elongation rate to be 0.1-0.4%.
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