CN108754328B - Normal-temperature aging resistant bake-hardened steel plate and manufacturing method thereof - Google Patents
Normal-temperature aging resistant bake-hardened steel plate and manufacturing method thereof Download PDFInfo
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- CN108754328B CN108754328B CN201810619478.0A CN201810619478A CN108754328B CN 108754328 B CN108754328 B CN 108754328B CN 201810619478 A CN201810619478 A CN 201810619478A CN 108754328 B CN108754328 B CN 108754328B
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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
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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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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
- C21D8/0221—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
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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
- C21D8/0221—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
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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
- 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
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
Abstract
The normal temperature aging resistant bake-hardened steel plate comprises the following chemical components in percentage by weight: c: 0.004-0.006%, Si: 0.03-0.08%, Mn: 0.20-0.60%, Al: 0.05 to 0.1%, Ti: 0.015 to 0.030%, Mo: 0.05-0.10%, B: 0.0: 2-0.004%, and limits N to less than 0.002%, P to less than 0.020%, S to less than 0.006%, and the balance of Fe and inevitable impurities. The invention has the beneficial effects that: 1) the addition of Mo remarkably reduces the activity of carbon in ferrite and inhibits the normal temperature aging of the steel plate; 2) the addition of B ensures that the solid-solution carbon is distributed in the crystal rather than the crystal boundary, thereby ensuring the baking and hardening effects of the steel plate; 3) the addition of Ti and Al can reduce the content of solid-solution nitrogen and solid-solution carbon in the steel plate, thereby not only ensuring the normal temperature aging resistance, but also ensuring the baking hardening effect. 4) The steel plate produced according to the invention has excellent comprehensive properties: the yield strength is more than 220MPa, the tensile strength is more than 350MPa, the elongation is more than 40%, the baking hardening value is more than 45MPa, the r value is more than 1.5, and natural aging does not occur after the product is stored for 6 months in summer.
Description
Technical Field
The invention relates to the field of metal materials, in particular to a normal temperature aging resistant bake-hardening steel plate and a manufacturing method thereof. The steel sheet of the present invention is mainly suitable for use in the manufacture of automotive panels.
Background
Since the twenty-first century, with the increasingly prominent energy crisis and environmental protection problems, the automotive industry is developing towards the trend of light weight and low pollution, and particularly, the performance of cars pursues high speed, safety, energy conservation, comfort, beauty and durability. The bake-hardened steel sheet has excellent stamping properties and greatly improved yield strength (generally over 35 MPa) in the post-forming paint baking process, so that the formed steel sheet has excellent dent resistance, and the bake-hardened steel sheet is widely applied to automobile panels. However, the steel is easy to age at normal temperature and has limited bake hardening capacity, which is always a main problem in production and is widely researched by various steel manufacturers.
The patent publication No. CN200810119820.7 discloses an ultra-low carbon bake-hardened steel sheet in which niobium and titanium are compositely added and a method for manufacturing the same, wherein P is added to an IF steel in which Nb-Ti composite is stable to improve the strength, but P is easily segregated in grain boundaries to be not beneficial to secondary punching.
The patent publication No. CN 200910013420.2-ultra low carbon bake hardening steel plate with excellent punching performance and its manufacturing process patent are C, N using Ti part to fix IF steel grade to ensure bake hardening performance of steel plate, but the normal temperature aging of the steel can not be avoided.
The patent publication No. CN 200910061108.0-220 MPa grade cold rolling baking hardened steel and the production method thereof ensure the baking hardening effect by adding a small amount of B into IF steel to inhibit the segregation of C in the grain boundary, but still can not solve the problem of normal temperature aging.
The publication No. CN 201010276618.2-a high-strength bake-hardening steel and a preparation method thereof, Cu-Ni is added on the basis of Nb-Ti-IF steel to improve the bake-hardening performance, and the normal temperature aging of the steel plate cannot be inhibited.
The publication No. CN 201611177925.9-an age-resistant cold-rolled bake-hardening steel 220BH and its production method patent adds P on the basis of Nb-IF steel to improve the strength, uses Mo to inhibit the normal temperature aging, but the bake-hardening effect is inhibited at the carbon content of 0.001-0.003%.
Disclosure of Invention
Aiming at the development requirements in the field of automobile steel, the invention provides a normal temperature aging resistant bake-hardening steel plate and a manufacturing method thereof, wherein the yield strength is more than 220MPa, the tensile strength is more than 350MPa, the elongation is more than 38%, the bake-hardening value is more than 45MPa, the r value is more than 1.5, and natural aging does not occur after the steel plate is stored for 6 months in summer.
In order to achieve the purpose, the invention adopts the following technical scheme:
the normal temperature aging resistant bake-hardened steel plate comprises the following chemical components in percentage by weight: c: 0.004-0.006%, Si: 0.03-0.08%, Mn: 0.20-0.60%, Al: 0.05 to 0.1%, Ti: 0.015 to 0.030%, Mo: 0.05-0.10%, B: 0.0: 2-0.004%, and limits N to less than 0.002%, P to less than 0.020%, S to less than 0.006%, and the balance of Fe and inevitable impurities.
The steel plate of the invention mainly has the following components:
c, carbon is the most main solid solution strengthening element in steel, and a certain amount of solid solution carbon can ensure the baking hardening effect. The carbon content is too high, which is not favorable for the deep drawing performance of the steel plate and increases the normal temperature aging sensitivity. If the carbon content is too low, it is difficult to ensure bake hardenability. The optimal range of carbon is 0.004-0.006%.
Si: silicon is a solid solution strengthening element, can improve the strength of the steel plate and increase the activity of carbon in the steel, is beneficial to bake hardening, but if the silicon is too high, the plasticity of the steel is reduced, and the steel plate is easy to age at normal temperature. While excessively high silicon may deteriorate the surface quality of the hot rolled steel sheet to cause troubles. The content of silicon in the invention is 0.03-0.08%.
Mn: manganese plays a role in solid solution strengthening and ferrite grain refinement. However, the manganese content is too high, and mixed crystals are easily caused. The content of manganese in the invention is 0.2-0.6%.
Al: the aluminum can form AlN for precipitation, fix nitrogen in the steel, and play a role in refining grains to a certain extent and inhibiting the normal-temperature aging of the steel plate. The range of aluminum in the invention is Al: 0.05 to 0.1 percent.
P: although phosphorus can improve the balance of the steel sheet, it seriously deteriorates cold formability of the steel, particularly secondary formability, and is limited to 0.020%.
S: sulphur causes harmful elements in the steel, manganese sulphide is formed to reduce the performance of the steel plate, and compounds formed by the sulphur reduce the beneficial effect of titanium. So that the smaller the content, the better, it is defined as 0.006%.
N: the solid solution N strongly increases the normal temperature aging sensitivity of the steel plate and must be reduced as much as possible, and the invention limits the N to be below 0.002 percent in consideration of smelting cost.
Ti: carbon and nitrogen combine to form fine carbonitride, which can refine grains, improve strength, and control the content of solid solution C, N in the steel sheet. The optimal range of the titanium content is 0.015-0.030%.
Mo: the molybdenum has larger atomic radius, causes larger lattice distortion when forming solid solution in steel, generates a stress field, thereby reducing the activity of carbon, inhibiting the normal temperature aging performance of the steel plate, and simultaneously generating remarkable solid solution strengthening effect. However, too high reduces the bake hardening effect and reduces the plasticity of the steel sheet. Therefore, the optimal range of the molybdenum content in the invention is between 0.05 and 0.10 percent.
B: b inhibits ferrite nucleation to refine grains and inhibits carbon segregation at grain boundaries to indirectly improve the bake hardenability of the steel sheet, but if the content is too high, compounds are easily formed to reduce the plasticity of the steel sheet. The optimal range of the molybdenum content in the invention is between 0.02 and 0.004 percent.
A method for manufacturing a normal temperature aging resistant bake-hardened steel sheet, comprising the steps of:
1) a heating process: heating the billet steel to 1150 +/-50 ℃ in a heating furnace, and preserving heat for 4 +/-0.5 hours;
2) the rolling process comprises the following steps: the final rolling temperature is 850-900 ℃, the coiling temperature is 580-650 ℃, and the temperature is kept for 8 +/-0.5 hours;
3) the cold rolling process comprises the following steps: the cold rolling reduction rate is not lower than 70 percent;
4) annealing process: keeping the temperature at 790 ℃ and 820 ℃ for 5 +/-0.5 minutes, cooling to 630 ℃ and 680 ℃ at 25 +/-5 ℃/s, keeping the temperature for 3 +/-0.5 minutes, and cooling to the room temperature at 5-10 ℃/s.
Compared with the prior art, the invention has the beneficial effects that:
1) the addition of Mo remarkably reduces the activity of carbon in ferrite and inhibits the normal temperature aging of the steel plate;
2) the addition of B ensures that the solid-solution carbon is distributed in the crystal rather than the crystal boundary, thereby ensuring the baking and hardening effects of the steel plate;
3) the addition of Ti and Al can reduce the content of solid-solution nitrogen and solid-solution carbon in the steel plate, thereby not only ensuring the normal temperature aging resistance, but also ensuring the baking hardening effect.
4) The steel plate produced according to the invention has excellent comprehensive properties: the yield strength is more than 220MPa, the tensile strength is more than 350MPa, the elongation is more than 40%, the baking hardening value is more than 45MPa, the r value is more than 1.5, and natural aging does not occur after the product is stored for 6 months in summer.
Detailed Description
The following examples are provided to further illustrate the embodiments of the present invention:
a normal temperature aging resistant bake-hardening steel plate is characterized in that on the basis of ULCB steel components, component optimization is carried out, Mo, B and Ti are added, and annealing process parameter control is carried out to obtain a steel plate with yield strength of more than 220MPa, tensile strength of more than 350MPa, elongation of more than 40%, bake-hardening value of more than 35MPa, r value of more than 1.5, and natural aging does not occur after 6 months of storage in summer. The chemical components by weight percentage are as follows: c: 0.004-0.006%, Si: 0.03-0.08%, Mn: 0.20-0.60%, Al: 0.05 to 0.1%, Ti: 0.015 to 0.030%, Mo: 0.05-0.10%, B: 0.0: 2-0.004%, and limits N to less than 0.002%, P to less than 0.020%, S to less than 0.006%, and the balance of Fe and inevitable impurities.
A manufacturing method of a normal temperature aging resistant bake-hardening steel plate adopts the chemical components and obtains the normal temperature aging resistant bake-hardening steel plate through smelting, hot rolling, cold rolling and annealing processes, and the manufacturing method comprises the following steps:
1) a heating process: heating the steel billet with qualified components to 1150 +/-50 ℃ in a heating furnace, and preserving heat for 4 +/-0.5 hours to fully dissolve alloy elements and make the components uniform;
2) the rolling process comprises the following steps: ordinary rolling and laminar cooling are adopted, the finish rolling temperature is 850-900 ℃, the coiling temperature is 580-650 ℃, and the heat preservation is 8 +/-0.5 hours; the precipitation of AlN and TiC is sufficient, and the precipitated phase is coarsened due to overhigh coiling temperature, so that the strength is not favorable; if the temperature is too low, the precipitated phase is too thin, and mixed crystals are easily generated after cold rolling and annealing;
3) the cold rolling process comprises the following steps: the cold rolling reduction rate is not lower than 70 percent;
4) annealing process: keeping the temperature at 790 ℃ and 820 ℃ for 5 +/-0.5 minutes, cooling to 630 ℃ and 680 ℃ at 25 +/-5 ℃/s, keeping the temperature for 3 +/-0.5 minutes, and cooling to the room temperature at 5-10 ℃/s.
The specific composition, temperature profile and properties of the steel sheets of 6 examples of the present invention are shown in tables 1 to 3.
TABLE 1 chemical composition of inventive examples (wt%)
TABLE 2 Hot Rolling Process, Cold Rolling reduction and annealing Process according to the examples of the present invention
TABLE 3 mechanical Property parameters of the examples of the invention
In the above examples, the slab weight was 80kg, the slab was heated after cutting the head and the tail, the thickness of the hot rolled sheet was 4.5mm, and the rolling process is shown in Table 2.
Claims (2)
1. The normal temperature aging resistant bake-hardened steel plate is characterized by comprising the following chemical components in percentage by weight: c: 0.005-0.006%, Si: 0.03-0.08%, Mn: 0.20-0.60%, Al: 0.05 to 0.1%, Ti: 0.015 to 0.030%, Mo: 0.05-0.10%, B: 0.002-0.004%, and limits N to less than 0.002%, P to less than 0.020%, S to less than 0.006%, and the balance of Fe and inevitable impurities; the yield strength is more than 220MPa, the tensile strength is more than 350MPa, the elongation is more than 38%, the baking hardening value is more than 45MPa, the r value is more than 1.5, and natural aging does not occur after the product is stored for 6 months in summer.
2. A method for manufacturing an ambient temperature aging resistant bake-hardened steel sheet according to claim 1, characterized by comprising the steps of:
1) a heating process: heating the billet steel to 1150 +/-50 ℃ in a heating furnace, and preserving heat for 4 +/-0.5 hours;
2) the rolling process comprises the following steps: the final rolling temperature is 850-900 ℃, the coiling temperature is 580-650 ℃, and the temperature is kept for 8 +/-0.5 hours;
3) the cold rolling process comprises the following steps: the cold rolling reduction rate is not lower than 70 percent;
4) annealing process: keeping the temperature at 820 ℃ for 5 +/-0.5 minutes in 790 ℃ and cooling the mixture to 680 ℃ in 25 +/-5 ℃/s, keeping the temperature for 3 +/-0.5 minutes and cooling the mixture to room temperature in 5-10 ℃/s.
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| CN108754328B true CN108754328B (en) | 2020-01-07 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP3855678B2 (en) * | 2000-04-28 | 2006-12-13 | 住友金属工業株式会社 | Manufacturing method of thin steel sheet with excellent room temperature aging resistance, workability, and paint bake hardenability |
| JP3958921B2 (en) * | 2000-08-04 | 2007-08-15 | 新日本製鐵株式会社 | Cold-rolled steel sheet excellent in paint bake-hardening performance and room temperature aging resistance and method for producing the same |
| CN101928875A (en) * | 2009-06-22 | 2010-12-29 | 鞍钢股份有限公司 | High-strength cold-rolled plate with favorable forming property and preparation method thereof |
| JP2013064169A (en) * | 2011-09-15 | 2013-04-11 | Jfe Steel Corp | High-strength steel sheet and plated steel sheet excellent in bake-hardenability and formability, and method for production thereof |
| JP2013076132A (en) * | 2011-09-30 | 2013-04-25 | Jfe Steel Corp | High strength thin steel sheet having excellent bake hardenability and formability and method for manufacturing the same |
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