CN113637902A - Cold-rolled automobile weathering steel containing rare earth and having yield strength of 280MPa and production method thereof - Google Patents
Cold-rolled automobile weathering steel containing rare earth and having yield strength of 280MPa and production method thereof Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 30
- 229910000870 Weathering steel Inorganic materials 0.000 title claims abstract description 16
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 16
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 11
- 230000007797 corrosion Effects 0.000 claims abstract description 47
- 238000005260 corrosion Methods 0.000 claims abstract description 47
- 238000005096 rolling process Methods 0.000 claims abstract description 25
- 238000000137 annealing Methods 0.000 claims abstract description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052802 copper Inorganic materials 0.000 claims abstract description 10
- 239000000126 substance Substances 0.000 claims abstract description 9
- 239000002253 acid Substances 0.000 claims abstract description 8
- 238000005266 casting Methods 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims abstract description 8
- 238000005097 cold rolling Methods 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 5
- 229910000831 Steel Inorganic materials 0.000 claims description 90
- 239000010959 steel Substances 0.000 claims description 90
- 238000000034 method Methods 0.000 claims description 18
- 230000008569 process Effects 0.000 claims description 17
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 238000003466 welding Methods 0.000 claims description 10
- 238000005554 pickling Methods 0.000 claims description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 5
- 238000003723 Smelting Methods 0.000 claims description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 239000001257 hydrogen Substances 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 5
- 229910000859 α-Fe Inorganic materials 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 4
- 229910001562 pearlite Inorganic materials 0.000 claims description 4
- 238000005238 degreasing Methods 0.000 claims description 3
- 238000006477 desulfuration reaction Methods 0.000 claims description 3
- 230000023556 desulfurization Effects 0.000 claims description 3
- 238000011010 flushing procedure Methods 0.000 claims description 3
- 238000004806 packaging method and process Methods 0.000 claims description 3
- 230000009467 reduction Effects 0.000 claims description 3
- 230000003009 desulfurizing effect Effects 0.000 abstract description 2
- 238000005406 washing Methods 0.000 abstract 3
- 239000010949 copper Substances 0.000 description 23
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 13
- 239000011572 manganese Substances 0.000 description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 8
- 229910052757 nitrogen Inorganic materials 0.000 description 8
- 238000005728 strengthening Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
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- 229910052698 phosphorus Inorganic materials 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 5
- 239000006104 solid solution Substances 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000010960 cold rolled steel Substances 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
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- 238000002360 preparation method Methods 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
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- 238000005204 segregation Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 206010057040 Temperature intolerance Diseases 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- 238000004090 dissolution Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
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- 230000002708 enhancing effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000008543 heat sensitivity Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical compound [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 229910052702 rhenium Inorganic materials 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
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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
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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
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- C22C38/002—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
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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- Mechanical Engineering (AREA)
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- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
A rare earth-containing cold-rolled weathering steel for automobiles with yield strength of 280MPa comprises the following chemical components in percentage by weight: c: not more than 0.09%, Si 0.10-0.40%, Mn: 0.10-0.30%, P0.05-0.11%, S less than or equal to 0.015%, Als: 0.010-0.03%, Cu: 0.2-0.35%, RE: 0.03-0.08%; the production method comprises the following steps: desulfurizing; heating a casting blank; washing the surface of the casting blank by high-pressure water; rough rolling; fine rolling; coiling; acid washing and acid washing, and then cold rolling; continuous annealing; and leveling according to different thicknesses of the cold-rolled finished products. The invention has the advantages of 280-360 MPa of yield strength, 380-460 MPa of tensile strength, more than 40% of elongation A, simple elements, good atmospheric corrosion resistance and weather resistance, and is particularly suitable for structural members which cannot be coated in the automobile and have large stamping deformation.
Description
Technical Field
The invention relates to cold-rolled steel and a production method thereof, in particular to cold-rolled automobile weathering steel containing rare earth and having yield strength of 280MPa and a production method thereof, which is particularly suitable for structural members which can not be coated in the automobile and have large stamping deformation.
Background
Atmospheric corrosion is the interaction of a material with its surrounding atmospheric environment, and ordinary ferrous materials are easily corroded (rusted) in the atmosphere. According to statistics, 1/6 in the world annual steel yield is lost due to corrosion, and the direct economic loss of China annually caused by steel corrosion exceeds 100 billion yuan.
The weathering steel, i.e. the atmospheric corrosion resistant steel, is made by adding a small amount of alloy elements into steel, so that a layer of compact amorphous spinel oxide film with the thickness of about 50-100 μm and good adhesion with the base metal is formed between the rust layer and the base, and because of the existence of the compact oxide film, oxygen and water in the atmosphere are prevented from permeating into the steel base, the deep development of rust to the steel material is slowed down, and the atmospheric corrosion resistance of the steel material is greatly improved. The weather-resistant steel has the atmospheric corrosion resistance 2-8 times that of common steel, and the longer the service life is, the more prominent the corrosion resistance is.
With the vigorous development of the automobile industry, the requirement of the automobile industry on the corrosion resistance of the automobile steel material is higher and higher, and meanwhile, a plurality of automobile parts cannot be coated due to the influence of the automobile structure and the like, so that the requirement of the parts on the corrosion resistance of the material is higher. The weathering steel prevents the matrix from being further corroded by the external environment by means of a rust-tight layer generated by the weathering steel, so that the purpose of coating-free is achieved.
After retrieval:
the document with Chinese patent application number 201910703774.3 discloses a cold-rolled weathering steel and a preparation method thereof, wherein the cold-rolled weathering steel comprises the following chemical components in percentage by weight: c: 0.05 to 0.08%, Si: 0.25 to 0.40%, Mn: 0.25-0.40%, P: 0.060 to 0.100%, S: less than or equal to 0.020%, Als: 0.008-0.030%, Ni: 0.12 to 0.20%, Cu: 0.25 to 0.40%, Cr: 0.30-0.50%, N: the steel is less than or equal to 0.0080 percent, the balance of Fe and inevitable impurities, and through reasonable chemical composition design, noble metal alloys such as Ti, Nb, B and the like are not added, and through the control of hot rolling, cold rolling, continuous annealing and leveling processes, cold-rolled weather-resistant steel with good surface quality is obtained, the yield strength is more than or equal to 350MPa, the tensile strength is more than or equal to 500MPa, the elongation of A50 is more than or equal to 30 percent, and the steel has good atmospheric corrosion resistance and welding performance. However, the addition of noble metals such as Cr and Ni increases the cost of the alloy.
The Chinese patent application No. 202010950167.X discloses a production method of cold-rolled weather-resistant steel with yield strength of more than 310MPa, which obtains a cold-rolled weather-resistant steel strip product with the thickness of 0.5-2.5 mm by reasonable chemical composition design, steelmaking smelting, hot rolling process, acid rolling process and continuous annealing process control, wherein the internal structure of the cold-rolled weather-resistant steel product is ferrite, pearlite and cementite; the mechanical property result of the finished cold-rolled weather-resistant steel product is that the yield strength is more than or equal to 310MPa, the tensile strength is more than or equal to 450MPa, the elongation after fracture is more than or equal to 28 percent, the mechanical property is stable, the forming and atmospheric corrosion resistance of the steel strip product are excellent, and the steel strip product can be applied to the relevant fields of air preheaters, plate heat exchangers and the like. However, the alloy cost is high because 0.10-0.25% of Ni element and 0.3-0.45% of Cr element are added. The atmospheric corrosion resistance of the steel sheet is not described.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides the weathering steel containing rare earth for the cold-rolled automobile with the yield strength of 280-360 MPa, the tensile strength of 380-460 MPa, the elongation A of more than 40 percent, simple elements and good atmospheric corrosion resistance and weather resistance, and the production method thereof.
The measures for realizing the aim are as follows:
a rare earth-containing cold-rolled weathering steel for automobiles with yield strength of 280MPa comprises the following chemical components in percentage by weight: c: not more than 0.09%, Si 0.10-0.40%, Mn: 0.10-0.30%, P0.05-0.11%, S less than or equal to 0.015%, Als: 0.010-0.03%, Cu: 0.2-0.35%, RE: 0.03-0.08%, and the balance of Fe and inevitable impurities; mechanical properties: the yield strength is 280-360 MPa, the tensile strength is 380-460 MPa, the elongation A is more than 40%, the metallographic structure is ferrite and a small amount of pearlite, the grain size reaches more than 9 grade, and the atmospheric corrosion resistance is less than or equal to 50% relative to the Q235 corrosion rate.
It is characterized in that: the RE accounts for 0.038-0.073 wt%.
A production method of rare earth-containing cold-rolled weather-resistant steel for automobiles with yield strength of 280MPa comprises the following steps:
1) carrying out desulfurization molten iron, smelting in a converter and pouring into a blank;
2) heating the casting blank, controlling the heating temperature to be 1230-1270 ℃, and preserving the heat for 130-160 min;
3) flushing the surface of the casting blank by high-pressure water, and controlling the pressure of the high-pressure water to be not lower than 160 MPa;
4) carrying out rough rolling, and controlling the rough rolling temperature to be 1040-1060 ℃;
5) carrying out finish rolling, and controlling the finish rolling temperature to be 860-890 ℃;
6) coiling, setting the coiling temperature according to the thickness of the hot rolled finished product:
when the thickness of the hot-rolled finished product is less than 3mm, the coiling temperature is controlled to be 686-694 ℃;
when the thickness of the hot-rolled finished product is more than or equal to 3mm and less than or equal to 5mm, controlling the coiling temperature to be 666-674 ℃;
when the thickness of the hot-rolled finished product is more than 5mm, controlling the coiling temperature to be 646-654 ℃;
7) rolling after acid pickling and acid pickling, and controlling the cold rolling reduction rate to be 48-70%; welding by adopting a laser welding machine;
8) annealing treatment is carried out in a bell-type furnace under the full hydrogen atmosphere:
the process comprises electrolytic degreasing, cover annealing, wet flattening, coiling and packaging;
in the cover annealing temperature, the hot spot temperature is 670- & ltwbr & gt 700 ℃, the cold spot temperature is 610- & ltwbr & gt 640 ℃,
9) leveling according to different thicknesses of cold-rolled finished products:
leveling by adopting a wet leveling process;
setting the flattening elongation according to the thickness of a cold-rolled finished product:
when the thickness of the cold-rolled finished product is less than or equal to 1.2mm, the flat elongation is controlled to be 0.8-1.2%
When the thickness of the cold-rolled finished product is more than 1.2mm, the flat elongation is controlled to be 1.2-1.6%.
It is characterized in that: the rough rolling temperature is 1042-1055 ℃.
The action and mechanism of each element and main process in the invention
C: carbon is a basic element in steel, and is also the most economical and effective strengthening element, and the strength of the steel sheet is obviously increased with the increase of the content of C, but the plasticity and the formability of the steel sheet are reduced, the welding performance is deteriorated, and the corrosion resistance of the steel sheet is influenced. Therefore, the C content is controlled to 0.09% or less.
Si: silicon is a solid solution strengthening element, is an economical strengthening element and has strong solid solution strengthening effect. The Si element can be used as a reducing agent and a deoxidizing agent to be added into steel in the smelting process, the hardenability and tempering resistance of the steel can be improved, the increase of the Si element can reduce the overall corrosion resistance rate of a steel plate, the Si element can be matched with Cu, P and other elements in the steel to improve the corrosion resistance of the steel, but the too high Si element can reduce the low-temperature toughness and the welding performance of the steel, and meanwhile, the Si element can easily form a compact oxide layer Mn on the surface of the steel plate2SiO4Seriously affecting the surface quality of the material. Therefore, the Si content is controlled to 0.10 to 0.40%.
Mn: manganese is a relatively economic strengthening element and mainly plays a role in solid solution strengthening and grain refinement. While the strength of the steel can be improved by adding a proper amount of Mn, excessive Mn causes coarsening of crystal grains, thereby causing temper brittleness, increasing the heat sensitivity of the steel, and deteriorating the center segregation of the steel sheet. Therefore, the Mn content is controlled to 0.10 to 0.30%.
P: phosphorus is a solid solution strengthening element, is a relatively economic strengthening element, can greatly improve the strength and hardness of steel, and is easy to segregate due to excessively high P element, so that the plasticity, low-temperature toughness and welding performance of the steel are obviously reduced. The element P is one of the most effective alloy elements for improving the weather resistance of steel, and has a special effect in promoting the rust layer to have amorphous properties. When P and Cu are added into the steel in combination, excellent synergistic weather resisting effect is shown, and under the condition of atmospheric corrosion, P in the steel is an anode depolarizer and can accelerate uniform dissolution of the steel and Fe2+The oxidation rate of (A) is favorable for forming a uniform FeO0H rust layer on the surface of steel and promoting the generation of FeO rich in amorphous light-base iron oxidex(OH)3-2XThe protective film is compact, thereby being a protective barrier for preventing corrosive media from entering a steel matrix and preventing the interior of the steel from being corroded by atmosphere. Therefore, the contribution of the P element to the strength is comprehensively considered, and the content of the P is controlled to be 0.05-0.11%.
S: sulfur is a harmful element. The S element in the steel is easy to form MnS inclusion with the Mn element, a pitting corrosion source is formed in the steel, the weather resistance of the steel plate is deteriorated, and meanwhile, the plasticity and the toughness of the steel are reduced. Therefore, the S content is controlled to 0.015% or less.
And Als: in the refining step, the steel is deoxidized to remove oxygen dissolved in the molten steel, and Als suppresses solid solution of nitrogen in ferrite to form AlN to suppress coarsening of crystal grains. Too high an amount of Als increases inclusions in the steel, and decreases the toughness of the steel. Therefore, the content of Als is controlled to be 0.01-0.03%.
Cu: copper is the most prominent element for improving the weather resistance of the steel plate, a barrier layer mainly comprising Cu and P can be formed between the substrate and the rust layer, the barrier layer is firmly combined with the substrate to have good protection on the steel plate, and in addition, Cu can offset the harmful effect of impurity element S in the steel plate and has important effect on the corrosion resistance of the steel plate. However, excessive Cu addition causes a problem of "Cu brittleness". Therefore, the Cu content is controlled to be 0.2 to 0.35%.
RE element is very active element, and is powerful deoxidant and desulfurizing agent to purify steel grain boundary. RE element can refine crystal grains, change the existence form of inclusions in steel, reduce the quantity of harmful inclusions and reduce the origin of the corrosive candles, thereby improving the atmospheric corrosion resistance of the steel. The RE element can reduce the macro segregation of P and make the distribution of P in steel more uniform. Meanwhile, the RE element can reduce the activity of carbon and nitrogen, increase the solubility of carbon and nitrogen, prevent the carbon and nitrogen from being dissolved into an internal stress area or a crystal defect, reduce the number of interstitial atoms of pinning dislocation, improve the plasticity and toughness of the steel, and influence the form, size, distribution, quantity and structure of carbide, thereby improving the strength of the steel. Therefore, the RE content is controlled to be 0.03-0.08%, preferably 0.038-0.073%.
The trace rare earth element (RE) is added, so that the stamping forming performance of the steel plate is more excellent, the plasticity and the toughness of the steel plate are better, the elongation is higher, and the requirement of manufacturing the automobile internal structural part with larger stamping deformation is met. The RE element is extremely active and is a strong deoxidizer and desulfurizer, so that the grain boundary of steel can be purified, grains can be refined, the existence form of inclusions in the steel can be changed, and the quantity of harmful inclusions can be reduced; meanwhile, the RE element can reduce the activity of carbon and nitrogen, increase the solubility of carbon and nitrogen, prevent the carbon and nitrogen from being dissolved into an internal stress area or a crystal defect, and reduce the number of interstitial atoms of pinning dislocation, thereby improving the plasticity and toughness of the steel. In addition, the RE element can also reduce the macrosegregation of P, so that the distribution of P in steel is more uniform, and the cracking of the steel plate in the stamping process is reduced. And because the RE element reduces the existence form of inclusions in the steel and the quantity of harmful inclusions, the original point of the corrosion candle can be reduced, and the atmospheric corrosion resistance of the steel is further improved. According to the experimental statistics, the atmospheric corrosion resistance of the steel plate is only 50% or less relative to the Q235 corrosion rate, and the atmospheric corrosion resistance of the steel plate without the rare earth element (RE) is 60% or less relative to the Q235 corrosion rate. This indicates that the steel of the present invention can be applied in the field of manufacturing of automotive parts which have a higher requirement for atmospheric corrosion resistance.
The invention controls the furnace time of the hot rolled plate blank to be kept at the temperature of 130-150 min, the dephosphorization high-pressure water pressure to be more than 160MPa and the rough rolling temperature to be 1040-1060 ℃, and mainly aims to reduce the occurrence of Cu brittleness. When the slab is addedThe heat temperature is higher than the melting point (1083 ℃) of the Cu element, the precipitated copper-rich phase is in a molten state, and when the copper-rich phase reaches a certain degree, a crack-shaped crack Cu brittle defect is formed on the surface in the deformation process. Therefore, the in-furnace time of the plate blank is reduced, the in-furnace time is controlled to be 130-150 min, and the diffusion of Cu elements in the grain boundary is reduced. And secondly, controlling the rough rolling temperature to be 1040-1060 ℃, avoiding the melting point temperature of the Cu element, and reducing the melting of the Cu element. Finally, Cu element is easy to be enriched at the interface between the iron sheet and the matrix in the hot rolling and heating process, and Si element is easy to form a compact oxide layer Mn on the surface2SiO4And the surface quality of the steel plate is influenced, so that the descaling effect is ensured and the scale pressing-in is eliminated by enhancing the descaling pressure of the rough rolling area. When producing common steel grades, the dephosphorization high-pressure water pressure is below 130MPa, so the hot rolling dephosphorization high-pressure water pressure is controlled to be above 160 MPa.
The coiling temperature adopted by the invention is set according to the thickness of the hot-rolled finished product, and is used for ensuring the uniformity and stability of the mechanical properties of cold-rolled steel sheets with different thickness specifications. The coiling temperature is controlled to 646-.
The invention adopts cover annealing production, and the sealing gas is annealed in a full hydrogen way, mainly because the requirements on the surface quality of the steel plate are not particularly high, the invention adopts the full hydrogen cover annealing, has less equipment investment and low production energy consumption, is beneficial to the requirement of reducing the current carbon emission in the steel industry, and can manufacture 280MPa grade cold-rolled weathering steel.
According to the invention, a wet leveling process is adopted, the leveling elongation is set according to the thickness of a cold-rolled finished product, and the wet leveling process is adopted to be better than the dry leveling process, so that the surface quality of the obtained steel plate is better, the rolling force of a leveling machine is smaller, the energy consumption is reduced, and the elimination of a steel plate yield platform is facilitated. The flat elongation is set according to the thickness of a cold-rolled finished product, so that the uniformity and stability of the mechanical properties of cold-rolled steel sheets with different thickness specifications are ensured, and meanwhile, the steel sheets are endowed with good surface quality and roughness.
Compared with the prior art, the invention has the following characteristics:
1) the invention only adds Mn, Si, P, Re and other relatively cheap alloy elements, and does not add Cr, Ni, Ti and other noble metals, thereby greatly reducing the manufacturing cost;
2) because RE is added, the steel plate has more excellent stamping forming performance, better plasticity and toughness and higher elongation, and because the RE element reduces the existence form of inclusions in the steel and reduces the quantity of harmful inclusions, the origin of the corrosion candle can be reduced, and the atmospheric corrosion resistance of the steel is further improved; based on the corrosion rate of Q235, the invention only accounts for 50 percent of the total corrosion rate, and the corrosion rate is reduced by 10 percent compared with the corrosion rate of steel without RE.
3) The problem of Cu brittleness is solved, measures such as hot rolling in-furnace time, dephosphorization high-pressure water pressure, rough rolling temperature and the like are mainly adopted, the occurrence probability and degree of Cu brittleness and iron scale are reduced, and the surface quality of the steel plate is improved;
4) the performance uniformity problem is solved by mainly adopting the process of designing hot rolling coiling temperature and cold rolling leveling elongation according to the thickness of a finished product, and the uniformity and stability of the mechanical properties of the steel plates with different finished product thicknesses are ensured.
5) The method is particularly suitable for structural parts which cannot be coated and have large stamping deformation in the automobile; and can also be used in industries which have requirements on corrosion resistance, such as household appliances.
Drawings
FIG. 1 is a metallographic structure diagram according to the present invention.
Detailed Description
The present invention is described in detail below:
table 1 is a list of values of the components of each example and comparative example of the present invention;
table 2 shows the values of the process parameters of the examples and comparative examples of the present invention;
table 3 is a table of experimental results of examples and comparative examples of the present invention.
The preparation method comprises the following steps:
1) carrying out desulfurization molten iron, smelting in a converter and pouring into a blank;
2) heating the casting blank, controlling the heating temperature to be 1230-1270 ℃, and preserving the heat for 130-160 min;
3) flushing the surface of the casting blank by high-pressure water, and controlling the pressure of the high-pressure water to be not lower than 160 MPa;
4) carrying out rough rolling, and controlling the rough rolling temperature to be 1040-1060 ℃;
5) carrying out finish rolling, and controlling the finish rolling temperature to be 860-890 ℃;
6) coiling, setting the coiling temperature according to the thickness of the hot rolled finished product:
when the thickness of the hot-rolled finished product is less than 3mm, the coiling temperature is controlled to be 686-694 ℃;
when the thickness of the hot-rolled finished product is more than or equal to 3mm and less than or equal to 5mm, controlling the coiling temperature to be 666-674 ℃;
when the thickness of the hot-rolled finished product is more than 5mm, controlling the coiling temperature to be 646-654 ℃;
7) rolling after acid pickling and acid pickling, and controlling the cold rolling reduction rate to be 48-70%; welding by adopting a laser welding machine;
8) annealing treatment is carried out in a bell-type furnace under the full hydrogen atmosphere:
the process comprises electrolytic degreasing, cover annealing, wet flattening, coiling and packaging;
the hot spot temperature in the cover annealing temperature is 670-:
leveling by adopting a wet leveling process;
setting the flattening elongation according to the thickness of a cold-rolled finished product:
when the thickness of the cold-rolled finished product is less than or equal to 1.2mm, the flat elongation is controlled to be 0.8-1.2%
When the thickness of the cold-rolled finished product is more than 1.2mm, the flat elongation is controlled to be 1.2-1.6%.
TABLE 1 list of chemical compositions (wt%) of inventive and comparative examples
TABLE 2 List of the main process parameters of the examples of the invention and the comparative examples
TABLE 2
TABLE 3 Table of the results of mechanical Properties measurements of the examples of the invention and the comparative examples
The corrosion resistance tests of the above examples and comparative examples are carried out, Q235 is used as a comparative sample, the chemical components of the test are shown in Table 4, the corrosion resistance tests are carried out according to TB/T2375, the test time is 72h, and the test results of the corrosion resistance are shown in Table 5.
TABLE 4Q 235 chemical composition
TABLE 5 Corrosion resistance test results
| Examples | Relative corrosion Rate% |
| 1 | 46 |
| 2 | 44 |
| 3 | 42 |
| 4 | 48 |
| 5 | 46 |
| 6 | 46 |
| 7 | 48 |
| 8 | 47 |
| 9 | 44 |
| 10 | 45 |
| Comparative example 1 | 45 |
| Comparative example 2 | 54 |
| Q235 | 100 |
The tensile test samples of the mechanical property are P4 samples of GB-T228.1. As can be seen from Table 3, the economic weather-resistant steel plate produced by the invention has the yield strength of 280-360 MPa, the tensile strength of 380-460 MPa, the elongation A of more than 40%, a metallographic structure of ferrite and a small amount of pearlite, the grain size of more than 9 grades, the atmospheric corrosion resistance of less than or equal to 50% relative to the Q235 corrosion rate, and good atmospheric corrosion resistance. Meanwhile, the performance of the steel plates with different finished product thicknesses is kept stable. As can be seen from the comparative example, in the comparative example 1, the edge Cu of the steel plate is seriously brittle due to the higher rough rolling temperature, so that the surface quality is influenced; comparative example 2, which does not contain a certain amount of RE element, has a relative corrosion rate of 54% higher than that of the example.
The above examples are merely preferred examples and are not intended to be exhaustive of the invention.
Claims (4)
1. A rare earth-containing cold-rolled weathering steel for automobiles with yield strength of 280MPa comprises the following chemical components in percentage by weight: c: not more than 0.09%, Si 0.10-0.40%, Mn: 0.10-0.30%, P0.05-0.11%, S less than or equal to 0.015%, Als: 0.010-0.030%, Cu: 0.2-0.35%, RE: 0.03-0.08%, and the balance of Fe and inevitable impurities; mechanical properties: the yield strength is 280-360 MPa, the tensile strength is 380-460 MPa, the elongation A is more than 40%, the metallographic structure is ferrite and a small amount of pearlite, the grain size reaches more than 9 grade, and the atmospheric corrosion resistance is less than or equal to 50% of the corrosion rate of Q235 steel.
2. The rare earth-containing weathering steel for cold-rolled automobiles with yield strength of 280MPa grade of claim 1, characterized in that: the RE accounts for 0.038-0.073 wt%.
3. The method for producing the cold-rolled weathering steel for automobile containing rare earth with yield strength of 280MPa according to claim 1, comprising the steps of:
1) carrying out desulfurization molten iron, smelting in a converter and pouring into a blank;
2) heating the casting blank, controlling the heating temperature to be 1230-1270 ℃, and preserving the heat for 130-160 min;
3) flushing the surface of the casting blank by high-pressure water, and controlling the pressure of the high-pressure water to be not lower than 160 MPa;
4) carrying out rough rolling, and controlling the rough rolling temperature to be 1040-1060 ℃;
5) carrying out finish rolling, and controlling the finish rolling temperature to be 860-890 ℃;
6) coiling, setting the coiling temperature according to the thickness of the hot rolled finished product:
when the thickness of the hot-rolled finished product is less than 3mm, the coiling temperature is controlled to be 686-694 ℃;
when the thickness of the hot-rolled finished product is more than or equal to 3mm and less than or equal to 5mm, controlling the coiling temperature to be 666-674 ℃;
when the thickness of the hot-rolled finished product is more than 5mm, controlling the coiling temperature to be 646-654 ℃;
7) carrying out cold rolling after acid pickling and pickling, wherein the cold rolling reduction is controlled to be 48-70%; welding by adopting a laser welding machine;
8) annealing treatment is carried out in a bell-type furnace under the full hydrogen atmosphere:
the process comprises electrolytic degreasing, cover annealing, wet flattening, coiling and packaging;
in the cover annealing temperature, the hot spot temperature is 670-700 ℃, and the cold spot temperature is 610-640 ℃;
9) leveling according to different cold rolled product thicknesses
Leveling by adopting a wet leveling process;
setting the flattening elongation according to the thickness of a cold-rolled finished product:
when the thickness of the cold-rolled finished product is less than or equal to 1.2mm, controlling the leveling elongation rate to be 0.8-1.2%;
when the thickness of the cold-rolled finished product is more than 1.2mm, the flat elongation is controlled to be 1.2-1.6%.
4. The method for producing the cold-rolled automobile weathering steel containing rare earth with yield strength of 280MPa according to claim 3, characterized in that: the rough rolling temperature is 1042-1055 ℃.
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