CN116145026A - 355 MPa-grade rare earth La weather-resistant steel plate and preparation method thereof - Google Patents
355 MPa-grade rare earth La weather-resistant steel plate and preparation method thereof Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 166
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 150
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 135
- 239000010959 steel Substances 0.000 title claims abstract description 135
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 128
- 229910000870 Weathering steel Inorganic materials 0.000 claims abstract description 44
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 24
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 19
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 12
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 11
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 10
- 239000012535 impurity Substances 0.000 claims abstract description 9
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 114
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 47
- 229910052751 metal Inorganic materials 0.000 claims description 29
- 239000002184 metal Substances 0.000 claims description 29
- 239000006104 solid solution Substances 0.000 claims description 23
- 229910052742 iron Inorganic materials 0.000 claims description 12
- 238000005266 casting Methods 0.000 claims description 11
- YTYSNXOWNOTGMY-UHFFFAOYSA-N lanthanum(3+);trisulfide Chemical compound [S-2].[S-2].[S-2].[La+3].[La+3] YTYSNXOWNOTGMY-UHFFFAOYSA-N 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 10
- 238000005096 rolling process Methods 0.000 claims description 10
- 229910000765 intermetallic Inorganic materials 0.000 claims description 9
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 8
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 6
- 238000003723 Smelting Methods 0.000 claims description 5
- 238000007670 refining Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 229910000859 α-Fe Inorganic materials 0.000 claims description 4
- UPIZSELIQBYSMU-UHFFFAOYSA-N lanthanum;sulfur monoxide Chemical compound [La].S=O UPIZSELIQBYSMU-UHFFFAOYSA-N 0.000 claims description 3
- 229910001562 pearlite Inorganic materials 0.000 claims description 3
- 238000005260 corrosion Methods 0.000 abstract description 47
- 230000007797 corrosion Effects 0.000 abstract description 47
- 229910045601 alloy Inorganic materials 0.000 abstract description 7
- 239000000956 alloy Substances 0.000 abstract description 7
- 230000000052 comparative effect Effects 0.000 description 33
- 239000011593 sulfur Substances 0.000 description 14
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 13
- -1 rare earth sulfide Chemical class 0.000 description 13
- 239000002893 slag Substances 0.000 description 12
- 229910000975 Carbon steel Inorganic materials 0.000 description 11
- 239000010962 carbon steel Substances 0.000 description 11
- 239000011572 manganese Substances 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 229910052684 Cerium Inorganic materials 0.000 description 7
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 238000006477 desulfuration reaction Methods 0.000 description 4
- 230000023556 desulfurization Effects 0.000 description 4
- 230000003009 desulfurizing effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 229910000640 Fe alloy Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- NNLJGFCRHBKPPJ-UHFFFAOYSA-N iron lanthanum Chemical compound [Fe].[La] NNLJGFCRHBKPPJ-UHFFFAOYSA-N 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical compound S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Classifications
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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
- 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
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention discloses a 355 MPa-level rare earth La weathering steel plate and a preparation method thereof, belongs to the technical field of weathering steel, and solves the problems of higher content of alloy elements and higher cost of the weathering steel in the prior art. The 355 MPa-level rare earth La weather-resistant steel plate comprises the following components in percentage by mass: 0.15 to 0.18 percent of C, 0.18 to 0.4 percent of Si, 1.10 to 1.40 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0010 percent of O, 0.0050 to 0.0350 percent of La, and the balance of Fe and unavoidable impurities. The 355 MPa-level rare earth La weather-resistant steel plate has good toughness and excellent corrosion resistance.
Description
Technical Field
The invention relates to the technical field of weathering steel, in particular to a 355 MPa-level rare earth La weathering steel plate and a preparation method thereof.
Background
The metal corrosion phenomenon is very serious in all fields. Therefore, students at home and abroad have conducted extensive and intensive research on improving the atmospheric corrosion resistance of materials, and developed a series of weathering steels. The existing weathering steel is added with Cu, P, cr, ni and other elements, and the performances of atmospheric corrosion resistance, strength and the like of the steel material are improved simultaneously due to the addition of Cu, P, cr, ni and other alloy elements, but the cost of the weathering steel is also greatly improved due to the addition of more alloy elements. Rare earth is a special resource in China, which has a large amount of idle low-cost lanthanum tailing resources, and scientifically utilizes surplus and idle rare earth, so that the rare earth has great strategic significance. At present, a plurality of patents exist for the application of rare earth in weathering steel at home and abroad, but most of the problems of unclear existence form of rare earth elements, invalid rare earth, high cost or complex process exist in the existence form of rare earth elements, and the requirements of mass production and practical application cannot be met.
Disclosure of Invention
In view of the above, the invention aims to provide a 355 MPa-level rare earth La weathering steel plate and a preparation method thereof, which are used for solving the problems of higher content of alloy elements and higher cost of the existing weathering steel.
The aim of the invention is mainly realized by the following technical scheme:
on one hand, the invention provides a 355 MPa-grade rare earth La weather-resistant steel plate, which comprises the following components in percentage by mass: 0.15 to 0.18 percent of C, 0.18 to 0.4 percent of Si, 1.10 to 1.40 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0010 percent of O, 0.0050 to 0.0350 percent of La, and the balance of Fe and unavoidable impurities.
Further, the 355 MPa-level rare earth La weather resistant steel plate comprises the following components in percentage by mass: 0.15 to 0.17 percent of C, 0.18 to 0.3 percent of Si, 1.15 to 1.35 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0009 percent of O, 0.0052 to 0.0350 percent of La and the balance of Fe and unavoidable impurities.
Further, the microstructure of the 355 MPa-level rare earth La weather resistant steel plate is ferrite and pearlite; the lanthanum exists in the steel plate mainly in the following forms: solid solution metal lanthanum, metal lanthanum/iron metal compound, lanthanum oxide, lanthanum oxysulfide, lanthanum sulfide; wherein, the existence form of 60-85% lanthanum in the steel plate is solid solution metal lanthanum and metal lanthanum/iron metal compound.
Further, in the 355 MPa-level rare earth La weather-resistant steel plate, the lanthanum content in sulfide is 0.0005% -0.003%.
Furthermore, in the 355 MPa-level rare earth La weather-resistant steel plate, the lanthanum content in sulfide accounts for less than 21% of the total lanthanum.
Further, in the 355 MPa-level rare earth La weather-resistant steel plate, the lanthanum content in the oxide is 0.0001-0.0005%.
Further, in 355 MPa-level rare earth La weather-resistant steel plate, the lanthanum content in the solid solution rare earth and intermetallic compound is 0.003-0.03%.
Further, in 355 MPa-level rare earth La weathering steel plate, the content of effective lanthanum in steel=solid solution metal lanthanum content+metal lanthanum/iron metal compound content+0.3×lanthanum sulfide content.
Further, in the 355 MPa-level rare earth La weather-resistant steel plate, the content of effective lanthanum in the steel is 0.0035-0.030%.
The invention also provides a preparation method of the 355 MPa-level rare earth La weather resistant steel plate, which is used for preparing the 355 MPa-level rare earth La weather resistant steel plate and comprises the following steps:
step 1: pretreating molten iron;
step 2: smelting in a converter;
step 3: LF refining;
step 4: continuously casting to obtain a casting blank;
step 5: heating the casting blank to 1150-1250 ℃, preserving heat for 1-3 hours, performing hot continuous rolling, and then controlling cooling, coiling and leveling to obtain 355MPa grade rare earth La weather resistant steel plate.
Compared with the prior art, the invention has the following beneficial effects:
a) According to the 355 MPa-level rare earth La weather-resistant steel plate, the oxygen content in steel is precisely controlled to be less than or equal to 10ppm, the sulfur content is controlled to be less than or equal to 15ppm, and La is controlled to be 0.0050% -0.0350%, so that the metallic state rare earth lanthanum content in the steel in the form of solid solution rare earth lanthanum and rare earth lanthanum/intermetallic compound is 60% -85% (namely, the metallic state rare earth lanthanum content accounts for 60% -85% of the total lanthanum content), for example, 65% -81%; the content of available lanthanum in the steel is calculated by the following formula: the content of effective lanthanum in the steel=solid solution metal lanthanum content+metal lanthanum/iron metal compound content+0.3 lanthanum sulfide content, so that the effective rare earth content is not less than 68% of the total lanthanum content, for example, the effective rare earth content accounts for 68.8% -85% of the total lanthanum content; thereby fully utilizing the effective rare earth lanthanum in the steel to greatly improve the atmospheric corrosion resistance of the rare earth La weather-resistant steel plate, and simultaneously ensuring the good toughness of the rare earth La weather-resistant steel plate.
b) The preparation method of 355 MPa-level rare earth La weather resistant steel plate is simple in process, strong in operability and suitable for industrial popularization.
c) The steel plate of the invention has strong strengthGood toughness and corrosion resistance, and has the yield strength of more than 370MPa (such as 375-385 MPa), the tensile strength of more than 480MPa (such as 480-500 MPa), the elongation A of more than 27 percent (such as 27.5-32 percent), the area shrinkage Z of more than 76 percent (such as 77-83 percent), and the impact power KV at 0℃) 2 Gtoreq 120J (e.g., 125-145J); the steel of the present invention has an improved corrosion resistance ratio to carbon steel of 5.5% or more.
d) The steel of the invention has low alloy element content, low cost, economy and practicability.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a graph showing the relationship between the effective rare earth content of the steel of the present invention and the corrosion resistance improvement ratio of the relative carbon steel.
Detailed Description
Preferred embodiments of the present invention are described in detail below with reference to the attached drawing figures, which form a part of the present invention and are used in conjunction with embodiments of the present invention to illustrate the principles of the present invention.
The invention provides a rare earth La weather-resistant steel plate with 355 MPa-grade yield strength, which comprises the following components in percentage by mass: 0.15 to 0.18 percent of C, 0.18 to 0.4 percent of Si, 1.10 to 1.40 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0010 percent of O, 0.0050 to 0.0350 percent of La, and the balance of Fe and unavoidable impurities.
The following is a specific description of the action and the selection of the amounts of the components contained in the invention:
c: although the addition of carbon can significantly improve the hardness strength of steel, too high carbon can reduce the plasticity and toughness of steel, and the carbon has very little influence on weather resistance in the conventional weathering steel composition range. Therefore, the invention comprehensively considers the comprehensive effects of strength and corrosion resistance, and controls the content to be 0.15-0.18%.
Si: can improve the quenching, normalizing and annealing temperatures of the steel, and improve the tempering stability and oxidation resistance of the steel. Silicon can be dissolved in ferrite and austenite to improve the strength, hardness, elasticity and wear resistance of the steel. Too high addition of Si may deteriorate the weldability of the steel. The content of the invention is controlled to be 0.18-0.4%.
Mn: can improve the hardenability of the steel and has obvious effect on improving the strength of common low alloy steel. When the manganese content is too high, the weldability of the steel is deteriorated, and the grain growth is promoted. Manganese has little effect on weather resistance in the conventional weathering steel composition range. The content of the invention is controlled to be 1.10-1.40%.
La: la exists in the form of solid solution metal lanthanum, metal lanthanum/iron metal compound, lanthanum oxide, lanthanum oxysulfide and lanthanum sulfide in steel, and the solid solution metal lanthanum, metal lanthanum/iron metal compound and lanthanum sulfide are all unstable in corrosive medium and release La after being corroded and decomposed 3+ Ion, la 3+ Ions are typical of anodic corrosion inhibitors in acidic industrial atmospheric corrosion environments. Too high an addition of La causes the formation of a large amount of lanthanum metal/iron metal compound in the steel, which causes the toughness of the steel to be greatly reduced. The inventors found in the study that: the content of effective lanthanum in steel=the content of solid solution metal lanthanum+the content of metal lanthanum/iron metal compound+0.3. The content of lanthanum sulfide, the relative carbon steel percentage proportion of rare earth lanthanum in steel for improving weather resistance=α. The content of effective lanthanum, wherein α varies with different corrosion environments, the capability of rare earth for improving weather resistance and the content of effective rare earth in steel show a linear relation, but have no definite relation with the total amount of rare earth in steel; therefore, the content of the invention is controlled to be 0.0050% -0.0350%.
S: sulfur exists mainly in the form of sulfides in steel. Sulfur reduces the strength, elongation and impact value of the steel, reducing the corrosion resistance of the steel. Since rare earth sulfide is not in corrosive mediumStable, and release La after corrosion decomposition 3+ Ion, corrosion resistance is improved by corrosion inhibition of rare earth ion, but H is generated after corrosion decomposition of rare earth sulfide 2 S、HS - Or S 2- H produced concomitantly 2 S, HS-or S 2- The anode dissolution in the initial stage of the iron matrix is poisoned, so that the corrosion of the iron and steel materials can be accelerated, therefore, the rare earth sulfide can only be calculated into part of effective rare earth, and the coefficient is introduced in the calculation of the effective rare earth, so that the influence of the rare earth sulfide on the corrosion resistance can be expressed more accurately. According to the research on the corrosion resistance of rare earth steel with different rare earth sulfur ratios, the invention considers that the higher content of rare earth sulfide in the steel can also affect the mechanical property, determines that the sulfur content is controlled to be less than or equal to 15ppm, and can better exert the capability of the rare earth to improve the corrosion resistance of steel materials; so the content thereof is controlled to be less than or equal to 15ppm (15 ppm is 0.0015%).
O: because the O content in the steel is too high, most of rare earth La and O can form rare earth oxide or rare earth oxysulfide, the inventor finds that the rare earth oxide and the rare earth oxysulfide are both invalid rare earth in the research process, and the rare earth oxide and the rare earth oxysulfide are refractory compounds and cannot be corroded and dissolved in a normal service corrosion medium of the steel material, so that rare earth ions with corrosion inhibition cannot be released to improve the corrosion resistance, and the oxygen content in the production process of the rare earth steel must be strictly controlled. The invention controls the oxygen content in the steel to be less than 0.0010 percent, thereby enabling the rare earth to exist in the form of effective rare earth (solid solution rare earth, rare earth/iron intermetallic compound and rare earth sulfide) in the steel as much as possible.
P: the plasticity and toughness of the steel can be obviously reduced, and the steel is more serious at low temperature, and the phenomenon is called cold brittleness. So the content is controlled to be less than or equal to 0.02 percent.
In order to further improve the comprehensive performance of the rare earth La weathering steel plate with the yield strength of 355MPa, the rare earth La weathering steel plate with the yield strength of 355MPa comprises the following components in percentage by mass: 0.15 to 0.17 percent of C, 0.18 to 0.3 percent of Si, 1.15 to 1.35 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0009 percent of O, 0.0052 to 0.0350 percent of La and the balance of Fe and unavoidable impurities.
Specifically, the microstructure of the rare earth La weathering steel plate with the yield strength of 355MPa is ferrite and pearlite, and the existence form of lanthanum with the content of 60% -85% (for example, 65% -81%) in the steel is solid solution state lanthanum and metal lanthanum/iron intermetallic compound, so that the content of effective lanthanum in the steel is maximized, and the effect of improving corrosion resistance of lanthanum is more effectively exerted.
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the lanthanum content in sulfide is 0.0005-0.003%, for example 0.0005-0.0027%.
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the lanthanum content in sulfide accounts for less than 21% of the total lanthanum, for example, the lanthanum content in sulfide accounts for 8% -21% of the total lanthanum.
Specifically, in the rare earth La weathering steel plate with 355 MPa-grade yield strength, the lanthanum content in the oxide is 0.0001-0.0005%, such as 0.0002-0.0005%.
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the lanthanum content in the oxysulfide is 0.0005-0.003%, for example 0.0006-0.0026%.
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the lanthanum content in the solid solution rare earth and intermetallic compound is 0.003-0.03%, such as 0.0034-0.025%.
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the content of effective lanthanum in steel is equal to the content of solid solution metal lanthanum, the content of metal lanthanum/iron metal compound and the content of lanthanum sulfide of 0.3.
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the content of effective lanthanum in the steel is 0.0035-0.030 percent, such as 0.00355-0.026 percent.
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the content of metallic state rare earth lanthanum in the form of solid solution rare earth lanthanum and rare earth lanthanum/intermetallic compound is 60% -85% (namely, the content of metallic state rare earth lanthanum accounts for 65% -81% of the total content of lanthanum).
Specifically, in the rare earth La weathering steel plate with the yield strength of 355MPa, the effective lanthanum content is not less than 68% of the total lanthanum content.
The invention also provides a preparation method of the rare earth La weather resistant steel plate with the yield strength of 355MPa, which comprises the following steps:
step 1: pretreating molten iron;
step 2: smelting in a converter;
step 3: LF refining;
step 4: continuously casting to obtain a casting blank;
step 5: heating the casting blank to 1150-1250 ℃, preserving heat for 1-3 hours, performing hot continuous rolling, and then controlling cooling, coiling and leveling to obtain the rare earth La weather-resistant steel plate with 355 MPa-grade yield strength.
Specifically, the step 1 includes: the KR is adopted to carry out pre-desulfurization treatment on molten iron, and CaO (the mass percentage is 90 percent) and CaF are adopted as desulfurizing agents 2 The mass percentage is 10 percent, the cleaning area of the desulfurization slag is more than or equal to 90 percent, and the sulfur content of molten iron entering the furnace is less than or equal to 20ppm.
Specifically, the step 2 includes: the converter smelting adopts low sulfur waste steel, the final slag alkalinity range is 3.2-3.8, T.Fe is less than or equal to 25%, and the oxygen content of the final molten steel is less than or equal to 800ppm.
Specifically, the step 3 includes: desulfurizing the LF refining white slag, wherein the alkalinity range of the slag is 5-7, the MI index (Mannessman index) is 0.2-0.24, (FeO+MnO)% -1.0% (i.e. the total content of FeO and MnO in the refined slag is less than 1.0%), and the white slag time is more than or equal to 25min; the soft blowing time after the calcium treatment is more than or equal to 8min, and lanthanum-iron alloy is added.
Specifically, the step 4 includes: and (3) adopting argon to seal the long nozzle and a magnesia tundish covering agent to protect and pour molten steel, wherein the superheat degree of the molten steel is more than or equal to 30 ℃.
Specifically, in the step 5, the initial rolling temperature of the hot continuous rolling is 980-1100 ℃, and the final rolling temperature is 850-880 ℃.
Specifically, in the step 5, the cooling control includes: and (3) cooling the hot-rolled steel billet to below 550 ℃ by water, and then cooling the steel billet to room temperature by air.
Specifically, the method ensures that the components of the rare earth La weathering steel plate with the yield strength of 355MPa grade obtained in the step 5 comprise the following steps of: 0.15 to 0.18 percent of C, 0.18 to 0.4 percent of Si, 1.10 to 1.40 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0010 percent of O, 0.0050 to 0.0350 percent of La, and the balance of Fe and unavoidable impurities.
Compared with the prior art, the 355 MPa-yield-strength rare earth La weather-resistant steel plate has the advantages that the oxygen content in the steel is controlled to be less than or equal to 10ppm, the sulfur content is controlled to be less than or equal to 15ppm, and the La content is controlled to be 0.0050-0.0350%, so that the metallic state rare earth lanthanum content existing in the steel in the form of solid solution rare earth lanthanum and rare earth lanthanum/intermetallic compound is 60-85% (namely, the metallic state rare earth lanthanum content accounts for 60-85% of the total lanthanum content), for example, 65-81%; the content of available lanthanum in the steel is calculated by the following formula: the content of effective lanthanum in the steel=solid solution metal lanthanum content+metal lanthanum/iron metal compound content+0.3 lanthanum sulfide content, so that the effective rare earth content is not less than 68% of the total lanthanum content, for example, the effective rare earth content accounts for 68.8% -85% of the total lanthanum content; thereby fully utilizing the effective rare earth lanthanum in the steel to greatly improve the atmospheric corrosion resistance of the rare earth La weather-resistant steel plate, and simultaneously ensuring the good toughness of the rare earth La weather-resistant steel plate.
The preparation method of the rare earth La weather resistant steel plate with the yield strength of 355MPa is simple in process, high in operability and suitable for industrial popularization.
The steel plate of the invention has good toughness and excellent corrosion resistance, the yield strength is more than 370MPa (375-385 MPa, for example), the tensile strength is more than 480MPa (480-500 MPa, for example), the elongation is more than 27 percent (27.5-32 percent, for example), the area shrinkage is more than 76 percent (77-83 percent, for example), and the impact power KV at 0 ℃ is higher than 2 Gtoreq 120J (e.g., 125-145J); the steel of the present invention has an improved corrosion resistance ratio to carbon steel of 5.5% or more. And the steel plate has low alloy element content, low cost, economy and practicability.
Examples 1 to 5
The following shows the advantages of the precise control of the composition and process parameters of the steel sheet of the present invention in specific examples and comparative examples. The embodiments 1-5 of the invention provide a rare earth La weather-resistant steel plate with 355 MPa-grade yield strength and a preparation method thereof.
The rare earth La weathering steel plates of examples 1-5 comprise the following components in mass percent: 0.15 to 0.18 percent of C, 0.18 to 0.4 percent of Si, 1.10 to 1.40 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0010 percent of O, 0.0050 to 0.0350 percent of La, and the balance of Fe and unavoidable impurities.
The preparation method of the rare earth La weather resistant steel plate of examples 1 to 5 comprises:
step 1: and (3) molten iron pretreatment: the KR is adopted to carry out pre-desulfurization treatment on molten iron, and CaO (the mass percentage is 90 percent) and CaF are adopted as desulfurizing agents 2 The cleaning area of the desulfurization slag is more than or equal to 90 percent, and the sulfur content of molten iron entering the furnace is less than or equal to 20ppm;
step 2: smelting in a converter: adopting low-sulfur scrap steel, wherein the final slag alkalinity range is 3.2-3.8, T.Fe is less than or equal to 25%, and the oxygen content of the final molten steel is less than or equal to 800ppm;
step 3: desulfurizing LF refining white slag, wherein the alkalinity range of the slag is 5-7, the MI index is 0.2-0.24, (FeO+MnO)% -1.0% (i.e. the total content of FeO and MnO in the refined slag is less than 1.0%), and the white slag time is more than or equal to 25min; the soft blowing time after the calcium treatment is more than or equal to 8min, and lanthanum-iron alloy is added;
step 4: continuous casting to obtain a casting blank: adopting argon to seal a long nozzle and a magnesia tundish covering agent to protect and pour molten steel, wherein the superheat degree of the molten steel is more than or equal to 30 ℃;
step 5: heating the casting blank to 1150-1250 ℃, preserving heat for 1-3 hours, performing hot continuous rolling, and then controlling cooling, coiling and leveling to obtain the rare earth La weather-resistant steel plate with 235MPa grade yield strength.
Specifically, in the step 5, the initial rolling temperature of the hot continuous rolling is 980-1100 ℃, and the final rolling temperature is 850-880 ℃.
Specifically, in the step 5, the cooling control includes: and (3) cooling the hot rolled steel billet to 550 ℃ by water, and then cooling the steel billet to room temperature by air.
The invention also provides 5 comparative steels, examples 1-5 and comparative 1-5 steels having chemical compositions as shown in Table 1. Comparative example 1 is carbon steel. Comparative example 2 is a high sulfur low oxygen comparative example to illustrate the accuracy of the sulfide rare earth calculation in the effective rare earth calculation formula. Comparative example 3 is a low sulfur high oxygen comparative example to illustrate that the rare earth oxide in the rare earth steel does not contribute any improvement in corrosion resistance. Comparative example 4 is a test steel with lanthanum content up to 0.0680% in the steel, and is used for explaining the phenomenon that the impact toughness of the steel is greatly reduced due to excessive solid solution rare earth and rare earth/iron metal compounds in the steel. Comparative example 5 is a test steel added with single rare earth cerium, and is used for explaining the phenomenon that the weather resistance of rare earth lanthanum is greatly improved over that of rare earth cerium under the condition that other alloy element components are similar.
TABLE 1 chemical composition wt%
| Steel grade | C | Si | Mn | P | S | O | La | Ce |
| Example 1 | 0.16 | 0.18 | 1.25 | 0.013 | 0.0013 | 0.0008 | 0.0052 | - |
| Example 2 | 0.16 | 0.19 | 1.26 | 0.012 | 0.0014 | 0.0009 | 0.0065 | - |
| Example 3 | 0.17 | 0.18 | 1.22 | 0.011 | 0.0013 | 0.0009 | 0.0115 | - |
| Example 4 | 0.16 | 0.18 | 1.23 | 0.012 | 0.0015 | 0.0008 | 0.0220 | |
| Example 5 | 0.16 | 0.20 | 1.27 | 0.011 | 0.0015 | 0.0009 | 0.0303 | - |
| Comparative example 1 | 0.16 | 0.19 | 1.26 | 0.012 | 0.0030 | 0.0030 | - | |
| Comparative example 2 | 0.16 | 0.19 | 1.25 | 0.013 | 0.0210 | 0.0009 | 0.0305 | |
| Comparative example 3 | 0.16 | 0.19 | 1.28 | 0.013 | 0.0013 | 0.0085 | 0.0325 | - |
| Comparative example 4 | 0.16 | 0.19 | 1.26 | 0.012 | 0.0015 | 0.0011 | 0.0680 | |
| Comparative example 5 | 0.17 | 0.19 | 1.25 | 0.013 | 0.0015 | 0.0008 | - | 0.0310 |
The mechanical properties of the examples and comparative examples are shown in Table 2. From examples 1 to 5, it can be seen that the impact toughness of the steel shows a decreasing trend with increasing rare earth La content. The impact energy of comparative example 2 was reduced to 83J, and the S content in comparative example 2 was higher to 0.0210%, and it was found that the impact toughness of the rare earth steel was reduced with a higher sulfur content than in example 5. The impact energy of comparative example 3 was reduced to 81J, the O content of comparative example 3 was higher to 0.0085%, and it was found that the impact toughness of the rare earth steel was reduced with a higher O content than in example 5. The rare earth content in the steel of comparative example 4 is as high as 0.068%, the impact toughness is greatly reduced to 46J, and the too high rare earth content in the steel can greatly reduce the impact toughness of the rare earth steel.
Table 3 shows the rare earth element content results in the different phases in the examples and comparative examples of the present invention.
TABLE 2 mechanical Properties
TABLE 3 mass percent of La or Ce in different phases and results of effective La or Ce content (%)
To illustrate the corrosion resistance of the steel sheet of the present invention, the steels of examples and comparative examples were evaluated for corrosion resistance by using the 72-hour cycle immersion accelerated corrosion test corrosion rate data (test standard TB/T2375-93) and compared with the comparative examples under the same test conditions. The results of the corrosion resistance test are shown in Table 4.
From tables 1 and 3, it is seen that the lanthanum content of comparative example 2 is 0.0305% and the effective rare earth content is 0.01069%, the corrosion resistance improvement ratio of comparative example 2 to carbon steel is 14.23%, the lanthanum content of example 5 is 0.0303% and the effective rare earth content is 0.02531%, the corrosion resistance improvement ratio of example 5 to carbon steel is 33.10%, which is significantly higher than that of comparative example 2, and it is seen that the corrosion resistance improvement capability of rare earth lanthanum is directly proportional to the effective rare earth content of rare earth lanthanum in steel and has no direct relation to the total amount of rare earth in steel.
As can be seen from tables 1 and 2, the lanthanum content of comparative example 3 was 0.0325%, the effective rare earth content was 0.0025%, and the corrosion resistance improvement ratio of comparative example 3 to carbon steel was 3.95%; the lanthanum content in example 5 was 0.0303%, the effective rare earth content was 0.02531%, the corrosion resistance improvement ratio of example 5 to carbon steel was 33.10%, which is significantly higher than that of comparative example 3, and it was found that the ability of rare earth lanthanum to improve corrosion resistance was directly proportional to the effective rare earth content of rare earth lanthanum in steel but not directly to the total amount of rare earth in steel.
From tables 1 and 3, it is understood that the cerium content of comparative example 5 is 0.0310%, the effective rare earth cerium content is 0.02636%, the corrosion resistance improvement ratio of comparative example 5 to carbon steel is 13.90%, the lanthanum content of example 5 is 0.0303%, the effective rare earth lanthanum content is 0.02531%, the corrosion resistance improvement ratio of example 5 to carbon steel is 33.10%, which is significantly higher than that of comparative example 5, and it is seen that the corrosion resistance improvement capability of rare earth lanthanum is far higher than that of rare earth cerium.
As can be seen from table 4 and fig. 1, as the effective rare earth content of lanthanum rare earth in the steel increases, the corrosion resistance of the test steel increases, and the effective rare earth content of lanthanum rare earth and the corrosion resistance of the test steel substantially show a linear relationship.
TABLE 4 Corrosion test data
As shown by analysis, the oxygen content in the rare earth La weather-resistant steel is controlled to be less than or equal to 10ppm, the sulfur content is controlled to be less than or equal to 15ppm, and La is controlled to be 0.0050% -0.0350%, so that the metallic state rare earth lanthanum content in the steel in the form of solid solution rare earth lanthanum and rare earth lanthanum/intermetallic compound is in the range of 60% -85% (namely, the metallic state rare earth lanthanum content accounts for 60% -85% of the total lanthanum content), and the effective lanthanum content in the steel is calculated by the following formula: the content of effective lanthanum in the steel=the content of solid solution metal lanthanum+the content of metal lanthanum/iron metal compound+the content of lanthanum sulfide is 0.3, so that the content of effective rare earth lanthanum is not less than 68% of the total content of lanthanum, thereby fully utilizing the effective rare earth lanthanum in the steel to greatly improve the atmospheric corrosion resistance of the rare earth La weather-resistant steel plate and simultaneously ensuring the good toughness of the rare earth La weather-resistant steel plate.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. The 355 MPa-level rare earth La weather-resistant steel plate is characterized by comprising the following components in percentage by mass: 0.15 to 0.18 percent of C, 0.18 to 0.4 percent of Si, 1.10 to 1.40 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0010 percent of O, 0.0050 to 0.0350 percent of La, and the balance of Fe and unavoidable impurities.
2. The 355 MPa-level rare earth La weathering steel plate according to claim 1, wherein the 355 MPa-level rare earth La weathering steel plate comprises the following components in percentage by mass: 0.15 to 0.17 percent of C, 0.18 to 0.3 percent of Si, 1.15 to 1.35 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.0015 percent of S, less than or equal to 0.0009 percent of O, 0.0052 to 0.0350 percent of La and the balance of Fe and unavoidable impurities.
3. The 355 MPa-grade rare earth La weathering steel plate of claim 1, wherein the microstructure of the 355 MPa-grade rare earth La weathering steel plate is ferrite + pearlite; the lanthanum exists in the steel plate mainly in the following forms: solid solution metal lanthanum, metal lanthanum/iron metal compound, lanthanum oxide, lanthanum oxysulfide, lanthanum sulfide; wherein, the existence form of 60-85% lanthanum in the steel plate is solid solution metal lanthanum and metal lanthanum/iron metal compound.
4. The 355 MPa-grade rare earth La weathering steel plate according to claim 1, wherein the lanthanum content in the sulfide is 0.0005% to 0.003% in the 355 MPa-grade rare earth La weathering steel plate.
5. The 355 MPa-level rare earth La weathering steel plate of claim 4, wherein the lanthanum content in the sulfide in the 355 MPa-level rare earth La weathering steel plate is 21% or less of the total lanthanum.
6. The 355 MPa-level rare earth La weathering steel plate according to claim 1, wherein the lanthanum content in the oxide in the 355 MPa-level rare earth La weathering steel plate is 0.0001% to 0.0005%.
7. The 355 MPa-level rare earth La weathering steel plate according to claim 1, wherein the lanthanum content in the solid solution rare earth and intermetallic compound in the 355 MPa-level rare earth La weathering steel plate is 0.003% -0.03%.
8. The 355 MPa-level rare earth La weathering steel plate according to claim 1, wherein in the 355 MPa-level rare earth La weathering steel plate, the content of effective lanthanum in the steel=solid solution metal lanthanum content+metal lanthanum/iron metal compound content+0.3 x lanthanum sulfide content.
9. The 355 MPa-level rare earth La weathering steel plate according to claim 1, wherein the content of effective lanthanum in the steel is 0.0035% -0.030%.
10. A method for preparing a 355 MPa-grade rare earth La weathering steel plate, characterized in that the method is used for preparing the 355 MPa-grade rare earth La weathering steel plate according to any one of claims 1-9, comprising:
step 1: pretreating molten iron;
step 2: smelting in a converter;
step 3: LF refining;
step 4: continuously casting to obtain a casting blank;
step 5: heating the casting blank to 1150-1250 ℃, preserving heat for 1-3 hours, performing hot continuous rolling, and then controlling cooling, coiling and leveling to obtain 355MPa grade rare earth La weather resistant steel plate.
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