CN115287530A - High-welding-performance 700 MPa-grade rare earth high-strength structural steel and production method thereof - Google Patents
High-welding-performance 700 MPa-grade rare earth high-strength structural steel and production method thereof Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 34
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 32
- 229910000746 Structural steel Inorganic materials 0.000 title claims abstract description 27
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 53
- 239000010959 steel Substances 0.000 claims abstract description 53
- 238000000034 method Methods 0.000 claims abstract description 47
- 230000008569 process Effects 0.000 claims abstract description 36
- 238000003466 welding Methods 0.000 claims abstract description 36
- 238000001816 cooling Methods 0.000 claims abstract description 26
- 238000005496 tempering Methods 0.000 claims abstract description 21
- 238000007670 refining Methods 0.000 claims abstract description 17
- 238000009749 continuous casting Methods 0.000 claims abstract description 13
- 239000000126 substance Substances 0.000 claims abstract description 10
- 238000005098 hot rolling Methods 0.000 claims abstract description 9
- 238000003723 Smelting Methods 0.000 claims abstract description 7
- 238000005096 rolling process Methods 0.000 claims description 19
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 229910052720 vanadium Inorganic materials 0.000 claims description 9
- 229910052786 argon Inorganic materials 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 238000005516 engineering process Methods 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- 230000009467 reduction Effects 0.000 claims description 6
- 229910052717 sulfur Inorganic materials 0.000 claims description 6
- 229910000636 Ce alloy Inorganic materials 0.000 claims description 5
- 238000007664 blowing Methods 0.000 claims description 5
- 238000005272 metallurgy Methods 0.000 claims description 4
- 238000009628 steelmaking Methods 0.000 claims description 4
- 238000005266 casting Methods 0.000 claims description 3
- 230000001186 cumulative effect Effects 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000009489 vacuum treatment Methods 0.000 claims description 3
- 230000003009 desulfurizing effect Effects 0.000 claims description 2
- 238000012938 design process Methods 0.000 abstract 1
- 229910001566 austenite Inorganic materials 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- 229910052758 niobium Inorganic materials 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 229910000734 martensite Inorganic materials 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000010953 base metal Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000012854 evaluation process Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- RMLPZKRPSQVRAB-UHFFFAOYSA-N tris(3-methylphenyl) phosphate Chemical compound CC1=CC=CC(OP(=O)(OC=2C=C(C)C=CC=2)OC=2C=C(C)C=CC=2)=C1 RMLPZKRPSQVRAB-UHFFFAOYSA-N 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
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
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- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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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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- 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
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- 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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
Abstract
The invention discloses a high-welding-performance 700 MPa-grade rare-earth high-strength structural steel and a production method thereof, belonging to the technical field of rare-earth high-strength steel production. The production method comprises the working procedures of converter smelting, LF refining, RH refining, continuous casting, hot rolling, ultra-fast cooling and tempering; an ultra-fast cooling process, wherein the open cooling temperature of a steel plate is 740 to 830 ℃, the cooling rate is more than or equal to 25 ℃/s, and the final cooling temperature is less than or equal to 200 ℃; and a tempering treatment process, wherein the tempering temperature is 580-630 ℃, and the steel plate is air-cooled after tempering. The invention obtains the 700MPa grade rare earth high-strength steel with good structure uniformity and low-temperature toughness and good welding impact performance through reasonable chemical component design and production process.
Description
Technical Field
The invention belongs to the technical field of rare earth high-strength steel production, and particularly relates to a high-welding-performance 700 MPa-level rare earth high-strength structural steel and a production method thereof.
Background
With the rapid development of industrial technology, steel structural members are gradually becoming larger and lighter, and the requirements for steel materials are reflected in the aspects of high strength, high toughness and the like. The strength of the high-strength steel is improved by adding alloy elements such as Nb, V, ti and the like and matching with corresponding controlled rolling, controlled cooling and heat treatment processes. At present, high-strength steel is widely applied to the fields of high-rise buildings, oil pipelines, ocean platforms, pressure vessels, engineering machinery and the like, and components in the application fields tend to be complicated gradually and are generally formed by welding a large number of simple components, so that the application and popularization of the high-strength steel are greatly limited by the welding processability of the material. However, although the addition of alloying elements in the high-strength steel ensures the strength of the material, the higher alloy content greatly affects the welding performance of the material, mainly manifested by the performance degradation of the welding heat affected zone.
The means for improving the welding heat affected zone at the present stage mainly include two major types, on one hand, the welding performance of the material is improved through the performance improvement, and on the other hand, the mechanical performance of the welding heat affected zone is improved through the welding process of low welding heat input, pre-welding preheating and post-welding treatment. But the welding process is adopted to improve the mechanical property of the heat affected zone, and has the disadvantages of complex process, low production efficiency and high cost.
Chinese patent publication No. CN109930070A discloses a method for improving toughness of a low-carbon equivalent steel sheet in a weld heat affected zone by using rare earth, but the base metal strength is about 490MPa, the weld heat input is large, and the impact energy is low. Chinese patent publication No. CN111893240A discloses a method for improving welding performance of Nb, ti microalloyed steel by using rare earth, which improves the strength of the steel plate by microalloying, wherein the strength can reach 700MPa or above, but the quenching and tempering temperature values in the heat treatment stage are high, and the energy consumption is high. The document of Chinese patent publication No. CN112626423A discloses a production process for improving the welding performance of rare earth high-strength steel, the strength of which can reach 700MPa, and the production cost is low, but the welding evaluation process needs to be preheated to 60 ℃ before welding, the use cost is increased in the aspect of welding, and the actual operation efficiency is influenced.
In order to meet the requirements of heavy equipment and engineering on the strength, toughness and welding performance of high-strength structural steel in adapting to the large-scale and complicated trend of engineering machinery and building components, the development of a high-strength steel plate with good welding performance and toughness is urgently needed.
Disclosure of Invention
The invention provides a high-welding-performance 700 MPa-grade rare earth high-strength structural steel and a production method thereof. By adopting the low-carbon design and reasonable production procedures such as the ultra-fast cooling process after rolling, the impact toughness of the steel plate is improved while the strength of the steel plate is ensured.
In order to solve the technical problems, the invention adopts the following technical scheme: the high-welding-performance 700 MPa-grade rare earth high-strength structural steel comprises the following chemical components in percentage by mass: 0.05 to 0.11%, si:0.15 to 0.3%, mn:1.25 to 1.55 percent, less than or equal to 0.0015 percent of P, less than or equal to 0.005 percent of S, cr:0.15 to 0.35%, mo:0.1 to 0.3%, nb:0.015 to 0.035%, V:0.02 to 0.06%, ti:0.01 to 0.035%, cu:0.25 to 0.45%, ni:0.125 to 0.225%, B:0.0015 to 0.0025%, ce:0.002 to 0.008 percent, als:0.025 to 0.045% and the balance of Fe and other inevitable impurities.
The high-strength structural steel comprises the following chemical components in percentage by mass: 0.07 to 0.10%, si:0.2 to 0.3%, mn:1.35 to 1.50 percent, less than or equal to 0.0015 percent of P, less than or equal to 0.005 percent of S, cr:0.2 to 0.3%, mo:0.2 to 0.3%, nb:0.020 to 0.030%, V:0.02 to 0.04%, ti:0.02 to 0.030%, cu:0.30 to 0.40%, ni:0.15 to 0.20%, B:0.0015 to 0.0025%, ce:0.004 to 0.006%, als:0.025 to 0.045 percent, and the balance of Fe and other inevitable impurities.
The high-strength structural steel comprises the following chemical components in percentage by mass: 0.08%, si:0.25%, mn:1.50%, P is less than or equal to 0.0015%, S is less than or equal to 0.005%, cr:0.25%, mo:0.25%, nb:0.025%, V:0.03%, ti:0.025%, cu:0.40%, ni:0.20%, B:0.0020%, ce:0.005%, als:0.025%, and the balance of Fe and other inevitable impurities.
The yield strength of the base metal of the high-strength structural steel is more than or equal to 700MPa, the tensile strength is more than or equal to 810MPa, the elongation is more than or equal to 15%, and the longitudinal impact energy at minus 20 ℃ is more than or equal to 180J.
The high-strength structural steel adopts an MAG welding process, preheating is not needed, the low-temperature impact energy at a welding seam is more than or equal to 100J, and the heat input is preferably 25KJ/cm.
The invention also provides a production method of the high-welding-performance 700 MPa-grade rare earth high-strength structural steel, which comprises the working procedures of converter smelting, LF refining, RH refining, continuous casting, hot rolling, ultra-fast cooling and tempering; in the ultra-fast cooling procedure, the open cooling temperature of a steel plate is 740 to 830 ℃, the cooling rate is more than or equal to 25 ℃/s, and the final cooling temperature is less than or equal to 200 ℃; in the tempering treatment process, the tempering temperature is 580 to 630 ℃, and the steel plate is air-cooled after tempering.
The converter steelmaking process of the invention comprises the following steps: the temperature of molten iron entering the converter is more than or equal to 1300 ℃, the terminal point P of the converter is less than or equal to 0.015 percent, the S is less than or equal to 0.008 percent, and oxygen is blown for smelting.
The LF refining process comprises the following steps: slagging and desulfurizing molten steel by adopting an oxide metallurgy technology, wherein the oxygen content of the steel is less than or equal to 0.002 percent, the S is less than or equal to 0.003 percent, and the temperature is more than or equal to 1580 ℃; the RH refining step: the RH vacuum treatment time is more than or equal to 23min, then rare earth Ce alloy is added, the vacuum circulation time is more than or equal to 15min after the rare earth Ce alloy is added, and the argon blowing stirring time is more than or equal to 8min.
The continuous casting process comprises the following steps: the casting temperature is more than or equal to 1525 ℃, the argon blowing pressure is ensured to be 0.5MPa in the continuous casting process, and the thickness of the continuous casting billet is 230mm.
The hot rolling process adopts two-stage controlled rolling, wherein the initial rolling temperature of the first stage is more than or equal to 1130 ℃, the final rolling temperature is more than or equal to 950 ℃, and the cumulative reduction rate is 65-72%; the rolling temperature of the second stage is 850-920 ℃, the final rolling temperature is 800-870 ℃, and the single-pass reduction rate is more than or equal to 14%.
In order to ensure the comprehensive mechanical property of the steel plate and the low-temperature toughness of the welded seam, the invention has the following beneficial effects of the following elements:
c: although the steel sheet performance is enhanced, too high a carbon content lowers the weldability of the steel sheet, and in order to prevent cold cracking during non-preheat welding, the generation of more hard brittle phases due to the high carbon content should be avoided.
Si: the solid solution strengthening improves the strength and hardness of the steel, and avoids the deterioration of plasticity and surface quality caused by excessively high content.
Mn: the conventional elements are strengthened and toughened, so that the transformation temperature from austenite to ferrite can be reduced, the grain size of hot-rolled ferrite is refined, but the crack sensitivity of a welding heat affected zone is easily caused when the grain size is too high.
Cr, mo and B: solid solution strengthening elements and strong carbide forming elements improve the hardenability of steel, but excessively increase the cost, and simultaneously reduce the grain boundary strength, significantly reducing the low-temperature brittleness of the steel sheet.
Nb, V and Ti: the design of the composite microalloy is beneficial to precipitation strengthening, grain refinement, steel strength and toughness improvement, and the comprehensive effect of Nb and B is utilized to improve precipitation strengthening and grain boundary segregation.
Cu: in the tempering process, the precipitation is fine, and the strength is further improved in a precipitation strengthening mode.
Ni: the low-temperature impact toughness is ensured again, and the heat cracking of the steel is prevented.
Ce: rare earth elements, the type, the quantity and the size of steel inclusions are controlled based on an oxide metallurgy technology, fine inclusions are utilized to pin austenite crystal boundaries in a welding process, coarse crystals are inhibited, and acicular ferrite is promoted to generate.
Compared with the prior art, the invention has the following remarkable advantages and effects:
1. the invention adopts low-carbon design to ensure good welding performance of a steel plate, adopts composite microalloying design of Nb, V and Ti to improve the strength and toughness, assists Cr, mo and B to comprehensively improve the hardenability of the steel, ensures that Cu is precipitated and strengthened in a tempering process to improve the steel performance, ensures low-temperature impact toughness and prevents hot cracking of the steel, ensures good welding structure by rare earth element Ce, and comprehensively achieves high-strength steel with good welding performance and obdurability.
2. The invention adopts the process of ultra-fast cooling after rolling, can effectively reduce energy consumption in the process, and can lead the final structure of the steel to be a bainite and martensite multiphase structure in effect through the control of the cooling rate, wherein the shear transformation of the bainite can nucleate on an austenite crystal boundary and penetrate through austenite crystal grains, thereby limiting the phase transformation of martensite in a smaller area, refining the martensite structure, inheriting high-density dislocation in the austenite processing process and improving the strength. After tempering treatment, bainite and martensite structures are coarsened, carbides are precipitated among original austenite grain boundary grade lath bundles, and the impact toughness of the steel is improved.
3. In the invention, a proper amount of rare earth Ce element is added in the RH refining process, the 700MPa grade rare earth high-strength steel with good tissue uniformity and low-temperature toughness is obtained by hot rolling and post-treatment by adopting TMCP technology in combination with ultra-fast cooling and tempering processes, the low-temperature impact energy at the welding seam after welding is more than or equal to 100J, and the impact property is good.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Examples 1 to 10
The production process flow of the high-welding-performance 700 MPa-grade rare earth high-strength structural steel comprises the following steps: converter smelting, LF refining, RH refining, continuous casting, hot rolling, ultra-fast cooling and low-temperature tempering. The specific operation steps are as follows:
(1) In the converter steelmaking process, the temperature of molten iron entering the converter is more than or equal to 1300 ℃, the end point P of the converter is less than or equal to 0.015 percent, the S is less than or equal to 0.008 percent, and oxygen is blown for smelting. The process parameter control of each example is shown in table 1.
TABLE 1 EXAMPLES 1-10 converter steelmaking Process parameters
(2) And in the LF refining process, an oxide metallurgy technology is adopted to slag and deoxidize the molten steel, the oxygen content of the molten steel is less than or equal to 0.003 percent, the S is less than or equal to 0.003 percent, and the temperature is more than or equal to 1580 ℃. The process parameter control of each example is shown in Table 2.
TABLE 2 EXAMPLES 1-10LF refining procedure parameters
(3) And in the RH refining process, the RH vacuum treatment time is more than or equal to 23min, the rare earth Ce alloy is added after 15 to 18min generally, the vacuum circulation time is more than or equal to 15min after the rare earth alloy is added, and the argon blowing stirring time is more than or equal to 8min. The process parameter control of each example is shown in table 3.
TABLE 3 chemical composition and weight percentage of steel plate of examples 1-10
(4) And (3) a continuous casting process, wherein the argon pressure is ensured to be 0.5MPa, the casting temperature is more than or equal to 1525 ℃, and the thickness of the continuous casting billet is 230mm. The process parameter control for each example is shown in table 4.
TABLE 4 continuous casting procedure parameters of examples 1-10
(5) The hot rolling process adopts two-stage controlled rolling, the initial rolling temperature of the first stage rough rolling is more than or equal to 1130 ℃, the final rolling temperature is more than or equal to 950 ℃, and the cumulative reduction rate is 65-72%; the rolling temperature of the second stage is 850-920 ℃, the rolling temperature of the final stage is 800-870 ℃, and the single-pass reduction rate is more than or equal to 14%. The process parameter control for each example is shown in table 5.
TABLE 5 Hot Rolling Process parameters of examples 1-10
(6) And (3) an ultra-fast cooling procedure, wherein the open cooling temperature of the steel plate is 740 to 830 ℃, the cooling rate is more than or equal to 25 ℃/s, and the final cooling temperature is less than or equal to 200 ℃. The process parameter control for each example is shown in Table 6.
(7) And (3) a low-temperature tempering process, wherein the low-temperature tempering temperature is 580-630 ℃, and the steel plate is air-cooled after tempering. The process parameter control for each example is shown in table 6.
TABLE 6 ultrafast cooling parameters of examples 1 to 10
Table 7 shows the chemical compositions and mass percentages of the steel sheets of examples 1 to 10 of the present invention.
Table 8 shows the mechanical property data of the steel sheets of examples 1 to 10 of the present invention.
Table 9 examples 1-10 steel sheets were evaluated for post-MAG weld performance.
TABLE 7 chemical compositions and mass percents of steel sheets of examples 1-10
TABLE 8 tabulation of mechanical property data for steel sheets of examples 1-10
TABLE 9 evaluation of post MAG welding Properties of the Steel sheets of examples 1 to 10
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and it is intended to cover in the claims the invention as defined in the appended claims.
Claims (10)
1. The high-welding-performance 700 MPa-grade rare earth high-strength structural steel is characterized by comprising the following chemical components in percentage by mass: 0.05 to 0.11%, si:0.15 to 0.3%, mn:1.25 to 1.55 percent, less than or equal to 0.0015 percent of P, less than or equal to 0.005 percent of S, cr:0.15 to 0.35%, mo:0.1 to 0.3%, nb:0.015 to 0.035%, V:0.02 to 0.06%, ti:0.01 to 0.035%, cu:0.25 to 0.45%, ni:0.125 to 0.225%, B:0.0015 to 0.0025%, ce:0.002 to 0.008 percent, als:0.025 to 0.045 percent, and the balance of Fe and other inevitable impurities.
2. The high-weldability 700 MPa-grade rare earth high-strength structural steel according to claim 1, wherein the high-strength structural steel comprises the following chemical components in percentage by mass: 0.07 to 0.10%, si:0.2 to 0.3%, mn:1.35 to 1.50 percent, less than or equal to 0.0015 percent of P, less than or equal to 0.005 percent of S, cr:0.2 to 0.3%, mo:0.2 to 0.3%, nb:0.020 to 0.030%, V:0.02 to 0.04%, ti:0.02 to 0.030%, cu:0.30 to 0.40%, ni:0.15 to 0.20%, B:0.0015 to 0.0025%, ce:0.004 to 0.006%, als:0.025 to 0.045 percent, and the balance of Fe and other inevitable impurities.
3. The high-weldability 700 MPa-grade rare earth high-strength structural steel according to claim 1, wherein the high-strength structural steel comprises the following chemical components in percentage by mass: 0.08%, si:0.25%, mn:1.50%, P is less than or equal to 0.0015%, S is less than or equal to 0.005%, cr:0.25%, mo:0.25%, nb:0.025%, V:0.03%, ti:0.025%, cu:0.40%, ni:0.20%, B:0.0020%, ce:0.005%, als:0.025%, and the balance of Fe and other inevitable impurities.
4. The rare earth high-strength structural steel with high weldability of 700MPa according to any one of claims 1 to 3, characterized in that the yield strength of the base material of the high-strength structural steel is not less than 700MPa, the tensile strength is not less than 810MPa, the elongation is not less than 15%, and the longitudinal impact energy at-20 ℃ is not less than 180J.
5. The production method of the rare earth high-strength structural steel with high welding performance of 700MPa according to any one of claims 1 to 3, wherein the high-strength structural steel adopts an MAG welding process, preheating is not needed, and the low-temperature impact energy at a welding seam is not less than 100J.
6. The production method of the rare earth high-strength structural steel with the high welding performance of 700MPa is characterized by comprising the working procedures of converter smelting, LF refining, RH refining, continuous casting, hot rolling, ultra-fast cooling and tempering;
in the ultra-fast cooling procedure, the open cooling temperature of a steel plate is 740 to 830 ℃, the cooling rate is more than or equal to 25 ℃/s, and the final cooling temperature is less than or equal to 200 ℃;
in the tempering process, the tempering temperature is 580 to 630 ℃, and the steel plate is air-cooled after tempering.
7. The production method of the rare earth high-strength structural steel with the high weldability of 700MPa grade according to claim 6, characterized in that the converter steelmaking process comprises the following steps: the temperature of molten iron entering the converter is more than or equal to 1300 ℃, the terminal point P of the converter is less than or equal to 0.015 percent, the S is less than or equal to 0.008 percent, and oxygen is blown for smelting.
8. The method for producing the rare earth high-strength structural steel with the high weldability of 700MPa according to claim 6, characterized in that the LF refining process: slagging and desulfurizing the molten steel by adopting an oxide metallurgy technology, wherein the oxygen content of the steel is less than or equal to 0.002 percent, the S is less than or equal to 0.003 percent, and the temperature is more than or equal to 1580 ℃;
the RH refining step: the RH vacuum treatment time is more than or equal to 23min, then rare earth Ce alloy is added, the vacuum circulation time is more than or equal to 15min after the rare earth Ce alloy is added, and the argon blowing stirring time is more than or equal to 8min.
9. The method for producing a rare earth high strength structural steel with high weldability of 700MPa according to any one of claims 6 to 8, characterized in that the continuous casting process: the casting temperature is more than or equal to 1525 ℃, the argon blowing pressure is ensured to be 0.5MPa in the continuous casting process, and the thickness of the continuous casting billet is 230mm.
10. The production method of the rare earth high-strength structural steel with the high welding performance of 700MPa according to any one of claims 6 to 8, characterized in that the hot rolling process adopts two-stage controlled rolling, the initial rolling temperature of the first stage is more than or equal to 1130 ℃, the final rolling temperature is more than or equal to 950 ℃, and the cumulative reduction rate is 65-72%; the rolling temperature of the second stage is 850-920 ℃, the final rolling temperature is 800-870 ℃, and the single-pass reduction rate is more than or equal to 14%.
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