CN114672734A - High-strength steel for welded structure and production method thereof - Google Patents

High-strength steel for welded structure and production method thereof Download PDF

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CN114672734A
CN114672734A CN202210335386.6A CN202210335386A CN114672734A CN 114672734 A CN114672734 A CN 114672734A CN 202210335386 A CN202210335386 A CN 202210335386A CN 114672734 A CN114672734 A CN 114672734A
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steel
less
equal
temperature
rolling
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杨建勋
李国宝
郑飞
王润港
王淑华
王杰
刘熙章
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SD Steel Rizhao Co Ltd
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SD Steel Rizhao Co Ltd
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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
    • 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
    • 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
    • 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
    • C21D8/0247—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
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • 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
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of 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
    • C21D2211/008—Martensite

Abstract

The invention relates to the technical field of steel, in particular to high-strength steel for a welding structure and a production method thereof, wherein the high-strength steel for the welding structure comprises 0.1-0.18% of C, 0.15-0.5% of Si, 0.9-1.7% of Mn, 0.1-0.8% of Ni, 0.2-0.9% of Cr0.2, 0.01-0.05% of Nb0.01, 0.018-0.05% of Alt0.018, 0.008-0.03% of Ti, 0.1-0.7% of Mo0.7%, 0.0008-0.003% of B, 0.0015-0.005% of Ca0.002, 0.002-0.008% of Mg0.02% of P, 0.008% or less of S, 40ppm or less of N, 20ppm or less of O, 2ppm or less of H, and the balance of iron and inevitable impurities. The steel has excellent mechanical property, and can be widely applied to the manufacturing of large-scale engineering equipment such as ocean platforms and the like.

Description

High-strength steel for welded structure and production method thereof
Technical Field
The invention relates to the technical field of steel, in particular to high-strength steel for a welded structure and a production method thereof.
Background
When large-scale engineering equipment such as an ocean platform and the like is manufactured, welding operation of structural steel is often involved. In order to improve the strength of structural steels, it is common to increase the carbon content of structural steels to increase the hardenability of the steel, but at the same time, the increase in carbon content also reduces the plasticity and impact toughness of the steel, increases the cold-embrittlement tendency and aging tendency, and deteriorates the weldability. The addition of precious micro-alloy while reducing carbon is a common method for ensuring the strength and welding performance of steel at present. For example, chinese patent CN101418418B discloses a method for manufacturing a low crack sensitivity steel plate with yield strength of 690MPa grade, which adopts Cr-Mo-V-Nb-Ti-B composite addition in the aspect of steel component design, and the yield strength of the steel is above 690MPa, and the tensile strength is above 770 MPa. Although this patent provides a method for producing 80kg grade steel plate with low weld crack sensitivity without any heat treatment, 0.04-0.12% of noble metal V is added, resulting in higher alloy cost of this steel grade.
The Chinese patent application CN102851604A discloses a method for producing a high-strength steel plate with a yield strength of 690MPa grade, a plate blank is produced by adopting an on-line quenching (DQ) and tempering (T) process after controlled rolling, Cr-Mo-V-Nb-Ti-B composite addition is adopted in the aspect of steel component design, and because the steel is designed by adopting a low-carbon (C: 0.04-0.09%) component system, a high-content ferrovanadium alloy (V: 0.05-0.07%) needs to be added, so that the alloy cost is high.
Disclosure of Invention
The high-strength steel for the welding structure has excellent mechanical property, the post-welding tensile strength of the high-strength steel is more than or equal to 610MPa, the heat affected macrocrystalline region impact at minus 40 ℃ is more than or equal to 120J, the Crack Tip Opening Displacement (CTOD) is more than or equal to 0.25mm, the crack arrest performance is excellent, and the high-strength steel can be widely applied to the manufacturing of large engineering equipment such as ocean platforms and the like.
In a first aspect, the present invention provides a method for producing a high strength steel for a welded structure, the high strength steel for a welded structure comprising, in terms of weight percent, C: 0.10% -0.18%, Si: 0.15% -0.50%, Mn: 0.90% -1.70%, Ni: 0.10-0.80%, Cr: 0.20% -0.90%, Nb: 0.01% -0.05%, Alt: 0.018-0.050%, Ti: 0.008% -0.030%, Mo: 0.10% -0.70%, B: 0.0008 to 0.0030%, Ca: 0.0015-0.0050%, Mg: 0.0020 to 0.0080 percent, less than or equal to 0.020 percent of P, less than or equal to 0.008 percent of S, less than or equal to 40ppm of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of iron and inevitable impurities;
the production method comprises the steps of smelting, casting, heating, rolling, cooling, quenching and tempering.
Further, the high-strength steel for the welded structure comprises the following chemical components in percentage by weight: 0.12% -0.18%, Si: 0.21-0.37%, Mn: 0.95% -1.56%, Ni: 0.21-0.69%, Cr: 0.20% -0.85%, Nb: 0.01% -0.045%, Alt: 0.018-0.027%, Ti: 0.012% -0.019%, Mo: 0.10% -0.62%, B: 0.0013% -0.0021%, Ca: 0.0023% -0.0041% and Mg: 0.0033 to 0.0071 percent, less than or equal to 0.020 percent of P, less than or equal to 0.004 percent of S, less than or equal to 40ppm of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of iron and inevitable impurities.
Detailed description of chemical components:
c is the most main solid solution strengthening element, can obviously improve the hardenability of the steel and plays a decisive role in the strength and the hardness of the martensitic steel, but the increase of the carbon content reduces the plasticity and the impact toughness of the steel, improves the cold brittleness tendency and the aging tendency, and deteriorates the welding performance. Considering that the steel strength can be ensured only by additionally increasing the content of other precious micro-alloys while reducing the carbon, and the cost is greatly increased, the proper amount of C is comprehensively considered to be controlled to be 0.10-0.18%.
Although Si enters ferrite to perform a solid solution strengthening action, Si significantly increases the ductile-brittle transition temperature of steel and deteriorates plasticity and weldability, and therefore, the appropriate amount of Si is controlled to 0.15% to 0.50%.
Mn can reduce the critical transition temperature Ar3, obviously improve the hardenability of the steel, simultaneously has a certain solid solution strengthening effect, and plays a role in improving the strength and the hardness of the steel. Because manganese and sulfur have high affinity, MnS has certain plasticity at high temperature, so that hot brittleness of steel is avoided, but excessively high Mn can influence the welding performance of the steel, and also aggravates the center segregation of a casting blank, so that the strip structure of a product is serious, and further impact toughness is influenced. Therefore, the appropriate amount of Mn is controlled to 0.90% to 1.70%.
P belongs to low-temperature brittle elements, the P obviously expands a two-phase region between a liquid phase and a solid phase, segregates among crystal grains in the solidification process of steel to form a high-phosphorus brittle layer, improves the level of a banded structure, causes the local structure of the steel to be abnormal, causes uneven mechanical properties, reduces the plasticity of the steel, causes the steel to be easy to generate brittle cracks, reduces the corrosion resistance, has adverse effects on the welding performance, increases the sensitivity of the welding cracks, and therefore, the content of phosphorus in the steel is reduced as much as possible. The content of P is controlled below 0.020% in consideration of production cost.
When S is present in the steel in the form of FeS, hot shortness is liable to occur if the S content is high. When S exists in the steel in the form of MnS, the S is often distributed in a strip shape along the rolling direction to form a serious strip structure, the continuity of the steel is damaged, the performance of the steel in different directions can be also influenced, the plasticity and the impact toughness of the steel are reduced, and the ductile-brittle transition temperature is improved. Therefore, the content of S is controlled to 0.008% or less.
Ni plays a role in strengthening ferrite by forming a simple substitutional solid solution, so that the strength of the steel can be improved, and meanwhile, Ni is an austenite stabilizing element, so that the low-temperature impact toughness of the steel can be remarkably improved. However, the price of the Ni plate is relatively expensive, and the appropriate amount of Ni is controlled to 0.10% -0.80% in consideration of cost.
Cr can prevent the graphitization tendency of Mo-added steel, belongs to stable austenite elements, can greatly improve the hardenability of the steel and improve the strength of the steel, but excessively high Cr can reduce the welding performance of the steel, and the proper amount of Cr is controlled to be 0.20-0.90 percent in comprehensive consideration.
Nb can produce remarkable grain refinement, precipitation strengthening and moderate precipitation strengthening effects. Nb dissolved in austenite can improve hardenability, while Nb (C, N) precipitate phase has a grain refining effect but reduces hardenability, and if the Nb content is too high, Nb tends to form low-melting eutectic with elements such as Fe and C, and to increase heat cracking in the weld heat affected zone. The proper amount of Nb is controlled between 0.01 percent and 0.05 percent by combining various factors.
Al can refine the crystal grains of the steel, improve the strength of the steel and simultaneously improve the impact toughness. Because A1 and N have stronger affinity, the aging sensitivity caused by N element can be eliminated, therefore, the content of Alt is determined to be 0.018-0.050%.
Ti can precipitate TiN particles at a high temperature of 1200-1300 ℃ and can be used as a precipitation core of Nb (C, N), thereby reducing the number of fine niobium precipitates and further reducing the crack sensitivity of Nb-containing steel. Ti can form fine carbide and nitride particles of titanium, and a fine austenite microstructure is obtained by preventing austenite grains from coarsening in the slab heating process. Ti and N are combined to generate a stable high-dispersion compound, so that free nitrogen in steel can be eliminated, the grain size can be controlled in a heat affected zone in the hot working process and welding, and the low-temperature toughness of each part of a steel structure is improved. Excessive Ti forms micron-sized liquated TiN, which cannot refine grains but deteriorates the toughness of the steel plate. Therefore, the appropriate amount of Ti is 0.008% to 0.030%.
Mo exists in a solid solution phase and a carbide phase in the steel, belongs to stable austenite elements, can greatly improve the hardenability of the steel, can strongly shift a C curve to the right to promote bainite 5 martensite transformation, and can improve the tempering brittleness, the low-temperature toughness and the delayed fracture resistance of the steel. The proper amount of Mo is controlled to be 0.10-0.70% by combining with the cost factor.
B is strongly biased to austenite crystal boundaries and other crystal defects, so that the hardenability of the steel can be increased, and the hardenability of the steel can be improved. The addition of trace B can obviously inhibit the nucleation of ferrite on austenite crystal boundary, and make ferrite transformation curve obviously move rightward to promote bainite 5 martensite transformation, but after the boron content exceeds 0.0030%, the above-mentioned action can be saturated, and can also form various B-containing precipitated phases which are unfavorable for hot-working property and toughness, and the boron content should be controlled at 0.0008% -0.0030%.
Ca is a strong deoxidizing element, the content of Ca is properly controlled to play a role in spheroidizing residual impurities in steel, but the excessive content of Ca easily causes water blockage, and the castability of molten steel is influenced, and the content of Ca is comprehensively considered to be controlled to be 0.0015-0.0050%.
Mg is a strong deoxidizing element, forms composite inclusions taking MgO as a core, can induce austenite crystals to generate a large amount of nucleation while refining the inclusions in steel, refines the full-thickness section structure of a thick plate, improves the crack arrest toughness of a heat-affected coarse crystal area of the steel plate, and comprehensively considers that the Mg content is controlled to be 0.0020-0.0080%.
Too high N content deteriorates the impact toughness of the high strength steel and is generally controlled to 40ppm or less.
The high content of O indicates that the steel contains too many inclusions and has adverse effects on various mechanical properties of the steel, so the content of O should be controlled below 20ppm as much as possible to improve the cleanliness of molten steel.
H is harmful, flaw detection is not good easily, low-temperature impact toughness is affected, and the content of H needs to be controlled below 2ppm by means of vacuum treatment and the like.
Further, the production method specifically comprises the following steps:
(1) smelting: smelting by adopting a converter or an electric furnace;
(2) casting: continuous casting or die casting is adopted;
(3) heating: in order to fully play the roles of delaying austenite recrystallization in the controlled rolling process, performing precipitation strengthening in the rolling process and the cooling process after rolling of microalloy elements such as Nb, Ti and the like, more microalloy elements are ensured to be dissolved into austenite, and the solid solution advantage is fully played, so the heating temperature of a billet is at least increased by more than 1150 ℃; meanwhile, considering that the austenite grains grow excessively due to overhigh heating temperature and are inherited to the rolled steel plate to cause adverse effects on the impact toughness of the steel plate, the tapping temperature of the steel billet is controlled below 1220 ℃ as far as possible.
(4) Rolling: and rolling the steel billet by a roughing mill to obtain an intermediate billet, and performing finish rolling after the temperature on a roller way reaches a target rolling temperature. In the finish rolling process, in order to ensure the grain refinement after rolling and improve the comprehensive mechanical property of the steel plate, the pinning dislocation of the second phase point Nb (C, N) needs to be fully exerted, the recrystallization of austenite is prevented, and the Tnr temperature (recrystallization termination temperature) is increased, so that the rolling control process window is expanded. In order to improve the rolling shape, the initial rolling temperature of finish rolling can be properly increased to reduce rolling resistance, and the mixed crystal phenomenon generated by the initial rolling temperature higher than Tnr is avoided, so the initial rolling temperature of finish rolling cannot be higher than 950 ℃, and meanwhile, in order to avoid excessive transformation of proeutectoid ferrite before the steel plate enters water, the action of micro-alloy carbonitride pinning dislocation is utilized to ensure that the steel plate structure is transformed from austenite to refined ferrite 5 bainite structure, so the initial rolling temperature of finish rolling cannot be lower than 840 ℃. The finish rolling temperature is 820-900 ℃.
The recrystallization of austenite grains is inhibited as the temperature of the intermediate billet is reduced below Tnr, the austenite grains are in a flattened and elongated state through rolling under high pressure, a large number of slip bands and dislocations are generated in the grains as the rolling reduction is increased, the effective grain boundary area is increased, the phase transformation refining effect is increased, the toughness of steel is improved, meanwhile, the enough rolling reduction of a rough rolling stage is ensured by considering an ultra-thick steel plate, the section structure of the steel plate is uniformly refined, the low-temperature impact toughness of the steel plate is improved, and the thickness of the intermediate billet is controlled to be 1.5-4.0 times of the thickness of a finished product comprehensively.
(5) And (3) cooling: in the production process of the steel plate, in order to ensure that the structure of the steel plate is basically austenite before entering water, the austenite is directly transformed into ferrite 5 bainite in the cooling process of the steel plate, and in order to avoid the formation of excessive proeutectoid ferrite in a matrix, the starting cooling temperature of the steel plate is not lower than 750 ℃; considering that the steel plate needs to travel on a roller way for about 10 seconds after rolling and before entering water, if the temperature of the steel plate is too high, the phenomena of strain induced austenite recrystallization, partial recrystallization or subgrain recovery can occur after rolling, so that grains of the steel plate are coarse before entering the water, and the low-temperature toughness of the extra-thick plate is influenced, and therefore, the open cooling temperature of the steel plate is not higher than 820 ℃.
The final cooling temperature is controlled below 680 ℃ in consideration of complete austenite transformation after cooling.
With the progress of cooling, the transformation of austenite to a low-temperature structure is realized, and the cooling speed is controlled within the range of 55 ℃ to 10 ℃ in consideration of the limitation of thin-specification plate shape control and the heat conduction capability of an ultra-thick steel plate.
(6) Quenching: through quenching treatment, complete austenitizing of a full-thickness structure of the steel plate is ensured, and then accelerated cooling is carried out to complete martensitic transformation. The quenching temperature is preferably controlled to be above Ac3, and excessive grain growth caused by overhigh furnace temperature and overlong heating time is avoided, the quenching temperature is 890-940 ℃, and the quenching heating coefficient is 1.0-2.5 min5 mm.
(7) Tempering: by carrying out reasonable tempering heat treatment on the steel plate, the structure is effectively homogenized, the ductility and toughness of the steel plate are improved, meanwhile, the sufficient precipitation of two-phase particles is promoted, the precipitation strengthening effect of microalloy elements in the steel is exerted, and the steel plate is ensured to obtain stable strength, plasticity and toughness indexes. Comprehensively considering, the tempering temperature is controlled within the range of 500-670 ℃, and the tempering heating coefficient is controlled within the range of 1.5-3.5 min5 mm.
Further, the production method specifically comprises the following steps:
(1) smelting: smelting by adopting a converter or an electric furnace;
(2) casting: continuous casting or die casting is adopted;
(3) heating: heating a steel billet obtained after casting, and controlling the tapping temperature of the steel billet to be 1200-1220 ℃;
(4) rolling: roughly rolling the heated steel billet in the step (3) to obtain an intermediate billet, wherein the thickness of the intermediate billet is 1.5-4.0 times of that of a finished product, the initial rolling temperature of the finish rolling of the steel billet is 840-950 ℃, and the final rolling temperature is 820-900 ℃;
(5) and (3) cooling: the start cooling temperature is 780-810 ℃, the final cooling temperature is not higher than 660 ℃, and the cooling speed is 5-10 ℃ and 55 ℃;
(6) quenching: the quenching temperature is 900-940 ℃, and the quenching heating coefficient is 1.5-2.5 min5 mm;
(7) tempering: the tempering temperature is 550-670 ℃, and the tempering heating coefficient is 2.5-3.5 min5 mm.
In a second aspect, the present invention provides a high-strength steel for welded structures obtained by the above production method.
Further, the maximum thickness of the high-strength steel for welded structures is 100 mm.
Furthermore, after 35KJ5cm heat input welding, the tensile strength of the high-strength steel for the welding structure is more than or equal to 610MPa, the heat affected coarse grain zone impact at minus 40 ℃ is more than or equal to 120J, and the CTOD is more than or equal to 0.25 mm.
The invention has the beneficial effects that:
(1) the requirement on the phosphorus content is loose, the smelting cost can be greatly reduced, and meanwhile, low-cost high-carbon ferromanganese can be adopted to replace low-carbon ferromanganese during alloying, so that the alloy cost of steel grades is greatly reduced, the technical transportability is strong, and the large-area popularization of the steel industry is facilitated;
(2) the components are reasonably designed, and the shape of inclusions in the steel is dispersed and micronized after the molten steel is treated by magnesium, so that the growth of grains in a welding coarse crystal area is effectively inhibited, the structure of a welding joint part is uniform, and the crack arrest toughness is excellent.
In conclusion, the high-strength steel for the welding structure, which is prepared by the invention, has excellent comprehensive mechanical properties, is not easy to break and destroy, is safe and reliable to use, and can be widely applied to the manufacturing of large engineering equipment such as ocean platforms.
Detailed Description
In order to make those skilled in the art better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The high-strength steel for the welding structure comprises the following chemical components in percentage by weight: 0.10% -0.18%, Si: 0.15% -0.50%, Mn: 0.90% -1.70%, Ni: 0.10-0.80%, Cr: 0.20% -0.90%, Nb: 0.01% -0.05%, Alt: 0.018-0.050%, Ti: 0.008% -0.030%, Mo: 0.10% -0.70%, B: 0.0008% -0.0030%, Ca: 0.0015-0.0050%, Mg: 0.0020 to 0.0080 percent, less than or equal to 0.020 percent of P, less than or equal to 0.008 percent of S, less than or equal to 40ppm of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of iron and inevitable impurities.
The production method of the high-strength steel for the welded structure comprises the steps of smelting, casting, heating, rolling, cooling, quenching and tempering, and specifically comprises the following steps:
(1) smelting: smelting by adopting a converter or an electric furnace;
(2) casting: continuous casting or die casting is adopted;
(3) heating: heating a steel billet obtained after casting, and controlling the tapping temperature of the steel billet to be 1150-1220 ℃;
(4) rolling: roughly rolling the heated steel billet in the step (3) to obtain an intermediate billet, wherein the thickness of the intermediate billet is 1.5-4.0 times of that of a finished product, the initial rolling temperature of the finish rolling of the steel billet is 840-950 ℃, and the final rolling temperature is 820-900 ℃;
(5) and (3) cooling: the start cooling temperature is 750-820 ℃, the final cooling temperature is not higher than 680 ℃, and the cooling speed is 5-10 ℃ and 55 ℃;
(6) quenching: the quenching temperature is 890-940 ℃, and the quenching heating coefficient is 1.0-2.5 min5 mm.
(7) Tempering: the tempering temperature is 500-670 ℃, and the tempering heating coefficient is 1.5-3.5 min5 mm.
Examples 2 to 9
The high-strength steel for welded structures of examples 2 to 9 had the main chemical components shown in table 1 below based on example 1, N not more than 40ppm, O not more than 20ppm, and H not more than 2ppm, with the balance being Fe and unavoidable impurities.
Table 1 main chemical composition (unit wt.%) of each example
Figure BDA0003576595370000081
Figure BDA0003576595370000091
The main process parameters of the production method of high-strength steel for welded structures of examples 2 to 9 are shown in table 2 below, and the unit of each parameter is described in example 1.
TABLE 2 Main Process parameters of the examples
Figure BDA0003576595370000092
Verification example 1
The mechanical properties of the high-strength steel for welded structures prepared in examples 2 to 9 after being subjected to 35KJ5cm heat input welding were measured, and the results are shown in table 3 below.
TABLE 3 Main mechanical Properties of the examples
Figure BDA0003576595370000093
Figure BDA0003576595370000101
Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention 5 any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention.

Claims (6)

1. The production method of the high-strength steel for the welded structure is characterized in that the high-strength steel for the welded structure comprises the following chemical components in percentage by weight: 0.10% -0.18%, Si: 0.15% -0.50%, Mn: 0.90% -1.70%, Ni: 0.10-0.80%, Cr: 0.20% -0.90%, Nb: 0.01% -0.05%, Alt: 0.018-0.050%, Ti: 0.008% -0.030%, Mo: 0.10% -0.70%, B: 0.0008% -0.0030%, Ca: 0.0015-0.0050%, Mg: 0.0020 to 0.0080 percent, less than or equal to 0.020 percent of P, less than or equal to 0.008 percent of S, less than or equal to 40ppm of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of iron and inevitable impurities;
the production method comprises the steps of smelting, casting, heating, rolling, cooling, quenching and tempering.
2. The production method according to claim 1, wherein the chemical composition of the high-strength steel for welded structures contains, in weight percent, C: 0.12% -0.18%, Si: 0.21% -0.37%, Mn: 0.95% -1.56%, Ni: 0.21-0.69%, Cr: 0.20% -0.85%, Nb: 0.01% -0.045%, Alt: 0.018-0.027%, Ti: 0.012% -0.019%, Mo: 0.10% -0.62%, B: 0.0013% -0.0021%, Ca: 0.0023% -0.0041% and Mg: 0.0033 to 0.0071 percent, less than or equal to 0.020 percent of P, less than or equal to 0.004 percent of S, less than or equal to 40ppm of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of iron and inevitable impurities.
3. The production method according to claim 1, characterized in that the production method comprises in particular the steps of:
(1) smelting: smelting by adopting a converter or an electric furnace;
(2) casting: continuous casting or die casting is adopted;
(3) heating: heating a steel billet obtained after casting, and controlling the tapping temperature of the steel billet to be 1150-1220 ℃;
(4) rolling: roughly rolling the heated steel billet in the step (3) to obtain an intermediate billet, wherein the thickness of the intermediate billet is 1.5-4.0 times of that of a finished product, the initial rolling temperature of the finish rolling of the steel billet is 840-950 ℃, and the final rolling temperature is 820-900 ℃;
(5) and (3) cooling: the start cooling temperature is 750-820 ℃, the final cooling temperature is not higher than 680 ℃, and the cooling speed is 5-10 ℃ and 55 ℃;
(6) quenching: the quenching temperature is 890-940 ℃, and the quenching heating coefficient is 1.0-2.5 min5 mm;
(7) tempering: the tempering temperature is 500-670 ℃, and the tempering heating coefficient is 1.5-3.5 min5 mm.
4. A high-strength steel for welded structures obtained by the production method according to any one of claims 1 to 3.
5. The high-strength steel for welded structures according to claim 4, wherein the maximum thickness of the high-strength steel for welded structures is 100 mm.
6. The high-strength steel for welded structures according to claim 4, wherein after welding at 35KJ5cm heat input, the high-strength steel for welded structures has a tensile strength of 610MPa or more, a heat-affected macrocrystalline region impact of 120J or more at-40 ℃ and a CTOD of 0.25mm or more.
CN202210335386.6A 2022-03-31 2022-03-31 High-strength steel for welded structure and production method thereof Pending CN114672734A (en)

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CN104278206A (en) * 2014-10-15 2015-01-14 山东钢铁股份有限公司 Steel plate with thickness of smaller than 60mm and yield strength of 690MPa and preparation method of steel plate
CN104404369A (en) * 2014-11-27 2015-03-11 宝山钢铁股份有限公司 Thick steel plate capable of being welded at large heat input and manufacturing method thereof
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JP6308337B1 (en) * 2017-04-04 2018-04-11 新日鐵住金株式会社 Vertical seam welded steel pipe
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Publication number Priority date Publication date Assignee Title
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CN104278206A (en) * 2014-10-15 2015-01-14 山东钢铁股份有限公司 Steel plate with thickness of smaller than 60mm and yield strength of 690MPa and preparation method of steel plate
CN104404369A (en) * 2014-11-27 2015-03-11 宝山钢铁股份有限公司 Thick steel plate capable of being welded at large heat input and manufacturing method thereof
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