958 results about "Bainite" patented technology

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 1960MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After high-carbon components containing trace B are designed, rolled and spun into a wire rod, online molten salt rapid quenching treatment is carried out, and the wire rod is firstly subjected to front-section molten salt treatment, so that the wire rod is cooled at the cooling speed of greater than or equal to 36 DEG C / s and enters a bainite and pearlite mixed phase region from an austenite state; the method comprises the following steps: quenching a steel wire rod to form a structure mainly comprising quenched bainite and a sorbite structure, carrying out rear-section molten salt treatment on the steel wire rod, increasing the molten salt temperature, promoting isothermal tempering of the quenched bainite and the sorbite structure, and carrying out roller way slow cooling to prepare the hot-rolled steel wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered sorbite, tempered bainite and ferrite, the composition system can be simplified, the strength and plasticity matching and rapid production of the wire rod are considered, the tensile strength is 1330-1380 MPa, the percentage reduction of area is 35%-40%, and the wire breaking risk in the wire drawing and twisting process of the stranded wire steel can be reduced.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2100MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod, after a C-Si-Mn-Cr-Mo high-carbon component system is rolled and spun into a wire rod, the wire rod is subjected to online molten salt strong quenching isothermal treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and is cooled at a cooling speed of greater than or equal to 33 DEG C / s, and enters a bainite phase region from an austenite state; the method comprises the following steps: firstly, carrying out first-stage molten salt treatment to promote transformation of austenite into bainite, then carrying out later-stage molten salt treatment to form a structure mainly comprising bainite, carrying out isothermal tempering on the structure, reserving part of untransformed retained austenite, and finally, carrying out roller way slow cooling to promote transformation of the untransformed retained austenite into martensite, and carrying out tempering, the microstructure of the hot-rolled wire rod comprises a complex-phase structure composed of tempered bainite and tempered martensite, the tensile strength of the hot-rolled wire rod can reach 1435-1485 MPa, the percentage reduction of area of the hot-rolled wire rod is 31%-36%, off-line heat treatment of follow-up machining is avoided, and the risk of wire breakage is reduced.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2060MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After high-carbon chemical components containing trace V are designed, rolled and spun into a wire rod, the wire rod is cooled at a cooling speed of more than or equal to 33 DEG C / s through on-line molten salt semi-quenching treatment, enters a bainite and pearlite mixed phase region from an austenite state, and is subjected to hot rolling and hot rolling at a cooling speed of more than or equal to 33 DEG C / s; the method comprises the following steps: quenching bainite and a sorbite structure to form a structure mainly comprising the quenched bainite and the sorbite structure, then carrying out isothermal tempering, and finally carrying out roller way slow cooling to prepare the hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered sorbite and tempered bainite, so that a component system can be simplified, the material cost can be reduced, network carbides can be effectively controlled, and meanwhile, the complex-phase structure can be regulated and controlled; the high strength and plasticity of the wire rod are matched, the tensile strength is 1390-1440 MPa, the percentage reduction of area is 32%-37%, and the steel wire rod is used for manufacturing 2060 MPa grade stranded wires and other application fields and is beneficial to downstream wire drawing and twisting processing.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2230 MPa grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After a Nb-containing high-carbon component is used for rolling and spinning at a spinning temperature to form a wire rod, online molten salt mixing quenching isothermal treatment is carried out, so that the wire rod is firstly subjected to front-section molten salt treatment and is cooled at a cooling speed of more than or equal to 35 DEG C / s, and enters a bainite and pearlite mixed phase region from an austenite state; the method comprises the following steps: firstly, carrying out heat treatment on austenite to promote part of austenite to be converted into bainite and sorbite, then carrying out later-section molten salt treatment, increasing the molten salt temperature, promoting unconverted retained austenite to be decomposed and converted into sorbite, carrying out isothermal tempering, and finally, carrying out roller way slow cooling, so as to prepare the hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered bainite and tempered sorbite, the drawing and hardening capacity can be improved, the production efficiency is considered, the tensile strength is 1522-1572 MPa, and the percentage reduction of area is 29%-34%, so that off-line heat treatment is avoided, and the wire breaking risk and cost of stranded wire manufacturing are reduced.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2200MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod, and the manufacturing method comprises the following steps: rolling and spinning to form a wire rod by adopting a high-hardenability component design, and then carrying out online molten salt mixed phase region quenching isothermal treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and enters a bainite and pearlite phase region from an austenite state; the method comprises the following steps: carrying out high-temperature treatment on austenite to promote part of austenite to be converted into bainite and sorbite, carrying out later-section molten salt treatment, increasing the molten salt temperature, reducing the molten salt circulation amount, promoting unconverted retained austenite to be decomposed and converted into bainite and sorbite, carrying out isothermal tempering, and finally carrying out slow cooling through a roller way, the hot-rolled wire rod with a microscopic structure comprising a complex phase structure composed of tempered bainite and tempered sorbite is prepared, the material cost can be reduced, the complex phase structure and the structure toughness can be regulated and controlled on line, the tensile strength is 1505-1555 MPa, the percentage reduction of area is 32%-37%, efficiency and energy consumption are both considered, off-line heat treatment is avoided, and high-efficiency production of stranded wires is promoted.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2360MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After a Mo-V high-carbon component system is rolled and spun into a wire rod, the wire rod is subjected to on-line molten salt weak quenching toughening treatment, so that the wire rod is subjected to front-section molten salt treatment to be quickly cooled, enters a bainite and sorbite mixed phase region from an austenite state, and is subjected to high-temperature heat treatment to form a high-strength complex-phase hot-rolled wire rod; the method comprises the following steps: firstly, carrying out heat treatment on residual austenite to form a structure mainly comprising bainite and sorbite, then carrying out later-section molten salt treatment, increasing the temperature of molten salt, promoting decomposition and conversion of unconverted residual austenite into sorbite, carrying out isothermal tempering, and finally, carrying out roller way slow cooling to prepare a hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered bainite and tempered sorbite, the method has the advantages that the structure toughness can be regulated and controlled on line, the tensile strength is 1574-1627 MPa, the percentage reduction of area is 28-33%, the mechanical property fluctuation is reduced, the material cost and the production efficiency are both considered, the ultra-high-strength stranded wire can be produced without off-line heat treatment, and the wire breaking risk is reduced.

The invention relates to a detection method and application of a bainite steel structure and / or grain boundary for nuclear power equipment, and relates to the technical field of new material detection. According to the detection method, the problem that the structure and the grain boundary of bainite steel for nuclear power equipment are difficult to display can be solved, a major breakthrough of a grain size detection technology is achieved, the clear and complete grain boundary can be accurately presented, and scientific evaluation of the grain size through a comparison method, a cut point method, an area method and the like according to standard requirements is further supported. When the detection method is used for evaluating the grain size, the results are highly consistent, the repeatability is good, and the problems of subjective experience dependence and measurement errors caused by blurred grain boundary display in a traditional nitric acid and alcohol corrosion method are effectively avoided.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2260MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod, after the high-carbon component design of C-Si-Mn-Cr-V-Nb-V is rolled and spun into a wire rod, the wire rod is subjected to online molten salt mixed quenching isothermal treatment, so that the wire rod is subjected to front-section molten salt treatment to be quickly cooled, enters a bainite and pearlite mixed phase region from an austenite state, and is subjected to hot rolling and hot rolling to form the high-strength complex-phase hot-rolled wire rod. The method comprises the following steps: carrying out first-stage molten salt treatment on austenite to promote transformation of part of austenite to bainite and sorbite, then carrying out later-stage molten salt treatment to increase the molten salt temperature, promoting decomposition and transformation of untransformed retained austenite into sorbite, carrying out isothermal tempering, and finally carrying out slow cooling through a roller way, a hot-rolled wire rod with a microscopic structure comprising a complex-phase structure composed of tempered bainite, tempered sorbite and ferrite is manufactured, the tensile strength is 1547-1597 MPa, and the percentage reduction of area is 27%-32%, so that when a high-strength stranded wire is manufactured, off-line heat treatment is not needed, the drawing pass number is reduced, and the wire breaking risk is reduced.

The bainite plastic die steel comprises the following components in percentage by mass: 0.01-0.15% of C, 0.25-1.0% of Si, 0.5-2.0% of Mn, less than or equal to 0.045% of P, less than or equal to 0.015% of S, 2.0-5.0% of Cr, 1.01-2.0% of Ni, 0.0010-0.0050% of B, 0.004-0.008% of N and the balance of Fe and other inevitable impurities, and the following requirements are simultaneously met: the hardness index is more than or equal to 28 and less than or equal to 13.8 + 132.8 C + 2.34 Mn + 1.84 Cr-1.12 Ni and less than or equal to 38, and the bainite index is C 0.5 * Mn 1.4 * Cr 4 * Ni * N-1. 05 / 20 and less than or equal to 2000. According to the die steel, the tensile strength is larger than or equal to 800 MPa, the hardness is 28-38 HRC, the hardness difference value of the section of a steel plate with the thickness of 15-300 mm is smaller than or equal to 2 HRC, the straightness is smaller than or equal to 2 mm / m, and the flaw detection quality meets the E / e level requirement in the SP1921-84 standard. The method can be applied to manufacturing of plastic parts in the fields of automobiles, household appliances, medical treatment, electronics and the like.

The invention relates to the technical field of metal material manufacturing, and discloses a manufacturing process of a super-strong wear-resistant tire protection chain, which comprises the following steps of: forming a chain link blank by adopting high-silicon high-manganese bainite steel through hot rolling and hot die forging; the core of the method is an integrated heat treatment step, specifically, surface functionalization co-permeation of copper and cerium elements is synchronously carried out in the austenitizing stage, then bainite isothermal quenching is carried out, and a composite structure of bainite and stable retained austenite is obtained in a matrix; the process further comprises the steps that a special high-toughness welding wire is adopted for welding, and local tempering treatment is conducted on a welding seam; by means of the scheme, the chain link is endowed with excellent obdurability and fatigue resistance through the phase transformation induced plasticity effect of the base body, the abrasion resistance is remarkably improved through the surface functionalization co-cementation layer, and the reliability of a joint area is ensured through accurate welding and postweld treatment. The technical problems that wear resistance and toughness of a traditional protection chain are difficult to consider at the same time, and a welding joint is prone to failure are systematically solved.

According to the high-strength complex-phase hot-rolled wire rod for the 2300 MPa grade stranded wire and the manufacturing method of the high-strength complex-phase hot-rolled wire rod, after Mo-V high-carbon components are rolled and spun into the wire rod, online molten salt section quenching isothermal treatment is conducted, the wire rod is subjected to front-section molten salt treatment and cooled at the cooling speed larger than or equal to 39 DEG C / s, the wire rod enters a bainite phase region from an austenite state, and then the high-strength complex-phase hot-rolled wire rod is obtained; the method comprises the following steps: carrying out high-temperature treatment on austenite to promote part of austenite to be converted into bainite, then carrying out later-section molten salt treatment, increasing the molten salt temperature, promoting unconverted retained austenite to be decomposed and converted into sorbite, carrying out isothermal tempering, and finally carrying out roller way slow cooling to prepare the hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered bainite, tempered sorbite and ferrite, by means of the method, complex-phase structure regulation and control and online toughening can be achieved, the material cost and the production efficiency are both considered, the tensile strength is 1552-1602 MPa, the percentage reduction of area is 32%-38%, and therefore off-line heat treatment is avoided, and ultrahigh-strength stranded wires are efficiently produced.

Provided is a steel sheet that may be used for automobile parts and the like, and to a steel sheet having an excellent balance of strength and ductility, an excellent balance of strength and hole expansion ratio, and an excellent yield ratio evaluation index, and a method for manufacturing the same. The steel sheet includes: by wt %, C: 0.1 to 0.25%, Si: 0.01 to 1.5%, Mn: 1.0 to 4.0%, Al: 0.01 to 1.5%, P: 0.15% or less, S: 0.03% or less, N: 0.03% or less, B: 0.0005 to 0.005%, a balance of Fe, and unavoidable impurities; and as microstructures, bainite, tempered martensite, fresh martensite, retained austenite and unavoidable structures.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2330MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After a Mo-containing high-carbon component is rolled and spun into a wire rod, the wire rod is subjected to online fused salt mixed quenching toughening treatment, so that the wire rod is subjected to front-section fused salt treatment and is rapidly cooled, and enters a bainite and sorbite mixed phase region from an austenite state; the method comprises the following steps: firstly, carrying out heat treatment on residual austenite to form a structure mainly comprising bainite and sorbite, then carrying out later-section molten salt treatment, increasing the temperature of molten salt, promoting decomposition and conversion of unconverted residual austenite into sorbite, carrying out isothermal tempering, and finally, carrying out roller way slow cooling to prepare a hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered bainite and tempered sorbite, according to the hot-rolled steel wire rod, complex-phase structure regulation and control and online toughening can be achieved, the production efficiency is considered, the tensile strength of the hot-rolled steel wire rod can reach 1563-1613 MPa, the percentage reduction of area can reach 29%-34%, offline heat treatment is not needed when the ultrahigh-strength stranded wire is produced, and the wire breaking risk is reduced.

The invention belongs to the field of metal materials, and provides 800MPa-grade alloyed galvanized complex phase steel with ultrahigh reaming performance for automobiles and a preparation method of the 800MPa-grade alloyed galvanized complex phase steel, and the steel plate comprises the following components in percentage by weight: 0.12%-0.17% of C, 1.90%-2.25% of Mn, 0.30%-0.65% of Si, 0.020%-0.040% of Ti, less than or equal to 0.030% of P, less than or equal to 0.002% of N, less than or equal to 0.005% of S and the balance of Fe and inevitable impurities. The preparation method comprises the steps of smelting, hot rolling, acid pickling, cold rolling, continuous annealing galvanizing and finishing. The microstructure of the steel plate produced by the method is mainly composed of bainite and tempered martensite, and the steel plate has ultrahigh hole expansion rate and excellent forming performance.

The invention discloses an anti-oxidation packaging material for hot rolling of thermoelectric materials and a preparation method of the anti-oxidation packaging material, and relates to the technical field of new materials. The packaging material is of a three-layer composite tubular structure and sequentially comprises, from inside to outside, an anti-oxidation barrier layer which is a composite material with an Fe-Al intermetallic compound as a matrix and Y2O3 particles dispersed and distributed; the transition layer is a Ni-Cr-Fe-Mn-C series solid solution alloy with Ni as a matrix; and the structure supporting layer is made of microalloyed low-carbon bainite steel. The layers are metallurgically bonded through hot isostatic pressing, and then the hollow composite pipe is manufactured through cold drawing. The packaging material has excellent high-temperature oxidation resistance, good plastic deformation capacity and structural strength, can effectively isolate oxygen, coordinate strain and maintain overall integrity in the high-temperature hot rolling process, is suitable for protection and densification of Bi2Te3-based, PbTe-based and SiGe-based thermoelectric materials and the like, and remarkably improves thermoelectric performance and production consistency of the thermoelectric materials.

One embodiment of the present invention provides a high-strength thin-wall API steel material having excellent deformation stability and a manufacturing method thereof, the thin-wall API steel material comprising, in weight %, C: 0.05-0.15 %, Si: 0.5 % or less (except 0 %), Mn: 0.5-2.5 %, Nb: 0.05 % or less (except 0 %), V: 0.004 % or less (except 0 %), Mo: 0.03-0.2 %, Cr: 0.1-0.3 %, P: 0.03 % or less (except 0 %), S: 0.015 % (except 0 %), Al: 0.05 % or less (except 0 %), N: 0.01 % or less (except 0 %), Fe and other inevitable impurities in a balance, and a microstructure comprising, in area %, 10-30 % of ferrite having an average grain size of 15-30 μm and a balance of bainite, the thin-wall API steel material comprising 3000 / μm 2 V-based precipitates below.

The invention relates to a preparation method of bainite steel with high toughness and strength at low temperature, and the strength and toughness of the bainite steel at low temperature are improved by designing process parameters and steel ingot components. The bainite steel with high toughness and strength at low temperature is finally obtained by designing the components of the steel ingot, avoiding the addition of elements such as nickel, molybdenum and vanadium, reducing the material cost and the processing difficulty and accurately controlling the cooling rate of heat treatment. The prepared bainite steel is composed of strip-shaped bainite and thin strip-shaped retained austenite, and the volume fraction of the retained austenite is 5-10%. The tensile strength is not lower than 1240 MPa, the normal-temperature impact is not lower than 120 J, and the impact toughness at-40 DEG C is not lower than 80 J.

The invention discloses a 1180MPa-grade ultrahigh-strength steel plate for an automobile and a preparation method of the 1180MPa-grade ultrahigh-strength steel plate, and belongs to the technical field of cold-rolled strip production. The steel plate comprises the following chemical components in percentage by mass: 0.17%-0.20% of C, 1.2%-1.6% of Si, 1.70%-2.10% of Mn, less than or equal to 0.008% of P, less than or equal to 0.005% of S, 0.30%-0.50% of Al, 0.15%-0.30% of Cr, 0.08%-0.12% of V, less than or equal to 0.0045% of N and the balance of Fe and impurities, wherein Ceq = C + Si / 30 + Mn / 20 + 2P + 4S < = 0.41. The preparation method comprises the steps of smelting, continuous casting, hot rolling, pickling cold rolling and continuous annealing. Through alloy component design and process collaborative optimization, the prepared ultrahigh-strength steel plate has high strength, high plasticity and high reaming performance, and the problem that existing bainite complex-phase steel is poor in comprehensive performance can be effectively solved.

Provided is a steel sheet for a CO2 transport line pipe that is suitably provided to a pipeline for transporting a liquid and / or supercritical state CO2. A steel sheet according to the present invention has: a component composition that contains, in mass%, 0.03-0.08% of C, 1.50-2.50% of Mn, 0.030% or less of P, 0.0100% or less of S, 0.0100% or less of N, 0.010-0.200% of Al, 0.10-1.00% of Si, and 0.0005-0.0050% of O, that further contains a prescribed amount of one or more selected from Cu, Ni, Cr, Mo, and W, that exhibits a [Si] / [O] value of 20-900, and in which the remaining portion comprises Fe and unavoidable impurities; a micro structure in which the area ratio of bainite is not less than 90% and the area ratio of island martensite is less than 3%; a strength where the tensile strength is not less than 625 MPa; and a toughness in which the Charpy impact absorption energy at -40°C is not less than 320 J.

The application discloses a low-carbon-equivalent 355MPa grade normalized rolled thick plate organization uniformity control method, wherein the temperature of the billet before charging is less than or equal to 400 DEG C, the temperature of the soaking furnace is 1130-1150 DEG C, the time of the soaking section is 45-55 minutes, the total furnace time is 170-185 minutes, the second opening temperature of the billet is 880-940 DEG C, the finishing rolling is 6-8 passes, the cumulative reduction is 60-70%, and the final rolling temperature is 860-900 DEG C; the steel plate cooling is realized by adopting a laminar flow cooling system, the full-automatic water pouring control cooling mode is adopted, the water inlet temperature is 720-740 DEG C, the red temperature is 640-660 DEG C, and the surface temperature of the steel plate after cooling is monitored. The head and tail and the full-thickness organization type of the normalized rolled steel plate are all 'ferrite + pearlite' organizations, the grain size level is all above 9.0, there is no obvious banded structure and no bainite structure, and the problem of the organization difference of the 355MPa grade thick plate product caused by the normalized rolling is solved.

The application discloses a process method for improving toughness of X70 anti-large-deformation pipeline steel, and ideal mechanical properties and organizational morphology are obtained through control of components, continuous casting, heating, rolling, cooling and other processes, finally, the organizational morphology of 70-80% ferrite and hard phase components such as bainite and martensite is obtained, the uniform elongation and toughness of the pipeline steel are improved, the yield strength ratio is low, and the deformation resistance and anti-large-deformation capacity are improved. The X70 anti-large-deformation pipeline steel plate has a Charpy impact toughness of 350 J or more at-20 DEG C, a drop hammer shearing area of 95% or more, a yield strength of 480-550 MPa, a tensile strength of 600-680 MPa, a yield strength ratio of 0.78 or less, a UEL of 12% or more, and a R t1.5 / R t0.5 of 1.15 or more. The product is widely applied to pipeline engineering prone to large plastic deformation such as ground slip deformation in earthquake-prone areas, ground liquefaction settlement caused by permafrost and submarine pipeline laying.

To provide a welded joint which has excellent low-temperature toughness, is suppressed in stress corrosion cracking caused by liquefied ammonia, and has 490 MPa or more of tensile strength, and a method for manufacturing the welded joint.SOLUTION: A welded joint has a base metal, a weld metal, and a welding heat affected zone. In the welded joint, each of the base metal and the weld metal has a chemical composition of a specific range, the area fraction of bainite structure from 1 / 4 thickness to 3 / 4 thickness in the sheet thickness direction from the surface of the base metal is 90% or more, Vickers hardness at the 1 mm position in the sheet thickness direction from the surface of the base metal is 210 or less, Vickers hardness in the welding heat affected zone is 210 or less, Vickers hardness in the weld metal is HVW or less (HVW=260-200×Ni), the tensile strength of the base metal and the welded joint is 490 MPa or more, and the absorption energy of the base metal and the weld metal in Charpy impact test is 47 J or more at -40°C.SELECTED DRAWING: None

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2160MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod, after high-carbon components containing trace Nb are rolled and spun into a wire rod, the wire rod is subjected to online molten salt micro-quenching isothermal treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and enters a bainite phase region from an austenite state, part of the austenite is promoted to be converted into bainite, and then the high-strength complex-phase hot-rolled wire rod is obtained. The method comprises the following steps: carrying out high-temperature tempering on the residual austenite, carrying out post-section molten salt treatment, increasing the molten salt temperature, promoting the unconverted residual austenite to be decomposed and converted into sorbite, carrying out isothermal tempering, and finally carrying out roller way slow cooling to prepare the hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered bainite, ferrite and tempered sorbite, so that network carbides and martensite structures can be inhibited, and the tensile strength of the hot-rolled wire rod is improved. And the structure type and toughness are regulated and controlled on line, the tensile strength is 1472-1505MPa, the percentage reduction of area is 31%-36%, the work hardening rate and the production efficiency of the hot-rolled wire rod are improved, and the production energy consumption is reduced, so that a high-strength grade stranded wire is obtained.

The present invention relates to the technical field of ferrous metallurgy, and in particular to an S420-grade marine steel and a production method therefor. The S420-grade marine steel comprises the following chemical components in mass percent: C: 0.05%-0.09%, Si: 0.10%-0.30%, Mn: 1.30%-1.60%, P: ≤0.015%, S: ≤0.003%, Nb: 0.020-0.040%, V: 0.020-0.050%, Ti: 0.008-0.030%, Cr: 0.10-0.30%, Ni: 0.10%-0.30%, Mo: 0.10-0.20%, Cu: ≤0.0:50%, Al: 0.020%-0.050%, B: ≤0.00050%, Ca: 0.0006%-0.0030%, N≤0.0050%, H≤0.0002%, and the balance Fe and inevitable impurities. The present invention uses the design of low-carbon combined fine grained strengthened alloy and the technology of clean steel smelting combined with heavy reduction casting to improve the core structure of casting billets, and uses a controlled rolling and controlled cooling process to achieve a structural form dominated by bainite, satisfying product requirements for welding, impact at -40 degree and CTOD performance.

Provided is a hot-rolled steel sheet by which excellent LME resistance can be achieved. A hot-rolled steel sheet according to the present disclosure contains, in terms of mass%, 0.030-0.110% C, 0.01-0.50% Si, 0.50-1.50% Mn, 0.025% or less P, 0.010% or less S, 0.010-0.070% Al, 0.0070% or less N, 0.055-0.200% Ti, 0.030-0.150% Nb, 0.0010-0.0050% B, 0-0.20% V, and 0-1.00% Cr, with the remainder consisting of Fe and impurities. The area ratio of bainitic ferrite is 85% or greater, and in a surface layer region from the surface of the hot-rolled steel sheet to a depth position of 0.2 mm in the sheet thickness direction, the total length of the prior austenite grain boundary in which BO2 - is detected by time-of-flight secondary ion mass spectrometry is 1.20-5.00 mm per 100 μm × 100 μm, and the B segregation degree at the prior austenite grain boundary is 40 or greater.

The invention belongs to the technical field of metal material heat treatment, and particularly relates to warm-rolled medium manganese steel with excellent low-temperature obdurability and a preparation method thereof.The preparation method comprises the following steps that S1, a cast ingot is obtained, and the cast ingot is subjected to homogenizing annealing to obtain an annealed cast ingot; s2, the annealed cast ingot is subjected to rough hot rolling and water cooling to the room temperature, and then a rough hot-rolled plate is obtained; s3, the rough hot-rolled plate is subjected to ferrite area warm rolling and air cooling to the room temperature, and then a warm-rolled plate is obtained; s4, bainite area tempering is conducted on the warm-rolled plate, a tempered warm-rolled plate is obtained, and the cooling mode of bainite area tempering is air cooling; and S5, the tempered warm-rolled plate is subjected to two-phase region annealing, warm-rolled medium manganese steel is obtained, and the cooling mode of two-phase region annealing is air cooling. The warm-rolled medium manganese steel with excellent low-temperature strength and toughness is prepared by adopting a homogenizing annealing, rough hot rolling, ferrite zone warm rolling, bainite zone tempering and double-phase zone annealing coupling process, the problem that the low-temperature strength and toughness of the medium manganese steel are not matched is solved, and the application field of the warm-rolled medium manganese steel is widened.

Provided in the present invention are a hardness evaluation method and system for a heat affected zone of a multi-layer and multi-pass welded joint of hull steel. The method comprises: establishing a finite element model of a welded joint, and acquiring welding thermal cycles at nodes in a heat affected zone of the finite element model; performing solving to obtain critical temperatures for microstructural transformations of a study object, and performing solving to obtain volume fractions of transformation products during the thermal cycles, and a volume fraction of an austenite-ferrite-pearlite mixture after all the thermal cycles; acquiring hardness values of a martensite and a bainite in each thermal cycle, and a hardness value of the austenite-ferrite-pearlite mixture after all the thermal cycles; and on the basis of the acquired hardness values of the martensite and the bainite in each thermal cycle, and the the acquired hardness value of the austenite-ferrite-pearlite mixture after all the thermal cycles, acquiring a comprehensive hardness value of the heat affected zone. The present invention can accurately reproduce heat conduction and a microstructure transformation process in a heat affected zone during multi-layer and multi-pass welding of full steel, thereby assisting engineers in evaluating a welding temperature field and the structure distribution of the heat affected zone.

The application provides a ferrite bainite steel and a preparation method thereof, and belongs to the field of steel preparation. The chemical composition of the ferrite bainite steel includes, in mass fraction, C: 0.18% to 0.22%, Si: 1.3% to 1.8%, Mn: 2.0% to 2.5%, P: less than or equal to 0.01%, S: less than or equal to 0.01%, N: less than or equal to 0.004%, and the balance of Fe and inevitable impurities. The metallographic structure of the ferrite bainite steel includes, in volume fraction, ferrite bainite: 50% to 65%, tempered martensite: 25% to 30%, MA island: 1% to 3%, and residual austenite: 7% to 10%. By reducing the coarse MA island and unstable blocky residual austenite, the crack initiation source is avoided, and the technical problems of poor hole expansion and elongation of the ferrite bainite steel in the prior art are solved.

The invention relates to a high-strength and high-toughness Q490DRL2 steel plate for a spherical tank and a production method thereof, and belongs to the field of metallurgy. The steel plate has a low-carbon bainite structure and comprises the following elements: 0.05%-0.09% of C, 0.15%-0.40% of Si, 1.20%-1.60% of Mn, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.30%-0.60% of Ni, less than or equal to 0.30% of Cr, less than or equal to 0.30% of Mo, less than or equal to 0.05% of Nb, 0.02%-0.06% of V, 0.020%-0.40% of Al, less than or equal to 0.030% of Ti, less than or equal to 0.002% of B, 0.0002%-0.003% of Ca, less than or equal to 0.19% of Pcm and the balance of Fe and inevitable impurities. The production thickness of the steel plate ranges from 10 mm to 60 mm, the yield strength ReL is larger than or equal to 490 MPa, the tensile strength Rm is larger than or equal to 610 MPa and smaller than or equal to 730 MPa, and the ductility A is larger than or equal to 17%. The low-temperature impact performance is as follows: the impact absorption energy at 1 / 4 and 1 / 2 of the thickness at-50 DEG C is more than or equal And the nil-ductility transition (NDT) temperature is lower than-50 DEG C.

The invention discloses a method for preparing bainite steel through multi-element microalloying, and belongs to the technical field of advanced steel and iron materials. The method comprises the following steps that a forged steel ingot is subjected to first austenitizing and cooling treatment, and a martensite matrix is obtained; and then secondary phase precipitation treatment, secondary austenitizing treatment and cooling are sequentially carried out, and the bainite steel is prepared. According to the invention, an innovative heat treatment process path of martensite initial structure-medium-temperature second phase precipitation-short-time austenitizing-salt bath isothermal bainite transformation is constructed, and the synergistic effect of microalloy elements such as V, Nb, Ti and B is combined, so that the heat treatment process has the advantages that the heat treatment efficiency is greatly improved on the premise of not depending on precious alloy elements such as Cr and Ni; and the superfine bainite steel which is uniform in structure and excellent in comprehensive performance is successfully prepared.