902 results about "Austenite" patented technology

The invention relates to the technical field of medium manganese steel, in particular to high-strength and high-toughness medium manganese steel and a preparation method thereof.The preparation method is characterized by comprising the steps that S1, smelting is conducted through an electric furnace according to the chemical component ratio of the medium manganese steel, then refining is conducted through a ladle refining furnace, then vacuum degassing treatment is conducted through a vacuum circulation degassing method, and then continuous casting is conducted to form a plate blank with the thickness being 200-300 mm; s2, the plate blank is heated to 1150-1250 DEG C in a walking beam furnace, heat preservation is conducted for 2-4 hours, and then a controlled rolling technology is adopted to machine the plate blank into a steel plate within the range of 4-20 mm; s3, after rolling is completed, the steel plate is treated through a composite cooling technology of ultra-fast cooling and laminar cooling; s4, the cooled steel plate is heated to 750-850 DEG C, heat preservation is conducted for 10-60 minutes, and a ferrite and austenite double-phase structure is formed; the comprehensive performance is greatly improved, and excellent strength, plasticity, low-temperature toughness and welding adaptability are shown.

The invention provides corrosion-fatigue-resistant ultrahigh-strength maritime work steel and a preparation method thereof, and relates to the technical field of maritime work steel manufacturing. The maritime work steel comprises the following components in percentage by mass: 0.04 to 0.07 percent of C, 0.20 to 0.26 percent of Si, 1.45 to 1.60 percent of Mn, less than or equal to 0.01 percent of P, less than or equal to 0.015 percent of S, 1.44 to 1.52 percent of Cr, 1.44 to 1.52 percent of Ni, 0.88 to 0.96 percent of Cu, 0.08 to 0.12 percent of Nb, 0.08 to 0.12 percent of Sb and the balance of Fe and inevitable impurities. The corrosion-fatigue-resistant ultrahigh-strength maritime work steel is prepared through raw material smelting and casting, austenitizing heat treatment, multi-pass hot rolling and cooling and temperature control. The corrosion resistance, the fatigue resistance and the corrosion fatigue resistance of the ultrahigh-strength maritime work steel are remarkably improved while the mechanical property of the ultrahigh-strength maritime work steel is improved, and the ultrahigh-strength maritime work steel has great significance in guaranteeing safe and stable operation of ocean engineering.

The application discloses a super-soft austenitic stainless steel and a preparation method thereof. The super-soft austenitic stainless steel is composed of carbon C, nitrogen N, silicon Si, manganese Mn, chromium Cr, nickel Ni, copper Cu and iron Fe. The mass percentage of each component in the super-soft austenitic stainless steel is as follows: C: 0.005%-0.02%, N: 0.05%-0.2%, Si: 0.01%-0.1%, Mn: 1.5%-6.5%, Cr: 15.5%-19.6%, Ni: 7.5%-13.5%, Cu: 1.8%-5.3%, and the balance is iron. The super-soft austenitic stainless steel has the characteristics of low tensile strength and hardness, low strain-induced martensite in the bending process, low crack initiation rate and low failure fracture.

This invention provides a high-strength, high-ductility austenitic stainless steel and its production method. The composition is: C 0.045%-0.085%, N 0.10%-0.40%, Si 0.90%-1.55%, Cr 16%-20.1%, Ni 7.5%-12.5%, Mn 1.5%-3.5%, Mo 1.5%-3.0%, Nb 0.08%-0.22%, Ti 0.015-0.065%, O≤0.005%, P≤0.003%, S≤0.003%, with the remainder being Fe and unavoidable impurities. Compared with existing technologies, this invention obtains a reasonable grain size and second-phase particles through nitrogen, titanium, and niobium alloying, combined with low-temperature rolling and appropriate annealing and aging heat treatment, thus developing an austenitic stainless steel with excellent mechanical properties. It achieves excellent ductility at a high strength level, with a strength-ductility product as high as 60 GPa·s.

The invention relates to the technical field of stainless steel production and manufacturing, and discloses a high-strength corrosion-resistant duplex stainless steel shaft forging method which comprises the steps of blank preparation, homogenization treatment, preheating treatment, multidirectional forging, interrupted cooling, solution treatment, aging treatment and surface finish machining. Uniformity of components in the blank and consistency of temperature distribution are guaranteed, a uniform microstructure basis is provided for subsequent forging, meanwhile, grains are refined through large deformation and multi-pass deformation in multi-directional forging, the strength and toughness of the shaft are improved, brittle phase formation is avoided, and the mechanical property is optimized; by interrupting cooling and solution treatment, controlling the cooling rate and heating parameters in real time, inhibiting harmful phase precipitation and optimizing the austenite-ferrite phase proportion, the shaft has high corrosion resistance, and by means of aging treatment, through a stable structure, the long-term durability of the shaft in a severe environment is guaranteed, and the corrosion weight loss and pitting corrosion risk are reduced.

The invention discloses a heat-treatment-free control method for inhibiting hydrogen-induced cracks in ultrahigh-strength steel welding, which belongs to the technical field of welding, and enables weld metal to obtain a low-phase-transition-temperature characteristic and a double-phase structure containing retained austenite under a specific dilution rate window by cooperatively regulating and controlling components of a welding material and welding process parameters. Therefore, preheating-free and post-heat-treatment-free efficient welding of the ultrahigh-strength steel is achieved. According to the method, the volume expansion effect generated by low-temperature martensite phase transformation of weld metal is utilized to actively counteract restrained tensile stress formed by welding cooling shrinkage; on the other hand, the effect of the retained austenite serving as an efficient'hydrogen trap 'is fully played, migration and enrichment of hydrogen to crack sensitive areas such as a heat affected zone or a fusion line are effectively blocked, and finally effective inhibition of hydrogen-induced cracks in ultrahigh-strength steel welding is achieved; the obtained welding joint is free of hydrogen-induced cracks and has the mechanical property level well matched with base metal.

The manufacturing method comprises the following steps: rolling and spinning high-carbon and high-silicon components of Nb-Mo to form a wire rod, and then carrying out online molten salt strong isothermal toughening treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and is rapidly cooled, and enters a sorbite phase region from an austenite state to form a structure taking a sorbite structure as a main structure; and then carrying out rear-section molten salt treatment, reducing the circulation volume of molten salt, promoting the unconverted retained austenite to be continuously converted into sorbite, carrying out isothermal tempering, promoting fusing of a part of sorbite lamellar layers, and finally carrying out slow cooling through a roller way, so as to prepare the hot-rolled wire rod of which the microscopic structure comprises a mixed structure consisting of tempered sorbite, ferrite and fused sorbite, according to the invention, abnormal tissues can be inhibited, the tensile strength is 1566-1616 MPa, the percentage reduction of area is 33%-38%, and the production efficiency is considered, so that the ultrahigh-strength stranded wire can be produced without off-line heat treatment, and the risk of wire breakage is reduced.

The invention provides low-cost low-alloy steel with the fracture toughness higher than 140 MPa.m < 1 / 2 > and the product of strength and elongation higher than 50 GPa% and a manufacturing method. The microstructure of the steel is as follows: 78-88% of martensite matrix, 10-20% of retained austenite, 1-3% of transition carbide and less than 1% of stable nano precipitated carbide. The steel comprises the following element components in percentage by mass: 0.60 to 0.70 percent of C, 1.25 to 1.75 percent of Mn, 1.25 to 1.75 percent of Si, 0.02 to 0.05 percent of Nb + V and the balance of iron. According to the manufacturing process, at least one time of normalizing treatment is carried out, and then a quenching-distribution-tempering (Q-P-T) heat treatment process is carried out. The mechanical property of the low-alloy steel is improved by designing a proper microstructure fraction, optimizing steel components and adjusting a heat treatment process, so that the fracture toughness of the low-alloy steel is higher than 140 MPa.m < 1 / 2 >, and the product of strength and elongation is higher than 50 GPa%.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a depth position of 1 / 4 from a surface in a sheet thickness direction, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value is 10.7 or more, an I value is 1.020 or more, a CS value is −8.0×105 to 8.0×105, a standard deviation of Mn concentrations is 0.60 mass % or less, a solute Cr concentration in an outermost layer region is 0.10 mass % or more, a number density of Cr oxides having a sphere equivalent radius of 0.1 μm or more at the surface is 1.0×104 pieces / cm2 or less.

The invention discloses a preparation method of a corrosion-resistant and impact-resistant high manganese steel wear-resistant lining plate, and relates to the technical field of wear-resistant materials, the preparation method comprises the following steps: S1, weighing raw materials according to the mass percentage; s2, raw material smelting; s3, rare earth purification is conducted, specifically, rare earth elements are added into the molten-state raw materials, and the molten-state raw materials are subjected to deoxidation and desulfurization treatment; s4, casting molding is conducted, the temperature from the bottom end of a casting to a riser is controlled to be decreased stage by stage, and directional solidification is achieved; s5, heat treatment is conducted, specifically, the casting is subjected to solution treatment and then subjected to water quenching to the room temperature; and S6, surface treatment is conducted, specifically, shot blasting treatment is adopted, surface oxide skin is removed, and a surface compressive stress layer is formed. The strength, hardness and high toughness of the high-manganese steel are guaranteed by controlling the content of carbon and manganese, meanwhile, single-phase austenite is obtained through solution treatment, the hardness is improved through carbon atom segregation through low-temperature aging, and the strength, hardness, toughness and corrosion resistance of the high-manganese steel lining plate are improved.

A preparation method for high-nitrogen austenitic stainless steel. The high-nitrogen austenitic stainless steel comprises the following chemical components in percentages by weight: carbon: ≤0.02%; silicon: 0.4-0.8%; manganese: 10.2-12.5%; chromium: 24.5-26.5%; nickel: 13.5-16.5%; molybdenum: 3.2-4.8%; nitrogen: 0.75-0.95%; phosphorus: ≤0.03%; sulfur: ≤0.0025%; vanadium: 0.016-0.022%; niobium: 0.026-0.034%; copper: 0.2-0.35%; aluminum: 0.01-0.02%; cerium: 0.015-0.025%; and the balance of iron and inevitable impurities. The preparation method comprises the steps of raw material charging, vacuum melting, refining, nitrogen-added alloying, deoxidation and desulfurization, casting, electroslag remelting, and secondary casting. The preparation is implemented by using the processes of smelting in a pressurized induction furnace and electroslag remelting under a protective atmosphere; and nitrogen is added by using a method in which a nitrogen alloy and pressurized nitrogen permeation are combined.

The invention relates to a hot-rolled wire rod for a 2300MPa-grade stranded wire and a manufacturing method of the hot-rolled wire rod, after high-Si and high-carbon components containing trace Nb are rolled and spun into a wire rod, the wire rod is subjected to online molten salt isothermal toughening treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and is rapidly cooled, and enters a sorbite phase region from an austenite state to form a structure taking a sorbite structure as a main structure; the method comprises the following steps: carrying out hot rolling on the austenite, carrying out post-section molten salt treatment, reducing the molten salt temperature and the molten salt circulation amount, promoting the unconverted retained austenite to be continuously converted into sorbite, carrying out isothermal tempering, promoting fusing of a part of sorbite lamellar layers, and finally carrying out roller way slow cooling to prepare a hot-rolled wire rod of which the microscopic structure comprises tempered sorbite, ferrite and fused sorbite. According to the invention, the cross-section shrinkage rate is 35%-40%, the mechanical property same-circle difference is less than or equal to 48MPa, and the material cost and the production efficiency are both considered, so that off-line heat treatment is not needed, and the efficient and stable production of the ultrahigh-strength stranded wire is promoted.

The invention provides a preparation method of ultrahigh-strength complex-phase medium manganese steel with yield strength not lower than 1.5 GPa, and relates to the technical field of medium manganese steel yield strength improvement. The method comprises the steps of forging stock preparation, austenite region hot rolling, primary two-phase region heating, primary cold rolling, secondary two-phase region heating, secondary cold rolling, linear cutting preparation of a stretching part and tempering treatment. The ultrahigh-strength complex-phase medium manganese steel with the yield strength not lower than 1.5 GPa is prepared through the heat treatment mode of two-phase region annealing, cold rolling, two-phase region annealing, cold rolling and tempering, the performance of the prepared medium manganese steel is controlled through different combination modes of temperature and rolling reduction, and therefore the production range is further expanded; the method is simple and easy to operate, environmentally friendly, low in cost, short in process, high in efficiency, wide in application range and beneficial to industrial large-scale production and popularization.

The invention belongs to the technical field of austenitic stainless steel pipes, and particularly relates to an austenitic stainless steel pipe for a heat exchanger and a preparation method and application thereof. The austenitic stainless steel pipe for the heat exchanger comprises the following components in percentage by mass: less than or equal to 0.03% of C, less than or equal to 0.75% of Si, 3-6% of Mn, less than or equal to 0.04% of P, less than or equal to 0.03% of S, 16-19% of Cr, 4-7% of Ni, 2-4% of Mo, 1-3% of Cu, 0.3-0.6% of Hf, 0.2-0.5% of Ti, 0.1-0.3% of Co and the balance of Fe and inevitable impurities. The austenitic stainless steel pipe for the heat exchanger has excellent mechanical performance and is resistant to chloride ions and microbial corrosion.

The invention relates to the technical field of steel rail shears, and discloses a heat treatment method of a multi-component alloy material for a movable steel rail shear tool, which comprises the following steps: sequentially carrying out solid solution pretreatment, spheroidizing annealing, austenitizing, nitrate bath quenching and tempering on a forge piece, the nitrate bath quenching condition comprises the steps that the austenitized forge piece is transferred into a first-section nitrate bath, the temperature interval of the first-section nitrate bath is Bs to Ms, the cooling gradient is 5-8 DEG C / min, then the austenitized forge piece is transferred into a second-section nitrate bath, the temperature interval of the second-section nitrate bath is Ms to Ms-(30-40) DEG C, the temperature gradient is 6-10 DEG C, and heat preservation is conducted for 8-15 min after each gradient is finished; according to the method, the impact toughness of the steel rail scissor tool under the condition of-40 DEG C can be remarkably improved, and the use reliability of the multi-element alloy material for the steel rail scissor tool in the alpine region is remarkably improved.

This invention relates to the field of metallic materials technology, and more particularly to a negative enthalpy duplex stainless steel material and its preparation method, which possesses high strength, high plasticity, and high corrosion resistance. The negative enthalpy duplex stainless steel material is Fe... a Cr b Ni c Mo d Mn e C f Si g Ti h Al i V j Wherein, a, b, c, d, e, f, g, h, i, and j correspond to the mass percentages of each element: a = 60-70 wt%, b = 15-20 wt%, c = 10-15 wt%, d = 0-5 wt%, e = 1-5 wt%, f = 0.015 wt%, g = 0-1 wt%, h = 0-3 wt%, i = 0-0.5 wt%, j = 0-0.5 wt%, and d, g, h, i, and j are not zero. This series of negative enthalpy duplex stainless steel materials all contain ferrite and austenite in their structure, and the microstructure and mechanical properties of the alloy can be controlled by adjusting the proportions of different metal elements. This series of negative enthalpy duplex stainless steel materials exhibits high strength and high ductility. Simultaneously, negative enthalpy duplex stainless steel materials exhibit excellent corrosion resistance.

This hot-rolled steel sheet has a desired chemical composition, in a microstructure at a position of ¼ from a surface in a sheet thickness direction, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value is 10.7 or more, an I value is 1.020 or more, a CS value is −8.0×105 to 8.0×105, a standard deviation of Mn concentrations is 0.60 mass % or less, at the surface, an area ratio of a region where a Ni concentration is 0.2 mass % or more is 10.0% or more, an area ratio of a region where an O concentration is 3.0 mass % or more is 3.0% to 50.0%, and a maximum value of sphere equivalent diameters of oxides is 5.00 μm or less, and a tensile strength is 980 MPa or more.

The invention provides a metal type flux-cored wire, a bimetal composite pipe for high-pressure hydrogen storage and transportation and a preparation method of the bimetal composite pipe. In the metal type flux-cored wire, a flux core comprises the following components in percentage by mass: 26%-34% of Cr powder, 12%-20% of Fe50Ni50 powder, 4.5%-9.5% of Fe20Mn80 powder, 1.0%-2.0% of Fe30Si70 powder, 0.20%-0.30% of CeN powder, 0.40%-0.50% of NbN powder, less than or equal to 0.1% of Re2O7 powder and the balance of Fe powder; the outer skin is a 314 austenitic stainless steel strip and comprises the following alloy components in percentage by mass: 24%-26% of Cr, 19%-21% of Ni, 1%-2% of Mn, 2%-3% of Si, 0.08%-0.10% of C, less than or equal to 0.0012% of S, less than or equal to 0.010% of P and the balance of Fe. The metal type flux-cored wire can be used for preparing a bimetal composite pipe used in a high-pressure or corrosive environment.

The invention relates to a hot-rolled wire rod for a 2330MPa-grade stranded wire and a manufacturing method of the hot-rolled wire rod, after the wire rod is formed by rolling and spinning Cr-V high-carbon and high-silicon components, the wire rod is subjected to online molten salt isothermal toughening treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and is rapidly cooled, and enters a sorbite phase region from an austenite state to form a structure taking a sorbite structure as a main structure; the method comprises the following steps: carrying out hot rolling on austenite, carrying out post-stage molten salt treatment, increasing the temperature of molten salt, reducing the circulation volume of molten salt, promoting unconverted retained austenite to be continuously converted into sorbite, carrying out isothermal tempering, promoting fusing of part of sorbite lamellas, and finally carrying out roller way slow cooling to prepare a hot-rolled wire rod with a microstructure comprising a mixed structure consisting of tempered sorbite, ferrite and fused sorbite, the material cost can be controlled, the tensile strength is 1558-1608 MPa, the percentage reduction of area is 34%-39%, the production efficiency and the energy consumption are both considered, off-line heat treatment is not needed, and efficient and stable production of the ultra-high-strength stranded wire is met.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a position of ¼ from a surface in a sheet thickness direction, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value is 10.7 or more, an I value is 1.020 or more, a CS value is −8.0×105 to 8.0×105, a standard deviation of Mn concentrations is 0.60 mass % or less, at the surface, a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.500 μm or more is 2.0×103 pieces / cm2 or less, and a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.005 μm to 0.050 μm is 1.0×105 pieces / cm2 or more.

The invention discloses a mechanical property treatment method, device and equipment for austenitic heat-resistant steel. The method comprises the following steps: determining mechanical property parameters and related factors of the austenitic heat-resistant steel in a target application scene; obtaining each value interval of each associated factor, and collecting the mechanical property measured value of the austenitic heat-resistant steel with the associated factor value in the value interval; constructing a mechanical property prediction model of the austenitic heat-resistant steel; determining a weight factor of each mechanical property parameter according to the target application scene, and weighting each mechanical property prediction value determined based on the mechanical property prediction model according to the weight factor to obtain a comprehensive mechanical property value; the comprehensive mechanical property values are clustered to obtain a clustering center, and at least two comprehensive mechanical property value intervals are determined according to the minimum performance threshold value of the target application scene and the center mechanical property value corresponding to the clustering center. According to the embodiment of the invention, the prediction precision and quality grading reliability of the comprehensive mechanical properties of the austenitic heat-resistant steel can be improved.

The invention discloses a cold-crack-resistant welding wire for thick-specification ultrahigh-strength steel and a welding method of the cold-crack-resistant welding wire, and belongs to the technical field of welding, a low-cost alloy system with Mn as a leading part and Cr as an auxiliary part is constructed, Mn is used for reducing the Ms point, the hardenability of Cr is improved, and the Ms point of weld metal is regulated and controlled to be in a low-temperature phase change interval of 100-150 DEG C; in the welding process, the inter-pass temperature is controlled to be higher than the Ms point all the time, all layers of welding beads are kept in the austenite state in the filling process, all the welding beads are uniformly cooled, low-temperature martensite phase transformation is synchronously generated, the situation that phase transformation of the welding beads which are firstly welded too early occurs, and consequently pressure stress relaxation is caused is avoided, and part of retained austenite is reserved is avoided. By means of the characteristics of a medium Mn alloy system, the common cold crack risk in thick plate high-restraint welding is effectively avoided, it is ensured that weld metal has the ultrahigh strength, meanwhile, the alloy cost is remarkably reduced, and therefore the technical bottleneck of thick ultrahigh-strength steel in the low-cost and efficient welding application aspect is broken through.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value that indicates periodicity of the microstructure is 10.7 or more, and an I value that indicates uniformity of the microstructure is 1.020 or more, a standard deviation of a Mn concentration is 0.60 mass % or less, and a tensile strength is 980 MPa or more.

The invention relates to a method for manufacturing a thermoformed steel sheet product, the method comprising the steps of: providing a steel sheet and creating a Si-rich surface layer on at least one surface of the steel sheet; cutting the steel sheet to obtain a coated steel blank; heating the steel blank to a temperature range between the austenitizing temperature of the steel and 950 DEG C; transferring the heated blank to a mold; thermoforming said heated blank in said mould, preferably in a temperature range of 600 DEG C to 830 DEG C, thereby obtaining a thermoformed steel sheet product; the heated product is cooled to a temperature below the Mf temperature of the steel.

This invention discloses a method for improving the wear and corrosion resistance of impact rollers, relating to the field of impact roller manufacturing technology. The method includes the following steps: S1: Milling the easily worn areas on the impact roller to form a filled area; S2: Filling the filled area with high-strength, wear-resistant martensitic stainless steel as the filler material, and performing laser cladding; S3: Processing the laser cladding position to match the profile of the impact roller; S4: Aging the processed roller at a temperature below the initial austenite transformation temperature (Ac1); S5: Grinding the surface of the aged impact roller until smooth. This invention can effectively improve the surface strength, hardness, and wear and corrosion resistance of impact rollers.

Method of manufacturing a steel strip comprising the steps of: - casting a molten steel into a slab; - reheating the slab at a temperature of 1150°C or more for a time of 1 hour or more; - hot rolling the steel into a strip, preferably using an average F1 slab entry temperature of more than 1000°C; - coiling the hot rolled steel strip; - batch annealing the steel strip: - at a temperature in the intercritical range (i.e. between Ac1 and Ac3), preferably less than 700°C; - in a non-oxidizing and non-nitrogenizing atmosphere; - for a total annealing time of at least 5 hours, preferably at least 10 hours so as to obtain: a Mn enrichment in austenite such that the Mn content is at least 1.25 times the overall Mn content of the steel; and a C enrichment such that the C content is at least 1.2 times the overall C content of the steel; - cooling the steel after batch annealing in air, forced air or water quenching.

This invention provides an engine valve and a method for manufacturing the same, which can suppress galvanic corrosion even when dissimilar metals are joined, and which exhibits excellent wear resistance and corrosion resistance, for use in engines that use CNG, LPG, or alcohol as fuel. [Solution] The engine valve 10 of the present invention is a joint member in which a shaft portion 14 made of martensitic heat-resistant steel SUH11 and a umbrella portion 12 made of austenitic heat-resistant steel SUH35 are joined. A nitride layer is formed only on the surface of the base material on the shaft portion 14 side from the joint portion 13 between the shaft portion 14 and the umbrella portion 12, leaving the surface of the base material exposed on the umbrella portion 12 side from the joint portion 13.

The invention discloses a production method for improving the structure uniformity of a 304 austenitic stainless steel medium-thickness plate, belongs to the field of stainless steel production, and solves the problem that mixed crystal structures often appear in the structure of the 304 austenitic stainless steel medium-thickness plate produced by an existing method. The method comprises the following steps: producing a 304 austenitic stainless steel continuous casting sheet billet; the plate blank is heated for the first time, the temperature of a heating furnace is set to be 1280-1300 DEG C, the heating time is 300-360 min, and natural cooling is conducted; the plate blank is remelted, heated and rolled again, the heating temperature is set to be 1250-1270 DEG C, the heating time is 240-300 min, and the remelted and reheated plate blank is rolled to the target thickness; and solution treatment is conducted, the solution treatment temperature ranges from 1050 DEG C to 1080 DEG C, the solution treatment time coefficient ranges from 1.0 min / mm to 2.0 min / mm, and water cooling is conducted to the room temperature. The structure uniformity of the 304 austenitic stainless steel medium plate produced by the method is obviously superior to that of a traditional method.

The invention belongs to the technical field of steel smelting, and relates to a method for improving low-temperature toughness of a surface layer and a core part of an EH47 steel plate with the thickness of 110mm. By adjusting the chemical components of the steel plate, the Ar3 phase transition temperature is increased to 735 DEG C or above, then a blank is rolled in an austenite single-phase region and an austenite and ferrite two-phase region, the rolling temperature of the last two passes of the steel plate is controlled within the range of Ar3-10 DEG C to Ar3-20 DEG C, and the rolling temperature of the last two passes of the steel plate is controlled within the range of 950 DEG C to 950 DEG C; deformation ferrite, equiaxed recrystallization ferrite and a small amount of refined pearlite clusters in a two-phase region are mainly arranged on the surface layer of the finished steel plate within 15 mm, the ballistic energy of the surface layer and the core of the steel plate at the temperature of-50 DEG C is larger than or equal to 180 J, and the yield strength of the steel plate with the thickness being 1 / 4 is larger than or equal to 470 MPa.

This invention relates to a 1900MPa grade ultra-high strength and toughness stainless gear steel and its preparation method. The chemical composition of the 1900MPa grade ultra-high strength and toughness stainless gear steel, by mass percentage, is: C 0.08-0.11%, Cr 10-12%, Ni 2-4%, Mo 2-5%, Co 10-13%, V 0.2-0.6%, Nb 0.02-0.05%, Al 0.5-1.0%, with the balance being Fe and unavoidable impurities. Its composition design must meet the following requirements: Chromium equivalent Cr... eq It is 17~18, with a nickel equivalent (Ni). eq The martensitic transformation point is 14-15. s The temperature range is 240~280℃. Its beneficial effects are: strengthening through the composite precipitation of intermetallic compounds NiAl and M₂C carbides, combined with Cr... eq Ni eq M s A synergistic design incorporating 5%–10% metastable austenite achieves an excellent balance between strength and toughness. The resulting steel exhibits tensile strength ≥1900 MPa, yield strength ≥1550 MPa, elongation ≥13%, fracture toughness ≥80 MPa·m¹ / ², and bending fatigue limit reaching 920 MPa. It is particularly suitable for manufacturing critical structural components requiring high load-bearing capacity and high reliability, such as aircraft engines, and has broad application prospects.