414 results about "Martensite" patented technology

The application discloses a kind of thick gauge 430 ferritic stainless steel laser weld low-temperature rollability processing method, comprising: using-1~‑2mm negative defocusing+8~10kW low-power laser welding, the grain of heat-affected zone is refined;NiCr-3 welding wire is preheated to 300~400℃ and carried out hot wire laser welding, reduces cooling rate;Weld is implemented 700 DEG C / 10-12 seconds short time induction annealing, decomposes martensite and releases residual stress;Weld is inducted to ≥50 DEG C before rolling and restores plasticity;Optimize five rack continuous rolling parameter, and the reduction of first rack is reduced to 15%-20%.The application is by welding-heat treatment-rolling whole process synergic control, makes weld low-temperature cracking rate from 2.6 times / month reduce to 1 times below, and-10 DEG C impact toughness is promoted to 22J, cup convexity qualification rate reaches 95%, and annual economic benefit is greatly improved, applicable to the thickness 3.0~8.0mm 430 stainless steel cold rolling production, solves the technical problem that thick gauge 430 stainless steel weld is easy to crack under low-temperature environment.

The invention belongs to the technical field of research and development of fast neutron reactor jackets and structural materials, and particularly relates to a high-temperature-lead-bismuth-corrosion-resistant high-silicon-content ferrite / martensite steel ladle tube and a preparation method thereof. According to the mass percentage, the composition mainly comprises the following components: 0.16-0.24% of C; 0.4 to 0.8 percent of Mn; cr: 11.6% to 12.4%; 1.2 to 1.8 percent of W; 0.1 to 0.4 percent of Ta; 0.2 to 0.4 percent of V; 1.0%-1.8% of Si and Fe. The preparation method comprises the steps of vacuum induction and vacuum arc remelting. Carrying out homogenization treatment and forging; extruding and annealing; cold rolling and annealing; and performing normalizing and tempering treatment. Through an efficient short-flow process route and reasonable smelting, pipe machining deformation and heat treatment processes, the microscopic structure of the material is remarkably improved, then the mechanical property and high-temperature lead and bismuth corrosion resistance of the finished pipe are improved, and the use requirement of the lead and bismuth cooling fast reactor fuel assembly cladding material under the high-temperature working condition is met.

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.

The invention discloses an ultrahigh-strength maraging steel wire as well as a preparation method and application thereof, and belongs to the field of steel product manufacturing. The steel wire alloy comprises the following components in percentage by weight: 0.02%-0.05% of C, 0.10%-0.35% of Si, 0.20%-0.60% of Mn, 0.60%-2.50% of Cr, 18.5%-22.0% of Ni, 8.0%-13.0% of Co, 1.2%-2.0% of Ti, 3.0%-5.5% of Mo, 0.10%-0.50% of Al, less than or equal to 1.50% of Cu, less than or equal to 1.50% of Nb, less than or equal to 0.05% of V, less than or equal to 0.04% of N, less than or equal to 0.02% of La + Ce and the balance of Fe and inevitable impurity elements. And the equivalence ratio Nieq / Creq of nickel to chromium is greater than or equal to 1.80. The steel wire provided by the invention has ultrahigh strength, excellent toughness and plasticity, wear resistance, heat resistance, drawing performance and bending and twisting performance.

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 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%.

The invention discloses a laser powder bed molten high-strength, high-plasticity and high-work-hardening titanium alloy and a preparation method and application thereof.The preparation method comprises the steps that two kinds of titanium alloy powder with different Mo equivalents are mixed according to a certain mass ratio to form mixed powder, and the mixed powder is put into laser powder bed melting equipment; the titanium alloy is finally obtained through layer-by-layer forming by laser powder bed melting equipment according to a slicing path and process parameters of a three-dimensional model, the microstructure of the prepared titanium alloy comprises hexagonal martensite alpha 'and orthorhombic martensite alpha', and in a preferable scheme, under the condition that heat treatment is not needed, the yield strength of the titanium alloy is larger than or equal to 950 MPa, the tensile strength is larger than or equal to 1250 MPa, and the tensile strength is larger than or equal to 1250 MPa. The alloy has the advantages of high strength, high plasticity and excellent work hardening capacity, can meet the requirements of forming and high mechanical properties of titanium alloy components in complex shapes, and is especially suitable for the fields of aerospace, automobiles, weapon armors, ships, oceans and the like, and the ductility is greater than or equal to 14%, and the work hardening capacity is greater than or equal to 250 MPa.

A transducer for determining a pressure of a hydrogen-containing fluid medium confined in a first space includes a pressure side end configured to be disposed facing the fluid medium. The transducer includes a housing, which defines a second space, and a measuring arrangement disposed in the second space. The pressure side end includes a diaphragm configured and disposed for hermetically separating the first space from the second space. The diaphragm includes a metallic material that is made of a high-alloy martensite.

The invention discloses a manufacturing process and equipment of a high-performance long-service-life cold working die. The process comprises the following steps: quenching and tempering a cold-work die steel blank to obtain a tempered martensite structure; plasma nitrocarburizing is carried out to form a reinforced diffusion layer; the micro-pit array is machined through pulse laser, and an annular heat-affected softening zone is formed around the opening of the pit; depositing a hard coating, and forming a cantilever structure on the edge of the micro pit; wherein plasma nitrocarburizing is carried out in a low-pressure plasma atmosphere, laser processing and coating deposition are carried out in a vacuum or protective atmosphere, and transfer among the steps is not exposed to the atmosphere. The invention further provides corresponding manufacturing equipment which comprises a heat treatment cavity, a plasma nitrocarburizing cavity, a surface micro-texture machining cavity, a coating deposition cavity and a vacuum transfer cavity. According to the invention, the hardness mutation between the coating and the matrix is relieved, a hardness gradient transition structure is constructed, the fatigue stripping resistance of the coating is obviously improved, and the service life of a mold is prolonged.

The invention relates to the technical field of coating preparation, in particular to a high-entropy alloy corrosion-resistant coating based on machine learning optimization and a preparation method thereof.The preparation method comprises the steps that a preparation data set of the high-entropy alloy coating is constructed, and coating element components, technological parameters and corrosion environment parameters in the preparation data set serve as input characteristics; taking the thickness, the hardness and the elastic modulus of the corrosion layer as output characteristics, training an artificial neural network model, and establishing a performance prediction model; a multi-objective particle swarm optimization algorithm is adopted, and magnetron sputtering process parameters are optimized and solved by taking the minimum thickness of a corrosion layer and the maximum hardness and elasticity modulus as optimization objectives; according to the optimal process parameter combination, preparing an AlCrFeMoTi high-entropy alloy coating on a ferrite / martensitic steel matrix by adopting a magnetron sputtering five-target co-deposition technology; and carrying out corrosion resistance test on the prepared coating, and comparing a test result with a predicted value of the model to verify the accuracy of the model.

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.

The invention relates to special-corrosion-resistant martensitic heat-resistant steel and a preparation method thereof, belongs to the technical field of nuclear heat-resistant steel, and solves the problems of poor oxidation corrosion resistance, low strength and poor impact toughness and plasticity of ferrite / martensitic steel in high-temperature liquid lead bismuth in the prior art. The heat-resistant steel comprises the following chemical components in percentage by mass: 0.10-0.13% of C; 0.9 to 1.4 percent of Si; mn: 0.5 to 0.7%; 8.5 to 9.0 percent of Cr; 0.4 to 0.6 percent of W; 0.7 to 0.8 percent of Mo; 0.25 to 0.40 percent of Ni; 0.15% to 0.20% of V; 0.05 to 0.07 percent of Nb; the content of N is 0.045 to 0.065 percent; compared with the prior art, the heat-resistant steel disclosed by the invention has the advantages that a compact Si-rich oxide layer is ensured to exist in the heat-resistant steel by increasing the content of Si, so that the high-temperature liquid lead / lead bismuth corrosion resistance of the material is improved; by adjusting the content of Mn, Cr, Ni, W, Mo and other elements, it is ensured that the material has a single martensite structure, the heat-resistant steel has good room-temperature and high-temperature mechanical properties at the same time, and the heat-resistant steel is suitable for lead-cooled fast reactor structural materials.

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.

The utility model relates to the technical field of air valve steel, and discloses a martensite air valve steel coil annealing ladle shape improving device which comprises an annealing furnace and a furnace cover arranged at the top of the annealing furnace, the martensite air valve steel coil annealing ladle shape improving device is provided with a supporting assembly, so that coiled coils can be conveniently and orderly placed, uneven heating and cooling caused by stacking are avoided, and the production efficiency is improved. Layered placement of a plurality of wire rods is facilitated through the first supporting disc, the connecting column, the second supporting disc, the fixing column, the supporting sleeve and the like, gaps are reserved between the wire rods, heat transfer is promoted, the first supporting disc and the second supporting disc drive the wire rods to rotate in the annealing furnace, the uniform heating effect is improved, and production efficiency is improved. By arranging the cooling assembly, cold air can be conveniently conveyed into the annealing furnace, cooling liquid circularly flows in the circulating pipe for refrigeration, cold air conveying is achieved through the first draught fan, the air supply pipe, the connecting pipe and the like, and under the rotation effect, uniform cooling is promoted, and the situation that the annealing ladle shape of a wire rod is poor is improved.

The application relates to a high-temperature high-strength plastic ferrite martensite steel and a preparation method thereof, the preparation method comprises the following steps: (1) obtaining original ferrite martensite steel through heat treatment of a steel ingot; (2) performing cold plastic deformation processing on the original ferrite martensite steel obtained in the step (1) at a temperature of not higher than 50 DEG C to obtain nanocrystalline or ultrafine-grain ferrite martensite steel; and (3) performing annealing treatment on the nanocrystalline or ultrafine-grain ferrite martensite steel obtained in the step (2) to obtain high-temperature high-strength plastic ferrite martensite steel. The ferrite martensite steel prepared by the application can have high strength and plasticity at a high temperature of 550 DEG C, so that the application prospect of the ferrite martensite steel in engineering application is further improved.

The invention discloses a martensite reinforced self-lubricating copper-based alloy coating and a laser cladding preparation method thereof, the martensite reinforced self-lubricating copper-based alloy coating comprises the following components in percentage by mass: 66 to 84 weight percent of Cu, 10 to 20 weight percent of Al, 3 to 10 weight percent of Ni, 3 to 10 weight percent of Mn, 0 to 2 weight percent of Sn and 0 to 2 weight percent of Pb. In the preparation process, the laser input energy density is controlled within the range of 8.96-13.27 J / mm, and the double strengthening effects of grain refinement and martensite content increase can be synchronously achieved. The main phase structure of the obtained coating is twin-crystal martensite, meanwhile, the coating contains a small amount of alpha-Cu lubricating phase, gamma phase and Fe-rich hard phase, and the dry friction coefficient of the coating is 1t; 0.35, and the solidification hardness gt; and the voltage is 350HV. Compared with the existing self-lubricating tin-based babbitt metal and copper-tin alloy with similar friction coefficients, the coating disclosed by the invention realizes synergistic improvement of high hardness and low friction performance, and is particularly suitable for dynamic friction and wear working conditions with higher impact resistance requirements, such as robot motion joints, precision mechanical transmission parts and the like.

The invention discloses a preparation method of a high-strength austenitic stainless steel band. The method comprises the following steps: firstly, controlling the contents of chromium, nickel, manganese, nitrogen and microalloying elements through alloy design; then the continuous casting sheet billet is subjected to soaking and two-stage hot rolling containing a specific temperature interval; immediately carrying out on-line solid solution and rapid quenching on the strip after hot rolling; then, the strip is cooled to a low-temperature interval to be subjected to large-deformation deep cooling warm rolling; and finally, relaxation annealing is conducted on the strip obtained after cryogenic warm rolling, nano carbonitride is induced to be separated out, and leveling and stabilizing heat treatment is conducted. According to the method, through a multi-step linkage process of hot rolling structure genetic control, online rapid solid solution freezing, introduction of nano defects through cryogenic warm rolling and relaxation annealing synergistic precipitation, on the premise that deformed martensite is not induced, a microstructure jointly strengthened by high-density dislocation, nano twin crystals and dispersed nano precipitated phases is constructed in an austenite matrix. The yield strength of the prepared stainless steel band is greatly improved.

A light high-entropy steel base material with the T0 temperature lower than the room temperature is selected, heat preservation is carried out for 4 hours at the temperature of 1100 DEG C, homogenizing annealing is carried out, then water quenching is carried out after the temperature is kept for 40 minutes at the temperature of 1100 DEG C, a structure containing BCC and FCC double phases is obtained, and at the room temperature, the T0 temperature of the light high-entropy steel base material is kept at the constant temperature of 1100 DEG C for 40 minutes, and the T0 temperature of the light high-entropy steel base material is kept at the constant temperature of 1100 DEG C for 40 minutes. And performing ultrasonic rolling treatment on the surface of the sample. The method has the advantages that BCC-to-FCC martensite inverse phase transformation can be induced on the surface layer of a workpiece, the magnetic domain of the surface layer basically disappears, the strength and plasticity are synchronously improved, and the method can be widely applied to the fields of electrical equipment, MRI devices, nuclear submarine shells, aerospace, automobile key components and the like.

The invention discloses a shape memory alloy phononic crystal interlayer unit and an array interlayer structure, and the shape memory alloy phononic crystal interlayer unit comprises a crystal cavity formed by an upper substrate, a lower substrate and rib plates, and a shape memory alloy phononic crystal installed in the crystal cavity; the shape memory alloy photonic crystal comprises a coating body, a scatterer and a plurality of Ni-Ti shape memory alloy particles, the Ni-Ti shape memory alloy particles comprise three different transformation forms of an austenite shape Ni-Ti shape memory alloy, an I-type martensite shape Ni-Ti shape memory alloy and an II-type martensite shape Ni-Ti shape memory alloy. According to the design of the shape memory alloy photonic crystal interlayer, a shape regulation band gap and a sound insulation curve can be changed through temperature control, and the temperature self-adaptive regulation performance can be promoted; and the sound insulation frequency band range of the sandwich structure can be widened, and the problems of light broadband self-adaptive sound insulation and the like are effectively solved.

A process for manufacturing compact coils of ultra-fine grained martensite-free steel bars, the process comprising the following phases: a) rolling a billet by means of a roughing mill (1) of the steel bar; b) performing at least one first cooling stage (2) so that the steel bar has a surface temperature higher than the martensite start temperature (Ms) and at least one first equalization stage in air; c) rolling the steel bar by means of at least one intermediate mill (3); d) performing at least one second cooling stage (4) always keeping the surface temperature higher than the martensite start temperature (Ms) and at least one second equalization stage in air; e) rolling the steel bar by means of a finishing mill (5) in the non-recrystallization temperature range, keeping the entire cross section of the steel bar in said non-recrystallization temperature range and wherein the total reduction is between 25% and 50% with respect to the cross section of the steel bar at the inlet of the finishing mill, so as to obtain an ultra-fine grained austenitic matrix; f) winding the steel bar into compact coils by means of at least one winding device (7) so that the ultra-fine grained austenitic matrix transforms into a mixture of ferrite and pearlite. After the winding operation is completed, the compact coils can be conveyed to a storage area by means of a conveying device (8), for example a walking beam, in which the coils are subjected to natural cooling or forced cooling or delayed cooling.

The application relates to the field of ultra-high-strength steel and processing technology, and discloses an ultra-high-strength martensite steel plate and a preparation method thereof, which comprises the following steps: proportioning alloys according to predetermined mass percentage contents, melting the proportioned alloys and casting ingots, uniformly treating the ingots, high-temperature forging the uniformly treated ingots to obtain slabs, high-temperature hot-rolling the slabs, water-cooling the hot-rolled slabs to room temperature to obtain first semi-finished plate materials, continuously and symmetrically warm-rolling the first semi-finished plate materials through multi-pass large deformation to obtain second semi-finished plate materials, continuously and asymmetrically warm-rolling the second semi-finished plate materials through multi-pass large deformation to obtain third semi-finished plate materials, and quenching the third semi-finished plate materials to room temperature to obtain the ultra-high-strength martensite steel plate. The prepared martensite steel plate has high hardness, high strength and high plasticity, and has the advantages of low cost, resource saving and excellent performance.

This invention discloses a method and system for predicting the creep fatigue behavior of martensitic heat-resistant steel, relating to the field of high-temperature creep fatigue performance evaluation technology. The method includes: acquiring the microstructure evolution of copper-containing martensitic heat-resistant steel during the test process, obtaining the cyclic strength change rate based on the microstructure evolution, and calculating the creep rate of the copper-containing martensitic heat-resistant steel in the dislocation climb hard phase, as well as the dislocation density under cyclic loading conditions; based on the cyclic strength change rate, creep rate, and dislocation density, obtaining the elastic strain tensor, plastic strain tensor, and creep strain tensor of the copper-containing martensitic heat-resistant steel, and predicting the stress-strain evolution of the copper-containing martensitic heat-resistant steel under cyclic loading conditions based on the elastic modulus tensor; this invention overcomes the limitations of macroscopic creep fatigue behavior prediction methods and provides a new approach to revealing the influence of microstructure on creep fatigue performance.

A steel sheet including: a chemical composition containing, by mass %, C: 0.12-0.40%, Si: 1.5% or less, Mn: more than 1.7% and 3.5% or less, P: 0.05% or less, S: 0.010% or less, sol. Al: 1.00% or less, N: 0.010% or less, Ti: 0.002-0.080%, and B: 0.0002-0.0050%, with the balance being Fe and inevitable impurities; a metallic structure in which an area ratio of martensite to an entire microstructure is 85% or more, and a ratio LS / LB satisfies a predetermined formula (1), where LS denotes a length of a sub-block boundary and LB denotes a length of a block boundary; and a tensile strength of 1310 MPa or more.

The invention belongs to the field of steel for automobiles, and particularly relates to low-yield-ratio 1180MPa-grade cold-rolled martensitic steel for automobiles and a preparation method. The steel comprises the following components in percentage by weight: 0.145%-0.175% of C, 0.20%-0.45% of Si, 1.75%-2.00% of Mn, less than or equal to 0.020% of P, less than or equal to 0.0050% of S, 0.08%-0.12% of Al, less than or equal to 0.0050% of N, 0.005%-0.008% of B, 0.03%-0.04% of Nb and the balance of Fe and other inevitable impurities. Through brand new matching design of component design and a heat treatment process, martensite serves as a matrix, a small amount of ferritic structures are introduced, the performance characteristic of the low yield ratio is successfully achieved, and the forming capacity of the 1180MPa-grade martensitic steel in the application process is effectively improved.

The application provides a 500MPa-grade low-yield-ratio high-corrosion-resistance hot-dip galvanized low-density steel and a manufacturing method, and the steel plate composition is as follows in percentage by weight: C: 0.065%-0.073%, Si: 0.42%-0.54%, Mn: 1.51%-1.62%, Al: 3.3%-6.5%, P: <=0.010%, S: 0.01-0.03%, RE: 0.01%-0.015%, and the balance is Fe and inevitable impurities. The manufacturing method of the steel comprises the following steps: blast furnace molten iron pretreatment, converter steelmaking, continuous casting, hot continuous rolling, pickling, cold rolling, hot-dip galvanizing; and the steel organization structure is as follows: delta-ferrite + martensite + residual austenite + sulfide, wherein the martensite content is 5.2%-7.0%, the residual austenite content is 3.5%-3.8%, and the sulfide composition is a small amount of dispersedly distributed MnS and RE-S-O, a small amount of MnS is dispersedly precipitated in ferrite and martensite, and RE-S-O is distributed along the ferrite grain boundary.

The application belongs to the technical field of heat treatment of bearing steel, and particularly discloses a heat treatment method for improving the organization stability of high-nitrogen stainless bearing steel, which comprises the following steps: firstly, high-temperature diffusion annealing is performed to reduce the segregation degree; then, forging is performed after heat preservation at 1140-1160 DEG C for 1-2 hours; and subsequently, normalizing, spheroidizing annealing, quenching, deep cooling, partitioning and tempering are sequentially performed after the forging. Through reasonable design of the heat treatment process, the problems of low impact toughness, too many residual austenite and poor stability of the high-nitrogen stainless bearing steel are effectively solved by the sequential partitioning and tempering, and the high-nitrogen martensitic stainless bearing steel with high strength and toughness and impact resistance is prepared.

A method for manufacturing a wave gear device comprises: a hot forming step of hot forming an alloy steel composed of nickel, copper, molybdenum, and silicon into a first molded product having a silk hat-type housing shape at a first temperature of 950 to 1300°C; a normalizing step of isolating the first molded product at the first temperature for a predetermined time and, after the isolating time has elapsed, slowly cooling the first molded product to a second temperature of 750 to 900°C; an austempering step of isolating the first molded product at the second temperature and then cooling it to a third temperature of 250 to 400°C to form residual austenite in the first molded product; a heat treatment step of isolating the first molded product that has undergone the austempering step at the third temperature and then cooling it at room temperature to stabilize the microstructure of the first molded product; and a gear forming step of turning and toothing the first molded product that has undergone the heat treatment step to form a second molded product having a soluble external gear shape. The method comprises a step and a trip step of applying impact to the surface of the second molded product to induce a processing-induced transformation in some of the austenite remaining in the second molded product, thereby transforming the surface of the second molded product into martensite.

The invention discloses a high-strength bolt, a steel material and a preparation method of the high-strength bolt, and relates to the technical field of alloy smelting, and the high-strength bolt is characterized by comprising the following components in percentage by mass: 0.18%-0.22% of C, 0.08%-0.12% of Nb, 0.02%-0.05% of Al, 0.004%-0.02% of Ti, 0.05%-0.08% of V, 0.0001%-0.002% of S, 0.00%-0.05% of Cu, 0.70%-0.90% of Mn, 0.20%-0.30% of Si, 0.90%-1.10% of Cr, 0.30%-0.50% of Ni, 0.15%-0.30% of Mo and the balance of Fe. The high-strength steel material has the advantages that the components of the high-strength steel material are optimized, an alloy structure composed of fine and uniform martensite, nanoscale precipitated phases and low internal stress is obtained, and the effects of improving the strength and the delayed fracture resistance are achieved.

A high-strength steel sheet has a tensile strength of 1180 MPa or more. The high-strength steel sheet has a component composition containing C: 0.090 mass % or more and 0.390 mass % or less, Si: 0.01 mass % or more and 2.00 mass % or less, Mn: 2.00 mass % or more and 4.00 mass % or less, P: 0.100 mass % or less, S: 0.0200 mass % or less, Al: 1.000 mass % or less, N: 0.0100 mass % or less, and O: 0.0100 mass % or less, with a remaining part consisting of Fe and inevitable impurities; and a microstructure. In the microstructure, an area ratio of martensite is 70% or more, an area ratio of ferrite is 10% or less, an area ratio of retained austenite is 10% or less, and a proportion of the number of martensite blocks in which metastable carbides are present to the number of martensite blocks is 2% or more.