29 results about "Martensitic microstructure" patented technology

The present application belongs to the field of metal materials, and particularly relates to a high-temperature carburizing process method of gear steel quenched by different media. The present application develops the carburizing process of gear alloy carburizing steel by finite element simulation mode, and proposes a double-medium quenching process to improve the phase organization of the core of the sample, reduce the martensite content of the core, increase the bainite content, thereby reduce the hardness of the core, and further improve the toughness of the core of the sample, on the basis of ensuring the control of production cost, without increasing the process flow and improving the use performance. The carburized surface is still martensite organization, and the high hardness of the surface layer is maintained.

The application discloses a high-strength dual-phase steel with excellent low-temperature toughness and corrosion resistance and a production method thereof, and belongs to the technical field of steel rolling production. The chemical composition and mass content of the dual-phase steel are as follows: C: 0.06-0.12%, Si: 0.15-0.4%, Mn: 1.8-2.5%, Cr: 0.3-0.6%, Nb: 0.015-0.03%, Mo: 0.20-0.25%, Cu: 0.2-0.4%, Ni: 0.3-0.8%, Ti: 0.008-0.018%, N: 0.0030% or less, P: 0.025% or less, S: 0.002% or less, and the balance of Fe and inevitable impurity elements. The production method comprises a slab heating, rolling and continuous annealing process. The obtained dual-phase steel has uniform ferrite and martensite structures, good strength and toughness matching, and excellent low-temperature toughness and corrosion resistance.

This disclosure provides an electrolytic corrosion method for martensitic structures in FeMnSi alloys, relating to the field of materials processing technology. The method includes: pretreatment operations such as grinding and polishing the FeMnSi alloy; mixing sodium hydroxide, sulfuric acid, and water to obtain an electrolyte for electrolytic corrosion; placing the pretreated FeMnSi alloy as the anode and a stainless steel plate as the cathode in an electrolytic cell containing the electrolyte to perform the electrolytic corrosion process; after the electrolytic corrosion process, removing the FeMnSi alloy, cleaning, and drying it. This disclosure can obtain a well-defined microstructure, meeting the needs of microscopic observation and analysis.

The application discloses a TMCP preparation method of a low-carbon equivalent high-strength steel of a ship plate, and belongs to the technical field of metal material processing. The steel material comprises C, Si, Mn, Ni, Cr, Mo, Al, Nb, P, S, Fe and impurities. The preparation method comprises the following steps: smelting and continuous casting, slab heating, controlled rolling, quenching treatment and reverse phase transformation annealing. The application adopts low-carbon medium-nickel collaborative design, replaces interstitial atom carbon with substitution atom nickel as an austenite stabilizing element, introduces high-density crystal defects through controlled rolling, obtains full martensite structure in combination with offline quenching, and then is subjected to two-phase zone reverse phase transformation annealing to obtain the final structure of a tempered martensite matrix with 10% to 20% thin film-shaped reverse transformation austenite distributed thereon. The obtained steel material has high yield strength and high impact energy at-80 DEG C, and welding does not need preheating, and has high strength, excellent low-temperature toughness and excellent welding performance, and is suitable for high-value-added application scenarios such as polar ships.

Disclosed in the present invention is a heat treatment method for a wear-resistant accessory of an ultra-large mining excavator. The method comprises the steps of: heating a wear-resistant accessory of an ultra-large mining excavator to the austenitizing temperature thereof, and homogenizing same; quenching the homogenized wear-resistant accessory to room temperature to obtain a wear-resistant accessory having a martensitic structure; rapidly heating the wear-resistant accessory, which has been subjected to primary quenching, to the austenitizing temperature or above again, subjecting same to heat preservation for a short period of time, and performing a complete austenitizing treatment, wherein the austenite structure does not significantly grow; performing secondary quenching, involving: rapidly cooling the wear-resistant accessory, which has been subjected to a complete austenitizing treatment, such that the structure still contains a certain amount of retained austenite; subjecting the wear-resistant accessory, which has been subjected to secondary quenching, to a partitioning treatment, followed by air cooling to room temperature; subjecting the partitioned wear-resistant accessory to a cryogenic treatment, and then heating same to room temperature; and performing a tempering treatment. In the present invention, by means of a readily achievable heat treatment process, a wear-resistant accessory product having excellent performance is obtained, thereby satisfying the performance requirements of wear-resistant accessories for ultra-large excavators.

The application provides a quantitative evaluation method for martensite structure of a ground rail surface, and belongs to the technical field of rail maintenance. The quantitative evaluation method comprises the following steps: selecting a ground rail, cutting a sample with a predetermined length along the longitudinal direction of the rail, and dividing a plurality of evaluation regions in the head part of the sample; observing the sample under a metallographic microscope, for each evaluation region, counting the total length of the martensite structure in the evaluation region, and calculating the ratio of the total length to the total length of the contour of the evaluation region to obtain the length proportion of the martensite structure in the evaluation region; and / or measuring the thickness of the martensite structure in the evaluation region and calculating the average value to obtain the average thickness of the martensite structure in the evaluation region; and drawing a distribution characteristic map or performing quantitative comparison according to the length proportion of the martensite structure in each evaluation region and / or the average thickness. The application can significantly improve the scientificity and accuracy of rail maintenance, and effectively guarantee the safety and economy of railway operation.

A welded rail according to an aspect of the present invention includes: a plurality of rail portions having a head portion and a web portion and having a height h; and a welded joint portion that joins the rail portions together, in which the rail portion has a predetermined chemical composition, a HAZ width of the welded joint portion is 60 mm or less, in a region of 0 to (⅔)×h from a head top portion outer surface in a cross section of the welded joint portion which is parallel to a longitudinal direction and an up-down direction of the welded rail and passes through a center of the welded joint portion and of ±5 mm in the longitudinal direction from a welding center, an area ratio of a martensite structure is 0.0006% or more and 0.1000% or less, and in the region, the number of martensite structures having a grain size of 20 to 200 μm is 3 to 80.

The application discloses a steel rail welding method and a steel rail. The method comprises the following steps: welding a steel rail to form a welded joint; performing induction normalizing heat treatment on the welded joint; after the holding is completed, performing first-stage air cooling on the welded joint by using a first air blowing pressure; after the welded joint is cooled to a first preset temperature, performing second-stage air cooling on the welded joint by using a second air blowing pressure which is smaller than the first air blowing pressure; and stopping air blowing after the welded joint is cooled to below a second preset temperature. The scheme provided by the application finally eliminates the martensite abnormal structure in the flash butt welded joint of the steel rail through the multi-process control method of the welding process, the post-welding heat treatment holding and the air cooling, the martensite structure does not appear in the full cross section of the joint, the remaining organizational performance of the joint meets the requirements, and the service performance and the running safety of the flash butt welded joint are improved.

This invention discloses a method for preparing microalloyed high-performance DP980 steel sheet and strip, belonging to the field of metal material processing technology. The method includes: 1) Nb, Mo, V, and Ti composite microalloying of DP980 steel; 2) forging; 3) low-temperature rolling after heating in the two-phase region; and 4) low-temperature coiling. This invention is based on low interface energy theory for composition design, combined with a two-phase region low-temperature large deformation rolling process. This promotes the high-density dispersion of nanoscale composite precipitates within ferrite, and forms an ultrafine layered ferrite + martensite structure. Through the synergy of composition and process, the resulting DP980 steel sheet and strip exhibit high yield strength, high ductility, high toughness, and excellent hole-expanding properties, resulting in a significant improvement in overall mechanical properties.

The application relates to the technical field of automobile steel plate production, in particular to a 2.2GPa-grade aluminum-silicon plated steel plate, a manufacturing method thereof, a hot stamping method and a hot stamping forming piece, molten steel meeting component requirements after smelting is subjected to hot dipping after being cast, hot-rolled and pickled, and through the synergistic design of components, structures and processes, an aluminum-silicon plated steel plate suitable for hot stamping forming is produced, the hot stamping forming piece obtained by adopting the steel plate and the matched hot stamping method contains more than 97% of martensite structure, the rest is ferrite + residual austenite + bainite, the plating layer is completely converted into a ferroalloy layer after hot stamping, the strength of the hot stamping forming piece can reach 2000-2400 MPa, the elongation is greater than 5%, the hot stamping forming piece has good strength and toughness matching, and simultaneously has excellent corrosion resistance and excellent anti-delayed cracking performance.

A method for producing a rolling bearing component includes providing a rolling bearing component formed from a rolling bearing steel, heating the rolling bearing component to form an austenitic microstructure, and cooling the rolling bearing component in a warm salt bath to a temperature below a martensite start temperature of the rolling bearing steel. The rolling bearing component has a wall thickness or a diameter of at least 85 mm at at least one point and includes a martensitic microstructure in an edge layer region and a microstructure consisting of pearlite and upper bainite in a core region after the cooling. A rolling bearing component produced by the method and a rolling bearing comprising the rolling bearing component are also disclosed.

This invention relates to a heat treatment process for large-diameter 17-4PH thin-walled short rings with diameters of 800mm to 1300mm, wall thicknesses of 20mm to 40mm, and lengths ≤800mm. After forging, controlled-temperature cooling promotes partial microstructural transformation and prevents grain regeneration in the thin-walled short rings. Solution annealing ensures uniform and refined microstructure and grain size in the forged billet. After solution annealing, high-temperature tempering and slow, rate-limited cooling in the furnace to a certain temperature removes structural stress, diffuses hydrogen, and softens the billet hardness, facilitating subsequent rough machining. High-temperature solution cooling employs a combination of pre-cooling, oil cooling, and air cooling to minimize thermal and structural stress, preventing cracking of the thin-walled short rings and ensuring complete microstructural transformation to obtain fine lath martensite. During solution removal from the furnace, slow hoisting prevents deformation of the large-diameter 17-4PH thin-walled short rings due to their own weight. The produced large-diameter 17-4PH thin-walled short rings exhibit uniform overall quality, are free of cracks, and have low ellipticity after heat treatment.

The application relates to the field of metal materials, and discloses a steel for small-size steel balls for mine grinding and a preparation method of the small-size steel balls. The steel for the steel balls comprises the following components: C: 0.4%-0.9%, Mn: 3.0%-5.0%, Si: 1.4%-1.8%, Cr: 0.8%-1.3%, Ni: 0.3%-0.6%, Mo: 0.2%-0.4%, V: 0.15%-0.25%, Nb: 0.02%-0.06%, the rest is Fe and inevitable impurities, and the contents of Mn, V and Nb need to be controlled in coordination. The small-size steel balls are forged and hot-rolled, and are subjected to non-heat-insulation grading quenching and deep cryogenic treatment. The steel ball components and the preparation process realize low-temperature martensite transformation, obtain fine and uniform martensite structure, and the steel ball has high hardness, high impact toughness and excellent impact fatigue resistance.

Provided in the present disclosure are a 1700 MPa grade hot-formed steel having excellent cold bending performance, a preparation method therefor, and the use thereof. A surface layer of the hot-formed steel has a soft-phase ferrite structure, a sub-surface layer has a mixed structure of soft-phase ferrite and martensite, and a core layer has a low-carbon martensite structure. The preparation method comprises any one or a combination of at least two of the following conditions: (A) the coiling temperature after hot rolling being 650-700°C; (B) the pickling speed being ≤ 150 m / min; (C) the continuous annealing temperature being 780-830°C; (D) the furnace atmosphere being a mixed gas of nitrogen and hydrogen; and (E) the dew point temperature being -35°C to -17°C.

The present application relates to the technical field of automobile wheel manufacturing technology, and particularly relates to a lightweight hot stamping wheel composite forming manufacturing method, comprising the following steps: S1, sequentially performing surface pretreatment on steel material, and forming a matching passivation protective layer; S2, feeding into a hot stamping die for processing to obtain a spoke and a rim blank with uniform structure; S3, performing composite quenching heat treatment to form a uniform martensite structure in the blank matrix; S4, performing surface cleaning on the quenched spoke and rim blank to remove the thin oxide layer generated in the heat treatment process; S5, annularly welding the spoke and the rim to form a wheel semi-finished product; S6, performing accurate secondary induction heating on the weld and the surrounding annealing area; S7, performing gradient accurate water cooling treatment to re-form a uniform and strengthened martensite structure in the weld and the surrounding area; and S8, obtaining a finished lightweight hot stamping wheel after quality inspection. The present application solves the technical problems that the weld strength cannot be accurately reinforced and the overall performance of the wheel is uneven.

The application relates to a heat treatment process for improving the grain size of Cr16Ni6 stainless steel, wherein the grain size is obviously improved to 4-6 levels after the heat treatment, and the product quality is improved; the process scheme is as follows: after forging, cooling treatment, one-time strengthening treatment, one-time tempering, two-time strengthening treatment and two-time tempering; the grain size is effectively improved; the forging organization is stabilized and part of the martensite organization is transformed through the after-forging cooling treatment, internal stress is reduced, and workpiece cracking is avoided; through the after-forging cooling treatment and the strengthening treatment, austenite is repeatedly transformed into fine lath martensite, nucleation is ensured in the subsequent high-temperature heating process, nucleation rate is increased, grain size is refined, and the grain size is improved from the original coarse 1-3 levels to the fine 4-6 levels.

This invention discloses a method for preparing high-strength, wear-resistant, heavy-duty railway rare-earth steel rails, comprising the following steps: hot metal pretreatment; converter smelting; LF furnace refining; VD vacuum degassing; continuous casting; rolling process; and heat treatment process. A gradient cooling heat treatment process is adopted, in which the rolled steel rail is fed into the heat treatment device at an incoming temperature of 750°C, first cooled to 610°C, and then further cooled to 538°C. By precisely controlling the cooling rate of each module, the formation of network cementite and martensite structures in the steel rail is avoided, and the final exit temperature of the steel rail is controlled at 500°C. This invention solves the problems of insufficient strength and poor wear resistance of existing heavy-duty steel rails through reasonable composition design and process optimization.

This invention relates to the field of metal material heat treatment technology, and provides an efficient continuous solution treatment process and system for 18Ni350 material. It employs a continuous atmosphere-protected heat treatment furnace for online processing. The process includes: continuously heating the wire to 820℃~860℃ in a protective atmosphere for solution homogenization; subsequently, continuously and forcibly cooling the wire in the protective atmosphere to achieve a complete martensitic structure. The protective atmosphere is a nitrogen-hydrogen mixture, and the continuous forced cooling method is continuous cooling through a water jacket under the protective atmosphere. Along the wire conveying direction, the system includes: a heating furnace, a wire feeding mechanism, a cooling chamber, several furnace tube assemblies, a gas conveying assembly, and a wire take-up mechanism. The gas conveying assembly is used to deliver protective gas into the furnace tube assemblies. This eliminates the cumbersome batch processing process of a vacuum furnace. The wire can be continuously conveyed through the wire feeding mechanism, furnace tube assemblies, and take-up mechanism, completing the entire continuous process of heating, solution treatment, cooling, and winding without downtime.

This invention discloses a high-strength and high-toughness heat treatment method for connecting rods of large-section diesel engines, belonging to the field of heat treatment technology. This method targets integral heat treatment samples of connecting rod sections with diameters ranging from φ150mm to 300mm, achieving high strength and toughness through precise control of the heat treatment process. The workpiece is heated to the quenching temperature and held there, with the heating temperature determined based on the carbon content and the holding time determined based on the cross-sectional dimensions. A dual-liquid quenching process of "water quenching + oil cooling" is employed to ensure a martensitic structure of over 95%. Subsequently, tempering is performed at a set tempering temperature, determined based on the carbon content, with the tempering holding time determined based on the cross-sectional dimensions. The method of this invention achieves a good balance between high strength and high toughness, significantly improving the first-pass yield and quality stability of the product.

The application provides a kind of biphase heterogeneous structure construction method of speed reducer gear, comprising the following steps: according to the size specification of speed reducer gear and the stress condition under actual working environment, determine the hard phase region and soft phase region of speed reducer gear;Configuration laser heat treatment processing head, so that it can output a strip-shaped composite spot and cover the hardening area completely;Start laser quenching process, and combine with paraxial pyrometer to monitor and control the laser surface irradiation temperature in real time, control the strip-shaped composite spot from one end of the tooth to the other end along the tooth width direction, until the scanning of all tooth surfaces of speed reducer gear is completed.The application can obtain a laser quenching hardened layer combining soft phase and hard phase, solve the problem that the surface hardened zone is all martensite structure in the traditional laser quenching process, and improve the wear resistance and fatigue life of the gear for speed reducer.

The application relates to a high-strength large-size structural member and a forming manufacturing method thereof, and belongs to the technical field of high-strength structural member forming manufacturing. The forming manufacturing method is as follows: a steel plate is heated to an austenitizing temperature and is kept warm; after the keeping warm, the steel plate is discharged from the furnace and is cooled to a pressing temperature; the steel plate is pressed and formed by using a press; the mold is removed after keeping pressure for a certain time; the formed member is cooled to room temperature, and the high-strength large-size structural member is prepared. By controlling the heating treatment process and the pressing process of temperature control forming, and matching the steel plate with a specific component system, a martensite structure with high tensile strength and good low-temperature toughness is obtained; the tensile strength is above 1700 MPa, and the impact toughness at-40 DEG C is above 35 J.

The application discloses a production method of high-strength high-low-temperature toughness 3.5Ni steel medium plate, and the production process comprises the following steps: molten iron pretreatment, converter, LF and RH / VD refining, continuous casting, heating, rolling, MULPIC cooling, finishing and heat treatment; the chemical components of the steel are as follows in percentage by weight: C=0.03%-0.10%, Mn=0.02%-0.12%, Si=0.05%-0.15%, Ni=3.2%-3.8%, P<=0.010%, S<=0.005%, Mo=0.20%-0.50%, and the rest is Fe and inevitable impurity elements. The application refines the grain through micro-alloying and controlled rolling+on-line quenching+intercritical quenching+tempering heat treatment process, optimizes the proportion of critical ferrite and reverse transformation austenite, obtains the ferrite and martensite structure between soft and hard phases, improves the strength and low-temperature toughness, and the yield strength is greater than or equal to 420MPa, the tensile strength is greater than or equal to 520MPa, the total elongation is greater than or equal to 18%, and the impact energy at-140 DEG C is greater than or equal to 100J.

This invention discloses a micro-alloyed high-toughness martensitic stainless steel cutterhead, its preparation method, and preparation mold. The stainless steel composition, by weight percentage, is: C: 0.3%~0.7%, Si: 0.3%~1.0%, Mn: 0.5%~1.5%, Cr: 16%~18.5%, Ni: 1%~2%, Mo: 0.3%~0.8%, V: 0.1%~0.35%, Nb: 0.1%~0.25%, S: ≤0.02%, P: ≤0.02%, with the balance being Fe. First, the raw materials are melted into molten iron; then, a deoxidizer is added to the molten iron, and a coated sand molding process is used to cast the cutterhead blank; the blank is then heat-treated; finally, the heat-treated cutterhead is shot-blasted and polished. Martensitic stainless steel cutterheads have a microstructure dominated by martensite, supplemented by austenite, with CrC, VC, and NbC particles dispersed throughout. Their hardness is 40-45 HRC, and their impact toughness reaches 92-95 J / cm². 2 The cutter head has longer wear resistance and service life, and its wear is reduced by 70% compared to cutter heads without added alloying elements.

This invention proposes a production method for 1300MPa martensitic high-strength steel, belonging to the field of continuous annealing cold-rolled steel sheet technology. The method involves adjusting the chemical composition of molten steel, pickling the hot-rolled coil after heat treatment, rolling the pickled coil using a single-stand six-pass rolling mill, and continuously annealing the hard-rolled coil. Specifically, the 100T leveling treatment in the pickling section improves the coil's shape, and the six-pass rolling in the cold rolling section, combined with 5.5% high-concentration emulsion lubrication, further avoids edge cracking defects during cold rolling, ensuring the uniformity of the hard-rolled coil's microstructure and shape. The continuous annealing process, through the synergistic effects of high-temperature austenitization, rapid cooling, low-temperature over-aging, and high-flattening force, ensures the full transformation of martensitic structure and eliminates quenching internal stress. The resulting product can stably achieve a tensile strength of 1300~1400MPa, a yield strength of 1200~1300MPa, an elongation after fracture (A50) ≥4%, and no cracking when bent at 90°. It fully meets the requirements for the use of high-strength steel square tubes, trailer door panels, automotive support components, and other structural components.

The application provides a kind of laser welding wire for aluminum-containing plated hot-formed steel and a welding method thereof, the composition of the welding wire satisfies 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%, [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%, using the welding wire as welding material, by controlling the composition of the welding wire, on the one hand, it can provide guarantee for the composition of the weld metal, realize that the weld is mainly martensitic structure, so as to improve the strength of the weld; on the other hand, when the composition of the welding wire satisfies the requirement, the formation interval of martensite after the molten pool metal cools down is the widest, which can inhibit the performance decline problem caused by the inhomogeneity of the weld composition, therefore, under extreme conditions, even if the local welding wire does not fuse with the aluminum-containing plated hot-formed steel, martensitic structure can also be formed after the welding wire melts and solidifies again, so as to guarantee the mechanical properties of the joint.

The application provides a high anti-delay fracture 1700MPa grade aluminum alloy coated hot forming steel plate and a production method, a hot forming steel component and an application, the composition is Si 0.10-0.50%, Mn 1.00-1.50%, Cr 0.10-0.80%, Ti 0.01-0.10%, Nb 0.01-0.10%, Mn+Cr+Si≤2.00%, Ti+Nb≤0.12%; compared with the prior art, the application controls the composition and process, thereby controlling the oxidation state of the substrate surface layer before hot forming, the thickness fluctuation of the FeAlSi inhibition layer, and finally controlling the size and quantity of the Cottrell holes after hot forming; the micro-alloying elements are added to refine the martensite structure, the hydrogen content in the raw material and the hydrogen absorption reaction during hot forming are controlled, the diffusible hydrogen content in the hot forming steel component is controlled, and the hot forming steel component has high anti-delay fracture performance, cold bending performance and coating corrosion resistance.