439 results about "Austenite grain" patented technology

The invention discloses a high-carbon high-alloy grinding ball steel rolling internal damage control method, and belongs to the technical field of metal material rolling machining. Comprising the following steps that high-carbon high-alloy grinding ball steel billets are subjected to high-temperature diffusion homogenization treatment and then subjected to staged temperature control rolling, the initial rolling temperature in the blooming stage is 1020-1080 DEG C, the single-pass reduction rate is 6-10%, the pass interval is larger than or equal to 20 seconds, the total reduction rate is 40-80%, and the core peak temperature is controlled to be smaller than or equal to 1150 DEG C; the finish rolling temperature is 800-850 DEG C; during rolling, atomized water is sprayed for dynamic cooling every 2-3 passes, and two-stage cooling (water cooling to 600-650 DEG C at 15-20 DEG C / s, and slow cooling to room temperature) is carried out after final rolling. According to the method, element diffusion, temperature rise inhibition and structure refinement are synergistically regulated and controlled, so that the core void ratio is reduced, the austenite grain size is larger than or equal to 8 grades, a uniform bainite and dispersed carbide composite structure is obtained, and the anti-fatigue performance of the grinding ball steel is remarkably improved.

The invention relates to an austenite structure display and grain size rating method, and belongs to the technical field of hot continuous rolling finishing mill production methods. According to the technical scheme, the method comprises the steps that an eroded sample is manufactured, and an austenite structure display graph is obtained; carrying out deep learning network training and grain boundary processing to obtain a boundary skeleton diagram; and grading the grain size by adopting a straight line intercept point method. The method has the beneficial effects that the Inconel 625 austenite structure with a uniform erosion surface and a clear and complete austenite grain boundary can be obtained, grain size rating is carried out on the austenite structure image through a deep learning algorithm, and compared with manual rating, the efficiency and accuracy of grain size rating are greatly improved.

The invention relates to the technical field of metallurgy, in particular to a hot galvanizing low-alloy high-strength steel plate which comprises the following chemical components in percentage by mass: 0.06%-0.08% of C, 0.20%-0.25% of Si, 1.20%-1.35% of Mn, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 0.020%-0.060% of Alt, 0.035%-0.050% of Nb, 0.010%-0.020% of Ti, less than or equal to 0.0050% of O, less than or equal to 0.0060% of N and the balance of Fe and inevitable impurities. The contents of C, Si and Mn in the chemical components are controlled, the welding performance of the hot-dip galvanizing low-alloy high-strength steel and the surface quality of a finished product are considered, Nb microalloying is mainly adopted, a proper amount of microalloy element Ti is added to form TiN, austenite grain coarsening is limited in the slab heating and heat preservation process, and fine and dispersed precipitated phases are finally obtained in combination with process control; the hot-dip galvanized low-alloy high-strength steel finished product is good in structure form and excellent in comprehensive performance.

The invention discloses a heat treatment method for optimizing a gear steel structure and refining grains, and belongs to the technical field of heat treatment process control. The method is particularly suitable for a production scene of cold forging gear parts such as three pin shafts; according to the method, a pre-normalizing or annealing heat treatment process with specific parameters is added after cold forging forming and before carburizing, so that an AlN precipitated phase in the steel forms segregation again at a grain boundary, the grain boundary is effectively pinned, and austenite grain growth is inhibited, and therefore the phenomenon of mixed crystals is avoided, the structure is refined, and the fatigue performance is improved. Experiments prove that after normalizing pretreatment at the temperature of 900 DEG C or above or annealing pretreatment at the temperature of 720 DEG C is adopted, the original cold forging mixed crystal area with the grain size of 0-4 grade can be increased to 7 grade or above, grains are uniform and compact, and the structure property is remarkably improved. The process parameters are clear, the flow is controllable, and the method is suitable for optimization and application of the batch gear steel heat treatment process.

The invention discloses a method for measuring the original austenite grain size of medium carbon steel. The method comprises the following steps: heating a medium carbon steel sample to a temperature above an original austenitizing temperature, and keeping the temperature for a period of time to precipitate carbides from an original austenite grain boundary; cutting and embedding the heat-treated medium carbon steel sample to prepare a medium carbon steel metallographic sample; carrying out grinding and fine polishing treatment on the medium carbon steel metallographic sample, and carrying out ultrasonic cleaning on the medium carbon steel metallographic sample in alcohol; immersing and corroding for a certain time by using nitric acid alcohol, then cleaning the surface of the medium carbon steel metallographic sample by using alcohol, and drying until an austenite grain boundary is clearly displayed; completing microscopic image rating; and calculating the austenite grain grade by adopting an intercept point method. According to the method, the original austenite grain boundary can be clearly displayed, and the effective size of the original austenite grain size of the medium carbon steel can be rapidly and accurately obtained.

Provide a steel material having high strength and excellent hydrogen embrittlement resistance characteristics. The steel material according to the present disclosure has a chemical composition in mass %, C: 0.25 to 0.30%, Si: 0.10 to 0.50%, Mn: 0.05 to 0.60%, P: 0.050% or less, S: 0.0100% or less, Al: 0.001 to 0.100%, Cr: 0.50 to 1.50%, Mo: 0.80 to 2.00%, Ti: 0.002 to 0.010%, V: 0.08 to 0.30%, Nb: 0.010 to 0.050%, B: 0.0001 to 0.0050%, N: 0.0100% or less, O: 0.0100% or less, and the balance consisting of Fe and impurities, a tensile strength of 900 to 1100 MPa, an original austenite grain size of 20.0 μm or less, and a dislocation density of 7.0×10 14 m -2 or less, and the Q value obtained from the line profile of X-ray diffraction is 2.35 or more.

The invention relates to the technical field of metallographic microstructure detection, and discloses a method for displaying the austenite grain size of a martensitic structure in stainless steel, which comprises the following steps: S1, sample preparation: cutting, grinding and polishing a stainless steel sample until no macroscopic scratch exists on the surface; s2, preparing an electrolyte: mixing 50%-70% of nitric acid and 30%-50% of deionized water to form a basic solution, and adding 3ml-7ml of phosphoric acid and 1ml-5ml of sulfuric acid into every 100ml of the basic solution; and S3, assembling an electrolysis device: a sample clamp made of martensitic stainless steel is adopted as an anode, austenitic stainless steel is adopted as a cathode, and the soaking area of the cathode is not less than 1500mm. By optimizing the electrolyte formula and process parameters, the original austenite grain size of the martensitic structure in the stainless steel can be clearly displayed. The method solves the problem of unclear display of the stainless steel grain boundary in a traditional method, is not only suitable for martensitic stainless steel, but also suitable for precipitation hardening type stainless steel, and has high universality and applicability.

A high strength steel sheet having 1180 MPa or higher tensile strength and a method for manufacturing the same are disclosed. The high strength steel sheet has a specific chemical composition and is such that in a region at ¼ sheet thickness, the area fraction of martensite is 80% or more, the volume fraction of retained austenite is 3% or more and 15% or less, the area fraction of the total of ferrite and bainitic ferrite is 10% or less, the average grain size of prior austenite is 20 μm or less, and the average of the proportions of packets having the largest area in prior austenite grains is 70% by area or less of the prior austenite grain.

This component is formed from a steel plate which has a predetermined chemical composition and in which, in a region extending from a depth of 1 / 8 the plate thickness from a surface to a depth of 3 / 8 the plate thickness from the surface, prior-austenite grains have an average aspect ratio of 3.00-5.50, the areal proportion of bainite is 70-95%, and the areal proportion of martensite is 5-30%, wherein the ratio of the total amount of Ti and Nb analyzed as electroextraction residues at a depth of 1 / 60 the plate thickness from the surface to the total amount of Ti and Nb analyzed as electroextraction residues at a depth of 1 / 4 the plate thickness from the surface is 1.5 or greater.

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

A coated steel sheet and press hardened steel part having a composition including, by weight percent: C 0.15-0.25%, Mn 0.5-1.8%, Si 0.1-1.25%, Al 0.01-0.1%, Cr 0.1-1.0%, Ti 0.01-0.1%, B 0.001-0.004%, P≤0.020%, S≤0.010%, N≤0.010% the remainder of the composition being iron and unavoidable impurities resulting from the smelting. The press hardened steel part includes a bulk having a microstructure including, in surface fraction, more than 95% of martensite and less than 5% of bainite, a coating layer at the surface of the steel part, a ferritic interdiffusion layer between the coating layer and the bulk, and a ratio between the ferritic grain width in the interdiffusion layer GWint over prior austenite grain size in the bulk PAGSbulk, satisfying following equation (GWint / PAGSbulk)−1≥30%.

The present invention provides a thick, fatigue-resistant, easily weldable, high-strength steel plate for wind power generation and a preparation method thereof. The steel plate comprises the following chemical composition by mass: C: 0.12% to 0.15%, Si: 0.15% to 0.35%, Mn: 1.30% to 1.50%, P ≤ 0.015%, S ≤ 0.005%, Nb: 0.015% to 0.030%, V: 0.015% to 0.030%, Ti: 0.005% to 0.020%, Al: 0.005% to 0.030%, with the remainder being Fe and unavoidable impurities. The preparation method comprises the steps of smelting, refining, continuous casting, heating, and rolling. The use of a low-C, high-Mn, Nb+V+Ti composite microalloying significantly inhibits austenite grain growth. The use of a normalizing rolling process results in a short process flow, low cost, and strong production line adaptability.

The invention provides a rolling method of cathode flat steel, which comprises the following steps: firstly, heating a casting blank to obtain a heated blank, then carrying out surface descaling on the heated blank, and carrying out multi-pass rough rolling to obtain an intermediate blank; the heating treatment comprises a preheating section and a soaking section; the heating treatment is specifically a heating treatment process for controlling the austenite grain size of the casting blank; the multi-pass rough rolling comprises multi-pass rough rolling of which the reduction rate is sequentially reduced; and carrying out multi-pass finish rolling on the intermediate billet obtained in the previous step, carrying out on-line cooling, and then carrying out stacking slow cooling to obtain the rolled and formed cathode flat steel. According to the method, directional improvement of the conductivity of the electrolytic aluminum cathode flat steel is achieved through rolling process optimization, heating under a rolling path of a low-temperature ferrite area and rolling pass reduction distribution design are focused, the ferrite grain size and the conductive texture of a material are cooperatively regulated, the normal conductivity of the cathode flat steel is improved, and the conductivity of the cathode flat steel is improved. And a core material support is provided for reducing ineffective current loss in the electrolytic aluminum industry.

The invention belongs to the technical field of ultralow-temperature materials, and discloses high-strength and high-plasticity steel for an ultralow-temperature environment and a preparation method of the high-strength and high-plasticity steel. A high-manganese and high-nitrogen component system is adopted, based on the austenite stabilization theory, low-cost manganese replaces expensive nickel to achieve austenite stabilization, and a high-manganese stable-phase and high-nitrogen reinforced synergistic mechanism is formed through the promotion effect of manganese and chromium on nitrogen solubility. The structure uniformity is guaranteed by strictly controlling the heating and finish forging temperature in the forging stage, sufficient solid solution of manganese and nitrogen is promoted through homogenization treatment before hot rolling, the finish rolling temperature is precisely controlled by adopting a controlled rolling process so as to retain high-proportion deformed austenite grains, the material strength is further improved, the cost of each ton of alloy is reduced by 75% or above, and meanwhile, the product quality is improved. The performance of the ultralow-temperature material is improved in a leap-over mode, and the excellent strength and plasticity matching that the yield strength is larger than or equal to 1600 MPa, the tensile strength is larger than or equal to 1900 MPa and the ductility is larger than or equal to 20% at the temperature of-269 DEG C is obtained.

Steel part having a chemical composition comprising, by weight %, 0.18 ≤ C ≤ 0.27, 0.18 ≤ Si ≤ 0.30, 1.0 ≤ Mn ≤ 1.5, 0.14 ≤ Cr ≤ 0.25, 0.02 ≤ Al ≤ 0.06, 0.02 ≤ Ti ≤ 0.06, 0.0020 ≤ B ≤ 0.0040, 0 ≤ S ≤ 0.008, 0 ≤ N ≤ 0.020, the remainder of the composition being iron and unavoidable impurities resulting from the elaboration process, having a microstructure comprising, in surface fraction, 95% or more of martensite and a prior austenite grain skin refinement ratio equal to or above 1.2, said ratio being defined as PAGS_B / PAGS_S, wherein PAGS_B is the average prior austenite grain diameter in the bulk (3) expressed in µm and PAGS_S is the average prior austenite grain diameter in the skin (2), also expressed in µm.

The invention provides welding wire steel for welding ultralow-temperature high manganese steel, a welding wire, a preparation method of the welding wire and a welding method. The welding wire steel for welding the ultralow-temperature high manganese steel comprises the following components in percentage by mass: 0.05 to 0.1 percent of C; 0.5 to 0.6 percent of Si; 24% to 25% of Mn; p is less than or equal to 0.01%; s is less than or equal to 0.01%; 0.05% to 0.1% of Al; 0.12 to 0.2 percent of Ni; 0.02% to 0.06% of N; 0.08% to 0.15% of Ti; v, 0.08% to 0.15%; 0.08% to 0.15% of Nb; 0.05% to 0.1% of Mo; and the balance of Fe and inevitable impurities. The welding wire composition design is optimized, only a small amount of Ni element is added, W and other high-melting-point elements are not added, and a small amount of C, N, Ti, V, Nb and other alloy elements are transited to a welding seam through the welding wire, so that nitride, carbide and other pinning grain boundaries are formed in the welding seam at the high temperature, austenite grain growth is effectively prevented, the austenite grain size is reduced, and the low-temperature impact toughness of the welding seam is improved; in addition, a small amount of Si element is transited to the welding seam through the welding wire, molten pool fluidity is improved, slag floating is promoted, and slag inclusion of the welding seam is avoided.

Provided is a hot-rolled steel sheet that exhibits excellent LME resistance. The hot-rolled steel sheet according to the present disclosure contains, in mass%, 0.030-0.110% of C, 0.01-0.50% of Si, 0.50-1.50% of Mn, 0.025% or less of P, 0.010% or less of S, 0.010-0.070% of Al, 0.0070% or less of N, 0.055-0.200% of Ti, 0.020-0.100% of W, 0.0010-0.0050% of B, and the balance being Fe with impurities. In the microstructure, the area ratio of bainitic ferrite is 85% or more. In a surface layer region from the surface of the hot-rolled steel sheet to a depth of 0.2 mm in the sheet thickness direction, the total length of the old austenite grain boundary in which BO2 - is detected by the time-of-flight secondary ion mass spectrometry is 0.80-5.00 mm per 100 μm x 100 μm. The B segregation degree at the old austenite grain boundary is 80 or more.

The invention relates to a corrosive agent and a corrosion method for displaying a 32CrNi3MoVE crystal boundary of alloy steel, which are characterized in that a common chemical product is used as an electrolytic corrosive agent after being simply proportioned, and the 32CrNi3MoVE steel quenched and tempered state original austenite crystal boundary is clearly displayed by a proper corrosion method. Chemical reagents used by the corrosive are economical and applicable, the corrosive is composed of alum, oxalic acid, dishwashing liquid, distilled water and the like which are existing in a laboratory, the proportioning of the corrosive is the key, the electrolytic corrosion method is simple to operate, alum can effectively display the grain boundary, oxalic acid provides a weak acid environment for oxidation reduction, and the corrosion effect is good. The dishwashing liquid slows down the corrosion rate of weak acid electrolyte to a metallographic specimen, weakens structure display, and improves the definition of crystal boundary display. The corroded sample is lightly polished in a polishing machine, and the corrosive agent ratio and the electrolytic corrosion method are combined to form an efficient novel corrosion method. The traditional corrosive agent capable of completely replacing saturated picric acid and a proper amount of detergent and the corrosion method effectively solve the problem of 32CrNi 3MoVE steel quenched and tempered state original austenite grain boundary display.

A Fe—Cr—Ni alloy material that has high strength and reduced strength anisotropy is provided. A Fe—Cr—Ni alloy material according to the present disclosure consists of, by mass %, C: 0.030% or less, Si: 0.01 to 1.00%, Mn: 0.01 to 2.00%, P: 0.030% or less, S: 0.0050% or less, Ni: 29.0 to 36.5%, Cr: 23.0 to 27.5%, Mo: 2.00 to 6.00%, Al: 0.01 to 0.30%, rare earth metal: 0.016 to 0.100%, N: 0.220 to 0.500%, and O: 0.010% or less, with the balance being Fe and impurities, and satisfies Formula (1). In a microstructure, a standard deviation of the grain size numbers of austenite grains is 0.80 or less. The tensile yield strength is 758 MPa or more:3×Ni-2×Cr-150×N<15.(1)where, a content of a corresponding element in percent by mass is substituted for each symbol of an element in Formula (1).

The invention discloses a processing method for improving surface cracks of high-strength 316L stainless steel, which comprises the following steps: S1, product smelting: selecting a low-sulfur raw material in an electric furnace charging stage, carrying out electric furnace crude smelting, pre-desulfurization treatment, AOD (Argon Oxygen Decarburization) refining and calcium line improvement, and then feeding the low-sulfur raw material to a continuous casting platform for casting to obtain a plate blank; s2, plate blank surface coping is conducted, specifically, two passes of coping are conducted on the two surfaces of the plate blank correspondingly; s3, hot rolling and calendaring: rough calendaring and fine calendaring. According to the method, firstly, by increasing the chromium content, the reasonable ferrite content of the plate blank is kept, and austenite grains are prevented from growing excessively in the heating and smelting process of an electric furnace; 2, by reducing the content of harmful elements such as oxygen and sulfur, intergranular separated sulfide is reduced, and intergranular binding force is improved; thirdly, the surface of the plate blank is ground, and the poor-quality part of the surface layer of the plate blank is eliminated; 4, refining surface crystal grains of the plate blank by adopting a hot rolling and light pressing process; through the means, crack defects are avoided, and the surface quality of a final product is improved.

The invention discloses a method for measuring the original austenite grain size of low-carbon hydro-electric steel, which comprises the following steps: sequentially carrying out pretreatment, heat treatment, grinding and polishing and corrosion on a to-be-measured sample, and then displaying the austenite grain size of the to-be-measured sample by adopting a ferrite network method, according to heat treatment, the heat treatment temperature is 880-900 DEG C, the heat preservation time is 0.5-1 h, and then water cooling is conducted after air cooling is conducted to 640-650 DEG C; the corrosion liquid is prepared from 5-8 g of citric acid, 4-8 drops of nitric acid and 100 mL of water. According to the method, the original austenite of the low-carbon hydroelectric steel can be clearly displayed, and the grade of the austenite grain size is accurately evaluated.

The invention discloses a corrosion method for the prior austenite grain size of a high-carbon pearlite steel rail, which comprises the following steps of: grinding and polishing a test surface of a sample, completely immersing the polished surface into a corrosive agent during corrosion, paying attention to not contacting the bottom of a container so as to avoid influencing the corrosion effect, and taking out and observing the corrosion surface at any time in the corrosion process. After the corroded surface is in a uniform dark grey frosted state, taking out, washing and drying, and finally, slightly polishing on a polishing machine to remove a redundant corrosion layer for observation; the corrosive agent comprises hydrochloric acid, acetic acid, ferric trichloride, benzalkonium bromide, shampoo and deionized water. According to the corrosion method for the original austenite grain size of the high-carbon pearlite steel rail, the original austenite grain boundary of the high-carbon pearlite steel rail can be clearly displayed, the problem that the original austenite grain size is difficult to corrode is solved, and meanwhile the used reagent is stable, safe and easy to store.

Steel part having a chemical composition comprising, by weight %, 0.18≤C≤0.27, 0.18≤Si≤0.30, 1.0≤Mn≤1.5, 0.14≤Cr≤0.25, 0.02≤Al≤0.06, 0.02≤Ti≤0.06, 0.0020≤B≤0.0040, 0≤S≤0.008, 0≤N≤0.020, the remainder of the composition being iron and unavoidable impurities resulting from the elaboration process, having a microstructure including, in surface fraction, 95% or more of martensite and a prior austenite grain skin refinement ratio equal to or above 1.2, the ratio being defined as PAGS_B / PAGS_S, wherein PAGS_B is the average prior austenite grain diameter in the bulk (3) expressed in μm and PAGS_S is the average prior austenite grain diameter in the skin (2), also expressed in μm.

The steel sheet has a prescribed chemical composition, and in the metallographic structure at a position 1 / 4 of the sheet thickness from the surface, the steel sheet contains, in area%, 60.0% or more but less than 90.0% of bainite, more than 10.0% but 40.0% or less of martensite, and 10.0% or less in total of ferrite, pearlite and retained austenite, with the balance being Fe and unavoidable impurities. The value obtained by dividing the standard deviation of the aspect ratio of the old austenite crystal grains by the average value of the aspect ratio of the old austenite crystal grains is 0.50 or less, and the average grain diameter of the old austenite crystal grains is 30 [mu] m or less.

The application discloses a production method of a mining rare-earth wear-resistant GN-14A hot-rolled round steel, and a steelmaking process is as follows: a converter is operated with double-slag, and an end-point basicity is controlled at 2.5; the end-point control target of the converter is C >= 0.08%, and P <= 0.020%; a VD deep vacuum time is >= 15 min, and a soft blowing time is >= 20 min; a superheat degree is <= 25 DEG C, a caster pulling speed is 0.55 m / min <= 0.60 m / min; a casting blank slow cooling time is >= 24 hours; and a rolling process is as follows: 1020 DEG C <= open rolling temperature <= 1050 DEG C; 780 DEG C <= final rolling temperature <= 850 DEG C; 450 DEG C <= entering slow cooling pit temperature <= 550 DEG C; and 50 DEG C <= exiting slow cooling pit temperature <= 150 DEG C. The hot-rolled round steel prepared by the application has a structure of ferrite + pearlite structure, inclusion levels of A class <= 1.5 level, B class <= 1.5 level, C class <= 1.0 level, D class <= 1.5 level, and austenite grain size >= 5 level.

The hot stamped body has a predetermined chemical composition and a metal structure in which the average grain size of the prior austenite grains is 5 to 25 μm and the standard deviation of the grain size of the prior austenite grains is 0.1 to 2.0 μm. In addition, the hot stamping steel sheet has a predetermined chemical composition and a metal structure in which the ferrite is composed of {100} <011> ~{223} <110> The average value of the pole density of the formed orientation group is less than 10.0; the proportion of the number of the above-mentioned ferrite containing carbides with an equivalent circle diameter of 0.2 μm or more in the grains of the entire ferrite is more than 20%; in terms of area ratio, pearlite is 10 to 90%, and ferrite is 10 to 90%.

The invention relates to the field of hub bearing machining, and discloses a hub bearing production process which comprises three stages: hot forging forming, residual temperature control cooling and structure stabilization stage, hot forging forming comprises upsetting, pre-forging, finish forging and rapid cooling, finish forging adopts a finish forging die for machining, an infrared thermometer is mounted on the finish forging die for monitoring, and the infrared thermometer is mounted on the finish forging die for cooling. During finish forging, the temperature fluctuation of the forge piece is controlled to be smaller than or equal to + / -15 DEG C, and the finish forging temperature is controlled to be 950-1050 DEG C; and the time interval from finish forging to rapid cooling starting should be smaller than or equal to 30 s. An infrared thermometer is adopted for monitoring the finish forging temperature, the fluctuation is controlled to be smaller than or equal to + / -15 DEG C, the temperature is maintained to be 950-1050 DEG C, it is ensured that the forge piece is located in an ideal thermal deformation interval, overheating or overburning or insufficient mold filling is avoided, and fine and uniform austenite grains are obtained; and the starting interval from finish forging to rapid cooling is smaller than or equal to 30 s, temperature drop fluctuation is reduced, cooling continuity is guaranteed, and structure coarsening is prevented.

The invention belongs to the technical field of steel and iron material processing and preparation, and discloses a low-temperature toughness optimization method for short-process multi-stage phase change control of a medium-thickness plate. Through the synergistic effect of two times of heating, two times of ultrafast cooling, one-stage rolling and cooling after rolling, the problem of refining the core structure of the medium-thickness plate under the low compression ratio is solved. After primary heating and heat preservation, ultrafast cooling is conducted to the surface room temperature, and secondary cooling is conducted after re-reddening; carrying out secondary heating and heat preservation to regulate and control the grain size of the original austenite, and carrying out multi-pass uniform rolling; and after rolling, laminar cooling is performed to reach the self-tempering temperature of 310-330 DEG C, and a polygonal ferrite and granular bainite double-phase structure is obtained after air cooling. The core impact energy of the steel plate produced through the method is not smaller than 200 J and not smaller than 100 J at the temperature of-80 DEG C and-120 DEG C respectively, the yield strength is larger than or equal to 540 MPa, and the steel plate has high strength and good low-temperature toughness, is suitable for the field of ocean engineering and has good industrial application value.

The invention discloses a method for prolonging the fatigue life of spring steel through rare earth treatment. The method specifically comprises the steps that the total adding amount of rare earth elements accounts for 0.02%-0.15% of the mass of molten steel; rare earth elements are added in the later stage of LF refining, after alloying is completed, small-gas-amount clean argon blowing is conducted for 10 min to 20 min, and the argon flow is 15 NL / min to 20 NL / min; after hot rolling, cooling to below 550 DEG C at the cooling speed of 10-20 DEG C / s; and heating the hot-rolled spring steel blank to 450-550 DEG C, keeping the temperature for 2-3 hours, and then performing air cooling. According to the method, molten steel is purified through rare earth elements, long-strip-shaped MnS and other inclusions are converted into spherical rare earth oxysulfide (such as Ce2OS), stress concentration sources are reduced, and the crack initiation probability is reduced. Austenite grain growth is inhibited through rare earth elements, so that the spring steel obtains a uniform and fine structure (the grain size is greater than or equal to 9 grades), and the crack propagation resistance of the material is enhanced. Through the synergistic effect of tempering treatment and rare earth treatment, the comprehensive mechanical property of the spring steel is improved, and the fatigue life is greatly prolonged.

Abstract: A follower bearing includes an inner member including an inner wall surface defining a through hole, an outer ring, and a plurality of rolling elements. A portion of the through hole with a smallest diameter has a diameter that is 40% or more of an outside diameter of a portion of the inner member with a smallest outside diameter. The inner member is composed of a steel containing not less than 0.12 mass% and not more than 0.39 mass% carbon, not less than 0.05 mass% and not more than 0.40 mass% silicon, not less than 0.55 mass% and not more than 0.95 mass% manganese, and not less than 0.60 mass% and not more than 1.25 mass% chromium, with the balance consisting of iron and unavoidable impurities, and includes a carburized layer so as to constitute at least a part of a surface thereof. In the carburized layer, the grain size number of prior austenite grains as specified in JIS G 0551 is not less than 8.6.