365 results about "Austenite grain" patented technology

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.

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.

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.

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 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.

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.

The invention belongs to the technical field of metal grain size detection, and particularly relates to a preparation method of a sample for detecting austenite grain size in steel by an oxidation method, which comprises the following steps: S1, grinding and polishing the detection surface of the sample until no macroscopic scratch exists, and immersing the sample in a container filled with electrochemical coke; s2, putting a container filled with the sample and the electrochemical coke into a heating furnace, heating to 860 + / -10 DEG C along with the furnace, keeping the temperature for 0.5-1 hour, then taking out the container, pouring the sample and the electrochemical coke on the ground at the same time, enabling the polished surface of the sample to be fully exposed in the air, and rapidly performing water quenching within 5 seconds; s3, dividing the primary polishing surface of the oxidized sample subjected to heat treatment into two parts, and grinding and polishing one part; and S4, corroding the secondary polished surface of the sample for 8-10 seconds by adopting a 15% hydrochloric acid alcoholic solution, cleaning by using analytically pure alcohol, and finally drying by blowing. The method has the advantage that the accuracy and reliability of the austenite grain size test result are ensured.

Provided is an austenitic heat-resistant steel having excellent creep rupture strength and excellent creep rupture ductility. The austenitic heat-resistant steel has a chemical composition comprising, in terms of mass%, 0.01-0.40% C, up to 3.00% Si, up to 3.00% Mn, up to 0.100% P, up to 0.100% S, 20.0-35.0% Cr, 20.0-48.0% Ni, 0.1-5.0% Mo, 0.01-1.50% Ti, 0.01-0.50% V, up to 0.030% N, up to 0.100% Al, 0.0001-0.0200% B, etc., and has an average austenite crystal grain size of 0.0-5.0 in terms of ASTM No. In the austenitic heat-resistant steel, the Ti, V, and Mo contents and a Ti amount, a V amount, and a Mo amount that are determined from an electrolytic extraction residue satisfy expression (i) and expression (ii).　(i): TiER+VER+MoER≤1.000 (ii): 1.00≤(Ti+V+Mo)-(TiER+VER+MoER)

The invention relates to the field of bearing steel forging, in particular to a construction method and application of a material model for predicting structural evolution of 100CrMo7-3 bearing steel in the forging process, and the model comprises an austenite grain growth model, a thermal deformation constitutive equation, an austenite dynamic recrystallization integral number model and an austenite dynamic recrystallization grain size model. By establishing the model, the whole chain prediction evolved from a microstructure to a macroscopic forging load is realized for the first time. By adopting the model, a process window can be locked only through single simulation, the grain size of the core of the forge piece is successfully compressed to be below an industry critical value, and compared with a traditional method, the forging load prediction precision is improved in a leap-over mode.

The invention provides a method and device for predicting the crack risk in the preparation process of a nuclear power steel material, and the method comprises the steps: building and training a high-precision crack risk prediction model through the quantification of the interaction of the die casting temperature, the cooling time, the austenite grain size, the precipitate size and the ferrite film thickness; through the trained crack risk prediction model, the crack risk coefficient of the to-be-tested nuclear power steel material can be predicted based on the preparation process parameters and the structural characteristic parameters of the to-be-tested nuclear power steel material, and the process adjustment necessity assessment is carried out according to the crack risk coefficient of the to-be-tested nuclear power steel material. Crack defects are pre-judged in advance, die casting process parameters are optimized, and ingot casting quality is improved.

A method for manufacturing a pearlitic steel rail having high surface hardness, relating to the technical field of iron and steel smelting. The method comprises: feeding molten steel having undergone preliminary smelting into a ladle refining furnace, and adding an alloying element for deoxidization and alloying treatment to obtain refined molten steel, so as to further obtain a continuous casting billet; heating the continuous casting billet to a preset temperature by means of a heating furnace, and feeding the heated continuous casting billet into a rolling mill for multi-pass rolling comprising first-pass rolling and second-pass rolling, wherein during the first-pass rolling, the rolling speed is 5.0-7.5 s-1, and the rolling deformation should be 10-15%; after the first-pass rolling, the original austenite grain size is 85-115 μm; and the number of rolling passes is 9-13, and the total deformation is 85-95%; and gradually reducing the gap between rollers of the rolling mill to obtain steel rail blocks having desired specifications and shapes and performing on-line heat treatment and processing treatment on the steel rail blocks to obtain steel rails.

The application discloses a preparation process of a new material cab turnover support for a heavy truck, and the cab turnover support is made of a new alloy material by adopting a temperature control rolling and air quenching and partitioning heat treatment process.The Ti element is added in the alloy composition, and compared with other alloy elements, the carbide of the Ti element has super-high hardness; the process of temperature control rolling is adopted, a large number of dislocations are introduced into austenite, and austenite grains are refined; the heat treatment process of air cooling quenching and partitioning is adopted, a kind of wear-resistant steel with a complex structure of martensite + austenite is obtained, the strength of the steel plate is improved, and good toughness and plasticity are simultaneously achieved.Compared with the cab turnover support made of the DC04 steel by adopting the cold continuous rolling and annealing heat treatment in the prior art, the cab turnover support has high strength and wear resistance, the mechanical property is improved by nearly 4 times, and the light weight requirement of the cab turnover support is met.

The present invention provides a high-manganese hot-rolled steel sheet with excellent wear resistance, a steel pipe manufactured using the above-mentioned hot-rolled steel sheet, and a method for manufacturing these. [Solution] A hot-rolled steel sheet containing, by weight percent, manganese (Mn): 10-20%, carbon (C): 0.6-2.0%, chromium (Cr): 5.0% or less, aluminum (Al): 0.5% or less, silicon (Si): 1.0% or less, phosphorus (P): 0.1% or less, sulfur (S): 0.02% or less, with the remainder being iron (Fe) and other unavoidable impurities, having a microstructure with austenite as the main phase, and containing film-like precipitates formed along the austenite grain boundaries.

Provided are: a steel sheet which has a prescribed chemical composition and has a metallographic structure containing, in area%, 90.0% or more of martensite and 3.0% or less of retained austenite, the average grain diameter of prior austenite grains being 30.0 [mu] m or less, the standard deviation of the grain diameter of the prior austenite grains being less than 4.0 [mu] m, and the average grain diameter of the prior austenite grains being 30.0 [mu] m or less; and the standard deviation of the dislocation density at seven positions of 5%, 10%, 15%, 20%, 25%, 30%, and 50% with respect to the total width at a position of 1 / 4 of the sheet thickness and in a direction from an end portion in the width direction toward a width center portion is 1.50 * 1015 / m2 or less.

The invention provides a hot rolled steel strip for a high-strength and high-corrosion-resistance anchor rod body and a preparation method and application of the hot rolled steel strip. The hot rolled steel strip is prepared from the following elements in percentage by weight: 0.18 to 0.24 percent of C, 0.20 to 0.30 percent of Si, 0.80 to 1.20 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.007 percent of S, less than or equal to 0.0040 percent of N, 1.40 to 1.55 percent of Cr, 0.25 to 0.35 percent of Cu, 0.02 to 0.05 percent of Ti, 0.04 to 0.08 percent of Sb, 0.1 to 0.13 percent of Als, 1.25 to 1.35 percent of Ni and the balance of Fe and impurities. Als and N are combined, so that the grain size inhibition effect can be exerted to the maximum extent, and austenite grains are refined; cr, Als and Sb are beneficial to formation of a compact protective rust layer on the steel surface, invasion of Cl <-> in the marine environment is inhibited, and the corrosion rate is reduced.

The invention relates to the technical field of steel forging, and particularly discloses a preparation method of a high-strength SF1900 steel bar, which comprises the following steps: preparing an SF1900 steel ingot, homogenizing at high temperature, forging and carrying out heat treatment. Forging: performing three-time upsetting and three-time drawing on the pretreated steel ingot obtained by high-temperature homogenization; wherein the heating temperature of the first heating number ranges from 1180 DEG C to 1220 DEG C; the heating temperature of the second heating number is 1080-1120 DEG C; the heating temperature of the third heating number is 1030-1050 DEG C; the upsetting deformation of each heating number is larger than or equal to 50%; and heat treatment is conducted, specifically, the fine-grain bar obtained through forging is subjected to normalizing and tempering treatment, and the high-strength SF1900 steel bar is obtained. According to the preparation method of the high-strength SF1900 steel bar, the original austenite grain size of the prepared SF1900 steel bar is larger than or equal to 7 grades, the ratio of the transverse mechanical property to the longitudinal mechanical property is 98%-102%, and the use requirements of aero-engine shaft materials can be completely met.