259 results about "Austenite grain" patented technology

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 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.

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 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.

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 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 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.

The invention relates to the technical field of metal material processing, in particular to a forging process for inhibiting GH4099 high-temperature alloy original austenite grain boundary carbide. According to the method, through scientific setting of a critical solid solution temperature interval and a multidirectional deformation cooperation mechanism, net-shaped precipitation of carbides at an original austenite grain boundary is effectively inhibited, the grain uniformity is remarkably improved, the high-temperature endurance life is remarkably prolonged, the impact toughness is remarkably improved, and the method is suitable for preparation of high-quality forgings of GH4099 high-temperature alloy and has good industrial application prospects.

The invention relates to the technical field of ferrous metallurgy, and discloses a hot-rolled structure homogenization controlled cooling method for improving the drawing performance of medium carbon steel, which comprises the following steps: S1, heating process, S2, rolling process temperature control, S3, post-rolling segmented controlled cooling process, S4, coil collection and heat preservation treatment, and S5, quality inspection and process adjustment. By adopting a heating process of'wide-range soaking temperature of 1050-1150 DEG C + sufficient in-furnace time of 120-200 minutes' and dynamically adjusting according to the specification of the steel billet (the upper limit of temperature is taken by small specification and the lower limit of temperature is taken by large specification), the problem of composition segregation caused by traditional uneven heating is effectively solved, the internal temperature fluctuation of the steel billet is controlled within + / -20 DEG C, and the steel billet has high tensile strength. The component homogenization degree is improved by 15%-20%; meanwhile, in the rolling stage, the finish rolling temperature (860-900 DEG C), the reducing sizing temperature and the spinning temperature are optimized according to specifications, the spinning temperature fluctuation is controlled within + / -15 DEG C, austenite grain coarsening is avoided, and conditions are created for forming fine and uniform structures after rolling.

The invention relates to the technical field of steel detection, in particular to a method for detecting the austenite grain size of low-carbon steel through an oxidation method. The method comprises the following steps: S1, cutting a metallographic specimen from low-carbon steel, and grinding and polishing the metallographic specimen; s2, the metallographic specimen ground and polished in the step S1 is subjected to segmented heat treatment; s3, removing an oxide layer on the detection surface of the metallographic sample subjected to segmented heat treatment in the step S2, and then polishing the detection surface; s4, corroding, washing and blow-drying the polished detection surface of the metallographic specimen in the step S3 by using 2-6% nitric acid alcohol; s5, the metallographic sample treated in the step S4 is observed under an optical microscope, and the austenite grain size grade of the low-carbon steel is determined, photographed and preserved; wherein in the step S2, the condition of the segmented heat treatment comprises the following steps: preserving heat for 40-60 minutes at the temperature of 850-920 DEG C, and then preserving heat for 20-30 minutes at the temperature of 720-800 DEG C. According to the method, the austenite grain size of the low-carbon steel is accurately and efficiently detected by optimizing a heat treatment process and a sample preparation process.

The purpose of the present invention is to provide a hot-rolled steel sheet which has a tensile strength of 980 MPa or more, while having excellent ductility, fatigue resistance, and shear workability.　This hot-rolled steel sheet has a predetermined component composition and has a microstructure that includes: an upper bainite phase; and one or both of a fresh martensite phase and a retained austenite phase, wherein the area ratio of the upper bainite phase is 90% or more, the total area ratio of the fresh martensite phase and the retained austenite phase is 10% or less, the average aspect ratio of prior austenite grains is 6.0 or less, the number density of MnS having a major axis of 10 μm or more in a cross section parallel to the rolling direction is 20 per mm2 or less, and the average particle diameter of Ti-based sulfides is 2.0 μm or less.

The invention relates to the technical field of an austenitic stainless steel sensitization process, in particular to an in-situ dynamic observation method for the austenitic stainless steel sensitization process. Aiming at the problem that dynamic precipitation of carbides on an original grain boundary cannot be clearly and continuously captured by the existing observation means, the method is realized by the following steps of: firstly, carrying out electrolytic polishing on a sample to obtain an observation surface without a deformation layer, and ensuring that only the original austenite grain boundary is shown at high temperature; secondly, executing a thermal cycle program including rapid solid solution and controllable cooling to a sensitization temperature in the HT-CLSM, and locking a precipitation process in a target isothermal stage; finally, automatic timing image acquisition is performed on the fixed field of view during an isothermal period. The method realizes clear, dynamic and visual observation of the whole sensitization process, especially initial nucleation, reveals carbide precipitation kinetics, provides an effective tool for research of a sensitization mechanism and material evaluation, and is suitable for austenitic stainless steel.

This invention provides an alloyed hot-dip galvanized steel sheet with a tensile strength of 590 MPa or higher, excellent ductility and microcrack resistance, comprising a steel plate and an alloyed hot-dip galvanized layer. The steel sheet has a carbon equivalent (Ceq) of 0.370 or higher and less than 0.520, and a total Nb and Ti content of 0.010 to 0.080% by mass. At one-quarter of the plate thickness, the martensite area fraction is 5 to 30%. From the surface of the steel sheet to a depth of 20 μm, the martensite area fraction is 5 to 30%, the original austenite grain size is 3.0 μm or less (martensite area fraction 50% or higher), and the total Nb and Ti content in precipitates smaller than 100 nm is 50 ppm by mass or more, while the total Nb and Ti content in precipitates larger than 100 nm is 350 ppm by mass or less. Within a range from the surface of the steel plate to a depth of 1 μm, the long sides of the Si and Mn oxides present at the grain boundaries are less than 200 nm.

The application discloses a 730MPa-grade ultra-high-strength high-rise building steel plate and a manufacturing method thereof, and belongs to the field of alloy steel manufacturing.The chemical components of the steel plate are as follows: C, Si, Mn, P, S, Cr, Ni, Cu, Nb, V, Ti, Al, and the balance of Fe and inevitable impurity elements.A low-C and micro-alloying method is adopted in the application, and a small amount of Cr, Ni and Cu elements are added; Nb and V micro-alloying elements are used to precipitate and separate out in a two-stage rolling process, so as to pin austenite grains, inhibit the growth of the austenite grains and refine the grain size; the rolling process is strictly controlled in the two-stage rolling process, and a subsequent rapid water cooling mode is controlled; through the control of a precise red temperature, a certain proportion of bainite and ferrite structures are obtained; the application has excellent comprehensive performance of low yield ratio, high strength, high elongation and high low-temperature toughness, and has important significance for the development of various building steel structures.

The invention discloses a method for displaying an original austenite grain boundary of X80 pipeline steel. The method mainly comprises the steps of sampling, sample preparation, corrosion and metallographic observation. The corrosive agent is characterized by comprising the following components in proportion: every 100 mL of corrosive liquid contains 5-10 g of glacial acetic acid, 10-15 g of oxalic acid, 5-10 g of ferric trichloride, 10-15 g of dishwashing liquid and the balance of high-purity water; putting the ground and polished grain size sample into the corrosive liquid with the grinding surface facing upwards, heating to 70 + / -2 DEG C, and keeping the temperature for 20-30 minutes; by adopting the method disclosed by the invention, the displayed sample grain boundary is clear and complete, and the rating requirements of manual and metallographic analysis software are met. The method provided by the invention provides more reliable conditions for accurately measuring the original austenite grain size of the X80 pipeline steel.

This invention discloses a thick-gauge bridge weathering steel with a compression ratio of less than 2.5 and its production method, belonging to the field of metallurgical technology. Addressing the problems of poor toughness and unsatisfactory flaw detection performance in thick-gauge bridge weathering steel with a compression ratio of less than 2.5, a synergistic process is adopted: "one-stage high-temperature high-reduction rolling + intermediate laminar flow rapid cooling to 900-950℃ + two-stage controlled rolling in the non-recrystallization zone + quenching and tempering heat treatment." The first-stage high reduction ensures core welding; the intermediate rapid cooling inhibits austenite grain growth and creates low-temperature conditions for finishing rolling; combined with quenching and tempering heat treatment, the microstructure is optimized. The resulting 60-75mm thick steel plate has a yield strength ≥400MPa, tensile strength ≥500MPa, elongation ≥25%, impact energy at -40℃ ≥200J, and ultrasonic flaw detection level II pass rate ≥95%, achieving a balance of high strength, high toughness, and high flaw detection pass rate at a low compression ratio.

The invention relates to a coated steel sheet and a press-hardened steel component having a composition comprising: 0.15 to 0.25 wt% of C, 0.5 to 1.8 wt% of Mn, 0.1 to 1.25 wt% of Si, 0.01 to 0.1 wt% of Al, 0.1 to 1.0 wt% of Cr, 0.01 to 0.1 wt% of Ti, 0.001 to 0.004 wt% of B, P < = 0.020 wt%, S < = 0.010 wt%, N < = 0.010 wt%, with the balance being Fe and unavoidable impurities. The remainder of the composition is iron and unavoidable impurities resulting from smelting. The press-hardened steel component comprises: a body having a microstructure comprising more than 95% martensite and less than 5% bainite in surface fraction; a coating at a surface of the steel component; a ferritic interdiffusion layer between the coating and the body, and a ratio between a ferritic grain width GW interdiffusion layer in the interdiffusion layer and a primal austenitic grain size PAGS body in the body satisfy the following equation (GW interdiffusion layer / PAGS body)-1 > = 30%.

Provided are a steel sheet and a member, having high strength and high delayed fracture resistance, and methods for manufacturing the steel sheet and the member. The steel sheet has a specific chemical composition and a microstructure in which the area fraction of martensite is 95% to 100%, with the balance being one or more of bainite, ferrite, and retained austenite. In the steel sheet, prior-austenite grains have an average grain size of 18 μm or less, 90 mass % or more of the total content of Nb and Ti contained is present as a carbonitride having an equivalent circular diameter of 100 nm or more, and a Nb carbonitride and a Ti carbonitride, having an equivalent circular diameter of 1.0 μm or more, are present at a rate of 800 pieces / mm2 or less in total. The steel sheet has a tensile strength of 1310 MPa or more.

The invention discloses a 9Ni steel plate with low Ni segregation and excellent low-temperature toughness and a preparation method and application of the 9Ni steel plate with low Ni segregation and excellent low-temperature toughness, and the preparation method of the 9Ni steel plate with low Ni segregation and excellent low-temperature toughness adopts the following smelting route: continuous casting, hot rolling, induction heating quenching, two-phase region quenching and tempering, wherein a casting blank obtained through continuous casting is subjected to soft reduction treatment so that the segregation index of the Ni element in the core of the casting blank can be smaller than or equal to 1.10, then hot rolling treatment is carried out so that the average size of austenite grains of the steel plate can be within the range of 9-12 microns, and then quenching treatment and tempering treatment are carried out twice. According to the preparation method, the structure uniformity and Ni segregation in the heat treatment process of the 9Ni steel rolling plate can be obviously reduced, the surface oxidation in the heating process of the 9Ni steel plate can be greatly reduced, the surface quality of the steel plate is ensured, and a powerful guarantee can be provided for obvious improvement of the transverse and longitudinal impact toughness at the temperature of 196 DEG C below zero and uniformity control of the steel plate.

The present invention provides: a steel sheet which is excellent in ultimate deformability isotropy and has high elongation and ultimate deformability in spite of having high strength; and a component including the steel sheet. Provided is a steel sheet having a predetermined chemical composition, the steel sheet being characterized in that the metal structure at a 1 / 4 thickness position from a surface contains, in terms of area%, 70%-95% of bainite and 5%-30% of martensite; the average aspect ratio of prior austenite grains at the 1 / 4 thickness position from the surface is 3.00-5.50; and the standard deviation of hardness in the region between a 3 / 8 thickness position and a 5 / 8 thickness position from the surface is 25 Hv or less.

This invention discloses a method for improving the performance of Q690C steel used in tunnel pre-embedded components. Through microalloying and strict desulfurization and deoxidation during the steelmaking stage, controlling the final rolling temperature of hot rolling / forging (820-880℃), combined with differential zone controlled cooling (7-10℃ / s in thin zones, 3.0-4.2℃ / s in thick zones) and uniform isothermal short-stop (330-350℃×10-15 min), deep cooling after quenching (-80 to -100℃×20-40 min), and two-stage tempering (420-480℃ and 200-260℃), a refined prior-austenite grain, uniform lower bainite / tempered martensite, and nano-precipitate composite microstructure is formed. Its -40℃ impact energy reaches 128-155J, CGHAZ grain size is 6-10μm, retained austenite ≤2.5%, and the toughness, corrosion resistance, and fatigue life of welded joints are significantly improved.

The invention provides a machining method for improving the yield strength and the product of high strength and elongation of a 10Mn medium manganese steel plate, and relates to the technical field of medium manganese steel. The 10Mn medium manganese steel plate with high yield strength and high product of strength and elongation is obtained through ingot casting, forging, hot rolling, warm rolling, cold rolling and tempering. The austenite grain size of the 10Mn medium manganese steel plate can reach 0.39 mu m, and the austenite content can reach 30.4%. According to the machining method, the yield strength and the product of strength and elongation of the 10Mn medium manganese steel plate can be remarkably improved under the condition that the production cost is slightly increased, the comprehensive requirements of the modern industry, especially the automobile industry, for material performance are met, and industrial production and application of medium manganese steel are promoted.

The invention relates to the technical field of steel and iron material metallurgy, and discloses a bainite non-quenched and tempered steel Al-Ti-N component collaborative regulation and control process which comprises the steps of S1 raw material pretreatment, S2 smelting process, S3 refining process, S4 continuous casting process, S5 rolling process and S6 finished product inspection. AlN and TiN effectively pinning austenite grain boundaries to inhibit grain coarsening, VN disperses and precipitates to strengthen a matrix, so that the grain size of the steel is stable to be greater than or equal to level 5, a metallographic structure is mainly bainite and only contains less than or equal to 6% of ferrite, no obvious martensite harmful structure exists, the tensile strength reaches 900-1060 MPa, the yield strength is greater than or equal to 650 MPa, the impact energy (20 DEG C) is greater than or equal to 28 J, and the strict requirements of automobile key parts on obdurability are completely met; according to the process, the structure and production stability is remarkably improved, and sulfide inclusions and the gas content are reduced through precise impurity control and component control design of raw material pretreatment and smelting refining.

The application relates to the technical field of metal material detection, and provides an alloy spring steel austenite grain size detection method, which comprises the following steps: carrying out heating and heat preservation treatment on an alloy spring steel sample, the temperature of the heating and heat preservation treatment is in a grain boundary segregation sensitization temperature interval of phosphorus elements, so that the phosphorus elements are segregated at original austenite grain boundaries; carrying out metallographic sampling on the alloy spring steel sample after the heating and heat preservation treatment to obtain a metallographic sample; carrying out corrosion treatment on the metallographic sample under heating conditions by using a water-based etching liquid, the water-based etching liquid comprises picric acid and a surfactant; and observing the metallographic sample after the corrosion treatment to obtain austenite grain size. The application simplifies a detection process, clearly shows original austenite grain boundaries, and improves grading accuracy.