137 results about "Ferrite pearlite" patented technology

The invention relates to steel for a long-service-life automobile water pump shaft connecting bearing and a production method of the steel, and belongs to the field of iron-based alloys, the steel comprises the following element components in percentage by weight: 0.80-0.90% of C, 0.65-0.85% of Si, 0.20-0.40% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, 1.60-1.70% of Cr, 0.40-0.50% of Ni, 0.30-0.40% of Mo, less than or equal to 0.050% of Al, 0.0010-0.0020% of rare earth La, less than or equal to 0.0020% of Ti, less than or equal to 0.0010% of Ca, less than or equal to 0.0010% of O and the balance of Fe and inevitable impurities. The production process of the steel comprises the steps of electric furnace or converter primary smelting, external refining, VD or RH vacuum degassing, continuous casting, continuous rolling, normalizing, finishing and piece making and warehousing. The metallographic structure of the steel surface layer is a ferrite and pearlite structure, and the metallographic structure of the core part is cementite and pearlite. The rolling contact fatigue rated life of the steel material under the contact stress of 4.5 GPa is more than 5 * 107 times.

The invention belongs to the technical field of metallurgy, and particularly relates to a production method of an annealing-free 10.9-grade and above high-strength alloy cold heading steel wire rod. The cold heading steel wire rod comprises the following chemical components in percentage by weight: 0.32%-0.38% of C, 0.15%-0.30% of Si, 0.60%-0.90% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, more than or equal to 0.020% of Al, 0.80%-1.10% of Cr, 0.15%-0.30% of Mo and the balance of Fe and inevitable impurities. Comprising the following key process steps: (1) reducing and sizing at the temperature of 780-820 DEG C; (2) the spinning temperature is 760-800 DEG C; (3) the temperature of entering a heat preservation cover is 690-730 DEG C; and (4) the temperature of discharging from a heat insulation cover is not more than 550 DEG The metallographic structure of the obtained cold forging steel is ferrite and pearlite, the specification is phi 5.5-phi 12.0 mm, and the tensile strength is smaller than or equal to 800 MPa. Therefore, the requirements of customers for reducing and avoiding the annealing process are met, and the purposes of saving energy, reducing emission, improving production efficiency and creating benefits for customers are achieved.

The invention relates to a high-performance non-quenched and tempered steel bar for a fan shaft and a manufacturing method of the high-performance non-quenched and tempered steel bar, and belongs to the field of iron-based alloys. The steel comprises the following chemical components in percentage by weight: 0.37 to 0.43 percent of C, 0.30 to 0.60 percent of Si, 1.20 to 1.70 percent of Mn, less than or equal to 0.025 percent of P, 0.030 to 0.070 percent of S, less than or equal to 0.50 percent of Cr, 0.10 to 0.30 percent of Ni, less than or equal to 0.30 percent of Mo, less than or equal to 0.30 percent of Cu, 0.010 to 0.030 percent of Al, 0.005 to 0.025 percent of Ti, 0.05 to 0.15 percent of V, 0.0100 to 0.0200 percent of N, less than or equal to 0.0002 percent of H, less than or equal to 0.0015 percent of O and the balance of Fe and inevitable impurity elements. The manufacturing process comprises the steps of converter / electric furnace smelting, LF furnace refining, RH / VD furnace vacuum degassing, continuous casting, casting blank reheating, cogging rolling, flame cleaning, intermediate blank finishing, intermediate blank heating, bar rolling, cooling and stress relief tempering. The total cross-section structure of the bar is a ferrite and pearlite structure. The bending degree per meter is smaller than or equal to 0.5 mm, the surface defect depth is smaller than or equal to 0.10 mm, and the internal quality meets the A-level requirement of the GB / T4162 standard.

The invention discloses a low-yield-ratio carbon-manganese low-temperature steel plate and a production method thereof, the steel comprises the following chemical components in percentage by mass: 0.07%-0.08% of C, 0.15%-0.25% of Si, 1.30%-1.40% of Mn, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.10%-0.20% of Ni, 0.012%-0.017% of Nb, 0.008%-0.020% of Ti, 0.020%-0.050% of Al and the balance of Fe and inevitable impurities, the structure type of the steel is ferrite and pearlite, and the grain size is 9-10 levels. The process comprises the steps of converter smelting, LF refining, vacuum degassing, continuous casting, heating, rolling and finishing. The yield strength of the steel plate is 315-440 MPa, the tensile strength is 440-520 MPa, the yield ratio is smaller than or equal to 0.85, the elongation is larger than or equal to 30%, and the-60 DEG C impact Akv is larger than or equal to 80 J; and excellent welding and firework process properties are achieved.

The invention discloses a 42CrMo forge piece quenching deformation calculation method, which comprises the following steps: based on three groups of cooling test results at different cooling rates, obtaining a change curve of a thermal expansion coefficient along with temperature, grinding, polishing and corroding a sample cooled at the three rates, observing a metallographic structure, and calculating the quenching deformation of a 42CrMo forge piece. Counting the volume fractions of ferrite, pearlite, bainite and martensite, and establishing a structure transformation model; and then, finite element software is used for inversely calculating phase change kinetic model parameters of the 42CrMo steel and thermal expansion coefficient curves of different tissues, so that the technical problem that phase change expansion cannot be predicted in the quenching deformation calculation process of the 42CrMo forge piece is solved, and the quenching deformation calculation precision of the forge piece is improved.

The application discloses a low-carbon-equivalent 355MPa grade normalized rolled thick plate organization uniformity control method, wherein the temperature of the billet before charging is less than or equal to 400 DEG C, the temperature of the soaking furnace is 1130-1150 DEG C, the time of the soaking section is 45-55 minutes, the total furnace time is 170-185 minutes, the second opening temperature of the billet is 880-940 DEG C, the finishing rolling is 6-8 passes, the cumulative reduction is 60-70%, and the final rolling temperature is 860-900 DEG C; the steel plate cooling is realized by adopting a laminar flow cooling system, the full-automatic water pouring control cooling mode is adopted, the water inlet temperature is 720-740 DEG C, the red temperature is 640-660 DEG C, and the surface temperature of the steel plate after cooling is monitored. The head and tail and the full-thickness organization type of the normalized rolled steel plate are all 'ferrite + pearlite' organizations, the grain size level is all above 9.0, there is no obvious banded structure and no bainite structure, and the problem of the organization difference of the 355MPa grade thick plate product caused by the normalized rolling is solved.

The invention relates to steel for an excavator driving gear and a manufacturing method thereof. The steel for the excavator driving gear comprises the following chemical components in percentage by mass: 0.24 to 0.28 percent of C, 0.30 to 0.45 percent of Si, 0.80 to 0.95 percent of Mn, 1.15 to 1.30 percent of Cr, less than or equal to 0.015 percent of P, 0.025 to 0.035 percent of S, 0.018 to 0.030 percent of Al, 0.0012 to 0.0018 percent of B, 0.05 to 0.10 percent of Cu, 0.16 to 0.28 percent of Ni, 0.06 to 0.12 percent of Mo, less than or equal to 0.003 percent of Sn, less than or equal to 0.003 percent of Sb, 0.006 to 0.0095 percent of N, less than or equal to 0.0010 percent of O and the balance of Fe and inevitable impurities. The method comprises the following steps: smelting in an electric furnace, refining in a refining furnace, vacuum degassing in a VD furnace, continuous casting, overall heating of a continuous casting blank, rolling into round steel, precise temperature control air cooling, and uniform slow cooling in a pit. The steel has the characteristics that the steel oxygen content O is smaller than or equal to 0.0010%, the steel oxide sum index K2 (O) is smaller than or equal to 20, the round bar center segregation is smaller than or equal to 0.5 level, the steel structure is uniform pearlite and ferrite, the diameter of the pearlite and the diameter of the ferrite are 18-25 micrometers, the hardness discrete value of each rolled round bar with the same furnace number is controlled to be smaller than or equal to 15 HBW, and the bending degree of the round bars is smaller than or equal to 2.0 mm / m.

Provided in the present invention are a hardness evaluation method and system for a heat affected zone of a multi-layer and multi-pass welded joint of hull steel. The method comprises: establishing a finite element model of a welded joint, and acquiring welding thermal cycles at nodes in a heat affected zone of the finite element model; performing solving to obtain critical temperatures for microstructural transformations of a study object, and performing solving to obtain volume fractions of transformation products during the thermal cycles, and a volume fraction of an austenite-ferrite-pearlite mixture after all the thermal cycles; acquiring hardness values of a martensite and a bainite in each thermal cycle, and a hardness value of the austenite-ferrite-pearlite mixture after all the thermal cycles; and on the basis of the acquired hardness values of the martensite and the bainite in each thermal cycle, and the the acquired hardness value of the austenite-ferrite-pearlite mixture after all the thermal cycles, acquiring a comprehensive hardness value of the heat affected zone. The present invention can accurately reproduce heat conduction and a microstructure transformation process in a heat affected zone during multi-layer and multi-pass welding of full steel, thereby assisting engineers in evaluating a welding temperature field and the structure distribution of the heat affected zone.

The invention discloses a high-toughness anti-fatigue high-pressure-resistant seamless steel tube and a gradient preparation method thereof, and relates to the technical field of metal material processing. The seamless steel tube forms a performance gradient from the inner wall to the outer wall in the wall thickness direction; the seamless steel pipe sequentially comprises a ferrite-pearlite structure layer, a transition structure layer and a tempered martensite structure layer from the inner wall to the outer wall, a Fe4N nitride layer and a Ni-Ti alloy layer are arranged on the inner wall, and a reinforced surface layer is formed on the outer wall through ceramic coating treatment. According to the seamless steel pipe, the performance gradient is formed along the wall thickness, the inner wall has high toughness and corrosion resistance, and the outer wall has high strength and fatigue resistance and adapts to complex working conditions; the gradient preparation method solves the problems that a traditional technology is large in heating temperature difference, uneven in rolling deformation, asynchronous in heat treatment phase change and the like, the comprehensive performance is improved, the technology is based on the prior art, the improvement cost is low, and industrial production is facilitated.

The invention provides an identification method of a steel ferrite pearlite metallographic structure, and relates to the technical field of computer vision, in particular to the technical field of image processing. The identification method of the steel ferrite pearlite metallographic structure comprises the following steps: carrying out image preprocessing on a to-be-detected metallographic image to obtain a metallographic binary image; extracting a pearlite region in the metallographic binary image to obtain a pearlite region image; the boundaries of ferrite grains in the metallographic binary image are extracted, and a grain boundary structure image is obtained; determining a ferrite grain distribution image including the pearlite according to pixel values of pixel points at the same positions in the pearlite area image and the grain boundary structure image; and identifying the ferrite grain distribution image to obtain an identification result.

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 invention relates to a thick hot-rolled spring wide steel plate, and belongs to the field of iron-based alloys. The steel comprises the following chemical components in percentage by mass: 0.47 to 0.55 percent of C, 0.17 to 0.37 percent of Si, 0.70 to 1.10 percent of Mn, 0.90 to 1.20 percent of Cr, 0.10 to 0.25 percent of V, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S and the balance of Fe and inevitable impurities, and the structure is uniform ferrite and pearlite. The production thickness ranges from 41 mm to 55 mm, the width is larger than 2000 mm, and the length is not smaller than 6000 mm; the straightness is less than or equal to 3mm / m, and the thickness tolerance range is within 1mm. The hardness is smaller than 280 HBW, the inclusions A, B, C and D are all smaller than 1.5 grades, and the sum of the inclusions A, B, C and D is smaller than or equal to 3.0 grades and is larger than or equal to 2.0 grades. High purity, longitudinal and transverse performance uniformity and accurate thickness control of the large-size spring steel plate are achieved, the thickness machining amount of the steel plate is reduced by four times compared with that of a forging technology, the higher yield is achieved, and the production cost of large-size springs is greatly reduced.

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 present application provides a flexible control method for the failure of flat coils of hot-rolled strip steel, which includes: Step 1, input the steel grade and evaluate the flat coil condition of the steel grade; Step 2, calculate or measure the Ar3 temperature in the phase transformation temperature of the steel grade; Step 3, obtain the isothermal transformation law of austenite, cool the hot-rolled strip steel by a segmented cooling method, and quickly cool the hot-rolled strip steel to the nose point T of ferrite, pearlite or bainite transformation by the front-stage rapid cooling method nose , and calculate the austenite phase transformation rate when the hot-rolled strip steel reaches the coiler mandrel #imgabs0#. Increase the austenite phase transformation rate by adjusting process parameters #imgabs1#, and perform a logical judgment on the austenite phase transformation rate #imgabs2#. When the austenite phase transformation rate is #imgabs3#, output the second flat coil control process; when the austenite phase transformation rate is #imgabs4#, output the third flat coil control process. This method can select different flat coil control processes and effectively control the occurrence of flat coils of the strip steel.

The application discloses a method for improving the production efficiency of normalized rolling Q420NE wind power steel, and the chemical components of the Q420NE wind power steel are as follows in percentage by weight: C: 0.16-0.18%; Si: 0.20-0.30%; Mn: 1.45-1.65%; Nb: 0.035-0.045%; V: 0.035-0.045%; Ti: 0.010-0.020%; P: less than or equal to 0.015%; S: less than or equal to 0.005%; Ca: 0.0008-0.0020%; Als: 0.015-0.030%; O: less than or equal to 0.0035%; N: less than or equal to 0.0052%; and the rest is iron and inevitable impurities; and a specific preparation process and control parameters are disclosed. The prepared steel plate has good strength, plasticity and toughness, and the structure is fine ferrite+pearlite+behenite.

This steel sheet has a prescribed chemical composition, wherein: the microstructure at a 1 / 4 thickness position that is the position at 1 / 4 the plate thickness in the plate thickness direction from the surface, is composed of, in area%, retained austenite: 3-10%, ferrite: 0-10%, pearlite: 0-5%, and martensite and bainite: 75-95% in total; and, in a cross section parallel to the plate thickness direction, when a region measuring 80 μm × 80 μm centered at the 1 / 4 thickness position in the plate thickness direction and measuring 80 μm in a direction perpendicular to the plate thickness direction is divided into 16 parts each measuring 20 μm × 20 μm, and the area ratio of retained austenite in each divided region is determined, σ1 / γave is 0.20 or less, where σ1 is the standard deviation and γave is the average of the area ratio of retained austenite in each divided region.

This invention discloses a ship plate steel with high plasticity, excellent impact toughness, and excellent weldability, and its production method. The composition of the ship plate steel includes C, Si, Mn, Als, P, S, Re, and the balance Fe and impurities. The preparation method includes: heating the billet at a temperature of 1150–1250℃, a heating rate of 8–12 min / cm, and a furnace exit temperature in the range of 1170±30℃; rolling: the first-stage rolling temperature is ≥1050℃, the intermediate billet thickness is 3 times the thickness H of the finished steel plate, and the second-stage rolling temperature is ≤960℃. The final rolling temperature is 830±30℃; the red-hot temperature after rolling is determined according to the thickness H of the finished steel plate. When H≤16mm, the red-hot temperature after rolling is 620±40℃; when 16<H≤25mm, the red-hot temperature after rolling is 640±30℃. The maximum thickness of the finished steel plate obtained by this invention is 25mm, the yield strength ReH≥320MPa, the tensile strength Rm≥420MPa, the elongation A≥30%, the longitudinal impact energy KV2≥200J at 0℃, and the steel plate microstructure is ferrite + pearlite. It is an economical high-plasticity ship plate steel.

The present application relates to a kind of thickness > 250 ~ 300mm low compression ratio S355NL extra-thick steel plate and its manufacturing method, the chemical composition of the steel plate: C:0.08 ~ 0.12%, Si:0.20 ~ 0.40%, Mn:1.45 ~ 1.65%, P:≤0.005%, S:≤0.001%, Al:0.02 ~ 0.05%, Nb:0.02 ~ 0.05%, V:0.03 ~ 0.06%, Ni:0.25 ~ 0.45%, Ti:0.01 ~ 0.03%, the balance is Fe and inevitable impurity element, carbon equivalent Ceq≤0.45%.Production using large thickness thick continuous casting slab, rolling compression ratio is less than 2.0.The internal quality and mechanical property of steel plate meet: yield strength ≥275Mpa, tensile strength ≥450Mpa, elongation after fracture ≥22%, the Charpy impact energy of transverse direction at-50 ℃ single value ≥100J, thickness direction tensile reduction of area ≥35%.Steel plate UT flaw detection can meet the requirement of NB / T47013.3 I level.The metallographic microstructure of steel plate is uniform fine ferrite + pearlite structure.

The present application relates to a kind of wind turbine gear box bearing steel and its production method, belong to the field of wind power steel.The steel is φ180-φ250mm round steel, metallographic structure is ferrite+pearlite, and a small amount of bainite.Adopting molten iron pretreatment-converter or electric arc furnace smelting-LF refining-RH or VD furnace vacuum degassing-large section continuous casting CCM large billet-rolled into round steel-finishing production process.The macrostructure of round steel: loose center ≤1.5 level, general loose ≤1.0 level, center crack ≤1.0 level, center segregation ≤1.0 level, no shrinkage cavity and subsurface crack.Inclusion: B fine ≤1.5 level, B coarse ≤0.5 level, D fine ≤1.0 level, D coarse ≤0.5 level, Ds ≤1.5 level.Macroscopic inclusion: image defect density ≤10mm / dm³, image single defect length ≤3mm, except 15% D in the center of bar.The banded structure is ≤3 levels.The present application is a kind of wind power steel with excellent purity, uniformity and density.

The invention belongs to the technical field of cold forging steel rolling, and particularly relates to a hot-rolled wire rod and a method for improving the plastic deformation capacity of the hot-rolled wire rod. The method comprises the following steps that S1, a first steel billet is obtained, and shot blasting treatment is conducted on the first steel billet to obtain a second steel billet; s2, the second steel billet is preheated, heated and subjected to heat preservation, and a third steel billet is obtained; s3, the third steel billet is subjected to first dephosphorization, rough rolling, second dephosphorization, rolling of a finishing mill, rolling of a reducing sizing mill, spinning and curling, and then a first hot-rolled wire rod is obtained; and S4, the first hot-rolled wire rod is put into a Stelmor cold conveying line to be cooled, and the hot-rolled wire rod is obtained. According to the hot-rolled wire rod and the preparation method thereof, structure regulation and control of the hot-rolled wire rod are achieved through cooperation of component optimization and process adjustment, transformation from coarse grain and high bainite proportion to fine grain and uniform ferrite and pearlite is achieved, the plastic deformation capacity of the hot-rolled wire rod is remarkably improved, the requirement of the downstream one-annealing and two-drawing process is met, and the production efficiency and the product percent of pass are greatly improved.

The invention relates to the technical field of metallographic analysis and detection, and particularly discloses a display method for accurately distinguishing multi-phase structures of a W780X hot rolled plate. Performing hot inlaying; performing grinding; polishing is conducted; corroding, namely soaking and corroding the polished sample in an aggressive agent sodium thiosulfate solution for 10-200 seconds, taking out, wiping the surface by using a hydrochloric acid alcohol cotton ball to remove a corrosion product on the surface, washing by using alcohol, and drying by blowing; the morphology, size and distribution state of ferrite, pearlite and martensite can be clearly displayed through metallographic microscope observation. Compared with the prior art, the etchant adopted by the invention is a solution prepared from 8-15g of sodium thiosulfate and 77-90ml of water, the three structures can be clearly displayed after corrosion, the cost is low, the etchant is safe and non-toxic, the preparation is convenient, and the morphology and distribution state of ferrite, pearlite and martensite in the metallographic structure of the W780X hot-rolled plate can be clearly and completely displayed; the method has the characteristics of low detection cost, rapidness, simplicity and accuracy.

The invention relates to a low-compression-ratio S355NL super-thick steel plate with the thickness larger than 250-300 mm and a manufacturing method of the low-compression-ratio S355NL super-thick steel plate. The steel plate comprises the chemical components of 0.08%-0.12% of C, 0.20%-0.40% of Si, 1.45%-1.65% of Mn, smaller than or equal to 0.005% of P, smaller than or equal to 0.001% of S, 0.02%-0.05% of Al, 0.02%-0.05% of Nb, 0.03%-0.06% of V, 0.25%-0.45% of Ni, 0.01%-0.03% of Ti and the balance Fe and inevitable impurity elements, and the carbon equivalent Ceq is smaller than or equal to 0.45%. A large-thickness thick continuous casting slab is adopted for production, and the rolling compression ratio is smaller than 2.0. The internal quality and mechanical properties of the steel plate meet the requirements that the yield strength is larger than or equal to 275 Mpa, the tensile strength is larger than or equal to 450 Mpa, the percentage elongation after fracture is larger than or equal to 22%, the transverse Charpy impact energy unit value at the temperature of-50 DEG C is larger than or equal to 100 J, and the thickness direction tensile area reduction rate is larger than or equal to 35%. And the UT flaw detection of the steel plate can meet the NB / T47013.3 I grade requirement. The metallographic microstructure of the steel plate is a uniform and fine ferrite and pearlite structure.

The invention relates to a 45 steel plate for punch forming of a high-strength chain wheel and a preparation method of the 45 steel plate. The steel comprises the following chemical components: 0.42%-0.48% of C, 0.20%-0.30% of Si, 0.55%-0.65% of Mn, less than or equal to 0.015% of P, less than or equal to 0.010% of S, 0.015%-0.025% of V, 0.15%-0.20% of Cr and the balance of Fe and impurities. The metallographic structure of the finished steel plate is a ferrite and pearlite mixed structure, and the volume fraction ratio of ferrite to pearlite is (45%-55%): (55%-45%); and the grain size grade is 8.0-10.0 grade. On the basis of traditional 45 steel components, a small amount of V and Cr elements are added, a specific controlled rolling and controlled cooling process is combined, under the condition that follow-up heat treatment is not carried out, hot-rolled strip steel which is small in grain size, uniform in structure and excellent in obdurability matching is directly obtained, and the finished steel product is particularly suitable for punch forming of chain wheels.

The invention provides a sulfur-resistant corrosion-resistant low-carbon alloy coiled tubing and a preparation method thereof, and relates to the technical field of coiled tubing. By means of the plasma welding mode, steel strip weld joint grains are refined, the structure is uniform, the strength is stable, and the strength and corrosion resistance of a plate connector are prevented from being reduced. According to the heat treatment process, weld grains are refined, the structure is more uniform, stress is removed, the strength of the whole pipe is stable, the structure is uniform, and the final purposes of high strength and high corrosion resistance are achieved. The metallographic structure of the sulfur-resistant and corrosion-resistant low-carbon alloy coiled tubing is ferrite and pearlite, the average grain size of metal in a weld joint, a heat affected zone and a base material reaches 10.0 grade or above, and the comprehensive performance can reach 90 steel grade.

The present invention provides: a continuously cast slab in which slab season cracking does not occur during cooling of the continuously cast slab even if the continuously cast slab has a low toughness; and a method for manufacturing the same. Disclosed is a continuously cast slab for high-strength steel, which has a specific component composition, the continuously cast slab being characterized in that: the average prior austenite grain size ratio (d20 / d10) of the average prior austenite grain size d20 at the position of 20 mm below a surface layer of the continuously cast slab to the average prior austenite grain size d10 at the position of 10 mm below the surface layer of the continuously cast slab is 1.0 to 4.0 inclusive; the microstructure is composed of ferrite, pearlite, bainitic ferrite, tempered martensite, quenched martensite, and retained austenite; and the microstructure at the position of 10 mm below the surface layer of the continuously cast slab and the microstructure at the position of 20 mm below the surface layer of the continuously cast slab are formed of a structure that has a specific area ratio.

The high-performance carbon steel comprises the following components in percentage by weight: 0.05 to 0.25 percent of C, 0.10 to 0.40 percent of Si, 0.55 to 2.0 percent of Mn, 0.01 to 0.05 percent of N, less than or equal to 0.020 percent of S, less than or equal to 0.018 percent of P, less than or equal to 0.005 percent of As, less than or equal to 0.008 percent of Sb, less than or equal to 0.008 percent of Sn and the balance of Fe and inevitable impurities, and the elements also need to simultaneously meet the following conditions: less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of As, less than or equal to 0.020 percent of Sb and less than or equal to 0.008 percent of Sn; the inevitable impurities comprise Cr, Mo and Mn, and (Cr + Mo + Mn) * N is controlled to be greater than or equal to 0.010%; the microscopic structure of the high-performance carbon steel is ferrite and pearlite, the high-performance carbon steel can be directly used in a hot rolling state, the postweld heat treatment inhibition performance is stable, the room-temperature yield strength is larger than or equal to 240 MPa, the tensile strength is larger than or equal to 415 MPa, the high-temperature instantaneous tensile yield strength at 350 DEG C is larger than or equal to 175 MPa, and the tensile strength is larger than or equal to 350 MPa.

This invention discloses a low-alloy angle steel (Q355B) with micro-niobium and low-manganese content, and its efficient short-process production method. The chemical composition of the angle steel is: C 0.14%~0.21%, Si 0.20%~0.45%, Mn 1.00%~1.25%, Nb 0.005%~0.014%, P≤0.025%, S≤0.020%, N≤0.009%, with the balance being Fe and unavoidable impurities. This method uses scrap steel as raw material, sequentially processing it through electric arc furnace smelting, LF refining, and continuous casting to obtain a high-temperature billet. The high-temperature billet is then directly conveyed to the heating furnace, achieving hot charging and hot delivery. Compared with existing technologies, this invention omits the billet cooling and secondary heating processes, significantly reducing energy consumption, shortening the production cycle, and reducing the formation of iron oxide scale. By substituting a small amount of Mn with Nb, and utilizing the dispersed precipitation of Nb(C,N) to simultaneously achieve grain refinement and precipitation strengthening, a ferrite + pearlite microstructure with an average grain size of 15~23μm is obtained, resulting in angle steel with excellent mechanical properties. This invention, while ensuring the strength and toughness of angle steel, also possesses the comprehensive advantages of energy saving, cost reduction, and efficiency control, and has promising prospects for industrial application.

The invention discloses a rare earth-containing complex-phase hot rolled steel for a wheel rim and a preparation method thereof, and belongs to the technical field of materials and metallurgy, the rare earth-containing complex-phase hot rolled steel comprises the following components: 0.055%-0.090% of C, 0.60%-0.90% of Si, 1.00%-1.60% of Mn, less than or equal to 0.010% of P, less than or equal to 0.001% of S, 0.020%-0.080% of Al, 0.040%-0.080% of Nb, 0.005%-0.020% of Ti, 0.22%-0.30% of Cr, less than or equal to 0.0045% of N, less than or equal to 0.0020% of O, 0.0100%-0.0300% of RE, RE / S is greater than 3, and the balance of iron and inevitable impurities. Wherein RE comprises La and / or Ce. The hot rolled steel produced by the method consists of ferrite, pearlite and granular bainite, and has good mechanical property, broaching property, welding property and fatigue property.

The invention provides a wire rod for enhancing the service performance of a high-strength tire bead wire and a structure control method. The wire rod comprises the following components in percentage by weight: 0.06%-0.12% of [C], 0.15%-0.25% of [Si], 0.50%-0.60% of [Mn], less than or equal to 0.015% of [P], 0.0030%-0.010% of [S], 0.0010%-0.0030% of total oxygen, 0.0005%-0.0015% of [Als], 0.0001%-0.0009% of [V] and 0.0002%-0.0011% of [Mg]. And the balance of Fe and inevitable impurities. The steel wire rod structure control method comprises the steps of smelting, continuous casting, heating, rolling, steel wire rod rolling and steel wire rod cooling. According to the wire rod produced through the method, the grain size is not larger than 25 microns, and the grain size difference is not larger than 2 levels. The wire rod structure is composed of ferrite and pearlite, and the ferrite content is larger than 90%. The tensile strength of the wire rod is 410-450 MPa, and the ductility is 30%-40%.

The invention discloses a production method of a high-toughness high-resistivity low-alloy steel medium plate. Steel comprises the following chemical components in percentage by weight: 0.06%-0.10% of C, 0.90%-1.30% of Si, 1.45%-1.7% of Mn, less than or equal to 0.015% of P, less than or equal to 0.004% of S, 0.020%-0.060% of Alt, 0.008%-0.020% of Ti, 1.3%-1.5% of Mn / Si, more than or equal to 3.42% of Ti / N and the balance of Fe and inevitable impurities. Through high-temperature finish rolling, the finish rolling temperature is 50 DEG C or above higher than the Ar3 temperature point, and complete recrystallization is ensured; after rolling, double-stage controlled cooling is adopted, the pearlite transformation temperature is skipped to 650-700 DEG C through fast cooling, and ferrite is promoted to grow sufficiently through slow cooling; the microstructure of the finally obtained steel plate is 85%-92% of ferrite and 8%-15% of pearlite, the grain size of the ferrite is 10-12 grades, high toughness and high resistivity are well matched, the alloy production cost is low, and the process is simple.