505 results about "Pearlite" patented technology

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 1960MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After high-carbon components containing trace B are designed, rolled and spun into a wire rod, online molten salt rapid quenching treatment is carried out, and the wire rod is firstly subjected to front-section molten salt treatment, so that the wire rod is cooled at the cooling speed of greater than or equal to 36 DEG C / s and enters a bainite and pearlite mixed phase region from an austenite state; the method comprises the following steps: quenching a steel wire rod to form a structure mainly comprising quenched bainite and a sorbite structure, carrying out rear-section molten salt treatment on the steel wire rod, increasing the molten salt temperature, promoting isothermal tempering of the quenched bainite and the sorbite structure, and carrying out roller way slow cooling to prepare the hot-rolled steel wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered sorbite, tempered bainite and ferrite, the composition system can be simplified, the strength and plasticity matching and rapid production of the wire rod are considered, the tensile strength is 1330-1380 MPa, the percentage reduction of area is 35%-40%, and the wire breaking risk in the wire drawing and twisting process of the stranded wire steel can be reduced.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2060MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After high-carbon chemical components containing trace V are designed, rolled and spun into a wire rod, the wire rod is cooled at a cooling speed of more than or equal to 33 DEG C / s through on-line molten salt semi-quenching treatment, enters a bainite and pearlite mixed phase region from an austenite state, and is subjected to hot rolling and hot rolling at a cooling speed of more than or equal to 33 DEG C / s; the method comprises the following steps: quenching bainite and a sorbite structure to form a structure mainly comprising the quenched bainite and the sorbite structure, then carrying out isothermal tempering, and finally carrying out roller way slow cooling to prepare the hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered sorbite and tempered bainite, so that a component system can be simplified, the material cost can be reduced, network carbides can be effectively controlled, and meanwhile, the complex-phase structure can be regulated and controlled; the high strength and plasticity of the wire rod are matched, the tensile strength is 1390-1440 MPa, the percentage reduction of area is 32%-37%, and the steel wire rod is used for manufacturing 2060 MPa grade stranded wires and other application fields and is beneficial to downstream wire drawing and twisting processing.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2230 MPa grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After a Nb-containing high-carbon component is used for rolling and spinning at a spinning temperature to form a wire rod, online molten salt mixing quenching isothermal treatment is carried out, so that the wire rod is firstly subjected to front-section molten salt treatment and is cooled at a cooling speed of more than or equal to 35 DEG C / s, and enters a bainite and pearlite mixed phase region from an austenite state; the method comprises the following steps: firstly, carrying out heat treatment on austenite to promote part of austenite to be converted into bainite and sorbite, then carrying out later-section molten salt treatment, increasing the molten salt temperature, promoting unconverted retained austenite to be decomposed and converted into sorbite, carrying out isothermal tempering, and finally, carrying out roller way slow cooling, so as to prepare the hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered bainite and tempered sorbite, the drawing and hardening capacity can be improved, the production efficiency is considered, the tensile strength is 1522-1572 MPa, and the percentage reduction of area is 29%-34%, so that off-line heat treatment is avoided, and the wire breaking risk and cost of stranded wire manufacturing are reduced.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2200MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod, and the manufacturing method comprises the following steps: rolling and spinning to form a wire rod by adopting a high-hardenability component design, and then carrying out online molten salt mixed phase region quenching isothermal treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and enters a bainite and pearlite phase region from an austenite state; the method comprises the following steps: carrying out high-temperature treatment on austenite to promote part of austenite to be converted into bainite and sorbite, carrying out later-section molten salt treatment, increasing the molten salt temperature, reducing the molten salt circulation amount, promoting unconverted retained austenite to be decomposed and converted into bainite and sorbite, carrying out isothermal tempering, and finally carrying out slow cooling through a roller way, the hot-rolled wire rod with a microscopic structure comprising a complex phase structure composed of tempered bainite and tempered sorbite is prepared, the material cost can be reduced, the complex phase structure and the structure toughness can be regulated and controlled on line, the tensile strength is 1505-1555 MPa, the percentage reduction of area is 32%-37%, efficiency and energy consumption are both considered, off-line heat treatment is avoided, and high-efficiency production of stranded wires is promoted.

The invention relates to the technical field of manufacturing of engineering machinery parts, and discloses an engineering machinery driving wheel made of a medium carbon alloy cast steel material. The invention also discloses a preparation process of the engineering machinery driving wheel material, which comprises the following steps: S1, casting treatment: melting the medium carbon alloy steel material, and casting into a driving wheel blank; s2, normalizing heat treatment: carrying out normalizing heat treatment on the driving wheel blank; s3, rough machining treatment; s4, quenching treatment: carrying out induction quenching treatment; and S5, finish machining treatment. The synergistic effect of alloy elements in a medium carbon alloy cast steel material is combined with an optimized air cooling process, so that the cast steel is normalized to obtain a uniform structure which mainly contains superfine pearlite and contains extremely little ferrite, the matrix hardness is stable, and the requirement of a high-performance driving wheel is completely met; after the process route is improved, tempering and shot blasting and flaw detection procedures after tempering are canceled; the technological process is greatly shortened, material turnover is reduced, and the production efficiency is improved.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2260MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod, after the high-carbon component design of C-Si-Mn-Cr-V-Nb-V is rolled and spun into a wire rod, the wire rod is subjected to online molten salt mixed quenching isothermal treatment, so that the wire rod is subjected to front-section molten salt treatment to be quickly cooled, enters a bainite and pearlite mixed phase region from an austenite state, and is subjected to hot rolling and hot rolling to form the high-strength complex-phase hot-rolled wire rod. The method comprises the following steps: carrying out first-stage molten salt treatment on austenite to promote transformation of part of austenite to bainite and sorbite, then carrying out later-stage molten salt treatment to increase the molten salt temperature, promoting decomposition and transformation of untransformed retained austenite into sorbite, carrying out isothermal tempering, and finally carrying out slow cooling through a roller way, a hot-rolled wire rod with a microscopic structure comprising a complex-phase structure composed of tempered bainite, tempered sorbite and ferrite is manufactured, the tensile strength is 1547-1597 MPa, and the percentage reduction of area is 27%-32%, so that when a high-strength stranded wire is manufactured, off-line heat treatment is not needed, the drawing pass number is reduced, and the wire breaking risk is reduced.

The invention relates to the field of screw forming, and discloses a screw cold heading forming process which is characterized by comprising the following steps: step 1, wire preparation and surface pretreatment: based on the requirement of screw forming on the surface quality of raw materials, a metal wire is treated by adopting a mechanical wiredrawing and chemical phosphating and saponifying composite process, and the surface of the metal wire is treated; surface oxide skin is removed, a lubricating film layer is formed, and the forming flowability and the service life of the die in the subsequent cold heading process are effectively improved. A raw material is subjected to spheroidizing annealing treatment in a continuous spheroidizing annealing furnace, internal pearlite is converted into spherical cementite, the ductility and deformation uniformity of the material are improved, then a continuous wire drawing machine is adopted for multi-stage drawing diameter reduction, a three-stage chemical phosphating-saponification treatment process is matched, a low-friction and high-adhesion lubricating film layer is formed, and the service life of the lubricating film layer is prolonged. And a stable material basis and a lubricating environment are provided for the subsequent cold heading process, so that the problems that the friction resistance generated in the forming process of a screw material is large, and a mold is quickly worn are solved.

The invention provides a heat treatment method for a wind power gear forge piece. The heat treatment method comprises the following steps that 1, after-forging waste heat temperature equalization is carried out; 2, segmented forced controlled cooling is carried out till the forge piece reaches a furnace entering window, and forced cooling is carried out on the forge piece; at least three temperature measuring points are arranged on the forge piece; 3, isothermal normalizing for the first time, wherein the forge piece is placed in an isothermal furnace; 4, low-temperature reaustenitizing is conducted, specifically, the forge piece subjected to the first isothermal normalizing is heated to 860-910 DEG C, heat preservation is conducted, and the forge piece is reaustenitized; 5, secondary isothermal normalizing is conducted, specifically, the forged piece obtained after austenitizing is cooled to 645-670 DEG C in a controlled cooling mode, and isothermal heat preservation is conducted; the forge piece is heated to 380-450 DEG C, heat preservation is conducted, then the forge piece is cooled to 200 DEG C or below along with a furnace, and the forge piece is taken out of the furnace for air cooling. According to the method, a uniform and refined ferrite and pearlite structure is obtained in the core of the large-section forge piece, the hardness is stabilized within the range of 165-185 HBW, and the subsequent carburizing and quenching distortion sensitivity is reduced.

The invention provides a full-pearlite steel rail and a production method and application thereof. According to the invention, by controlling the content of elements in the steel rail, especially the C, Mn and Cr elements and the content ratio thereof, and optimizing the online heat treatment process of the steel rail, the steel rail with a full pearlitic structure is obtained under the condition that other production processes of the steel rail are not limited, and the tensile strength of the steel rail is greater than or equal to 1100MPa, the percentage elongation after fracture is greater than or equal to 10%, and the surface hardness is greater than or equal to 330HB. Meanwhile, the production method of the all-pearlite steel rail is simple and easy to operate, and large-scale application and popularization of the all-pearlite steel rail in lines such as high-speed railways and passenger and freight mixed transportation railways are facilitated.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a depth position of 1 / 4 from a surface in a sheet thickness direction, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value is 10.7 or more, an I value is 1.020 or more, a CS value is −8.0×105 to 8.0×105, a standard deviation of Mn concentrations is 0.60 mass % or less, a solute Cr concentration in an outermost layer region is 0.10 mass % or more, a number density of Cr oxides having a sphere equivalent radius of 0.1 μm or more at the surface is 1.0×104 pieces / cm2 or less.

The invention discloses a method for refining and homogenizing crystal grains of a 9%-12% Cr steel thick-wall large forge piece, and belongs to the field of ferrous metallurgy. According to the method, the large forge piece is heated to be close to the critical point of the complete austenitizing temperature in a stepped mode, the large forge piece is subjected to heat treatment by regulating and controlling dispersive precipitation of carbides in an initial structure and uniform nucleation of austenite and / or introducing a small amount of undissolved ferrite, residual precipitated phases and multi-phase interfaces and controlling the cooling speed; nucleation particles of pearlite transformation in the vibration heat preservation process are remarkably increased, uniform distribution of granular pearlite in the supercooled austenite is promoted, structural inheritance is cut off and eliminated, and the purpose of grain refining and homogenizing after performance heat treatment is achieved. According to the method, the grains of the thick-wall large forge piece are refined to 5 grades or above, the cross section grain size difference is within 2 grades, a series of problems that in the production process, grass waves exist in ultrasonic flaw detection, the grain size is unqualified, and the low-temperature impact toughness does not reach the standard can be solved, the product percent of pass and the production efficiency are remarkably improved, and meanwhile the production energy consumption is reduced.

The invention relates to the technical field of cast iron alloys, in particular to a preparation method of high-carbon-equivalent gray cast iron, which comprises the following steps: taking scrap steel as a main material, taking scrap castings, silicon carbide and a carburant as auxiliary materials, and smelting according to a determined raw material ratio and a determined carbon equivalent value range; sampling smelted molten iron to obtain a first cooling curve of the molten iron, extracting characteristic points, performing thermal analysis to determine the metallurgical state of the molten iron, and adjusting the content of pre-inoculated silicon carbide or analyzing the possibility of over-inoculation; pre-inoculation is conducted on the smelted molten iron, the smelted molten iron is secondarily sampled to obtain a second cooling curve of the molten iron, feature points are extracted, the pearlite form is determined, and the sensitivity index of the smelted molten iron to inoculation is calculated according to the change condition of the feature points of the first cooling curve and the second cooling curve. Through pre-inoculation adjustment and tapping inoculation and pouring inoculation, the problems that graphite is thick and large and the performance is reduced easily due to high carbon equivalent are solved.

The invention relates to gray cast iron and a smelting method thereof, in particular to high-strength gray cast iron and a smelting method thereof. According to the high-strength gray cast iron and the smelting method thereof, the defect that in the prior art, alloying is adopted for improving the strength of the gray cast iron, and consequently the texture of the gray cast iron is poor is overcome, the tensile strength of an attached casting test bar of the high-strength gray cast iron is larger than 300 MPa, and the hardness is larger than 190 HB; the metallographic structure of the high-strength gray cast iron in an as-cast state can achieve more than 98% of pearlite, less than 1% of cementite and more than 90% of A-type graphite, and the strength and the metallographic structure of the alloyed gray cast iron are effectively improved.

This invention relates to a vermicular cast iron alloy with high mechanical strength and thermal conductivity requirements to replace the conventional gray and vermicular cast irons and introduces a manufacturing process for high mechanical strength and thermal conductivity vermicular cast iron alloy and internal combustion engine parts produced from said alloy. The alloy includes carbon, manganese, tin, copper, molybdenum, silicon, magnesium, rare earths, chromium, titanium, niobium, vanadium, tungsten, phosphorus, sulfur, aluminum, and nickel. The alloy has a graphite microstructure consisting of up to 70% of vermicular particles and up to 30% of nodular particles in area, with a matrix in area up to 80% pearlitic and up to 20% ferritic, with presence of segregating carbides of up to 1%.

The invention relates to the technical field of steel structure grain size analysis, in particular to a microscopic image segmentation result-based steel structure grain size analysis method, which comprises the following steps of: performing format conversion and size unification on a segmentation result of a deep learning segmentation model to generate a complete mask, and performing mask optimization on the complete mask; and generating a visual distribution diagram based on the distribution states of the ferrite masks and the pearlite masks in the complete masks, performing superposition and proportional scale labeling on the original microscopic images, and quantifying the distribution characteristics of the ferrite and the pearlite by combining a uniformity index and a spatial correlation index. According to the method, the ferrite and the pearlite in the microscopic image are accurately segmented through the deep learning segmentation model, the visual distribution diagram is generated on the basis, and quantitative analysis is performed on the tissue distribution in combination with the uniformity index and the spatial correlation index, so that quantitative and objective tissue structure characterization can be realized.

The invention discloses steel for a 420 MPa grade arctic circle oil and gas exploitation platform and a preparation method of the steel. The steel plate comprises the following chemical components in percentage by weight: 0.06%-0.12% of C, 0.15%-0.35% of Si, 1.00%-1.60% of Mn, less than or equal to 0.008% of P, less than or equal to 0.008% of S, 0.025%-0.060% of Nb, 0.030%-0.080% of V, 0.020%-0.040% of Al, 0.010%-0.020% of Ti, 0.20%-0.60% of Ni, 0.10%-0.30% of Cr, less than or equal to 0.0040% of N and the balance of Fe and inevitable impurity elements. The carbon equivalent CEV is less than or equal to 0.42%, and the cold crack sensitivity index Pcm is less than or equal to 0.20%. The manufacturing process of the steel plate comprises the steps of KR, electric furnace smelting, LF, VD, casting, slab slow cooling, heating, rolling, steel plate pile slow cooling, heat treatment and the like. The matrix structure of the obtained steel plate is a uniform and fine ferrite and tempered pearlite mixed structure, and the grain size ranges from 6 micrometers to 15 micrometers. The steel plate has excellent low-temperature impact toughness, lamellar tearing resistance, fracture resistance and low-temperature strain aging resistance, is easy to weld, and can meet the extremely cold service environment of the arctic circle.

This hot-rolled steel sheet has a desired chemical composition, in a microstructure at a position of ¼ from a surface in a sheet thickness direction, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value is 10.7 or more, an I value is 1.020 or more, a CS value is −8.0×105 to 8.0×105, a standard deviation of Mn concentrations is 0.60 mass % or less, at the surface, an area ratio of a region where a Ni concentration is 0.2 mass % or more is 10.0% or more, an area ratio of a region where an O concentration is 3.0 mass % or more is 3.0% to 50.0%, and a maximum value of sphere equivalent diameters of oxides is 5.00 μm or less, and a tensile strength is 980 MPa or more.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a position of ¼ from a surface in a sheet thickness direction, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value is 10.7 or more, an I value is 1.020 or more, a CS value is −8.0×105 to 8.0×105, a standard deviation of Mn concentrations is 0.60 mass % or less, at the surface, a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.500 μm or more is 2.0×103 pieces / cm2 or less, and a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.005 μm to 0.050 μm is 1.0×105 pieces / cm2 or more.

The invention relates to a heat treatment process for EN26 shaft products, which combines the multi-step and large-section size shape of an EN26 shaft, takes the large step at the tail end as a symmetric base point before heat treatment, is designed according to the double-length size, and adopts the modes of low-temperature preheating, high-temperature normalizing, air cooling after normalizing and tempering after forging to effectively cut off the structure inheritance. The method solves the problem of mixed crystal or coarse crystal grains caused by non-equilibrium structures due to weaving inheritance, promotes pearlite with small interlamellar spacing to be converted into austenite structures through a rapid heating and repeated austenitizing mode, improves the nucleation rate so as to achieve the effect of refining the grain size, and improves the grain size through reasonable quenching cooling strength. According to the method, the structural transformation from high-temperature austenite to martensite is guaranteed, the risk of product cracking caused by overlarge thermal stress and structural stress is avoided, the overall stability of a forge piece is guaranteed through high-temperature tempering, the strength, plasticity, toughness and hardness are well matched, the overall quality and production efficiency of the EN26 shaft produced through the method are improved, and the production cost is reduced. And after finish machining, single-length sawing and delivery are carried out.

The invention relates to cold drawing steel for a high-straightness precision lead screw and a manufacturing method of the cold drawing steel, and belongs to the technical field of metallurgy. The steel comprises the following chemical components in percentage by mass: 0.50 to 0.60 percent of C, 0.15 to 0.40 percent of Si, 0.60 to 0.90 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, 0.10 to 0.30 percent of Cr, less than or equal to 0.25 percent of Ni, less than or equal to 0.25 percent of Cu, less than or equal to 0.10 percent of Mo, 0.010 to 0.030 percent of Al, 0.0040 to 0.0080 percent of N and the balance of Fe and inevitable impurity elements. Sorbite, pearlite and a small amount of ferrite structures are obtained in an XDWP water bath and stelmor cooling mode, excellent structure conditions are provided for spheroidizing annealing, the spheroidizing structure obtained through one-time annealing reaches the fifth level or above, higher drawing straightness is obtained, the straightness is smaller than 0.5 mm / m, and the requirement for cold drawing steel for a high-grade lead screw is met.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure, in terms of area %, residual austenite is less than 3.0%, ferrite is less than 15.0%, and pearlite is less than 5.0%, an E value that indicates periodicity of the microstructure is less than 10.7, and an I value that indicates uniformity of the microstructure is less than 1.020, a standard deviation of a Mn concentration is 0.60 mass % or less, and a tensile strength is 780 MPa or more.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value that indicates periodicity of the microstructure is 10.7 or more, and an I value that indicates uniformity of the microstructure is 1.020 or more, a standard deviation of a Mn concentration is 0.60 mass % or less, and a tensile strength is 980 MPa or more.

A steel sheet made of a steel having a composition including, C: 0.3-0.4%, Mn: 0.5-1.0%, Si: 0.4-0.8%, Cr: 0.1-1.0%, Mo: 0.1-0.5%, Nb: 0.01-0.1%, Al: 0.01-0.1%, Ti: 0.008-0.03%, B: 0.0005-0.003%, P≤ 0.020%, Ca≤0.001%, S≤0.004%, N≤0.005% and including optionally Ni<0.5%, having a microstructure including, in surface fraction, from 60% to 95% of ferrite, the rest being martensite-austenite islands, pearlite or bainite, and including a bulk and a skin layer occupying the outermost 10% of the thickness on either sides of the bulk, the skin layer having a skin layer inclusion population wherein the surface fraction of oxides is equal to or below 60*10−6.

The present application belongs to the field of rail material research and manufacturing, and specifically discloses a rail structure for a subway humid environment. According to the distribution of pearlite lamellar spacing, the rail head cross-section structure can be divided into cap layer 1, cap layer 2, cap layer 3 and base material layer. The pearlite lamellar spacing distribution of cap layer 1 is 130-150 nm, the pearlite lamellar spacing distribution of cap layer 2 is 90-120 nm, the pearlite lamellar spacing distribution of cap layer 3 is 140-170 nm, and the pearlite lamellar spacing distribution of the base material layer is 200-230 nm. The present application designs cap-shaped structures with different depths and different pearlite lamellar spacing in the rail head. By accelerating the cooling speed of the heat treatment of the hot-rolled rail in different stages, the reasonable gradient structure distribution of the pearlite structure of the rail material is realized, the expansion speed of the rolling contact fatigue crack of the rail in the humid environment to the internal material is effectively slowed down, the rolling contact fatigue damage is reduced, and thus the comprehensive performance and service life of the rail are improved.

The application discloses a low-temperature high-strength container steel with tensile strength greater than or equal to 600 MPa, which comprises C, Si, Mn, P, S, Ni, Mo, Alt, Cr, V, Fe and residual elements; the steel plate obtained through controlled rolling and controlled cooling and normalizing and fast cooling has a main structure of 60-75% of bainite, 25-35% of ferrite and a small amount of pearlite, the yield strength of the heat-treated delivery state steel plate is 533-620 MPa, the tensile strength is 640-700 MPa, the elongation is greater than or equal to 19%, and the impact energy at-20 DEG C is 200-310 J; after maximum die welding at 580-620 DEG C for 10-12 h, the yield strength is 530-600 MPa, the tensile strength is 630-680 MPa, the elongation is greater than or equal to 20%, and the impact energy at-20 DEG C is 170-250 J. The scheme has low alloy cost and short production process, the obtained steel plate has stable performance, and after maximum die welding, the tensile strength and impact energy of the steel plate still meet the use requirements of low-temperature container steel.

The present invention provides a steel material that can suppress the occurrence of cracks during cold forging, even when cold forging is performed without spheroidizing annealing. [Solution] The steel material of this embodiment has a chemical composition in mass%, consisting of C: 0.30-0.60%, Si: 0.01-0.10%, Mn: 0.30-2.00%, P: less than 0.050%, S: 0.001-0.050%, Al: 0.001-0.200%, N: less than 0.020%, Cr: 0.01-0.40%, O: 0.0030% or less, and the remainder being Fe and impurities. The total area ratio of ferrite and perlite is 90% or more, the area ratio of perlite is 40% or more, the average particle size dP of perlite grains is 10.0 to 40.0 μm, the average particle size dP of perlite grains and the standard deviation σP of perlite grain size satisfy equation (1), the average particle size dF of ferrite grains is 25.0 μm or less, and the difference between the hardness of ferrite and the hardness of perlite is 140 HV or less. σP / dP<0.80 (1)

Disclosed in the present invention is a cold-rolled fine blanking steel, comprising Fe and inevitable impurities. In addition, the cold-rolled fine blanking steel further comprises the following chemical elements in percentages by mass: 0.26-0.38% of C, 0.60-1.60% of Mn, 0.10-0.20% of Cr, 0.03-0.06% of Nb, 0.10-0.20% of Ni, 0.10-0.20% of Mo, and 0.001-0.005% of B; and the microstructure of the cold-rolled fine blanking steel after spheroidizing annealing is granular pearlite. Correspondingly, further disclosed in the present invention is a method for manufacturing the cold-rolled fine blanking steel, the method comprising the steps of: smelting and continuous casting; hot rolling: controlling the hot rolling coiling temperature to 550-650ºC; pickling and cold rolling: controlling the cooling reduction to be greater than or equal to 40%; spheroidizing annealing; and skin-pass rolling and fine blanking. The present invention can effectively avoid welding defects in fine blanking steel.

Provided are a high-strength hot-rolled steel sheet having high strength, high ductility, excellent strain dispersibility, high stretch flangeability, and bendability, a member, and methods for manufacturing the same.　The high-strength hot-rolled steel sheet has a prescribed component composition, and has a steel structure in which, in terms of area ratio, the total of bainite and tempered martensite is 80.0% or more, pearlite is 10.0% or less, retained austenite is 15.0% or less, the total of retained austenite and pearlite is 1.0% or more, the total of tempered martensite and bainite having a circle-equivalent diameter of 5.0 μm or more is 10.0% or less, and the proportion of line segments having a hard phase fraction of 20.0% or more among line segments having a length of 200 μm parallel to the rolling direction is 30.0% or less, the tensile strength TS (MPa) and the component composition (mass%) satisfy the expression 0 ≦ 730 + 2000 × (C + Si / 16 + Mn / 40 + Al / 18 + Cr / 40 + Ni / 40 + Mo / 20 + Ti / 3) – TS ≦ 250, where each element symbol in the formula represents the content (mass%) of each element, and the high-strength hot-rolled steel sheet has a tensile strength of 980 MPa or more.

The invention belongs to the technical field of steel smelting, and relates to a method for improving low-temperature toughness of a surface layer and a core part of an EH47 steel plate with the thickness of 110mm. By adjusting the chemical components of the steel plate, the Ar3 phase transition temperature is increased to 735 DEG C or above, then a blank is rolled in an austenite single-phase region and an austenite and ferrite two-phase region, the rolling temperature of the last two passes of the steel plate is controlled within the range of Ar3-10 DEG C to Ar3-20 DEG C, and the rolling temperature of the last two passes of the steel plate is controlled within the range of 950 DEG C to 950 DEG C; deformation ferrite, equiaxed recrystallization ferrite and a small amount of refined pearlite clusters in a two-phase region are mainly arranged on the surface layer of the finished steel plate within 15 mm, the ballistic energy of the surface layer and the core of the steel plate at the temperature of-50 DEG C is larger than or equal to 180 J, and the yield strength of the steel plate with the thickness being 1 / 4 is larger than or equal to 470 MPa.

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%.