325 results about "Acicular ferrite" patented technology

A composition and method of making a high-strength low-alloy hot-rolled steel sheet, strip, or plate bearing titanium as the principal or only microalloy strengthening element. The steel is substantially ferritic and has a microstructure that is at least 20% acicular ferrite. The steel has a minimum yield strength of at least 345 MPa (50 ksi) and even over 621 MPa (90 ksi) adding titanium as the lone microalloy element for strengthening, with elongation of 15% and more. Addition of vanadium, niobium, or a combination thereof can result in yield strengths exceeding 621 MPa (90 ksi). Effective titanium content, being the content of titanium in the steel not in the form of nitrides, oxides, or sulfides, is in the range of 0.01 to 0.12% by weight. The manufacturing process includes continuously casting a thin slab and reducing the slab thickness using thermomechanical controlled processing, including dynamic recrystallization controlled rolling.

The invention is about the X70 needle ferrite in-line steel, which has the toughness of crack arrest. The percentage composition is C 0.020-0.060,Mn 1.45-1.75,Si 0.100-0.500,S¿Q0.0020,P0.004-0.012,Nb0.050-0.080,Ti0.005-0.025,V0.010-0.060,Mo0.10-0.30,Cu¿Q0.30,Ni¿Q0.30,Ca0.0015-0.0040,N¿Q0.0080,Altotal0.015-0.045. The process is: a. refining by coverter or electric furnace; b. refined outside of the furnace, vacuum degass by RH, desulfurating by LF, Ca treatment; c. continuous metal cast process; d. hot rolling, the terminal temperature of the coarse crushing is 950-1000 Deg C.,the terminal temperature of finish rolling is 780-880 Deg C., the compression ratio of the non-recrystallized region is above 70%; e. batching, temperature is 480-580 Deg C..

The invention discloses weathering steel, which comprises the following chemical compositions in percentage by weight: 0.06 to 0.12 percent of C, 0.20 to 0.40 percent of Si, less than or equal to 1.6 percent of Mn, 0.08 to 0.22 percent of P, less than or equal to 0.008 percent of S, 0.01 to 0.06 percent of Al, 0.20 to 0.80 percent of Cu, 0.40 to 0.75 percent of Cr, 0.12 to 0.40 percent of Ni, 0.001 to 0.006 percent of Ca and the balance of iron and inevitable impurity elements. The weathering steel is manufactured by a thin strip continuous casting process. The manufacturing process comprises the following steps of: performing deep desulfurization on molten steel, performing composite blowing on the top and bottom of a converter, performing RH vacuum circular degassing process, and simultaneously performing calcium treatment; performing twin-roll continuous casting, and making the temperature of the molten steel in a molten bath not lower than 1,535DEG C; controlling rolling in the reduction ratio of not less than 30 percent; controlling cooling at the speed 30 to 50 DEG C / s; and coiling at the temperature of between 600 and 650 DEG C. The weathering steel of which the texture is acicular ferrite has good weatherability and can be widely applied to structural materials.

The invention relates to high-strength low-temperature steel with high hydrogen induced cracking (HIC) and sulfide stress corrosion cracking (SSC) resistance and a manufacturing method thereof. A low alloy steel component system with ultra-low C content, low Si content, medium Mn content, low Als content, low N content, a little alloyed Ni and Mo and trace Ti and Nb is adopted, Mn / C is more than or equal to 22, the segregation index 1.32 (percent C)*[(1.53 (percent Mn)+1.37 (percent Si)+1.15 (percent Mo)+1.06 (percent Cr)+(percent Cu)+0.86 (percent Ni)]*[(30 (percent P)+10 (percent S)] is less than or equal to 0.060, [(percent Si)+(percent Als)]*(percent C) is less than or equal to 0.0035, Pcm is less than or equal to 0.018 percent, Nib / Ti is 1.5 to 3.5, Ca treatment is performed, Ca / S is 0.80 to 3.00, the microstructure of a finished steel plate product consists of uniform and fine acicular ferrites and a few upper bainites by optimizing a thermal mechanical control processing (TMCP) technology, and the average particle size is less than 10mu m; and the characteristics of high strength, toughness and HIC and SSC resistance are achieved, high heat input welding can be performed, and the steel is particularly suitable for manufacturing a low temperature storage tank, a low temperature pressure steel pipe, an ocean platform in an ice sea area, and the like.

A low-alloy high-strength steel plate with high yield strength (460 MPa) contains C (0.13-0.20 wt.%), Si (0.2-0.5), Mn (1.3-1.7), Nb (0.01-0.02) Ti (0.005-0.01), Al (0.005-0.015) and Fe (rest). Its preparing process features that two-stage rolling at 1200-1250 deg.C and quick cooling. Its advantages are multi-phase structure including polygonal and acicular ferrite, pearlite and bainite, high yield strength and low cost.

The invention discloses a method for smelting a steel plate with the excellent performance in a high-heat-input-welding heat affected zone. The method sequentially includes the steps of molten steel pretreatment, combined-blowing converter steelmaking, LF refining, RH vacuum refining, alloy cored wire feeding and continuous casting. According to the method, the content of oxygen in molten steel and the adding conditions of key alloy materials at key stations are controlled, the content of Ti, the content of O, the content of Mg and the content of Zr in the steel meet the design requirements accordingly and can meet the conditions that Ti / O is larger than 5 and smaller than 12, (Mg+Zr) / (Ti+Al) is larger than 0.02, and one or two kinds of a large quantity of Ti-Mg composite-oxide inclusions, a large quantity of Ti-Zr composite-oxide inclusions and a large quantity of Ti-Mg-Zr composite-oxide inclusions with the size smaller than 1 micron are contained in the steel accordingly; in addition, the mass percents of chemical compositions of the inclusions meet the conditions that the mass percent of Ti is larger than 2% and smaller than 40%, the mass percent of Mg is larger than 2% and smaller than 30%, the mass percent of Zr is larger than 2% and smaller than 30%, and the mass percent of O is larger than 5% and smaller than 50%; and the areal density is larger than 300 per mm<2>. Due to the inclusions, growth of austenite crystal grains of the welding heat affected zone can be effectively pinned; and meanwhile nucleus forming of needle-shaped ferrite in the grains is promoted, and therefore the excellent performance in the high-heat-input-welding heat affected zone is guaranteed.

The invention provides a manufacture method of an extremely-stick steel plate for a hydropower station through a continuous-cast billet, and belongs to the technical field of production of continuous-cast steel plates. The manufacture method comprises the technological processes of continuous casting, rolling, cooling after rolling, austenite quenching, subcritical quenching and high-temperature tempering, thus a composite-phase structure of ferrite, acicular ferrite, small granular bainite and small residual bainite can be formed in the core part of the steel plate after the high-temperature tempering. The manufacture method has the advantages that the extremely-thick steel is given the same performance as the thin steel plate under the combination and organizational control of heat treatment process based on the smaller proportion; and compared with the methods of die casting and forging, the manufacture method provided by the invention is simple, convenient, easy to carry out and high in yield, and reduces the producing cost.

The invention discloses an isothermal quenching nodular cast iron roller for a push-pull vehicle on a heat treatment production line and a production method thereof. The nodular cast iron roller at least comprises Fe and also comprises the following elements in percentage by mass: 3.20-4.0 percent of carbon, 2.10-2.90 percent of silicon, 0.3-0.65 percent of manganese, less than or equal to 0.1 percent of phosphorus and less than or equal to 0.1 percent of sulfur. The nodular cast iron roller is made of isothermal quenching nodular cast iron, adopts a casting mode and isothermal quenching heat treatment and has high graphite self-lubricating performance, and a hardened layer can be generated in the operating process. Because the roller adopts the casting mode, the complex shape can be cast to be close to the final size, and the roller is subjected to heat treatment in an airtight environment with atmosphere protection after one-step finish machining only, so that surface oxidation and decarbonization are avoided. Then, the roller is transferred into a quenching tank with a speed-regulating stirring and water supply device for performing isothermal quenching heat treatment in an atmosphere protection environment, and acicular ferrite and high-carbon austenite metallographic structures are obtained.

The invention discloses thick-specification high-tenacity X70 acicular ferrite pipe line steel and a manufacturing method thereof. The thick-specification high-tenacity X70 acicular ferrite pipe linesteel comprises components as follows in percentage by weight: C: 0.03%-0.06%. Si: 0.15%-0.25%, Mn: 1.55%-1.75%, P: 0.012%-0.020%, S: less than or equal to 0.003%, Cu: 0.20%-m0.35%, Nb: 0.06%-0.08%, Ti: 0.01%-0.02%, AIs: less than or equal to 0.05%, and Mo: 0.20%-0.30%. The manufacturing process of the thick-specification high-tenacity X70 acicular ferrite pipe line steel is characterized in thatcontinuous casting speed is 1.2-1.8m / min; casting temperature of plate blanks is above 550 DEG C; the temperature is raised to 1100-1250 DEG C and kept for 80-120min; the roughing delivery temperatureis 920-1080 DEG C; the finish rolling delivery temperature is 760-880 DEG C; the cooling speed is 10-30 DEG C / s; and the coiling temperature is 450-570 DEG C. The thick-specification high-tenacity X70 acicular ferrite pipe line steel meets and is superior to the performance requirement of API 5LX70 acicular ferrite pipe line steel; meanwhile, the thick-specification high-tenacity X70 acicular ferrite pipe line steel has excellent HIC resistance and is suitable to tick-specification large-caliber high-pressure gas transmission pipelines which requires to be continuously enlarged.

A preparation method of easy welding high strength toughness X80 pipe line steel for magnesium treatment belongs to the production field of low alloy high strength steel, including first preparing materials according to constituent mixing rate, then smelting in a vacuum induction furnace, forging casting blank and controlling rolling and cooling. The preparation method is characterized in that the heating temperature is 1170-1230 DEG C prior to forging blank residues; the thermal time is 60-120min; and the beginning temperature of coarse rolling is 1100-1180 DEG C; the finishing temperature of coarse rolling is no less than 980 DEG C, the temperature-holding thickness of intermediate blank is 45-50mm; the beginning temperature of finish rolling is no more than 880 DEG C; the finishing temperature of finish rolling is 780-810 DEG C; the pressing rate of finish rolling is more than 3T (T: target thickness of finished products); and the target thickness of finished products is 10-15mm. After finish rolling, the product rapidly enters ACC for cooling control, with the cooling speed being 15-35 DEG C / s. the self-tempering temperature is 400-550 DEG C. The produced high strength toughness X80 pipe line steel has typical acicular ferrite tissue, as well as favorable comprehensive mechanical property and high input energy welding property.

The invention relates to a method for producing an Mo-free low-Nb X80 pipeline steel hot rolled steel plate. The method comprises the following steps of: preparing raw materials in a ratio; smelting the raw materials by using a converter or an electric furnace; refining the smelted raw materials out of the furnace; casting the refined raw materials; reheating a plate blank; and performing controlled rolling and controlled cooling. The method is characterized in that: the heating temperature of the plate blank is of between 1,100 and 1,250 DEG C; the starting temperature of the controlled rolling in a recrystallization zone is of between 1,080 and 1,200 DEG C; the final temperature of the controlled rolling in the recrystallization zone is of between 950 and 1,080 DEG C; the starting temperature of the controlled rolling in a non-recrystallization zone is of between 860 and 950 DEG C; the compression ratio of the controlled rolling in the non-recrystallization zone is more than or equal to 75 percent; the final rolling temperature is of between 730 and 860 DEG C; the final cooling temperature is of between 300 and 550 DEG C; the cooling rate is of between 10 and 35 DEG C / s; produced steel has acicular ferrite and bainite structures and meets the requirement of API SPEC 5L on the performance of X90 pipeline steel; and production-manufacturing is low.

Weld metals suitable for joining high strength, low alloy steels are provided. These weld metals have microstructures of acicular ferrite interspersed in a hard constituent, such as lath martensite, yield strengths of at least about 690 MPa (100 ksi), and DBTTs lower than about -50 DEG C. (-58 DEG F.) as measured by a Charpy energy versus temperature curve. These weld metals include about 0.04 wt % to about 0.08 wt % carbon; about 1.0 wt % to about 2.0 wt % manganese; about 0.2 wt % to about 0.7 wt % silicon; about 0.30 wt % to 0.80 wt % molybdenum; about 2.3 wt % to about 3.5 wt % nickel; about 0.0175 wt % to about 0.0400 wt % oxygen, and at least one additive selected from the group consisting of (i) up to about 0.04 wt % zirconium, and (ii) up to about 0.02 wt % titanium.

The invention relates to a method for identifying and assessing needle-like ferrite pipe line steel tissues, which comprises the following steps: simplifying various ferrite tissues into ferrite and bainite; and by a heat dyeing experiment, enabling the different tissues and crystalline grains in the material to display the different contrast from white to yellow and brown, wherein the assessing of the needle-like ferrite pipe line steel banded tissue is divided into four levels. The measuring method for the ferrite crystalline grains of the needle-like ferrite pipe line steel comprises: a comparative method and a resection method are selected for the judging method of the ferrite crystalline grains; the comparative method is used for production inspection, if dispute exists, the resection method is the arbitration method; the comparative method is as follows: judging the grain size rank by comparing with a standard rating graph; and the resection method is as follows: assessing the grain size rank by counting the measureing segment of given length and number of the points of the grain boundary resection. The invention solves the problem that practical steel rolling tissue is difficult to analyze and identify, improves the contrast difference of phase and grain of components in the tissue, is convenient for tissue identifying and pipe line steel grain size assessing, makes up the defect of the national standard, and has reasonable and feasible quality control, check and evaluation on the line steel tissue.

The invention discloses a high-strength-toughness and high-temperature hot rolled steel plate and a preparation method thereof. The high-strength-toughness and high-temperature hot rolled steel plate is prepared from the following chemical components in percentage by weight: 0.04-0.15 percent of C, 0.05-0.35 percent of Si, 0.5-2.5 percent of Mn, 0.005-0.025 percent of Ti, smaller than or equal to 1.0 percent of Cr, smaller than or equal to 0.5 percent of Mo, smaller than or equal to 1.0 percent of Ni, smaller than or equal to 0.5 percent of Cu, smaller than or equal to 0.003 percent of B, smaller than or equal to 0.02 percent of P, smaller than or equal to 0.01 percent of S, smaller than or equal to 0.007 percent of N, 0.001-0.006 percent of O, smaller than or equal to 0.03 percent of the total content of elements including Al, Zr, Mg, Ca and rare earth and the balance of Fe and inevitable impurity elements. The preparation method of the steel plate comprises the following steps: smelting and casting according to the components, carrying out high-temperature continuous rolling by adopting an austenite, carrying out accelerated cooling by watering the steel plate after being rolled, and then air cooling to room temperature, wherein the heating temperature of a steel billet is 1150-1260 DEG, the cooling temperature is larger than or equal to 5 DEG C / s. and the finish cooling temperature is 550-650 DEG C . As a microscopic structure of the steel plate is a fined acicular ferrite type structure, the steel plate is good in strength and toughness properties. The preparation method of the steel plate is flexible in process and simple in operation, saves the cost and improves the production efficiency.

The invention aims at providing a V-N microalloyed Q550 grade medium plate and a preparation method thereof which are specific to the condition that in the prior art, the Q550 grade medium plate expensive alloy is in large consumption and the preparation process is complex. The chemical constitutions of the steel are as follows by weight percentage: 0.06 to 0.12 percent of C, 1.20 to 2.00 percent of Mn, 0.10 to 0.50 percent of Si, 0.002 to 0.01 percent of S, 0.003 to 0.01 percent of P, 0.01 to 0.05 percent of Al, 0.06 to 0.15 percent of V, 0.01 to 0.02 percent of N and the balance of Fe and other unavoidable impurities; the preparation method comprises the steps of heating a steel billet to 1000 to 1200 DEG C along with a furnace and performing heat preservation for 3 to 4 hours, and further carrying out hot rolling on the steel billet to form a hot rolled plate being 20 to 50mm in thickness, wherein the beginning temperature and the finishing temperature in a rough rolling stage are respectively 1030 to 1150 DEG C and 980 to 1020 DEG C, and the beginning temperature and the finishing temperature in a finish rolling stage are respectively 908 to 925 DEG C and 820 to 845 DEG C; cooling the plate by water to 545 to 650 DEG C after the hot rolling, and then cooling by air to room temperature. The plate is a high-toughness ultra-low-carbon medium-manganese medium plate, and the metallographic structure of the plate is a fine crystalline ferrite, a pearlite and an acicular ferrite; the method is simple in operation process, has no need of quenching and tempering treatment, and is easy to realize industrial production.

The invention discloses a manufacturing method of low-yield-ratio carbon-manganese low-temperature steel. The chemical components of the low-yield-ratio carbon-manganese low-temperature steel comprises, by weight, 0.05-0.09% of C, 0.10-0.40% of Si, 1.30-1.50% of Mn, less than or equal to 0.010% of P, less than or equal to 0.003% of S, less than or equal to 0.010% of Nb, 0.030-0.060% of Al, and thebalance Fe and inevitable impurities. By adopting the design of low-carbon, high-manganese and high-aluminum components, fine quasi-polygonal ferrites and a few acicular ferrites and pearlitic structures through cooperation of the dynamic soft reduction control technology during the continuous casting process and high-temperature heavy reduction and fast cooling control process after rolling during the rolling process. Compared with steel for liquefied petroleum gas tankers, the low-yield-ratio carbon-manganese low-temperature steel has the characteristics of being pure in steel quality, lowin yield ratio, high in toughness and excellent in low-temperature welding performance. The ductile-brittle transition temperature of a steel plate in the thickness direction is lower than minus 80 DEG C, and the postwelding welding performance at minus 70 DEG C is excellent. Moreover, there is no need to add microalloy elements such as Cu and Cr, and the manufacturing cost is low.

The invention relates to a quantitative measurement method for acicular ferrite of pipeline steel, which utilizes an electron backscattered diffraction (EBSD) assembled on a scanning electron microscope (SEM) to carry out quantitative measurement on the acicular ferrite of the pipeline steel and comprises the following steps: grinding the cross section of a pipeline steel sample into a metallographical polished surface; etching the polished surface with natal, eliminating surface stress and showing an acicular texture; utilizing a conductive adhesive to fix the prepared sample on an EBSD sample stage; controlling the sample stage to rotate for 70 degrees by utilizing the SEM; vacuumizing an electron microscope sample chamber; when the vacuum degree reaches the electron microscope operating requirements, applying operational high pressure to acquiring an image, and finding a typical viewing field; stretching the probe of the EBSD into the sample chamber, and acquiring EBSD pattern data; and carrying out statistical treatment on the EBSD pattern data to obtain the effective crystallite dimension of the acicular ferrite texture. The invention is applied to the quantitative measurement of the acicular ferrite texture with unsharp boundaries in the pipeline steel.

The invention relates to wear-resistant steel for an ore slurry delivering welded pipe line and a manufacturing method thereof. The wear-resistant steel comprises the following components in percentage by weight: 0.04-0.10% of C, 1.00-1.70% of Mn, 0.20-0.60% of Cr, no more than 0.025% of Ti, no more than 0.06% of Nb, 0.02-0.06% of V, 0.10-0.40% of Si, no more than 0.05% of Al, no more than 0.008% of N, no more than 0.015% of P, no more than 0.008% of S and the balance of Fe and inevitable impurities; Pcm is no more than 0.18%, the steel plate is in a multiphase complex tissue of acicular ferrite+bainite+MA, and micro VC second-phase high-hardness particles are dispersed and precipitated in the tissue; and the transverse yield strength Rt0.5 of the steel plate is 490-705 MPa, the transverse tensile strength Rm is 570-825 MPa, and the yield ratio is Rt0.5 / Rm(0.85, hardening index n)1.10. According to the invention, the steel plate is simple in chemical composition and low in production cost, and the low carbon equivalent is beneficial to weldability; and due to the low yield ratio, the steel plate has the characteristics of easy pipe forming, high hardening index, high wear resistance and the like, and the wear resistance is almost doubled in comparison with a common line pipe.

The invention discloses a high-strength water riser main-pipe with excellent anti-fatigue performance and a manufacturing method thereof. the water riser main-pipe comprises the following chemical components: by weight, 0.04-0.08% of C, 0.15-0.35% of Si, 1.55-1.85% of Mn, P being less than or equal to 0.015%, S being less than or equal to 0.003%, Ni being less than or equal to 0.30%, Cr being less than or equal to 0.30%, Cu being less than or equal to 0.25%, Mo being less than or equal to 0.25%, 0.02-0.060% of Nb, V being less than or equal to 0.06%, 0.008-0.06% of Ti, 0.010-0.040% of Al and N being less than or equal to 0.008%, Al / N being greater than or equal to 3, Ni+Cu+Mo+Cr being less than or equal to 0.70%, and Nb+V+Ti being less than or equal to 0.12%. Carbon equivalent Ceq is less than or equal to 0.45, and cold crack coefficient Pcm is less than or equal to 0.23. A microstructure is a composite fine-grain structure of acicular ferrite+bainite. The invention provides an X80 high-strength water riser main-pipe with fatigue resistance and high dimensional accuracy. The water riser main-pipe is characterized by having excellent comprehensive performance such as plasticity, low-temperature toughness, fracture resistance, corrosion resistance and the like.

The invention provides a method for producing a thin-wall X70 pipeline steel coiled plate with low cost. A continuous casting and rolling production process of a medium-thin plate blank is adopted in the method, the thickness of the plate blank is 130 to 170 millimeters, the charging temperature is more than or equal to 800 DEG C, and the heating temperature is 1,100 to 1,150 DEG C. The method comprises the following steps of: after 3 to 5 times of rough rolling, holding the temperature; when the surface temperature of the middle blank is below 950 DEG C, performing rolling in a precision rolling machine, and controlling the temperature of a precision rolling outlet to be between 820 and 790 DEG C; and performing laminar cooling in a cooling mode of quick cooling and then slow cooling, and then performing coiling and air cooling. The steel grade component design is reasonable, does not add V and has low cost; the production process is simple; and by adopting hot charging, low-temperature heating, rolling control and sectional cooling after rolling, the energy consumption is saved, the production period is shortened, the production efficiency is improved, the purpose of reducing the production cost can be fulfilled, and a polyphase structure using fine acicular ferrite as a main component can be obtained so that the mechanical property of thick specification is ensured.

The invention provides high-damp-heat-resistant marine atmosphere high-strength weathering-resistant steel and belongs to the technical field of weathering-resistant steel. The weathering resistant steel comprises chemical ingredients of, in percentage by weight, 0.01-0.03 wt% of C, 0.30-0.50 wt% of Si, less than or equal to 0.01 wt% of P, less than or equal to 0.007 wt% of S, 0.30-0.50 wt% of Mn, 0.80-1.00 wt% of Cu, 2.90-3.10 wt% of Ni, 0.10-0.30 wt% of Mo, 0.20-0.30 wt% of Sn, 0.05-0.10 wt% of Sb, 0.40-0.60 wt% of Cr, less than or equal to 0.02 wt% of Nb, 0.01-0.03% of RE and the balance Fe and other inevitable impurity elements. Ultra-low carbon is adopted for ingredient design, the Sn, Sb and RE corrosion-inhibition alloy elements are added on the basis of a Cu-Ni-Cr-Mo alloy system in a compounded manner, and a great number of thin and small needle-shaped ferrite tissues are obtained supplemented by the microalloyed element Nb. The high-damp-heat-resistant marine atmosphere high-strength weathering resistant steel has the advantages that the steel has excellent weathering resistance and is particularly resistant to the high-damp-heat-resistant marine atmosphere environment, and corrosion resistance of the steel is increased by about three times that of plain carbon steel Q345 and is increased by about two times that of traditional weathering resistant steel Q450NQR1; and meanwhile, the steel has strength of 700 MPa level, the yield strength ratio is less than or equal to 0.80, and the extension rate is larger than or equal to 15%.

The invention belongs to the technical field of low-alloy high-strength steel, and particularly relates to a thick steel plate suitable for large heat input welding in EH420 grade marine engineering and a preparation method of the thick steel plate. The steel plate comprises the following chemical components of, by mass percentage, 0.05-0.12% of C, 0.1-0.3% of Si, 1.0-1.7% of Mn, 0.001-0.01% of P,0.001-0.005% of S, 0.01-0.04% of Nb, 0.005-0.025% of Ti, 0.2-0.5% of Cu, 0.2-0.5% of Ni, 0.001-0.006% of N, 0.001-0.005% of O, 0.005-0.025% of Al, 0.0005-0.005% of Mg, 0.0005-0.005% of Ca and the balance of Fe. Al-Mg-Ti-Ca-Mn-O-S composite inclusions account for more than 10% of inclusions with the sizes of 0.5-5 [mu]m in the steel plate and have special compositions. The steel plate is preparedaccording to the steps of adding silicon and manganese when steel is discharged from a converter, and feeding calcium wires, titanium wires, magnesium wires and aluminum wires during LF and RH refining; and adopting two-stage controlled rolling and controlled cooling. Particles of the inclusions in the steel plate are favorable for fine dispersion and distribution, have a better capability of promoting acicular ferrite nucleation, and can obviously improve low-temperature toughness of large heat input welding.

The invention discloses a manufacturing method of age-hardened thin-strip casting low-carbon microalloyed steel strip. The method comprises the following steps of: 1) smelting, and continuously casting a thin strip, wherein the weight percents of the components are as follows: 0.01-0.25% of C, not more than 0.4% of Si, 0.6-2.0% of Mn, not more than 0.015% of P, not more than 0.01% of S, not more than 0.006% of N, not more than 0.008% of O, 0.0005-0.004% of B, 0.005-0.1% of Nb, 0.005-0.1% of V, 0.005-0.1% of Ti, and 0.05-0.5% of Mo, and the balance of Fe and unavoidable impurities, and the casting thickness in the dual-roller continuous casting machine is 1-5mm; 2) cooling the cast strip, wherein the cooling rate is more than 20DEG C / s; 3) hot-rolling at 1050-1250 DEG C, wherein the reduction rate is 20-50%, and the deformation rate is more than 20s-1; 4) cooling, wherein the cooling rate is 10-80DEG C / s; 5) reeling at 550-700 DEG C; 6) performing age-hardening treatment, wherein the age-hardening temperature is 500-800 DEG C, and the heating time is 0.1-30 minutes. The austenite online recrystallization of the cast strip after hot-rolling is realized, the obtained steel strip is provided with uniformly distributed bainite and acicular ferrite, the structure comprises nanoscale precipitation such niobium carbonitride, and a product has high strength and extensibility.

The present invention relates to a weld metal joint subjected to flux cored arc welding (FCAW) used for weld structures, such as ships, buildings, bridges, marine structures, steel pipes, and line pipes, and a steel member having the weld metal joint, and more particularly, to a flux cored arc weld (FCAW) metal joint having excellent CTOD properties at low temperature and a steel member having the FCAW metal joint. A flux cored arc weld metal joint having excellent CTOD properties at low temperature may include, by weight: 0.01 to 0.2% C, 0.1 to 0.5% Si, 1.0 to 3.0% Mn, 0.5 to 3.0% Ni, 0.01 to 0.1% Ti, 0.0010 to 0.01% B, 0.005 to 0.05% Al, 0.003 to 0.006% N, at most 0.03% P, at most 0.03% S, 0.03 to 0.07% O, the FCAW metal joint satisfying a relation of 0.7<=Ti / O<=1.3, 6<=Ti / N<=12, 7<=O / B<=12, and 1.2<=(Ti+4B) / O<=1.9, and the balance of Fe and unavoidable impurities, the FCAW metal joint including a microstructure having acicular ferrite of 85% or more and at least one of the balance of bainite, grain boundary ferrite, and polygonal ferrite. A steel member includes the metal weld joint. According to the invention, there is provided a flux cored arc weld metal joint having a high- strength property and CTOD properties at low temperatures and a steel member having the metal weld joint.

A steel plate for linepipes having ultra-high strength and excellent low temperature toughness, and a method for manufacturing the same are disclosed. The steel plate has a strength of 930 MPa or more and excellent toughness even with much smaller amounts of alloying elements than that of conventional steel plates, and a method for manufacturing the same. The steel includes by weight %: 0.03˜0.10% C; 0˜0.6% Si; 1.6-2.1% Mn; 0˜1.0% Cu; 0-1.0% Ni; 0.02-0.06% Nb; 0-0.1% V; 0.1-0.5% Mo; 0-1.0% Cr; 0.005-0.03% Ti; 0.01-0.06% Al; 0.0005-0.0025% B; 0.001-0.006% N; 0-0.006% Ca; 0.02% or less P; 0.005% or less S; and the balance Fe and unavoidable impurities. The microstructure includes at least about 75 area percent of a mixture of bainitic ferrite and acicular ferrite.

The invention discloses a polygonal ferrite-acicular ferrite two-phase steel plate / belt and a production method thereof and belongs to the technical field of high-strength low-alloy steel. The low-alloy steel comprises the following chemical components in percentage by weight: 0.03%-0.12wt% of C, 0.10wt%-1.5wt% of Si, 0.5wt%-2.1wt% of Mn, not more than 0.02wt% of P, not more than 0.01wt% of S, 0.02wt%-0.1wt% of Nb, 0.05wt%-0.45wt% of Mo, the balance being Fe and inevitable impurities. A few alloy elements including 0-0.4wt% of Cu, 0-0.5wt% of Ni, 0-0.5wt% of Cr and the like are added in the low-alloy steel. The production process comprises the following steps of: steel-making, continuous-casting, re-heating, rough-rolling, finish-rolling, cooling, relaxing and preserving the heat and quickly cooling. The polygonal ferrite-acicular ferrite two-phase steel plate / belt has the advantages of high toughness and plasticity in addition to high strength level, and is applicable to the vehicle plate filed and the pipeline steel filed with high requirements on strength, plasticity and toughness.

A manufacturing method for strip casting 700 MPa-grade high strength atmospheric corrosion-resistant steel, comprising the following steps: 1) smelting, where the chemical composition of a molten steel in terms of weight percentage is that C is between 0.03-0.1%, Si≦0.4%, Mn is between 0.75-2.0%, P is between 0.07-0.22%, S≦0.01%, N≦0.012%, Cu is between 0.25-0.8%, Cr is between 0.3-0.8%, and Ni is between 0.12-0.4%, additionally, also comprised is at least one micro-alloying element among Nb, V, Ti, and Mo, where Nb is between 0.01-0.1%, V is between 0.01-0.1%, Ti is between 0.01-0.1%, and Mo is between 0.1-0.5%, and where the remainder is Fe and unavoidable impurities; 2) strip casting, where a 1-5 mm-thick cast strip is casted directly; 3) cooling the cast strip, where the cooling rate is greater than 20° C. / s; 4) online hot rolling the cast strip, where the hot rolling temperature is between 1050-1250° C., where the reduction rate is between 20-50%, and where the deformation rate is >20s−1; austenite online recrystallizing after hot rolling, where the thickness of the hot rolled strip is between 0.5-3.0 mm; and, 5) cooling and winding, where the cooling rate is between 10-80° C. / s, and where the winding temperature is between 520-670° C. The microscopic structure of a steel strip acquired is primarily constituted by evenly distributed bainite and acicular ferrite.

The invention is a flux-cored wire used for welding high strength structure steel plate. The proportioning of the flux-cored wire is as following by weight percentage: 30-50% of fluorite, 2%-5% of one or more than one of the sodium fluoride, sodium cryolite and potassium cryolite, 1%-3% of potassium titanate, 2%-6% of potassium feldspar, 2%-6% of one or two of the rutile and zircon sand, 3%-6% of Cr converted by alloy powder containing chrome such as light carton chromium and steel powder, metal manganese powder and the like, 9%-14% of Mn converted by alloy powder containing manganese such as light carbon manganese and steel powder, metal manganese power and the like, 3%-6% of Mo converted by alloy powder containing molybdenum such as molybdenum and steel powder, metal molybdenum powder and the like, 0.04%-0.1% of B converted by ferroboron or B2O3, 2%-5% of rare earth silicon, 2%-6% of ferrotitanium, 14%-18% of nickel powder, and the rest being ferrous powder. The flux-cored wire in the invention is a basic slag system of which the welding metal has high purity, adopts multi-element alloy by which the metallographic structure of the weld metal is acicular ferrite and the weld metal has fine mechanical property, and is suitable for welding the steel plate at Q690-Q800 strength grading.

The invention relates to a casting and producing method of a front shaft of a heavy-duty car, which belongs to the enginery. The method adopts copper-nickel alloying isothermal quenching magnesium iron which has higher strength and tenacity compared with the traditional copper-molybdenum alloying isothermal quenching magnesium iron, thereby the service life of the front shaft can be improved; a front shaft blank is cast by adopting a sand-coated iron mould process; the spheroidization of the blank is carried out by adopting a tundish-cover crushing method so that the spheroidization is more stably; a process of mechanical processing firstly and isothermal quenching later ensures that the front shaft does not deform; and the isothermal quenching treatment is performed on a salt bath furnace production line with shielding gas atmosphere to produce an austenite plus acicular ferrite matrix, thereby the tenacity of the front shaft is greatly improved. The method achieves the material revolution that forging is substituted by casting and steel is substituted by iron, saves a heavy forging device or the die investment, shortens the production period, and has obvious economic and social benefits.

The invention discloses a resource-saving Q345 low-alloy series steel plate and a production method thereof. The steel plate comprises the following chemical components in percent by weight: 0.15 to 0.18 percent of C, 0.15 to 0.50 percent of Si, 1.10 to 1.25 percent of Mn, not more than 0.030 percent of P, not more than 0.035 percent of S, 0 to 0.045 percent of Alt, not more than 0.44 percent of carbon equivalent, and the balance of Fe and inevitable impurities. The production process of the steel plate comprises 150 t converter, LF external refining, slab continuous casting, slab heating, steckel mill controlled rolling, controlled cooling, thermal straightening, cooling, shearing and mark warehousing. The resource-saving Q345 low-alloy series steel plate, produced by the production method, has the yield strength of 360 to 420 MPa, the tensile strength of 500 to 550 MPa, and the elongation of 24 to 32%, and acicular ferrite with the thickness of 3 to 6 mm, polygonal ferrite, degenerate perlite and a small amount of granular bainite are arranged on the surface layer of the steel plate.