1465 results about "Bainite" patented technology

Provided is a high-strength steel sheet having excellent member strength, ductility, stretch flangeability, bendability of a shear end surface, and low-temperature toughness. A high-strength steel sheet having a prescribed component composition and a steel structure in which the area ratio of martensite is 10%-80%, the area ratio of bainite is 2%-70%, the area ratio of ferrite is 80% or less, and the area ratio of retained austenite is 15% or less at a position at 1 / 4 of the sheet thickness. The ratio of the number of martensite blocks in which metastable carbides are present relative to the number of martensite blocks is 2% or more, and the standard deviation [sigma] n of the nano-hardness relative to the average value [Hn] ave of the nano-hardness is 0.60 x [Hn] ave or less when the nano-hardness at 225 points or more is measured at a position of 1 / 4 of the sheet thickness.

The purpose of the present invention is to provide: a high-strength steel sheet that has a tensile strength of 980 MPa or greater and that is excellent in ductility, fatigue strength, and blanking properties; and a method for manufacturing the same.　The high-strength steel sheet is characterized by: having a prescribed component composition; the main phase being a bainite phase composed of granular bainite and upper bainite having an area ratio of 85% or greater; the area ratio of a hard second phase that includes fresh martensite and / or a residual austenite phase being less than 15%; the area ratio of the granular bainite to the area ratio of the upper bainite in the bainite phase being 5% to 40%; the difference |Hv1 - Hv2| between the hardness Hv1 at the 1 / 2 position the sheet thickness and the hardness Hv2 at the 1 / 4 position of the sheet thickness being 30% or less in relation to 0.3 TS; and the average crystal grain size of the upper bainite phase being 7 μm or less.

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 2100MPa bridge cable 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 C-Si-Mn-Cr-Mo chemical components into a wire rod, and carrying out online molten salt tail end quenching isothermal treatment, so that the wire rod firstly passes through front-section molten salt and is cooled at a cooling speed of more than or equal to 35 DEG C / s to enter a sorbite phase region from an austenite state; the method comprises the following steps of: controlling part of austenite to be converted into sorbite, cooling to a bainite phase through rear-section molten salt, carrying out end quenching, controlling bainite phase change, carrying out isothermal tempering to remove stress, and finally carrying out roller way slow cooling to prepare a complex-phase structure comprising tempered sorbite and tempered bainite, so that abnormal structures of network carbides and martensite can be effectively controlled; the high-strength composite phase structure control and plasticity matching are achieved, the tensile strength is 1530-1560 MPa, the percentage reduction of area is 30%-35%, and the method is suitable for manufacturing 2100 MPa-grade ultrahigh-strength bridge cables with large drawing amount and beneficial to reducing the risk of wire breakage.

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2100MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod, after a C-Si-Mn-Cr-Mo high-carbon component system is rolled and spun into a wire rod, the wire rod is subjected to online molten salt strong quenching isothermal treatment, so that the wire rod is firstly subjected to front-section molten salt treatment and is cooled at a cooling speed of greater than or equal to 33 DEG C / s, and enters a bainite phase region from an austenite state; the method comprises the following steps: firstly, carrying out first-stage molten salt treatment to promote transformation of austenite into bainite, then carrying out later-stage molten salt treatment to form a structure mainly comprising bainite, carrying out isothermal tempering on the structure, reserving part of untransformed retained austenite, and finally, carrying out roller way slow cooling to promote transformation of the untransformed retained austenite into martensite, and carrying out tempering, the microstructure of the hot-rolled wire rod comprises a complex-phase structure composed of tempered bainite and tempered martensite, the tensile strength of the hot-rolled wire rod can reach 1435-1485 MPa, the percentage reduction of area of the hot-rolled wire rod is 31%-36%, off-line heat treatment of follow-up machining is avoided, and the risk of wire breakage is reduced.

The invention discloses a wide and thick steel plate for a 700MPa-grade corrosion-resistant anti-fatigue marine tendon pipe and a production method of the wide and thick steel plate. According to the component design of the wide and thick steel plate, CEIIW is controlled to be 0.41-0.47%, CEPcm is controlled to be 0.16-0.20%, low-Nb and low-Mo design is adopted, the phase change temperature is increased, and phase change of polygonal ferrite is promoted; rE solid solution, interface segregation and other effects are fully utilized to improve the strength and corrosion resistance, and the RE and Ca act together to purify molten steel and modify and disperse inclusions. On the basis of component design, low-temperature heating, rough rolling multi-stage thickness section high-temperature gradient deformation and low-temperature rolling, intermediate temperature-waiting blank rapid cooling after rough rolling is finished, finish rolling low-temperature deformation, multi-stage water cooling and other methods are adopted to obtain a microstructure of lath bainite, granular bainite and polygonal ferrite, and the proportion, size and distribution control of all phases is ideal; the method plays an important role in obtaining good comprehensive performance of the steel plate.

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 discloses a hot-rolled high-weather-resistance steel plate with extremely low yield ratio and 850 MPa-grade tensile strength as well as a manufacturing method and application of the hot-rolled high-weather-resistance steel plate. The steel plate comprises chemical components in percentage by weight as follows: 0.06%-0.08% of C, 0.40%-0.60% of Si, 0.40%-0.60% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.005% of S, 2.50%-3.00% of Cr, 0.25%-0.30% of Cu, 0.13%-0.15% of Ti, 0.020%-0.040% of Alt, smaller than or equal to 0.0040% of N, smaller than or equal to 0.0030% of O and the balance of Fe and inevitable impurities. The high Cr + high Ti design is adopted, the tensile strength reaches 850 MPa, the weather resistance index I value is larger than or equal to 8.0, addition of precious metal Ni is omitted, the addition amount of the strong hardenability element Cr in the steel exceeds 2.50%, a fine grain ferrite and bainite double-phase structure is obtained in combination with the controlled rolling and controlled cooling process, meanwhile, the precipitation strengthening and fine grain strengthening effects of Ti are fully exerted, control over high strength and the extremely-low yield ratio smaller than 0.65 is achieved, and the high-strength and low-yield-ratio steel is obtained. The forming performance is excellent, the corrosion rate is smaller than 40% relative to Q345B, and good atmospheric corrosion resistance is achieved.

The invention relates to a production method of a wire rod for an alloy welding wire, and belongs to the technical field of steel manufacturing. Mn, Cr and Ni alloying and V and Ti microalloy strengthening are adopted, and a certain amount of B is added, so that the requirement of a 60-kilogram-level alloy welding wire is met. The process route is designed as follows: molten iron pretreatment, converter smelting, LF furnace external refining, 150mm / 180mm square billet continuous casting, heating furnace heating, rolling, roller way slow cooling and heat preservation vestibule heat preservation. Molten steel with stable components, good castability and gas content meeting the requirement is obtained through the technologies of molten iron pretreatment, converter smelting, LF furnace external refining and the like, after the molten steel is poured into a continuous casting blank, stack cooling or hot delivery and hot charging are conducted for 24 hours, and the technologies of high-temperature rolling, high-temperature spinning, roller way slow cooling and heat preservation vestibule are adopted for high-speed wire rolling. By adopting the process of the scheme, the wire rod can be prevented from generating abnormal structures such as martensite and bainite which influence drawing, and the wire rod for the high-strength alloy welding wire with the specification of phi 5.5 mm, which has stable components and can be drawn into filaments with the specification of phi 1.2 mm without annealing, is obtained.

The invention relates to a 1200MPa-grade high-strength tool steel wire rod and a manufacturing method thereof, after V-containing chemical components are designed, rolled and spun into a wire rod, the wire rod is subjected to online molten salt isothermal quenching treatment, and the wire rod is controlled to enter a bainite phase region from a high-temperature austenite state at a cooling speed greater than or equal to 32 DEG C / s; the steel wire rod with a microscopic structure comprising tempered bainite and ferrite is prepared through isothermal tempering, toughening and destressing treatment, carbide precipitation control and roller way cover opening and slow cooling, so that generation of deteriorated structures such as martensite can be avoided, the structure state can be effectively adjusted, strong plasticity matching of the steel wire rod is achieved, and the service life of the steel wire rod is prolonged. And the tensile strength is 1120-110MPa, the percentage reduction of area is 63-67%, and the steel is suitable for the application fields of manufacturing 1200MPa-grade high-strength tool steel and the like, and is favorable for being directly processed into tool parts after being subjected to cold processing molding.

The invention provides a production method of 440MPa-grade normalized high-strength structural steel for a ship body, and belongs to the field of ship body structural steel manufacturing, the production process route of the steel comprises smelting, die casting, rolling, rapid cooling, finishing, normalizing and tempering, the thickness of a produced steel plate is 8-20mm, and the steel comprises the following chemical components in percentage by mass: 0.06-0.10% of C; si: less than or equal to 0.40%; mn is equal to 0.90%-1.20%; less than or equal to 0.015% of P; s: < = 0.005%; the ratio of Ni to Cr is (0.90%-1.30%): (0.50%-0.65%); v is equal to 0.030 percent to 0.050 percent; cu is equal to 0.15%-0.35%; n is less than or equal to 0.0040%, and the balance is Fe and inevitable impurities. The microstructure of the steel is a bainite tempered structure and ferrite, and the average grain size of the ferrite is smaller than or equal to 10 micrometers. The yield strength of the steel is larger than or equal to 440 MPa, the tensile strength is larger than or equal to 600 MPa, the yield ratio is smaller than or equal to 0.75, the impact absorbing energy at the temperature of 60 DEG C below zero is larger than or equal to 200 J, the ductile-brittle transition temperature is not higher than 80 DEG C below zero, and a product has good corrosion resistance.

The invention relates to a 1100MPa-grade high-strength tool steel wire rod and a manufacturing method thereof, the wire rod adopts a middle-carbon Nb-V-containing chemical component design, after a steel billet is rolled and spun into the wire rod according to the spinning temperature of more than or equal to 860 DEG C, online molten salt semi-quenching isothermal treatment is performed, the wire rod is controlled to be subjected to front-section molten salt treatment, and then the steel wire rod is subjected to hot rolling and hot rolling to obtain the 1100MPa-grade high-strength tool steel wire rod. According to the method, the steel wire rod enters a bainite phase region from a high-temperature austenite state at the cooling speed of more than or equal to 30 DEG C / s to form a structure taking quenched bainite as a main component, and then is subjected to rear-section molten salt heating isothermal tempering and toughening destressing treatment, and finally is subjected to roller way slow cooling to prepare the steel wire rod with a microscopic structure comprising tempered bainite and ferrite, so that the material cost can be reduced, and the production efficiency is improved. The method has the advantages that martensite brittle structures are effectively avoided, the structure state of the hot-rolled wire rod is controlled, the plasticity and cold working performance of the wire rod are improved, the tensile strength of the product can reach 980-1030 MPa, the percentage reduction of area is 61%-66%, and the product can be directly machined into tool parts after cold forming.

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 provides a method for obtaining the optimal low-temperature impact toughness and a welded body, and the method comprises the following steps: S1, obtaining chemical components of sample steel, and calculating the cooling rate corresponding to the bainite phase change curve nose tip temperature of the sample steel; s2, the cooling rate serves as the key cooling rate of the welding heat cycle process, and the corresponding welding heat input amount is calculated; s3, cutting a plurality of cuboid thermal simulation initial samples of which the length directions are parallel to the rolling direction of the steel plate from the sample steel; s4, two-pass welding thermal simulation cycle experiments at different temperatures are set; s5, two thermocouples are welded to the center of the cuboid thermal simulation initial sample for temperature measurement, and a welding simulation experiment is completed; and S6, size machining is conducted on the welding sample, a low-temperature impact experiment is conducted, impact energy under different technologies is measured, and the optimal impact toughness of CGHAZ and ICCGHAZ is determined. The method can be used for developing and optimizing the welding process with insufficient low-temperature impact toughness of the submerged-arc welding heat affected zone of the low alloy steel.

The invention belongs to the field of steel rail manufacturing, and discloses a method for improving the impact toughness matching performance of a dissimilar material steel rail welding joint. The method comprises the following steps: carrying out first-stage cooling on a welding joint formed by welding the eutectoid pearlite steel rail and the bainite steel rail; carrying out full-section normalizing heating on the welded joint; the welding joint is subjected to second-stage cooling, a heat affected zone on one side of the heat treatment type eutectoid pearlite steel rail is cooled to 350-400 DEG C at the cooling rate of 4.0-7.0 DEG C / s, and a heat affected zone on one side of the hot rolling type bainite steel rail is cooled to 290-315 DEG C at the cooling rate of 2.0-3.0 DEG C / s; the welding joint is heated to a bainite transformation temperature interval for isothermal treatment; and naturally cooling the welding joint in an air environment. According to the method provided by the invention, the room-temperature impact toughness of the heat affected zone on one side of the hot-rolled bainite steel rail can be obviously improved, so that the performance of the hot-rolled bainite steel rail is better matched with that of a hot-rolled bainite steel rail base material.

A method to achieve a yield ratio of 0.60 or more in a component from non-heat-treated steel having bainitic microstructure. The component includes a predetermined chemical composition, in mass %, in amounts such that a value of F1 obtained by Formula (1) is 0.65% or more, with the balance as Fe and inevitable impurity. Bainitic microstructure area fraction is 85% or more and Retained austenite area fraction is 5% or less. Crystal grains of the bainitic microstructure have an average diameter of 10 μm or more and 25 μm or less, an average aspect ratio of 0.5 or more, and an average ratio of crystal grain boundary length to crystal grain circumference of 60 or less.F⁢1=C+Si / 24+Mn / 6+Ni / 40+Cr / 5+Mo / 4+V / 14(1)

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 a high-strength complex-phase hot-rolled wire rod for a 2360MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After a Mo-V high-carbon component system is rolled and spun into a wire rod, the wire rod is subjected to on-line molten salt weak quenching toughening treatment, so that the wire rod is subjected to front-section molten salt treatment to be quickly cooled, enters a bainite and sorbite mixed phase region from an austenite state, and is subjected to high-temperature heat treatment to form a high-strength complex-phase hot-rolled wire rod; the method comprises the following steps: firstly, carrying out heat treatment on residual austenite to form a structure mainly comprising bainite and sorbite, then carrying out later-section molten salt treatment, increasing the temperature of molten salt, promoting decomposition and conversion of unconverted residual austenite into sorbite, carrying out isothermal tempering, and finally, carrying out roller way slow cooling to prepare a hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered bainite and tempered sorbite, the method has the advantages that the structure toughness can be regulated and controlled on line, the tensile strength is 1574-1627 MPa, the percentage reduction of area is 28-33%, the mechanical property fluctuation is reduced, the material cost and the production efficiency are both considered, the ultra-high-strength stranded wire can be produced without off-line heat treatment, and the wire breaking risk is reduced.

The invention discloses a production method for eliminating martensite and bainite of a 70Kg-grade steel wire rod for welding, which comprises the working procedures of steel billet heating, controlled rolling, compensation heating and cooling and waste heat isothermal heat treatment, in the steel billet heating procedure, the heating time of a rectangular billet in a heating furnace is greater than or equal to 5 hours, the heating temperature is 1120-1180 DEG C, and the soaking temperature is 1140-1200 DEG C; in the controlled rolling process, the finish rolling temperature is 900-960 DEG C, and the spinning temperature is 920-980 DEG C; in the compensation heating process, a coil runs on a Stelmor roller way for 14-18 minutes, the temperature is reduced to 650-700 DEG C, and the coil is collected; according to the waste heat isothermal heat treatment procedure, the coiled wire rod enters a 610-650 DEG C heat preservation gallery with temperature compensation, enters a slow cooling gallery after heat preservation is conducted for 2-3 h, is slowly cooled to 450-500 DEG C and is taken out of the slow cooling gallery to be naturally cooled to 200 DEG C or below, and packaging is conducted.

This hot-rolled steel sheet has a predetermined chemical composition, a microstructure includes 80% or more of tempered martensite by a volume percentage and a remainder consisting of one or more of ferrite, pearlite, bainite, fresh martensite, and residual austenite, the tempered martensite includes 5×109 pieces / mm3 or more of precipitates containing Ti and having an equivalent circle diameter of 5 nm or less per unit volume, in a surface layer region that is a range from a surface to a 1 / 10 position of a sheet thickness, a sum of an average pole density of a crystal orientation group consisting of {211}<111> to {111}<112> and a pole density in a crystal orientation of {110}<001> is 6.0 or less, and a tensile strength is 980 MPa or more.

The invention provides bainite non-quenched and tempered steel and a preparation method thereof.The preparation method comprises the following steps that blast furnace molten iron is sequentially subjected to molten iron pretreatment, converter smelting, ladle refining, vacuum refining, vacuum degassing, continuous casting and rolling, and the bainite non-quenched and tempered steel is obtained; the content of P at the smelting end point of the converter is less than or equal to And the content of S in the molten steel subjected to vacuum refining is 0.038%-0.045%. The bainite non-quenched and tempered steel with excellent comprehensive performance is obtained through reasonable smelting, refining, continuous casting and rolling process design of blast furnace molten iron designed by adopting specific chemical components, the preparation process is simple, and the preparation cost is low.

The invention relates to a detection method and application of a bainite steel structure and / or grain boundary for nuclear power equipment, and relates to the technical field of new material detection. According to the detection method, the problem that the structure and the grain boundary of bainite steel for nuclear power equipment are difficult to display can be solved, a major breakthrough of a grain size detection technology is achieved, the clear and complete grain boundary can be accurately presented, and scientific evaluation of the grain size through a comparison method, a cut point method, an area method and the like according to standard requirements is further supported. When the detection method is used for evaluating the grain size, the results are highly consistent, the repeatability is good, and the problems of subjective experience dependence and measurement errors caused by blurred grain boundary display in a traditional nitric acid and alcohol corrosion method are effectively avoided.

The invention discloses a high-carbon high-alloy grinding ball steel rolling internal damage control method, and belongs to the technical field of metal material rolling machining. Comprising the following steps that high-carbon high-alloy grinding ball steel billets are subjected to high-temperature diffusion homogenization treatment and then subjected to staged temperature control rolling, the initial rolling temperature in the blooming stage is 1020-1080 DEG C, the single-pass reduction rate is 6-10%, the pass interval is larger than or equal to 20 seconds, the total reduction rate is 40-80%, and the core peak temperature is controlled to be smaller than or equal to 1150 DEG C; the finish rolling temperature is 800-850 DEG C; during rolling, atomized water is sprayed for dynamic cooling every 2-3 passes, and two-stage cooling (water cooling to 600-650 DEG C at 15-20 DEG C / s, and slow cooling to room temperature) is carried out after final rolling. According to the method, element diffusion, temperature rise inhibition and structure refinement are synergistically regulated and controlled, so that the core void ratio is reduced, the austenite grain size is larger than or equal to 8 grades, a uniform bainite and dispersed carbide composite structure is obtained, and the anti-fatigue performance of the grinding ball steel is remarkably 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 a 1300 MPa-grade high-strength tool steel wire rod and a manufacturing method thereof, after a Cr-Nb-V medium carbon component design is adopted for rolling and spinning to form a wire rod, the wire rod is subjected to online molten salt micro-quenching tempering treatment, the wire rod is controlled to enter a lower bainite phase region from a high-temperature austenite state at a cooling speed greater than or equal to 31 DEG C / s, and a quenching structure mainly comprising quenching bainite is formed; the steel wire rod with a microscopic structure comprising tempered bainite and ferrite is prepared by carrying out isothermal tempering and toughening destressing treatment on a quenched structure and finally carrying out roller way slow cooling, so that the material cost can be properly controlled, the strength and plasticity matching of the steel wire rod is improved, the tensile strength is 1255-1305MPa, and the percentage reduction of area is 58-63%, so that the steel wire rod can be directly processed into a part after being subjected to cold processing molding, and the service life of the steel wire rod is prolonged. And tool steel production energy consumption, cost reduction and efficiency improvement are facilitated.

A steel for forging mechanical parts including of the following elements, expressed in percentage by weight: 0.15%≤C≤0.22%; 1.6%≤Mn≤2.2%; 0.6%≤Si≤1%; 1%≤Cr≤1.5%; 0.01%≤Ni≤1%; 0%≤S≤0.06%; 0%≤P≤0.02%; 0%≤N≤0.013%; and having optional elements 0%≤Al≤0.06%; 0.03%≤Mo≤0.1%; 0%≤Cu≤0.5%; 0.01%≤Nb≤0.15%; 0.01%≤Ti≤0.03%; 0%≤V≤0.08%; 0.0015%≤B≤0.004%; the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of said steel having microstructure by area percentage including of cumulative presence of residual austenite and martensite-austenite island between 1% and 20%, the remaining microstructure being bainite having at least 80%, wherein the fraction of grain boundaries of bainite with a misorientation angle of 59.5° are at least 7% and with an optional presence of martensite between 0% and 10%.

The invention belongs to the field of steel for petroleum casings, and discloses a bainite / martensite multiphase petroleum casing and a preparation method of the bainite / martensite multiphase petroleum casing. The preparation method comprises the following steps: smelting and casting a bainite steel billet containing C, Mn, Si, Cr, Ni, Mo, Nb, V, Ti, Cu and Fe to obtain bainite round steel; the bainite round steel is heated, hot-rolled and air-cooled to obtain a steel pipe; the hot-rolled steel pipe is naturally cooled to the bainite phase transformation starting temperature at a first cooling speed, cooled to the martensite phase transformation ending temperature from the bainite phase transformation starting temperature at a second cooling speed and then naturally cooled to the room temperature, and the bainite / martensite multiphase steel pipe is obtained; and tempering and straightening the bainite / horse complex-phase steel pipe to obtain the bainite / horse complex-phase petroleum casing pipe. According to the invention, through reasonable component design and phase change latent heat of the casing, redistribution of carbon is promoted, so that the corrosion-resistant bainite / martensite multiphase oil casing with ultrahigh toughness is prepared.

The bainite plastic die steel comprises the following components in percentage by mass: 0.01-0.15% of C, 0.25-1.0% of Si, 0.5-2.0% of Mn, less than or equal to 0.045% of P, less than or equal to 0.015% of S, 2.0-5.0% of Cr, 1.01-2.0% of Ni, 0.0010-0.0050% of B, 0.004-0.008% of N and the balance of Fe and other inevitable impurities, and the following requirements are simultaneously met: the hardness index is more than or equal to 28 and less than or equal to 13.8 + 132.8 C + 2.34 Mn + 1.84 Cr-1.12 Ni and less than or equal to 38, and the bainite index is C 0.5 * Mn 1.4 * Cr 4 * Ni * N-1. 05 / 20 and less than or equal to 2000. According to the die steel, the tensile strength is larger than or equal to 800 MPa, the hardness is 28-38 HRC, the hardness difference value of the section of a steel plate with the thickness of 15-300 mm is smaller than or equal to 2 HRC, the straightness is smaller than or equal to 2 mm / m, and the flaw detection quality meets the E / e level requirement in the SP1921-84 standard. The method can be applied to manufacturing of plastic parts in the fields of automobiles, household appliances, medical treatment, electronics and the like.

The invention provides a high-strength extremely thick steel plate and a manufacturing method thereof. This high-strength extremely thick steel plate has a specific component composition, has a texture in which the X-ray intensity ratio of the (211) plane of the rolled surface at a position 1 / 2 of the plate thickness is 1.70 or more, and has a steel structure at a position 1 / 2 of the plate thickness, the steel structure at the position of 1 / 2 of the sheet thickness is a mixed structure comprising a bainite phase having an area fraction of 85-100% and a ferrite phase having an area fraction of 0-15%, the average crystal grain size of the bainite is 20 [mu] m or less, the equivalent circle diameter of the maximum pore remaining in the center of the sheet thickness is 200 [mu] m or less, the steel structure at the position of 1 / 2 of the sheet thickness is provided, the sheet thickness is 50-100 mm, and the thickness of the steel structure at the position of 1 / 2 of the sheet thickness is 50-100 mm. The yield strength at a position 1 / 2 of the sheet thickness is 500 MPa or more, the vTrs at a position 1 / 2 of the sheet thickness is-105 DEG C or less, and the value of Kca (-10 DEG C) is 9000 N / mm3 / 2 or more.

The invention discloses pipeline steel for carbon dioxide conveying and a production method thereof, and relates to the technical field of steel production, and the pipeline steel comprises the following chemical components in percentage by mass: 0.03%-0.07% of C, 0.10%-0.40% of Si, 1.00%-1.40% of Mn, less than or equal to 0.013% of P, less than or equal to 0.0020% of S, 0.030%-0.070% of Nb, less than or equal to 0.010% of V, 0.008%-0.030% of Ti, 0.20%-0.40% of Cr, 0.10%-0.30% of Ni, 0.05%-0.15% of Mo, less than or equal to 0.010% of Cu, 0.015%-0.055% of Al, less than or equal to 0.00050% of B, 0.0006%-0.0030% of Ca, less than or equal to According to the invention, a structure form taking bainite as a main component is realized, and the performance requirement of a product is met.