Abstract: In a high-tensile steel plate according to the invention, the carbon equivalent Pcm represented in Expression (1) is from 0.180% to 0.220%, the surface hardness is a Vicker's hardness of 285 or less, the ratio of a Martensite Austenite constituent in the surface layer is not more than 10%, the ratio of a mixed structure of ferrite and bainite inside beyond the surface layer is not less than 90%, the ratio of the bainite in the mixed structure is not less than 10%, the thickness of the lath of bainite is not more than 1 ?m, the length of the lath is not more than 20 ?m, and the segregation ratio as the ratio of the Mn concentration in the center segregation part relative to the Mn concentration at a part in a depth equal to ¼ of the thickness of the plate from the surface is not more than 1.3. Pcm=C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B . . . (1) where the element symbols in Expression (1) represent the % by mass of the respective elements.

Abstract: The present invention provides steel plate for line pipe excellent in strength and ductility and a method of production of the same. The steel plate has a steel composition containing, by mass %, C: 0.04 to 0.15%, Si: 0.05 to 0.60%, Mn: 0.80 to 1.80%, P: 0.020% or less, S: 0.010% or less, Nb: 0.01 to 0.08%, and Al: 0.003 to 0.08%, having a balance of iron and unavoidable impurities, and having a value of Ceq shown by the following formula <1> of 0.48 or less, comprised of a mixed structure of ferrite and pearlite or ferrite and pearlite partially containing bainite in which a ferrite percentage is 60 to 95%, having a yield strength of 450 MPa or more, and having an amount of hydrogen contained in the steel of 0.

Abstract: The present invention provides a fire resistant steel material excellent in high temperature strength, toughness, and reheating embrittlement resistance containing, by mass %, C: 0.001% to 0.030%, Si: 0.05% to 0.50%, Mn: 0.4% to 2.0%, Nb: 0.03% to 0.50%, Ti: 0.005% to less than 0.040%, N: 0.0001% to less than 0.0050%, and Al: 0.005% to 0.030%, limiting P: 0.03% or, less and S: 0.02% or less, satisfying C—Nb/7.74?0.005 and 2?Ti/N?12, and having a balance of Fe and unavoidable impurities and, further, a process for production of a fire resistant material comprising heating a steel slab comprised of this chemical composition to 1100 to 1350° C. and hot rolling it by a cumulative reduction rate at 1000° C. or less of 30% or more.

Abstract: A high carbon content and high strength heat-treated steel rail including by weight 0.80-1.20% carbon, 0.20-1.20% silicon, 0.20-1.60% manganese, 0.15-1.20% chromium, 0.01-0.20% vanadium, 0.002-0.050% titanium, less than or equal to 0.030% phosphorus, less than or equal to 0.030% sulfur, less than or equal to 0.010% aluminum, less than or equal to 0.0100% nitrogen, and iron. The steel rail has excellent wear resistance and plasticity and can satisfy the requirement for overloading. A method for producing the steal rail by heating a slab to a heating temperature, multi-pass rolling, and accelerated cooling, wherein a maximum heating temperature (° C.) of said slab is equal to 1,400 minus 100[% C], [% C] representing the carbon content (wt. %) of said slab multiplied by 100.

Abstract: A spring steel having a high strength of 1900 MPa or more and superior in the brittle fracture resistance, as well as a method for manufacturing the same, are provided. The high strength spring steel comprises, as basic components in mass %, C: 0.4-0.6%, Si: 1.4-3.0%, Mn: 0.1-1.0%, Cr: 0.2-2.5%, P: 0.025% or less, S: 0.025% or less, N: 0.006% or less, Al: 0.1% or less, and O: 0.003% or less, the amount of solute C being 0.15% or less, the amount of Cr contained as a Cr-containing precipitate being 0.10% or less, and a TS value represented by the following equation being 24.8% or more, and in point of structure, the pre-austenite grain diameter being 10 ?m or smaller, wherein TS=28.5*[C]+4.9*[Si]+0.5*[Mn]+2.5*[Cr]+1.7*[V]+3.7*[Mo] where [X] stands for mass % of element X.

Abstract: Steel for machine structure use excellent in tool lifetime in a broad range of cutting speeds regardless of continuous machining, intermittent machining, or other systems and further in various machining environments such as use of a cutting fluid or a dry, semidry, and oxygen enriched environment, having a chemical composition containing, by mass %, C: 0.01 to 1.2%, Si: 0.005 to 3.0%, Mn: 0.05 to 3.0%, P: 0.0001 to 0.2%, S: 0.0001 to 0.35%, N: 0.0005 to 0.035%, and Al: 0.05 to 1.0%, satisfying [Al %]?(27/14)×[N %]?0.05%, and having a balance of Fe and unavoidable impurities and forming an Al2O3 coating on the surface of a cutting tool by machining using a cutting tool coated on the surface contacting the machined material by metal oxides with a value of a standard free energy of formation at 1300° C. of that value of Al2O3 or more, and a machining method of the same.

Abstract: A high-strength galvanized steel sheet has excellent mechanical properties such as a TS of 1200 MPa or more, an El of 13% or more, and a hole expansion ratio of 50% or more and a method for manufacturing the same. A high-strength galvanized steel sheet excellent in formability contains 0.05% to 0.5% C, 0.01% to 2.5% Si, 0.5% to 3.5% Mn, 0.003% to 0.100% P, 0.02% or less S, and 0.010% to 0.5% Al on a mass basis, the remainder being Fe and unavoidable impurities, and has a microstructure which contains 0% to 10% ferrite, 0% to 10% martensite, and 60% to 95% tempered martensite on an area basis as determined by structure observation and which further contains 5% to 20% retained austenite as determined by X-ray diffractometry.

Abstract: A magnetic material for magnetic refrigeration has a composition represented by (R11-yR2y)xFe100-x (R1 is at least one of element selected from Sm and Er, R2 is at least one of element selected from Ce, Pr, Nd, Tb and Dy, and x and y are numerical values satisfying 4?x?20 atomic % and 0.05?y?0.95), and includes a Th2Zn17 crystal phase, a Th2Ni17 crystal phase, or a TbCu7 crystal phase as a main phase.

Abstract: In a cold-rolled steel sheet in relation with the present invention, metallurgical structure of the steel sheet is made a mixture structure including bainite, residual austenite and tempered martensite, particularly, when the metallurgical structure is observed with a scanning electron microscope, bainite is constituted of composite structure of high temperature range forming bainite with 1 ?m or above average distance between neighboring residual austenite and/or carbide and low temperature range forming bainite with below 1 ?m average distance between neighboring residual austenite and/or carbide, and when the area ratio of the high temperature range forming bainite with respect to total metallurgical structure is made a and the total area ratio of the low temperature range forming bainite and the tempered martensite with respect to the total metallurgical structure is made b, a: 20-80%, b: 20-80%, and a+b: 70% or above are satisfied.

Abstract: A high strength steel sheet having composition includes, on a percent by mass basis, C: 0.17% to 0.73%; Si: 3.0% or less; Mn: 0.5% to 3.0%; P: 0.1% or less; S: 0.07% or less; Al: 3.0% or less; and N: 0.010% or less, satisfies Si+Al?0.7%, and the remainder includes Fe and incidental impurities, with a microstructure that has an area percentage of a total amount of lower bainite and whole martensite 10% to 90% relative to the whole steel sheet microstructure, an amount of retained austenite is 5% to 50%, an area percentage of bainitic ferrite in upper bainite is 5% or more relative to the whole steel sheet microstructure, as-quenched martensite is 75% or less of the total amount of lower bainite and whole martensite, and an area percentage of polygonal ferrite is 10% or less relative to the whole steel sheet microstructure, an average amount of C in retained austenite is 0.70% or more, and tensile strength is 980 MPa or more.

Abstract: A high-strength steel sheet has good ductility and stretch-flangeability and has a tensile strength (TS) of 980 MPa or more. The steel sheet contains 0.17%-0.73% C, 3.0% or less Si, 0.5%-3.0% Mn, 0.1% or less P, 0.07% or less S, 3.0% or less Al, and 0.010% or less N, in which Si+Al is 0.7% or more.

Abstract: A high-strength galvanized steel sheet has a TS of at least 590 MPa and excellent ductility and stretch flangeability and a method for manufacturing the high-strength galvanized steel sheet. The galvanized steel sheet contains, on the basis of mass percent, C: 0.05% to 0.3%, Si: 0.01% to 2.5%, Mn: 0.5% to 3.5%, P: 0.003% to 0.100% or less, S: 0.02% or less, and Al: 0.010% to 1.5%. The total of Si and Al is 0.5% to 2.5%. The remainder are iron and incidental impurities, contain 20% or more of ferrite phase, 10% or less of martensite phase, and 10% to 60% of tempered martensite, on the basis of area percent, and 3% to 10% of retained austenite phase on the basis of volume fraction. The retained austenite has an average grain size of 2.0 ?m or less.

Abstract: Steel sheets containing residual austenite of not more than 7 vol. %, crystallized and/or precipitated compounds with particle diameters of 0.01 to 5.0 ?m of 100 to 100000 particle/mm2 and C of 0.05 to 0.3 mass %, Si of not more than 3.0 mass %, Mn of 0.01 to 3.0 mass %, P of not more than 0.02 mass %, S of not more than 0.02 mass %, Al of 0.01 to 3.0 mass %, N of not more than 0.01 mass % and Mg of 0.0002 to 0.01 mass %, with the remainder comprising iron and unavoidable impurities.

Abstract: A high strength steel sheet excellent in formability which has a chemical composition in mass %: C: 0.03 to 0.20%, Si: 0.005 to 0.3%, Mn: 1.0 to 3.1%, P: 0.001 to 0.06%, S: 0.001 to 0.01%, N: 0.0005 to 0.01%, Al: 0.2 to 1.2%, Mo?0.5%, and the balance: Fe and inevitable impurities, with the proviso that the values of mass % for Si and Al satisfy the following formula (1): (0.0012×[objective value of TS]?0.29?[Si])/2.45<Al<1.5?3×[Si] . . . (1) wherein [objective value of TS] represents a design strength value for the steel sheet in an Mpa unit, and has a metal structure containing ferrite and martensite. The above high strength steel sheet is also excellent in formability and the capability of being chemically treated and that of being hot-dip zinc sheeted.

Abstract: The present invention has as its object the provision of hot rolled steel sheet (hot coil) for line pipe use in which API5L-X80 standard or better high strength and low temperature toughness and ductile fracture arrest performance are achieved and a method of production of the same. For this purpose, the hot rolled steel sheet of the present invention comprises C, Si, Mn, Al, N, Nb, Ti, Ca, V, Mo, Cr, Cu, and Ni in predetermined ranges and a balance of Fe and unavoidable impurities, in which the microstructure is a continuously cooled transformed structure, in which continuously cooled transformed structure, precipitates containing Nb have an average size of 1 to 3 nm and are included dispersed at an average density of 3 to 30×1022/m3, granular bainitic ferrite and/or quasi-polygonal ferrite are included in 50% or more in terms of fraction, furthermore, precipitates containing Ti nitrides are included, and they have an average circle equivalent diameter of 0.

Abstract: The present invention provides high strength thick steel plate superior in crack arrestability high in strength, free of deterioration of HAZ toughness, and free of anisotropy, that steel plate containing, by mass %, C: 0.03 to 0.15%, Si: 0.1 to 0.5%, Mn: 0.5 to 2.0%, P: ?0.02%, S: ?0.01%, Al: 0.001 to 0.1%, Ti: 0.005 to 0.02%, Ni: 0.15 to 2%, and N: 0.001 to 0.008% and having a balance of iron and unavoidable impurities as chemical components, having a microstructure of a ferrite and/or pearlite structure with bainite as a matrix phase, and having an average circle equivalent diameter of crystal grains with a crystal misorientation angle of 15° or more of 15 ?m or less in the regions of 10% of plate thickness from the front and rear surfaces and of 40 ?m or less in the other region including the center part of plate thickness.

Abstract: A high strength galvanized steel sheet has a TS of 590 MPa or more and excellent processability. The component composition contains, by mass %, C: 0.05% to 0.3%, Si: 0.7% to 2.7%, Mn: 0.5% to 2.8%, P: 0.1% or lower, S: 0.01% or lower, Al: 0.1% or lower, and N: 0.008% or lower, and the balance: Fe or inevitable impurities. The microstructure contains, in terms of area ratio, ferrite phases: 30% to 90%, bainite phases: 3% to 30%, and martensite phases: 5% to 40%, in which, among the martensite phases, martensite phases having an aspect ratio of 3 or more are present in a proportion of 30% or more.

Abstract: Provided are the following cold-rolled steel sheets: 1) a cold-rolled steel sheet having higher stretch flangeability than conventional steels; 2) a cold-rolled steel sheet having a higher balance between elongation and stretch flangeability than conventional steels; and 3) a cold-rolled steel sheet heightened in all of yield stress, elongation, and stretch flangeability. The cold-rolled steel sheets are characterized by containing 0.03-0.30 mass % carbon, up to 3.0 mass % (including 0 mass %) silicon, 0.1-5.0 mass % manganese, up to 0.1 mass % phosphorus, less than 0.01 mass % sulfur, up to 0.01 mass % nitrogen, and 0.01-1.00 mass % aluminum and having a structure which comprises tempered martensite in an amount of 50% or more (including 100%) in terms of areal proportion and in which the remainder is ferrite.

Abstract: This invention provides a high-strength hot-rolled steel sheet having strength of at least 980 N/mm2 at a sheet thickness of from about 1.0 to about 6.0 mm and excellent in hole expandability, ductility and ability of phosphate coating, which steel sheet is directed to automotive suspension components that are subjected to pressing. The high-strength hot-rolled steel sheet contains, in terms of a mass %, C: 0.01 to 0.09%, Si: 0.05 to 1.5%, Mn: 0.5 to 3.2%, Al: 0.003 to 1.5%, P: 0.03% or below, S: 0.005% or below, Ti: 0.10 to 0.25%, Nb: 0.01 to 0.05% and the balance consisting of iron and unavoidable impurities; satisfies all of the following formulas <1> to <3>: 0.9?48/12×C/Ti<1.7??<1> 50,227×C?4,479×Mn>?9,860??<2> 811×C+135×Mn+602×Ti+794×Nb>465??<3>, and has strength of at least 980 N/mm2.

Abstract: In order to provide a high tensile strength steel having excellent low temperature toughness and which can withstand large heat input welding, a steel comprises, in mass percent, C: 0.01-0.10%, Si: at most 0.5%, Mn: 0.8-1.8%, P: at most 0.020%, S: at most 0.01%, Cu: 0.8-1.5%, Ni: 0.2-1.5%, Al: 0.001-0.05%, N: 0.0030-0.0080%, O: 0.0005-0.0035%, if necessary at least one of Ti: 0.005-0.03%, Nb: 0.003-0.03%, and Mo: 0.1-0.8%, and a remainder of Fe and impurities, and the N/Al ratio is 0.3-3.0.

Abstract: A high tensile strength galvanized steel sheet with excellent formability and anti-crush properties contains, in terms of % by mass, 0.05 to 0.3% of C, 0.01 to 2.5% of Si, 0.5 to 3.5% of Mn, 0.003 to 0.100% of P, 0.02% or less of S, 0.010 to 1.5% of Al, 0.007% or less of N, in addition, 0.01 to 0.2% in total of at least one element selected from Ti, Nb, and V, the remainder being Fe and unavoidable impurities, the steel sheet having a microstructure composed of, in terms of area fraction, 20 to 87% of ferrite, 3 to 10% in total of martensite and residual austenite, and 10 to 60% of tempered martensite, and a second phase composed of the martensite, residual austenite, and tempered martensite having an average crystal grain diameter of 3 ?m or less.

Abstract: High strength hot rolled steel sheet having at least a 590 N/mm2 tensile strength and excellent in elongation and ability of phosphate coating, that is, high strength hot rolled steel sheet excellent in burring, elongation, and ability of phosphate coating having a tensile strength of 590 N/mm2 or more comprising a steel composition containing, by mass %, C: 0.02 to 0.08%, Si: 0.50% or less, Mn: 0.50 to 3.50%, P: 0.03% or less, S: 0.01% or less, Al: 0.15 to 2.0%, and the balance of iron and unavoidable impurities, satisfying Mn+0.5×Al<4, having a microstructure of the steel sheet having a ratio of ferrite having a grain size of 2 ?m or more of 40% or more.

Abstract: A steel having few alumina clusters prepared by casting liquid steel deoxidized with Al, with the addition of one or more rare-earth metals (REM) selected from the group of Ce, La, Pr and Nd in which: (a) The REM-oxide-content in oxide-based inclusions consisting mainly of alumina and REM-oxides is 0.5 to 15 mass % of said oxide-based inclusions, or (b) The mass ratio of total REM to total oxygen (T.O.), REM/T.O., in liquid steel is not less than 0.05 and not more than 0.5, in addition to (a), or (c) The total REM-content is not less than 0.1 ppm and less than 10 ppm and the dissolved-REM-content is less than 1 ppm.

Abstract: Ultra-high-strength linepipes having excellent low-temperature toughness manufactured by welding together the edges of steel plates comprising C of 0.03 to 0.07 mass %, Si of not more than 0.6 mass %, Mn of 1.5 to 2.5 mass %, P of not more than 0.015 mass %, S of not more than 0.003 mass %, Ni of 0.1 to 1.5 mass %, Mo of 0.15 to 0.60 mass %, Nb of 0.01 to 0.10 mass %, Ti of 0.005 to 0.030 mass %, Al of not more than 0.06 mass %, one or more of required amounts of B, N, V, Cu, Cr, Ca, REM (rare-earth metals) and Mg, with the remainder consisting of iron and unavoidable impurities and having a (Hv-ave)/(Hv-M) ratio between 0.8 and 0.9 at 2.5?P?4.0, wherein Hv-ave is the average Vickers hardness in the direction of the thickness of the base metal and Hv-M is the martensite hardness depending on C-content (Hv-M=270+1300C) and a tensile strength TS-C between 900 MPa and 1100 MPa; P=2.7C+0.4Si+Mn+0.8Cr+0.45(Ni+Cu)+(1+?)Mo?1+? (?=1 when B?3 ppm and ?=0 when B<3 ppm).

Abstract: The ultrahigh-strength steel sheet contains, in mass %, C: 0.05-0.25%, Si: 1.00-2.5%, Mn: 2.0-4.0%, P: 0.1% or below (not inclusive of 0%), S: 0.05% or below (not inclusive of 0%), Al: 0.01-0.15%, Ti: 0.003-0.10%, N: 0.01% or below (not inclusive of 0%), the balance comprising iron with inevitable impurities, and is a composite structure steel sheet comprising 10-50 area % ferrite and 50 area % or above martensite, in which the average circle-equivalent grain diameter of ferrite grains is 2.0 ?m or below, the average aspect ratio of ferrite grains is 2.0 or below, and the tensile strength is 1,100 MPa or above. Accordingly, the ultrahigh-strength steel sheet is excellent in hydrogen embrittlement resistance and workability.

Abstract: The present invention provides high temperature strength and fire-resistant steel superior in weld joint reheat embrittlement resistance and toughness which is produced using steel of a room temperature strength of the 400 to 600N/mm2 class containing as main ingredients C: 0.010% to less than 0.05%, Si: 0.01 to 0.50%, Mn: 0.80 to 2.00%, Cr: 0.50% to less than 2.00%, V: 0.03 to 0.30%, Nb: 0.01 to 0.10%, N: 0.001 to 0.010%, and Al: 0.005 to 0.10%, limiting the contents of Ni, Cu, Mo, and B, and satisfying the relationship of 4Cr[%]-5Mo[%]-10Ni[%]-2Cu[%]-Mn[%]>0.

Abstract: This hot rolled steel contains, in terms of mass %, C: 0.01 to 0.1%, Si: 0.01 to 0.1%, Mn: 0.1 to 3%, P: not more than 0.1%, S: not more than 0.03%, Al: 0.001 to 1%, N: not more than 0.01%, Nb: 0.005 to 0.08%, and Ti: 0.001 to 0.2%, with a remainder being iron and unavoidable impurities, wherein a formula: [Nb]×[C]?4.34×10?3 is satisfied, a grain boundary density of solid solution C is not less than 1 atom/nm2 and not more than 4.5 atoms/nm2, and a grain size of cementite grains precipitated at grain boundaries within the steel sheet is not more than 1 um. This method for manufacturing a hot rolled steel sheet includes: heating a steel slab having the same composition as the above hot rolled steel sheet at a temperature that is not less than a temperature of SRTmin (° C.) and not more than 1,170° C.; performing rough rolling at a finishing temperature of not less than 1,080° C. and not more than 1,150° C.

Abstract: The present invention provides high strength hot rolled steel plate for line-pipes superior in low temperature toughness, and a method of production of the same, containing, by mass %, C: 0.01 to 0.1%, Si: 0.05 to 0.5%, Mn: 1 to 2%, P: ?0.03%, S: ?0.005%, O: ?0.003%, Al: 0.005 to 0.05%, N: 0.0015 to 0.006%, Nb: 0.005 to 0.08%, and Ti: 0.005 to 0.02%, where N?14/48×Ti>0% and Nb—93/14×(N?14/48×Ti)>0.005%, and a balance of Fe and unavoidable impurities, said steel plate characterized in that its microstructure is a continuously cooled transformed structure, a reflected X-ray intensity ratio {211}/{111} of the {211} plane and {111} plane parallel to the plate surface in the texture at the center of plate thickness is 1.1 or more, and an in-grain precipitate density of the precipitates of Nb and/or Ti carbonitrides is 1017 to 1018/cm3.

Abstract: The present invention provides a fire resistant steel material excellent in high temperature strength, toughness, and reheating embrittlement resistance containing, by mass %, C: 0.001% to 0.030%, Si: 0.05% to 0.50%, Mn: 0.4% to 2.0%, Nb: 0.03% to 0.50%, Ti: 0.005% to less than 0.040%, N: 0.0001% to less than 0.0050%, and Al: 0.005% to 0.030%, limiting P: 0.03% or, less and S: 0.02% or less, satisfying C—Nb/7.74?0.005 and 2?Ti/N?12, and having a balance of Fe and unavoidable impurities and, further, a process for production of a fire resistant material comprising heating a steel slab comprised of this chemical composition to 1100 to 1350° C. and hot rolling it by a cumulative reduction rate at 1000° C. or less of 30% or more.

Abstract: A steel pipe with excellent expandability, comprises, by mass %, C: 0.1 to 0.45%, Si: 0.3 to 3.5%, Mn: 0.5 to 5%, P: less than or equal to 0.03%, S: less than or equal to 0.01%, soluble Al: 0.01 to 0.8% (more than or equal to 0.1% in case Si content is less than 1.5%), N: less than or equal to 0.05%, O: less than or equal to 0.01%, and balance being Fe and impurities, having a mixed microstructure comprising ferrite and one or more selected from fine pearlite, bainite and martensite, and has a tensile strength of more than or equal to 600 MPa and a uniform elongation satisfying the following formula u-el?28?0.0075 TS, wherein u-el is uniform elongation (%) and TS is tensile strength (MPa).

Abstract: The present invention provides hot rolled steel plate for spiral pipe superior in low temperature toughness, thick in gauge, for example, having a plate thickness of 14 mm or more, and having a high strength of the API-X65 standard or more spiral pipe and a method of production of the same, that is, steel plate containing, by mass %, C: 0.01 to 0.1%, Si: 0.05 to 0.5%, Mn: 1 to 2%, P?0.03%, S?0.005%, O?0.003%, Al: 0.005 to 0.05%, N: 0.0015 to 0.006%, Nb: 0.005 to 0.08%, Ti: 0.005 to 0.02%, N?14/48×Ti>0%, Nb?93/14×(N?14/48×Ti>0.005%, Mo: 0.01% to less than 0.1%, Cr: 0.01 to 0.3%, and Cu: 0.01 to 0.3%, and having a balance of Fe and unavoidable impurities, characterized in that an elongation rate of a microstructure unit in a cross-section in the pipe circumferential direction after pipemaking is 2 or less.

Abstract: An exemplary hot rolled steel sheet can included, in terms of percent by mass, C of 0.01 to 0.2%; Si of 0.01 to 2%; Mn of 0.1 to 2%; P of ?0.1%; S of ?0.03%; Al of 0.001 to 0.1%; N of ? 0.01%; and as a remainder, Fe and unavoidable impurities. For example, a microstructure can be substantially a homogeneous continuous-cooled microstructure, and an average grain size of the microstructure may be more than 8 ?m and 30 ?m or less. An exemplary method for manufacturing a hot rolled steel sheet can include subjecting a slab having the above composition to a rough rolling so as to obtain a rough rolled bar, subjecting the rough rolled bar to a finish rolling so as to obtain a rolled steel under conditions in which a finishing temperature is (Ar3 transformation point +50° C.) or more; and starting cooling the rolled steel after 0.5 seconds or more pass from the end of the finish rolling at a temperature of the Ar3 transformation point or more.

Abstract: According to an exemplary embodiment of the present invention, a bake-hardening hot-rolled steel sheet with excellent workability can be provided. The exemplary steel sheet can contain, in terms of mass %, C of about 0.01 to 0.2%, Si of about 0.01 to 2%, Mn of about 0.1 to 2%, P of about 0.1% or less, S of about 0.03% or less, Al of about 0.001 to 0.1%, N of about 0.01% or less, Nb of about 0.005 to 0.05%, and as the remainder, Fe and unavoidable impurities. A microstructure of the steel sheet can be a polygonal ferrite and/or a continuous-cooled microstructure having an average particle diameter of about 2 ?m to 8 ?m, and the grain boundary abundance ratio of solute C and/or solute N may be about 0.28 or lower. An exemplary embodiment of the present invention can also be directed to a method for manufacturing a hot-rolled steel sheet. In this exemplary method, a slab containing aforementioned components can be heated to at least a temperature satisfying the equation of SRT (° C.)=6670/{2.

Abstract: High strength, hot rolled steel plate providing high level of bore expandability and high level of ductility. Also, method of manufacturing same. In first aspect, steel plate comprises steel having, by mass, C:0.01-0.15%; Si:0.30-2.00%; Mn:0.50-3.00%; P?0.03%; S?0.005%; Ti:0.01-0.50%; and/or Ni:0.01-0.05%, with balance Fe and unavoidable impurities. In this steel, ?80% of all grains have ratio of minor axis to major axis of ?0.1. This steel plate has steel structure comprising ?80% ferrite and balance bainite. In second aspect, steel plate has above composition, and ferrite-bainite duplex steel structure in which proportion of ferrite having grain diameter ?2 ?m is ?80%. In third aspect, steel plate has above composition. wherein contents of C, Si, Mn, Ti, and Nb satisfy requirement represented by formula: 115 ?(917?480[C %]+100[Si %]?100[Mn %])?(790×([Ti %]+[Nb %]/2)0.05)?235. This steel plate has steel structure comprising ?80% ferrite and balance bainite.

Abstract: High cleanliness spring steel useful in manufacturing a spring with SiO2-based inclusions being extremely controlled and excellent in fatigue properties is provided. High cleanliness spring steel which is steel containing; C: 1.2% (means mass %, hereafter the same with respect to the component) or below (not inclusive of 0%), Si: 1.2-4%, Mn: 0.1-2.0%, Al: 0.01% or below (not inclusive of 0%), and the balance comprising iron with inevitable impurities, wherein; the total of oxide-based inclusions of 4 or above of L (the large diameter of an inclusion)/D (the short diameter of an inclusion) and 25 ?m or above of D and oxide-based inclusions of less than 4 L/D and 25 ?m or above of L, in the oxide-based inclusions of 25 mass % or above of oxygen concentration and 70% (means mass %, hereafter the same with respect to inclusions) or above of SiO2 content when Al2O3+MgO+CaO+SiO2+MnO=100% is presumed, out of inclusions in the steel, is 20 nos./500 g or below.

Abstract: The present invention relates to novel non-ferromagnetic amorphous steel alloys represented by the general formula: Fe—Mn-(Q)-B-M, wherein Q represents one or more elements selected from the group consisting of Sc, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and M represents one or more elements selected from the group consisting of Cr, Co, Mo, C and Si. Typically the atomic percentage of the Q constituent is 10 or less. FIG. 2B represents a differential thermal analysis plot for several exemplary alloys according to the invention.

Abstract: The present invention provides a high-strength thin steel sheet drawable and excellent in a shape fixation property and a method of producing the same. For the steel sheet, on a plane at the center of the thickness of a steel sheet, the average ratio of the X-ray strength in the orientation component group of {100}<011> to {223}<110> to random X-ray diffraction strength is 2 or more and the average ratio of the X-ray strength in three orientation components of {554}<225>, {111}<112> and {111}<110> to random X-ray diffraction strength is 4 or less. The arithmetic average of the roughness Ra of at least one of the surfaces is 1 to 3.5 ?m; the surfaces of the steel sheet are covered with a composition having a lubricating effect; and the friction coefficient of the steel sheet surfaces at 0 to 200° C. is 0.05 to 0.2.

Abstract: This disclosure proposes a high-strength hot rolled steel sheet having excellent anti-die-galling property and anti-fatigue property, in which the steel sheet has a composition including C: not less than 0.02 mass % but not more than 0.2 mass %, Si: not less than 0.2 mass % but not more than 1.2 mass %, Mn: not less than 1.0 mass % but not more than 3.0 mass %, Mo: not less than 0.1 mass % but not more than 1.0 mass %, Al: not less than 0.01 mass % but not more than 0.1 mass %, P: not more than 0.03 mass % S: not more than 0.01 mass % and the remainder being substantially Fe and inevitable impurities, and has a steel microstructure containing not less than 55 vol % of ferrite and not less than 10 vol % but not more than 40 vol % of martensite provided that a total of both is not less than 95 vol %, and a ratio ds/dc of an average crystal grain size ds of the ferrite in a surface layer portion of the steel sheet to an average crystal grain size dc of the ferrite in a center portion of the steel sheet is 0.

Abstract: A high-strength hot-rolled steel sheet excellent in shape fixability having ferrite or bainite as the phase of the largest volume percentage, satisfying all of the following at least at ½ sheet thickness: a mean value of X-ray random intensity ratio in the orientation component group of {100}<011> to {223}<110> to X-ray random diffraction intensity ratio of at least 2.5; a mean value of X-ray random intensity ratio in the three crystal orientation components of {554}<225>, {111}<112>, and {111}<110> to X-ray random diffraction intensity ratio of 3.5 or less; an X-ray intensity ratio to X-ray random diffraction intensity ratio at {100}<011> of at least the X-ray random intensity to X-ray random diffraction intensity ratio at {211}<011>; and an X-ray random intensity ratio to X-ray random intensity ratio diffraction intensity ratio at {100}<011> of at least 2.

Abstract: The present invention provides high strength steel plate and high strength welded pipe excellent in ductile fracture characteristic and methods of production of the same, that is, high strength steel plate excellent in ductile fracture characteristic, and high strength welded pipe using that steel plate as a base material, having a tensile strength corresponding to the X100 class of the API standard, containing, by mass %, C: 0.01 to 0.5%, Si: 0.01 to 3%, Mn: 0.1 to 5%, P: 0.03% or less, and S: 0.03% or less and a balance of Fe and unavoidable impurities, having a microstructure comprised of, by area ratio, 1 to 60% of ferrite and the balance of bainite and martensite, having a maximum value of the {100} accumulation degree of the cross-section rotated 20 to 50° from the plate thickness cross-section about the rolling direction as an axis of 3 or less, and having plate thickness parallel cracks measured by ultrasonic flaw detection of less than 1 mm.

Abstract: Accordingly to an exemplary embodiment of the present invention, a high tensile strength, refractory steel can be provided which comprises, in mass %, approximately C: 0.04 to 0.14%, Si: 0.50% or less, Mn: 0.50 to 2.00%, P: 0.020% or less, S: 0.010% or less, Nb: 0.01 to 0.05%, Mo: 0.30% or more and less than 0.70%, Al: 0.060% or less, N: 0.0010 to 0.0060%, and the balance consisting of iron and unavoidable impurities. For example, a weld crack sensitive composition PCM can be defined by the following equation may be about 0.25% or less: PCM=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B. An area fraction of polygonal ferrite or pseudo polygonal ferrite in a ¼ thick position in the plate thickness direction of the steel plate of the final rolling product is about 10% or less.

Abstract: The invention relates to a steel part coated with a compound consisting, over more than 90% of its thickness, of at least one Fe/Zn-based phase, the iron weight content of which is equal to 65% or higher and the Fe/Zn ratio of which is between 1.9 and 4, said compound being formed by at least one heat treatment for alloying between said steel and a precoat, said precoat consisting of a zinc alloy comprising, the contents being expressed by weight, between 0.5 and 2.5% aluminum and, optionally, one or more elements chosen from: Pb?0.003%; Sb?0.003%; Bi?0.003%; 0.002%?Si?0.070%; La<0.05%; Ce<0.05%, the balance consisting of zinc and inevitable impurities.

Abstract: A hot-rolled wire rod excelling in wire drawability is provided, in which breakage can be suppressed even in heavy work from a large diameter. A hot-rolled wire rod contains C: 0.35 to 0.65% (percent by mass, hereinafter expressed as well), Si: 1.4 to 3.0%, Mn: 0.10 to 1.0%, Cr: 0.1 to 2.0%, P: 0.025% or less (exclusive of 0%), S: 0.025% or less (exclusive of 0%), N: 0.006% or less (exclusive of 0%), Al: 0.1% or less (exclusive of 0%), and O: 0.0030% or less (exclusive of 0%), with the remnant consisting of Fe and inevitable impurities; wherein the content of hydrogen in steel is 2.50 ppm (ppm by mass, hereinafter expressed as well) or less, and hardness (HV) is 460×C00.1 or less (C0 indicates the content of C (percent by mass) in a position of depth of D/4 (D: diameter of the wire rod)).

Abstract: A graphite-containing, heat-resistant cast iron for exhaust equipment members used at temperatures exceeding 800° C., comprising 3.5-5.6% of Si and 1.2-15% of W on a weight basis, and having intermediate layers, in which W and Si are concentrated, in the boundaries of graphite particles and a matrix. An exhaust equipment member formed by this heat-resistant cast iron has an AC transformation point is 840° C. or higher when measured from 30° C. at a temperature-elevating speed of 3° C./minute, and a thermal cracking life of 780 cycles or more in a thermal fatigue test, in which heating and cooling are conducted under the conditions of an upper-limit temperature of 840° C., a temperature amplitude of 690° C. and a constraint ratio of 0.25.

Abstract: The present invention provides a method of production of oil country tubular goods having a small drop in collapse pressure after expansion and having a collapse pressure recovering by low temperature ageing at about 100° C. and oil country tubular goods obtained by this method of production. This method of production comprises hot rolling a steel slab having amounts of addition of C, Mn, P, S, Nb, Ti, Al, and N in specific ranges and having a balance of iron and unavoidable impurities and shaping the steel strip coiled at a temperature of not more than 300° C. as it is into a tube. Alternatively, it comprises heating steel pipe having amounts of addition of C, Mn, P, S, Nb, Ti, Al, and N in specific ranges and having a balance of iron and unavoidable impurities to a temperature of the Ac3 [° C.] to 1150° C., then cooling it in a range of 400 to 800° C. at a rate of 5 to 50° C./second.

Abstract: The present invention provides a method for manufacturing high tensile strength steel plate having 570 MPa (N/mm2) or larger tensile strength and having also extremely superior balance of strength and toughness both before PWHT and after PWHT to that of the conventional steel plates, by specifically specifying the temperature-rising rate at the plate thickness center portion of a quenched and tempered material during tempering, and to be concrete, the method has the steps of: casting a steel consisting essentially of 0.02 to 0.18% C, 0.05 to 0.5% Si, 0.5 to 2.0% Mn, 0.005 to 0.1% Al, 0.0005 to 0.008% N, 0.03% or less P, 0.

Abstract: A lead-free steel for machine structural use with excellent machinability and low strength an isotropy, which does not contain Pb and is equal to or higher than a conventional D Pb-containing free cutting steel in properties, is provided. This steel includes, on the weight basis, C: 0.10 to 0.65%; Si: 0.03 to 1.00%; Mn: 0.30 to 2.50%; S: 0.03 to 0.35%; Cr: 0.1 to 2.0%; Al: less than 0.010%; Ca: 0.0005 to 0.020%; Mg: 0.0003 to 0.020%; 0: less than 20 ppm; and the balance being Fe and inevitable impurities.

Abstract: The present invention provide a TRIP-type composite structure steel plate of the TPF steel type in which elongation and stretch flange formability at room temperature are improved by controlling the morphology of the second-phase structure. In a composite structure sheet steel comprising 0.02 to 0.12% C, 0.5 to 2.0% Si+Al and 1.0 to 2.0% Mn, with the remainder being Fe and unavoidable impurities, and comprising 80% or more polygonal ferrite (steel structure space factor) and 1 to 7% retained austenite, with the remainder being bainite and/or martensite, wherein the elongation and stretch flange formability of the composite sheet steel are improved by reducing the number of bulky, massive second phases with an aspect ratio of 1:3 or less and a mean grain size of 0.5 ?m or more in the second phase of this composite structure, which comprises retained austenite and martensite.

Abstract: A galvannealed steel sheet contains, by % by mass, about 0.05 to about 0.25% of C, about 2.0% or less of Si, about 1 to about 3% of Mn, about 0.1% or less of P, about 0.01% or less of S, about 0.3 to about 2% of Al, less than about 0.005% of N, about 1% or less of Cr, about 1% or less of V, about 1% or less of Mo, less than about 0.005% of Ti, and less than about 0.005% of Nb, and satisfies the relations, Si +Al >0.6% and Cr +V +Mo =0.1 to 2%, the balance being Fe and inevitable impurities.

Abstract: According to a low alloy steel of the present invention, compositional elements thereof are limited, and a metal structure thereof comprises bainite or martensite. Further, a proper amounts of Nd inclusions are formed by appropriately selecting timings of deoxidation and Nd addition in melting a steel. Consequently, compatibility between high-temperature creep strength and long-term creep ductility, which is hardly established in conventional steels, can be achieved even in hostile conditions. Accordingly, the low alloy steel of the present invention can be widely applied as the material for the heat-resistant structural member used for a long time under the high-temperature and high-pressure conditions such as power plant boilers, turbines, and nuclear power plants.