Abstract: The present invention has as its technical problem the provision of a part excellent in contact fatigue strength or wear resistance in addition to the rotating bending fatigue strength. In the present invention, the contents of the constituents of the steel, in particular C, Mn, Cr, V, and Mo, are adjusted in accordance with the targeted properties and nitrided parts are prepared while controlling the nitriding potential.

Abstract: A core side of a plastic injection molding tooling set for use in conjunction with a cavity side of the tooling set is disclosed. The core side may have the following composition in percent by weight: 0.25-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.80% silicon, 1.40-2.00% chromium, 0.10-0.55% molybdenum, a maximum of 0.040% aluminum, a maximum of 0.025% phosphorous, a maximum of 0.20% sulfur, a balance of iron, and incidental impurities.

Abstract: A method in accordance with the present application includes sending a raw tube from a drum to an unwinding side capstan while the raw tube is rotated around a central axis perpendicular to a winding shaft of the drum by rotating the drum and the unwinding side capstan about the central axis concurrently with unwinding of the raw tube from the drum holding the raw tube, on an inner surface of which multiple straight grooves along a longitudinal direction of the raw tube are formed with an interval in a circumferential direction, in a coil shape, to wind the raw tube around the unwinding side capstan, and drawing in which the unwound raw tube is drawn while the diameter of the raw tube is reduced, and then the raw tube is wound around the drawing side capstan to twist the raw tube and obtain an inner spiral grooved tube.

Abstract: A lower carbon steel alloy with specific substitutional alloying additions. The alloy is useful in the production of ASTM A516 grade pressure vessel steel plates with excellent HIC resistance. The material has a ferrite-pearlite microstructure, in normalized and stress relieved condition, appropriate for resisting hydrogen induced cracking, with isolated ferrite and pearlite constituents and no continuous pearlite bands. The material exhibits significant low temperature toughness.

Abstract: A steel sheet includes a predetermined chemical composition, and includes a steel structure represented by, in a volume fraction, tempered martensite and bainite: 70% or more and less than 92% in total, retained austenite: 8% or more and less than 30%, ferrite: less than 10%, fresh martensite: less than 10%, and pearlite: less than 10%. A number density of iron-base carbides in tempered martensite and lower bainite is 1.0×106 (pieces/mm2) or more, and an effective crystal grain diameter of tempered martensite and bainite is 5 ?m or less.

Abstract: An ultra-heavy steel plate with low cracking sensitivity and low yield ratio, the mass percentages of chemical components of the steel plate are C 0.05-0.09; Si 0.2-0.4; Mn 1.3-1.6; Al 0.02-0.04; Nb 0.03-0.08; V 0.03-0.08; Cr 0.1-0.5; Ni 0.1-0.5; Mo 0.1-0.3; Cu 0.2-0.5; Ti 0.01-0.02; P?0.015; S?0.003; N?0.007, the balance being Fe and inevitable impurities; the carbon equivalent is ?0.43, the cold cracking sensitivity coefficient Pcm is ?0.20. A low cracking sensitivity and low yield ratio steel plate with a thickness of 40-70 mm is manufactured by the process steps of KR molten iron pretreatment-converter smelting-LF refining-RH vacuum degassing-continuous casting-lid-covering slow cooling for the continuous casting slabs-casting slabs heating-controlled rolling-controlled cooling-hot straightening-air cooling and so on.

Abstract: A steel material comprising, by mass%, C: greater than 0.05% to 0.2%, Mn: 1% to 3%, Si: greater than 0.5% to 1.8%, Al: 0.01% to 0.5%, N: 0.001% to 0.015%, Ti or a sum of V and Ti: greater than 0.1% to 0.25%, Ti: 0.001% or more, Cr: 0% to 0.25%, Mo: 0% to 0.35%, the balance: Fe and impurities, comprising a multi-phase structure having a ferrite main phase and a second phase containing one or more of bainite, martensite and austenite, wherein an average nanohardness of the second phase is less than 6.0 GPa, an average grain diameter of all crystal grains in the main phase and the second phase is 3 ?m or less, and a proportion of a length of small-angle grain boundaries where the misorientation is 2° to less than 15° in a length of all grain boundaries is 15% or more.

Abstract: A high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa with its chemical components, in weight percentages, being C 0.02-0.05%, Si?0.5%, Mn 1.5-2.5%, P?0.015%, S?0.005%, Al 0.02-0.10%, N?0.006%, Nb 0.01-0.05%, Ti 0.01-0.03%, 0.03%?Nb+Ti?0.06%, Cr 0.1%-0.5%, Mo 0.1-0.5%, B 0.0005-0.0025%, and the balance of Fe and unavoidable impurities, and a preparation method thereof. The present invention acquires, via direct quenching, an ultra-low carbon martensite structure with a yield strength of 800 Mpa and an impact energy of more than 100J under a temperature of ?80° C.

Abstract: The present invention relates to a part obtained from an age hardening type bainitic microalloyed steel, a process for producing the part, and the age hardening type bainitic microalloyed steel. In particular, the present invention relates to a part which has been controlled so as to have higher values of strength than conventional parts, a process for producing the part, and the age hardening type bainitic microalloyed steel.

Abstract: A piercing plug includes a plug main body, and a sprayed coating which is formed on a surface of the plug main body and includes iron and iron oxide. A chemical composition of the sprayed coating includes, in addition to the iron and the iron oxide, by mass %, C: 0.015% to 0.6%, Si: 0.05% to 0.5%, Mn: 0.1% to 1.0%, and Cu: 0 to 0.3%.

Abstract: The invention concerns a component made of a steel alloy comprising iron and as alloying element copper, in particular consisting of (in wt % in relation to the total alloy, wherein the sum of all constituents equals 100 wt %) iron?96, carbon 0.04 to 0.12, copper 0.5 to 2.0, manganese+silicon+chromium+nickel 0.5 to 2.5, titanium 0 to 0.1, boron 0 to 0.005, and typical unavoidable impurities. In the production of semi-finished goods and of components, a combination of cold working and annealing treatment below the recrystallization temperature is used in order to thus obtain advantageous properties with regard to strength and ductility.

Abstract: A mold steel that is a steel having a composition containing, in terms of mass %: 0.07 to 0.15% of C; more than 0 and less than 0.8% of Si; more than 0 and not more than 1.0% of Mn; less than 0.05% of P; less than 0.02% of S; more than 0 and not more than 0.5% of Ni; more than 0 and less than 0.8% of Mo and W, either alone or as a complex (Mo+½W); more than 0 and less than 0.15% of V; and 0.25 to 1.5% of Cu, with the balance consisting of Fe, Cr and unavoidable impurities, wherein the content of Cr is more than 4.9% and not more than 5.3% and the hardness of the mold steel is 30 to 42 HRC.

Abstract: Disclosed herein are embodiments of a seamless quenched and tempered steel pipe which can have a wall thickness WT higher than or equal to 6 mm and lower than or equal to 35 mm. Some embodiments of the steel pipe can have a chemical composition comprising C, Mn, Si, Cr, Ni, Mo, Al, N, Ca, Nb, Ti, V, Zr, and Ta based on the composition weight, the remaining being iron and impurities. In some embodiments, wherein (V+Nb) content is lower than 0.07 wt %; defining a first parameter P1=(60×C)+Cr+[5×e(35×Mo/WT)]+50×(V+Nb), the chemical composition satisfies a first condition P1?14.5.

Abstract: Disclosed herein are embodiments of a seamless quenched and tempered steel pipe having a wall thickness (WT) higher than or equal to 35 mm and lower than or equal to 80 mm. Embodiments of the steel pipe can comprise C, Mn, Cr, Ni, Mo, Al, Ca, N, Nb, Ti, Zr, and Ta. Further, for some embodiments of the steel pipe wherein, defining a first parameter P1=50×C+Cr+10×Mo+70×V, the chemical composition can satisfy a first condition P1?8.0.

Abstract: A high-tensile-strength hot-rolled steel sheet is provided having a composition which contains 0.02 to 0.08% C, 0.01 to 0.10% Nb, 0.001 to 0.05% Ti and Fe and unavoidable impurities as a balance, wherein the steel sheet contains C, Ti and Nb in such a manner that (Ti+(Nb/2))/C<4 is satisfied, and the steel sheet has a structure where a primary phase of the structure at a position 1 mm away from a surface in a sheet thickness direction is one selected from a group consisting of a ferrite phase, tempered martensite and a mixture structure of a ferrite phase and tempered martensite, a primary phase of the structure at a sheet thickness center position is formed of a ferrite phase, and a difference ?V between a structural fraction (volume %) of a secondary phase at the position 1 mm away from the surface in the sheet thickness direction and a structural fraction (volume %) of a secondary phase at the sheet thickness center position is 2% or less.

Abstract: A process for producing high strength steel is provided. The process includes providing a steel slab having a chemical composition in weight percent within a range of 0.025-0.07 C, 1.20-1.70 Mn, 0.050-0.085 Nb, 0.022 max Ti, 0.065 max N, 0.0040 max S, 0.10-0.45 Si, 0.070 max P, with the balance being Fe and incidental impurities. The steel slab is soaked within a temperature range of 1150-1230° C., hot rolled using a roughing treatment in order to produce a transfer bar and further hot rolled using a finishing treatment in order to produce hot rolled strip. The hot rolled strip is cooled using a cooling rate between 10-100° C./second (sec) and coiled within a temperature range of 580-400° C. Finally, the coiled hot rolled strip has a yield strength of at least 80 ksi and a DWTT transition temperature equal or less than ?20° C.

Abstract: A steel for high-strength spring has an Ac3 transformation temperature as an indicator of the decarburization performance, which is calculated by Equation (1) below, is from 859 to 885° C., a maximum hardened diameter DI as an indicator of the hardening performance, which is calculated by Equation (2) below, is from 70 to 238 mm, and a temper hardness HRC as an indicator of the spring performance, which is calculated by Equation (3) below, is from 50 to 55. Ac3=910?203×?{square root over (C)}?15.2Ni+44.7Si+104V+31.5Mo+13.1W??(1) DI=DO×fSi×fMn×fP×fS×fCu×fNi×fCr??(2) HRC=38.99+17.48C+2.55Si?2.28Ni+2.37Cr+8.04Ti??(3) wherein, D0=8.65×?{square root over (C)}, fSi=1+0.64×% Si, fMn=1+4.10×% Mn, fP=1+2.83×% P, fS=1?0.62×% S, fCu=1+0.27×% Cu, fNi=1+0.52×% Ni, and fCr=1+2.33×% Cr.

Abstract: In a steel sheet having a specific chemical composition and having a microstructure including ferrite that is a soft first phase by 20-50% in terms of the area ratio, the remainder being tempered martensite and/or tempered bainite that is a hard second phase, the microstructure of steel of a surface layer section of the steel sheet from the surface to the depth of 100 ?m and a center section of t/4-3t/4 (t is the sheet thickness) is controlled.

Abstract: This bearing steel material satisfies a predetermined elemental composition, and is characterized by having, in the region (boundary region) from the boundary surface of spheroidal cementite to a position at 20 nm away in a base material, no greater than 0.6% (excluding 0%) of Si (boundary Si), no greater than 0.10% (excluding 0%) of Ni (boundary Ni), no greater than 0.10% (excluding 0%) of Cu (boundary Cu), no greater than 0.03% (including 0%) of Mo (boundary Mo), no greater than 0.10% (excluding 0%) of Mn (boundary Mn), and no greater than 0.9% (excluding 0%) of Cr (boundary Cr), and the circularity coefficient of the spheroidized cementite being at least 0.80. The bearing steel material exhibits favorable cold-workability during the production of a bearing component by means of cold working.

Abstract: In a high strength cold-rolled steel plate having a specific chemical composition, a soft first phase (ferrite) has an area ratio of 20-50%, the remainder being a hard second phase (tempered martensite and/or tempered bainite), among all the ferrite grains, ferrite grains that have an average grain diameter of 10-25 ?m account for a total area ratio of 80% or more, the number of the cementite grains that have an equivalent circle diameter of 0.3 ?m or more is more than 0.15 piece and 1.0 piece or less per 1 ?m2 of ferrite, and the tensile strength is 980 MPa or more.

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 steel wire for spring is provided which exhibits high strength even without adding a large amount of alloy elements, and is for obtaining a cold winding spring having excellent coiling performance and improved hydrogen embrittlement resistance. The steel wire for spring is characterized in that C: 0.40-0.65% (mass %), Si: 1.0-3.0%, Mn: 0.6-2.0%, P: 0.015% or less (exclusive of 0%), S: 0.015% or less (exclusive of 0%), and Al: 0.015 percent by mass or less (excluding 0%) of S, and Al: 0.001-0.10% are satisfied, with the remainder consisting of iron and inevitable impurities, tempered martensite: 70 area % or more and retained austenite: 6-15 area % with respect to the total microstructure, the prior austenite grain size number obtained by a method stipulated in JIS G 0551 is No. 10.0 or more, and the tensile strength is 1,900 MPa or more.

Abstract: Disclosed is a spring steel wire rod that comprises C in a range of 0.35 to 0.65% (mass %, the same applies to respective elements described hereinafter), Si in a range of 1.4 to 2.2%, Mn in a range of 0.10 to 1.0%, Cr in a range of 0.1 to 2.0%, P not more than 0.025% (0% excluded), and S not more than 0.025% (0% excluded), balance comprising iron, and unavoidable impurities, wherein an average grain size Dc of a central part of the steel wire rod is not more than 80 ?m while an average grain size Ds of a surface layer part of the steel wire rod is not less than 3.0 ?m.

Abstract: A steel plate has a chemical composition containing, by mass %, C: 0.03% or more and 0.08% or less, Si: 0.01% or more and 1.0% or less, Mn: 1.2% or more and 3.0% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.08% or less, Nb: 0.005% or more and 0.07% or less, Ti: 0.005% or more and 0.025% or less, N: 0.010% or less, O: 0.005% or less and the balance being Fe and inevitable impurities, a structure being a dual-phase structure consisting of a bainite phase and island martensite, wherein the area fraction of the island martensite is 3% to 15%, the equivalent circle diameter of the island martensite is 3.0 ?m or less, and the remainder of the structure is a bainite phase.

Abstract: There is provided a seamless steel pipe having high strength and high toughness even if having a thick wall. A seamless steel pipe according to the present embodiment consists of: in mass %, C: 0.03 to 0.08%, Si: not more than 0.25%, Mn: 0.3 to 2.0%, P: not more than 0.05%, S: not more than 0.005%, Al: 0.001 to 0.10%, Cr: 0.02 to 1.0%, Ni: 0.02 to 1.0%, Mo: 0.02 to 0.8%, N: 0.002 to 0.008%, Ca: 0.0005 to 0.005%, and Nb: 0.01 to 0.1%, the balance being Fe and impurities, and has a wall thickness of not less than 50 mm.

Abstract: A high-strength cold-rolled steel sheet has a specific chemical composition and has a steel microstructure meeting conditions: a total content of bainitic ferrite (BF) and tempered martensite (TM) is 65% (in area percent, hereinafter the same for steel microstructure) or more; a fresh martensite (M) content is 3% to 18%; a retained austenite content is 5% or more; and a polygonal ferrite (F) content is 5% or less. The steel sheet has a specific average KAM<1.00° of 0.50° or more and has a tensile strength of 980 MPa or more. The high-strength cold-rolled steel sheet excels in formability and shape fixability.

Abstract: The present invention provides a high tensile strength steel plate having a chemical composition containing, in percent by mass, 0.03% to 0.12% of C, 0.01% to 0.30% of Si, 0.5% to 1.95% of Mn, 0.008% or less of P, 0.005% or less of S, 0.015% to 0.06% of Al, 0.011% to 0.05% of Nb, 0.005% to 0.02% of Ti, 0.001% to 0.006% of N, 0.0005% to 0.003% of Ca, optionally, one or two or more of Cr, Mo, V, Cu, and Ni, in which Ceq is 0.44 or less, Ti/N is 1.5 to 3.5, and parameter formulas composed of specific elements for controlling the sulfide morphology and the degree of center segregation in the steel are satisfied, and the balance being Fe and incidental impurities, in which the hardness of the center segregation area of the steel sheet is further specified.

Abstract: A high-strength welded steel pipe is obtained by welding a seam weld portion of a steel plate that are formed in a pipe shape. In the high-strength welded steel pipe, a base metal of the steel plate includes, by mass %, C: 0.010% to 0.080%, Si: 0.01% to 0.50%, Mn: 0.50% to 2.00%, S: 0.0001% to 0.0050%, Ti: 0.003% to 0.030%, Mo: 0.05% to 1.00%, B: 0.0003% to 0.0100%, O: 0.0001% to 0.0080%, N: 0.006% to 0.0118%, P: limited to 0.050% or less, Al: limited to 0.008% or less, and the balance of Fe and inevitable impurities, Ceq is 0.30 to 0.53, Pcm is 0.10 to 0.20, [N]?[Ti]/3.4 is less than 0.003, the average grain size of the prior ? grains in heat affected zones in the steel plate is 250 ?m or less, and the prior ? grains include bainite and intragranular bainite.

Abstract: A carburized component with improved fatigue strength has a base steel containing, by mass %, C: 0.15-0.25%, Si: 0.03-0.50%, Mn: more than 0.60% and not more than 1.5%, P?0.015%, S: 0.006-0.030%, Cr: 0.05-2.0%, Al?0.10%, N?0.03%, and O?0.0020%, and optionally at least one element selected from Mo, Cu, Ni, B, Ti, Nb and V, the balance being Fe and impurities. A surface hardened layer portion satisfies: (a) average carbon concentration in the region from the outermost surface to a point of 0.2 mm depth of 0.35-0.60 mass %, (b) surface roughness Rz?15 ?m, and (c) ?r(0)??800 MPa, ?r(100)??800 MPa, and residual stress intensity index Ir?80000, wherein Ir is calculated by [Ir=?|?r(y)|dy], where y ?m is the depth from the outermost surface and ?r(y) is the residual stress for the points from the outermost surface to a depth of 100 ?m with the range of y from 0 to 100 (?m).

Abstract: In a hot stamped steel, when [C] represents an amount of C (mass %), [Si] represents an amount of Si (mass %), and [Mn] represents an amount of Mn (mass %), an expression of 5×[Si]+[Mn])/[C]>10 is satisfied, a metallographic structure includes 80% or more of a martensite in an area fraction, and optionally, further includes one or more of 10% or less of a pearlite in an area fraction, 5% or less of a retained austenite in a volume ratio, 20% or less of a ferrite in an area fraction, and less than 20% of a bainite in an area fraction, TS×?, which is a product of TS that is a tensile strength and ? that is a hole expansion ratio is 50000 MPa·% or more, and a hardness of the martensite measured with a nanoindenter satisfies H2/H1<1.10 and ?HM<20.

Abstract: The present invention provides a steel sheet for a rotor core for an IPM motor, wherein the steel sheet has a magnetic flux density B8000 of 1.65 T or more as measured when magnetic field strength is 8000 A/m, and a residual magnetic flux density Br of 0.5 T or more as measured at that time, and optionally, a coercivity Hc of 100 A/m or more as measured after magnetization reaches 8000 A/m. By using the steel sheet of the present, invention for a rotor core of an IPM motor, it is possible to increase further an output torque in a high-speed rotational range and raise further the maximum, rotational speed.

Abstract: A method is provided with which a bearing steel, even when obtained from an ingot, is made to have a segregation part reduced in the degree of segregation and maximum inclusion diameter. The ingot contains 0.56-0.70 mass % C, 0.15-0.50 mass %, excluding 0.50 mass %, Si, 0.60-1.50 mass % Mn, 0.50-1.10 mass % Cr, 0.05-0.5 mass % Mo, up to 0.025 mass % P, up to 0.025 mass % S, 0.005-0.500 mass % Al, up to 0.0015 mass % O, and 0.0030-0.015 mass % N, with the remainder comprising Fe and incidental impurities. The ingot has a degree of segregation of 2.8 or less and a predicted value of the maximum diameter of inclusions present in 30,000 mm2 of the ingot, as calculated by extreme value statistics, of 60 ?m or less.

Abstract: A method of producing a mold steel, the method including a first process of preparing a molten steel A that is obtained after vacuum refining and has a component composition including from 0.005% to 0.1% by mass of C, from 1.0% to 5.0% by mass of Ni, from 3.0% to 8.0% by mass of Cr, more than 0% but less than or equal to 2.0% by mass of Mo, more than 0% but less than or equal to 3.5% by mass of Cu, and more than 0% but less than or equal to 2.0% by mass of Al, in which an amount of O is 0.005% by mass or less and an amount of N is 0.03% by mass or less; a second process of reducing the amount of O and the amount of N in the molten steel A, by slag refining the molten steel A, to obtain a molten steel B; and a third process of casting the molten steel B, is provided.

Abstract: A cold rolled steel sheet with excellent bendability contains C at 0.15 to 0.30%, Si at 0.01 to 1.8%, Mn at 1.5 to 3.0%, P at not more than 0.05%, S at not more than 0.005%, Al at 0.005 to 0.05% and N at not more than 0.005%, the balance being Fe and inevitable impurities, and has a steel sheet superficial soft portion satisfying: Hv(S)/Hv(C)?0.8??(1) wherein Hv(S) is hardness of the steel sheet superficial soft portion, and Hv(C) is hardness of a steel sheet core portion, 0.10?t(S)/t?0.30??(2) wherein t(S) is thickness of the steel sheet superficial soft portion, and t is the sheet thickness.

Abstract: A high-strength cold-rolled steel sheet includes, by mass %, C: 0.10% to 0.40%, Mn: 0.5% to 4.0%, Si: 0.005% to 2.5%, Al: 0.005% to 2.5%, Cr: 0% to 1.0%, and a balance of iron and inevitable impurities, in which an amount of P is limited to 0.05% or less, an amount of S is limited to 0.02% or less, an amount of N is limited to 0.006% or less, the microstructure includes 2% to 30% of retained austenite by area percentage, martensite is limited to 20% or less by area percentage in the microstructure, an average particle size of cementite is 0.01 ?m to 1 ?m, and 30% to 100% of the cementite has an aspect ratio of 1 to 3.

Abstract: This steel plate for cold forging includes a hot-rolled steel plate, wherein the hot-rolled steel plate includes: in terms of percent by mass, C: 0.13% to 0.20%; Si: 0.01% to 0.8%; Mn: 0.1% to 2.5%; P: 0.003% to 0.030%; S: 0.0001% to 0.008%; Al: 0.01% to 0.07%; N: 0.0001% to 0.02%; and O: 0.0001% to 0.0030%, with a remainder being Fe and inevitable impurities, an A value represented by the following formula (1) is in a range of 0.0080 or less, a thickness of the hot-rolled steel plate is in a range of 2 mm to 25 mm, and an area percentage of pearlite bands having lengths of 1 mm or more in a region of 4/10t to 6/10t when a plate thickness is indicated by t in a cross section of a plate thickness that is parallel to a rolling direction of the hot-rolled steel plate is in a range of not more than a K value represented by the following formula (2), A value=O%+S%+0.033Al%??(1) K value=25.5×C%+4.5×Mn%?6??(2).

Abstract: A semi-manufactured steel material has a chemical composition including, by mass %, C: 0.055% to 0.15%, Si: not more than 0.2%, Mn: not more than 1.3%, P: not more than 0.03%, S: not more than 0.007%, Al: not more than 0.1%, N: not more than 0.01%, and Ti: 0.14% to 0.30%, the balance comprising Fe and inevitable impurities. In the composition, 1.0 ([C]/12)/([Ti*]/48) is satisfied ([C], [S], [N] and [Ti]: contents (mass %) of the respective elements, and [Ti*]=[Ti]?3.4×[N]?1.5×[S]), and the contents of niobium and boron as impurities are limited to Nb: less than 0.03% and B: less than 0.0005%.

Abstract: There are provided a high-strength hot-rolled steel sheet securing low-temperature toughness and having excellent stretch flangeability by controlling a structural fraction and a hardness difference among structures, and a manufacturing method thereof. A hot-rolled steel sheet contains: C: 0.01 to 0.2%; Si: 0.001 to 2.5% or less; Mn: 0.10 to 4.0% or less; P: 0.10% or less; S: less than 0.03%; Al: 0.001 to 2.0%; N: less than 0.01%; Ti: (0.005+48/14[N]+48/32[S]) % or more and 0.3% or less; Nb: 0 to 0.06%; Cu: 0 to 1.2%; Ni: 0 to 0.6%; Mo: 0 to 1%; V: 0 to 0.2%; Cr: 0 to 2%; Mg: 0 to 0.01%; Ca: 0 to 0.01%; REM: 0 to 0.1%; and B: 0 to 0.002%, and has: an texture in which, at a central portion of a sheet thickness located between ? to ? thickness positions of the sheet thickness from a surface of the steel sheet, an average value of X-ray random intensity ratios of a group of {100}<011> to {223}<110> orientations of a sheet plane is 6.

Abstract: A hot stamped steel according to the present invention satisfies an expression of (5×[Si]+[Mn])/[C]>11 when [C] represents an amount of C by mass %, [Si] represents an amount of Si by mass %, and [Mn] represents an amount of Mn by mass %, a metallographic structure after hot stamping includes 40% to 90% of a ferrite and 10% to 60% of a martensite in an area fraction, a total of an area fraction of the ferrite and an area fraction of the martensite is 60% or more, a hardness of the martensite measured with a nanoindenter satisfies an H2/H1<1.10 and ?HM<20, and TS×?, which is a product of a tensile strength TS and a hole expansion ratio ? is 50000 MPa·% or more.

Abstract: Provided is a low yield ratio, high strength and high uniform elongation steel plate having excellent strain ageing resistance equivalent to API 5L X70 Grade or lower and a method for manufacturing the same. In particular, the steel plate contains 0.06% to 0.12% C, 0.01% to 1.0% Si, 1.2% to 3.0% Mn, 0.015% or less P, 0.005% or less S, 0.08% or less Al, 0.005% to 0.07% Nb, 0.005% to 0.025% Ti, 0.010% or less N, and 0.005% or less O on a mass basis, the remainder being Fe and unavoidable impurities. The low yield ratio, high strength and high uniform elongation steel plate has a metallographic microstructure that is a two-phase microstructure consisting of bainite and M-A constituent, the area fraction of the M-A constituent being 3% to 20%, the equivalent circle diameter of the M-A constituent being 3.0 ?m or less.

Abstract: A steel is used for providing a bolt that has a high strength and still exhibits excellent hydrogen embrittlement resistance. The steel contains C of 0.30% to 0.50%, Si of 1.0% to 2.5%, Mn of 0.1% to 1.5%, P of greater than 0% to 0.015%, S of greater than 0% to 0.015%, Cr of 0.15% to 2.4%, Al of 0.010% to 0.10%, N of 0.001% to 0.10%, Cu of 0.1% to 0.50%, Ni of 0.1% to 1.0%, Ti of 0.05% to 0.2%, and V of 0% to 0.2%, with the remainder including iron and inevitable impurities, in which a ratio [Ni]/[Cu] is 0.5 or more, and a total content [Ti]+[V] is 0.085% to 0.30%.

Abstract: A steel sheet includes, by mass %: C: 0.020% to 0.080%; Si: 0.01% to 0.10%; Mn: 0.80% to 1.80%; and Al: more than 0.10% and less than 0.40%; and further includes: Nb: 0.005% to 0.095%; and Ti: 0.005% to 0.095%, in which a total amount of Nb and Ti is 0.030% to 0.100%, and the steel sheet includes, as a metallographic structure, ferrite, bainite, and other phases, an area fraction of the ferrite is 80% to 95%, an area fraction of the bainite is 5% to 20%, a total fraction of the other phases is less than 3%, a tensile strength is 590 MPa or more, and a fatigue strength ratio as a fatigue strength to the tensile strength is 0.45 or more.

Abstract: The invention provides a steel pipe excellent in deformation characteristics, most notably a steel pipe for expandable-pipe oil well and a low-yield-ratio line pipe, and a method of producing the same without conducting water cooling requiring large-scale heat treatment equipment, namely a method of producing a steel pipe excellent in deformation characteristics whose microstructure is a two-phase structure including a martensite-austenite constituent at an area fraction of 2 to 10% and a soft phase, which method comprises: heating at Ac1+10° C. to Ac1+60° C. and thereafter cooling a precursor steel pipe which contains, in mass %, C: 0.04 to 0.10% and Mn: 1.00 to 2.50%, is limited to Si: 0.80% or less, P: 0.03% or less, S: 0.01% or less, Al: 0.10% or less and N: 0.01% or less, further contains one or more of Ni: 1.00% or less, Mo: 0.60% or less, Cr: 1.00% or less and Cu: 1.00% or less, where content of Mn and content of one or more of Cr, Ni, Mo and Cu satisfy Mn+Cr+Ni+2Mo+Cu?2.

Abstract: A high-strength cold-rolled steel sheet includes, as a component composition, by mass %: C: 0.075% to 0.300%; Si: 0.30% to 2.50%; Mn: 1.30% to 3.50%; P: 0.001% to 0.050%; S: 0.0001% to 0.0100%; Al: 0.001% to 1.500%; and N: 0.0001% to 0.0100%, in which a surface microstructure contains residual austenite of 3% to 10% and ferrite of 90% or less by volume fraction, an inner microstructure at a depth of t/4 from the surface assuming that a sheet thickness is t contains residual austenite of 3% to 20% by volume fraction, a ratio Hvs/Hvb between a surface hardness Hvs of the steel sheet surface and a hardness Hvb at a depth of ¼ of the thickness is more than 0.75 to 0.90, and a maximum tensile strength is 700 MPa or more.

Abstract: A steel sheet and a method for producing the same are disclosed. The steel sheet has a composition containing 0.015% to 0.05% C, less than 0.10% Si, 0.1% to 2.0% Mn, 0.20% or less P, 0.1% or less S, 0.01% to 0.10% Al, 0.005% or less N, and 0.06% to 0.5% Ti in percent by mass, C and Ti satisfying the inequality Ti*/C?4, where Ti* (mass percent)=Ti-3.4N and Ti, C, and N represent the content (mass percent) of each element. The steel sheet has a microstructure which contains a ferrite phase as a base, in which the average grain diameter of the ferrite phase is 7 ?m or more, and in which the ratio of the rolling-direction average grain diameter to thickness-wise average grain diameter of the ferrite phase is 1.1 or more.

Abstract: When the amount of C, the amount of Si and the amount of Mn are respectively represented by [C], [Si] and [Mn] in unit mass %, the cold rolled steel sheet satisfies a relationship of (5×[Si]+[Mn])/[C]>10, the metallographic structure contains, by area ratio, 40% to 90% of a ferrite and 10% to 60% of a martensite, further contains one or more of 10% or less of a pearlite by area ratio, 5% or less of a retained austenite by volume ratio and 20% or less of a bainite by area ratio, the hardness of the martensite measured using a nanoindenter satisfies H20/H10<1.10 and ?HM0<20, and TS×? representing the product of TS that is a tensile strength and ? that is a hole expansion ratio is 50000 MPa·% or more.

Abstract: A hot-press formed product can be achieved which has regions corresponding to a shock resistant portion and an energy absorption portion within a single formed product without applying a welding method and achieves the balance of high strength and elongation with a high level according to each region by means of having a first forming region exhibiting a metal structure containing martensite: 80-97 area % and retained austenite: 3-20 area % respectively, the remaining structure being 5 area % or less, and a second forming region exhibiting a metal structure containing annealed martensite or annealed bainite: 30-97 area %, martensite as quenched: 0-67 area %, and retained austenite: 3-20 area %.

Abstract: A low density high strength steel sheet including 0.15% to 0.25% C, 2.5% to 4% Mn, 0.02% or less P, 0.015% or less S, 6% to 9% Al and 0.01% or less N, the balance being iron and inevitable impurities, wherein 1.7·(Mn—Al)+52.7·C is at least 3 and at most 4.5. A method of producing the low density and high strength steel sheet.

Abstract: A high-strength hot rolled steel sheets with excellent stretch flangeability has small variations in mechanical properties in individual coils. Variations in strength from place to place in a coil are decreased by minimally reducing the Si and Mn contents to suppress the occurrence of problems such as segregation. Further, the microstructure of the steel sheets is configured such that a ferrite phase represents an area ratio of not less than 95%, the ferrite crystal grains have an average grain size of not less than 1 ?m, and the ferrite crystal grains contain TiC with an average particle size of not more than 7 nm dispersed in the crystal grains.

Abstract: A hot rolled steel sheet having a chemical composition containing, by mass %, C: 0.04% or more and 0.20% or less, Si: 0.7% or more and 2.3% or less, Mn: 0.8% or more and 2.8% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.1% or less, N: 0.008% or less, and the balance being Fe and inevitable impurities. The microstructure of the hot rolled steel sheet includes ferrite and pearlites, in which the area ratio of the ferrite is 75% or more and less than 95%, the mean grain size of the ferrite is 5 ?m or more and 25 ?m or less, the area ratio of pearlite is 5% or more and less than 25%, the mean grain size of pearlite is 2.0 ?m or more, and the mean free path of pearlite is 5 ?m or more.