Abstract: To provide a steel sheet excellent in painting bake hardenability and anti aging property at room temperature: containing, in mass, 0.0001 to 0.20% of C, 2.0% or less of Si, 3.0% or less of Mn, 0.15% or less of P, 0.015% or less of S, and, in addition, 010% or less of Al and 0.001 to 0.10% of N so as to satisfy the expression 0.52Al/N<5 and, further, one or more of 2.5% or less of Cr, 1.0% or less of Mo and 0.1% or less of V so as to satisfy the expression (Cr+3.5MO+39V) ≧0.1, with the balance consisting of Fe and unavoidable impurities; having the value of BH170, evaluated after applying a 2% tensile deformation and then a heat treatment at 170° C. for 20 min., being 45 MPa or more, and any of the value of BH160, evaluated after applying a 2% tensile deformation and then a heat treatment at 160° C. for 10 min., and the value of BH150, evaluated after applying a 2% tensile deformation and then a heat treatment at 150° C. for 10 min.

Abstract: A high-strength steel pipe excellent in weldability on site and a method for producing the steel pipe by improving the reliability of the low temperature toughness of a steel are provided. For example, the steel pipe includes elements to enhance hardenability for furthering high-strengthening and also improving toughness at a weld heat affected zone subjected to double or more layer welding. In the method, the steel is made to consist of a structure composed of bainite and/or martensite by containing prescribed amounts of C, Si, Mn, P, S, Ni, Mo, Nb, Ti, Al and N, and, as occasion demands, one or more of B, V, Cu, Cr, Ca, REM, and Mg, and regulating C, Si, Mn, Cr, Ni, Cu, V and Mo. Such elements enhancing hardenability, by a specific relational expression. The diameter of prior austenite grains may be regulated in a prescribed range.

Abstract: The present invention relates to a high strength steel sheet consisting essentially of 0.04 to 0.1% C, 0.5% or less Si, 0.5 to 2% Mn, 0.05% or less P, 0.005% or less 0, 0.005% or less S, by weight, having 10 &mgr;m or less of average ferritic grain size, and 20 mm/mm2 or less of generation frequency A, which generation frequency A is defined as the total length of a banded secondary phase structure observed per 1 mm2 of steel sheet cross section along the rolling direction thereof. The steel sheet is manufactured by, for example, a method comprising the steps of: hot-rolling a continuously cast slab having the composition described above at temperatures of Ar3 transformation point or above directly or after reheating thereof; and cooling the hot-rolled steel sheet within 2 seconds down to the temperatures of from 600 to 750° C. at cooling speeds of from 100 to 2,000° C./sec, followed by coiling the cooled steel sheet at temperatures of from 450 to 650° C.

Abstract: A case hardening steel having good-grain coarsening prevention properties during carburization. The steel comprises, by weight, 0.1 to 0.4%. C, 0.02 to 1.3% Si, 0.3 to 1.8% Mn, 0.001 to 0.15% S, 0.015 to 0.04% Al, 0.005 to 0.04% Nb, 0.006 to 0.020% N, one, two or more selected from 0.4 to 1.8% Cr, 0.02 to 1.0% Mo, 0.1 to 3.5% Ni, 0.03 to 0.5% V, and in which P is limited to not more than 0.025%, Ti is limited to not more than 0.010%, and O is limited to not more than 0.0025%, with the balance being iron and unavoidable impurities, the steel being characterized in that, following hot rolling, the steel has a Nb(CN) precipitation amount of not less than 0.005% and an AlN precipitation amount that. is limited to not more than 0.005%.

Abstract: The method for manufacturing steel sheet comprises the steps of: rough-rolling to form a sheet bar; finish-rolling the sheet bar to form a steel strip; applying primary cooling and secondary cooling to the finish-rolled steel strip; and coiling the secondary-cooled steel strip. The primary cooling is conducted at cooling speeds of 120° C./sec or more down to the temperatures of from 500 to 800° C. The secondary cooling is conducted at cooling speeds of less than 60° C./sec.

Abstract: The present invention aims to produce a cold rolled metal coated multi-phase steel, characterized by a tensile strength of at least 500 MPa, a yield ratio (Re/Rm) lower than 0.65 in skinned conditions, lower than 0.60 in unskinned conditions, and with good metal coating adhesion behavior. In the case of the aluminized steel according to the invention, the steel also has superior resistance to temperature corrosion up to 900° C. and excellent mechanical properties at this high temperature. The hot metal coated steel product having a steel composition with a manganese content lower than 1.5%, chrome content between 0.2 and 0.5%, molybdenum content between 0.1 and 0.25%, and a relation between the chrome and molybdenum content as follows Cr+2 Mo higher than or equal to 0.7%, undergoes a thermal treatment in the hot dip metal coating line defined by a soaking temperature between Ac1 and Ac3, a primary cooling speed higher than 25° C./sec and a secondary cooling speed higher than 4° C./sec.

Abstract: The present invention provides a steel sheet having a chemical composition comprising 0.15% or less C, 2.0% or less Si, 3.0% or less Mn, P, S, Al and N in adjusted amounts, from 0.5 to 3.0% Cu, or one or more of Cr, Mo and W in a total amount of 2.0% or less, and having a composite structure comprising ferrite and martensite having an area ratio of 2% or more. The steel sheet is in the form of a high-strength hot-rolled steel sheet, a high-strength cold-rolled steel sheet, or a hot-dip galvanized steel sheet. There is thus available a steel sheet excellent in press-formability and in strain age hardening property as represented by a &Dgr;TS of 80 MPa or more.

Abstract: A high tensile strength hot-rolled steel sheet comprises 0.04 to 0.09% C, 0.1% or less Si, 0.5 to 1.5% Mn, 0.02% or less P, 0.01% or less S, 0.1% or less Al, 0.001 to 0.008% N, and 0.01 to 0.15% Ti, by mass %, the content of ingredient there each satisfying the equation (1), and the ferritic grain size &agr; (&mgr;m) satisfying the equation (2): [C]+7×[Si]+0.1×[Mn]+[P]+14×[S]+1.75×[Al] +23×[N]+[Ti]+18×[O]+7×[Cu]+18×[Sn]+7×[Mo]+ 1.7×[Cr]+70×[B]+7×[Ca]+14×[Zr]+14×[V]+7×[Nb] ≦2  (1) 3≦&agr;≦60×[Ti]+8  (2) where, [X] denotes the content (mass %) of element X.

Abstract: A process for enhancing precipitation strengthening in steel and for making a high-strength micro-alloy steel, and a steel made from the process. The process includes the step of deforming the steel containing a suitable precipitate strengthening substance, at a temperature at which the microstructure of the steel is essentially stable and at which those precipitation strengthening particles that form are of a desirable particle size for precipitation strengthening. Deforming the steel introduces dislocations in the crystal structure of the steel, which increases the kinetics of precipitation by increasing the number of precipitation nucleation sites and accelerating the rate of diffusion of the precipitate material. The steel may be deformed by bending or rolling the steel. Preferably the process also includes the step of cooling the steel at a rapid rate so as to minimize the formation of precipitate particles of a larger-than-desired size.

Abstract: The method for manufacturing steel sheet comprises the steps of: forming a sheet bar; forming a steel strip; primary-cooling; air-cooling; secondary-cooling; and coiling. The sheet bar is finish-rolled at finish temperatures of (Ar3 transformation point −20° C.) or more. The primary cooling cools the finish-rolled steel strip at cooling speeds of more than 120° C./sec down to the temperatures ranging from 500 to 800° C.

Abstract: A steel plate for paint use which contains C (0.12% or less), Si (1.0% or less), Mn (2.5% or less), P (0.05% or less), S (0.02% or less), and Cr (0.05% or less), Cu (0.05-3.0%), Ni (0.05-6.0%), Ti (0.025-0.15%), and Cu+Ni (0.50% or more), with Pa being 0.23% or less, in terms of mass %. Said steel plate may contain at least one additional component selected from B (0.0005-0.0030%), Al (0.05-0.50%), Ca (0.0001-0.05%), Ce (0.0001-0.05%), La (0.0001-0.05%), Nb (0.002-0.05%), V (0.01-0.10%), Zr (0.002-0.05%), and Mo (0.05-0.5$), in terms of mass %.

Abstract: A welding structural steel product having fine complex precipitates of TiN and CuS is provided which contains, in terms of percent by weight, 0.03 to 0.17%C, 0.01 to 0.05% Si, 0.4 to 2.0% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.008 to 0.030% N, 0.0003 to 0.01% B, 0.001 to 0.2% W, 0.1 to 1.5% Cu, at most 0.03% P, 0.003 to 0.05% S, at most 0.005% O, and balance Fe and incidental impurities while satisfying conditions of 1.2≦Ti/N≦2.5, 10≦N/B≦40, 2.5≦Al/N≦7, 6.5≦(Ti+2Al+4B)/N≦14, and 10≦Cu/S≦90, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 &mgr;m or less.

Abstract: A steel for forming a high strength steel sheet contains, in mass %, C: at most 0.04%, Si: at most 0.4%, Mn: 0.5-3.0%, P: at most 0.15%, S: at most 0.03%, Al: at most 0.50%, N: at most 0.01%, and Mo: 0.01-1.0%. Steel sheet formed from the steel is suitable for use as automotive panels.

Abstract: In CrMoV based heat resistant steels and tungsten-containing CrMoV based heat resistant steels, trace impurities, such as phosphorus, sulfur, copper, aluminum, arsenic, tin, and antimony are reduced lower than a specific level. Furthermore, alloy steels having increased creep strengths in a creep test on an unnotched test piece by addition of trace impurities such as cobalt, tantalum, nitrogen, boron, or the like is used. The production process therefor includes heating a turbine rotor member having the specific composition at a temperature between 980° C. and 1100° C. at a part corresponding to the high-pressure part thereof and at a temperature between 850° C. and 980° C.

Abstract: A heat resistant steel can be produced at a low cost and has an excellent high temperature strength. A high-strength heat-resistant steel is provided which comprises carbon in an amount of 0.06 to 0.15% by weight, silicon in an amount of 1.5% by weight or less, manganese in an amount of 1.5% by weight or less, vanadium in an amount of 0.05 to 0.3% by weight, chromium in an amount of 0.8% by weight or less, molybdenum in an amount of 0.8% by weight or less, at least one selected from niobium, titanium, tantalum, hafnium, and zirconium in an amount of 0.01 to 0.2% by weight, nitrogen in an amount of 20 to 200 ppm, and the balance being iron and unavoidable impurities, and the high-strength heat-resistant steel comprising a bainite structure.

Abstract: An object is to provide a heat-resistant steel which can be produced at a low cost but possesses an excellent high-temperature strength. A high-strength heat-resistant steel is provided which comprises C in an amount of 0.06 to 0.15% by weight, Si in an amount of 1.5% by weight or less, Mn in an amount of 0.5 to 1.5% by weight, V in an amount of 0.05 to 0.3% by weight, and at least one of Nb, Ti, Ta, Hf, and Zr, in an amount of 0.01 to 0.1% by weight, the balance being Fe and unavoidable impurities, wherein the high-strength heat-resistant steel has a structure consisting mainly of a bainite structure.

Abstract: Process for the production of a hot rolled metal strip of very high strength, usable for shaping and particularly for stamping, characterized in that a steel of the following weight composition: carbon, 0.12-0.25%; manganese, 1-2%; aluminum, 0.03-2.5%; silicon, 0.03-2%; chromium, 0.04-2%; phosphorus, 0.02-0.09%; sulfur optionally up to 0.01%; titanium up to 0.15%; niobium up to 0.15%; vanadium up to 0.

Abstract: Surface defects in rolled steel are remedied by quenching a surface layer of the steel product downstream of the caster and upstream of the reheat furnace by transversely differentiated quenching to match the transverse temperature profile of the steel product. The flow rate of the quench spray is differentially adjustable across the width and optionally the length of the steel product. An array of spray nozzles controlled in transversely or longitudinally arranged groups provides the quench spray.

Abstract: Hot-rolled steel with very high elasticity limit and mechanical resistance usable in particular for auto parts production, characterized by the following composition by weight: 0.08%<carbon<0.16% 1%<manganese<2% 0.02%<aluminum<0.1% silicon<0.5% phosphorus<0.03% sulfur<0.01% vanadium<0.3% chromium<1% nitrogen<0.015% molybdenum<0.6%.

Abstract: A bar or wire product for use in cold forging, characterized in that it comprises a steel having the chemical composition, in mass %: C: 0.1 to 0.6%, Si: 0.01 to 0.5%, Mn: 0.2 to 1.7%, S: 0.001 to 0.15%, Al: 0.015 to 0.05%, N: 0.003 to 0.025%, P: 0.035% or less, O: 0.003% or less and balance: Fe and inevitable impurities, and it has, in the region from the surface thereof to the depth of the radius thereof×0.15, a structure wherein ferrite accounts for 10 area % or less and the balance is substantially one or more of martensite, bainite and pearlite, and the average hardness in the region from the depth of the radius thereof×0.5 to the center thereof is less than that of the surface layer thereof by 20 or more of HV; and a method for producing the bar or wire product.

Abstract: Disclosed herein is a high-strength hot-rolled steel sheet superior in stretch-flanging properties and fatigue properties which comprises (in mass %) 0.01-0.10% C, less than 2% Si (including 0%), 0.5-2% Mn, less than 0.08% P (including 0%), less than 0.01% S (including 0%), less than 0.01% N (including 0%), 0.01-0.1% Al, and at least one of 0.1-0.5% Ti and less than 0.8% Nb (including 0%), with the granular bainitic structure accounting for more than 80% (by area) in its sectional metallographic structure. Disclosed also herein is a process for producing said steel sheet.

Abstract: A rotary forging and quenching apparatus and method forms and rapidly cools an axial-symmetric object from a spin formable material. The process uses a preheated billet which is clamped between opposed fixture mandrels which have a circumferential die shape and with quench solution channels running through the fixtures. The mandrels are spun and at least one contour roller of a mating circumferential die shape is brought into bearing contact against the billet in order to spin-form the material into the desired die shape. The mandrel and peripheral margin of the spinning billet are flooded with a quench solution coolant while being spin formed. This process streamlines the manufacturing of wheels or other axial-symmetric parts like cylinders, hemispheres, cones, etc. Typically, parts that require heat treatment, like aluminum alloys, will benefit from this process. The process minimizes the distortion encountered in heat treatment and eliminates the need to add extra material to ensure final dimensions.

Abstract: The present invention provides a high tensile cold-rolled steel sheet having superior ductility, strain age-hardening characteristics, and crash resistance properties, and also provides a manufacturing method therefor. As a particular means, a thin cold-rolled steel sheet containing 0.05% to 0.30% of C, 0.4% to 2.0% of Si, 0.7% to 3.0% of Mn, 0.08% or less of P, 0.02% or less of Al, and 0.0050% to 0.0250% of N on a mass % basis is manufactured in which N/Al is 0.3 or more. This thin cold-rolled steel sheet is heated to a temperature between (an Ac1 transformation point) and (an Ac3 transformation point+50° C.), is cooled at a cooling rate of 5 to 150° C./second in the range of at least 600 to 500° C., and is held in the temperature range of 350 to 500° C. This steel sheet has superior ductility, strain age-hardening characteristics having a &Dgr;TS of 50 MPa or more, and crash resistance properties.

Abstract: The invention relates to a high strength hot-dip galvanized and galvannealed steel sheets with excellent drawability for press forming and excellent plating adhesion that is useful as a member for automobiles, construction, electric devices and the like, and to a process for its manufacture. According to an embodiment of the invention, the steel sheet contains in terms of weight percent, C: 0.05-0.2%, Si: 0.2-2.0%, Mn: 0.2-2.5%, Al: 0.01-1.5%, Ni: 0.2-5.0%, P: <0.03% and S: <0.02%, the relationship between Si and Al being such that 0.4(%)≦Si+0.8 Al(%)≦2.0% and the remainder consisting of Fe and unavoidable impurities, the volume percentage of the retained austenite is 2-20% and the steel sheet surface wherein the relationship between the Ni and Si, Al in 0.5 &mgr;m of the steel sheet surface layer is such that Ni(%)≦¼ Si+⅓Al(%), has a Zn plating layer comprising Al: ≦1% with the remainder Zn and unavoidable impurities.

Abstract: A metal forming method is used for manufacturing vehicle wheels. The invention comprises manufacturing of a wheel block comprising a central part and initially formed rim; drawing of the rim by hot rolling to obtain a wheel profile that approximates a finished wheel, and a final wheel treatment process. The rolling is conducted from either side of the wheel block, which may comprise any granular microstructure. Rolling temperature-strain rate conditions correspond to the microstructure. For a coarse-grain microstructure, the rim includes a shoulder with a thickness greater than that of the finished wheel, and thickness differences transform the microstructure into a recrystallized and/or polygonized microstructure. For a fine-grain microstructure, the rim includes a shoulder or flange with a thickness close to a thickness of a finished wheel. For mixed microstructures, the rim includes a shoulder and has a thickness greater or equal to a finished wheel.

Abstract: The present invention provides a hot rolled steel wire rod or bar for machine structural use having, in the as-hot-rolled condition, cold workability equal to that of the conventional wire rods or bars softened through annealing after hot rolling, and a method to produce the same: and relates to a hot rolled steel wire rod or bar for machine structural use, characterized in that; the wire rod or bar is made from a steel consisting of, in weight, 0.1 to 0.5% of C, 0.01 to 0.5% of Si, 0.3 to 1.5% of Mn, and the balance comprising Fe and unavoidable impurities and containing strengthening elements as required; its microstructure consists of ferrite and pearlite; its ferrite crystal grain size number defined under Japanese Industrial Standard (JIS) G 0552 is 11 or higher; and a granular carbide 2 &mgr;m or less in circle-equivalent diameter and having an aspect ratio of 3 or less accounts for a percentage area of 3 to 15%.

Abstract: The present invention relates to an ultra-high strength cold rolled steel sheet having 880 to 1170 MPa of tensile strength, that consists essentially of 0.01 to 0.07% C, 0.3% or less Si, 0.1% or less P, 0.01% or less S, 0.01 to 0.1% sol.Al, 0.0050% or less N. 1.6 to 2.5% of sum of at least one element selected from the group consisting of Mn, Cr, and Mo, by mass, and balance of Fe, and that has an inner zone deeper than 10 &mgr;m from the surface of the steel sheet being substantially martensitic single phase structure. Since the steel sheet has hole expansion ratio of 75% or more, specified by the Standard of Japan Iron and Steel Federation, JFST1001-1996, tensile strength in a range of from 880 to 1170 MPa, and excellent mechanically joining property, it is suitable for automobile seat frames.

Abstract: A method of making a high-strength low-alloy (HSLA) hot rolled steel. A high-strength low-alloy steel is made by hot rolling a steel slab of a specified composition. The hot rolling step is carried out at an austenitic hot roll finishing temperature. The hot rolled steel is coiled at a temperature ranging from 1120° F. to 1180° F. The steel is characterized by a yield strength of at least 110 ksi. The steel may be further characterized by a ferrite-bainite microstructure.

Abstract: A conventional steel C-channel used as a side rail in a truck frame is strengthened by forming, after heat treating, strengthening lips on the edges of the C-channel flanges while the C-channel is still hot from the final tempering step of the heat treating process. The method obviates the need to use more expensive quenching dies and is advantageously performed immediately after tempering.

Abstract: A process for manufacturing an aluminum-killed low-carbon steel strip by supplying a hot-rolled steel strip having by weight from 0.022 to 0.035% of carbon, from 0.15 to 0.25% of manganese, from 0.040 to 0.70% of aluminum, from 0.0035 to 0.0060% of nitrogen, the remainder being iron and trace impurities, passing the strip through a first cold-rolling, annealing the cold-rolled strip, in which the annealing is continuous using a cycle including: a temperature rise up to a first temperature higher than an onset temperature of pearlitic transformation Ac1, holding the strip above the first temperature for a duration of longer than 10 seconds, rapidly cooling the strip to a second temperature below 100° C. at a cooling rate in excess of 100° C. per second, thermally treating the strip at a temperature from 100° C. to 350° C. for a duration in excess of 10 seconds, and cooling the strip to room temperature.

Abstract: In rolling bearings used in a circumstance undergoing high temperature, large loads and large vibrations, it has been known that early flaking phenomenon more tending to occur in the rolling element than in the bearing ring. In view of the above, according to the present invention, a rolling element with improved rolling contact fatigue resistance can be obtained while keeping hardness by devising a combination of mechanical surface hardening treatment and a heat treatment to a surface of a rolling element. A rolling bearing of long life can be provided even under large loads and large vibrations by incorporating the rolling element.

Abstract: Process for the production of a hot rolled metal strip of very high strength, usable for shaping and particularly for stamping, characterized in that a steel of the following weight composition: carbon, 0.12-0.25%; manganese, 1-2%; aluminum, 0.03-2.5%; silicon, 0.03-2%; chromium, 0.04-2%; phosphorus, 0.02-0.09%; sulfur optionally up to 0.01%; titanium up to 0.15%; niobium up to 0.15%; vanadium up to 0.15%; is subjected to: rolling at a temperature below 880° C.; a first short cooling, carried out over a time less than 10 seconds, a second controlled cooling with a cooling speed V ref1 comprised between 20° C./sec. and 150° C./sec., the temperature at the end of the second cooling being comprised between 700° C. and 750° C., holding at a temperature level, a third cooling, also controlled, whose speed is comprised between 20° C./sec. and 150° C./sec., the temperature at the end of the third cooling being comprised between 350° C and 550° C.

Abstract: A method of producing a ultra fine grain steel made of ferrite having a mean grain size of not larger that 3 &mgr;m as the base phase, after ingoting raw materials, by austenitizing the ingot by heating it to a temperature of at least an Ac 3 point, then, applying compression working of a reduction ratio of at least 50% at a temperature of from an Ae 3 point or lower to an Ar 3 point −150° C., or at a temperature of at least 550° C., and thereafter, cooling, wherein the strain rate as compression working is in the range of from 0.001 to 10/second.

Abstract: Provided is a non heat-treated steel that requires no particular controls over cooling rates and no aging treatments after hot working, that can sufficiently increase tensile strength, yield strength and toughness even at lightly deformed parts, and furthermore, that has excellent material anisotropy and machinability as an alloy steel for machine structures. In other words, it is a non heat-treated steel that contains: C: more than 0.05 mass % to less than 0.10 mass %; Si: 1.0 mass % or less; Mn: more than 2.2 mass % to 5.0 mass %; S: less than 0.020 mass %; Cu: more than 1.0 mass % to 3.0 mass %; Ni: 3.0 mass % or less; Cr: 0.01 to 2.0 mass %; Al: 0.1 mass % or less; Ti: 0.01 to 0.10 mass %; B: 0.0003 to 0.03 mass %; N: 0.0010 to 0.0200 mass %; O: 0.0060 mass % or less; and the balance Fe and inevitable impurities, and that the steel structure is bainitic having block structures at 10% or more in area ratios.

Abstract: The present invention relates to an H-shaped steel used as a building structure such as a column material or the like for highrise and super highrise building structures. In the bainite structure of extra-low-carbon steel, diffusive &agr;q is finely dispersed in &agr;B to ensure tensile strength at the 590-MPa level and significantly improve toughness in the direction of the flange thickness. Fine dispersion of &agr;q is achieved by controlling Mn and Cu in proper ranges. In other word, the present invention provides 590MPa class heavy gauge H-shaped steel with excellent as-rolled toughness in the direction of the flange thickness, containing 0.001 to 0.025 wt % of C, 0.6 wt % or less of Si, 0.4 to 1.6 wt % of Mn, 0.025 wt % or less of P, 0.010 wt % or less of S, 0.1 wt % or less of Al, 0.6 to 2.0 wt % of Cu, 0.25 to 2.0 wt % of Ni, 0.001 to 0.050 wt % of Ti, and 0.0002 to 0.0030 wt % of B, wherein Mn/Cu≦2.0 and 250≦117 Mn (wt %)+163 Cu (wt %)≦350 are satisfied.

Abstract: A hot-dip galvanized steel sheet is produced by rough rolling a steel, finish rolling the rough rolled steel at a temperature of Ar3 point or more, coiling the finish rolled steel at a temperature of 700° C. or less, and hot-dip galvanizing the coiled steel at a pre-plating heating temperature of Ac1 to Ac3. A continuous hot-dip galvanizing operation is performed by soaking a pickled strip at a temperature of 750 to 850° C., cooling the soaked strip to a temperature range of 600° C. or less at a cooling rate of 1 to 50° C. per second, hot-dip galvanizing the cooled strip, and cooling the galvanized strip so that the residence time at 400 to 600° C. is within 200 seconds. The steel sheet has a structure consisting essentially of ferrite and martensite.

Abstract: Rolled H-shapes having high strength and high toughness, and which can be produced using cheaper alloy components than conventional products and which can be manufactured with a high productivity, are disclosed. A method for manufacturing the H-shapes is also disclosed. The rolled H-shapes include 0.03 to 0.1 wt. % of Nb and 0.005 to 0.04 wt. % of Ti. The method includes a rough universal rolling process in which an accumulated reduction at a rolling temperature of 950° C. or lower is 5% or larger, and reverse operation is conducted fast; and a finishing universal rolling, in which the rolling temperature is 750° C. or higher. Preferably, in the rough universal rolling, the accumulated reduction at a rolling temperature of 950° C. or lower is 50% or more.

Abstract: A steel sheet having a composition comprising C: 0.05-0.20 mass %, Si: 0.3-1.8 mass %, Mn: 1.0-3.0 mass %, Fe of the balance and inevitable impurities is subjected to a primary step of primary heat treatment and subsequent rapid cooling to Ms point or lower, a secondary step of secondary heat treatment and subsequent rapid cooling, and a tertiary step of galvanizing treatment and rapid cooling, so as to turn the structure of the steel sheet into a composite structure of 20% or more by volume of tempered martensite, 2% or more by volume of retained austenite, ferrite and a low-temperature transformation phase. A galvanized layer is deposited on the surface of the steel sheet. It is preferred to cool the steel sheet to 300° C. at a cooling rate of 5 ° C./sec. or more after the galvanizing treatment. After the galvanizing treatment, alloying treatment may be conducted.

Abstract: This invention provides a steel for cold forging, excellent in surface layer hardness and softening properties by annealing, which contains, in terms of wt %, C: 0.1 to 1.0%, Si: 0.1 to 2.0%, Mn: 0.01 to 1.50%, P: not greater than 0.100%, S: not greater than 0.500%, sol. N: not greater than 0.005% and the balance consisting of Fe and unavoidable impurities, wherein a pearlite ratio in the steel structure is not greater than 120×(C %) % and the outermost surface layer hardness is at least 450×(C %)+90 in terms of the Vickers hardness HV, and a production method thereof. The invention provides also a steel for cold forging, which has a structure wherein a ratio of graphite amount to the carbon content in the steel exceeds 20%, a mean grain diameter of graphite is not greater than 10×(C %)⅓ &mgr;m and a maximum grain diameter is not greater than 20 &mgr;m.

Abstract: Steel for the manufacture of a component for bearings, the chemical composition of which comprises, by weight: 0.6%≦C≦1.5%; 0.4%≦Mn≦1.5%; 0.75%≦Si≦2.5%, 0.2%≦Cr≦2%; 0%≦Ni≦0.5%; 0%≦Mo≦0.2%; 0%≦Al≦0.05%; S≦0.04%; the balance being iron and impurities resulting from smelting and the composition furthermore satisfying the relationships: Mn≦0.75+0.55×Si and Mn≦2.5−0.8×Si. Process for the manufacture of a bearing component.

Abstract: A bar product prepared from microalloyed bar steel is provided. The bar product is prepared by hot rolling and heat treating a microalloyed bar steel. The hot rolled and heat treated microalloyed bar steel is prepared by steps of hot rolling a preform of the microalloyed bar steel at a temperature of between about 1,400° F. and about 2,200° F. to provide a steel bar having a diameter of between about ¾ inch and about four inches, cooling the steel bar to provide a surface temperature of below about 1,100° F., and heat treating the steel bar in an environment having a temperature of between about 500° F. and about 1,300° F. The bar product is preferably prepared without a step of cold drawing. In particular, the bar product is preferably prepared without a step of drawing to provide a 10% to a 35% reduction.

Abstract: A flat product made of multiphase steel and a method for preparing the steel includes hot rolling at a temperature at which the austenite phase is stable, then tempering to form a C and Mn-enriched phase in a matrix, followed by a heat treatment to form austenite islands and/or enriching in Mn the already formed austenite and cooling down to room temperature so as to obtain a final product with a ferrite matrix containing residual austenite, bainite and/or martensite islands.

Abstract: Steel for the manufacture of a component for bearings, the chemical composition of which comprises, by weight: 0.6%≦C≦1.5%; 0.4%≦Mn≦1.5%; 0.75%≦Si≦2.5%; 0.2%≦Cr≦2%; 0%≦Ni≦0.5%; 0%≦Mo≦0.2%; 0%<Al≦0.05%; S≦0.04%; the balance being iron and impurities resulting from smelting and the composition furthermore satisfying the relationships: Mn≦0.75+0.55×Si and Mn≦2.5−0.8×Si. Process for the manufacture of a bearing component.

Abstract: The process for manufacturing a metallic component, such as a wheel part for the rolling system of a vehicle, which includes, in an initial stage, forming the component of a metallic material in a semi-solid state and having a thixotropic structure, and in a subsequent cold-treatment stage, cold-treating at least part of said component by blasting it with projectiles with a view to plastic deformation thereof. A wheel in which a metallic disk is welded to a wheel rim and in which the metallic disk is obtained by the manufacturing process.

Abstract: A 590 MPa-class rolled steel shape of high strength and excellent toughness for use as a building structural member and a method of producing the high-tensile rolled steel shape are provided. Strength optimization by an alloy that elevates hardenability, texture refinement obtained by fine dispersion of Ti oxides and TiN owing to Ti addition, precipitation strengthening by Cu addition, and formation of a fine bainite texture by temperature-controlled rolling, cooling control and the like enable a high-strength, high-toughness rolled steel shape of high-strength and excellent toughness having mechanical properties of a tensile strength of not less than 590 MPa, a yield strength or 0.2% proof strength of not less than 440 MPa and a Charpy impact absorption energy at 0° C. of not less than 47 J, and method of producing the same.

Abstract: The invention relates to drawn pieces made of steel plate, particularly for motor vehicles bodies, and to a process for manufacturing such drawn pieces. In order to be able to manufacture drawn pieces with a high piece strength but of a low weight and with a low susceptibility to denting in a simple manner, according to the invention, a spring steel plate which is already hardened in the initial state, particularly bainitized—for example, CK60 or C63 or 67SiCr5—is used during the drawing of the vehicle body parts. The yield point of the heat-treated plate bar material is approximately in the range of from 800 to 1,800 N/mm2; the tensile strength is above that. Because of these strength values, plate bars of a plate thickness of approximately 0.3 mm to 0.6 mm can be used, whereby approximately 20 to 60% of the previous piece weight can be saved. The drawn piece according to the invention is therefore a definite lightweight part.

Abstract: The invention provides a thin high-strength hot-rolled steel sheet with a thickness of not more than 3.5 mm which has excellent stretch flangeability and high uniformity in both shape and mechanical properties of the steel sheet, as well as a method of producing the hot-rolled steel sheet. A slab containing C: 0.05-0.30 wt %, Si: 0.03-1.0 wt %, Mn: 1.5-3.5 wt %, P: not more than 0.02 wt %, S: not more than 0.005 wt %, Al: not more than 0.150 wt %, N: not more than 0.0200 wt %, and one or two of Nb: 0.003-0.20 wt % and Ti: 0.005-0.20 wt % is heated at a temperature of not higher than 1200° C. The slab is hot-rolled at a finish rolling end temperature of not lower than 800° C., preferably at a finish rolling start temperature of 950-1050° C. A hot-rolled sheet is started to be cooled within two seconds after the end of the rolling, and then continuously cooled down to a coiling temperature at a cooling rate of 20-150° C./sec. The hot-rolled sheet is coiled at a temperature of 300-550° C.

Abstract: A high tensile strength hot-rolled steel sheet comprises 0.04 to 0.09% C, 0.1% or less Si, 0.5 to 1.5% Mn, 0.02% or less P, 0.01% or less S, 0.1% or less Al, 0.001 to 0.008% N, and 0.01 to 0.

Abstract: In a heat treatment method for producing boundary layer-hardened long products and flat products of unalloyed or low-alloy steel, the workpiece is cooled for producing a martensitic grain within a boundary layer of the workpiece by repeating several sequential cooling process steps. Each sequential cooling process step has a cooling phase, in which the workpiece is cooled to a temperature below a martensite starting temperature for martensitic conversion of only a portion of the boundary layer of the workpiece, and a temporal stress-relief phase for relieving stress within already formed martensitic grain areas and already formed martensite/austenite boundary areas. Subsequently, the workpiece is cooled at a cooling rate below a lower critical cooling rate for cooling the workpiece core.

Abstract: The Cu precipitation strengthened steel of the invention comprises, on the mass percent basis, C: 0.02-0.10%, Mn: 0.3-2.5%, Cu: 0.50-2.0%, Ni: 0.3-4.0% and Ti: 0.004-0.03% and further comprises Si: 0.01-0.4% and/or Al: 0.001-0.1%, with the contents of incidental impurities being P: not more than 0.025%, S: not more than 0.01%, N: not more than 0.006% and Se: not more than 0.005%, with the value of Pcm defined by the formula (1) given below being not more than 0.28. The steel material made of this Cu precipitation strengthened steel has good and stable CTOD toughness and is suited for use as a steel material for the construction of large industrial machines, ships, marine structures, line pipes, tanks, bridges and like welded structures.