Abstract: Provided are a cold-rolled steel sheet which undergoes a small load at the time of cold-rolling, has excellent press formability and high strength, and a method of manufacturing the cold-rolled steel sheet. A hot-rolled steel sheet having the composition comprising by mass %, 0.10 to 0.30 C, 0.2 or more Mn, 0.01 or more Ni, 0.5 to 2.5 Mn+Ni, 1.2 to 9.0 Cr, and Fe and unavoidable impurities as a balance, and has a tensile strength of 1000 MPa or less is subjected to pickling and, is subjected to cold rolling at a total rolling reduction of 60% or more thus forming a cold-rolled steel sheet. A final continuous annealing treatment is performed at a soaking temperature of 750° C. or above and at a cooling rate of 3° C./s to 100° C./s so that the cold-rolled steel sheet which has a tensile strength of 1280 MPa or more, breaking elongation of 3% or more, and a thickness of 0.05 to 0.60 mm is manufactured.

Abstract: The present invention provides an electrical steel sheet core for a low-noise transformer capable of effectively lowering noise by suppressing vibration perpendicular to the surfaces of the steel sheets and reducing vibration, and relates to an electrical steel sheet for a low-noise transformer characterized by randomly inserting viscoelastic layers with both viscosity and elasticity into the gaps of the steel sheet lamination layers, and a low-noise transformer formed by using said electrical steel sheet.

Abstract: The present invention provides an electrical steel sheet core for a low-noise transformer capable of effectively lowering noise by suppressing vibration perpendicular to the surfaces of the steel sheets and reducing vibration, and relates to an electrical steel sheet for a low-noise transformer characterized by randomly inserting viscoelastic layers with both viscosity and elasticity into the gaps of the steel sheet lamination layers, and a low-noise transformer formed by using said electrical steel sheet.

Abstract: The present invention provides an electrical steel sheet core for a low-noise transformer capable of effectively lowering noise by suppressing vibration perpendicular to the surfaces of the steel sheets and reducing vibration, and relates to an electrical steel sheet for a low-noise transformer characterized by randomly inserting viscoelastic layers with both viscosity and elasticity into the gaps of the steel sheet lamination layers, and a low-noise transformer formed by using said electrical steel sheet.

Abstract: A thin ferritic steel sheet having an excellent shape fixability capable of being used for bending is provided, comprising: at least 0.027 to less than 0.05 mass % of C, 0.01 to 1.0 mass % of Si, 0.01 to 2.0 mass % of Mn, not more than 0.15 mass % of P, not more than 0.03 mass % of S, 0.01 to 0.1 mass % of Al, not more than 0.01 mass % of N, not more than 0.007 mass % of O, the balance being Fe and inevitable impurities, wherein a ratio of presence of {100} planes parallel with a face of the steel sheet to {111} planes is not less than 1.0, and TS×El, which represents a product of maximum tensile strength (TS) multiplied by rupture elongation (El) of the steel sheet, is at least 13,860 MPA %.

Abstract: The present invention provides a cold-rolled steel sheet and a hot-dip galvanized steel sheet having good bake hardenability, non-aging properties at room temperature and good formability and a process for producing the same. An extra low carbon steel or an extra low carbon steel containing at least one element selected from Ti and Nb is annealed at a temperature of not lower than the AC.sub.3 transformation point to bring the structure after annealing to a structure of low-temperature transformation products. This makes it possible to provide a steel sheet that has a combination of high paint-bake hardenability and non-aging properties at room temperature and is excellent also in formability in respect of average r value (deep drawability) and elongation (punch stretchability). In particular, with respect to paint-bake hardenability, a BH property on a high level up to about 10 kgf/mm.sup.

Abstract: The present invention provides a non-aging at room temperature ferritic single-phase cold-rolled steel sheet or hot-dip galvanized steel sheet for deep drawing and having excellent fabrication embrittlement resistance and paint-bake hardenability, by heating a slab comprising, in terms of % by weight, 0.0001 to 0.0015% of C, not more than 1.2% of Si, 0.03 to 3.0% of Mn, 0.01 to 0.15% of P, 0.0010 to 0.020% of S, 0.005 to 0.1% of Al, 0.0001 to 0.0080% of N and 0.0001 to 0.0030% of B and optionally 0.1 to 3% of Cr with the balance consisting of Fe and unavoidable impurities, hot-rolling the heated slab at a finishing temperature of not lower than (Ar.sub.3 --100).degree. C., cooling the hot-rolled coil within 1 sec after the hot rolling at a rate of not less than 50.degree. C./sec from the finishing temperature to a temperature in the range of from 600.degree. to 750.degree. C.

Abstract: The present invention provides a cold rolled steel sheet and a hot dip zinc-coated cold rolled steel sheet excellent in paint bake hardenability, non-aging properties and formability, and a process for producing the same. In the present invention, an extremely low carbon steel or extremely low carbon steel containing at least one element selected from the group consisting of Ti and Nb is used as a base steel, and Mn and Cr are positively added thereto, whereby the resultant steel has a mixed structure after annealing. Accordingly, there can be obtained a steel sheet having both a high paint bake hardenability and non-aging properties, and being excellent in formability such as an average r-value (deep drawability). With regard to the paint bake hardenability, the present invention may provide a cold rolled steel sheet and a hot dip zinc-coated cold rolled steel sheet to which paint bake hardening may be optionally imparted in an amount as large as about 10 kgf/mm.sup.

Abstract: A high-strength cold-rolled steel strip or a molten zinc-plated high-strength cold-rolled steel strip which have a low yield strength, containing, by weight, of 0.0005-0.01% C, not more than 0.8% Si, more than 0.5% but not more than 3.0% Mn, 0.01-0.12%: P. 0.0010-0.015% S, 0.01-0.1% Al, 0.0005-0.0060% N, not less than 0.0001% but less than 0.005-0.1% the content of Nb being made to satisfy Nb .gtoreq.93/12 (C-0.0015), or instead of 0.005-0.1% Nb, 0.0005-0.1% Ti and 0.003-0.1% Nb, the content of Nb and the content of Ti being made satisfy, Ti.gtoreq.3.42N, and the balance Fe and incidental impurities is provided. Another steel strip or molten zinc-plated strip is provided that contains 0.2-3.0% Cr but does not require B, and includes both Ti and Nb. The method of producing such is also provided.

Abstract: A process for producing a non-aging galvanized steel sheet having good formability in a continuous galvanizing production line, which comprises heating a low carbon, Al-killed cold rolled steel sheet at a temperature not lower than a recrystallizing temperature, reducing the surface of the steel sheet thus heated in a reducing atmosphere, cooling the steel sheet to a temperature (T.sub.E) ranging from 200.degree. to 350.degree. C. from a temperature not lower than 600.degree. C. at a cooling rate not less than 30.degree. C/s, holding the steel sheet at the temperature (T.sub.E) for 0 to less than 10 seconds, reheating the steel sheet to a temperature ranging from 430.degree. to 500.degree. C. at a heating rate not less than 10.degree. C/s, immersing the steel sheet into a molten zinc bath, cooling the steel sheet thus galvanized to a temperature not higher than 370.degree. C., and subjecting the steel sheet to an overaging treatment to a temperature range from 250.degree. to 320.degree. C.

Abstract: A heat-treatment-hardenable cold-rolled steel sheet having a high r value, comprising 0.010% or less of carbon, 0.05 to 0.5% of manganese, 1.0% or less of silicon, 0.001 to 0.030% of sulfur, 0.03% or less of phosphorus, 0.0050% or less of nitrogen, 0.005 to 0.10% of sol. aluminum, and 0.8 to 2.2% of copper with the balance being iron and unavoidable elements and, optionally incorporated therein, either or both of titanium and niobium and further nickel and optionally boron. The steel sheet can be manufactured by subjecting a cold-rolled steel sheet having this composition to recrystallization annealing at a temperature of 750.degree. C. or above and then heat-treating the steel sheet at a temperature ranging from 450.degree. to 700.degree. C. for 1 minute or longer. Alternatively, after the recrystallization annealing, the sheet can be cooled to a temperature of 450.degree. C. or below within 1 minute, followed by work deformation and heat-treating the work-deformed product at a temperature of 450.degree. C.

Abstract: A zinc-plated steel sheet with an ageing resistance is produced from an Al-killed steel by hot dip type, continuous zinc plating including recrystallization and annealing, where after recrystallization and grain growth, the steel sheet is quenched at a cooling rate of 30.degree..about.250.degree. C/sec from 720.degree..about.600.degree. C. to 310.degree..about.200.degree. C.; after keeping the steel sheet at the same temperature for 0 to 15 seconds, the steel sheet is reheated to a molten zinc bath temperature; then the steel sheet is dipped into the molten zinc bath for zinc-plating; and then the steel sheet is cooled at a cooling rate of 250 to 5.degree. C./sec from that temperature to 350.degree. C.; and then the steel sheet is cooled at a specific average cooling rate in a temperature region of 350.degree. C. to 300.degree. C. and at a specific average cooling rate in a temperature region of from 300.degree. C. to 285.degree..about.220.degree. C.

Abstract: A cold rolled steel sheet having a good ageing resistance is produced by subjecting a cold rolled steel sheet to continuous annealing including recrystallization, grain growth, quenching, supercooling, reheating and overageing according to inclinatory cooling, where after the recrystallization and the grain growth, the steel sheet is quenched at a cooling rate of 50 to 250.degree. C./sec from 720-600.degree. C. to 200-310.degree. C.; after retaining the steel sheet at the same temperature for 0 to 15 seconds, the steel sheet is reheated by at least 40.degree. C. up to 320-400.degree. C.; then the steel sheet is retained at the same temperature or cooled at a rate of not more than 0.7.degree. C./sec including the time for retaining the steel sheet at the same temperature; and then the steel sheet is cooled at an average cooling rate of not more than 10.degree. C./sec in a temperature zone of higher than 350.degree. C., at a specific average cooling rate in a temperature zone of 350.degree. C. to 300.degree. C.

Abstract: A heat-treatment hardenable hot-rolled steel sheet having remarkably excellent cold workability comprising 0.0005 to 0.015% of carbon, 0.05 to 0.5% of manganese, 0.001 to 0.030% of sulfur, 1.0 to 2.2% of copper, 0.100% or less of phosphorus, 1.0% or less of silicon, 0.0050% or less of nitrogen, and 0.002 to 0.10% of sol. aluminum with the balance being iron and unavoidable elements and substantially comprising a ferritic single phase structure free from occurrence of pearlite. The steel may also contain 0.01 to 0.2% titanium, 0.005 to 0.2% niobium, 0.15 to 0.45% nickel and/or 0.0001 to 0.0030% boron. The steel sheet is produced by hot-rolling the steel at a temperature above the Ar.sub.3 point and coiling the hot-rolled steel strip at a temperature of, preferably, 350.degree. C. or below. The resultant steel sheet is relatively easy to work, and its strength can be dramatically increased by heat treatment for a short period of time after working.

Abstract: Disclosed is a process for producing titanium-containing cold rolled steel sheets and strips which can stand very severe press forming, which process comprising hot rolling, coiling at a temperature not lower than 700.degree. C., cold rolling and continuous annealing at a temperature, from 700.degree. to 900.degree. C., for 20 seconds to 2 minutes.

Abstract: In a method for producing a cold-rolled steel sheet by continuously casting, hot-rolling, cold-rolling, and continuously annealing Al-killed steel, it is known to coil a hot-rolled strip at a coiling temperature of 630.degree. C. to 710.degree. C. so as to attain satisfactory precipitation of AlN in the hot-rolling step. When the direct-rolling of a continuously cast strand (DR method) is employed to produce a cold-rolled strip, it is impossible to attain satisfactory precipitation of AlN even by carrying out the known coiling method. The present invention is characterized in that an extremely high coiling temperature of at least 780.degree. C. is used to essentially prevent aging due to the precipitation of AlN, and, further, the carbon content of a continuously cast slab is 0.005% at the highest so as to essentially prevent the occurrence of orange peel. Heat conservation due to use of the DR method and excellent properties of the cold-rolled steel strip are simultaneously attained.

Abstract: A method of producing a non-ageing cold rolled steel strip having excellent deep-drawability, with a r value of 1.5 or higher and ageing index of not higher than 3 kg/mm.sup.2 from an Al-killed steel with a lowered carbon content between 0.001 and 0.0035% and with no special additives such as titanium by a relatively low temperature coiling in the hot rolling, and a short-time continuous annealing without over-ageing, thus over-coming the disadvantages caused by a high temperature coiling and by additional over-ageing.

Abstract: A method for producing a low carbon deep drawing quality steel or high strength steel in the form of a strip or sheet. At least one of carbide or nitride forming elements is added to the low carbon steel to provide therein 0.015 to 0.10% Sol Al, 0.01 to 0.10% Nb, 0.01 to 0.10% Ti and 0.01 to 0.15% V. The steel is cast or bloomed to form a slab which is held above the Ar.sub.3 point for keeping the carbide and nitride forming elements in a dissolved state. Then, without allowing the temperature to fall below the Ar.sub.3 point, hot rolling and hot finishing rolling are directly carried out at a temperature above the Ar.sub.3 point. Thereafter, if necessary and desirable, the thus-rolled slab or sheet is subjected to cold rolling and annealing.

Abstract: A method for treating a continuously cast steel slab suitable for production of a hot rolled or cold rolled steel sheet, the steel slab being obtained by continuously casting a molten steel containing 0.01 to 2.5% by weight of Al, which method comprises holding the slab at a temperature within the range of from the Ar.sub.3 point to 650.degree. C for at least 20 minutes to precipitate nitrides, and hot rolling the slab.