Abstract: The invention relates to a method of manufacturing a high-strength steel sheet by annealing the steel sheet after cold rolling. In order to obtain the low-yield ratio, high-strength steel sheet having high strength and good ductility, resistance to secondary cold-work embrittlement and spot weldability at low cost, the steel sheet containing 0.03-0.15% of P and specified amounts of C, Mn and Al as basic components and optionally containing, as a selective component, at least one element selected from a group of Si, Cr, Mo and B and a group of Nb, Ti, and V in such amounts as to meet the relation formula restricting the total content of Mn, Si, P, Cr and Mo is subjected to annealing under the conditions that the sheet is heated at a temperature of from Ac.sub.1 transformation point to 950.degree. C. for from 10 seconds to 10 minutes and cooled in such a control manner that an average cooling rate between 600.degree. C. and 300.degree. C.

Abstract: A tin-free steel strip comprising a steel strip, 40 to 150 mg/m.sup.2 of a metallic chromium layer on the steel surface, and 5 to 25 mg/m.sup.2 of a chromium compound containing layer thereon wherein the metallic chromium layer contains a plurality of protrusions, exhibits improved corrosion resistance and weldability and is thus useful in the manufacture of welded cans. Preferably, 1.times.10.sup.11 to 1.times.10.sup.14 protrusions having a diameter of 5 to 1000 nm at the base thereof are present per square meter of the metallic chromium layer surface. The tin-free steel strip is produced by chromium plating a steel strip in an aqueous solution containing CR.sup.6+ preferably to a weight of 40 to 140 mg/m.sup.2, subjecting the chromium plated strip to anodic electrolysis, preferably at an eectricity quantity of 0.1 to 10 C/dm.sup.2, and subjecting the strip to a cathodic treatment in an aqueous solution containing Cr.sup.

Abstract: A process for producing a formable thin steel sheet excellent in ridging resistance. Said process comprises finishing a low carbon steel at a strain rate of not less than 300 (s.sup.-1) in a temperature range of 800.degree. to 300.degree. C. in at least one pass when the low carbon steel is rolled into a specified thickness, and subsequently performing recrystallization annealing.

Abstract: Steel strips having a Zn-Fe-P alloy electroplated thereon exhibit improved corrosion resistance, particularly perforation corrosion resistance, as long as the plating contains 5 to 30% by weight of iron and 0.0003 to 0.5% by weight of phosphorus.

Abstract: Highly corrosion resistant plated steel strips or sheets adapted for phosphate treatment and cathodic electrodeposition and intended for use in automobiles, are produced by electroplating at least one surface of a steel strip with an alloy consisting essentially of 0.0003 to 15% by weight of phosphorous, balance essentially iron, in a plating bath containing Fe.sup.2+ ions in an amount of from 0.3 mol/liter to the solubility limit and hypophosphorous acid and/or a hypophosphite in an amount of 0.001 to 25 g/liter expressed as NaH.sub.2 PO.sub.2.H.sub.2 O at a pH of 1.0 to 5.0, a temperature of 30.degree. to 60.degree. C., and a current density of from more than 20 to 200 A/dm.sup.2, preferably 40 to 150 A/dm.sup.2. A top coat can be applied thereover, of one element selected from the group consisting of Ni, Zn, Mn, and Ti, deposited on the Fe-P plating layer to a build-up of 5 to 50 mg/m.sup.2.

Abstract: Surface-treated steel strips suitable for electric resistance welding are prepared by forming a first layer of iron-nickel alloy on a steel strip, said first layer having a weight ratio of Ni/(Fe+Ni) in the range between 0.02 and 0.50 and a thickness of 10 to 5,000 angstroms, forming a second layer of tin or iron-tin-nickel alloy on said first layer by tin plating to a coating weight of 0.1 to 1 g/m.sup.2 of tin and optionally, causing the tin to reflow, and forming a third layer on said second layer by effecting an electrolytic chromate treatment, said third layer consisting essentially of metallic chromium and hydrated chromium oxide in a total amount of 5 to 20 mg/m.sup.2 calculated as elemental chromium. More preferably, the electrolytic chromate treatment is controlled such that at least 2 mg/m.sup.2 of metallic chromium is present in the third layer.

Abstract: The present invention provides a method for producing a thin cold rolled steel sheet, which is adapted to be formed into, for example, an external automotive plate. The method includes an appearance-finishing step by bake-coating as a final step after drawing (such as press molding), and has a remarkably high baking hardenability. The baking hardenability is a property for improving the yield strength due to the heating during the bake coating treatment and is particularly advantageous for producing a light weight automobile and for compensating the deterioration of dent resistance of the automotive plate due to the lowering of its weight, (without deteriorating the r value). The latter is an indication of the press moldability of the thin steel sheet. Furthermore, the present invention discloses an effective compounding amount of Ti which acts to fix C, S and N contained in the steel, and a continuous annealing condition properly selected depending upon the effective amount of Ti.

Abstract: Based on the investigation as to the correlative relationship between the composition of a steel material, particularly the content of carbon and a soaking temperature for the hot rolling, the improvements of the stretch formability, deep-drawability and aging resistance of the cold rolled steel sheet and the peculiar behaviors of the effective additive ingredients under the above correlative relationship, a cold rolled steel sheet having excellent press-formability is obtained by soaking at 800.degree.-1,100.degree. C., a steel slab consisting of not more than 1.2% by weight of Si, 0.05-1.00% by weight of Mn, not more than 0.150% by weight of P, at least one of elements selected from the group consisting of Nb, Cr, Ti, Al, B and W in a total amount of 0.002-0.150% by weight in an extremely low range of not more than 0.005% by weight of C, followed by ordinary hot rolling, cold rolling and recrystallization annealing.

Abstract: Surface-treated steel strips suitable for electric resistance welding are prepared by forming a first layer of iron-nickel alloy on a steel strip, this first layer having a weight ratio of Ni/(Fe+Ni) in the range between 0.02 and 0.50 and a thickness of 10 to 5,000 angstroms, forming a second layer of tin or iron-tin-nickel alloy on the first layer by tin plating to a coating weight of 0.1 to 1 g/m.sup.2 of tin and optionally, causing the tin to reflow. A third layer is formed on the second layer by effecting an electrolytic chromate treatment, this third layer consisting essentially of metallic chromium and hydrated chromium oxide in a total amount of 5 to 20 mg/m.sup.2 calculated as elemental chromium. Preferably, the electrolytic chromate treatment is controlled so that at least 2 mg/m.sup.2 of metallic chromium is present in the third layer.

Abstract: A dual phase-structured hot rolled steel sheet having a composition consisting of 0.03-0.15% by weight of C. 0.6-1.8% by weight of Mn, 0.04-0.2% by weight of P, not more than 0.10% of Al, not more than 0.008% by weight of S, and the remainder being substantially Fe, and having a microstructure consisting of ferrite and martensite dispersed therein, the area fraction of said ferrite being at least 70% and that of said martensite being at least 5% at the section of the steel sheet, has a high tensile strength and a low yield ratio of not higher than 70%, and has excellent formability. The steel sheet can be produced in a simple manner by cooling directly a hot rolled sheet at an ordinary cooling rate without the use of a particular cooling pattern.

Abstract: The present invention provides high tensile strength cold rolled steel sheets having excellent formability, which consist of 0.002-0.015% of C, not more than 1.2% of Si, 0.04-0.8% of Mn, 0.03-0.10% of P, 0.02-0.10% and not less than N%.times.4 of Al, C%.times.3-{C%.times.8+0.020%} of Nb and the remainder being substantially Fe, as the high tensile strength steel sheets which reduce the weight of automobiles and the like. The steel sheet is produced by hot rolling a steel slab having the above described composition to obtain a hot rolled coil, in the hot rolling the total reduction rate being at least 90%, the rolling speed in the finishing rolling being at least 40 m/min and the coiling-up temperature being at least 600.degree. C.; cold rolling the above described hot rolled coil in a conventional process to obtain a cold rolled steel strip having a final gauge; subjecting the above described cold rolled steel strip to a continuous annealing at a temperature of 700.degree.-900.degree. C.

Abstract: Steel strips are electroplated with a Zn-Fe base alloy containing 10 to 30% by weight of iron in a chloride bath which contains zinc and ferrous chlorides to give a total concentration of zinc and ferrous ions of from 1.0 mol/l to the solubility limit with a weight ratio of Fe.sup.2+ /Zn.sup.2+ between 0.10 and 0.35, and chloride ions in a total concentration of at least 6.0 mol/l under electrolytic conditions: pH 1.0-6.0, current density 80-200 A/dm.sup.2, and relative flow velocity 30-200 m/min. The bath may further contain a polycarboxylic acid such as citric acid and a Zn-Fe-P alloy plating may be deposited when the bath further contains hypophosphorous acid.

Abstract: This invention provides a tin-free steel sheet, having superior lacquer adhesion, comprising metallic chromium and chromium oxide coatings on a steel sheet, characterized in that the chromium oxide coating is controlled such that I.sub.Cr.sup.580 /(I.sub.Cr.sup.580 +I.sub.Cr.sup.660) has a value of 0.5 or more provided that I.sub.Cr.sup.580 is the percent transmission corresponding to ol linkage and I.sub.Cr.sup.660 is the percent transmission corresponding to oxo linkage in the infrared absorption spectrum of said chromium oxide coating as measured by Fourier transform infra-red spectroscopy.

Abstract: The present invention belongs to a technical field of cold rolled steel sheet. The present invention provides a thin steel sheet suitable to be formed into, for example, an external automotive plate by a method including an appearance-finishing step by bake coating as a final step after drawing (such as press molding). The present invention aims to improve remarkably the yield strength, so-called bake hardenability, of the thin steel sheet in order to produce advantageously a light weight automobile. In addition, the invention aims to compensate advantageously the deterioration of dent resistance of the automobile due to the lowering of the weight, without deteriorating the r value, which is an indication of the press moldability of the thin steel sheet. Accordingly, the present invention discloses an effective compounding amount of Nb, which acts to fix C and N in the steel in the presence of a proper amount of Al, and an annealing condition capable of developing effectively the contribution of Nb.

Abstract: A lightweight composite material consisting of two metal sheets and an intermediate layer consisting of a mixture of resin and graphite and held between the metal sheets. The intermediate layer has a specifically limited thickness and a specifically limited graphite content, and the graphite has a specifically limited particle size distribution. The composite material is excellent in the spot weldability, bending rigidity, vibration-damping property and heat insulating property, and can be expected to be widely used as a material for automobile and further materials for industrial machine and architecture.

Abstract: The present invention provides high tensile strength cold rolled steel sheets having excellent formability, which consist of 0.002-0.015% of C, not more than 1.2% of Si, 0.04-0.8% of Mn, 0.03-10% of P, 0.02-0.10% and not less than N%.times.4 of Al, C%.times.3-{C%.times.8+0.020%} of Nb and the remainder being substantially Fe, as the high tensile strength steel sheets which reduce the weight of automobiles and the like. The steel sheet is produced by hot rolling a steel slab having the above described composition to obtain a hot rolled coil, in the hot rolling the total reduction rate being at least 90%, the rolling speed in the finishing rolling being at least 40 m/min and the coiling-up temperature being at least 600.degree. C.; cold rolling the above described hot rolled coil in a conventional process to obtain a cold rolled steel strip having a final gauge; subjecting the above described cold rolled steel strip to a continuous annealing at a temperature of 700.degree.-900.degree. C.

Abstract: A process for producing aromatic carbamates in high yield is described, which comprises reacting aromatic nitro compounds, organic compounds containing a hydroxy group, and carbon monoxide in the presence of a catalyst comprising: (1) a platinum group metal or its compound, (2) metallic vanadium or its compound, (3) metallic iron or its compound, (4) a halogen atom, and (5) a tertiary amine, wherein the amount of each component used and the composition are adjusted within specific ranges.

Abstract: Tin-free steel sheets exhibiting improved retorting resistance with respect to paint adhesion are produced by chromium plating a steel sheet through cathodic electrolysis in a chromium ion-containing solution, reversely electrolyzing the sheet by a successive anodizing treatment in said solution, and subjecting the sheet to an electrolytic treatment in an aqueous chromate solution. The SO.sub.4.sup.-- concentration of the chromate solution used in the electrolytic chromate treatment should be limited to the range of 0.01 to 0.10 gram per liter of the solution.

Abstract: Dual-phase high-tensile steel sheets having a composite structure consisting of martensite and ferrite and a tensile strength of the order of 50-80 kg/mm.sup.2 in an as-hot-rolled state are produced by a method which comprises preparing as a starting material a slab comprising 0.03-0.15% C, 0.5-1.0% Mn, 0.8-2.0% Si, 0.6-2.0% Cr, 0.01-0.1% Al, the balance being essentially Fe and accompanying impurities, heating said slab at a temperature of 1,050.degree.-1,220.degree. C., hot rolling the heated slab, completing the hot rolling at a temperature of 800.degree.-900.degree. C., thereafter cooling the hot-rolled sheet to a temperature of 350.degree.-500.degree. C., and winding the sheet into a coil at the latter temperature.

Abstract: Non-ageing cold rolled steel sheets having a very excellent formability are produced by hot rolling a steel consisting of not more than 0.008% of C, not more than 0.20% of Si, 0.04-0.30% of Mn, not more than 0.03% of P, 0.01-0.10% of Al, a content of Al being more than N%.times.4, not more than 0.02% of S, not more than 0.01% of N, 0.01-0.07% of Nb, a content of Nb being C%.times.3-{C%.times.8+0.02}%, and the remainder being substantially Fe, at a total reduction of not less than 90%, a rolling speed of not less than 40 m/min in the finishing rolling and a finishing temperature of not lower than 830.degree. C., coiling the hot rolled strip at a temperature of 600.degree.-800.degree. C., cold rolling the coiled strip following a conventional manner to obtain a cold rolled strip having final gauge and then continuous annealing or hot-dip galvanizing the cold rolled strip within a temperature range of 700.degree.-900.degree. C. for 10 seconds-5 minutes.