Disclosed is a treatment line for the continuous treatment of metal strips having a dual purpose, i.e. for producing strips that are annealed and dip-coated with a metal alloy and for producing strips that are annealed and not coated, comprising a dual-purpose cooling tower, i.e. for cooling strips that are annealed and not coated in a non-oxidizing atmosphere and for air-cooling strips that are annealed and coated.

A sealing device is installed in heating treatment equipment through which a steel strip passes, the device including a rotary damper which is placed above the steel strip so as to be in contact with the steel strip, and a roll which is placed below the steel strip so that the roll opposes the rotary damper to form a pair consisting of the rotary damper and the roll opposing each other, the steel strip passing through a gap, which is formed between the rotary damper and the roll opposing each other, in which two pairs each of which is the pair consisting of the rotary damper and the roll opposing each other are arranged in tandem in a moving direction of the steel strip in the heating treatment equipment, and an inert gas is fed into a space defined by the two pairs arranged in tandem.

A hot dipped high manganese steel and a manufacturing method therefor. The high manganese steel comprises a steel base plate and a coating on the surface of the steel base plate. The core of the steel base plate is austenite. The surface layer of the steel base plate is a ferrite fine grain layer. The ferrite fine grain layer comprises an oxide of Al. Furthermore, the steel base plate of the hot dipped high manganese steel comprises, in mass percentages, 10 to 30% of Mn element, 1 to 2% of Al element, and 0.4 to 0.8% of C element. The manufacturing method comprises: 1) manufacturing strip steel; 2) primary annealing and acid washing; 3) secondary annealing and hot dipping.

A high-strength galvanized steel sheet includes a steel sheet having a steel composition having a specific component composition, a steel structure containing martensite and bainite at more than or equal to 70% (including 100%), ferrite at less than 20% (including 0%), and retained austenite at less than 5% (including 0%) in terms of area ratio, the amount of diffusible hydrogen in steel being less than or equal to 0.20 mass ppm; and a galvanizing layer provided on a surface of the steel sheet, having a content amount of Fe of 8 to 15% in mass %, and having an coating weight per one surface of 20 to 120 g/m.sup.2, wherein the amount of Mn oxides contained in the galvanizing layer is less than or equal to 0.050 g/m.sup.2, and a tensile strength is more than or equal to 1100 MPa and a yield ratio is more than or equal to 0.85.

A steel strip annealing furnace with a dew point control system. The furnace/control system can be more readily controlled to the desired dew point than the prior art control system and can handle the set point changes required as different types of steel coils are continuously run therethrough.

A method for producing a grain-oriented electrical steel sheet which has an intermediate layer containing silicon oxide as a main component on a surface of a base steel sheet in which a forsterite film is substantially absent and has an insulation coating on a surface of the intermediate layer includes: a decarburization annealing process of obtaining a decarburization-annealed steel sheet which has the oxygen content or 320 ppm or less and the carbon content of 25 ppm or less by subjecting a cold rolled steel sheet containing Si to decarburization annealing; a final annealing process of heating the decarburization-annealed steel sheet in a state in which a surface of the decarburization-annealed steel sheet is coated with an annealing separator to subject a steel sheet to secondary recrystallization; a removal process of obtaining a finally-annealed steel sheet by removing the annealing separator on the steel sheet which has been subjected to the final annealing process; an intermediate layer forming process of forming the intermediate layer by subjecting the finally-annealed steel sheet to thermal oxidation annealing; and an insulation coating forming process of forming the insulation coating on the finally-annealed steel sheet having the intermediate layer formed thereon.

An austenitic stainless steel according to the present invention has a chemical composition containing, by mass %: C: 0.01 to 0.15%; Si: 2.0% or less; Mn: 3.0% or less; Cr: 10.0 to 20.0%; Ni: 5.0 to 13.0%; N: 0.01 to 0.30%; Nb: 0 to 0.5%; Ti: 0 to 0.5%; and V: 0 to 0.5%, with the balance: Fe and impurities, wherein an average grain size is 10.0 μm or less, a difference in value of an average lattice constant d.sub.Ave. (={d.sub.γ(111)×I.sub.γ(111)+d.sub.γ(200)×I.sub.γ(200)+d.sub.γ(220)×I.sub.γ(220)+d.sub.γ(311)×I.sub.γ(311)}/{I.sub.γ(111)+I.sub.γ(200)+I.sub.γ(220)+I.sub.γ(311)}) of an austenite phase between a surface portion and a center portion is 0.010 Å or more, and a value of a diffraction peak integrated intensity ratio r (=100×ΣI.sub.γ/ΣI.sub.ALL) at a surface is 95% or more.

A method for producing a metallic coated steel sheet is provided. The method includes continuously annealing a steel sheet in a continuous annealing furnace and hot dip coating the steel sheet.

The invention relates to a chamber (1) for the controlled oxidation of metal strips in a furnace for annealing a continuous production line of strips which are hot-coated, for example by galvanisation, the oxidation chamber allowing the oxidation of the metal strips by means of an oxidising gas injected on at least one of the faces of a strip (15), the oxidation chamber comprising oxidation portions (17) extending over the width and/or length thereof, each portion comprising at least one blow opening (4) and at least one suction opening (5) between which an oxidising gas circulates, each portion being controllable in a different way so as to adjust the oxidation induced on the strip over the width and length of the oxidation chamber.

The invention relates to a method for treating metal strip in a directly fired furnace through which the metal strip is guided. The furnace is fired directly by gas burners and has a non-fired zone through which the exhaust gases from the fired zone flow and thus heat the metal strip. After leaving the non-fired zone, the exhaust gases from the furnace undergo post-combustion in an afterburner chamber. According to the invention, methane is injected into the non-fired zone, which causes nitrogen oxides contained in the waste gas to be converted into hydrogen cyanide.