Abstract: A device minimizes or eliminates surface flaws caused by metal dust on a metal strip to be coated in a continuous hot-dip coating process, where at least some segments of the metal strip to be coated are conveyed through the device in an axial direction. The device may comprise a blowing/sucking unit with blow-in openings for applying protective gas to the metal strip, which blow-in openings are positionable on first and second sides of the metal strip. The blowing/sucking unit may further include suction openings for extracting protective gas laden with metal vapor and/or metal dust, which suction openings are positionable on the first and second sides of the metal strip. The blowing/sucking unit may have a blow-in region in which the blow-in openings are arranged, and a suction region downstream of the blow-in region in which the suction openings are arranged.

Abstract: A device minimizes or eliminates surface flaws caused by metal dust on a metal strip to be coated in a continuous hot-dip coating process, where at least some segments of the metal strip to be coated are conveyed through the device in an axial direction. The device may comprise a blowing/sucking unit with blow-in openings for applying protective gas to the metal strip, which blow-in openings are positionable on first and second sides of the metal strip. The blowing/sucking unit may further include suction openings for extracting protective gas laden with metal vapor and/or metal dust, which suction openings are positionable on the first and second sides of the metal strip. The blowing/sucking unit may have a blow-in region in which the blow-in openings are arranged, and a suction region downstream of the blow-in region in which the suction openings are arranged.

Abstract: The invention relates to a method and to an apparatus for avoiding surface defects, which are caused by zinc dust, on galvanized metal strip in continuous strip galvanization, in which metal strip which is to be galvanized and is heated in a continuous annealing furnace is moved through a furnace pipe in protective furnace gas and is immersed into a zinc bath, wherein the furnace pipe is provided with injection openings via which the front side and the rear side of the metal strip can be acted upon with protective furnace gas, and wherein extraction openings for extracting protective furnace gas loaded with zinc vapor are arranged adjacent to the injection openings.

Abstract: A flat steel product having a tensile strength of at least 1200 MPa and consists of steel containing (wt %) C: 0.10-0.50%, Si: 0.1-2.5%, Mn: 1.0-3.5%, Al: up to 2.5%, P: up to 0.020%, S: up to 0.003%, N: up to 0.02%, and optionally one or more of the elements “Cr, Mo, V, Ti, Nb, B and Ca” in the quantities: Cr: 0.1-0.5%, Mo: 0.1-0.3%, V: 0.01-0.1%, Ti: 0.001-0.15%, Nb: 0.02-0.05%, wherein ?(V, Ti, Nb)?0.2% for the sum of the quantities of V, Ti and Nb, B: 0.0005-0.005%, and Ca: up to 0.01% in addition to Fe and unavoidable impurities. The flat steel product has a microstructure with (in surface percent) less than 5% ferrite, less than 10% bainite, 5-70% untempered martensite, 5-30% residual austenite, and 25-80% tempered martensite, at least 99% of the iron carbide contained in the tempered martensite having a size of less than 500 nm.

Abstract: An apparatus and a method for the treatment of a flat steel product, taking place in throughput. The apparatus includes an indirectly heated annealing furnace chamber, a conveyor device for continuously conveying the flat steel product over a conveyor path leading from an entry to an exit of the annealing furnace chamber, and nozzle arrangements for feeding atmosphere gas, which is reactive in relation to the flat steel product, into the annealing furnace chamber. A controlled treatment of the flat steel product includes a first nozzle arrangement, from which a gas jet induces a first gas flow towards the entry of the annealing furnace chamber and sweeping over the surface of flat steel product to be treated. A second nozzle arrangement includes a gas jet which induces a second gas flow directed towards the exit of the annealing furnace chamber and sweeping over the surface of flat steel product.

Abstract: The invention relates to a method and to an apparatus for avoiding surface defects, which are caused by zinc dust, on galvanized metal strip in continuous strip galvanization, in which metal strip which is to be galvanized and is heated in a continuous annealing furnace is moved through a furnace pipe in protective furnace gas and is immersed into a zinc bath, wherein the furnace pipe is provided with injection openings via which the front side and the rear side of the metal strip can be acted upon with protective furnace gas, and wherein extraction openings for extracting protective furnace gas loaded with zinc vapour are arranged adjacent to the injection openings.

Abstract: A flat steel product having a tensile strength of at least 1200 MPa and consists of steel containing (wt %) C: 0.10-0.50%, Si: 0.1-2.5%, Mn: 1.0-3.5%, Al: up to 2.5%, P: up to 0.020%, S: up to 0.003%, N: up to 0.02%, and optionally one or more of the elements “Cr, Mo, V, Ti, Nb, B and Ca” in the quantities: Cr: 0.1-0.5%, Mo: 0.1-0.3%, V: 0.01-0.1%, Ti: 0.001-0.15%, Nb: 0.02-0.05%, wherein ?(V, Ti, Nb)?0.2% for the sum of the quantities of V, Ti and Nb, B: 0.0005-0.005%, and Ca: up to 0.01% in addition to Fe and unavoidable impurities. The flat steel product has a microstructure with (in surface percent) less than 5% ferrite, less than 10% bainite, 5-70% untempered martensite, 5-30% residual austenite, and 25-80% tempered martensite, at least 99% of the iron carbide contained in the tempered martensite having a size of less than 500 nm.

Abstract: An apparatus and a method for the treatment of a flat steel product, taking place in throughput. The apparatus includes an indirectly heated annealing furnace chamber, a conveyor device for continuously conveying the flat steel product over a conveyor path leading from an entry to an exit of the annealing furnace chamber, and nozzle arrangements for feeding atmosphere gas, which is reactive in relation to the flat steel product, into the annealing furnace chamber. A controlled treatment of the flat steel product includes a first nozzle arrangement, from which a gas jet induces a first gas flow towards the entry of the annealing furnace chamber and sweeping over the surface of flat steel product to be treated. A second nozzle arrangement includes a gas jet which induces a second gas flow directed towards the exit of the annealing furnace chamber and sweeping over the surface of flat steel product.

Abstract: A process for melt dip coating a strip of high-tensile steel with alloy constituents including zinc and/or aluminum includes the following steps. The strip is heated in a continuous furnace initially in a reductive atmosphere to a temperature of approximately 650° C., at which the alloy constituents diffuse to the surface in small amounts. The surface, consisting predominantly of pure iron, is converted into an iron oxide layer by a short heat treatment at a temperature of up to 750° C. in a reaction chamber which is integrated in a continuous furnace and has an oxidizing atmosphere. In a subsequent annealing treatment at a higher temperature in a reductive atmosphere, this iron oxide layer prevents the alloy constituents from diffusing to the surface. In the reductive atmosphere, the iron oxide layer is converted into a pure iron layer to which the zinc and/or aluminum are applied in the molten bath with optimum adhesion.

Abstract: A method for coating a flat steel product manufactured from a high strength steel with a metallic coating, wherein the flat steel product is initially subjected to a heat treatment, in order then, in the heated state, to be hot-dip galvanized with the metallic coating in a melting bath containing overall at least 85% zinc and/or aluminum. The heat treatment includes heating the steel product in a reducing atmosphere, followed by converting a surface of the flat product to an iron oxide layer by a heat treatment lasting 1 to 10 secs in an oxidizing atmosphere, followed by annealing in a reducing atmosphere over a period of time which is longer than the duration of the formation of the iron oxide layer such that the iron oxide layer is reduced at least on its surface to pure iron, followed by cooling the product to a melting bath temperature.

Abstract: A method for coating a flat steel product manufactured from a high strength steel with a metallic coating, wherein the flat steel product is initially subjected to a heat treatment, in order then, in the heated state, to be hot-dip galvanized with the metallic coating in a melting bath containing overall at least 85% zinc and/or aluminum. The heat treatment includes heating the steel product in a reducing atmosphere, followed by converting a surface of the flat product to an iron oxide layer by a heat treatment lasting 1 to 10 secs in an oxidizing atmosphere, followed by annealing in a reducing atmosphere over a period of time which is longer than the duration of the formation of the iron oxide layer such that the iron oxide layer is reduced at least on its surface to pure iron, followed by cooling the product to a melting bath temperature.

Abstract: A process for melt dip coating a strip of high-tensile steel with alloy constituents including zinc and/or aluminum includes the following steps. The strip is heated in a continuous furnace initially in a reductive atmosphere to a temperature of approximately 650° C., at which the alloy constituents diffuse to the surface in small amounts. The surface, consisting predominantly of pure iron, is converted into an iron oxide layer by a short heat treatment at a temperature of up to 750° C. in a reaction chamber which is integrated in a continuous furnace and has an oxidizing atmosphere. In a subsequent annealing treatment at a higher temperature in a reductive atmosphere, this iron oxide layer prevents the alloy constituents from diffusing to the surface. In the reductive atmosphere, the iron oxide layer is converted into a pure iron layer to which the zinc and/or aluminium are applied in the molten bath with optimum adhesion.

Abstract: The invention relates to a coated steel sheet or strip with a ground coating made of steel, onto at least one upper side of which a coating is applied by hot-dip galvanizing, the coating being formed from a melt consisting of 0.05-0.30% by weight Al and 0.2-2.0% by weight Mg, the remainder being zinc and unavoidable impurities, and, with a coating thickness of a maximum of 3.5 ?m on each side and a coating weight of a maximum 25 g/m2 on each side, guarantees that the steel sheet, in the salt spray mist test carried out in accordance with DIN 50021-SS, shows the first formation of red rust at the earliest after 250 hours. With such a sheet or strip, a flat steel product is provided which possesses an optimum combination of high corrosion resistance and optimum weldability and which is particularly well-suited for use as a material for motor vehicle chassis construction or for the construction of domestic appliances.

Abstract: The present invention relates to a method for the manufacture of galvannealed metal sheet, wherein a hot strip is produced from an IF steel containing 0.01 to 0.1 wt. % silicon, wherein the hot strip is coiled at a coiler temperature no lower than 700° C. and no higher than 750° C., wherein a cold strip is rolled from the coiled hot strip, wherein the cold strip is recrystallization-annealed in an annealing furnace in an annealing gas atmosphere, wherein the cold strip thus annealed is provided with a zinc coating in a zinc bath, and wherein the coated cold strip is post-annealed at a galvannealing temperature no lower than 500° C. and no higher than 540° C. The invention also relates to a galvannealed metal sheet which possesses improved adhesion of the coating layer to the base material and proposes a method which is suited for the manufacture of metal sheet having such properties.

Abstract: The present invention relates to a method for the manufacture of galvannealed metal sheet, wherein a hot strip is produced from an IF steel containing 0.01 to 0.1 wt. % silicon, wherein the hot strip is coiled at a coiler temperature no lower than 700° C. and no higher than 750° C., wherein a cold strip is rolled from the coiled hot strip, wherein the cold strip is recrystallisation-annealed in an annealing furnace in an annealing gas atmosphere, wherein the cold strip thus annealed is provided with a zinc coating in a zinc bath, and wherein the coated cold strip is post-annealed at a galvannealing temperature no lower than 500° C. and no higher than 540° C. The invention also relates to a galvannealed metal sheet which possesses improved adhesion of the coating layer to the base material and proposes a method which is suited for the manufacture of metal sheet having such properties.