Abstract: A box annealing furnace for annealing a metal sheet includes an oxygen removal unit for removing oxygen from the atmosphere in a box annealing furnace, with a gas circulation system for withdrawing atmosphere from the box annealing furnace during annealing, treating the gas, and for refeeding the deoxidized gas to the box annealing furnace. The box annealing furnace may also include a moisture removal unit for removing moisture from the gas. The oxygen removal unit and the moisture removal unit can reliably remove oxygen and moisture from the gas and suppress the formation, during annealing, of oxide film on a ferrous metal sheet.

Abstract: A continuous annealing line for annealing a cold-rolled strip of a ultra-low-carbon steel comprising a heating furnace for heating the strip which is fed continuously, with or without a soaking furnace following the heating furnace, a cooling furnace in which the heated steel strip is cooled, and a carburizing/nitriding furnace disposed between the heating furnace or the soaking furnace and the cooling furnace. The carburizing/nitriding furnace may be divided into a plurality of zones, each of which is provided with control means for controlling the carburizing/nitriding atmosphere and carburizing/nitriding temperature in the zone. The continuous annealing line may further comprise a plurality of carburizing/nitriding furnaces and have an arrangement for conducting a switching between a mode in which the carburizing/nitriding furnace is used for carburizing/nitriding the steel strip and a mode in which the carburizing/cooling furnace is used for cooling the steel strip.

Abstract: The present invention relates to method and apparatus for heating a strip of metallic material in a continuous annealing furnace and more particularly to an improvement relating to a method and apparatus for heating a strip of metallic material in a continuous annealing furnace in which annealing of the strip is continuously carried out in such a manner that a gas serving to adjust temperature of the strip, is blown toward the strip through a plurality of gas jet nozzles which are arranged on one side or both sides of the strip, wherein the temperature and flow rate of the strip are properly determined to a required level in response to the changing of the operating conditions such as the heat cycle, line speed, thickness of strip, width of strip and the like.

Abstract: A work roll has a regularly and geometrically patterned uneven dulled section on the roll surface. Eavh uneven dulled section is composed of a crest and concavity and is of crater-like configuration. In order to obtain good performance in temper rolling, the crest is in a form of an annular ring extending around the edge of the concavity. According to the invention, pattern of arrangement of the uneven dulled sections is determined in relation to the diameter of the ring-shaped crests of the uneven dulled section so as to obtain optimum performance in producing good quality, exhibiting substantially high image clarify as coated by paint, enamel or so forth.

Abstract: The present invention relates to method and apparatus for heating a strip of metallic material in a continuous annealing furnace and more particularly to an improvement relating to a method and apparatus for heating a strip of metallic material in a continuous annealing furnace in which annealing of the strip is continuously carried out in such a manner that a gas, serving to adjust temperature of the strip, is blown toward the strip through a plurality of gas jet nozzles which are arranged on one side or both sides of the strip, wherein the temperature and flow rate of the strip are properly determined to a required level in response to the changing of the operating conditions such as the heat cycle, line speed, thickness of strip, width of strip and the like.

Abstract: A painting steel sheet having an improved distinctness of image after painting has such a surface roughness profile that a center-line average roughness is within a range of 0.3-3.0 .mu.m and a microscopic shape is comprised of mountain portions, groove-like valley portions and middle flat portions satisfying particular dimension relations, and is produced by temper rolling a steel sheet at a draft of not less than 0.3% with work roll dulled to particular dimensions through a high density energy source.

Abstract: A painting steel sheet having an improved distinctness of image after painting has a waviness curve of section profile satisfying given relationships, and is produced by temper rolling a steel sheet with work rolls dulled to particular dimensions through laser.

Abstract: A laser butt welding apparatus including a pair of clamp elements at least one of which is movable reciprocally along the steel strip-feed line direction and which are adapted to clamp the edge portions of preceding and trailing steel strips, a shear which is advanceable and retractable between the pair of the clamp elements in a perpendicular direction to the line and cuts the edge portions of the preceding and trailing steel strips, structure for butting the cut faces of the preceding and trailing steel strips while being clamped by means of the clamp elements, and a laser torch adapted to condense a laser beam from a laser oscillator on an off-line at a weld zone and movable in a width direction of the steel strips to be welded together.