Abstract: A furnace for the formation of a black oxide film on the surface of a thin metal sheet is disclosed which comprises a tunnel-like furnace proper provided at one terminal side thereof with an inlet and at the other terminal side thereof with an outlet, conveying means laid inside the furnace proper from the inlet through the outlet thereof for conveying a thin metal sheet from the inlet to the outlet, openable shutter means for partitioning the interior of the furnace proper into at least first and second regions on the front and rear sides respectively in the direction of conveyance of the thin metal sheet, first gas supply means for feeding into the first region on the inlet side of the furnace proper partitioned by the shutter means a mixed gas containing carbon dioxide and carbon monoxide and containing substantially no oxygen or a mixed gas containing carbon dioxide, carbon monoxide, and steam and containing substantially no oxygen, second gas supply means for feeding into the second region on the outlet

Abstract: A furnace for the formation of a black oxide film on the surface of a thin metal sheet is disclosed which comprises a tunnel-like furnace proper provided at one terminal side thereof with an inlet and at the other terminal side thereof with an outlet, conveying means laid inside the furnace proper from the inlet through the outlet thereof for conveying a thin metal sheet from the inlet to the outlet, openable shutter means for partitioning the interior of the furnace proper into at least first and second regions on the front and rear sides respectively in the direction of conveyance of the thin metal sheet, first gas supply means for feeding into the first region on the inlet side of the furnace proper partitioned by the shutter means a mixed gas containing carbon dioxide and carbon monoxide and containing substantially no oxygen or a mixed gas containing carbon dioxide, carbon monoxide, and steam and containing substantially no oxygen, second gas supply means for feeding into the second region on the outlet

Abstract: In a gas laser device according to this invention, a gas inlet having an electrode protrudes within each of expanded portions protruding on the side, where the gas inlet is disposed, of the principal portion of the discharge tube. Gas medium ejected from the gas inlet in the principal portion of a discharge tube collides with the inner surface of the principal portion of a discharge tube, while forming a flame extending along the ejected gas medium from the electrode and is divided into two partial flows. One of them flows along the wall of the expanded portion; collides with the gas inlet; and is divided further into two partial flows. Therefore it does not collide with the gas medium within the gas inlet. Consequently the gas medium and the flame fluctuate hardly and are stabilized. In this way it is possible to stabilize the laser output.