Importance

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Abstract

Method for coating the inside surface of an elongated metal tubular body which includes placing a plurality of elongated pieces of coating metal into the bore of the tubular body in alignment with the axis thereof, to provide a constant amount of coating metal along the length of the bore. The coating metal melts below the melting point of the tubular body. The bore is freed of oxygen by evacuation or by purging with inert gas. The tubular body and the elongated pieces of coating metal within the bore are then rotated at a high rotational speed sufficient to distribute the elongated pieces against the bore surface while maintaining the constant amount of coating metal along the length of the bore. The rotating tubular body is then heated sufficiently to melt the coating metal pieces and insufficiently to melt the tubular body. Melted coating metal is spread about the bore surface by means of the centrifugal force imposed upon the melted coating metal by the continued rotation of the tubular body. In one apparatus configuration, the rotating tubular body is passed through a heating device and into a cooling zone, and the tubular body is then withdrawn from the cooling zone with a uniform layer of solid metal coating upon the bore surface. In another apparatus configuration, the heating device is passed over and alongside of a rotating but stationary tubular body.

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First Claim