MECHANICAL HYDROFORMING WITH IMPROVED LUBRICATION

摘要

A process of mechanical hydroforming, in which a hollow tube is caused to expand against the interior surface of a die that surrounds the tube by hydraulic pressure applied to a liquid that fills the interior of the tube, is improved by coating the part of the exterior surface of the tube that comes into contact with the die surface against which it expands with a wax that is solid at normal room temperature but can be maintained fully melted and in contact with air, without showing any visible evidence of decomposition, at a temperature that is at least 75 degrees C. Preferably, the wax is applied to the surface to be hydroformed by spraying from melt onto the surface while the latter is maintained above the melt temperature of the wax. Shortly after the wax has been thus applied to the surface, the wax is cooled until it solidifies. Most preferably, the wax is an "oxidized hydrocarbon" wax that is about 95% hydrocarbon and 5% straight chain carboxylic acids and contains a wide variety of molecular weights of both hydrocarbons and carboxylic acids.