This invention relates to the art of
drawing wire, and is concerned more particularly with the provision of lubricant compositions adapted for use in that art.
In the past, wire to be reduced in cross-sectional area has been coated with a lubricant for the purposes, inter alia, of reducing the amount of power required for the draw and of improving the surface characteristics of the drawn wire.
For this purpose there have been employed graphite, aluminum metal in the form of fine plates, and fatty acid soaps of, for example, sodium. In certain drawing technique it is common to associate lime with dry soap, the admixture being employed as a wire drawing lubricant composition.
The underlying function of a useful lubricant in this art appears to be this, that a readily deformable film, i. e., a film of comparatively low internal friction, is interposed between the die and the metal undergoing drawing. Employment of a lubricant has become even more important since the advent of drawing dies as hard as diamond or substantially so. Thus, the modern-day dies of tungsten carbide, tungsten carbide plus cobalt, and boron carbide, which have hardness of about that of diamond in addition to high strength (preventing rupture under considerable pressure or impact), do not, of themselves, lubricate,-that is to say, they do not attract films not readily detached from their surfaces. This makes all the more necessary the employment of lubricant films which cling to the metal surfaces and/or to the die with considerable adhesive force.
My researches on use of soaps as wire drawing lubricants have indicated that their effectiveness is in inverse proportion to their total molecular weights, while the amounts required to be used are directly proportional to their total molecular weights. Also they indicate that the replacement of the removable hydrogen of a fatty acid does not impair the attraction of the fatty acid to metal surfaces provided the base used to replace the hydrogen be not of very high molecular weight so as to impair to any considerable degree the relative amount of oxygen in the fatty acid soaps molecule. If, on the other hand, the fatty acid be of relatively low molecular weight, or if it contains in its constitution more than the normal content of oxygen, or oxygen plus halogen, or halogen, the attraction of that fatty acid compound for metal surfaces is greatly enhanced.
