Requirements for graphite-containing lubricants and equipment for applying to a controlled-moving mandrel in the manufacture of pipes from stainless steel grades in a continuous mill line

Abstract

In order to reduce the negative impact of temperature-deformation conditions on a working surface of a controlled-movable mandrel and improve the quality of resulting pipes, graphite-containing lubricants are used in modern pipe rolling mills in the line of a continuous rolling mill in the production of pipes, which is applied in the form of an aqueous suspension. Thus, the resulting continuous separating graphite coating makes it possible to reduce the coefficient of friction when the mandrel contacts the deformable metal. This, in turn, ensures the stable operation of the rolling equipment, increasing the durability of the mandrels and the quality of finished pipes. A lubricant is made up of several components, the most important of which is graphite. It is its properties that largely determine the quality and effectiveness of the resulting lubricating coating. The paper presents the results of studies of various properties of graphite, on the basis of which the requirements for its use as a lubricant were developed. The requirements for a suspension of graphite-containing lubricant and equipment for its application to the surface of a controlled-movable mandrel are also indicated, which together make it possible to obtain a high-quality graphite coating. The non-compliance of the properties of the graphite-containing lubricant with the requirements, as well as its poor application to the working surface of the mandrel, leads to incomplete separation of contact surfaces during the hot deformation of the metal. This can cause mandrels to rolling lap, reduce the quality of the inner surface of finished pipes, primarily from stainless steel grades, due to the formation of various defects in the form of deep scratches, cavities, and flaw, as well as a source of reducing the durability of continuous mill mandrels.