The present invention pertains to a process for continuously preparing powder lubricants to use in dry wiredrawing and/or in cold metal rolling, the apparatus to put the process into practice, and the powder lubricants thus obtained.
By wiredrawing it is generally meant a process in which a material being worked is cold deformed without removal of chips by pulling it through special matrices called dies so as to reduce its section up to the desired diameter or profile the section thereof according to the desired shapes.
Cold rolling is instead a process by which a material being worked is cold deformed without removal of chips by means of special rotating rolls. Obviously the friction of the wire through the die or rolls is in both cases very strong.
In order to eliminate or reduce said friction it is necessary to resort to lubrication, which consists in interposing substances which may be greasy, solid or liquid and are exactly called lubricants, between the sliding surfaces.
Currently, powder lubricants are increasingly used in the field of dry wiredrawing and/or cold rolling. They generally consist of metal salts of fatty acids added with inert mineral charges and additives.
The first wide-spread procedure to prepare powder lubricants consisted in mixing the components in a mixer until a homogeneous mass was achieved, then the product was distributed into appropriate tray-like containers and finally said containers were disposed in a furnace in which baking took place. The finished product thus obtained was then ground and brought to the desired granulometry.
It is clear that such a procedure needed very long working times, gave a reduced yield and involved an important waste of man-power and energy while offering insufficient security to the persons attending to the apparatus.
A further method of production substantially quicker and less hard than the preceding one, provides the use of a bladed mixer, heated to a temperature of 100.degree. to 300.degree. C., in which components are simultaneously mixed and baked during a period of time ranging between 60 and 90 minutes.
The mixture is afterwards taken out and then ground.
Although the last mentioned method is better than the preceding one, it suffers the disadvantage that at the end of the mixing and baking operations the production cycle must be interrupted to allow the discharging of the baked product and the charging of raw materials necessary for the next working cycle.