Lubricant, Cooling

any of the liquid, multicomponent systems used primarily for lubricating and cooling machinery, tools, and workpieces in the processing of metal. Cooling lubricants reduce wear in tools and machinery and improve the precision of the metalworking process. They also have a number of other functions, such as washing away abrasive dust and chips, protecting the workpiece, tools, and equipment from corrosion, and improving the sanitary and hygienic level of working conditions.

Cooling lubricants form three groups, depending on composition. Pure mineral oils or oils that contain antiwear and anti-scuff additives of fatty materials and organic compounds of sulfur, chlorine, and phosphorus constitute the first group. Antirust, antifoam, and antioxidant additives, in quantities of 5–50 percent, are frequently used with the oils of this group. Aqueous emulsions of mineral oils make up the second group of cooling lubricants. These lubricants are prepared at the place of usage by diluting with water emulsifying oils that contain 40–80 percent mineral oil and 20–60 percent emulsifiers, binders, corrosion inhibitors, antifrothing agents, and bactericides. The third group of lubricants includes aqueous solutions of surface-active agents and low-molecular-weight polymers. Like the emulsions of the second group, these lubricants are obtained from concentrates containing 40–60 percent surface-active agents, polymers, corrosion inhibitors, antifrothing agents, and bactericides and 40–60 percent water. The concentration of working emulsions and solutions depends on the conditions of use and usually amounts to 2–10 percent. Cooling lubricants are prepared by compounding (mixing) the base material with the additives.

Cooling lubricants are used principally in the machining and pressure shaping of metals and in the processing of plastic and cermet. In each case, the selection of cooling lubricant is determined by such factors as the type and conditions of the process, the composition and properties of the tools, equipment, and workpiece, the required quality of the finished surface, and the method of feeding the lubricant. Petroleum cooling lubricants, owing to their excellent lubricating properties, are widely used in heavy-duty operations (low speeds, very deep cutting). Aqueous lubricants, because of their good cooling properties, are used principally in high-speed processes.