Abstract: A lubricant composition comprising from 0.1 to 10% by weight of a phosphate glass, characterized in that said phosphate glass comprises from 45 to 75 mole % of P.sub.2 O.sub.5, from 10 to 35 mole % of M.sub.2 O (M represents alkaline metals) and from 0 to 45 mole % of B.sub.2 O.sub.3. Phosphate glasses are in the form of powder with white to ash-colored appearance, and do not cause dirt of working surroundings. Phosphate glasses are less expensive than solid lubricants which are conventionally used, and also excellent load carrying capacity can be attained by adding a small amount of phosphate glass to a lubricant composition. Accordingly, the lubricant composition of the present invention shows better load carrying capacity than a conventional lubricant composition.

Abstract: Disclosed is a lubricating composition for hot-rolling steel, which comprises a base oil or base grease and a heat-insulating agent. Especially, (A) an inorganic compound which is melted by an absorption of heat at a temperature lower than 1200.degree. C. and (B) an inorganic powder which is not melted or decomposed at a temperature lower than 1200.degree. C. and has a heat conductivity lower than 0.01 cal/cm.s. .degree.C. at room temperature and a friction coefficient smaller than 0.7 are incorporated in specific amounts singly or in combination in the composition. This lubricating composition has an excellent heat-insulating effect and effectively prevents the thermal crown of a work roll.