Patent ID: 8863564

Claim:
A lubricant composition for hot metal working of a billet by piercing-rolling mill, the lubricant composition comprising: (1) water; (2) a first glass frit having viscosity of 10 3 to 10 6 dPa·s at 1200° C. and containing 60 to 70 mass % of SiO 2 , 5 to 20 mass % of Al 2 O 3 , 0 to 20 mass % of CaO; (3) a second glass frit having viscosity of 10 3 to 10 6 dPa·s at 700° C. and containing 40 to 60 mass % of SiO 2 , 0 to 10 mass % of Al 2 O 3 , 20 to 40 mass % B 2 O 3 , 0 to 10 mass % of ZnO, 5 to 15 mass % of Na 2 O; (4) an anti-slipping agent comprising alumina or silica to increase a friction coefficient between the billet and a roll of the piercing-rolling mill; (5) a dispersion-suspension agent to dispersively suspend a solid component including the glass frit and the anti-slipping agent in the water wherein said first and second glass frits respectively have different softening points from each other.