Lubricant composition for hot metal working and method of hot metal working using the same

1. 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.

2. The lubricant composition according to claim 1 , wherein the dispersion-suspension agent comprises clay or bentonite.

3. A method for producing seamless pipe, the method comprising steps of:

providing a billet;

coating, onto the surface of the billet, the lubricant composition according to claim 1 ;

heating the billet after coating the lubricant composition;

producing a hollow shell by piercing-rolling of the billet; and

drawing-rolling and sizing the hollow shell.