3. Non-Newtonian lubricants

3.1 Solid" lubricants: the case of cold forging and wire drawing

Lubricant working conditions are particularly severe in cold forming in two major processes:

• cold forging operations, which require the metal to undergo considerable deformation, since the metal, in the succession of passes, undergoes large surface expansions which risk dangerously thinning the lubricating film, damage to the film being favored by two other factors: high contact pressures, due to the geometry of the operation (extrusion, in particular) and the significant work hardening of the metal, and high temperatures;...