In deep drawing, conventional material tends to suffer from various disadvantages. Cast iron for example may have good sliding properties, but the rate of wear of the tool is far too high. Tools from hardened steel have satisfactory working lives but have pick-up tendencies. If coated, the result will be better, but after a certain number of shots the sliding properties will
tend to decrease, consequently increasing the coefficient of friction. (See graph on the next page).
AMPCO® 21, 22 and especially AMPCO® 25 combine very high strength and hardness with remarkably low resistance to friction. These qualities are derived from hardness associated with very special metallurgical structure.
Due to the exceptional resistance of AMPCO materials to corrosive or atmospheric influences, no special arrangements are necessary to prevent oxidation. Because of the higher linear coefficient of expansion of AMPCO, the drawing gap between die and punch must be approximative +12% of hot-rolled blank thickness and +10% of cold-rolled blank thickness.
The face which are subjected to stresses (drawing edges) must definitively be polished. (And
AMPCO alloys polishes well). Care must be taken to ensure that faces are perfectly flat and
not wavy! Unevenness can be created by hand polishing, affecting surface finishing and reducing tool life.
Over tool steel: Lower friction, no galling, tool manufacturing without
heat treatment, easier modification.
Over commercial bronze: Higher hardness and quality due to homogeneous
microstructure. Better sliding properties and lower wear.
Over coated materials: Bigger wear area definition possible. Changes of
geometry possible at any time, solid proof that the “best coating in the world is the one you do not need”.