Two new methods for testing lubricants for cold forging

Two new variants of the twist-compression test are presented, enabling evaluation of solid-film lubricants in cold forging under controlled and variable surface enlargement, sliding length and normal pressure. Investigations have been performed with: AlMgSi1 as the work-piece material; cold-working steel, HSS and TiC/TiN coated HSS as the tool material; and various lubricants for aluminium.

The friction stress has been estimated as a function of the tool material, the lubricant and the process parameters of surface enlargement, sliding length and normal pressure. Furthermore, lubricant performance has been investigated. The threshold surface enlargement/sliding length curve for the breakdown of the lubricant film has been found for the various tool materials and lubricants investigated.