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Abstract
The ring test has previously been used to assess various cold-forming lubricants, including viscous lubricants with chemical additives for extreme pressure. However, the conditions of the test (room temperature and low strain rate) probably compare unfavourably with the operational conditions of most lubricants as the temperature may increase from ambient to several hundred degrees Celsius within the short time offorming and at the high strain rates usually encountered. Hence, caution should be exercised in using the results of the ring test to shortlist lubricants for further testing. The relative effectiveness of a number of extreme pressure lubricants has been evaluated in the making of a typical industrial backward extrusion of steel. The results for these lubricants are compared with the conventional zinc phosphate-sodium stearate system.