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A series of experimental steels has been made to determine the effects of steel composition and material condition on the thermally aided critical instability strain and thereby on cold forgeability. The stress-strain-temperature characteristics of the steels have been determined using compression testing techniques. The results have been used to calculate the empirical constants in a constitutive equation from which the critical instability strains have been determined for each of the steels. Statistical analysis of the steel compositions has indicated that increasing the carbon, silicon, phosphorus, sulphur and nitrogen contents increased the failure rate experienced in cold forging. Also that aluminium has a significant effect on the critical instability strain. The critical instability strains determined in torsion were found to compare favourably with those determined in compression. This adds credence to the applicability of a model of a thermally aided instability criterion to high strain rate compressive forming techniques. The work has shown that to improve the cold forging performance of low carbon steels it is necessary to control both the steel composition and processing of the steels to produce a material having a high critical instability strain.

Additional information

Authors: TURNER A, British Steel, Swinden Technology Centre, Rotherham (GB);SMITH H, British Steel, Swinden Technology Centre, Rotherham (GB)
Bibliographic Reference: EUR 15845 EN (1996) 75pp., FS, ECU 11.50
Availability: Available from the (2)
ISBN: ISBN 92-827-7199-7
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