20th International Forgemasters Meeting - IFM 2017

In order to ensure closure of a voids in a large steel ingot and obtain a good internal quality, it is necessary to establish the quantitative evaluation method for void closure in multi-pass forging. Although many evaluation formulas with equivalent strain, εeq, have been proposed as evaluation methods for void closure in single-pass forging, there is few reports of detailed study on it in multi-pass forging. The authors have investigated the void closure behavior in multi-pass forging by numerical experiments to consider the appropriate evaluation factors for void closure in multi-pass forging. The results obtained are as follows: 1) The void closure behavior in multi-path forging can be predicted with not εeq but true strain in z-direction, εz . 2) In the case of closing the voids by reduction in z-direction, the εz used in multi-pass forging is quite similar to the value in single-pass forging. 3) If εz required for void closure in multi-pass forging is less than the value in the single-pass forging, the void closure behavior of the multi-pass forging can be evaluated by the single-pass forging.