Effect of Mechanical Properties on Formability in Hydroforming of ERW tubes

In the simple free bulging tests of straight tubes, expandability of tubes is affected by the both n- and r-value when axial-feeding is applied. Especially, the effect of the r-value was about 9 times larger than that of the n-value. Also, as for the hydroformability of pre-bent tubes, it was found that the effect of the r-value was about 2.5 times larger than that of n-value.

Based on these results, warm-reduced tubes produced by the HISTORY process newly developed by JFE Steel Corporation were examined in the hydroformability tests as suitable products for THF. In consequence of the tests, it was found that the HISTORY tubes have higher hydroformability than the conventional ERW tubes.