Investigation into the compactability of metal powders during rolling

Evaluating and Modifying Johanson's Rolling Model to Improve its Predictability

“…Figure indicates that RC requires higher maximum roll surface pressure than that of die compression to achieve the same ribbon density. This is different from the conclusion drawn from prior studies . Prior studies indicate that similar ribbon density can be achieved with a relatively lower maximum roll surface pressure.…”

“…This is different from the conclusion drawn from prior studies . Prior studies indicate that similar ribbon density can be achieved with a relatively lower maximum roll surface pressure. However, data obtained in Figure clearly indicate that at the same ribbon density, the predicted maximum roll surface pressure is much higher than the pressure applied from die compression.…”

“…By this approach, nip angle is the angular position of roll bite at the intersection of pressure gradients between the slip and nonslip region according to Eqs. (1) and (6). Many factors can affect the nip angle.…”

“…Therefore, by equating Eqs. (1) and (6), nip angle can be determined. This can be performed graphically by plotting the pressure gradients from both slip and nonslip region in the same plot.…”

“…It is believed that this stress path difference will lead to differences in ribbon density and tensile strength. Katashinskii and Vinogradov and Mal'tsev conducted a direct comparison of the maximum roll surface pressure in plane strain of RC versus the maximum axial stress in die compression using various metal powders and found that axial stress from die compression has to be larger in order to achieve the same ribbon density. The explanation is that larger shear stress during rolling enhanced the material consolidation and resulted in denser ribbons.…”