Some aspects of barreling in sintered plain carbon steel powder metallurgy preforms during cold upsetting

Abstract

The present research establishes a relationship of bulged diameter with densification and hydrostatic stress in forming of sintered iron (Fe) powder metallurgy preforms cold upset under two different frictional conditions, namely, nil/no and graphite lubricant condition. Sintered plain carbon steel cylindrical preforms with carbon (C) contents of 0, 0.35, 0.75 and 1.1% with constant initial theoretical density of 84% and aspect ratio of 0.4 and 0.6 were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 minutes at 1200 °C. Each sintered preform was cold upset under two different frictional constraints. It is seen that the degree of bulging reduces with reducing frictional constraints at the die contact surface. Further, it is found that the bulging ratio changed as a function of relative density and hydrostatic stress, respectively, according to the power law equations.

Evaluation of the Mechanical Properties of Carbon Nanotube (CNT) Reinforced Aluminum (6061) Composites Using Closed Die Forging

“…This indicates that CDF can significantly increase the relative density of 3vol% CNTs composites with low elongation. The free upsetting due to the changes in diameters as a result of the barreling phenomenon, has the risk of cracking prior to the densification of the sample [14]. Moreover, barreling also causes closing porosities at uniform pressure.…”

Some Studies on the Bulging Characteristics of Cold-Upset Steel Preforms

“…In addition to the friction condition, the preform geometry also found to play a significant role in barreling. For instance, smaller aspect ratio specimens possess less dead metal zone at die contact surface, which helps for uniform deformation during upsetting process, however this is other way for higher aspect ratio, yet the severity of bulging in higher aspect ratio can found to be significantly reduced by employing proper lubricant [3]. In the present investigation an attempt has been made to establish the deformation and densification behaviour of Fe-0.8%C, Fe-0.8%C-1.0%Mo and Fe-0.8%C-2.0%Mo with respect to the different frictional conditions namely dry and zinc stearate employed lubricant condition against bulge ratio.…”