Effects of temperature (in)homogeneity during hot stamping on deformation behavior, structure, and properties of brass valves

Abstract

Herein, assessing the effects of initial temperature (in)homogeneity on a hot-stamped CuZn40Pb2 medical gas valve (fitting) via numerically and experimentally defining mutual relations of selected deformation parameters and optimizing temperature distribution within the original semi-product heated via induction are focused. For these purposes, three preheating regimes are simulated, and deformation behaviors are evaluated. The predicted results are validated by experimental stamping and subsequent evaluation of the structure and properties of stamped fittings. The results show that preheating the semi-product with a certain temperature gradient occurring between the axial and (sub)surface regions is favorable, as homogeneous initial temperature distribution results in rapid surface cooling by the effect of heat transfer from semi-product to die, which imparts inhomogeneous stress distribution, local changes in structural phases, and possible occurrence of oxides. Too low (sub)surface temperature of the semi-product can result in a significant (local) increase in flow stress, which consequently results in the danger of occurrence of forming defects. The brass fitting stamped with the optimized preheating procedure features an average grain size of 5.8 mu m, uniform grains' orientations with maximum texture intensity of two times random, and ultimate tensile strength of almost 400 MPa, while maintaining elongation to failure of more than 35%.