Thermal Behavior of Ti-64 Primary Material in Electron Beam Melting Process.

Jean-Pierre Bellot,Julien Jourdan,Thibault Quatravaux,Alain Jardy,Jean-Sébastien Kroll-Rabotin

doi:10.3390/ma14112853

Abstract

The Electron Beam Melting (EBM) process has emerged as either an alternative or a complement to vacuum arc remelting of titanium alloys, since it is capable of enhancing the removal of exogenous inclusions by dissolution or sedimentation. The melting of the primary material is a first step of this continuous process, which has not been studied so far and is investigated experimentally and numerically in the present study. Experiments have been set up in a 100 kW laboratory furnace with the aim of analyzing the effect of melting rate on surface temperature of Ti-64 bars. It was found that melting rate is nearly proportional to the EB power while the overheating temperature remains roughly independent of the melting rate and equal to about 100 °C. The emissivity of molten Ti-64 was found to be 0.22 at an average temperature of about 1760 °C at the tip of the bar. In parallel, a mathematical model of the thermal behavior of the material during melting has been developed. The simulations revealed valuable results about the melting rate, global heat balance and thermal gradient throughout the bar, which agreed with the experimental values to a good extent. The modeling confirms that the overheating temperature of the tip of the material is nearly independent of the melting rate.

Highlights

Among the secondary remelting techniques, the EBM (Electron Beam Melting) process applies a high-power electron beam on the metallic material for melting, refining and controlling the casting and solidification stages
The oscillation of the melting rate can be readily explained by the ablation of mesh cells, whose temperatures are greater than Toh
Experiments of melting Ti-64 bars in a laboratory electron beam furnace were compared to a numerical model accounting for the various heat transfers in the titanium bar and at its surfaces

Summary

Introduction

Among the secondary remelting techniques, the EBM (Electron Beam Melting) process applies a high-power electron beam on the metallic material for melting, refining and controlling the casting and solidification stages. The EBM process can be used in two ways: Electron Beam Cold-Hearth Melting (EBCHM) and Electron Beam Drip Melting (EBDM) In the final solidification step, the molten metal is cast into a withdrawing watercooled copper mold and solidified to form an ingot. All these operations are performed inside a vacuum chamber (10−4 to 10−3 mbar) in order to guarantee proper operation of the electron guns and to avoid alloy contamination. Melting is conducted in a higher vacuum and for a longer time, enabling more complete degassing and dissolution of exogenous inclusions such as low-density inclusions known as hard-alpha [1,2]

Methods

Results

Conclusion