Numerical Modeling and Optimization of Electrode Induction Melting for Inert Gas Atomization (EIGA)
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Numerical Modeling and Optimization of Electrode Induction Melting for Inert Gas Atomization (EIGA) SERGEJS SPITANS, HENRIK FRANZ, and EGBERT BAAKE Electrode Induction Melting Inert Gas Atomization (EIGA) is the state-of-the-art process for the high-quality spherical powder production for additive manufacturing needs. The growing demand for EIGA powders drives the interest for the scale-up of well-established atomization of small Ø50 mm Ti-6Al-4V electrodes, as well as atomization of new refractory materials like Tantalum. However, during first tests with Ø150 mm Ti-6Al-4V and Ø50 mm Tantalum electrodes, the difficulties with melting stability were observed. In order to overcome these difficulties and to improve understanding of details of inductive coupling and favorable melting conditions, a numerical model for the electrode induction melting has been developed and applied. https://doi.org/10.1007/s11663-020-01934-5 The Minerals, Metals & Materials Society and ASM International 2020
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INTRODUCTION
IN recent years, the demand for metal powders has grown significantly due to remarkable breakthroughs in 3D metal printing and other additive manufacturing (AM) technologies.[1] AM requires spherical powders with good rheological flow characteristics, and promises the manufacture of complex structures and parts with minimized raw material usage and at a lower cost compared with conventional manufacturing routes. The Electrode Induction Melting Inert Gas Atomization (EIGA) process was developed and patented by ALD[2] as an alternative, ceramic-free melting and atomizing process that is especially suited for production of high-purity, reactive and refractory metal powders. Today EIGA is one of the leading processes for manufacturing Titanium, Zirconium, Niobium, and precious metal alloy high-quality spherical powders for aerospace, medical, energy, chemical, electronic, and other industry applications.[3] In the EIGA process, the pre-alloyed cylindrical electrode is mounted on an electrode feeding device which continuously lowers the electrode into a conical induction coil (Figure 1). Then, energy is coupled into
SERGEJS SPITANS and HENRIK FRANZ is with the ALD Vacuum Technologies GmbH, Otto-von-Guericke-Platz 1, 63457 Hanau, Germany. Contact e-mail: [email protected] EGBERT BAAKE is with the Institute of Electrotechnology, Leibniz University, Wilhelm-Busch-Str. 4, 30167 Hannover, Germany. Manuscript submitted January 22, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
the electrode using a high-frequency electromagnetic (EM) field. In order to achieve more uniform (axisymmetric) melting, the electrode is slowly rotating around its symmetry axis (1 to 10 rpm). As a result, a melt film is formed on the electrode surface and a molten metal stream or droplets fall from the electrode tip into the inert gas nozzle where a high-velocity gas stream atomizes the melt.[4] By this means, the generated micro-droplets solidify while traveling down in the atomization tower and form spherical-shaped fine powders which are colle
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