introduction cold crucible induction · pdf file · 2011-02-10introduction ! cold...

2010.06.08

!  Introduction

!  Cold Crucible Induction Melting –  Description of the process

–  Advantage/Disadvantage

!  Physical experimentation (work in progress)

!  Numerical modelling (work in progress)

!  Conclusions

2 2010.06.08

INTRODUCTION

2010.06.08 COLD CRUCIBLE INDUCTION MELTING FOR THE FABRICATION OF TITANIUM MEDICAL PROSTHESES

COLD CRUCIBLE INDUCTION MELTING

PHYSICAL EXPERIMENTATION CONCLUSIONS NUMERICAL

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INTRODUCTION

This work is being developed by the Advanced Material Forming Processes group of the Engineering Faculty of Mondragon Unibertsitatea.

In the name of the investigation group, Advanced Material Forming Processes, are included two key words of their investigating activity: Processes and Materials. The generation of knowledge for the development and optimization of both as a whole is the central core of the scientific activity of the group, without losing sight of the functionality of the formed material and higher added value.

From an operative point of view, the activity of the group is organized in a matrix form. In one axis there are the command of the different technologies and knowledge areas. For example, the metallic materials (Al, Mg, Steel, …), the deformation of sheet materials (superplastic forming, microforming, hydroforming, hot deep drawing, …), the transformation of bulk materials (thixoforming, sintering, hot forging, …) and the monitoring, modeling and control of materials and processes. In the other axis there are the sectors to which that knowledge is transferred. For example automotive, aeronautics, goods and services, health (implants), etc.

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!  Titanium and its alloys are getting much attention " Why? –  Light weight.

–  Excellent balance of mechanical properties.

–  Excellent corrosion resistance.

–  Excellent biocompatibility.

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!  Main challenge: difficult to cast these alloys by conventional casting techniques because the titanium at high temperatures reacts with the crucible and mould components.

COLD CRUCILBE INDUCTION MELTING

An innovative process for melting titanium alloys

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!  COLD CRUCILBE INDUCTION MELTING An innovative process where the casting and the melting is made in vacuum (or in a

controlled atmosphere) and we use a water cooled segmented cooper crucible instead of a typical ceramic crucible.

COLD CRUCIBLE INDUCTOIN MELTING

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!  Process steps 1) Casting:

The magnetic field supplied by the induction coil passes through the crucible segments and the induced currents heat and melt the metal charge (joule effect). As the titanium alloy melts, it solidifies against the wall, forming a thin skin or “skull” on the surface. Titanium has a low thermal conductivity, so the skull insulates the molten metal from the cooling effect of the crucible. Moreover, the effective power input is so high that the molten metal is partially levitated, which further reduces heat exchange between the liquid metal and the skull.

2) Melting: The molten metal is tilted in order to pour its content into a ceramic mould. As the conventional SiO2 refractory investment casting cause big reactions among metal and ceramic, it is important to consider mold materials containing MgO, Al2O3, ZrO2, Y2O3 and CaO in order to minimize these reactions.


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!  Advantages –  Melting in vacuum and absence of ceramics.

–  Melting stock for ISM can be anything that fits into the crucible.

–  A controlled superheat.

–  Good chemical composition control due to the stirring. !  Disadvantage: Poor efficiency

Physical experiments + Numerical Modelling

Optimization of process parameters: Power supply, frequency, coil design, crucible design,…


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!  The installation of Mondragon University

PHYSICAL EXPERIMENTATION

Seco\Warwick Pour operation view port, Melting operation view

port, Electrical power feedthroughs, Thermocouple feedthrough, Vacuum system, Rotating mold table,

Temperature control, Alloy additions feeder, Argon

gas partial pressure

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!  Experimental work –  Fabrication of a prototype

–  Temperature measurement

–  Meniscus height

–  Microestructural characterization

–  Mechanical testing

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!  Numerical modelling of the step 1 of the process (casting)

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!  First step of the process: Physical principles

–  Ampere’s Law.

–  Faraday’s Law.

–  Importance of slits.

–  Joule effect.

–  Phase change " solid-liquid.

–  Lorentz forces.

–  Liquid movement " temperature homogenization.

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NUMERICAL MODELLING

ELECTROMAGNETIC ANALISIS

HEAT TRANSFER

ANALISIS

PHASE CHANGE

SOLID-LIQUID

FLUID FLOW ANALISIS

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!  Linear problem 1)  Electromagnetic fields (Maxwell’s equations) (frequency domain)

2)  Thermal field (Poisson equation) (time domain)

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!  Non-Linear problem (time domain) 1)  Fluid flow phenomena (Navier Stokes)

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!  Literature review

–  Ernst et al.

–  Bojarevics et al.

!  Ernst et al. (2005,2007) –  COMSOL

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3D electromagnetic model

2D electromagnetic/fluid mechanic coupled model in

deformed mesh

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NUMERICAL MODELLING

3D electromagnetic/fluid mechanic coupled model in

deformed mesh

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!  Bojarevics et al. (2009) –  Pseudo-spectral solution

–  Time dependent turbulent flow and heat transfer equations

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!  Our approach (preliminary work) –  We use COMSOL

–  Axisymetric approximation (verification)

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A radiation of a loop antenna wrapped around a metallic cylinder into a conductive medium

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!  Our approach (preliminary work) –  Analytical results (Pazynski et al.)

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!  Our approach (preliminary work) –  Numerical modeling results

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!  Our approach (preliminary work) –  Computational domain

–  Geometry

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Air domain

Wire

I=1000 A

f=20000 Hz

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!  Our approach (preliminary work) –  Computational domain

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!  Our approach (preliminary work)

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!  Conclusions –  Cold Crucible Induction Melting an innovative technology

–  Comparison of experimental work and simulation

–  Simulation step by step

–  Electromagnetic analysis

–  Computational domain

CONCLUSIONS

Thanks for your attention

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!  Our approach (preliminary work)

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introduction cold crucible induction · pdf file · 2011-02-10introduction ! cold...

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