Induction Skull Melting of Ti-6Al-4V: Process Control and Efficiency Optimization

Xabier Chamorro,Daniel Bernal,Iñaki Hurtado,Nuria Herrero-Dorca

doi:10.3390/met9050539

Abstract

Titanium investment casting is one of the leading and most efficient near-net-shape manufacturing processes, since complex shape components are possible to obtain with a very low amount of material waste. But melting these reactive alloys implies the usage of specific melting technologies such as the Induction Skull Melting (ISM) method. In this work the ISM was extensively studied with the aim of deepening the characteristics of this specific melting method and improving the too low energy efficiency and overall process performance. A 16 segment copper crucible and 3 turns coil was employed for the melting of 1 kg of Ti-6Al-4V alloy. Through the calorimetric balance, real-time evolution of the process parameters and power losses arising from the crucible and coil sub-assemblies was displayed. Results revealed the impact of coil working conditions in the overall ISM thermal efficiency and titanium melt properties, revealing the use of these conditions as an effective optimization strategy. This unstudied melting control method allowed more heat into charge and 13% efficiency enhancement; leading to a shorter melting process, less energy consumption and increased melt superheat, which reached 49 °C. The experimental data published in this paper represent a valuable empiric reference for the development and validation of current and future induction heating models.

Highlights

The upward trend for titanium and intermetallic TiAl alloy employment in new commercial aircrafts is one of the main reasons for CO2 and NOx emission reductions [1,2], since these lightweight materials function effectively in high-temperature and corrosive environments [3,4]
In the first melting water outlet, temperature of crucible and coil increased according to the applied power steps. 77 ◦ C and 95 ◦ C were the respective maximum values (Figure 3a)
In the second trial process the parameters were changed and chiller threshold was reduced to 20 ◦ C in order to reduce the coil working temperature

Summary

Introduction

The upward trend for titanium and intermetallic TiAl alloy employment in new commercial aircrafts is one of the main reasons for CO2 and NOx emission reductions [1,2], since these lightweight materials function effectively in high-temperature and corrosive environments [3,4]. The direct impact of this increasing demand on the manufacturing technologies is evident, which productivity and cost must keep under control to bring competitive products [5]. Additive manufacturing (AM) processes have been getting more attention for the manufacturing of complex Ti-6Al-4V and TiAl components in aeronautics [6,7,8]. Melting route is in demand because of its remarkable mass production and price reduction. This fact is mainly due to the implementation of the Induction Skull Melting (ISM) for the melting of such alloys [2]. An additional contribution to cost savings is the introduction of the recycling technology for

Methods

Discussion

Conclusion