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Oxidation of MgF
2
Particles in SF
6
/Air Atmosphere at High
Temperatures
H K Chen
*
, L Chang and Y Y Jie
Baoji University of Arts and Science, Baoji 721013, PR China
Corresponding author and e-mail: H K Chen, hk7115@yahoo.com
Abstract. High temperature o xidation of MgF
2
particles in the atmosphere of air containing
different concentrations of SF
6
were studied by using XRD and EDS. The results show that
the oxidation of MgF
2
in SF
6
/air at mosphere was mainly related to the concentration of SF
6
,
temperature and reaction time. In the at mosphere of air containing higher SF
6
concentration,
MgF
2
underwent a very weak oxidation. With the decrease of SF
6
concentration, the increase
of temperature and the prolongation of reaction time, the degree of MgF
2
oxidation increased.
The particle size o f MgF
2
and the mixed gas flow have little effect on the high temperature
oxidation of MgF
2
. The results can provide a theoretical basis for the study of the protection
mechanism of SF
6
gas on magnesium and its alloy melt.
1. Introduction
Magnesium and its alloy are being widely used in the automotive industry, aerospace industry, 3C
products and other fields due to their excellent properties such as low density and high specific
strength. However, magnesium is a very active element. It has extremely high affinity for oxygen and
high vapor pressure, which causes molten magnesium to rapidly oxidize in air. Therefore, it is
necessary to take measures to prevent the melt from oxidizing or burning in the process of melting
and casting operations. Many methods have been investigated to inhibit the oxidation of molten
magnesium and its alloy in air. Among them, the protection method of SF
6
gas is considered to be the
most effective method [1]. The protection of SF
6
gas for magnesium and its alloy melt is based on a
dense MgF
2
and MgO composite protective film on the surface of the melt. MgF
2
, as a major
component of the film, plays a key role in the protection of magnesium melt against its combustion
by SF
6
and other fluorine-containing gases [2-4].
It is generally believed that MgF
2
is a stable compound under normal circumstances. However,
some studies have found that MgF
2
become less stable at high temperatures in air and it has a
tendency to change to MgO [5, 6]. In a previous study, we also found this phenomenon [7,8]. In
SF
6
/air atmosphere, whether MgF
2
will oxidize at high temperatures and what rule it follows if the
oxidation occurs, these problems are unclear. In view of the important role of MgF
2
in the protection
of magnesium melt by SF
6
, it is necessary to study the high temperature oxidation behavior of MgF
2
in the atmosphere. In this work, the oxidation characteristics of MgF
2
particles in SF
6
/air atmosphere
at high temperatures were studied. The effects of the concentration of SF
6
, temperature, and reaction
time on the oxidation characteristics were investigated. The purpose of this paper is to elucidate the
Chen, H., Chang, L. and Jie, Y.
Oxidation of MgF2 Particles in SF6/Air Atmosphere at High Temperatures.
In Proceedings of the International Workshop on Materials, Chemistr y and Engineering (IWMCE 2018), pages 507-512
ISBN: 978-989-758-346-9
Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
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