Introduction of magnesite(3)

In order to use mineral resources scientifically, reasonably and economically, the Ministry of Metallurgy re-established the industrial standard YB/T 5208-1993 of magnesite in 1993. The standard adds a new grade LMT1-47, w (MgO) ≥ 47%, w (CaO) ≤ 0.5%, w (SiO2) ≤ 0.5%, w (Al2O3 + Fe2O3) ≤ 0.6% (including w (Fe2O3) ≤0.4%).

Magnesite is decomposed into brucite, MgO and CO2 at 670～680℃. The melting point of brucite is 2800℃, which is a high melting point oxide. It is used as an alkaline refractory raw material for its low-grade value. After purification, it can be used in chemical industry And electrical materials.

There are two methods of heat treatment magnesite: sintering and fused. In the refractory industry, they are called sintered magnesia and fused magnesia. The former is divided into low-temperature sintering (light burning) and high-temperature sintering (dead burning), neither of which is fixed. Temperature range, so the crystal size and volume density are significantly different. High-temperature sintered magnesia is more difficult to sinter because of the higher purity of the original ore, so there are two-step sintered materials that are firstly burned at low temperature and then crushed into balls and then sintered at high temperature, which is beneficial to densification and crystal growth.

There is a large crystallization desire for fused magnesia, which seems to be one-sided, and it is not possible to determine how much benefit is made to the quality and use effect of refractory products. All types of magnesia are graded according to MgO content.

The current fused magnesia has different raw material composition and structure in the same furnace, and needs to be manually selected: the pure white material in the center part has a very high purity, up to >99.5%, and the crystal can reach the centimeter level, even single crystal, can be used for Electrical materials; furnace side material is rich in impurities, commonly known as "skin sand", and the quality is not as good as sintered material.