Magnesia chrome bricks are called by different production processes

Similar to most nonferrous metal kilns, ISA furnace is mainly composed of furnace bottom, furnace shaft and furnace top.

The bottom of ISA furnace is reverse arched and inclined to the discharge port by about 2%, which can also be built into a flat bottom. The total thickness of the furnace bottom is about 8001000mm, which is generally made of clay bricks, magnesia chrome bricks and magnesia chrome ramming materials.

The following conditions shall be met before the masonry of ISA furnace:

(1) The roof of the workshop around ISA furnace has been installed and can be protected from rain and snow;

(2) After the installation of the worktable in front of the furnace, it can be used as the material stacking site for bricklaying;

(3) All metal components of furnace body have been installed;

(4) All installed cooling parts have passed the on-site pressure test;

(5) There is a position for installing hoisting equipment;

The preparation work fully meets the construction requirements and safety requirements.

1. What is magnesia chrome brick?

Magnesia chrome brick is a refractory product with magnesia (MgO) and chromium trioxide C, O as the main components and periclase and spinel as the main mineral components. This kind of brick has high fire resistance, high temperature strength, strong resistance to alkaline slag erosion, excellent thermal stability, and certain adaptability to acid slag. The main raw materials for manufacturing magnesia chrome bricks are sintered magnesia and chromite. The purity of magnesia raw material should be as high as possible, and the chemical composition of chromite should be: C, O, 30%~45%, and Cao should not be greater than 1.0%~1.5%. The production process of magnesia chrome brick is similar to that of magnesia brick. In order to eliminate the loose effect caused by the expansion of spinel formed by the reaction of Mo and C, O, a, O, or iron oxides during the firing process of bricks, the synthesized common sinter can also be used to make magnesia chrome bricks. In addition, there are unfired magnesia chrome bricks, for example, unfired magnesia chrome bricks combined with inorganic magnesium salt solution. Unburned magnesia chrome brick has the advantages of simple production process, low cost and good thermal stability, but its high temperature strength is far less than that of fired brick. In the late 1950s, a so-called "direct bonding" magnesia chrome brick was developed. This kind of brick is characterized by pure raw materials, high firing temperature, direct combination between high-temperature phases such as periclase and spinel, and isolated island distribution of low melting phases such as silicate. Therefore, the high-temperature strength and slag resistance of the brick are significantly improved.

It is an effective measure to eliminate the loosing effect by using the fine powder produced by CO grinding and calcining the compact with chrome ore and magnesia and mixing it with coarse magnesia particles to make bricks. Compared with ordinary magnesia chrome bricks, magnesia chrome bricks made by this method have lower porosity, higher compressive strength, load softening temperature and flexural strength. The magnesia chrome brick made of synthetic magnesia chrome sand calcined at high temperature with chromite magnesia powder compacts has better slag resistance and high temperature strength than other magnesia chrome bricks.

In addition, there are fused magnesia chrome bricks produced by direct casting of fused magnesia chrome materials in an electric arc furnace, and fused magnesia chrome bricks produced by the electric fused magnesia chrome materials according to the brick making process.

Magnesium chromium bricks are mainly used in the metallurgical industry, such as the construction of open hearth furnace top, electric furnace top, external refining furnace and various non-ferrous metal smelting furnaces. The high-temperature part of the ultra-high power electric furnace wall is made of fused magnesia chrome bricks, the high erosion area of the refining furnace outside the furnace is made of magnesia chrome bricks made of synthetic materials, and the high erosion area of the non-ferrous metal flash smelting furnace is made of fused magnesia chrome bricks and magnesia chrome bricks made of synthetic materials. In addition, magnesia chrome bricks are also used in the firing zone of cement rotary kiln and the regenerator of glass kiln.

2. What are the classifications of magnesia chrome bricks according to the production methods?

Magnesia chrome brick is an alkaline refractory product containing 55%~80% MgO and 38%~20% C and O, which is composed of periclase, composite spinel and a small amount of silicate phase. Composite spinels include spinel solid solutions such as MgAl₂O₄, MgFe₂O₄, MgCr₂Oa and FeAl₂O₃

Magnesia chrome bricks have developed rapidly since the 1960s due to the improvement of raw material purity and firing temperature. At present, magnesia chrome bricks can be divided into ordinary bricks, directly bonded bricks, CO fired bricks, re bonded bricks and fused cast bricks according to different production methods.

(1) Ordinary magnesia chrome brick

This is a traditional product, with chrome ore as coarse particles and magnesia as fine powder. Or the two materials are composed of graded particles, and the firing temperature is generally 1550~1600 ℃. The microstructure of this brick shows that there is little direct bonding between chromite particles and periclase, and most of them are silicate (CMS) cementation or fracture isolation; There are few desolved phases in periclase and few direct bonding in the matrix. This kind of brick has poor mechanical properties and slag corrosion resistance.

(2) Directly bonded magnesia chrome brick

The direct bonded magnesia chrome brick is developed on the basis of ordinary magnesia chrome brick. Its production features mainly have two points, one is the use of pure raw materials, the other is the use of higher firing temperature. The so-called direct bonding means that there is more direct contact between chrome ore particles and periclase in the brick, because there is less 502 in the raw material (controlled below 1%~25%), less silicate is generated, and the silicate is extruded into the corner of the solid particles by means of high-temperature sintering. So as to improve the direct bonding of solid phase.

Easygoing refractory:

Due to the high degree of direct bonding, the directly bonded magnesia chrome brick has high high temperature strength, slag resistance, erosion resistance, erosion resistance, excellent thermal shock stability and volume stability at 1800 ℃.