High-grade refractories with low porosity

Porosity is the basic technical index of most refractory materials, and its size affects almost all the properties of refractory materials, especially strength, thermal conductivity, slag resistance and thermal shock resistance. High-grade refractories with low porosity recommend magnesia bricks to you. The porosity of refractory bricks increases and the strength decreases, which is not only due to the decrease in the cross-sectional area of the solid and the actual stress increases, but also the pores are defects of the material, which will cause stress concentration and reduce the strength, and the influence of coarse pores is more significant. The increase of porosity can significantly reduce the thermal conductivity, and the atmospheric porosity increases the penetration of slag to the product.

Low porosity refractory bricks

Magnesia chromium brick with magnesium oxide (MgO) and chromium trioxide (Cr2O3) as the main components, magnesia and spinel as the main mineral components of refractory products. This kind of brick has high refractory degree, 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 bricks are sintered magnesia and chromite. The purity of magnesia raw materials should be as high as possible, and the requirements for the chemical composition of chromite are: Cr2O3: 30~45%, CaO: ≤1.0~1.5%.

The fine powder made after calcination with chrome ore-magnesia co-grinding billet, and the method of brick making with magnesia coarse particles, is an effective measure to eliminate the loose effect. Compared with ordinary magnesia chromium bricks, the porosity of the bricks is low, and the compressive strength, load softening temperature and flexural strength are higher. Magnesia bricks made of chrome ore-magnesite powder compacted and synthetic magnesia chromium sand calcined at high temperature have better slag resistance and high temperature strength than other magnesia chromium bricks.

In addition, the high-grade refractory materials with low porosity also include the molten magnesium chromium brick obtained by direct casting of the molten magnesium chromium material in the electric solitary furnace, and the molten particles produced by the electrofused magnesium chromium material according to the brick making process and then combined with the magnesia chromium brick.

It can be seen from the study that the high temperature strength change law of magnesium-chromium refractories of different processes is as follows: silicate combined with magnesium-chromium refractory < directly combined with magnesium-chromium refractory < semi-combined magnesium-chromium refractory < electrofusion and then combined with magnesium-chromium refractory. Since the high temperature flexural strength mainly represents the bonding of various minerals in the brick, this indicates that the bonding strength of electrofusion combined magnesia chromium brick is the largest, so its erosion resistance and erosion ability is the best at high temperature.

Since the permeability of the liquid phase between different grains is lower than that between the same grains, when the liquid phase content is fixed, the appearance of the second solid phase will increase the solid-solid contact, thereby improving the high temperature strength of the brick. In the production of electrocautery combined magnesia chromium bricks or semi-combined magnesia bricks, pre-synthetic magnesia chromium sand is added as raw material, thereby increasing the content of the second solid phase and increasing the high temperature strength of the bricks.