Directly bonded magnesia-chrome brick and fused magnesia-chrome brick are two common high-performance refractories, and they are significantly different in production technology, performance characteristics and application fields. The following is a detailed comparison:

I. Production technology

Directly bonded magnesia-chrome brick:

Using high-purity magnesia and chrome ore as raw materials, after high-pressure molding, it is sintered at a high temperature above 1700℃.

In the production process, by controlling the content of SiO₂ in raw materials (usually less than 2%), the formation of silicate liquid phase is reduced, and the direct combination between periclase and magnesia-chrome spinel is formed.

Fused and recombined magnesia-chrome brick;

Firstly, light burned magnesia and chrome ore are melted by electric arc furnace to make fused magnesia-chrome sand, and then it is crushed, ground, blended, shaped and sintered.

In this process, magnesia-chrome synthetic materials with complete spinel, high direct bonding rate and uniform phase distribution are prepared in advance by means of electric melting method.

II. Performance characteristics

Directly bonded magnesia-chrome brick:

High high-temperature strength: due to the direct combination between periclase and magnesia-chrome spinel, high high-temperature mechanical strength.

Good slag resistance: low silicate content reduces the penetration and erosion of slag.

Excellent thermal shock stability: able to withstand large temperature changes.

Fused and recombined magnesia-chrome brick;

Higher corrosion resistance: because of its high purity of raw materials and electrofusion treatment, it has better corrosion resistance.

Higher load softening temperature: suitable for higher temperature working environment.

Thermal shock resistance is slightly worse: compared with directly bonded magnesia-chrome bricks, its thermal shock resistance is slightly lower.

III. Microstructure

Directly bonded magnesia-chrome brick:

In the microstructure, silicate liquid phase is isolated and dispersed between the main crystal grains, and a continuous matrix structure cannot be formed.

There is a direct bond between periclase and magnesia-chrome spinel.

Fused and recombined magnesia-chrome brick;

The matrix is mainly fused magnesia-chrome sand, which is in a dense network shape, with direct bonding between refractory grains and no silicate bonding phase.

IV. Application areas

Directly bonded magnesia-chrome brick:

Widely used in RH and DH vacuum degassing devices, VOD furnaces, AOD furnaces and other external refining devices.

Fused and recombined magnesia-chrome brick;

Suitable for high erosion areas such as the middle and lower grooves of RH furnace.

It is also used in harsh parts of refining equipment such as AOD and VOD.

V. Cost and cost performance

Directly bonded magnesia-chrome brick:

The production cost is relatively low and the cost performance is high.

Fused and recombined magnesia-chrome brick;

Due to the adoption of the electrofusion process, the production cost is high.

VI. Summary

The direct combination of magnesia-chrome brick and fused magnesia-chrome brick have their own advantages, which should be weighed according to the specific working conditions. If the working conditions require high temperature strength and corrosion resistance, it is suggested to choose fused magnesia-chrome brick; If more attention is paid to thermal shock stability and cost control, it is a better choice to directly combine magnesia-chrome bricks.