Affects of Firing on MgO-C Bricks Performance and Structure

MgO-C brick performance will change greatly due to different firing conditions.
In order to study the mechanism of MgO-C changes in performance, Japan Kurosaki Harima company's technical staff make
8% lower graphite-based MgO-C brick as test material, by changing the firing time to investigate the thermal shock resistance of MgO-C, the matrix organizational structure and changes in composition distribution.

 

Sample Mgo-C brick is of 8% flake graphite and fused magnesia 92, plus 1% of aluminum metal powder, fired at 1400 ℃ for 10h and 30h.

 

Then look at the sample thermal shock resistance and organizational changes. Thermal shock test specimen is immersed in the molten iron 1600 ℃ 90s, and then cooled 30s, 3 cycles,
Compare the case of the test piece cracks appearance and cross section appears. Microstructure of the matrix using FE-SEM, EDS observation.

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Sectional image of the test sample after the thermal shock shows that 30h firing sample is with obvious cracks and poor thermal shock resistance.

 

Micrograph shows that the distribution of matrix of aluminum, magnesium, silicon, calcium After 30h fired sample,
the original fine powder of magnesium, silicon and calcium are still there.

 

This indicates that, due to the long time baking, the second combine is active in matrix, coupled with a high impurity content,
causing low melting material sintering, resulting in increased of elastic modulus, so thermal shock resistance is lowered.

 

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