Spinel-bonded magnesite brick for high-tonnage electric arc furnaces

Conclusions

The manufacture of an experimental batch of spalling resistant magnesite-chrome brick with a spinel binder has made it possible to improve the technological norms for the production of these parts and has shown the possibility of making them at the new shop at the “Magnezit” Plant.

The parts produced show good characteristics: refractoriness-under-load of 2 kg/cm² — 1650–1720°; additional shrinkage during heating to 1650° with subsequent holding for three hours −0.1%; spalling resistance 7–13 water-heating-cooling cycles (heating to 1300°); apparent porosity 15–17%; compressive strength 620 kg/cm².

To obtain parts with good physical-chemical properties it is essential to use MK magnesite powder; to add at least 6–8% industrial alumina to the charge (in terms of Al₂O₃); to make certain the magnesite-alumina mixture is highly dispersed so that it helps to complete the spinel formation reaction during the firing; to use a mixture of the following grain composition: not less than 20% fraction 3–1 mm; 55–60% finer than 0.5 mm, including 30–35% finer than 0.06 mm; to press the parts at 1200–1500 kg/cm²; to fire the parts at a temperature not less than 1600°, batching them far apart so as to avoid the formation of an uneven structure.

The use of magnesite brick with a spinel binder for the walls of high-tonnage electric arc furnaces used to melt transformer steel ensures satisfactory strength of the walls in the slag belt and prevents the steel becoming contaminated with chromium.