Corundum spinel porous plug

At present, the materials of ladle vent bricks mainly include chrome corundum (spinel) and corundum spinel, which are usually prepared by casting molding and high temperature sintering process. Chromium corundum permeable bricks contain chromium, which will form Cr ⁶ ＋ and pollute the environment. Their output is getting smaller and smaller, and they are gradually being replaced by corundum spinel ladle permeable bricks. The corundum spinel castable combined with pure calcium aluminate cement has three kinds of high melting point mineral phases after high temperature sintering, namely calcium hexaaluminate (CA ₆, melting point 1890 ℃), aluminum magnesium spinel (MA, melting point 2100 ℃), and corundum (melting point 2050 ℃).

The tabular calcium hexaaluminate in the matrix forms a good combination with corundum or spinel, which makes this material have excellent slag resistance and high temperature strength. It is called the best matrix system, but its thermal shock resistance is relatively poor, which is easy to cause thermal spalling and structural spalling during use, limiting its service life. There have been many research reports on improving thermal shock resistance of corundum spinel materials, mainly including heat treatment temperature, particle size and addition amount of spinel, fine powder content, addition of ZrO2 or zirconium corundum, and addition amount of cement, as follows:

The flexural strength of corundum spinel castable at room temperature and the flexural strength and strength retention rate after 1300 ℃ air-cooled thermal shock increase first and then decrease with the increase of heat treatment temperature, and the thermal shock resistance of the sample after 1600 ℃ sintering is the best. After calcination at 1600 ℃. The damage caused by cyclic thermal shock at 1000-1600 ℃ is the most significant.

With the increase of ≤ 0.074 fine powder mass fraction (31%, 35%, 41%) in Al ∈ O ｜ - spinel castable, the residual strength of the sample after thermal shock decreased significantly. With the increase of the addition of fine spinel powder, the high temperature bending strength of corundum spinel castable gradually increases, and the thermal shock resistance becomes worse at first and then gradually improves; When spinel particles and fine powder are added, the thermal shock resistance is improved. With the increase of spinel particles and the decrease of fine spinel powder, the lattice constant of spinel becomes larger due to the solid solution to the spinel, and some microcracks will occur around the spinel and corundum, which improves the thermal shock resistance. On the other hand, it also causes a large permanent line change of the sample.

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