Aluminosilicate refractories: fireclay bricks

Question 1

What are the three composition ranges of aluminosilicate refractories?

Answer 1

1. silica < 6 mol% Al2O3
2. fireclay: 6-60 mol% Al2O3
3. high alumina: > 72 mol% Al2O3

Question 2

What effect do high alumina compositions have on these refractories?

Answer 2

> raise eutectic liquid temp to 1840C with MULLITE and ALUMINA equilibrium phases

Question 3

How are fireclay bricks made?

Answer 3

> pressed from clay and grog

Question 4

What is grog? What are the phases of grog? What applications is it used for?

Answer 4

> PRE-FIRED CLAY AGGREGATE that FACILITATES REDUCED FIRING SHRINKAGE
mullite and cristobolite
lower temp applications in iron/steel manufacture

Question 5

What are pure mullite refractories made from? How are they made?

Answer 5

> mixtures like kyanite (metastable Al2O3*SiO2) and bauxite (hydrous alumina)
the aggregate is initially formed via sintering or fusion, then crushed, pressed, and sintered with low firing shrinkage

Question 6

What are the qualities of pure mullite refractories?

Answer 6

> high strength retention

Question 7

What are the qualities of pure AL2O3 refractories?

Answer 7

> formed from bauxite, have good volume stability to 1815C