ON THE THERMO-PHYSICAL PROPERTIES OF MAGNESIA BRICKS

Abstract

The auther investigated the thermo-physical properties of the magnesia bricks, 2 of those are made in Germany, 3 of them are made in Japan, and the other 2 are made in the authers Laboratory.
The chemical composition of the bricks are as follows: by other small content and by the microstructure, considered possible minerals in the minerals are considered Tested thermo-physical properties are as following:
Specific gravity. porosity, absorption, coef. of thermal expansion, crushing strength normal and under heating, Softening pt, under the load. thermal conductivity, difusibility, specific heat.
The most inportant test for magnesia brick, the slake test is also made.
After examined these proper-ties, & compared with the literatures. The auther proposed the normal properties for the magnesia brick with will be used in open Hearth steel fr.
1. Chem. component. MgO 87-88% enough; CaO small as posible, SiO₂ under 2% Fe₂O₃ under 7%
2. Specific gr. above 2-8, porosity under 23%
3. Crushing strength will be 1000kg/cm², at & heated 1000°C. 500kg/cm² at least,
4. Thermal expansion coef. 1000°C 1.35%, 1300°C 1.95%, 1500°C, 2.1%; and at 1600°C it will be no contraction.
5. Softening pt. under load will be above 1450°C under the load of 2kg per. squar cm.
6. Sp. heat is at 400°C, 0.2241, at 600°C, 0.2448 at 1000°C, 0.2554: thermal conductivity is at 400°C 0.01024, at 650°C 0.00968, at 800°C 0.00939.
7. For spalling under sudden cooling, when tested by crushing strength 500kg/cm² after heating 1hr. at 1500°C and droped in the water at 18°C.
8. For slake test in the vapour press. of 1.5 atcs. it must hold the original figure at least 6hrs.