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Micrograph 149 and full record
- Micrograph no
- 149
- Brief description
- Magnesia-chrome refractory brick
- Keywords
- aluminium
, brick , calcium , ceramic , chromium, iron, magnesium, silicon - Categories
- Ceramic
- System
- MgO-Cr2O3
- Composition
- MgO 70, Cr2O3 19, Al2O3 4, Fe2O3 4, CaO 1, SiO2 1 (wt%)
- Standard codes
- Reaction
- Direct bonded brick i.e. fine MgO and Cr<sub>2</sub>O<sub>3</sub> react to form MgCr<sub>2</sub>O<sub>4</sub> spinel bonds
- Processing
- MgO and Cr2O3 grain and finer bond powders pressed with organic binder and fired to 1850 °C in neutral atmosphere.
- Applications
- Secondary steel making e.g. high wear areas of vacuum degassers. Were used extensively in cement kiln linings but formation of carcinogenic Cr<sup>6+</sup> in use means they are no longer used.
- Sample preparation
- Polished but unetched.
- Technique
- Reflected light microscopy
- Length bar
- 100 μm
- Further information
- The micrograph shows the detail of the bond system which glues the large grain particles together. In particular, small (5mm) Cr2O3 precipitates are seen in the MgO. Fine particles react to form spinel which directly bond the aggregates conferring high temperature strength.
- Contributor
- Prof W E Lee
- Organisation
- Department of Engineering Materials, University of Sheffield
- Date
- 10/05/02
- Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International- Related micrographs
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