scope:

This part of ISO 21068 gives definitions and specifies techniques for the preparation of samples for the chemical analysis of silicon-carbide-containing raw materials and refractory products including:

graphite brick containing silicon carbide;

silicon carbide brick (includes the bricks containing silicon nitride);

refractories containing carbon and/or silicon carbide mixed with clay;

refractories containing carbon and/or silicon carbide mixed with silica (and fused silica);

refractories containing carbon and/or silicon carbide mixed with high alumina material;

refractories containing carbon and/or silicon carbide mixed with magnesia (and dolomite);

refractories containing carbon and/or silicon carbide mixed with chrome mineral or magnesia-chrome materials;

refractories containing carbon and/or silicon carbide except those described in a) to g) above.

The items of chemical analysis described in ISO 21068, Parts 1 to 3 are as follows:

loss on drying (LOD);

loss on ignition (LOI);

total carbon, C_total;

free carbon, C_free;

silicon carbide, SiC;

free silicon (Si_free);

free aluminium (Al_free);

free magnesium (Mg_free);

free iron (Fe_free);

silicon(IV) oxide (SiO₂);

aluminium oxide (Al₂O₃);

iron(III) oxide (total iron oxide calculated as Fe₂O₃);

titanium(IV) oxide (TiO₂);

calcium oxide (CaO);

magnesium oxide (MgO);

sodium oxide (Na₂O);

potassium oxide (K₂O);

chromium(III) oxide (Cr₂O₃);

zirconium oxide (ZrO₂);

boron oxide (total boron calculated as B₂O₃);

nitrogen;

oxygen;

nitrides (undifferentiated: Si₃N₄, AlN, BN, sialon, oxy-nitrides, etc.).