The colour of Acid Open-Hearth furnace slag changes according to the refining condition, so it is very important to judge the properties of molton metal and the condition of slag. Though Mr. Sisco and Mr. Hamilton publisheda deciding article to some extent, I was not be satisfied with it and has gained a different result after some research.
The Colour of Slag changes according to the degree of Oxidation, amounts and kinds of Chemical Content. The stronger the Oxidation, the darker the Slag colour, and at length it becomes Black. FeO which is a light coloured low grade Oxide cau be easily reduced; Fe
3O
4 and Fe
2O
3 which is a thick coloured high grade Oxide cau be hardly reduced. For this reason, it must be avoided to act a strong Oxidising flame.
Next, the Color of Slag chiefly due to Iron Oxide (FeO) and as the percentage of Iron Oxide in the Slag decreases the Color of Slag becomes lighter. and the Color is changed by the amount of manganese Oxide (MnO). It is green as the amount is relatively low, but becomes to broun by increasing its amount, and again increasing its amount it becomes light yellowish green.
After all, on the Color of Slag, light yellowish green which is induced by the large amount of manganese Oxide is most desirable. But from the point of view of economy, brown is the best one.
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