Engineering Materials
Duralumin contains

3.5 to 4.5% copper, 1.2 to 1.7% manganese, 1.8 to 2.3% nickel, 0.6% each of silicon, magnesium and iron, and rest aluminium
4 to 4.5% magnesium, 3 to 4% copper and rest aluminium
3.5 to 4.5% copper, 0.4 to 0.7% magnesium, 0.4 to 0.7% manganese and rest aluminium
5 to 6% tin, 2 to 3% copper and rest aluminium

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Engineering Materials
The brown smoke during the operation of a Bessemer converter indicates that the

Air is burning out silicon and manganese
The converter must be titled to remove the contents of the converter
The brown smoke does not occur during the operation of a Bessemer converter
Silicon and manganese has burnt and carbon has started oxidizing

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