6. Choose the correct answer

i)  The most powerful dexodizer for steel is

(a) Silicon

(b) Magnesium

(c) Aluminium

(d) Chromium

ii) Calcium carbide injection is done

(a) To remove hydrogen gas

(b) To increase calcium content of steel

(c) To modify inclusions

(d) To remove sulphur from hot metal

iii) Calcium silicide injection into liquid steel is done mainly for

(a) Deoxidation

(b) Inclusion modification

(c) Dehydrogenation

(d) Dephosphorizarion

iv) Hydrogen in liquid steel is dissolved

(a) In the form of tiny gas bubbles

(b) In atomic form

(c) In molecular form

(d) In ionic form

v) In a good rimming steel

(a) Carbon and silicon content should be low

(b) Silicon content should be low but carbon cintent should be high               

(c) Both Carbon and silicon content should be high

(d) Silicon content should be high but carbon cintent should be low

vi) Activity of   in the steelmaking slag is lowered by

(a) Increase in slag basicity

(b) Decrease in slag basicity

(c) Increase in bath temperature

(d) None of the above