Calcium in Steels

Calcium in Steels Calcium (Ca) (atomic number 20 and atomic weight 40.08) has density of 1.54 gm/cc. Melting point of Ca is 842 deg C and boiling point is 1484 deg C. Ca additions are made during steel making for refining, deoxidation, desulphurization, and control of shape, size and distribution of oxide and sulphide inclusions . Ca is not used as alloying element since its solubility in steel is very low. Further it has a high vapour pressure since it boiling point is lower than the temperature of the liquid steel. It has a high reactivity and hence special techniques are necessary for its introduction and retention  of even a few parts per million in the liquid steel. Advantages directly attributable to Ca treatment include greater fluidity, simplified continuous casting and improved cleanliness (including reduction in nozzle blockage), machinability, ductility and impact strength in the final product. Available forms Ca is added to steel in the stabilized forms of calcium silicon (CaSi), calcium manganese silicon (CaMnSi), calcium silicon barium (CaSiBa) and calcium silicon barium aluminum (CaSiBaAl) alloys or as calcium carbide (CaC2). Elemental Ca is difficult and dangerous to add to liquid steel. CaSi in steel sheath (also called cored wire) is the most commonly used addition agent for Ca addition. The cored wire is injected into the liquid steel with help of wire injection system. It has higher recovery of Ca in steel than the virgin Ca / CaSi lumps addition into the ladle. The CaSi cored wire contains 4.5 % of iron (Fe) and 55 % to 65 % of Si. Ca content is usually in three ranges of 28 % to 31 %, 30 % to 33 %, and 32 % to 34 %. It contains around 1 % carbon (C)...