Let us consider the evolution of CO gas. According to equation 9,

12 Kg C produces 22.4 CO (1 atm and 273K)

1 Kg C produces 1.87  CO (1 atm and 273K) which is equivalent to 12.83 CO (1 atm and  1873 K)

Now for 1000 Kg hot metal and 0.2% carbon in steel

CO production would be 488  (1atm, 1873 K) / ton of hot metal. This volume of CO will evolve no doubt over a period of time but at any time large amount of CO will be escaping the system. Escaping of this gas will agitate the bath and contribute to enhanced rates of mass transfer reactions. Also care must be taken for the easy and unhindered escape of CO gas from the vessel failing which foaming and eventually expulsion of slag may occur.

Rimming reaction

Other aspect of carbon reaction is the evolution of CO during solidification of steel. As the temperature of molten steel decreases from 1873K to 1773K,  increases from 494 to 532 which results in decrease in    as steel cools. This will lead to CO evolution during solidification and is called rimming reaction. Rimming reaction induces stirring in the solidifying liquid steel and minimizes segregation of solutes.

Reference

• A. Ghosh and A. Chatterjee; Ironmaking and steelmaking
• R. Tupkary et.al. Modern methods of steelmaking
• A.K.Chakrabarti: Steelmaking