EFFECT OF FURNACE ATMOSPHERE
Furnace atmosphere influences in following ways:
- The furnace atmosphere might be oxidizing or reducing. In case if the atmosphere is oxidizing than it favours oxidizing processes and in case of reducing nature it promotes reduction processes.
- The furnace atmosphere might content harmful impurities which if mixed with product might cause unwanted reactions and properties.
- In most cases, the furnace atmosphere is oxidizing, and therefore, oxygen can pass continuously from the atmosphere to metal.
PASSAGE OF OXYGEN FROM GASEOUS PHASE TO METAL
The passage of oxygen from the gaseous phase through slag to metal can occur in the following ways:
- By direct contact of oxidizing phase with metal.
- By beads (droplets) of molten metal which are always present in slag.
- Due to oxygen transfer from gaseous phase through slag to metal.
BLOWING METAL WITH OXYGEN OR AIR
When the bath is blown with air or oxygen, the furnace atmosphere also contains gas bubbles (O2, N2, CO, etc) which have passed through the bath. With a low intensity of blowing, gas bubbles simply pierce the bulk of the metal and, in case ,if blown with higher intensity metal droplets may turn out to be suspended in the gas flow.
OXIDATION OF CARBON
Steel making process almost always involves the reaction of carbon oxidation; which is one of the main reactions of the process. During oxidation of carbon, i.e. burning off of carbon, the metal is said to be ‘boil’, which is due to evolution of carbon monoxide. Bath boiling results in agitation of the metal, equalization of it’s composition and temperature, and increased surface of contact between metal and slag, which in turn accelerates all process at the metal slag interface.