The Degassing Technique for Cast Iron

Sulfur Content

• Sulfur is a naturally occurring contaminant that can be found in cast iron. Sulfur affects not only the hardness and strength of the finished product, but also plays a role in cast iron's ability to fend off rust. Varying levels of sulfur in a finished cast iron product will determine whether it is classified as gray cast iron or white cast iron.

Gray Cast Iron Vs. White Cast Iron

• Gray cast iron is the most used variety of cast iron as it is strong, can be effectively used for many different products and is durable. Gray cast iron has a low sulfur content, which makes it less prone to cracking, rust and breakage. White cast iron has a higher concentration of sulfur and has some industrial uses because it is actually harder than gray cast iron, but is limited in that it can break more easily.

Vacuum Degassing Technique

• Vacuum degassing is a process of removing gases by siphoning the air above the molten metal. Carbon monoxide and argon are introduced to molten steel and moved throughout the liquid metal. The additives, in addition to stirring of the mix eliminate the presence of sulfur and encourage the resulting sulfuric gas and other gasses to travel upward into the environment above the surface of the molten steel. A vacuum component is then utilized as it sucks the gas-laden air away from the molten steel, leaving it free of damaging contaminants. Once decontaminated, the metal can be poured and used in various manufacturing applications, and when cooled becomes cast iron.

Manganese Additive Degassing Technique

• Another technique for degassing cast iron is adding manganese to the mix. By adding manganese to molten steel in a proportion of up to 1 percent, sulfur is effectively eliminated or brought to an ineffective level, so that when cooled, gray cast iron is achieved.