Introduction:
Killed steels are a type of steel that is produced with a controlled amount of oxygen to ensure that the steel is free from any impurities. This process is essential to enhance the mechanical properties and overall quality of the steel.

Explanation:
Killed steels are produced by a specific steelmaking process known as the LD process, which stands for Linz-Donawitz process. This process involves the removal of impurities to obtain a high-quality steel product. There are several key characteristics of killed steels that make them desirable for various applications.

Minimum Impurity Level:
Killed steels have a minimum impurity level, which means they are produced with a controlled amount of impurities. Impurities, such as phosphorus and sulfur, can negatively affect the mechanical properties and overall quality of steel. Therefore, by minimizing the impurity level, killed steels offer improved strength, toughness, and weldability.

Zero Percentage of Phosphorus and Sulfur:
Killed steels have almost zero percentage of phosphorus and sulfur. Phosphorus can cause brittleness in steel, reducing its ductility and impact resistance. Similarly, sulfur can lead to the formation of sulfides, which can weaken the steel's structure. By minimizing these elements, killed steels ensure a high-quality product with enhanced mechanical properties.

LD Process:
The LD process is the most commonly used method for producing killed steels. In this process, a mixture of iron ore, limestone, and coke is fed into a blast furnace, where it is heated to high temperatures. This process helps to remove impurities, such as carbon, silicon, and manganese, from the molten iron. The molten iron is then transferred to a converter, where it is further refined and decarburized. The addition of a controlled amount of oxygen during the LD process ensures that all the impurities are removed, resulting in a high-quality steel product.

Free from Oxygen:
The key characteristic of killed steels is that they are free from oxygen. This is achieved by adding a deoxidizer, such as aluminum or silicon, to the molten steel. The deoxidizer reacts with the oxygen present in the steel, forming solid oxide compounds that float to the surface and are removed. This deoxidation process ensures that the steel is free from any residual oxygen, which can cause the formation of undesirable oxides and impede the steel's mechanical properties.

Conclusion:
In summary, killed steels are produced with a minimum impurity level and almost zero percentage of phosphorus and sulfur. They are manufactured using the LD process, which involves the removal of impurities to obtain a high-quality steel product. The key characteristic of killed steels is that they are free from oxygen, which is achieved by adding a deoxidizer during the steelmaking process. This ensures that the steel has improved mechanical properties and can be used for various applications.