Explain what is meant by a killed steel and a semikilled ste

Explain what is meant by a “killed steel” and a “semi-killed” steel and describe the forms of porosity that exist in each type.

Solution

Carbon steel is catagorized into 4 types. and they are killed steel,semi-killed steel,capped steel,rimmed steel

Killed steel:This steel is full deoxidized.Oxygen is removed completely due to the adding of an agent before casting.So there is no evalution of gas during solidification.So it is free from porosity.These types of steels are free from blow holes and segregation.

Semi-killed steel: More gas is evolved in semi-killed steel than in killed steel. But less than capped and rimmed.Incompletely deoxidized steels containing some amount of oxygen which forms CO during solidification. Structural steels containing 0.15 to 0.25% carbon are generally semi-killed.In semi-killed , the aim is to produce metal free from surface blow hole and pipe.These type of steels are suitable for drawing process.