Killed steels are defined as those, which are thoroughly deoxidized during melting process. Deoxidation is accomplished by use of silicon, manganese and aluminium additions to combine with dissolved gases, usually oxygen, during steel making. This results in cleaner, better quality steel which has fewer gas pockets and inclusions.
Killed carbon steel is specified for major equipment in the following services to
minimize the possibility or extent of hydrogen blistering and hydrogen embrittlement:
- Where hydrogen is a major component in the process stream.
- Where hydrogen sulfide H2S is present with an aqueous phase or where liquid water containing H2S is present;
- Process streams containing any amount of Hydroflouoric acid (HF), boron trifluoride (BF3) or (BF) compounds; or
- Monoethanolamine (MEA) and diethanolamine (DEA) in solutions of greater than 5 weight percent.
Killed steel is also used for equipment designed for temperatures greater than (482 deg. C) since the ASME boiler and Pressure Code does not list allowable stresses for carbon steel over 900 deg. F (482 deg. C).