"KILLED STEEL"? 2

[11echo]

I'm looking at pipe material, inparticular A106-B & A53-B. I've been told these are identical materials only that testing process is different on materials. ...So I've been trying to look up the characteristics of each. The A106-B says it's made from "killed steel". At's OVER MY HEAD, what are they saying in layman language? THX! ...Mark

 

[TVP]

A killed steel means that it has been fully deoxidized. Al is frequently used for this purpose, usually as the last step before moving to the ladle metallurgy station where other alloying elements are added, etc.

 

[unclesyd]

I would change TVP's statement to strongly deoxidized instead of fully. This is done in the mill in an attempt to get more uniform chemical and mechanical properties.

 

[stanweld]

A-106 B seamless pipe deoxidixed with addition at least .10%Silicon.
A-53 B may be seamless or welded pipe; deoxidized, partially deoxidized or nondeoxidized - since the strong deoxidizing elements, silicon and/or aluminum, are not controlled.
The term "killed" originally referred to the appearance of the molten steel. Non deoxidized molten steels appear to boil and bubble (or act lively) as oxygen chemically reacts with the molten steel while the highly deoxidized steels appear still and quiet or "killed".

 

[Metalguy]

And what counts for the designer/spec. writer is that killed steels *usually* have much better low-temp. impact/toughness properties.

 

[limct]

Both TVP and Unclesyd are correct. Killed steel is a steel which has been "strongly deoxidised" by the addition of Al and Si, all the voids then are kept at the upper section. By parting away this upper section, the usable portion can be considered as "fully deoxidised".

 

[Mike450]

Killed steel is as has been described earlier a steel which has had Al & or Si added to tie up the soluble oxygen so that the ingot or billet does not contain gross cavities. It was eloquently described to me as lowering the dissolved oxygen to a level where it will no longer react with the carbon in the steel (this reaction is referred to as the carbon boil) Prior to continuous casting the steel mills made balanced steels, and rimming steels in ingots where the gas bubbles were at the skin and contributed to a clean smooth surface when the ingot was later rolled into sheet.
Oxygen can also be removed exclusively by vacuum treatment of the liquid steel (to "kill" it). Without controlling the oxygen content, the mechanical properties would not be attained and alloy additions would be wasted.