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Calcium aluminum treatment

Does anybody out there have a clue of what this is "calcium aluminum treatment". Its being called up on a drawing. The part is made of aisi 4340 Q.T.

Gerry Piccone
manufacturing, aircraft simulators - Canada
April 22, 2008

I'm hoping that someone out there could help me with this. I have a stainless steel shaft made from AISI E 4340. The shaft has no finish on it. It does have a manufacturing option to perform a calcium/aluminum treatment. I have no clue what this is? I'm not an expert in this field. Normally, we perform a pasavate finish on some types of stainless. Is this the same thing?

One last point. These shafts have surface rust. Is it possible that the calcium/aluminum treatment provide a protective finish to avoid this surface rust?

Any help would be great.

By the way, these shafts are being used on a aircraft simulator.


Gerry Piccone
manufacturing, aircraft simulators - Canada
April 23, 2008

First, 4340 steel is not stainless, so it will corrode/rust just like any typical carbon or alloy steel without some type of surface protection. With regards to "calcium aluminum treatment", this is referring to the steelmaking process, and not any type of coating/surface treatment. Steel is typically deoxidized with either silicon or aluminum, with the product usually being referred to as silicon killed or aluminum killed. I believe that the drawing note is indicating that the 4340 steel should be deoxidized with aluminum. Calcium treating steel is a method for modifying the non-metallic inclusions so that they are less detrimental for fracture toughness. Instead of long "stringers", the inclusions are short and discontinuous.

Toby Padfield
Automotive module supplier - MI, USA
April 28, 2008

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