316 for high temperature application?

[arunmrao]

I have received a drawing for a small casting (60 mm round 300 mm long) used in a heating furnace for temperatures of 800 Celsius. The material ordered is 316. This is being used as it was supplied by OE .

I have suggested Gr HH ASTM A297 for this purpose. This will be a cheaper and more suitable instead of using expensive 316 alloy.

The customer insists on 316 please suggest if it is ok?

 

[metengr]

arunmrao;
What is the furnace atmosphere, and will it be cyclic operation?

 

[arunmrao]

It is a cyclic operation. atmosphere I am not too sure,but they stack electric motor stampings after rivetting them. The complete process is not known to me .

Essentially I am in the parts or spares business and thus I need to compete with many others like me.

 

[metengr]

Well, one of the available reference materials that I have at the moment to provide information has a published scaling temperature for 316 SS of 850 deg C in air.

Since you are close to this temperature in operation, and you are dealing with cyclic operation and possible fumes from stamped parts, I would agree with your recommendation on using the ASTM A 297 Grade HH material to provide added margin for scaling temperature.

In addition to scaling, the 316 SS will warp because of the drop off in mechanical properties at 800 deg C and will have a shortened life in comparison to the cast, heat resistant grades of SS.

 

[arunmrao]

Thanks metengr. I fail to understand why designers specify 304 or 316 for such applications.We are abusing a low carbon material (I always value it) which can instead be put to better use.

Hope mcguire emhasises this in his book about wasteful specifications and recommendations too!!

 

[mcguire]

Arunmrao
No small reason for the book is the sheer volume of misuse and over- and mis-specification of stainless. Part of the reason for this is that the technical expertise of the mills is separated from the end users by the service centers. They are a very effective barrier to technical knowledge.

I will try to have sections on all relevant categories of end use with as much truly pertinent information, technical and economic.