316 Dual grade material

[Bmechz]

One of our client is asking us to use 316(Dual grade) material for Div-2 vessel and they need mechanical properties of material as per 316 and chemical composition as per 316L(carbon content less than 0.03%).
I believe that the mechanical design of the vessel shall be based on 316L allowable stress, because if we reduce the carbon content then automatically the strength of the material will also reduce.
Kindly correct me if I am wrong.
Our client is insisting us to consider 316 material allowable stress instead of 316L to reduce the flange rating and thickness.
Can anybody ensure me that we can get the material with mechanical properties of 316 and chemical properties as per 316L.


Baijuz

 

[fegenbush]

Baijuz,

Dual grade is exactly what you are asking for. It will meet the requirements of both 316 (including tensile and yield strength) and 316L (including chemical composition). It is quite possible and common.

 

[JStephen]

I believe in the design, you can treat it as either one, provided it is treated consistently all the way through. (IE, you can't assume one grade for notch toughness and then assume it's the other grade for allowable stress).

"because if we reduce the carbon content then automatically the strength of the material will also reduce."- If they kept the composition identical, it would, but they are able to vary the other alloying metals within the allowable range of the standards and still meet the strength requirements.

 

[GenB]

Use 316 for ASME. Provide proof of L to the customer.

 

[EdStainless]

The only time that this a bad idea is when you are near the creep limit line.
The 316L may have room temp properties much higher than required for 316, but it will have lower creep strength.
If you are getting near that temp then you need to specify 316H.

If you go out and buy 316 (straight grade) in Western Europe, North America, or Japan you will get 316L, almost every time.
There is very little metal produced that is between 0.03% and 0.05% C.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube