Carbon Equivalent of forged flanges

[MaxNeg63]

Our supplier is proposing a carbon steel F52 forged flange with a CEV of 0.42, while our client specification is asking for 0.39 saying that the line is sour service. In my personal opinion once we adopt a welding procedure capable to maintain hardness below 22HRc (248 HV10) the request for 0.39 is meaningless (considering also that the supplier has already said he cannot reach such value!)
Anybody has more experience on this subject?
Thanks

 

[metengr]

This is not necessarily true, and your supplier is not exactly the best source of information (trust but verify). The alloy element that directly effects carbon equivalent of steels is carbon content. The higher the carbon content, the higher the strength both before and after post weld heat treatment.

In this case, your client is absolutely correct in specifying an upper limit to CE for base metals. Just because you are using a weld procedure that has been qualified will not assure you will have 22 HRc after welding.

 

[MaxNeg63]

Thanks metengr. Fact is that carbon content is well below the prescribed limit as are contents of all the other alloy elements with the exception of Vanadium which is above the maximum of 0.02% and this brings CE to 0.42.
Besides supplier gives us the flange but we will perform all welding qualification therefore we will be able to verify if after welding harness is <22HRc or not

 

[metengr]

MaxNeg63;

with the exception of Vanadium which is above the maximum of 0.02% and this brings CE to 0.42

The vanadium concerns me because it promotes increased resistance to softening (hardness reduction) during and after thermal treatment (such as PWHT). I totally agree with your approach to qualify this material.

 

[SJones]

Speaking as a 'client' myself, I would tell you to go and find a flange supplier that can comply with the CEV requirement. There are plenty in the world but, unfortunately for contractors, they may not be the cheapest. This is only F52 not F65+!

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/