Welding Higher Carbon Steels

1. Since you are on pressure vessel, this type of alternate plate is usuallly not in order.

2. Ceq of 0.47 will bring it to almost the same category, ie medium carbon steel.

However even if you establish the WPS for this, it is most likely not acceptable especially since it may be a stamped vessel (as is almost definite by the plate thicknesses)

However you may like to have a look on this paper

http://www.technonet.co.kr/qa/files/Ceq-Pcm.pdf

Don't due it.

You have no authority to disregard client spec.

milo

You may make a test welding with the proceedures for Cev=0.43 and test both radography and ultrasonic. If both pass, the WPS is ok.

Have you thought of a Hf weld/heat for this. You will have better control over welding parameters with the ability to vary the frequency based on material properties. Would need to know plate width and speed. It will also give you the advantage of a truely forged weld. Let me know if you need more help.

I am really just speculating here without doing research in the ASME code books but you will probably have to raise your pre heat to 350-400 degrees F and maintain a min. inter-pass temp. of 350 during welding. I would suggest using a controlled type of pre heat so that you can keep the item very close to the required temp. and do a very slow cooling after welding is complete. Once X-ray or other NDT is performed and the welding has been accepted then a post weld stress reliving will probably be required. You will write your WPS and then your PQR to have the pre and post weld heating included but it will not be necessary to qualify new WPQ's on your welders as long as they are qualified on this P number material IMO. The main thing is to do your research in the code books and get client approval before going forward.

When welding such HCE steels one needs to be cautious about the interpass temp & time the weld is held there, lest grain coarsening and subsequent problems seep in..same goes for preheat. A metallurgist needs to be consulted.

Nachi

Please explain what welding depth you require. Also it has to be a seam welding or pulse welding.

The question still remains raised earlier and seconded by Milo, is the replacement plate in order with the PV code ?

Definitely it is not. And for a stamped vessel, , you are working in sour service.

And if it is a ASME vessel, the customers acceptance will necessarily not make the vessel acceptable.

Also 516 is a common material, Check for other source, why you want to compromise ?

I agree with Pipewelder on what will be required to weld this. However, the larger point is what engineering has gone into this material substitution to sell it to the AIs (Authorized Inspectors) and your customer. They are doubtless aware of the problems associated with welding medium and high carbon steels, and will justifiably want solid, well engineered procedures that diminish these problems into non-existence. This is the whole reason for Codes; to assure a reasonable expectation of product quality and performance.

Dear Engineers,

Thank you very much for your replies. I would like to give more information on the vessel that I will fabricate. This vessel is designed based on ASME VIII Div 2 (U-stamp) and we have got approval from ASME's Registed Engineer in US. Our client has agreed to use the plate that we proposed i.e SA 516 Gr 70N + HIC + Cev = 0.47% provided we have to qualified new WPS/PQR using the actual plate material. We have sourcing almost all plate manufacturers in Japan and Europe but due to the plate is very thick (148mm), all manufacturers can not comply with HIC requirement except one manufacturer Dillinger Hutte in Germany can comply on HIC requirement but not on Cev=0.43% (max). They can produce plate with Cev=0.47%. Order has been placed to purchace that plate with size of ID 5300mm x 19900mm x 148mm t for shell and ID 5300mm x 77mm t for heads. Plate wil be welded by SAW+SMAW or SAW+FCAW process both with backgouging. From my knowledge, there are diffculties in welding on material with high carbon content. Therefore, I need some guidance and tips from engineers to perform good welding during WPS qualification and production to minimize welding failures.

Thanks & regards

You will be better off if you design to have smaller weld passes than running large fast fill type beads that introduce a ton of heat into the plate. With the thicknesses you speak the pre heat, inter-pass, and post weld heat temps as well as the slow cooling rates are crucial in medium carbon steel weldments to prevent cracking.