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UNS S31803 Duplex welding

UNS S31803 Duplex welding

UNS S31803 Duplex welding

I got an assignment to weld UNS S31803 Duplex steel. thickness to be welded is 30mm. So i have decided to use same thickness for PQR.
Can somebody help me to get welding consumables for this. Process will be GTAW+SMAW.
Design code is 31.3 & MDMT is -50 deg C. PED compliance is also required.
Does impact applicable for PM ,WELD & HAZ per design code or PED?
If impact is really required then what will be min & max thickness qualified of below.
1 per Sec IX it will be 16 to 60
2 per 31.3, it will be 15 to 36 &
3 per EN 15614-1 it will be 15 to 60

I want absolute sure before proceeding.

RE: UNS S31803 Duplex welding

Under B31.3, only the weld metal and HAZ need to be tested as -50 deg is within the allowable temperature limit and assuming that the stress ratio will exceed 0.3.

EC Directive 97-23-EC states

"Materials for pressurized parts must:
(a) have appropriate properties for all operating conditions which are reasonably foreseeable and for all test conditions, and in particular they should be sufficiently ductile and tough."

The problem you will face is setting Charpy energy acceptance criteria as A790 and A928 do not contain any. You may wish to examine ASTM A923 acceptance criteria, with the modification of the test temperature, as a means of complying with the EC directive. This can then be taken into consideration when selecting consumables.

Steve Jones
Materials & Corrosion Engineer


All answers are personal opinions only and are in no way connected with any employer.

RE: UNS S31803 Duplex welding

Steve, I thought that per PED Annex 7.5 there are some specific requirements (when applicable per PED Guideline 7/17) on impact energy values.

Second smart143, you may also want to purchase a copy of API TR 938-C. It contains some relevant do's and dont's, guidelines on making proper welding procedures, useful information etc on duplex welding. Controlled heat input will be very relevant for your case, to ultimately get good ferrite contents and acceptable impact values.

RE: UNS S31803 Duplex welding

Using the A928 requirements is both in line with API TR 938-C and PED requirements by virtue of the statement in the API document:

The former test is done not to show adequate toughness for service (although this is also achieved and meets any requirements for toughness testing per Code),

It also kills the second PED bird, presence of intermetallics, with the same stone

Steve Jones
Materials & Corrosion Engineer


All answers are personal opinions only and are in no way connected with any employer.

RE: UNS S31803 Duplex welding

why API TR 938-C to use.
Is above material is tough to weld? Will above spec will have relevant consumables as well?
Do you think to have a welding consultant will be a good idea as i don't want to waste time & money by traying own.

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