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Hi all,

I have the following issue:
We are going to weld steam traps out of dissimilar material; body cast 16Mo3 (P3) with flanges A182F11 (P4), size 1"XXS (33,4 x 9mm)
Max work. temp. is 415C and max. pressure 80 bar

We need to qualify a PQR for GTAW and Im preparing the following WPS;

-Code ASME-IX + B31.3 and EN15614 (it is for refinery purpose)
-3x Buttwelds in pipe A335-P11, size 1-1/2" 160s (48,3 x 7,14mm)
-Filler F6 ER80S-B2 (I have read somewhere; For selecting a electrode/filler metal for two dissimilar metal you have to choose the Electrode/filler metal of higher grade material.i.e, in this case for the P4)
-Preheat max. 120C (Table 330.1.1)
-Interpass 175-230C (max 315C)(Table 330.1.1)
-PWHT: In B31.3 para 331 I dont see anyting about dissimilar materials. If I go to B31.1 para 132.2 (B): When parts of two different P-Numbers are joined by welding, the postweld heat treatment shall be that
specified for the material requiring the higher PWHT temperature. So I go for P4.
B31.1 table 132 general note says: PWHT is not mandatory for P-No. 4 material under the following conditions:
(a) welds in pipe or attachment welds to pipe complying with all of the following conditions:
(1) a nominal material thickness of 1⁄2 in. (13.0 mm) or less
B31.3 at table 331.1.1 says more or less the same.
So no PWHT......?????

-Destructive Testing: According to ASME-IX, Table QW-451.1 – Groove-Weld Tension Tests and Transverse-Bend Tests
2x tension test, 2x bend test, 2x root bend
If no PWWHT then no hardness measurements

I love to get into these ASME codes but its no daily job for me.
Can someone tell me if Im on the right track with the above info to make the right WPS for the PQR?

Thanks in advance
BR Remco


331.2.3 Dissimilar Materials
(a) Heat treatment of welded joints between dissimilar
ferritic metals or between ferritic metals using dissimilar
ferritic filler metal shall be at the higher of the temperature
ranges in Table 331.1.1 for the materials in the joint.

Do not forget the maximum carbon content for exemption from PWHT


Hi DekDee, thanks for your reply, I missed this one...

So if thikness is >13mm I follow PWHT specs for P4
And with thikness <13mm and C<0,15% preheat at 120C and no PWHT nessecary.

Is my conclusion correct?






There is no absolute rule requiring the use of the higher alloy matching filler metal. Design conditions often permit the use of the lower alloy filler metal, which may be more resistant to hydrogen assisted cracking. In your case, I would have no problem using E7018-A1 equivalent filler metal.


Hi weldstan, thank for your reaction.

If I’m right the E7018-A1 is a SMAW electrode.
Think the equivalent for this as TIG rod is the ER80SG with analysis: C=0,1 – Si=0,6 – Mn=1,1 – Mo=0,5

The analysis for ER80 SB2, the one I’m pretended to use for the weld test is: C=0,11 – Si=0,65 – Mn=1,0 – Mo=0,5 – Cr=1,2

The coupons for the weld test are P4 to P4 but at the end the procedure need to be suitable for the P4-P3 connection.
So if a lower alloy filler metal is better for resistant to hydrogen assisted cracking then the ER80SG might be better then..?


It should be but what you are planning is not wrong and is often done as well. Your PQR proposal can be used to support WPS's for P4 to P4, P4 to P3 and P4 to P1, which is cost beneficial depending on the amount of dissimilar welds being made.


Preheat 120C is minimum, no maximum.
Interpass temp is not in table 330.1.1 for this case.



Hello r6155. A word of caution here. Only 16Mo3 classified under EN 10216-2 can be called as P-No. 3. Not all 16Mo3 metals can be called as P-No. 3. For example, 16Mo3 classified under EN 10028-2 is NOT P-No. 3 material (interpretation IX-23-26 confirms this). I too wrongly thought for a long time that all 16Mo3 metals are P-No. 3.

If the 16Mo3 that you use in your job is anything other than EN 10216-2 16Mo3, then it must be understood as an unassigned metal. In which case, the P-No. 4+ P-No. 4 PQR that you plan to do will not support your P-No. 4 + 16Mo3 production weld (because your 16Mo3 is an unassigned metal).

For unassigned metals, you must do your procedure qualification with the same grade of unassigned metal that will be seen in the job. So, perhaps you might need to do you coupon with P-No. 4 + 16Mo3 combination, instead of the P4 + P4.

Other than that, the procedure you described in seems just fine to me. You may want to use ER70S-A1 + E7018-A1 fillers for the coupon. These fillers match the composition of 16Mo3. I hope this helps.

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