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Up Topic Welding Industry / Technical Discussions / Parameters for -50F
- - By SFIENG (**) Date 10-13-2008 15:18 Edited 10-13-2008 17:58
Hi All,

I was wondering if anyone would share your welding parameters for welding P1 G1/G2 materials to pass CVNs at -50F per B31.3.  I will be performing PQR's in GTAW and FCAW on 1/4" and 1/2" material in the 3G position.  I am using ER70S-2 with 100% Argon in the GTAW process and E81T1-Ni1 with 75%Ar/25%CO2 in the FCAW process.  I know that low heat input is critical for the CVN testing. 

Thanks in advance 
Parent - - By fit.to.a.flange (*) Date 10-14-2008 06:15
Firstly the materials you have quoted here are normal carbon steels, hence to me, the welding parameters used during your PQR for GTAW & FCAW are basically pretty the same as performing a PQR without notch toughness. I had once use a PQR with no CVN and re-run the same PQR with the exact welding parameters with CVN. The results of these proof to be satisfactory and acceptable.

Rgds, John boy...
Parent - - By SFIENG (**) Date 10-14-2008 12:19
Thanks for your reply.  I have read many posts on this forum that state the heat input must be controlled.  Is there a specific level of heat input level that one should stay below to achieve successful CVNs?  
Parent - - By js55 (*****) Date 10-14-2008 12:44
No.
Parent - - By SFIENG (**) Date 10-14-2008 12:48
Just No?  Is there a recommended range or is it truly just trial and error? 
Parent - - By js55 (*****) Date 10-14-2008 13:32
I noticed you are using Ni for your FC. This will be pretty forgiving actually. I would worry about the S-2 except I've achieved
-50's with GTAW with as much as 50kj/in with quite a margin. You will generally see the heat input for the GTAW will be higher because of the travel speed. Even though FC is run at much higher amps and volts the travel speed factor in the equation is larger.
I really think that when it comes to achieving -50's with C steel wire that dilution from the base metal is more detrimental.
If your qualifying on Grade B steel your carbon could be as high as .2X. With the high dilution you get with a root pass and feather edges the carbon content of your root pass is going to skyrocket. If your running it for B31.3 you have to take your impacts from 1/16" from the ID.
I'd say run normal root parameters but low dilution techniques (i.e. wider gap and landings perhaps).
But yes, there is a lot of trial and error with impact testing. Thats part of the reason they make you qualify. One of the other reasons is that lower heat input gives generally finer grain size which is good for impacts, but higher heat input tempers deeper into previous beads which is good for impacts. Its not exact.
Parent - - By SFIENG (**) Date 10-14-2008 13:51
js55,

Thanks for taking the time to pass on this valuable knowledge.  It is appreciated!

Yes I am qualifying these PQRs to Section X / B31.3 using dual certified SA-516 GR60/70 normalized plate in the 3G position.
Parent - - By js55 (*****) Date 10-14-2008 14:10
The thing is too, the general thinkings to keep heat input low, but as an engineer you also have productivity to keep in mind. Finding that balance of good impacts and parameters allowing high productivity is the trick.
Parent - - By SFIENG (**) Date 10-21-2008 20:56 Edited 10-21-2008 20:59
js55,

Can you ball park what you feel would be low and high heat input values for FCAW and GTAW in the 3G up position?  I did see that you mentioned that 50kj/in was high for GTAW, correct.
Parent - By Fredspoppy (**) Date 10-22-2008 12:48
Heat input for GTAW of 50kJ/in is fairly high.  150 amps, 12 volts, 3 ipm travel gives you 36kJ/in.  The important thing with GTAW is that heat input is totally independent from the amount of filler metal that is added to the weld joint.  In general, for all other processes, the higher the heat input the more filler is consumed.  Actually, you could double the heat input for a GTA weld, without adding any more filler, in fact you could add less.

It is therefore very important that the welder is prudent with filler metal addition.  You are using FCAW with Ni and could do the same with the GTAW filler.  This would help to assure meeting the required CVN values.
Parent - - By fit.to.a.flange (*) Date 10-14-2008 14:13
I hope you don't mind that I ask. I initially assumed that you would qualify this PQR on Section VIII rather than B31.3. I am just curious why are you using B31.3 to qualify for impact testing on plates (even though there are no restriction) ? And secondly, why wouldn't you use SMAW process instead of FCAW?

Rgds, John boy..
Parent - - By SFIENG (**) Date 10-14-2008 14:39 Edited 10-14-2008 14:41
John boy,

In production (pipe spools to B31.3) I will be using SA-333 GR 6 (P1/G1) / A350 GR LF2 (P1/G2) / SA-420 GR WPL6 (P1/G2) which will be supplied impact tested to -50F.  I am looking to limit the number of PQRs so for the procedure testing I am looking to join SA-516 GR 60 (P1/G1) to SA-516 GR 70 (P1/G2) to qualify the procedure to weld the stated production materials.

We do all of our welding in house and do not use SMAW.
Parent - By js55 (*****) Date 10-22-2008 12:43
25 to 50 kj/in is a good target for both. Towards the upper end for production sake. An deven if you go over I think you'll find its not critical.
And unless you have the pipe sittin around why not just order dual cert material. One piece, cut in half.
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