Submerged Arc Welding of SA387 1

[weldgal]

Running into a problem passing tensile and bend tests (incomplete joint penetration) on a Vee groove coupon of 1 1/2" SA387 gr. 22 class 2 plate with 1/4" land. FCAW backing pass, and sub arc welded with 1/8" dia OK Autrod 13.20SC with OK Flux 10.63 at approx. 550 amps, 31 volts, 15 IPM. My first reaction is that I need to increase amps, but I'd appreciate any input you all can give.

 

[metengr]

What is your weld prep angle?

 

[weldgal]

37 1/2 for a total of 75 degrees.

 

[metengr]

For this plate thickness have you looked at using a compound bevel or J-groove versus a simple vee-groove? For a compound bevel something like a 25-30 degree angle off of the land for about a 1/2-5/8" height followed by a 15 degree angle for the remainder of the joint.

 

[weldgal]

I'd considered a change in joint design, but didn't know if that (or my amps) was the more significant factor for the incomplete penetration.

 

[weldgal]

Not sure we can achieve the compound bevel without machining it, and may have to stay with a single bevel and a smaller land. With that in mind, I'm leaning towards increasing the amps from the avg 550 amps to 650 amps in order to achieve full penetration. What are your thoughts?

 

[unclesyd]

Could we have a little more detail about the FCAW backing pass?

 

[weldgal]

Used 1/16" E91T1-B3.

 

[metengr]

Increasing the amps may result in poor toughness properties of the weld/HAZ (if this is a concern) at the root. I would probably look at reducing travel speed using the same amp setting and see if this improves your situation.

 

[weldgal]

That's a great suggestion metengr, thanks for the help.

 

[GRoberts]

Are you expecting to penetrate a full 1/4"? I know 550A can a well fused bead with 1/8" solid wire, but I don't know about 1/4" penetration.

What is your electrical stick out? Too large can really cut down on penetration, and make your weld look cold. How does your bead profile look? Is there a root gap? Are you butting the 1/4" land up with 0 root gap and then welding the back side with FCAW?

What you need to do is get a plate and run it like you are doing a test, but just weld the FCAW backing and the root pass. Then cut a weld cross section to examine the cross section of the SAW root pass. If is not fused all the way to the bottom, you need to increase your penetration. Turning your amps up is usually an easy way. If you are worried about heat input, you can increase your travel speed. You can also increase your chance of full penetration by incresing your root opening, decreaseing your land, or increasing your FCAW penetration from the back.

Also, 60 degrees is considered penty of groove angle for SAW welding. Anything beyond that just makes extra work. If you go beyond 1 1/2" plate, do consider a different prep as Metengr suggests to cut down on welding. Double sided welding would more than cut the amount of welding in half.