American Welding Society Forum
We are currently in the process of qualifying a procedure for welding 514 Grade B to 514 Grade H using the FCAW process. This procedure needs to have successful CVN testing per AWS D1.1:2015 (table 4.14) we failed the CVN test with low impact values in the weld metal (10,9,10) HAZ in both material was 50-90 range) my question is what would result in low impact in the weld metal?
Here are the testing parameters…
Position: 3G (up)
Gas: 75/25 AR/C02
Flow Rate: 50psi
Wire: ESAB e111T (.045”)
Wire speed: 310-330
Heat Input: 33.33 Kj/in
Joint: Double Vee (root angle= 45deg. opening= 1/16” Face= 1/8”)
Preheat: 100F / Max. 400F
Just a quick thought.
FCAW welding operators often prefer to use a weave type deposition technique as opposed to stringer beads.
The weave technique, even when split layers are employed on thicker base metals, will always result in a slower point to point travel speed for each individual pass when compared to stringers at the same WFS. That slower travel speed of course adds heat and expands the HAZ while changing mechanicals at the same time.
Just 2 cents
Ditto what Lawrence said, keep an eye on the travel speed(forward advancement).
Thank you for the advice but please clarify, my understanding is by doing the calculation for heat input that Voltage,Amps and travel speed all come down to one number. I think the heat input is too low but I'm looking for some confirmation from others that might have gone though this same exercise. I also see an error in the Pre-heat too, it should have been 125f min but what is the the solution to higher impacts?
Higher heat input?
Interpass temps at 250F minimum?
I intentionally left out that we tried this same test with 45 Kj/in, we had better results, 19, 14, 23 (one below the 15 min and average below the 20 min)
So is the solution more heat input? we are hesitant to continue this experimentation as it cost 3k for each "try" so we need a good methodical approach.
If you decide increased heat input is what you need that should be an easy fix.
The WFS and current you report are very much at the lower end of most .045 E71T-1 manufacturers recommendations even for vertical-up.
My experience with both ESAB 710X and Lincoln 71M is that operators are much more comfortable with the higher end of the range even with vertical-up and overhead... More along the lines of 350-400 IPM and 240-260 Amps.
You initial post said you are getting 50 to 90 Ft/lbs charpy tests in the base metal?
What temperature are you doing these at? ASTM 514 doesn't have specified minimum impacts but our tests on this Q&T base metal are typically in the 15 - 40 ft.lb. at -40deg. Our plate arrives @ 235 - 293 BHN.
Are you doing any post weld heat treatment /stress relief before impacts?
PWHT for A514 is a dangerous process and in almost all cases, should be avoided. Cracking from heat treatment can occur if conditions are suitable.
Is that something you perform?
Happy Memorial Day!!!!
I checked your heat input calculation using the average values for the welding parameters. I calculated about 25-26 kJ/inch. That seems to be on the low side and would tend to result in fusion type defects.
I wouldn't expect to see a significant detrimental affect on the notch toughness until you got up around 50 to 55 kJ/inch. You didn't mention the thickness of the plate used for qualification. For plate thickness on the order of 1-inch or thicker, the heat input can increase up to about 60 kJ/inch.
Excessive preheat or interpass temperature can be counter productive, but sufficient preheat is need to mitigate the potential for cracking. Use the methodology for determining the minimum preheat found in the Annex of D1.1. Assume you are meeting the H2 level of hydrogen control and assume the joint is "high restraint" just because of the length and thickness you are welding. If you are using a fixture, do not over tighten the clamps. Allow the maximum degree of movement during cooling while still controlling the angular distortion. You might considered flipping the plate back and forth a few times while welding to balance the residual stresses and maintaining the "flatness" of the plates.
You didn't mention a back gouge operation before welding the second side. Make sure the back gouge operation extends deep enough to obtain sound metal. A magnetic particle test of the back gouge is a good idea. Don't let the assembly cool down without supplementing the preheat before resuming welding.
Considering the low heat input described, I am surprised there was no mention of fusion type defects and slag inclusions. Upping the heat input will mitigate the potential for those typical type of defects which should also provide better test results results. However, don't let the interpass temperature climb while welding. 500 degrees F is a typical maximum interpass temperature, i.e., it seems to be an industry standard based on experience, when notch toughness is an issue.
Before performing the destructive tests, subject the plate to UT and use the acceptance criteria for cyclic loading. If the UT detects any defects, step back and weld another assembly.
The attached file is a way to provide the welder with the welding parameters that is easy to use. I've had very good success with this method of presenting the data. It is easy to use and it works. By the way, CTWD is contact tip to work distance. It is not standard terminology, but I find the welders have an easier time monitoring it when compared to electrode extension. With electrode extension they have to add the arc length. It is just more confusion when I'm trying to simplify. CTWD seems to work better.
Good luck - Al
Do the heat input limitations from the steel producer need to be considered per AWS D1.1:2015 clause 5.7? I recognize this is in the fabrication section of the code as opposed to the qualification section; but one would expect the WPS being followed during fabrication would need to specify the heat input limitations recommended by the steel producer for welding their product.
For example, ArcelorMittal has some recommendations for heat input limitations for welding certain A514 grades in the form of T-1 steels. http://usa.arcelormittal.com/~/media/Files/A/Arcelormittal-USA-V2/what-we-do/steel-products/plate-products/How-to-weld.pdf
The manufacturer's recommendations are based on their experience and test results. It would make sense to follow them unless there is a reason not to.
Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill