by Jason Becker
Stringers vs. Weaves, could there be a more controversial topic amongst a group of welders? Ive heard this debate so many times throughout my career.
No one has ever had any evidence though, it has always been ones opinion with little to no facts supporting it. I have always had the assumption that stringers were indeed stronger, mostly due to the more refined grain structure that is formed by keeping the interpass temperature to a minimum. When using a weave technique, you are putting in additional heat into the base metal due to the slower/wider travel speed. This causes a more complex grain structure that just doesn't have the same mechanical properties as its stringer counterpart. That however is strictly my opinion with a little science sprinkled in to back up my claim.
We decided to take a stab at this highly debated topic and see what science has to say about it. We setup two identical sample specimens to perform the test. Our friends up a Select Arc Inc. sent us some Select 730 to use for the test along with a WPS to follow so that we could keep everything equal on each sample. We welded both pieces at the same time with the only difference being technique, one welded with a weave, the other with stringers. We kept the interpass temperature on both pieces below 350°F so that we could keep things as fair as possible.
The test took just over an hour to weld out, we then mailed both samples up to the Select Arc Facility in Troy Ohio where their lab technicians would cut the necessary specimens from each sample to do a micrographic etch, tensile pull, and charpy v-notch tests on both plates. Although we couldn't show the specimen preparation process, we can talk about some of the steps to come up with the final pieces. They first machine down both caps of the plates and then water jet the sample pieces out of the original test piece, that way there is no additional heat being added to the plates. Once they are cut out, they are machined the rest of the way for the requirements of each test.
The results were exactly what I expected, after the tensile pulls, 5 charpy v-notch samples and a micrographic etch, the stringers reigned supreme. Check out the video to see the entire testing process as it is very interesting and gives a more in depth look into the testing requirements. I hope you all were able to learn something from this test. Until Next Time, Make Every Weld Better Than Your Last.