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View Full Version : mig penetration and what should be full break streanth



lortech
06-22-2011, 05:40 PM
Hi all,

New to mig welding but done some tourch long ago.

Picked up a Lincoln 100 weldpak 100hd a week ago, and doing some welding with it. So far, my welds are pass, or to much weld material.

The question I have to know is, how can you test how strong a weld is? Is there standards that are used against welds to see how much stress thay can take, before breaking?

I am making a slide out platform that slides out from my truck. The length of the platform is around 94 inches long by 56 inches wide. I want it to handle 1,000 bls. What grade of angle iron or tube steel should I buy? what wall thickness?

Also, how do I know what full penetration should look like? Should I see it on the other side of the metal? I did some welding and it was really strong, but did not see penetration on the other side of a butt weld.

Should welds break, or bend?

Thanks

Rbeckett
06-22-2011, 05:51 PM
Lo, the final yeild of a weld depends on many factors. If you are using 70-6 you should get a yeild of 70K psi, but if properly welded the base metal usually fails in the heat affected zone and not in the weld itself. Conditions, depth of penetration, cleanliness, fit up and a bunch of other thing all affect this so overkill is always better. The tests you were interested in are the Bend, Notch, elongation and even X-ray. There are a ton of tests depending on what you are welding and how critical the weld is. Cant speak to material size off the top of my head since so many things come into play, send up a drawing and maybe the smarter guys can give you some direction on material and strength.. Hope this helps
Bob

joedirt1966
06-22-2011, 06:33 PM
Picked up a Lincoln 100 weldpak 100hd a week ago, and doing some welding with it. So far, my welds are pass, or to much weld material.

I am making a slide out platform that slides out from my truck. The length of the platform is around 94 inches long by 56 inches wide. I want it to handle 1,000 bls. What grade of angle iron or tube steel should I buy? what wall thickness?

Thanks

Your Lincoln 100 weldpak may not adequately penetrate 1/8" even if you use fluxcore (which runs a bit hotter than MIG).

I'd be a little nervous about being too close to a fully loaded (1000 lbs.) and fully extended slide out platform welded by a novice with one of the smaller 110Volt welders.

It would be advisable to perform a lot of practice welds on the type of material you will be using, cut them up, and then inspect for adequate penetration before considering any welding on a project that experiences significant loading.

If your welds cannot adequately and consistently penetrate 1/8", i'd think twice about proceeding further with this project.

DSW
06-22-2011, 10:09 PM
Your Lincoln 100 weldpak may not adequately penetrate 1/8" even if you use fluxcore (which runs a bit hotter than MIG).

I'd be a little nervous about being too close to a fully loaded (1000 lbs.) and fully extended slide out platform welded by a novice with one of the smaller 110Volt welders.

It would be advisable to perform a lot of practice welds on the type of material you will be using, cut them up, and then inspect for adequate penetration before considering any welding on a project that experiences significant loading.

If your welds cannot adequately and consistently penetrate 1/8", i'd think twice about proceeding further with this project.

Agreed. Small 110v migs are notorious for making cold welds that "look" fine. Thinner materials are tougher to test because often the base material will bend before you get a good idea about the weld. At the tech school, the students have to weld a 3/8" thick plate that is then sectioned, ground and bent to determine if the weld bonded to the base material or if there were slag issues and so on. Your machine dosn't have the balls to do this test. You might be able to sort of duplicate this test with a smaller diameter mandrel rather than the usual 1 1/2 round bar, say 1/2" or 3/4" instead. Search bend tests and you'll get some examples of test rigs here.


As far as design, there are too many variables to give a simple answer. is the 1000 lbs supported evenly or is it a point load? if so where is the load located in relation ship to the support? How is the farme designed vs materials used? and so on... Thats what they pay Engineers for, to crunch all those numbers and come up with the answers, as well as tell you whats the most ecconomical and/or lightest way to do this. 2 12" deep wideflanges would probably support your weight with no issues. Your machine can't weld them, and after the beams are installed the truck might not have the capasity left to carry your load. Of course the mounting designed for the unit might not be able to take the weight of the 2 beams and the load...