wire recomendation

[barh]

am welding old semi trl frame. metal is very dirty. can't get in corner to clean properly. welding vertical up. could someone please help me with wire coice . frame is 1/4 in. was wondering about E70S-6. Thanks Darryll

[Mike Sherman]

Darryll, do not weld a truck or trailer frame with short circuit mig, particularly when it is dirty. You need to find a way to clean the steel. Even if it means removing more steel than you would prefer to. Perhaps a die grinder or a dremel type tool. You need to achieve full penetration on this weld. Perhaps E6010 for the root and then E7018 out. Another possibility is to open the root up, clean everything real well, put the root or a backing weld in with the short arc mig (a very small bead) and then flux core out. If you put a backing weld or a backing plate in, make certain you grind the crack out to obtain good fusion with the backing weld or the backing plate.

[barh]

thanks mike i'll give it a shot. was having a problem with cold cracking using 7018 so thought i would try something different. Darryll

[Mike Sherman]

E7018 will cold crack, which is the hydrogen diffusing out of solidified metal, if there is a source of hydrogen, martensitic microstructure and adequate stress. You can get the microstructure and the stress simply from welding, the hydrogen can come from several places. 1) Old electrodes 2) dirt, oil, rust 3) pulling a long arc on an open root will help introduce hydrogen from the atmosphere, among other things, none of them good. So, are your E7018 rods in an oven? If not, this could be at least part of your problem, although hydrogen cracking is not that common in thinner metals, in a tempered steel like a truck or trailer frame it is still the appropriate electrode to use. Let me know how you intend to proceed.

[barh]

i bought new sealed 7018 rods as ed heim suggested. this i thought was the key worked well on several cracks.went back 2 it on another day and same problem again. guess i'll try your method. also was suggested 12018 rod.any thoughts? Also my understanding of a hydrogen crack must be wrong as i was told it takes time (usually up to seventy two hrs. for a hydro. crack to show and the if im getting a crack as it cools its not a hydro. i dont understand. Thanks Darryll

[Mike Sherman]

I probably wasn't clear enough. Hydrogen cracking is caused by hydrogen diffusing out of the solidified weld metal. It usually shows up the next day, not as the weld is cooling. But, it can show up as the weld is cooling. Usually you do not have hydrogen cracking in thin material. I wish I could see the joint you are working on. You can get cracks from an improper depth to width ratio, too wide of a root, bad electrodes, base metal/ambient tempertature too cold, and probably several things I have forgotten. I have welded many truck frames, including stretching and shortening trucks. I have never had a failure. I believe it is from proper preperation that I can say this. One thing you can try if you can get to both sides of the joint, put a backing weld in on the back, grind the front out to the weld, put your weld in with 3/32" E7018 from the front. Without having anymore info on the joint, this is all I can suggest.

[barh]

Thanks Mike, I did as you suggested using a backing weld then grinding. Must have been the trick as I've repaired 12 breaks and not one has cracked so far. This is a 6 axle trl. the area that breaks(should say cracks) is everywhere a spring perch is mounted certainly from being twisted and pulled during cornering as they are not lifting axles. These are the breaks I've been having the trouble at. I've one more trl. to do tomorrow if it happens again I'll try to get some pics. Thank You again you've been a great help to me .Darryll