why "low hydrogen"

[arrow]

I split my wedge off of the splitter so now I have to re-weld it back on. The splitter came from Northern 16 years ago but I am assume they used their own splitting wedge when they built this one. At any rate, they call for a "low hydrogen" rod to weld their wedges on. Low hydrogen to me means a 7018 rod. Curious as to why a 3/4" thick piece of metal or any thickness for that matter needs low hydrogen otherwise is there an important reason why I cannot use 6011 for the root and 7014 for the fillets?.

 

[Gary Fowler]

The wedge should be hardened steel and 60xx rods are not ductile enough to use. The weld on to hardened steel will be way too susceptible to cracking. LH rods in the as welded condition are very ductile and much higher tensile strength than the 6011. I have never seen a 7014 rod with the weld characteristics to hold a thick piece of steel. A couple hits with a hammer will snap them off even with 2 or more passes. Save yourself some rework time and get some 7018 or even 8018 to weld it back with and "do it once-do it right".

 

[arrow]

The wedge should be hardened steel and 60xx rods are not ductile enough to use. The weld on to hardened steel will be way too susceptible to cracking. LH rods in the as welded condition are very ductile and much higher tensile strength than the 6011. I have never seen a 7014 rod with the weld characteristics to hold a thick piece of steel. A couple hits with a hammer will snap them off even with 2 or more passes. Save yourself some rework time and get some 7018 or even 8018 to weld it back with and "do it once-do it right".

Good enough Gary, Thanks

 

[dstig1]

The problem is called hydrogen embrittlement. Hydrogen is a very small molecule/atom, and so it tends to get into very tiny spaces that other things won't be able to fit into. In this case, it is the grain boundaries between the grains in the steels that form as it cools. As the Hydrogen reform into H2 molecules, it expands and causes trouble. They cause weakness and make the steel fail at much lower forces than it normally would. Only really happens when the steel is hot enough to be molten or near molten, which is the perfect description of welding. Low hydrogen rods mainly mean lack of water, as that is the primary source of hydrogen in welding. That is why you have to keep them in an oven to dry, so they don't absorb water.

Wiki link if you are curious

Hydrogen embrittlement - Wikipedia, the free encyclopedia

 

[arrow]

Thanks dstig for the more technical explanation making perfect sense. I welded it back up using the Tractor supplies' Hobart E7018. It is no wonder the 7018 is a almost everyone's go to rod as it is just about idiot proof. Best welds I've made and I stink at welding. There was a bit of an undercut on the 1/8th rod at 115* on my inverter welder but I think I was going a bit slow. Anything less temp wise seemed to stick the rod. At any rate I'm glad I bought a bunch. Thanks Gary for the gentle lead.

 

[BukitCase]

If you "bought a bunch" of 7018, you might want to get one of these for each size you have -

Welding Rod Keeper

Put ALL the rod in those BEFORE they draw dampness and KEEP it there, tightly closed - otherwise, you'd be better off just buying a few sticks as you use it.

Lo Hy rod is the only kind this is really necessary for, and if it gets wet it can (sorta) be "rejuvenated", but it takes a hot oven and several HOURS to do - if it's KEPT dry, that can be done as simply as these cannisters or a small refrigerator repurposed as a "dry box" - a light bulb inside and a small vent hole in the top works pretty good... Steve

(If you're doing Xray quality welds, ignore all this and do what the inspector says

 

[arrow]

If you "bought a bunch" of 7018, you might want to get one of these for each size you have -

Welding Rod Keeper

Put ALL the rod in those BEFORE they draw dampness and KEEP it there, tightly closed - otherwise, you'd be better off just buying a few sticks as you use it.



Lo Hy rod is the only kind this is really necessary for, and if it gets wet it can (sorta) be "rejuvenated", but it takes a hot oven and several HOURS to do - if it's KEPT dry, that can be done as simply as these cannisters or a small refrigerator repurposed as a "dry box" - a light bulb inside and a small vent hole in the top works pretty good... Steve

(If you're doing Xray quality welds, ignore all this and do what the inspector says

Thanks Bukit. This case you're showing me seems a lot handier as you just unscrew the lid when you need rods. Much easier than what I was going to do when I thought to simply tape up the seam of the plastic case the rods came in. Someone wanting me to do xray quality welds is akin to me taking out your appendix. You wouldn't want me for that either even if I am cheaper than most docs. You would be on an outpatient basis however as we go out for pizza after most surgeries done in sterile environment of the garage.

 

[Big Barn]

If you "bought a bunch" of 7018, you might want to get one of these for each size you have - Welding Rod Keeper Put ALL the rod in those BEFORE they draw dampness and KEEP it there, tightly closed - otherwise, you'd be better off just buying a few sticks as you use it. Lo Hy rod is the only kind this is really necessary for, and if it gets wet it can (sorta) be "rejuvenated", but it takes a hot oven and several HOURS to do - if it's KEPT dry, that can be done as simply as these cannisters or a small refrigerator repurposed as a "dry box" - a light bulb inside and a small vent hole in the top works pretty good... Steve (If you're doing Xray quality welds, ignore all this and do what the inspector says

In addition to what Steve said, these portable ovens set at 300 degrees come up for sale used quite often. I am relatively new to 7018 but they run 'sooooo' nice right out of the oven.



Terry

 

[bigdeano]

You might want to put a desiccant packet in those rod storage tubes if you're going to keep the rods a long time. Air and other gasses go thru plastic over time.

 

[arrow]

You might want to put a desiccant packet in those rod storage tubes if you're going to keep the rods a long time. Air and other gasses go thru plastic over time.

Good idea Bigd