welding rod sizes

[bdog]

95% of my welding I do with 1/8" rods, the other 5% 5/32. I use two rods types 5P+ (6010) and 7018.

Anything smaller than 1/4" thick I usually weld with my MIG. My Arc welding is usually 1/4-1/2" thick material with occasional thicker stuff like 3/4".

I was looking at some charts and they recommend for those sizes of metal to use 5/32, 3/16, or even 1/4" rods.

Anytime I weld thicker materials I just make multiple passes. Now that I have a 300 amp machine on the way I am wondering if I would be better served using larger diameter rods?

 

[Bigfoot62]

. . . Anytime I weld thicker materials I just make multiple passes. Now that I have a 300 amp machine on the way I am wondering if I would be better served using larger diameter rods?

It would just be quicker, not necessarily better.

 

[Shield Arc]

I can only think of one time where we had a WPS that required 3/16-inch 7018. Had to weld a 6" x 8" rolled square stock to a round tank for a lifting ring. You don't want to make a mistake carrying 3/16" 7018 over head.
Majority of the time if I had to use 5/32" rod I'd break out the LN-25 and use dual shield, or self shielded wire.

 

[Arc weld]

There is sort of a cut off for rod sizes but it usually applies to 3/32" because it doesn't put enough heat into thick plate. For production and economy figures they recommend larger rods but on some jobs they do recommend smaller dia. rods and/or stinger beads instead of weave beads in order to get a finer grain structure in the weld metal. On some applications, like stainless, you also want to limit heat input. 1/4" can be a real pain to weld with and even worse if you get arc blow. 3/16" can get arc blow but overall is still nice to weld with.

 

[Gary Fowler]

As for LH rods, I never found the 5/32 to weld "right". They seem to be a problem with the flux not burning off evenly and that is with all brands. I have found very little welding jobs that need anything larger than 1/8" if all position. If you can weld everything flat, then larger rods are ok but on 1/2" material a 1/4" rod would melt thru even in flat position. I wouldn't trust that chart you have if it recommends 3/16 and 1/4" on that size plate. For one reason the heat input would be too great not to mention the weld puddle control.
5/32 and even 3/16" E60xx rods would be ok on 1/2" thick pipe welded in position downhill but not uphill (to much heat input)

My Advice: Stick with 1/8" as your largest rods in Low Hydrogen and max of 5/32" in the 60XX rods. Personally I keep nothing but 3/32 and 1/8" E7018 and 1/8" 6010+ rods in stock. They weld 99% of the stuff I need and do it efficiently. 3/32 E 60XX would be the smallest I would ever buy as anything smaller is too limber to use and is really hard to keep from sticking and even the 3/32 don't put out enough weld metal to hardly weld with and also get too hot by the time half the rod is used so it is a waste of money to buy them.

 

[Arc weld]

I've seen guys roll weld 4" heavy wall pipe and do the cap with 1/4" 7018. It requires a lot of skill and puts one wide bead very fast but 2 passes side by side with 3/16" has a lot better appearance. 1/4" 7018 is used on larger diameter pipe spooling all the time. I know a guy who could roll weld 12'' dia. and up pipe with 1/4" 7018 that was almost as smooth as sub arc. 1/2" plate isn't a problem as long as you don't get arc blow. For 99% of the stuff you'd ever encounter, you don't need 1/4" rods though. If I had a big job with 1/2" or thicker plate, I'd use 3/16".

 

[Gary Fowler]

I've seen guys roll weld 4" heavy wall pipe and do the cap with 1/4" 7018. It requires a lot of skill and puts one wide bead very fast but 2 passes side by side with 3/16" has a lot better appearance. 1/4" 7018 is used on larger diameter pipe spooling all the time. I know a guy who could roll weld 12'' dia. and up pipe with 1/4" 7018 that was almost as smooth as sub arc. 1/2" plate isn't a problem as long as you don't get arc blow. For 99% of the stuff you'd ever encounter, you don't need 1/4" rods though. If I had a big job with 1/2" or thicker plate, I'd use 3/16".

Having a positioner and rolling out a weld on that small of a piece of pipe is still putting too much heat into the weld which would be in violation of any welding procedure I have ever seen (I have seen a lot of them too) Not saying it cant be done but there is what is called inter-pass temperature which is the maximum allowance for the weld to be when you start another pass, this is set when doing the WPS and is critical that it be followed so that you don't exceed the transformation range of the metal when welding with the max sized rods allowed per the WPS. I am not saying that a good welder couldn't weld with 1/4" rods on a 6" schedule 80 pipe but that it is not a good idea and would in most cases heat the pipe material to way more than would be allowed.
I shall tell of an instance I had once with a couple of welders that were brother-in-lawing (that is supposed to be 2 welders welding on one pipe weld with one on each side of the pipe) on a 24" pipe (in position) that was 1 1/4" wall thickness and was 1 1/4% chrome 1/2Moly pipe material. I drove by checking on the work and both welders were welding on the same side of the pipe rather than one on one side and one on the other as would have been the correct way. One welder was left handed and other right handed so it worked out ok. They were welding in the same puddle with one welder filling half the puddle on the right and the other the left. They had put in one heavy filler pass after the root and then were filling the bevel full ready for a cap pass. This in itself was in violation of the maximum fill rate not to mention the twin welding arcs going on. I had to admit that the weld looked very good but the pipe was glowing red hot where the were welding. I had to go back to my office to get a thermocouple device to accurately read the temps which took me about 15 minutes and the pipe temperature was still over 1000F when I got back. Other than violating all the parameters of the welding procedure specification (WPS) it wasn't good for the geometry of the pipe either because of excessive weld shrinkage on one side which would cause the joint to be out of plumb and square and inducing too much stress into the other side which could have caused a crack in the weld.

My comment in post #5 was concerned with personal use and stocking various sized rods. There is not a need for home shop welders to keep as big an assortment of rods as a large construction site. While it may be worthwhile to have 3/32-1/4" E7018 rods on a construction site for the really heavy jobs down to the light work to keep production up to its highest rate, it isn't economical for a homeowner to buy boxes of every size rod. Most homeowners don't burn 100# of rods per day like a production welder in a shipyard, and most don't even burn that much in a year so why bother to keep a bunch of rods on hand that you may never need. Not too many folks will be welding anything thicker than 1/2" and mostly it will be thinner than that, so a 1/8" in E7018 and E6010 will do the job just as well as a larger rod in almost the same amount of time and for someone with less than professional skill level, the welds will look much better.

For the professional welders here, recall when you were learning to weld, you didn't start out trying to weld with 1/4" rods, you started with the smaller ones and then worked up to larger and larger ones till you could proficiently handle the molten metal with the larger rods. The same holds true for the majority of folks who post on this forum, they are not professional welders and are asking for advise for the use of an average homeowner welding machine owner. If they were professional welders, they wouldn't be asking questions about rod size in the first place.

 

[Arc weld]

It was done on 100% x-ray welds in an ASME certified vessel shop. There are some misconceptions in welding too. Some are based solely on what was done in the past. A prime example is the width of weave for an uphand weld on mild steel. Lots of procedures limit weave width to 2 1/2 or 3 times rod diameter. I was having a discussion with a CWI a few years ago and wanted to find out the truth. I e-mailed Walter Sperco who is pretty much the top engineer for establishing ASME welding codes. He said he would challenge ANY procedure that calls for ANY limitation on the weave width of a vertical weld. He said putting more heat in is better and as long as you don't have slag inclusions, there's nothing wrong with a wide weave. I was a little shocked. I'll see if I can find the e-mail.

For a home shop there is no need for 1/4" rods, well maybe for gap rods. If you have 300+ amps and are doing a big job, why not take advantage of it? 5/32" would be plenty for most people though.

 

[CJONE]

I ran a lot of vert up with 5/32 7018 once you got used to it and get you heat correct you could lay some sweet looking beads. It would cut a lot of time off of 1/8" but I can't imagine going any bigger. This was 2 passes on 1/2" and 3/4" plate steel. The only time we would jump to the bigger stuff was 7024 and you better have a cooling bucket. CJ