Welding thick steel

300jk · Nov 25, 2016

So the last few weeks I have been working with one of the company's concrete crushers. Normal procedure to clean the fines from around the tail pulleys is take a piece of 3/4 inch road plate chained to forks on the loader and push it in and pull it out to clean debris. Problem is the plate ( 5'x8') is all over the place. Slides off the forks and is a pain. So I was in the shop Monday and cut steel to make 4 u shaped fork pockets for the plate. I left them there and the company welder fabbed them up for me and I am going to weld them on the plate Monday morning. Problem is I have never welded anything that thick. Any suggestions ? I will be using a miller bobcat and 7018. This will be on site also. Don't think the company welder wants to come out and play in the cold so it's up to me. I have welded plenty of 1/2 inch but this is 3/4 and will have a fair amount of stress. Thanks in advance !

Stan in Oly, WA · Nov 25, 2016

I'm not completely sure of what you're describing, so the suggestions I have might not apply to your situation. If what you are welding is the legs of the four U's to the plate, then there are several things you might do to make the welds stronger: 1) Bevel the open ends of the legs of the U's so that less than 3/4" width will be against the plate. This will give you much stronger welds than the fillet welds of 3/4" thick steel legs against the plate---particularly if you can only make fillet welds on the outside of each leg. 2) Use a propane or, preferably, an oxy/acetylene torch to preheat the metal to be welded before each first weld. Increasing the temperature of the metal even a hundred degrees will greatly increase the chances of good welds. 3) Make multiple overlapping passes to fill the beveled space of each leg. Beating the slag off each pass is also of some benefit in peening the stress out of the welded joint, so have at it pretty good.

I hope there's something here you can use.

Stan

300jk · Nov 25, 2016

Thanks ! It was good info. I was going to bevel the joints on the u's where they are getting welded. Never thought about preheating. And that's another good tip. Should I grab some 6010 for my root pass or will the 7018 be ok? Usually for my 1/2 welding I use 6011 cause I have an Ac. And then 7014 for covers. Would this work basically the same with 6010 and 7018 ?

dpendzic · Nov 25, 2016

use 7018ac rods if your welder is ac

Sparktrician · Nov 25, 2016

Not exactly a pro welder....but I'd root pass with 6010, then ,7018.

300jk · Nov 25, 2016

Will be welding with miller bobcat at work. Between me and dad we have a Hobart trailer welder. Old. Has a Willey's four cylinder for power. That welds good. Also have an old linc-welder welder 180k Ac that is my favorite and a Lincoln weld pack 155 mig. Just not sure about the welder I will be using . I use my 1950's linc-welder welder for almost everything. Have used the old Hobart but very limited.

300jk · Nov 25, 2016

That's what I was thinking too. I am not a pro welder either but I do ok. At work I am really an operator but sometimes a welder,sometimes a carpenter and sometimes a labor. Some people say a jack of all trades. I like to think like I am more of a swiss army knife ! Thanks for your reply !

markct · Nov 25, 2016

Same procedure as you have done for 1/2" just more passes.

Stan in Oly, WA · Nov 26, 2016

6010 is great for open root passes, but that's not a problem in this case. If you decide to bevel the legs as I suggested, I'd advise you to leave landings (which will be flat against the plate) of at least 1/8". Without open roots to deal with, I'd just go ahead and use 7018 for the whole thing. There's nothing wrong with doing your root passes with 6010 if you like it, but I'd say there's no advantage in this case, and if you do it all with 7018, you won't have to change settings or your technique.

Stan

Dick L · Nov 26, 2016

I have no idea why one would use a lower tinsel welding rod as a root pass. When I was trained to weld high pressure pipe in the 1960's with 7018 rod we used a smaller diameter rod for the root pass. We would place the bare end of the rod between the two pieces when clamped in place. The root pass had to form a bead on the inside of the pipe as well as the inside. Without porosity the slag would peal off quite clean. The thickness of the pipe determined the amount of passes with the next size larger rod. The connection needed to be all weld without porosity. Weld on pipe fittings are tapered. We tapered thick saw cut pipe with blow rod that then was chipped and wire brushed.

I have always welded thick steel in the same manor. I have repaired a three inch thick cracked plastic mold cavity this way. Used blow rod to give a V to the bottom of the crack and welded back to be re machined to a usable cavity for a plastic part. In building tables with pipe and square tubing I always place the 1/8" bare rod end between the legs and the table base. Strongest weld is all weld.

jon f mn · Nov 26, 2016

Folks get over technical on these welding threads. If your welding to the cutting edge you need 7018, but if your welding to the bucket plates then any rod is more than adequate including mig if your welder is adequate. I would use mig since I have a good one. If your used to 6011 then that is also a good choice, and better than 7018 if you are not used to it and do poorer welds because of it. That being said, 7018 is also a great choice and what I would use if I was going to stick weld it. Other than that, just bevel the edges so you get good penetration. Pre heat won't hurt but isn't neccessary with the welders you list and for this job.

Welding man · Nov 26, 2016

A 3/4 in plate 5 ft x 8 Ft weighs 1200 lbs. Dropping a plate that heavy onto some due to a defective weld could easily kill or seriously injure someone. This is not the kind of job that you learn on. Tell the boss to hire a professional and take a welding class at a vocational school,before the lawsuit begins.

300jk · Nov 26, 2016

Welding man I agree that some projects aren't for beginners and any welding that needs to be done where someone can be injured should be left to a certified welder. I guess I didn't do a good job describing how the plate works. The four u shaped pieces will be welded to the plate two per fork. One at the front of the fork and one at the rear. Once welded the plate will be flipped upside down and slid into the forks through the u shaped fork pockets. The plate is then chained to the back of the fork frame in two locations to keep it from sliding off. The u shaped fork pockets being welded are only there to stabilize the plate on the forks. The weight of the plate and material on the plate is supported by the plate itself. Hope that makes things a little easier to understand.

Mel in SW Iowa · Nov 26, 2016

I like to chip root passes and each following pass or cap on thicker steel with an air powered needle scaler. It gets all of the slag and stress relieves the welded area.

Welding thick steel

300jk

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Stan in Oly, WA

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300jk

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dpendzic

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Sparktrician

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300jk

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300jk

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markct

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Stan in Oly, WA

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Dick L

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300jk

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