Issues Welding a Melting Pot

[Uptickk]

I am having some issues with the welds being lead tight on my melting pot. I paid a guy to weld a piece of 8’’x10’’x ½’’ rectangle tube to an 8’’x10’’x1’’ base plate. I recently purchased a welder but didn’t think I wanted my first project to be something that holds +100 lbs of molten lead (plus it isn’t the proper welder to go at 1’’ thick steel). As a result the guy welded the inside of the rectangle tube to the base plate. He water tested it in front of me to show the pot held water just fine. I then tested it with lead once I got home and it also held. The second time I fired it up it started to leak. My thought is that the two pieces of steel expanded at different rates creating tiny holes in the weld for the lead to escape through. I should note that the base plate has 3 - 5/8’’ holes by which the pot is heated. I wasn’t able to get a hold of the welder so I decided to weld the crud out of the outside of the pot this time. Fired it up once again and it held lead. Fried it up another time and it started to leak again… So my mind goes back to the same thought of the steel expanding at different rates thus breaking the weld, again. Being the inexperienced welder that I am I was wondering if there is any merit in trying to heat the pot up and then weld it. Just thinking out loud here but maybe with the two pieces of steel already headed and thus expanded that the weld might be less likely to break. Any suggestions would be greatly appreciated.

Thank you

[chsparkman]

I'm certainly no expert in the field, but maybe brazing the welds might fill in the gaps and would be more flexible than the steel? I've sealed welds that way before, but not to hold hot lead so I'm not sure about it as a solution. I know some experts will chime in soon.

[Zymurgy50]

Multiple passes should do the trick. Root pass with 6010, fill with 6010 or 7018, and cover with 7018. If it works for 600lb steam lines it should work for a lead pot. Grind out the old weld and get it done right. If you make a boo-boo dont try to cover it up, grind it out and do it over.

[375RUGER]

Dissimilar thickness material is not the problem. Weld integrity is the problem.
Post a pic.

[trapper9260]

I say that the way it sounds is that you might try to preheat and then weld. But do like is stated the Boo Boo needs to be grinded out.and then welded.Also use the rod that is stated of 6010 or 7018, but I say if you can do it all with 7018 you will be better off.Unless you usen a mig welder then put the heat to it to have a nice flow.but still need to preheat.That is what i would do.Maybe someone have a better idea.

[D Crockett]

there is a easy fix for your problem . go to swapping & sallin look up my add think it is on page 5 titled " smelting pots &ingot molds " see what you think of them if you like them pm me there is pictures D Crockett

[country gent]

The thickness of the metals being welded and the amount of mass to them will suck the welders heat away really quick. Gring out the old weld in a u shape with the edge of a grinding disk to 3/4 of the thickness or so. What you are more than likely dealing with are Slag inclusions in the weld. Thats fux thats been trapped in the fill due to coolness. Grind it out as stated then set it on a burner and heat it good and hot so its already hot when you start to weld. Lay a small consistent root pass around the inside then a small blend pass to the base asmall blend pas to the body and a fill pass overall of it. If arc welding chip and wire brush when ever you start a new rod and between passes. Everything has to be clean and dry start to finish. Now let it cool and again grind the u shaped fill channel around the out side 1/2 way thru or so. Repeat the welding process of heating root pass, blend passes and fill passes, chiping and brushing as stated. The joint when finished will be solid weld and preheating chipping and brushing the weld will allieviate the slag inclusions. Any time you run out of rod or stop you risk an pourous spot. If using a wire feed welder grind out pre heat and weld with the 4 passes wire brushing oftenstopping as little as possible. ( If your welder uses flux core wire you may never get a really good weld. If it was just a "butt" weld with that thickness of metal and no pre heat you may not have gotten the penetration needed for a good flow / blending of the weld. When welding metal prep is important clean fitted joints clean dry rods temps that allow metal to flow and mix. The U shaped channel allows the rod to be worked to blend the fill with the base metals easier than the V grooves. Bu going to the depths above the fill and base metals are blended thru the weld.
Chances are good when grinding the old weld out you will see "pockets" in the weld these are the inclusions that are allowing leaks as they warm and heat the slag breaks flows leaving openings or pourous spots allowing leaks.

[Bullshop Junior]

First off what kind of welder are you using?

Ok next. Why 1" steel. 1/2 would hold up fine and is much easier to weld on. Welding 1" would will probabably need to preheat unless welding with a BIG welder that will run 1/4" rods. No way will it happen with a mig. Not enough heat.

I'm guessing inproper weld prep. Clean it. Grind all the old welding off. And then grind down into your matterial about 2/3 of the way. In a nice V groove. And then weld it. Weld it layers. Your weld shouldn't be more then 1.5 times wider then the width of your rod. High heat input. And then lap weld it, when the edge of your new weld is in the middle of the old weld.

If you are close enough, I can help you weld it up. I have a couple of big welders, and promise I can make it work right.

The problem is your welds are just gluing the pieces together. Not melting them together.

If you really wanna learn how to weld, take a class. My first one was only about $600 and Iearned a lot. Really eeeythinf I needed to know for basic projects.

Welding for dummy's is a great book too.

[jonas302]

I think the problem might be slag inclusions they heat and cool and then pop off if your using stick welders this is very likely people have described the proper methods for high pressure pipe fitting but it take a talented skilled welder to pull it off

This job does not require full penetration xray quality welds and I can't imagine any job shop not using MIG on that project it just wouldn't be practical I am not a professional welder but I do 1 inch quite often with a 200 amp mig latest was a 45 ton log splitter a couple passes on the outside with the wire feed and that pot would never leak again there is no way to reach 10 inches into a 8 inch pipe and get a good weld you cant see or position your welder well

[Bullshop Junior]

Lap welding is fairly easy. I would weld on the outside, although the inside is not impossible. A 6011 is what I would use, since it has more flex, or a 70-S6 mig wire duel shield.

[country gent]

Pressurized pipe is only welded on the outside of the joint veed and set with 1/16" gap root pas fills and blends the metals together then blending/ fill passes easch side and and accross the fill beads. Cleaning often. Then a if needed a fill pass accross the joint to blend surfaces. When done the metal is on continuous seam. Here by bending rods in an arc the inside can be welded also. The big issue now is going to be getting all the lead out of the joint before re welding as this will also cause porosity in the weld. On thick metals pre heating is required to get the penetration and flow needed. With 100 lbs of lead in it the weld is actual a pressure weld as the wireght of the lead will produce pressure on the joint. If you cant get the inside because of space Grind outside to with in 1/8" of thru in a U shape pre heat to around 1000 degrees on your burner and weld while hot root passes and chipping cleaning wire brushing frequently until filled. Weld should be continuous and consistent looking. A deep wide U shaped groove is you friend here allowing you to blend and fill also allows room to chip and wire brush easier. Corners are going to be the roughest part holding the angles and motion to blend fill around them. ANother trick if you want to do this yourself is to lay some welds and sacrifice them . Weld let cool and cut apart at seam to see the fill blending is complete with no voids or gaps.

[dikman]

1/2" thick tube and 1" plate! You don't mess around, do you? If you want to make it yourself, a propane cylinder cut in half is more than adequate for melting a lot of lead, and much easier to work with. If you can't be bothered making it, buy one from Mr. Crockett.

The chaps here have explained what's needed to weld your stuff properly, but you really need to separate the two parts first to clean up all the old welds and crud associated with them. How you get a round grinding wheel down into the square corners will be an interesting exercise.

[KYCaster]

The thickness of the metals being welded and the amount of mass to them will suck the welders heat away really quick. Gring out the old weld in a u shape with the edge of a grinding disk to 3/4 of the thickness or so. What you are more than likely dealing with are Slag inclusions in the weld. Thats fux thats been trapped in the fill due to coolness. Grind it out as stated then set it on a burner and heat it good and hot so its already hot when you start to weld. Lay a small consistent root pass around the inside then a small blend pass to the base asmall blend pas to the body and a fill pass overall of it. If arc welding chip and wire brush when ever you start a new rod and between passes. Everything has to be clean and dry start to finish. Now let it cool and again grind the u shaped fill channel around the out side 1/2 way thru or so. Repeat the welding process of heating root pass, blend passes and fill passes, chiping and brushing as stated. The joint when finished will be solid weld and preheating chipping and brushing the weld will allieviate the slag inclusions. Any time you run out of rod or stop you risk an pourous spot. If using a wire feed welder grind out pre heat and weld with the 4 passes wire brushing oftenstopping as little as possible. ( If your welder uses flux core wire you may never get a really good weld. If it was just a "butt" weld with that thickness of metal and no pre heat you may not have gotten the penetration needed for a good flow / blending of the weld. When welding metal prep is important clean fitted joints clean dry rods temps that allow metal to flow and mix. The U shaped channel allows the rod to be worked to blend the fill with the base metals easier than the V grooves. Bu going to the depths above the fill and base metals are blended thru the weld.
Chances are good when grinding the old weld out you will see "pockets" in the weld these are the inclusions that are allowing leaks as they warm and heat the slag breaks flows leaving openings or pourous spots allowing leaks.




Country Gent is right, but doesn't go quite far enough.

The origin of the problem is probably slag inclusions, like he says. Molten lead will dissolve the slag and leave a hole that allows the lead to leak out. It didn't leak with water because the hole is plugged with slag and water will not dissolve it.

Once the slag is gone, the hole is now filled with lead. Any subsequent attempt to weld the same area will vaporize the lead and blow holes in the filler metal, causing more leaks.

The pot you have will be extremely difficult to salvage. Best to save yourself a bunch of grief and start from scratch.

Been there, done that........didn't even get a t-shirt.

Jerry

[JSnover]

...buy one from Mr. Crockett.

What he said. I made a bottom pour ladle years ago from scrap metal. It worked but it weighed a ton. It's good to have the ability to fabricate whatever you need but some times it just isn't worth it.

[40-82 hiker]

I am a professional welder and here is my recommendation: Pitch it and cut a 20lb. propane cylinder in half. Don't HAVE to weld anything, and it holds over 100 pounds of lead, and weighs nothing compared to your pipe and base. Handles help, and maybe a spout for the last couple of pounds, but you can get by with nothing but the bottom half of the tank as long as you do not try to lift the pot to get the last molten lead in it. I don't like the idea of using C clamps like some, as they just might not be screwed down tight enough. What you can't ladle out will freeze and will come right out when cool. You'll enjoy the diameter of the setup much better than what you now have.

Oh, BTW, screw the valve out if it has not been taken before you cut and let it vent for a while. You can use a right angle grinder with a cutting wheel very easily to cut the tank just below the seam (or above if you want-I cut below).

[freebullet]

I'm no expert but i would grind down the welds. Weld both sides after preheating then grind them again to make certain they were solid and give it an additional pass. You could also add extra supports on the outside to prevent expansion cracks. I tend to over build things, they rarely break that way. Sounds like your steel is a bit thick even for me. Takes a heck of a welder to get good penetration on that thick of steel.

[dikman]

I'm with hiker. I welded rebar handles on mine (for safety, something to grab onto just-in-case) and on one I forged a pour spout, but didn't bother on the second one. Simple, easy, cheap and works well.

[jmorris]

It doesn't take much to seal in lead, just a weld that has no inclusions. Even though this one wouldn't cut it for a lot of projects I have done (visual, die penetrant or X ray) is had never leaked lead.

Pot is 3/8" with a 1/4" bottom with a single pass, one start/stop bead of .035" L56 (ER70s-6) wire. You can just make out the weld at the top of this photo.
http://i121.photobucket.com/albums/o213/jmorrismetal/caster3.jpg

Depending on how bad a job the guy did it might be easiest to clean it up and lay down a decent bead with a TIG. The inclusions will show up as a crater and can be filled or ground out until they can be. Or use silicon bronze filler and you can seal right over the less than ideal weld.

[Uptickk]

You guys are simply amazing, thank you for all your help!

There are a few things to address here. First the thickness of the metal is indeed over kill but I couldn’t find any rectangle tubing in the size I wanted that was less than ¼’’ thick. I also needed the base plate to be 1’’ thick to fit the 5/8’’ heaters into the base. My welder is inadequate for this type of welding as it is my first welder and I didn’t want to break the bank before knowing how much welding I would do. I also didn’t intend on welding this thick of steel (why I farmed the gig out). If I could do it over again I would have spent the cash for a proper welder. I have a 125amp flux core welder which works well enough for the little stuff I have been working on with the exception of this. With that said I grinded down the welds and saw the inclusions that were mentioned. This isn’t a top of the line welder so I get a decent amount of pop corning while welding which I think is one cause for the inclusions along with starting and stopping. I re-welded the outside trying to stop as few times as possible and then re-cleaned it when I did stop. The result was 2 of the 4 sides held, the two that didn’t are the two with the heaters. The leaks are minimal but leaks nevertheless. Of course when I put the heaters to heat the pot up in one of them got stuck. I tried cooling the pot but no beans, that guy isn’t coming out. I will try to re-grind and see what I can do with the two leaking sides. I thought about restarting the project from scratch but with one heater in there I would prefer not to have to buy another heater for the new project.

I like the idea of brazing the tiny leaks but I don’t have the materials for that. If re-welding doesn’t work out for me does anyone know what it would cost someone to braze the few holes if that is a viable solution? Also, thank you for the suggestions on the cylinder if this route doesn’t work that might be my solution but I have the supplies and would prefer to see this through if able to do so.

Thanks again to everyone for their knowledge dump and Bullshop I appreciate the offer to help but I am in Illinois otherwise I would jump at the offer.

[40-82 hiker]

I like the idea of brazing the tiny leaks but I don’t have the materials for that. If re-welding doesn’t work out for me does anyone know what it would cost someone to braze the few holes if that is a viable solution? Also, thank you for the suggestions on the cylinder if this route doesn’t work that might be my solution but I have the supplies and would prefer to see this through if able to do so.

I still question your efforts as chasing a bad concept with more bad. Sorry. I'm thinking out loud here, and mean no disrespect.

Here are my thoughts:

1) Have you considered how much energy it is going to take just to heat all of that steel up to temp as well as the lead in it? That is a lot of energy.

2) I really do not think you have much room to work with. Room to work is a virtue when smelting for stirring, straining sawdust off of the surface, and ladling. Also, ease of handling is going to be an issue. What does that thing weigh?

More thoughts on this, but don't want to bombard you, nor sound disrespectful, which I hope you do not think of me. Though I am somewhat grounded now for health reasons, I have been a professional welder a number of years specializing in aluminum welding with TIG, and think you are trying to force a solution in the wrong direction, especially concerning your welder. You really don't need to get a bigger welder to fix this, as the problem, IMHO, is the design to begin with.

In my years of welding and fabrication I have seen myself get caught up in chasing a bad design on occasion, thinking that easier than going back to the beginning. You might be surprised how much easier this could become if you rethink where you are with this project.

Good luck. Let me know if I can help. Not sure how, but willing...

[CGT80]

Uptickk, what process did that welder use for welding the inside of your pot? Stick, Mig/wire with gas, flux core wire feed, tig? Was the inside of the tube beveled when the first guy welded it?

What prep did you do before you welded the outside and did you grind a groove to get some penetration or did you just weld the 90 degree joint? Did you preheat the part?

You might be able to cut the tube/weld and clean it up and have it welded again, this time with a bevel and Mig or tig welding to avoid slag inclusions. It might not be worth it though. I also don't know if welding will damage the heating element. The heat may not, but movement or warping of the plate might crack the element. What kind of element did you use?

I thought about making my own pot, so this project is interesting. I am not a pro welder but can mig and tig some half decent beads. My mig is only a 135 amp machine, but I run ER70S6 and Argon/CO2 blend to get a cleaner weld. Flux core is a pita and I only use it when I have to. My tig will put out 470 amps, but my branch circuit will only supply enough power for 250 amps. If I was nearby, I would offer to help you, to keep your costs down.

I wonder if the first welder didn't do a good job or if they used the wrong equipment or method. I would have expected a clean weld on hot steel to hold. I would have beveled the sides like suggested and welded from the outside to make it easy to grind and weld as necessary.

A pre made pot with no seams would be easier, but you still would have to somehow add your heating elements.

[DaveInFloweryBranchGA]

After reading the entire post, I'm with the advice that says get a 20 lb propane tank and cut it in half. What you have now is going to be a pain in the neck to clean up and once you have it right, you're going to be wasting a ton of propane heating it up to melt your lead.

Sometimes less is more. In the case of smelters, a smaller pot that has shielding around the burner to focus the heat, shielding around the pot to insulate/hold in the heat and a lid to keep heat inside the pot from rising out is a much better expenditure of money for steel than a huge thick steel pot.

I have a very small cast iron dutch oven I use for smelting lead. I can smelt five very full buckets of wheel weights in 4 hours, including all the setup, sorting (this is about 3 hours of the total time), heating, fluxing, cleaning, dipping, ingot making and final clean up/put up. Sometimes it's not about the size, but about the efficiency.

[Uptickk]

40-82 hiker – I know there is no disrespect intended on your part, you are just trying to help a guy out and it is much appreciated. You are 100% right that I might already be down the path of chasing a bad concept. Basically I am trying to create a pot that is similar in design to the magma bullet master. My thought is if it works for them why not me right? The thickness of the steel is over kill for sure (I wasn’t able to track down anything thinner in the size I wanted for rectangle tubing and I thought tubing was the best route to go since I would have less seams for leaks) but that will also hold its heat once up to temperature plus the ceramic wool I have insulating it. Regarding its weight, I plan to keep it in a garage which is a reason I went with the heating elements as oppose to a burner.

If I cannot get it work out in the next round or two (self realization of being stubborn here) I will probably try to track down someone else to properly weld the pot, possibly with it redesigned.

Update on the most recent go around. I rewelded the two sides that were still leaking and so far do not have any leaks which is a bit surprising but I have only run it once since then so I am anticipating it will leak the next time. My shop is an hour drive each way so my time there is limited.

CGT80 – The guy used a Hobart 230v Mig welder with gas. He did not bevel the inside. He actually welded it in front of me and basically took the tubing and set it on the 1’’ base plate and welded the inside. He filled it with water to see if it held and I was on my way. I would most likely have the next person create a bevel and weld both in the inside and outside if I kept this design. I had just purchased my welder so was a complete novice and figured the guy knew what he was doing so I didn’t really question his approach, plus it held water at the time.

Since the base plate and the tubing are the same dimensions my prep consisted of grinding the old weld off and simply welding where the two pieces came together (not 90 degrees just a flat joint) and then re-welding a line on each side. Creating a grove would have been preferable and will probably occur on a next pass if needed.

The elements are watlow cartridge heaters that slide into the base. The welder also drilled those 5/8’’ holes in the 1’’ base plate for me as well.

I agree with a premade pot being the way to go (why I used the tubing on the top) but as you pointed out the heating elements would be an issue. I honestly thought the welding of the two pieces of steel together would be the easiest part since I farmed it out, turns out is has been the hardest.

DaveinFlowery BranchGA – Thanks for the propane tank suggestion. If I cannot seem to get this to work that might be one of the redesign approaches though I would prefer not to use an open flame in the garage.

Thanks again to everyone for their input!

[dikman]

As a long-time amateur welder (!), one thing I did find was that it's easier to weld thick, heavy steel using a decent size rod and a very basic arc welder running flat out!! The key is to make sure that the steel is clean. Any weld that didn't look right I ground off and re-welded. Many many years ago I built a trailer to tow off-road bikes, using 2" square steel tubing and that basic arc welder.

Uptickk, once you get the hang of it you should be able to get welds good enough for what you need - if not grind them off and re-weld. The biggest problem I found with an arc welder is the potential to warp flat plates!

[oger]

As a welder in an oil refinery for too many years the one thing I can say is in most cases using a mig welder on heavy old used steel can get you in trouble. The good thing is that he didn't use core wire so you really shouldn't have slag problems just miner weep holes or some cold lap. I would grind out the outside and reweld it with 6011 (ac machine) 6010 (dc machine) that should clear up your problems.

[DaveInFloweryBranchGA]

DaveinFlowery BranchGA – Thanks for the propane tank suggestion. If I cannot seem to get this to work that might be one of the redesign approaches though I would prefer not to use an open flame in the garage.

Smelting or casting in your garage is a bad idea unless you're going to be installing fume hoods with exhaust fans. Lead fumes are NOT good for your health. The flames of the smelter would be the least of my worries in my garage. I smelt/cast outside, use a fan to blow the lead fumes away and wear an appropriate mask with fresh filter elements installed every year. Lead fumes are nothing to fool with or take lightly.

If I missed reading you are taking the safety precautions mentioned, I apologize.

[FLYCUTTER]

If you are determined to use that pipe because you most likely already purchased the heater for it I would put a wrap-around the pipe, mark it with a soap stone, take a torch and cut that pipe on the line with a bevel. Junk the 1" and use 3/8 or 1/2 " plate and stick weld it up as described in above posts. Sometimes starting over is a lot easier.