Argon over the casting pot?

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  • Last Post 18 September 2009
featherhead posted this 05 August 2009

I think I've read every post in casting 101 and am waiting on my gear to arrive. Thinking about my heat treating process for knife making and wondering if anyone ever considered pumping a little Argon over the melting pot?  To create an oxygenless environment.  Thinking about fitting a piece of metal tubing say 3-4” high over the pot with a plate glass top for viewing and a fitting to pump the Argon.  I've not watched a casting pot lately, but assuming it starts out with wheel weights that have been cleaned and smelted from a large batching process, the pot's been fluxed and the temp is right; what would ya'lls opinion be as to the influence of atomospheric oxygen on the surface of the melt?

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Duane Mellenbruch posted this 05 August 2009

Some folks just apply a thin layer of clean, dry cat litter to cut off the oxygen and insulate the surface to hold in the heat.  Adding ingots is not an issue either.   Argon sounds expensive.  Do you think the set up would be cost effective when casting with WW or scrap alloy?   Duane

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RicinYakima posted this 05 August 2009

Atomospheric oxygen is the main problem with keeping the tin from oxidizing and the reason for so much fluxing. Anything you can do will help. I have tried fitting a metal cover over the bottom pour pot and adding a tablespoon of sawdust to creat a CO2 covering. It helps but is a pain to add ingots and then when you flux, you have to scrap all the unburned carbon out of the melt. Ric

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featherhead posted this 05 August 2009

If you have a TIG welding setup, you're ready to go.  I was thinking about matching a metal (AL) ring say 3” high over the pot and milling a shoulder on top to drop in a piece of plate glass for viewing.  Then drill and tap for an inlet valve.  An 8 sec flow from the TIG torch ought to be enough to create an oxygenless environment.  I wonder how much of what we think is dross and other contaminants is actually just surface oxidation?  How many minutes does it take the average melt in a casting pot to turn competely black on top? And what exactly is happening with the TIN?  Is it rising to the surface and does the flux drive it back into solution with the lead?

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King Mud posted this 05 August 2009

I think that you are on to something. It doesn't take too long for oxidation to start, esp if you are running your melt a little warm. I have heard that tin oxidises much easier than lead, so it would stand to reason that the first thing to come out would be your tin.

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featherhead posted this 05 August 2009

Cool,  Midway has warp speed shipping, my pot arrived today, so I'm thinking about a short sleeve with maybe a metal lid with cut outs for the valve arm assembly and probably a thermometer.  Since the Argon is heavier than O2 it should stay put as long as there is no significant draft going on.  My lead is on its way so I ought to be able to offer some feedback soon.

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RicinYakima posted this 05 August 2009

featherhead,

There will be a lot (!) of draft going on. That has been the down fall of the designs of the past. There is a constant air current up the outside of the pot of room air the makes turbulance over the open top. I think it is doable, but I don't have the metal working skills to make it happen.

Ric

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Lillard posted this 05 August 2009

A lite breeze will blow the argon out from under the nozzle on my mig welder. I think the argon will get out of the pot pretty easy. I have a flow meter on my welder a very low flow setting would keep gas in the pot all the time. I wonder if a long casting session would use to much gas. I am interrested in how your set up works when you get up and going if you can post a photo.

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corerf posted this 05 August 2009

Checking into the Argon conversation. I TIG weld! Argon will settle like water on the top of the pot. Similar to backgassing an aluminum weld (blind joints), adding argon thru a copper tube in a foil tent will absolutely gas off the O2 and other air components. Poke a small pinhole (at top) in foil to allow some positive upflow, hang the argon pipe in the pot like a washing machine waste hose, cover with foil as best as you can. Better load the pot full, reloading will require a second backgas. Keep flow of argon at 5 CFH and I am willing to bet you have very little loss of tin....maybe 7 CFH. Run the gas from the time the pot is loaded with cold ingots till your down to 300 degrees at end of session.

Can't liken this to a TIG weld and blown off argon at a weld. The argon is confined and pushes the air up inside the tent. It's a positively pressurized environment, with continuous argon flowing.

Commenting on Yakima Rics statement about constant circulation due to heat rising, in a sealed environment (tent) only argon is present, so circulate as it may.

Argon bottles are not cheap, $50-70 (80 cubic feet) plus $34 for a fill, plus 5 yr hydrotests. At 80 Cu feet bottle, you'll get 16 hrs of service at 5 CFH rate. Thats alot of casting. Thats also almost the smallest bottle worth having. A 55 cf. is too little. Flow to 10 CFH, still 8 hrs of continuous duty. I think 5 CFH is too much. You can antifoul a patch about .5 by .5 inch at 20-22 CFH in free air in 2 MPH WIND. So 5 CFH contained is a no brainer!

Oh yeah, go to harbor freight tools for a cheesy regulator to flow with reasonable accuracy if you dont have a pocket mig or a tig system already to bastardize.

Awesome Idea. Thats my .02 dollars

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codarnall posted this 06 August 2009

As long as you are in a well ventilated area crushed charcoal for the BBQ will insulate the melt and flux the metal at the same time. Carbon monoxide is why you need to be in the open etc. It's the reducing agent to keep the metal fluxed. Little or no smoke too.---Charlie

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featherhead posted this 06 August 2009

Awesome input and suggestions here, I'm honored to have you guys as resources. 30 years ago there were no forums. But sometimes depsite the forums there is a wide range of outcomes reflected by various postings that end up comparing apples to oranges. I'm not talking about this post, but the one about mold release agent varied wildy in outcomes. I think a lot of it had to do with pot contamination and dropping raw WWs into the pot vs smelting down to pristine lead alloy and keeping a clean pot.  I'm going to have to melt some lead soon and get my own hands on.  Given my equiptment, skills and preferences I'd like to see a clean shiny (terminator III style) liquid metal looking melting pot if possible. So while my Lee 40 molds are on backorder I think I'll look around for a piece of 5 to 6” thick wall AL tubing and try to mill it to fit down over the top the of Lee pot. Then I'm thinking a flat AL plate on top to keep the argon in but allow quick access for refills, temp checks and visual inspection.  I'm guessing that I may be able to simply keep my TIG torch handy and give the pot an 8 sec post flow on occasion and see how that works before using a constant flow.   

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Dale53 posted this 06 August 2009

Gentlemen; "I have no dog in this hunt", BUT-T-T-T, you are trying to make something simple REALLY difficult!

I use mostly four cavity and six cavity moulds. I can empty my RCBS 22 lb pot in 1.0-1.5 hrs. There is little (unmeasurable) change in my alloy from start to finish. Talking about pistol bullets, I can cast them plus or minus a couple of tenths of a grain from beginning to end. I am talking MATCH QUALITY BULLETS.

I flux my pot ONE time, and that is when I fill it. I start with clean metal (I do my smelting in a Fish/Turkey Fryer and a 12” dutch oven and NEVER put dirty metal in my casting pots).

Metalurgists tell me tin does NOT separate from the mix once alloyed (read Dennis Marshall's information in the Lyman Cast Bullet Handbook, 3rd Edition).

You are trying to combat a problem that doesn't exist in any meaningful way. I have cast, conservatively, 300,000 pistol bullets in the past 50+ years (I sold cast bullets to help my shooting costs in my early, low earning days). I'll put my bullets up against anybody's cast bullets for quality. This is not to brag but merely to point out that I DO have a bit of experience. Please don't make this so hard - if you do, you'll find something else to occupy your time and we need you as fellow bullet casters and reloaders.

FWIW Dale53

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featherhead posted this 06 August 2009

Thanks DALE,

I'll be casting 40 cal 175gr TC in a Lee 6 cavity mold.  Buying my lead from some Ebay guys who seem to know how to clean up WWs pretty well.  Got the 20lb bottom pour Lee pot. Ya I'm guilty of reading too many threads. I'll let  ya know how it goes. 

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featherhead posted this 07 August 2009

Just read Richard Lee's book on Casting prep. He says fill it with lead, turn it to 7, wait for the lead to melt, add a pea sized lump of beeswax, stir well, skim the gray matter and it's ready to go. He says the #1 problem is zinc.  The least amount will cause casting problems. Possibly a reason why so many guys on the board report all sorts of difficulty. He does go into a rather complex mold prep process.

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featherhead posted this 25 August 2009

Casted my first 200 slugs this afternoon.  Everything went smoothly.  The WW ingots melted nicely and the pot fluxed well with parafin wax. Have a long handle paddle and welding gloves on when the parafin flames. The Lee 6 cavity released very well.  700 degree was the sweet temperature.  625 cause some slowing of the drip and poor filling. Had to watch the thermometer as the temp fluctuated as much as 100 degrees with a small touch of the thermostat.

Just have to load a few up and see how they shoot.

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hunterspistol posted this 25 August 2009

A lite breeze will blow the argon out from under the nozzle on my mig welder.   Yes, that's what I do for a living too.

That's great, you're on your way to shooting.  Show us some pics of the casting set up if you can.  It's always nice to see someone starting out.  My biggest problem is working out more than one caliber at a time. The ones that work are the ones that have my undivided attention. Might be the biggest reason they do work!

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featherhead posted this 26 August 2009

Yeah Man,  I set up on all steel.  Use my welding cart with a metal stand to get the pot up to a high working height to see the lead pour.  Plus I have a dust extraction system not shown with a port about 16" above the pot to suck fumes.  I filled my shop with fumes yesterday real good before I turned on the extractor.

Set the pot up nice and high

Got bonus storage room under the pot stand

 

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hunterspistol posted this 26 August 2009

   I like that, you have it set up so it's up in the light and you can see what's going on.  Of course, the Miller and steel rack have me biased a bit too, lol.  

     I found a deal on ebay for parafin wax.  Camphill village candle shop has a 10lb block for $25.  It's a little purer than the Gulf wax even if I don't know if it matters.  They pay $11.50 for the shipping, so it's a pretty good deal.

      Oh yeah, that's a well-equipped good looking shop there.  You have things looking really good.  I have a crumby old carport but, it works.

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featherhead posted this 14 September 2009

Been casting my little heart out all weekend.  Here's the aftermath.

Probably did about 800 slugs.  170 gr TC 40 S&W.  Out of a Lee 6 cavity mold.

What have I learned?

Don't need argon over the casting pot. one good fluxing is all it takes to empty a hot pot.

Parrifin wax?  Better have a long handled spatula and gloves and fume extraction ready for when it starts smoking up the shop and especially when it flashes into flames.  Possible the commercial flux guys saw this problem and set out to solve it by developing a high flash point low fuming product.

Lee mold are good to go out of the box!  I Read volumes about how guys are tearing down their molds and remanufacturing them, remachining, polishing sanding and what not. Clean the cavities only with a good solvent.  Just give em a good smoking wih a butane lighter.  Lube the pins and hinges with liquid alox.  Pre heat em to about 250 and start casting.

Wheel weight lead ingots are pretty clean and cast well.  After first session I left an inch of lead in the pot, remelted some sprue, fluxed the pot and shut down.  Got about 200 slug from 10 lbs.  Second session, I put in 10 ingots, recast the sprue and got 10 lbs of bullets out.  About 400 bullets.  First session I did water drops, second and third sessions I just dropped onto a towel.  Since I'm shooting at 1000 fps I think it'll be better to keep the lead softer.

Watch the lead stream fill the molds.  If there's one factor that I think it critical to a good bullet, it's a good consistant stream of lead pouring into the old.  The Lee bottom pour pot is touchy and I had to be on the ball with adjustments on the screw to keep a steady lead stream.  Too slow and the bullets wrinkle. too fast and the sprue hole floods over top. I tried to keep the stream pouring down the side of the sprue hole and let it pile up real good on top and try to connect all the sprues so jut one big blob will cut,  makes it easier to put em back in the pot.

Casting temps vary wildly.  The Lee pot can swing from 600 to 800 in no time at all, with no adjustment.  I felt comfortable leaving the thermometer in the pot and tried to keep the temp at 700.  You can get good bullets at either temp if you pour the mold quick enough.  As the mold heats up, the sprue will cut with no effort.  Cool it down on a wet towel and it gets a bit tougher to cut. 

Couple ?????

The Lee 4-20 pot ..... 20 lb capacity?  Why can I only fit 10 1 lb ingots and it fills to the top?

Lubing bullets?  Lee recommends lubing, sizing and relubing.  I wonder why go through the process twice.  Lead is so soft it'll go through the Lee bullet sizing die with no lube at all. It puts a nice shiny ring on the bullet lands and brings them into full concentricity.  Then one lubing and it done.

 

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largecaliberman posted this 18 September 2009

featherhead wrote: I think I've read every post in casting 101 and am waiting on my gear to arrive. Thinking about my heat treating process for knife making and wondering if anyone ever considered pumping a little Argon over the melting pot?  To create an oxygenless environment.  Thinking about fitting a piece of metal tubing say 3-4” high over the pot with a plate glass top for viewing and a fitting to pump the Argon.  I've not watched a casting pot lately, but assuming it starts out with wheel weights that have been cleaned and smelted from a large batching process, the pot's been fluxed and the temp is right; what would ya'lls opinion be as to the influence of atomospheric oxygen on the surface of the melt?

Argon is expensive.  A lot bullet casters are scroungers (like myself) and for the majority of bullet casters are frugle like myself.  To minimize oxygen entering the pot, after firing up my buner, I would cover my pot with a lid to seal off a majority of the O2.  By doing this, I will also keep a lot of the stinky smoke in the pot.  After the batch is melted down, I would skim off all the crud from the surface and I usually flux well with parafin (2 times) then flux again with Marvelux and pour the metal into ingots.

On my Lee 20# casting pot, I would cover it with a lid from a tea pot that fits perfectly - same principle.;}  The amount of money (lead) lost through oxidation does not outweigh the cost of argon. That's just my 2 cents.

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