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iron dust in flux?


Brian Myers
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I've read in several places about putting iron dust in your flux. Opinions vary lol. I can see how those tiny particles would melt and aide in welding...but if the heat gets too high I can also see the carbon burning out and you're left with an impurity in the weld. What is your general opinion?

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Don't know but will stay tuned for answers! If your theory holds up then, in theory you could raise the carbon by adding high carbon iron dust in the flux. I would think that if you hit the correct welding temp needed to weld, it should not burn out! Then again this is just a theory in my head and not a real educated deduction! focus.gif I understand there is a lot of science going on here that most including me do not always understand. It is funny though people like Kevin Cashen actually understand it and actually can explain the science in lay-men's terms gossip.gif where if I read it about three times even I can understand it, help.gif most of the time, that is! banghead.gifbiggrin.gif

 

Pardon all the smilies, I am just in one of those moods this morning. But will seriously be waiting to hear from those in the know!

C Craft Customs ~~~ With every custom knife I build I try to accomplish three things. I want that knife to look so good you just have to pick it up, feel so good in your hand you can't wait to try it, and once you use it, you never want to put it down ! If I capture those three factors in each knife I build, I am assured the knife will become a piece that is used and treasured by its owner! ~~~ C Craft

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My take on it is that it depends on what you're trying to do. I recently mixed up a batch of flux for use on mild steel that won't weld to itself any other way in which I mixed anhydrous borax, boric acid, a touch of fluorspar, and a fair amount of steel dust from the bandsaw swarf pile. It worked on a mild-to-mild weld that straight borax/boric acid/fluorspar wouldn't touch. Why is this? There are a few different things going on here:

 

1. The steel dust does hit welding heat sooner, and having tiny particles of welding-heat steel swimming in the flux is a good thing, as it sort of presets the weld, if you follow that, because:

 

2. The steel dust is higher carbon (it's a mix of everything I cut, from wrought iron to O-1, but mostly 5160 and 1084 with a lot of 1018) than the mild steel. High carbon welds both more easily and at lower temperature than mild steel. Jim Austen uses a bit of 1095 shim stock between the mild steel scarfs on his assymmetrical axe-eye welds for just this reason. The mild-to-high carbon weld will almost always work beautifully, while a mild-to-mild weld is probably the hardest one you can do because of the temperature required, which is just short of burning the steel. Having that thin layer of higher carbon in the joint allows you to get the weld a couple of hundred degrees cooler than would otherwise be possible in a coal forge. This is why some of the "secret formula" welding powders aimed at the ornamental smithing market such as Cherry Heat and E-Z Weld have cast iron filings in them. The cast, being even higher carbon, actually melts and diffuses carbon into the steel, allowing a lower temperature weld. My batch I mixed up is basically a copy of E-Z Weld.

 

Now then, you are not actually raising the carbon content very much because of the small amount of HC stuff and the fact that carbon diffuses so quickly at welding heat. Another way to think of it is, you're basically just throwing a can of lighter fluid on a fire that's not starting well, you're not using a flamethrower.

 

What are the cons? You do not really want to use steel powder flux on pattern-welded blades. This is because there are so many weld surfaces in a typical damascus blade that you will indeed mess with the carbon content, but more importantly you are introducing some funky alloying elements into what should be a very clean line of only two alloys. This results in a fuzzy weld line, and since for a damascus blade you are using at least one high-carbon steel to begin with you do not need the extra stuff in your flux.

 

I resorted to the steel powder when I had two hawk head failures in a row. I use mild steel for the body, and I do not etch these, so the bright line in the weld will not show when polished. For the bit weld, I use straight borax only because you will see the weld line between the 1084 and the 1018/A-36 when it's polished up.

 

I hope that helps.

 

Edit: I forgot to address the "burning out" question. The answer is no, if you're burning the carbon you've boiled off all the flux and it's not going to weld anyway. A few sparks is okay on mild steel or wrought iron, dangerous on high carbon, and if you have a full-out sparkler effect the steel is ruined no matter what the carbon content. Cut off the burned part and start over. There's no free pass to any of this, you have to pay attention at all times.

Edited by Alan Longmire
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I have used flux like that and it works best on parts that need heavy forging after you weld them as it leaves a bumpy surface if it doesn't get touched enough by the hammer. I have used it to close up voids in my first damascus billet when I was forging my wife's ring out of it. Worked great. If I was doing flower and leaf welds I wouldn't use it as the stem would be left with this bumpy surface so often I use it in conjunction with my borax the iron included flux used directly on the faces to be welded and only there. The borax then used on the rest of the metal that will be up to a welding heat to try and protect it from scaling away as I weld the parts together. Just another tool in the box to help with my welds.

"Remember to live life to the fullest and without regret for the joy of life is that it ends." Me http://ipneto.deviantart.com/

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Alan - Have you ever etched a hawk that you used this flux on? As you say, there isn't very much HC stuff there and the C will diffuse a bit. Just curious as to whether or not you even COULD make the seam show up like that? Re-phrased: Would the bright line really show up?

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I have not, but in the interest of science I'll etch this last one when the time comes. I doubt much will be visible myself. It'll be a couple of weeks before I do it, so have patience. ;)

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Darn Alan, I'm quite impatient... So I'll be suffering! :(

To become old and wise... You first have to survive being young and foolish! ;) Ikisu.blogsot.com. Email; milesikisu@gmail.com mobile: +27784653651

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I forge weld a lot. Except for the axes, all my welding is mild on mild. I've come to use pure iron powder and anhydrous borax for most of my welds, sometimes just the borax. I find using the iron powder makes the weld go almost effortlessly. However, I don't mix my iron and borax, I first put on the iron powder and then the borax, I find that works better then mixing the two together. I had never heard that mild steel was harder to weld, learn something new :-)

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mild steel is indeed harder to weld if you are used to welding high carbon steel in a gas forge...which is nice and easy....

Although I find that its really a case of switching hats properly before attempting one material after a long time using the other.

forging soul in to steel

 

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I'm glad this came up, I won a jar of EZ-Weld from Batson's shop, according to the donor, in the Iron In The Hat at F&B this last weekend. I have no idea what's in it, but I saw the little metal shavings, and wondered what was going on in there. The rest just looks like ash.

The Tidewater Forge

Christopher Price, Bladesmith

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mild steel is indeed harder to weld if you are used to welding high carbon steel in a gas forge...which is nice and easy....

Although I find that its really a case of switching hats properly before attempting one material after a long time using the other.

My skill base is the mild steel. Except for the axes, I've never welded high carbon steel. And that has been maybe 15 times?

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  • 5 years later...
On 3/23/2014 at 11:08 AM, Alan Longmire said:

My batch I mixed up is basically a copy of E-Z Weld.

What percent cast iron filings did you use?

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That's about what I was thinking. I found some cast iron filings that is used in making sparklers And some cast iron powder used in pyrotechnics. What would be the best bet? The powder is quite a bit more expensive.

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That makes things a little easier. I have a bunch of cast window weights that were left in the house we bought. I can drill a bunch of holes in them and collect the remains. 

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