forge welding mild steel

[evfreek]

Hi. I spent some time working in someone else's shop, and I was having great luck forge welding. Wire brush, no wire brush, hot or cold, everything was sticky. If it came apart, it stuck right back together again. No lines. I thought it was the forge, or the coal. It was a kind of smelly sulphurous coal that I had never used before. Before I secretly stashed a small bag to bring home , I brought out a partially completed piece that I was having troubles with back home. It was still difficult :confused:. The same old slippery problem. The metal would never get very sticky in the fire, and the joints would often shear apart. Then, I suddenly realized that almost all the troubles I was having came from one lot of hot rolled A36 that I bought from a single supplier.

On some searches, I have found that people have observed slight composition (and therefore forge welding differences) between different pieces of hot rolled A36. Is this reasonable? Is there any good method for dealing with this problem?

[Woody]

Most welds fail for one of two reasons. 1. Not getting the metal hot enough, 2. Hitting the metal too hard when trying to fuse the weld. My guess is that you are not getting the metal quite hot enough. Remember that color is a relative thing, what looks like welding color in one shop may look differently in another shop due to variation in lighting between the two shops. Also if you hit it too hard with the first few blows you will cause the almost molten face of the metal to be squeezed out of the joint and the weld won't take. I would shuggest that you get a vise close to your forge, clean the metal thoroughly, heat to dull red, flux with borax, then take it to welding heat and put it in the vise and squeeze it together, see if that makes your weld stick. Also mild steel welds at a hotter temperature than higher carbon steels and some alloys.

[CurlyGeorge]

I agree with Woody on the two most common reasons for welds not taking. I had an old smith tell me to put my hammer down. Now pick up the smallest hammer that you have and just tap the weld together. Right away I started getting better welds. Try it. It works.

[hill.josh]

The only problem I've ever had with forge welding is not getting it hot enough on the inside because if it doesn't soak long enough it loses it's heat to fast just moving from the forge to the anvil.. and thats what it sounds like to me. There might be something in the steel (im not an expert but) i do have alot more trouble welding rebar than higher quality steels...

[Mills]

I have had some trouble with a stick of HR. After using it up my troubles disappeared.

[Alan B]

Evfreek,
Most A36 now days is remelt. They don't do a real picky job of sorting the steel before remelting it and casting it into new bars and such. I had a piece of A36 I was working with one time, quench and harden to the point that a cobalt drill bit would not cut it. Pretty good chance you may be experiencing a similar problem forge welding.

[Jymm Hoffman]

Don't forget that scale could be the problem. If you wait too long and all the flux is burnt off, scale will build up, not flowing off and prevent a good weld. Sometimes people wait too long while trying to "soak" the steel in the fire. Is your fire shallower than the one you had great success. If that is the case, you may be too close to the air source which may also cause excess scaling in comparison to the other fire. Also, if there happens to be more carbon in it, the welding temperature may be lower, not higher. Most of my welds are done at a bright orange, not white. I find that having both (or all) sides to be welded are the same color with the flux dripping or flowing. Quick light hits were mentioned earlier, but also turning so that the anvil is not sucking the heat out of one side only, back to trying to get or keep everything at the same temperature.

[Donnie]

I've had similar problems forge welding mild to mild. I seem to have no problem with mild to high carbon. But .....mild to mild......very frustrating.

[Frosty]

Jymm:

What are you fluxing with?

Thanks

Frosty

[Avadon]

Can someone reccomend a good flux? (for working A36 and most mild steel?) can it be bought locally?

[Jymm Hoffman]

I mix my own flux, 4 parts anhydrous borax to 1 part boric acid. Works fine in both gas and charcoal (so I it should be fine in coal as well, just haven't been around a coal fire to try it.)

[ThomasPowers]

Well I have had problems with certain sticks of mild myself and a lot of my projects use forgewelding---just cause I can---I have a spangen helm where I welded the bands together, forge welded trivits, lots of pattern welding of bandsaw blade and pallet strapping.

One suggestion I have heard is to take a grinder and remove the bark on the piece as the surface put on at the mill seems to resist welding more than the metal just underneath it.

Me I generally switch to another piece and leave that one for projects that don't require welding.

[hill.josh]

Can someone reccomend a good flux? (for working A36 and most mild steel?) can it be bought locally?

Avadon, I just use brazing borax from home depot in the soldering section.. it works pretty good for me. Or at least i think so, I get about a 95% sucess rate with it. Only thing I've ever used though..

[Frosty]

I mix my own flux, 4 parts anhydrous borax to 1 part boric acid. Works fine in both gas and charcoal (so I it should be fine in coal as well, just haven't been around a coal fire to try it.)

Thanks Jymm, that's the same mix I use though I don't use anhydrous as a little foam has never bothered me.

I think I'll have to try welding at orange heat soon.

Borax as in 20 mule team borax found in the laundry section of your local mega mart. Boric acid can be found in the pharmacy section or in the insecticide section as roach killer "RoachPruf" being a national brand name.

Do NOT use BoraxO the hand cleaner, it has soap in it with the borax as an abrasive and surfacant it doesn't work as welding flux at all.

You can dry borax in the oven at 220f to 240f and remove about 90%+ of the moisture. You can also melt to a hard glassy mass and grind it to a powder to remove the last couple % (hygroscopic water) and have anhydrous borax but keep it in a sealed container or it'll absorb moisture from the air and all the hard work (and it is hard work) will be for naught.

Frosty Edited September 13, 2008 by Frosty

[Dutchmancreek]

One suggestion I have heard is to take a grinder and remove the bark on the piece as the surface put on at the mill seems to resist welding more than the metal just underneath it.

I nearly always grind the surface of the weld area. The mill scale or whatever surface it is can make a weld very difficult. Some steel has it and some doesn't, but I treat it all the same.

Steve

[ThomasPowers]

Roach Proof is a LOT cheaper than buying USP boric acid at the pharmacy! (98% boric acid IIRC with a tad of colouring to it so you can identify which flux you are using!)

[Avadon]

Avadon, I just use brazing borax from home depot in the soldering section.. it works pretty good for me. Or at least i think so, I get about a 95% sucess rate with it. Only thing I've ever used though..

Thanks Josh, too bad I didn't read this earlier.. i was just right there at lowes lol.. but next i'll get some.

[Avadon]

Well I have had problems with certain sticks of mild myself and a lot of my projects use forgewelding---just cause I can---I have a spangen helm where I welded the bands together, forge welded trivits, lots of pattern welding of bandsaw blade and pallet strapping.

One suggestion I have heard is to take a grinder and remove the bark on the piece as the surface put on at the mill seems to resist welding more than the metal just underneath it.

Me I generally switch to another piece and leave that one for projects that don't require welding.

Thomas, i've heard you talk about these forge welding projects a few times. Any chance you could give us newbs a little picture tutorial or step by step on how to weld up sections of metal strapping, hacksaw blades, etc. into these "billets" and then forge welding them into something. Or if you've already explained the process would you mind linking me to a thread? Much appreciated.

[KYBOY]

Mild steel from my supplier is bad to have a very heavy coating on it..If its not taken off it can hamper welding badly...I beat my brains out trying to figure out what was wrong :D

[blafen]

I use borax, sometimes with iron filings in it. i heard if you mix boric acid (roach killer) with the borax you get an extra aggresive mix, A few years ago I heard Jim Hrisoulas refer to a mix that he would not divulge as it eats refractory at an extremely high rate and used dangerous chemicals.

[evfreek]

Hi. Thanks for all the suggestions. I'll try them out (except the ones about getting the piece hotter and making sure the fire is deeper-I tried these already). The interesting thing is that most of the scrap lying around the shop was cold rolled, and that seemed easier to weld. It may well be the mill bark, which looks more like than paint than scale. The problem is that I usually work in period shops, where there is no grinder. But I have an hand crank grinder, so this should work.

The suggestion about lighter blows is a good one. But, I have not had consistent results with it. Sometimes there is a little bit of stick that shears apart immediately. Contrast this with my experience with another piece of steel (good welding quality) which I can hit any way, crosswise, diagonal, at some funny angle, hard, soft, etc., and it just will not shear.

I did some experiments with the funny piece of steel. A spark test shows no anomalies. I can spot the presence of even a small amount of chromium when spark testing, due to lots of training with samples, and I don't see it in this piece. Anyway, a little chromium does not make the weld impossible. Perhaps it could be some other tramp element. I have noticed that some A36 is water hardenable, and I can even get it to crack, but this shouldn't, in itself, affect weldability. This funny piece welds just fine with TIG (grinder used ) or stick (6011 =>no grinder ).

As for scale issues, I am not so sure that this is the problem. I just saw two demo's back to back in which the demonstrators intentionally did not use a wire brush before forge welding. The first one even went so far as to list it as one of the "myths of forge welding". He challenged anyone who had any questions about this to consult the composition of Easy Weld, which is made up of a large proportion of scale. He then went on to say that if you don't wire brush, you get the ingredient for free, you don't have to pay the higher price, and you get a superior flux. The other demonstrator did not use a wire brush simply because he was from Williamsburg, and it was not period accurate. He said that stubborn build up's of scale could be removed with a "scale scraper" (anyone have a blueprint for one of these?), but he did not use one in his demo. By the way, I purposely tested the "good" steel, and it forge welded just fine with zero wire brushing.

All these tests were done with plain 20 mule team borax. I have also tried borax with boric acid and iron filings in it. Similar results. Someone told me that with a stubborn piece of A36, even the addition of fluospar does not help, but I have not tried this. Interestingly enough, in a web search, I saw an excerpt from Machinerys Handbook suggesting the addition of iron, not steel filings, to the flux. These days, it is hard to get iron filings. I have a whole bunch of mild steel saw swarf. I make sure to clean up really well after cutting alloy steels, so there should be little contamination. Is this stuff useful (and the caution from the Handbook somewhat out of date)?

[Woody]

Beware when using fluospar, the fumes given off by heating it are very toxic. Hydrogen Fluoride to be exact.

[Rich Hale]

Brake drums are cast iron and when they resurface them the by product is iron filings.....

[ThomasPowers]

Of course mild steel is not period appropriate for Williamsburg either becomming commercially important after 1856 with the Bessemer process...

Real wrought iron is pretty well self fluxing due to the entrained silicates and can take the higher temps as well.

[pinetar]

I am trying to understand the welding process and still considering a used Johnson gas 121 oven which takes 50 minites to get to 2300 deg. How does that compare to coal?

What about the popular gas forges mentioned here, how long do they need to fire t reach 2300?

gary