I have decided to try forge welding. Should I use flux or not? And, what size of stock would be best to start with?

Arkham - Use flux.  Borax (not Boraxo) works well.  You can find borax in the laundry section of some big box stores.  The band name I get is "20-Mule Team."  Try 1/2 inch square stock.  Be prepared for frustration.  Really, your best bet is get with a smith who is good at forge welding and learn hands on.  Three critical issues are 1) Getting the right temperature (judging the color), 2)  How and where to hit it, and 3) When to stop hitting and reheat and refine the weld.  These things have been discussed a lot on this site, but hands-on with someone is the best way to learn. 

 

Walking Dog

Yes use flux! You can use borax, or there's a product called iron mountain flux. It has iron in it and it makes forge welding super easy. I've had no bad experiences with it. Down side is, it costs a lot more than a box of mule team. 

Flat stock works well to start with. Make rungs out of them. And after welding, and cooled, they will ring if welded. If not, it's just a thud. 

Borax works well you can also mix borax with iron powder purchased online for fairly inexpesive and make your own iron laden flux 

i caint give a recipe as i havent tried it 20 mule is cheap and it works 

 

 

You should use the flux that's good for the alloy(s) you are going to weld---which you didn't say.

You should use the size of stock that's easy to heat in your size of forge---which you didn't describe 

I hope this answer is specific enough for you!

well, if you are welding wrought iron you dont need flux. I would recommend wrought iron if you want something easy to forge weld, though if you are wanting to practice forge welding to work your way up to pattern welded steel, than I recommend practicing on scrap high carbon steel, practicing on wrought iron or even mild steel is a completely different animal than welding high carbon. 

                                                                                                                                                     Littleblacksmith 

I think you should start with thin stock (like 1/8 - 3/16”) and do some faggot welds just to get a handle on temperature and color.  @jlpservicesinc taught me how easily thin stock welds.  Try to make the weld before it starts sparking.  Once you get that working consistently you can try out making some scarfs and welding thicker stock.  Check out Rowan Taylor on YouTube,  he has a great video on scarf welding and he is highly talented.  Denis Frechette (DF in the shop on YouTube) has a great project making a “squirrel cooker” that I did as my first project requiring a scarf weld.  Mark Aspery also has a great video on “scarf theory” you can’t miss just by searching for his name and the words in quotes.

Thin stock will get you success.  The thicker stock will lead you to inevitable but necessary failure.  Good luck.  

Thomas’s response was 100% on, though.  Forge welding is very situation specific, so you lack of detail in your question would lead one to believe you weren’t ready.  Follow my advice and you will be.  How do I know?  I’ve been through it relatively recently.

Lou

And are you burning charcoal, coke or coal??

Use flux no matter what material you are welding.. Start off with chain making or fireplace poker making.. https://www.youtube.com/watch?v=uS0CqaXwNNc&t=1081s

 

In order of mistakes they run about like this:  The biggest problem with new people and forge welding is not having the both pieces of metal at the same temperature, bad scarfs, to hard a hit, not fast enough with the hits. or to low a temperature.. 

biggest thing is.. If the metal does not stick on the first hit of the hammer.. Stop, clean and reflux and take another heat..  Ideally as soon as both pieces touch if you give it a little wiggle you will feel it stick, then light fast taps to tack the weld solid, then  clean, flux and take a full welding heat and finish up.. 

Scarf length plays into how long it will take to finish off a weld.. A short scarf will finish out faster than a long scarf.. With that being said a lap T joint can be a long scarf but if the scarf is forged properly it's a 2 heat deal..  

The most important part of the scarf is the tapered out ends.. These should be tapered right out with no square edge..  

One other thing.. is stock selection.. I have found that a material that ='s about 3/8"-1/2" to be about the easiest for a beginner..  Square or retangular is best vs round..   = is 1/8"X1 has nearly the same  mass per foot as 1/2 sq,

  3/8sq, so it won't roll if welding 2 bars together  or  1/2" round if making chain (will not roll as it's bent into the U before welding.. 

Thanks for all the advice, especially jlpservices, by the way, love your videos. I will probably rewatch some of the chain making videos and start there. By the way, I am using coal. 

I had an interesting observation last Saturday when trying out forge welding in a coal forge.

When you constantly watch your piece, checking the colour, in, out, check again, rotate, etc... it never, ever, gets up to temperature, not even after several minutes....
However, when you turn your back for less than two seconds to talk to someone or fetch another tool.... boom... instant burning metal.

It's almost as if the fire were sentient.

I had to resort to starting a conversation, then quickly spin around mid sentence to catch the forge off guard, and had about an 80% success rate of catching it at the exact right temperature to weld flux free.... highly scientific methods... it must be the winter solstice approaching or the lunar position relative to uranus.

@JustAnotherViking, that was a good morning chuckle. Also, so true!

I am of the age when I *KNOW* the Universe is out to get me!  Good job tricking it...

If you were making a flux with Iron oxide in it - what kind of iron oxide would you get? I see yellow, red, black, some labeled synthetic - most seem to be used as a dye.

Iron powder is not iron oxide powder, iron oxide is rust, rust is not good. Clean, well matched and hot make forge welds, rust violates clean. Iron powder is esentualy iron filings an extension of the welding plates used a hundred years ago to stick finicky aloys together. 

 

Iron oxide containing earths have been used since mankind began painting on rock walls. There a number of earth colors that are still used to tint 'paints' to this day. Example are the Ochers, Siennas (regular and burnt), and umber colors etc ).

I suspect that adding finely divided iron would act as a very good oxygen scavenger and iron oxide not quite as effective (e.g. Fe2O3, and even less so Fe3O4, if at all).

The iron and also scale chemically locks up the oxygen acting as a flux which allows the iron to fuse (weld).

Iron oxide will get in the way of a good weld, resulting in a failure to weld.

Many boron and silicon compounds do the same job.

As I was typing Mr. Stevens scooped me. But I am posting this anyways. I am not trying to steal your thunder, Senor.

I have to learn to type faster, I guess.

SLAG.

Edited December 12, 20178 yr by SLAG
Corrrecting dreadful penmanship

You simply expanded the explanation...

1 hour ago, John in Oly, WA said:

If you were making a flux with Iron oxide in it - what kind of iron oxide would you get? I see yellow, red, black, some labeled synthetic - most seem to be used as a dye.

You don't need to add anything, But if you wanted to you can use dust from the bandsaw..  

If you use a cast iron and steel sheet metal pan it will pick up all the iron oxide that is needed.. 

99% of the people out there feel that adding or melting borax is simply un needed.. 

Personally I melt all my borax then crush it all back up..  It  comes out to about a 3.5 to 1 ratio.. In other words it take about 3.5Pints of hydrous borax to make about 1 pint of anhyxrous borax..    I just recently bought a hand operated grinder as I go through more flux now.. 

This means for a given amount it will cover/coat the steel or what ever better with less product (as you are actually using more) 

I wanna say about 20 or so minutes in the last ( Rutland Historical day demonstration) video on the tube, I show where the flux is applied and you can see just how clean the is under the flux.. It bright and shiny.. 

In the good ol days they did not stop and grind off the scale or flux before the next welds..   They had a clean fire,  fluxed well and the job was done.. 

 

Here is is in a large baking tray during and after.. The reason for the color green is because of the iron it has picked up from the pan.. yOu can see just how clean the pan is when the flux is removed ready for crushing.. 

 

The video is 70 meg so fairly large..  for those that can't veiw this let me know and I'll tube it as well.. 

Video of the melt..    This might be a big No, NO.. If it is Moderators just delete and let me know.. I'll post it to the tube instead.. 

 

20170918_171442.mp4

Please avoid inhaling the fumes whilst driving off the hydrated water of the (hydrous) borax.

Some boron compounds are toxic.

SLAG.

2 minutes ago, SLAG said:

Please avoid inhaling the fumes whilst driving off the hydrated water of the (hydrous) borax.

SLAG.

+1,  no problem here as the stack sucks everything up and out..

"In the good old days" they were forge welding real wrought iron which is pretty self fluxing on it's own due to the ferrous silicates.

There were also using alloys without a lot of things like Ni and Cr in them even as tramp elements and so did not need a very active flux.  "old school" fluxes included: ground glass, clean quartz sand, dirt daubers nests, rice straw, wood ashes---in general silica containing items that worked more as a barrier to O2 than as an active scavenger of oxides.  As such they tended to weld at quite high temperatures---where the scale would liquefy on it's own (and where many modern alloys would be burning up!)

As I recall there was a bit of discussion in "Practical Blacksmithing" from the late 19th century about the "new material"---Bessemer steel and having to modify their methods to weld it.

All great points and so true.. 

My point was to use a flux.. But also to keep in mind scarf design which can be equally important especially on some of the trickier welds like butt  (jump) welds or T welds where maximum strength is needed at the joint.. 

Thanks everyone for the info. I was just trying to replicate JPH's "Steel Glue" which listed Iron Oxide as an ingredient - specifying "real" iron oxide, not the concrete dyes. Maybe I don't need to get that complicated?

iron oxide is scale..  I can send you an envelope of it the next time I have a major forging session..  

Just posted a new video on how I do flux. It's in the alchemy section.. 

 

https://www.youtube.com/watch?v=jXYIYnLyXVk

 

Scale is one type of iron oxide, rust is another. (Fe3O4 Magnetite, Fe2O3 Hematite and the rare FeO)