forge welding workshop experience

[evfreek]

Hi. I participated in a forge welding workshop, and I had a couple of interesting observations and questions. The instructor gave a quick demo and asked us to try something that was new. For me, this was a small to large stock weld, single-handed.

They did not have any new steel to use, so I fished a piece of scrolled 5/8" square and some twisted rebar tie wire. The instructor said that the rebar tie wire was especially low in carbon, so it would weld easily Both were a pain to straighten, especially the scrolled 5/8. When I tried to heat them to welding temperature in the coal fire, I noticed that I was having a terrible time getting my test pick to stick to either piece. I have always found that "if they don't stick in the fire, they won't stick on the anvil." Lots of rules of thumb, and maybe not so much common sense.

Anyway, I couldn't get the pieces to stick on the anvil, either. And, I got burned, which is quite rare. Technically, I did not injure myself, but I goofed up a perfectly nice pair of jeans. :mad: The instructor said for a single-handed lap weld, a right hander places the heavier piece of stock on the anvil on the right, then pivots the lighter piece of stock in the left hand over the heavier one. The rationale is that the heavier stock should be on the bottom, since it suffers less heat loss to the anvil (lower surface area to volume ratio). Also, it was suggested to practice the movement cold. You can probably guess what happened. Everything was fine cold, but when the small piece (5/16") was hot, it could not pivot the large piece down on the anvil. The smaller piece, much softer when hot, deformed and sent the larger piece flying under its own weight. The white hot end brushed my pants leg. Although I did not feel it, it left a flashbulb like burn on the surface of the cloth. Not charred, as a cooler piece may have done, but "bleached". Maybe I'll have to go over it with a permanent marker, since it is pretty obvious what happened, and it looks really embarrassing.

OK, so a common sense modification to the rules is to put the heavy piece in the controlling hand if it is hard to control. And tilt the lighter piece above the anvil to avoid excessive cooling before the hammer strike. Also, it helps to line the pieces along the long axis of the anvil, even if you have to reach over the top awkwardly, since the pivoting is easier to control. Big piece on bottom, unless the size difference is too big.

As I mentioned earlier, the pieces were not stick in the fire. I took a break and took them out for a little grinding. The large piece was pretty much mild steel, but I was surprised to find that the rebar tie wire tested as 1060. Somewhere between a hammer and a chisel. This was different than the "rule of thumb" that rebar tie wire is soft stuff.

So, I pulled the smaller piece to a cooler part of the fire. And, I forgot about the poker test. I got the mild steel piece good and hot, and placed them in position and gave a good wallop. Not a tap. There was a huge shower of forked sparks, and the two pieces stuck! After that, it was pretty easy closing the flaps and dressing out the weld lines.

I let the piece cool and stuck it in the vise and bent it over. It promptly broke about 1/2" away from the weld on the thinner side. :mad: The instructor noticed this and said "bad weld". She said look very closely at the broken area and you will see a scale pocket. She said that if one of the pieces is higher carbon, you have to be very careful to apply flux far afield of the joint. Tiny pockmarks will cause a "weld" failure. The weld itself is well fluxed and sound, but there is not enough flux to protect the steel outside the area. Again, the "rule of thumb" that people usually apply too much flux does not always apply. Sometimes, one has to just use common sense.

One question, does the harder blow help when the pieces don't stick in the fire? My experience is that pieces that are really sticky in the fire weld readily, but I have seen smiths stick welds that are not sticky in the fire. How does this work? Confidence?

[ThomasPowers]

One Quick Note: you can carburize things the thickness of wire in a reducing fire at welding heat *really* fast...

[evfreek]

Hi Thomas. You are absolutely correct. The "wire" is about 5/16", and the fire was definitely reducing (coal was provided ). I should have brought the failed weld home to examine, but I couldn't bear to look at it. I have a bunch of rebar tie wire, but I suspect that I know what I'll find if I spark test it.

[HWooldridge]

Well, nobody else answered all of your questions so I'll take a stab at it...

The basic mating surfaces should be close to the same size. In other words, it is not recommended to stick 5/16 straight to 5/8 without a transition. Generally, that means upsetting the smaller and drawing down the larger so they are similar. A corollary to this is that - at least for me - the pieces are square in cross section. Rounding up can be done later if the stock is round, although Francis Whitaker talked of welding in swages so it could be completed in one heat with no extra work. In addition, the scarfs should match and I find it easier to make points rather than a straight chisel edge. For me, a straight edge sometimes causes a notch that weakens the parent stock, while a point blends well.

You figured out that putting the heavy piece lengthwise on the anvil helped so I won't comment further but keep in mind that there were helpers by the dozen in old shops and four hands is better than two for this type of work. You may think I cheat and that's OK, but I make up the proper joints for a forge weld and then dot the sides with the MIG. It's certainly not homogenous until forge welded but I don't have to fight with two pieces just to prove I can do it.

A proper forge welding heat on mild steel is a glassy looking, incandescent yellow white. It should hurt your eyes just a bit to look at the fire and the steel. The exterior will start to appear almost liquid (I really think you overheated the pieces, which is why the piece broke in the vise and you got a huge shower of sparks. The only thing coming off a forge weld should be some flux). More importantly than fluxing the entire bar is getting enough heat on both sides of the weld. In reality, very litte flux is required and some smiths are renowned for not using any at all so 'less is more'. For example, welding 1/2 to 1/2 requires at least 4-5 inches of high heat on each piece so put them together and you'll have a good 8 inches or so of bright yellow with the ends incandescent and lightly sparking.

I weld early in the day if the work permits to insure a clean fire. If that is not possible, I let the fire cool and clean it thoroughly. I bring the blast up quickly in a deep fire, watch the fire for that bright, lemon white color then reduce the blast to let the pieces soak and catch up to temp. A few bursting sparks at the top of the fire and it's out and under the hammer. A good weld should go "Spat!" when you hit it. I can't explain the noise but you'll know it when you hear it.

Re hitting it hard - if you tap and it doesn't stick, then no harm to the material. Clean and reweld it. If you clobber it, the scarfs are shot and you'll have to start all over. However, once stuck all the way around, drawing down under heavy hammering helps finish the joint. If they don't stick, don't go any further - cool the pieces, clean them thoroughly to get rid of all scale and go back for another try.

Other points:
After upsetting, the center of the scarfs should touch first. If they don't do this cold, you will probably get a cold shut in the center of the weld from trapped scale.

Don't hammer a fresh weld (first heat) at too low a temp - they will often split. It's not a sin to take a second heat to finish it. Most welds are a glue job anyway unless you can reduce the stock size quite a bit so upsetting 3/8 to 1/2 and bringing a good weld back to 3/8 will make the weld take much better. I do a lot of pieces of 3/4 to 3/8 (both square) so the small stock gets a big upset and the large stock gets drawn to 5/8. The last step is to use the power hammer to bring the joint down to 3/8, which makes the weld typically disappear. I have twisted through these and they won't split but the scarf tips are usually about 2-3 inches apart so the upset areas move quite a bit.

Practice some faggot welds with the 5/8 square. Cut most of the way through on the hardy, fold back, flux and weld. After cooling, put the bar in the vise and hit the short piece from the side. A bad weld will split and break away.

Above all, practice makes perfect so don't get discouraged.

[JerryCarroll]

Even with being pretty good at forge welding I always enjoy reading a good article on it--this is one great metal working site!!

[evfreek]

Hi HWooldridge. Thanks for the informative reply. There are a lot of good tips in there. I am very familiar with the sound that a good weld makes. The problem that I was having was that the metal just did not feel sticky. I brought it up to heat slowly, and I did upset and scarf the small piece, and taper the large one. They just did not seem to stick, including in the fire. I used the same forge with an older fire the day before in the previous workshop, the only difference is that the previous day had someone working there quite a while before I got there. So, presumably, the fire was dirtier. The metal was really sticky in the fire, though, and the weld was successful on the first try. The only difference here was that on the previous day, they provided new steel (paid vs. free workshop ).

What I was wondering was how I managed to stick the weld the second day. It was really tough, taking about 3 hours to do the job. I had to cut the bad ends off the bars and start over a couple of times. The metal never felt sticky either in or out of the fire. The main difference was the sparking and the hardness of the blow. The lower carbon piece was hotter, and was sparking slightly at the end. The higher carbon (smaller) piece was not sparking. The main amount of sparks showed up when I hit the weld, and they did not look like flux. They looked like forked steel grinder sparks. So, it appears that the heavy blow heated up the joint kinetically, or enough metal was knocked out of the flux protected area to create these different sparks. The smaller piece was definitely NOT burning. Hot, perhaps too hot, and heavily scaled, but not burning.

I often work alone, but do not have a welder at the farm. When I get arc-tacked stuff, it is much easier. There is a lot less to worry about.

So, I wonder if the thin poker test is bogus. Some smiths shuffle nervously when I mention it or when they see me do it. But they don't say anything except maybe that it ummmm doesn't work for them. It seems that the rule of thumb may be more like "if it doesn't stick in the fire, it still might stick on the anvil."

[Alwin]

I do a lot of forge welding. I have had the experience of having metal in the fire where it looks really close to being at welding heat but just won't get sticky. It generally is caused by a clinker or occassionally a full ash dump blocking the air flow. The metal will just sit right below welding temperature and develop a thick layer of oxidation. Make sure you have at least three inches (depth that's needed will vary with air flow and the size of the material-bigger material needs more heat to get to temperature and therefore more coke) of coke below your metal, an inch of clinker and two inches of coke will cause your metal to be in an oxidizing fire.
The key to getting a really strong weld without reducing the stock size much at all, is using a few welding heats with only fast light blows, and only hitting the steel when it is at welding heat. A very short scarf overlap will make the weld much faster than a longer one and is generally easier to blend in.

[Alwin]

I would guess that the reason the hard hit allowed the metal to stick is because it broke through the layer of oxidation that had formed around the steel. In my experience the welds that only take when you hit them hard are quite weak.
To forge weld, you heat the metal to the point at which the surface of the steel is starting to turn into a liquid but the core is still solid. At that temperature, you can take the metal from the fire and mix those surfaces with hammer blows. Hard hammer blows force much of the liquid( or almost liquid) metal that you are mixing out from between the pieces. Light fast blows work best for mixing the liquid metal surfaces and allow for the most molecular bonds to take place between the surfaces.
When forge welding half inch square mild steel with only a little upset into one piece on which it is hard to find the weld, I find that when the steel is at room temperature I can consistently bend the bar almost 180 degrees before the weld starts separating.

[Glenn]

Alwin
go to the top of the forum page and click on user cp
click on edit profile
go to the bottom of the page, enter your location, and save.

We would like to know where in the world you are located.

[Alwin]

Glenn,
I edited my profile. I'm in Asheville, NC. I teach two weekend beginning blacksmith classes at John C. Campbell Folk School. I also do a great deal of demoing, largely with the Southern Highland Craft Guild which promotes crafters in the Southern Appalachian Mtns.. I have a website which hasn't been updated in two years and lacks pictures of custom work but still will give you an idea of what I do; www.wagenerforge.com..

[HWooldridge]

Evfreek,

I didn't know what your experience level was so tried to write an all encompassing commentary - I apologize if I overstated the obvious.

Before I learned to forge weld, I had several years of welding with an O/A torch and that helped me at the forge. The basic fire characteristics and appearance of the steel are similar but you are hammering instead of puddling. "White and sparkly" is bad in either process.

I believe a large part of successful forge welding is related to fuel and fire size. I have pretty much always used bad coal and been mildly successful (and I've never been able to consistently weld in the gas forge - sometimes it works and sometimes not) but it was always a fight even in a coal forge. The problem was that I didn't know what good coal was and bought several tons of substandard stuff so I had to use it - it's hot but clinkers VERY quickly. I used to watch demonstrators at workshops hit forge welds all the time and kept wondering why I had so much trouble.

Several years ago, I demo'ed at a folklife fair and used their forge with high quality coal from the Midwest. The fire stayed clean for a long time and was very hot so I started playing with a variety of different forge welds. I wound up hitting every one - this was working in front of a crowd by myself. I used Sure Weld for flux and the welds did not spray everywhere - just a few small squirts (the crowd was behind a barrier so I felt safe doing this). At the end of 8 hours, there were two small clinkers about 2" wide in the pot near the blast and I had 9-10 welded pieces laying around. More than anything else, this impressed on me the need for high quality fuel. I asked for and was given a bucket of coal, which I took home and used in my forge. The results were the same - easy and fast welds with little effort. Unfortunately, I don't know where the coal came from - but it was typical stoker size that coked easily and burned a long time.

I think Alwin's comments are spot on and with all that said, a large portion of your problems could be related to fuel quality, fire size and how dirty it gets between heats - or it could simply be how you are holding your tongue...:-0

[evfreek]

Hi HWooldridge. No problem about judging experience level--we are all learning. And for me, the failures help me generate more questions and hopefully answers. I do not have enough experience to select the best coal/charcoal for welding. I do know that it matters, and I have been in situations in which the metal would not stick, no matter what I did. Other times it was so sticky that you could stick the pieces in the fire and take them right to the anvil . The odd thing is that I used the same forge with the same coal (but new steel) the previous day and it worked great. It probably was a funny clinker, or somebody threw a penny in (just kidding).

The one time that I just couldn't get anything to stick was in a coke forge fueled with buckwheat coke. Now, I know a lot of other people who can weld with this, so I chalk it up to poor fire management technique (by me). I was trying to make some tongs at "midnight madness". A kind old fellow came up to me and tapped me on the shoulder and offered to help. When this happens, you should always say YES! He said this'll fix that rein problem. Get some bigger stock, make the jaws and come on over here to the air hammer. He could tell I was a first timer the way my eyes went wide as I drew the reins out in one heat. Then, he offered kindly advice on how to get the air hammer purchase past my wife . Didn't learn much about welding, but sure learned a lot nonetheless!

[Glenn]

Then, he offered kindly advice on how to get the air hammer purchase past my wife .

I do hope you took notes. This tidbit of information would seem to be worth the price of admission. (grin)