How to weld with poor coal?

[Dave Shepard]

I could use some suggestions for trying to weld with really poor coal. We got in a new batch at the Village, but it has rocks, hard coal, and is just really poor. I had no problem in the past with welding, I just did the usual clinker check and made sure I didn't have any green coal in the pot and all was fine. This coal is so bad that the clinkers don't settle into one chunk in the bottom, but seem to be all through out the fire. Also the coal doesn't seem to be coking right. Any suggestions? I really don't want to have to supply my own coal.


Dave

[JerryCarroll]

I have a barrel of coal I got for cleaning out a bin that sounds like what you have. I could not get a decent weld with the stuff so I just use it for heating stock to bend or teach basic hammer technics. My recent purchase of a load of pocohantis from W. V. is great for welding tho. From experence I can tell you bad fuel is discouraging! I would suggest another batch of coal if you have to weld--unless you don't have a choice.

[Dave Shepard]

I kinda thought that would be the verdict. Last fall after the main season closed down, and I was the only smith there I bought a couple bags of smithing coal, but starting this weekend, the other smiths will be back, and they will just use the coal out of the bin. We probably use 2-300 pounds per week, and I can't afford to buy for everyone. Oh well.


Dave

[Glenn]

Blueprint BP0131 Coal, Coke, and Rocks may help.

I have some power plant coal that has to be sifted. The slag - rocks - junk can be used to heat with, but you can not weld with it. The fines are better for heating and may or may not weld on a good day. I use it because it came at a very good price. "Real" coal out works this stuff hands down.

Get some good coal for the forge welds. Keep it in a 5 gallon bucket in the trunk of your car if needed.

[Dave Shepard]

I'll check out that blueprint. I was going to buy a pallet of the good coal, but unless they get rid of the junk they have, the good coal will get contaminated. The junk didn't show up until the end of the year last fall, so I am the only one who has had to work with it. Once the other smiths come back next week, there may be enough complaints to get something done about it.


Dave

[Tyler Murch]

Use a lot of flux. Hitting it harder might help as well.

[patrickrock]

How about this... after a day of smithing and your fire is dead, clean out all the good/salvageable coke. Save it.

When you have to weld start a fire using only the coke.

Every day before I forge I clean out my firepot, sift it for coke, and then safe the coke for when I want to work w/just coke.

[jayco]

DMS---If your forge is large enough to handle the extra bulk, you might try charcoal (the home made kind). It's easy to make and much better than bad coal for welding.

[Ed Thomas]

The problem with this sort of coal is that it barely cokes at all. The amount in any fire is neglible so there is nothing left to save. Furnace grade coal generates more fly ash than clinker, although there is a good bit of debris in the bottom of the fire. Since it doesn't bind into coke, the coal itself is burning without much intermediate stage, which mean less concentrated heat per volume of fuel. The pieces of coal fall into the bottom too easily, blocking the air flow and making an "oven" for surrounding heat very difficult.

DMS: I cut my forge-welding teeth on coal such as you describe. It was several tons of free coal, and wasn't worth the price. The secret to forge-welding in this stuff is to keep in mind the characteristics I just described. The oxygen in the air coming in the bottom is not going to be consumed as quickly as with good coal because the amount of ready fuel in its path to the top is less. So if you force the air too fast past a bed of coal that is too shallow, the heated air that reaches your steel will still have oxygen which wil scale up your piece and put a difficult barrier in the weld attempt. This is true in any forge-weld, but very pronounced when using bad coal.

In other words, you have two conflicting problems... 1) you have to keep oxygen from burning your piece so you have to go more slowly, and 2) the fuel is bad so you need to provide more forced air to get the temperature up. Address this problem by mounding your coal higher, but not too tightly packed. Get it going fairly well and put the pieces to be welded 2/3 up the mound. Ideally, you don't want too much coal on the pieces, but in bad coal sometimes it just can't be helped. Shake that stuff off quickly as the pieces come out of the fire to weld.

Other problems with bad coal are:

1) the grate in the bottom clogging, which diffuses the air making a strong central heat impossible. Correct this by dumping the ash and shaking the clinker breaker. Without a clinker breaker, just shake things up a bit and test the fire pattern until you are happy with it before welding.

2) Debris on the pieces from fly ash and coal dust. It is much worse with bad coal. Compensate by making sure you have good coverage with flux, and then shake that off quickly when the pieces come out of the fire.

I do not bring things out of the fire and hit hard. When you are having trouble welding, all this does is mash all the debris together, the scale into the steel, the flux into the middle... and the weld fails. I hit firmly and quickly, trying to drive out the remaining debris and liquid scale by rolling it out in a rapid serious of blows from the middle to the outside or middle to the end.

Getting the pieces to welding temperature is harder but still possible. You really have to be patient and shape the coal mound to concentrate the heat as best you can. As I said, this often means a higher mound than you might think, yet keeping the air path clear. Not easy, but can be done.

There is a point where the coal is so bad that it really is not worth the effort because of the high failure rate. But once you get a knack for it, you can weld reliably in more poor coal than you'd think. And then when you get the good coal... you can weld while reading the paper, drinking coffee and eating a sandwich with your eyes closed.