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I Forge Iron

What am I doing wrong


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Finally decided to burn some coal for my forging project today instead of the gasser.
I wanted to build a few fire pokers and wanted to try forge welding the bar back onto itself to make the poker ends.

Try as I might though I could not get the steel past a barely yellow brightness.
I tried welding anyway and I definatly wasn't hot enough.

To build my welding fire I tried making an extra deep fire that I could sink the material into. I spent about 2 hours building it and got good 4" sphere of hot coals and kept piling the coal ontop while I was cranking the blower. A moderate crank was ok for forging heat but to get it up to yellow I really had to crank on the blower. after about a halfhour in the fire I still wasnt getting even close to a weld heat so I tried cranking really hard on the blower. I started buring coal like a bugger, I lost my mound but I had a good intense flame coming up along side my material. Thats when I was able to get a barely yellow colour to the steel but definatly not hot enough to weld together I don't think.

The coal I'm using is fairly fine stuff I got from a friend who uses it in a coal boiler for home heating. the grains are about 1/2" square.
it burns fast and not as hot as I was expecting.

after several attempts I shut the fire down and as I was taking the fire apart I discovered a large 4" disk of clinker from the bottom. This was after only a couple hours of burning, is it normal to be producing this much slag?

Anything obvious from my story that I might be doing wrong?

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It may not have sufficient BTU's for forging. Many years ago, I was given some low-yield heating coal that spec'd out at 9,000 BTU's; it would not get above a bright orange color and burned up quickly. Best to get some coal or coke specific for blacksmithing, which will be 14-16,000 BTU and able to form a coke button.

I also have some really hot coal that clinkers up very quickly so your mention of that makes me think you have some relatively dirty and low-yield coal.

Another thing to keep in mind is that fines often work best if wetted with water prior to use in order to form a paste. This will tend to coke better than dry fines that are heaped onto the fire. The initial fire may be harder to start but will perform better once it is going.

Hope this helps - good luck...

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If it will get your iron up to yellow with a dirty great clinker blocking your air flow why not try bringing the air in sideways (making a side draft) which is easy for a test with some black pipe. The clinker will sink below the tyuere for the test but make sure your pipe is buried in some ashes for the test or you will lose it quickly.

Working your way around problems is a major pleasure of hobbies for me.

After saying that, I can forge for half a day before I have to worry about clinkers with my coal. Cleaner coal would certainly be a good choice but if you have this stuff then work out how to use it would be my advice.

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I did some reading last night and learned that you should be able to burn out a hollow cavity in the fire in which u can place your material, this is when you produce coke in the fire and it binds together and is able to hold shape. Sounds pretty cool. Fired up the forge again today and I couldnt get the coal to do anything like that. All I could do was make a mound of coal, as soon as any of it burns up underneith the roof just caves in to fill the void. I spray water on it enough to make the dust quite wet but it didnt really want to stick together when it was raw or while it was burning. If I crank vigorously on the blower the coal all burns up and I'm left with clinker and ash in no time. I wasnt able to reproduce the yellow brightness this time, the best I could get was orange after 10minutes of a good amount of cranking. I had to be careful where I placed the material though, simply stuffing it into the fire wasn't good enough I needed to find a spot where flame was escaping and place it directly over it, then bury it. The hot spot in the fire seemed to move around according to how the air was flowing through the mound. I fired up my propane to compare heats and the coal was way outmatched.

Something definatly aint right, either I'm doing something completely wrong or maybe this coal is junk. It definatly shouldnt be this hard to work with.

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  • 2 weeks later...

It may be hard anthracite and does not have the volatiles that bituminous smithing coal has. This means that it will not coke up. Use it for non-welding sessions.

I don't know about that. I have been using hard anthracite for months (it was what is easy for me to get) and I can hit welding temps no problem. It doesn't clump or coke like good bituminous does it burns more like lump charcoal. I think he just has some real low grade coal.

Freelance could you take a good picture of your coal and post it up.
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It's impossible to tell what's wrong without a lot more info -- pictures would indeed be worth a thousand words -- but it certainly doesn't take two hours to build a fire. Starting with coke from the last session, I can go from no fire to forging heat in a matter of minutes, really.

With dirty coal I commonly find some noticeable clinkers in there after half an hour of forging. If I let it go an hour without cleaning them out, they can be pretty big and ugly.

Some of the bad coal I've worked with doesn't get sticky.

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