Coal Causing Rough Surface?

[caintuckrifle]

Recently I have been experimenting with some coal available locally. I am noticing that even when I allow the coal to coke properly and  wire brush frequently, I am getting a very rough surface finish. Also keep in mind that I am not overheating the steel or burning it. I am aware that this is a lower grade coal but it appears to coke up and form a mound great. Could it be the coal causing this rough finish, or perhaps something in it? I have never had this problem with coke or other coals that I have used. Any help or insight?

[Michael Cochran]

What kind of rough surface are you asking about? Is it just scale, or somethin else? 

[arkie]

If it seems to be scale, wire brush it hard and briskly while red hot or hotter.  Scale is harder to remove when cool.

[Squirrelonastick]

I've heard certain kinds of coal cause more oxidation then others.  What kind of coal did you get?

[JHCC]

2 hours ago, Squirrelonastick said:

I've heard certain kinds of coal cause more oxidation then others.  What kind of coal did you get?

Fuel type probably matters less than air flow. Too much air, and you get an oxidizing fire. Not enough, and you get a reducing flame (and not enough heat). Just right, and you get a neutral flame. Keep in mind that pretty much any coal fire will be oxidizing where the air comes in, reducing at the top, and neutral right in between. You want to balance your air flow so that the fire as a whole doesn't tend either oxidizing or reducing, and then make sure to keep your metal as much in the neutral area as possible. Wire brush your work to remove any scale, especially in the finishing stages.