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how to get rid of furnace scale "by hand"?

P

pso

Joined
Oct 29, 1998
Messages
494
Hello

I was happily filing away at my piece of 1074 and got one side mostly done. When I flipped it over to file the other side, I found the file skating across the surface of the steel. The whole surface of the second side seems to be covered in furnace scale(?). The first side did not have much scale and was easy to file. The scale can be made to flake off if scraped with a screwdriver but a lot of pressure is required. Is there an easier way of getting the scale off so that I can cut the metal beneath it? Buying a grinder is not really an option right now, or I wouldn't be filing it out. I have heard of people soaking the steel in some sort of solution but I don't recall what it was.

What is the possibility that one side of the steel, 1/16" thick, is still hard? It was from a large bandsaw blade. I annealed it in an electric heat treating oven.

Thanks in advance for your help.

Phil
 
You can try the Japanese way, keep the anvil wet and the hammer. It sounds like a 22 cal. going off on the initial hit.
 
Soaking in vinegar overnight reduces the scale to a coating that is easily sanded or filed off....kind of makes the shop smell like a salad bar though. :D

Probably soaking in ferric chloride would work as well but I have no direct experience with this method. Acids are goood stuff for removing scale and the like if you are short on a belt grinder.

Saves belts if you soak off the scale too!

Brian
 
I have heard of people soaking the steel in some sort of solution but I don't recall what it was.
Click to expand...

You can soak it in muriatic acid (swimming pool chemical) or vinegar. The muriatic acid will work faster but the fumes are terrible. I've used both and prefer the vinegar. It's slower but not so noxious. After soaking in vinegar, probably overnight or even a few days if it is really tough, you will still have to scrub it with a scotch brite pad. This will take off the black hard stuff.
 
One of the easiest ways I know to remove scale is to just "pickle" it off in a container of plain ol' vinegar. Works great and requires no work, wasting of belts or dulling of files (and venegar is cheap by the gallon!)

This takes the "bark" off of rolled stock also.

If you are interested you can then use the vinegar/dissolved steel solution from your container as a black dye on oak tanned leather. This is an old leather dye recipe and an easy way to make a batch is to soak a bunch of steel wool in apple cider vinegar.

Tim Lively freezes his vinegar and just uses the unfrozen, concentrated portion to remove forge scale from his knives.
 
Was the steel clean before you anealed it ? What was the proceedure that you used ? I ask because I have found it unneccessary to go higher than about 1400 degrees f. during the annealing cycle that I use. At this temp I get hardly any scale forming on my forged blades.

Bill
 
George, Brian and Guy

Thanks for the tip regarding vinegar. I will get some tomorrow. I don't think that my wife would appreciate me using up her fancy bottle. Besides, it is probably a bit small. I'll try the idea about concentrating the vinegar by freezing it.

Bill

I had annealed 4 pieces at the same time in the heat treat oven at work. The accuracy of controller on the oven is not known and we don't have any thermocouples rated to go that high. I put the stack of 4 in the oven and turned it on. The controller was set to 1400 (the Celcius equivalent). About three hours later, I checked it with a magnet and found it still stuck. I turned the oven up just a bit (25 C). When I checked 45 minutes later, the magnet did not stick. I turned the oven off and left it to cool overnight. The pieces were still a bit too uncomfortable to touch 16 hours or so later when I took them out.

The piece that I am having trouble with was one of the two pieces that were on the outside. The surfaces that were up against another piece of the steel while in the oven had little or no scale, just some discoloration (grey).

Thanks again for your help.

Phil
 
I use vinegar and soak the blade in a sealed container for 1 hour and then steel wool. Keep dipping the steel wool to keep the steel wet while 'scrubbing'. Takes maybe two minutes per side, and comes out real clean. Just my way- sure there are many others.

Dave
 
Thanks to all of you made suggestions to soak the steel in vinegar. I was able to rinse all the crud off under running water after 36 hours. My wife was impressed at how clean it got "her" knife. The files now cut instead of merely making the surface shiny.

It was a little puzzling because on closer examination, I found that all four blanks had scale on one side. It was as if one side of the steel formed scale and the other did not. The steel was from a big bandsaw blade that was used in a timber mill.

Thanks again for all your help.

Phil
 
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