Thread: Ran the forge this afternoon

Well, I tried it for the 3rd time yesterday afternoon and it appears that I hit the mark this time. It sharpened right up on the DMT after it was quenched. I haven't tempered it yet, but I'm not sure that I'm going to. Over the course of three heat treatments, the steel may have lost too much carbon and tempering may cause it to loose too much hardness. However, this is still new territory for me, so if some of the old hats think it would benefit from tempering, I'm willing to give it a shot.

I don't think I know the difference between hardening and tempering. I thought they were the same thing.

Hardening is the process of taking a piece of steel to the austenizing temperature, and then quenching it in a coolant.
At that point, there are still residual stresses left in the steel, and it can be very brittle.
If you'd clamp it in a vise at that point and pull, it'll snap with a loud crack.

Tempering is the process of putting your hardened piece, and heating it to a couple hundred degrees. The temperature varies with the type of steel. For carbon steel I've seen temperatures advertized from 150 to 250 celsius. The steel is left at that temperature for 1 or 2 hours, which causes the residual stresses to disappear. The steel will lose a couple of points on the hardness scale (for example from 63 to 61) and it will be much stronger and tougher.

I am amazed at the quality of information shared on this site!!! Thanks, Bruno.

Bruno beat me to it. I'm going to clean the knife up this afternoon and then temper it and see if it'll sharpen up like I hope it will. It gets sharp now, but just doesn't quite get to where I'd like it to be.

Myers,

How did the blade turn out?

Wow! And my adventure for the month was to try to roast some green coffee beans!

It didn't turn out too well. I think I over heated the steel too many times, and now it doesn't get hard enough to really hold a proper edge. I've been wanting to try again, but I've got to find another suitable file.

Two things come to mind.....
1. You may have started with a file that has low carbon steel that was case hardened. Be sure to use an old file, not one of recent manufacture.

2. At high temps the steel will lose carbon rapidly, thus the inability to hold an edge. Simply put the steel in the forge and watch it closely. Do not attach a magnet to it. The heat will destroy the magnetism in the magnet. Watch the color changes in the steel. when it is close to being hot enough you will see the dark "shadows" getting smaller and smaller. Then is the time to pull out the steel and start testing with a magnet. When the magnet no longer "sticks" to the steel then it is time to quench. You might also start thinking about just what portion of the blade you really want to pay attention to. The edge will get to non-magnetic faster than the spine will. To me, the hardness of the spine is nowhere near as important as retaining the maximum carbon in the edge and getting a proper heat treat on the edge.

Just my $.02

You could also wash a light clay coating over the blade to shield it from oxygen.