First successful(?) heat treat

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BChou-E29

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Dec 4, 2009
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Yes! Sort of... I finally decided enough was enough and heat treated my knife which I had been working on since January :o It is made of 1095 steel. I built a charcoal forge lined with ash. It has an in-line tuyere like the one made by Tim Lively which is fed by a hand crank blower. I got a good bed of charcoal and I placed the knife blade down in the fire. I started cranking until the knife got a nice deep red. When I got the color I wanted, I started my timer, pre-set to 4:30 for the soak time, and put a hot piece of mild steel and dropped it into a jar of canola oil I was using for quenchant. When the timer rang, I quenched the knife in the oil and agitated until it was cool enough to touch. After checking for hardness with a file, I tempered in the coals by checking the color of the oxides. Then I let the knife soak overnight in white vinegar to get rid of the scale. This morning I cleaned the knife off a bit a wire brush and sandpaper. What I saw under the scale was this...
10242010334.jpg

Is this normal? Will filing off these imperfections ruin the knife since 1095 is shallow hardening?

Thanks for the help guys

EDIT: pictures added
 
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Not seeing an image. And 1095 is shallow hardening but shallow is a relative term, a knife's full thickness is generally inside the hardening range.
 
Before doing any more work on the knife it needs a proper temper. It is most likely too brittle as it is now, and may snap while you are working on it.I would not trust the temper done in the coals.
Place the knife in a kitchen oven at 400F for 2 hours. Take it out and rinse with water to cool off. Put back in for 2 more hours. Tempering needs time, and the few seconds in the coals isn't enough. Hopefully the blade wasn't ruined by the tempering in the coals, as it is easy to over draw the temper and have soft spots along the edge.

The surface of the knife will need to be sanded down. Use Wet-or-Dry paper backed with a hardwood block. It goes slow, but is the same process you did when sanding the knife before HT.
 
@remyrw
Thanks for the info. I was not aware of that.

Stacy, so the appearance of the steel is a normal byproduct of the HT? I just want to make sure I wasn't burning the steel or anything like that. As for the temper, I'll probably be redoing this HT and I'll make sure I give it a proper temper. Thanks for the heads up.

Tattoedfreak, how did that story end? ;)
 
Since you and I have no idea what temperature the blade was at, I can't tell you there is no burning, blistering, or other damage to the blade. I can tell you that it always needs to be cleaned up after quench and tempering. A wash coating of satanite can help avoid the amount of scale and decarb ( what you probably have....and that is normal) and make cleanup easier. Mix it like thin pancake batter and just put a thin coating on the whole blade. Let it dry and then harden the blade. Most of it will come off in the quench. The rest can be scraped off with a paint scraper, and scrubbed off with a stiff wire brush.
After the quench and temper, soak the blade in white vinegar overnight. This will remove a lot of the hard scale, making the sanding easier.
 
I know, i am much too low tech... But I'm going to give myself the benefit of the doubt and assume the condition of the steel is decarb. When I re-HT I will try coating the blade in furnace cement since I had a pail on hand. Thanks a bunch for the help Stacy.
 
If you use furnace cement, thin it down and just make a coating like paint on the blade. Most furnace cement has sodium silicate in it, so the resulting metal surface may be etched. Since you have to sand it down after HT anyway, give it a try, but I have found that satanite works much better as far as the final surface looks.

As I said before, the knife needs to be re-sanded after HT in a repeat of the sanding before HT. Prior to HT most folks go to 220 grit,some go up to 400 grit. After HT, start at least one grit below where you stopped pre-HT. Then go up the grits to as high a grit as desired, depending on the look you want.

A general note to new makers ( it applies to all makers):
A knife blade must be sanded down after HT to expose the hard steel that is "hidden" under the layer of scale and decarb. This take time and hard work. Grinders help, but plain old elbow grease works just fine. One reason you leave the edge at .030-.040" thick is to allow for removing about .010 - .015" per side from the whole blade after HT. This exposes the nice hard martensite that will take a nice polish and/or a good etch. Many new makers try and take a short cut by leaving the dark patches, dips and dings, and scale on the blade and just grinding an edge on it. They say it makes the blade look "Old Fashioned" or "Antique". What it makes the blade look like is "Made by and Amateur". Old blades are not poorly made, but may have obtained a lot of patina and some rust pitting over their many years. This effect can be added by etching the blade in FC or some other acid like mustard or vinegar.
 
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