Oil hardening, has anyone done it? I'm thinking of making fly reels, but need a tried and true method of hardening stainless and a36. Also would like to make a few custom knives for this summer in Aspen. Looking for a better Idea..........
You need to start with a truley hardenable material. A36 may or may not get somewhat hard, the non magnetic SS will work harden some, but not get real hard. You should be looking at 1095 carbon steel, 01 tool steel or 440c stainless. The first 2 are carbon steel and wil rust. The 440c is what many SS knives are made of, there are some other SS aloys used for knives too, check on the blade forrums. To heat treat the carbon steel You heat it till it no longer sticks to a magnet and then slightly hotter, and quench in oil, preferably a large quantity of vegtable oil for health reasons. You must shove the hot steel ALL THE WAY UNDER THE OIL and swish it arround. This will reduce the chance of the oil catching fire and keep exposing the part to fresh oil. The steel will be hard but brittle. Before the steel cools to room temperature put it into a 400 deg f oven for a good hour to temper. If the part is thick it takes longer for it to get up to temp, so leave it in longer.This will make the part less brittle, but still really hard. for a tougher part but not as hard the temp will be higher, about 600 f for spring temper. As this is too hot for a home oven You need to use something else, like a pot of molten solder. Tempil crayons or whatever You have for preheat and interpass temp. can be used for temp measurement. Another method is to shine the part up with emery cloth and wach for color change while heating. The slightest pale yellow is a bit over 400, while [roughly] spring temper is blue. The problem is You can't do this for an hour, so do it 2 or 3 times. This is trickey to do with a torch, the colors come from oxygen exposure, so don't keep the part blanketed in the torch flame. For SS You have to go to someone other than Me for help.
Sourdough,
Recycling old power hacksaw blades into knives is another idea.... I've seen some beauties.
waste not want not.
I agree with Dave. Tool steels like 4140, 01, A/D2 or even some of the high 400 stainless alloys will take the quench/ temper much better and hold an edge longer. I would not recomend using a torch because of the time the steel must be held at the higher temps prior to oil quench. Also heed his warning of keeping the peice totaly under the oil to avoid flame up when it's exposed to the air. As a rule of thumb we use 1 hour per inch of thickness for "soak time" at high temps for any tool steel. We weld repair/ build up many die sections for stamping presses, and use an electric oven to get the high 1100-1200 temps to soak, and a regular house oven to temper at the 400-450 temps.
Forget the A36 for a Knife blade unless to intend to inlay something for the edge. What SS did you have in mind?
Farm/Estate auctions, yard/garage sales are a fantastic source of steel files which are fantastic for knife blades. Also another cheap source is auto/truck leaf springs. Plenty of carbon in these steel sources for heat treating.
You can harden in water too. It's more agressive so you can harden things with a lower carbon content but it's more likely to cause cracks in larger pieces. It doesn't catch fire though. I understand most original Bowie knives were made from worn out horseshoers rasps. My favorite kitchen knife is one I made from a piece of leaf spring. I can attest to the fact that it hardens nicely and holds an edge well. Alex Bealers book "The Art of Blacksmithing" has a good bit on knifemaking.
Bill
In any case if You get an air hardening steel [like A6, A2 or D2] DO NOT quench in oil or water. It might even shatter from the shock.
sourdough, I am not an expert on steel hardening. Although I am aquainted with a world class farrier. He taught me that there are basically two things that need to happen to harden steel. To heat the steel to its critical temerature. The trick to that is to take a magnet and slowly heat the metal until just before it totally loses its magnetic field. Then quickly quench the metal in water. Find steel that has more carbon than A36. You will get better results. I use a broken blade from my ingersoll rand needle gun / chipper to make nice center punches that last years before needing sharpened. You might find this interesting.I have a tool that was made by the same farrier which I have used many times, washed many times and it is still as black as midnight no rust what so ever. I can't get that trick out of the hat but I feel that there must be some magic in the process of using coal fire to work the metal which leaves a black finish. I heard rumors that beeswax is applied as a last step treatment of finished products. good luck on your projects..................Barry
BCT
One old "seceret" for keeping hand forged iron and steel pretty and black is a final heating and application of bees wax.... Am told this was how it was done in the olden days. Never tried it but since my wife and I keep bees I just remember that kind of stuff when I hear it.
The bees wax is OK for indoor use, but it isn't up to weather exposure.
For fly reels and A36 you may want to consider case hardening. I don't think for fly reels you would need the entire cross section hardened. You also have an aesthetic value to case hardening. There are many colt single actions out there (among others) and it works and looks good. Something to consider
The color You see in those case hardened parts I am told is developed by having air bubbled up through the quench water. I have used Casenit, a manufactured case hardening compound, and quenched in a bucket of water. There were no colors like on gun parts.
Quenching is only one half of the process. I do not think you want to leave a knife edge in the hard quenched condition.
The next step is to Draw or Temper your work and the Temperature you use do it at determines the hardness, and if you shine the work up real clean and bright you can see the color of the metal at each temperature. If you quench again at a color it will remain until you remove it.
There are charts available that give the colors and different temperatures.
Carbon Steel is Blue around 500'-550' F.
I guess there is no reason that You couldn't temper a case hardened part, but I don't know that it is ever done. If You are refering to parts made from steel that will fully harden You are absolutly right, tempering is mandatory and should be done before the parts get to room temperature from quenching.
I was just putting my 2 cents about coloring the metal and some earler post. I cant think of any reason to Temper case hardened work.
Sorry for the mis-understanding.
Wasn't "Damascus Steel' quenched in blood?
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