I will be making a propane powered forge. There is no simple formula or magic bullet. The steel will retain heat and survive a few seconds in the air as you move from heat to quench. Also, do not exceed 1900°F. quenching from the annealing temperature. This steel is sold as die steel that is machinable (just barely) with ordinary machine tools. Soak times at austenitizing temperature are usually extremely short – in the neighborhood of one to five minutes once the tool has reached temperature. 6. I heat the steel to temperature and put it all in the vermiculite to cool down slowly using the vermiculite as an insulator. Detailed Instructions
Salt baths can be used to harden, temper or anneal. Reference data: ASM Book: Practical Heat Treating by Boyer. Place blades in the furnace and stand up on edge, you may use a special furnace rack for this purpose. If your tempering block is fairly large just let it and the blade both cool together. Normal annealing as done by jewelers --- heat to very dull red (about 1200°F)
The splendid smith Burnham-Kidwell pointed out that when he changed from automotive drain oil (the old standard
2 pieces for an average hunter and four for a big bowie. Put your knife in the pile of charcoal and heat it up. The item now is hardened and would need to be brought back up to the 1100°F and quick quenched to be worked on again. THEN you have to be able to actually do the heattreating within the temperature limits determined. Simple, heat it to non-magnetic, give it another minute or so to heat a bit more, quench. Evenheats' Set-Pro control can be programmed to automatically soak, for any amount of time desired, once temperature is reached. In place of that, use low viscosity motor oil or even canola, vegetable or peanut oil. Heat treating has obvious hazards. The blade should be quenched either point first or spine first in order to minimize the chance of cracking or warping. Use an oven thermometer to get close to your target oven temperature. If you must use automotive oils use ATF. Q7: Aluminum is expensive! This rack will hold the blades in an upright position for minimizing warpage. Drawing, or tempering the blade is done by heating the steel in an oven. In general, use the highest tempering temperature that will provide the necessary hardness for the tool. Bury the two pieces next to each other but not quite touching. The blades should be warm (approx. Bending the half round file produces a semi-spherical surface. Most steels are tempered in the 500 to 600°F range. The method used by many bladesmiths is a vertical furnace or vertical salt pot. Barium cloride is used for high temps (like 2500F). You will read about guys using acetone in dry ice. Do not put any paper in foil. Harden at 1950°F and temper at 350°F. These steels don't need a long soak time. Heat until it becomes non-magnetic then pull it out of the fire and let it cool on a
Note: Rob really nailed the question of using a pyrometric cone for temperature measurement.
Some guys use lime instead of vermiculite. You should slowly agitate the blade up and down or side to side along the thin edge. If put into service in this condition, most tool steels would shatter. Most heatreat salt pots are heated simply by passing an electric current thru, controled by thermostat. Try to get the heat color evenly across the blade. Agitate so the fluid moves evenly over both sides of the blade. Sterling silver is age hardening, but the solution temperature(1300-1350°F) is close to the liquidus
Generally, most guys heat to temperature in their forge as the last heat of the day, turn off the forge and let the steel cool in the forge overnight. It will help if you pre-heat the oil to around 100F. (B) The other choice is to wrap in tool wrap. 5. 1. Double crimp all edges of the foil being careful to avoid having even a pin hole in the foil. To test the above cooling rate, heat your part to above non-magnetic and put into your annealing medium (lime or
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H-13: H-13 makes very good Power Hammer dies. 60 RC. Step by Step
Tempering: If you did everything right quenching, your steel is around 66RC and fragile as glass. 2. THEN there is the matter of temperature control. Make sure the floor around your oven is free from combustibles and please resist the urge to catch the falling blade. A guy knocks over the oil, drops the red hot steel into the oil and instant fire! Q8: How do I know if it hardened and tempered properly. 4. Al, Si, Mg, Pb trace (no greater than 0.1% each)
To harden an item after all work is done I place the
To anneal a small piece of tool steel you may need to bury it with a larger piece of steel heated much hotter (an
To anneal for a predominately speroidized structure heat to 1460°F and
low-rent quenchant) to used deep-fry oil his shop went from smelling like a lousy auto repair shop to a cheap deli...a
The more precise you are about heat treating your steel, the better result you will have. Cooling slower in the forge works better but cooking in the vermiculite works fairly well also. You will see somewhere, a lot of places in fact, that the steel really needs to be cooled off at a high rate, like 1 to 2 seconds and that is absolutely true. It is then quenched in water, oil or air depending on the type of steel. Some guys do one low temper heat at at 300F to 350F sometimes called a “snap temper” to take some of the stress out of a hardened blade before cryo. Not very scientific but it works. Experiment at your own risk. I recommend that also. For temps to 3000F magesium fluoride can be
Avoid it please. The higher carbon grades are typically used for such applications as stamping dies, metal cutting tools, etc. Then quench in warm water. malleable until my pounding/shaping work hardens the material. Wrap blades in heat treat foil. We use brown paper (no idea why brown just what we use) in pieces about 2 x 2 inches. However, proper heat treating of these steels is important for adequate performance, and there are many suppliers who provide tooling blanks intended for oil quenching. A good precaution is to preheat the brine to around 100 degrees F prior to quenching. The Japanese sword smith avoided all this and only hardened a narrow strip of the edge. High carbon and many alloy steels can only be cooled slow enough in a temperatue controlled furnace since the cooling rate must be only 20 degrees F per hour for several hours. Although it may only represent 10% or less of the cost of the tool, the heat treat process is probably the single most important factor in determining the performance of a tool. Leave the blade in there for about 15 to 20 minutes. Wrap blades in tool wrap. Poor Man’s heat treating of 1095 – 1080 - 1084, Midwest Knifemakers Supply, LLC at www.USAKnifemaker.com, Knife Dogs Knife Forum at www.KnifeDogs.com. Organics mixed with nitrates can produce dangerous situations. The oil quench is well suited to a large blade where toughness is more needed whereas the brine quench is more suited to the small skinner and folder blades where holding an edge is important. For consistent results, you should keep your blades in a more or less consistent place in the chamber. You should have a wire basket in the quench tank for raising and lowering the blades rather than have them lie still. It still wouldn’t hurt to do it. Air quenching, Oil quenching, Salt baths, Vacuum furnaces
. Q2: Why do you leave blades in the foil to plate quench them. Gases are released in the quench and would form a "trap" around the steel unless you keep them moving for a minute or so.