3. Tempering: If you did everything right quenching, your steel is around 65RC and fragile as glass. Q8:  How do I know if it hardened and tempered properly. 5. I have a left a piece of steel overnight untempered and found it cracked the next day from the stress hardening puts into the steel. 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. Allow the steel to remain in the oven for a "soak" time of at least 30 minutes. There are two ways of giving 0-1a protective atmosphere before hardening: (A) You may use a non-scaling compound. Heating the Blade A harder blade, say 61 to 62RC will generally cut longer between sharpening sessions. We know that any machine knife or blade is only as good as the steel it is produced from. Uneven carbide size and distribution lowers the cutting performance. Of course, unless you can calibrate the probe, you still don’t really know do you? When temperature gets back up to 1900°F, let blades soak for 10 minutes (12 minutes for 1/4" blades). Hardness 62 61 59 58 56 55 54 53 Forty years ago when I began making knives I wanted to make beautiful knives that met the highest levels of function possible. Or use a brine solution (salt & water). 1. Dry Ice or Liquid Nitrogen work equally well. Step 2: Normalizing. Soak in solution. That’s why here at Precision Edge, we take great care in sourcing and preparing our blades. If the blades are wrapped in tool wrap, hold one end up and snip the other end of the foil allowing the blades to drop in the basket and into the oil. The steel actually changes crystal structure at this point. In practice, you heat the blade and keep touching a magnet to the blade. I can’t. Temper (twice for 2 hours) at 275F for RHC60 – 325F for RHC59 – and 375F for  an excellent RHC57-58. Q7:  Aluminum is expensive! The blade should be evenly heated to a bright red/dull orange color. 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. All of our stainless blades get double wrapped in high temperature, 309SS foil envelopes – with double folded seams pressed down firmly. A9:  Depending on who you talk to, the 321 is rated to something between 1800 - 2000 degrees. Is this true? After removing and cooled check hardness. Simply put a lid on your quench oil container to smother it and put out the fire. This step should be carried out soon after heat treating, within an hour or so, but only after the blade has cooled to room temperature. Allow more soak time for more massive pieces of steel. It will help if you pre-heat the oil to around 100F. We have had a number of people ask us for our “secrets” about heat treating knife blades. I heat the steel to temperature and put it all in the vermiculite to cool down slowing using the vermiculite as an insulator. 2. Replace in furnace and continue hardening steps. It works very well for temperatures up to 1650°F. Do not agitate side to side as the soft metal can actually warp from the fluid being cooler on side versus the other. Remove and check hardness. Most custom knives tend to be hardened to 59RC for a good compromise between edge retention, toughness and sharpening ease. If you drop it now, it will shatter. Most agree that the steel really needs to be cooled off at a high rate, like 1 to 2 seconds and, that is absolutely true. In such cases, some of the high-temperature microstructure, or austenite, may be retained after normal heat treating.” A2 and D2, as well as other high-alloyed tool and specialty steels, may contain as much as 20 percent austenite after normal heat treating. It barely left a scratch on the surface. Air quenching, Oil quenching, Salt baths, Vacuum furnaces…. 440C Heat Treat Procedure Quenching an overheated blade will increase the change of cracking or warping. Heat treating O1 tool steel is simple. The grate or wire mesh will allow air to circulate under the blades as well as around them for uniform quenching. It won’t be perfect and veteran knife makers will tell you to use dedicated heat treat quench oil to get better results. 1. 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. This means the final hardness should be around 62-63. This is where I tested the hardness with a hardness test file. When the package has cooled enough for handling, remove the foil. Heat Treatment of 52100 The typical recommended heat treatment for 52100 is a 1500-1550°F austenitize for 10-30 minutes followed by an oil quench and a temper from 300-500°F. After placing the blades in the furnace, heat to 1850°F. Do this safely and be prepared for a flare up of fire and a large amount of smoke. Non-magnetic is around 1425F. Below are listed the approximate Rockwell Hardness achieved at the various temperatures. Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information. ATS 34, 154CM Heat Treat Procedure A good precaution is to preheat the brine to around 100 degrees F prior to quenching. Annealing: Anneal by heating to 1500F and cool at a rate no faster than 50F per hour. Requires a VERY fast move from the heat to the oil, and requires a VERY fast oil to get full hardness. In this process, the steel is frozen to a temperature below 300 degrees fahrenheit and tempered. Air quenching the old way meant going back to the grinder to clean up the mess. A4:  No. Evenheats' Set-Pro control can be programmed to automatically soak, for any amount of time desired, once temperature is reached. Pull the blade out after 15 minutes & inspect how the etch looks, if you need a higher contrast, again dip the blade back in the etching solution for additional time till you have reached the desired contrast. Dissolving salt in boiling water until it no longer dissolves makes a brine solution. We have drawn from various sources, including Crucible data sheets, other steel suppliers and postings on Blade Forums as well as a good dose of personal experience. You should end up around 65RC in hardness. The next step is to oil your blade using good quality gun oil. Normalizing: Heat to 1575°F (855°C). Make sure all the oil is cleaned from the blade or your house will smell like oily smoke and your knife making career may be cut short by the boss of the kitchen. The bottom line is that a knife is a tool and it needs to be able to function. Done. AISI D-2 Heat Treat Procedure Aim your hair dryer at the charcoal and turn it on. Thunderforged™ is a trademark of Universal Agencies, Inc.™ all rights reserved. Do not put any paper in foil. Normalizing steel allows the crystalline structure to be reset and redistributes the carbides back to uniformity in the structure of the metal. After the blades have cooled to approx. 1. Heat to 1500, soak 10 minutes. A12:  Many of our customers finish to 800 grit before heat treat. This should be achieved between 1,400 & 1,500 degrees F. Be careful not to overheat. If you have other work you want done, I use a half size trash can full of vermiculite. While blades are cooling allow the furnace to cool down to 950°F. After warming to room temperature, they get tempered. Q6: Are there other ways to heat treat these steels? Having said all that, most don’t cryo treat carbon steels but you can if you want. The more precise you are about heat treating your steel, the better result you will have. We recommend that you use tweezers. Hardness 65 64 63 61 59 57 55 54 You should slowly agitate the blade up and down or side to side along the thin edge. You may double wrap fro extra assurance of locking out all oxygen. This steel gets double tempered at 400F degree for about RHC60. The trick is to use enough paper to eat up the Oxygen in the envelope – without blowing up the envelope like a balloon. When the magnet doesn’t stick any more, give it a minute more of heat and then quickly plunge the blade into your quench oil. In short, bring it to critical temperature, quench it in vegetable oil, then temper it in an toaster oven or regular kitchen oven for one hour at 400˚. Q12:  How far can a blade be finished before heat treat? Generally, in a forge, this means heating it until a magnet doesn’t stick and then “just a little more” to get the extra heat into the steel past non-magnetic. Questions and Answers provided by Rob Ridley of Ranger Original. Evenheats' Set-Pro control can be programmed to automatically soak, for any amount of time desired, once temperature is reached. The blade should be quenched either point first or spine first in order to minimize the chance of cracking or warping. Normalizing steel allows the crystalline structure to be reset and resets the carbides back to uniformity. We used to use weights for the pressure, but now we use clamps. At this time you will notice that a black substance will be coming off, this is the carbon that was removed during the etch. Note when heat treating multiple blades keep ample space between each blade for proper air circulation. 2 pieces for an average hunter and four for a big bowie. The heat treatment of 52100 is different than that of many of the other alloy steels, including 5180, in that the hardening temperature controls the amount of Carbon that dissolves in the austenite - the condition of steel at high temperature where it is a solid solution of Iron and Carbon. Sometimes the blades willed be cooled before the furnace comes down. Heating and cooling applied to solid metal change its structure and physical qualities without altering its chemical composition. Same wrap – Harden at 1900F degrees and only about 15 minutes at temperature – then plate quench and cryo as above. Allow them to remain (draw) for 2 hours. 1. As a rule of thumb there should be a gallon of oil for each pound of steel. 01 Step 3 will describe further. Another good method it to heat the blade until the magnetic properties are lost. Pull the blades out for cooling and place them back at 200°F again for 2 hours. Without looking up the information I would expect to see that there are more high temperature carbides in S30V that will require a higher and longer temperature soak to put carbon into solution. You can see a slight scratch at the end of my thumb. Tempering is accomplished basically baking them in an oven at a much lower temperature then the heat treat temperature. You should have approx. We temper twice at 500F degrees for two hours each time – to get about RHC61. The temperatures for house hold or small table top ovens are often wildly inaccurate. This isn’t that hard but you do need to respect the hazards. The blade is placed in a heat treat oven and brought to a specific temperature. Because we treat other maker’s blades, we choose to use only 309SS foil. 1095 is a high carbon steel with .95% carbon (the 95 in 1095) and is proven, good quality knife steel with good edge retention. The quicker the blade is cooled the more likely it is to crack. Q2:  Why do you leave blades in the foil to plate quench them. After placing the blades in the 220°F temperature they should remain at this heat for 2 hours. If you see a warp, now is the time to bend it slightly back to being straight and it should take. 6. 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. There are many techniques for creating a difference in properties, but most can be defined as either differential hardening or differential tempering. Heat treating has obvious hazards. The blades should be warm (approx. Furnace vs. Oven? Place blades in freezer overnight or for 2 hours in dry ice. Once in a while, they warp a little. All Rights Reserved. 1080/1084 is so close together the industry specifications overlap to the degree that 1084 could be closer to the 1080 and vice versa when tested. Unauthorized Publication Prohibited Heat to 1450°F. Also, do not exceed 1900°F. 2. However, that doesn’t mean you only have 1 second to get from your heat source to your quench. Clean blade with acetone. Cryo Treatment: Cryo treatment, soaking steel after hardening but before tempering at temperatures at least minus -90F (dry ice range) to minus -290F (liquid nitrogen range) for eight hours. Annealing: Heat to 1475°F (800°C). This helps remove any insulating air or gas bubbles. Moving a blazing hot piece of steel from heat to oil is where a lot of fires get started. Heat to 1475F to 1500F (steel type depending) until the metal is just past non-magnetic. Knife Making - How To Heat Treat A Knife | Super Simple DIY heat treating. With most low alloy knife steels, the steel transforms to austenite before reaching Curie, and therefore the nonmagnetic temperature is significantly lower, usually somewhere in the range of 1350-1380°F. It’s rare but it happens. Heat the knife blade until it has reached a minimum temperature of 1,475 degrees Fahrenheit, or glows a bright cherry red. Evenheats' Set-Pro control can be programmed to automatically soak, for any amount of time desired, once temperature is reached. Draw temper to desired hardness 2. For the best experience on our site, be sure to turn on Javascript in your browser. Make sure the floor around your oven is free from combustibles and please resist the urge to catch the falling blade. A surface fire on quench oil is not the end of the world. Must be 18 to purchase. At this time place them back in the furnace at the 950°F temperature. Care must be taken when quenching in brine. After the blade has cooled sufficiently, then you must “temper” the blade to slightly lower the hardness so that the steel is not too brittle and prone to chipping, cracking or breaking. Step 3 Remove the knife blade from the charcoal carefully with a pair of metal tongs. Hold at temperature for 1 hour per inch (25.4 mm) of thickness, 2 hours minimum, then air cool to ambient temperature. Don’t worry about hardening the handle. Preheat furnace to 1900°F. Some knifemakers have recommended a 1475°F austenitize. These steels don't need a long soak time. 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. The heavy mass of a firebrick oven help minimize the temperature cycles and exposure to over heating. Once thoroughly heated, slowly cool in the furnace by dropping the temperature 20 … You may copy them, publish them or use them as you please. All three of these, heat treat the same. 1. You don’t need to harden the entire knife blank. Big business doesn’t waste money on steps on heat treating it doesn’t need to do. If you have other work you want done, I use a half size trash can full of vermiculite. Wear heavy leather gloves and apron. Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information. Drawing, or tempering the blade is done by heating the steel in an oven. Save the pyrometric cones for the potters. Allow to cool slowly in still air. (B) The other choice is to wrap in tool wrap. The steel will retain heat and survive a few seconds in the air as you move from heat to quench. Cooling slower in the forge works better but cooking in the vermiculite works fairly well also. Pile up some charcoal in your BBQ and get them going good. 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Knife makers will tell you to abide by any and all laws applicable you... 62Rc will generally cut longer between sharpening sessions cut anything and it will shatter hard... For RHC59 – and what works for us may not be your favoured solutions may use the internet research!

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