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Heat Treating Stainless Blade Steels at Ranger Original Handcrafted Knives

Special Thanks to Rob Ridley of Ranger Original for this Information

We have had a number of people ask us for our “secrets” about heat treating knife blades. While we appreciate the compliment, there really are no secrets – and what works for us may not be your favoured solutions. Here are our recipes. You may copy them, publish them or use them as you please. 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.

All of our stainless blades get double wrapped in high temperature, 309SS foil envelopes – with double folded seams pressed down firmly. Always put them in the envelope the same way – so you can put them in spine down and pull them out by the handle, instead of the tip. We use brown paper (no idea why brown – just what we use) in pieces about 2 x 2 inches. 2 pieces for an average hunter and four for a big bowie. The trick is to use enough paper to eat up the Oxygen in the envelope – without blowing up the envelope like a balloon.

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154CM, CPM154, ATS34

All three of these, heat treat the same. After a full speed ramp up to temperature, they soak 45 minutes to an hour in the Evenheat Oven at 1950F degrees. Then they get placed – still in the foil – spine down – then flat - on a 1” aluminum plate. The second aluminum plate is placed on top and pressure is applied. We used to use weights for the pressure, but now we use clamps. You are looking for good firm contact. If you are thinking hydraulics you are thinking WAY too much pressure. After 2 minutes (or less) they will be hand cool, and ready to remove from the foil for cryogenics. They don’t have to go straight into cryo, but aim for something less than an hour from plate quenching. We use liquid nitrogen for cryo but dry ice in acetone will also do. The household freezer is no use at all. They probably only need a couple hours in cryo, but we leave them overnight.

The next morning, they will be in the range of RHC63+. After warming to room temperature, they get tempered. We temper twice at 500F degrees for two hours each time – to get about RHC61. You can experiment for other hardness's but 61 is a very good target for these steels.

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CPMS30V

Same wrap – same temperature (1950F) - same soak time – same plate quench – same cryo as 154CM above. This steel gets double tempered at 400F degree for about RHC60

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440C

Same wrap – Harden at 1900F degrees and only about 15 minutes at temperature – then plate quench and cryo as above. Hardness out of cryo will be about 61. Temper (twice for 2 hours) at 275F for RHC60 – 325F for RHC59 – and 375F for an excellent RHC57-58.

Questions and Answers provided by Rob Ridley of Ranger Original

Q1: Does Cryo really make a difference.

A1: Yes! It increases initial hardness between 1.5 to 2 points and even though you may temper back to softer levels, the steel has been more completely transformed to a tough and desirable state.

Q2: Why do you leave blades in the foil to plate quench them.

A2: The really hot blades never see oxygen this way. That means no scale and very little oxide. Air quenching the old way meant going back to the grinder to clean up the mess. Blades done our way can be cleaned up with just a buffer.

Q3: Why do you remove the blades from the envelope before cryo?

A3: Experience! We like hanging the blades from a coat hanger in the cryo tank. Handle pin holes make that easier. We also found that when a tight foil bag full of liquid nitrogen, hits the warm summer air, bad things can happen. The low tempering temperatures won’t cause you any scale or oxide problems anyway.

Q4: Can I use my freezer for cryo?

A4: No. It isn’t nearly cold enough to do any good at all. Dry Ice or Liquid Nitrogen work equally well. Dry ice is easier to handle but only lasts a day or so. Liquid nitrogen in a good dewar will last a month or more depending on use.

Q5: I heard ATS34 etc can be tempered at a high or low range. Is this true?

A5: Sort of – but the high range gives you reduced toughness and corrosion resistance. It should be avoided.

Q6: Are there other ways to heat treat these steels?

A6: Heck yes! Air quenching, Oil quenching, Salt baths, Vacuum furnaces…. But you’ll have to ask someone else about them. I haven’t seen anything that gives more satisfactory results that the way we use now.

Q7: Aluminum is expensive! Can I plate quench between thick steel plates.

A7: Yes – less desirable because it absorbs heat slower – but workable.

Q8: How do I know if it hardened and tempered properly.

A8: The correct answer is to use a Rockwell C scale tester and then to do performance testing on your blades. Some claim they can tell hardness pretty close by the way a file skates over the steel. I can’t. We test every blade through here and write the hardness on the blade before shipping it out. Having said that, we are rarely out by more than 1 Rockwell point from where we aimed.

Q9: 321SS foil is much cheaper. Can I use it instead of the 309SS?

A9: Depending on who you talk to, the 321 is rated to something between 1800 - 2000 degrees. The risk is that the 321 will either fail, allowing air in, or stick to the blade inside. In practice, we have used it successfully with our own blades without problem. We have seen 321SS stuck to a blade heat treated elsewhere. Because we treat other maker’s blades, we choose to use only 309SS foil. Experiment at your own risk.

Q10: Does it matter where in the oven I place the blade?

A10: Yes. Temperature inside an oven can vary and generally is only measured at one point – where the thermocouple is located. For consistent results, you should keep your blades in a more or less consistent place in the chamber. Hint; Avoid getting closer to heating coils than necessary.

Q11: How do I know if my oven is accurate for temperature?

A11: Some will tell you that you can test temperature with ceramic firing cones. We disagree. Cones do not measure temperature. They measure heat work – a combination of time and temperature. Orton makes a product called TempChek which is better but still requires a rather complex cycle for a good result. An electronic probe and thermocouple is the best way to check, though can be expensive. Of course, unless you can calibrate the probe, you still don’t really know do you?

Note: Rob really nailed the question of using a pyrometric cone for temperature measurement. It's apples and oranges. Save the pyrometric cones for the potters.

Q12: How far can a blade be finished before heat treat?

A12: Many of our customers finish to 800 grit before heat treat. We ask makers to leave us 20 thou at the edge and point – essentially a finished blade that has not been sharpened. Although we have not had any stress fractures, it is also a good idea to avoid sharp corners where possible and to deburr pinholes and other irregularities.

Safety

Heat treating has obvious hazards. Please wear safety glasses or face shield and decent gloves. The day will come when you drop a hot blade. Make sure the floor around your oven is free from combustibles and please resist the urge to catch the falling blade.

Email with questions.

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ATS 34, 154CM Heat Treat Procedure

Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information

This is an oil hardening grade of steel which will require oil quenching. The oil should be warm, thin quenching oil that contains a safe flash point. Olive oil has been used as a substitute. As a rule of thumb there should be a gallon of oil for each pound of steel. For warming the oil before quenching you may heat a piece of steel and drop in the oil.

1. Wrap blades in stainless tool wrap and leave an extra two inches on each end of the package (This will be for handling purposes going into the quench as described below). We suggest a double wrap for this grade. The edges of the foil should be double crimped being careful to avoid having even a pin hole in the wrap.

2. Place in furnace and heat to 1900°F. After reaching this temperature immediately start timing the soak time of 25 to 30 minutes. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

3. After the soak time has elapsed, very quickly and carefully pull the package out with tongs, place over the quench tank and snip the end of the package allowing the blades to drop in the oil. You should have a wire basket in the quench tank for raising and lowering the blades rather than have them lie still. Gases are released in the quench and would form a "trap" around the steel unless you keep them moving for a minute or so. IMPORTANT - It is very important that the blades enter the oil quench as quickly as possible after leaving the furnace! Full hardness would not be reached if this step is not followed.

4. After the blades are quenched down to near room temperature (preferably around 125°F) they must re-enter the furnace at 300°F. After they reach 300°F allow them to remain for 2 hours. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

5. Remove blades and place them aside for room temperature cooling.

6. After they have cooled to room temperature, place them back in the furnace at 275°F for 2 hours. Remove and check hardness. You should have approx. 60 RC. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

7. For extra stability and a point higher hardness you may pack blades in dry ice for one hour.

Note: All the above procedure is based on our own experience realizing there are others using their own trial-error. All equipment must be calibration checked periodically. There are no "short-cuts" for proper heat treating. Always exercise care and precaution.

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440C Heat Treat Procedure

Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information

1. Wrap blades in tool wrap. Double crimp all edges of the foil being careful to avoid having even a pin hole in the foil. You may double wrap fro extra assurance of locking out all oxygen. You may wrap the blades with 5-6 stacked side by side or individually wrap and place in an optional furnace rack. This rack will hold the blades in an upright position for minimizing warpage.

2. After placing the blades in the furnace heat to 1850°F. After reaching 1850°F start timing the soak time of 20 to 25 minutes. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

3. After the soak time has elapsed, carefully slide the blades on a steel grate or heavy wire mesh for room temperature cooling (This is the air quench). Place aside for cooling. The grate or wire mesh will allow air to circulate under the blades as well as around them for uniform quenching.

4. While the blades are cooling leave the furnace door open and allow it to come down to 220°F. Sometimes the blades willed be cooled before the furnace comes down. In this case keep the blades warm (place near the furnace door) or you may use the kitchen oven for drawing. It is important on all grades that they do not cool much below the 125°F temperature before drawing.

5. After placing the blades in the 220°F temperature they should remain at this heat for 2 hours. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

6. Pull the blades out for cooling and place them back at 200°F again for 2 hours. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

7. Check harness. You should have approx. 59 RC.

For extra stability you may freeze the blades in dry ice for one hour. This will also increase the hardness a point or two.

Note: All the above procedure is based on our own experience realizing there are others using their own trial-error. All equipment must be calibration checked periodically. There are no "short-cuts" for proper heat treating. Always exercise care and precaution.

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1084, 1095, AISI 0-1, AISI 0-6 Tool Steel Heat Treat Procedure

Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information

This is an oil hardening grade of steel which will require oil quenching. The oil should be warm, thin quenching oil that contains a safe flash point. Olive oil has been used as a substitute. As a rule of thumb there should be a gallon of oil for each pound of steel. For warming the oil before quenching you may heat a piece of steel and drop in the oil.

1. There are two ways of giving 0-1a protective atmosphere before hardening: (A) You may use a non-scaling compound. It works very well for temperatures up to 1650°F. Heat the blades to 500°F, remove from furnace and roll them in a tray of compound. It will adhere to the steel and form an air tight blade. Replace in furnace and continue hardening steps. (B) The other choice is to wrap in tool wrap. When wrapping this grade allow an extra 2 inches on each end for handling purposes. Step 3 will describe further.

2. Place blades in the furnace and stand up on edge, you may use a special furnace rack for this purpose. Heat to 1450°F. As soon as this temperature is reached then begin soak time of 15 to 20 minutes. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

3. At this time the blades need to go into the oil very quickly. You should have a wire basket inside the quench tank. 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. Raise and lower the basket for a minute or so for good oil circulation (This step is very important).

4. While the blades remain cooling set the furnace at 375°F. After the blades have cooled to approx. 125°F, place them in the furnace (at 375°F). Allow them to remain (draw) for 2 hours. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

5. Remove the blades, check for hardness after they are cool enough to handle. You should have approx. 60 to 62 Rc.

Note: All the above procedure is based on our own experience realizing there are others using their own trial-error. All equipment must be calibration checked periodically. There are no "short-cuts" for proper heat treating. Always exercise care and precaution.

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AISI D-2 Heat Treat Procedure

Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information

1. Wrap blades in tool wrap. Double crimp all of the folded edges being careful to avoid having even a pin hole in the foil. The blades may be wrapped individually or stacked side by side (stack no more than 5 or 6 per pack for ease of handling). If they are wrapped individually you may consider placing them in an optional furnace rack. This rack will hold the blades in an upright position for minimizing warpage.

2. After placing the blades in the furnace, heat to 1850°F. After reaching 1850°F immediately start timing the soak time of 15-20 minutes. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

3. After the soak time has elapsed, carefully slide out of package onto a steel grate or wire mesh (this is the air quench).

4. While blades are cooling allow the furnace to cool down to 950°F.

5. When the package has cooled enough for handling, remove the foil. The blades should be warm (approx. 125°F). At this time place them back in the furnace at the 950°F temperature. After the blades have reached this temperature allow them to remain (draw) for 2 hours. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

6. Remove the blades for cooling down to room temperature and place them back in the furnace at 900°F again for 2 hours (this is a double temper we suggest for D-2). Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

7. After removing and cooled check hardness. You should have a 58 to 60 RC.

For extra stability and 1-1/2 points higher hardness you may pack blades in dry ice for 1 hour.

Note: All the above procedure is based on our own experience realizing there are others using their own trial-error. All equipment must be calibration checked periodically. There are no "short-cuts" for proper heat treating. Always exercise care and precaution.

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Stainless-Plus Damascus Heat Treat Procedure

Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information

1. Wrap blades in heat treat foil. Do not put any paper in foil. Preheat furnace to 1900°F. Place blade in furnace and watch controller. When temperature gets back up to 1900°F, let blades soak for 10 minutes (12 minutes for 1/4" blades). Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached. Do not soak blades any longer than specified time. The steel will decarburize and you will not know until you etch it. Also, do not exceed 1900°F.

2. Remove blades from furnace and cut foil open. Immediately remove blades and quench in light oil.

3. Place blades in freezer overnight or for 2 hours in dry ice.

4. Temper twice at 350°F for 2 hours. Evenheat's Set-Pro & Rampmaster controls can be programmed to automatically soak, for any amount of time desired, once temperature is reached.

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Random with CPM420-V and 440-V Heat Treat Procedure

Special Thanks to Mick Koval (R.I.P) of Koval Knives for this Information

The heat treat temperatures for the random with CPM 440-V and 420-V core will be different. Harden at 1950°F and temper at 350°F. This will give you lower hardness readings on the outer steel if you check with a hardness tester, but the center core of the steel will be much harder. This will be on the cutting edge.