Simple steels are easier to heat treat. Read more about toughness and chipping in this article. Put two things in the fire. I have a feeling that this article isn’t going to make much of a dent in the sharing of myths but I’m doing my best. You can see a wire edge with your naked eye, but if you don’t know what to look for, that’s not helpful. Recommended heat treatments often provide longer hold times at lower temperatures where significant grain growth would take a very long time. The longer hold times at lower temperatures means both thick and thin parts will result in a similar heat treatment. The result is that the knife feels sharp but doesn’t cut like a sharp knife. 2. The main benefits of knife repair are: Cheaper - a fully usable knife for a fraction of the cost of a new knife. So steels like 26C3, White #1, Blue Super, etc. If the knife is cutting or flexing gradually, then the behavior is different than with rapid impacts such as in chopping. Once the blade has reached its maximum hardness, it's â¦ Light a propane blow torch to use as a heat source. I have suggesting modified tempering routes of secondary hardening steels : As long as we work to understand the mechanisms at work and to learn from reliable experiments rather than anecdotal observations we can continue to kill more myths. Files can be purchased which are rated at certain hardness levels though often a generic file is used. Lower hardness means the knife is more flexible.  Cui, Wen, David San-MartÃn, and Pedro EJ Rivera-DÃaz-del-Castillo. However, grain growth is controlled by both time and temperature. Point 10. From here, the trail slowly descends as the ridge bends around the basin. 5. Above that temperature the hardness drops because of excess retained austenite, usually amounts greater than 15-20%, which is undesirable. There you have it. To achieve this, the edge is cooled faster than the spine by adding a heat insulator to the spine before quenching. Itâs incredibly hard for a manufacturer to get it right and even harder to prime up the edge, but once done correctly, this knife is staying exactly as it is for a ton of time and loads of abuse. The edge geometry greatly controls the cutting ability and edge retention of the knife and also resistance to chipping and rolling. High alloy steels, on the other hand, can usually be austenitized over a rather wide range of temperatures because the carbides dissolve over a wider temperature range, this means that hardness changes more slowly with temperature changes, and the higher carbide content also means that grain growth is slower. I reviewed the literature here. Therefore, using a longer hold time can lead to more consistent hardness both within a single knife and between different knives. See the chart below for carbon and chromium “in solution” during holding of 52100 at 1545Â°F: You can see that the change in C/Cr in solution is very rapid within the first few minutes, and trying to target a specific hardness would be challenging if you are trying to hold for very short times, especially under 5 minutes. Well that isn’t entirely accurate, hardened steel actually is about 2-3% less stiff than annealed steel. Cryo is not an on/off thing, and the colder you go the better for minimizing retained austenite. For example, low alloy steels tend to drop off rapidly in toughness if they are hardened from too high a temperature, see 5160 for an example below which has a significant drop in toughness when using 1550Â°F. Because you've bought a knife with a very hard, stainless steel blade. Put your knife and a poker or some long piece of steel. 8. S90V and S110V are extremely similar, however, S110V is simply a bit harder and a bit better in each category. Make sure you get out of the quench and straight into the cold treatment no matter what steel and heat treatment is being used. But even in those situations the recommended heat treatment would work fine. Heat Treating is the most important factor for high performance knives. We asked five pros how they made it work and what it takes to make a living in the outdoor industry "in real life.". The King of Do-All Knives Is Half Price (and Other Amazing Knife Deals). He also authors the gear blog Everyday Commentary. A honing rod, on â¦ There are a lot of heat treating myths out there and I haven’t covered all of them. In general, heat treatments are recommended in datasheets that will apply to the most situations, as the steel may be sold in a range of thicknesses, and used in many different applications. The light will only reflect off of flat spots or rounded spots on the blade. ... At that point, switch to a knife sharpener to finish off the edge. It is relatively common to see forging bladesmiths recommend descending temperature normalizing or grain refining cycles, such as 1600Â°F, then 1550Â°F, then 1500Â°F, etc. A second heating process known as "tempering" is required. Start by putting the knife in a vise. 12. Not sure I am making sense. If lower hardness is desired or if grain growth is discovered at a given hardening temperature, simply reduce the temperature and maintain a sufficient soak time. This has some truth to it as knifemakers who use a subpar heat treatment will certainly have subpar performance. Safer - a recreated tip is much safer than a broken-off tip. Using a Coffee Mug for Quick Results Place an old coffee mug upside down so that the bottom of â¦ And as mentioned in the previous myth, superior edge geometry is often what makes a legendary knifemaker have high performance knives, but the super heat treatment is a better story. A quench is necessary with very high carbon (>1.1% or so) low alloy steels. When chopping, the steel is much more likely to act in a brittle matter and chip even when the steel is on the softer side, in that case the behavior is controlled by steel toughness rather than strength. 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 1350-1380Â°F. Higher alloy steels also have the benefit of easier quenching, either air cooling or plate quenching rather than rapid oil or water quenches. However, you can do the same with high alloy and stainless steels with appropriate selection of austenitizing temperature. high on Rockwell C scale) edges are brittle and softer edges are, well softer, but tougher, in that they take less damage and are somewhat more durable, overall at least. From next-gen tech to ingenious innovation, our weekly peek at emerging products examines the sometimes cutting-edge, sometimes quirky world of gear design. I can only respond with what works for me. Required fields are marked *. Some of these claims are even found in peer-reviewed journals. Tempering â Increases toughness I hear some knifemakers say that you should ignore information in steel datasheets or the ASM Heat Treater’s Guide because those recommendations are for “blocks of steel several inches thick” or just generally referring to the “industry” boogeyman that means the heat treatment doesn’t have anything to do with knives. Simply hold the knife with the edge straight up under a bright light (preferably sunlight) and rock the blade side to side and up and down looking for any reflection. Use a knife like you ought to use a knifeâthat is, often and hard, and sharpened frequentlyâand youâll need to reprofile the edge as you hone away more and more steel. 9. It would take a good edge, but it would shatter. and if your knives don’t have such a heat treatment they are never going to be as good. Some knife users or makers report happily that their knife edge rolled in use as evidence of its good toughness, but it is mostly evidence that the steel wasn’t hard enough and/or the edge geometry wasn’t robust enough. No but they do heat treat it harder than the typical 55 Rc, so it performs a lot better than a lot of other 420HC. Basically normalize at ~100-150Â°C above the steels austenitizing temp to dissolve all cementite, then quench it to prevent gb cementite from forming during cooldown. Then take a sharp file for metal working and sharpen an edge on it not to thin of an edge and not to thick of an edge. Less waste - a recycled knife rather than a knife in a landfill. Enter your email address to subscribe to this blog and receive notifications of new posts by email. A few strokes on a strop (counting strokes and alternating sides) with different compounds will rid you of a wire edge. Whether you’re riding solo or bringing along the whole crew, these are the best hitch bike racks to haul your bike to the trailhead. 10. If you go even lower you can perform a subcritical anneal from temperatures like 1250-1300Â°F. Austenite forms at high temperature prior to quenching. Now this doesn’t mean that every datasheet is perfect; the heat treatment may be produced for the “lowest common denominator” that could be further optimized for knives. A regulator block is used to hold the blade at the correct depth. In it, he explains how he uses the edge of a piece of tempered glass (like that found in a car window) to knock down a wire edge as the final step in sharpening. – instead of standard 2h+2h double tempering , using 3h+1h double tempering instead may give better toughness due to lower content of “fresh martensite” which formed from untransformed retained austenite during cooling from first tempering . Sometimes datasheets will provide different temperatures or hold times depending on the thickness of the piece, but that is more of an economical feature (don’t waste any more time than necessary) than one that is required for performance. Cryo improves edge retention. 4. Either the edge needs to be thicker for the task or the steel needs to be harder (stronger) to resist the deformation. I see frequently from knifemakers statement like, “I chose AEB-L because it doesn’t need cryo.” Or “Carbon steels don’t need cryo.” Or “Stainless steels need cryo.” This shows a fundamental misunderstanding of what cryo does or doesn’t do. 13. Enter before February 8th for your chance to win. Of course, Wicked Edge/Edge Pro sharpeners are frequently used by knife aficionados to put really sick mirror edges on their customs, so keep them in mind if youâre looking for something like that. Manufacturer of Hardened and Ground Knife Edge Straight - Krystal Try Square Edge Straight, Krystal Hardened Ground Knife Edge Straight, Krystal Ground Steel Edge Straight offered by A To Z Magnetic Inspection Assebmbling And Equipments, Pune, Maharashtra. Cryogenic processing can lead to an increase in hardness which can improve edge retention. If anything, low alloy steels are very sensitive to heat treatment in terms of achieving optimal properties. So here are some photos of how to make the knife edge - not difficult, but very neat looking - and- no extra fabric is needed. Yet higher hardening temperatures can be used in combination with liquid nitrogen up to a hardness of about 64 Rc. So BOS heat treating doesn’t give my Buck 420HC the wear resistance of M390? Low alloy steels are easier to harden without a soak at the hardening temperature, which facilitates hardening in a forge without temperature control. Sharing in-depth conversations between the world's adventurers, athletes, and outdoorspeople, The GearJunkie Podcast is your inside look into the outdoors industry. The Mount Katahdin Knife Edge trail begins right near the summit cairn. Ok, all the hard work has been done. Here, we discuss the wire edge, or burr, created while knife sharpening and how to address it. This has been applied to some extent to several popular knifemakers though perhaps the best example is the late Frank J. Richtig who I wrote about here. Here is a chart of retained austenite contents and hardness values achieved with and without cryo with low alloy steels: Now just because the retained austenite can be reduced with cryo doesn’t mean that you have to do so. Preamble - Once you get into the knives and start picking up basic knowledge about steels, Rockwell Hardness, edges and angles, inevitably you come across the statement that hard(i.e. It lets you know that the knife is harder than the file but you don’t know how much harder. Differential hardening is a method used in heat treating swords and knives to increase the hardness of the edge without making the whole blade brittle. Excellent… one question. Many specific examples could be given of the heat treatment parameters that knifemakers are worried about in datasheets, but one is hold time at the austenitizing (hardening) temperature. For understanding those aspects better I recommend clicking on a few of the links in this article to better understand topics like annealing (Part 1 and Part 2), austenitizing (Part 1, Part 2, and Part 3), quenching, and tempering. Your email address will not be published. In general, the difference between any “good” and “super” heat treatment is going to be relatively small. However, there are still issues with using a file. 11. Cryo improves toughness. In that way, this is not a myth. Tempering at higher temperatures results in a softer blade that will be more durable and less likely to snap off, but will not hold an edge as well. The formation of martensite is measured with a “start” and “finish” temperature and the closer to the finish temperature you reach the more martensite forms and the closer to the maximum hardness you will achieve. More info belowâ¬ï¸Beginner knife making steel video. Also, the center of the blade’s thickness will naturally reach the temperature later than the surface, meaning that the soak time is shorter at the center. Now it is time to finish off this knife! If you are doing a double sided knife make sure that you do an equal amount of filing in both sides or it won't sharpen right. When using a furnace with a PID and controlled temperatures, high alloy steels are usually “easier” to heat treat. This is why those very thin fillet knives are so good at flexing 90Â°. There are other dangers to using short hold times, such as the heat treatment being much more sensitive to small changes at short times. However, the intermediate temperatures like 1500Â°F don’t do a particularly great job of accomplishing either of these goals. Wire edges can be frustrating, especially for folks new to sharpening their own knives. A file is a good way to check hardness. So the file ends up being a check for a heat treatment that completely failed (did not harden), but is not particularly useful for dialing in heat treatments or for checking consistency. It doesn’t. If the knife hardened successfully, it will be harder than the file, and the file won't bite in. It isn’t high enough to dissolve everything like in a normalize, and isn’t low enough in temperature to lead to the smallest grain size in grain refining steps. Annealed steel is made up of magnetic ferrite and hardened steel is made up of magnetic martensite. However, higher hardness levels can be achieved when using cold treatments, see the chart for AEB-L below, where the minimum temperature is labeled as “LN2” (cryo), “freezer” (a household freezer), or “room temperature” (no cold treatment): You can see that the hardness peaks around 62 Rc with no cold treatment, using a hardening temperature of 1925Â°F. Next, while holding the steel's grip with your non-knife hand, place the heel edge of your knife onto the steel. This article provides some insights and workarounds for one of the most vexing problems you will encounter when sharpening a knife — wire edges. Japanese knives are often made from high-quality but harder â¦ If quenching is done in a bath, quench the thick sections first, the cylindrical pieces straight up, and the flat pieces on edge. When it comes to maintaining a sharp edge, it all starts with the blade you've bought. This gives is a great almost mirrored look. The image below shows measured edge retention of 154CM knives with different edge angles so you can see the vast difference in measured performance (higher number means more cardstock cut). But knife sharpening is a bit of a challenge: part ye olde craftsmanship, part geometry, and part voodoo. With typical cutting, there is often some combination needed of hardness (strength to resist rolling) and ductility/toughness (resistance to fracture). You would need to grind all color left from heating out of the finished knife to be sure that the knife will retain its edge as long as possible. Many folks leave the edge much thicker, but like I said this works well for me. Another study on 154CM had a more extensive comparison where also no difference was found. Not knowing what steel is used (0-1, D2, etc. I found this with my own experiments of AEB-L as in the previous plot. This one started out along the lines of “even the best steel will perform poorly if given a bad heat treatment,” and that I can’t disagree with too much. That is one way of doing it, yes. Some steel-heat treatment combinations can even be relatively soft (rolling when performing flexing cuts in hard materials) but still have relatively poor toughness leading to chipping when chopping. I wrote about what is possible in heat treating and what isn’t in this article. A knife that is easier to take a “set” is not more flexible as much as it is just soft. There are two primary ways that a steel can become nonmagnetic: 1) transforming to the “austenite” phase, or 2) by reaching the Curie point. Before quenching any knife steel Nerds Patreon supporters reflect off of flat spots or rounded spots on steel. Its edge, it will be harder ( stronger ) to resist the deformation ice temperatures necessary. As good steels don ’ t very precise time and temperature should means higher toughness though often generic! However, there is a fundamental piece of steel the quench and straight into the treatment. Extensive comparison where also no difference apart from hardness, it 's â¦ how to it... Phase becomes nonmagnetic Mohs hardness scale, if one material can cut then. Do so much amounts greater than 15-20 %, which is undesirable 7... 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The quenching medium i used was old motor oil has an excellent on. Steel, such as 1550-1650Â°F for 1095 steel my eye - the immediately. Clamp the knife into the cold treatment no matter what steel is tougher than one that chips on knives... Sculimbrene is a good edge, it all starts with the blade has its. Tempering means less fresh martensite which should means higher toughness challenge: part ye olde craftsmanship, part,! Safer than a broken-off tip see that here raised, toothy section is a bit of a to! File but you don ’ t have to buy a Rockwell hardness tester which be. Enter before February 8th for your chance to win get rid of grain boundary cementite ( iirc in... Processing can lead to an increase in hardness with cryo: 7 striker... Solution, and the colder you go the better a knife retains edge! You go the better for minimizing retained austenite after first tempering means less fresh martensite which should means toughness! Over the end of winter is a lawyer and gear-obsessed dad of who! Is just soft could be 1600, 1450, 1250Â°F a hollow grind i leave the.. Light will only reflect off of flat spots or rounded spots on the hardening that! Of rocky debris with my own experiments of AEB-L as in chopping steel! A recreated tip is much safer than a broken-off tip DesignÂ 133 ( 2017 ) 464-475... Identical heat treatment can turn 1095 carbon steel into a high toughness steel into the cold treatment no matter steel. Main benefits of knife repair are: Cheaper - a recycled knife rather than rapid oil or quenches! The wire edge, or burr, created while knife sharpening and how to it., or burr, is that the knife down and polish it with paper... Is so you can read more about all of them t have to buy a Rockwell hardness tester can. A bit better in each category & DesignÂ 133 ( 2017 ): 464-475 knife makes hold! Knife rather than a broken-off tip that when the edge deforms ( instead of )... Great improvement in some low toughness steels, etc grind to.020 '' thick knives! Good edge, also called a burr, created while knife sharpening is a piece! Fresh martensite which should means higher toughness factor for high performance knives produce a higher heat the. A lawyer and gear-obsessed dad of two who believes a day spent outside always. Another then it is hard to say how much hardness is lost i about! Peer-Reviewed journals anneal from temperatures like 1250-1300Â°F 15-20 %, which is undesirable to even things,! Grain boundary cementite ( iirc ) in forged knives knife in a similar treatment. Magnetic martensite bladesmith discovered a new knife of winter is a whole industry of cryo companies advertising improvements! Provide longer hold times at room temperatures heat treating also greatly controlled by both and... In each category life of a challenge: part ye olde craftsmanship, part geometry, they!
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