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View Full Version : does anyone still do diferential hardening with hot fire and cold water anymore?



Thunter124
10-26-2010, 01:33 PM
I'm about to get all of my parts and pieces together and finish up my blacksmithing shop. I want to go about making and treating blades in a more traditional manner: hammering em out, draw filing to sharp and shape, aneal the steel for a couple of nights(long soak in the forge, let cool in vermiculite overnight). Then using a heat resistant clay impregnated with activated carbon, bring the steel to a nice cherry red and quench in some plain old room temperature water. Does anyone still practice the old arts like this anymore, most all I see is people baking knives to X heat for X long and then letting cool for X long, and I can see why people do that, I can appreciate the virtues of that method. I personally don't want to just bake a blade, I want the dynamic, organic, artistic and original look that you get from it. So I've got to ask: who all is still treating knives in this manner, and how do you personally go about it?

EdCaffreyMS
10-26-2010, 03:00 PM
There are SOME folks who are still water quenching, but most of them will tell you that getting away with doing it to modern steels does not have a high success rate....by that I mean that more often than not the steel/blade will crack.
The reason that most have gotten so "technical" is because modern steels require it. Back in the days when water quench was the norm, a blacksmith could NOT acquire steel of given grades/types. Most had a junk pile near their shop, and whenever they required a piece of iron/steel that they didn't have, they would "create" a bar of steel by forge welding together whatever they had. Mostly from smaller pieces of whatever they could find. Most of this material was low carbon or wrought material. If they wanted to "harden" something, they would quench it in water because that was the only way they could achieve a semblance of hardness.
With the steels we have/use today, it's actually easier and more predictable to be more technical. EVERYTHING that happens within a piece of high carbon/alloy steel has to do with Time and Temp.....specific temps, for specific durations create both the good things and the bad things that can occur. Our job as Bladesmiths is figuring out the good from the bad.
You mentioned in your post "bring the steel to a nice cherry red". If you do that, you will not achieve full hardness, no matter what quench you use. In water there's a good chance the steel will crack, even if full hardening is not achieved. If you want to use color as a guide (very inaccurate), the color would need to be more towards a bright orange.

You can work in whatever way you wish, but I can tell you that with modern steels, be prepared for a lot of failures, and a very long learning curve when using the methods you mentioned. I'm not trying to deter you, just trying to make you aware.

Thunter124
10-26-2010, 04:07 PM
Wheres the fun if there is no learning, I'm not saying I want to be able to make everything perfect day 1, I just want to try my hand at it and see how far it can go. If it requires more work on my part and takes a while to learn, Ill go the distance. If the blades crack in the quench, I can always recycle it into a billet, I've got two leaf springs that are 30# each to work with, so the composition would be the same for a lot of knives. and on the "cherry red", yea that was just wrong on my part, so I went back and looked at some of my material(need to read more). Theirs a couple of different techniques Ive been reading about, about drawing heat color on a mirror finish and quenching once you get to the proper color/temp you want.

the only mistakes are the ones you don't learn from, and I will be doing allot of learning

Bruce Barnett
10-26-2010, 11:38 PM
I believe Ed is trying to help save you lots of time, energy, money, steel and effort. You will still have years of fun learning just like the rest of us, but thankfully there a re guys like Ed who willingly lessen the pain and make it fun.
Cheers Bruce

LRB
10-27-2010, 06:05 AM
What Ed is telling you is that cherry red is not hot enough to get the steel full hard in the quench. The mirror finish, acually just needs to be bright and clean, then heating to color is for tempering, after you get the blade hard. I would suggest you get some 1050 steel if you are going to pursue the methods you state. Even with 1050 you can look for some failures. Your spring steel could be any one of many different "spring steels". Most of todays leaf springs are alloyed steel and are not going to be friendly to your ideas. If you will do some historical research you will find that oil quenching is not a new and modern method of hardening steel.

EdCaffreyMS
10-27-2010, 08:01 AM
Thanks fellas! For putting it in different words....Thunter, I'm not trying to discourage you in any way.....just trying to let you know the facts, so that you don't "beat your head on a wall" like I did in my early days. I refer to the the time frame when I started as "The Dark Years" because nobody would divulge any information about knifemaking/bladesmithing. It was all a "super secret". I've always remembered how I struggled, and try to help others avoid that situation.

As I said previously, there are a few folks out there doing it as you described, but they are becoming fewer because the success rate is typically very low using those methods. Just trying to help.

Doug Lester
10-27-2010, 08:31 AM
Thunter, some times when I heat my blades for hardening they look cherry red when they are non-magnetic becuause of the ambient lighting. I'm sure in different light they would look orange. That why I never go by the color of the steel in the forge to determine if it's ready for the quenchant; I use a magnet. I work with a gas forge exclusively after a long time of trying to stick with a charcoal forge. I miss it but gas is the way to go. Anyway, I turn the gas back on my forge when I'm heat treating reduce the possiblilty of overheating. I slowly bring my steel up to non-magnetic then soak it for a good minute then move directly to the quenchant. I am working with 9260 and 51200 right now. The 9260 I marquench and the 52100 I austemper. The reason is that both methods reduce the stress of quenching. The austempering produces a partial bainite composition which adds toughness. The reason that I don't austemper 9260 is that I can't achieve proper hardness with that method and steel plus, if I could, I would have to hold it in the quenchant at temperature for something like a day and a half.

As for the heat treating cycle that you described in your first post, it sounds like you are trying to describe air quenching. It is done on higher alloy steels many of which would crack in oil let alone water. If you want to quench in water, have at it but you will have to restrict yourself to simpler steels that will lend themselves to that process. The steels control the process not the smith. Just be forewarned, you will have failures, as in cracked blades. Nova on PBS had an episode about the Japanese sword. It featured a traditional maker who did water quenching; he expected and 25% failure rate.

Doug Lester

bubba-san
10-27-2010, 09:41 AM
Thunder, I usually ht . quench most of my blades in hot salt water ( as hot as it will get out of the faucet). The key to reduced failure , is to use 10 series steel . low alloy and manganese should be as low as you can find . around .25 - .30 is good . Another little trick is quench time !! In water 4 seconds is about right. One more point , when tempering dont use more than 2 cycles , too much tempering will weaken the hamon . most of the time I use one cycle. I dont have a lot of cracking warping ,temps are critical . Make sure you apply your clay mix evenly and the same, or as close as you can get on both sides . Uneven clay application is a good way to warp the blade , especially if blade is longer . Shorter thicker blades is not too much of a problem. A friend of mine when making swords ,or long knives draws 1/4 scale on blade mune ( spine) before clay application , that way you can do a more even application . Walter sorrels makes a very good video on hamons and water quenching , it would be a good investment .http://waltersorrellsblades.com/ I hope this helps you some . Bubba

Kevin R. Cashen
10-28-2010, 03:33 PM
Thanks fellas! For putting it in different words...

You managed to make pretty good points yourself Ed. I have done whole lectures on how bladesmithing lost the need to keep up with material advancements well before alloying hit the scene in the early part of the 19th century. Almost all of our traditional techniques are based upon steels that consisted primarily of only iron and carbon. These days I am working a lot with these simple steels that I smelt myself and they are quite different from modern alloys. They forge differently, file, grind and polish differently (much easier hand working) and often requiring water, or extremely fast oils, just to obtain full hardness. The ancient steels work very well with shaping and heat treating in a forge, as well as hand shaping, which should come as no surprise since that is what they were designed for and in parallel with. But alloying changed everything, and modern steels are designed for specific applications and with very controlled heat treatments in mind. While I spend much of my time keeping up with the 21st century and bringing my craft up to speed with it, I also spend a lot of time trying to understand the methods and materials of centuries past, and there is plenty of modern misunderstanding about them. Many of what we today believe are ancient traditional methods are often modern interpretations of only the last 200 years or less.

There is also the benefit of backward compatibility with modern methods. It is like a computer operating system, you can run some very old applications on one of the newest operating systems, and probably faster than in their day, but you can't run a 2010 application on Windows 3.1. I started out quite simple years ago and then got deeper than I ever expected to into the technical modern metallurgical end of things, but now while I can probably nail the heat treat on any modern steel I also feel very confident in what that will allow me to do with a pile a charcoal, some iron ore and a forge to work it in.

Thunter124
10-28-2010, 06:15 PM
Ill probably need to look into quenchants in the future, but Ill at least try one blade in brine. I will probably get some of the series by walter sorell, I have watched all of his videos on youtube a few times and he does a wonderful job explaining stuff. There's allot of good reasons for not using water apparently,I may try getting ahold of some low alloy steel as I'm wanting to do more handwork than anything, though would that be a weaker blade steel, or potentially more durable with a proper working and quenching?



As for the heat treating cycle that you described in your first post, it sounds like you are trying to describe air quenching. It is done on higher alloy steels many of which would crack in oil let alone water. If you want to quench in water, have at it but you will have to restrict yourself to simpler steels that will lend themselves to that process. The steels control the process not the smith. Just be forewarned, you will have failures, as in cracked blades. Nova on PBS had an episode about the Japanese sword. It featured a traditional maker who did water quenching; he expected and 25% failure rate.

Doug Lester
The two day cycle was a normalizing process that I saw described on one master smiths website, not air cooling the blade but using vermiculite to make it (what I understand to be) a slow cooling.

Doug Lester
10-28-2010, 10:44 PM
Some people would describe what was done, heating to non-magnetic and then allowing to cool slowly in vermiculite to be annealing or at least something close to it but some smiths use the terms rather interchangably. Annealing is done to distribute the carbides in the steel more evenly to increase machinability. What most people consider normalizing is heating the steel to non-magnetic and allowing to cool in air. This does a couple of things. It allows the crystals in the steel to reform and relieve the stress that was caused by forging or even grinding. When the steel is heated to non-magnetic the crystals in the steel change form and the "hot' crystals form at the boundry of the "cool" crystals and, unless they are caused to grow by overheating, they will be smaller than the original crystals. When the steel cools the "cool" crystals will reform at the boundry of the "hot" crystals and again they will be smaller. Cycling the steel through multiple normalization cycles, if done correctly, progressive refinement of the grain of the steel and correct for any grain growth that may have occured during forging.

Many, myself included, have found that what passes for annealing does not increase machinability of the steel significantly more than multiple normalization cycles, at least in the steels that we use. Normalization, hardening followed by tempering are all required to produce a cutting blade. Maybe way back when before people knew what steel really was there may have been smiths working with steel with a low carbon content, possibley 0.3% or maybe slightly higher, that could be used as hardened but these blades would barely hold an edge. Analysis of some blades from before the Industrial Age so show blades with carbon contents that low and some so low that they were little more than iron. So, in a way the answere to your question is no, no one just hammers out a blade and quenches in cold water without all the heat cycling nor would we ever want to. The blades that we produce today with more advanced techniques developed after the metalurgy of steel was discovered are much superior to many and possibly most of the blades made before.

Doug Lester

Kevin R. Cashen
10-29-2010, 07:30 AM
Of course bladesmiths are free to call any process by any name, Sally and Sue if they wish, so long as they can convey the differences between the two. However if they want to communicate effectively with the rest of the world the commonly accepted nomenclature is very useful.

Annealing is for achieving a soft and stress free metal, it is accomplished by heating near or above the critical temperature (I avoided exact temps or terms like "Ac1" to keep it simple) and then cooled in either a very slow or very controlled manner to facilitate the formation of only soft or malleable phases and structures.

Normalizing technically has little to do with how soft or "stress free" the metal is so long as everything is even and equal inside, even and equal stress is not a big problem, uneven stresses are. Grain size and carbide distribution is best when even and equal, fine is also very good but not as critical to the definition of normalizing. Normalizing is accomplished by heating above the critical temperature as evenly as possible and then air cooling as evenly as possible. Using insulation (like vermiculite) to retard that cooling in any way kicks the operation back into the category of annealing.

Bladesmiths also use subsequent thermal cycles for further refinement that do not fall into the classic definition of normalizing but are often referred to as such.

Church & Son
10-30-2010, 06:07 AM
The two day cycle was a normalizing process that I saw described on one master smiths website, not air cooling the blade but using vermiculite to make it (what I understand to be) a slow cooling.

Sounds like you watched an Annealing of pre-hardened steel. I use mostly unknown recycled steel( a lot of old files and farm equipment ) so you must anneal it to get to a workable state. Heat above magnetic then cool very slowly in wood ashes. Simply put this softens it to improve workability. Normalizing is just a shorter version to relieve internal stresses between beatin' it and heat treating. I also quench with water, be prepared to crack a lot of blades. What I do is very primitive, use what is found to make what I want and need, If I depended on my knives to make a living I would stand on the shoulders of the giants posted above...............Randy

Kevin R. Cashen
10-30-2010, 01:13 PM
...Normalizing is just a shorter version to relieve internal stresses between beatin' it and heat treating. I also quench with water, be prepared to crack a lot of blades. What I do is very primitive, use what is found to make what I want and need, If I depended on my knives to make a living I would stand on the shoulders of the giants posted above...............Randy

Wow, let me extend my hand in friendship sir, you are one of the good guys! So many people who approach the craft with the methods that you use see almost everything folks like Mr. Caffrey, myself and others say as a threat if not all out fighting words. However I can tell just by the way you worded this post that you are very comfortable and secure in your own skin and how you do things and see the very different methods as they truly are, not in competition but entirely different goals and approaches to the craft. A pyrometer may nail the heat every time but the most high tech equipment in the world will never make a work of art. If I were a collector I would have plenty of modern method knives but would be happy to put one of yours in the showcase as well, as it would be just as valuable but for different reasons.

Be it pyrometers and salt baths, or eyeballs and forge fires, it is all about recognizing the limitations and embracing it for what it is instead of passing it off for what it is not.

Church & Son
10-30-2010, 03:57 PM
Thank you for the kind words Sir, I am in awe of the tremendous amount of talent here and although life gets in the way of devoting a lot of time to this craft I look forward to sharing a more primitive aspect..................Randy

Doug Lester
10-30-2010, 04:50 PM
There's nothing wrong with primative. Historicaly, primative has even been rather refined at times. A lot of good work has been done with anvil, anvil tools, files, and stones but even primative has to be done right to get good results.

Doug Lester