Heat Treating, art or science?

[eyeeatingfish]

I am starting to learn more about heat treating as I get into making knives and I am trying to understand something.

I understand that stainless steels need long soaks and have more complicated rules (lets call them recipies.) Whereas some of the carbon steels (all?) can be done in a forge by eye without a complicated recipie.

Is heat treating stainless steels pretty much down to a simple science? Put the knife in the knife oven, punch in the recipie and out pops a perfectly hardened knife ready to go? Tempering included?

Does the stainless steel done in those ovens not need to be quenched?

Whereas the carbon steels you look for a certain color, and see if it is magnetic and quench it in some liquid that can be any number of products and then temper in a oven. It seems more of an art. Can the kiln ovens heat treat carbon steels? 1095, D2 O1 etc?

I read about the knife competitions, people showing how strong their blades are and how they dont break, but how is that competition when anyone can stick a piece of metal int eh computer controlled oven and out pops a blade?
Im sure that you can use different recipies if you want the stainless at different hardnesses for different uses, but does the computer kiln pretty much take any guesswork out of knife making?

I read a lot about the different ways to build ovens and heat treat this or that, various techniques for better results. Does the automatic oven not pretty much take the guess work out of the metal hardening? In that sense also, shouldnt any sizeable company be able to turn out a 440C blade with a great heat treat? (some companies have better reputations for their heat treats while some have worse )


The only heat treating I did was on some thin sheet steel. I think it was 304 steel, used for liners. I got it from Jantz. I wanted strikers for the flint rods I bought from goinggear.com. I just held it with pliers at a corner and heated it up witha propane torch till it wouldnt get any brighter red color and quenched in warm water. I know this is of course not proper or optimal but I did notice an increase in hardness. At least it felt less pliable and it worked as a striker. A little soft still but definately worked.

 

[Justin King]

All steels need to be cooled at the correct rate from austenizing temp. in order to be hardened. I don't know of a single steel that will harden in a hot oven. High alloy steels and stainless steels are often what we call air hardening, which means that air cooling from austenizing temp. is fast enough to cause them to harden, due to the alloying. Many of these steels can also be plate quenched, which means pressing them between two cold metal plates, which draws the heat out of the blade somewhat faster than air cooling, but still slower than oil or water.

Simpler steels generally require a faster quench, such as oil or water.

One can approach the subject with whatever philosophy one leans towards, but the fact is that most of the steels we use today are developed scientifically and have fairly specific heat treating requirements in order to maximize their potential.

Not everyone uses the exact same HT with any given steel, having a precisely controlled oven allows you to experiment in a controlled and repeatable fashion that is difficult to emulate with a forge. Get it perfect once in a forge, then try to get exactly the same results 10 more times...good luck.

If your definition of the term artist requires it you can go to the length of producing your own steel so that your work is absolutely unique. There are some who prefer to do it that way and artist is an apt term for them I think, but they do likely have a good deal of technical knowledge as well to be doing so with any consistency.

 

[Rossi Knives]

Short answer: Science.

Long answer: Read Kevin's Stickies.

-Nick

 

[Tinbasher]

Short answer: Science.

Long answer: Read Kevin's Stickies.

-Nick

What he said

Richard

 

[Mark Behnke]

Good question
Great answers

 

[mete]

D2 is more a stainless steel rather than carbon. O-1 is not a 'simple' carbon steel !
The rule for all ---" The better you can control time and temperature the better the results will be !! "

 

[eyeeatingfish]

Ok, didnt realize that most of those stainless steels were air hardening like that. I mean I had heard the term but did not realize that it applied to that kind of thing.

I think I consider this good news. Meaning that a new person, like me can build knives in stainless steel that come out consistent and reliable without having to go through all the learning curve of forge work.

That being said I am still drawn into dorge work, with the fire and the banging and the more artful way of doing it. Indeed there is a science behind it but its not so rigid.

Can someone use one of those computer ovens to heat treat simple carbon steels like 1095? Since you need a quench could you just open the door when the knife was at the appropriate temperature then throw it in the quench liquid?

 

[Rossi Knives]

That being said I am still drawn into dorge work, with the fire and the banging and the more artful way of doing it. Indeed there is a science behind it but its not so rigid.

Can someone use one of those computer ovens to heat treat simple carbon steels like 1095? Since you need a quench could you just open the door when the knife was at the appropriate temperature then throw it in the quench liquid?

eyeatingfish,

The science applies ESPECIALLY to forging. There are "rules" to working with all steels weather you are grinding to shape or forging to shape. If you break these rules you get a compromised knife. A lot more can go wrong forging than grinding.

Read Kevin's stickies! The answers to all your questions and so much more live there.

You can heat treat any steel in a Kiln. It is often prefered by people who forge their blades to shape as well as grind.

-Nick

 

[Justin King]

I wanted to forge for many years before I got set up to actually do it. I even gave up doing the stock removal knives I had been doing because I didn't enjoy just grinding them out and sending out for HT.
I have been forging now for several years, and ironically am wandering back toward stock removal methods, although I just built a HT oven and am now able to do that myself with some precision now.
Forging has it's place and it's appeals but just because you can forge does not mean you should forge everything. If you can get your desired alloy in the correct size to cut and grind efficiently then there is absolutely nothing wrong with those methods.

 

[Rick Marchand]

Design, look, feel(ergonomics), hammer/grinding technique are open for interpretation and IMO, can fall into the Art dept.

Heat treat is an exact science. If you choose to judge by colour, shadow, magnetism, sound... you are doing nothing other than taking a primitive, less accurate approach to metallurgy. That is not a bad thing. I work with a simple forge. I just has it's limitations.

A maker using simple tools and judging heat by eye can produce a great performing knife.

I have said this before... not sure if it's worth coining, though... ha!

"The romance of knife making can still be present, as long as it is anchored in metallurgical science."

 

[Kevin R. Cashen]

For centuries steel was simply an alloy of iron and carbon (with some “accidental” trace elements), in this period most of the basics of heat treatment were developed as more of an art form via trial and error. Then in the early 19th century science gave us the knowledge and control for alloying- and alloying changed EVERYTHING!

With simple carbon/iron alloys all heat treatments can be artistic or creative variations on the same basic methods, e.g. all blades were quickly heated in a forge and then quenched mostly in water, but the Japanese used clay to retard cooling on the spine and give differential hardness, while Europeans used tempering to adjust hardness and toughness.

However when you start adding Mn, Cr, V, Mo, W, Si, etc… suddenly chemistry gets involved and using the simple methods of iron/carbon steels just won’t cut it. Modern alloys were developed with science and chemistry and ignoring the principles and rules of those disciplines will get you mediocrity at best. Unfortunately most bladesmiths never find a reference to contrast with in order to realize this, but if you have the means to measure the properties and you compare modern alloys treated with ancient methods to ones treated via scientific methods the differences are very profound. But since all a knife really has to do is cut something softer than itself these differences are seldom acknowledged.

I have worked both ancient and modern steel types and the old stuff works quite well with most simple bladesmithing techniques, however the new stuff is more than capable of out performing ancient steels on almost every level if it is worked with modern techniques, but if worked with ancient methods it is on par at best.

Look at your steels chemistry and ask yourself how complex it is, then ask yourself if your skills and equipment match that complexity- a shade tree mechanic has a hard time working on a formula 1 race car. The first decision in making a knife is proper steel selection, and it is the one many makers go wrong with. Success comes from choosing a steel best suited for your task based upon the desired properties its chemistry will give you. Do you want a fine slicer or tough chopper? Look for the chemistry that will accomplish this and you already are two steps ahead in the game. Far too many bladesmiths use a steel because somebody else uses it, they have a bunch of it given to them, or they read it in a magazine that it was “the” steel to use. They then have to resort to all kinds of quirky heat treating acrobatics or compromises in order to force a square peg into a round hole where chemistry versus properties are concerned.

In the ancient world steel was steel, there was low carbon and there was high carbon, but as long as you got it hard you could heat treat however you liked. Today you choose the specific steel to do the job best given your equipment and each of these steels have a specific heat treatment to unlock their potential.

Edited to add- there is still some art in the process when we start with a basic heat treat spec that industry uses for similar applications but in different sizes, cross sections and actions, as bladesmiths we then adjust the parameters of temp, soak time and pre treatments to best suit our specific application. But the secret is to start with the proven specs instead of blindly stabbing at a process and deluding ourselves that we have out smarted the people who made the steel and wrote those specs. Reinventing the wheel is a huge time vampire!

 

[KnifeMaker.ca]

It is, like all physics - pure science but!.....

• It is rare that the available data was developed for our exact purpose.
• It is rare that we have certs or much knowledge at all about the exact makeup of the bar in our hands.
• There can be many paths to to a good outcome - and many definitions of a good outcome.
• There can be even more paths to a poor outcome - and reluctance to define anything as such.
• Most people who sound like they know what they are talking about are - to a large extent - full of sh*t. (Kevin, Mete and Stacy are exceptions that come to mind.) I personally, am somwhat F.O.S.

In summary, see my signature tagline.

Oh yeah - you made a comment about just throwing the quenchant in the oven. I know it was an honest question but I have to admit I enjoyed the visuals a bit. Picture opening a 2000 degree oven and pouring in either flammable oil or -300 degree liquid nitrogen. It was actually a fair question though, because some vacuum ovens do quench with inert gas. Good questions. Expect a learning curve that lasts a lifetime.

Rob!

 

[Kentucky]

Well coming from a blacksmith that plays at being a bladesmith I learned to temper by "running the colors"..I dont do that with knives anymore but I still do with all the forged tools we make, including Axe's,Hawks,Chisels, Adz's ect..To me, personally this way is moe Art than science..When I start coating with clays and using ovens it goes more the science route.

 

[sunshadow]

I look at metal through a microscope as a day job (OK that's an oversimplification of what I do) the transformations that happen at a crystalline level through the actions of heat and cooling on the various phases are what make various metals do things. The better you can control the process the better you can make the metal do what you want it to

The art in in the form, the science enables the function

-Page

 

[Kevin R. Cashen]

...[*]Most people who sound like they know what they are talking about are - to a large extent - full of sh*t. (Kevin, Mete and Stacy are exceptions that come to mind.) I personally, am somwhat F.O.S. ...

I would take it one step further and say that everybody is F.O.S. to some degree or another, from time to time, and, due to human error, including some of your exceptions. This is why it is most important to do our own research and verify what we read or are told. When we do this we help ourselves but do an even greater favor to those "trusted sources" we either validate or correct. Since each and every one of us can get a little F.O.S. the only thing that keeps us from getting saturated with it are peers with vigilant critical thinking. Without sheep there could be no shepherds, and how F.O.S. an "expert" can get is only limited by how much we allow. Healthy questioning and self education keeps the B.S. levels reasonable.

It is this principle that formed one of my rules for filtering information- the more known, and the more P.R. an "expert" has, the greater scrutiny his claims must be given, for he has gotten too used to not being questioned and thus most likely has been allowed to get totally F.O.S.

 

[Tai Goo]

I look at it as art, but like any other art form it involves some science. The science will give you good guidelines, but in the end getting the results you want for any given knife or knife concept will involve skill, experience, timing, and making “value judgments” etc...

Science studies heat treating, but HT in itself not a science.

If you consider hamons and fancy quench lines, working with simple steels etc., you should be able to see the art in it. However, some approaches to heat treating may appear to lean more towards the scientific.

I think it also depends how you define "art". Art can be defined in terms of the “object“, and/or in terms of the “process”. Once you begin to concern yourself with the “aesthetics of the process”, (which we all do to some degree, whether it be using a salt pot or a charcoal forge)… it’s definitely art.

All science does is study, gather and supply information about the effects of various heat treatments on metals. Once we start making judgments on the information,... interjecting our own personal preferences, philosophies, opinions and such… it’s no longer science.

In order to appreciate the art of heat treating,... you have to look beyond the science.

... At any rate, the question "Heat treating, art or science?", is philosophical in nature and can't be answered scientifically.

 

[Tai Goo]

Art does involve science, but can science involve art... and still be science?

No.

 

[Rick Marchand]

Art does involve science, but can science involve art... and still be science?

No.

Good post Tai.

Developing theory and models has to start from the abstract.(a thought/notion) I'm sure there is method/technique to finding truth... how any one scientist goes about developing concepts and breaking ground within a new field has to involve some art, I would think.

How does science become science?

Rick

 

[Tai Goo]

One of the main differences between art and science is that art has always involved various fields of study and knowledge,… in essence, all fields of study and knowledge. On the other hand, science is a field of study isolated, limited and unique from other fields of study and knowledge, but does often lean heavily on mathematical theory, which is really more it's more philosophical side...

Science has boundaries and limitations,... but art does not.

For example. Art can involve culture, religion and philosophy,... but science can not.

Science is only concerned with the lower physical plane, and is also exempt from making value judgments like, good or bad, right or wrong etc... Those things are more social, political, ethical and cultural in nature.

"Scientism" is a philosophical position, (not science), that science is the only true path to knowledge and correctness.

 

[Alarion]

Here is my view, at high risk of "fullofshitness", so I'll leave any final comment to the real pros here (Kevin and Mete come to mind): heat treating is BOTH art and science.

First of all, we must make a distinction between science and technology.
Science governs the heat treatment of both low alloy and high alloy steels, metallurgy being a science and subject to the scientific method, but whereas the first kind can be done with low tech equipment (a hand blown coal forge suffices), the second requires hi-tech equipment (i.e.: a numeric control oven).

This said, heat treating a blade is science as said, but also an art, because it has to combine various properties of steel that are often mutually exclusive, like hardness and resiliency. So, while science governs which procedures will produce a given set of properties, art governs which sets of properties you aim to achieve for a given blade, among the numerous compromises available.
The better the science, the more your results will come close to your goals.
The better the art, the more said goals will be fit to the kind of blade you are heat treating.
Without proper scientific method, no matter which properties you want to achieve (toughness for an axe blade, extreme hardness for a thick skinner blade or a razor, flexibility and extreme resiliency for a rapier) without proper scientific method not only you'll have a hard time achieving them, but whichever the results, good or bad, you'll never know why, and you'll have an even harder time at replicating results or correcting mistakes.
Hope the shitmeter didn't record to high a level... :foot: