Hardening a blade and what a maker's goal is

bluntcut said:
Goal is to uniformly distributed elements & particles(MC and MxCy forms), most importantly sufficient Carbon in solution (FCC phase) to form a martensite matrix at target hardness (up to 72rc). Certainly, you want particles in the right form and are as small as feasible.

What is MC and MxCy?

Recently to keep thing simple and enable basic communication. I split steels into 2 main group.
G1 - those steels austenite at temperature below 1600F. Most of these are low (Cr+Mo) steels.
G2 - The rest.

Stainless mostly refer to where free Cr at least 13%.


Cementite basic form is Fe3C but can have many shape. fine spheroidized form is prefer because of its strength & not a brittle as bainite&pearlite fern/finger/rod shape.

When I see the word spheroidized it's often used with euctoid/euctetic and hypereuctoid. What does this mean? And also, are you saying cementite is the basic steel matrix? Would a perfectly pure steel with only iron and carbon be nothing but cementite?

Pearlite = mostly ferrite and cementites (nominally finger fern pattern).
Austenite = iron & carbon in FCC (face center cubic) phase/shape
Martensite = iron and carbon in BCT (sheared from FCC form). Lath martensite is stronger & tougher than plate martensite.

What is BCT and FCC?

... out of time...
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Awesome
 
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Why would a company like Peter's produce a heat treated blade that performs better than something from, say, Benchmade? Does Peter's spend more time than BM studying this stuff? If someone had an S30V blade at the same size and geometry as a BM blade (not trying to pick on BM, you could insert whatever mass production company in its spot) but HTed by someone like Peter's then it'll likely perform better. Why? Does Peter's only heat treat say, a dozen blades at a time whereas BM does 100? What variables could be introduced to make a mass produced knife perform poorer than an individually produced knife, all things being equal? Do these mass produced companies not hire metallurgists who make it a point to study what all this stuff does?

Simply put, if BM produced an S30V blade that was heat treated in accordance with their metallurgist's instructions, why would it perform differently than an equally sized and shaped blade heat treated by someone like Phil Wilson or whoever? The temperatures are not as accurate in the BM heat treatment dept? Wouldn't it make sense for a big company like BM to invest in more accurate thermocouples?
 
bodog said:
I don't know what else I'd call a knife maker other than a knife maker, but if you feel it's better over there, then ok. I thought since most people visit general knife discussion then having a reader's digest compilation of some stuff that generally pertains to knives would be acceptable here where most people could/ would see it. My apologies.

Well, it's already moved. I thought it was a good idea while it lasted. Now I'm just saying some basic stuff to a bunch of guys who probably already know it. Appreciate it, Rev.
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Are you really surprised this was moved? Secondly, are you really surprised people are questioning your motives? It's not your first rodeo man, and I'm sorry but what do you want from these type of posts? If you want to inform people about something by all means just post it as information and I'm sure you will be better received. This post seems an aweful lot like fishing... whether for compliments or an argument, I don't know (maybe neither) and you could be totally well intentioned, but it doesn't come off this way. if you don't want to be picked on and argued with, stop structuring some things up so that they seem to have an alternate agenda.
 
rustyrazor said:
Are you really surprised this was moved?

A little

Secondly, are you really surprised people are questioning your motives?

A little

It's not your first rodeo man, and I'm sorry but what do you want from these type of posts?

Information for myself and others who may be curious but don't know enough to feel comfortable asking on their own

If you want to inform people about something by all means just post it as information and I'm sure you will be better received.

I don't know enough to post some of the more in depth information. I can post some stuff but cannot tie it together

This post seems an aweful lot like fishing... whether for compliments or an argument, I don't know (maybe neither) and you could be totally well intentioned, but it doesn't come off this way.

Only good intentions. It seems like a lot of people believe what they believe out of a lack of familiarity with what actually happens to steel at its different phases of production, quite possibly myself included. I wanted some good guys who know fact from fiction to come in and give a basic rundown of what makes something better or worse than something else. Most of the misconceptions are talked about in general knife discussion subforum so that leads me to believe most of those guys don't know where to look to find info. If they do find someplace with the info, it's either really scattered or so in depth it's hard to understand because makers don't talk about the fundamentals when speaking to each other.
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.....
 
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rustyrazor said:
Not trying to neccesarily give you a hard time... just trying to help alleviate future issues with posts that can be misread.
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I try to structure things in a way that's not insulting but makes people think about what they believe. It won't go over well with people who truly know the facts because they feel insulted that someone is arguing or questioning what they know. I don't blame them, but I'm not trying to do that. I'm hoping they step in with some real facts, not beliefs, to set the record straight. Other people blindly follow and have some kind of deep seated beliefs and to them it's like asking whether God exists and positing that he may not if they cannot explain it. People don't like having their blind faith questioned. I also understand that. I don't mean harm, but if someone believes in God they should be able to say why without getting offended. People get offended a lot around here. My intentions are good. I just want people, myself included, to know and understand enough to justify saying what we say. A certain mod feels it's trolling. I want us as a community to know what the hell we're talking about. You makers lead the way, we consumers follow.

If we were on a race car forum, I don't think a lot of mechanics would allow people to say aluminum is stronger than steel. There may be advantages, but it's not stronger. If someone said aluminum was stronger and someone asked for an explanation, that's not trolling. I don't want to argue but someone should be able to say why they think what they think. I was hoping this thread would help resolve that issue.
 
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All that stuff !! Would take me a long time to sort out and correct mistakes !
If you apply definitions to blades it might be different than for other uses.
Cryogenic cooling reduces RA and permites formation of eta carbides on tempering .The RA part is a martensitic transformation. Eta carbide formation is a diffusion process .Both involve -300 F[Liquid nitrogen temp ]
Secondary hardening occurs in some alloys at about 900 F .The formation of these new carbides has little use in blades.
Galling is 'cold welding' - not desired !
ecetera, ecetera and so forth !!!
 
Continuing... (also probably repeat or butcher other poster's good answers)

bodog said:
Once you're past .6% carbon and you're going into high carbon steels, what forms in the blade at each stage?
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Carbon can be in many different states depend on temperature and steel element composition. Thermal chemistry favor lowest potential energy, whether in heating or cooling or ambient. Net effect of where carbon end up in the microstructure is highly depend on composition + heating & cooling (control or lack of control). In hardened state - certain amount of carbon locked in BCT(body center tetragonal) crystal - building blocks of bulk lattice material aka matrix. Excess carbon will usually participate in some form of carbide.

And what is a secondary hardening?
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It's a high tempering temperature ~900-1025F, where 1. RA convert to untemper-martensite (add to hardness) + precipitation(softening) + other transformation. 2. carbon precipitate out of the matrix(softening) and alloy up(hardening) with other elements such as Cr & Mo, at the same time coarsening existing carbides. A big part of these alloying&coarsening taken place in the grain boundaries. Doing this step blindly usually lead to lower performing knives... unless RA as massive then it isn't bad to go from lousy to adequate via this step.

What does cryo treatment do to a blade? Do big manufacturers perform this step? Is it even that important?
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'Treatment' is to facilitate fresh RA-> martensite conversion. While long cryo soak is an 'Enhancement', when sufficient energy taken away to collapse Cubic(BCT) lattice crystal vertices , once with energy provided (next tempering) hexagonal particle (aka eta carbide) taken place.

Properly Cryo or not would totally depend on steels and ht.

What causes a blade to keep its shape at the thinnest part of the apex?
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Microstructure. Edge stability is a direct benefactor of microstructure with compact & coherent lattice. Largest size of fracture unit is the weak-link, so minimize this weak-link directly translate into higher stability.
 
I have done a fair amount of research with sort of the opposite approach. When I searched online and through forums like this I never found more than a "Martensite is preferred" type answer to these sorts of questions. I think this makes sense because this material requires a pretty broad scientific background or a hell of a lot of time to understand well.

I feel there's enough basic information out there in standard places (wikipedia, knive maker websites, this forum, etc) that any enthusiast is going to easily find it and get going.

If you arr like me, and after reading lots of coles notes you want more of the guts, I highly recommend watching the YouTube channel of a guy named Torbjorn Carlberg. He takes more of a general metallurgy approach but he goes as far scientifically as I feel is needed to trully start to understand the why's of steel and metal. I learned a lot from his videos and it helped my tie in chemistry principles I already knew to my knife collecting and researching hobby. Might need a coffee to get through his delivery...
 
bodog said:
What is MC and MxCy?
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Primary carbide and intermediate transitional & persistence carbides. x = 2,3,6,23,.. y = 1,3,6,..

When I see the word spheroidized it's often used with euctoid/euctetic and hypereuctoid. What does this mean? And also, are you saying cementite is the basic steel matrix? Would a perfectly pure steel with only iron and carbon be nothing but cementite?
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spheroidize is Fe3C (mostly but could also agglomerated with other carbide form) in spheroidal shape. Excess carbon (not use by matrix and low alloy steels harden form) take default cementite structure, in certain temperature it takes spheroid form. Eutectoid/tic is just carbon saturation point in a solution. Hypo/per-eutectoid is just categorize steel base on saturation point. Note - this saturation point is a ratio between Iron & Carbon, so use balance/net avail Fe & C, e.g. Fe in s110v is a lot less than 1060.

What is BCT and FCC?
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BodyCenterTetragonal and FaceCenterCubic crystal structures. Martensite in BCT, Austenite in FCC.
 
Thanks for YT rec to Torbjorn Carlberg. Prof Bhadeshia is responsible for my costly spiraling into metallurgy rabbit hole. Maybe I can coffee-up and duct-tape TC stuff, making a flash light, so I can see where I am going :p

stewartianj said:
I have done a fair amount of research with sort of the opposite approach. When I searched online and through forums like this I never found more than a "Martensite is preferred" type answer to these sorts of questions. I think this makes sense because this material requires a pretty broad scientific background or a hell of a lot of time to understand well.

I feel there's enough basic information out there in standard places (wikipedia, knive maker websites, this forum, etc) that any enthusiast is going to easily find it and get going.

If you arr like me, and after reading lots of coles notes you want more of the guts, I highly recommend watching the YouTube channel of a guy named Torbjorn Carlberg. He takes more of a general metallurgy approach but he goes as far scientifically as I feel is needed to trully start to understand the why's of steel and metal. I learned a lot from his videos and it helped my tie in chemistry principles I already knew to my knife collecting and researching hobby. Might need a coffee to get through his delivery...
Click to expand...
 
mete said:
All that stuff !! Would take me a long time to sort out and correct mistakes !
If you apply definitions to blades it might be different than for other uses.
Cryogenic cooling reduces RA and permites formation of eta carbides on tempering .The RA part is a martensitic transformation. Eta carbide formation is a diffusion process .Both involve -300 F[Liquid nitrogen temp ]
Secondary hardening occurs in some alloys at about 900 F .The formation of these new carbides has little use in blades.
Galling is 'cold welding' - not desired !
ecetera, ecetera and so forth !!!
Click to expand...

So the website simply tool steels isnt accurate or reliable? Was it so far off the mark as to be disregarded out of hand? If so, I'll delete those posts because I don't want to be the cause of crap info being put out.
 
"Accurate or Reliable"....Accurate and reliable are results from "Peter's Heat Treating....Take a big pocket full of money and drop it on Doug's desk and ask why his heat treat works....you'll find that is all they do so they are specialists at heat treating not at knife manufacturing. Pay for a Professionals time to explain how and why they do what they do.....might just get what you are looking for.
 
bluntcut said:
Thanks for YT rec to Torbjorn Carlberg. Prof Bhadeshia is responsible for my costly spiraling into metallurgy rabbit hole. Maybe I can coffee-up and duct-tape TC stuff, making a flash light, so I can see where I am going [emoji14]
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No problem! I watched several of Prof Bhadeshia's lectures as well, but I preferred TCs style. I feel like he did all his videos at 2am while his wife was sleeping or something.. But his fluid progression and no bs was refreshing.
 
Busto said:
"Accurate or Reliable"....Accurate and reliable are results from "Peter's Heat Treating....Take a big pocket full of money and drop it on Doug's desk and ask why his heat treat works....you'll find that is all they do so they are specialists at heat treating not at knife manufacturing. Pay for a Professionals time to explain how and why they do what they do.....might just get what you are looking for.
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Thanks buddy
 
1. Heat Treating Services are generally good & versatile, business model driven by contracts - what's good (improvement) for edge tools could breach the contract for some other parts where wear/tear rate has been accounted for. Also not easy to explain to customers when you improved something, which could interpret as your old ht works are not as good.

2. Mass production companies, such as Kai, BM, Spyderco, ColdSteel, etc.. on the other hand, their business is driven by profitability. Ht is a small part in P&L and ultimately seeking BS in the black. Pertain to ht, they would buy/hire/borrow whatever skills/secrets to have an business advantage over the competitors. Essentially, this is an autonamous setting, will adapt/change in order to thrive or survive.

3. Private small or individual Heat Treaters, most are here to fill-in gaps in offer high-performance; customize; small qty works. High-performance hters require high level of metallurgy skills and adaptability.

Knife makers are lucky to have between option 1 & 2 to choose from. As a consumer, you want to be well inform in choosing an end product from 1.2.3., as a tool whichever serves you best. In practice, on-hand experience/assessment would help narrow down best products for you. Talk/theory/belief/fan are usually free & cheap and getting cheaper by the tonnage :p

bodog said:
Why would a company like Peter's produce a heat treated blade that performs better than something from, say, Benchmade? Does Peter's spend more time than BM studying this stuff? If someone had an S30V blade at the same size and geometry as a BM blade (not trying to pick on BM, you could insert whatever mass production company in its spot) but HTed by someone like Peter's then it'll likely perform better. Why? Does Peter's only heat treat say, a dozen blades at a time whereas BM does 100? What variables could be introduced to make a mass produced knife perform poorer than an individually produced knife, all things being equal? Do these mass produced companies not hire metallurgists who make it a point to study what all this stuff does?

Simply put, if BM produced an S30V blade that was heat treated in accordance with their metallurgist's instructions, why would it perform differently than an equally sized and shaped blade heat treated by someone like Phil Wilson or whoever? The temperatures are not as accurate in the BM heat treatment dept? Wouldn't it make sense for a big company like BM to invest in more accurate thermocouples?
Click to expand...
 
bodog you will find all the information you seek here on bladeforums, it is up to you to answer all the questions. Just start testing it all out. Make a knife or twenty.
 
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