Is this true? set me straight.

[jiminy]

Here's a prime example:

as it matters little to me what others may think.

Bad choice of words. I care a lot of what others think ...their opinion. The point I meant to convey was that I care little what others think of me. I value others opinions, as there is much wisdom to be gained hereabouts. I don't always agree with what everyone say, but that is what discussion is about.
One valuable thing I learned was to think for myself ...to take in facts and opinions and formulate my thoughts based on what I believe to be accurate and inaccurate. I challenge everyone to do the same. Don't take what I or anyone else says at face value ...look at the available information on the subject and form your own opinions.
That's the problem with this country today ...too many folks take what people say at face value without looking into the facts of the matter for themselves and drawing their own conclusions on what is 'true' and what is 'false'.

 

[Matt Shade]

Is there a reference online somewhere that I can use to learn how to read the TTT curves, and further what's a good resource for general HT info that I can have nearby?



So what suggestions do you have for me to learn enough to understand the forgoing discussion? Thanks for any input,

Dave
First thing you want to find is an iron carbon phase diagram. This, coupled with a TTT curve for the steel your heat treating is pretty much your bible on the subject.
The phase diagram will show you the different states that steel is in as you raise the temperature. This all depends on the carbon content, so you have a chart that shows % carbon along the X-axis and temperature along the Y-axis. This is the quick way to figure out forging temperature for your alloy,critical temp for heat treating, and all that. You see, iron is a funny material in that its crystal structure changes when its heated above a certain point. This is what allows us to forge iron alloys (steel). It changes from face centered cubic to body centered cubic (dear lord don't let me have that backwards! ) which is a much more flexible structure allowing the crystals to slide past each other.
The critical temperature is determined by the temperature that the carbon has completely dissolved to form austenite. There is a whole range this can happen in depending on the carbon content.The temperature austenite forms actually decreases as carbon content moves from 0% to .8% and then raises again as you move towards 2% (at which point you get into cast iron rather than steel) You have to find out where it is for your alloy, so you can dissolve the carbon and then lock it into the crystal structure forming martensite when you quench.
The TTT curve is the result of cooling a given alloy at many different rates and plotting all their results. It shows you the transformation pattern of the steel as it cools off. This will make a lot more sense if you have the phase diagram to look at with it, because you can see all the different things that form (martensite, pearlite, cementite etc.) as temperature changes. The TTT curve lets you see how fast you have to cool the steel down to form the desired compound. It shows nothing about the actual curve the steel follows with your quench Your quench, unless something specially engineered, will most likely cool the steel with a curve that follows a fairly straight steeply sloped line until you get fairly close to the temp of your quenchant. Your goal, to form martensite is to use a quench where that line stays to the left, and does not intersect the TTT curve (which would indicate you've gotten into the range where pearlite, or something other than martensite has formed).
This is the basic idea behind simple carbon steels. If you can't find a phase diagram and stuff let me know and I'll see if maybe I can track mine down and post scans or something.
If you want to know about the more complex alloys you'll have to ask someone more knowledgeable. I don't know about when you start adding things to the alloy and forming different types of carbides and all that.

 

[fitzo]

But cripes, argue the point ...don't turn it into a personal attack, as it only makes you look ignorant, and degrades the whole forum experience for everyone.

Yer cracking me up, by gosh!! Pot calling the kettle black about looking ignorant, I'm saddened to have to tell you. If you fail to realize it, YOU are the one degrading the forum experience here.

One loses credibility quickly when they blame their ignorance of a subject on someone elses failure to explain it to them. When you jump into a thread on a technical subject acting like you know what you're talking about, you don't blame someone else when your ignorance is self-exposed. There's that old saying about big dogs and the porch.

If you were someone I gave a crap about, I would probaby counsel them, "Shut up now, cut your losses, and go wash the egg off your face before it goes so far that people won't even get involved in a thread you're on." But, I don't give a crap, so blather away.....

 

[jiminy]

Mikes Right ..MHO
if we have a name and know who we are talking to it makes for a more
valued conversation I think.. if that is the word for it.

This is the internet, and everything on these forums gets 'Googled' in about ten seconds flat. I have enough problems protecting my privacy without posting personal data regarding myself in a public forum. Now, if you choose to do otherwise, than have at it, that's your decision to make.

I'm an unknown knifemaker. Big deal. I am neither looking for fame or recognition, just looking for some good discussions on the subject and to sell some of the blades that I make. If I wanted fame and recognition I would have become an actor or a politician.

Not to mention the fact that in this day and age, making and selling 'weapons' exposes one to a fair amount of liability should someone choose to pursue the matter. I'd rather avoid that particular circumstance altogether, hence the nom-de-plume. It's sad that it comes down to that, but there it is nonetheless.

 

[jiminy]

Yer cracking me up, by gosh!! Pot calling the kettle black about looking ignorant, I'm saddened to have to tell you. If you fail to realize it, YOU are the one degrading the forum experience here.

One loses credibility quickly when they blame their ignorance of a subject on someone elses failure to explain it to them. When you jump into a thread on a technical subject acting like you know what you're talking about, you don't blame someone else when your ignorance is self-exposed. There's that old saying about big dogs and the porch.

Hey, believe what you like. You're another one that appears to wallow about around here with a chip on your shoulder, dissing those who aren't 'technical' enough for your liking. If you go back and read the thread, what I said was accurate ...different quenchants can affect the hardness of the steel. Post all the fancy charts you want, it still doesn't change the facts of the matter.

And the TTT curve, is in fact, a wide boundry that can can contain any number of different curves for the steel within it's boundaries ...which is also something that I said from the get-go, that there is no one exact curve or plot that all steels of a type follow exactly. Penalize me for not recognizing how to interpret the chart that was posted, if you like. My bad.

 

[fitzo]

Hey, believe what you like. You're another one that appears to wallow about around here with a chip on your shoulder, dissing those who aren't 'technical' enough for your liking. If you go back and read the thread, what I said was accurate ...different quenchants can affect the hardness of the steel. Post all the fancy charts you want, it still doesn't change the facts of the matter.

And the TTT curve, is in fact, a wide boundry that can can contain any number of different curves for the steel within it's boundaries ...which is also something that I said from the get-go, that there is no one exact curve or plot that all steels of a type follow exactly. Penalize me for not recognizing how to interpret the chart that was posted, if you like. My bad.

Actually, I think you'll hardly ever find me saying something condescending to someone who simply doesn't know something technical. I may be terse and blunt, but I know that we all learn as we go along. However, when we get a poseur continuing to argue about something as if they know their stuff when they don't, then it tends to get on my nerves, yes. I offer no apology for developing a "chip on my shoulder" for your BS. I've grown weary of it over the past months. We will simply have to ignore one another henceforth.

BTW, you really, really need to go out and get a better understanding of a TTT curve if you want to comment on them, as you are still displaying either poor descriptive skills or more likely continuing ignorance. I may be an a$$hole, but you have damaged your credibility. I'd much rather be called an AH.

This will be my last post on this thread. I grow weary of you. :yawn:

 

[jiminy]

It changes from face centered cubic to body centered cubic (dear lord don't let me have that backwards! )

LOL! Yeah, no kidding! Heaven forbid you're wrong about something ...as you'll have "damaged your credibility"! Too funny

Apparently what appears to be occurring is that some folks get their feathers ruffled whenever someone posts an opinion that counters an 'experts' opinion. While I'm not an 'expert' by any stretch of the imagination, nor did I ever profess to be, I surely don't have to believe everything that self-proclaimed 'experts' claim is true, particularly when there is documentation to the contrary readily available elsewhere. It's called 'critical thinking' ...and that is the process whereby you review the available data and then form your own opinion based on what you find, as opposed to believing outright what any self-proclaimed 'expert' may or may not say.

I think I'll just let the readers of this thread go back and review what was posted and let them decide for themselves who is 'credible' or not.

 

[billf]

I say everyone take a deep breath and have a beer! Jiminy, I don't recall Sean declaring himself "an expert", but in fact he is a regular and is quite knowledgeable, and in fact quite correct about the TTT chart. There ARE an infinite number of curves, both left and right of the TTT , but you have to be on the CORRECT side of the curve to form the microstructure you want. Different quenchants DO cause different hardnesses, but that is easily explained by the curve. If you quench too slowly to beat the pearlite nose, you don't get full martensite transformation. If you quench too fast for a given steel, you may well beat the nose, but form too stressed a microstructure, leading to "pings" cracks or warps.
Critical thinking is always important, but if you don't have knowledge to the contrary, only a contrary opinion, you might consider asking for clarification rather than continuing to insist on your point.

The point of all this is learning all the time, as I have from people such as Kevin Cashen, Mete, Sean etc. After all, we're all interested in the same thing, aren't we?

 

[Laredo7mm]

Back in Post #16 I claimed not to know it all, but I will tell what I know.

The 0.25mm over 1000mm was an example. We were not talking about strength we were talking about heat treating. I don't know what the tolerance was on the required HRC was for the tubes. And a CPK of 1.33 is not an easy thing to hold when you are talking about 80,000 pieces per day. And 1.33 is the accepted minimum in the Auto industry, any higher than that would add undo cost to the process with little gain in the quality of the finished product.

Anyway, I am not going to argue back and forth anymore. I turned to a personal attack because you were not listening and continuing to argue about things that you don’t have enough knowledge on to argue about. It may not have been the right thing to do, but it worked.

I also implore all readers to re-read this post. I stand by what I said and I will do it all over again to try to not let false or inaccurate information to be conveyed. Everything I know about heat treating was learned from books, classes, publications, personal experience, and from the guys here that have forgotten more than I will ever know about it.

 

[jiminy]

Just for the record, heres the TTT chart you posted:

Here's a TTT diagram for Eutectoid steel (Fe-Fe3C), which is defined as "a steel that contains 0.9% carbon":

Why, what do you know ...they're different! But pay no attention ...you're just imagining things.

And here's where you can find the chart.

(Sorry, link fixed ...it's a .pdf file, i.e. Adobe Acrobat file)

 

[billf]

Jiminy,

Geez, what's with the continued attitude? The curve you posted is NOT for 1095, which is what this whole thread started about. "eutectoid" steel could have any # of other elements, each of which changes the curves.
Plus, "oil" is not very specific - for example, Park #50 oil can be used to quench water hardening steel, as it is very fast. Park AAA, on the other hand, will probably NOT quench 1095 fast enough, but will work well for O1 or L6 or 5160.
I don't know you from Adam, and you have every right to protect your privacy - God knows there's too much out there about us all. But it's probably not very productive to get into an Internet flame war with a bunch of really good guys who have been very helpful to large numbers of fellow knife-nuts. FWIW

 

[Terry_Dodson]

jiminy the weblink did not work.

Can someone explain to me what i am looking for related to blademaking on a TTT chart? Or how do i read it? I know nothing about these charts but think i probably need to

 

[jiminy]

No 'attitude' here whatsoever. And I don't recall being the one that started with the insults, just a differing opinion.

(Sorry, link fixed. It's a document from the University of Tennessee)

 

[Laredo7mm]

Well they should be different if it is not 1095 steel. Each alloy of steel has its own TTT curve. 90 points of carbon may be the eutectoid for that particular alloy, but for plain 10XX series steels the eutectoid is around 76 or 77 points of carbon. Other alloying elements like nickel and chromium will raise and lower the eutectoid temperature and % of carbon for the eutectoid alloy.

All steels have their own independant TTT curve depending on the chemical make up of the alloy. That is why some steels can harden in air (A2 and D2) and other need faster cooling.

Keep posting and showing your ignorance on the topic. This is turning into a very good and informitive post dispite my personal attack.

 

[Laredo7mm]

Terry-

I hope I can explain it. The TTT curve shows the temperature on the vertical axis and time (log scale) on the horizontal axis. The curves mapped out is what microstructures the steel will go through upon cooling.

For example looking at the TTT curve that Jiminy posted; if you heat the steel up to 900°C, cool it to 350°C in 3 seconds and hold at that temperature for 100 seconds you will have a microstructure of bainite.

The actual cooling curve can be traced out on the TTT curve, like the ones I posted showing the difference between a typical quench and austempering. What I described above would be considered austempering. TTT curves tell you how to obtain each individual microstructure by displaying the times and temps required. The TTT curve is not a cooling curve to tell you how to only make martensite.

Another exaple for the same TTT curve would be to heat the steel to 900°C, cool it to 550°C in 3 seconds, hold at that temp for 100 seconds and you will have pearlite. It is the same times as the first example, but just a different temperature taht you quench to, and you end up with pearlite instead of bainite.

I hope that helped, let me know if it didn't and I can try to explain it better.

 

[jiminy]

The document states that it is for a "plain carbon steel" right at the top of the paper.

 

[ddavelarsen]

Dave
First thing you want to find is an iron carbon phase diagram. This, coupled with a TTT curve for the steel your heat treating is pretty much your bible on the subject.
The phase diagram will show you the different states that steel is in as you raise the temperature. This all depends on the carbon content, so you have a chart that shows % carbon along the X-axis and temperature along the Y-axis. This is the quick way to figure out forging temperature for your alloy,critical temp for heat treating, and all that. You see, iron is a funny material in that its crystal structure changes when its heated above a certain point. This is what allows us to forge iron alloys (steel). It changes from face centered cubic to body centered cubic (dear lord don't let me have that backwards! ) which is a much more flexible structure allowing the crystals to slide past each other.
The critical temperature is determined by the temperature that the carbon has completely dissolved to form austenite. There is a whole range this can happen in depending on the carbon content.The temperature austenite forms actually decreases as carbon content moves from 0% to .8% and then raises again as you move towards 2% (at which point you get into cast iron rather than steel) You have to find out where it is for your alloy, so you can dissolve the carbon and then lock it into the crystal structure forming martensite when you quench.
The TTT curve is the result of cooling a given alloy at many different rates and plotting all their results. It shows you the transformation pattern of the steel as it cools off. This will make a lot more sense if you have the phase diagram to look at with it, because you can see all the different things that form (martensite, pearlite, cementite etc.) as temperature changes. The TTT curve lets you see how fast you have to cool the steel down to form the desired compound. It shows nothing about the actual curve the steel follows with your quench Your quench, unless something specially engineered, will most likely cool the steel with a curve that follows a fairly straight steeply sloped line until you get fairly close to the temp of your quenchant. Your goal, to form martensite is to use a quench where that line stays to the left, and does not intersect the TTT curve (which would indicate you've gotten into the range where pearlite, or something other than martensite has formed).
This is the basic idea behind simple carbon steels. If you can't find a phase diagram and stuff let me know and I'll see if maybe I can track mine down and post scans or something.
If you want to know about the more complex alloys you'll have to ask someone more knowledgeable. I don't know about when you start adding things to the alloy and forming different types of carbides and all that.

Thanks Matt!

 

[Laredo7mm]

The document states that it is for a "plain carbon steel" right at the top of the paper.

The paper is written to be what looks like a lab experiment for a 1018, 1045, and 1095 carbon steel. All The curves are not for 1095. There are curves in there for 1045 and I am sure other alloys. The caption to the left of the TTT curve you posted says it is for "a eutectoid steel" not a specific alloy.

 

[jiminy]

I was under the impression that the definition of the term 'eutectoid steel' is a steel that contains 0.9% carbon. Since the paper refers to using three plain carbon steels in the experiment, a 1018, a 1045, and a 1095 ...it would appear to be safe to assume that the chart is for a 1095 steel, like it or not.

 

[Laredo7mm]

Well you know what happens when you assume.

1095 is a hypereutectoid steel and that is a fact. Go back and re-read post #54.