Grain Growth due to Overheating???

[kelsil]

I would agree to what you posted but there are more factors involved. Mete knows his stuff. Temperature, time and alloying all play a part. It is like a crime scene... you can piece together what happened if there is enough evidence... otherwise, you do what you can and hope for the best. Severe overheating can ruin even the most forgiving steel. For example... lately, I've been hearing folks calling 5160 and 52100 "forgiving" steels. I don't see 5160 and 52100 in that light... common? Yes. Doable with simple means? Yes. Forgiving/beginner steels? No. 5160 is picky about forging temperatures and it's low carbon/alloying does require some attention when heat treating. 52100 is hypereutectiod and carries with it all the "fun" involved with that. Read the "working the three steel types" sticky.

If you suspect slight overheating during the quench, run a couple descending thermal cycles and HT again. If you suspect severe overheating, run the cycles, HT and be sure to run some hardness and basic task-oriented tests.

*** Thank you much for your words of wisdom Rick. And I have to apologize for typing "Chad" above when I actually quoted you.

***************************************************************************************************************************

kelsil, so I can learn from this thread...could you please specify which steel(s) you are asking about as Mr. Andrews has requested earlier?
Thanks,
Jim

*** Hi Jim, there was no particular steel in mind when this question was asked. Grain growth as I've learned in this forum is a demon to all kinds of steel when overheated then quenched to be hardened. So, the question was asked if this bad effect(grain growth) of overheating the steel could be brought back to normal sizes again. And like I said above, I'm learning here that grain growth is reversible to some types of steel(i.e. simple carbon steels) and irreversible to the complex high alloy steels.
As to specific type of steels, we could ask in here which kind are reversible and which kind are irreversible. I would guess though that the 10XX series steel and the W2 would be forgiving but the 5160 and 52100 as Rick said are not.

 

[Stag & Steel]

Thanks kelsil, these are not steels I use, but is interesting to learn a little about.
Jim

 

[Rick Marchand]

I would guess though that the 10XX series steel and the W2 would be forgiving but the 5160 and 52100 as Rick said are not.

It is still really confusing.... the more I learn about metallurgy and knifemaking in general, the more I realize how little I know. With a bit of familiarity, 5160 and 52100 can be forgiving.... so my statements could be viewed as misleading. When it comes to 10xx series, 1084 is a forger's best friend as far as simple heat treat, yet 1095(which doesn't sound like a big jump) needs special attention. So, even though 1095 has the potential to make a better performing blade, someone with a simple forge set up would get greater results with 1084. It is really all dependent on understanding the steel you are using and choosing the right one for its intended use. The first commandment of knifemaking "Thou shalt know thy steel."

I really think the worst thing a new maker can do is succeed from the get go. I'm a firm believer that you need to make and break crappy knives before you can truly understand your craft. With internet sites like this, you have access to step by step recipes for success. But what does that really teach you? It's like following a map that only has one route visable... what happens when you stray from the marked path and have no reference points to find your bearing?

"If at first you only succeed, you're not trying hard enough."R.Marchand

 

[R. M. Perkins]

You know, Rick, I wasn't going to weigh in here. I was going to bite my tongue regarding your statement to Chad2:

20knives is not even scratchng the surface(no pun intended) yet, brother. I admire your intent to share experiences but with only a few isolated observations, it is dangerous to draw conclusions and even more so, to present them as fact.

As if someone who has only made 20 knives has no right to draw from his experiences or express an opinion on this forum. IMO, someone who has made 20 knives is well on their way into the learning curve. And who's to say how much Chad2 has read on the subject or what his life experiences might have been, beyond just the 20 knives? Maybe he's worked for 30 years in a tool-and-die shop working with, and heat-treating, all different kinds of steel.

Frankly, I thought Chad2 gave good, solid advice in this post:

yes knowing the steel is 90% of the battle when i first started heat treating i was using a brick forge and over heated the blade and had some bad grain growth but i normalized it 3 times and reheat treated it and it was just fine after words. but i was using 5160 steel which is very forgiving. some other steels not so much. if it is a carbon steel you should be good. i dont know about stainless and grain growth.

I just think he might have been a little off when he started talking about the "bubbling like effect". I believe what he was seeing was actually splotchy decarburization resulting from overheating steel for a prolonged period of time in an oxygen rich environment, with different areas of the surface of the steel having different degrees of access to oxygen and that the bubbly appearance of the steel's surface was not due to grain size.

But then you go on to say:

For example... lately, I've been hearing folks calling 5160 and 52100 "forgiving" steels. I don't see 5160 and 52100 in that light... common? Yes. Doable with simple means? Yes. Forgiving/beginner steels? No.

Still wasn't going to say anything, except that kelsil picks that up as fact:

As to specific type of steels, we could ask in here which kind are reversible and which kind are irreversible. I would guess though that the 10XX series steel and the W2 would be forgiving but the 5160 and 52100 as Rick said are not.

And it's not a fact.

Sad to say that maybe you could give yourself the same advice you gave Chad2, earlier.

5160 and 52100 are forgiving steels, with regards to knifemaking, in two respects:

First, the alloying element chromium in 5160 and 52100 significantly reduces grain growth, should a knifemaker overshoot his targeted critical temperature by a hundred degrees or so. And that's real easy to do.

In the best-case scenario of using a digitally controlled kiln, it is quite possible to get some part of a blade just a little too close to a heating element and overheat it. And those of us using gas, coal, etc. and trying to rely on our senses and proper diligence will overshoot our mark quite frequently, more often than most of us probably know, I think.

Points are especially susceptible.

Well, the grains in a chromium alloy steel like 5160 and 52100 will grow to approximately 1/2 the diameter of those grains that will grow in a 10XX steel, if both are subjected to same degree of error. Now that's 1/2 the grain size, by diameter, but 1/8 the grain size, by volume.

Second, that same chromium alloying element in 5160 and 52100 significantly increases how much “quench time” a knifemaker has to work with. With a non-alloy steel, a 10XX steel, for instance, you have a mere .5 seconds to transform austenite to martensite ... to complete the quench process, in other words. But with 5160 and 52100, you have a full 5 seconds to complete the quench process.

So a knifemaker who fumbles his tongs while he's going from heat source to quench tank and drops his 10XX blade on the floor will almost assuredly miss his window of opportunity to quench. But a knifemaker who does the exact same thing with 5160 or 52100 still has a pretty fair amount of time to pick that blade back up and get it into the quench tank, with no ill-effects with regard to quenching.

Now that's what I call forgiveness.

But I do want to say, Rick, that your picture depicting grain size is about the best one I have seen on the internet. Thank you so much for posting it.

Above, I am citing "Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel" by John D. Verhoeven, Emeritus Professor, Iowa State University. Verhoeven has graciously granted copyright permission to "download and print a copy of this book for personal use," which I highly recommend.

A lot of Verhoeven's paper is written over the heads of most of us regular folks, but there is still plenty of good information for the knifemaker to glean from it.

 

[chad2]

ok 5160 and 52100 are little easier for me to work with and are more forgiving to me because i have a paragon electric kiln. i can do annealing and normalizing to specifications but if you are a forger and only have a forge it can get really trick because when normalizing, you need to bring the steel past the nonmagnetic state to a pretty specific temperature for example 5160 needs to be brought to 1600 degrees and then air cool this is past the nonmagnetic state by 175 to 185 degrees

so if i was to over heat 5160 for to long i could simply normalize the steel three times and retry my heat treat but for a forger you would have to bring it to nonmagnetic and a little further but whos to say how far because who knows how hot your forge is or how long to hold it in the forge after nonmagnetic.

same goes with 52100 the normalizing temperature for this steel is 1625 degrees making it also about 175 to 200 degrees past nonmagnetic.

with simple carbon steel 10XX it is the same the steel needs to be brought above nonmagnetic about 175 to 200 degrees but this temperature is more forgiving in these steels easier to do in a forge

we wont talk about the annealing procces for these steels lol

like everyone has said it can be done in a forger it is just that much easier to do in an electiricly controlled kiln

hope this helps with the confusion on why 5160 and 52100 are not as easy as people say, because a lot of people have electric kilns which does make it easy for them but also a lot of people only have a forge which is not as easy as pressing a couple buttons.

 

[chad2]

thanks perkins but i did give bad info and would not want that to happen to me. we must have been typing at the same time you just got yours out before me lol

 

[Rick Marchand]

ETA: Wecome to the forums, Mr Perkins... I'm honoured to have elicited your first post in 2years... lol.... just messin

I agree with some of what you said, R.M.P. I was out of line with some of my remarks. (Upon reading my posts several times, I think I was fair and correct in the information I presented) I think if Chad's experience was beyond 20knives in 2yrs, he could have stated it... "yrs/knives" was just an example. Chad seems like a sincere guy and I definately didn't want to offend, nor did I want to imply he was inexperienced from the get go. Though, from his statement about the bubbles, any new maker could have interpreted that as fact and scrapped perfectly good blades because of it.... that is what I felt was dangerous. Personally, I have to remain solid on 20knives(in itself) not being enough experience to confidently troubleshoot HT practices for others. Openers like "I have noticed" or "in my opinion/experience" can make a big difference in presenting information with intellectual honesty.

I think you are misinterpreting "Quench Time" with amount of time to get from the heat source to the quench tank. The .5 seconds you refer to begins when the steel hits the quenchant, NOT from when it is removed from the heat source. Of course you have to be realistic but that time to get it past the curve has more to do with choosing the proper quenchant (and using it correctly) than getting it from forge to oil. I hope you are not worrying yourself or frantically swinging hot blades in an attempt to get the steel into the oil in less than half a second. The window is bigger than you think. The 5 second speed of 5160 only tells me that I can get by with a slower oil and probably shouldn't expect to pull a fancy hamon out of it.

I also admitted to the fact that my statements were a bit misleading concerning 5160 and 52100. But considering one is Hypoeutectiod and the other is Hypereutectiod and both need to be forged hotter and soaked longer, they do indeed require more attention to detail than 1075-1084.

I have not heard of chromium inhibiting grain growth. From what I understand it increasse corrosion resistance, increase hardenability, improves high-temperature strength. Chromium also goes into solution in austenite slowly so a soak is needed to reach it's full potential. Vanadium, on the other hand can help keep grain boundries tight(pinned).

Unfortunately that is not my picture with the grain size comparison.... I found it on the net. I have better lookin fingers than that!

 

[Rick Marchand]

Chad.... please please please don't take this as an insult...

...you need to bring the steel past the nonmagnetic state to a pretty specific temperature for example 5160 needs to be brought to 1600 degrees and then air cool this is past the nonmagnetic state by 75 to 85 degrees

....same goes with 52100 the normalizing temperature for this steel is 1625 degrees making it also about 75 to 100 degrees past nonmagnetic.

This is the type of honest misinformation I am talking about..... The Curie Point (non-magnetic) for iron is 1414F-1418F(depending on which book you read). You are not trying to deceive us but anyone doing a search on "non-magnetic" could stumble upon this and get it dead wrong. Please understand where I'm coming from. I get corrected all the time.... it is part of learning. I don't mind at all when I get called on bogus statement I've made because it keeps me grounded. We need to do that for eachother.

and Chad... if you would have come back at me and said you had 14yrs experience in the tool and die industry and have made 1000 knives.... i would have been rethinking my own knowledge base.


Rick

 

[mete]

Keep grain boundaries tight ?? For grains to grow the grain boundaries must move and one grain will absorb another [hostile takeover]. Vanadium in small amounts like .25 % will concentrate in the grain boundaries and inhibit or pin grain boundary movement .

 

[Rick Marchand]

Sorry Mete.... poor descriptor choice.... I agree. "Toight like a Tiger" Did the rest look okay to you?

 

[mete]

Yes , that will do for now !

 

[Rick Marchand]

Good.... I'm out before I start messing up really bad.

 

[chad2]

Chad.... please please please don't take this as an insult...





This is the type of honest misinformation I am talking about..... The Curie Point (non-magnetic) for iron is 1414F-1418F(depending on which book you read). You are not trying to deceive us but anyone doing a search on "non-magnetic" could stumble upon this and get it dead wrong. Please understand where I'm coming from. I get corrected all the time.... it is part of learning. I don't mind at all when I get called on bogus statement I've made because it keeps me grounded. We need to do that for eachother.

and Chad... if you would have come back at me and said you had 14yrs experience in the tool and die industry and have made 1000 knives.... i would have been rethinking my own knowledge base.


Rick

i did not know that this was wrong. 52100 goes nonmagnectic at 1425 oops i mean 175 to 200 degrees bad math lol

if that is wrong maybe i should just shut up.

 

[chad2]

just wondering, because i edited the post on temperatures, if it is good now i had some bad math in there lol

 

[Brian Ayres]

Nonmagnetic is 1414 not 1425.

 

[R. M. Perkins]

ETA: Wecome to the forums, Mr Perkins... I'm honoured to have elicited your first post in 2years... lol.... just messin

Thanks, Rick. Yeah, I guess I've been lurking long enough, huh?

 

[Stacy E. Apelt - Bladesmith]

I'm glad to see a feisty debate stay that way.
Egos could have flared and insults might have been hurled...but instead the principals talked it over, came to a common ground, expressed the points that had them upset, and made adjustments in their statements. Kudos to all of you.

Advise to all parties in situations like this-

Double check these things before posting:

SPELLING ( Example - Spell cheek is your fiend, butt red what you hyped, ass it may no sat what you wanted too sat. Translation - Spell Check is your friend, but read what you typed, as it may not say what you wanted to say.)

LOOK UP TEMPERATURES IN A RELIABLE METALLURGICAL MANUAL ( Google is often your friend, but in many cases it gives you wrong info)

CHECK MATH ( I am finding that head math is not as reliable as it used to be.)

 

[Rick Marchand]

Stacy... do you mean posting, then going back in 17 times to edit grandmer an speeling is not an efficient way to go about it?

Thanks, Rick. Yeah, I guess I've been lurking long enough, huh?

Ya mon, jump in... you are obviously a maker. Have at'er.
ETA: Thanks for posting that link to the sanctioned pdf of Verhoven's book!

 

[chad2]

I'm glad to see a feisty debate stay that way.
Egos could have flared and insults might have been hurled...but instead the principals talked it over, came to a common ground, expressed the points that had them upset, and made adjustments in their statements. Kudos to all of you.

Advise to all parties in situations like this-

Double check these things before posting:

SPELLING ( Example - Spell cheek is your fiend, butt red what you hyped, ass it may no sat what you wanted too sat. Translation - Spell Check is your friend, but read what you typed, as it may not say what you wanted to say.)

LOOK UP TEMPERATURES IN A RELIABLE METALLURGICAL MANUAL ( Google is often your friend, but in many cases it gives you wrong info)

CHECK MATH ( I am finding that head math is not as reliable as it used to be.)

ah yes spelling and math obviously they were my best subjects in school lol

 

[kelsil]

You know, Rick, I wasn't going to weigh in here. I was going to bite my tongue regarding your statement to Chad2:



As if someone who has only made 20 knives has no right to draw from his experiences or express an opinion on this forum. IMO, someone who has made 20 knives is well on their way into the learning curve. And who's to say how much Chad2 has read on the subject or what his life experiences might have been, beyond just the 20 knives? Maybe he's worked for 30 years in a tool-and-die shop working with, and heat-treating, all different kinds of steel.

Frankly, I thought Chad2 gave good, solid advice in this post:



I just think he might have been a little off when he started talking about the "bubbling like effect". I believe what he was seeing was actually splotchy decarburization resulting from overheating steel for a prolonged period of time in an oxygen rich environment, with different areas of the surface of the steel having different degrees of access to oxygen and that the bubbly appearance of the steel's surface was not due to grain size.

But then you go on to say:



Still wasn't going to say anything, except that kelsil picks that up as fact:



And it's not a fact.

Sad to say that maybe you could give yourself the same advice you gave Chad2, earlier.

5160 and 52100 are forgiving steels, with regards to knifemaking, in two respects:

First, the alloying element chromium in 5160 and 52100 significantly reduces grain growth, should a knifemaker overshoot his targeted critical temperature by a hundred degrees or so. And that's real easy to do.

In the best-case scenario of using a digitally controlled kiln, it is quite possible to get some part of a blade just a little too close to a heating element and overheat it. And those of us using gas, coal, etc. and trying to rely on our senses and proper diligence will overshoot our mark quite frequently, more often than most of us probably know, I think.

Points are especially susceptible.

Well, the grains in a chromium alloy steel like 5160 and 52100 will grow to approximately 1/2 the diameter of those grains that will grow in a 10XX steel, if both are subjected to same degree of error. Now that's 1/2 the grain size, by diameter, but 1/8 the grain size, by volume.

Second, that same chromium alloying element in 5160 and 52100 significantly increases how much “quench time” a knifemaker has to work with. With a non-alloy steel, a 10XX steel, for instance, you have a mere .5 seconds to transform austenite to martensite ... to complete the quench process, in other words. But with 5160 and 52100, you have a full 5 seconds to complete the quench process.

So a knifemaker who fumbles his tongs while he's going from heat source to quench tank and drops his 10XX blade on the floor will almost assuredly miss his window of opportunity to quench. But a knifemaker who does the exact same thing with 5160 or 52100 still has a pretty fair amount of time to pick that blade back up and get it into the quench tank, with no ill-effects with regard to quenching.

Now that's what I call forgiveness.

But I do want to say, Rick, that your picture depicting grain size is about the best one I have seen on the internet. Thank you so much for posting it.

Above, I am citing "Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel" by John D. Verhoeven, Emeritus Professor, Iowa State University. Verhoeven has graciously granted copyright permission to "download and print a copy of this book for personal use," which I highly recommend.

A lot of Verhoeven's paper is written over the heads of most of us regular folks, but there is still plenty of good information for the knifemaker to glean from it.

*** You're right Mr. Perkins. I thought that it could be etched in stainless steel that 5160 and 52100 are NOT forgiving steels but looks like he did not say that with confidence. Anyway, thanks so kindly for this very informative response of yours and specially for the link to that book of Prof. Verhoeven. The forgiveness though that I'm looking for, for lets say 5160 and 52100(to be specific) is their ability to get back to their normal grain sizes by annealing, or normalizing if or when, grain growth is inadvertently induced into them. Would appreciate your words of wisdom about this curiousity. Thanks again.