Troubleshooting and the effects of cruising on cognitive abilities.

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Kevin R. Cashen

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Sep 9, 2003
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I was recently doing some testing on an oil hardening alloy of .5% carbon content and had some troubling mysteries thrown at me. When marquenching/martempering other alloys I work with (e.g. O1 or L6) I get very consistent as-quenched Rockwell numbers and have a predictable variation of one to two points less from a full quenched piece due to autotempering effects, which will then level out to match up fine after subsequent tempers. However this other steel was giving me a much larger discrepancy from martempering giving much cause for concern on achieving full hardness. The steel is well suited for martempering yet I was more than 4 points lower from that treatment! This is the sort of thing that will make me into a baggy-eyed monster from lack of sleep. I heat treated and re-heat treated looking for some clues; I didn’t have time to do any metallography so a look at the internal structures are not a tool at my disposal this time. Why is martempering so successful with my normal steels yet failing on this new one?

Then last week while cruising on my motorcycle down to Tim Lawler’s shop, I found a wonderfully winding riverside road and just zoned out taking the curves. In that relaxed yet focused state of mind all the metallurgical data just sort of flowed in and out of my head and as I came out of a curve I suddenly reversed a stream of information and focused on some numbers. BINGO! It was like a stroke of lightning when I saw it clear as day, and I also felt like a damned idiot for not seeing something so obvious before then! I did not abandon logical use of metallurgical data for some new form of biker bladesmithing, but here is a challenge to explore the difference- Can one find the same answers without all this horribly misleading, evil and soulless metallurgy?

Here is the information available- You have three steels, one at .9%C, one at .75%C and the other at .5%C, all have enough chrome to be fully oil hardening yet the last one shows a marked drop in hardness using the same quench i.e. heated in high temp salts and then quenched into 420F Thermoquench salts until equalized and then allowed to air cool.

If one dabbles in all this useless and destructive metallurgy all the information you need for your answer is right there, and while some may call it “science” and go all tin foil hat about it, really it is just common sense and applying data to solve a problem, that is no more “scientific” than working out that adding 1 marble to 2 marbles gives you three marbles (until you loose them all from dabbling in such dark arts).

But I am curious what answers can be gleaned without the use of any metallurgy at all. No curves, charts or graphs, no discussion of phases or microstructures, and although it is not fair, folks like Mete and other academic or technical types are not allowed to try since they are part of the great scientific conspiracy. No copping out by simply writing it off that martempering is itself "scientific" thus without it there would be no problem, various forms of the same techniques have been used for centuries (interrupted quenching) and would give similar issues.

Some could wonder what my point is or the relevancy? I think it is very much on topic and such conundrums are faced by knifemakers every day, and I could do a dozen more threads with other puzzling issues we constantly face. In all my years I have yet to find any tool that has been more useful in saving troubleshooting or time planning or predicting than metallurgical information. So I am incredibly curious to see how things can be done in other ways that do not include it.
 
O.K. Kevin, I'll take the bait. :)
It's so hot out, I'm just laying around inside. I must be really bored...

It depends on what you mean by metallurgy. I'm not sure it's really that easy to define. On the one hand anyone that works with metal and gets it to do what they want can be considered a metallurgist and using metallurgy, regardless of their knowledge of microstructures, curves, charts, graph etc... I think history proves that one. So from that standpoint you can't do anything with metal without using metallurgy... a metalsmith or metalworker IS a metallurgist.

On the other hand, I think that a modern western definition of metallurgy as a “material science” is something quite different. It attempts to explain what folks were already doing with metal in terms of microstructures, graphs, charts etc... and lay down a set of "principles" that metals will most likely follow. The problem and advantage with principals or "ideals" is that they tend to simplify things to make them easier to understand or grasp. However, reality is much more complicated and messy and doesn't always follow our principals and ideals perfectly.

You're probably getting tired of the Dharma Haven links, but I think this one might apply. It's kind of long and boring, but...

Problems with principals:
http://dharma-haven.org/science/limits-of-logic.htm

Anyway,... it's all good if kept in perspective.
 
I don't think it really matters how you solved your immediate problem. The important part is that you figured it out some how... no matter how unscientific it may have seemed.

"Unscientific" is just a temporary perspective...

The fact is, that you were engaged in a metalsmithing goal oriented pursuit of knowledge, and you found your answer. It doesn't matter if it came to you in a dream, or a little birdie told you...

... It's all metallurgy! That's how it works,... That's what metallurgists do! :D
 
I think the 420 may be too far from Ms for your .5% steel. I don't know as much about this stuff as some folks, so maybe I'm far off. I'd guess you're using something like 6150, which I thought should be marquenched closer to 500F.
 
There must be a scientific explanation...

Only question is,… which area of science?
 
I'm guessing that the marquench at 420f caused some tempering to occur and you ended up with less martensite due to the temp. Since you had less carbon to start with, that martensite reduction was more noticible....or something.... :)

-d
 
Tai Goo said:
O.K. Kevin, I'll take the bait. :)
It's so hot out, I'm just laying around inside. I must be really bored...

It depends on what you mean by metallurgy. I'm not sure it's really that easy to define. On the one hand anyone that works with metal and gets it to do what they want can be considered a metallurgist and using metallurgy, regardless of their knowledge of microstructures, curves, charts, graph etc... I think history proves that one. So from that standpoint you can't do anything with metal without using metallurgy... a metalsmith or metalworker IS a metallurgist.

On the other hand, I think that a modern western definition of metallurgy as a “material science” is something quite different. It attempts to explain what folks were already doing with metal in terms of microstructures, graphs, charts etc... and lay down a set of "principles" that metals will most likely follow. The problem and advantage with principals or "ideals" is that they tend to simplify things to make them easier to understand or grasp. However, reality is much more complicated and messy and doesn't always follow our principals and ideals perfectly.

You're probably getting tired of the Dharma Haven links, but I think this one might apply. It's kind of long and boring, but...

Problems with principals:
http://dharma-haven.org/science/limits-of-logic.htm

Anyway,... it's all good if kept in perspective.
Click to expand...

What of this addresses the question in this thread? You disappoint me with merely a continuation of your scientific rape thread.

Bait? Tai if this were a trap the mechanism would still be taut under the spring with the cheese untouched while you stayed at a safe distance back peddling and redefining what you could mean by metallurgy or science. Now we are all metallurgists of sorts? Technical charts and graphs suddenly aren’t so bad? Which part of it all is raping us then? Exactly what part of metallurgical science is it that has your shorts in a bind? Are we to assume that there is a certain level of science that is still safe and you will let us know when that invisible line is crossed?

Actually I promise that this question was not aimed at you, but was instead some mental exercise for the normally rational people who can get so bored that your rape thread actually made it to three pages! This one will not take as long since I am certain one cannot even speak the answer without uttering some dangerously technical terms and if I know the good folks here they will be interested in the technical explanation. But if you would like to take a shot, who am I to stop you.

Please don’t think of this as bait or a trap, consider it a prime opportunity to one up the scientific nonsense and put it in its place. Remember intuition can’t be wrong. What does your intuition tell you?
 
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Now not knowing the cause of the problem we can take one of several courses of action:

A. Screw it! Rockwell numbers are just part of the lying scientific conspiracy so I choose to ignore them and continue on because I know my knives are just fine the way they are.

B. Abandon martempering, and toss all my equipment on the scrap pile out back since the ancients didn’t have this problem I will solve it with a forge and some water to quench in!

C. Although I just bought 1000 lbs. of this new steel I will throw it on the scrap pile instead and just stick with the only two steels I know will work. If I never leave this safety zone again I will never have any problems and not have to worry about knowing anything more than I do now; after all ignorance is bliss!

D. Break down and admit that knowledge is power and the more tools I have at my disposal the better. In other words, decide that self imposed ignorance for the preservation of fantasy is far more costly than taking the risk of being wrong in pursuit of deeper knowledge of my materials. Admit that we all use physical facts everyday in the simplest of tasks without being mad scientists.

I am not intentionally being provocative or sarcastic, but eventually one needs to speak up and ask for a reality check! We gather and process data all the time, whether it is just with our own senses or if we decide to extend our reach with tools beyond ourselves. We can hide in a cave and never trust data because it could change or somebody could have the common sense to drive the first stake to measure from and actually build something! Hiesenburg (I know another nutjob scientist:rolleyes:) told us in the fundimental level that no measurement during certain observation is absolute but I think rulers still work regardless!
 
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Inadequate soak or too low austenitizing temp; Carbon tied up with chromium = Carbon lean martensite? Through me bone here man...
 
AcridSaint said:
I think the 420 may be too far from Ms for your .5% steel. I don't know as much about this stuff as some folks, so maybe I'm far off. I'd guess you're using something like 6150, which I thought should be marquenched closer to 500F.
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Ohh no! AcridSaint, you went right for the scientific approach of using terms like Ms and applying it to exact temperatures, we can’t have that! It reveals your unhealthy penchant for technical knowledge! As I said, I don’t even think one could give the answer without using such terms because we no longer live in Neolithic times and have to deal with reality once and a while. However thank you for pointing out how little time and effort is spent working out problems when we break down and decide to use the tools available to us instead of avoiding anything that could disturb our world view! One could take a very long time working out ways to approach this and express the results without using the information or terms that material science has already provided.

Now to take the medieval blinders and gag off… yes AcridSaint you have it! What struck me was that lower carbon content raises Ms, and quite quickly I might add! This allowed for as much as 90% of my martensite to be formed before I stopped the cooling at 420F. Temper any hypoeutectoid at 420F and see what hardness you get. O1 is just getting started forming martensite at the same interrupt point so very little of it gets a full temper at this heat range. And yes I confirmed my suspicions by interrupting at higher temps and comparing samples that where air cooled to ones that were cooled to room temp quicker.

Very scientific stuff! Now let’s apply it to practical and traditional bladesmithing! You have 1095 and you have 1050 you plan on getting around the hardenability issues by interrupting a quicker quench, do you stop at the same point for both? The 1050 is not going to like that! The 1095 will actually be less of a problem to do this with. But then you wouldn’t have to worry about it if you didn’t bother checking hardness, I guess it is that knowledge that made you unhappy. But there you have it, a completely scientific and technical approach being wonderfully useful in a most ancient blademaking technique. Can the craft survive such knowledge?:eek:

AcridSaint let the cat out of the bag, but the challenge still stands for the anti-technical-knowledge folks to find a way to even communicate or express what he worked out in seconds with “scientific” data.
 
Maybe the fact that .5C is hypoeutectoid combined with the chrome content and the temperature caused an excess of chromiumcarbides robbing the austenite of carbon (no spare carbon like hypereutectoid steels, although the .75 should exhibit similar behavior by that logic, if less) and reducing the amount of martensite that can be formed, thereby reducing the hardness. Either that or you had your tin foil hat on backwards...

Cheers rody
 
Ms[F] = 930 - 600x % C - 60x % Mn -50 x% Cr -30 x % Ni -20x % Si -20 x % Mo -20 x % W It's all just a numbers game !!
 
Rody said:
Maybe the fact that .5C is hypoeutectoid combined with the chrome content and the temperature caused an excess of chromiumcarbides robbing the austenite of carbon (no spare carbon like hypereutectoid steels, although the .75 should exhibit similar behavior by that logic, if less) and reducing the amount of martensite that can be formed, thereby reducing the hardness. Either that or you had your tin foil hat on backwards...

Cheers rody
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You know, Rody... I think it is remarkable that you and I were wrong in the exactly same way at almost exactly the same time. And I'm kinda glad too, makes me feel better...
 
mete said:
Ms[F] = 930 - 600x % C - 60x % Mn -50 x% Cr -30 x % Ni -20x % Si -20 x % Mo -20 x % W It's all just a numbers game !!
Click to expand...

Mathematics, chemistry and metallurgy! How many scientific disciplines are you willing to use at once? I knew you were a bad egg mete!;)
 
Nathan the Machinist said:
You know, Rody... I think it is remarkable that you and I were wrong in the exactly same way at almost exactly the same time. And I'm kinda glad too, makes me feel better...
Click to expand...


Your conclusions were the same because you have facts that are objective and stand on their own. I would submit that neither of you were wrong since your conclusions were based upon entirely viable facts and in another circumstance would have been a valid explanation. Often troubleshooting is a process of zeroing in on the most likely of several possiblities by eliminating the least likely by the number of the symtoms they can account for. It sure as heck beats random guessing or not trying because there may be different information on another day.
 
We can talk about Ms and its effects, or how riding a sporty bike can help clear the mind, or anything less pointed if you folks would like. My reason for all this mental excercise is to bring into focus how useful information is whether somebody wants to label it "scientific" or not, and how if we get caught up in irrationality of rejecting knowledge we can simply cease to function. Not only is the concept of this real problem untouchable without the technical knowledge, we can't even express it without proper technical terms. My hopes are that this thread would come to mind when deciding how much bandwith to use on the next anti-science thread:rolleyes: Not that we shouldn't have any kind of thread people want to start, I always believe in presenting better counter-information over stopping the free flow of any, but how can we continue to go several pages on such a non-topic?
 
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