Quench oil that is too fast for a given steel?

I have a question about oil being too fast for certain steels.

I am aware of the downsides of an oil being too slow for a certain steel.

But what about oils that are too fast? I have come to understand that you only want an oil just fast enough to get the job done sufficiently. Other wise you risk an increased chance of cracks right?

But is there more? Can an oil that's too fast have a negative effect on getting full hardness or even prohibit full hardness?

Say for example, using Parks 50 for steels like 52100, 5160 or 80CrV2.

And as a follow up, what if you did use Parks 50 but at a temperature around 50 or 60 degrees F.? Would that be okay? Certainly not Parks 50's fastest temperature range.

Any thoughts anyone?

You ask an interesting question. However, aside from an academic discussion, can any real world user distinguish any good knife steel, heat treating process or quenchant from another IF his conclusions were based solely on real world knife tasks?

I look forward to learning more from this academic discussion - thank you for starting it.

Geoff

I have quenched a few blades of O1 in parks 50 and got about 6 points lower on the RC scale out of the quench than with the slower oil . The parks was at room temperature . I was curious about that. In my small test I was able to keep it at 58 RC after tempering at 350 . I get 64/63 out of the quench with the slow oil and can put the final hardness on the tempered blade anywhere I want with temp control. This just the way it happened to me it may be different for others

There should not be a loss of hardness, but an increase in strain effects from the faster quench. These effects will manifest themselves in possible fracture and an increase in distortion problems. I just had a conversation with another mastersmith to fine tune his heat treating regimen and he was using temps that could give some of the same issues, and my answer on the topic was that if he was not having fracture/distortion issues, good for him and keep doing it until he does. But then there are the possible invisible effects of such strain. In plate martensitic systems there could be an increase in plate microfractures due to high angle impingement. But once again, if there are no overt signs of such issues can one just be happy and go with it? One thing that I must note is that often when things that shouldn't work so well are seemingly working often something else that is not quite right is making that possible. For example I have seen folks who have quenched steels in water that should not tolerate it at all, but in almost every case they are under-austenitizing in order to accomplish it; of course a medium carbon steel will survive such a quench, and that is essentially what you have when you deprive a high carbon steel of full solution. In every case when I got the proper solution that would give me full hardness in O-1 with a medium speed oil, I got distortion or fracturing in something like Parks #50.

Then you have the given properties for the intended application. A fine slicing knife can still excel in abrasion resistance and edge stability with the aforementioned issues, but impact toughness will not be the same in a steel with those strain issues. so you may never notice it in your skinner or kitchen knife, but you will in your camp knife or machete, whereas if you under-austenitize to accommodate for in inappropriate quenchant your machete may be tougher, yet need more sharpening, but you chefs knife wont hold near the edge it should.

Heating most oils will increase the heat extraction ability up to around 150F where things level off and then start to get lousy as you near 200F, but this is not the case with Parks #50. That oil is best in a range from 80F to around 108F and no more (think body temp). Below 80F and things start to slow down and above 120F and the life of the oil will suffer as well as provide spotty results.

This is yet another thing that is hard to convince people that there are ideal and less than ideal courses of action, because if the blade survives and seems to function it is hard to convince somebody not to believe their own eyes. But it is what their eyes are seeing and how it is interpreted that is issue. The reason I assembled the laboratory like facility that I have is to see and interpret things that my eyes alone can't and to determine how much my eyes were getting right. What I have found, almost every time, is that the steel working industry has developed things that work for good reasons and when you have the testing equipment to accurately measure those reasons it all sort of clicks into place for you.

Thanks guys.

Kevin, there is some good detailed info there. It makes a lot of sense now. Thanks for your reply.

Yes Kevin thank you .. I remember when I first started doing my own heat treat. I was working with 1095 and quenching in canola oil and using my forge and I would overheat the steel and then quench. I would make the blade and it would seem like it was good and would hold an edge. But once you put any lateral pressure on it ... Snap . So I was deceived by my own eyes when all I was looking for was if it was hard and if it would cut. It took me a little while to figure out 1095 but I like that steel. So if you think you can heat treat 1095 and not play close attention to the details .. Put it in a vise , Give it a little push .

So, we've all seen the crucible spec sheets that say things like 440C and 154CM can be oil quenched. Now, with these steels, you've got something like three days to get under the pearlite nose. OK, I'm exaggerating a lot - but the principle is there. If we are supposed to use the slowest oil that will accomplish the task, I'm thinking we've just found a new market for Alberta Oil Sands bitumen.

Kidding aside, does anyone know what oil you'd use for quenching martensitic stainless blade steels?

Hope this isn't a hi-jack. Just taking the OP question to the next level.

Rob!

Because you have "three days" (I like your exaggeration) to get under the PN, I don't think it matters much which oil...just don't use nasty motor oils. At what point does quenching stainless in oil cause a problem...as in too much stress and micro cracking? Why bother.....when the PN is the PN....and getting there faster doesn't do anything except strain the steel?

I recently touched this topic on another forum. We move into a an entirely new set of parameters when dealing with stainless, all the phase zones rest far to the right of where the pearlite nose would be in simpler steels (even on a cct curve, if the equlibrium nature of the I-t curve bothers you), in fact there may be no pearlite nose at all. In steels where the pearlite nose is shoved to the right, or even eliminated, it is supplanted by the upper bainite chin. This is whole new order of times that make it so comparing water quenching a low alloy steel with oil quenching an air hardening steel an apples and oranges type of thing. On one you are condensing transformations into fractions of a second while on the other you are working with minutes. This is why the time scale of the I-T curve (yes, I know it is not dynamic like a cct, bear with me people I am using the one people are familiar with) is logarithmic, so we can see the things that happen in fractions of a second and not have the right hands side take up half a room. So in order to get time scales that better match you would need to compare it to quenching stainless in brine. Quenching in oil just helps out with the inevitable retained austenite that you should get with simpler steels with proper austenization.