Hardening .....water & oil

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Natlek

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Jun 9, 2015
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Ok , I often read here that when hardening steel 10-20 degrees +- make huge difference .Now , in this link / very highly valued company / https://steelselector.sij.si/steels/OW3.html they recommended for 1.2519 steel this HT ......

Hardening
Harden from a temperature of 780-820oC, 800-860oC followed by water or oil quenching. Hardness after quenching is min. 64-65 HRC.
So my question is what difference will be between steel heated to 780-820 C and quench in water and steel heated to 800-860 and quenched in oil ?
 
It largely depends on what the structure was before it was hardened as well as the thickness of the object being hardened. That steel is often in a spheroidized state, which would use a higher austenitization temperature.
 
@Stacy , I guess that the structure is the same , ready for hardening in both case .Difference in soaking temperature is because quenching medium ..at least that how I understand this ? In both case hardness after quench will be same ? So what is happening here ? Same result with that much difference in temperature ??
 
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Do your own testing and tell us!!!!??? Generally, you use the lower temps with water, and the higher temps with oil. If you have access to a fast oil like Parks50 or DT48 you can use the lower range of temps as these type of oils simulate the speed of water.
 
And the structure of “as received” 1.2519 should be ready to harden. Soak at temp for 10 minutes. And for that alloy I recommend 1525F, quench in a medium to medium fast oil. 130f canola works great for this alloy. Easy Peezy.
 
It is given the full range based on the specifications.
Actual batch values within the specifications will get optimal treatment somewere in that range.
Also the shape and thickness of the piece will dictate which is the quenching medium of choice.
Then, the rate of heating will "move" your "target" temperature, as the elements would "lag behind" due to hysteresis...you will find the balance between rate of heating, final temperature and soak time, which are all related. Of course they are also related to the microstructure arrangement you are working from "as delivered".
In the end those recommended are the ballpark indications for that steel, then you (and industry as well) know where to start optimizing the treatment of your steel in your production environment.
Giving a full optimized procedure would be pointless without knowing the public having a standardized setup for the treatments and the same exact expectations.
 
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samuraistuart said:
Do your own testing and tell us!!!!??? Generally, you use the lower temps with water, and the higher temps with oil. If you have access to a fast oil like Parks50 or DT48 you can use the lower range of temps as these type of oils simulate the speed of water.
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So , this means that ten minutes on 780 degrees and ten minutes on 860 degrees is same thing ,of course under the condition that the steel is prepared in right way for HT ? I mean , what need to be happen inside steel would be same in both temperature ?
If it's like that , it turns out that quenching..............is most important part of HT process and that precise temperature is not critical ?
 
Natlek. That is the recommend range for it to harden in. No one here can tell you what condition the piece of steel that YOU have is in. They also cannot tell you how your own equipment works.

Water is a more violent quench so most people try to avoid it if they can get good results out of oil. samuraistuart samuraistuart has told you that he gets good results with canola oil so its unlikely that water is needed. You are only talking about a 100 C range anyway. Run 4 samples 25 degrees apart as a start and then work it from there. How fast YOUR equipment heats up. How YOU do the timing of the soak. The temp, type, condition, quantity heck 3ven the shape of the container for YOUR quenchant will affect things. I assume that those are industrial heat treatment numbers. If so they are for larger pieces and YOU will have to adjust as needed. They also do not write new ones for each heat so YOU will have to dial them in with YOUR material.
Hope that helps. There is only so much we can do to help. I would start with what samuraistuart samuraistuart is running and adjust from there.
 
Thanks ! What I wanted to discuss is not HT proces but about quenching medium .
Please correct me if I'm wrong.
Let say we have two equal piece of 1.2519 steel with the best possible process /normalization, stress relief ....etc/ needed to be done before HT and we have good properly calibrated oven . We soak one piece for say 10 minutes on 780 Celsius and quench in water /we should assume that that was done in quench tank with proper agitation/ and we get say 65 HRC .Other piece in other oven soaked for 10 minutes on 860 Celsius and quenched in adequate oil with proper agitation . Hardness , toughness , abrasion resistance after quench should be the same ?
Simple as I see it they say this .... If you want to use water to quench this steel use this temperature .If you want to use oil for quenching use this temperature .Final result will be the same in both case .
 
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Except that the water quenched blade may crack or break in the quench.
There is a good reason most makers do not quench in water unless it is absolutely necessary, like in yaki-ire.
 
As I understand it, lower austenitization temperatures can mean a higher percentage of lath vs plate martensite. A lower austenitization temperature should also yield a finer final grain size in the hardened blade. More lath martensite and finer grain may mean more toughness, but you have to balance that with the fact that a more violent quenchant such as water may lead to more brittleness, possibly cancelling the benefits you get from the lower aus temperature (If I'm off base with this, someone please tell me).

Edit: I know Parks 50 is supposed to approach the speed of water, but I don't think it's actually as fast?
 
I found several study where they say that water can replace oil for quenching where smoke and fire hazard is concern. They say that water with proper agitation is safe to use ,but that study was for industry not about thin knife. I plan first to HT steel then start to work on knife shaping , drilling hole , grinding bevels........I think that it is good approach . So far I try water quench on small pieces of 5160 , 1095 , 80crv2 and 52100 steel with improvised tank and agitation and it works....
 
Why do you want such a fast quenchant? Agitation further accelerates the quenching speed. I think if you have a specific reason for wanting to use water on steels specified as water hardening, then have at it, but even then you risk cracking on thinner blades. I do use water on my laminated blades made with Hitachi steels, but I definitely wouldn't want to quench a 5160 blade in water...
 
Most cracking and deformation are predominantly affected by the uniformity of the quench and not from the quenchant itself .At least that was what most study I read say ....
 
But still, why use water? Good, fast quench oil does the job perfectly, without as much risk in ruining your work.
 
Uniformity cooling isn't possible because cooling is inward (from exterior to interior). Symmetrical cooling isn't possible for KSO, unless making a sphere-shape-knife-object (a ball :)).

Dimension asymmetrical changes (bct has lower packing ratio than fcc = dimensional expansion) is the mechanism of/cause cracks.

imho... Lately, there is a curious ht movement toward higher aust couple with slower quenchant. For sake of simplifying argument - factoring out hardness, toughness as equal for lower aust+fast quenchant and higher aust+slower quenchant - there are other attributes must taken into accounts. Attrs such as: grain diameter, ra%, elasticity+plasticity ranges, ys, uts. In other words - approach with caution/informed to avoid ht regression. *keep in mind, I am not saying - which aust temp; quenchant are good or bad.

Natlek said:
Most cracking and deformation are predominantly affected by the uniformity of the quench and not from the quenchant itself .At least that was what most study I read say ....
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bluntcut said:
Uniformity cooling isn't possible because cooling is inward (from exterior to interior). Symmetrical cooling isn't possible for KSO, unless making a sphere-shape-knife-object (a ball :)).

Dimension asymmetrical changes (bct has lower packing ratio than fcc = dimensional expansion) is the mechanism of/cause cracks.

imho... Lately, there is a curious ht movement toward higher aust couple with slower quenchant. For sake of simplifying argument - factoring out hardness, toughness as equal for lower aust+fast quenchant and higher aust+slower quenchant - there are other attributes must taken into accounts. Attrs such as: grain diameter, ra%, elasticity+plasticity ranges, ys, uts. In other words - approach with caution/informed to avoid ht regression. *keep in mind, I am not saying - which aust temp; quenchant are good or bad.
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You are right , I should have been more precise .Uniform cooling of core of steel in first stage of quenching....
 
Fellows, I don't think he wants our explainations and advise. Just let him do what he wants to. He will learn why we don't use water for knives quickly.
 
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