How To Identify quenchant speed

[Mstrick96]

i've been researching different quenchants and trying to relate them to the data from the CCT diagrams. I've found a couple of quenchants from McMaster that identify the quench speed as 11 second and 28 second for their oils. Other than that, I haven't been able to track down anything except general information.

The heat treat instructions I have found for different steels only list water quench, oil quench, or air quench. No spcific recommendations on products.

I've found information on historical quenchants used, like blood from rutting rams, caterpillar and bug juice, kerosene, diesel fuel, etc. looks like almost anything in liquid form has been tried. Also, I've found information on various blends of quenchants that have been used.

What I've been able to deduce so far, is that various quenchants go in order of fast to slow from:

Water, brine, canola and other veggie oils, McMaster 11 second, McMaster 28 second, then air quenching. I have no idea where other available quenchants lie. Perhaps, some of the "expensive" books and society publications have more information, but that's too much $$$ for me unless I know beforehand that the information in the publication is useful.

Is there any information on relative quenchant speeds? Or am I stiuck with anecdotal, "rule of thumb" information?

 

[Mstrick96]

Found an interesting paper that partially answers my questions. This paper evaluates different mineral oil based quenchants. My takeaway from this article is that viscosity/wetability of different quenchants is the primary determining factor in quenching rate.

A less viscous, more wettable quenchant is faster. This allows the inherent thermal conductivity of the quenchant to take effect.

https://www.jstage.jst.go.jp/article/isijinternational/54/6/54_1426/_html/-char/en

 

[joedhiggins]

Approximate order:

Brine
Water
Fast oils (parks #50, Maxim DT48)
Canola
(maybe other vegetable oils fall in here)
11+ second oils and polymer bath quenchants
Plate quenching
Air quenching

Brine is in all ways superior to water as a quenchant, but it is still very tough on steel.

Fast oils will attain full hardness in every knife steel I am aware of, but are overkill for steels with anything but the lightest alloying. DT48 is a great quenchant that will fully harden 1095, w1, w2, 1084, 1070 when heated to 120, but will behave more like an 11 second oil at room temperature, allowing you to quench O1, 52100, 5160, 80CRV2, and others without undue stress.

The slower quenchants are appropriate for some steels that are on the verge of being air hardening (O1 comes to mind, I am sure there are plenty of others) and very thick sections of air hardening steels.

AFAIK pretty much everyone heat treating knives made from air hardening steels uses a plate quench as it helps prevent warping in those blades by holding the steel in place as it cools.

Many people use interrupted quench techniques as well, for a variety of reasons. For hamon (differential tempering line) activity, some will quench into brine for about 1 second, just enough time to get the steel past the nose, and then move into oil right after. I commonly will quench steel for a few seconds in oil to get past the nose and then clamp between plates prior to the steel reaching Ms. In this zone, the steel is still austenitic and plastic. Clamping in plates during the martensite transformation seems to eliminate any significant warping that may occur.

 

[joedhiggins]

Found an interesting paper that partially answers my questions. This paper evaluates different mineral oil based quenchants. My takeaway from this article is that viscosity/wetability of different quenchants is the primary determining factor in quenching rate.

A less viscous, more wettable quenchant is faster. This allows the inherent thermal conductivity of the quenchant to take effect.

https://www.jstage.jst.go.jp/article/isijinternational/54/6/54_1426/_html/-char/en

This seems likely, though different quenchants definitely have different coefficients of heat transfer, as well as different specific heats. Both of these qualities will matter to quench speed. Boiling/smoke points also matter.

As I remember, brine has a bunch of advantages over water, but at sufficient concentrations, salt in water delays the formation of a vapor jacket and thusly when combined with agitation gives a better, more even rate of cooling.

 

[Mstrick96]

Thanks! I had water and brine reversed. Also appreciate your adding the commercial quenchants I wasn't sure about.

Plate quenching and interrupted quenching sound interesting. From studying the Transformation diagrams for steels, it looked to me like it would be difficult to avoid passing through the nose with some of them. I need to research those techniques some more!

 

[joedhiggins]

I am unaware of a knife steel that can not reach full hardness in parks 50 or dt48 in the thickness we build knives. It is likely that if you were to make a 1/4" spine 1095 knife that you might not get full hardening of the center of the spine. The edge however should be fully through hardened.

 

[scott.livesey]

go to quenchant website or the data sheet that comes with quenchant. example https://www.houghtonintl.com/sites/default/files/data-sheets/houghto-quench_100_1506_us.pdf this says quench speed of 15-22 seconds. an issue is the test standard has changed, it is currently ASTM D6200-01, Standard Test Method for Determination of Cooling Characteristics of Quench Oils by Cooling Curve Analysis which uses a 1/2" diameter probe. the houghton oil uses a GM Quenchometer which uses a 1" diameter probe. so when you read the data sheets make sure you are doing apples to apples. when you read thru the Houghton site, they have low viscosity fast and medium oils.

 

[Mstrick96]

Thanks again! All this is good information.

I've seen information on steel/quenchant combinations and have no doubt that I can get to full hardness in knife blades with most steels. I see Parks and Dt 48 recommended over and over. I need to look into the Houghton oils. Good reminder on the data sheets.

My motivation in looking into all of this is to understand everything as thoroughly as possible. The better I know my materials, the better job I can do.

Thanks for your help!

 

[HSC ///]

As I remember, brine has a bunch of advantages over water, but at sufficient concentrations, salt in water delays the formation of a vapor jacket and thusly when combined with agitation gives a better, more even rate of cooling.

Brine is in all ways superior to water as a quenchant

Do these comments apply only to the quench of a homogenous steel? Any different for the quench of a laminated steel?

 

[joedhiggins]

Do these comments apply only to the quench of a homogenous steel? Any different for the quench of a laminated steel?

I have never heard an argument made for the use of water over brine. As I understand it, brine quenches slightly faster than water and is simultaneously more gentile on steel because of the more even cooling rate due to reduction in vapor jacket.

Maybe someone else can add more info, but I cant imagine a reason you would pick water over brine for a laminate. I am assuming you are going for a hamon with your laminate, otherwise I think I would aim for an oil quench.