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water quench questions..


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What is so difficult about a water quench with water hardening steels? I realize it puts a tremendous amount of initial stress on a blade, but what is the factor that makes some fail, while others succeed?

 

Anything that has a say.. It doesn't make sense to me that anything could have a 50% success rate, if all the other factors are controlled. If you grind to the same thickness and finish, use the same steel, normalize the same ammount, and heat to the same temp before the quench, where is the variable that causes the death rate?

 

I have a kiln, and a pyrometer, so I can hit the neccessary temp pretty much spot on, and soak it as much as I need too. I can leave the blade thick and polished as well.

Anyway, I'm just trying to figure out what is the cause of some blades failing while others of the same build do not.

 

thanks for the help.

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What is so difficult about a water quench with water hardening steels? I realize it puts a tremendous amount of initial stress on a blade, but what is the factor that makes some fail, while others succeed?

 

Anything that has a say.. It doesn't make sense to me that anything could have a 50% success rate, if all the other factors are controlled. If you grind to the same thickness and finish, use the same steel, normalize the same ammount, and heat to the same temp before the quench, where is the variable that causes the death rate?

 

I have a kiln, and a pyrometer, so I can hit the neccessary temp pretty much spot on, and soak it as much as I need too. I can leave the blade thick and polished as well.

Anyway, I'm just trying to figure out what is the cause of some blades failing while others of the same build do not.

 

thanks for the help.

 

Its a modern day steel thing no two batches are spot on the same Iv even seen it aocour in the same bar buggerd if i know why as its all computor controled / the water temp may be off from one blade to the next or as we say in aussy Murphys law even the japanese smith's only get 3 out of 5 to quench sucsessfully

maybe the dreaded fire Kami of the forge as the japanese think but im with you its a pain in the ass

 

tell

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I know I am new and don't have alot of experience, but if I am over simplifying this someone please correct me, Every piece of Iron and Steel is different thus the stresses it undergoes in each piece is unique no matter how we try to do the same thing over and over, thus how it reacts during hardening will be different each and every time, sometimes failure sometimes success.

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Another variable is the vapor jacket that forms when the water converts to steam. That vapor jacket alters the rate of heat extraction and does not happen uniformly.

 

Minerals in the water have also been implicated in failures.

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lets back up a bit............ first off in the choice of steel, as i am sure you know different steels perform differently in different quench mediums.........not all steels need the speed of water quenching and can safely be oil quenched to full hardness will almost no failures.

 

there are some steels that must be water quenched to get the ultimate performance from them.........the very high carbon steels such as hitachi yss white paper #1... the steel must be brought thru the nose of the cooling curve very quickly and a wash of clay to reduce the vapor pocket and water are the answer. the downside is that this rapid quenching walks the fine line between the ultimate edge and disaster.

 

now to your question.......... if a large batch of blades ( 'identical') were made from one batch of steel i believe a temperature and soak time, clay wash coating, water temperature combination could be found that would give consistent results with no breakage.... trial and error until the right combination is found.

 

how far this would be from the ultimate edge is hard to say....... kinda like car racing if you dont crash a few you are not driving on the edge :)

Edited by john marcus
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do we use distilled for quenching then?

Thankyou

 

 

the hardness of the water does play a roll...its just part of the overall picture ........ if your water is consistent then consistent results will follow.... i am not aware of any smiths not using tap water........but i am sure we will hear from them now :)

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I think the idea that we ought to be able to completely control quench cracking is similar to the idea that we ought to be able to predict weather with 100% accuracy. In both cases our efforts are frustrated by the fact that the variables are just too numerous, and too small, to fully account for them.

 

My understanding is that the main danger in water quenching comes from the factor Don identified: uneven cooling due to the unstable vapor jacket. I'm not sure I understand why this is especially a problem with water, but apparently it is.

 

By the way, the salt in brine serves one of the same functions as a clay coat, in that they both help break up the vapor jacket and even out cooling. This is why some folks say that brine, though faster than water, is actually less apt to cause cracking. (Not sure if I believe that, but I've seen the claim and it makes a certain amount of sense.) And the professional heat treaters say that agitating the quench bath -- which helps break up the vapor jacket -- is a massive help in reducing quench cracking. Again, it all seems to come back to that darned vapor jacket.

Edited by Matt Bower
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Rain barrel water works or you can buy distilled, it isn't expensive. I am not sure how much it factors in, but if you want limit your variables that is one you can do easily.

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we run off a spring, so its pretty decent water.

 

On the steel point, is there any performance gain to hardening the 10xx steels in water as apposed to a fast oil? I imagine the hamon would be more active as it is with w2, unless im mistaken.

Its all very interesting :)

thank you all for the insightful posts.

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I don't use 10XX steels and don't water quench much but I did some serious experimentation with 1050, clay, and water some years ago before I settled on using low alloy steel exclusively. I found that water is absolutely critical and that even very small amounts of dissolved minerals (spring water would be very hard I'd guess meaning that it probably has a very large amount of dissolved solids in it...) can make a very big difference.

 

I solved about 50% of my cracking problems by controlling my water quality. I did this by collecting the water from the dehumidifier in the basement during the Summer and collecting the water from the air conditioner. This is essentially water removed from the atmosphere and it has no mineral content and acts just like distilled water. It is very constant and predictible.

 

The other 50% of my cracking issues were solved by using an interrupted quench and being careful about how much of the blades edge was being exposed in the quench....there is a balance between hardened edge and soft back and it's my opinion that most blades crack in a water quench because the newly formed, untempered Martensite at the edge gets pulled apart as the back of the blade continues to cool and flexes the blade.

 

Even in un clayed blades the thinner cross section of the edge hardens way before the thicker back does and this causes a flexation that literally pulls the edge until it cracks. Newly formed Martensite is very brittle and it simply cannot take this tiny amount of flex. Interrupting the quench allows some of the heat from the back to be drawn back into the edge and temper it a bit.

 

Remember that with 10XX water quenched steels it only takes less than 1 second to get behind the nose of the curve so if you quench for 3 seconds into water and then pull it out for 3 seconds the edge will still get plenty hard without the dreaded *PiNg!* of death.

 

Sometimes. :)

 

As far as fast oil goes I have seen some pretty active and beautiful hamon (as well as very hard edges) on steels with .6% - 1% carbon done in fast oil. I'm not sure as I have not used oil much (stinky, smokey, ucky...) but I'd bet with a quench oil specifically designed to be a fast quench you would not give up much hardness unless the steel was of marginal hardenability.

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I think the problem is pretty much summed up by John's answere, only no two blades are going to be the same. Each forged blade has a unique history. The geometry is not going to be the same. The hammer blows are not going to be even or be applied at the same temperature. The grain size may well be different. Not to mention things like once I had a bar of steel that had an inclusion at one spot that didn't show up until grinding. Theoretically, if you control all the variables you would get consistant results but that is well nigh on impossible.

 

Doug Lester

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How's that work, Sam?

 

 

This is all based on some different observations, and there is alot of variables as said with geometries, water hardness (I only ever have seen plain tap water fed by a well), clay thickness and pattern and such things, but I personally think it sets down a good base to build off of. Also, brine was used not just plain water, but again I think the same or similar rules will apply, so take it with a grain of salt hehe :D . Mainly 1075 and sometimes 1095 has been used in most all of the situations I have ever seen using this method with a 99% success rate. Also, this method was always used to achieve a hamon in conjunction with a clay coated spine with a thin wash along the edge. ALso, this was always done exclusively with swords.

 

IMO cracking in the quench occurs at the point where martensite starts to form. If you feel masochistic, grind out a blade and quench it in water in a well lit environment, and actually watch what happens without focusing or getting all excited and nervous about trying to get it to survive the quench go into it with the goal of cracking it, I think you will notice that just about everytime the cracks will start to occur at the last couple seconds of the quench. This is of course barring the fact you are using a steel that is entirely unsuitable for water quenching such as O1 or 5160. That tells me that you have to halt the blade's cooling before it hits the "tink tink tink point :)" or the point where martensite starts to form, to avoid the dreaded ping. This is what marquenching is, quenching down to the martensite formation start point, holding it there for everything to equalize out a bit, then letting it air cool and form that good hard steel nice and easy. In simplistic terms, for most simple carbon steels that are suitable for water quenching this martensite start point is 400F-450F.

 

So the goal will be to cool the steel in the water to where it will get down to about 500F in the water, then get it to hold there. I am not sure of the danger aspects of putting a wet clay coated blade in low temperature salts, but I don't think it would be very good, nor do I think putting a dripping wet blade into an electric kiln or oven set at 450F is a very good idea either. The method I have seen used was 400F oil, and while it also isn't a good idea to put water into such hot oil, it atleast won't explode in your face or shock you to death, it at most will just overflow some bubbling hot oil, I will leave the safety aspects of dealing with that to the individual, but I will say it can easily be dealt with with a catch pan or bucket or leaving some expansion room in the hot oil tank and leather gloves and an apron and full face shield and such are common sense.

 

This will give you your water/brine quench, then your equalization medium. You will quench into the water for your predetermined amount of time based on personal experience or just a 3 or 4 second count (or look at the TTT diagram, how long will it take to get to the martensite start point with a very fast medium like water/brine?) Then go into your 400F-450F equalization medium, then out to air cool (which gives the added benefit of a couple seconds to straighten any warp you probably got from quenching in the water, one of the BEST benefits of marquenching IMO). If all done correctly, You have successfully beaten the pearlite nose, if you are going for a hamon you have gotten some great amounts of activity from the water/brine as well as positive curvature, and don't have a blade that is much shorter than what you started with (or a hand full of pieces).

 

In simple forms, you use the water to get below the pearlite nose and just above the martensite start point, the oil to equalize the blade just above the martensite start point (where the cracking occurs), and then still ambient air to finish everything off nice and easy.

Edited by Sam Salvati
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  • 1 month later...

I find that tap water in my area (processed hard water from lake michigan) is BAD for 10xx steels. I have quenched 1095 in rain water with no problems, but similar size/shape 1095 blades with the same soak time/temp quenched in hard water all developed fatal cracks.

So far with 1075,1080,1095 and W1,W2, rain water with interrupted quench has been reliable. I've been holding them in the quench just until the color is gone (which is too long IMO), then put them back into the cooling HT furnace and hold them at around 450 degrees, let them cool with the furnace. Generally the HT furnace is still around 1500 degrees when I pull them from the quench, so I just pass them through a few times until it drops to 450.

This is kinda dumb, but I haven't set up another tank for heating oil yet. Sam's description is exactly what I'm shooting for. W2 is a little different, but the same theory applies, just slightly different temps.

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  • 4 weeks later...

Has anyone done water quenching in pre-heated water? Sub boiling? Is it possible that would help the issue?

 

What about adding a detergent to alter the vapor jacket formation?

 

Great discussion, by the way!

 

-Jim

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