Benefits of cryogenic freezing?
10-07-2002, 03:26 AM
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Benefits of cryogenic freezing?
Was reading through Lindsey's site and saw the cryo process they offer. What would be the benefits of freezing the head or block, I know rotors are more resiliant to heat and stress, does the same apply to the head, etc.? Anyone ever have it done?
10-07-2002, 11:06 AM
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walt disney is rumored to currently be in cryogenic suspension, as soon as they come up w/ a cure for death they'll thaw him out......oooohhh you meant engine parts heheheh.
10-07-2002, 12:06 PM
#3
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There was an article in Machine Design on Cryogenic stress relieve a few years ago. Machine Design is an Engineering Magazine that I used to get a few years ago. I have not use them or had any direct experience with those who had. I wrote this to a friend to provide a little theory on why it *might* work. I am a Mechanical Engineer, but I do not have any hard data. Read on if you have time as this is LONG! Maybe some you college guys can as your friendly Material Engineering Prof. about this idea and see what he says..
I am using drilled rotors now on my race car. No cracks yet, but they are known to crack, but also considered highy by many experinced racers and he Porsche factory.
BTW I think they (drilled or frozen) only make a difference on the track.
(Warning Long technical explaination.. head may hurt while reading )
The basic chemistry behind cryo rotors makes sense. On the basic goals in heat treatment of steels ,particularly tool steels, is to adjust the material properties to endure high loads, temperatures, abrasion and be both hard and tough (basically all properties rotors need also).
The processes in heat treatment typically involve Normalizing, Annealing, Austenitizing, Quenching, and Tempering. The cryogenic treatment is basically a form of tempering. The most important phases of heat treating are Austenitizing, Quenching, and Tempering.
Austenitizing is a process of elevating the material temperatures above 1450 F for most tool steels. This heating causes a transformation in the crystal lattice structure of the material to a form known as austenite. Quenching is a process by which the material is rapidly cooled from the austenitizing temperature by water, oil or air baths. The goal of this procedure to from a different lattice structure called martensite. This structure is much harder and in general more desirable that austenite however in as-quenched form can be quite brittle.
Tempering is used to revise the properties of quenched material to a more desirable mix. A result from the quenching process is that not all of the austenite has been transformed to martensite. Tempering is process by which the material is heated ,slowly this time, once again to 300F to 800F depending on the alloy and then left a temperature for a given time of typically at least 1 hour. The material is then cooled slowly. This procedure transforms the remaining austenite to martensite and can adjust the properties of the martensite to be less brittle and tougher at the expense of some hardness. It is not uncommon to double or triple temper certain steels to achieve a specific quality. The key to tempering is the slow rates of heating and cooling. This allows the crystal lattice structure to slowly adjust itself and provide the desired properties.
The cryogenic treatments are fairly new to the field of heat treatments and not much is know about them yet. I do not believe the process is a magic show intended to charge people more money for something does not work. There is a scientific basis for this and clearly there are many people, outside the brake rotor industry, that are excited about it’s potential.
My theory about why it works as follows. The controlled cooling does two things. First the minimal differential change in temperature across the part will cause natural waves of contraction during cooling and expansion during heating in the grain structure of the part allowing the residual stresses to flow though the part and be dissipated. Thus a significant portion of residual stresses from the more aggressive such as quenching, initial casting or cold working can be reduced thus increasing the fatigue life of the part. This is similar to the effect of the more common elevate temperature stress relieve, but without the risk of causing distortion in the part. Second the cooling also provides and additional tempering phase that generates more martensite in the part which generates a slightly harder surface that although more brittle, has better wear resistance. I believe the effect of the stress relieve counter acts the added brittleness to form and overall net positive in toughness.
It seems to me that since people willing to apply it to $100,000 tooling to increase their life that the results must be positive. It seems well worth the risk to apply it to a $250 brake rotor.
I am using drilled rotors now on my race car. No cracks yet, but they are known to crack, but also considered highy by many experinced racers and he Porsche factory.
BTW I think they (drilled or frozen) only make a difference on the track.
(Warning Long technical explaination.. head may hurt while reading )
The basic chemistry behind cryo rotors makes sense. On the basic goals in heat treatment of steels ,particularly tool steels, is to adjust the material properties to endure high loads, temperatures, abrasion and be both hard and tough (basically all properties rotors need also).
The processes in heat treatment typically involve Normalizing, Annealing, Austenitizing, Quenching, and Tempering. The cryogenic treatment is basically a form of tempering. The most important phases of heat treating are Austenitizing, Quenching, and Tempering.
Austenitizing is a process of elevating the material temperatures above 1450 F for most tool steels. This heating causes a transformation in the crystal lattice structure of the material to a form known as austenite. Quenching is a process by which the material is rapidly cooled from the austenitizing temperature by water, oil or air baths. The goal of this procedure to from a different lattice structure called martensite. This structure is much harder and in general more desirable that austenite however in as-quenched form can be quite brittle.
Tempering is used to revise the properties of quenched material to a more desirable mix. A result from the quenching process is that not all of the austenite has been transformed to martensite. Tempering is process by which the material is heated ,slowly this time, once again to 300F to 800F depending on the alloy and then left a temperature for a given time of typically at least 1 hour. The material is then cooled slowly. This procedure transforms the remaining austenite to martensite and can adjust the properties of the martensite to be less brittle and tougher at the expense of some hardness. It is not uncommon to double or triple temper certain steels to achieve a specific quality. The key to tempering is the slow rates of heating and cooling. This allows the crystal lattice structure to slowly adjust itself and provide the desired properties.
The cryogenic treatments are fairly new to the field of heat treatments and not much is know about them yet. I do not believe the process is a magic show intended to charge people more money for something does not work. There is a scientific basis for this and clearly there are many people, outside the brake rotor industry, that are excited about it’s potential.
My theory about why it works as follows. The controlled cooling does two things. First the minimal differential change in temperature across the part will cause natural waves of contraction during cooling and expansion during heating in the grain structure of the part allowing the residual stresses to flow though the part and be dissipated. Thus a significant portion of residual stresses from the more aggressive such as quenching, initial casting or cold working can be reduced thus increasing the fatigue life of the part. This is similar to the effect of the more common elevate temperature stress relieve, but without the risk of causing distortion in the part. Second the cooling also provides and additional tempering phase that generates more martensite in the part which generates a slightly harder surface that although more brittle, has better wear resistance. I believe the effect of the stress relieve counter acts the added brittleness to form and overall net positive in toughness.
It seems to me that since people willing to apply it to $100,000 tooling to increase their life that the results must be positive. It seems well worth the risk to apply it to a $250 brake rotor.
10-07-2002, 12:25 PM
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OUCH.. Yep, you did make my head hurt. The only flaw I see in your logic is the last sentence, about the "$250 brake rotor". I've found rotors for my 89 Turbo for UNDER $100. It is one of the few relatively CHEAP parts on our cars. Since the cryo process costs that much, (or more with shipping) Unless you are enduro racing, it's easier to just have a spare set.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
10-07-2002, 12:33 PM
#5
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[quote]Originally posted by Dan P:
<strong>OUCH.. Yep, you did make my head hurt. The only flaw I see in your logic is the last sentence, about the "$250 brake rotor". I've found rotors for my 89 Turbo for UNDER $100. It is one of the few relatively CHEAP parts on our cars. Since the cryo process costs that much, (or more with shipping) Unless you are enduro racing, it's easier to just have a spare set.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> </strong><hr></blockquote>
My $250 was directed toward 911 guy figuring the cost of process as well.
It is really hard for me to know how well it works, just that it should work. It is kind of like strut tower braces... In theory they work, but do they make a difference on the track. Can't really say.
<strong>OUCH.. Yep, you did make my head hurt. The only flaw I see in your logic is the last sentence, about the "$250 brake rotor". I've found rotors for my 89 Turbo for UNDER $100. It is one of the few relatively CHEAP parts on our cars. Since the cryo process costs that much, (or more with shipping) Unless you are enduro racing, it's easier to just have a spare set.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> </strong><hr></blockquote>
My $250 was directed toward 911 guy figuring the cost of process as well.
It is really hard for me to know how well it works, just that it should work. It is kind of like strut tower braces... In theory they work, but do they make a difference on the track. Can't really say.
10-07-2002, 03:05 PM
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Your rotors ordered directly from Porsche will not need cryogenic tempering. They are are already built/treated/engineered to higher standards. Its your "OEM" cheap as you can find them rotors made in Japan that will need the cryo treatment in order to last and perform longer/better.
This is something a mechanic of mine (who also builds and races 911's in a major circuit) once told me when I asked about cryo treatment.
This is something a mechanic of mine (who also builds and races 911's in a major circuit) once told me when I asked about cryo treatment.
10-07-2002, 05:23 PM
#7
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So I take it cryo-treating aluminum won't have the same effect as steel? Although by going with a 7000-series aluminum to begin with, you'll have twice the strength as 6000-series anyway...
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10-07-2002, 05:34 PM
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Have seen some stuff on Cryogenic treating of steel. However, the important thing is that it is usually simple shapes (Like rotors). Since they are super cooled (liquid Nitrogen) there is a fair amount of contraction, and complex shapes (like a head or block) could esperience stress fractures. Not to mention uneven cooling as a result of spaces inside not getting cooled right away like the water jacket. Don't think it would be a good thing for parts like that, and pretty sure it would be very bad for Aluminum. But might be good for Pistons and cylinder sleeves made of steel. Definitely would be good for valves and the like.
Another cool (hehehe) feature of this process is that big honking solid bars treated this way ring like a bell.
Another cool (hehehe) feature of this process is that big honking solid bars treated this way ring like a bell.
10-07-2002, 06:35 PM
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I thought that several alum alloys were aged through the use of cyro treatment thereby changing their properties. I checked with a couple of folks who work on such things and pretty much their input is that it sounds like a great sales ploy. Changes during heat treatment and though the transtion phase from austenite to martensite cant really be duplicated with a bucket of liquid nitrogen. It all comes down to who is doing it and how it is contolled and the alloy you are using since many alloys will receive no benefit at all from the treatment. Not claiming to be an expert or knowing aything at all, just my $.02
10-07-2002, 06:57 PM
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Ok, this cryo process is form of heat treatments. I do not know much other than there are theoritical benefits from cyro temeperature heat treatments seen in some industries. That said like all heat treatments it is not a simple as heat & cool or cool then heat. It is relativly simple procress, but does require precise temperature conrtols to get the heating cooling to the proper temperatures. It mostly the rate of change of these temperatures that causes the effects that are desireable. Just because you dunk a rotor or a head in liquid nitrogen does not mean that is has been done right.
My only point is the there appears to be physical basis for cyro treatments on metals. Also there companies doing this to very expensive tooling so it is not all smoke and mirros. That is not to say company XYZ does it right, but it appears that they could and would have some benefits here.
Heck at my company (large Aerospace firm) on the common operations all aluminum and magnesuim castings when through was the "subharmonic stress relieve". This was basicly a fancy very of the coil operated vibro beds in cheap motels. Did it work? Not sure... Nobody knows.. But we still do it cause its cheap, it "might" work, and we are afraid to find out it foes not.
BTW... Danno Aluminium can also be heat treated. That is what the "T6" at the end of 6061-T6 Aluminium. Also 6000 & 7000 series are typically forged materials and 300 series are cast.
My only point is the there appears to be physical basis for cyro treatments on metals. Also there companies doing this to very expensive tooling so it is not all smoke and mirros. That is not to say company XYZ does it right, but it appears that they could and would have some benefits here.
Heck at my company (large Aerospace firm) on the common operations all aluminum and magnesuim castings when through was the "subharmonic stress relieve". This was basicly a fancy very of the coil operated vibro beds in cheap motels. Did it work? Not sure... Nobody knows.. But we still do it cause its cheap, it "might" work, and we are afraid to find out it foes not.
BTW... Danno Aluminium can also be heat treated. That is what the "T6" at the end of 6061-T6 Aluminium. Also 6000 & 7000 series are typically forged materials and 300 series are cast.
10-07-2002, 07:27 PM
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Yes, I know that alluminum can be heat-treated, but I was mainly referring to cryo-freezing of aluminum.
Isn't T6 a solution heat-treatment? When I was building bike-frames, we'd do post-weld heat-treatment of 6061-T6 up to just under the melting point.. Some of the frames ended with tubing that had a slight sag...
Isn't T6 a solution heat-treatment? When I was building bike-frames, we'd do post-weld heat-treatment of 6061-T6 up to just under the melting point.. Some of the frames ended with tubing that had a slight sag...
10-07-2002, 07:42 PM
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[quote]Originally posted by Danno:
<strong>Yes, I know that alluminum can be heat-treated, but I was mainly referring to cryo-freezing of aluminum.
Isn't T6 a solution heat-treatment? When I was building bike-frames, we'd do post-weld heat-treatment of 6061-T6 up to just under the melting point.. Some of the frames ended with tubing that had a slight sag...</strong><hr></blockquote>
I don't have by specs in front of me, but I T6 is more of a temper than a solution heat treat. Solution heat treats are use to normalize the material (Stress relieve)by slow heating to high temps After this process they usally require a temper which involves the controlled rate cooling to achieve certain hardness. Typicall Solution heat treats are very ductile, but low strength. A T6 will have a higher strength, but less ductility (ie more brittle). This is where material property "tuning" takes place.
As for welding. You typicall want to do post weld heat treat to improve the strength of the weld be reducing the residual stress. The localized heating will cause residual stress that can be elimnated through a solution & temper heat treatment. Distortion is an issue with all heat treatment process so final maching is always done after heat treatments. I also think the this one of the stated benefits of the cryo process. Less distorion and still some benefit of stress relief.
<strong>Yes, I know that alluminum can be heat-treated, but I was mainly referring to cryo-freezing of aluminum.
Isn't T6 a solution heat-treatment? When I was building bike-frames, we'd do post-weld heat-treatment of 6061-T6 up to just under the melting point.. Some of the frames ended with tubing that had a slight sag...</strong><hr></blockquote>
I don't have by specs in front of me, but I T6 is more of a temper than a solution heat treat. Solution heat treats are use to normalize the material (Stress relieve)by slow heating to high temps After this process they usally require a temper which involves the controlled rate cooling to achieve certain hardness. Typicall Solution heat treats are very ductile, but low strength. A T6 will have a higher strength, but less ductility (ie more brittle). This is where material property "tuning" takes place.
As for welding. You typicall want to do post weld heat treat to improve the strength of the weld be reducing the residual stress. The localized heating will cause residual stress that can be elimnated through a solution & temper heat treatment. Distortion is an issue with all heat treatment process so final maching is always done after heat treatments. I also think the this one of the stated benefits of the cryo process. Less distorion and still some benefit of stress relief.
