Everyone has read articles on Cyrogentic teating how it releaves dislocations in the metal's latice structure. However, several of these articles are written by cryotreatment companies. They recomend that every metal part should be cryo treated including pistons and rotors. However, here is where my question comes in

I am an early materials engineering student. I have not taken any hard core classes yet, however, I have taken alot of intro to material classes and have a good amount of background information on hardening processes.

For steel, the goal for cryotreatment is to convert austinic steel into martinsite steel. Martinsite steel is an extremely hard steel, however, with when hardness increases, brittleness increases aswell. Typically, Martinsite is formed by heating austinic steel to elevated tempatures (over 700 degrees) and then quickly cooled to room tempature (quenching in water is one way) Bring the metal to even lower tempatures (cryo treatment) causes remaining austinic steel to convert to martinsite. This rapid cooling causes internal stresses inside the metals microstructure. Martinsite by itself is a worthless material because of how brittle it is. However, when martinsite is heated up again to elevated tempatures again, but this time, slowly cooled, the grain structure become substantually finer and the ductility and toughness increases dramitically, however hardness is slightly lowered.


The problem is, when the metal is brough back up to 723*c or 1333*f, tempered martinsite will change go back into the austinite region reversion the tempering process. In high performance brakes, I could see the tempature being high enough to reverse this process making the cyro treatment a marketing gemic for rotors.


For aluminum, when heated to high tempatures (those seen inside engines) the aluminum's grain structure grows into larger grains in a process called annealing. This is where I see cyro treating being more of a marketing ploy vs a true solution. Normal engine tempatures (as in combustion cylinder) are large enough to cause annealing to occur and when this occurs, I would see the effects of cryo treatment being reversed for parts like pistons and valve heads.

Are there any people in here with material engineering backgrounds that could give some insight on these topics.

**Quick Edit. I left all my material books at my house up at school so most of this info is primarly coming from past knowledge. If anything is wrong, it is because my last really indepth materials class was in the fall semester so its been a while.





Modified by asmallsol at 12:48 PM 5/22/2006

 

While everything you say is valid, brake rotors are made out of cast gray iron rather than steel.

Component Wt. %
C 3.1 - 3.4
Fe 94
Mn 0.6 - 0.9
P 0.1
S 0.15
Si 1.9 - 2.3

 

I couldn't see this application working outside of a strict controlled process. Where the cryo treatment was used in millisecond bursts. Maybe just to reduce the cooling time down a couple of minutes. It has always been my understanding that the water, and or oil bath method was the preferred choice of metal workers. Of course, I've only been around artisan and cutlery manufactures so, my knowledge is very limited. Sorry.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ED609 &raquo;</TD></TR><TR><TD CLASS="quote">I couldn't see this application working outside of a strict controlled process. Where the cryo treatment was used in millisecond bursts. Maybe just to reduce the cooling time down a couple of minutes. It has always been my understanding that the water, and or oil bath method was the preferred choice of metal workers. Of course, I've only been around artisan and cutlery manufactures so, my knowledge is very limited. Sorry.</TD></TR></TABLE>

When cryo treatment first started, basicly they dipped parts into liquid nitrogen. The problem with this was the sudden change in 300*F tempatures would cause thermal shock which could result rapid internal shrinkages that would can cause fracturing to occur.

Modern cryotreatment takes alot longer. As I was reading on diffrent cryotreating places, they take around 12+hours (if not longer) to slowly cool the peice down to the extreme tempature, then around 12 hours to treat, then another 12+ hours to slowly bring it back to room tempatures.

High end Cutlery actually uses a large amounts of hardening and other material processing.

But as I said, its not really a question of cryo treating in some applications (Cutlery expessially) however, in automotive uses, things like brakes and pistons seems like a gemic and nothing else.

 

You know? You could write a pretty lengthy paper on this topic. If I were you, I'd call up some older engine block manufactueres(DART for instance) and, get they're professional opinions of this technique. I'd be surprised if any of them used it. A big leap like that in metalurgy wouldn't go unnoticed by aftermarket engine builders. But, in my opinion, sounds to expensive. Especially, since steel isn't as utilized as it once was in automotive manufacturing.

 

From what I understand ,annealing in aluminum engines,is prevented by sleeving the block. But, I could be mistaken.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ED609 &raquo;</TD></TR><TR><TD CLASS="quote">From what I understand ,annealing in aluminum engines,is prevented by sleeving the block. But, I could be mistaken.</TD></TR></TABLE>

I think he was talking about the pistons, but I believe they are heat treated. I really don't know thouth, this is what happens when you ask an EE about materials

 

:shudder:

Phase diagrams... thought i'd never see one of those again.

&lt;-- slams door and runs away

RJ - holds a materials science minor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nfn15037 &raquo;</TD></TR><TR><TD CLASS="quote">

I think he was talking about the pistons, but I believe they are heat treated. I really don't know thouth, this is what happens when you ask an EE about materials </TD></TR></TABLE>He may have been talking about pistons but, he mentioned annealing in engines. I thought engine designers use the sleeves in the block to withstand warping among other benefits. I know I've seen pistons and valves advertised as heat treated,and "hardened" but, never seen a box that said cryo treated on it.

 

What's an EE?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ED609 &raquo;</TD></TR><TR><TD CLASS="quote">He may have been talking about pistons but, he mentioned annealing in engines. I thought engine designers use the sleeves in the block to withstand warping among other benefits.</TD></TR></TABLE>

What about aluminum cylinder heads? The chamber is exposed directly to combustion and they work fine. Also, many engine manufacurers use aluminum blocks without sleeves (ala H22 w/FRM sleeves, Alusil and Nikasil are a couple others).

I think the main scope of this thread was to discuss the cryo treating of brake rotors, which are really being pushed by people like Frozen rotors. Personally, I have never found the need for anything besided good 'ole Brembo blanks or Autozone specials.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nfn15037 &raquo;</TD></TR><TR><TD CLASS="quote">Personally, I have never found the need for anything besided good 'ole Brembo blanks or Autozone specials.</TD></TR></TABLE>

Then you're not going fast enough.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by backpurge &raquo;</TD></TR><TR><TD CLASS="quote">

Then you're not going fast enough </TD></TR></TABLE>

The less you use the brakes, the faster you go. $13 autozone blanks for me on my racecar.

 

On a slower car that needs momentum, that would be true. But on a real "racecar" better brakes allow you to brake into a corner much deeper than with crappy brakes, allowing you to carry more speed overall.

 

im sticking with my brembo blanks :D

 

please remove that terrible phase diagram... no more school... no more material science!!! I have terrible nightmares of polishing material samples for hours trying to get a decent grain structure picture...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by backpurge &raquo;</TD></TR><TR><TD CLASS="quote">But on a real "racecar" better brakes allow you to brake into a corner much deeper than with crappy brakes, allowing you to carry more speed overall.</TD></TR></TABLE>

All cars are momentum cars - Braking deeper by itself doesnt lend create higher cornering speed - if you brake 10 feet later you might gain .01s/lap, if you accelerate 10 feet earlier you can gain .1s/lap.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ED609 &raquo;</TD></TR><TR><TD CLASS="quote">What's an EE? </TD></TR></TABLE>
What's a ME? (more suited to this post = material and mechanical)
What's a CE?
What's a IE?
What's a AE?
What's a GE?
What's a NE?
What's a RE?
etc....

What's a PE?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nate &raquo;</TD></TR><TR><TD CLASS="quote">please remove that terrible phase diagram... no more school... no more material science!!! I have terrible nightmares of polishing material samples for hours trying to get a decent grain structure picture... </TD></TR></TABLE>

lol, fun times....

 

At my work we use SEM & TEM imaging for that ****.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">All cars are momentum cars - Braking deeper by itself doesnt lend create higher cornering speed - if you brake 10 feet later you might gain .01s/lap, if you accelerate 10 feet earlier you can gain .1s/lap.</TD></TR></TABLE>

To a certain extent. Say around a certain corner, maximum speed your car is capable of cornering is 80 mph, on a lower hp car a driver usually uses the brakes less because they have to decelerate less to obtain 80 mph. Whereas a high hp car is going to be on the brakes hard to slow down to 80 mph, therefore needing better brakes than the slow car.

So all I'm saying is that a 'racecar' that uses Autozone rotors is probably not really a 'racecar'. At a certain point, yeah, any car in a race is a 'racecar', but people start bullshitting themselves at some point. A stock Civic or Ford Festiva in a race isn't a 'racecar' IMO.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by backpurge &raquo;</TD></TR><TR><TD CLASS="quote">So all I'm saying is that a 'racecar' that uses Autozone rotors is probably not really a 'racecar'. </TD></TR></TABLE>
Don't tell that to over 1/2 of the H-C H2 field.

 

Sometimes the truth hurts.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">
$13 autozone blanks for me on my racecar.</TD></TR></TABLE>


RJ doesn't drive fast enough to have more expensive brakes

The faster you go, the more expensive things get.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by backpurge &raquo;</TD></TR><TR><TD CLASS="quote">To a certain extent. Say around a certain corner, maximum speed your car is capable of cornering is 80 mph, on a lower hp car a driver usually uses the brakes less because they have to decelerate less to obtain 80 mph. Whereas a high hp car is going to be on the brakes hard to slow down to 80 mph, therefore needing better brakes than the slow car.

So all I'm saying is that a 'racecar' that uses Autozone rotors is probably not really a 'racecar'. At a certain point, yeah, any car in a race is a 'racecar', but people start bullshitting themselves at some point. A stock Civic or Ford Festiva in a race isn't a 'racecar' IMO. </TD></TR></TABLE>

So by that logic most any IT, HC, and lots of Showrooms tock cars aren't racecars? By 'racecar' I mean a vehicle that has all the modifications (safety or otherwise) that make it suitable for wheel-to-wheel racing. Whether or not you consider something a 'race car' or not is pretty much irrelevant to this discussion and any other IMHO.

So, does anyone have any insightful comments actually regarding the topic at hand (cryo treated rotors for those of you who forgot)?