Now in one of my classes at college i have access to an oven that can heat treat a number of items (up to about the size of a stub shaft), now would it be of benefit to heat treat the stubs shafts, ujoints, and drive flanges? and maybe even the spindles?

 

Crunchy toasted outside while soft and moist in the middle. I've been doing this to my bread for years and it works wonders.



I'm no expert on this at all so I'll be curious to see what people in the know have to say. My theory is that you risk more trouble than anything in the cooling process. Make sure you butter while it's still warm.

 

Stubs are already heat treated. It wouldn't surprise me if the spindles weren't heat treated too.

 

Head on over to the science lab building and ask to see their Cryo Chamber!!

 

Thta'd be fun .

The stubs are not fully heat treated, just the first 1/4" or something (this is what my instructor thought they were). now the 4340 alloys and what not are fully heat treated, and that along with the chorium and moly alloy's are the only strenght additives to that type of axle, but i still don't know if i'd gain anything by heat treating the stubs and what not.

 

The center of the shaft is not heat treated for a reason. When heat-treated correctly, the metal becomes hard. This leads to problems if the shaft is through-hardened because the entire shaft becomes brittle. In fact, it becomes brittle to the point where it WILL NOT TWIST or even bend slightly making it impossible to use as an axleshaft. Any shock loading will kill a through-hardened shaft.

Another thing to consider is (like Ivan said) the cooling process. It's easier to control the cooling rate of the "first 1/4 inch" than the center of the shaft. Say the shaft is 1.31" diameter. That means that the center .81" of the shaft is left untreated. If this area were to be heated rapidly then expected to cool at the same rate as the outer 1/4"....it ain't happenin'. Most all of the characteristics engineered into heat treating metal is from the science involved in the cooling process. A minute makes a difference.


Cody

 

It all boils down to that heat treating is an exact science, and done improperly can actually leave the material weaker. Especially, if already heat treated, which your stubs should be. I'd just leave them alone.

 

From the few weeks of class in materials 232 that i've taken here's a quick bit of info (what i understand so far ), the idea of heat treating is to 1. reduce/enlarge grain size, the smaller the grain size the stronger and tougher (ie abilty to take a punch) the material is, but at higher temperatures the material tend to creep, the larger the grains the exact opposite is true 2. To reilive internal stresstes and regain a certian amount of ductility (there's more but i'm tired , but i'll list more tomorrow if i get on).

Now the biggest thing with heat treating is the cooling rate, the faster it cools the stronger it becomes, but to fast and it becomes brittel (ANY steel that has high strenght is brittle, period). All of this info applies to loads applied in compression/tension, but i'm not sure how well this works out with torisional forces tthough and thus this topic. But from what has all been said it appears that this wouldn't be worth it correct, but nonethe less its interesting.

 

Speaking of torsional forces, I thought that this might be interesting......

My dad used to work with a guy that moved up here from Iowa. He used to drag race on the cheap and had lots of experiences with axle shafts (don't get ahead of me here!!). He used the 9 inch axle exclusively for obvious reasons. Here's what he told me about what he learned:

As far as shock loading goes (on non-transbrake launches), the factory 28 spline shaft tended to last longer without breaking than the 31 spline models. Now I'm not sure what year shafts he was using, but I can see merit in this after telling you about the experiment he did with a few sets of axles. He used paint to make a straight line down each of the axle shafts. Then he'd make a few runs and wait until he had either breakage or until he thought he should change axleshafts. What he found amazed him. With the 31 spline shafts, the axle shaft would twist very slightly and then break off a few inches from the splines. With the 28 spline axles, the shaft would deform and twist nearly 1/4 of a turn without breaking.

I believe that the method (or depth) of the heat treat on the 28 spline axles was about right to maintain toughness and flexibility. Maybe it's just the smaller diameter of the shaft, who knows?

I know it's not really relevant, but it's some food for thought.

Cody

 

From what i can tell you about that is that the 28spline shafts probably had a lower carbon content (higher the carbon content the more bittle it becomes, IE cast iron is extremely brittle and has a carbon content of 2% or higher where as our axle are in the neighborhood of .4% carbon) than that of the 31spline shaft. But there is no difference in the diameter of the axle shafts other than at the splines, my guess is that they are heat treated different due to the fact that that a smalle spline count is used and thus a slighly smaller diameter, or maybe its the carbon content. Who knows, but tommorow i get to destroy stuff in my materials lab (shock loading )

 

Here we go.. this sounds like another grade 5 verses grade 8 posting war

 

No way dood!!! They each have their places.

All I posted was some food for thought. You can make your own assumptions from there.

I'm just the innocent bystander who gets caught in these fits of rage between all of you warmongers!!


Cody

 

you need to know the specific steel that you have in order to heat treat it for any purpose, just getting it hot usually doesn't help, it hurts
factory parts are hardened for specific requirements, like ends of axels for wear resistance in the spider gears and fully hardening would be expensive and difficult to control, not just to heat it, but the type and rate of quench and normalize
like was mentioned, you can make the parts too brittle for the application

 

On that note, anyone know what alloy a set of stock shafts on from a dana 60 front axle is? I was told 1541 and the 41 part is quite odd.