heat treatment

[Camillo60]

Hello everyone,

I have to make special chain crowns.

the goal is to minimize wear of the crown. precise that the chain rotates slowly and with very low loads (the positioning of a transducer results).

I have currently experimented with water tempered c45 with good results, however, I have found that the hardness is quite variable from point to point with values ranging from 63 to 52 hrc. post cooling distortion is also quite pronounced.

I was thinking of adopting a cementing steel but I have no experience with this treatment and before trying I wanted to ask if maybe
it can convent to try with a steel a little more noble than the c45 always for total hardening.

Any suggestions?

I discard the induction hardening of the teeth only because for various reasons I have to perform it myself and I am not equipped.

Thank you.
Camillus

 

[meccanicamg]

the induction tempering and maybe laser was ideal for c45.
for total hardening without cementing...which makes no sense...there are tool steels even if wasted or a 42crmo4 alloy or 39crnimo3 that do not cost much, they have more hardening of the c45.

 

[ceschi1959]

the crowns of the bikes are made of alloy of 7075, the carbo-cemented steel pinions.

 

[TECNOMODEL]

I understand you're gonna tempt it, so you're gonna get an oven and cold in a bowl, right?

That already limits you a lot. I would follow the advice of mechanicmg and use 39nicrmo3 by cooling it in oil and then making a temp.

to evaluate the deformation, especially if it is a big crown, it may be necessary to foresee a post-hard working

 

[Camillo60]

si, mould oven and cooling in container with water.

in the past I have performed the tempering in oil of some trees in 39nicrmo3 but the obtained hardness was quite poor, it seems to me around 48 hrc.

The crowns have gods. 120mm and average thickness of 10mm. after treatment I carry out grinding operation.

Camillus

 

[TECNOMODEL]

but did you get that hardness after the discovery?
if you have mistaken the finding, too high temperature or too long time.
otherwise you're wrong, probably for too low temperature.

 

[Camillo60]

It's been a while so I don't remember perfectly yet, certainly after the discovery.

How long should I expect from a 39nicrmo3?

 

[TECNOMODEL]

It is not that you expect a hardness, based on or what you want to get tempting calibers.
Now I do not have the hardening curves of that material, however when tempri you have the maximum hardness, with the tempering you get what you want.
the more time it stays at the tempting temperature and the more it will heat the hardness.

 

[320i S]

normally those who provide you with raw material, can also provide you with all data for treatments

 

[meccanicamg]

the hardness you get is above 56 hrc. look at the curves of the materials.

 

[Camillo60]

Okay, I'll prepare an audition, and I'll do a test following the manufacturer's data.

Thank you.

Camillus

 

[Camillo60]

Dear friends, after a long time I can say that the hardness obtained by components in 39nicrmo3 can be very variable according to the size and the means of shutting down.
Small pieces in oil and larger pieces in water provide hardness between 55 and 60hrc immediately after tempering.

 

[meccanicamg]

Dear friends, after a long time I can say that the hardness obtained by components in 39nicrmo3 can be very variable according to the size and the means of shutting down.
Small pieces in oil and larger pieces in water provide hardness between 55 and 60hrc immediately after tempering.

but above all the difference between small and large pieces is the depth of tempra.
on large pieces it tends to make induction tempra/laser turn off in water additivata....see gears.
small pieces make them all tempered in cassette and turned off in oil.