Crack in A485-1 ring during plug quenching 1

[HaranSR]

I am facing quench cracking during plug hardening of ring with oil quench (`40C).
Hardening temp at 830C. Ring is transfered to plugging press and quenched with oil.
Material is A485-1, ring dia is 250mm and thickness is 23mm.
Crack always in the same location of undercut. Any reasons / solution ?

 

[HaranSR]

What is the expected risk if we take out the parts from quench at 100C and do an air cooling?
Oil flash point is 175 C is there any risk of fire because if the part surface is at 100C then the core may be at higher temperature.
So after some time the surface temp may increase and if it reaches 175 C it may fire.
Is this can happen ? Also part dimension may distort to some level.
Any other reason for not recommending this concept.?
THanks

 

[Maui]

If you pull these parts from the oil prematurely and you are not below the martensite finish temperature then distortion is a very real concern. I do not know what your martensite finish (Mf) temperature is for this particular alloy, but I suspect that the Mf temperature is probably in the neighborhood of 200 to 250 degrees F. So if you pull it out of the oil at 100C, it may not be done transforming. And if it is too hot coming out of the oil, then other transformation products could precipitate. And this could result in hardness variations and lower than expected hardness readings. That would be bad. Very bad. I don't recommend it.

And yes, fire could also be a concern if you decide to do this.

Maui

 

[Maui]

Haran,

What were the results of your testing with the reduced oil flow rate? Did you implement any of the other recommendations?

Maui

 

[HaranSR]

Hi Maui,
Reducing the oil flow did not help, upon further reduction we are getting NMTP.
Undercut design change not possible. Will update you all after further trials.
Thanks for all your ideas.

 

[Maui]

Haran, if you free quench these parts in an open oil tank and don't use your quenching machine, do they still crack?

Maui

 

[HaranSR]

No it does not crack.
In quench press with out die only with quenching also it cracks.

 

[mfgenggear]

Hi HaranSR

Look at the pressure of outer expander and if used, the inner expander of the press.
lower all pressure to the minimum.

what is the size of the id of the part and what is od of the plug quench. what is the diffrence in size.

also very little information on the heat treat cycle and temp's. is the oil slow or medium quench.
when ruff turning these parts is it possible to do a stress relief. or can this steel be normalize.
I could not find any data sheets on this stuff, if any one can supply that it would help.
what is the heat treat procedure, or what heat treat specification.

the press outer expander plate may be cracking the parts do to the configuration of the part.
pressing with to much pressure. with parts like this I want my supplier to use slow acting oil with the
highest oil temperture possible. as to not crack parts. if permissible.
so the term mar quench or martemper. but not as high.