physical deformation

[alpha970]

Hello,

During annealing of rolled metal rings at around 840 c , I have a problem that some rings show intens physical deformation! I could use some tips of how to go about this!

thanks

 

[unclesyd]

Comeback with a little more information like the material, sizes and the full details of your current annealing process.

 

[alpha970]

more info :

product : rings of low carb/ high nickle-cobalt steel
dia around 40 cm / thickness below 0.3 mm / by cold rolling made.

process : warm up to 250 then to 840 under (N+H gasses)
annealing time about 8 minutes.

thanks

 

[metman]

Are sure it is rolled? 0.3 mm is quite fine wire which would normally be drawn but maybe the cross section is not round. In any case it would probably be welded and that would leave residual stresses that could be causing the distortion.

You might try loading the ring by adding a weight of a flat piece of heat resistant material (309/310 S.S.?) about 8-10mm thick and hold the time at annealing temperature to 16 minutes. If that works, you could incrementally reduce the time to determine minimum required annealing time.

 

[alpha970]

Hi metman, thanks for the tips
Let me finetune the description a bit more.

rings have a width of around 10mm.

Actually we have made these rings by cold rolling so per difinition they contain lots of internal stress. and the purpose of annealing is partially to get them stress free, but the side effect of intense deformation comes and goes.

To get the rolling process under control is not feasible, so in reality I am trying to find the best parameters of the oven to get the least amount of deformation.

The oven is conveyor type, so the rings get in on one side and get out on the other side.

Should I try gradual temerature rise or a sudden rise? increase or decrease speed? and so on.

thanks

 

[metman]

I would try slowing the conveyor speed to give a more gradual ramp up and ramp down of temperature and this will also increase time at temperature all of which should tend to decrease distortion.

Can you weight the rings as suggested? You might need to coat the weights with stop-off or use fiberfrax in between the part and weight to prevent sticking of weight ot part.