9310 carb 1

[Turda]

Hi, I realy have hard time to obtain a surface hardness of 60-61 HRC on 9310 carburised steel.Finaly I've found a way to get less retained austenite (>15%) but surprise.....58 HRC only. Any ideas way?

9310 FUN

 

[arunmrao]

Should it not be <15% instead of >15% retained austenite.
Clarificaton please!

 

[Turda]

On my first trials I obtained more than 30 % retained austenite. I need 0.6 mm effective case depth and 60-61 on surface. I dont have deep freeze option to transform the retained austenite and eventualy gain 1-2 HRC. THX

 

[Goahead]

Do you quench from carburizing temperature?
Better results may be obtained by queching from lower temperature after reheating. Double tempering might help.

http://www.welding-advisers.com/

 

[Turda]

Carburizing 1600 F 0.9 carbon ....difuzion 1.5 hrs .8 carb and quench from 1500. tis is the recipe with less retained austenite. THX

 

[Carburize]

Without a deep freeze option you are always going to have a hardness problem. For a sample of 9310 with a chemistry in the middle of the specification range at a case carbon of 0.8% the martensite transformation will not be even theorotically complete until the case is cooled to below minus 20C. If the batch of material runs at the high side of the specification range it will be even lower.
If sub zero treatment is really not possible you could try to run a lower carbon potential and aim for a case carbon of 0.6% which has a higher martensite finish temperature and hence less retained austenite.

 

[Flesh]

From Hodge and Orehoski's work, you will need at least 90% martenstite at a carbon content of 0.80%C to obtain a minimum of 60 HRC.