Same composition, same hardness nut not the same machning !!!

[stanislasdz]

We two parts produced in steel casting wich have the same composition (GS20Mn6) and the same hardness, but one part can be machning and the other one can'not be maching !!

I don't kno why ?

Any help ?

Stan

 

[Yallapragada1022]

Can you give us more details about the processing on these castings? What is the hardness for these 2 castings? Have you looked at the microstructure to see if there are any differences? Sometimes microstructure can cause problems with machining the parts.

Rao Yallapragada

 

[arunmrao]

Most likely, one of the castings must have been weld repaired after heat treatment,hence you are encountering hard spots.Or the other casting has numerous slag inclusions on the surface which once again maakes machining difficult.

Please provide more details of the castings and the chemistry too alonwith heat treatment cycles.

 

[stanislasdz]

Thanks all !

1- For this time i have only the hardness of the part

229 à 241 HB for 204/242

2- I haver not yet investigate the microstructure !

3- Heat treatment is QT

4- There is 20 parts which can not be machniing all the part are OK ! These 20 parts are in the same pourring reference.

Thanks again

 

[arunmrao]

Why do you need to oil quench for this hardness levels. You might as well achieve by Normalizing and Tempering. However,you need to give more information to get a better response.

 

[stanislasdz]

it's sunday when i cam back to the foundry tomorow. i will givae you more details ...

Thanks arunmrao !