Hidden Quench cracks 3

[evan_z]

Has anyone ever heard of a quench crack that cannot be seen by wet mag? I am new to my company, and it has been said that these cracks occur after quench and temper, but can only be found if the surface is ground.

 

[mfgenggear]

it has been my experience if it is very fine sub surface cracks. but very very rare will not pick the indications, and it has more to do with the operators experience. NDT Inspectors., otherwise mag is very good. flo penetrant will pick up these types of cracks. it does not matter if it is ground or not. Mag will indicate cracks and/or indications if it is there.

 

[EdStainless]

It depends on surface condition, if the as HT surface is too rough (scale or texture) then it will be hard to find small indications. This is a signal to noise ratio issue.

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P.E. Metallurgy, Plymouth Tube

 

[Tmoose]

The method of magnetization can influence how well sub surface defects are revealed.

https://app.aws.org/itrends/2005/04/025/

Seems I was reading a MIL spec fairly recently that said something similar