ultrasonic testing of free cutting steels

In principle any discontinuity could interfere/reflect the ultrasonic wave.

But in your case, the size of manganese sulphide/selenide or any other component different from steel structure which is expressly formed to improve the machinability wouldn't have to affect the results of ultrasonic examinations: the size is usually smaller than the normal acceptance standards maximum flaw size.

Which is your acceptance level? or standard reference flaws (slots, holes...) Or do you use the DGS method for estimating the flaw size?

Anyway if you use the lower admissible frequency the possibility of reject an item because normal expected MnS inclusions should be minimum.

Kind regards

Dear Kwetz,

Thanks for the inputs. It has really helped me in coming to a good solution for the problem.

Regards,

Swapna

Guest, i defer to the expertise of the NDT professionals who have posted. In my experience as a producer of these steels I would offer the following:

1) we don't test for cracks with ultrasonics. Ultrasonics are for internals (innies). Externals Such as cracks, seams, and laps we would try to find using eddy current methods, not Ut.

2) we did not do ultrasonics testing on free machining steels.

3) UT testing was performed on clean steels for exacting applications, Not inclusion laden resulfurized materials.

4) Our policy was that ut inspection of resulfurized free machining steels was technologically inappropriate.

my two cents,

milo