I am working on a job right now (4340 hook) that I have to get Magnetic particle inspected after I get it heat treated. There are no surface cracks allowed anywhere on the forging. After the HT the part will be covered in scale which I have to remove for the test. Will shotblasting, sandblasting, power wirebrushing or hitting with a sanding disk cause any problems with the MPI. Appart from being careful not to get any shuts are there any problems I have to worry about forging this?

No experience on this, but something down inside me is saying stay away from the sanding disc? Shot blasting maybe?

For MPI almost any cleanup is O.K. Even sanding won't cause any magnetic anomalies, takes a surface (or deeper) fracture to show up.

what he / said...:)

Thanks I wanted to make sure before I did anything to mess this up. I really don't want to pay to test an extra one. Or make an extra forging for that matter.

my two cents.......

Having to deal with MPI, and Dye pen testing daily with structural steel welding, unless you have a good crack, a type of cold lapping, or any other "structural" anomaly, go ahead and clean it up. Since it is a hook, wire wheel (grinder wire wheel), bead/sand blast should do a very nice job cleaning.

Is this hook made from one piece with folding over forge weld in it? If it has a fold over I am surprised they did not say they wanted a NDT (x-ray) of the weld.

Good luck with it, it is easy to pass. See if they will give you a copy of the report, looks good for your work.