Pearlite Banding Problem

[demsha]

Hi All,

We have found pearlite banding layer running across the parent plate below the weld. These plates are being used to manufacture caisson shoes. We understand that if, Manganese is too much it can segregated to weld and cause brittleness.

Does anyone knows an inspection method which filter out abnormal amounts of pearlite banding or abnormal volumes of inclusions which can have effect on material integrity? UT does not distinguish between the two.

Thanks in advance

 

[CoryPad]

Metallographic specimens, etched, with a competent evaluator at a microscope (preferably an inverted metallograph)

 

[mrfailure]

If you cannot do the destructive examination CoryPad suggests, you can make a surface replica of the base metal to do the same examination.

 

[demsha]

Thanks. But we cannot do destructive testing. will the surface replica method catch the pearlite banding (structural changes) 1 inch below the surface?
I don't think so. do you know any other inspection techniques?

 

[mrfailure]

The structure on the plate surface away from the weld should be the same as 1" below the weld. You should be able to find out through replication unless I am missing something.

 

[demsha]

As to my understanding replication method only good to find out metallurgical problems just below the surface.
However this pearlite banding thing occurs 0.5 - 0.75 in.below the surface of the base plate.

Thanks

 

[Ripz]

Replica provides surface conditions only, not even slightly below surface.

 

[Ripz]

If the density of the banding is different from the surrounding metal, you can try radiography.

 

[mrfailure]

I'm assuming you do not see banding due to a lot of decarb at the surface. However, you still can replicate the unetched structure to see inclusions - especially manganese sulfides. That seems to be the real question you are asking.