Test for Casting Cleanliness

This is an intersting question. All along cleanliness of steel referred to micr and macro inclusions observed in steel castings. what is the application for such casting? Is it machined surface or as cast?

The surfaces in some areas of the casting are used in the as-cast condition. The parts go into a super-clean application "outside of the earths atmosphere" and the end user is concerned about the introduction of contamination trapped in the unmachined surface.

Sorry my experience stops at food grade castings. Experts in this forum must be able to help. When a super clean environment is demanded why do you need to retain as cast surface. Remove it by machining or electro chemical means. It might reduce the risk of contamination.

Different metals may use different methods to determine their cleanliness. If it is an on-line measurement, the techniques used for metals with low melting points (such as light metals AL, Mg) may fail in molten iron or steel. The following methods are used:

1) inclusion count with the help of a microscope (solid sample)
2) detection of inclusions in the molten metal with a) ultrasound, b) electrical resistivity, or other refractory filter based filtration methods,
3) chemical analysis of inclusion forming elements.
etc.

Sorry I should have made my question clearer - the issue is not one of micro or macro cleanliness of the metal of the casting but the amount of material such as cleaning compounds trapped in the surface.

I guess I'd start with an ultrasonic wash with water then use a vacuum filter set up and a series of ever finer filter papers. This is all readily available from a supply house.

We do this as a rough check in the lab. Basically we stop filtering when the last paper doesn't show anything. E.G. do a 25 micron, 10 micron. 5 micron and if the 5 is clean then stop. If the 5 is dirty then go on to a 2.5 and so on.

You can also measure flow through a filter paper. As the paper gathers crud the flow slows down.

If we are serious we use an outside lab and they have a laser counter. Try the yellow pages and tell them what you want to do.

Tom