In my work with electrical iron, I have done a lot of research to try to understand how to determine the quality of it. Is there a simple way to test for the saturation point? Some of the methods I read about involved very expensive BH curve tracers, and with some of them you were supposed to use a specific size and shape of a metal sample. I was hoping to take a stator or rotor and test the iron quality without destroying it.
Saturation in motors is very much influenced by the width of the air gap and the overall geometry of the design. You can run a saturation test and plot a magnetization curve, but it will be difficult to evaluate the quality of the lamination steel. As the motor becomes more fully saturated, the current increases more rapidly as the voltage increases, but there is not a very dramatic or sudden increase.
It might help if you could refine your question. The first part of the question is quite general, but the final sentence seems to describe a very specific situation that is focused on motors. If you are primarily interested in a specific motor problem, it might help to describe it in more detail. Why are you concerned about the quality of the iron rather than the overall performance of the motor? Depending on your situation, you may want to have a very small sample metallurgically analyzed.
The material saturation field strength (or B-H curve) will be much harder to test in an uncontrolled situation than the saturation current of the winding and core in situ.
If you can remove 1 gram or so of the material, it's possible to use a VSM (Vibrating Sample Magnetometer) to analyze the material characteristics. You would pay someone to do that- the machines are very expensive and fairly needy (requiring cryogens and such like).