Tube Magnetic Core in Solenoid Actuator

i am not sure which tube you mean, here is a typical trip solenoid used in an MCB. The magnetic parts are made usually from Silicon Steel, whose properties do not deteriorate in any measurable way over the lifetime of the product, say 10 years.

Is this anywhere near what you wanted to know?

I think he means tube & Magnetic core assembly in solenoids. Hmmm, I can think of the duty or mechanical wear.

There are a variety of fail safe and latching solenoid designs. The cores, plungers and guides are usually made low carbon steels to create a low reluctance magnetic path and good solenoid efficiency. They can be solid or hollowed out for mechanical or actuation (bounce) reasons as long as they do not become magnetically saturated (lose efficiency). Some often have an external tube to both protect the coil windings and provide a magnetic return path for maximum efficiency.

Other than some small residual magnetism induced, these parts do not magnetically degrade with time & use. Depending on the environment and the part's corrosion protection (plating, etc.) on the mating faces or sliding surfaces, the solenoid performance could degrade, or if severe could become inoperable.

If you have a specific structure you can show us, we can better answer your questions.