Pull strength is a very subjective measure that is dependent upon many factors such as: 1. Type of material being pulled against; 2. Surface conditions; 3. Physical contact; 4. Magnet characteristics such as plating composition; and 5. Presence or absence of lateral and rotational forces. All that being said, our 1 inch diameter by 1/8 inch thick plated Nd-Fe-B disc magnet will lift about 10lbs of ferrous steel under ideal conditions.
The grade of a magnet directly refers to the Maximum Energy Product of the material that composes the magnet. It in no way refers to the physical properties of the magnet. Simplistically, grade is generally used to describe how "strong" a permanent magnet material is. The energy product is specified in the units Gauss Oersted. One MGOe is 1,000,000 Gauss Oersted. A grade forty (N40) would have a Maximum Energy Product of 40 MGOe. The higher the grade the stronger the magnet.
Sintered Nd-Fe-B magnets will remain magnetized indefinitely. They experience a miniscule reduction in flux density over time. Generally the magnet will experience a degradation in its physical properties, such as corrosion, prior to it demagnetizing because of age. However, heat and high magnetic fields can demagnetize these magnets.
Yes, if you heat them beyond 170 degrees Fahrenheit (80 degrees Celsius) the magnets will quickly loose their magnetic properties. Sustaining these temperatures for a length of time or heating the magnet significantly higher than this will permanently demagnetize it. Other types of magnets such as Samarium-Cobalt have higher heat resistance. There are also other types of Nd-Fe-B magnets that are not as susceptible to heat induced flux degradation.
A magnetic field is generated when electric charge carriers such as electron move through space or within an electrical conductor. The geometric shapes of the magnetic flux lines produced by moving charge carriers (electric current) are similar to the shapes of the flux lines in an electrostatic field. But there are differences in the ways electrostatic and magnetic fields interact with the environment.
