What is the relationship among surface magnetic field, remanence, and magnetic flux?
Surface magnetic field, remanence, and magnetic flux are three crucial indicators of the performance of magnetic steel. They are interrelated yet distinct from one another, and are sometimes easily confused. Today, we will discuss the similarities, differences, and mutual relationships among these three concepts.
The surface magnetic field refers to the magnetic induction intensity at a specific point on the surface of magnetic steel. It is the value measured when a gauss meter comes into contact with the magnet, with units in gauss or tesla. The surface magnetic field varies at different points on a magnet, typically exhibiting a characteristic of being lower at the center and higher at the edges. Therefore, the surface magnetic field does not fully represent the overall performance of the magnetic steel. For fields that require the use of spatial magnetic fields, the surface magnetic field at specified points is often considered an important technical requirement. The surface magnetic field is easier to measure than remanence and magnetic flux because gauss meters are relatively inexpensive and simple to operate. Consequently, many buyers of magnetic steel use the surface magnetic field as a performance parameter. Some buyers and users of magnetic steel may not know the specific grade of the magnet but only its maximum or minimum surface magnetic field. In such cases, the remanence can be calculated based on the shape, size, and surface magnetic field value of the magnet, thereby inferring the grade of the magnetic steel.
Remanence is the magnetic induction intensity retained within the magnet after it has been magnetized to saturation by an external magnetic field and the external magnetic field is then gradually reduced to zero. It is denoted by BR and also has units in gauss or tesla. Remanence is determined by the composition and crystal structure characteristics of the magnetic steel itself. For the same magnet under specific conditions, the remanence remains constant. Detecting remanence requires the use of a professional magnetic property detector, making it not easily measurable for users of magnetic steel. So, what is the relationship between remanence and the surface magnetic field? Generally, if two magnets have identical shapes and sizes, the one with higher remanence will also have a higher surface magnetic field. However, if the shapes and sizes differ, the surface magnetic field alone cannot be used to simply determine the magnitude of remanence; there is no direct correspondence between them.
Finally, let’s discuss magnetic flux. The magnetic flux through a plane can be vividly illustrated by the number of magnetic field lines passing through that plane. It is denoted by Φ and has units in webers (Wb). Magnetic flux is the product of the magnetic pole area and the magnetic induction intensity. Measuring magnetic flux requires the use of a flux meter in conjunction with a measuring coil. Unlike the single-point measurement of the surface magnetic field, magnetic flux measures the overall magnetic performance of the magnetic steel, making it a more accurate and reference-worthy performance indicator than the surface magnetic field. When the magnetic circuit of the magnet is closed, a flux meter can be used to measure the magnetic flux, and then the remanence can be calculated. This method yields more accurate results for calculating remanence than using the central surface magnetic field.
Among these three performance parameters—surface magnetic field, remanence, and magnetic flux—remanence is an inherent characteristic of the magnet material and is unaffected by its shape and size. In contrast, both the surface magnetic field and magnetic flux are measured for magnets of specific shapes and sizes. The surface magnetic field only reflects the magnetic performance at a single point on the magnet, while magnetic flux reflects the overall magnetic performance of the magnetic steel. If you have any further questions about the surface magnetic field, remanence, and magnetic flux, feel free to leave a comment and engage in discussions with us.
