Ferrite magnets are widely used in a range of applications due to their cost-effectiveness, corrosion resistance, and stable magnetic properties under various environmental conditions. Among the various shapes, the square-shaped ferrite magnet is particularly favored for use in sensors, motors, speakers, and various electromagnetic devices due to its simple geometry and ease of integration. However, the manufacturing of ferrite square shape magnets involves a series of well-considered processes. Each step must be carefully selected and controlled to ensure consistent magnetic performance, mechanical strength, and dimensional precision.

The production of ferrite magnets typically begins with the selection of raw materials. The common type of ferrite used for square magnets is hard ferrite, particularly strontium ferrite (SrFe₁₂O₁₉) or barium ferrite (BaFe₁₂O₁₉), which exhibit good magnetic properties and resistance to demagnetization.

Material Mixing: Iron oxide (Fe₂O₃) is mixed with either strontium carbonate (SrCO₃) or barium carbonate (BaCO₃) in specific ratios. Additional additives may be included to improve sintering behavior or magnetic properties.

Pre-calcination: The mixed powders undergo calcination at around 1000°C to form the ferrite phase. This step helps initiate the formation of the desired hexagonal crystal structure, which is essential for strong magnetic characteristics.

Consideration: Proper control of the composition and homogeneity of raw materials directly influences the magnetic performance of the final product.

After calcination, the resulting ferrite material is coarse and must be further processed.

Ball Milling: The calcined material is milled to reduce particle size to the micrometer or sub-micrometer range. Finer particle size enhances sintering efficiency and final magnet density.

Binder Addition: A temporary binder, often a type of organic polymer, is added to aid in pressing and shape retention.

Granulation: The powder may be granulated to achieve uniform particle distribution, which helps in achieving consistent press density during the forming stage.

Consideration: The fineness of the powder affects both the mechanical strength and the magnetic flux density of the square magnet.

Forming is one of the critical steps in shaping the ferrite magnet into a square.

Dry Pressing: For square shapes with flat surfaces and uniform thickness, uniaxial dry pressing is a suitable method. A steel or carbide die is used to compact the powder into a green body under high pressure.

Isostatic Pressing (if needed): For higher density and better uniformity, cold isostatic pressing may be considered, although it is less commonly used for simple shapes like squares.

Magnetic Field Alignment (Optional): In some cases, an external magnetic field is applied during pressing to align magnetic domains and enhance anisotropic magnetic properties.

Consideration: Die wear and powder flow characteristics should be monitored to maintain consistent shape and minimize cracks or density variations.

The green bodies are then sintered in a kiln to develop their final properties.

Sintering Temperature: Ferrite magnets are typically sintered at temperatures between 1200°C and 1300°C for several hours. This promotes grain growth and densification.

Atmosphere Control: The sintering atmosphere, often air or controlled oxygen flow, is crucial to avoid undesirable phase formation and to retain desired magnetic characteristics.

Consideration: Uneven heating or cooling may result in warping or internal stress, especially in square shapes where edge deformation can affect dimensional accuracy.