1. Technical Basics of Magnetic Material Mixing and Granulation

Magnetic materials are key functional materials in modern industry, and the uniformity of raw material mixing and granulation quality are crucial during their preparation. The mixing and granulation process is a key step in molecularly dispersing magnetic powders (such as ferrite and NdFeB) with additives (binders, lubricants, modifiers, etc.) to form uniform granules. This process directly impacts the efficiency of subsequent pressing and molding, as well as the magnetic and mechanical properties of the final product. Traditional mixing processes suffer from technical bottlenecks such as insufficient mixing uniformity, severe dust pollution, difficulty in controlling oxidation, and poor granulation consistency, hindering the production of high-performance magnetic materials.

Modern magnetic material mixing and granulation equipment addresses these technical challenges by combining mechanochemical reactions with precise process control. Its core principle is to utilize a multi-dimensional rotor or agitator to apply shear, extrusion, and centrifugal forces to the powder, achieving nanoscale dispersion of the different components in a short period of time. Through the synergistic effects of temperature control, a protective atmosphere (vacuum or inert gas), and a liquid spray system, efficient mixing and granulation are achieved within a single, enclosed space, preventing external contamination and controlling particle morphology.

This technology system has become a key component in the production of high-end sintered permanent magnets, anisotropic bonded magnetic powders, soft magnetic composites, and other products. Equipment performance is directly related to core magnetic material indicators such as magnetic permeability, coercivity, and remanence. The following article systematically analyzes the technical types and innovative designs of current mainstream mixing and granulation equipment.

2 Main Equipment Types and Technical Features

Magnetic material mixing and granulation equipment can be divided into several types based on their structural principles and functional characteristics. Each type is specifically optimized for specific material systems and process requirements. The following is a detailed technical analysis of mainstream models:

2.1 Inclined Intense Mixing and Granulating Equipment

Structural Innovation: This equipment utilizes a unique inclined design (typically adjustable from 15° to 30°) combined with a high-speed, three-dimensional mixing tool (continuously adjustable speed, 100-2000 rpm). The combined effects of centrifugal force and gravity create a spiral motion in the material. This design significantly expands the material flow space, eliminating the "bottom dead zone" problem of traditional vertical mixers.

Integrated mixing and granulation: After the mixing stage, there's no need to transfer materials. Simply adjust the rotor speed and add a liquid binder to proceed directly to the granulation stage. The high-speed rotor creates friction and impact on the wet material, causing particles to agglomerate through a combination of capillary and mechanical forces. By adjusting the rotor speed, spray rate, and cycle time, the final particle size can be precisely controlled (typically within a range of 0.1-2.0 mm).

Application Advantages: This equipment is particularly suitable for the large-scale production of ferrite magnetic materials. Its integrated process can increase production efficiency by over 40%. Furthermore, by eliminating the risk of segregation caused by material transfer, product consistency is significantly improved. Experience in manganese-zinc ferrite production has shown that granules produced using this equipment exhibit a higher bulk density (approximately 15%) and a more uniform particle size distribution (D90 deviation <5%).

2.2 Vacuum-Protected Mixer (Warm Mixer)

Anti-Oxidation Technology: This equipment is specifically designed for rare earth permanent magnet materials such as NdFeB and SmCo. It features a three-stage vacuum system (maximum vacuum exceeding -0.076 MPa) and a high-purity argon gas displacement device. Prior to mixing, the oxygen content in the mixing chamber is reduced to below 10 ppm, effectively preventing oxidation and degradation of the rare earth elements during the mixing process.

Precise Temperature Control: The mixing chamber is equipped with a dual-circuit temperature control system (typically ranging from -20°C to 150°C) using thermal oil in a jacket for rapid temperature increase and decrease. Anisotropic NdFeB bonded magnetic powder can be mixed at low temperatures (-10°C to 0°C) to prevent premature curing of the binder and ensure proper orientation of the magnetic powder.