Introduction
As an important technology in the field of powder material processing, ball mill grinding technology achieves particle refinement and uniform mixing through the mechanical action of grinding media. However, the frequent cold welding phenomenon of soft materials during ball milling often leads to particle agglomeration, equipment adhesion and even process failure.
Soft materials that are prone to cold welding during ball milling usually have the characteristics of low hardness, high plasticity and surface activity, such as magnesium, aluminum, rubber, polymer, etc. The reason why soft materials are more prone to cold welding during ball milling is mainly related to their physical properties and the mechanical action during ball milling:
Reasons why soft materials are prone to cold welding
· High ductility and plastic deformation
Soft materials have high ductility, and they are more likely to undergo plastic deformation rather than brittle fracture when impacted by grinding balls. The surface of the particles forms a large area of fresh contact surface due to repeated extrusion, providing basic conditions for cold welding.
· Low hardness accelerates surface activation
The lower material hardness causes particles to be more easily flattened or stretched during collisions, leading to frequent rupture of the surface oxide layer. This exposes highly reactive unoxidized metal surfaces, thereby promoting diffusion bonding between atoms.
Soft materials exhibit a weak work hardening effect. Under repeated deformation, it is difficult for them to resist further deformation by increasing their own hardness, resulting in continuous expansion of the cold welding area.
Control measures for cold welding
· Surface coating: adding process control agent (PCA)
By adding PCA, e.g: stearic acid and alcohol, to reduce direct contact by physically isolating particle surfaces.
Take aluminium powder as an example:
Stearic acid is an economical and efficient aluminum powder modifier, especially suitable for inhibiting cold welding during ball milling. Usually the addition amount is 0.5%~2% of the aluminum powder mass. It can optimize the dispersion process and subsequent treatment, and it can also significantly improve the processing performance of aluminum powder and the quality of the end product. And if you want to get a better modification effect, you can use composite modification, that is :adding stearic acid + silane coupling agent to aluminum powder. This can further enhance the interface bonding and oxidation resistance.
Qingdao Epic Powder Machinery Co., Ltd. est un fabricant spécialisée dans la production d'équipements de traitement de poudre.
Our products include: 4 types of air classifier mills, broyeur à boulets, broyeur à rouleaux, jet mill, various impact mills, 5 types of air classifiers, powder coating and modification equipment and équipements auxiliaires associés. Among them, powder coating and modification equipment includes: modificateur de broyeur à broches, modificateur de broyeur à trois rotors et modificateur de turbo-broyeur. The high-speed mechanical force combined with surface coating technology can effectively improve the performance of soft materials, such as cold welding resistance, dispersibility and functionalization, etc.
· Adjust ball milling parameters
Reduce rotation speed, grinding media size or grinding time to reduce excessive deformation.
· Choose ball mill lining or media of high quality material
For example, choose steel ball mill lining or alumina grinding media to reduce the adhesion of soft materials to grinding chamber.
Conclusion
The primary drivers of cold welding in soft materials are deformation-induced surface conformity, suppressed oxidation, and high atomic/molecular mobility. Controlling these factors through material modification, surface engineering, or environmental management is essential to mitigate adhesion.
If you need modification equipment to modify soft materials or other materials, or need other powder processing equipment, please Contactez notre équipe directly, we will customize the most suitable solution for you.