Why is zinc alloy casting required when installing cone crusher liners?
In the field of cone crusher installation and maintenance, when installing the crushing liner (moving cone liner) and the bowl liner (fixed cone liner)， the ‘zinc alloy casting’ process must be used, which is a core technical step in ensuring the efficient operation of the equipment. I. What is the ‘zinc alloy casting’ process?
The zinc alloy casting process is a manufacturing method, in which molten zinc alloy is injected into a mould cavity, to produce castings of the desired shape after cooling and solidification.
The key points are as follows:
1. Process principle Taking advantage of the zinc alloy’s low melting point and good fluidity, the alloy is heated to a molten state (typically 420–460 °C) and fills the mould cavity under the action of gravity or pressure, forming a casting upon cooling.
2. Main Types Gravity casting: Relying on the molten metal’s own weight to fill the mould, this is suitable for castings with simple shapes and low precision requirements, such as small mechanical parts and decorative components. Pressure casting: Molten metal is forced into the mould by external pressure (such as pneumatic or hydraulic pressure), which increases filling speed and improves the density of the casting. This method is suitable for complex, thin-walled castings, such as automotive components and electronic housings.
3. Process Flow Mould preparation: The mould is designed and manufactured to ensure dimensional accuracy of the cavities, surface finish and a well-designed venting system. Alloy Melting: Raw zinc alloy materials (such as zinc ingots, aluminium ingots and copper ingots) are mixed in the correct proportions and heated in a melting furnace until molten; temperature and time are controlled to ensure uniform composition. Casting: The molten metal is poured into the mould. In this period, the pouring speed, temperature and filling pressure are controlled to ensure smooth filling of the mould and to prevent defects such as porosity and cold shuts. Cooling and Solidification: The casting cools within the mould; the cooling rate is controlled to optimise microstructural properties and prevent deformation or cracking. Demoulding and Cleaning: Once solidified, the casting is removed from the mould; gates, flash and burrs are removed, followed by surface treatment (such as sandblasting or electroplating).
4. Process Characteristics Advantages: High production efficiency and low cost; capable of producing complex-shaped castings with high dimensional accuracy and good surface quality. Disadvantages: Defects such as porosity and shrinkage may be present within the castings; mechanical properties are relatively low and require improvement through subsequent treatment. II. Key Technical Rationale for Zinc Alloy Casting
Eliminating gaps to achieve zero-to-zero contact: Micro-gaps exist between the crushing wall and the conical body, as well as between the mill shell and the adjustment ring, following machining. Zinc alloy possesses excellent fluidity in its molten state, enabling it to completely fill these gaps. The shrinkage stresses generated upon solidification cause the liner and the cone to form a tight ‘full-contact’ state, ensuring the liner receives uniform support and preventing stress concentrations caused by point contact.
Preventing loosening and withstanding enormous impact loads: Cone crushers are subjected to extremely high impact loads during operation. Relying solely on mechanical fasteners such as U-bolts makes it difficult to withstand high-frequency vibrations. Once the cast zinc alloy has solidified, it forms an intermediate layer with high ductility and strength, acting as a ‘retaining washer’ that effectively prevents the liner from loosening, displacing or rotating during operation. This is key to ensuring that the crushing wall and the bowl liner maintain a fixed crushing chamber configuration.
Shock absorption and vibration damping to extend the service life of wear parts: Zinc alloy is a low-melting-point alloy with good plasticity and toughness. Acting as an intermediary between the liner and the cone, it effectively cushions the impact forces generated during the crushing process, reducing fatigue damage to both the cone and the liner, thereby extending the service life of wear parts—particularly the high-manganese steel crushing walls and bowl liners. III. Specialised Requirements for the Casting Process
During casting operations, contact surfaces must be strictly preheated to the specified temperature to remove moisture and prevent ‘spatter’ injuries during casting; at the same time, gaps must be tightly sealed with asbestos or clay to prevent zinc alloy leakage and ensure a single-pour moulding. Following the installation of new or replacement liners, after the equipment has operated under load for 6–8 hours, it must be shut down for inspection and the U-bolts retightened to compensate for the minute gaps caused by the contraction of the zinc alloy and the elongation of the bolts.
