Zirconia blocks
Zirconium oxide blocks, also known as zirconium dioxide (ZrO₂), are a type of ceramic material. Common applications include refractory materials, ceramic knives, dental materials, etc. Pressing zirconia blocks means pressing zirconia powder into blocks and then sintering them to obtain dense ceramic blocks.
Hydraulic press is an effective tool for pressing zirconia blocks, but it is necessary to optimize powder processing, mold design and pressing parameters. For high precision or complex shapes, isostatic pressing or hot pressing is required. In practical applications, the best process conditions are determined through experiments to ensure the quality of the green body and sintering performance.
Pressing characteristics of zirconia materials
Material properties
Zirconia (ZrO₂) is a high-performance ceramic with high hardness, high temperature resistance, wear resistance and chemical stability. Its powder usually requires high pressure molding to increase the density of the green body.
Pressing requirements
Zirconia powder needs to be formed into a uniform and dense green body under high pressure (usually tens to hundreds of MPa) to reduce the porosity after sintering.
Adaptability of hydraulic press
Pressure range
Hydraulic press can provide pressure from tens to thousands of tons to meet the pressing needs of zirconium oxide powder. For example, pressing a zirconia blank with a diameter of 50mm may require about 100-300 tons of pressure.
Pressing method
Unidirectional/bidirectional pressing: suitable for simple-shaped blanks, low cost, but may have uneven density distribution.
Isostatic pressing (special equipment required): provides isotropic pressure and more uniform density, but the hydraulic press needs to be used with a flexible mold to achieve it.
Key process parameters
Powder pretreatment
Granulation: Improve fluidity, binder (such as PVA) or lubricant (such as zinc stearate) can be added.
Particle grading: Optimize particle size distribution to increase filling density.
Pressing parameters
Pressure: Usually 50-200MPa, depending on powder characteristics.
Dwelling time: About 10-60 seconds to ensure stress release.
Pressing speed: Slow pressurization to avoid air entrapment.
Mold design
Material: carbide or tool steel (such as SKD11), surface polished to reduce friction.
Demolding slope: About 1-3°, easy to demold.
Shrinkage compensation: reserve sintering shrinkage (usually 15-25%).
Subsequent sintering process
Sintering temperature
about 1400-1600°C (depending on the phase of zirconium oxide and additives).
Sintering atmosphere
air or vacuum (to avoid contamination by impurities).
Densification
Hot pressing sintering (combining pressure and high temperature) can further increase the density, but requires special equipment.
Application scenarios
Laboratory
Customized hydraulic presses (such as 50-100 tons) can meet the requirements.
Industrial mass production
Automated hydraulic production lines are required, integrating feeding, pressing, and demoulding functions.