Raw Material Preparation and Batching
Brown Corundum Abrasive: Based on the required cutting force and surface finish, select brown corundum of appropriate grit size (e.g., 46#, 60#, 80#, etc.).
Binder: Select and weigh a specific proportion of ceramic raw materials such as clay and feldspar.
Temporary Binder: Add a small amount of dextrin, resin liquid, or water to make the powder plastic during pressing.
Pore-Forming Materials: To increase porosity, sawdust, naphthalene particles, etc. are added. These materials will burn or evaporate during the sintering process, leaving voids.
Mixing
Place all the weighed raw materials, including the brown corundum abrasive, binder, and pore-forming agent, in a mixer (such as a plowshare mixer) and mix thoroughly and evenly. This is a critical step in ensuring consistent product performance.
Forming
The mixed bulk material is placed into a mold of a specific shape (such as a rectangle, triangle, or circle).
A press is used to press and form the material under pressures ranging from tens to hundreds of tons, producing a “blank” with a certain initial strength.
Drying
The pressed blank is dried in a low-temperature oven. This primarily removes the moisture added during mixing and some of the solvent in the temporary binder, preventing cracking during direct sintering.
Firing
This is the core process. The dried blank is placed in a high-temperature kiln (typically around 1250°C to 1350°C) and sintered according to a specific heating, holding, and cooling profile.
During this process, the vitrified binder melts to form a glassy phase, encapsulating the hard brown corundum particles and firmly bonding them together. Simultaneously, the pore-forming agent combusts and evaporates, forming a uniform pore network. After cooling, the polishing block achieves its final strength and performance.
Processing & Inspection
After sintering, the product may require finishing, processing (such as surface smoothing), and marking.
Finally, rigorous inspections, including hardness checks, balance checks, and appearance checks, are conducted to ensure product quality.
III. Critical Control Points
Formula: The ratio of abrasive, binder, and porosity is a core secret, directly determining the hardness grade (e.g., G, H, K), microstructure (porosity), and performance of the polishing block.
Grit Size: Coarse grit (e.g., 46#) is used for rough grinding, resulting in high efficiency but a rough surface. Fine grit (e.g., W20) is used for fine grinding and polishing, resulting in a smooth surface but low efficiency.
Hardness: This refers to the bond’s grip on the abrasive particles. Abrasives with high hardness have less abrasive grain loss and are wear-resistant, but are prone to blunting. Abrasives with low hardness have more abrasive grain loss and better self-sharpening properties, but wear more quickly.