Forming Technology of Zirconia Ceramic knife

Knives are an inseparable part of our life. Previously, we used alloy tools, but in recent years a new type of tool has entered our life - zirconia ceramic tools. Zirconia Ceramic knife was first developed by Kyocera and put on the market. Once it came out, it was favored and sought after by people. It is a high-tech product in recent years. Zirconia Ceramic knife is unique in jade like luster, fashion and elegance, known as "noble knife". Its blade is extremely sharp, and its wear resistance is dozens of times higher than that of a steel knife, making it "never worn out". Zirconia ceramics have high chemical stability, resistance to acid and alkali corrosion, easy cleaning without rusting, and no odor when cut, making them a typical "green and environmentally friendly product". At present, it has been widely used in developed countries such as Japan, the United States and Europe. There are also many enterprises in China that produce zirconia Ceramic knife in an industrial way, and export them in large quantities and present them to each other as valuable gifts. At present, most domestic and foreign enterprises use 3% Y2O3-ZrO2 granulation powder produced by chemical co precipitation method as raw material, and use dry pressing forming method to produce zirconia blade blanks. The degree of mechanization in dry pressing forming is high, resulting in low cost and high production efficiency. However, the density of the billet is low, the structure is uneven, the shrinkage rate during sintering is too large, and it is easy to deform and crack, resulting in poor product quality. Therefore, for larger tool blanks, the cold isostatic pressing process is adopted to improve the density and structural uniformity of the blanks, in order to solve the above problems. However, this will undoubtedly increase equipment and process costs, and greatly reduce production efficiency. After dry pressing, even after cold isostatic pressing, the distribution of pores in the ceramic body will still show multi peak distribution in varying degrees. There will inevitably be pores in the body, which will affect the quality of Ceramic knife. Zirconia Ceramic knife is prepared by water-based material casting forming. gel casting is a near net size forming process developed in the 1990s, which was first proposed by Omatete et al. of Oak Ridge National Laboratory in the United States. This process can form green bodies with complex shapes, uniform microstructures, high strength, and high density, and can be directly machined. It is significantly superior to other forming processes for complex shaped components and has been widely applied in the field of engineering ceramics. The mechanism of injection molding is to form a polymer network structure through the polymerization reaction of external organic monomers and crosslinking agents, thereby solidifying and shaping ceramic powders in situ. In this process, there is no loss of solvent medium, and its volume basically does not shrink. The initial volume density of gel body basically maintains the volume density of slurry itself, which is an ideal process for producing high-quality zirconia Ceramic knife.

Introduction to Common Ceramic Forming:

（1） The concept of ceramic forming: Forming is the process of making preforms (green billets) with a certain shape and size from prepared billets using various methods.

（2） Classification of ceramic forming: From a technological perspective, the forming methods of ceramics can be divided into three categories based on the properties and water content of the billet: injection molding, plastic molding, and compression molding.

1. Grouting forming - common types include ordinary grouting and high-pressure grouting, with a wide range of applications, commonly used for making hollow billets and special-shaped billets.

2. Plastic forming - common methods include rolling, spinning, extrusion, rolling, plastic pressing, drawing, stamping, rolling, and sculpture. There are many forming methods, and they are often used to make gyroscopes, flat billets, and can also be used to make large or irregular products.

3. Pressed forming - common methods include dry pressing and isostatic pressing. Household ceramics are commonly used for making plates and dishes, while architectural ceramics are commonly used for making flat ceramic tiles.

4. Hot press injection molding - generally used for the molding process of special ceramics.

（3） Requirements to be met for molding:

Due to different forming methods having different requirements for the technological performance of the billets, the forming process should meet the required properties for firing, such as the dry strength of the billets, the density of the billets, the moisture content of the billets entering the kiln, and the regularity of the shape. Therefore, the forming process should meet the following requirements:

1. The green body should meet the required green shape and size of the product (shrinkage should be considered).

2. The billet should have sufficient mechanical strength to facilitate subsequent operations.

3. The body structure is uniform and has a certain density.

4. The forming process is suitable for organizing production in a multi, fast, good, and economical manner.

（4） Selection basis for forming method

The most basic basis for choosing a ceramic forming method is: the product's shape, yield, and quality requirements, the performance and economic benefits of the billet, usually considering the following aspects: 1. the shape, size, thickness, etc. of the product;

2. The process performance of the product;

3. Product quality and quality requirements;

4. The forming equipment is easy to operate, has low operating intensity, good operating conditions, and is easy to link or automate with the previous process;

5. High technical indicators, good economic benefits, and low labor intensity.

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