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Material Selection of Hot Bending Molds in Glass Production - Boron Nitride or Graphite

28-June-2023

Hot curved glass (also known as curved glass) can be made into a variety of curved surface and complex appearance according to the requirements. It can meet the high quality needs of modern architectural decoration, smart phones, cars and customized furniture and other fields with beautiful style, beautiful lines and other characteristics.

 

Hot bending glass is a hot bending glass product that places the cut flat glass in a hot bending mold designed according to the bending arc, and then heats the glass to soften it, and then presses the softened glass through the mold to form a specific curved surface. The hot bending mold is a key component in the production of hot bending glass, which is directly related to the surface finish, dimensional accuracy, production cost and efficiency of hot bending glass. Therefore, the material selection of hot bending molds should meet the requirements of high high temperature bending strength, small high temperature creep, good high temperature oxidation resistance, no infiltration with glass, high thermal conductivity, easy processing and polishing, and suitable thermal expansion coefficient.

 

At present, graphite material has become the main mold material for hot bending of curved glass due to its comprehensive properties such as good thermal conductivity, easy processing and non-deformation. However, the oxidation resistance of graphite is poor, and the softening and forming temperature of glass is generally 700-800°C. At this temperature, the graphite mold is easily oxidized and ablated, resulting in:

(1) The forming process of curved glass using graphite molds needs to be carried out under a protective atmosphere, which increases production costs and reduces production efficiency;

(2) During the use of graphite molds, the inevitable slight oxidation will reduce the precision of the mold polishing surface and affect the product quality;

(3) The graphite mold needs to be polished and repaired regularly, which increases the cost of the mold and reduces the life of the mold.

 

In order to overcome the problem of poor oxidation resistance of existing graphite molds, an aluminum nitride with boron nitride composite ceramic material is provided, which can replace graphite as a new curved glass hot bending mold material to produce hot bending molds. The hot bending mold utilizes The high thermal conductivity, high oxidation resistance and high flexural strength of aluminum nitride and the easy processing characteristics of boron nitride. The prepared hot-bending mold has more excellent high-temperature oxidation resistance, which has a significant impact on reducing the production cost of hot-bending glass and improving production efficiency.


The content is derived from translations of published papers, rather than original research.

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