What are the advantages of isostatic graphite in 3D hot bending glass?
[ Date: 2019-11-16 14:44:22 Author: Popularity: ]
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With the development of the times, the industry requires carbon materials to have more uniform fine particle structure and more stable performance. In this context, the industry pioneers of artificial graphite developed isotropic graphite. The graphite material is formed by cold isostatic pressing (CIP), then sintered and graphitized at high temperature. It has fine particles and isotropic structure and properties. Nowadays, isotropic graphite has been widely used in many industries, such as rapid quenching heat treatment industry, rapid development of semiconductor industry, environment-friendly new energy industry, mold industry with high precision requirements, atomic energy industry with high reliability requirements. In recent two years, a new application of high-end isostatic pressure graphite has been added, which is used to make hot bending 3D curved glass mold.


In 2016, 3D curved glass entered a stage of rapid development. The curved screen is more in line with consumers' use habits. The appearance and feel of the curved screen are softer, and more edge virtual shortcut keys and reminder functions can be added. At present, curved surface display is also used in wearing equipment. As a fashion, curved surface display is expected to be more widely used in the future.


Curved glass means that the whole glass is not in a plane, and it usually has arc, J-shape, V-shape, hyperbolic curved shape, S-shape, etc. At present, the shape of curved glass for mobile phones is relatively small, and there are two common types: double arc and single arc. The composition of glass is determined according to its performance requirements, generally there are three types: the first is alkali aluminosilicate composition, the second is borosilicate composition, and the third is sodium calcium glass composition.


Graphite mold advantages:

At present, the materials used to make the hot bending glass mold in the mainstream molding equipment need to have good thermal stability, wear resistance, corrosion resistance, self lubrication, thermal conductivity, and thermal expansion coefficient similar to that of the hot bending glass. Good thermal stability ensures that the mold will not produce obvious deformation in repeated use of high and low temperature. Wear resistance and corrosion resistance are conducive to reduce the surface of the mold, such as fine fall off, pits and other defects. The self-lubricating property makes the glass not adhere to the mold during the hot bending process and demoulding. Good thermal conductivity is conducive to the rapid and uniform heating of glass, thus shortening the time of hot bending process, improving production efficiency, and uniform heating is conducive to avoid the generation of hot bending defects of glass.


In addition, the material is better to have good processability, economy and sustainable supply, in order to obtain better cost performance, and ensure timely supply in mass production. From the research and development stage of hot bending equipment to now, high-end isostatic pressure graphite is considered to be the most suitable material for hot bending die. Compared with stainless steel, ceramics, tungsten steel and other materials, graphite has the best evaluation of properties.


In general, the graphitization temperature of isostatic pressure graphite is about 3000 ℃, and its thermal stability has been verified for a long time in the application of high-temperature vacuum furnace. For example, it is widely used as heater, tool and fixture in the gas quenching furnace of heat treatment, sometimes the cooling rate reaches 60 ~ 70 ℃ / s, and there is no obvious deformation, cracking and other defects in repeated use.


The shore hardness of high-end graphite can reach more than 75, with good wear resistance. Graphite does not react with most of acid and alkali, so it has excellent corrosion resistance and self lubrication.


Graphite has good thermal conductivity, and the linear expansion coefficient is close to that of glass (the average linear expansion coefficient of glass for this purpose is (6.5 ~ 7.5) × 10-6 / K from normal temperature to 700 ℃). For specific data, please refer to Fig. 1 and Fig. 2.


The industry forecasts that the application of graphite in 3D curved glass for mobile phones, automobiles and wearables will enter an explosive period in the last three years. At present, all parties in the industry chain are actively developing and upgrading, and suppliers of graphite mold are constantly exploring and innovating. On the one hand, new curved glass models are constantly launched, which puts forward more new requirements for graphite mold design; on the other hand, new Research and development evaluation of graphite materials major raw material suppliers are bidding at the same time, such as nano ceramic coating materials, graphene like coating materials. I believe that practitioners will bring us more surprises and expect curved screens to bring us more sensory feast.