Vacuum furnace graphite moldIt is a special mold designed for forming, sintering or heat treatment processes in vacuum or inert atmosphere high-temperature environments, widely used in the manufacturing process of advanced materials such as hard alloys, powder metallurgy, ceramics, semiconductors, carbon/carbon composite materials and high-temperature alloys. Its core advantages lie in the excellent high-temperature stability, good thermal conductivity, low thermal expansion coefficient, and outstanding thermal shock resistance of graphite material, which enables it to work stably for a long time under extreme conditions above 2000 ℃.
Graphite molds are usually processed from high-purity, high-density, high-strength isostatic pressed graphite (such as ISO 80, Morgan SGL series) or molded graphite, with a dense and uniform microstructure that can effectively reduce the impact of impurity volatilization on product purity. In a vacuum furnace, graphite molds are not only used as load-bearing materials for forming cavities, but also often serve as heating elements or insulation components to achieve efficient and uniform thermal field distribution. For example, in the hot pressing sintering of hard alloys, the graphite mold is placed in a vacuum environment together with the sample to complete densification under high temperature and high pressure; During the growth of monocrystalline silicon or carbonization of carbon fiber preforms, graphite molds provide precise geometric constraints and thermal conduction paths.
Vacuum furnace graphite moldAs a core process equipment widely used in multiple industrial fields, its specific application scope is as follows:
1、 High temperature sintering and heat treatment field
Powder metallurgy and sintering of hard alloys
Graphite molds can withstand high temperatures above 2000 ℃ and are used for pressing powder metallurgy products (such as tungsten alloys and titanium alloys) and hard alloys (such as cutting tools and molds) in vacuum hot pressing furnaces, ensuring material densification and dimensional accuracy.
Typical application: Hard alloy sintering molds need to be sintered under pressure at 1450 ℃. Graphite molds achieve uniform heating through high thermal conductivity, while their self-lubricating properties reduce demolding resistance and improve yield.
Ceramic Materials and Glass Manufacturing
In ceramic sintering, graphite molds are used as sintering plates or forming molds, utilizing their low thermal expansion coefficient to prevent cracking and ensure product surface smoothness.
In glass manufacturing, graphite molds are used to produce glass tubes, bends, shaped bottles, etc. Their heat shock resistance and chemical inertness prevent contamination of glass components, and they have high dimensional stability.
Vacuum heat treatment process
Graphite molds are used as brackets or fixtures for processes such as vacuum quenching and annealing, supporting metal workpieces and uniformly conducting heat to prevent deformation.
Typical case: Vacuum heat treatment of aerospace parts requires strict control of temperature uniformity, and graphite molds improve thermal conductivity efficiency through optimized design (such as honeycomb structure).
2、 Semiconductor and Electronics Industry
Single crystal silicon growth and processing
Graphite crucibles are used in single crystal silicon growth furnaces and must meet ultra-high purity (metal impurities<10 ppm) and low ash content (<0.1%) to prevent impurity contamination of silicon crystals.
Graphite molds are also used for supporting and positioning processes such as silicon wafer cutting and polishing, ensuring machining accuracy.
Electronic Device Packaging and Testing
Graphite molds, as heat sink materials, are used for heat dissipation and packaging of electronic components. Their high thermal conductivity (>100 W/m · K) effectively extracts heat and prolongs device life.
In the manufacturing of vacuum electronic devices such as traveling wave tubes and magnetrons, graphite molds are used for the molding and sintering of precision components to ensure stable electrical performance.
3、 In the field of new energy and new materials
Sintering of negative electrode materials for lithium batteries
Graphite molds are used for vacuum sintering of negative electrode materials for lithium batteries, such as graphite and silicon carbon composite materials. Their chemical stability avoids reaction with the materials, while their high thermal conductivity shortens the sintering cycle.
Typical requirement: The mold needs to withstand a high temperature of 1200 ℃ and have a surface roughness Ra<1.6 μ m to prevent material adhesion.
Carbon fiber and composite material processing
In the graphitization treatment of carbon fiber insulation materials and carbon carbon composite materials, graphite molds, as heating elements or support structures, need to work stably for a long time at 2600-3000 ℃.
For example, in a horizontal vacuum graphitization furnace, graphite molds are used for high-temperature treatment of materials such as carbon paper and graphene, and their high purity (>99.99%) avoids the introduction of impurities.
4、 Aerospace and High Tech Manufacturing
High temperature alloy and titanium alloy forming
Graphite molds are used for vacuum precision casting of high-temperature alloy parts such as aerospace engine blades and turbine disks. Their high temperature resistance and low thermal expansion coefficient ensure the dimensional accuracy of the parts.
Typical case: Titanium alloy casting molds need to withstand corrosion from 1600 ℃ silicon melt, while graphite molds improve their oxidation resistance life through surface coating technology (such as SiC coating).
Thermal protection system and structural components
Graphite composite materials are used for spacecraft thermal protection systems (such as re-entry surfaces), with their lightweight and high-strength properties reducing weight, while also resisting atmospheric frictional heat flux with high temperature resistance.
Graphite molds are also used to manufacture key components such as rocket engine nozzles and combustion chambers, which must meet high pressure (≥ 50 MPa) and extreme temperature gradient (Δ T>500 ° C/min) requirements.
5、 Chemical and metallurgical industries
Application in corrosive media environment
Graphite molds are used in chemical equipment to manufacture reaction vessels, heat exchangers, etc. Their corrosion resistance (corrosion rate<0.1 mm/year) is suitable for harsh environments such as molten metals (such as aluminum) and acidic gases (such as Cl ₂).
Typical application: Graphite boats are used for polycrystalline silicon reduction furnaces in the photovoltaic industry, requiring high permeability (porosity of 15-20%) to evenly transport gases.
Continuous casting of non-ferrous metals
Graphite molds, as continuous or semi continuous casting molds for non-ferrous metals such as copper and aluminum, have improved thermal conductivity and self-lubricating properties, enhancing the quality of ingots (smooth surface, uniform crystallization) and reducing subsequent processing allowances.
For example, in the vertical continuous casting method, graphite molds increase the production efficiency of copper alloy ingots by 30% and reduce the scrap rate by 15%.