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 moldIts preservation needs to take into account moisture resistance, pollution prevention, mechanical damage prevention, and environmental control to extend its service life and ensure processing accuracy. The following are specific storage methods and key points:
1、 Environmental condition control
Temperature and humidity management
Temperature range: The storage environment temperature should be stable at 15-25 ℃, avoiding extremely high temperatures (>40 ℃) or low temperatures (<5 ℃), to prevent microcracks or embrittlement of graphite due to thermal expansion and contraction.
Humidity control: The relative humidity should be ≤ 60%. Use a dehumidifier or desiccant (such as silica gel) to maintain a dry environment and prevent the strength of graphite from decreasing or surface condensation after absorbing moisture.
Avoid light storage: Avoid direct sunlight to prevent ultraviolet rays from accelerating graphite surface oxidation or causing local high temperatures.
Cleanliness requirements
Dust free environment: The storage area should meet ISO Class 7 or higher cleanliness standards to prevent dust, metal particles, and other impurities from adhering to the surface of the mold and affecting subsequent processing accuracy.
Corrosion resistant gas: Keep away from corrosive gases such as acids, alkalis, and organic solvents to avoid surface corrosion or increased porosity caused by the reaction between graphite and chemical substances.
2、 Physical protective measures
Prevent mechanical damage
Independent storage: The mold should be placed separately on a dedicated tray or shelf to avoid direct contact with other hard objects (such as metal tools, other molds) and prevent collision or scratching.
Anti tipping design: Use grooved trays or customized brackets to secure the mold, preventing tipping from causing edge damage or crack propagation.
Handle with care: Clean gloves should be worn during transportation to avoid hand sweat and grease contamination of the mold surface; Use soft lifting straps or vacuum suction cups to transport large molds to prevent scratches on the fixtures.
Pollution prevention and isolation
Sealed packaging: Unused molds can be wrapped in dust-free paper, then placed in anti-static plastic bags or aluminum foil bags, and finally placed in a sealed box to isolate dust and moisture in the air.
Partition storage: Store according to mold type (such as sintering mold, quenching mold), size, or frequency of use, and label clearly to avoid mixing or misoperation.
3、 Regular inspection and maintenance
Visual inspection
Monthly visual inspection: Observe the surface of the mold for cracks, peeling, discoloration (such as oxidation blackening), or signs of contamination, with a focus on inspecting stress concentration areas such as edges and holes.
Dimensional review: Use calipers or coordinate measuring instruments to check key dimensions (such as aperture and depth) every quarter to ensure that the tolerance is within ± 0.01mm. If it exceeds the tolerance, it needs to be repaired or scrapped.
performance testing
High temperature pretreatment: Before reusing molds that have been stored for a long time, they need to be baked in a vacuum furnace at a low temperature of 100-200 ℃ for 2-4 hours to remove adsorbed moisture and gases and prevent the formation of pores or cracks during processing.
Test piece verification: For key molds, small batch processing can be carried out using test pieces to test the surface quality (such as roughness Ra ≤ 0.8 μ m), dimensional accuracy, and defect free rate of the finished product. After passing the inspection, it can be put into formal production.
4、 Special scenario handling
Long term disuse and storage
Coating protective layer: Spray a thin layer of graphite emulsion or specialized rust inhibitor evenly on the surface of the mold to form a protective film that isolates air and moisture.
Nitrogen protection: After placing the mold in a sealed box, fill it with high-purity nitrogen gas (purity ≥ 99.99%) to replace the air inside the box and further reduce the risk of oxidation.
Transportation protection
Shockproof packaging: use foam plastic or air column bags to fill the gap between the mold and the packaging box, to prevent the mold displacement or collision caused by transportation vibration.
Fixed device: Design a dedicated card slot or bracket inside the packaging box to fix the mold in the central position, avoiding relative movement caused by bumps during transportation.