The following is a comprehensive analysis of the usage details of coated graphite tubes, covering the key points of the entire process from selection to maintenance:

1、 Core functions and applicable scenarios

basic definition

Made from high-purity graphite substrate modified by surface coating, it combines the high temperature resistance of graphite with the functional enhancement of the coating.

Typical application areas

Energy sector: Lithium battery negative electrode material carrier, fuel cell bipolar plate;

Chemical industry: High temperature reactor lining, catalyst support;

Electronics industry: semiconductor single crystal growth crucible, LED epitaxial wafer tray;

Research equipment: vacuum sintering furnace heating element, atomic absorption spectrometer atomizer.

2、 Key preparations before use

1. Preprocessing stage

Degreasing and cleaning:

Soak in acetone to remove processing oil stains, and then use deionized water to ultrasonically clean residual impurities.

Pre oxidation treatment:

When in use, heat up at a rate of 5 ℃/min to half the working temperature of the coating and hold for 2 hours to activate the compactness of the coating.

2. Installation compatibility check

Size matching: Confirm that the outer diameter tolerance of the tube body (usually ± 0.05mm) is compatible with the furnace seal;

Thermal expansion reserve: Leave a 3% -5% expansion gap in the length direction to prevent cracking due to thermal cycling stress;

Electrical connection test: If used for conductive working conditions, the resistance value needs to be measured to see if it meets the design requirements (generally<0.1 Ω).

3、 Key points of operation process control

1. Management of heating system

Segmented heating:

Phase 1 (room temperature → 300 ℃): ≤ 5 ℃/min → remove adsorbed moisture;

Second stage (300 ℃ → target temperature): ≤ 10 ℃/min → avoid thermal shock;

Special working conditions (such as rapid quenching): A gradient temperature control system is required.

Prohibition of sudden cooling and heating: When the temperature difference exceeds 200 ℃, it must be naturally cooled slowly, otherwise it will cause coating peeling.

2. Atmosphere and environment regulation

Inert gas protection: argon/nitrogen gas is introduced to maintain an oxygen content of<10ppm, preventing oxidation of the graphite substrate;

Active gas restriction: SiC coatings should be used with caution in hydrogen containing atmospheres (chemical reactions may occur);

Pressure balance: The vacuum degree should be controlled within the range of 10 ⁻³~10 ⁻¹ Pa, as excessive pressure can easily cause coating evaporation.

3. Load condition monitoring

Dynamic load limit: The maximum load-bearing capacity during continuous operation shall not exceed 60% of the yield strength of the pipe material;

Vibration suppression: Install rubber shock absorbers to isolate mechanical resonance, and stop the machine for troubleshooting when the amplitude is greater than 0.1mm;

Material Contact Specification: Solid materials should be loaded at a height of ≥ 50mm from the pipe mouth, and liquid media should not be directly poured and impacted on the pipe wall.

4、 Common problem solutions

1. Coating peeling and detachment

Cause diagnosis: Improper substrate pretreatment/uncontrolled heating and cooling rate/corrosive gas infiltration;

Emergency response: After local polishing, apply the same coating for reinforcement. If there is a large area of failure, replace the entire pipe.

2. Localized overheating and discoloration

Root cause location: uneven current distribution/blocked heat dissipation channels/foreign object bridging short circuit;

Repair measures: Adjust the electrode contact pressure, remove thermal barriers, and replace damaged sections if necessary.

3. Crack propagation warning

Monitoring methods: Infrared thermal imaging captures hot spot areas, and acoustic emission sensors capture micro crack signals;

Disposal plan: Inject epoxy resin filler for reinforcement and simultaneously reduce operating power to a safe threshold.

5、 Special safety precautions

Prohibition of high-risk operations:

It is strictly prohibited to touch the high-temperature pipe body with bare hands (>80 ℃ may cause third degree burns);

Do not open the protective cover for inspection while powered on;

Positive pressure respirators must be worn during operations in toxic media environments.