RSiC Thermocouple Protective Tube

Recrystallized silicon carbide (R‑SiC) is produced from high‑purity SiC raw materials without any binding additives, resulting in an exceptionally pure material. It exhibits outstanding oxidation resistance and sulfur‑corrosion resistance at elevated temperatures. The maximum continuous service temperature is 1650 °C, making it well suited for demanding high‑temperature environments such as glass melting furnaces and industrial incinerators where corrosive flue gases are present.

R‑SiC tubes are made from high‑purity coarse and fine silicon carbide particle size gradations, with no sintering aids or binders. After extrusion forming and low‑temperature drying, the green body is sintered at 2200–2400 °C in an inert atmosphere. Densification occurs via an evaporation‑condensation mechanism of sub‑micron SiC particles, which grow necks at particle contacts to form a bonded structure. The resulting material retains a stable micro‑porous framework and achieves a SiC purity exceeding 99 %. It offers excellent high‑temperature oxidation resistance, outstanding resistance to sulfur‑bearing atmospheres, and very good thermal shock resistance. The maximum service temperature reaches 1650 °C. The main challenges are the extremely high sintering temperature, stringent process control requirements, and demanding furnace equipment.

R‑SiC protection tubes are primarily deployed in glass melting, precious‑metal processing, and incinerators with aggressive sulfur‑bearing flue gases. However, because of their semi‑permeable nature, they are not recommended for applications requiring absolute gas sealing, and Pt‑Rh thermocouples must be shielded with an additional alumina or similar liner.

1. High‑temperature resistance – capable of long‑term service at the thermocouple’s upper temperature limit without degradation, deformation, or excessive oxidation.

2. Corrosion resistance – sufficient service life in acidic/alkaline media, molten salts, sulphides, and other corrosive environments, with particular resilience against sulphur and its compounds.

3. Gas tightness – effectively prevents external aggressive gases or melts from penetrating into the tube, protecting the temperature‑sensing element from damage.

4. Thermal conductivity – high thermal conductivity and low time constant ensure rapid thermal response.

5. Thermal shock resistance – withstands sudden temperature changes without cracking; this is collectively influenced by high thermal conductivity and low thermal expansion coefficient.

6. Chemical stability – no harmful reactions with external media, insulating materials, or thermoelectrode materials during long‑term service, and no release of gases that could contaminate or degrade the thermocouple.

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