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According to standards: T/CMES 20023-2025 "Technical Specifications and Quality Grading of Ceramic Ball Valve", Clause 5.7.1: “The ceramic lining should be combined with the valve body by hot fitting. ”(See appendix for full text) 1. Core mechanism: The inevitable choice based on the mechanical properties of ceramics. Although the mechanical strength of structural ceramic materials is much higher than that of ordinary ceramics, they are still brittle materials, and their mechanical properties show significant "tension-compression asymmetry." According to the material performance indicators stipulated in the standard, the core of the hot matching process is to "leverage strengths and avoid weaknesses". This is also the fundamental reason why ceramic ball valves adopt hot fitting technology. The relative relationship between the typical numerical ranges of mechanical property indicators. Engineering significance: Compressive strength 1600-2800MPa is 8-15 times the tensile strength. The inherent advantages of the material should be fully utilized. The brittle weak item of the tensile strength 150-300MPa benchmark (1 times) must be strictly avoided. Bending strength 280-1200MPa is 2-4 times the tensile strength. The conclusion of medium load-bearing capacity: The essence of the hot fitting process is to use the entire compressive stress generated by the cooling and shrinkage of the metal to completely offset the tensile stress generated by the medium pressure, so that the ceramic lining is always in a safe working condition of "pressure" and eliminate the risk of brittle fracture. 2. Multi-dimensional technical advantages of the hot-fitting process 1. Suppress brittle failure and improve structural safety. Hot-fitting keeps ceramics under pressure, offsets the tensile stress caused by medium pressure, temperature changes, and mechanical impact, and solves the fatal brittleness defect of ceramics from the material properties. 2. Compensate for thermal expansion mismatch and improve thermal shock resistance. The thermal expansion coefficients of ceramics and metals are significantly different, and temperature fluctuations can easily produce additional thermal stress. Material type Thermal expansion coefficient (×10⁻⁶/℃) and metal matrix compatibility Metal matrix (WCB/304) 11~16 Benchmark zirconia (ZrO₂) 10~12 Optimal matching Alumina (Al₂O₃) 8~9 The difference is about 20% Silicon carbide/silicon nitride 4~5 is only 1/3 of metal Thermal matching can form a microscopic transition bonding layer to buffer thermal stress ； Combined with compressive stress constraints, the thermal shock resistance and shedding resistance are greatly improved. 3. Achieve high-strength and reliable bonding. Shrink Fit is an interference mechanical bonding. The bonding strength is much higher than that of gluing, thread compression, etc. There is no gap, no loosening, and no peeling. It can meet the requirements of medium, high-pressure, and large-diameter working conditions. 4. Improve structural stability and pressure-bearing capacity. Combining the advantages of high wear resistance and corrosion resistance of ceramics with high toughness and high strength of metals, ceramic ball valves can be stably used in conditions of strong corrosion, strong abrasion, and high pressure differentials. 5. Ensure dimensional accuracy and sealing performance. The heat-matched ceramic outer circle and valve body hole have strict size and shape tolerance requirements, which can ensure the precise coordination of the lining, ball core and valve seat, and improve the valve sealing level and operational stability. 3. Key points of project implementation In order to ensure the quality of hot distribution, the following parameters need to be strictly controlled: 1. Calculation of interference amount: The interference must be accurately calculated based on material purity, sintering shrinkage and operating temperature. Insufficient interference causes high pressure to fall off, and excessive interference causes ceramics to burst. 2. Timeliness treatment: The standard stipulates that "ceramic blanks should undergo natural aging to eliminate sintering stress." Before assembly, it is necessary to ensure that there is no residual stress inside the ceramic lining. 3. Heating control: Direct flame injection is strictly prohibited. It is recommended to use electromagnetic induction or hot oil bath heating to prevent metallographic changes or thermal shock damage to ceramics caused by local overheating of metal. 4. Summary In the manufacturing of ceramic ball valves, hot fitting is not only a process method, but also an extension of structural design. By combining the high toughness of metal with the high corrosion resistance/wear resistance of ceramics under compressive stress, the contradiction between "pressure bearing" and "corrosion resistance" that cannot be taken into account by a single material is solved. It is the preferred technical solution under medium-high pressure and strong corrosion conditions.