Chemical and Metallurgy

The chemical and metallurgical industries are characterized by extreme environments characterized by high temperatures, high pressures, severe wear, and severe corrosion. This is precisely where advanced ceramic materials can best demonstrate their irreplaceable advantages. Alumina (Al₂O₃), zirconium oxide (ZrO₂), silicon carbide (SiC), and silicon nitride (Si₃N₄) play key roles.

The following is a detailed introduction, advantages, and application areas of these ceramics in the chemical and metallurgical industries.

In the chemical and metallurgical industries, material selection is based on longevity, reliability, and purity. The advantages of these ceramics are:

• Extreme chemical resistance: They can withstand attack by most acids, alkalis, salts, and molten metals, with a lifespan far exceeding that of stainless steel and specialty alloys.
• Excellent high-temperature resistance and thermal stability: They can maintain their shape and strength at temperatures exceeding 1600°C without oxidation or creep.
• Excellent wear resistance: Their extremely high hardness allows them to withstand high-speed erosion and particle abrasion.
• High strength and stiffness: They provide structural support, especially at high temperatures, with much less strength degradation than metals.
• High purity and pollution resistance: Ceramics do not introduce metal ion contamination when producing high-purity chemicals, semiconductor materials or precision alloys.

1. Alumina (Al₂O₃)
Alumina is the most widely used and cost-effective engineering ceramic, with purity ranging from 95% to 99.9%, depending on the operating conditions.
Advantages: Corrosion resistance, wear resistance, high hardness, electrical insulation, and relatively low cost.
Specific Applications:

• Core Components for Chemical Pumps and Valves: Manufacturing mechanical seals, impellers, sleeves, valve cores, and valve seats for pumps transporting corrosive media (such as concentrated sulfuric acid, hydrochloric acid, and lye). This is its most classic application. 
• Wear-Resistant Linings: Used for lining silos, chutes, pipes, and fan blades, protecting equipment from erosion and wear caused by particulate matter.
• Grinding Media: Used as grinding balls and lining bricks in ball mills, they are used to grind pigments, dyes, ceramic powders, magnetic materials, and other materials to prevent metal contamination.
• Catalyst Carriers: Porous alumina balls or bars have a large surface area and are widely used as catalyst carriers in the petrochemical industry.

2. Zirconia (ZrO₂)

Known for its high toughness, it is particularly suitable for applications subject to mechanical and thermal shock.
Advantages: Highest fracture toughness among ceramics, high wear resistance, low thermal conductivity (insulation), and corrosion resistance.

Specific Applications:

• Metallurgical Continuous Steel Casting: Sizing nozzles are a core application. Zirconia's excellent resistance to molten steel corrosion allows it to maintain a stable aperture, ensuring a stable continuous casting process and high-quality ingots. 
• Specialty Fibers and Glass Processing: Used in the manufacture of stirring rods, furnace linings, and electrode shields in glass melting furnaces due to their excellent corrosion resistance to molten glass.
• Wear-Resistant Parts: Used in applications subject to both wear and impact, such as high-quality ceramic scissors, knives, and wear plates.

3. Silicon Carbide (SiC)
This super ceramic offers the most comprehensive performance, making it irreplaceable in applications requiring high heat, high conductivity, and high wear resistance.
Advantages: Extremely high thermal conductivity (excellent heat dissipation), excellent high-temperature strength, superior thermal shock resistance (resistance to rapid cooling and heating), extremely high hardness and wear resistance, and resistance to corrosion by various acids and melts.
Specific Applications:

• Key Kiln Components: Used in the manufacture of kiln furniture, such as rollers, crossbeams, saggers, and push plates. Its lightweight, high-strength, and high-temperature resistance significantly save energy, increase loading capacity, and extend service life.
• Heat Exchangers: Used in the manufacture of ceramic heat exchangers to recover heat from high-temperature flue gases (above 1000°C), a task that metal heat exchangers cannot handle. 
• Burner Components: Used in the manufacture of nozzles and orifice plates for high-efficiency, energy-saving burners, enabling high-temperature air combustion technology.
• Chemical Corrosion Protection: Used in the manufacture of heat exchange tubes, filters, and sealing rings for handling high-temperature, highly corrosive media.
• Metallurgical Industry: Used in aluminum electrolytic cell linings, zinc powder condensers, and other applications to resist corrosion from molten metals and alloys.

4. Silicon Nitride (Si₃N₄): 

One of the ceramics with the best overall mechanical properties, it is renowned for its thermal shock resistance, metal non-wetting properties, and high strength and toughness.

Advantages: Excellent thermal shock resistance, high fracture toughness, low density, self-lubricating properties, and non-wetting properties (non-adhesion) to most molten metals.
Specific Applications:

• Metallurgical Continuous Casting: Used as separator rings for horizontal continuous casting. Its key characteristic is its non-wetting properties with molten metals (such as copper, copper alloys, aluminum, and cast iron), ensuring smooth separation of the ingot from the mold and a smooth surface finish. 
• Steel Rolling Industry: As rollers, especially for hot-rolled wire rod, they offer excellent high-temperature strength, wear resistance, and thermal shock resistance.
• High-Temperature Structural Parts: Used in the manufacture of thermocouple protection tubes, metal processing crucibles, and brackets, capable of long-term operation in molten metal.
• High-Performance Bearings: Full-ceramic or hybrid ceramic bearings are used in specialized operating conditions, such as highly corrosive environments or high-temperature, non-lubricated environments.