Application of Cobalt Alloy Bushings in Metallurgical Valves

In modern blast furnace ironmaking production, the reliability of hot air system valves directly impacts blast furnace output and continuous production. As an innovator in the field of metallurgical valve equipment, Qinye Company has developed energy-saving hot air valves, link-type butterfly valves, eccentric butterfly valves, and other products that are widely applied in blast furnace hot air systems and throughout the entire metallurgical process.

To address the stringent requirements of high temperatures, high wear, and strong corrosion in metallurgical conditions, our company provides Qinye Company with a full range of cobalt alloy bushings. Through material performance and process innovations, we help their valve products achieve breakthroughs in long service life, low maintenance, and high reliability.

Challenges of Traditional Bushings

Qinye Company's metallurgical valves are primarily used in blast furnace hot blast stoves, gas systems, dust removal systems, and other scenarios. Traditional bushings face three significant challenges:

• High-temperature creep: Hot blast valves operate at temperatures exceeding 550°C. Ordinary alloy bushings are prone to deformation and jamming due to high-temperature strength degradation.

• Particle wear: Dust particles (e.g., Fe₂O₃, SiO₂) in gas and flue gas erode the bushing surface, shortening valve lifespan.

• Corrosion fatigue: Sulfur-containing and acidic flue gas causes corrosion, which, combined with mechanical stress, leads to fatigue cracking.

Advantages of Cobalt Alloy Bushings

Cobalt alloy bushings use cobalt as the base material, forming a triple protective structure through the microstructure of chromium carbide (Cr₇C₃) phases combined with a ductile cobalt matrix:

• Wear-resistant layer: Hardness reaches HRC38–44; particle wear resistance is far superior to stainless steel bushings.

• Corrosion-resistant layer: With >20% chromium content, a passivation film forms to resist chloride and sulfide corrosion.

• Temperature-resistant layer: Operates stably from -196°C to 950°C; offers better high-temperature creep resistance than nickel-based alloys.

Scene-specific Applications

Hot Air Valves and Reverse Flow Air Valves

Equipped with cobalt alloy bushings, Qinye’s energy-saving hot air valves perform exceptionally in high-temperature environments. The bushing's surface roughness is controlled below Ra 0.8 μm, ensuring precise fit with the valve stem and achieving ANSI VI-grade zero leakage. Additionally, the thermal expansion coefficient of cobalt alloy matches the valve body, maintaining stable opening and closing torque.

Linkage-Type Butterfly Valve

Serving as a lightweight alternative to traditional gate valves, the linkage-type butterfly valve sees frequent actuation in cold air and gas pipelines. The cobalt alloy bushing adopts a three-dimensional eccentric design, which reduces friction and wear during operation. Measured torque is reduced by 25%, prolonging drive mechanism lifespan.

Cold Air Vent Valves and Gas Vent Valves

In dust-laden gas and cold air environments, cobalt alloy bushings demonstrate excellent corrosion and wear resistance. For blast furnace gas with dust content <15%, chromium carbide particles resist erosion with a wear rate of only 0.01 mm per thousand cycles. In systems with H₂S ≤1000 ppm, cobalt alloy bushings comply with NACE MR0175 standards, effectively preventing sleeve cracking and leakage.

Full-Size Customization Services

Based on Qinye’s full valve portfolio, we offer custom cobalt alloy bearing sleeve solutions with diameters from φ20mm to φ300mm. Our manufacturing supports multiple industry standards, including GB (China), API (USA), and EN (Europe). Depending on service conditions, we employ casting, forging, or powder metallurgy to ensure optimal performance and durability.