In the metallurgical field, flanges serve as critical connection and sealing components, playing a vital role throughout the entire process of steel and non-ferrous metal production—covering smelting, rolling, and refining. Designed to withstand the industry's core operating conditions—such as "high temperature, high dust levels, severe corrosion, and heavy-load impacts"—flanges ensure the detachable connection between equipment and pipelines, resist extreme environmental erosion, and reliably facilitate the safe transport of process media (e.g., high-temperature flue gases, molten slag, and corrosive solutions). These functions can be further detailed through the following key metallurgical processes:

1. Steel Smelting Process: Withstands erosion from high-temperature flue gases and molten slag, ensuring continuous smelting operations

Steel smelting—covering blast furnace ironmaking, basic oxygen steelmaking, and electric arc furnace steelmaking—is the core process in the metallurgy field. Flanges are primarily used in smelting furnace accessories, flue gas treatment pipelines, and cooling system connections, requiring careful handling to ensure reliability and efficiency. High temperatures exceeding 1000°C, erosion from high-temperature molten slag, and corrosion by acidic flue gases Three major challenges.

• Blast Furnace Ironmaking System The top charging equipment of the blast furnace (such as the charging bell and distributor) connects to the furnace body, while the blast furnace gas extraction pipes link up with dust collectors—both connections rely on high-temperature-resistant flanges. For instance, the flanges used in blast furnace gas pipelines must withstand gas temperatures ranging from 200°C to 400°C, as well as the corrosive acidic media like hydrogen sulfide (H₂S) and carbon dioxide (CO₂) present in the gas. Materials commonly chosen for these flanges include heat-resistant low-alloy steels (e.g., 15CrMoG) or weathering steels (Q355NH). The sealing surfaces are designed with a male-and-female configuration to minimize dust accumulation, paired with flexible graphite-metal wound gaskets that can endure temperatures up to 450°C and resist acidic corrosion, ensuring no gas leaks that could lead to explosions or pose risks of poisoning to personnel. Meanwhile, the connection flanges between the blast furnace cooling walls (the core component of the cooling system) and the cooling water pipes, where the medium is circulating cooling water at ambient temperature and pressures between 0.8 and 1.2 MPa, are typically made from Q235B carbon steel. These flanges feature raised-face sealing surfaces, combined with nitrile rubber gaskets known for their excellent water resistance and tight sealing performance, preventing cooling water leakage that might otherwise cause uneven cooling of the furnace shell and compromise its structural integrity.
• Converter / Electric Furnace Steelmaking System The connections between the converter flue (which discharges high-temperature flue gas) and the waste heat boiler, as well as between the electric furnace dust removal duct and the baghouse filter, must utilize high-temperature-resistant flanges. Specifically, the converter flue flange needs to withstand the scouring effect of flue gases at temperatures ranging from 800°C to 1200°C; therefore, materials such as high-chromium heat-resistant steel (e.g., Cr25Ni20) or cast steel (ZG35Cr24Ni7SiN) are selected. The flange design features a "thick-walled flange with reinforcing ribs" to enhance its resistance against high-temperature deformation. Additionally, the sealing surface is designed as a flat type—facilitating the application of high-temperature-resistant coatings—and is paired with ceramic fiber gaskets that can endure temperatures exceeding 1200°C while providing excellent thermal insulation, effectively preventing scalding injuries caused by escaping hot flue gases. Meanwhile, the water-cooled cable connector flange used in the electric furnace—a critical component for cooling cables—must simultaneously resist both the heat generated by electrical current (ranging from 150°C to 200°C) and corrosion from circulating cooling water. For this reason, the flange material is made of oxygen-free copper, which offers superior thermal conductivity. The sealing surface adopts a tongue-and-groove design, complemented by fluororubber gaskets that are highly resistant to both temperature and water exposure, ensuring safe isolation between the water-cooling system and the cables and preventing electrical breakdown through the gasket.

II. Non-ferrous Metal Smelting Process: Designed to withstand multi-medium corrosion and wet-process operations, ensuring prevention of solution leakage

In non-ferrous metal smelting processes—such as copper pyrometallurgy, aluminum electrolysis, and zinc hydrometallurgy—the flanges must withstand Highly corrosive solutions (acids, bases, salt solutions), high-temperature molten salts, and dusty environments The core requirements are "corrosion resistance" and "sealing reliability," ensuring that corrosive media do not leak, contaminating the environment or damaging equipment.

• Copper / Lead-Zinc Pyrometallurgy The flange connecting the flue gas duct of the copper flash furnace to the acid-making system (which converts sulfur dioxide into sulfuric acid) must withstand corrosion from the concentrated sulfuric acid produced during the process—specifically, acid with a concentration of 98% and temperatures ranging from 60°C to 80°C. For this application, the material must be either acid-resistant stainless steel (such as 316L) or fiber-reinforced plastic (FRP), which offers lightweight properties and exceptional resistance to strong corrosive environments. The sealing surface should feature a tongue-and-groove design to prevent sulfuric acid from leaking along the joint, paired with a PTFE gasket that is highly resistant to concentrated acids, capable of enduring temperatures up to 260°C without reacting with sulfuric acid. In contrast, the flange for the blast furnace slag-handling pipeline in lead-zinc smelting operations faces a vastly different challenge: the medium being conveyed is extremely high-temperature molten slag, with temperatures ranging from 1200°C to 1400°C. In this case, the flange must be constructed using a high-alumina refractory castable rather than a conventional metal flange, ensuring it can withstand the intense heat without melting. To further enhance sealing integrity, the flange’s sealing surface is treated with fireclay mortar, effectively preventing molten slag from leaking out and solidifying inside the pipeline, which could otherwise lead to blockages once the slag cools down.
• Aluminum Electrolysis and Hydrometallurgy The connection flange (in certain scenarios) between the anode busbar and conductive rod of an aluminum electrolytic cell must withstand both the high operating temperature of the cell—ranging from 950 to 1000°C—and corrosion caused by the electrolyte (cryolite-alumina molten salt). To address these challenges, the material is selected as high-purity aluminum, which offers excellent conductivity and outstanding compatibility with the electrolyte. Additionally, the flange surface undergoes anodizing treatment to further enhance its corrosion resistance. This flanged joint serves a dual purpose: ensuring reliable electrical conduction while providing a secure seal. For the connection flanges in wet-process zinc smelting systems—specifically those linking leaching tanks (where zinc concentrate is leached using sulfuric acid) and purification tanks (designed to remove impurities)—the medium involved is dilute sulfuric acid at concentrations of 20%–30% and temperatures between 50°C and 60°C. In such cases, glass-fiber reinforced plastic (GRP) flanges or rubber-lined carbon steel flanges are typically used. These options combine a carbon steel base with a durable rubber lining, offering cost-effective performance while significantly improving corrosion resistance. The sealing surfaces feature flat designs, paired with EPDM rubber gaskets that provide exceptional resistance to dilute acids and long-term aging, effectively preventing sulfuric acid leakage that could otherwise corrode the plant floor or contaminate surrounding soil.

3. Metallurgical Rolling and Advanced Processing: Equipped with heavy-load and cooling systems to ensure product precision.

Metallurgical rolling—both hot and cold rolling—and advanced processing (such as sheet cutting and tube forming)—are critical steps in transforming raw metallurgical materials into finished products. Flanges are primarily used in rolling equipment. Hydraulic system, cooling system, transmission system , it must withstand "overload impacts, high-pressure hydraulic oil, and circulating water corrosion," ensuring stable rolling processes and meeting product precision standards.

• Hot-Rolling / Cold-Rolling Systems The connection flange between the cooling water pipe (used to cool the hot rolling mill rolls) and the collection pipe must withstand circulating water pressure ranging from 1.5 to 2.5 MPa, as well as vibrations generated during the rolling process—specifically, high-frequency vibrations caused by rolling operations. The material selected is Q345B low-alloy high-strength steel, which offers excellent resistance to vibration-induced shocks. Additionally, the sealing surface features a male-and-female design to enhance sealing performance under vibrational conditions, paired with a metal-jacketed gasket that is both water-resistant and capable of preventing gasket displacement caused by vibration. This ensures no cooling water leakage occurs, thereby maintaining optimal cooling efficiency for the rolls and avoiding surface defects in the rolled products. For the hydraulic system flanges in the cold rolling mill—such as those connecting hydraulic cylinders to oil lines—the components must endure extremely high-pressure hydraulic oil, typically ranging from 30 to 50 MPa. To meet these demands, the material chosen is either high-quality 20# carbon steel or 45# steel, both known for their exceptional strength and ability to handle such extreme pressures. The sealing surface employs a flat-face design, complemented by specialized high-pressure hydraulic gaskets, such as copper-jacketed asbestos gaskets, which are engineered to resist both high pressure and the swelling effects of hydraulic oil. This setup effectively prevents hydraulic oil leaks, ensuring stable control of rolling pressure and maintaining precise operational integrity during the rolling process.
• Advanced processing equipment : The hydraulic drive system flanges for the steel plate shearing machine and the cooling water pipe flanges for the steel tube forming machine share similar application scenarios to those of rolling equipment—but operate under relatively milder conditions (pressure ranging from 10 to 20 MPa, with ambient temperatures). For the shearing machine’s hydraulic flanges, 45# steel is selected as the material, paired with oil-resistant rubber gaskets. In contrast, the cooling flanges for the tube-forming machine are made from 304 stainless steel (to prevent rust caused by circulating water), combined with nitrile rubber gaskets. A key requirement here is "ease of maintenance," since deep-processing equipment often requires regular inspections of hydraulic valves and tool replacements. To facilitate quick disassembly and assembly, flat-welded or threaded flanges are predominantly used—offering high efficiency in installation and removal.

4. Metallurgical Auxiliary Systems: Designed to meet utility and environmental requirements, ensuring stable operation across the entire process

Metallurgical production relies heavily on numerous auxiliary systems—such as power systems, water treatment systems, and environmental protection systems—where flanges play a "universal connection" role, adapting to various media (steam, compressed air, wastewater, chemicals) while balancing "cost" with "functionality."

• Power and Steam Systems : The connections between the metallurgical plant’s boiler (which supplies steam) and the steam pipelines, as well as between the steam turbine (used for power generation or equipment drive) and the steam lines, must utilize high-temperature and high-pressure flanges. Specifically, the boiler outlet flange needs to withstand pressures ranging from 4.0 to 10 MPa and temperatures between 400°C and 450°C. For these applications, 20G boiler steel or 12Cr1MoVG heat-resistant steel is recommended as the material, with a raised-face sealing surface paired with a metal ring gasket—such as an octagonal gasket—which offers excellent resistance to high pressure and temperature while ensuring reliable sealing performance. Meanwhile, for the plant’s compressed air pipelines (operating at pressures of 0.6 to 1.0 MPa) connecting to pneumatic equipment like pneumatic valves and pneumatic clamps, the connecting flanges are made from Q235B carbon steel. These flanges feature a flat sealing surface and are fitted with rubber gaskets, making them cost-effective and ideal for easy, large-scale installation.
• Water Treatment and Environmental Protection Systems In the wastewater treatment plant of the metallurgical factory—designed to handle both rolling mill wastewater and smelting effluents—the connecting flanges for sedimentation tanks, filtration units, and pipelines are made from either fiberglass-reinforced plastic (FRP) flanges or lined carbon steel flanges, paired with neoprene gaskets that offer excellent resistance to oily contaminants and heavy metal ions in the corrosive wastewater. For the desulfurization and denitrification system—used to treat sulfur dioxide and nitrogen oxides emitted from smelting flue gases—the connecting flanges between absorption towers and chemical supply lines (such as ammonia water or limestone slurry pipelines) must withstand corrosion from alkaline chemicals. These flanges are fabricated from 316L stainless steel or rubber-lined flanges, featuring a tongue-and-groove sealing surface paired with PTFE gaskets to prevent chemical leakage and safeguard the environment from contamination.

V. Core Technical Requirements for Flanges in the Metallurgy Field

The "high temperature, high corrosion, and high vibration" characteristics of the metallurgical industry dictate that flange applications must meet specific technical requirements—distinct from those of general-purpose industrial flanges.

1. Extreme Environmental Performance For high-temperature applications—such as smelting furnace flues and waste heat boilers—materials like heat-resistant steel (Cr-Mo steel, high-chromium steel) or refractory material flanges should be selected to prevent deformation or melting under extreme heat. In corrosive environments—like acid production systems or wastewater treatment processes—corrosion-resistant materials (e.g., 316L stainless steel, fiberglass-reinforced plastic, or rubber-lined/plastic-lined carbon steel) are recommended, paired with corrosion-resistant gaskets (made of PTFE or fluoroelastomer) to ensure the flange body and sealing components remain intact and functional despite exposure to harsh chemicals.
2. Vibration Resistance and Heavy-Load Capacity For vibration-heavy-load scenarios involving rolling equipment, smelting furnace bodies, and similar applications, flanges should be designed with thick-walled structures or rigid flanges equipped with reinforcing ribs. Material selection should prioritize low-alloy high-strength steels such as Q345B or 15CrMoG. Bolts used must be of Grade 8.8 or higher, and they should be tightened evenly to the specified torque to prevent loosening caused by vibrations, which could lead to misalignment of sealing surfaces and subsequent medium leakage.
3. Adapting to Process Continuity : Metallurgical production typically involves continuous processes (such as blast furnace ironmaking and continuous rolling lines), so flanges must feature "long life and low maintenance"—for instance, by opting for metal-wound gaskets (which offer excellent temperature and corrosion resistance with an extended service life) instead of conventional rubber gaskets that tend to degrade over time, thereby minimizing downtime caused by gasket replacements. Additionally, flange connections should be designed for easy and rapid maintenance—for example, by using loose-type flanges or quick-connect flanges—to reduce the time required for troubleshooting and ensure uninterrupted production.

In summary, the application of flanges in the metallurgy industry essentially involves "selecting a combination of 'high-temperature/ corrosion-resistant materials + vibration-resistant design + reliable sealing' tailored to the specific operating conditions of smelting, rolling, and auxiliary systems." Their performance directly impacts the safe operation of metallurgical equipment, the quality of the final products, and compliance with environmental standards—making them a critical component for ensuring efficient, stable, and eco-friendly production throughout the metallurgical supply chain.