In industrial production, heat exchange is an essential link in energy conversion and utilization. With the continuous development of industries such as power generation, petrochemical, and metallurgy, heat exchange systems are increasingly operating under harsh conditions (high temperature, high pressure, corrosive media, and high dust), which put forward higher requirements for the performance of heat transfer components. Traditional smooth steel tubes have the disadvantages of small heat transfer area, low heat transfer efficiency, and poor resistance to high-temperature oxidation and corrosion, which are difficult to meet the efficient and stable operation needs of modern industrial heat exchange systems.

Cast steel finned tubes, as an improved high-efficiency heat transfer component, integrate the excellent mechanical properties and corrosion resistance of cast steel with the enhanced heat transfer effect of fin structures. Different from finned tubes made of other materials (such as copper, aluminum), cast steel finned tubes have outstanding high-temperature resistance (can withstand temperatures up to 800℃ or higher) and corrosion resistance, and the fin and tube body are integrally formed, avoiding the problem of fin falling off caused by poor bonding between fin and tube body in welded finned tubes. These advantages make cast steel finned tubes widely used in high-temperature, high-pressure and corrosive industrial heat exchange scenarios.

 

At present, there are various types of cast steel finned tubes on the market, and their structural forms, manufacturing processes and application scenarios vary greatly. For practitioners, a systematic understanding of the types, manufacturing processes, application scenarios and performance influencing factors of cast steel finned tubes is the basis for rational selection, design and application. This paper focuses on the core technology of cast steel finned tubes, systematically sorts out the classification, manufacturing processes, application scenarios and technical development trends, and combines industry standards and practical engineering experience to provide a comprehensive technical analysis, helping practitioners avoid technical mistakes and improve the efficiency and reliability of heat exchange systems.

 

 

 

Cast steel finned tubes can be classified into different types according to structural form, material grade, fin configuration and heat transfer direction. Each type has its own unique structural characteristics, mechanical properties and applicable scenarios. The detailed classification is as follows, which provides a basis for the selection of cast steel finned tubes in different industrial scenarios.

 

 

The structural form of cast steel finned tubes is mainly determined by the connection mode between the fin and the tube body and the distribution of fins. According to the structural form, it can be divided into three main types: integral cast finned tubes, welded-cast composite finned tubes and inserted cast finned tubes.

 

- Integral Cast Finned Tubes: The fin and the tube body are integrally cast and formed, without any bonding interface between the fin and the tube body. This type of finned tube has the advantages of strong structural stability, high bonding strength, good heat transfer continuity, and no risk of fin falling off. It is suitable for high-temperature, high-pressure and high-vibration working environments. The common structural forms include external finned tubes, internal finned tubes and internal-external double finned tubes. External finned tubes are mainly used to enhance the heat transfer of the tube outer wall (such as in air-cooled heat exchangers); internal finned tubes are used to enhance the heat transfer of the tube inner wall (such as in liquid-liquid heat exchangers); internal-external double finned tubes are suitable for scenarios where both internal and external heat transfer need to be enhanced (such as in high-efficiency waste heat recovery systems).

 

- Welded-Cast Composite Finned Tubes: The tube body is made of cast steel, and the fins are made of high-performance cast steel or alloy steel, which are connected by welding after casting. This type of finned tube combines the advantages of casting (good forming performance) and welding (flexible fin configuration), and can be designed with different fin sizes and densities according to actual needs. It is suitable for scenarios where the heat transfer requirements are high and the fin configuration needs to be adjusted flexibly. The key to this type of finned tube is to ensure the welding quality, avoid welding defects such as cracks and pores, which will affect the heat transfer efficiency and structural stability.

 

- Inserted Cast Finned Tubes: The fin is cast separately, and then inserted into the pre-processed groove on the cast steel tube body, and fixed by interference fit or welding. This type of finned tube has the advantages of simple manufacturing process, low cost, and easy replacement of fins. It is suitable for low-temperature, low-pressure and non-corrosive working environments, such as ordinary industrial waste heat recovery and HVAC systems. The disadvantage is that the bonding strength between the fin and the tube body is relatively low, and it is easy to produce gaps at the connection, which affects the heat transfer efficiency.

 

 

The material grade of cast steel finned tubes is determined according to the working temperature, pressure and corrosive environment of the heat exchange system. Common cast steel materials include carbon cast steel, alloy cast steel and stainless cast steel, each of which has different mechanical properties and corrosion resistance.

 

- Carbon Cast Steel Finned Tubes: Made of carbon cast steel (such as ZG230-450, ZG270-500), which has the advantages of low cost, good casting performance and high mechanical strength. It is suitable for low-temperature (below 400℃), low-pressure and non-corrosive working environments, such as ordinary industrial boilers, waste heat recovery pipelines and low-temperature heat exchangers. The disadvantage is poor high-temperature oxidation resistance and corrosion resistance, which is not suitable for high-temperature and corrosive scenarios.

 

- Alloy Cast Steel Finned Tubes: Adding alloying elements (such as chromium, molybdenum, nickel) to carbon cast steel to improve its high-temperature resistance, corrosion resistance and mechanical properties. Common alloy cast steel includes chromium-molybdenum cast steel (ZG20CrMo), nickel-chromium cast steel (ZG1Cr18Ni9), etc. This type of finned tube is suitable for medium-temperature (400-600℃), medium-pressure and slightly corrosive working environments, such as petrochemical reactors, metallurgical furnace heat exchangers and high-temperature waste heat recovery systems.

 

- Stainless Cast Steel Finned Tubes: Made of stainless cast steel (such as ZG0Cr18Ni9, ZG0Cr17Ni12Mo2), which has excellent corrosion resistance, high-temperature oxidation resistance and mechanical properties. It can withstand high temperature (up to 800℃ or higher) and strong corrosive media (such as acid, alkali, salt solution). It is suitable for high-temperature, high-pressure and strong corrosive working environments, such as nuclear power plant heat exchangers, chemical industry corrosion-resistant heat exchangers and marine heat exchange systems. The disadvantage is high cost, which limits its application in some ordinary industrial scenarios.

 

 

The fin configuration directly affects the heat transfer area and heat transfer efficiency of cast steel finned tubes. According to the fin configuration, it can be divided into rectangular finned tubes, spiral finned tubes, annular finned tubes and serrated finned tubes.

 

- Rectangular Finned Tubes: The fins are rectangular, arranged vertically or horizontally on the tube body. This type of finned tube has a simple structure, easy manufacturing, and large heat transfer area. It is suitable for low-velocity fluid heat exchange scenarios, such as air-cooled heat exchangers and low-velocity liquid heat exchangers. The disadvantage is that the fluid resistance is relatively large, and the heat transfer efficiency is not as high as that of spiral finned tubes.

 

- Spiral Finned Tubes: The fins are arranged in a spiral shape on the tube body. This type of finned tube can enhance the turbulence of the fluid, reduce the boundary layer thickness, and improve the heat transfer efficiency. At the same time, the spiral fins can reduce the fluid resistance, making it suitable for high-velocity fluid heat exchange scenarios, such as high-temperature flue gas heat exchangers and gas-liquid heat exchangers. It is the most widely used fin configuration in industrial production.

 

- Annular Finned Tubes: The fins are annular, arranged at equal intervals on the tube body. This type of finned tube has a uniform heat transfer distribution, good structural stability, and is suitable for scenarios where the fluid flows radially around the tube body, such as shell-and-tube heat exchangers and tube bundle heat exchangers. The disadvantage is that the manufacturing process is relatively complex, and the cost is higher than that of rectangular and spiral finned tubes.

 

- Serrated Finned Tubes: The fins are serrated, which can break the boundary layer of the fluid, enhance the heat transfer effect, and reduce the fluid resistance. This type of finned tube has higher heat transfer efficiency than rectangular and annular finned tubes, and is suitable for high-heat-flux and high-velocity fluid heat exchange scenarios, such as high-temperature waste heat recovery boilers and gas turbines.

 

 

 

The manufacturing process of cast steel finned tubes directly determines their structural integrity, mechanical properties and heat transfer performance. At present, the common manufacturing processes of cast steel finned tubes include centrifugal casting, sand casting, investment casting and welding-casting composite processes. Each process has its own characteristics, applicable scenarios and quality control points. The selection of manufacturing process should be based on the type of cast steel finned tube, material grade, fin configuration and application requirements.

 

 

Centrifugal casting is the most widely used manufacturing process for integral cast steel finned tubes, which uses the centrifugal force generated by high-speed rotation to make the molten cast steel fill the mold evenly, forming a dense and uniform tube body and fin structure. The process flow mainly includes mold preparation, molten steel smelting, centrifugal casting, cooling and solidification, mold stripping, and post-processing.

 

- Process Characteristics: The cast steel finned tube produced by centrifugal casting has dense structure, uniform wall thickness, high mechanical strength, and good bonding between the fin and the tube body. The process has high production efficiency, low cost, and is suitable for mass production of integral cast steel finned tubes with simple fin configurations (such as spiral fins, annular fins). The disadvantage is that it is not suitable for manufacturing finned tubes with complex fin configurations (such as serrated fins) and small-size finned tubes.

 

- Key Process Parameters: The key parameters of centrifugal casting include rotational speed of the mold, pouring temperature, pouring speed and cooling rate. The rotational speed directly affects the density and uniformity of the castings; the pouring temperature (usually 1500-1600℃ for cast steel) affects the fluidity of the molten steel and the forming quality of the fins; the pouring speed should be stable to avoid defects such as cold shut and shrinkage; the cooling rate should be controlled to avoid thermal stress and cracks in the castings.

 

- Quality Control Points: The main quality defects of centrifugal casting include shrinkage, porosity, cracks, uneven fin thickness and poor surface quality. To control the quality, it is necessary to strictly control the chemical composition of the molten steel, optimize the mold design, adjust the process parameters, and perform post-processing (such as heat treatment) to eliminate internal stress.

 

 

Sand casting is a traditional manufacturing process for cast steel finned tubes, which uses sand as the mold material to make the mold according to the shape of the finned tube, and then pours the molten cast steel into the mold to form the finned tube. The process flow includes mold making, core making, mold assembly, molten steel smelting, pouring, cooling and solidification, mold stripping, and post-processing.

 

- Process Characteristics: Sand casting has strong adaptability, can produce cast steel finned tubes of various sizes, shapes and fin configurations (including complex fin configurations), and the mold cost is low. It is suitable for small-batch production and trial production of cast steel finned tubes. The disadvantage is that the production efficiency is low, the surface quality of the castings is poor, the structure is relatively loose, and the mechanical properties are not as good as those of centrifugal casting.

 

- Key Process Parameters: The key parameters of sand casting include sand mold density, pouring temperature, pouring speed and cooling time. The sand mold density affects the surface quality and dimensional accuracy of the castings; the pouring temperature and speed are the same as those of centrifugal casting; the cooling time should be sufficient to avoid premature mold stripping leading to casting deformation and cracks.

 

- Quality Control Points: The main quality defects of sand casting include sand inclusion, slag inclusion, porosity, shrinkage and dimensional deviation. To control the quality, it is necessary to improve the sand mold quality, strictly control the molten steel purity, optimize the pouring system, and strengthen the post-processing (such as cleaning, grinding and heat treatment).

 

 

Investment casting, also known as lost-wax casting, is a precision casting process for cast steel finned tubes. It uses wax to make the prototype of the finned tube, coats the wax prototype with multiple layers of refractory material to form a shell, melts the wax prototype to form a hollow mold, and then pours the molten cast steel into the shell to form the finned tube. The process flow includes wax pattern making, shell making, dewaxing, roasting, pouring, cooling and solidification, shell breaking, and post-processing.

 

- Process Characteristics: Investment casting can produce cast steel finned tubes with high dimensional accuracy, good surface quality, complex fin configurations and thin fin thickness. It is suitable for manufacturing high-precision, small-size and complex-structure cast steel finned tubes, such as finned tubes used in aerospace and precision instruments. The disadvantage is that the process is complex, the production cycle is long, the cost is high, and it is not suitable for mass production.

 

- Key Process Parameters: The key parameters of investment casting include wax pattern accuracy, shell thickness, roasting temperature and pouring temperature. The wax pattern accuracy directly affects the dimensional accuracy of the castings; the shell thickness affects the heat insulation performance and strength of the mold; the roasting temperature (usually 800-1000℃) is used to remove residual wax and moisture, and improve the strength of the shell; the pouring temperature is slightly higher than that of centrifugal casting and sand casting.

 

- Quality Control Points: The main quality defects of investment casting include cracks, porosity, shrinkage, surface roughness and dimensional deviation. To control the quality, it is necessary to ensure the accuracy of the wax pattern, optimize the shell making process, strictly control the roasting and pouring parameters, and perform precision machining and inspection after casting.

 

 

Welding-casting composite process is a combination of casting and welding processes. First, the cast steel tube body and cast steel fins are manufactured separately by casting process, and then the fins are welded to the tube body by welding process to form the cast steel finned tube. The common welding methods include argon arc welding, submerged arc welding and laser welding.

 

- Process Characteristics: Welding-casting composite process has flexible operation, can combine different materials of tube body and fins (such as cast steel tube body and alloy steel fins), and can design and manufacture finned tubes with complex fin configurations and large fin density. It is suitable for large-scale, high-heat-flux and special-performance cast steel finned tubes. The disadvantage is that the welding quality is difficult to control, and there may be welding defects such as cracks, pores and incomplete fusion, which affect the structural stability and heat transfer efficiency.

 

- Key Process Parameters: The key parameters of welding-casting composite process include welding method, welding current, welding voltage, welding speed and heat treatment parameters. Different welding methods have different process parameters; the welding current and voltage affect the welding depth and width; the welding speed affects the welding quality and efficiency; the post-welding heat treatment is used to eliminate welding stress and improve the mechanical properties of the joint.

 

- Quality Control Points: The main quality defects of welding-casting composite process include welding cracks, pores, incomplete fusion, fin deformation and poor joint strength. To control the quality, it is necessary to select the appropriate welding method and process parameters, strictly inspect the welding joint, and perform post-welding heat treatment and non-destructive testing (such as ultrasonic testing, radiographic testing).

 

 

 

Cast steel finned tubes, with their excellent high-temperature resistance, corrosion resistance, structural stability and high heat transfer efficiency, are widely used in various industrial fields that require efficient heat exchange under harsh working conditions. Their application fields cover power generation, petrochemical, metallurgy, waste heat recovery, marine engineering and other industries. The specific application scenarios are as follows, combined with practical engineering cases to illustrate their application advantages and key technical requirements.

 

 

The power generation industry (thermal power, nuclear power, biomass power) has high requirements for heat exchange efficiency and reliability of heat transfer components, and the working environment is usually high temperature and high pressure. Cast steel finned tubes are widely used in boilers, heat exchangers and waste heat recovery systems of power plants.

 

- Thermal Power Plant Boilers: In thermal power plants, cast steel finned tubes are used in the economizer, air preheater and superheater of boilers. The economizer uses cast steel finned tubes to recover the waste heat of flue gas, heat the feed water, improve the boiler efficiency; the air preheater uses cast steel finned tubes to heat the combustion air with flue gas waste heat, enhance the combustion efficiency; the superheater uses high-temperature alloy cast steel finned tubes to heat the saturated steam into superheated steam, improving the power generation efficiency. For example, in a 600MW thermal power plant, the economizer adopts spiral integral cast steel finned tubes, which increases the heat transfer area by 3-5 times compared with smooth tubes, and the boiler efficiency is improved by 2-3%.

 

- Nuclear Power Plant Heat Exchangers: Nuclear power plants require heat transfer components to have excellent corrosion resistance and radiation resistance. Stainless cast steel finned tubes are used in the heat exchangers of nuclear power plants, such as the primary circuit heat exchanger and secondary circuit heat exchanger, to transfer the heat generated by nuclear fission to the working fluid, ensuring the safe and stable operation of the nuclear power plant.

 

 

The petrochemical industry involves a large number of heat exchange processes, and the working medium is usually corrosive (such as acid, alkali, oil vapor), and the working conditions are high temperature and high pressure. Cast steel finned tubes are widely used in reactors, heat exchangers, condensers and waste heat recovery systems of petrochemical plants.

 

- Petrochemical Reactors: In the catalytic cracking, hydrocracking and other processes of petrochemical plants, cast steel finned tubes are used as internal heat transfer components of reactors to transfer the heat generated by the reaction to the cooling medium, control the reaction temperature, and ensure the reaction efficiency and product quality. For example, in a catalytic cracking reactor, alloy cast steel spiral finned tubes are used, which can withstand high temperature (up to 600℃) and corrosive oil vapor, and the heat transfer efficiency is improved by 40% compared with smooth tubes.

 

- Waste Heat Recovery Systems: A large amount of high-temperature flue gas (temperature 500-800℃) is generated in the petrochemical production process. Cast steel finned tubes are used in the flue gas waste heat recovery system to recover the waste heat, heat the process fluid or generate steam, improving energy utilization efficiency and reducing environmental pollution.

 

 

The metallurgical industry (steel, non-ferrous metals) generates a lot of high-temperature waste heat during the smelting process, and the working environment is harsh (high temperature, high dust, corrosive flue gas). Cast steel finned tubes are widely used in the waste heat recovery and cooling systems of metallurgical furnaces.

 

- Metallurgical Furnace Waste Heat Recovery: In steel plants, blast furnaces, converter furnaces and electric furnaces generate a large amount of high-temperature flue gas (temperature 600-1000℃). Cast steel finned tubes are used in the flue gas waste heat recovery boiler to recover the waste heat, generate steam for power generation or heating, reducing energy consumption. For example, in a blast furnace flue gas waste heat recovery system, high-temperature alloy cast steel annular finned tubes are used, which have good high-temperature oxidation resistance and dust wear resistance, and the waste heat recovery efficiency reaches 70% or more.

 

- Metallurgical Equipment Cooling: Cast steel finned tubes are used in the cooling systems of metallurgical equipment (such as blast furnace cooling walls, converter cooling water pipes) to transfer the heat of the equipment to the cooling water, ensuring the safe operation of the equipment.

 

 

Waste heat recovery is an important part of energy conservation and emission reduction. Cast steel finned tubes, with their high heat transfer efficiency and good adaptability, are widely used in various industrial waste heat recovery systems, such as industrial boiler waste heat recovery, industrial furnace waste heat recovery and exhaust gas waste heat recovery.

 

- Industrial Boiler Waste Heat Recovery: A large amount of low-temperature flue gas (temperature 150-300℃) is discharged from industrial boilers. Cast steel finned tubes are used in the flue gas waste heat recovery device to recover the waste heat, heat the boiler feed water or domestic water, reducing fuel consumption and improving boiler efficiency.

 

- Industrial Furnace Waste Heat Recovery: High-temperature waste heat (temperature 400-800℃) is generated in industrial furnaces (such as ceramic furnaces, glass furnaces). Cast steel finned tubes are used in the waste heat recovery system to recover the waste heat, generate steam or hot air, which is reused in the production process, reducing energy waste.

 

 

In addition to the above fields, cast steel finned tubes are also widely used in marine engineering, HVAC systems and environmental protection equipment:

 

- Marine Engineering: Marine environments are highly corrosive (saltwater corrosion). Stainless cast steel finned tubes are used in marine heat exchangers (such as seawater cooling heat exchangers, marine boiler heat exchangers) to transfer heat, ensuring the normal operation of marine equipment and resisting seawater corrosion.

 

- HVAC Systems: In large-scale HVAC systems (such as central air conditioning, industrial ventilation), cast steel finned tubes are used in air coolers and heat exchangers to enhance heat transfer efficiency, adjust the indoor temperature and humidity, and improve the energy efficiency of the system.

 

- Environmental Protection Equipment: In environmental protection equipment (such as flue gas desulfurization and denitrification equipment), cast steel finned tubes are used in heat exchangers to transfer the heat of flue gas, ensuring the normal operation of desulfurization and denitrification processes and improving environmental protection efficiency.

 

 

 

The performance of cast steel finned tubes (heat transfer efficiency, service life, structural stability) is affected by many factors, including material selection, structural design, manufacturing process and service environment. Understanding these factors is crucial for optimizing the design and application of cast steel finned tubes. At the same time, with the continuous development of industrial technology, cast steel finned tube technology is showing new development trends.

 

 

- Material Selection: The material grade of cast steel directly affects the high-temperature resistance, corrosion resistance and mechanical properties of finned tubes. Selecting the appropriate material according to the working temperature, pressure and corrosive environment is the basis for ensuring the performance of finned tubes. For example, in high-temperature and corrosive scenarios, stainless cast steel or alloy cast steel should be selected instead of carbon cast steel.

 

- Structural Design: The fin configuration (fin type, fin density, fin thickness), tube body diameter and wall thickness directly affect the heat transfer area and heat transfer efficiency of finned tubes. A reasonable structural design can balance the heat transfer efficiency and fluid resistance. For example, spiral fins have higher heat transfer efficiency than rectangular fins, but the manufacturing cost is higher.

 

- Manufacturing Process: The manufacturing process affects the structural integrity, bonding strength and surface quality of finned tubes. Centrifugal casting can produce finned tubes with dense structure and high bonding strength, while sand casting has poor surface quality and loose structure. The welding quality of welding-casting composite finned tubes directly affects the structural stability and heat transfer efficiency.

 

- Service Environment: Factors such as working temperature, pressure, corrosive media, dust and vibration in the service environment affect the service life of finned tubes. High temperature will accelerate the oxidation and aging of cast steel; corrosive media will cause corrosion of the tube body and fins; dust will block the fins, reducing heat transfer efficiency; vibration will cause fatigue damage to the fins and tube body.

 

 

With the continuous demand for energy conservation and emission reduction and the development of industrial technology, cast steel finned tube technology is developing towards high efficiency, high temperature resistance, corrosion resistance, intelligence and lightweight. The main development trends are as follows:

 

- High-Efficiency Heat Transfer: By optimizing the fin configuration (such as serrated fins, variable-pitch fins) and surface treatment technology (such as thermal spraying, surface coating), the heat transfer efficiency of cast steel finned tubes is improved. For example, the serrated finned tube has a higher heat transfer coefficient than the traditional spiral finned tube, and the heat transfer efficiency can be improved by 15-20%.

 

- High-Temperature and Corrosion-Resistant Materials: The development of new high-temperature alloy cast steel and corrosion-resistant stainless cast steel (such as nickel-based alloy cast steel, duplex stainless cast steel) improves the high-temperature resistance and corrosion resistance of finned tubes, making them suitable for more harsh working environments (such as temperature above 1000℃, strong corrosive media).

 

- Lightweight and Compact Design: By optimizing the structural design and using high-strength cast steel materials, the weight and volume of cast steel finned tubes are reduced, realizing lightweight and compact design, which is suitable for equipment with limited space (such as marine equipment, aerospace equipment).

 

- Intelligent Manufacturing and Detection: Combining intelligent manufacturing technologies (such as 3D printing, robot welding) with non-destructive testing technologies (such as ultrasonic testing, radiographic testing), the manufacturing accuracy and quality of cast steel finned tubes are improved, and the intelligent detection and monitoring of finned tubes during operation are realized, reducing maintenance costs and improving operation reliability.

 

- Composite Material Integration: The development of composite cast steel finned tubes (such as cast steel base + ceramic coating, cast steel base + metal composite layer) combines the advantages of different materials, further improving the corrosion resistance, wear resistance and heat transfer performance of finned tubes, expanding their application scope."