How to choose ductile iron or cast steel? Performance comparison and application analysis
Since ductile iron was developed in the 1950s, its application range has been continuously expanding. Nowadays, it has rapidly developed into the second most widely used cast iron material after gray cast iron, and there is even a saying of "replacing steel with iron", which fully demonstrates its importance in practical applications.
From the perspective of mechanical manufacturing, ductile iron is often used to produce parts that bear complex forces and have high requirements for strength, toughness, wear resistance, etc. For example, the crankshafts and camshafts of automobiles, tractors, and internal combustion engines, as well as the medium-pressure valves of general machinery, all rely on ductile iron. In the manufacturing of these key components, it ensures the stable operation and good working condition of the machinery with its excellent properties.
In municipal construction, ductile iron pipes have become the preferred material for pipelines due to their good properties and convenient and fast installation. Whether it is the water transmission pipelines in urban water supply systems or various pipelines used in sewage treatment plants to control water flow and prevent backflow, ductile iron pipes play an irreplaceable role and provide reliable guarantees for urban infrastructure.
In the field of agricultural machinery, since it needs to bear considerable loads and impacts, the high strength and wear resistance of ductile iron parts are highlighted, making it an ideal material choice and helping agricultural machinery to operate stably under various complex working conditions.
Moreover, ductile iron also has a wide range of applications in many fields such as architecture and energy. For example, in some structural components in buildings that need to bear certain pressures and weights, as well as related equipment components in the energy transmission process, the application of ductile iron can be seen.
Given the excellent performance and indispensable application value of ductile iron in many fields, it is of great significance for relevant industries to further optimize material selection and improve product performance by discussing its advantages over cast iron and cast steel. Next, we will conduct an in-depth analysis on this.
Comparison of Advantages between Ductile Iron and Cast Iron
Comparison of Strength
In terms of strength, ductile iron has an absolute advantage over cast iron. We can intuitively show this difference through some specific data. The tensile strength of ductile iron can reach 60k, while that of cast iron is only 31k, and the gap is very obvious. Moreover, ductile iron has a yield strength of 40k. In contrast, cast iron does not show yield strength and will eventually break when the force reaches a certain level.
This strength advantage enables ductile iron to bear more complex working conditions in practical applications. For example, in the automotive manufacturing field, the crankshaft of a car needs to bear the complex forces such as the repeated forces brought by the up and down movement of the piston and the torque force during the transmission process. Ductile iron can well meet the use requirements of the crankshaft with its high strength and ensure the stable operation of the car engine. If cast iron is used to manufacture the crankshaft, due to its insufficient strength, it is easy to be damaged during use and cannot maintain a normal working state for a long time.
Another example is in some mechanical manufacturing. For key components that need to bear large tensile and compressive forces, such as the connection brackets of large equipment, ductile iron has also become the preferred material due to its strength advantage. It can ensure that these components will not be easily deformed or broken when the equipment is running, thus maintaining the reliability and stability of the entire mechanical device. Cast iron, due to its limited strength, seems powerless in these application scenarios with high strength requirements.
Comparison of Toughness and Ductility
The graphite in cast iron generally has a flake or block structure, which will lead to a relatively serious stress concentration inside the material, making the toughness and ductility of cast iron poor. When subjected to external forces such as impacts, it is easy to have brittle fractures.
However, during the manufacturing process of ductile iron, by adding nodulizers such as magnesium to the molten iron, the original graphite morphology is transformed into a spherical shape. This spherical graphite structure greatly changes the properties of the material, making ductile iron have a significant improvement in toughness and ductility. Spherical graphite can effectively disperse stress. When subjected to external impact, the stress can be more evenly dispersed throughout the material through the spherical graphite, avoiding the situation where stress concentrates at one place and causes crack propagation until fracture.
For example, in the manufacturing of some parts that require good toughness and ductility, such as plows in agricultural machinery, when plowing, they will continuously be subjected to the impact force from the land and various complex resistances. The plows made of ductile iron can better adapt to this complex external force environment with their own good toughness and ductility and will not be easily broken or damaged, thus ensuring the normal progress of agricultural production. If cast iron is used to manufacture the plows, due to its insufficient toughness and ductility, cracks or even fractures may occur quickly when encountering large impact forces, affecting the use effect and service life.
Comparison of Application Scenarios
The common application scenarios of cast iron are mostly concentrated in places where the requirements for strength and toughness are relatively not so high. For example, like the sewer covers in buildings, which mainly play a covering and protective role and have low requirements for their ability to bear complex external forces. Cast iron can meet the use requirements with its relatively low cost and simple casting. Another example is some simple stove fittings. In normal use, they only need to bear relatively stable temperatures and small external forces, and cast iron can also be competent in such working scenarios.
Due to its more excellent comprehensive performance, the application scenarios of ductile iron are more extensive and tend to be places where the forces are complex and the requirements for strength, toughness, etc. are higher. In municipal engineering, ductile iron pipes are widely used in water supply and drainage systems because they need to bear certain water pressures and adapt to different underground environments, including possible soil pressures and ground vibrations. The high strength, good toughness and corrosion resistance of ductile iron enable it to cope well with these complex situations and ensure the long-term stable operation of the pipelines.
In the industrial field, many key components inside automobiles, tractors, etc., such as crankshafts and connecting rods, need to bear huge explosive forces, frictional forces and alternating stresses during the operation of the engine. Ductile iron has become the ideal material for manufacturing these components with its excellent comprehensive performance and can ensure that the mechanical equipment can still work reliably under long-term and high-intensity operating conditions.
In general, due to its advantages in strength, toughness, ductility and other aspects, ductile iron shows irreplaceable value in more important and complex application scenarios compared with cast iron, and its application range is also wider.
Comparison of Advantages between Ductile Iron and Cast Steel
Comparable Strength
The strength of ductile iron and that of cast steel are comparable, which gives it the potential to replace cast steel in many application scenarios. In terms of yield strength, ductile iron shows an obvious advantage. Its yield strength can reach at least 40k, while that of cast steel is only 36k. For example, in some mechanical manufacturing fields, like some small and medium-sized power transmission equipment, for key connection components that need to bear certain tensile and torsional forces, ductile iron can fully meet the corresponding work requirements with such strength characteristics and ensure the stable operation of the equipment. Moreover, while meeting the strength standard, it can also bring other advantages, which is beyond the reach of cast steel.
In some industrial equipment manufacturing that has high requirements for structural strength but is not super-large or super-heavy, ductile iron can also replace cast steel. For example, in the frame structure part of some general machinery, ductile iron can better adapt to the overall manufacturing process and cost control requirements on the basis of meeting the strength requirements, enabling the product to achieve a better balance between performance and economy. Therefore, this characteristic of comparable strength and better yield strength makes ductile iron a powerful substitute for cast steel in many fields.
Comparison of Corrosion Resistance and Oxidation Resistance
In most municipal application fields, such as in environments of water, salt water, steam, etc., the corrosion resistance and oxidation resistance of ductile iron are very outstanding, even exceeding those of cast steel. Water, as a common medium in municipal engineering, whether it is in water supply pipelines or drainage pipelines, materials are easily corroded when they are in a humid environment for a long time. In such a water environment, ductile iron can maintain its structural stability for a long time with its good corrosion resistance and avoid problems such as thinning of the pipe wall and perforation caused by corrosion, thus ensuring the normal operation of the water supply and drainage systems.
In environments where salt water exists, such as some municipal infrastructures in coastal cities or related facilities around areas where salt water is used for snow removal, the corrosion resistance advantage of ductile iron is even more prominent. Compared with cast steel, ductile iron can better resist the erosion of salt water and extend its service life. In application scenarios involving steam, like some heating pipelines, the oxidation resistance of ductile iron can prevent the rapid oxidation and peeling of the pipe surface, maintain good thermal conductivity and structural integrity, reduce the frequency of maintenance and replacement, and lower the maintenance cost. Overall, it shows an advantage of being more suitable for such environments than cast steel.
Cost and Machining Advantages
From the cost perspective, ductile iron has an obvious advantage over cast steel. Its cost is lower, which makes it more favored in many engineering projects. In large-scale production and manufacturing, such as when laying a large number of ductile iron pipes in municipal engineering, the lower material cost can greatly save project expenses. Moreover, the casting efficiency of ductile iron is higher. It can complete molding faster during the casting process and shorten the production period. For some projects that need to be delivered quickly, this is undoubtedly an important advantage.
At the same time, the machining cost of ductile iron is also lower. Because of its own material characteristics, when performing machining operations such as cutting and drilling, compared with cast steel, the wear on processing tools such as cutters is smaller, and the machining difficulty is also lower, which can further reduce the overall manufacturing cost. For example, in the production of batch ductile iron valves, whether in the casting stage or the subsequent machining stage, the cost advantage can be reflected, making the product more price-competitive in the market and also bringing better economic benefits to enterprises.
Damping Capacity Comparison
Ductile iron has a unique spherical graphite microstructure. Based on this structural characteristic, it is superior to cast steel in reducing vibration ability. In practical applications, when equipment is running or a structure is subjected to vibration due to external forces, ductile iron can effectively absorb and disperse these vibration energies, thus better reducing stress. For example, in some industrial equipment with vibration sources such as motors, if ductile iron is used to manufacture the base or supporting structure, it can reduce the transmission of vibration to the surroundings, avoid the loosening and damage of other components due to long-term vibration, and protect the reliability and stability of the entire equipment.
In the transportation field, like some expansion devices of bridges that need to cope with the vibration impact brought by vehicle driving, if made of ductile iron, its damping capacity can reduce the impact of vibration on the overall structure of the bridge, extend the service life of the structure, and also improve the driving comfort. In the building field, for some facilities that are sensitive to vibration, such as the placement platforms of precision instruments, the damping advantage of ductile iron can also play an important role, ensuring that the instruments are not interfered by vibration and work normally. It can be seen that its advantage in vibration environment application scenarios is very significant.
Conclusion
In summary, ductile iron compared with cast iron and cast steel has many significant advantages. In terms of mechanical properties, its high strength, good toughness, yield strength is outstanding, able to work stably under complex stress conditions; in terms of corrosion resistance and oxidation resistance, it performs well in a variety of environments, prolonging the service life of the product; in terms of cost and processing performance, it has obvious economic advantages, reducing the cost of production and improving production efficiency; in terms of vibration-damping capacity and physical properties, it also shows unique characteristics, meeting the needs of different application scenarios. Its wide range of application cases fully proves its important value in municipal engineering, industrial manufacturing and many other fields.
As an innovative leader in the industry, EATHU plays an important role in the research, development, production and application promotion of ductile iron, and with its advanced technology and rich experience, EATHU continuously optimizes the production process of ductile iron to ensure the stability and consistency of product quality. Through rigorous raw material selection and precise composition control, EATHU's ductile iron meets or exceeds industry standards for key properties such as strength and toughness.
In the field of application, EATHU actively works with various industry partners to explore innovative applications of ductile iron. For example, in municipal engineering, EATHU provides customized ductile iron piping solutions for urban water supply systems, combining advanced anti-corrosion technology and intelligent monitoring systems to ensure the safety and efficiency of urban water supply; in the field of industrial manufacturing, EATHU cooperates with automobile manufacturers to research and develop high-performance ductile iron automotive parts, helping automobile lightweighting and performance improvement.