The production process of ductile iron has undergone a transformation from laboratory to large-scale industrial production, and in this process, scientists have continuously explored and improved, making the quality of ductile iron more stable and the performance of continuous improvement. With the application of new processes and technologies, the production cost of ductile iron has gradually decreased, further promoting its wide application in various industries. Looking forward to the future, the production process of ductile iron will continue to be optimized to provide more powerful impetus for the prosperity and development of various industries.
Production process
First of all, through the smelting process, raw materials such as pig iron, scrap steel and return material are placed in an electric furnace or cupola, and after high-temperature smelting, the composition of the required molten iron is obtained. This is followed by spheroidization, which is a central step in ductile iron production. In this process, a nodularizing agent, such as a magnesium alloy or a rare earth magnesium alloy, is added to the molten iron to promote the nodularization of graphite in the molten iron. The type of nodularizer, the amount of nodularizer added, and the method of addition will have a significant impact on the final spheroidizing effect. Finally, in order to further improve the mechanical properties of ductile iron, it is necessary to inoculate the molten iron after spheroidization. This step involves the addition of inoculants, such as ferrosilicon or calcium silicate alloys, to the molten iron to improve the morphology and distribution of the graphite spheres.
Pouring molding: The molten iron, which has been spheroidized and inoculated, is poured precisely into a pre-designed mould at the right temperature. Under the action of gravity, the molten iron is filled and gradually solidified, and finally a high-quality ductile iron casting is formed.
(1) Preparation and modulation of molten iron
The preparation of molten iron is a core link in the production of ductile iron. First, the raw material is heated to the proper melting temperature, a process that is closely monitored to ensure the quality of the molten iron. Generally, the temperature of molten iron is controlled between 1400°C and 1500°C.
Then, the exact blending of raw materials, such as pig iron, scrap and recycled iron, is used to meet specific production needs to ensure that the chemical composition of ductile iron meets the standards.
Spheroidization is a key step in this process. By adding nodularizing agents, such as magnesium and rare earths, graphite in cast iron is promoted to exist in a spherical form. The effect of nodularization has a direct impact on the properties of ductile iron, and nodularity is an important indicator to measure its performance. Therefore, the amount and time of addition of nodularizing agent need to be strictly controlled in this process.
(2) Centrifugal casting and annealing
Centrifugal casting is a common production method for ductile iron. With a water-cooled metal centrifuge, the molten iron is evenly distributed in the mold under high-speed rotation, resulting in a dense casting. This process requires fine control of the casting speed and temperature to ensure the quality of the casting.
After the casting is completed, the casting needs to be annealed. Annealing is designed to eliminate internal stresses and improve toughness and plasticity of castings. This process is usually done in an annealing furnace and is slowly cooled after a certain period of heating and holding.
After annealing, a comprehensive performance test of ductile iron is required, including mechanical properties, metallographic structure and hardness. Only the castings that have passed the inspection can enter the finishing process, such as removing burrs and flashes, so that the surface of the casting can reach the standard of smooth and flat.
In summary, the production process of ductile iron is quite complex, requiring strict control of the quality and temperature conditions at each stage to ensure that the quality of the final product meets a high standard.
Post time: Mar-20-2025
