influence of metallurgical elements for gray cast iron
The main factors affecting the mechanical properties of gray cast iron: chemical composition (C, Si, Mn, P, S alloying elements), mechanical properties of gray cast iron, metallographic structure; shape, size, distribution of graphite; process factors and metallurgical factors and quantity And the matrix organization process, metallurgical factors, etc.
The homepage of this article introduces the influence of metallurgical factors, mainly cooling rate, overheating of molten iron, inoculation treatment, charge characteristics, etc.
1.Regarding the influence of cooling rate. Cast iron is a material that is very sensitive to the cooling rate. The thick-walled and thin-walled parts of the same casting may have a very different structure inside and outside, which is commonly known as structure inhomogeneity. Because the graphitization process largely depends on the cooling rate. There are many factors that affect the cooling rate of castings: casting wall thickness and weight, type of casting material, pouring riser and weight, and so on. Since the wall thickness, weight and structure of castings depend on the working conditions and cannot be changed at will, their influence on the organization should be considered when choosing chemical compositions.
2.Regarding the influence of molten iron inoculation treatment. The inoculation treatment is to add the inoculant to the molten iron to change the metallurgical state of the molten iron before the molten iron enters the casting cavity, thereby improving the microstructure and performance of the cast iron. For gray cast iron, the inoculation treatment is to obtain the structure of A-type graphite, pearlite matrix, and fine eutectic clusters, and to reduce the tendency of whitening at the thin walls or corners of the casting and the sensitivity to the wall thickness of the casting; For malleable cast iron, it is to shorten the short annealing cycle, increase the allowable wall thickness of the casting and improve the structure of the structure; for nodular cast iron, it is to reduce the tendency of castings to whiten, increase the spheroidization rate and improve the roundness of graphite.
3.Regarding the influence of molten iron overheating. Increasing the overheating temperature of molten iron can:
(1)Increase the content of combined carbon and correspondingly reduce the content of graphite carbon.
(2)Refine the graphite, and make the formation of dendritic graphite.
(3)Eliminate the "heredity" of cast iron.
(4)Improve the uniformity of the structure of the casting section.
(5)Conducive to the feeding of castings. Similarly, the heat preservation of molten iron also has a similar effect on the overheating of molten iron.
4.Regarding the influence of charge characteristics. In actual production, it is often found that the metal charge is changed (for example, the use of pig iron from different origins or the ratio of the charge, etc.) and the chemical composition does not seem to change. The cast iron has different structures and properties, which indicates the nature of the raw material. It directly affects the properties of cast iron smelted from it, which is called cast iron: "hereditary". For this reason, increasing the temperature of molten iron and using a variety of iron ingredients can eliminate this "hereditary" and improve the structure and structure of cast iron. performance.
In summary, the process factors and metallurgical factors of cast iron have a great influence on the mechanical properties of cast iron. Therefore, the control of these influencing factors should not be neglected.
Anyang Huatuo Metallurgy Co.,Ltd has in the raw materials for more than 20 years, own rich experience in the production of gray cast iron, so if any confused or requirement can consult us.