The Change For The Tensile Strength Of Gray Ductile Iron

In the industry, it is customary to decide whether the gray ductile iron is qualified not depends on whether its tensile strength is qualified. While the tensile strength of the gray ductile Iron is determined by the carbon content. In addition to ensuring the basic chemical composition is qualified. With the increase of carbon content, the tensile strength will decrease. From the basic characteristics of gray nodular iron castings, it can be seen that if a small amount of carbon is added to the raw materials, the tensile strength can be improved. Therefore, in the carbon content of gray iron castings, try to make the carbon content reach 2.6% - 3.6%, and the silicon content is 1.2% - 33.0%. It is necessary to add some manganese properly when the wall thickness of gray iron castings is determined. At the same time, alloying method can also be used to improve the tensile strength of gray nodular iron castings, or adding a proper amount of microalloys, such as chromium, molybdenum, tin and other elements. It is also one of the ways to improve the tensile strength of gray iron castings. But the corresponding molten iron inoculation should be done well. It should be noted that carbon and silicon affect the strength of gray nodular iron castings in different ways. With high carbon content, it will increases the graphite content, promotes the coarsening of graphite flakes, relatively reduces the austenite dendrite content, and reduces the tensile strength. Therefore, when the carbon equivalent is constant, increasing the silicon content, the carbon equivalent is relatively reduced, the graphite content is correspondingly reduced. And the primary austenite content is increased. The Silicon with ferrite can strengthen and improve the strength. However, silicon can increase the eutectoid transition temperature and coarsen the pearlite. In a word, if the carbon equivalent is low, increasing the ratio of silicon to carbon, or reducing the ratio of silicon to carbon properly. The tensile strength of gray nodular iron castings will be improved. But if the ratio of silicon to carbon is too low, it is easy to produce white spots. In this case, inoculation treatment is needed.