gray cast iron inoculation

Gray cast iron is basically a eutectic alloy composed of iron, carbon and silicon, in which carbon mainly exits in the form of graphite. To produce high-quality castings, it is very important to control the shape of the graphite formed during the solidification of the cast iron and the matrix metal structure.

Inoculation treatment is one of the most important links in the production process of gray cast iron. Good inoculation treatment can make gray cast iron have a micro-structure that meets the requirements, thereby ensuring the mechanical properties and processing properties of the casting. Adding an inoculant to the liquid cast iron can form a large number of submicroscopic cores and promote the formation of eutecic clusters in the liquid phase,when the eutectic solidification temperature is approaching, fine graphite flakes are first formed at the nucleation site, and then grow into eutectic clusters. The formation of each eutectic cluster will release a small amount of heat to the surrounding liquid phase. The more eutectic clusters formed, the lower the solidification rate of cast iron. The decrease of the solidification rate helps solidify according to the iron-graphite stable system, and can obtain the A-type graphite structure.

Good inoculation treatment has the following effects: 

1.Eliminate or reduce the tendency of white mouth; 

2.Avoid the appearance of supercooled structure; 

3.Reduce the wall thickness sensitivity of cast iron parts, so that the difference in micro-structure at thin and thick sections of the casting is small, and the difference in hardness Small; 

4.Conducive to the nucleation of eutectic clusters and increase the number of eutectic clusters; 

5.The graphite in cast iron is mainly fine and uniformly distributed A-type graphite, thereby improving the mechanical properties of cast iron. Good cast iron has better fluidity, reduces shrinkage of castings, improves processing performance, and reduces residual stress.

The mechanical properties of gray cast iron are determined by the distribution of its matrix structure and flake graphite. In order to obtain high strength, it is hoped that the matrix structure is mainly pearlite and the ferrite content is minimized. If the amount of ferrite is too much, not only will the strength of the cast iron be low, but also the tool will overheat during processing, which will significantly reduce the life of the tool. Unlike spheroidal graphite cast iron, gray cast iron cannot have ductility and toughness requirements, only its strength is required, so it is generally better to have high pearlite content. The graphite flakes in gray cast iron have the function of cutting the metal matrix, destroying its continuity, and reducing its strength. In terms of strength, it is necessary to avoid producing long and thin graphite flakes and thick graphite flakes. Graphite flakes with obvious directionality have a particularly strong influence. Controlling the distribution of graphite flakes is the key to ensuring the performance of gray cast iron.

If want to produce high quality gray cast iron, except inoculant, there are others need to pay attention, such as the alloy additive, recarburizer etc, Anyang Huatuo has in the raw materials for gray cast iron for more than 20  years, own rich experience for the production of gray cast iron, if any confused, welcome for your consult.