The figure shows the matrix structure of spiral cast iron with different wall thickness. Among them, figures (a) – (c) are the matrix structure diagrams of samples with thickness of 20,40 and 60mm respectively.
The statistical values of pearlite content in Vermicular Cast Iron with different wall thickness are shown in the table.
|Sample wall thickness /mm||20||40||60|
|Ferrite content /%||46.2||55.5||60.4|
It can be seen from the figure and table that the ferrite content in cast iron increases with the increase of sample wall thickness, which is mainly related to the alloy cooling rate caused by sample wall thickness. The larger the sample wall thickness, the slower the cooling rate, the faster the diffusion rate of carbon atoms in the alloy, and the longer the diffusion time of carbon atoms, resulting in the obvious growth of graphite and the increase of ferrite content in the alloy.