1.Graphite Ball Alienation
Irregular graphite appears in the dissimilation of graphite balls, such as clumps, tadpoles, worms, horns, or other non-spherical shapes. This is because the local crystal growth mode and growth rate deviate from the normal growth law when the spherical graphite grows along the radiation direction.
2.Graphite floating
In thick-walled ductile iron parts with hypereutectic composition, there is often a dense area of graphite at the top of the pouring position, that is, the phenomenon of "floating from beginning to end". This is because the density of graphite and molten iron are different, and the graphite directly precipitated by hypereutectic molten iron is subjected to buoyancy.
3.Inverted
In general, the white structure of iron castings tends to appear in the surface, sharp corners, and drape seams that cool faster. On the contrary, the white mouth defects are reversed. The carbide phase appears in the middle section center and hot joints of the casting. When the residual amount of spheroidizing elements is too much, it can promote the generation of anti-white defects.
4.Hypodermic pinhole
The hypodermic pinholes mainly contain hydrogen, but also a small amount of carbon monoxide and nitrogen. When the amount of residual magnesium is too high, it also strengthens the tendency to absorb hydrogen from the wet type, thereby increasing the probability of subcutaneous pinholes. In addition, the long residence time of spheroidized molten iron can also increase the number of pinholes.
5.Shrinkage
Shrinkage cavity often appears in the final solidification part of the casting (hot joint, riser neck and casting connection, inner corner or inner gate and casting connection), it is a hole hidden inside the casting or connected to the outside. Shrinkage porosity appears macroscopically at the hot joints, and most of the tiny shrinkage holes are interconnected inside the holes. Related to the spheroidizing element is that the residual magnesium and rare earth must not be too high, which has a significant effect on reducing the macroscopic and microscopic shrinkage. The shrinkage tendency is almost proportional to the spheroidizing element.
6.Black slag
It generally occurs on the upper part of the casting (pouring position), and is mainly divided into block, rope and fine black slag. Magnesium silicate, the main component of black slag, is formed by the reaction of MgO and SiO2 in molten iron and is affected by its relative content.
7.Spheroidization
This is because the spheroidized molten iron stays for a long time, the residual magnesium is gradually reduced, the slag is not removed in time, and the sulfur will return to the molten iron, reducing or even disappearing the graphite in the solidified structure, and decays into irregular, worm-like or Flake graphite.
ABOUT KEVA
Keva Casting is a professional casting company that focuses on Construction, Machinery, Automobile, Hardware, Pipeline and many other industries.
We provide top quality products with the best service based on our complete production chain including our own mold design, advanced production techniques, and full management of the supply chain. Keva Casting has two factories located in Zhucheng, China's Shandong province.
We use "shell molding", which is a new technique that has been developed in recent years.This new technique has simplified production procedures and reduced air pollution compared with traditional sand casting and investment casting. Shell making and core making are faster to ensure production in enormous quantities. The dimensions and surface finishing are satisfactory for all kinds of industrial requirements. Besides supplying our own formwork & scaffolding systems, our casting products also supply OEM services in various industries.