The name grey iron is because of the gray color of the fracture it forms, which is due to the presence of graphite. Grey iron die casting is the most common and widely used casting material.
Grey iron is so popular in engineering applications because of its relatively low cost and the properties it presented. The grey iron has good galling and wears resistance because the graphite flakes self lubricates, and it also gives the gray iron part an excellent damping capacity because it absorbs the energy and converts it into heat.
Grey iron is very suitable for casting works. But during the casting process, a less solidification shrinkage than other casting iron shall be considered. The silicon promotes good corrosion resistance and increased fluidity when casting.
Below is a reference chart of other ASTM standards affecting grey iron.
ASTM A395 & ASME SA395: ferritic ductile iron pressure-retaining castings for
use at elevated temperatures
ASTM A439: austenitic ductile iron castings
ASTM A476 & ASME SA476: ductile iron castings for paper mill dryer rolls
ASTM A536 & SAE J434: ductile iron castings
ASTM A571 & ASME SA571: austenitic ductile iron castings for pressure-containing parts suitable for low-temperature service
ASTM A874: ferritic ductile iron castings suitable for low-temperature service
ASTM A897: austempered ductile iron castings
Ductile iron
Description of Gray Cast Iron
Gray cast iron is a type of cast iron. Carbon is present in cast iron in the form of flake graphite. The fracture is gray in color. It has good casting and cutting properties and good wear resistance. Gray cast iron is used in the manufacture of frames, boxes, etc. The graphite of gray cast iron is in the form of flake. The effective bearing area is relatively small, and the graphite tip is easy to produce stress concentration, so the strength, plasticity, and toughness of gray cast iron are lower than other cast iron. However, it has excellent vibration damping, low notch sensitivity, and high wear resistance.
Introduction to Cast Iron Molding
Cast iron moldings are broadly defined as objects cast in iron, which is the most commonly used metal.
Numerical simulation of the solidification process of thick and large section ductile iron castings with the application of computer was carried out for the temperature field. Increasing the strength of the mold shell, baking temperature and decreasing the pouring temperature are beneficial to reduce the scrap rate of castings and improve the quality of ductile iron castings.
Factors Affecting the Performance of Gray Cast Iron
The influence of chemical composition
In production, the quality fraction of carbon and silicon is mainly controlled. If the mass fraction of carbon and silicon is too low, the cast iron is easy to appear white mouth organization, and the mechanical properties and casting performance are very low; if the mass fraction of carbon and silicon is too high, the graphite flakes are too much and coarse, and even the graphite floats on the surface of the iron, which reduces the performance and quality of the castings. Therefore, the carbon and silicon content of gray cast iron is generally controlled at 2% to 4% C; 1.0% to 2.0% Si; 0.5% to 1.4% Mn.
The effect of cooling rate
Under certain casting process conditions, the cooling rate of the casting has a great impact on the degree of graphitization. Castings of different wall thickness with the increase in wall thickness, the cooling rate slows down, and carbon atoms have sufficient diffusion time. It is conducive to the full graphitization process, room temperature organization is easy to form gray iron organization; but thin-walled parts in the cooling process, the cooling rate is too fast, easy to form a white mouth iron organization.
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