White mouth and gray mouth appear in casting, how to effectively solve it?

In the casting process, there will be more or less white mouth and gray mouth. How to solve it effectively?

First of all, understanding the working principle of casting can effectively avoid unnecessary waste.

White mouth: All the iron in cast iron exists in the form of infiltrated carbon body. Because the fracture is bright white, it is called white cast iron.

Due to the large amount of hard and brittle fe3c, white cast iron has high hardness and brittleness and is difficult to process. Therefore, it is rarely used directly in industrial applications. It has high surface hardness and wear resistance, and is only used for a few parts that require wear resistance without impact, such as wire drawing dies, ball mill iron balls, etc. Mostly used as a billet for steelmaking and malleable cast iron.

Gray: Most or all of the carbon in cast iron exists as free-state flake graphite, and the fracture is gray.

It has good casting performance, good machinability, good wear reduction and wear resistance, plus it has simple melting ingredients and low cost, and is widely used in the manufacture of complex structural castings and wear-resistant parts. Due to the presence of flake graphite in gray cast iron, graphite is a component with low density, low strength, low hardness, and zero plasticity and toughness. Its existence is like the existence of a large number of small gaps in the steel matrix, which reduces the bearing area and increases the crack source. Therefore, gray cast iron has low strength and poor toughness, and cannot be processed under pressure.

Solution: In order to improve its performance, add a large amount of inoculants such as ferrosilicon, silicon calcium and other inoculants to the molten iron before casting to refine the pearlite matrix, which can be effectively improved.