High Quality Cast Iron

What is cast iron?

Cast iron is made from pig iron, which is the product of melting iron ore in a blast furnace. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants.

What type of metal is cast iron?

Cast iron,an alloy of iron that contains 2 to 4 percent carbon,along with varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace.

What are the types of cast iron?

It can be generally divided into White cast iron, Grey cast iron, Ductile cast iron, Malleable cast iron, Alloy cast iron and so on.

Cast iron is not pure iron, it is a kind of Fe, C, Si as the main components and has a eutectic transformation during the crystallization process. 

Chemical composition is generally: C2.5%-4.0%, SI1.0%-13, 0%, P0.4%-1.5%, S0.02%-02%. In order to improve the mechanical properties of cast iron, a small amount of Cr, Ni, Co, Mi and other alloying elements are usually added to the cast iron composition to make alloy cast iron.

First, the characteristics of cast iron

1. Composition and organizational characteristics

Compared with carbon steel, the chemical composition of cast iron in addition to a higher C, Si content (C2.5% ~ 4, 0%, Si1.0%-3.0%), but also contains higher impurity elements Mn, P, S, in the special properties of alloy cast iron, also contains some alloying elements. The existence and content of all these elements will directly affect the properties of cast iron.

Since the carbon in cast iron is mainly in the form of graphite (G), the organization of cast iron is composed of a metal matrix and graphite.Therefore, the structural characteristics of cast iron can be seen as the distribution of different shapes of graphite on the matrix of steel.

2.Performance characteristics of cast iron

The tensile strength, ductility and toughness of cast iron are lower than that of carbon steel.Although the mechanical properties of cast iron are not as good as those of steel, due to the presence of graphite,cast iron has many properties that steel cannot achieve. Such as good wear resistance,high vibration resistance,low notch sensitivity and excellent cutting performance.In addition,the carbon content of cast iron is high,its composition is close to eutectic composition,so the melting point of cast iron is low, about 1200 °C or so,the fluidity of molten iron is good,due to the volume expansion of graphite crystallization,so the transmission shrinkage rate is small,its casting performance is better than steel,so it is usually used in casting method to make castings, so called cast iron.

Second, the classification of cast iron

There are many ways to classify cast iron. According to the form of carbon can be divided into three types:

1. White iron (referred to as white iron)

The carbon in white cast iron mainly exists in the form of iron carbide,and the fracture is white and bright.Its performance is hard and brittle,and it is difficult to cut.In addition to a few used to manufacture high hardness,wear-resistant,do not need to process parts or surface requirements of high hardness,wear-resistant cold castings (such as crusher pressure plate,roll,train wheel,etc.),can also be used as steel raw materials and blanks of malleable cast iron.

2. Gray cast iron (referred to as gray iron)

The carbon in gray cast iron mainly exists in the form of flake graphite,and the fracture is gray.Gray cast iron has good casting performance and machining performance,and low price,convenient manufacturing,so it is widely used.

3. Mote cast iron (referred to as mote iron)

The carbon in mote cast iron exists in both iron carbide form and graphite state.The fracture is mixed with white free iron carbide and dark gray graphite,so it is called mottled iron.Mote iron is rarely used in production.

According to the different shapes of graphite,cast iron is divided into the following four types:

(1) Gray cast iron,the shape of graphite in cast iron is sheet-like.

(2) Most of the graphite in ink cast iron is short.

(3) Nodular cast iron,the graphite in the cast iron is irregular.

(4) ductile iron: the graphite in the cast iron is spherical.

In addition, in order to obtain some special properties, the conventional elements in the cast iron should be high and specified content, and a certain alloying element should be added, which is called special performance cast iron. For example, wear-resistant cast iron, heat-resistant cast iron and corrosion-resistant cast iron.