Composition and Properties of Iron

examine the properties of cast iron, which determine the specificity

Composition and properties

For cast irons are alloys of iron with carbon content exceeding 2.14%, in these alloys is usually present as silicon, and some amount of manganese, sulfur and phosphorus, and sometimes other elements introduced as alloying additives to impart specific properties of cast iron. These alloying elements include nickel, chromium, magnesium, etc.

Depending on the structure of cast irons are divided into white and gray. In white cast iron all the carbon is connected to the chemical compound iron carbide Fe 3 C - cementite. In gray cast iron is a significant part of the carbon in the structure-free state in the form of graphite. If the gray cast iron well to machining, White has a very high hardness and cutting tool can not be processed. Therefore, the white cast irons are used for the manufacture of products is extremely rare, they are used mainly as intermediate for the so-called malleable cast iron. Getting a white or gray cast iron depends on its composition and cooling rate.

Depending on the structure of cast irons are classified as high-strength (nodular) and malleable. According to the degree of doping irons are divided into simple, low-alloy (up to 2.5% alloying elements), srednelegirovannye (2.5 - 10% alloying elements) and high (over 10% alloying elements). The most widely used are simple and low-alloyed gray cast iron.

Cast iron became widespread as a structural material in engineering, metallurgy and other industries due to a number of advantages over other materials, such as in the first place should be mentioned are: low cost, good casting properties. Products made from it have a sufficiently high strength and wear resistance due to friction at work and are less than steel sensitivity to stress concentrators. Along with these advantages the product made from gray cast iron is well handled by the cutting tool. This, together with good casting properties to evaluate iron as a highly technological material.

The main process of forming the structure of cast iron - the process of graphitization (emphasis in structural carbon-free form), since it determines not only the number, shape and distribution of graphite in the structure, but also a metal base (matrix) of iron. Depending on the degree of graphitization of the matrix can be pearlite-cementite (n-f-C), pearlite (P), pearlitic-ferritic (P B-F) and ferritic (F). Pearlite eutectoid cementite is called, the rest of the cement - the structural-free. Some of the elements introduced in the cast (in order of potency: C, Si, Ni, Co, Cu), promote graphitization, while others - prevent (S, V, Cr, Sn, Mo, Mn). The greatest effect is grafitiziruyuschee carbon and silicon, the smallest - cobalt and copper.

The most severely retard the process of graphitization (have a bleaching action), sulfur, vanadium, tin. Therefore, in gray cast irons always contain a significant amount of silicon.

See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color