Alloy cast iron
Alloy cast iron – specifications and uses
Alloy cast iron is known for many of its unique properties – increased wear resistance, heat resistance, lower price compared to steel. That is why this type of cast iron is very popular in a wide variety of areas.
Depending on the level of alloying, low-alloyed (the total number of alloying elements is less than 2.5%), medium-alloyed (2.5-10%), and high-alloyed (more than 10%) cast irons are distinguished. Low-alloyed cast irons have a pearlitic or bainitic structure, medium-alloyed ones have a martensitic structure, and high-alloyed ones have an austenitic or ferritic structure.
Alloy cast iron contains alloying components – chromium, vanadium, nickel, copper and others. These components in the composition of cast iron give it alloying properties:
- Increased wear resistance;
- Heat resistance;
- Corrosion Resistance;
- Antifriction properties.
Grades of alloy cast iron named depending on the main components. It can be chromium alloyed cast iron, vanadium alloyed cast iron, nickel alloyed cast iron and others.
The main types of alloy cast iron are:
- White cast iron;
- Gray cast iron;
- Malleable cast iron.
Use of alloy cast iron
Castings made of alloy cast iron are most often used in places where there is a possibility of high wear, for example, when operating units in friction, high temperatures, or in an aggressive environment. It is important not to forget that cast iron is quite fragile and does not withstand large shock loads.
Most often, cast iron is smelted in blast furnaces, it is made from iron ore, which is subsequently processed into steel and is called pig iron. For the manufacture of shaped castings, cast iron is used.
Depending on the application of the casting and what characteristics are needed for operation, the formulation components are determined. So, it can be castings with the following properties:
- Heat resistant;
- Cold resistant;
- Wear resistant;
- Corrosion resistant;
- Low magnetic.
Alloy castings processing
Castings can be processed in different ways. The most popular types of processing for castings are:
- High-temperature annealing – reduces hardness;
- Exposure with normalization – reduces magnetic permeability and at the same time increases ductility and strength;
- Normalization – allows you to increase the hardness of your casting;
- Tempering – allows you to remove internal stress;
- High-temperature tempering – reduces hardness and facilitates the processing of castings.
The time for processing and heating the castings is selected for each casting individually, depending on its weight and size. All the basic properties that the casting should have been determined by the end-users, depending on the future operating conditions of the product.