Basic uses of nickel-iron alloys
The main role of nickel in stainless steel is that it changes the crystal structure of the steel. One of the main reasons for the addition of nickel to stainless steel is the formation of an austenitic crystal structure, which improves stainless steel properties such as ductility, weldability and toughness, so nickel is known as an austenite former.
Nickel content up to 5% can improve the tensile strength and hardness of low carbon structural steel. The inclusion of 3% nickel in carbon steel improves its tensile strength, impact toughness, yield point and deformability. NiCrMo structural steel with nickel content of 1%-4% is very suitable for automobile, locomotive and machine manufacturing due to the appropriate ratio of tensile strength to mass. In addition to these elements, steel for wear-resistant components also contains carbon. The most important nickel-containing steel grades and the largest users are stainless steels and heat-resistant special steels. For example, a series of heat-resistant stainless steels such as Cr18Ni9Ti and Cr17Ni11Mo2 have good thermal processing properties and are widely used in machinery, medical treatment, national defense, and light industry.
Nickel has a slight graphitization effect in cast iron, stabilizing pearlite and reducing ferrite content. The nickel in cast iron therefore contributes to a uniform and one-piece structure and good properties. Adding a small amount of nickel (Ni0.1%-1.0%) will lead to the formation of fine pearlite, and when the nickel content is high, martensite and austenite will be formed. Fine and stable pearlite can make cast iron have good machinability and hardness. Therefore, nickel-added iron castings can be used to make castings in the automotive industry.
