Several common elements of stainless steel and their functions

The content and distribution of carbon in steel determine the properties and structure of steel. In stainless steel, the influence on the structure is mainly reflected in two aspects:

1. Carbon is an element that stabilizes austenite

2. Carbon and chromium can form carbides

The strength and corrosion resistance of carbon in stainless steel are contradictory. Stainless steel with different carbon content can be selected according to different use requirements

The decisive role of chromium in stainless steel

Every kind of stainless steel contains chromium. At present, there is no stainless steel without chromium

The addition of chromium to the steel grade promotes the contradictory movement inside the stainless steel to be conducive to the development of corrosion resistance

The function of nickel in stainless steel is to cooperate with chromium

Nickel is an excellent corrosion-resistant material and an important element of alloy steel. The corrosion resistance of low carbon nickel steel can be significantly changed only when the pure austenite structure is obtained and the nickel content is 27%. Therefore, nickel cannot form stainless steel alone. Nickel can change the structure of chromium steel and improve the corrosion resistance and physical properties of stainless steel.

The effect of manganese on austenite is similar to that of nickel

Manganese cannot form austenite. It can reduce the quenching speed of steel, increase the stability of austenite during cooling and inhibit the decomposition of austenite. Therefore, although there are austenitic steels alloyed with manganese, they cannot be used as stainless steel

The role of nitrogen is to stabilize austenite

Nitrogen is an austenite forming element. Nitrogen is a gas. It is not directly integrated into steel. Manganese can be integrated into a certain amount of nitrogen. 200 series stainless steel is to add manganese to replace nickel to form austenitic structure. The lower the content of nickel, the more nitrogen and manganese are needed to replace it.

Role of other elements in stainless steel

Titanium: to prevent intergranular corrosion

Molybdenum: improve the corrosion resistance of stainless steel

Cobalt: improve the hardness of stainless steel

Boron: reduce the melting point of weld

Silicon: it is an element forming ferrite and an impurity element often existing in stainless steel

Phosphorus, sulfur and selenium: impurity elements are often found in stainless steel