SUS316 austenitic stainless steel tube

Stainless steel tubes are iron based alloys with mass fractions ranging from 12% to more than 50% of alloyed elements. Alloying elements affect the stability of austenite, ferrite and martensite phases, thus affecting the equilibrium relationship between the phases related to the stability. The elements added to stainless steel can be divided into stable ferrite and stable austenite. Martensite is a phase change product formed when austenite is cooled from high temperature to low temperature. If no austenite is formed at high temperature, then no martensite phase is obtained at low temperature.

SUS316 stainless steel chemical composition
P≤0.035
S≤0.03
Ni: 10.0-14.0
Cr: 16.0-18.5
Mo: 2.0-3.0

SUS316 stainless steel mechanical properties
Tensile strength (Mpa) 620 MIN
Yield strength (Mpa) 310 MIN
Elongation (%) 30 MIN
Area reduction (%) 40 MIN

SUS316 austenitic stainless steel tubes contain high nickel content and other austenitic forming elements, which contribute to the formation of austenitic phase and make it stable at room temperature or even lower. Ferrite seamless tubes contain elements that attenuate austenite formation such as high chromium content, making ferrite the dominant phase component. Martensitic stainless steel tubes are austenitic at high temperatures. However, this austenite is unstable and changes during cooling. The microstructure of stainless steel tubes can be controlled by the balance between austenite forming elements and ferrite forming elements. The adjustment of the balance between the two elements plays an important role in the mechanical properties, corrosion resistance and weldability of stainless steel tubes.