What is the difference between 316 and 316L stainless steel?

The main difference is the level of carbon content, 316 stainless steel has a 0.08% max carbon content while 316L has a 0.03% max carbon content. Since SS316L has a lower carbon content than SS316, SS 316L stainless steel wire is softer than SS 316.

Chemical compositions

The”L” in 316L refers to the extra low concentration of Carbon in the steel. The reduction in carbon content helps to prevent an effect called “sensitization”, where carbon combines to chromium, reducing the chromium-free content.This allows the steel to be welded without the formation of potentially weakening carbides.

316L is low carbon with 0.03% maximum to prevent the loss of corrosion resistance caused by chromium carbide formation during welding. 316 is 0.08% carbon maximum. Neither grade has a specified minimum carbon content. The strength requirements for 316 are a little higher than for 316L.

Mechanical Properties

Another different at minimum yield strength of type 316L (170 Mpa) is less than 316 (200 MPa).

Type 316L

Type 316 

Type 316/316L are grouped in Gr. A or B accordance to AWS D1.6 (depending on material specification).

Type 316/316L are grouped in Gr. 1 accordance to ASME section IX.

Conclusion

Type 316L normal offer for design and welding, but it is limited the minimum yield strength. So, the design engineering shall also offer a dual grades.

That reason lead to the manufacturer always offer the dual grades such as type 316/316L. Dual type means compliance with a minimum of yield strength and low carbon for weldability.

Running PQR should offer dual grade/type TP316/316L.

Nguyen Duy Bien
 

Enjoy learning and researching, reading book. Knowledge welding inspection painting inspection.

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