Letter 14356

Differences between 316 and 316L [Singapore] 

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What are the differences between 316 and 316L, as it semms that there are some differences. Would 316L be any much difference to corrosion resistance than 316?

Richard Ashley
- Singapore

Richard,

316L has lower carbon allowed. It will be less susceptible to sensitization, a condition caused when carbon combines with chromium around the grain boundaries, thereby depleting the grain boundary areas of chromium. That would make the grain boundary areas less corrosion resistant. Sensitization occurs with heating into the 800F to 1300F region, so it's a welding or annealing problem.

The 316L will also be softer than straight 316, again due to the lower carbon.

Good luck!

Lee Gearhart
- East Aurora, NY

The difference between 316 and 316L is the amount of carbon that is in the material.

316 has .08 Max carbon content while 316L has a .03 Max carbon content.

I am not aware that there is a significant difference in the corrosion resistance of one over the other. The primary reason for using an L grade of stainless steel is that this will reduce the tendendancy of the material to crack after welding.

If you use a stainless steel with a high carbon content the welds may crack spontaneously as they cool down from the welding. This type of cracking is known as "hot brittleness".

In short, if the item you are fabricating will be welded then use an L grade material. If it is not then it does not matter.

I hope this helps you.

John Holroyd
- Elkhorn, WI, USA

316 and 316L differ only by the amount on carbon in them. As I understand it, 316 L has lower carbon such that when welded the chromium carbide that forms does not deplete the chromium to the point where the corrosion of the stainless is deleterioulsy impacted. This effect, known as chromium depletion, shows itself in most plating shops where 316 welded tanks are used. The welded corners typically rust whereas the bulk of the exposed stainless is untouched. 316 has a carbon content of 0.08% Max whereas 316L is 0.03% Max.

Milt Stevenson, Jr. Anoplate Corp Syracuse, NY, USA

The main difference is the lower carbon content, 316 being 0.030, 316L being as low as 0.016. Other elements are also somewhat lower,such as sulfur, phosphorus and copper. The 316L is more ductile when annealed, and is markedly more corrosion resistant, especially after welding. 316L is much more weld friendly than 316, as it is less susceptible to intergranular corrosion, after welding or air service up to 1600F (intermittent) 1700F (continuous), due to carbide precipitation. In 316 carbide precipitation will occur between 900F-1070F after 9 hours, wheras 316L will precipitate carbides between 900F-1010F after 181 hours, 316L showing much more resistance to sensitization.

Jeff Swayze
- Kelowna, B.C., Canada

The Temperatures at which the precipitation of Chromium carbides is present is between 1004-1553 F.

Source: ASM Materials Engineering Dictionary [link is to product info at Amazon]

Purusha Bonnin
- Barberton, OH, US

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