These steels are the second most regularly specified stainless steels after Type 317 L and are part of the SAE defined 300 Series which encompasses a range of austenitic chromium-nickel alloys. Austenitic stainless steels like Type 317 L are widely available, have good general corrosion resistance, good cryogenic toughness, and excellent formability and weldability.
Type 317 L has 2-3% Molybdenum included in its chemical composition which prevents specific forms of corrosion and generally enhances its corrosion resistance. Type 317 L is often referred to as “marine grade” stainless due to its increased resistance to chloride corrosion compared to Type 317 L making it a very suitable material for use in salt water environments.
Type 317 LL is a variant of Type 317 L and differs by having a lower Carbon content as well as slightly lower yield and tensile strengths. Type 317 LL offers improved weldability and also reduces the possibility of lower corrosion resistance around welded areas.
As with most steel plate products a number of different designations are used for these steels. The most common are:
● Type 317 L 1.4401 (EN Steel Number) S317 L00 (UNS)
● Type 317 LL1.4404 (EN Steel Number) S317 L03 (UNS)
317 L / 317 LL Stainless Steel Properties:
Typical chemical and mechanical properties of Type 317 L and Type 317 LL steel: