317 vs 317L Stainless Steel: Molybdenum-Enhanced Alloys

 

How do their chemical compositions differ?​

317 contains 18-20% chromium, 11-15% nickel, 3-4% molybdenum, and 0.08% max carbon. 317L has the same alloy content but with carbon ≤0.03%, preventing chromium carbide formation in weld zones.​

 

Which offers better corrosion resistance?​

Both excel in chloride-rich and chemical environments, but 317L has better resistance to intergranular corrosion after welding. 317 is better for non-welded parts needing slightly higher strength at high temperatures.​

 

How do they compare in mechanical properties?​

317 has a slightly higher tensile strength (around 515 MPa) than 317L, but both have similar ductility (elongation up to 40%). 317L is more ductile in welded joints, making it better for welded structures.​

 

What about their fabrication properties?​

317L is more weldable than 317, with no need for post-weld heat treatment to maintain corrosion resistance. 317 is slightly easier to machine in its annealed state but requires more care with welded joints.​

 

Where are 317 and 317L commonly used?​

317 is used in non-welded chemical processing equipment. 317L finds applications in welded tanks, offshore oil rigs, and industrial waste treatment systems where post-weld corrosion resistance is critical.