Alloy 317L (UNS S31703) is a molybdenum-containing austenitic stainless steel that offers higher chemical resistance than traditional chromium-nickel austenitic stainless steels such as Alloy 304. In addition, Alloy 317L has higher creep, stress-break and tensile strengths at elevated temperatures compared to conventional stainless steels. It is a low carbon or "L" grade that resists sensitization during welding and other thermal processing.
General properties
Alloy 317L (UNS S31703) is a low-carbon, corrosion-resistant austenitic chromium-nickel-molybdenum stainless steel. The high content of these elements ensures that the alloy has better chloride pitting and general corrosion resistance than conventional 304/304L and 316/316L grades. This alloy has higher resistance than 316L in highly corrosive environments containing sulfur media, chlorides and other halides.
The low carbon content of Alloy 317L renders it immune to intergranular corrosion due to chromium carbide precipitation during welding, allowing it to be used in the welded condition. With the addition of nitrogen as a strengthening agent, the alloy can be dual certified as Alloy 317 (UNS S31700).
Alloy 317L is nonmagnetic in the annealed condition. It cannot be hardened by heat treatment, but the material can be hardened by cold working. Alloy 317L can be easily welded and machined through standard shop fabrication practices.
application
Air Pollution Control - Flue Gas Desulfurization Systems (FGD)
Chemical and petrochemical processing
dynamite
Food and Beverage Processing
Petroleum refining
Electricity generation - condenser
pulp and paper
standard
ASTM.......A 240
ASME..........SA 240
Corrosion resistance
The higher molybdenum content of Alloy 317L ensures excellent overall and localized corrosion resistance in most media compared to 304/304L and 316/316L stainless steels. Environments that are not corrosive to 304/304L stainless steel will not generally corrode 317L. However, one exception is strongly oxidizing acids such as nitric acid. Alloys containing molybdenum generally do not perform well in these environments.
Alloy 317L has excellent corrosion resistance to a wide range of chemicals. It resists attack by sulfuric acid, acid chlorine and phosphoric acid. It is used to handle hot organic acids and fatty acids frequently found in food and pharmaceutical processing applications.
The corrosion resistance of 317 and 317L should be the same in any given environment. An exception is where the alloy will be exposed to chromium carbide precipitation temperatures in the range of 800 – 1500°F (427 – 816°C). Due to its low carbon content, 317L is the material of choice for preventing intergranular corrosion in this service.
Generally speaking, austenitic stainless steels are prone to chloride stress corrosion cracking in halide service. Although 317L is more resistant to stress corrosion cracking than 304/304L stainless steel, it is still susceptible due to its higher molybdenum content.
The higher chromium, molybdenum and nitrogen content of 317L enhances its ability to resist pitting and crevice corrosion in the presence of chlorides and other halides. The Pitting Resistance Equivalency (PREN), which includes the Nitrogen Number (PREN), is a relative measure of pitting resistance. The chart below provides a comparison of Alloy 317L and other austenitic stainless steels.
physical properties
density
0.285 lbs/in3
7.89 g/cm3 specific heat
0.12 BTU/lb-°F (32 – 212°F)
502 J/kg-°K (0 – 100°C) elastic modulus
29.0 x 10 6 psi
200 GPa
Thermal conductivity 68°F (20°C)
8.1 BTU/(hr x ft x °F)
14 W/(mx K)melting range
2540 – 2630°F
1390 – 1440°C Resistivity
33.5 Microhm-in at 68°C
85.1 Microhm-cm at 20°C
manufacturing data
Alloy 317L can be easily welded and machined through standard shop fabrication practices.
cold forming
The alloy is very ductile and forms easily. The addition of molybdenum and nitrogen means more powerful processing equipment may be required compared to standard 304/304L grades.
Thermoforming
For thermal processing, an operating temperature of 1652 – 2102°F (900 – 1150°C) is recommended. Do not process this alloy below 1742°F (950°C). If the final molding temperature is below this threshold, a solution anneal of 1976 – 2156°F (1080 – 1180°C) is required. Rapid quenching is required.
welding
Alloy 317L can be easily welded by most standard processes. No post-weld heat treatment required
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