A Corrosion Resistant Austenitic Stainless Steel with a High
Molybdenum and Nitrogen Content Developed for Use in Chloride
Containing Environments.
Available thicknesses for Alloy 317LMN:
| 3/16" | 5/16" | 3/8" | 1/2" | 5/8" | 3/4" |
|---|
| 4.8mm | 7.9mm | 9.5mm | 12.7mm | 15.9mm | 19mm |
|
|
Alloy 317LMN (UNS S31726) is an austenitic
chromium-nickel-molybdenum stainless steel with corrosion
resistance superior to 316L and 317L. The higher molybdenum
content, combined with an addition of nitrogen, provides the alloy
with its enhanced corrosion resistance, especially in acidic
chloride containing service. The combination of molybdenum and
nitrogen also improves the alloys resistance to pitting and crevice
corrosion.
The nitrogen content of Alloy 317LMN acts as a strengthening agent
giving it a higher yield strength than 317L .Alloy 317LMN is also a
low carbon grade which enables it to be used in the as-welded
condition free from chromium carbide precipitation on the grain
boundaries.
Alloy 317LMN is non-magnetic in the annealed condition. It cannot
be hardened by heat treatment, only by cold working. The alloy can
be easily welded and processed by standard shop fabrication
practices.
Specification Sheet Overview
for Alloy 317LMN (UNS S31726)
W. Nr. 1.4439:
Applications
- Air Pollution Control—flue gas desulfurization systems, stack
liners, absorbers, ducts, dampers, and fans
- Chemical and Petrochemical Processing
- Food and Beverage Processing
- Pharmaceutical Equipment
Standards
ASTM........A 240
ASME........SA 240Corrosion Resistance
The higher molybdenum and nitrogen content of Alloy 317LMN assures
superior general and localized corrosion resistance in most media
when compared with 304/304L, 316/316L and even 317L stainless
steels. Environments that don’t attack 304/304L stainless steel
will normally not corrode 317LMN. One exception, however, are
strongly oxidizing acids such as nitric acid. Alloys that contain
molybdenum generally do not perform as well in these environments.
Alloy 317LMN has excellent corrosion resistance in a wide range of
chemicals. It resists attack in sulfuric acid, hydrochloric acid,
acidic chlorine and phosphoric acid. It is used in handling hot
organic and fatty acids often present in food and pharmaceutical
processing applications.
Because of its low carbon content, Alloy 317LMN should be utilized
when it will be exposed to temperatures in the chromium carbide
precipitation range of 800-1500°F (427-816°C). The higher nitrogen
content of 317LMN further retards the precipitation of sigma phase
as well as carbides.
In general, austenitic stainless steels are subject to chloride
stress corrosion cracking in halide service. Although 317LMN is
somewhat more resistant to stress corrosion cracking than 304/304L
stainless steels, because of its higher molybdenum content, it is
still susceptible.
The higher chromium, molybdenum and nitrogen content of 317LMN
enhance its ability to resist pitting and crevice corrosion in the
presence of chlorides and other halides. The Pitting Resistance
Equivalent including Nitrogen number (PREN) is a relative measure
of pitting resistance. The following chart offers a comparison
Alloy 317LMN and other austenitic stainless steels.
| ALLOY | PRE | ALLOY | PRE |
|---|
| 316 | 25 | 317LMN | 38 |
| 317L | 30 | SSC-6MO | 48 |
| 317LM | 34 | 625 | 52 |
| 904L | 36 | 276 | 69 |
PRE = Cr + 3.3Mo + 30N
Chemical Analysis
Weight % (all values are maximum unless a range is otherwise
indicated)
| | | |
|---|
| Chromium | 17.0 min.-20.0 max. | Manganese | 2.00 |
| Nickel | 13.5 min.-17.5 max. | Phosphorus | 0.045 |
| Molybdenum | 4.0 min.-5.0 max. | Sulfur | 0.030 |
| Nitrogen | 0.10 min.-0.20 max. | Silicon | 0.75 |
| Carbon | 0.030 | Iron | Balance |
Physical Properties
Density
0.290 lbs/in3
8.0 g/cm3Specific Heat
0.12 BTU/lb-°F (32 – 212°F)
502 J/kg-°K (0 – 100°C)Modulus of Elasticity
29.0 x 106 psi
200 GPaThermal Conductivity 212°F (100°C)
8.7 BTU/hr/ft2/ft/°F
1.26 W/m-°KMelting Range
2540 – 2630°F
1393 – 1443°CElectrical Resistivity
33.5 Microhm-in at 68°C
85.1 Microhm-cm at 20°C| Temperature Range | |
|---|
| °F | °C | in/in °F | cm/cm °C |
|---|
| 68-212 | 20-100 | 8.9 x 10-6 | 16.03 x 10-6 |
Mechanical Properties
Typical Values at 68°F (20°C)
Yield Strength
0.2% Offset | Ultimate Tensile
Strength | Elongation
in 2 in. | Hardness | Reduction
in Area |
|---|
| psi (min.) | (MPa) | psi (min.) | (MPa) | % (min.) | (max.) | % |
|---|
| 35,000 | 205 | 80,000 | 550 | 40 | 96 Rockwell B | 69 |
Fabrication Data
Alloy 317LMN can be easily welded and processed by standard shop
fabrication practices.
Cold Forming
The cold formability of Alloy 303 is adversely impacted by the high
sulfur content. The alloy may be bent with a generous bend radius,
however, when cold forming is required, 304 should be utilized.
Hot Forming
The alloy is quite ductile and forms easily. The addition of
molybdenum and nitrogen implies more powerful processing equipment
may be necessary when compared with the standard 304/304L grades.
Machining
The cold work hardening rate of Alloy 317LMN makes it less
machinable than 410 stainless steel. The table below provides
relevant machining data.
| Operation | Tool | Lubrication | CONDITIONS |
|---|
| | | Depth-mm | Depth-in | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min |
|---|
| Turning | High Speed Steel | Cutting Oil | 6 | .23 | 0.5 | .019 | 11-16 | 36-52 |
| Turning | High Speed Steel | Cutting Oil | 3 | .11 | 0.4 | .016 | 18-23 | 59-75 |
| Turning | High Speed Steel | Cutting Oil | 1 | .04 | 0.2 | .008 | 25-30 | 82-98 |
| Turning | Carbide | Dry or Cutting Oil | 6 | .23 | 0.5 | .019 | 70-80 | 230-262 |
| Turning | Carbide | Dry or Cutting Oil | 3 | .11 | 0.4 | .016 | 85-95 | 279-313 |
| Turning | Carbide | Dry or Cutting Oil | 1 | .04 | 0.2 | .008 | 100-110 | 328-361 |
| | | Depth of cut-mm | Depth of cut-in | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min |
|---|
| Cutting | High Speed Steel | Cutting Oil | 1.5 | .06 | 0.03-0.05 | .0012-.0020 | 16-21 | 52-69 |
| Cutting | High Speed Steel | Cutting Oil | 3 | .11 | 0.04-0.06 | .0016-.0024 | 17-22 | 56-72 |
| Cutting | High Speed Steel | Cutting Oil | 6 | .23 | 0.05-0.07 | .0020-.0027 | 18-23 | 59-75 |
| | | Drill ø mm | Drill ø in | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min |
|---|
| Drilling | High Speed Steel | Cutting Oil | 1.5 | .06 | 0.02-0.03 | .0007-.0012 | 10-14 | 33-46 |
| Drilling | High Speed Steel | Cutting Oil | 3 | .11 | 0.05-0.06 | .0020-.0024 | 12-16 | 39-52 |
| Drilling | High Speed Steel | Cutting Oil | 6 | .23 | 0.08-0.09 | .0031-.0035 | 12-16 | 39-52 |
| Drilling | High Speed Steel | Cutting Oil | 12 | .48 | 0.09-0.10 | .0035-.0039 | 12-16 | 39-52 |
| | | | | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min |
|---|
| Milling Profiling | High Speed Steel | Cutting Oil | | | 0.05-0.10 | .002-.004 | 10-20 | 33-66 |
Welding
Alloy 317LMN can be readily welded by most standard processes
including TIG/GTAW, MIG/GMAW, MMAW and SAW. A post weld heat
treatment is not necessary.
