stainless steels
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STAINLESS STEELS - by www.hghouston.com
Stainless Steels - Atmospheric Corrosion Resistance
Atmospheric Corrosion Resistance of Stainless Steels
Alloy Finish % Stained Area % Rusted Pit Density (A-537)
201 CR 15 1 7
301 CR 20 3 8
302 CR 5 3 8
304 CR 3 0 8
304L 2B 15 3 9
316 CR 2 0 9
316L 2B 1 0 10
321 2B 10 5 8
347 2B 15 5 8
410 no. 2 100 80 1
430 CR 100 20 8
Reference: Baker, E.A. and Lee, T.S. "Long Term Atmospheric Corrosion Behaviour of Various Grades of Stainless
Steels". ASTM Symposium on Degradation of materials in the Atmosphere. Philadelphia, PA. May 12-13, 1986
Cleaning Stainless Steels
The final operation after fabrication or heat treatment is cleaning to remove surface
contamination and restore corrosion resistance of the exposed surfaces. Degreasing to
remove cutting oils, grease, crayon markings, fingerprints, dirt, grime and other organic
residues is the first step.
Degreasing: Non-chlorinated solvents should be used in order to avoid leaving residues of
chloride ions in crevices and other locations where they can initiate crevice attack, pitting,
and/or stress corrosion later on when the equipment is placed in service.
Machined components: After degreasing, machined components are sometimes
"passivated" in 10% nitric acid. Nitric acid enhances the natural oxide surface film.
Fabrications: After degreasing, metallic surface contaminants such as iron embedded in
fabrication shop forming and handling, weld splatter, heat tint, inclusions and other metallic
particles must be removed in order to restore the inherent corrosion resistance of the
stainless steel surface.
Nitric-HF pickling, (10% HNO3, 2% HF at 49C to 60C (120 to 140F), is the most widely used
and effective method removing metallic surface contamination. Pickling may be done by
immersion or locally using a pickling paste.
Electropolishing, using oxalic or phosphoric acid for the electrolyte and a copper bar or plate
for the cathode can be equally effective. Electro-polishing may be done locally to remove heat
tint alongside of welds or over the whole surface.
Both pickling and electropolishing remove a layer several atoms deep from the surface.
Removal of the surface layer has the further benefit of removing surface layers that may have
become somewhat impoverished in chromium during the final heat treatment operation.
Glass bead or walnut shell blasting are very effective in removing metallic surface
contamination without damaging the surface. It is sometimes necessary to resort to blasting
with clean sand to restore heavily contaminated surfaces such as tank bottoms, but care must
be taken to be certain the sand is truly clean, is not recycled and does not roughen the
surface. Steel shot blasting should not be used as it will contaminate the stainless steel with
an iron deposit.
Stainless steel wire brushing or light grinding with clean aluminum oxide abrasive discs or
flapper wheels are helpful. Grinding or polishing with grinding wheels or continuous belt
sanders tend to overheat the surface layers to the point where resistance cannot be fully
restored even with subsequent pickling.
More information on cleaning and finishing may be found in: "Heat Treating, Cleaning and Finishing", Metals
Handbook, 10th Edition.
ASTM A 380, "Recommended Practice for Cleaning and Descaling Stainless Steel Parts, Equipment and Systems",
ASTM, 1916 Race Street, Philadelphia, PA 19103.
Tuthill, A. H., "Fabrication and Post Fabrication Cleanup of Stainless Steel", NiDI literature, Item 10 004.
Pettibone, J. S., "Burgers, Fries, Coke, and Stainless Steel" NiDI literature, Item 10 009.
AISI, "Cleaning and Descaling Stainless Steel, NiDI literature, Item 9 001.
Cold Working Properties
The austenitic chromium-nickel stainless steels are cold formed (bent, drawn, shaped) and
the cold forming imparts a higher strength than for the original starting annealed condition. It
is not typical to heat these stainless steels for forming as is often done with carbon steel. The
following are the designations of cold worked tempers as defined by ASTM A 666, Standard
Specification for Austenitic Stainless Steel, Sheet, Strip, Plate & Flat Bar.
1/4 Hard, 1/2 Hard, 3/4 Hard, Full Hard
Reheating the cold worked austenitic stainless steels at temperatures below 370C (700F)
increases the tensile strength. Reheating above 425C (900F) lowers the strength and
increases the ductility.
Cold working increases the fatigue strength of the austenitic stainless steels. However, the
fatigue strength of these cold worked alloys is reduced by notches, as compared to notched
fatigue strength in the annealed condition.
Fatigue Strength (Endurance Limits) of Cold Worked Stainless Steels
AISI Type Temper Endurance Limit - ksi
301 Full Hard 80
302 Full Hard 75
303 1/4 Hard 48
304 Annealed 35
304 1/2 Hard 70
304 3/4 Hard 92
347 3/4 Hard 88
Minimum Tensile Strength of Cold Rolled Sheet & Strip for 304
The other common 300 series alloys are similar.
Temper Tensile ksi Yield ksi Elong. % Rockwell C
Hardness
1/4 Hard 125 75 23 25
1/2 Hard 150 110 16 32
3/4 Hard 175 135 11 37
Full Hard 185 140 8 41
Extra Full
Hard200 - - 45
Tensile Strength of Cold Drawn Cr-Ni Stainless Steel Wire
Diameter Range of 0.126 - 0.375"
AISI TYPE TEMPER YIELD-ksi TENSILE-ksi ELONG.%
302 1/4 hard 90-125 120-140 15-25
1/2 hard 120-150 145-176 10-17
3/4 hard 150-180 170-200 5-10
*Full hard 180-220 190-230 2-5
*Typical of wires used in making stranded wire rope
304 1/4 hard 90-110 120-140 20-30
1/2 hard 120-140 130-170 10-18
3/4 hard 140-170 170-200 5-10
Full hard 170-210 200-240 2-5
309S 1/4 hard 80-90 110-130 15-25
1/2 hard 105-125 125-155 10-11
3/4 hard 125-150 140-180 8-12
Full hard 150-185 160-190 4-8
310S 1/4 hard 80-90 110-130 15-25
1/2 hard 105-125 125-155 10-11
3/4 hard 125-150 140-180 8-12
Full hard 150-185 160-195 3-6
316 1/4 hard 80-100 110-130 20-30
1/2 hard 105-125 135-155 12-20
3/4 hard 135-165 165-195 8-12
Full hard 155-185 185-215 3-6
321 1/4 hard 90-110 120-140 20-30
1/2 hard 120-140 150-170 10-18
3/4 hard 140-170 170-200 5-10
Full hard 170-210 200-240 2-5
347 1/4 hard 85-105 115-135 15-25
1/2 hard 110-130 140-160 10-13
3/4 hard 140-170 170-200 5-10
Full hard 160-190 190-220 3-6
TENSILE PROPERTIES OF AUSTENITIC STAINLESS STEELS
FOR VARIOUS AMOUNTS OF COLD WORKING
STRENGTH IN ksi for % COLD REDUCTION SHOWN
Alloy 0 10% 20% 30% 40% 50% 60%
301
Tensile 120 150 168 184 198 210 222
Yield 40 87 120 148 170 185 202
Elong. 75% 58% 42% 32% 22% 15% 6%
302
Tensile 93 108 122 138 152 168 180
Yield 37 91 107 120 134 147 160
Elong. 67% 42% 30% 20% 15% 10% 6%
303
Tensile 91 106 125 148 171 196 n/a
Yield n/a n/a n/a n/a n/a n/a n/a
Elong. 75% 58% 42% 32% 22% 15% 6%
304
Tensile 86 98 113 130 146 158 169
Yield 34 69 97 120 135 145 152
Elong. 53% 36% 25% 16% 13% 10% 6%
304L
Tensile 83 106 122 138 154 170 n/a
Yield 32 72 97 120 138 152 n/a
Elong. 57% 35% 23% 15% 10% 5% n/a
309S
Tensile 80 87 98 115 135 151 165
Yield 37 57 82 102 122 140 153
Elong. 55% 45% 30% 14% 9% 5% 3%
310S
Tensile 86 108 126 140 153 166 174
Yield 45 67 97 125 140 148 152
Elong. 45% 29% 15% 8% 6% 5% 5%
316
Tensile 85 95 110 130 142 150 169
Yield 38 70 98 118 128 137 148
Elong. 60% 40% 21% 12% 8% 6% 5%
321
Tensile 88 100 115 135 150 160 168
Yield 32 70 100 120 134 142 145
Elong. 55% 45% 26% 13% 8% 5% 4%
347
Tensile 96 105 122 144 159 168 173
Yield 40 78 109 128 138 143 149
Elong. 50% 33% 12% 8% 7% 6% 5%
Chemical Compositions of Stainless Steels
Wrought Stainless Steels
Alloy C Mn P S Si Cr Ni Mo Others
201 0.15 6.50 0.060 0.030 1.00 17.00 4.50 - 0.25N
202 0.15 9.00 0.060 0.030 1.00 18.00 5.00 - 0.25N
301 0.15 2.00 0.045 0.030 1.00 17.00 7.00 - -
302 0.15 2.00 0.045 0.030 1.00 18.00 9.00 - -
303 0.15 2.00 0.20 0.15 1.00 18.00 9.00 0.60 -
303Se 0.15 2.00 0.20 0.06 1.00 18.00 9.00 0.60 0.15Se
304 0.08 2.00 0.045 0.030 1.00 19.00 9.25 - -
304L 0.03 2.00 0.045 0.030 1.00 19.00 10.0 - -
309S 0.08 2.00 0.045 0.030 0.75 23.00 13.5 - -
310S 0.08 2.00 0.045 0.030 1.50 25.00 20.5 - -
316 0.08 2.00 0.045 0.030 1.00 17.00 12.0 2.5 -
316L 0.03 2.00 0.045 0.030 1.00 17.00 12.0 2.5 -
317 0.08 2.00 0.045 0.030 1.00 19.00 13.0 3.5 -
317L 0.03 2.00 0.045 0.030 1.00 19.00 13.0 3.5 -
321 0.08 2.00 0.045 0.030 1.00 18.00 10.5 - Ti 5 X C
329 0.10 2.00 0.045 0.030 1.00 27.50 4.5 1.50 -
330 0.08 2.00 0.040 0.030 1.00 18.50 35.5 - -
347 0.08 2.00 0.045 0.030 1.00 18.00 11.0 - Cb+Ta 10 X C
409 0.08 1.00 0.045 0.045 1.00 11.50 - - Ti 6 x C
410 0.15 1.00 0.040 0.030 1.00 12.50 - - -
416 0.15 1.25 0.040 - 1.00 13.00 - 0.60 S =0.15 min.
416Se 0.15 1.25 0.060 0.060 1.00 13.00 - - 0.15 Se
420 0.15 min. 1.00 0.040 0.030 1.00 13.00 - - -
430 0.12 1.00 0.040 0.030 1.00 17.00 - - -
440C 1.00 1.00 0.040 0.030 1.00 17.00 - - -
442 0.20 1.00 0.040 0.030 1.00 20.50 - - -
904L 0.02 2.00 0.045 0.035 1.00 21.00 25.5 4.5 Cu 1.5
17-4 PH 0.07 1.00 0.045 0.035 1.00 16.5 5.5 - Cu 3-5, 0.4 Al
17-7 PH 0.09 1.00 0.045 0.035 1.00 17.0 7.0 - .75-1.5 Al
2205 0.03 2.00 0.030 0.020 1.00 22.0 5.5 3.0 0.15 N
Cast Stainless Steels
CA-6NM 0.06 1.00 0.045 0.035 1.00 12.50 4.00 0.70 -
CA-15 0.15 1.00 - - 1.50 12.50 1.00 - -
CA-40 0.40 1.00 - - 1.50 12.50 1.00 - -
CF-3 0.03 1.50 0.040 0.040 2.00 19.00 10.00 - -
CF-3M 0.03 1.50 0.040 0.040 1.50 19.00 10.00 2.5 -
CF-8 0.08 1.50 0.040 0.040 2.00 19.00 9.00 - -
CF-8M 0.08 1.50 0.040 0.040 2.00 19.50 10.00 2.5 -
CH-20 0.20 1.50 0.040 0.040 1.50 20.00 10.00 - -
CK-20 0.20 2.00 0.040 0.040 2.00 25.00 20.00 - -
HF 0.30 2.00 0.040 0.040 2.00 19.00 9.00 - -
HH 0.35 2.00 0.040 0.040 2.00 25.00 12.00 - 0.2 N
HK 0.30 2.00 0.040 0.040 2.00 25.00 20.00 - -
Heat Treating Stainless Steels
Wrought stainless steels are solution annealed after processing and hot worked in
order to dissolve carbides and sigma. Carbides may form during heating in the 425 to
900C (800 to 1650F) range or during slow cooling through this range. Sigma tends to form at
temperatures below 925C (1700F). Specifications normally require solution annealing to be
done at 1035C (1900F) with a rapid quench. The molybdenum-containing grades are
frequently solution annealed at somewhat higher temperatures in the 1095 to 1120C (2000 to
2050F) in order to better homogenize the molybdenum.
Stainless steels may be stress relieved. There are several stress relief treatments. Guidelines
follow.
Stress redistribution at 290 to 425C (550 to 800F), which is below the sensitization range.
When stainless steel sheet and bar are cold reduced greater than about 30% and
subsequently heated to 290 - 425C (550 - 800F), there is a significant redistribution of peak
stresses and an increase in both tensile and yield strength. Stress redistribution heat
treatments at 290 - 425C (550 - 800F) will reduce movement in later machining operations
and are occasionally used to increase strength. Since stress redistribution treatments are
made at temperatures below 425C (800F), carbide precipitation and sensitization to
intergranular attack (IGA) are not a problem for the higher carbon grades.
Stress relief at 425 to 595C (800 to 1100F) is normally adequate to minimize distortion that
would otherwise exceed dimensional tolerances after machining. Only the low carbon "L"
grades or the stabilized 321 and 347 grades should be used in weldments to be stress
relieved above 425C (800F) as the higher carbon grades are sensitized to IGA when heated
above about 425C (800F).
Stress relief at 815 to 870C (1500 to 1600F) is occasionally needed when a fully stress
relieved assembly is required. Only the low carbon "L" grades, 321 and 347 should be used in
assemblies to be heat treated in this range. Even though the low carbon and stabilized grades
are used, it is best to test for susceptibility to IGA per ASTM A262 to be certain there was no
sensitization during stress relief treating in this temperature range.
Thermal stabilization treatments at 900C (1650F) minimum for 1 to 10 hours are occasionally
employed for assemblies that are to be used in the 400 to 900C (750 to 1650F) temperature
range. Thermal stabilization is intended to agglomerate the carbides, thereby preventing
further precipitation and intergranular attack (IGA). As with 815 to 870C (1500 to 1600F)
stress relief, it is best to test for susceptibility to IGA per ASTM A262.
"Heat Treating, Cleaning and Finishing", Metals Handbook, 10th edition, Vol. 4 in the section
entitled "Heat Treatment of Stainless Steels and Heat-Resisting Alloys".
High Temperature Properties
Cyclic Oxidation Resistance
WEIGHT GAIN - GRAMS PER SQUARE METER OF SURFACE FOR
TEMPERATURES SHOWN
ALLOY 705C 815C 980C 1090C
409 0.1 0.8 1430* 10,000*
430 0.4 1.3 1660* 10,000*
304 0.2 1.7 3400 10,000*
309 0.2 2.7 120 910
NOTE: These were cyclic tests for 100 hours duration in air containing 10% water vapor.
Cycled every 2 hours to room temperature then back to test temperature. Weight gain (or
loss) measured without purposeful removal of scale.
*Some of the higher temperature tests were for much shorter time than the 100 hours.
TENSILE and YIELD STRENGTH AT TEMPERATURES SHOWN (ksi)
24C 540C 650C
Alloy Tensile Yield Tensile Yield Tensile Yield
304 87 39 55 18 44 16
309S 90 45 67 36 54 28
310 95 45 70 24 58 19
316 84 40 67.5 28 55 24
321 79 31 57.5 26 45 21
347 95 40 60 20.5 50.5 20
*403 110 75 65 52 87 n/a
*410 125 108 75 n/a 20 n/a
NOTE: Alloys indicated by * were tested in heat treated condition, others in annealed
condition.
1000 HOUR STRESS-RUPTURE AT TEMPERATURES SHOWN
Alloy 538C 650C 815C
304 37 17 4
309S n/a 19 4
310S 32 18 6
316 n/a 24 7
347 49 23 4
410 19 n/a n/a
430 18 5 1
GENERAL INFORMATION ON HIGH TEMPERATURE PROPERTIES:
Allowable stresses for austenitic (300 series) stainless steel unfired pressure vessels are
found in Section VIII of the ASME Boiler Code, table UHA-23. Additional information on high
temperature properties can also be found in the ASM Metals Handbook, Volume 3, 10th
Edition.
POISSON'S RATIO AT TEMPERATURES SHOWN
TEMPERATURE
ALLOY 150C 260C 370C 480C 595C 705C 815C
304 0.28 0.30 0.32 0.28 0.29 0.28 0.25
309 0.28 0.30 0.30 0.29 0.27 0.32 0.25
310 0.32 0.31 0.31 0.32 0.34 0.34 0.29
316 0.26 0.29 0.34 0.30 0.32 0.31 0.24
321 0.23 0.25 0.27 0.30 0.29 0.27 n/a
347 0.30 0.31 0.29 0.33 0.31 0.35 0.28
By definition, Poisson's ratio is the ratio of lateral strain to longitudinal strain for a material
subjected to uniform longitudinal stresses within the proportional limit.
Sheet Finishes
ASTM A 480 "Standard Specification for General Requirements for Flat Rolled
Stainless & Heat Resisting Steel Plate, Sheet & Strip" covers finish requirements in detail.
Refer to this specification for more complete explanations of finishes for sheet, strip and plate
product forms.
Also see NiDI publication 9 012 "Finishes for stainless steels"
FINISH FOR SHEET:
No. 1 Finish - Hot-rolled, annealed and descaled.
No. 2D Finish - Cold-rolled, dull finish.
No. 2B Finish - Cold-rolled, bright finish.
Bright Annealed Finish - Cold-rolled bright finish obtained by final
anneal in controlled atmosphere furnace.
No. 3 Finish - Intermediate polished finish, one or both sides.
No. 4 Finish - General purpose polished finish, one or both sides.
No. 6 Finish - Dull satin finish, Tampico brushed one or both sides.
No. 7 Finish - High luster finish.
No. 8 Finish - Mirror finish.
TR Finish - Cold-worked to obtain specified properties.
Specification Cross Reference
U.S.
ALLOY
FRENCH
AFNOR
GERMAN
DIN
UK
B.S.
JAPAN
JIS
SWEDEN
SS
301 Z 12CN18.07 1.4310 301 S 21 SUS 301 2331
303 Z 10CNF18.09 1.4305 303 S 21 SUS 303 2346
304 Z 6CN18.09 1.4301 304 S 15 SUS 304 2333
304L Z 2CN18.10 1.4306 304 S 11 SUS 304L 2352
309S Z 15CN24.13 1.4833 309 S 16 SUS 309S
310S Z 8CN25.20 1.4845 310 S 16 SUS 310S 2361
316 Z 6CND17.11 1.4401
1.4436
316 S 31
316 S 33
SUS 316 2343
2347
316L Z 2CND17.12 1.4435 316 S 11
316 S 13
SUS 316L 2353
2348
317 1.4436 317 S 16 SUS 317 2366
317L Z 2CND19.15 1.4435 317 S 12 SUS 317L 2367
321 Z 6CNT18.10 1.4541 321 S 31 SUS 321 2337
329 1.4460 SUS 329J1 2324
330 Z 12NCS35.16 1.4864 SUH 330
347 Z 6CNNb18.10 1.4550 347 S 17 SUS 347 2338
403 Z 6C13 1.4000 403 S 17 SUS 403 2301
409 Z 6CT12 1.4512 409 S 19 SUH 409
410 Z 13C13 1.4024 410 S 21 SUS 410 2302
416 Z 12CF13 1.4005 416 S 21 SUS 416 2380
420 Z 20C13 1.4021 420 S 45 SUS 420J2 2303
430 Z 8C17 1.4016 430 S 17 SUS 430 2320
440C Z 100CD17 SUS 440C
904L Z 2NCDU25.20AZ 1.4539 2562
17-4PH Z 4CNUNb16.4M 1.4542
2205 Z 3CND22.05AZ 1.4462 318 S 13 2377
Chloride Stress Corrosion Cracking
Austenitic stainless steels may be susceptible to chloride stress corrosion cracking (CSCC).
The standard 304/304L and 316/316L grades are most susceptible. Increasing nickel content
above 18 to 20% or the use of duplex, or ferritic stainless steels improves resistance to
CSCC. High residual or applied stresses, temperatures above 65-71C (150-160F) and
chlorides increase the likelihood of CSCC. Crevices and wet/dry locations such as liquid
vapor interfaces and wet insulation are particularly likely to initiate CSCC in susceptible
alloys. Initiation may occur in several weeks, in 1-2 years or after 7-10 years in service.
Methods of minimizing chloride stress corrosion cracking:
1. Improve design.
Examples: Fill or seal crevices, paint under insulation, keep tensile stresses below
the yield strength, shot peen, provide galvanic or cathodic protection.
2. Select a higher nickel content austenitic alloy.
Examples: Alloy 330, 904L.
3. Select a ferritic stainless steel if the lower corrosion resistance is acceptable.
Examples: 439, 26Cr 1Mo, 18Cr 2Mo
4. Select a duplex stainless steel.
Examples: 329, 2205.
5. Evaluate stress relief.
Note! Stress relief treatments above 425C (800F) may sensitize stainless steel to
intergranular corrosion.
American Society of Mechanical Engineers
ASME Specifications
STAINLESS STEEL PIPING/TUBING:
SA-213 Seamless Ferritic & Austenitic Alloy Boiler Tubes
SA-249 Welded Austenitic Steel Boiler & Heat Exchanger Tubes
SA-268 Seamless & Welded Ferritic/Martensitic Stainless Tubing
SA-312 Seamless & Welded Austenitic Stainless Steel Pipe
SA-358 Welded Austenitic Alloy Pipe for High Temperature Service
SA-376 Seamless Austenitic Pipe for High Temperature Service
SA-403 Wrought Austenitic Stainless Piping Fittings
SA-409 Welded Large Diameter Austenitic Pipe for Corrosion or High Temperature
Service
SA-430 Austenitic Forged & Bored Pipe for High Temperature Service
SA-450 General Requirements for Carbon, Ferritic & Austenitic Alloy Steel Tubes
SA-451 Centrifugally Cast Austenitic Steel Pipe for High Temperature
SA-452 Centrifugally Cast Austenitic Steel Cold Wrought Pipe for High Temperature
Service
SA-688 Welded Austenitic Stainless Feedwater Heater Tubes
SA-731 Seamless & Welded Ferritic/Martensitic Stainless Steel Pipe
SA-789 Seamless & Welded Ferritic/Austenitic Stainless Tubing for General Service
SA-790 Seamless & Welded Ferritic/Austenitic Stainless Steel Pipe
SA-813 Single or Double Welded Austenitic Stainless Steel Pipe
SA-814 Cold Worked Welded Austenitic Stainless Steel Pipe
SA-815 Wrought Ferritic, Austenitic & Martensitic Stainless Pipe Fittings
STAINLESS STEEL CASTINGS:
SA-217 Castings of Martensitic, Stainless & Alloy Steel for Pressure Containing Parts
for High Temperature Service
SA-351 Austenitic Steel Castings for High Temperature Service
SA-352 Ferritic & Martensitic Steel Castings for Pressure Containing Parts for Low
Temperature Service
SA-703 General Requirements - Steel Castings for pressure Containing Parts
SA-781 Common Requirements of Steel & Alloy Castings for General Industrial Use
STAINLESS STEEL PLATE, SHEET & STRIP:
SA-240 Heat Resisting Cr & Cr-Ni Stainless Plate, Sheet & Strip for Pressure Vessels
SA-264 Stainless Cr-Ni Steel Clad Plate, Sheet & Strip
SA-412 Stainless & Heat Resisting Steel Plate, Sheet, Strip
SA=480 General Requirements for Flat Rolled Stainless & Heat Resisting Steel Plate,
Sheet & Strip
STAINLESS FORGINGS & BOLTING:
SA-192 Alloy & Stainless Steel Bolting Materials for High Temperature
SA-484 General Requirements for Stainless & Heat Resisting Bars, Billets & Forgings
SA-705 Age-Hardening Stainless & Heat Resisting Steel Forgings
SA-745 Ultrasonic Examination of Austenitic Steel Forgings
STAINLESS BARS & SHAPES:
SA-479 Stainless & Heat Resisting Steel Bars & Shapes for Use in Boilers & Other
Pressure Vessels
SA-484 General Requirements for Stainless & Heat Resisting Bars, Billets & Forgings
SA-564 Hot Rolled & Cold Finished Age-Hardening Stainless & Heat Resisting Steel
Bars & Shapes
Seawater Resistance of Stainless Steels
Stainless steels are susceptible to crevice or pitting attack in chloride bearing waters.
Their behavior has been studied by a number of investigators. There is considerable variation
in the percentage of apparently identical sites where attack occurs, when it occurs. It is useful
to describe results in terms of the percentage of apparently identical sites where attack occurs
at a given chloride concentration. Very tight crevices increase the likelihood of attack. Rough
surfaces, sheared edges, scratches and similar imperfections also tend to increase the
incidence of attack. Crevice or pitting attack also occurs under deposits and under biofouling
growths attached to the metal surface.
Relative resistance can be described by the chloride concentration below which there is little
likelihood of crevice attack occurring. The ability of chlorides to concentrate in some crevices
means that occasional attack may occur at lower concentrations than shown in the following
table. Nevertheless, the table provides useful guidelines.
Guidelines for relative resistance of stainless steels to crevice attack in natural waters
AlloyChloride concentration below which
crevice corrosion is rare
400 series: crevice attack occurs in fresh waters
304SS: 100-200 ppm
316SS: 1000 ppm
The 4 1/2% Mo and duplex stainless steels are more resistant than type 316, but suffer
varying degrees of crevice attack in brackish water and seawater.
The 6% Mo stainless steels have excellent resistance to crevice attack in seawater.
For further information: NiDI 11 003 "Guidelines for Selection of Stainless Steels for Marine
Environments, Natural Waters and Brines"
Properties at Cryogenic Temperatures
The austenitic stainless steels remain tough and ductile to very low temperatures. Metals
such as iron and constructional steels undergo a marked decrease in ductility at lower
temperatures.
COMMON CRYOGENIC TEMPERATURES:
Environment Degrees C Degrees F
Boiling Helium - 268.6 - 454
Boiling Hydrogen - 252.5 - 418
Freezing Nitrogen - 209.9 - 346
Boiling Nitrogen - 195.8 - 319
Boiling Methane - 164.0 - 265
Solid Carbon Dioxide - 78.5 - 108
Boiling Freon 12 - 29.8 - 22
Water as ice 0.0 32
EFFECT OF TEMPERATURE ON MODULUS OF ELASTICITY:
AlloyRoom Temp. Tensile -
ksiDegrees C Degrees F
Room Temp. At -196øC
301 106 25.4 x 10-6 28.6 x 10-6
302 88 26.2 27.2
304 87 24.4 26.2
347 95 23.3 27.6
MECHANICAL PROPERTIES AT CRYOGENIC TEMPERATURES:
Strength by Alloy Listed in ksi
301 302 304 304L 3105 316 321 347
0øC
Yield 42 42 38 28 35 40 40 40
Tensile 160 120 115 98 88 90 100 100
Elong. 60% 50% 60% 58% 50% 68% 58% 60%
Charpy keyhole notch in ft.
lb.39 34 37 - 38 35 32 29
301 302 304 304L 3105 316 321 347
-40øC
Yield 44 43 40 30 40 45 45 45
Tensile 180 135 135 115 94 105 120 115
Elong. 40% 58% 55% 55% 70% 67% 55% 58%
Charpy keyhole notch in ft.
lb.- - - - - - - -
301 302 304 304L 3105 316 321 347
-78øC
Yield 50 58 45 35 48 57 50 50
Tensile 162 164 165 138 110 120 138 136
Elong. 52% 52% 48% 50% 78% 65% 53% 52%
Charpy keyhole notch in ft.
lb.21 27 26 - 30 26 25 23
301 302 304 304L 3105 316 321 347
-168øC
Yield 62 62 55 40 62 73 58 50
Tensile 210 210 208 175 140 160 185 180
Elong. 44% 43% 42% 44% 90% 61% 47% 45%
Charpy keyhole notch in ft.
lb.5.5 9.5 21 16 24 19 22 19
301 302 304 304L 3105 316 321 347
-196øC
Yield 55 62 57 45 75 80 60 52
Tensile 275 225 225 192 151 180 211 195
Elong. 30% 40% 38% 42% 93% 19% 22% 19%
Charpy keyhole notch in ft.
lb.- - - - - - - -
301 302 304 304L 3105 316 321 347
-253øC
Yield - 62 69 50 96 93 68 65
Tensile - 258 250 220 180 230 248 230
Elong. - 38% 27% 41% 71% 55% 34% -
Charpy keyhole notch in ft.
lb.- - - 19 - - - -
Plate Finishes
FINISH FOR PLATE: See also ASTM A 480
Hot-Rolled, or Cold-Rolled and Annealed, or Heat Treated - Scale not removed.
Hot-Rolled, or Cold-Rolled and Annealed, or Heat Treated, and Blast Cleaned or
Pickled. - Essentially a No. 1 finish.
Hot-Rolled, or Cold-Rolled and Annealed, or Heat Treated, and Surface Cleaned and
Polished - Like a No. 4 sheet finish.
Hot-Rolled, or Cold-Rolled and Annealed, or Heat Treated, and Descaled and Temper
Passed - A smoother finish.
Hot-Rolled, or Cold-Rolled and Annealed, or Heat Treated and Descaled and Cold-
Rolled and Annealed, or Heat Treated and Descaled and Optionally Temper Passed -
Smooth finish with greater freedom from surface imperfections.
Intergranular Corrosion
When austenitic stainless steels are heated or cooled through the temperature range 425-
900C (800-1650F), chromium tends to combine with carbon to form chromium carbides. The
carbides precipitate preferen- tially at grain boundaries depleting chromium from the adjacent
areas. This reduces the corrosion resistance of the chromium depleted areas, sensitizing the
alloy to Intergranular Attack (IGA). The extent of carbide formation is dependent upon time at
temperature and the carbon content of the alloy. Thus, exposure in the temperature range
stated does not automatically mean that sensitization, or IGA will occur.
Sensitization may also result from slow cooling from solution annealing temperatures, or
stress relieving - after welding - in the 425 to 900C (800 to 1650F) temperature range. In
welded fabrications, sensitization and IGA may occur in corrosive environments in a rather
narrow band on either side of or on the side opposite the weld, known as the heat affected
zone (HAZ).
It is important to note that even if sensitization does occur, it is not of significant consequence
unless the alloy is exposed to a corrosive environment. Sensitized stainless steel performs in
a normal manner and safe manner in non-corrosive applications.
Order of Resistance
904L Highest This table lists some of the
common stainless steels as to
general resistance to pitting or
crevice corrosion in aqueous
environments where corrosive
conditions may exist.
317L
329
316/316L
304/304L
430
410
420 Lowest
Methods of Minimizing Intergranular Attack - IGA
1) Solution anneal above 1040C (1900F) followed by a rapid quench.
2) Use type 347, a Cb stabilized grade, or 321, a Ti stabilized grade.
3) Use a low carbon, 0.03% max. carbon grade such as 304L, 316L, 317L or 904L.
With today's technology, carbon is economically reduced to very low residuals. The low
carbon grades are the standard for welded fabrication.
ASTM A262 practice A to E are standard tests to determine susceptibility to IGA. Practice E,
the Huey test, is widely used.
Categories of Stainless Steels
I. Austenitic - A family of alloys containing chromium and nickel (and manganese and
nitrogen when nickel levels are reduced), generally built around the type 302 chemistry of
18% Cr, 8% Ni, and balance mostly Fe. These alloys are not hardenable by heat treatment.
II. Ferritic - This group of alloys generally containing only chromium, with the balance mostly
Fe, are based upon the type 430 composition of 17% Cr. These alloys are somewhat less
ductile than the austenitic types and again are not hardenable by heat treatment.
III. Martensitic - The members of this family of stainless steels may be hardened and
tempered just like alloy steels. Their basic building block is type 410 which consists of 12%
Cr, 0.12% C, and balance mostly Fe.
IV. Precipitation-Hardening - These alloys generally contain Cr and less than 8% Ni, with
other elements in small amounts. As the name implies, they are hardenable by heat
treatment.
V. Duplex - This is a stainless steel alloy group, or family, with two distinct microstructure
phases -- ferrite and austenite. The Duplex alloys have greater resistance to chloride stress
corrosion cracking and higher strength than the other austenitic or ferritic grades.
VI. Cast - The cast stainless steels, in general, are similar to the equivalent wrought alloys.
Most of the cast alloys are direct derivatives of one of the wrought grades, as C-8 is the cast
equivalent of wrought type 304. The C preceding a designation means that the alloy is
primarily used for resistance to liquid corrosion. An H designation indicates high temperature
applications.