UNS S32100 · W.Nr. 1.4541 · X6CrNiTi18-10 · 17.0-19.0% Cr – 9.0-12.0% Ni – C ≤ 0.08% – Ti 5×(C+N) minimum to 0.70% maximum – balance Fe. The silicon ceiling CHANGES WITH THE SPECIFICATION: 0.75% in ASTM A240; 1.00% in ASTM A276, A182 and EN 1.4541. The EN 1.4541 band is: C ≤ 0.08%, Si ≤ 1.00%, Mn ≤ 2.00%, Cr 17.00-19.00%, Ni 9.00-12.00%, Ti from 5×C to 0.70% (the EN multiplier is 5×C, the ASTM one is 5×(C+N)). It is an austenitic stainless steel: NOT PRECIPITATION HARDENABLE, it cannot be hardened by heat treatment; strength is raised only by cold work. The titanium is NOT a hardener, it is A CARBON BINDER.
Bought for parts that are fabricated by welding and then run for long periods in the 425-850 °C band: exhaust manifolds and expansion bellows, furnace parts, heat exchangers, hot process piping, refinery equipment.
Forms
Round bar · flat bar · plate · sheet · strip · seamless and welded pipe · seamless and welded tube · forging · ring · flange · wire · welding wire. All forms are supplied to order.
Standards
AMS: 5510 (sheet, strip, plate) · 5645 (bar, wire, forging) · 5570 (seamless tube) · 5576 (welded tube) · 5557 (seamless/welded tube) · 5559 (thin-wall welded tube). ASTM: A240 / SA-240 (plate, sheet, strip) · A276 (bars and shapes) · A479 / SA-479 (bar for boilers and pressure vessels) · A312 / SA-312 (seamless and welded pipe) · A213 / SA-213 (seamless boiler and heat-exchanger tube) · A249 / SA-249 (welded tube) · A182 / SA-182 (F321 forged flanges, fittings and valve parts) · A314 (billets and bars for forging) · A473 (forgings) · A580 (wire) · A484 (general requirements). EN: 1.4541 · 10088-2 · 10088-3 · 10028-7 · 10216-5 · 10217-7 · 10222-5. 321 DOES have AMS numbers; in that respect it differs from grades such as 316Ti and 314. The ones confirmed by four independent sources are AMS 5510 (sheet/strip/plate), 5645 (bar/wire/forging) and 5570 (seamless tube).
Advantage
The stress-relief anneal may be carried out INSIDE the sensitization band. ATI states that 321 may be stress relief annealed within the carbide precipitation range of 427 to 816 °C (800 to 1500 °F) without any danger of subsequent intergranular corrosion;
Welding
FILLER METAL: ER347 / E347 (niobium stabilized). The 321 chemistry is not used in covered electrodes; Hobart Brothers gives the reason plainly — ‘recovery of titanium across the arc of covered electrodes is poor’.
Limits
1) THE LIMIT OF TITANIUM STABILIZATION: the protection depends on the ratio of titanium to carbon. The ASTM specifications require Ti ≥ 5×(C+N); below that ratio free carbon remains and the stabilization is incomplete.
Compiled from manufacturer data sheets · confirm against the current specification before ordering
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Standards by Product FormWelding, Heat Treatment and Machining321, 347 and 304LFrequently Asked Questions
Corrosion resistance: AISI 321 stainless steel resembles grade 304 in structure, but thanks to the maximum 0.7% titanium it contains this stainless material has good resistance to corrosion. Not recommended for severely corrosive environments, grade 321 is suitable for many everyday environments. Grades 310 or 310S are recommended for harsher environments and for higher temperatures.
Temperature capability: Grade 321 (1.4541) can readily be specified where both high temperature conditions and a friction environment are involved. It should be remembered, however, that the temperature must not exceed 800 °C.
Weldability: Sharing welding characteristics with 316Ti, grade 321 (1.4541) gives good results in terms of weldability performance when the correct electrodes are chosen.
Machinability: Although grade 321 (1.4541) is generally regarded as having adequate machinability, grades 303 or 430F offer an advantage where extensive machining is involved. On the other hand, 321 (1.4541) with a homogeneously distributed composition and produced to a good standard will not create a machining problem.
Heat treatment: Because AISI 321 is an austenitic stainless steel, a hardening treatment cannot be applied.
Applications: Advantageous in terms of cost, grade 321 (1.4541) proves its adequacy through the properties it offers. It is most used in machine building, in the production of mechanical components and in the production of chemical machinery and parts. Thanks to its attractive price it is also heavily used in food production lines, in bolt products, in screws and in transport vehicle components.
Chemical Composition
DEFENCE METAL
C
Max. 0.08
Mn
Max. 2.00
Si
Max. 0.75
P
Max. 0.045
S
Max. 0.03
Cr
Min. 17.00 · Max. 19.00
Ni
Min. 9.00 · Max. 12.00
N
Max. 0.10
Mechanical Properties
DEFENCE METAL
Tensile Strength (MPa)
515
Proof Stress (MPa)
205
Elongation A50 mm
40
Hardness Brinell
217 Max HB
Density
8.00 g/cm3
Melting Point
1398 – 1446 °C
Modulus of Elasticity
193 GPa
Electrical Resistivity
720 Ω.m
Thermal Conductivity
16.1 W/m.°C
Thermal Expansion
16.6 μm/m
Standards and Equivalents · AISI 321
DEFENCE METAL
Trade name
AISI 321
UNS
S32100
W.Nr (DIN/EN)
1.4541
AMS
5510 · 5557 · 5559 · 5570 · 5576 · 5645
ASTM
A240 · A276 · A314 · A484
Available forms
Round bar · Flat bar · Plate · Sheet · Tube · Forgings All forms are supplied to order.
Standards by Product Form
STANDARDS BY PRODUCT FORM
DEFENCE METAL
Product form
Standards
Plate
AMS 5510 (sheet, strip and plate). ASTM A240 / ASME SA-240 (S32100) · ASTM A480 (general requirements) · EN 10088-2 · EN 10028-7 · ISO 15510.
Sheet and strip
AMS 5510 (sheet, strip and plate). ASTM A240 / ASME SA-240 (S32100) · EN 10088-2 · ISO 15510.
Round bar and flat bar (including square and hexagon)
AMS 5645 (bar, wire and forging). ASTM A276 (bars and shapes) · ASTM A479 / ASME SA-479 (bar for boilers and pressure vessels) · ASTM A484 (general requirements) · EN 10088-3.
Wire and welding wire
AMS 5645 (bar, wire and forging). ASTM A580 (wire) · EN 10088-3 · EN 10263-5. Welding consumables fall under SEPARATE standards: AWS A5.9 / SFA-5.9 (ER321, ER347) and AWS A5.4 / SFA-5.4 (E347).
Forging and ring
AMS 5645 (bar, wire and forging). ASTM A182 / ASME SA-182 (F321) · ASTM A314 (billets and bars for forging) · ASTM A473 (forgings) · ASTM A484 · EN 10222-5 · EN 10250-4.
Flange
THERE IS NO SEPARATE AMS NUMBER FOR THIS FORM; AMS 5645, which covers forgings, applies. ASTM A182 / ASME SA-182 (F321) — forged flanges, fittings and valve parts · dimensions to ASME B16.5 / B16.47 · EN 10222-5.
Seamless and welded pipe
AMS 5557 (seamless/welded tube) is NOT written directly for pipe. ASTM A312 / ASME SA-312 (TP321, seamless and welded) · ASTM A999 (general requirements) · EN 10216-5 (seamless) · EN 10217-7 (welded).
THERE IS NO SEPARATE AMS NUMBER. ASTM A182 / ASME SA-182 (F321) for forged fittings · dimensions to ASME B16.9 / B16.11. ASTM A403 WP321 was seen on vendor pages, the scope COULD NOT BE CONFIRMED and it has not been written.
321 DOES HAVE AMS NUMBERS. Those confirmed by four independent sources are: AMS 5510, AMS 5645, AMS 5570. AMS 5557, 5559 and 5576 were seen in three independent sources and are marked accordingly. AMS 5689, AS7325 and AMS 7490, which the SSINA handbook lists for S32100, were found in only one source and have NOT been put on the map. ASTM A312 contains TP321; the same text contains NEITHER TP310 NOR TP314. Because the scope of ASTM A403 WP321 could not be confirmed, only A182 is given on the fitting row. The EN numbers are for information; the current edition of whichever specification the order is placed to is the binding one.
AISI 321 is a titanium-stabilised 18Cr-9Ni austenitic stainless steel. Two points matter when ordering: the H grade (321H) has its own UNS number (S32109) and must be specified separately for high-temperature code work; and the welding filler is 347, not 321 (see below).
Standards by Product Form · AISI 321 (S32100 / 1.4541)
DEFENCE METAL
Sheet · Plate · Strip
ASTM A240 / ASME SA-240 (321, 321H) · AMS 5510 · EN 10088-2 · EN 10028-7
Mechanical minimums in the annealed condition (ASTM A240): tensile ≥ 515 MPa, yield ≥ 205 MPa, elongation ≥ 40%, hardness ≤ 217 HB / 95 HRB. Titanium limit: Ti = 5 × (C+N) minimum, 0.70% maximum. In 321H the carbon range is 0.04–0.10%, giving markedly better creep and stress-rupture strength above 537 °C.
Welding, Heat Treatment and Machining
HEAT TREATMENT — SCHEMATIC
DEFENCE METAL
1 · SOLUTION ANNEAL — this is the as-delivered condition
Step
1 · SOLUTION ANNEAL — this is the as-delivered condition
Summary
It reverses cold work, takes the carbides into solid solution and renews the grain structure. IT DOES NOT RAISE STRENGTH, IT LOWERS IT. ASTM A240, A276, A479, A312, A213, A249 and A182 require the material in this condition.
Temperature
The sources diverge at the ends of the band, ALL GIVEN WITH THE SOURCE NAME: ATI and Jacquet 928-1093 °C (1800-2000 °F) · Carpenter 954-1066 °C (1750-1950 °F) · AZoM and Atlas 950-1120 °C · AGST, Rodacciai and Rostfrei-Stahl 1000-1100 °C. NO SINGLE NUMBER HAS BEEN WRITTEN AND NO AVERAGE HAS BEEN TAKEN. Practical envelope: approximately 950-1120 °C. The specification floor is a separate matter: 1040 °C.
Time
No single soaking time could be confirmed by four independent sources, so none is written. The time follows from bringing the whole section to temperature; extending it brings grain growth, not benefit.
Cooling
RAPID COOLING IS MANDATORY, not a preference. Carpenter says water quench; ASTM A213, A249 and A312 say ‘quenched in water or rapidly cooled by other means’; AGST, Rodacciai and Rostfrei-Stahl say water or air (air is enough as the section gets thinner). The purpose is to pass through the carbide precipitation band without re-precipitation.
Note
On 321 this step serves the same purpose as it does on 304 and 316; the titanium changes nothing about it. The effect of the titanium appears in the next step and in service.
Requirement
THE SPECIFICATION FLOOR IS THE BINDING ONE: ASTM A213, A249 and A312 require a minimum of 1040 °C (1900 °F) for TP321, followed by a water quench or an equivalent rapid cool. ASTM A249 notes that temperatures above 1950 °F (1065 °C) may impair corrosion resistance.
DEFENCE METAL
2 · STABILIZING ANNEAL — the SEPARATE step that distinguishes 321 from 304
Step
2 · STABILIZING ANNEAL — the SEPARATE step that distinguishes 321 from 304
Summary
It is carried out AFTER the solution anneal and is a SEPARATE operation from it. It binds the carbon as titanium carbide. IT RAISES NEITHER HARDNESS NOR STRENGTH. It is NOT an ageing step.
Temperature
843-899 °C (1550-1650 °F) — ATI, Jacquet, Carpenter and Rolled Alloys ALL FOUR give the same band. AZoM and Atlas give 870-900 °C, which overlaps the upper half of the other band. Practical envelope: approximately 843-900 °C.
Time
ATI and Jacquet: up to 5 hours depending on thickness. AZoM and Atlas: 1 hour per 25 mm of thickness. The two statements differ and HAVE NOT BEEN REDUCED TO A SINGLE NUMBER.
Cooling
Air (Rolled Alloys and AZoM say air cool explicitly). No water quench is needed at this step.
Note
The heart of it: the solution anneal dissolves the carbon and the titanium; the stabilizing anneal then holds the material at a temperature where TiC is stable but chromium carbide is not yet dominant, and so BINDS the carbon to the titanium. The carbon is then not left free to form chromium carbide even when the sensitization band is crossed in service. On heavily welded parts that will run hot, skipping this step means the full benefit of the titanium stabilization is not obtained.
Requirement
Carpenter and Rolled Alloys give the same condition: the treatment is applied when temperatures up to about 871 °C (1600 °F) are expected in service. Rolled Alloys also writes that this treatment gives the best resistance to polythionic acid stress corrosion cracking.
DEFENCE METAL
3 · SENSITIZATION (carbide precipitation) BAND — not a treatment but a REGION TO AVOID
Step
3 · SENSITIZATION (carbide precipitation) BAND — not a treatment but a REGION TO AVOID
Summary
The temperature range in which chromium carbide precipitates at the grain boundaries of an unstabilized austenitic stainless steel. 321 is bought in order to work inside this range.
Temperature
427-816 °C (800-1500 °F) — ATI, Jacquet, Sandmeyer and Rolled Alloys/Quest4Alloys give the same band. AZoM and Atlas widen it to 425-850 °C. Hobart Brothers gives 800-1600 °F (427-871 °C). NO SINGLE NUMBER HAS BEEN WRITTEN.
Time
The measure Hobart Brothers gives: at a typical carbon level, less than a minute at 1200 °F (649 °C) is enough to sensitize. That explains why the welding thermal cycle is sufficient.
Cooling
Not applicable.
Note
This is the reason 321 exists: because the titanium binds the carbon, a hold in this band does not produce chromium carbide. Sandmeyer puts it as ‘excellent resistance to intergranular corrosion following exposure to this temperature range’; the numerical expression of it is the ASTM A262 intergranular corrosion test.
Requirement
This is not a treatment recipe; it is shown on the diagram as a band.
DEFENCE METAL
4 · STRESS RELIEF
Step
4 · STRESS RELIEF
Summary
The most concrete practical advantage of 321 shows here.
Temperature
427-816 °C (800-1500 °F) — ATI. This statement could not be confirmed by four independent sources (ATI, and the Quest4Alloys text repeating it, were found), so it is given WITH THE SOURCE NAME.
Time
Could not be confirmed by four independent sources; not written.
Cooling
Could not be confirmed by four independent sources; not written.
Note
On a heavily welded part at risk of knife-line attack it is safer to use the 843-899 °C stabilizing anneal instead of a stress relief; that treatment both lowers the residual stress and re-forms the dissolved TiC.
Requirement
ATI’s wording: 321, 347 and 348 ‘may also be stress relief annealed within the carbide precipitation range 800 to 1500 °F (427 to 816 °C), without any danger of subsequent intergranular corrosion’. Unstabilized 304 sensitizes in that same band.
The diagram is schematic; the time axis is not to scale. No published TTT/CCT curve was used, so no curve has been drawn. THIS ALLOY IS AUSTENITIC: IT IS NOT PRECIPITATION HARDENABLE. There is NO AGEING STEP such as H900 / H1025 / H1075 / H1150 and no ageing diagram has been drawn. The STABILIZING ANNEAL below is NOT an ageing step; it raises neither hardness nor strength, it only binds the carbon as titanium carbide. Strength is raised only by COLD WORK. This alloy IS NOT PRECIPITATION HARDENABLE. There is NO ageing step (H900, H1025, H1075, H1150 and the like) and no ageing diagram has been drawn. The stabilizing anneal is NOT an ageing step; it raises neither strength nor hardness, it only binds the carbon as TiC. It is shown on the diagram as a SEPARATE step. The solution anneal cycle is in essence the same for 304, 316 and 321. The only structural extra step on 321 is the stabilizing anneal. The stabilizing anneal temperature of 843-899 °C is confirmed by FOUR independent producer sources (ATI, Jacquet, Carpenter, Rolled Alloys). No single band for the solution anneal temperature could be confirmed by four sources; what was found is given WITH THE SOURCE NAMES and no average has been taken. The binding figure is the 1040 °C floor of ASTM A213/A249/A312. The stress-relief statement was found only in ATI and is given with the source name; it did not pass the four-source threshold. The time axis is not to scale; no published TTT/CCT curve was used.
Welding
TIG, MIG/MAG, covered electrode, submerged-arc, plasma, laser and resistance welding are all applicable. No preheat is required and post-weld heat treatment is not normally needed. The filler is ER347 / E347 — not ER321. The reason is metallurgical: titanium does not transfer well across the arc and its recovery in a covered electrode is poor, which is why there is no E321 electrode classification. Niobium-stabilised 347 filler keeps its stabiliser through the arc and protects the weld metal against sensitisation as well. Nb-stabilised weld metal is somewhat more prone to hot cracking — use a stringer bead technique, controlled heat input and no weaving. For dissimilar joints, ER309/309L or a nickel-base filler is used.
Heat treatment
It is a solid-solution austenitic grade and cannot be hardened by heat treatment. Titanium ties up carbon as TiC, preventing chromium from forming carbides at the grain boundaries. Solution anneal: roughly 950–1120 °C, in practice 1010–1070 °C, followed by rapid cooling. Stabilising anneal: 843–899 °C, air cooled, 1–2 hours per 25 mm of thickness. Its purpose is to precipitate the remaining dissolved carbon deliberately as TiC, so that no free carbon is left to form chromium carbide when the part later operates in the 427–816 °C range. It is not mandatory for routine welded fabrication, but is applied where long-term service in that band or refinery-type polythionic acid exposure is expected. Stress relief can be carried out between 427 and 816 °C without risk of intergranular corrosion — a direct benefit of the stabilised grade. Hot working is done at 1149–1260 °C; do not forge below 927 °C.
Machining
Machinability is in the same class as 304, slightly harder. The austenitic structure work-hardens quickly: a steady, adequate feed is essential and the tool must never dwell on the workpiece. Use a sharp cutting edge with positive rake, rigid clamping and short overhang; with carbide tooling cutting speeds can be 2–3 times those used with HSS. Apply a generous, high-pressure coolant supply. Titanium carbides are abrasive and tool life is somewhat shorter than with 304. 321 does not polish well and is not recommended for decorative or mirror-finish work — use 304L or 316L for that.
321, 347 and 304L — Which and When?
The reason stabilised grades are specified today is not corrosion but high temperature. Modern melting practice means 304L already solves post-weld intergranular corrosion in practice; 321 and 347 provide the hot strength and the permanent stabilisation that 304L cannot.
Selection Guide · Stabilised Austenitics
DEFENCE METAL
AISI 321 (Ti stabilised)
More resistant to hot cracking during welding; advantage in cost and availability
AISI 347 (Nb+Ta stabilised)
Slightly better in aqueous and low-temperature environments and in strongly oxidising conditions; matches the filler metal exactly
Where only post-weld corrosion resistance is needed — cheaper and more readily available, but with lower hot strength
321H
Carbon 0.04–0.10%; higher creep and stress-rupture strength above 537 °C. Specified separately for high-temperature code work
Chromium carbide precipitation range
427–816 °C — 304L will still sensitise if held in this band, while the TiC in 321 is a permanent solution
Interchangeable?
321 and 347 have separate UNS numbers (S32100 / S34700) and are not automatically equivalent, though they may be substituted where the specification allows
Note that 321 contains no molybdenum, so it does not offer the chloride pitting resistance of 316L and is not suitable for seawater.
Frequently Asked Questions
Should I buy 321 instead of 304L?
If you only need resistance to post-weld intergranular corrosion, 304L is sufficient — it is cheaper and easier to source. But if the part will operate for long periods in the 427–816 °C range, the low carbon of 304L is not enough: carbides precipitate over time and its hot strength is lower. The titanium stabilisation in 321 is a permanent solution, and stabilised grades hold markedly better 0.2% yield strength at elevated temperature. Exhaust systems, manifolds, expansion joints and heat exchangers are typical cases for 321.
Which filler metal should I weld 321 with?
Use ER347 bare wire (AWS A5.9) or E347 covered electrodes (AWS A5.4). Because titanium does not transfer well across the arc, there is no E321 electrode classification; niobium-stabilised 347 filler protects the weld metal against sensitisation as well. Nb-bearing weld metal is slightly more prone to hot cracking, so stringer bead technique and controlled heat input matter. Preheat and post-weld heat treatment are not normally required.
What is the maximum service temperature of 321?
A single figure would be misleading, because sources use different criteria. For oxidation and scaling resistance the continuous service limit is quoted between 816 and 871 °C, and some sources go to 925 °C in air. For ASME code work the maximum use temperature is cited as 816 °C — confirm this from the ASME BPVC Section II Part D tables for your project. The chromium carbide precipitation range is 427–816 °C, and 321 is protected in that band by its stabilisation. Where creep governs under sustained load, specify 321H rather than 321.
ASTM A182 / ASME SA-182 · forged flanges, fittings and valve parts (F321)
—
205
515
30%
EN 10088 · 1.4541 flat product (worldstainless table)
—
220
500-700
40% (longitudinal)
EN 10088-3 · 1.4541 bar ≤ 100 mm (Rodacciai / AGST table)
215 HB max.
190
500-700
40%
DEFENCE METAL
Additional information
Note
EVERY ROW IS A SPECIFICATION MINIMUM for room temperature; these are NOT typical values, and a typical value never goes into a calculation. BECAUSE THIS ALLOY IS NOT PRECIPITATION HARDENABLE, the rows are split by SPECIFICATION and PRODUCT FORM, not by ageing condition; there is NO condition column such as H900 or H1075. The stabilizing anneal is not a strength condition either and has no column in this table. NOTE — THE PRODUCT FORM CHANGES THE MINIMUM: for one and the same material the yield minimum is 205 MPa in plate but 170 MPa in seamless pipe with a wall above 9.5 mm under ASTM A312. The elongation minimum also changes with the form: 40% in plate, 30% in bar and forgings, 35% in tube and pipe. COLD-FINISHED BAR IS A SEPARATE ROW; cold work raises the yield minimum from 205 MPa to 310 MPa and lowers the elongation minimum from 40% to 30% — on this alloy that is the ONLY way strength is raised. The EN rows are for information; the EN yield minimums (190-220 MPa) and the ASTM minimum (205 MPa) are NOT the same number and cannot be substituted for one another.
EVERY ROW IS A SPECIFICATION MINIMUM for room temperature; these are NOT typical values, and a typical value never goes into a calculation. BECAUSE THIS ALLOY IS NOT PRECIPITATION HARDENABLE, the rows are split by SPECIFICATION and PRODUCT FORM, not by ageing condition; there is NO condition column such as H900 or H1075. The stabilizing anneal is not a strength condition either and has no column in this table. NOTE — THE PRODUCT FORM CHANGES THE MINIMUM: for one and the same material the yield minimum is 205 MPa in plate but 170 MPa in seamless pipe with a wall above 9.5 mm under ASTM A312. The elongation minimum also changes with the form: 40% in plate, 30% in bar and forgings, 35% in tube and pipe. COLD-FINISHED BAR IS A SEPARATE ROW; cold work raises the yield minimum from 205 MPa to 310 MPa and lowers the elongation minimum from 40% to 30% — on this alloy that is the ONLY way strength is raised. The EN rows are for information; the EN yield minimums (190-220 MPa) and the ASTM minimum (205 MPa) are NOT the same number and cannot be substituted for one another. In the chart, a value given as a range is drawn at its lower bound; the full range is in the table. No row is a typical value; every row is a specification minimum. The tensile and yield minimums of 321 are THE SAME as 304 (515 / 205 MPa) and 30 and 35 MPa above 304L. That is where the numerical value of 321 lies: the sensitization resistance comes without paying the strength price of lowering the carbon. In ASTM A312 the minimums DROP to 485 / 170 MPa once the wall of a seamless pipe exceeds 9.5 mm. That is the point most often missed on data cards. The hardness ceiling differs across three specifications: 217 HBW / 95 HRBW in A240, 192 HBW / 200 HV / 90 HRB in A213, 90 HRB in A249. No single number has been written. The ASTM A276 and A479 tables give no hardness ceiling; those cells are left BLANK. Cold-worked tempers are taken only as the two rows given by ASTM A276; cold-drawn values from vendor pages were not counted as sources. The EN rows are for information; the table of whichever specification the order is placed to is the binding one.
321 — 321H — 347 COMPARISON
A · CARBON AND STABILIZING ELEMENT — ASTM A240 composition table (THE SAME TABLE)
The ASTM A240 / ASME SA-240 composition table; the ATI 321/347/348 bulletin reproduces this table as it stands.
DEFENCE METAL
Criterion
AISI 321
AISI 321H
AISI 347
Difference
Carbon (C) ceiling
0.08% max.
0.04-0.10%
0.08% max.
321H also has a LOWER limit on carbon; carbon is wanted there for creep strength. The ceiling of 321 and 347 is the same.
Stabilizing element
Ti, 5×(C+N) minimum to 0.70% maximum
Ti, 4×(C+N) minimum to 0.70% maximum
Cb+Ta, 10×C minimum to 1.00% maximum
321 is stabilized with titanium, 347 with niobium plus tantalum. The multiplier on 321H is 4× rather than 5× because its carbon is higher.
Chromium (Cr)
17.00-19.00%
17.00-19.00%
17.00-19.00%
NO DIFFERENCE
Nickel (Ni)
9.00-12.00%
9.00-12.00%
9.00-12.00%
NO DIFFERENCE
Silicon (Si) ceiling, A240
0.75%
0.75%
The 347 row was not read in the A240 text searched
The A240 silicon ceiling of 321 is 0.75% and its A276 and A182 ceiling is 1.00%. For 347 this figure was not confirmed and is left BLANK.
B · SPECIFICATION MINIMUMS — ASTM A240 mechanical table (THE SAME TABLE, room temperature, solution annealed)
The ASTM A240 / ASME SA-240 mechanical table. The values are SPECIFICATION MINIMUMS, not typical values.
DEFENCE METAL
Criterion
AISI 321
AISI 321H
AISI 347
Difference
Tensile strength minimum
515 MPa (75 ksi)
515 MPa (75 ksi)
515 MPa (75 ksi)
NO DIFFERENCE — ATI gives the same minimum for all three grades.
Yield strength minimum (0.2%)
205 MPa (30 ksi)
205 MPa (30 ksi)
205 MPa (30 ksi)
NO DIFFERENCE. The stabilizing element has NO effect on room-temperature strength; the whole of the difference lies in corrosion and high-temperature behaviour.
Elongation minimum (50 mm)
40%
40%
40%
NO DIFFERENCE
Hardness ceiling
217 HBW · 95 HRBW
217 HBW · 95 HRBW
Not confirmed
Read from A240 for 321 and 321H; the 347 row was not read in the text searched and is therefore BLANK.
C · BEHAVIOUR OF THE STABILIZING ELEMENT — Hobart Brothers technical guide (THIS IS NOT A NUMERICAL COMPARISON)
This block is not a comparison of measured numbers; it is the direct comparison a single independent source (Hobart Brothers) makes within one text, and it is given WITH THE SOURCE NAME.
DEFENCE METAL
Criterion
AISI 321
AISI 321H
AISI 347
Difference
Susceptibility to knife-line attack
MORE SUSCEPTIBLE
Not separately assessed
Less susceptible
The reason Hobart Brothers gives: ‘Ti carbides are dissolved at a lower temperature than Cb carbides, resulting in a wider sensitized zone.’
Use as filler in covered electrodes
Not used
Not used
This is the standard filler
Hobart Brothers: ‘recovery of titanium across the arc of covered electrodes is poor’. That is also why 321 base metal is welded with E347.
Tendency to hot cracking
Lower
Not separately assessed
Higher
ATI: ‘Columbium stabilized stainless steels are more prone to hot cracking than titanium stabilized stainless steels.’ The two grades are therefore not one above the other; their advantages run in opposite directions.
RULE: every block on this diagram is read from a SINGLE TABLE of a SINGLE SPECIFICATION. Different specifications are not compared on the same row. All three grades are WITHIN THE SCOPE of the tables below, that is, they are listed side by side under the same acceptance criteria. THE BLOCKS ARE NOT ADDED TOGETHER AND ARE NOT PUT ON ONE AXIS. Every block is read from a single table of a single specification; different specifications are not mixed on one row. The room-temperature minimums are THE SAME for all three grades (515 / 205 MPa / 40%). The stabilizing element has no effect on room-temperature strength. Block C is not a numerical comparison; it is the comparison a single source makes within its own text and it is given with the source name. The A240 silicon ceiling and hardness ceiling of 347 were not read in the texts searched and are left BLANK. This diagram contains NO numerical comparison between 321 and 304; no 304 rows were opened because they were not read from the same table in four independent sources.
