UNS S32900 · W.Nr. 1.4460 · in ASTM A240 and A789: 23.0-28.0% Cr – 2.50-5.00% Ni – 1.00-2.00% Mo – C ≤ 0.08% – Mn ≤ 1.00% – Si ≤ 0.75% – balance Fe. NITROGEN IS NOT SPECIFIED: ASTM A789 puts ellipses on the nitrogen column of the S32900 row, meaning ‘there is no minimum and analysis for the element need not be determined or reported’. THIS IS THE SINGLE MOST IMPORTANT POINT THAT SEPARATES 329 FROM THE OTHER FOUR GRADES. It is a ferritic-austenitic (duplex) stainless steel and belongs to the FIRST GENERATION of duplex grades; its molybdenum and nickel sit below those of the modern duplex grades. It is NOT PRECIPITATION HARDENABLE and NOT AGED; its only heat treatment is solution annealing followed by rapid cooling.
It is an older-generation duplex stainless and is bought today not for new design in place of a modern duplex, but to replace an equivalent part in an existing plant.
Forms
Round bar · Flat bar · Plate · Sheet · Pipe and tube · Forgings. All forms are supplied to order.
Standards
THERE IS NO AMS. ASTM: A240 / SA-240 (plate, sheet and strip) · A789 / SA-789 (seamless and welded tube) · A790 / SA-790 (seamless and welded pipe). EN: 1.4460. IT IS NOT WITHIN THE SCOPE OF ASTM A276, A479, A182 OR A815 — see ‘standart_notu’ for the detail. THE SCOPE LIMIT is the most often missed feature of this grade: S32900 appears in NONE of the modern duplex bar and forging specifications.
Advantage
Its minimum yield strength in ASTM A240 is 485 MPa, which is ABOVE the 450 MPa of S32205 in the same table. So although 329 has the lowest PREN of the five, it is not behind standard duplex 2205 on yield strength.
Welding
ITS WELDABILITY IS POOR, and that is a direct consequence of its being first generation. IMOA writes of the first-generation duplex grades: ‘These first-generation duplex stainless steels provided good performance characteristics but had limitations in the as-welded condition’, and states the…
Limits
IT IS NOT THE RIGHT CHOICE FOR CHLORIDE OR SEAWATER SERVICE: its PREN is the lowest of the five (26.3-34.6 calculated from the composition band; IMOA typical 30-31) because the nitrogen term is absent. For the same duty, S32205 (floor 34.1) or a super duplex grade should be assessed separately.
Compiled from manufacturer data sheets · confirm against the current specification before ordering
On this page · click to jump
Standards by Product FormWeldingHeat Treatment, Machining and Forming329 or 2205?Frequently Asked Questions
Corrosion resistance: With AISI 329 (1.4460 – SS2324) you obtain an acid resistant stainless steel designed for machining. The steel has excellent corrosion properties.
Weldability: 1.4460 can be welded and does not have to be welded with consumables matching the parent material. The steel should be welded as an austenitic material with the lowest possible heat input. It can be both cold and hot formed. The steel is easier to work and its machinability is significantly better, but its corrosion resistance is slightly poorer than that of 1.4462.
Machinability: Duplex grade 1.4460, also known as 329 and SS2324, is a stainless, acid resistant duplex steel with improved machinability. Because the machinability of the steel has been improved, it is suitable for producing detailed parts involving extensive machining. The steel has very good corrosion resistance particularly in chloride-bearing environments and is especially resistant to pitting corrosion, crevice corrosion, stress corrosion cracking and corrosion fatigue. It also has high strength and toughness.
Heat treatment: Because it is an austenitic-ferritic duplex stainless steel, conventional heat treatment methods may differ somewhat.
Applications: Some typical application areas for 1.4460 are propellers and pumping, pump and valve components, pistons, agitators and screws.
Advantages of the material. High corrosion resistance: AISI 329 shows excellent durability in aggressive environments such as sulphuric acid and chloride solutions. High strength: its ferritic structure provides high tensile and yield strength. Good weldability: weldability is high, but appropriate welding techniques are required. High temperature capability: it is durable under high temperature conditions and can be used up to approximately 600-650 °C.
Chemical Composition
DEFENCE METAL
C
Max. 0.05
Mn
Max. 2.00
Si
Max. 1.00
P
Max. 0.035
S
Max. 0.015
Cr
Min. 25.00 · Max. 28.00
Ni
Min. 4.50 · Max. 6.50
N
Min. 0.05 · Max. 0.20
Mo
Min. 1.30 · Max. 2.00
Mechanical Properties
DEFENCE METAL
Tensile Strength (MPa)
650-880
Proof Stress (MPa)
–
Elongation A50 mm
8-25
Hardness Brinell
– Max HB
Density
7.70 g/cm3
Melting Point
1350-1510 °C
Modulus of Elasticity
200 Gpa
Electrical Resistivity
0.55 x10^-6 Ω .m
Thermal Conductivity
25.0 W/m.K
Thermal Expansion
10 x10^-6 /K
Standards and Equivalents · AISI 329
DEFENCE METAL
Trade name
AISI 329
UNS
S32900
W.Nr (DIN/EN)
1.4460
ASTM
A276
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
NO AMS. ASTM A240 / ASME SA-240 · EN 1.4460
Sheet and strip
NO AMS. ASTM A240 / ASME SA-240
Seamless and welded pipe
ASTM A790 / ASME SA-790
Seamless and welded tube
ASTM A789 / ASME SA-789
Round bar and flat bar
NO SPECIFICATION FOR S32900: there is no S32900 row in the tables of ASTM A276 or A479. A bar order must state the chemical composition and heat treatment requirements separately.
Forgings and flanges
NO A182 CLASS CODE FOR S32900: S32900 does not appear in the duplex class list of ASTM A182 (F50, F51, F52, F53, F54, F55, F57, F59, F60, F61, F65).
Fitting
S32900 is NOT within the scope of ASTM A815.
DEFENCE METAL
Additional information
AMS note
No AMS number could be confirmed for this alloy; since the four independent source threshold was not met, no AMS number has been put on the card. The real finding of this map is not the absence of AMS but the fact that S32900 is OUTSIDE THE SCOPE of the modern duplex bar and forging specifications.
Being outside a specification’s scope does not mean the material cannot be supplied; it means the acceptance criteria have to be written into the contract separately.
AISI 329 (UNS S32900 / EN 1.4460) is a first-generation duplex stainless steel. One thing separates it from today’s duplex grades, and this whole page rests on it: there is no deliberate nitrogen addition. Nitrogen is what lets modern duplex grades re-form austenite in the weld heat-affected zone (HAZ); without that reserve, 329’s HAZ stays excessively ferritic in the welded condition.
Standards by Product Form · AISI 329 (S32900 / 1.4460)
DEFENCE METAL
Sheet · Plate · Strip
ASTM A240 / A240M (S32900 is listed). Not covered on the EN side: BS EN 10088-2 does not list 1.4460 among its current duplex grades
Bar
ASTM A276 / A276M. Still current on the EN side: BS EN 10088-3 lists it as X3CrNiMoN27-5-2 (1.4460)
Seamless tube (general purpose)
BS EN 10297-2 — 1.4460 is current: Rp0.2 ≥ 460 MPa, Rm ≥ 620 MPa, A ≥ 20%
Seamless tube (pressure purposes)
BS EN 10216-5 — 1.4460 has been dropped
Welded pipe · tube
BS EN 10296-2 — 1.4460 has been dropped (only 1.4362 / 1.4462 / 1.4410 are covered)
Butt-weld fittings
BS EN 10253-3 / -4 — 1.4460 has been dropped
Forgings · flanges
— (S32900’s presence in the current ASTM A182 edition could not be confirmed)
Welding wire · electrode
— (no AWS filler class qualified specifically for 329 could be verified. Industry practice is to use a higher-alloyed, nitrogen-bearing 2209-type filler)
What that table means is plain: 1.4460 has been removed from the current EN standards governing welded and pressure product forms, and remains current only for bar and non-pressure general-purpose seamless tube. Moreover, none of the three major duplex service centres surveyed (Sandmeyer, Rolled Alloys, Penn Stainless) stock 329 at all; all carry 2101 / 2304 / 2205 / 2507. 329 today is a grade bought for matching and repair on legacy installations, not for new fabrication.
Composition (ASTM/UNS S32900, indicative): C ≤0.08% · Si ≤0.75% · Mn ≤1.00% · P ≤0.040% · S ≤0.030% · Cr 23.0–28.0% · Ni 2.0–5.0% · Mo 1.00–2.00% · Nitrogen: no specified value. With PREN = %Cr + 3.3×%Mo + 16×%N and the nitrogen term at zero, PREN works out at roughly 26–33; for comparison, AISI 318 (2205) has a PREN of 35–36. Even though 329’s chromium range overlaps or exceeds 2205’s, its corrosion resistance is structurally lower — the gap comes almost entirely from the missing nitrogen.
WARNING — an equivalence trap. The formal EN designation for 1.4460 is X3CrNiMoN27-5-2, and the “N” in that name means nitrogen; the published ASTM/UNS S32900 composition, by contrast, carries no nitrogen specification. So the claim “1.4460 = 329 = S32900, identical” is not as safe as it looks. Ask any supplier offering EN 1.4460 material for the actual nitrogen range on the cast analysis.
Welding — the Central Issue for This Grade
329 became established after the Second World War and was used extensively as heat exchanger tubing in nitric acid service. In the welded condition, however, the duplex fabrication literature records plainly that it showed low toughness because of excessive ferrite and significantly lower corrosion resistance than the base metal.
Why it happens
Weld cooling happens in seconds. Modern duplex grades (2205 and similar) carry 0.14–0.20% nitrogen, which lets austenite re-nucleate rapidly from the high-temperature ferrite. With no nitrogen reserve, 329’s HAZ cools before enough austenite can form and is left abnormally ferrite-rich. That costs two things directly: ferrite is more brittle (toughness falls, especially at low temperature), and the loss of the balanced two-phase structure together with chromium nitride and carbide precipitation lowers pitting and crevice resistance exactly where it is needed most — at and near the weld.
Practical rules
Heat input: duplex resists hot cracking and tolerates relatively high heat input; conversely too low a heat input drives excess ferrite (worse still in a first-generation grade with no nitrogen buffer), while too high a heat input risks sigma phase. Maximum interpass temperature: 150 °C for standard duplex. Preheat: generally not recommended for duplex; at most about 100 °C simply to drive off surface moisture in cold conditions. Filler: duplex fillers are over-alloyed in nickel by 2–4% relative to the base metal, and more highly alloyed fillers are suitable for welding lower-alloyed duplex products — which points to a nitrogen-bearing 2209-type filler for 329 rather than a matching one. Do not stress relieve: stress relief above 315 °C is harmful to duplex; if heat treatment is done at all it must be a full solution anneal plus water quench.
Heat Treatment, Machining and Forming
HEAT TREATMENT — SCHEMATIC
DEFENCE METAL
1 · SOLUTION ANNEAL + RAPID COOLING — this is the only valid heat treatment
Step
1 · SOLUTION ANNEAL + RAPID COOLING — this is the only valid heat treatment
Summary
It takes intermetallic phases back into solid solution and sets the ferrite-austenite balance. IT DOES NOT RAISE STRENGTH. This is the delivery condition.
Temperature
925-955 °C [1700-1750 °F]. Table 1 of ASTM A789 and ASTM A790 gives this band. The same tables give 1020-1100 °C for S32205, 1025-1125 °C for S32750 and 1070-1140 °C for S32760 — the band for 329 is BELOW ALL FOUR of the others. No other independent source gave a numerical annealing temperature, so the single band is taken from these two.
Time
Until the whole section is at temperature. No numerical time was found in four independent sources, so none is given.
Cooling
RAPID COOLING IS MANDATORY. ASTM A789 and A790 state the requirement as ‘rapid cooling in air or water’. Slow cooling leaves the part sitting in the sigma band and lowers both toughness and corrosion resistance.
Resulting hardness
The ASTM A240 ceiling is 269 HBW.
DEFENCE METAL
2 · AFTER WELDING — REPEATING THE SOLUTION ANNEAL SHOULD BE TREATED AS THE NORM
Step
2 · AFTER WELDING — REPEATING THE SOLUTION ANNEAL SHOULD BE TREATED AS THE NORM
Summary
Because it is a first-generation duplex, the heat-affected zone does not reach base metal properties in the as-welded condition; repeating the solution anneal is the rule here, not the exception.
Temperature
The temperature of stage 1 above: 925-955 °C (ASTM A789, A790).
Time
Until the whole section is at temperature; no separate numerical time could be confirmed.
Cooling
Rapid cooling in air or water.
Resulting hardness
The hardness of the solution annealed condition (A240 ceiling 269 HBW).
Warning
IMOA on the first-generation duplex grades: ‘The heat-affected zone (HAZ) of welds had low toughness because of excessive ferrite, and significantly lower corrosion resistance than that of the base metal.’
The intermediate-temperature anneal that is routine on an austenitic stainless is not applied here.
Temperature
Roughly 600-1000 °C is the sigma band and roughly 300-525 °C is the 475 °C embrittlement band. No safe stress-relief window between the two could be confirmed across four independent sources, so NO FIGURE IS GIVEN on the card.
Time
—
Cooling
—
Resulting hardness
Where a heat treatment is required, a full solution anneal and rapid quench is performed.
DEFENCE METAL
4 · PRECIPITATION HARDENING — THERE IS NONE
Step
4 · PRECIPITATION HARDENING — THERE IS NONE
Summary
This alloy has NO ageing stage such as H900 / H1025 / H1075 / H1150 and cannot be hardened by ageing.
Temperature
—
Time
—
Cooling
—
Resulting hardness
IMOA: ‘Duplex stainless steels will not form martensite during cooling. High strength and hardness in a duplex stainless steel are the result of high nitrogen content, the duplex structure itself, and work hardening.’ The only way to raise strength is cold work, and cold work leaves residual stress.
DEFENCE METAL
TWO SEPARATE FORBIDDEN BANDS — (1) sigma and intermetallic precipitation, (2) 475 °C embrittlement
Step
TWO SEPARATE FORBIDDEN BANDS — (1) sigma and intermetallic precipitation, (2) 475 °C embrittlement
What happens
BAND 1 — SIGMA AND INTERMETALLIC PHASES (about 600-1000 °C): sigma, chi and similar intermetallics precipitate from the ferrite. IMOA: ‘The presence of sigma phase decreases the pitting resistance of duplex stainless steels, due to the depletion of chromium and molybdenum in surrounding areas’ and ‘Toughness and ductility are also sharply reduced when intermetallic phase precipitation occurs.’ IMOA also states ‘Detrimental phases can form in a matter of minutes at the critical temperature’ — this band is measured in minutes, not hours. BAND 2 — 475 °C EMBRITTLEMENT (about 300-525 °C): alpha prime (α’) precipitates inside the ferrite, the material hardens and loses toughness. IMOA: ‘Alpha prime can form in the ferrite phase of duplex stainless steels below about 525 °C.’ This band sets the SERVICE TEMPERATURE CEILING of duplex steels; IMOA: ‘The upper temperature limit for duplex stainless steel service is controlled by alpha prime formation.’
As named in the source
SIGMA / INTERMETALLIC BAND, every figure with its source: IMOA 700-1000 °C (‘Sigma phase and other intermetallic phases such as chi can precipitate from the ferrite … on cooling too slowly through the temperature range of 700-1000 °C’), and 700-950 °C for the 2205 sigma field · Outokumpu 600-1000 °C (‘Intermetallic phases such as sigma phase occurs in the temperature range 600-1000 °C’) · Industeel 1000-600 °C (‘At high temperature: 1000-600 °C (1830-1110 °F), the α phase may transform in α, χ,… intermetallic phases’) · Rolled Alloys 1300-1800 °F, i.e. 704-982 °C (‘Sigma phase will precipitate upon exposure to temperatures within the 1300-1800 °F range’) · Sandmeyer 1300-1800 °F, i.e. 704-982 °C. PRACTICAL ENVELOPE: about 600-1000 °C. NO SINGLE FIGURE IS GIVEN AND NO AVERAGE IS TAKEN. 475 °C EMBRITTLEMENT BAND, every figure with its source: IMOA 300-525 °C · Rolled Alloys 650-980 °F, i.e. 343-527 °C (‘Exposure to temperatures in the 650-980 °F range causes the precipitation of alpha prime in the ferritic portion of the material. This phenomenon is also referred to as 885 °F embrittlement’) · Outokumpu 350-500 °C (‘decomposition of ferrite occurs in the range 350-500 °C (475 °C embrittlement)’) · Industeel 300-500 °C (‘At lower temperature (300-500 °C) the α phase transforms in α′ resulting in a hardening’). PRACTICAL ENVELOPE: about 300-525 °C.
Kinetik uyarisi
KINETICS NOTE — SPECIFIC TO 329: the solution annealing band of this grade (925-955 °C in ASTM A789 and A790) does not sit above the sigma band, it looks INTO it. Modern duplex grades are annealed between 1020 and 1140 °C, i.e. above the sigma band; in 329 the margin between annealing temperature and forbidden band is narrow. Against that, the alloy content of 329 (molybdenum in particular, 1.00-2.00%) is lower than that of a super duplex, and IMOA’s rule is ‘Precipitates tend to form quicker with increasing alloy content.’ So its precipitation kinetics are slower than those of S32750 and S32760; that offsets the narrow annealing margin but does not remove it. The absence of nitrogen works the other way: IMOA states ‘The addition of nitrogen significantly delays formation of these phases’, and 329 does not have that retardant.
En sik hata
THE MOST COMMON MISTAKE: cooling slowly after solution annealing, or leaving the part in the furnace to cool on its own. Rolled Alloys puts the measure plainly: ‘It is important to cool to below 700 °F as quickly as possible. If the cooling rate is too slow, it will lead to decreased corrosion resistance and lowered impact strength.’ IMOA says the same: ‘Allowing a plate or a fitting to cool into the 700-980 °C range prior to quenching may lead to the formation of intermetallic phases.’ THE SECOND MISTAKE: applying an intermediate-temperature stress-relief anneal as one would on an austenitic stainless — on a duplex steel that anneal lands inside the sigma band.
The diagram is schematic; the time axis is NOT to scale. No published TTT/CCT curve was used, so no curve is drawn. THIS ALLOY IS A DUPLEX (ferritic-austenitic) STAINLESS STEEL: it is NOT PRECIPITATION HARDENABLE, it is NOT AGED, and it does not transform to martensite on cooling. There is NO ageing step such as H900 / H1025 / H1075 / H1150 and no ageing diagram is drawn. IMOA states: ‘Duplex stainless steels will not form martensite during cooling. High strength and hardness in a duplex stainless steel are the result of high nitrogen content, the duplex structure itself, and work hardening.’ The only valid heat treatment is SOLUTION ANNEALING FOLLOWED BY RAPID QUENCHING; strength comes from the composition, the two-phase structure and cold work. The diagram is schematic; the time axis is not to scale. No published TTT/CCT curve was used, so no curve is drawn. The stages are NOT ageing stages; this alloy is not precipitation hardenable.
Heat treatment
Duplex grades cannot be hardened by heat treatment; their strength comes from the two-phase structure and from nitrogen and interstitial strengthening. Solution annealing: minimum annealing temperatures across the duplex family run 980–1120 °C depending on grade (the exact figure for 329 could not be verified and should be confirmed against a mill datasheet). Water quenching is mandatory: the most rapid quench achievable from the annealing temperature is required, because sigma and related intermetallics form within minutes in the 700–1000 °C band, while alpha-prime (475 °C embrittlement) forms between 300 and 525 °C. Slow cooling gives both reactions time and destroys the toughness/corrosion balance. Delivery condition:+AT (solution annealed) for EN 10088-3 bar.
Machining and forming
Duplex requires higher cutting forces and wears tools faster than austenitic grades, and because sulphur is deliberately kept low for corrosion resistance, chip breaking is harder too. The work-hardening rate is at least comparable to the common austenitics. Use coated carbide inserts with positive chip-breaker geometry, rigid setups, minimal tool overhang and scheduled tool changes. Coolant: generous EP-additive cutting oil or emulsion for turning and drilling; dry cutting is preferred in milling to aid chip ejection. Forming: duplex elongation is lower than austenitic (typically 15–30% against about 40%), so a more generous bend radius or an intermediate solution anneal is needed, and springback is markedly greater than with 316L.
In current EN welded / pressure product standards?
329: NO (dropped from welded tube, pressure tube and butt-weld fitting standards) · 2205: yes
In current EN bar / general-purpose tube?
329: yes · 2205: yes
As-welded toughness
329: poor — the HAZ over-ferritises · 2205: good, it was designed for it
Service temperature
About 250–315 °C for the duplex family. This is a toughness limit, not an oxidation limit — 475 °C embrittlement (300–525 °C) and sigma phase govern
Magnetic
Strongly magnetic, like all duplex grades — a reliable field test to distinguish them from austenitics
Verified typical application
Heat exchanger tubing in nitric acid service (historical, well documented). General duplex application lists should not be borrowed from 2205 literature
Frequently Asked Questions
Should 329 still be specified for new welded work, or is 2205 the right modern choice?
For new welded work 2205 is the right choice, and the reason is documented standards data rather than reputation: the current EN 10088 family has dropped 1.4460 from the welded tube (EN 10296-2), pressure-purpose seamless tube (EN 10216-5) and butt-weld fitting (EN 10253-3/-4) standards, while 2205 remains current in all of them. None of the three major duplex service centres surveyed stock 329. The duplex fabrication literature describes 329’s as-welded HAZ as low in toughness and lower in corrosion resistance than the base metal, a defect rooted in the alloy having no nitrogen. Specify 329 only for matching or repairing an existing installation; for anything new, 2205 (or 2304 for lighter duty) is the current, standards-supported and stocked choice.
Why does the nitrogen content matter so much for this grade?
Nitrogen is what lets a duplex alloy re-form austenite fast enough in the weld HAZ, where cooling happens in seconds. Modern grades such as 2205 carry 0.14–0.20% nitrogen precisely for this reason; 329, developed before that metallurgy became standard practice, has no nitrogen specification at all. The practical result is that 329’s welded HAZ ends up abnormally ferrite-rich, with measurably lower toughness and lower corrosion resistance. It shows up numerically too: 329’s verified composition gives a PREN of roughly 26–33 against 2205’s 35–36, a gap attributable almost entirely to the missing 16×%N term in the formula — despite 329’s chromium range overlapping, and in places exceeding, 2205’s.
What does the sigma-phase / embrittlement temperature limit actually rule out?
Duplex steels begin to embrittle through alpha-prime formation from as low as 300 °C, and continuous service is capped at roughly 250–315 °C depending on grade and welded condition. This is a toughness limit, not an oxidation limit — it bites well before the steel would visibly degrade. In practice it rules duplex, 329 included, out of any process stream running continuously above about 300 °C: higher-temperature steam, hot process fluids, and thermal excursions that linger in the 300–525 °C band, since even intermittent time there degrades toughness. For those services the correct specification is an austenitic or a specialty high-temperature alloy, however attractive duplex’s strength and chloride resistance look on paper.
STRENGTH VALUES
DEFENCE METAL
Condition
Hardness
Yield MPa
Tensile MPa
Elongation
ASTM A240 / ASME SA-240 · plate, sheet and strip
269 HBW max.
485
620
15%
ASTM A790 / ASME SA-790 · seamless and welded pipe
—
485
620
20%
ASTM A789 / ASME SA-789 · seamless and welded tube
—
485
620
20%
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. Different specifications can give different minimums for the same UNS number; that is a difference of test-piece geometry and acceptance criteria, not of the material. COLD-WORKED TEMPERS are NOT in this table unless stated otherwise. Every row is a specification minimum, not a typical value. There is NO bar or forging row for S32900: ASTM A276, A479, A182 and A815 do not cover this UNS number. Its yield minimum (485 MPa) is higher than that of S32205 (450 MPa); that does not make 329 the better grade — PREN is what ranks them.
THE FIVE DUPLEX / SUPER DUPLEX GRADES COMPARED BY PREN
PITTING RESISTANCE EQUIVALENT NUMBER (PREN). This is the quantity that ranks these grades; yield or tensile strength does not.
A · PREN — calculated from the ASTM A240 composition band (SAME FORMULA, SAME TABLE)
ASTM A240 / ASME SA-240 composition table. All five UNS numbers are in it. The figures are calculated, not measured.
DEFENCE METAL
Criterion
Criterion
Bilesim a240
Bilesim a240
Pren hesap
Pren hesap
Pren yayimlanan
Pren yayimlanan
Note
Note
AISI 329 · UNS S32900 · 1.4460
AISI 329 · UNS S32900 · 1.4460
Cr 23.0-28.0% · Mo 1.00-2.00% · N NOT specified
Cr 23.0-28.0% · Mo 1.00-2.00% · N NOT specified
26.3 – 34.6
26.3 – 34.6
IMOA typical 30-31
IMOA typical 30-31
THE NITROGEN TERM IS ZERO. ASTM A240 and A789 set no nitrogen requirement for S32900, so the third term of PREN never forms in this grade. This is the lowest PREN of the five.
THE NITROGEN TERM IS ZERO. ASTM A240 and A789 set no nitrogen requirement for S32900, so the third term of PREN never forms in this grade. This is the lowest PREN of the five.
AISI 318 / 2205 · UNS S32205 · 1.4462
AISI 318 / 2205 · UNS S32205 · 1.4462
Cr 22.0-23.0% · Mo 3.00-3.50% · N 0.14-0.20%
A standard duplex. It is NOT a super duplex; its PREN floor is below 40.
A standard duplex. It is NOT a super duplex; its PREN floor is below 40.
UNS S31803 · 1.4462 (the older, wide-band version of 2205)
UNS S31803 · 1.4462 (the older, wide-band version of 2205)
Cr 21.0-23.0% · Mo 2.50-3.50% · N 0.08-0.20%
Cr 21.0-23.0% · Mo 2.50-3.50% · N 0.08-0.20%
30.5 – 37.8
30.5 – 37.8
IMOA 33-35
IMOA 33-35
THIS IS THE MOST IMPORTANT ROW OF THE COMPARISON: the lower end of the S31803 band falls to PREN 30.5, so a fully COMPLIANT S31803 heat can sit 3.6 points below the S32205 floor of 34.1. The two carry the same W.Nr. (1.4462) but they are NOT equivalent.
THIS IS THE MOST IMPORTANT ROW OF THE COMPARISON: the lower end of the S31803 band falls to PREN 30.5, so a fully COMPLIANT S31803 heat can sit 3.6 points below the S32205 floor of 34.1. The two carry the same W.Nr. (1.4462) but they are NOT equivalent.
F255 / Ferralium 255 · UNS S32550 · 1.4507
F255 / Ferralium 255 · UNS S32550 · 1.4507
Cr 24.0-27.0% · Mo 2.90-3.90% · N 0.10-0.25% · Cu 1.50-2.50%
Cr 24.0-27.0% · Mo 2.90-3.90% · N 0.10-0.25% · Cu 1.50-2.50%
35.2 – 43.9
35.2 – 43.9
IMOA 38-41 · Langley Alloys above 40
IMOA 38-41 · Langley Alloys above 40
THE SPECIFICATION BAND DROPS BELOW 40 (floor 35.2), whereas commercial Ferralium 255 heats hold nitrogen at 0.20-0.25% and lift PREN above 40 (Langley). ASTM A240 sets NO PREN ≥ 40 requirement for S32550 — the only grade it imposes that on is S32760. Copper is NOT in the PREN formula; the copper in S32550 does not raise PREN.
THE SPECIFICATION BAND DROPS BELOW 40 (floor 35.2), whereas commercial Ferralium 255 heats hold nitrogen at 0.20-0.25% and lift PREN above 40 (Langley). ASTM A240 sets NO PREN ≥ 40 requirement for S32550 — the only grade it imposes that on is S32760. Copper is NOT in the PREN formula; the copper in S32550 does not raise PREN.
F55 / Zeron 100 · UNS S32760 · 1.4501
F55 / Zeron 100 · UNS S32760 · 1.4501
Cr 24.0-26.0% · Mo 3.00-4.00% · N 0.20-0.30% · W 0.50-1.00% · Cu 0.50-1.00%
Cr 24.0-26.0% · Mo 3.00-4.00% · N 0.20-0.30% · W 0.50-1.00% · Cu 0.50-1.00%
THIS IS THE ONLY ONE OF THE FIVE WHOSE PREN IS BOUND BY THE SPECIFICATION. ASTM A240 carries the footnote ‘Cr + 3.3 Mo + 16 N = 40 min.’ on the S32760 row; 40 is therefore not a computed result but an ACCEPTANCE CRITERION. With the tungsten formula the same composition gives 37.9-45.7 and Rolled Alloys states it plainly: ‘With this formula ZERON 100 has a PREN > 41.’
THIS IS THE ONLY ONE OF THE FIVE WHOSE PREN IS BOUND BY THE SPECIFICATION. ASTM A240 carries the footnote ‘Cr + 3.3 Mo + 16 N = 40 min.’ on the S32760 row; 40 is therefore not a computed result but an ACCEPTANCE CRITERION. With the tungsten formula the same composition gives 37.9-45.7 and Rolled Alloys states it plainly: ‘With this formula ZERON 100 has a PREN > 41.’
F53 / 2507 · UNS S32750 · 1.4410
F53 / 2507 · UNS S32750 · 1.4410
Cr 24.0-26.0% · Mo 3.00-5.00% · N 0.24-0.32%
THE TOP OF ITS CALCULATED BAND IS THE HIGHEST OF THE FIVE (47.6), because the molybdenum band runs up to 5.00% and the nitrogen band is the highest of all (0.24-0.32%). But its floor is not bound to 40 as S32760’s is; there is NO PREN footnote on the S32750 row of A240.
THE TOP OF ITS CALCULATED BAND IS THE HIGHEST OF THE FIVE (47.6), because the molybdenum band runs up to 5.00% and the nitrogen band is the highest of all (0.24-0.32%). But its floor is not bound to 40 as S32760’s is; there is NO PREN footnote on the S32750 row of A240.
B · SOLUTION ANNEALING TEMPERATURE — ASTM A790 and A789 heat treatment table (SAME TABLE)
ASTM A790 (seamless and welded duplex pipe) and ASTM A789 (duplex tube), Table 1. All five UNS numbers are in it.
DEFENCE METAL
Criterion
Criterion
AISI 329 (S32900)
AISI 318 / 2205 (S32205)
F255 (S32550)
F55 (S32760)
F53 (S32750)
F255 (S32550)
Difference
Difference
AISI 329 (S32900)
AISI 318 / 2205 (S32205)
F55 (S32760)
F53 (S32750)
Solution annealing temperature — ASTM A790 and A789 (SAME TABLE, seamless and welded pipe/tube)
Solution annealing temperature — ASTM A790 and A789 (SAME TABLE, seamless and welded pipe/tube)
925-955 °C [1700-1750 °F]
1020-1100 °C [1870-2010 °F]
1040 °C [1900 °F] min.
1070-1140 °C [1960-2085 °F]
1025-1125 °C [1880-2060 °F]
1040 °C [1900 °F] min.
The annealing temperature of 329 is BELOW ALL FOUR of the others, and the top of its band (955 °C) sits inside the sigma band. Modern duplex grades are annealed ABOVE the sigma band; 329 is annealed at its edge. This is the concrete measure of why 329 is regarded as first generation.
The annealing temperature of 329 is BELOW ALL FOUR of the others, and the top of its band (955 °C) sits inside the sigma band. Modern duplex grades are annealed ABOVE the sigma band; 329 is annealed at its edge. This is the concrete measure of why 329 is regarded as first generation.
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Cooling requirement — ASTM A790 and A789
Cooling requirement — ASTM A790 and A789
Rapid cooling in air or water
Rapid cooling in air or water
Rapid cooling in air or water
Rapid cooling in air or water
Rapid cooling in air or water
Rapid cooling in air or water
NO DIFFERENCE — rapid cooling is MANDATORY on all five. On the forging side ASTM A182 states it more tightly: ‘solution treat and quench’, in a liquid medium down to 260 °C [500 °F].
NO DIFFERENCE — rapid cooling is MANDATORY on all five. On the forging side ASTM A182 states it more tightly: ‘solution treat and quench’, in a liquid medium down to 260 °C [500 °F].
ASTM A240 / ASME SA-240 mechanical table. The values are SPECIFICATION MINIMUMS, not typical values.
DEFENCE METAL
Criterion
Criterion
AISI 329 (S32900)
AISI 318 / 2205 (S32205)
F255 (S32550)
F55 (S32760)
F53 (S32750)
Difference
Difference
AISI 329 (S32900)
AISI 318 / 2205 (S32205)
F255 (S32550)
F55 (S32760)
F53 (S32750)
Minimum tensile strength
Minimum tensile strength
620 MPa (90 ksi)
655 MPa (95 ksi)
760 MPa (110 ksi)
750 MPa (108 ksi)
795 MPa (116 ksi)
F53 (S32750) is the highest, 329 the lowest.
F53 (S32750) is the highest, 329 the lowest.
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Minimum yield strength (0.2%)
Minimum yield strength (0.2%)
485 MPa (70 ksi)
450 MPa (65 ksi)
550 MPa (80 ksi)
550 MPa (80 ksi)
550 MPa (80 ksi)
NOTE: on minimum yield, 329 is ABOVE 2205 (485 vs 450 MPa). Yield strength does not rank this family; the quantity that ranks it is PREN. All three super duplex grades are equal at 550 MPa.
NOTE: on minimum yield, 329 is ABOVE 2205 (485 vs 450 MPa). Yield strength does not rank this family; the quantity that ranks it is PREN. All three super duplex grades are equal at 550 MPa.
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Minimum elongation (ASTM A240, plate)
Minimum elongation (ASTM A240, plate)
15%
25%
15%
25%
15%
S32205 and S32760 require 25%; the other three 15%.
S32205 and S32760 require 25%; the other three 15%.
15%
25%
15%
25%
15%
Hardness ceiling (ASTM A240, Brinell)
Hardness ceiling (ASTM A240, Brinell)
269 HBW
293 HBW
302 HBW
270 HBW
310 HBW
The hardness ceiling does not follow the strength order; the ceiling for S32760 is lower than that for S32205.
The hardness ceiling does not follow the strength order; the ceiling for S32760 is lower than that for S32205.
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D · NAMING — ASTM A182 forging class codes (SAME TABLE)
The duplex class list of ASTM A182 / ASME SA-182. This is where market names and specification codes get confused.
DEFENCE METAL
Criterion
Criterion
AISI 329 (S32900)
AISI 318 / 2205 (S32205)
F255 (S32550)
F55 (S32760)
F53 (S32750)
AISI 329 (S32900)
F255 (S32550)
Difference
Difference
AISI 318 / 2205 (S32205)
F55 (S32760)
F53 (S32750)
ASTM A182 forging class code
ASTM A182 forging class code
NONE — S32900 is not listed in ASTM A182
F60 (S32205) · F51 (S31803)
F61 — there is NO A182 class called ‘F255’
F55
F53
NONE — S32900 is not listed in ASTM A182
F61 — there is NO A182 class called ‘F255’
The duplex class list of ASTM A182 is: F50 (S31200), F51 (S31803), F52 (S32950), F53 (S32750), F54 (S39274), F55 (S32760), F57 (S39277), F59 (S32520), F60 (S32205), F61 (S32550), F65 (S32906). F255 is NOT on the list.
The duplex class list of ASTM A182 is: F50 (S31200), F51 (S31803), F52 (S32950), F53 (S32750), F54 (S39274), F55 (S32760), F57 (S39277), F59 (S32520), F60 (S32205), F61 (S32550), F65 (S32906). F255 is NOT on the list.
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Origin of the market name
Origin of the market name
An AISI type number (old AISI 300/400 series logic)
‘2205’ comes from the composition: ~22% Cr, ~5% Ni. ‘AISI 318’ is an old type name.
‘255’ comes from the Ferralium 255 TRADE NAME; the letter ‘F’ was attached to it later by the market, not by A182.
‘F55’ IS a genuine ASTM A182 class code. Zeron 100 is the licensed trade name.
‘F53’ IS a genuine ASTM A182 class code. ‘2507’ comes from the composition: ~25% Cr, ~7% Ni.
An AISI type number (old AISI 300/400 series logic)
‘255’ comes from the Ferralium 255 TRADE NAME; the letter ‘F’ was attached to it later by the market, not by A182.
TWO of the three names (F53, F55) are genuine A182 class codes; ONE (F255) is not. Specifying the alloy by its UNS number on the order removes this confusion by itself.
TWO of the three names (F53, F55) are genuine A182 class codes; ONE (F255) is not. Specifying the alloy by its UNS number on the order removes this confusion by itself.
‘2205’ comes from the composition: ~22% Cr, ~5% Ni. ‘AISI 318’ is an old type name.
‘F55’ IS a genuine ASTM A182 class code. Zeron 100 is the licensed trade name.
‘F53’ IS a genuine ASTM A182 class code. ‘2507’ comes from the composition: ~25% Cr, ~7% Ni.
PREN(W) = %Cr + 3.3 × (%Mo + 0.5 × %W) + 16 × %N — meaningful only for S32760
Pren formulu tungstenli
PREN(W) = %Cr + 3.3 × (%Mo + 0.5 × %W) + 16 × %N — meaningful only for S32760
Ortak sinir
WHAT ALL FIVE SHARE AS A LIMIT: none of them is PRECIPITATION HARDENABLE, and none of them goes into continuous service much above 300 °C. IMOA’s ASME and TÜV ceilings: 2205 unwelded 315 °C (ASME) and 280 °C (TÜV), welded 315 °C (ASME) and 250 °C (TÜV); 2507 seamless tube 315 °C (ASME) and 250 °C (TÜV). Rolled Alloys gives 600 °F (316 °C) for 2205 and 2507 and 300 °C for Zeron 100; Sandmeyer gives 570 °F (299 °C) for 2507; Penn Stainless gives 572 °F (300 °C) for 2205; Industeel gives 280 °C for 2205 and 270 °C for super duplex. The reason is one and the same: 475 °C embrittlement.
Ortak sinir
WHAT ALL FIVE SHARE AS A LIMIT: none of them is PRECIPITATION HARDENABLE, and none of them goes into continuous service much above 300 °C. IMOA’s ASME and TÜV ceilings: 2205 unwelded 315 °C (ASME) and 280 °C (TÜV), welded 315 °C (ASME) and 250 °C (TÜV); 2507 seamless tube 315 °C (ASME) and 250 °C (TÜV). Rolled Alloys gives 600 °F (316 °C) for 2205 and 2507 and 300 °C for Zeron 100; Sandmeyer gives 570 °F (299 °C) for 2507; Penn Stainless gives 572 °F (300 °C) for 2205; Industeel gives 280 °C for 2205 and 270 °C for super duplex. The reason is one and the same: 475 °C embrittlement.
RULE: every block in this diagram is read from ONE TABLE OF ONE SPECIFICATION; different specifications are never compared on the same row. All five UNS numbers fall within the scope of ASTM A240, A789 and A790, so they are listed side by side under the same acceptance criteria (the scope of A182 and A479 is not the same for all five, and that is stated separately). THE PREN COLUMN IS A CALCULATION, NOT A MEASUREMENT: the lower and upper ends of the ASTM A240 composition band were substituted into PREN = %Cr + 3.3×%Mo + 16×%N. Published PREN values are given in a separate column WITH THE NAME OF THE SOURCE; the two columns must not be mixed. THE BLOCKS ARE NOT ADDED TOGETHER AND NOT PLACED ON A COMMON AXIS. The figures in the PREN column are CALCULATED, NOT MEASURED; the ends of the ASTM A240 composition band were substituted into the formula. A calculated PREN band and the PREN of commercial heats are not the same thing: a producer works inside the band and typically aims at its upper half. CPT (critical pitting temperature) and CCT (critical crevice temperature) values have NOT been put on this diagram; the reason is given under ‘atlananlar’. Copper (Cu) does not appear in the PREN formula. The 1.50-2.50% copper of S32550 and the 0.50-1.00% copper of S32760 do not raise PREN; their effect is on behaviour in reducing media and is measured separately. All five grades are supplied SOLUTION ANNEALED AND RAPIDLY QUENCHED; none of them is precipitation hardenable.
