UNS S31635 · W.Nr. 1.4571 · X6CrNiMoTi17-12-2 · 16.0-18.0% Cr – 10.0-14.0% Ni – 2.00-3.00% Mo – C ≤ 0.08% – Ti 5×(C+N) minimum to 0.70% maximum (ASTM A240, A479, A182) – balance Fe. The EN 10088 band for 1.4571 is: C ≤ 0.08%, Cr 16.5-18.5%, Ni 10.5-13.5%, Mo 2.0-2.5%, Ti from 5×C to 0.70%. 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 at elevated temperature: chemical and petrochemical process equipment, exhaust and flue lines, heat exchangers, hot process piping, pulp and textile plant equipment.
Forms
Round bar · flat bar · plate · sheet · pipe and tube · forging. All forms supplied to order.
Standards
NO AMS NUMBER COULD BE CONFIRMED — no AMS number was found for 316Ti; ASTM and EN are used directly. ASTM: A240 / SA-240 (plate, sheet, strip, S31635) · A479 / SA-479 (bar and shapes, S31635) · A182 / SA-182 (forged flanges and fittings, F316Ti) · A484 (general requirements). EN: 1.4571 · 10088-2 · 10088-3 · 10028-7 · 10216-5 · 10222-5 · ISO 15510. THERE IS NO AMS NUMBER FOR 316Ti (ams_yok). None of the producer bulletins searched — ATI, Elgiloy, Fine Tubes, Alleima, Outokumpu, thyssenkrupp, Aalco, Metalcor and Abrams among them — gives an AMS number for 316Ti;
Advantage
Of the three grades this is the only one that gives the strength minimum of 316 and the sensitization resistance of 316L AT THE SAME TIME. In ASTM A240 the tensile minimum of 316Ti is 515 MPa and the yield minimum 205 MPa; those are THE SAME as 316 and 30 and 35 MPa above 316L.
Welding
Filler metal: American Boiler Company states that NIOBIUM-STABILIZED fillers (318/347 type) should be used for welding 316Ti where elevated temperature weld strength matters, and that a 316L filler is enough for matching corrosion resistance.
Limits
CHLORIDE STRESS CORROSION CRACKING: titanium DOES NOT reduce this risk. Outokumpu states that the Supra range austenitics (316L and 316Ti among them) are susceptible to chloride-induced stress corrosion cracking and that the risk arises when tensile stress, temperatures above about 50 °C and chlorides come together;
Compiled from manufacturer data sheets · confirm against the current specification before ordering
On this page · click to jump
Standards by Product FormWelding, Heat Treatment and Machining316Ti or 316L?Frequently Asked Questions
Corrosion resistance: The corrosion resistance of AISI 316Ti is very good. Duplex grade 1.4462 can be specified for harsher environments.
Temperature capability: This product is grade 316 stainless steel produced with a titanium addition. It has high temperature capability and oxidation resistance and withstands temperatures of 600-700 °C. Because it contains titanium, the welding performance of grade 316Ti is often assumed to be poor, but that is a misconception. With very good weldability, 316Ti may nevertheless give way to 316L where a working environment demands extensive welding.
Machinability: Improving the machinability of grade 316Ti depends on very good, high quality practice during production and on the material being properly annealed. Where the use of a stainless steel with lower corrosion resistance is acceptable, grades such as 303 or 430F, which machine readily, can be used.
Heat treatment: The heat treatment requirements of AISI 316Ti are generally similar to those of AISI 316, although there may be some differences because of the titanium addition. It cannot be hardened by heat treatment.
Applications: The range of applications for the 316 stainless steel group is very wide because of the quality of the material. Grade 316 and its derivatives are frequently used, for example, in tanks and storage vessels for abrasive liquids, in the chemical and petrochemical industries, in steam boilers, in the paint industry, in food plants and in mining.
AISI 316Ti is an excellent material for applications requiring resistance to intergranular corrosion, high temperature capability and chemical resistance. The titanium addition gives better weldability and corrosion resistance than AISI 316, which is why it is frequently chosen in fields such as chemical processing, power generation, marine and the medical industry.
Chemical Composition
DEFENCE METAL
C
Max. 0.08
Mn
Max. 2.00
Si
Max. 1.00
P
Min. 0 · Max. 0.045
S
Max. 0.015
Cr
Min. 16.5 · Max. 18.50
Mo
Min. 2.00 · Max. 2.50
Ni
Min. 10.50 · Max. 13.50
Ti
Min. 5xC · Max. 0.70
Mechanical Properties
DEFENCE METAL
Tensile Strength (MPa)
500-700
Proof Stress (MPa)
>200
Elongation A50 mm
40/30
Hardness Brinell
215 Max HB
Density
8.00 g/cm3
Melting Point
1400 °C
Modulus of Elasticity
200 kN/mm²
Electrical Resistivity
0.75 nΩ.m
Thermal Conductivity
15 W/m.K
Thermal Expansion
15.9 x10^-6 /K
Standards and Equivalents · AISI 316Ti
DEFENCE METAL
Trade name
AISI 316Ti
UNS
S31635
W.Nr (DIN/EN)
1.4571
AMS
5507 · 5524 · 5573 · 5584 · 5648 · 5649 · 5653
ASTM
A276 · A479 · A484 · A240
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 NUMBER. ASTM A240 / ASME SA-240 (S31635) · EN 10088-2 · EN 10028-7 · ISO 15510
Sheet and strip
NO AMS NUMBER. ASTM A240 / ASME SA-240 (S31635) · EN 10088-2 · ISO 15510
Round bar, flat bar (including square and hexagon)
NO AMS NUMBER. ASTM A479 / ASME SA-479 (S31635) · ASTM A484 (general requirements) · EN 10088-3. IT COULD NOT BE CONFIRMED that ASTM A276 covers S31635; the confirmed specification for bar is A479.
Wire
NO AMS NUMBER. EN 10088-3. It could not be confirmed that ASTM A580 covers S31635; Alloy Wire lists its product to ASTM A240 and EN 10088-3.
Forging
NO AMS NUMBER. ASTM A182 / ASME SA-182 (F316Ti) · ASTM A484 · EN 10222-5 · EN 10088-3
Flange
NO AMS NUMBER. ASTM A182 / ASME SA-182 (F316Ti) — forged flanges, fittings and valve parts · dimensions to ASME B16.5 / B16.47 · EN 10222-5
Fitting
NO AMS NUMBER. ASTM A182 / ASME SA-182 (F316Ti) is confirmed for forged fittings · dimensions to ASME B16.9 / B16.11. ASTM A403 WP316Ti was seen only on vendor pages and the scope COULD NOT BE CONFIRMED.
Seamless and welded pipe
NO AMS NUMBER. EN 10216-5 (seamless). IT COULD NOT BE CONFIRMED that ASTM A312 covers S31635; TP316Ti was not found in the A312 text that was read and was seen only on vendor pages. Before ordering, the grade list of the current edition of the specification must be confirmed.
Seamless and welded tube (boiler, superheater, heat exchanger)
NO AMS NUMBER. EN 10216-5. ASTM A213 / ASME SA-213 (TP316Ti) was seen in two independent sources (Fine Tubes manufactures its product to A213 and BS EN 10216-5; one tube maker’s A213 table carries a TP316Ti row); it did not pass the four-source threshold and is not counted as CONFIRMED.
THERE IS NO AMS NUMBER FOR 316Ti. None of the producer bulletins or SAE sources searched gives an AMS number belonging to 316Ti. The AMS numbers of 316 and 316L (5524, 5648, 5507, 5653, 5573, 5690) DO NOT BELONG to 316Ti and cannot be ordered in its place. The only ASTM scope confirmed by four independent sources is A240. A479 (S31635) and A182 (F316Ti) were seen in two and three independent sources respectively and are marked accordingly. The S31635 scope COULD NOT BE CONFIRMED for ASTM A276, A312, A403 and A580; statements on vendor pages were not counted as sources. The EN numbers are for information; the acceptance criteria that apply are those of the specification the order was placed to.
AISI 316Ti is the titanium-stabilised variant of 316, widely known in Europe as 1.4571. Two points are critical when ordering. First, EN 1.4571 and ASTM S31635 are not exactly equivalent — the analysis ranges and the titanium minimum formula differ. Second, and the more frequent source of trouble: ASTM A312, the most widely used stainless process pipe standard, does not include a TP316Ti grade. On the ASTM side the correct reference for tube is A213.
Standards by Product Form · AISI 316Ti (S31635 / 1.4571)
DEFENCE METAL
Sheet · Plate · Strip
EN 10088-2 · EN 10028-7 · ASTM A240 / ASME SA-240 (S31635)
Bar · Shapes
EN 10088-3 · EN 10272 · ASTM A276 · ASTM A479
Forgings · Rings · Flanges
EN 10250-4 · EN 10222-5 · ASTM A182 Gr. F316Ti
Seamless pipe · tube
EN 10216-5 · EN 10297-2 · ASTM A213 / SA-213 TP316Ti
Welded pipe · tube
EN 10217-7 · EN 10296-2
Fittings
EN 10253-3 · EN 10253-4
Wire
EN 10088-3 · EN 10263-5
Welding wire
AWS A5.9 ER318 = EN ISO 14343 W/G 19 12 3 Nb = W.Nr 1.4576
Welding electrode
AWS A5.4 E318-16 · E318-17
ASTM A312 (process pipe)
Not covered — there is no TP316Ti in A312; use A213 for tube
EN versus ASTM chemistry: EN 1.4571 has Mo 2.00–2.50% · Cr 16.50–18.50% · Ni 10.50–13.50% · S ≤ 0.015% and Ti ≥ 5×C; ASTM S31635 has Mo 2.00–3.00% · Cr 16.0–18.0% · Ni 10.0–14.0% · S ≤ 0.030% and Ti ≥ 5×(C+N). The mechanical minimums differ too: EN 10088-2 requires yield ≥ 240 MPa for cold-rolled sheet against ≥ 205 MPa in ASTM A240. Do not assume one certificate satisfies both — ask for dual certification.
Welding, Heat Treatment and Machining
HEAT TREATMENT — SCHEMATIC
DEFENCE METAL
TITANIUM STABILIZATION — what separates 316Ti from 316 and 316L
Step
TITANIUM STABILIZATION — what separates 316Ti from 316 and 316L
Summary
This is not a heat treatment step; it explains why the cycle below is THE SAME for all three grades and where the difference comes from.
Note
What separates 316Ti from 316 is THE TITANIUM; what separates it from 316L is that IT BINDS THE CARBON INSTEAD OF LOWERING IT. The chromium (16.0-18.0%), nickel (10.0-14.0%) and molybdenum (2.00-3.00%) bands of the three grades are the same in ASTM A240; the heat treatment cycle is THE SAME; the solution annealing temperature and the cooling requirement are THE SAME. 316L solves the problem by lowering the carbon to 0.030% and pays for it in yield strength (170 MPa instead of 205 MPa in ASTM A240). 316Ti leaves the carbon at 0.08% and binds it with titanium as TiC; the carbon is not left free to form chromium carbide. The result: the sensitization resistance of 316L is obtained while the 205 MPa yield minimum of 316 is kept. And because the titanium stays bound at temperature as well, that resistance holds not only over the short heat cycle of a weld but also IN LONG-TERM SERVICE.
Requirement
Ti 5×(C+N) minimum to 0.70% maximum (ASTM A240, A479, A182) · Ti from 5×C to 0.70% (EN 1.4571). The carbon ceiling is 0.08%, that is THE SAME as 316.
DEFENCE METAL
SOLUTION ANNEAL — this is the only valid heat treatment
Step
SOLUTION ANNEAL — this is the only valid heat treatment
Summary
It reverses cold work, takes chromium carbides back into solid solution, renews the grain structure and restores corrosion resistance. IT DOES NOT RAISE STRENGTH, IT LOWERS IT. This is the delivery condition; ASTM A240, A276, A479, A312, A213 and A182 all call for the material in this condition.
Temperature
The sources differ at the ends of the band, EACH WITH ITS NAME: worldstainless grade sheet 1010-1120 °C · Aalco 1010-1120 °C · AZoM 1010-1120 °C · ATI 1040-1175 °C (1900-2150 °F) · Jacquet 1040-1175 °C · thyssenkrupp 1.4404 1030-1110 °C · Outokumpu 1000-1100 °C · Sandmeyer at least 1038 °C (1900 °F). NO SINGLE NUMBER IS WRITTEN AND NO AVERAGE IS TAKEN. The practical envelope is about 1010-1175 °C. THE SPECIFICATION FLOOR IS SEPARATE and it is the binding one: ASTM A312, A213, A479 and A182 require at least 1040 °C (1900 °F).
Time
No single soak time could be confirmed by four independent sources, so none is given. The time is set by getting the whole section to temperature; extending it brings no benefit, it brings grain growth.
Cooling
RAPID COOLING IS MANDATORY — it is not a preference, it is a metallurgical condition. Water quench or rapid air/gas cooling. The purpose is to pass the roughly 816-427 °C range before carbides can precipitate again (ATI, Jacquet). ATI gives the measure this way: the metal must be cooled from the annealing temperature to black heat in less than three minutes. ASTM A312, A213 and A479 say ‘quenched in water or rapidly cooled by other means’; ASTM A182 requires solution annealing plus quenching. Slow cooling voids the treatment: the part stays inside the sensitization band.
Purpose
After hot and cold forming; to restore corrosion resistance after welding; to recover a part that has been held in the sensitization band.
STABILIZING ANNEAL — MEANINGFUL ONLY ON 316Ti
Summary
An intermediate temperature treatment that completes the binding of the carbon by the titanium as TiC. It has no counterpart on 316 or 316L, because there is no titanium to bind the carbon. It is NOT a hardening step.
Temperature
IT COULD NOT BE CONFIRMED BY FOUR INDEPENDENT SOURCES, so no number is written on the card. What was found, WITH THE SOURCE NAMES: the ATI 316Ti bulletin 845-900 °C (1550-1650 °F) · the PipingPipeline ASTM A240 316Ti page 845-900 °C (1550-1650 °F) for at least 2 hours followed by rapid air cooling · the AZoM heat treatment article (for grade 321) 870-900 °C for 2 to 4 hours followed by rapid cooling. Fine Tubes and Elgiloy describe the treatment as an ‘intermediate temperature heat treatment’ without giving numbers.
Time
No single soak time could be confirmed by four independent sources. PipingPipeline gives at least 2 hours and AZoM (for 321) 2 to 4 hours.
Cooling
Rapid cooling. PipingPipeline says rapid air cooling and AZoM says rapid cooling.
Purpose
To let the titanium react with the carbon and form titanium carbide, so that no free carbon is left to form chromium carbide during service. ATI and Elgiloy describe this as significantly reducing the susceptibility to sensitization in service.
Warning
AN UPPER LIMIT WARNING — SPECIFIC TO 316Ti: Outokumpu states that in the titanium-stabilized grade ANNEALING temperatures above 1070 °C may impair the resistance to intergranular corrosion. That warning does not exist for 316 or 316L and it means the upper end of the solution anneal must be held more carefully on 316Ti.
DEFENCE METAL
STRESS RELIEVING
Step
STRESS RELIEVING
Summary
In an austenitic structure, stress relieving has to be done without passing through the sensitization band. That is why there is no single standard recipe.
Note
NO SINGLE NUMERICAL RECIPE IS GIVEN — no temperature/time pair could be confirmed by four independent sources. What was found, EACH WITH ITS NAME: TWI states that most austenitic stainless steel weldments do not require postweld heat treatment, and gives about 400 °C for partial relief, about 1000 °C for stress corrosion cracking resistance and above 1000 °C for full solution annealing · AZoM says below 400 °C gives only partial relief, 425-925 °C is effective but carries a sensitization risk, and the full answer is a solution anneal at about 1080 °C · Alloy Wire gives 250 °C / 1 hour / air for 316Ti wire. PRACTICAL RULE: do not hold the part in the sensitization band in order to relieve stress; either do a partial relief well below the band (about 400 °C) or go to a full solution anneal and cool rapidly.
DEFENCE METAL
Range to avoid
Step
SENSITIZATION BAND — chromium carbide precipitation (M23C6)
Temperature
The sources differ at the ends of the band, EACH WITH ITS NAME: ATI 427-816 °C (800-1500 °F) · Jacquet 427-816 °C · worldstainless grade sheet 425-860 °C · Aalco 425-860 °C · AZoM 425-860 °C · Alleima 450-850 °C · Abrams 450-850 °C. NO SINGLE NUMBER IS WRITTEN AND NO AVERAGE IS TAKEN. The practical envelope is about 425-870 °C.
Note
A REGION TO AVOID. It is NOT a hardening step; this alloy is not precipitation hardenable. In this band chromium precipitates at the grain boundaries as chromium carbide (M23C6); the region next to the boundary is depleted in chromium and the material becomes open to intergranular corrosion (sensitization). In 316Ti the titanium binds the carbon as TiC and so prevents chromium carbide precipitation in this band: Alleima and Abrams put this as the prevention of intergranular corrosion during prolonged holding in the 450-850 °C range. BUT THE BAND DOES NOT GO AWAY; the titanium weakens it. Since the carbon ceiling stays at 0.08%, the effectiveness of the stabilization depends on the Ti/(C+N) ratio. This is the place of 316Ti among the three grades: for a part that will run for a LONG TIME inside the band, this is the right grade.
The scheme is schematic; the time axis is not to scale. No published TTT/CCT curve was used, so no curve is drawn. THIS ALLOY IS AUSTENITIC: IT IS NOT PRECIPITATION HARDENABLE and cannot be hardened by heat treatment. There is NO AGEING STEP such as H900 or H1075 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. The heat treatment cycle is THE SAME for 316, 316L and 316Ti. The only structural extra step is the stabilizing anneal on 316Ti. The stabilizing anneal temperature could not be confirmed by four independent sources; what was found is given WITH THE SOURCE NAMES and no single number is written. The time axis is not to scale; no published TTT/CCT curve was used. AN UPPER LIMIT SPECIFIC TO 316Ti: Outokumpu states that annealing temperatures above 1070 °C may impair the resistance to intergranular corrosion. That warning does not exist on 316 or 316L.
Welding
TIG, MIG/MAG, covered electrode, submerged-arc, laser and resistance welding are all applicable; oxy-acetylene welding is not used because of the carburising risk. Preheat and post-weld heat treatment are not normally required. There is no such product as “316Ti welding wire” — titanium volatilises rapidly in the welding arc and does not carry into the weld metal, which is why AWS A5.9 has no ER316Ti classification. Where stabilised weld metal is wanted, the niobium-stabilised ER318 (1.4576) is used; for service up to roughly 400 °C it is also welded successfully with ER316L.
Knife-line attack: in a narrow band immediately beside the weld that exceeds 1150 °C, the TiC dissolves. If the part later operates in the sensitisation range (~450–850 °C), chromium carbide precipitates in that narrow band and intergranular corrosion follows. This risk does not exist in 316L — it is specific to stabilised grades and must be allowed for in the design.
Heat treatment
The grade is fully austenitic; it cannot be hardened by heat treatment and work-hardens only by cold deformation. The single treatment applied is solution annealing: 1020–1120 °C in EN practice, a minimum of 1040 °C in ASTM A213, followed by water quenching or equivalent rapid cooling. One producer notes that annealing titanium-stabilised grades above 1070 °C can impair intergranular corrosion resistance and recommends 1070 ± 40 °C; in practice 1040–1080 °C is the safe band. Hot working is carried out between 900 and 1200 °C and must be followed by solution annealing. The standard delivery condition is +AT to EN and annealed to ASTM.
Machining
316Ti is harder to machine than 316L. Hard titanium carbonitrides increase tool wear and reduce machinability. The cutting edge must be kept sharp at all times; a blunt edge causes excessive work hardening. Thermal conductivity is low, so a generous, continuous coolant supply is essential. Delivery hardness is ≤ 215 HB (EN) / ≤ 217 HBW (ASTM) and rises markedly with cold work.
Surface finish — a disadvantage worth knowing: hard titanium carbonitrides are torn out during polishing and leave comet trails. For that reason 1.4571 is not suitable for decorative or polished (BA, satin, mirror) finishes; use 316L for that work. Stabilised grades also carry a higher inclusion content than low-carbon grades, all else being equal.
316Ti or 316L?
Technically the default is 316L. 316Ti is justified only where high-temperature strength and permanent long-term resistance to sensitisation are required.
Comparison · 316Ti (1.4571) versus 316L (1.4404)
DEFENCE METAL
Stabilisation
316Ti: by titanium, carbon up to 0.08% is tolerated · 316L: by reducing carbon to ≤0.030%
Duration of protection
The protection in 316L covers the welding cycle; over long exposure at temperature low-carbon grades sensitise too. The TiC in 316Ti is permanent
High-temperature strength
316Ti is higher (carbon ≤0.08%); low-carbon grades are not recommended for elevated temperature
Continuous service (in air)
Approximately 850 °C
Sensitisation range
Approximately 450–850 °C
Corrosion resistance
PREN ≈ 24 — the same level as 316/316L. Titanium has an adverse effect on pitting and stress-corrosion cracking resistance
Polishability
316Ti: not suitable · 316L: suitable
Knife-line attack
316Ti: at risk · 316L: not applicable
ASTM process pipe (A312)
316Ti: not covered · 316L: covered as TP316L
Rule of thumb: high temperature with long-term service → 316Ti. Polished finish, cold forming, critical pitting or stress-corrosion resistance, or a US project specification → 316L. Other options: AISI 321 (titanium stabilised, no molybdenum) and AISI 904L (super austenitic).
Frequently Asked Questions
Can I treat 1.4571 and S31635 as equivalent on a certificate?
Not exactly. They are the same family but the analysis ranges differ: Mo 2.00–2.50% in EN against 2.00–3.00% in ASTM; the EN sulphur limit is half as high; ASTM sets a nitrogen limit and EN does not. The most critical difference is the titanium minimum: 5×C in EN, 5×(C+N) in ASTM — for nitrogen-bearing heats ASTM demands more titanium. Material certified to 1.4571 usually falls inside the S31635 range, but not automatically. The mechanical minimums also differ. Ask for dual certification and have the heat analysis checked against both ranges.
Which filler metal should I use for 316Ti?
There is no 316Ti filler. Where stabilised weld metal is required, use the niobium-stabilised ER318 (EN ISO 14343 W/G 19 12 3 Nb, W.Nr 1.4576); the covered-electrode equivalent is E318-16 / E318-17. Alternatively it welds successfully with ER316L, which is adequate for service up to roughly 400 °C. Post-weld heat treatment is not normally required, but if the part will later operate between 450 and 850 °C, allow for the knife-line attack risk in the design.
Why is 316Ti common in Europe and 316L in the US?
The reason is specification inertia more than technical merit. Once modern melting practice (AOD/VOD) made low-carbon grades practical, 316L largely replaced the stabilised grades. In Europe, particularly in the chemical industry, 1.4571 continues in use as the “traditional” grade because of the cost of changing specifications on existing design drawings. On the US side the system recognises 316Ti only in A240/A276/A479/A213/A182; the most common process pipe standard, A312, has no TP316Ti grade, and AWS has no ER316Ti classification.
ASTM A479 / ASME SA-479 · bar and shapes for boilers and pressure vessels (S31635), annealed
—
205
515
NOT CONFIRMED BY FOUR SOURCES — not given
ASTM A182 / ASME SA-182 · forged flanges, fittings and valve parts (F316Ti)
—
205
515
NOT CONFIRMED BY FOUR SOURCES — not given
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 SPECIFICATION SCOPE IS NARROW ON 316Ti: the only specification fully confirmed by four independent sources is ASTM A240. In the ASTM A479 (S31635) and ASTM A182 (F316Ti) tables the tensile and yield minimums were seen as 515 / 205 MPa, and because those two values are the same for S31635 across several specifications they have been put in the table; but the ELONGATION and REDUCTION OF AREA values of those two specifications did not pass the four-source threshold and are LEFT BLANK (the values found are in the ‘atlananlar’ list). Because S31635 COULD NOT BE CONFIRMED in the texts of ASTM A276 and A312, no row has been opened for those two specifications. The tensile and yield minimums are THE SAME as 316 (515 / 205 MPa) and 30 and 35 MPa above 316L; that is where the practical value of 316Ti lies. COLD-WORKED TEMPERS ARE NOT IN THIS TABLE. No row is a typical value; every row is a specification minimum. The tensile and yield minimums are THE SAME as 316 (515 / 205 MPa) and 30 and 35 MPa above 316L. That is the numerical advantage of 316Ti. Only the ASTM A240 row is fully confirmed by four independent sources; for A479 and A182 only tensile and yield are given. Because the scope could not be confirmed for ASTM A276 and A312, those rows are left BLANK; the phrases ‘A276 316Ti’ and ‘A312 TP316Ti’ on vendor pages were not counted as sources. A hardness ceiling was found only in A240 (217 HBW / 95 HRB). The 620 MPa tensile / 248 MPa yield / 54% elongation / 76 HRBW figures given by Elgiloy and Combmet are TYPICAL values, not specification minimums, and they have NOT been put in the table.
316 — 316L — 316TI COMPARISON
A · CARBON AND TITANIUM — ASTM A240 composition table (SAME TABLE). This is where the three grades start to differ.
ASTM A240 / ASME SA-240 composition table. All three UNS numbers are in this table.
DEFENCE METAL
Criterion
AISI 316
AISI 316L
AISI 316Ti
Difference
Carbon (C) ceiling
0.08% max.
0.030% max.
0.08% max.
316L carries 2.7 times LESS carbon than 316. The carbon of 316Ti is THE SAME as 316 — 316Ti solves the problem with titanium, not by lowering carbon.
Titanium (Ti)
Not in the specification
Not in the specification
5×(C+N) minimum, 0.70% maximum
This is the ONE element that sets 316Ti apart. Titanium ties up the carbon as TiC, so the carbon is not free to form chromium carbide.
Chromium (Cr)
16.0-18.0%
16.0-18.0%
16.0-18.0%
NO DIFFERENCE
Nickel (Ni)
10.0-14.0%
10.0-14.0%
10.0-14.0%
NO DIFFERENCE
Molybdenum (Mo)
2.00-3.00%
2.00-3.00%
2.00-3.00%
NO DIFFERENCE. Molybdenum is the same in all three; it is what separates the 316 family from 304 in pitting resistance, not what separates these three grades from each other.
ASTM A479 / ASME SA-479 heat treatment requirement; every austenitic grade falls under the same row. ASTM A312 and A213 state the same requirement.
DEFENCE METAL
Criterion
AISI 316
AISI 316L
AISI 316Ti
Difference
Type of treatment
Solution anneal + rapid cooling
Solution anneal + rapid cooling
Solution anneal + rapid cooling
NO DIFFERENCE — NONE OF THE THREE IS PRECIPITATION HARDENABLE. None of them has an ageing step such as H900 or H1075.
Minimum temperature
1040 °C (1900 °F)
1040 °C (1900 °F)
1040 °C (1900 °F)
NO DIFFERENCE
Cooling
Quenched in water or rapidly cooled by other means
Quenched in water or rapidly cooled by other means
Quenched in water or rapidly cooled by other means
NO DIFFERENCE
Additional step
None
None
STABILIZING ANNEAL — only meaningful on 316Ti (see the heat treatment diagram)
This is the only structural difference in the heat treatment cycle of the three grades.
D · SENSITIZATION RESISTANCE — mechanism; this is NOT numerical laboratory data
This block is not a laboratory table; it is the direct consequence of the carbon and titanium difference in block A and is the common statement of the producers’ technical bulletins. No numerical sensitization time/temperature curve could be confirmed by four independent sources, so NONE IS GIVEN.
DEFENCE METAL
Criterion
AISI 316
AISI 316L
AISI 316Ti
Difference
Mechanism
None — the carbon is free
The carbon ceiling is lowered (0.030%); there is little carbon to precipitate
Titanium ties the carbon up as TiC; the carbon cannot form chromium carbide
316L REDUCES the carbon, 316Ti BINDS it. Two different routes to the same end.
Intergranular corrosion resistance after welding
Weld heat can precipitate carbides at the grain boundaries; on heavy sections and multi-pass welds the risk is real. A post-weld solution anneal is needed to recover the resistance.
Can be used as-welded; a post-weld solution anneal is not normally required.
Can be used as-welded; thyssenkrupp states that ‘due to the Ti-alloy, resistance to intergranular corrosion is guaranteed after welding’.
On this row 316L and 316Ti are both ahead of 316.
LONG-TERM service in the 425-870 °C band
Not recommended if corrosion resistance in an aqueous environment is wanted afterwards.
Precipitation is much slower, but THE BAND DOES NOT GO AWAY; in long-term service the carbon still precipitates. The high temperature strength of 316L is also lower than that of 316.
The titanium stays bound at temperature as well. Alleima and Abrams put this as the prevention of intergranular corrosion during prolonged holding in the 450-850 °C range; ATI states that the alloy ‘can be used for extended periods at elevated temperatures without compromising its corrosion resistance’.
THE REAL ADVANTAGE OF 316Ti IS ON THIS ROW. 316L wins over the short heat cycle of a weld; 316Ti wins in long-term elevated temperature service.
Price paid in yield strength
Does not pay it (205 MPa)
Pays it (170 MPa)
Does not pay it (205 MPa)
This is the criterion that separates the three grades in one sentence: 316Ti gives the sensitization resistance of 316L while KEEPING the yield minimum of 316.
E · HIGH TEMPERATURE CEILING — no single number is given, the sources are named instead
This block is NOT read from a single table of a single specification; producer bulletins and code sources use different criteria. For that reason the block is given as A LIST OF NAMED SOURCES rather than a numerical comparison, and it is not put on the same axis as the other blocks.
DEFENCE METAL
Criterion
AISI 316
AISI 316L
AISI 316Ti
Difference
Oxidation resistance (non-pressure)
worldstainless, Aalco, AZoM: 870 °C in intermittent service, 925 °C in continuous service
worldstainless, Aalco, AZoM: the same band is given as for 316
thyssenkrupp UK 925 °C continuous / 870 °C intermittent · Alleima 850 °C in air, 750 °C in steam · Abrams 850 °C in air · Outokumpu about 800 °C non-pressure · Virgamet 870 °C
The sources differ; no single number is written.
Pressure vessel code ceiling
ATI and Jacquet: 816 °C (1500 °F) for ASME Section VIII, Division 1
ATI and Jacquet: 454 °C (850 °F) for ASME Section VIII, Division 1
Not confirmed by four independent sources — not given. Outokumpu writes that pressure code design values are given up to 400 °C.
This 362 °C gap between 316 and 316L was found in TWO sources (ATI, Jacquet) and did not pass the four-source threshold; it is given here with the source names for the record and has not been put on the card as a number.
RULE: every block in this diagram is read from A SINGLE TABLE OF A SINGLE SPECIFICATION. Different specifications are not compared on the same row. All three UNS numbers (S31600, S31603, S31635) are WITHIN THE SCOPE of the specifications below, that is, they are listed side by side in the same tables under the same acceptance criteria. THE BLOCKS ARE NOT SUMMED 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 heat treatment cycle is THE SAME for all three grades. The difference does not come from heat treatment: it comes from the carbon band in 316, from low carbon in 316L and from titanium stabilization in 316Ti. Molybdenum is 2.00-3.00% in all three grades; the pitting resistance difference is between the 316 family and the 304 family, not between these three grades. Block E is not a numerical comparison; because the sources differ, it is given with the source names. No row is a typical value; every number in block B is an ASTM A240 specification minimum.
