Stainless SteelType 316Ti

Austenitic Stainless Steel (UNS S31635)

Data are typical and should not be construed as maximum or minimum valuesfor specification or for final design. Data on any particular piece of material mayvary from those shown herein.

GENERAL PROPERTIESAllegheny Ludlum Type 316Ti (UNS S31635) is a titaniumstabilized version of Type 316 molybdenum-bearingaustenitic stainless steel. It is also known as DIN/ENdesignation No. 1.4571. The Type 316 alloys are moreresistant to general corrosion and pitting/crevicecorrosion than the conventional chromium-nickelaustenitic stainless steels such as Type 304. They alsooffer higher creep, stress-rupture and tensile strength atelevated temperature. Type 316 stainless steel can besusceptible to sensitization � the formation of grainboundary chromium carbides at temperatures betweenapproximately 900 and 1500 °F (425 to 815 °C) � whichcan result in rapid corrosion. Reduced carbon Type 316Lis resistant to sensitization; however, extendedexposures in this temperature range will eventually resultin sensitization of even the low carbon grade. Resistanceto sensitization is achieved in Type 316Ti with titaniumadditions to stabilize the structure against chromiumcarbide precipitation, which is the source of sensitization.This stabilization is achieved by an intermediate-temperature heat treatment, during which the titaniumreacts with carbon to form titanium carbides. Thissignificantly reduces susceptibility to sensitization inservice by limiting the formation of chromium carbides.Thus, the alloy can be used for extended periods atelevated temperatures without compromising itscorrosion resistance. Like Types 316 and 316L, the Type316Ti alloy also offers excellent resistance to generalcorrosion and pitting/crevice corrosion.

COMPOSITION (Weight percents)

Element Minimum Maximum*

ChromiumMolybdenum

NickelManganesePhosphorus

SulfurSiliconCarbon

NitrogenTitanium

Iron

2.0010.0

5 x %(C+N)balance

18.03.0014.02.000.0450.0300.750.080.100.70

* ASTM Specification A 240

16.0

SPECIFICATION COVERAGEType 316Ti is included in ASTM A 240 for plate, sheet,and strip products.

Property Value Units

Density at 72°F (22°C)

Thermal Conductivity at212 °F (100°C)Thermal Expansioncoefficient at 68-212°F(20-100°C)

Melting Range

8.000.289

8.414.6

9.216.5

2450 °F �2630 °F

g/cm3

lb/in3

BTU/hr·ft·°FW/m·K

µ in/in/°Fµ m/m/°C

PHYSICAL PROPERTIES

10.118.2

µ in/in/°Fµ m/m/°C

10.819.5

µ in/in/°Fµ m/m/°C

Thermal Expansioncoefficient at 68-932°F(20-500°C)Thermal Expansioncoefficient at 68-1832°F(20-1000°C)

1345 °C �1440 °C

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Data are typical and should not be construed as maximum or minimum valuesfor specification or for final design. Data on any particular piece of material mayvary from those shown herein. 2

Stainless Steel Visit our Website atType 316Ti www.alleghenyludlum.com

MECHANICAL PROPERTIESTypical Room Temperature properties

Typical Elevated Temperature Properties

1 0.2% Offset2 In 2-inch gauge length

Fatigue ResistanceThe fatigue strength or endurance limit is the maximumstress below which a material is unlikely to fail in 10million cycles in an air environment. For austenitic stain-less steels as a group, the fatigue strength is typicallyabout 35 percent of the tensile strength. However, sub-stantial variability in service results is experienced sinceadditional variables such as corrosive conditions, typeof loading and mean stress, surface condition, and otherfactors affect fatigue properties. For this reason, nodefinitive endurance limit value can be given which isrepresentative of all operating conditions.

Type 316Ti is a single phase austenitic (face centeredcubic) stainless steel at all temperatures up to the melt-ing point. The alloy can not be hardened by heat treat-ment. The alloy is nonmagnetic in the annealed condi-tion. Its magnetic permeability is typically less than 1.02at 200 H (Oersteds). Permeability values for cold de-formed material vary with composition and the amountof cold deformation, but are usually higher than that forannealed material.

Property Typical Value ASTM A 240Yield Strength0.2% offsetUltimate TensileStrengthElongation in2" (51 mm)

Hardness

36ksi248 MPa

90 ksi620 MPa

54%

76 HRB

30 ksi*205 MPa*

75 ksi*515 MPa*

40%*

217 Brinell**95 HRB**

* minimum, ** maximum

( °F/ °C) ksi (MPa) ksi (MPa) (%) 200 / 93

600 / 316 400 / 204

800 / 4271000 / 5381200 / 649

1400 / 760

30.2 (208)26.0 (179)23.1 (159)21.2 (146)21.0 (145)21.1 (146)21.1 (146)

75.2 (518)66.0 (455)64.2 (443)62.7 (433)61.3 (423)54.4 (375)37.9 (261)

39.528.026.025.023.019.523.0

Test Temperature

1600 / 871 1800 / 982

Yield Strength1

16.2 (112) 8.0 (55)

Tensile Strength Elongation2

22.5 (155)11.3 (78)

48.041.0

OXIDATION RESISTANCEType 316Ti alloy exhibits excellent resistance to oxida-tion and a low rate of scaling in air atmospheres at tem-peratures up to 1600-1650°F (870-900°C). Weightchange vs. time data for exposure of Type 316Ti to airover a range of temperatures may be seen in the follow-ing figure. The performance of Type 316Ti is slightly in-ferior to that of Type 304 stainless steel, which hasslightly higher chromium content (18% vs. 16% for Type316Ti). The rate of oxidation is greatly influenced by theatmosphere encountered in service and by operatingconditions. For this reason, no data can be presentedthat is applicable to all service conditions.

Like other molybdenum bearing alloys, Type 316Ti issubject to catastrophic oxidation at high temperaturesin stagnant air atmospheres, such as in the heattreatment of closely packed items. This occurs due tothe formation of low melting molybdenum trioxide (MoO3),which reacts with the alloy causing deep pitting and metalloss. When air is allowed to circulate, the MoO3 willevaporate from the metal surface and excessiveoxidation is avoided.

Technical Data BLUE SHEET

Data are typical and should not be construed as maximum or minimum valuesfor specification or for final design. Data on any particular piece of material mayvary from those shown herein.3

CORROSION PROPERTIESGeneral Corrosion Resistance

The molybdenum bearing grades such as Types 316and 316Ti stainless steels are more resistant toatmospheric and other mild types of corrosion than the18Cr-8Ni stainless steels. In general, media that do notcorrode 18-8 stainless steels will not attack themolybdenum-containing grades. One known exceptionis highly oxidizing acids such as nitric acid to which themolybdenum bearing stainless steels are less resistant.Types 316 and 316Ti are considerably more resistantthan any of the other chromium-nickel types to solutionsof sulfuric acid. Where condensation of sulfur-bearinggases occurs, these alloys are much more resistant thanother types of stainless steels. In sulfuric acid solutions,the acid concentration has a strong influence on the rateof attack.

Pitting CorrosionResistance of austenitic stainless steels to pitting and/or crevice corrosion in the presence of chloride or otherhalide ions is enhanced by higher chromium (Cr) andmolybdenum (Mo) content. A relative measure of pittingresistance is given by the PRE (Pitting ResistanceEquivalent) calculation, where:

PRE = Cr + 3.3Mo

The PRE of Type 316Ti (23.0) is higher than that of Type304 (PRE =19.0), reflecting the better pitting resistancewhich Type 316Ti offers due to its Mo content. Type 304stainless steel is considered to resist pitting and crevicecorrosion in waters containing up to about 100 ppmchloride. Type 316Ti alloy on the other hand, due to itsMo-content, will handle waters with up to about 2000ppm chloride. This alloy is not recommended for use inseawater (~19,000 ppm chloride). Type 316Ti alloy isconsidered adequate for some applications that areexposed to salt spray. Type 316Ti stainless steel exhibitsno evidence of corrosion in the 100-hour, 5% salt spray(ASTM B117) test.

Intergranular CorrosionType 316 stainless steel is susceptible to precipitationof chromium carbides in grain boundaries when exposedto temperatures in the 800°F to 1500°F (425°C to 815°C)range. Such �sensitized� steels are subject to inter-granular corrosion when exposed to aggressiveenvironments. Type 316L alloy is available to avoid thehazard of intergranular corrosion. Type 316L providesresistance to intergranular attack even after short periodsof exposure in the 800-1500°F (425-815°C) temperaturerange. Stress relieving treatments falling within theselimits can be employed without affecting the corrosionresistance of the metal. Accelerated cooling from highertemperatures for the �L� grades is not needed when veryheavy or bulky sections have been annealed. Type 316Tipossesses the same mechanical properties as thecorresponding higher-carbon Type 316, and offersresistance to intergranular corrosion. Although the shortduration heating encountered during welding or stressrelieving does not produce susceptibility to intergranularcorrosion, continuous or prolonged exposure at 800-1200°F (422-650°C) can produce sensitization of Type316Ti (and of Type 316L).

The combined influences of molybdenum and titaniumreduce the resistance of Type 316Ti stainless steel tohighly oxidizing environments including the nitric acidenvironment of the ASTM A 262 practice C "Huey" testand the ferric sulfate environment of the ASTM A 262Practice B "Streicher" test. However, testing in the lessoxidizing ASTM A 262 Practice F test (Copper-CopperSulfate-50% Sulfuric Acid environment) has demon-strated the resistance of Type 316Ti stainless steel tosensitization.

Weight change vs. time for Type 316Ti exposed tovarious temperatures in air.

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

0 20 40 60 80 100 120Time, hours

Wei

ght c

hang

e (m

g/cm

²)

1200°F (650°C)1400°F (760°C)1600°F (870°C)1800°F (980°C)

Data are typical and should not be construed as maximum or minimum valuesfor specification or for final design. Data on any particular piece of material mayvary from those shown herein. 4

Stainless Steel Visit our Website atType 316Ti www.alleghenyludlum.com

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Stress Corrosion CrackingAustenitic stainless steels are susceptible to stresscorrosion cracking (SCC) in halide environments.Although the Type 316, 316L and 316Ti alloys are moreresistant to SCC than the 18 Cr-8 Ni alloys, they stillare quite susceptible. Conditions that produce SCC are:

(1) Presence of halide ion (generally chloride),(2) Residual tensile stresses, and(3) Temperature in excess of about 140°F (60°C).

Stresses result from cold deformation or thermal cyclesduring welding. Annealing or stress relieving heat treat-ments may be effective in reducing stresses, therebyreducing sensitivity to halide SCC. Although thestabillized Type 316Ti and low carbon �L� grades offerno advantage as regards SCC resistance, they are bet-ter choices for service in the stress relieved conditionin environments which might cause intergranular cor-rosion.

FABRICATION AND WELDINGFabrication

The austenitic stainless steels, including the Type 316Tialloy, are routinely fabricated into a variety of shapesranging from the very simple to very complex. Thesealloys are blanked, pierced, and formed on equipmentessentially the same as used for carbon steel. Theexcellent ductility of the austenitic alloys allows them tobe readily formed by bending, stretching, deep drawingand spinning. However, because of their greater strengthand work hardenability, the power requirements for theaustenitic grades during forming operations areconsiderably greater than for carbon steels. Attentionto lubrication during forming of the austenitic alloys isessential to accommodate the high strength and gallingtendency of these alloys.

AnnealingThe austenitic stainless steels are provided in the mill-annealed condition ready for use. Heat treatment maybe necessary during or after fabrication to remove theeffects of cold forming or to dissolve precipitatedchromium carbides resulting from thermal exposures.For the Type 316Ti alloy the solution anneal isaccomplished by heating in the 1900-2150°F (1040-1175°C) temperature range followed by air cooling or awater quench, depending on section thickness. Formaximum resistance to sensitization, Type 316Ti shouldbe given a stabilizing heat treatment at 1550-1650°F(845-900°C) to precipitate titanium carbides and preventthe precipitation of chromium carbides during lowertemperature exposure. Type 316Ti cannot be hardenedby heat treatment.

WeldingThe austenitic stainless steels are considered the mostweldable of the stainless steels. They are routinely joinedby all fusion and resistance welding processes. Twoimportant considerations for weld joints in these alloysare (1) avoidance of solidification cracking, and (2)preservation of corrosion resistance of the weld and heat-affected zones. Type 316Ti stainless steel often is weldedautogenously. If filler metal must be used for weldingType 316Ti, it is advisable to utilize the low carbon Types316L or E318 filler metals. Contamination of the weldregion with copper or zinc should be avoided, since theseelements can form low melting point compounds, whichin turn can create weld cracking.

Stabilized austenitic stainless steels, such as Type 316Ti,can be attacked by intergranular corrosion under cer-tain special conditions after welding. One such condi-tion results in what is known as �knifeline attack.� Thismanifests itself as a very narrow band of severe corro-sion adjacent to a weld. This occurs when the metaladjacent to the weld is heated to a high temperature(greater than 2100°F) so that the titanium carbides aredissolved, and then subsequently exposed to tempera-tures in the sensitizing region (800°�1500°F; 425°C�815°C). At these temperatures, the rate of formation oftitanium carbides is sluggish, and the free carbon reactswith chromium to form grain boundary carbides in theheat affected zone.

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