duplexes catalogo columbus

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T

e c h n i c a l

B

r o c h u r e

®

COLUMBUS

STAINLESS[Pty] Ltd

www.columbusstainless.co.za

D U P L E X

S T A

I N

L E S S

S T E E L S

U n

i t y

A I S I

U N

S

E N

U - 2

0 0 1

-

S 3 2 0 0 1

1 . 4

4 8 2

U - 2

3 0 4

2 3 0 4

S 3 2 3 0 4

1 . 4

3 6 2

U - 2

2 0 5

2 2

0 5

S 3 2 2 0 5

1 . 4

4 6 2

S 3 1 8 0 3



IntroductionThe duplex stainless steels have a microstructure, whenheat treated properly, o nearly equal proportions o austenite and errite. This microstructure ensures thatthe duplexes are much more resistant to stress corrosioncracking (SCC) than austenitic stainless steels.

The specication 0.2% Proo Stress o the duplexes is

more than double that o austenitic stainless steels suchas the U-304 types and U-316L types. This oten allowsdown gauging in the design, depending on Young’sModulus and buckling limitations.

The duplexes have a ductile to brittle transition tempera-ture o about -40°C or lower. These steels can also be-come embrittled when exposed to temperatures between300°C and 550°C (475°C embrittlement) and 550°Cand 1 000°C (sigma (σ) and chi (χ) phase ormation).Thus, application temperatures are generally limited rom-50°C to 300°C.

U-2001 has similar general and pitting corrosion resist-ance to the U-304 types. U-2304 has similar generaland pitting corrosion resistance to the U-316L types. BothU-2001 and U-2304 are classied as lean duplexes.

The good strength, toughness, corrosion resistance andresistance to SCC make the lean duplexes suitable orapplications such as process and storage tanks, ood andbeverage industry, structural applications, etc. U-2304will be used in applications requiring better corrosionresistance, such as environments containing chlorides andpolluted marine environments, desalination plants, etc.

The higher chromium, molybdenum and nitrogen contentsgive U-2205 signicantly improved pitting and crevicecorrosion resistance in the presence o chlorides. U-2205also has better general corrosion resistance than the U-316L types in most environments.

U-2205 is a highly suitable material or service in envi-ronments containing chlorides and hydrogen sulphidesuch as marine environments and the oil and gas extrac-tion and processing industries.

Typical applications also include the chemical industry(processing, transport and storage, e.g. pressure

vessels, tanks and piping), the pulp and paperindustry (digesters and liquor tanks) and the

mining industry.

U-2205 has thus ound widespread usein production tubing and fowlines or

the extraction o oil and gas romsour wells, in reneries and in

process solutions contaminatedwith chlorides. U-2205 is also

particularly suitable orheat exchangers where

chloride bearing wateror brackish water is

used as the coolingmedium.

Product rangeThe latest revision o the Product Catalogue should be consulted, asthe product range is subject to change without notice.

The Product Catalogue is available rom the Technical Department orcan be ound at www.columbusstainless.co.za

Specifcations and tolerances

Columbus Stainless (Pty) Ltd supplies the duplexes to theColumbus Stainless mill specication, ASTM A240, ASME SA240,EN 10088-2 and EN 10028-7.

Columbus Stainless (Pty) Ltd normally supplies material to theollowing tolerances:

HOT ROLLEDASTM A480MISO 9444 - material processed as coilISO 18286 - material processed as plate

COLD ROLLEDASTM A480MISO 9445

Other specications and tolerances may be available on request.Further inormation is available in the Product Catalogue, whichcan be obtained rom the Technical Department or can be ound atwww.columbusstainless.co.za

TECHNICAL

Columbus Stainless (Pty) Ltd

PO Box 133 • Middelburg • 1050 • South Africa

Tel: +27 (13) 247 3343

Fax: +27 (13) 247 2289

E-mail: [email protected]

COMMERCIAL

Columbus Stainless (Pty) Ltd

PO Box 133 • Middelburg • 1050 • South Africa

Tel: +27 (13) 247 2020

Fax: +27 (13) 247 2771

E-mail: [email protected]

Date o Issue : May 2011

Further inormation

DisclaimerThe material contained in this manual has been designed as a guide or customers o Columbus Stainless (Pty) Ltd. However, the material contained herein is not intendedas a substitute or any person’s procedures and should not be used or relied uponor any specic or general application without rst obtaining competent advice.Furthermore, Columbus Stainless (Pty) Ltd disclaims any responsibility or the suitabilityo the steel in question or any particular purpose or or the perormance or selectiono the steel, unless Columbus Stainless (Pty) Ltd specically and expressly authorisesthe purpose or selection. The material contained in this manual does not purport to bea comprehensive or exhaustive statement o all relevant material applicable to specialand general steel products and no representation, condition or warranty, express orimplied, is given by Columbus Stainless (Pty) Ltd as to the accuracy or completeness o this manual and, so ar as is permitted by law, Columbus Stainless (Pty) Ltd, its mem-bers, sta and consultants disclaim any duty o care in relation to the preparation o this manual and the inormation that it contains and shall not be liable or any direct,indirect or consequential loss, damage or injury suered by any person, howsoever

caused as a result o relying on any statement in or omission to this manual and anysuch liability is expressly disclaimed. [Columbus Stainless (Pty) Ltd shall not be liablein the event o a breakdown, malunction or ailure occurring due to aulty design,material or workmanship o the steel, whether based on the inormation containedherein or not, and shall not, under any circumstances, be liable or any damages,either direct or indirect, particularly consequential damages, including but not limitedto damages or loss o prots.] o

n e



Chemical compositionIn accordance with the Columbus Stainless mill specication, ASTM A240 and EN 10088-2.

PROPERTIES AT ELEVATED TEMPERATURES

The properties quoted below are typical o annealed duplex stainless steels. These values are given as a guideline only, and

should not be used or design purposes.

The upper temperature limit or long-term service is 300°C. Exposure o the steel or extended periods between 300°C and950°C may embrittle the steel and lower the corrosion resistance. At the lower temperature range, the embrittlement is due to theprecipitation o α’ (475°C embrittlement) and nitrides or carbides.

In the high temperature range, χ and σ phases precipitate. However, during normal production and abrication procedures, thetimes at these critical temperatures are such that the risk o embrittlement and/or a decrease in corrosion resistance are small. Inaddition, this eect does not necessarily aect the behaviour o the material at the operating temperature and is less pronouncedin thinner gauges. For example, heat exchanger tubes are used at high temperatures without any problems. A ull anneal andrapid cooling treatment will restore the toughness and corrosion resistance o the duplexes.

The adjacent graph shows the embrittlement that occurs in the high temperature range (attributable to α and σ phase precipita-

tion). This was dened by the room temperature Charpy impact toughness alling below 100J.

• Compositionsarerangesormaximumvalues.

t w o

Unity C Si Mn P S N Cr Mo Ni Others

U-2001 0.03 1.0 4.0 0.035 0.015 0.05 19.5

0.61.0

Cu: 1.0 max

6.0 0.17 21.5 3.0

U-2304 0.03 1.0 2.0 0.035 0.0150.05 22.0 0.1 3.5

Cu: 0.1 to 0.6

0.20 24.0 0.6 5.5U-2205 0.03 1.0 2.0 0.035 0.015

0.14 22.0 2.5 4.5 0.20 23.0 3.5 6.5

Mechanical propertiesIn accordance with ASTM A240 and EN 10088-2.

• Minimumvalues,unlessmaxorrangeisindicated.

• ()indicatesapplicablegaugerange.

• HRishotrolled,CRiscoldrolled.

• ThetableassumescertifcationtobothASTMA240andEN10088-2.

Unity Rm (MPa) Rp0.2 (MPa) El (%) Max BHN

U-2001 620 450 25

U-2304

650 to 850 (≤6mm) 450 (CR)25 290

630 to 800 (>6mm) 400 (HR)

U-2205700 to 950 (≤6mm) 500 (CR)

25 293

640 to 840 (>6mm) 460 (HR)

T e m e p e r a t u r e 0 C

1 050

950

850

750

650

550

450

0 . 0

1 0 . 1 1

1 0

1 0 0

Time (hours)

U-2205

U-2001U2304



t h r e e

FATIGUE CONSIDERATIONS

The high strength o the duplexes also results in a high atigue strength. For example, U-2205 and U-316L-1.4404 have been testedunder reverse bending stresses at room temperature and the atigue limit is close to the yield strength, i.e. about twice as high orU-2205. In many applications, atigue interacts with corrosion giving reduced atigue strength. In such cases, the duplexes oersconsiderable advantages over mild steel and other stainless steels.

IMPACT CONSIDERATIONS

The duplexes possesses good toughness both at room and sub-zero temperatures. The ductile to brittle transition temperature (DBTT)curves is shown in the adjacent diagram. As can be seen, the DBTT o the duplexes is between -20 and -50°C, although the mini-mum energy requirement o 50J (which is considered to be the lower limit or ductile behaviour) is easily met or temperatures as lowas -100°C.

PROPERTIES AT ELEVATED TEMPERATURES (CONTINUED)

Short time elevated temperature tensile strength (MPa)

Maximum recommended service temperature

Short time elevated temperature 0.2% proof stress (MPa)

Unity 100°C 200°C 300°C 400°C

U-2001 590 540 510 480

U-2304 540 500 480 450

U-2205 630 580 560 550

Unity 100°C 200°C 300°C 400°C

U-2001 380 330 300 270

U-2304 330 280 250 220

U-2205 365 315 285 275

• Inoxidisingconditions.

• Maximumrecommendedservicetemperatureis300°C.

Unity Continuous (°C) Intermittent (°C)

U-2001 880 880U-2304 980 980

U-2205 980 980

C V N i m p a c t t o u g h n e s s ( J )

300

250

200

150

100

50

0

- 1 4 0

- 1 2 0

- 1 0 0

- 8 0

- 6 0

- 4 0

- 2 0 - 0

2 0

4 0

6 0

Temperature 0C

U - 2 2

0 5

U - 2 3 0 4

U - 2 0 0 1



Physical properties

The values given below are or 20°C, unless otherwise stated and apply to all three duplexes.

Thermal processing and abrication

ANNEALING

Annealing o the duplexes is achieved by heating to between 1 020°C and 1 100°C or 90 minutes per 25mm thickness(3.5min/mm) ollowed by quenching in an agitated water bath down to room temperature. Controlled atmospheres arerecommended in order to avoid excessive oxidation o the surace.

STRESS RELIEVING

The duplexes can be stress relieved at 525°C to 550°C or 60 minutes per 25mm thickness (2.5min/mm) in special cases but it ispreerable to ully anneal. Stress relieving contributes signicantly to improving the resistance to stress corrosion cracking by loweringthe residual tensile stresses.

HOT WORKINGThe duplexes can be readily orged, upset and hot headed. Uniorm heating o the steel in the range o 1 150°C to 1 250°C isrequired. Initial hot working should be aected without large reductions or change o shape (especially i upsetting or staving up).Once the material starts to fow, progressively more deormation can be accomplished.

The nishing temperature should not be below 950°C. I the temperature ater orging is still above 1 000°C, rapid cooling (waterquenching) can be carried out directly rom the working temperature. Otherwise, all hot working operations should be ollowed byannealing and pickling and passivating to restore the mechanical properties and corrosion resistance.

COLD WORKING

The duplexes have good ormability, but due to the higher proo strength, more power is required or most cold orming operationsthan austenitic stainless steels. Roll orming can be readily applied to the duplexes, but loadings will be about 60% higher than

or mild steel and slower speeds should be used. Severe deep draws may require an intermediate anneal. Cold bendingreduces the maximum gauge capacity o the machine by about hal, compared with austenitics. The minimum inner bendradius or the duplexes is three times the plate thickness and our times is recommended. Severe bends should be carriedout transverse to the rolling direction. The duplexes exhibits greater spring back than mild steel and this should becompensated or by slight over bending.

MACHINING

The high strength that makes the duplexes useul in many applications also reduces their machinability. U-2001has the best machinability o the deects and is similar to the U-316L types. In general, or the duplexes,cutting speeds are approximately 20% slower than those or U-304. Machine tools should be ground toclose tolerances to avoid the risk o excessive work hardening in the outer layer o the stock. Larger toolsshould be used to give stability and ecient heat dissipation.

Tools with large rake angles, sharp edges and smooth suraces reduce the work hardening andthe risk o built up edges. Relatively large eed rates and cutting depths minimise the workhardening o the surace layer. A suitable cutting fuid should be used to minimise the risk o built up edges. The work should be fooded to ensure maximum heat removal.

Density (kg/m3) 7 860

Modulus o elasticity in tension (GPa) 200

Specic Heat Capacity (J/kg K) 470

Thermal conductivity at 100°C (W/m K) 17.0

500°C (W/m K) 21.1Electrical resistivity (x10-9 Ω m) 610

Mean coecient o thermal expansion rom 0 to 100°C (x10-6 K-1) 13.0

0 to 300°C (x10-6 K-1) 14.0

0 to 500°C (x10-6 K-1) 14.5

0 to 700°C (x10-6 K-1) 15.0

Melting range (°C) 1 410

1 460

Magnetic yes

f o u r



f i v e

Thermal processing and abrication (continued)

WELDING

The duplexes have good weldability in most applications, provided that the recommended procedures are adopted. They can bewelded with most standard welding methods (MMA/SMAW, MIG/GMAW, TIG/GTAW, FCAW, SAW and PAW). I the duplexesare autogenously welded, the abrication should be solution annealed to restore the desirable duplex microstructure and hence thetoughness. Only welding consumables specically specied or the duplexes should be used to ensure that the deposited metal hasthe correctly balanced duplex microstructure. 2209 ller welding electrodes are recommended or optimum properties. Nitrogen,

added to the shielding gas, will also assist in ensuring adequate austenite in the microstructure.The heat input should be controlled to between 1 and 2kJ/mm in order to keep the Heat Aected Zone (HAZ) narrow and to ensurethere is at least 20% austenite in the HAZ. The interpass temperatures should not exceed 150°C. The lower coecient o thermalexpansion o the duplexes, compared to austenitic stainless steels, reduces distortion and the associated stresses.

Preheating, although not essential, is benecial on thicker gauge sections. Typical preheat temperatures are between 100°C and250°C. Post-weld heat treatment is not normally required, but solution annealing will restore the toughness and coner the optimumstress corrosion cracking resistance to the abrication.

Corrosion resistance

The above diagram summarises the corrosion (pitting) resistance o the austenitic and duplex stainless steels produced

at Columbus. This would indicate that the corrosion resistance o U-2001 is similar to U-304L, U-2304 is similar toU-316L-1.4404 and U-2205 has superior corrosion resistance, suitable or seawater application.

GENERAL CORROSION

The duplex stainless steels generally have similar general corrosion resistance to the U-304L and U-316L types, butthis is dependant on the corrosion media. For example, U-2001 has signicantly better corrosion resistance than

U-316L-1.4404 in sulphuric acid (H2SO4) solutions.

40

38

36

34

32

30

28

26

24

22

2018

16

14

12

0

P R E = C

r + 3 . 3

M o + 1 6 N

U - 3 2 1

U - 2 0 2

U - 3 0 4

U - 3 0 4 L

U - 3 1 6 L

1 . 4

4 0 4

U - 3 1 6 L

1 . 4

4 3 6

U - 3 1 6 T i

U - 2 0 0 1

U - 2 3 0 4

U - 2 2 0 5

Seawater

Marine

General purpose

Industrial



PITTING CORROSION

Pitting resistance is important, mainly in applications involving contact with chloride solutions, particularly in the presence o oxidising media. These conditions may be conducive to localised penetration o the passive surace lm on the steel and a singledeep pit may well be more damaging than a much greater number o relatively shallow pits.

Where pitting corrosion is anticipated, steels with high pitting resistance equivalents (PRE), such as the duplexes, should beconsidered. The adjacent diagram shows the critical temperature or initiation o pitting (CPT) at dierent chloride contents or U-304,U-316L and U-2205 types (potentiostatic determination at + 300mV SCE, pH = 6.0).

ATMOSPHERIC CORROSION The atmospheric corrosion resistance o duplex stainless steels is unequalled by virtually all other uncoated engineering materials.

U-2001 is normally sucient in urban and industrial environments. U-2304 is suitable in marine environments and U-2205 should be

used in areas where the atmosphere is highly polluted with chlorides, sulphur compounds and solids, either singly or in combination.

OXIDATION RESISTANCE The duplexes have good oxidation resistance, both in intermittent and continuous service, up to 980°C or U-2205 and U-2304

and 880°C or U-2001. However, continuous use o the duplexes between 300°C and 950°C may embrittle the steel and lower the

corrosion resistance. At the lower temperature range, the embrittlement is due to the precipitation o α’ (475°C embrittlement) and

nitrides or carbides. In the high temperature range, χ and σ phases precipitate. However, during normal production and abrication

procedures, the times at these critical temperatures are such that the risk o embrittlement and/or a decrease in corrosion resistance

are small.

In addition, this eect does not necessarily aect the behaviour o the material at the operating temperature and is less pronounced

in thinner gauges. For example, heat exchanger tubes are used at high temperatures without any problems. A ull anneal and

rapid cooling treatment will restore the toughness and corrosion resistance o the duplexes.

INTERGRANULAR CORROSION Sensitisation may occur when the Heat Aected Zones o welds in some austenitic stainless steels are cooled through

the sensitising temperature range o between 450°C and 850°C. At this temperature, a compositional change may

occur at the grain boundaries.

I a sensitised material is then subjected to a corrosive environment, intergranular attack may be experienced.

This corrosion takes place preerentially in the heat aected zone away rom and parallel to the weld.

Susceptibility to this orm o attack, oten termed ‘weld decay’, may be assessed by the ollowing standard

tests:

a) boiling copper sulphate/sulphuric acid test as specied in ASTM A262-98, Practice E.

b) or non titanium stabilised grades only, boiling nitric acid test as specied in ASTM A262-98,

Practice C.

100

90

80

70

60

50

40

30

20

10

0

C P T ( 0 C ) . 3 0 0 m V S C E

1 0 0

1 0 0 0

1 0 0 0 0

Chlorides (ppm)

U-304

U-316L

U-2205

Likely to pit

Unlikely to pit

s i x



INTERGRANULAR CORROSION (CONTINUED) a) boiling copper sulphate/sulphuric acid test as specied in ASTM A262, Practice E.

b) or non titanium stabilised grades only, boiling nitric acid test as specied in ASTM A262, Practice C.

The Columbus Stainless Cr-Ni-Mo austenitics have low carbon contents and are resistant to sensitisation and can be specied or

welded structures unless the higher carbon types are required or their increased strength at elevated temperatures. In this case, U-

316Ti should be specied.

STRESS CORROSION CRACKING Stress corrosion cracking (SCC) can occur in austenitic stainless steels when they are stressed in tension in chloride environments at

temperatures in excess o about 60°C. The stress may be applied, as in a pressure system or it may be residual arising rom cold

working operations or welding. Additionally, the chloride ion concentration need not be very high initially, i locations exist in which

concentrations o salt can accumulate.

Assessment o these parameters and accurate prediction o the probability o SCC occurring in service is thereore dicult. Where

there is a likelihood o SCC occurring, a benecial increase in lie can be easily obtained by a reduction in operating stress and

temperature. Alternatively, specially designed alloys, such as duplex stainless steels, will have to be used where SCC cracking is

likely to occur.

EROSION CORROSION Austenitic stainless steels are attacked by erosion corrosion i exposed to fowing media containing highly abrasive solid particles,

e.g. sand, or to media with very high fow velocities. Owing to its combination o high initial hardness, work hardenability and

corrosion resistance, the duplexes displays very good resistance under such erosion corrosion conditions.

CORROSION FATIGUE The duplexes possesses higher strength and better corrosion resistance than ordinary austenitic stainless steels. The duplexes, there-

ore, also possess better atigue strength under corrosive conditions than such steels. For example, in rotary bending atigue tests in a

3% NaCl solution (6 000rpm, 40°C, pH 7), U-2205 required 430MPa stress in the unnotched condition to bring about rupture ater

2x107 cycles, while U-316N ailed at only 260MPa. The corresponding notched gures were 230MPa and 140MPa or U-2205

and 316N respectively.

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duplexes catalogo columbus

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