Alleima® 6R35 Tube and pipe, seamless

Datasheet updated

2022-06-30 12:29
(supersedes all previous editions)

Alleima® 6R35 is an austenitic, titanium-stabilized stainless chromium-nickel steel. It is suitable for wet-corrosive service but also has good mechanical strength at high temperatures.

Standards

  • ASTM: TP321, TP321H
  • UNS: S32100, S32109
  • EN Number: 1.4541, 1.4940
  • EN Name: X6CrNiTi18-10, X7CrNiTi18-10
  • W.Nr.: 1.4541, 1.4878
  • DIN: X6CrNiTi 18 10, X12CrNiTi 18 9
  • SS: 2337
  • AFNOR: Z6CNT18-10
  • BS: 321S31, 321S51

Product standards

Seamless tube and pipe

  • ASTM A213, A312, A269, A376, (A511)
  • EN 10216-5
  • BS 3059, 3605, 3606
  • DIN 17456, 17458
  • SS 14 23 37
  • NFA 49-117, 49-217

Approvals

PED (Pressure Equipment Directive) 2014/68/EU and AD2000

Chemical composition (nominal)

Chemical composition (nominal) %
C Si Mn P S Cr Ni
0.05 0.5 1.3 ≤0.030 ≤0.015 17.5 10.5

Ti=>5xC

Chemical composition (nominal) %

CSiMnPSCrNiTi
0.05 0.5 1.3 ≤0.030 ≤0.015 17.5 10.5 >5xC

Applications

Good resistance to hydrogen sulfide gas and intergranular corrosion coupled with good high temperature strength make Alleima® 6R35 a suitable material for applications as tubes in heating furnaces and heat exchangers in sulfurization and hydro-treating plants. In the petrochemical industry the steel is used in cracking furnaces for the production of ethylene and vinyl chloride. It is also frequently used for heat exchangers and piping in the chemical and petrochemical industries.

Corrosion resistance

General corrosion

Alleima® 6R35 has with some limitations (nitric acid) the same resistance as the unstabilized steel ASTM 304. Consequently, the grades have good resistance to

  • Organic acids at moderate temperatures
  • Salt solutions, e.g. sulfates, sulfides and sulfites
  • Caustic environments at moderate temperatures

Intergranular corrosion

The stabilization with titanium gives Alleima 6R35 improved resistance to intergranular corrosion.

Pitting and crevice corrosion

Pitting and crevice corrosion may occur even in solutions of relatively low chloride content. However, the stabilization with titanium results in a somewhat better resistance than that of ASTM 304.

Stress corrosion cracking

Austenitic steels, like Alleima® 6R35 are susceptible to stress corrosion cracking. This may occur at temperatures above about 60°C (140°F), if the material is subjected to tensile stresses and at the same time comes into contact with certain solutions, particularly those containing chlorides. Such service conditions should therefore be avoided. Conditions when plants are shut down must also be considered as the condensates which are then formed can develop a chloride content that leads to both stress corrosion cracking and pitting.

In applications demanding high resistance to stress corrosion cracking we recommend the austenitic-ferritic steel SAF™ 2304.

Gas corrosion

Alleima® 6R35 can be used in:

  • Air up to 850°C (1560°F)
  • Steam up to 750°C (1380°F)
  • Synthesis gas (ammonia synthesis) up to about 550°C (1020°F)

Creep should also be taken into account when using the steel in the creep range.

In flue gases containing sulfur, the corrosion resistance is reduced. in such environments this steel can be used at temperatures up to 600-750°C (1110-1380°F) depending on service conditions. Factors to consider are whether the atmosphere is oxidizing or reducing, i.e. the oxygen content, and whether impurities such as sodium and vanadium are present.

Bending

Annealing after cold bending is not normally necessary, but this point must be decided with regard to the degree of bending and the operating conditions. Heat treatment, if any, should take the form of stress-relieving or solution annealing.

Hot bending is carried out at 1100-850°C (2010-1560°F) and should be followed by solution annealing.

Forms of supply

Seamless tube and pipe-Finishes and dimensions

Seamless tube and pipe in Alleima® 6R35 is supplied in dimensions up to 260 mm outside diameter in the solution-annealed and white-pickled condition or solution-annealed in a bright-annealing process.

Hollow bar

Hollow bars are supplied solution-annealed and white-pickled.

Sizes in stock

Seamless tube and pipe
Seamless tube and pipe are stocked in a wide range of sizes according to ISO and ANSI both in hot extruded as well as in the cold finished and annealed condition. Details of our manufacturing and stock programme are given in catalogue S-110-ENG.

Hollow bar
Hollow bar is stocked in large number of sizes. Our standard size range for stock comprises 32-250 mm (1.3-9.8 in.) O.D. See catalogue S-110-ENG.

Heat treatment

The tubes are normally delivered as described above. If additional heat treatment is needed after further processing the following is recommended.

Solution annealing

Tp 321

1040-1100 °C (1905-2010 °F), 2-5 min, rapid cooling in air or water.

Tp321H

Stabilization treatment: 1040-1100 °C (1920-2010 °F), 2-5 min rapid cooling in air or water. However, annealing above 1100°C (2010 °F) may be required in order to meet grain size requirements. This treatment should be followed by a stabilization treatment.

Stress relieving

850-950 °C (1560-1740 °F), 10-15 minutes, cooling in air.

Mechanical properties

At 20°C (68°F)

Proof strength Tensile strength Elong. Hardness
Rp0.2a) Rp1.0a) Rm Ab) HRB
MPa ksi MPa ksi MPa ksi %
≥210 ≥30 ≥240 ≥35 515-690 75-100 ≥35c) ≤90

1 MPa = 1 N/mm2
a) Rp0.2 and Rp1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.
b) Based on L0 = 5.65 √S0 where L0 is the original gauge length and S0 the original cross-section area.
c) NFA 49-117 and NFA 49–217 with min 45% can be fulfilled.

Impact strength

Due to its austenitic microstructure, Alleima® 6R35 has very good impact strength both at room temperature and at cryogenic temperatures.

Tests have demonstrated that the steel fulfils the requirements (60 J (44 ft-lb) at -196 oC (-320 oF)) according to the European standards EN 13445-2 (UFPV-2) and EN 10216-5.

At high temperatures

Metric units
Temperature Proof strength c)
Rp0.2 Rp1.0
°C MPa MPa
min min
50 195 230
100 180 210
150 170 195
200 160 185
250 150 180
300 140 175
350 135 170
400 130 165
450 130 165
500 125 160
550 125 160
600
120
155
Imperial units
Temperature Proof strength c)
Rp0.2 Rp1.0
°F ksi ksi
min min
200 26.0 30.5
400 22.5 26.5
600 19.5 25.0
800 18.5 23.5
1000 17.5 23.0
1100
17.0
22.0

c) For extruded tube and pipe with wall thickness greater than 10 mm (0.4 in.) the proof strength may fall short of the stated value by 20 MPa (2.9 ksi) at 100°C (200°F) and by 10 MPa (1.4 ksi) in the temperature range 200-600°C (400-1100°F).

Creep rupture strength
Temperature 10 000 h 100 000 h
°C °F MPa ksi MPa ksi
approx. approx. approx. approx.
550 1020 234 34.0 184 26.7
575 1065 175 25.4 126 18.3
600 1110 143 20.7 94 13.6
625 1155 110 16.0 75 10.9
650 1200 90 13.1 58 8.4
675 1245 76 11.0 48 7.0
700 1290 59 8.6 39 5.7
750 1380 29 4.2 16 2.3

Physical properties

Density: 7.9 g/cm3, 0.29 lb/in3

Thermal conductivity
Temperature, °C W/m °C Temperature, °F Btu/ft h °F
20 14 68 8
100 15 200 8.5
200 17 400 10
300 19 600 11
400 21 800 12
500 22 1000 13
600 24 1200 14
700 25 1400 15
800 26 1600 16
900 28 1800 16.5
1000 29 2000 17.5
1100 30
Specific heat capacity
Temperature, °C J/kg °C Temperature, °F Btu/lb °F
20 465 68 0.11
100 490 200 0.12
200 515 400 0.12
300 540 600 0.13
400 560 800 0.14
500 580 1000 0.14
600 595 1200 0.14
700 610 1400 0.15
800 625 1600 0.15
900 640 1800 0.16
1000 650 2000 0.16
1100 665
Thermal expansion 1)
Temperature, °C Per °C Temperature, °F Per °F
30-100 17.5 86-200 9.5
30-200 17.5 86-400 10
30-300 18 86-600 10
30-400 18 86-800 10
30-500 18.5 86-1000 10.5
30-600 18.5 86-1200 10.5
30-700 19 86-1300 10.5

1) Mean values in temperature ranges (x10-6)

Modulus of elasticity 1)
Temperature, °C MPa Temperature, °F ksi
20 200 68 29.0
100 194 200 28.2
200 186 400 26.9
300 179 600 25.8
400 172 800 24.7
500 165 1000 23.5

1) (x103)

Welding

Welding

The weldability of Alleima® 6R35 is good. Welding must be carried out without preheating and subsequent heat treatment is normally not required. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice.

For Alleima® 6R35, heat input of <1.5 kJ/mm and interpass temperature of <150°C (300°F) are recommended.

Recommended filler metals

TIG/GTAW or MIG/GMAW welding

ISO 14343 S 19 9 Nb / AWS A5.9 ER347 (e.g. Exaton 19.9.Nb)

MMA/SMAW welding

ISO 3581 E 19 9 Nb R / AWS A5.4 E347-17(e.g. Exaton 19.9.NbR )

ISO 14343 S 19 9 Nb / AWS A5.9 ER347 (e.g. Exaton 19.9.LNb) wire or strip electrodes are recommended for overlay welding of tube sheets and high-pressure vessels in cases where corrosion resistance, equal to that of Alleima 6R35, is required.

Machining

Alleima® 6R35 has good machining properties. Please contact Alleima for detailed recommendations on the choice of tools and cutting data.

Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for Alleima materials.