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Datasheet updated

2023-11-09 14:41
(supersedes all previous editions)

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Alleima® 7RE10 is an austenitic, stainless chromium-nickel steel of the 25/20 type, suitable for high-temperature applications. The grade is characterized by:

  • Good resistance to carburization, sulphidation, and oxidation combined with moderate creep strength and structural stability.
  • A maximum service temperature in air of 1100°C (2010°F).

Standards

  • ASTM: TP310S, TP310H
  • UNS: S31008, S31009
  • EN Number: 1.4845
  • EN Name: X 8 CrNi 25-21
  • W.Nr.: 1.4845
  • DIN: X 12 CrNi 25 21
  • SS: 2361
  • AFNOR: Z 12 CN 25.20

Product standards

Seamless tube and pipe

  • ASTM A213, A312
  • EN 10297-2
  • Stahl-Eisen-Werkstoffblatt 470
  • SS 14 23 61
  • NFA 49-117

Chemical composition (nominal)

Chemical composition (nominal) %
C Si Mn P S Cr Ni
0.06 ≤0.75 1.5 ≤0.030 ≤0.015 24.5 21

Applications

The good, general high temperature corrosion resistance of Alleima® 7RE10 makes it suitable for a wide range of applications:

  • Furnace tubes
  • Recuperators
  • Muffle tubes in continuous wire annealing furnaces
  • Thermocouple protection tubes
  • Radiant tubes
  • Tube hangers in petroleum and steam boilers
  • Burners

Corrosion resistance

Alleima® 7RE10 has very good resistance to oxidation and sulphidation. It can be used in:

  • Air up to 1100°C (2010°F)
  • Sulphur-containing atmospheres up to 650-1050°C (1200-1920°F), depending on service conditions. Factors to consider are whether the atmosphere is oxidizing or reducing and whether impurities such as sodium and vanadium are present

The high chromium content of Alleima® 7RE10 makes the material resistant to oxidizing aqueous solutions. Alleima® 7RE10 also has better resistance to chloride induced stress corrosion cracking than lower alloyed steels of type ASTM 304 and 316.

Alleima® 7RE10 has good resistance in cyanide melts and neutral salts melts at high temperature. The material is insensitive to "green rot" attack.

Bending

Annealing after cold bending is not normally necessary, but this should be reviewed depending on the degree of bending and the operating conditions.

Heat treatment, if any, should take the form of stress relieving or solution annealing. See under "Heat treatment". Solution annealing is recommended for tubes used at temperatures above 750°C (1380°F), and when the highest possible creep strength is required in the bent tube.

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® 7RE10 is supplied in dimensions up to 260 mm outside diameter, in the solution annealed and white-pickled condition or in the bright annealed condition.

Stock sizes

Alleima® 7RE10 is stocked in sizes ranging from 13.5 mm to 168.28 mm (6") outside diameter. Additional data concerning sizes and finishes is available on request from your nearest Alleima office.

Heat treatment

Tubes are generally delivered in the solution annealed condition. If another heat treatment is needed after further processing the following is recommended:

Stress relieving

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

The temperature should not be allowed to fall below 850°C (1560°F), because of the risk of sensitization.

Solution annealing

1000-1150°C (1830-2100°F), 5-20 minutes, rapid cooling in air or water.

Mechanical properties

At 20°C

Metric units
Proof strength Tensile strength Elong. Hardness
Rp0.21) Rp1.01) Rm A2) A2" HRB
MPa MPa MPa % %
≥220 ≥250 530-750 ≥35 ≥35 ≤90

At 68°F

Imperial units
Proof strength Tensile strength Elong. Hardness
Rp0.21) Rp1.01) Rm A2) A2" HRB
ksi ksi ksi % %
≥32 ≥35 77-109 ≥35 ≥35 ≤90

1 MPa = 1 N/mm2
1) Rp0.2 and Rp1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.
2) Based on L0 = 5.65 √S0 where L0 is the original gauge length and S0 the original cross-sectional area.

At high temperatures

Metric units
Temperature Proof strength
°C Rp0.2 Rp1.0
MPa MPa
min min
50 213 238
100 192 217
150 176 201
200 161 186
250 150 175
300 141 166
350 134 159
400 129 154
450 125 150
500 123 148
550 121 146
Imperial units
Temperature Proof strength
°F Rp0.2 Rp1.0
ksi ksi
min min
200 28.3 31.9
300 25.6 28.9
400 23.2 26.8
500 21.4 25.1
600 20.1 23.8
700 19.1 22.8
800 18.4 22.0
900 17.9 21.6
1000 17.6 21.2

Creep strength

Creep rupture strength 10 000 h, average values

Metric units Imperial units
Temperature, °C MPa Temperature, °F ksi
525 155 1000 20.9
550 133 1050 18.0
575 113 1100 14.6
600 96 1150 12.0
625 81 1200 9.9
650 68 1250 7.8
675 55 1300 6.2
700 44 1350 5.0
725 36 1400 4.1
750 30 1450 3.3
775 25 1500 2.8
800 21 1550 2.3
825 18 1600 1.8
850 15 1650 1.5
875 12 1700 1.1
900 10 1750 0.8
925 8
950 6

Values for creep strain 1% can be given on request.
Creep rupture strength 100 000 h, average values

Metric units Imperial units
Temperature, °C MPa Temperature, °F ksi
525 105 1000 13.8
550 85 1050 10.7
575 68 1100 8.6
600 56 1150 6.7
625 45 1200 5.3
650 36 1250 4.1
675 29 1300 3.4
700 24 1350 2.8
725 20 1400 2.3
750 17 1450 1.8
775 14 1500 1.4
800 11 1550 1.1
825 9 1600 0.8
850 7 1650 0.6
875 5 1700 0.5
900 4 1750 0.4
925 4
950 3

Values for creep strain 1% can be given on request.

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  13  68  7.5
 100  15  200  8.5
 200  17  400  10
 300  19  600  11.5
 400  21  800  12.5
 500  23  100  13.5
 600  25  1200  14.5
700 26 1300 15
Specific heat capacity
Temperature, °C J/kg °C Temperature, °F Btu/lb °F
20 470 68 0.11
100 495 200 0.12
200 530 400 0.13
300 555 600 0.13
400 580 800 0.14
500 600 1000 0.15
600 615 1200 0.15
700 630 1300 0.15
Thermal expansion, mean values in temperature ranges (x10-6)
Temperature, °C Per °C Temperature, °F Per °F
20-100 15.0 68-200 8.5
20-200 15.5 68-400 8.5
20-300 16.0 68-600 9.0
20-400 16.5 68-800 9.5
20-500 17.0 68-1000 9.5
20-600 17.5 68-1200 9.5
20-700 18.0 68-1400 10.0
20-800 18.5 68-600 10.0
20-900 19.0 68-1800 10.5
20-1000 19.0
Modulus of elasticity (x103)
Temperature, °C MPa Temperature, °F ksi
20 195 68 28.3
100 190 200 27.6
200 182 400 26.4
300 174 600 25.1
400 166 800 23.8
500 158 1000 22.5

Structural stability

Like other austenitic stainless steels, Alleima® 7RE10 has better structural stability than high alloyed ferritic steels. At temperatures between 800 and 900°C (1470-1650°F), however, the structural stability will be slightly impaired. For service in this temperature range, we recommend the use of Sanicro® 31HT, which has better structural stability.

Welding

The weldability of Alleima® 7RE10 is good. 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.

In common with all fully austenitic stainless steels, Alleima® 7RE10 has low thermal conductivity and high thermal expansion. Welding plans should therefore be carefully selected in advance, so that distortions of the welded joint are minimized. If residual stresses are a concern, solution annealing can be performed after welding.

Welding of fully austenitic stainless steel can entail the risk of hot cracking in the welded joints, particularly under high constraint.

For Alleima 7RE10, heat-input of <1.0 kJ/mm and interpass temperature of <100°C (210°F) are recommended. A string bead welding technique should be used.

Recommended filler metals

TIG/GTAW or MIG/GMAW welding

ISO 14343 S 25 20 / AWS A5.9 ER310 (e.g. Exaton 25.20.C)

MMA/SMAW welding

ISO 3581 E 25 20 B / AWS A5.4 E310-15 (e.g. Exaton 25.20.B)

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.