Sandvik 6R44

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Description

Sandvik 6R44 is an austenitic, niobium-stabilized stainless chromium-nickel steel for use at temperatures up to 850°C (1560°F).


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Sandvik 6R44


Datasheet updated 2019-09-02 09:19 (supersedes all previous editions)

Related Standards

Equivalent Materials

Los datos sobre este material han sido proporcionados por Sandvik Materials Technology.

A menos que se indique lo contrario, todas las medidas corresponden a condiciones de temperatura ambiente. A menos que se indique lo contrario, se utilizan las unidades del SI.
Las normas armonizadas son similares a uno o varios estándares del proveedor. Es posible que algunas normas armonizadas se ajusten al estándar original, mientras que otras pueden quedar fuera de su alcance.

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Propiedades

General

PropertyTemperatureValueComment

Densidad

23.0 °C

7.9 g/cm³

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Recycled Content

82.1 %

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Average recycled content

Mecánica

PropertyTemperatureValueComment

Creep strength 10^4 cycles

540.0 °C

253 MPa

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ISO values, at 10000h

550.0 °C

237 MPa

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ISO values, at 10000h

580.0 °C

192 MPa

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ISO values, at 10000h

600.0 °C

166 MPa

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ISO values, at 10000h

620.0 °C

142 MPa

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ISO values, at 10000h

650.0 °C

112 MPa

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ISO values, at 10000h

670.0 °C

96 MPa

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ISO values, at 10000h

700.0 °C

74 MPa

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ISO values, at 10000h

800.0 °C

28 MPa

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ISO values, at 10000h

Creep strength 10^5 cycles

540.0 °C

186 MPa

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ISO values, at 100000h

550.0 °C

172 MPa

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ISO values, at 100000h

580.0 °C

135 MPa

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ISO values, at 100000h

600.0 °C

115 MPa

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ISO values, at 100000h

620.0 °C

97 MPa

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ISO values, at 100000h

650.0 °C

74 MPa

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ISO values, at 100000h

670.0 °C

61 MPa

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ISO values, at 100000h

700.0 °C

48 MPa

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ISO values, at 100000h

800.0 °C

16 MPa

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ISO values, at 100000h

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Dureza Vickers

23.0 °C

155 [-]

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Elongación

23.0 °C

40 %

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min.

Energía de impacto Charpy

-196.0 °C

60 J

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EN 13445-2 (UFPV-2) and EN 10216-5

Límite elástico Rp 0,2

20.0 °C

220 MPa

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min.

50.0 °C

195 MPa

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min.

100.0 °C

175 MPa

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min.

150.0 °C

165 MPa

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min.

200.0 °C

155 MPa

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min.

250.0 °C

147 MPa

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min.

300.0 °C

139 MPa

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min.

350.0 °C

133 MPa

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min.

400.0 °C

129 MPa

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min.

450.0 °C

126 MPa

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min.

500.0 °C

124 MPa

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min.

550.0 °C

118 MPa

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min.

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Límite elástico Rp0.1

20.0 °C

250 MPa

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min.

50.0 °C

232 MPa

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min.

100.0 °C

210 MPa

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min.

150.0 °C

195 MPa

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min.

200.0 °C

185 MPa

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min.

250.0 °C

175 MPa

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min.

300.0 °C

167 MPa

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min.

350.0 °C

162 MPa

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min.

400.0 °C

159 MPa

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min.

450.0 °C

156 MPa

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min.

500.0 °C

155 MPa

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min.

550.0 °C

152 MPa

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min.

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Módulo elástico

20.0 °C

200 GPa

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100.0 °C

194 GPa

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200.0 °C

186 GPa

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300.0 °C

179 GPa

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400.0 °C

172 GPa

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500.0 °C

165 GPa

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Resistencia a la tracción

23.0 °C

515 - 690 MPa

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Aplicaciones térmicas

PropertyTemperatureValueComment

Calor específico

20.0 °C

485 J/(kg·K)

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100.0 °C

500 J/(kg·K)

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200.0 °C

515 J/(kg·K)

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300.0 °C

525 J/(kg·K)

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400.0 °C

540 J/(kg·K)

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500.0 °C

555 J/(kg·K)

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600.0 °C

575 J/(kg·K)

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Coeficiente de dilatación térmica

100.0 °C

1.7E-5 1/K

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for 30°C to the mentioned temperature

200.0 °C

1.75E-5 1/K

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for 30°C to the mentioned temperature

300.0 °C

1.75E-5 1/K

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for 30°C to the mentioned temperature

400.0 °C

1.8E-5 1/K

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for 30°C to the mentioned temperature

500.0 °C

1.85E-5 1/K

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for 30°C to the mentioned temperature

600.0 °C

1.85E-5 1/K

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for 30°C to the mentioned temperature

700.0 °C

1.9E-5 1/K

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for 30°C to the mentioned temperature

800.0 °C

1.95E-5 1/K

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for 30°C to the mentioned temperature

900.0 °C

1.95E-5 1/K

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for 30°C to the mentioned temperature

1000.0 °C

2E-5 1/K

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Conductividad térmica

20.0 °C

14 W/(m·K)

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100.0 °C

15 W/(m·K)

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200.0 °C

17 W/(m·K)

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300.0 °C

18 W/(m·K)

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400.0 °C

20 W/(m·K)

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500.0 °C

21 W/(m·K)

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600.0 °C

23 W/(m·K)

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Chemical properties

PropertyValueComment

Azufre

0.015 %

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max.

Carbono

0.05 %

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max.

Cromo

17.5 %

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Fósforo

0.03 %

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max.

Hierro

Balance

Manganeso

1.7 %

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Niobio

0.7 %

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Níquel

10 %

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Silicona

0.6 %

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Technological properties

Property
Application areas

Sandvik 6R44 is used for superheater tubes in steam power plants.

It is also frequently used for cooling tubes in ammonia converters, because of its good resistance to nitrogen absorption and good corrosion resistance. With its good hot-strength, and good resistance to hydrogen sulfide and intergranular corrosion, Sandvik 6R44 is a suitable material for furnace tubes in refineries. Furnace tubing used in vinyl chloride production is another example of applications in which this steel is often used.

Cold Forming

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, see under "Heat treatment".

Corrosion properties

Wet corrosion: Sandvik 6R44 is generally used at temperatures above 500°C (930°F), where wet corrosion is not relevant. The stabilization with niobium gives Sandvik 6R44 good resistance to intergranular corrosion. The steel may be sensitive to pitting and crevice corrosion even in solutions of relatively low chloride content. Austenitic steels are susceptible to stress corrosion cracking. This may occur at temperatures above about 60°C (140°F), if the steel is subject 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.


Gas corrosion: Sandvik 6R44 can be used in air up to 850°C (1560°F) and in steam up to 750°C (1380°F). It is suitable for use in mild synthesis gas up to about 550°C (1020°F).


Creep behavior 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.

Heat Treatment

The tubes are delivered in heat treated 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.

Solution annealing: 1000-1100°C (1830-2010°F), 5-20 minutes, rapid cooling in air or water.

Hot forming

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

Other

Forms of supply:

Seamless tube and pipe in Sandvik 6R44 is supplied in dimensions up to 260 mm outside diameter in the solution-annealed and white-pickled condition or in the bright annealed condition.

Welding

The weldability of Sandvik 6R44 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 Sandvik 6R44, 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)
    • ISO 14343 S 19 9 Nb Si / AWS A5.9 ER347Si (e.g. Exaton 19.9.NbSi)
  • 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 Sandvik 6R44, is required.