Heat Resistant Alloys

NAS H840

An austenitic stainless steel with powerful resistance to oxidation, NAS H840 is also resistant to high temperatures and corrosion in chloride environments. It is therefore suitable for high-grade sheath heater cover tubes. Nippon Yakin produces this product in sheet and strip forms.

  • Image: Coil
    Coil
  • Image: Sheet
    Sheet

Designation / Standard

Nippon Yakin Grade ASTM A240 EN JIS
NAS H840 UNS S33400 ― ―

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Chemical Composition

NAS H840

  C Si Mn P S Ni Cr Al Ti
Min ― ― ― ― ― 18 18 ― ―
Max 0.08 1.00 1.00 0.030 0.015 22 22 0.60 0.60

UNS S33400

  C Si Mn P S Ni Cr Al Ti
Min ― ― ― ― ― 19 18 0.15 0.15
Max 0.08 1.00 1.00 0.030 0.015 21 22 0.60 0.60

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Physical Properties

Specific heat (J/kg･K) 450
Specific resistivity (μΩ･cm) 90.0
Thermal conductivity (W/m･K) 13.0
Thermal diffusivity (m²/s) 3.7 x 10-6
Coefficient of thermal expansion(10-6/℃) 20–300℃ 16.7
20–500℃ 17.4
20–800℃ 18.6
20–1000℃ 19.4

 

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Mechanical Properties

Mechanical Properties at Room Temperature

UNS S33400

0.2% Yield strength (N/mm2) Tensile strength (N/mm2) Elongation (%) Hardness (HRB)
≥ 170 ≥ 485 ≥ 30 ≤ 92

Temperature dependency of the coefficient of thermal diffusivity for NAS H840

Image: Temperature dependency of the coefficient of thermal diffusivity for NAS H840

Temperature dependency of the specific heat of NAS H840

Image: Temperature dependency of the relative heat of NAS H840

Temperature dependency of the thermal conductivity of NAS H840

Image: Temperature dependency of the thermal conductivity of NAS H840

High-Temperature Strength

Temperature dependency of the 0.2% yield strength and tensile strength of NAS H840

Image: High-Temperature Strength

Acid Resistance

Cyclic oxidation resistance of various alloys (weight change)

Image: Heat Resistance

Stress Corrosion Cracking Resistance

  TestI TestII
20% NaCl + 1% Na2Cr2O7 (boiled for 330 hr) 30% MgCl2 (boiled for 110 hr)
NAS H840 No SCC No SCC
NCF 800 No SCC No SCC
SUS 316 SCC SCC
SUS 304 SCC SCC

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Weldability

NAS H840 has superior weldability. No cracks occur in bending tests or 30 percent pulling tests after plasma welding.

Emission Ratio

Effect of the heating temperature on the emission ratio of various alloys (held in a LPG oven for five minutes)

Image: Emission Ratio

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