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Invar 36 Sheet & Plate

Invar 36 Sheet & Plate (UNS K93600,1.3912)

Invar 36 is a unique iron-nickel alloy with an extremely low coefficient of thermal expansion (CTE). With a nickel content of approximately 36%, Invar 36 maintains remarkable dimensional stability across temperature variations, making it indispensable in precision engineering applications. Available in sheet and plate forms, this material is widely used in industries requiring accurate and stable components.

 

Key Features of Invar 36 Sheet & Plate

Low Thermal Expansion: The most notable feature of Invar 36 is its minimal expansion rate, even under temperature changes, ensuring consistent dimensions in critical applications.
High Strength and Toughness: Despite its low CTE, Invar 36 exhibits excellent mechanical strength and impact resistance.
Corrosion Resistance: It offers good resistance to oxidation and corrosion in various environments, enhancing its durability.
Workability: The alloy is easy to machine, weld, and form, allowing it to be tailored to specific design requirements.

 

Technical Specifications:

  • UNS Number: K93600
  • DIN/EN Designation: 1.3912
  • Standards Compliance: ASTM A240/A240M

Available Thickness

1/4″3/8″1/2″5/8″3/4″1″1 1/4″
6.3mm9.5mm12.7mm15.9mm19mm25.4mm31.8mm
1 1/2″1 3/4″2″2 1/2″3″3 1/2″4″
38.1mm44.5mm50.8mm63.5mm76.2mm88.9mm101.6mm
invar-36

Application

  • Automotive
  • Chemical and Pharmaceutical
  • Fertilizer
  • Food Processing and Handling
  • Manufacturing
  • Mining
  • Oil & Gas
  • Phosphate Mining

Standard

  • ASTM A240 / A240M
  • ASTM A276 / A276M
  • ASTM A312 / A312M
  • ISO 15510
  • EN 10088-2
  • IN 10204
  • HE G4304
  • HE G4305
  • ASME SA240 / SA240M

Worldwide Equivalent Grades of INVAR 36

Country/RegionStandardGrade
USAASTMUNS K93600
GermanyDINW. Nr. 1.3912
FranceAFNORFe-Ni36
EuropeEN1.3912
UKBSNilo 36
JapanJISCFE-Ni36
RussiaGOST36N
InternationalISOFe-Ni36

Corrosion Resistance

  • Atmospheric Corrosion: INVAR 36 exhibits moderate corrosion resistance in atmospheric environments. It can develop a protective oxide layer in the air, which helps reduce the rate of corrosion. However, in highly polluted or marine environments, its corrosion resistance can be compromised, leading to surface rusting over time.
  • Chemical Corrosion: INVAR 36 is not particularly resistant to corrosive chemicals. It can be attacked by acids, particularly hydrochloric acid and sulfuric acid. Alkaline environments can also lead to corrosion, although it may resist mild alkalies better than acids.
  • Galvanic Corrosion: When INVAR 36 is in contact with more noble metals (like copper or stainless steel) in the presence of an electrolyte, it can suffer from galvanic corrosion. Care should be taken to avoid such combinations unless the environment is controlled or protective coatings are applied.
  • Pitting and Crevice Corrosion: INVAR 36 is susceptible to pitting and crevice corrosion in chloride-containing environments. Even mild exposure to chloride ions (e.g., from saltwater or de-icing salts) can lead to localized attack, especially in crevices where oxygen levels are low.

Chemical Composition of INVAR 36

ElementComposition (%)
Nickel (Ni)35.0 – 37.0%
Iron (Fe)Balance
Carbon (C)≤ 0.10%
Manganese (Mn)≤ 0.60%
Silicon (Si)≤ 0.35%
Sulfur (S)≤ 0.025%
Phosphorus (P)≤ 0.025%
Cobalt (Co)≤ 0.50%
Chromium (Cr)≤ 0.25%

Physical Properties of INVAR 36

PropertyValue/Composition
Density8.1 g/cm³ (8100 kg/m³)
Thermal Expansion Coefficient (20°C to 100°C)1.2 x 10⁻⁶ /°C
Specific Heat Capacity515 J/kg·°C
Electrical Resistivity0.78 µΩ·m
Curie Temperature230°C
Thermal Conductivity10.2 W/m·K

Mechanical Properties of INVAR 36

PropertyValue/Composition
Tensile Strength490 – 690 MPa
Yield Strength (0.2% Offset)240 – 345 MPa
Elongation30 – 50%
Hardness (Rockwell B)70 – 90 HRB
Modulus of Elasticity148 GPa

Fabrication Data

Forming:
  • INVAR 36 can be hot or cold formed, though cold forming is preferred for tighter tolerances.
  • Annealing is recommended after cold working to reduce stresses.
Machining:
  • Machinability of INVAR 36 is similar to austenitic stainless steels.
  • Use sharp tools with slow speeds, heavy feeds, and ample cutting fluids.
Welding:
  • INVAR 36 is weldable using common welding methods like TIG, MIG, and resistance welding.
  • To avoid cracking, it’s advisable to preheat to 200-300°C and post-weld anneal at 800-900°C.
Heat Treatment:
  • Annealing: Heat to 830-900°C for 1-2 hours, followed by furnace cooling or air cooling.
  • Stress Relieving: Heat to 530-700°C, hold for 1-2 hours, and cool in air.
Surface Treatment:
  • Can be polished, pickled, or electroplated to improve surface finish and corrosion resistance.
Corrosion Resistance:
  • INVAR 36 has moderate corrosion resistance in various environments but can be prone to rusting in humid or acidic conditions. Protective coatings may be necessary.
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