{"id":3575,"date":"2026-09-16T11:01:54","date_gmt":"2026-09-16T08:01:54","guid":{"rendered":"https:\/\/www.defencemetal.com\/index.php\/en\/invar-36\/"},"modified":"2026-09-25T16:27:54","modified_gmt":"2026-09-25T13:27:54","slug":"invar-36","status":"publish","type":"page","link":"https:\/\/www.defencemetal.com\/index.php\/en\/invar-36\/","title":{"rendered":"Invar 36"},"content":{"rendered":"

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Invar 36 \/ (1.3912) \/ UNS K93600<\/h1>\n
DEFENCE METAL<\/span><\/p>\n
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Invar 36<\/div>\n
UNS K93600 (the same alloy also appears as K93601 and K93603 in ASTM and producer records) \u00b7 W.Nr. 1.3912 \u00b7 FeNi36 \/ Ni36 (DIN 1715, SEW 385) \u00b7 ~36% Ni \u2013 balance Fe. Specification limits: Ni 35.0-37.0% \u00b7 C 0.10% max \u00b7 Mn 0.60% max \u00b7 Si 0.35% max \u00b7 Cr 0.50% max \u00b7 Mo 0.50% max \u00b7 Cu 0.50% max \u00b7 P 0.025% max \u00b7 S 0.025% max. It is an austenitic iron-nickel alloy; it is not stainless and is not protected by chromium.<\/div>\n
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Not to be confused with<\/div>\n

Kovar<\/a><\/div>\n<\/div>\n

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For what<\/div>\n
The iron-nickel alloy with the lowest thermal expansion. It is NOT PRECIPITATION HARDENABLE and cannot be hardened by heat treatment; its distinguishing property is not mechanical strength but its COEFFICIENT OF THERMAL EXPANSION.<\/div>\n<\/div>\n
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Forms<\/div>\n
Round bar \u00b7 flat bar \u00b7 plate \u00b7 sheet \u00b7 strip \u00b7 tube \u00b7 wire \u00b7 forging. All forms are supplied to order.<\/div>\n<\/div>\n
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Standards<\/div>\n
AMS \u2014 NO independent AMS product specification belonging to Invar 36 could be found. AMS-I-23011 (‘Iron-Nickel Alloys for Sealing to Glasses and Ceramic’) uses a class system and Invar 36 is listed as Class 7 of that specification; this class assignment could be verified in only two independent sources. \u00b7 ASTM F1684 \u2014 iron-nickel and iron-nickel-cobalt alloys for low thermal expansion applications; it was the principal product specification for Invar 36 and was WITHDRAWN IN 2024 WITH NO REPLACEMENT. The last valid edition is F1684-06(2021). \u00b7 ASTM B753 Alloy T36 (thermostat metal) \u00b7 AFNOR NF A54-301 \u00b7 DIN 1715 \u00b7 SEW 385 \u00b7 GB\/T 4J36 \u00b7 Boeing D-33028 (producer\/customer specification).
UNS TRAP: this alloy is not identified by a single UNS number. Special Metals gives ‘K93600 and K93601’ for NILO alloy 36, Carpenter gives ‘K93601 \/ K93603’ for its own Invar 36, while ASTM F1684 lists only K93603 (plus the free-machining K93050 and the\u2026<\/span><\/div>\n<\/div>\n
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Advantage<\/div>\n
Over 20-100 \u00b0C the mean linear coefficient of thermal expansion is about 1.2-1.5 ppm\/K (Special Metals NILO 36: 1.5 for 20-100 \u00b0C; Carpenter: 1.30 for 25-93 \u00b0C; Rolled Alloys: 1.44 for 21-100 \u00b0C; Nickel Institute and ESPI: 0.70 x 10-6\/\u00b0F over -18 to 93 \u00b0C = 1.26 ppm\/K;<\/div>\n<\/div>\n
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Welding<\/div>\n
GTAW (TIG) and short-circuiting GMAW (MIG) are recommended (Nickel Institute). The filler metal must match the composition; matching filler wires sold as Invarod and CF36 are used. Heat input must be limited and the molten pool must not be overheated (Carpenter \/ High Temp Metals).<\/div>\n<\/div>\n
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Limits<\/div>\n
ABOVE THE CURIE TEMPERATURE (about 277-279 \u00b0C) IT LOSES ITS LOW-EXPANSION PROPERTY. The expansion coefficient begins to rise well before that point: the 20-200 \u00b0C mean is 2.6 ppm\/K, the 20-300 \u00b0C mean 5.5 ppm\/K and the 20-500 \u00b0C mean 10.1 ppm\/K (Special Metals). Special Metals puts the inflection point at 220 \u00b0C, ESPI at 190 \u00b0C (375 \u00b0F).<\/div>\n<\/div>\n
REQUEST A QUOTE<\/a>All nickel alloys →<\/a>TECHNICAL DETAILS ↓<\/span><\/div>\n
Compiled from manufacturer data sheets \u00b7 confirm against the current specification before ordering<\/div>\n<\/div>\n<\/div>\n

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