invar 36 in precision instruments industry Invar 36 / ASTM F1684 is also know as W.NR 1.3912,UNS K93600,UNS K93601,AWS 090,Invar alloy,ASTM F1684,Alloy 36,W.NR:1.3912 (FeNi36),Nilo 36. Characteristic Invar 36 alloy is a nickel-iron ,low-expansion alloy containing 36% nickel .It maintains nearly constant dimensions over the range of normal..