Invar 36 UNS K93600 UNS K93603 1.3912 Ni36 Nickel Alloy

Invar 36 is a nickel-iron, low-expansion alloy containing 36% nickel. It maintains nearly constant dimensions over the range of normal atmospheric temperatures, and has a low coefficient of expansion from cryogenic temperatures to about 500°F. The alloy also retains good strength and toughness at cryogenic temperatures. Invar 36 is a 36% nickel-iron alloy possessing a rate of thermal expansion approximately one-tenth that of carbon steel at temperatures up to 400°F(204°C)

Applications

This alloy has been used for applications where dimensional changes due to temperature variation must be minimized such as in radio and electronic devices, aircraft controls, optical and laser system, etc. Invar 36 alloy has also been used in conjunction with high expansion alloys in applications where a motion is desired when the temperature changes, such as in bimetallic thermostats and in rod and tube assemblies for temperature regulators.

Specifications

AFNOR NF A54-301 (chemistry only), ASTM F 1684-06, EN 1.3912, UNS K93600, UNS K93603, Werkstoff 1.3912

Chemical Composition

Mechanical Properties Typical Room Temperature Mechanical Properties Mill Annealed

Material Advantages

Invar 36 can be hot and cold formed and machined using processes like austenitic stainless steels and is also weldable using Filler Metal CF26. Some of the other benefits associated with the use of Invar nickel alloy 36 include: Superior dimensional stability,  Numerous workability aspects, Extremely low coefficient of thermal expansion (CTE).

Welding

Invar 36 can be welded by the convetional methods. Caution must be taken so as not to overheat the molten metal. This will avoid spattering of the molten metal and pits in the welded area. When filler rod is required , Invarod has been used.

Corrosion properties

Invar 36 is corrosion resistant in dry atmospheres at room temperature. Under unfavourable conditions, i.e., in humid or moist atmospheres, corrosion can occur in the form of rust.

Machinability

Invar is tough and ductile and therefore somewhat difficult to machine. It should be machined in the annealed condition. The machining characteristics of Invar 36 are similar to austenitic stainless steels. Because of its high ductility, the chips formed during machining tend to be stringy and tough and may thus impose rapid wear on the cutting tool edges. In general, slow speeds and light feeds should be used to avoid excessive heat and minimize the possibility of the generated heat affecting the expansion characteristics. An adequate depth of cut is important, however, in order to cut below any previously formed work-hardened zone. High speed steel or sintered carbide tools should be used and cutting edges should be kept sharp.

Forging

The principal precaution to observe in forging is to heat quickly and avoid soaking in the furnace. Long soaking may result in a checked surface due to absorption of sulfur from the furnace atmosphere and/or oxide penetration. A forging temperature of 2000/2150øF (1100/1180øC) is preferred. Invar alloy 36 may also be swaged and cold upset.