Auerhammer Metallwerk Gmbh, Germany Manufactures DILATON 29/18 which has many popular trade names like DILATON 29/18, Kovar, UNS K94610, ASTM F15, 29-17 alloy, FeNiCo Low Expansion Alloy, DIN 1.3981, Controlled Expansion Alloy and FeNi29Co18.
DILATON 29/18 Alloy is a vacuum melted, iron-nickel-cobalt and a low expansion alloy whose chemical composition is controlled within narrow limits to assure precise uniform thermal expansion properties. Extensive quality controls are employed in the manufacturing of this alloy to ensure uniform physical and mechanical properties for ease in deep drawing, stamping, and machining.
DILATON 29/18 is an iron-nickel-cobalt alloy with a coefficient of thermal expansion similar to that of hard borosilicate glass. It expands and contracts at the same rate as borosilicate glass and something you will see in everyday life but never give a second glance. This makes it especially suitable for uses which require a matched-expansion seal between metal and glass parts. Thus DILATON 29/18 finds wide usage in the electronics industry for metal parts bonded to hard glass envelopes for such devices as power tubes, x-ray tubes, etc. and other applications requiring glass-to-metal seals. It works at -80°C and can remain stable up to -196°C.
Chemical Composition:- Ni 28-29, Co 17-18, Mn 0.5, Al ≤ 0.1, Cu ≤ 0.2, Cr ≤ 0.2, Si ≤ 0.2, Bal Fe.
DILATON 29/18 Alloy has been used for making Hermetic seals with harder Pyrex glasses and ceramic materials.
This alloy has found wide application in Computer, hybrid, power tubes, microwave tubes, transistors and diodes. In integrated circuits, it has been used for the flat pack and the dual-in-line package.
Density 8.2 g/cm3
Melting Temperature 1440 °C
Electrical resistivity at 20 °c 0.45
Thermal conductivity at 20 °c 17
Modulus of elasticity 157
THERMAL EXPANSION CHARACTERISTICS
|AMW-trade name||Average linear thermal expansion coefficient 1 0. 6/k, base temperature 20 °c, temperature s °c||Inflection point/Curie temperature|
Yield strength Rp 0.2 350 MPa
Tensile strength Rm 540 MPa
Elongation 35 %
Brinell hardness 155 HB
Because of its effect on the actual structure of the material, there is a distinction made between heat treating the material to facilitate fabrication and heat-treating the material to ensure optimum conditions for glass sealing, plating or brazing.
Stress Relief Annealing: To relieve stress and work hardening of parts at intermediate stages of fabrication. It is intended particularly for drawing,
Forming and Spinning Operations:-
- Wash and degrease parts.
- Anneal in atmosphere controlled furnace. The atmosphere may be wet or dry hydrogen, dissociated ammonia, cracked gas or similar neutral atmosphere.
- The annealing temperature is not critical; however, high temperatures (greater than 900°C) or extended-time period (longer than 60 minutes) should be avoided because such treatments promote grain growth. Typical cycle: 850°C for 30 minutes.
- Parts should be held at temperature for the indicated time and then furnace cooled to less than 175°C to avoid oxidation and/or thermal shock (which may cause distortion).
Heat Treatment for Oxidation:-
- Make sure that proper methods are used to clean, degree and bright dip parts.
- Oxidation – Heat treat in an electric air furnace to 850°C to 900°C until parts are cherry red (dull red heat). The length of the heat cycle is approximately 3 minutes, but due to differences in humidity and furnaces, the proper cycle has to be varied. Then reduce heat approximately 10°C per minute. When parts are cooled, the oxide will be formed. The oxide may appear from light grey to black colour. Black is normally considered to be over oxidation and is not necessarily desirable for a good glass to metal seal.