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Alloy 27 ASTM F-256 UNS K92801, 4J28 glass sealed and controlled expansion alloy
Note:
Glass Sealing UNS K92801 is a glass-to-metal sealing and
iron-chromium alloy. Nominally with 28% of Chromium, in forms of
strip, bar, wire and rod. It is used primarily for sealing to glass
in electronic applications. UNS K92801 should only be considered
for use at service temperatures below 300°C. The alloy is prone to
sigma phase formation at temperatures close to 620°C, and exhibits
brittle mechanical behavior after prolonged exposures at
temperatures close to 475°C.
Grade and Chemical Composition (see Table 1)
Table 1 Grade and Chemical Composition
Grade | Chemical Composition (%) | ||||||||
C | P | S | Mn | Si | Ni | N | Cr | Fe | |
≤ | |||||||||
4J28 | 0.12 | 0.02 | 0.02 | 1.00 | 0.70 | 0.50 | 0.20 | 27.0~29.0 | Balance |
Notes:
1. Under condition that the average coefficient of the linear
expansion meets the requirements of the standard, the content of
chromium is allowed to deviate from the stated range.
2. The shape and dimensions of the alloys are in compliance with
GB/T14985.
Physical Property (see Table2 & Table 3)
Table 2 Coefficient of Linear Expansion
Grade | Heat Treatment of the Samples | Average Coefficient of Linear Expansion |
20~530°C | ||
4J28 | Heat to 1100±20°C, hold for 15min., cool to room tempreture in the air. | 10.8~11.4 |
Note:
The hardness of the annealed strip should be no more than 170.
Hardness inspection is not required when the thickness of the strip
is less than 0.2mm.
Table 4 Coefficient of Linear Expansion
Grade | Average Coefficient of Linear Expansion ā/(10-6/K) | |||||||
20~200℃ | 20~300℃ | 20~400℃ | 20~450℃ | 20~500℃ | 20~600℃ | 20~700℃ | 20~800℃ | |
4J28 | 10.0 | 10.5 | 10.8 | - | 11.1 | 11.2 | 11.6 | 11.6 |