Nov 25 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forming
Welding
Heat Treatment
Forging
Hot Working
Cold Working
Annealing
Hardening
Applications
Introduction
Super alloys or high performance alloys have an ability to function at temperatures above 540ºC (1000ºF) with deformation resistance and high surface stability. As they have good oxidation and creep resistance, super alloys can be commonly forged, rolled to sheet or produced in various shapes. Iron-base, nickel-base and cobalt-base alloys are the major types of super alloys. Nickel-base and cobalt-base super alloys may be cast or wrought based on its composition or application. The iron-base super alloys are generally wrought alloys with stainless steel technology. These alloys can be strengthened by precipitation hardening, work hardening and solid-solution hardening.
The following section will provide a detailed description of Nichrome™, which can withstand temperature up to 1028ºC (1850ºF).
Chemical Composition
The following table shows the chemical composition of Nichrome™.
|
Elements |
Content (%) |
|
Iron, Fe |
21-25 |
|
Chromium, Cr |
14-18 |
|
Manganese, Mn |
1 max |
|
Silicon, Si |
0.75-1.6 |
|
Carbon, C |
0.15 max |
|
Sulfur, S |
0.01 max |
|
Nickel, Ni |
Balance |
Physical Properties
The physical properties of super alloy Nichrome™ are given in the following table.
|
Properties |
Metric |
Imperial |
|
Density |
8.4 g/cm³ |
0.304 lb/in³ |
|
Melting point |
1399ºC |
2550ºF |
Other Designations
Other designations that are equivalent to super alloy Nichrome™ include the following:
-
AMS 5676
-
ASTM B344
-
DIN 2.4867
Fabrication and Heat Treatment
Machinability
Nichrome™ can be easily machined using conventional techniques.
Forming
Forming of Nichrome™ can be performed through any standard techniques as it has good ductility.
Welding
Nichrome™ can be welded using all conventional means.
Heat Treatment
Nichrome™ is heat treated at 1066 to 1093ºC (1950 to 2000ºF) and then air cooled.
Forging
Forging of Nichrome™ can be performed at 1093ºC (2000ºF).
Hot Working
Nichrome™ can be hot worked at 760 to 1038ºC (1400 to 1900ºF).
Cold Working
Nichrome™ can be readily cold worked due to its ductility.
Annealing
Annealing of Nichrome™ is performed at 1066 to 1093ºC (1950 to 2000ºF) followed by air cooling.
Hardening
Nichrome™ can be hardened only by cold working.
Applications
Nichrome™ finds its application in the manufacture of heating elements used for household appliances.