Dec 18 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesFabrication and Heat Treatment Machinability Forming Tempering HardeningApplications
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, that can be strengthened by precipitation hardening, work hardening and solid-solution hardening.
The following datasheet provides a detailed description of super alloy 21-4N valve steel.
Chemical Composition
The following table shows the chemical composition of super alloy 21-4N valve steel.
| Elements |
Content (%) |
| Chromium, Cr |
21 |
| Manganese, Mn |
9 |
| Nickel, Ni |
3.88 |
| Carbon, C |
0.53 |
| Silicon, Si |
0.25 max |
Physical Properties
The physical properties of super alloy 21-4N valve steel are given in the following table.
| Properties |
Metric |
Imperial |
| Density |
7.7 g/cm³ |
0.278 lb/in³ |
Mechanical Properties
The mechanical properties of super alloy 21-4N valve steel are displayed in the following table.
| Properties |
Metric |
Imperial |
| Tensile strength |
950-1200 MPa |
13778-17404 psi |
| Modulus of elasticity |
215 GPa |
31183 ksi |
| Elongation |
8% |
8% |
| Reduction |
10% |
10% |
| Hardness |
32 |
32 |
Fabrication and Heat Treatment
Machinability
Super alloy 21-4N valve steel can be machined similar to that of the standard 18-8 stainless steels.
Forming
Forming of super alloy 21-4N valve steel can be performed at 950 to 1100ºC (1742 to 2012ºF).
Tempering
Super alloy 21-4N valve steel can be tempered at 730 to 780ºC (1346 to 1436ºF)
Hardening
Super alloy 21-4N valve steel can be hardened at 1140 to 1180ºC (2084 to 2156ºF) and then water quenched.
Applications
Super alloy 21-4N valve steel is widely used in the manufacture of automotive valve.