Sep 21 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forming
Welding
Heat Treatment
Cold Working
Annealing
Tempering
Hardening
Applications
Introduction
Alloy steels are designated by AISI four-digit numbers. They contain different kinds of steels having compositions which exceed the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va set for carbon steels.
AISI 300M alloy steel is a low alloy and vacuum melted steel. It is a modified version of AISI 4340 steel. It has high content of molybdenum and silicon than that of AISI 4340 steel. It has high strength, good toughness, fatigue strength and ductility. The following datasheet gives more details about the AISI 300M alloy steel.
Chemical Composition
The chemical composition of the AISI 300M alloy steel is tabulated below.
|
Element |
Content (%) |
|
Iron, Fe |
93.4 - 94.8 |
|
Nickel, Ni |
1.65 - 2.0 |
|
Silicon, Si |
1.45 - 1.80 |
|
Chromium, Cr |
0.70 - 0.95 |
|
Manganese, Mn |
0.65 - 0.90 |
|
Carbon, C |
0.40 - 0.460 |
|
Phosphorous, P |
0.035 |
|
Molybdenum, Mo |
0.30 - 0.45 |
|
Vanadium, V |
0.050 |
|
Sulfur, S |
0.040 |
Physical Properties
The physical properties of AISI 300M alloy steel are outlined in the following table.
|
Properties |
Metric |
Imperial |
|
Density |
7.87 g/cm3 |
0.284 lb/in³ |
|
Melting point |
1422°C |
2590°F |
Mechanical Properties
The following table shows the mechanical properties of AISI 300M alloy steel.
|
Properties |
Metric |
Imperial |
|
Shear modulus (typical for steel) |
80 GPa |
11600 ksi |
|
Elastic modulus |
205 GPa |
29700 ksi |
|
Poisson's ratio |
0.28 |
0.28 |
Other Designations
Other designations that are equivalent to AISI 300M alloy steel include:
-
AMS 6417
-
AMS 6419
-
ASTM A579 (32)
-
ASTM A646 (300M-8)
-
MIL S-8844 (3)
-
MIL S-8844 Class 2
Fabrication and Heat Treatment
Machinability
AISI 300M alloy steel can be easily machined in normalized, or normalized and tempered conditions. Due to hardness of the heat treated alloy, the grinding process is performed with extreme care. After grinding, stress relief annealing is performed at 288°C (550°F).
Forming
AISI 300M alloy steel can be formed in the annealed condition using conventional techniques.
Welding
AISI 300M alloy steel can be welded using flash resistance welding or fusion welding methods. Approved procedures such as including pre and post-heating practice are followed for performing the fusion welding method because this alloy can be air-hardened due to the heat produced by welding. This process is followed by re-normalizing, or re-normalizing and tempering before heat treatment.
Heat Treatment
AISI 300M alloy steel is normalized at 927°C (1700°F). It is then heated at 872°C (1600°F) followed by oil quenching oil and tempering.
Cold Working
AISI 300M alloy steel has good ductility, and can be cold worked in the annealed or normalized condition using conventional techniques.
Annealing
AISI 300M alloy steel is annealed at 844°C (1550°F) followed by slowly cooling in the furnace. It can be then air cooled.
Tempering
AISI 300M alloy steel can be tempered at (600°F) to achieve 300 ksi strength.
Hardening
AISI 300M alloy steel can be hardened by cold working and heat treatment.
Applications
AISI 300M alloy steel is used in high strength bolts, airframe parts, and aircraft landing gear.