Jul 10 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Introduction
Air-hardening, medium alloy, cold work steels also known as group A steels include A2, A3, A4, A6, A7, A8, A9, and A10. Sufficient amounts of manganese, molybdenum and chromium present in group A steels provide full hardness in sections comprising thickness of at least 100 mm (4 in.) in diameter when air cooled.
Group A steels have a carbon content of 0.5 to 2%. These steels have air hardening characteristics that allow minimum cracking and distortion on quenching.
The data below will provide an overview of A8 air-hardening, medium-alloy, cold-work tool steels.
Chemical Composition
The chemical composition of A8 tool steels is outlined in the following table.
|
Element |
Content (%) |
|
Chromium, Cr |
4.75-5.50 |
|
Molybdenum, Mo |
1.15-1.65 |
|
Tungsten, W |
1.00-1.50 |
|
Silicon, Si |
0.75-1.10 |
|
Carbon, C |
0.50-0.60 |
|
Manganese, Mn |
0.5 |
|
Nickel, Ni |
0.3 |
|
Copper, Cu |
0.25 |
|
Phosphorus, P |
0.03 |
|
Sulfur, S |
0.03 |
Physical Properties
The following table shows the physical properties of A8 tool steels.
|
Properties |
Metric |
Imperial |
|
Density |
7.87 g/cm³ |
0.284 lb/in³ |
Mechanical Properties
The mechanical properties of A8 tool steels are displayed in the following table.
|
Properties |
Metric |
Imperial |
|
Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
|
Elastic modulus |
190-210 GPa |
27557-30457 ksi |
|
Bulk Modulus (typical for steels) |
140 GPa |
20300 ksi |
|
Shear modulus (typical for steels) |
80 GPa |
11600 ksi |
|
Hardness, Rockwell C |
48 - 57 |
48 - 57 |
|
Machinability (based on carbon tool steel) |
65 |
65 |
Other Designations
Equivalent materials to A8 tool steels are:
-
ASTM A681
-
FED QQ-T-570
-
UNS T30108