Sep 13 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesOther Designations
Introduction
Steels of the type A2, A3, A4, A6, A7, A8, A9, and A10 are called air-hardening, medium alloy, cold work steels or group A steels. 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.
The carbon content group A steels range from 0.5 to 2%. These steels are provided with air hardening characteristics that allow minimum cracking and distortion on quenching.
The data below will provide an overview of A6 air-hardening, medium-alloy, cold-work tool steels.
Chemical Composition
The chemical composition of A6 tool steels is outlined in the following table.
Element |
Content (%) |
C |
0.65-0.75 |
Mn |
1.80-2.50 |
Si |
0.5 |
Cr |
0.90-1.20 |
Ni |
0.3 |
Mo |
0.90-1.40 |
Cu |
0.25 |
P |
0.03 |
S |
0.03 |
Physical Properties
The following table shows the physical properties of A6 tool steels.
Properties |
Metric |
Imperial |
Density |
8.03 g/cm3 |
0.290 lb/in3 |
Mechanical Properties
The mechanical properties of A6 tool steels are displayed in the following table.
Properties |
Metric |
Imperial |
Hardness, Rockwell C (as air quenched from 845°C, tempered for 2 hours. 61-62 HRC at 95°C temper, 60-61 HRC at 150°C temper, 58-59 HRC at 205°C temper, 56-57 HRC at 260°C temper, 55-56 HRC at 315°C temper, 52-53 HRC at 425°C temper, 50-51 HRC at 480°C temper, 48-49 HRC at 540°C temper) |
61.0-62.0 |
61.0-62.0 |
Bulk modulus (typical for steels) |
140 GPa |
20300 ksi |
Machinability (based on carbon tool steel) |
65% |
65% |
Shear modulus (estimated from elastic modulus) |
77.0 GPa |
11200 ksi |
Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
Elastic modulus |
190-210 GPa |
27557-30457 ksi |
Thermal Properties
The thermal properties of A6 tool steels are given in the following table.
Properties |
Conditions |
T (°C) |
Treatment |
Thermal expansion |
11.5 x 10-6/ºC |
20-100 |
- |
Other Designations
Equivalent materials to A2 tool steels are:
- ASTM A68i
- FED QQ-T-570
- UNS T30i06
- ASTM A681 (A-6)
- UNS T30106