Topics CoveredIntroductionChemical CompositionPhysical PropertiesMechanical PropertiesOther Designations
Steels of the type A2, A3, A4, A6, A7, A8, A9, and A10 form 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 a thickness of at least 100 mm (4 in.) in diameter when air cooled.
Carbon is present in the range of 0.5 to 2% in group A steels. These steels are provided with air hardening characteristics that allow minimum cracking and distortion on quenching.
The sections below will provide an overview of A4 air-hardening, medium-alloy, cold-work tool steels.
The chemical composition of A4 tool steels is outlined in the following table.
The following table shows the physical properties of A4 tool steels.
The mechanical properties of A4 tool steels are displayed in the following table.
|Hardness, Rockwell C (as air quenched from 845°C, 61 HRC at 150°C temper, 60 HRC at 205°C temper, 59 HRC at 260°C temper, 58 HRC at 315°C temper, 57 HRC at 370°C temper, 56 HRC at 425°C temper, 54 HRC at 480°C temper, 53 HRC at 540°C temper, 50 HRC at 595°C temper, 40 HRC at 650°C temper.)
|Bulk modulus (typical for steels)
|Machinability (based on carbon tool steel)
|Shear modulus (typical for steels)
Equivalent materials to A4 tool steels are:
- ASTM A681
- FED QQ-T-570
- UNS T30104