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Topics covered
introduction
Chemical composition
Physical properties
Mechanical properties
Other designations
introduction
Steels of type A2, A3, A4, A6, A7, A8, A9 and A10 form air hardening, medium alloy steels for cold working or steels of group A. Sufficient amounts of manganese, molybdenum and chromium present in Group A steels provide total hardness in sections having a thickness of at least 100 mm (4 in) in diameter when cooled in air.
Carbon is present at 0.5 to 2% in steels of group A. These steels have air hardening characteristics which allow a minimum of cracking and deformation during quenching.
The sections below provide an overview of cold working, air hardened A4, medium alloy tool steels.
Chemical composition
The chemical composition of A4 tool steels is described in the following table.
| Element | Content (%) |
|---|---|
| VS | 0.95-1.05 |
| Mn | 1.80-2.20 |
| Yes | 0.50 |
| Cr | 0.90-2.20 |
| Or | 0.30 |
| Mo | 0.90-1.40 |
| Cu | 0.25 |
| P | 0.03 |
| S | 0.03 |
Physical properties
The following table shows the physical properties of A4 tool steels.
| Properties | Metric | Imperial |
|---|---|---|
| Density | 8.03 g / cm3 | 0.290 lb / in3 |
Mechanical properties
The mechanical properties of A4 tool steels are shown in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Hardness, Rockwell C (as air quenched from 845 ° C, 61 HRC at 150 ° C tempered, 60 HRC at 205 ° C tempered, 59 HRC at 260 ° C tempered, 58 HRC at 315 ° C tempered, 57 HRC at 370 ° C tempered, 56 HRC at 425 ° C tempered, 54 HRC at 480 ° C tempered, 53 HRC at 540 ° C tempered, 50 HRC at 595 ° C tempered, 40 HRC at 650 ° C tempered.) | 63 | 63 |
| Bulk modulus (typical for steels) | 140 GPa | 20300 ksi |
| Machinability (based on carbon tool steel) | 65% | 65% |
| Shear modulus (typical for steels) | 80.0 GPa | 11600 ksi |
| Poisson coefficient | 0.27-0.30 | 0.27-0.30 |
| Elasticity module | 190-210 GPa | 27557-30457 ksi |
Other designations
Materials equivalent to A4 tool steels are:
- ASTM A681
- FED QQ-T-570
- UNS T30104
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