AISI S7 Tool Steel.
AISI S7 tool steel is a Shock-Resisting Steel with the highest hardenability and elevated temperature softening resistance of the S-series steels. Due to these properties, S7 material is popular in shock-resistant applications. They are moderately resistant to decarburization and grain growth.
S7 Tool Steel Properties
S7 tool steel properties such as chemical composition, physical and mechanical properties are summarized below.
Chemical Composition
| Chemical Composition, % | |||||||||
| Standard | AISI (UNS) | C | Si | Mn | P, ≤ | S, ≤ | Cr | Mo | V, ≤ |
| ASTM A681 | S7 (T41907) | 0.45-0.55 | 0.20-1.00 | 0.20-0.90 | 0.030 | 0.030 | 3.00-3.50 | 1.30-1.80 | 0.35 |
Physical Properties
| Physical Properties | Metric | Imperial |
| Density | 7.76 g/cm3 | 0.280 lb/in3 |
| Coefficient of thermal expansion (CTE) | 12.6 μm/m·K (20-200 °C) | 7.0 μin./in.°F (70-400 °F) |
| 13.3 μm/m·K (20-425 °C) | 7.4 μin./in.°F (70-800 °F) | |
| 13.7 μm/m·K (20-500 °C) | 7.6 μin./in.°F (70-930 °F) | |
| 13.3 μm/m·K (20-200 °C) | 7.4 μin./in.°F (70-1200 °F) |
Mechanical Properties of S7 Steel
Nominal room-temperature mechanical properties of S7 steel
| Steel | Condition, Fan cooled from 940 °C (1725 °F) and single tempered at: | Tensile strength, MPa (ksi) | 0.2% yield strength, MPa (ksi) | Elongation in 2 in. (50mm), % | Reduction in area, % |
Hardness, HRC | Charpy unnotched impact, J (ft·lbf) |
| S7 | 205 °C (400 °F) | 2170 (315) | 1450 (210) | 7.0 | 20 | 58 | 244 (180) |
| 315 °C (600 °F) | 1965 (285) | 1585 (230) | 9.0 | 25 | 55 | 309 (228) | |
| 425 °C (800 °F) | 1895 (275) | 1410 (205) | 10.0 | 29 | 53 | 243 (179) | |
| 540 °C (1000 °F) | 1820 (264) | 1380 (200) | 10.0 | 33 | 51 | 324 (239) | |
| 650 °C (1200 °F) | 1240 (180) | 1035 (150) | 14.0 | 45 | 39 | 358 (264) | |
| Annealed | 640 (93) | 380 (55) | 25.0 | 55 | 95 HRB | – |
Heat Treat for S7 Shock-resisting Tool Steel
The heat treating of S7 tool steel is listed below.
Normalizing and Annealing Temperatures
- Normalizing: Do not normalize.
- Annealing: 815-845 °C (1500-1550 °F), the upper limit of the range should be used for large sections and the lower limit for smaller sections. Time held at temperature varies from 1 hour for light sections to 4 hours for heavy sections and large furnace charges of high alloy steel.
- Rate of cooling: ≤ 14 °C/h (25 °F/h)
- Annealed Brinell hardness: 187-223 HB.
S7 Material Hardening and Tempering
- Rate of heating: Slowly
- Hardening
- Preheat temperature 650-705 °C (1200-1300 °F);
- Austenitizing temperature 925-955 °C (1700-1750 °F)
- Time at temperature: 14-45 minutes for open furnace heat treatment
- Quenching medium: Air or oil
- Quenched Rockwell C hardness, 60-61 HRC
- Tempering temperature: 205-620 °C (400-1150 °F)
- Approximate tempered Rockwell C hardness: 45-57 HRC
Applications
S7 steel is primarily used for chisels, punches, rivet sets, stamps, screwdrivers and other applications that require high toughness and resistance to shock loads. Also used for hot punching and shearing where some heat resistance is required.
AISI S7 Steel Equivalent Material
AISI S7 steel equivalent material is listed in the table below, including European EN, ISO, German DIN, Chinese GB and Japanese JIS standard, etc.
| AISI S7 Tool Steel Equivalent Material | |||||||||||||||||||
| US | European Union | ISO | Germany | China | Japan | Australia | India | Rusia | Korea | ||||||||||
| Standard | Steel (UNS) | Standard | Steel Name (Material Number) | Standard | Designation | Standard | Steel Name (Material Number) | Standard | Steel Grade | Standard | Steel Grade | Standard | Grade | Standard | Grade | Standard | Grade | Standard | Grade |
| AISI, SAE; ASTM A681 |
S7 (T41907) | EN ISO 4957 | 5OCrMoV13-15 (1.2355) | ISO 4957 | 5OCrMoV13-15 | DIN EN ISO 4957; DIN 17350, |
5OCrMoV13-15 (1.2355) | GB/T 1299 | 5Cr3MnSiMo1V | – | – | ||||||||
