What is S7 tool steel?
In tool steel standard ASTM A681, shock-resisting tool steels are designated as group S steels according to the AISI classification system. S1, S2, S5, S6, and S7 are the types of shock-resisting tool steels. AISI S7 tool steel is a shock-resistant air hardening steel. AISI S7 steel has exceptional impact properties plus the highest hardenability of shock resisting grades of tool steel. Steel S7 also possesses good softening resistance at high temperatures which gives it hot work capabilities. Since S7 steel hardens in air, it is also safe and stable in heat treatment.
AISI S7 tools steel has an unusual combination of properties, making it suitable for an extremely wide range of tool and die work – where shock-resistance, medium hot-work properties, or ease of machining and heat-treatment are most important.
Otai special steel is professional supplier of S7 tool steel materials as below range and technical requirements. We could supply AISI s7 Round Bar, S7 Drill Rod, S7 Rectangular Bar, S7 Flat Bar, S7 Square Bar and Plate. Welcome to contact us for more information and ask for a quick quote anytime.
1. Supply Range of AISI S7 Tool Steel
S7 Steel Round Bar: diameter 8mm – 1000mm
S7 Steel Plate: thickness 2mm –600mm x width 200mm – 2200mm
Other sizes of S7 steel per customer’s requirements
Surface Finish: Black, Rough Machined, Turned or as per given requirements.
Process: Hot rolled, Forged, Cold drawn etc.
2. Relevant Steel Specification for S7 Tool Steel
| Country | USA | German |
| Standard | ASTM A681 | DIN EN ISO 4957 |
| Grades | S7/T41907 | 1.2355/50CrMoV13-15 |
3. AISI S7 Steel Chemical Composition and Steel Equivalents
| ASTM A681-2008 | C | Si | Mn | P | S | Cr | V | Mo | ||||||
| S7/T41907 | 0.45 | 0.55 | 0.20 | 1.00 | 0.20 | 0.90 | 0.03 | 0.03 | 3.00 | 3.50 | – | 0.35 | 1.30 | 1.80 |
| DIN ISO 4957 | C | Si | Mn | P | S | Cr | V | Mo | ||||||
| 1.2355/50CrMoV13-15 | 0.45 | 0.55 | 0.20 | 0.80 | 0.50 | 0.90 | 0.03 | 0.02 | 3.00 | 3.50 | 0.15 | 0.35 | 1.30 | 1.70 |
4. S7 Tool Steel Mechanical Properties
S7 Steels Mechanical Properties
| Properties | Metric |
| Hardness, Rockwell C (air cooled from 941°C, 649°C temper temperature) | 41 |
| Hardness, Rockwell C (air cooled from 941°C, 449°C temper temperature) | 53 |
| Hardness, Rockwell C (air cooled from 941°C, 149°C temper temperature) | 57 |
| Modulus of elasticity | 207 GPa |
| Charpy impact (V-notch; air cooled from 941°C; 425°C temper temperature) | 13.6 J |
| Charpy impact (V-notch; air cooled from 941°C; 649°C temper temperature) | 16.3 J |
| Charpy impact (V-notch; air cooled from 941°C; 200°C temper temperature) | 16.9 J |
| Machinability (1% carbon steel) | 70.0 – 75.0% |
| Poisson’s ratio | 0.27-0.30 |
Tool Steel S7 Physical Properties
| Elastic Modulus | 207GPa | |
| Density | 7.83 g/cm³ | |
| Thermal Conductivity | W/m- °K | Cal/cm-s-°C |
| at 95°C | 28.5 | 0.068 |
| Thermal Properties | ||
| Critical Temperature: | 800c | |
| CTE, linear 20°C | 12.59µm/m- °C | |
| CTE, linear 250°C | 13.33µm/m- °C | |
| CTE,linear 500°C | 14.27µm/m- °C | |
| Transformation Temperature | 785 °C | |
5. Forging of AISI Steel S7
Preheat 1200°-1300°F. Forge at 2000°-2050°F. Stop at 1700°F and cool slowly.
6. AISI S7 Tool Steel Heat Treatment
Annealing
Anneal in a protective atmosphere. Heat rapidly to 1500 to 1550°F and hold at that temperature for one and one-half hours for each inch of greatest thickness. To obtain best machining properties, cool slowly to 1000°F, and then air-cool. This annealing procedure should produce a hardness of Brinell 197 max.
Stress Relief S7 steel Material: When desirable to relieve the strains of machining, heat slowly to 1050°-1250°F, allow to equalize, then cool in air.
Hardening
- Preheat: Warm steel S7 slightly before charging into the preheat furnace 1200°-1300°F, prior to hardening.
- Harden: 1750°F. Quench S7 tool steel in air if cross section is 2-1/2″ or smaller; sections 2-1/2″ to 6″ should be oil quenched to black (1000°F) followed by air cooling to 150°F. Larger cross sections of S7 steel should be oil quenched to 150°F.
- Quench: Quench in still air or dry air blast.
- Temper: Tool steel S7 is normally tempered one hour per inch of section thickness to desired heating rate of 2 hours per inch. Cool in air to room temperature between the two tempers. The tempering temperature varies according to the intended use. Suggested: For cold-working and similar applications, the recommend400°-500°F. Hot working applications: apply a tempering temperature of 900°-1000°F. Never temper at less than 400°F.
7. Machinability of Tool Steel S7
When S7 steel annealed to Brinell 197 max, steel S7 is rated at 95, as compared to a rating of 100 for a 1.00 pct carbon tool steel.
8. Applications of ASTM A681 S7 Tool Steel
Because of its unusual combination of properties, S7 tool steel is suitable and versatile for a wide range of tool and die applications. AISI S7 Steel can be used for hot and cold shock applications, medium hot-work dies and medium-run cold work tools and dies.
Other uses include: Bull Riveters, Concrete Breakers (Moll Points), Riveting Dies, Powder Metal Dies, Notching Dies, Dowels, Drills, Drill Plates, Hubs, Plastic Mold Dies, Cold Forming Dies, Blanking Dies, Bending Dies, engraving dies, machined cavities for plastic molding dies, die-casting dies, shear blades and Master Hobs.
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