S7 Shock-Resisting Tool Steel: Properties, Heat Treatment & Die Applications
ASTM A681 / UNS T41907 · Published: 2026-06-01 · Updated: 2026-06-02
S7 is an air-hardening shock-resisting tool steel with a unique combination of high impact toughness and moderate wear resistance. Unlike high-carbon cold-work steels (D2, A2) which are brittle when fully hardened, S7 retains Charpy V-notch...
S7 is an air-hardening shock-resisting tool steel with a unique combination of high impact toughness and moderate wear resistance. Unlike high-carbon cold-work steels (D2, A2) which are brittle when fully hardened, S7 retains Charpy V-notch impact values of 15-25 J even at 56-58 HRC — making it the preferred material for tooling subjected to impact loading. The air-hardening characteristic (critical cooling rate <5°C/min) means large sections can be hardened uniformly with minimal distortion — oil quenching is not required. Typical applications: chisels, punches, shear blades, pneumatic tool bits, rivet sets, bull riveters, and plastic mold components requiring impact resistance.
Heat treatment: austenitize at 930-955°C, soak 30 minutes per 25mm of section thickness, air cool (or oil quench for maximum hardness in large sections). Temper immediately after quenching — double temper at 200-300°C for 56-58 HRC (high hardness/ moderate toughness) or 400-500°C for 50-54 HRC (maximum toughness with lower hardness). Avoid tempering between 300-400°C — this range causes tempered martensite embrittlement (TME) and reduces impact toughness by 30-50%. S7 is not suitable for applications requiring wear resistance comparable to D2 or M2 — its chromium content (3.25%) is too low to form the hard M7C3 carbides that provide D2's wear resistance.
Quick Facts
| Category | Tool Steel |
| Standard | ASTM A681 / UNS T41907 |
| Density | 7750 kg/m³ |
| Yield Strength | 1,600-1,800 MPa (hardened & tempered) |
| Tensile Strength | 1,800-2,000 MPa |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| AISI S7 | Compare |
| UNS T41907 | Compare |
| EN 1.2355 50CrMoV13-15 | Compare |
Related Materials
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Frequently Asked Questions
What is the difference between S7 and H13 tool steel?
S7 is a shock-resisting steel optimized for impact toughness at room temperature — ideal for cold-work impact tools (chisels, punches, rivet sets). H13 is a hot-work steel optimized for strength and thermal fatigue resistance at elevated temperatures (up to 600°C) — ideal for die casting dies, extrusion dies, and hot forging tooling. S7 is not suitable for hot-work applications because its temper resistance is poor above 500°C. H13 is not suitable for cold-work impact applications because its impact toughness at room temperature is lower than S7.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu