AISI Type S7 Tool Steel Wire (UNS T41907)

AISI Type S7 Tool Steel Wire (UNS T41907) Product Information -:- For detailed product information, please contact sales. -: AISI Type S7 Tool Steel Wire (UNS T41907) Synonyms -:- For detailed product information, please contact sales. -:

AISI Type S7 Tool Steel (UNS T41907) Product Information -:- For detailed product information, please contact sales. -: # **Product Introduction: AISI Type S7 Tool Steel (UNS T41907)** ## **Overview** **AISI S7 (UNS T41907)** is the premier **chromium-molybdenum air-hardening shock-resisting tool steel**, renowned worldwide for its **exceptional combination of high toughness and good wear resistance**. It represents the pinnacle of modern shock steel technology, offering **superior impact resistance, excellent dimensional stability during heat treatment, and reliable performance**. S7 is the benchmark against which other shock-resistant steels are measured, making it the first choice for the most demanding cold work applications where tools must withstand brutal impact without chipping or cracking. ## **1. Chemical Composition (Nominal %)** S7's chemistry is a masterful balance for achieving supreme toughness through air hardening. | Element | Content (%) | Primary Function | |---------|------------|------------------| | **Carbon (C)** | 0.45 - 0.55 | Provides the foundation for hardness and strength. Optimized to maximize toughness at high hardness levels. | | **Chromium (Cr)** | 3.00 - 3.50 | **Key element.** Provides deep hardenability for air hardening, improves wear resistance, and contributes to toughness. | | **Molybdenum (Mo)** | 1.30 - 1.80 | **Key element.** Dramatically increases hardenability, refines grain structure, and is a potent toughening agent. Critical for the air-hardening capability and high impact strength. | | **Silicon (Si)** | 0.20 - 0.35 | Provides solid solution strengthening and improves toughness. Kept moderate to optimize machinability and prevent decarburization issues. | | **Vanadium (V)** | ≤ 0.25 | Grain refiner; improves wear resistance and toughness by inhibiting grain growth. | | **Manganese (Mn)** | 0.20 - 0.90 | Supports hardenability and works as a deoxidizer. | | **Iron (Fe)** | Balance | Base metal. | **Key Chemistry Note:** The **synergistic combination of chromium (~3.25%) and molybdenum (~1.50%)** is the heart of S7. This duo provides exceptional **air hardenability**, allowing full hardening of large sections with minimal distortion and quench cracking risk. Molybdenum is particularly effective in promoting a fine, tough martensitic microstructure. The **moderate carbon content** is precisely tuned to deliver hardness in the mid-50s HRC range where toughness is maximized. ## **2. Physical & Mechanical Properties** *Typical properties in the hardened and tempered condition (54-57 HRC).* | Property | Typical Value / Condition | |----------|--------------------------| | **Density** | 7.80 g/cm³ (0.282 lb/in³) | | **Melting Point** | ~1515°C (2760°F) | | **Thermal Conductivity** | ~42 W/m·K (Moderate) | | **Coefficient of Thermal Expansion** | 11.5 × 10⁻⁶/K (20-100°C) | | **Modulus of Elasticity** | 205 GPa (29.7 × 10⁶ psi) | | **Annealed Hardness** | 192-229 HB | | **As-Quenched Hardness (Air)** | ~58-60 HRC | | **Hardened & Tempered Hardness** | **54-57 HRC** (The **optimum working range** for S7, where it exhibits its legendary toughness). | | **Tensile Strength** | ~1850-2000 MPa (268-290 ksi) at 56 HRC | | **Yield Strength (0.2% Offset)** | ~1650-1800 MPa (239-261 ksi) | | **Elongation** | ~12-14% | | **Reduction of Area** | ~35-45% | | **Impact Toughness (Charpy V-Notch)** | **Outstanding.** Typically **90-130 J (66-96 ft-lbf)** at 56 HRC. **This is among the highest impact resistance of any commercially available tool steel.** | | **Wear Resistance** | **Good.** Adequate for most impact tool applications; superior to S5. | | **Machinability (Annealed)** | Fair (approx. 55% of 1% carbon steel baseline). | | **Grindability** | Good. | | **Dimensional Stability** | **Excellent.** Minimal distortion and size change during air quenching. | ## **3. International Standards & Cross-References** S7 is a globally recognized and standardized premium grade. | Standard | Designation | |----------|------------| | **UNS** | T41907 | | **AISI/ASTM (USA)** | S7 (ASTM A681) | | **ISO (International)** | **~50CrMoV12-1** (ISO 4957: Tool steels) – A close functional match. | | **DIN (Germany)** | **1.2550** | | **BS (UK)** | **BS7** | | **JIS (Japan)** | **SKS8** (Note: SKS8 is similar but not always an exact 1:1 match). | | **GB (China)** | **5Cr3NiMoSiV** (A close equivalent, reflecting the Cr-Mo-V system) | | **Common Name** | **Chromium-Molybdenum Air-Hardening Shock Steel** | ## **4. Product Applications** S7 is the **go-to material** for critical applications where tool failure due to chipping or fracture is unacceptable. **Primary Applications:** * **Heavy-Duty Punching and Shearing:** * **Punches** and **dies** for cold forging, stamping, and hole punching in thick plate. * **Shear blades** for steel plate, bars, and structural shapes. * **Bolt cutters** and **cable cutters**. * **Chisels and Impact Tools:** * **Cold chisels** and **masonry chisels** for severe service. * **Demolition tool bits** (chipping hammers, scaling hammers). * **Driver bits** for high-torque impact wrenches. * **Die Casting and Forging Tooling:** * **Ejector pins**, **core pins**, and **inserts** for aluminum die casting (benefiting from its heat check resistance). * **Hot work chisels** and **hot punches** (for moderate temperatures). * **Plastic Injection Molds:** * **Mold components** subject to high impact or clamping stress, such as **interlocks**, **wear plates**, and **ejector sleeves**. * **Knives and Blades:** * **Severe-duty slitter knives** and **industrial cutting blades**. ## **5. Heat Treatment Guidelines** S7's air-hardening characteristic makes its heat treatment forgiving and reproducible. * **Annealing:** Heat to 815-845°C (1500-1550°F), slow furnace cool. Annealed hardness: 192-229 HB. * **Hardening:** 1. **Preheating:** Preheat to **650-700°C (1200-1290°F)**. This step is still important to minimize thermal stress, even for air hardening. 2. **Austenitizing:** Heat to **925-955°C (1695-1750°F)**. A common target is **940°C (1725°F)**. Soak for 30-45 minutes per inch of cross-section. 3. **Quenching:** **Cool in still or forced air.** For maximum hardenability in very thick sections (>6 inches), oil quenching can be used but is rarely necessary and increases distortion. * **Tempering (Critical for S7's Performance):** * **Temper immediately** after reaching near room temperature. * To achieve the optimal toughness-hardness balance (54-57 HRC), temper at **315-455°C (600-850°F)**. * **Double tempering is standard practice.** Hold for 2 hours per inch minimum per temper. This ensures complete stress relief and microstructure stabilization. * S7 exhibits a **strong secondary hardening peak** around **510-540°C (950-1000°F)**. Tempering in this range can achieve hardness up to ~58 HRC with still-excellent toughness, but the classic 54-57 HRC range is preferred for maximum impact resistance. ## **6. Key Advantages & Why It's the Benchmark** * **Unmatched Toughness at Usable Hardness:** Delivers the highest impact resistance in its class at a hardness (54-57 HRC) that provides excellent strength and moderate wear resistance. * **Air Hardening:** Provides **minimal distortion, excellent dimensional stability, and virtually no risk of quench cracking**. This simplifies tool design and reduces finishing costs. * **Consistent & Reproducible:** Heat treatment is less critical than with water- or oil-hardening grades, leading to more reliable results in production. * **Versatile Performer:** Excels in both cold work and moderate hot work applications. **Conclusion:** AISI S7 is the **definitive shock-resisting tool steel** for engineers and toolmakers who cannot afford failure. Its unparalleled combination of extreme toughness, dimensional stability, and good overall performance makes it the **first and most reliable choice** for the world's most demanding punching, shearing, and impact applications. While other steels may excel in one specific property, S7's balanced excellence across the board has secured its status as an industry standard for severe-duty tooling. --- **Disclaimer:** Although S7 is air hardening, proper preheating and controlled austenitizing are still essential for optimal properties and to prevent thermal shock. While its tempering response is wide, following the recommended ranges (especially double tempering) is critical to achieving its legendary toughness. For applications involving very high temperatures (>540°C / 1000°F), hot-work steels like H13 may be more appropriate. S7 is a premium material, and its cost is justified by its performance and reliability in critical applications. -:- For detailed product information, please contact sales. -: AISI Type S7 Tool Steel (UNS T41907) Specification Dimensions Size： Diameter 20-1000 mm Length <6764 mm Size:We can customized as required Standard： Per your request or drawing We can customized as required Properties（Theoretical） Chemical Composition -:- For detailed product information, please contact sales. -: AISI Type S7 Tool Steel (UNS T41907) Properties -:- For detailed product information, please contact sales. -:

Applications of AISI Type S7 Tool Steel Wire (UNS T41907) -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI Type S7 Tool Steel Wire (UNS T41907) -:- For detailed product information, please contact sales. -:

Packing of AISI Type S7 Tool Steel Wire (UNS T41907) -:- For detailed product information, please contact sales. -: Standard Packing: -:- For detailed product information, please contact sales. -: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and Steel Wire drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3235 gallon liquid totes Special package is available on request. E FORUs’ is carefully handled to minimize damage during storage and transportation and to preserve the quality of our products in their original condition