Bohler-Uddeholm,BÖHLER S400(M7) High Speed Steel Rod/Bar

Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Rod Product Information -:- For detailed product information, please contact sales. -: Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Rod Synonyms -:- For detailed product information, please contact sales. -:

Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Product Information -:- For detailed product information, please contact sales. -: # **Böhler-Uddeholm BÖHLER S400 (M7) High Speed Steel** ## **Product Overview** **BÖHLER S400** is a high-performance **molybdenum-tungsten-vanadium alloyed high-speed steel** conforming to the AISI M7 specification. As an intermediate-grade high-speed steel, it bridges the performance gap between standard M2-type steels and premium high-vanadium/cobalt grades. S400 is engineered to provide an **excellent balance of wear resistance, toughness, and grindability**, making it a versatile and cost-effective choice for a wide range of cutting tools and wear components that demand higher performance than M2 but do not require the extreme hot hardness of cobalt-bearing grades. --- ## **1. Key Characteristics & Advantages** * **Excellent Balance of Wear Resistance and Toughness:** Offers superior abrasive wear resistance compared to M2 due to higher vanadium content, while maintaining good toughness for shock resistance. * **Good Hot Hardness (Red Hardness):** Maintains cutting edge integrity at elevated temperatures typical of high-speed machining operations. * **Favorable Grindability:** Exhibits better grinding characteristics than higher-vanadium steels like M4 or M42, simplifying tool fabrication and resharpening. * **Good Through-Hardening Capability:** Can be uniformly hardened in substantial sections, ensuring consistent properties in larger tools. * **Cost-Effective Performance:** Provides a significant performance upgrade over M2 at a lower cost premium than cobalt or high-vanadium super high-speed steels. * **Versatile Application Range:** Suitable for both cutting and selected cold work applications. --- ## **2. Typical Chemical Composition (Weight %)** | Element | Carbon (C) | Tungsten (W) | Molybdenum (Mo) | Chromium (Cr) | Vanadium (V) | | :--- | :---: | :---: | :---: | :---: | :---: | | **Content** | **0.97 - 1.05** | **1.40 - 2.10** | **8.20 - 9.20** | **3.50 - 4.00** | **1.75 - 2.25** | **Alloying Rationale:** * **High Molybdenum (8.7%):** The primary alloying element, providing strong secondary hardening, good hardenability, and contributing to the steel's hot hardness at a lower cost than equivalent tungsten content (the "molybdenum equivalent" principle). * **Vanadium (2.0%):** Increased compared to M2 (~1.0%). Forms hard vanadium carbides (VC) that significantly improve abrasive wear resistance. * **Tungsten (1.75%):** Works synergistically with molybdenum to enhance hot hardness and tempering resistance. * **Chromium (3.75%):** Provides hardenability and contributes to wear resistance. * **Carbon (~1.0%):** Balanced to form sufficient carbides with vanadium and other elements without compromising toughness excessively. --- ## **3. Physical & Mechanical Properties** ### **Physical Properties:** * **Density:** ~8.10 g/cm³ * **Thermal Conductivity:** ~26 W/(m·K) at 20°C * **Modulus of Elasticity:** ~215 GPa * **Coefficient of Thermal Expansion:** ~11.3 x 10⁻⁶/K (20-400°C) ### **Heat Treatment & Mechanical Data:** * **Annealed Hardness:** ~240 HBW (max) * **Austenitizing Temperature:** 1190 - 1210°C (2175 - 2210°F) * **Quenching Medium:** Salt bath, vacuum/pressurized gas, or oil. * **Tempering:** **Double tempering is essential.** Temperature range: 540 - 580°C (1005 - 1075°F). * **Achievable Hardness:** **64 - 66 HRC** * Typical operating hardness is **64-65 HRC** after tempering at 550-560°C. * **Hot Hardness (600°C):** ~55-57 HRC * **Transverse Rupture Strength:** ~3000 - 3300 MPa * **Impact Toughness:** Good for its wear resistance level; better than M4 at equivalent hardness. --- ## **4. Primary Applications** BÖHLER S400 (M7) is well-suited for a broad spectrum of cutting and wear applications requiring a step up from M2 performance. * **Cutting Tools:** * **End mills, drills, and reamers** for machining alloy steels, stainless steels, and cast iron. * **Gear hobs and shaper cutters** for general gear manufacturing. * **Broaches** and form tools. * **Saw blades** and milling cutters. * **Cold Work Tooling:** * **Punches and dies** for cold forming and blanking of medium-strength materials. * **Thread rolling dies** for standard fastener production. * **Wear Parts:** Components such as guides, bushings, and wear plates in machinery. --- ## **5. Relevant International Standards & Comparable Grades** BÖHLER S400 is the Böhler-Uddeholm designation for AISI M7 high-speed steel. | Standard | Grade / Designation | Country/Region | Note | | :--- | :--- | :--- | :--- | | **AISI / ASTM A600** | **M7** | USA | Direct equivalent. | | **ISO 4957** | **HS2-9-2** | International | Corresponding ISO designation (approx. 2%W, 9%Mo, 2%V). | | **DIN / Werkstoff** | **~1.3348** | Germany/EU | Not a direct 1:1 in DIN; often grouped with M2 variants or specified by chemistry. | | **JIS G4403** | **SKH59** | Japan | The Japanese M7 equivalent (note: SKH9 is M2, SKH55 is M35). | | **Comparable Grades** | **M2 (High-Vanadium Variant)** | N/A | S400/M7 has systematically higher Mo and V than standard M2. | | **Performance Position** | Between **M2** and **M4** | N/A | Offers more wear resistance than M2, less than M4; generally tougher than M4. | --- ## **6. Processing & Fabrication Guidelines** * **Supply Form:** Round bars, square bars, and flat stock. * **Machining:** Machine in the soft-annealed condition. Use sharp carbide tools. The higher vanadium content makes it slightly more abrasive to machine than M2. * **Grinding:** **Good grindability for a high-speed steel.** Easier to grind than M4 or high-cobalt grades. Use aluminum oxide or CBN wheels with adequate cooling. * **EDM:** Suitable. Follow with a stress-relieving temper (e.g., 500-550°C) to mitigate the transformed surface layer. * **Heat Treatment:** Requires controlled atmosphere or vacuum heat treatment to prevent decarburization. 1. **Preheating:** 800-850°C and 1050-1100°C is recommended. 2. **Austenitizing:** Temperature control is critical for optimal properties. 3. **Quenching:** Oil, salt bath, or pressurized gas quenching are all applicable. 4. **Tempering:** **Double temper immediately after quenching.** A third temper can be beneficial for dimensional stability. * **Surface Treatment:** Responds well to standard PVD coatings (TiN, TiCN, TiAlN) which further enhance performance for cutting tools. --- ## **7. Conclusion** **BÖHLER S400 (M7)** is a strategically important **workhorse high-speed steel** that offers a **practical and economical performance upgrade** from the ubiquitous M2 grade. Its balanced alloy design—featuring high molybdenum for hot hardness and a meaningful increase in vanadium for wear resistance—makes it an exceptionally versatile material for both toolmakers and end-users. For applications where M2 tools show excessive wear but the jump to more expensive, harder-to-grind grades like M4 or cobalt steels is not justified, S400 provides the ideal solution. It extends tool life, improves productivity in demanding cutting operations, and maintains good manufacturability. It represents a smart, cost-effective choice for a wide range of industrial cutting and wear applications, solidifying its position as a reliable and high-value grade in the high-speed steel family. -:- For detailed product information, please contact sales. -: Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Specification Dimensions Size： Diameter 20-1000 mm Length <6902 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. -: Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Properties -:- For detailed product information, please contact sales. -:

Applications of Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Rod -:- For detailed product information, please contact sales. -: Chemical Identifiers Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Rod -:- For detailed product information, please contact sales. -:

Packing of Bohler-Uddeholm BÖHLER S400(M7) High Speed Steel Rod -:- 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 Rod 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 3373 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