Crucible Steel REX® M7N High Speed Steel, AISI M7

Crucible Steel REX® M7N High Speed Steel, AISI M7 Product Information -:- For detailed product information, please contact sales. -: Crucible Steel REX® M7N High Speed Steel, AISI M7 Synonyms -:- For detailed product information, please contact sales. -:

Crucible Steel REX® M7N High Speed Steel, AISI M7 Product Information -:- For detailed product information, please contact sales. -: # **Product Introduction: Crucible Steel REX® M7N High Speed Steel (AISI M7)** Crucible Steel REX® M7N is a premium, high-molybdenum, high-vanadium high-speed steel (HSS) that conforms to the AISI M7 specification. Positioned as a high-performance workhorse within the M-series, M7 is engineered to deliver an **exceptional balance of wear resistance, hot hardness (red hardness), and toughness**. It is distinguished by having one of the highest molybdenum contents among standard HSS grades, with a significant vanadium addition, making it a powerful and cost-effective alternative to more expensive tungsten-rich grades like M2 and M4 for many demanding applications. The "N" suffix may denote a specific melt practice or quality level within Crucible's production (e.g., normalized structure or controlled nitrogen content for refined grain). REX® M7N leverages molybdenum's efficiency as a hardenability and hot hardness agent, resulting in a steel that offers **superior abrasion resistance and edge retention compared to M2**, while maintaining better grindability and often better toughness than higher-vanadium grades like M3 or M4. It is a versatile choice for machining abrasive materials, high-strength alloys, and for tools requiring a durable cutting edge under both thermal and mechanical stress. --- ## **1. Chemical Composition (Weight %)** M7's composition is characterized by very high molybdenum and substantial vanadium, with moderate tungsten. | **Element** | **Carbon (C)** | **Molybdenum (Mo)** | **Vanadium (V)** | **Tungsten (W)** | **Chromium (Cr)** | **Cobalt (Co)** | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | **Content** | 1.00 - 1.10 | **8.20 - 9.20** | **1.70 - 2.20** | 1.40 - 2.10 | 3.50 - 4.50 | - | | **Role** | Provides the base for high hardness and carbide formation. Optimized level supports the high alloy content. | **Dominant alloying element.** Primary contributor to deep hardenability, hot hardness, and secondary hardening. A highly efficient strengthener. | **Key wear element.** Forms a high volume of hard vanadium carbides (VC), providing excellent abrasion resistance at the cutting edge. | Contributes to hot hardness and wear resistance; stabilizes the alloy system. | Ensures deep and uniform hardenability and provides oxidation resistance. | Not present in standard M7. (Separate cobalt grades like M42 exist). | *Note: Iron (Fe) constitutes the remainder. The high Mo/V ratio is a signature of M7, giving it unique characteristics.* --- ## **2. Physical & Mechanical Properties** *Typical properties after proper heat treatment to a working hardness of 64-66 HRC.* * **Density:** ~8.00 g/cm³ (0.289 lb/in³) – Slightly lower than tungsten-heavy M2 due to higher molybdenum content. * **Modulus of Elasticity:** ~215 GPa (31.2 x 10⁶ psi) * **Thermal Conductivity:** Moderate. * **Hot Hardness (Red Hardness):** **Very Good to Excellent.** Maintains high hardness at elevated temperatures (exceeding 550°C / 1020°F), enabling efficient high-speed machining. * **Hardness (Typical Working Range):** **63 - 67 HRC.** Most commonly used at **64-66 HRC**. * **Abrasion Resistance:** **Excellent.** Superior to M2 and comparable to M3-1, thanks to its significant vanadium carbide content. Provides excellent tool life in abrasive conditions. * **Toughness:** **Very Good for its wear resistance level.** Often cited as having better toughness than M2 at equivalent hardness, due to its fine-grained molybdenum-based carbide structure. It is generally tougher than M3 or M4, making it more resistant to chipping. * **Grindability:** **Fair to Good.** Generally better than M3 or M4 due to a more favorable carbide type and distribution, though more challenging than M1 or some M2 variants. --- ## **3. Heat Treatment** Precise heat treatment is essential to fully develop M7's balanced properties. * **Annealing:** Heat to 850-870°C (1560-1600°F), slow cool. Annealed hardness: 230-270 HB. * **Stress Relieving:** 600-650°C (1110-1200°F), hold, then slow cool. * **Preheating:** **Critical.** Use a double preheat: First at 540-650°C (1000-1200°F), then at 815-870°C (1500-1600°F). * **Austenitizing:** **1190-1220°C (2175-2230°F).** A common temperature is **1205°C (2200°F)**. The high molybdenum content provides excellent response at these temperatures. * **Quenching:** Air quench, salt bath quench, or controlled gas quench. * **Tempering:** **Mandatory Multiple Tempers.** Temper immediately after quenching. **Two to three tempers**, each for 2 hours, are standard. **Typical tempering range: 540-570°C (1000-1060°F).** Exhibits a pronounced secondary hardening response. * **Sub-Zero Treatment:** Commonly applied between quenching and tempering to maximize hardness and dimensional stability. --- ## **4. Key Applications** REX® M7N is a versatile high-performance HSS suitable for a wide range of demanding machining and tooling applications. * **General-Purpose High-Performance Cutting Tools:** Drills, taps, reamers, end mills, and milling cutters for machining alloy steels, stainless steels, and cast irons where longer tool life than M2 is required. * **Gear and Thread Manufacturing:** Hobs, shaper cutters, and thread mills for high-volume production. * **Cold Work Tooling for Tough Materials:** Punches, dies, and form tools for stainless steel and other high-strength alloys. * **Woodworking Tools for Abrasive Materials:** Knives and cutter heads for processed woods and composites. * **Wear Parts:** Components requiring a combination of high hardness, good wear resistance, and reasonable toughness. --- ## **5. International Standards & Cross-References** Crucible REX® M7N conforms to the AISI M7 specification. * **AISI/SAE:** **M7** * **UNS:** T11307 * **European (EN):** **HS 2-9-2** (This designation can broadly cover M1/M7 types; specific M7 composition aligns closely). * **Japanese (JIS):** **SKH 58** is a common equivalent for high-molybdenum, high-vanadium HSS like M7. * **ISO:** HS2-9-2 * **Common Trade Names:** M7 HSS, Molybdenum-Vanadium HSS. --- ## **6. Advantages & Limitations** **Advantages:** * **Excellent Wear & Toughness Balance:** Arguably offers one of the best practical balances of abrasion resistance and chipping resistance among standard HSS grades. * **High Hot Hardness:** Suitable for productive high-speed machining. * **Cost-Effective Performance:** Often provides better performance per dollar than tungsten-heavy grades like M2, especially where toughness is a factor. * **Good Grindability (Relative):** Easier to sharpen than M3 or M4, facilitating tool maintenance. * **Proven Reliability:** A well-established grade with predictable behavior. **Limitations:** * **Not the Ultimate in Wear Resistance:** Outperformed by higher-vanadium grades like M3 Class 2 or M4 in pure abrasive wear. * **Anisotropic Properties:** As a wrought steel, properties vary with direction. * **Requires Proper Heat Treatment:** Like all HSS, requires precise thermal processing for optimal results. * **Not for Extreme Temperatures:** For very high-temperature machining (e.g., superalloys), cobalt-bearing grades are superior. --- ## **7. Summary** **Crucible Steel REX® M7N is a highly capable and often underrated high-speed steel that delivers premium performance through intelligent chemistry.** By maximizing molybdenum and strategically employing vanadium, it achieves a synergy of wear resistance, hot hardness, and toughness that makes it an exceptionally versatile and reliable choice for severe-duty tooling. For manufacturers and toolmakers seeking to upgrade from M2 or navigate the selection between wear-centric and toughness-centric grades, M7N presents a compelling middle path. It is the high-performance workhorse for those who need a tool steel that can handle abrasion, heat, and intermittent cutting without being overly specialized or difficult to maintain. In many demanding applications, M7N is not just an alternative but the optimal choice. -:- For detailed product information, please contact sales. -: Crucible Steel REX® M7N High Speed Steel, AISI M7 Specification Dimensions Size： Diameter 20-1000 mm Length <6986 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. -: Crucible Steel REX® M7N High Speed Steel, AISI M7 Properties -:- For detailed product information, please contact sales. -:

Applications of Crucible Steel REX® M7N High Speed Steel, AISI M7 -:- For detailed product information, please contact sales. -: Chemical Identifiers Crucible Steel REX® M7N High Speed Steel, AISI M7 -:- For detailed product information, please contact sales. -:

Packing of Crucible Steel REX® M7N High Speed Steel, AISI M7 -:- 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 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 3457 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