Bohler-Uddeholm,BÖHLER M261 Extra Plastic Lens Mold Steel Sheet,Plate

Bohler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel Sheet/Plate Product Information -:- For detailed product information, please contact sales. -: Bohler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel Sheet/Plate Synonyms -:- For detailed product information, please contact sales. -:

Bohler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel Product Information -:- For detailed product information, please contact sales. -: # **Böhler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel** ## **Product Overview** **BÖHLER M261 Extra** is a premium **nickel-aluminum-copper precipitation hardening mold steel** specifically engineered for **high-precision optical lens molds and components requiring exceptional surface integrity**. This material represents a significant advancement in mold steel technology, combining the manufacturing advantages of pre-hardened steels with metallurgical characteristics optimized for ultra-high polishability. Through its unique age-hardening mechanism, M261 Extra achieves superior **microstructural homogeneity, outstanding polishability, and excellent dimensional stability** without requiring conventional quenching operations. --- ## **1. Key Characteristics & Advantages** * **Ultimate Polishability:** Engineered specifically for achieving optical-grade mirror finishes (SPI A-0 standard and beyond) without micro-pitting or directional polishing lines. * **Exceptional Microstructural Homogeneity:** Produces flawlessly uniform surfaces under high-magnification inspection, critical for lens molding applications. * **Age-Hardening Mechanism:** Achieves final hardness through low-temperature aging (approximately 500-550°C) after machining, minimizing distortion and eliminating quench-related stresses. * **Superior Etching Performance:** Provides excellent results for photochemical etching and laser texturing due to its fine, consistent microstructure. * **Good Corrosion Resistance:** Offers better resistance to cooling water and atmospheric corrosion than standard P20-type steels. * **High Dimensional Stability:** Exhibits minimal size change during aging treatment (typically <0.05%), enabling precision machining of complex optical geometries. * **Isotropic Properties:** Uniform mechanical characteristics in all directions ensure consistent polishing and predictable tool performance. --- ## **2. Typical Chemical Composition (Weight %)** | Element | Carbon (C) | Nickel (Ni) | Aluminum (Al) | Copper (Cu) | Manganese (Mn) | Silicon (Si) | | :--- | :---: | :---: | :---: | :---: | :---: | :---: | | **Content** | **≤ 0.03** | **3.80 - 4.20** | **1.00 - 1.30** | **1.30 - 1.70** | **0.40 - 0.70** | **0.10 - 0.40** | **Alloying Rationale:** * **Ultra-Low Carbon (≤0.03%):** Minimizes carbide formation, eliminating potential polishing defects and ensuring excellent weldability. * **Nickel (4.0%) & Aluminum (1.15%):** Form the primary precipitation hardening system through Ni₃Al intermetallic phases during aging treatment. * **Copper (1.50%):** Provides additional precipitation hardening through copper-rich phases and enhances corrosion resistance. * **"Extra" Quality Designation:** Indicates superior melting practice (typically vacuum or electro-slag refined) ensuring exceptional cleanliness and homogeneity. --- ## **3. Physical & Mechanical Properties** ### **Physical Properties:** * **Density:** ~7.8 g/cm³ * **Thermal Conductivity:** ~30 W/(m·K) at 20°C * **Modulus of Elasticity:** ~190 GPa * **Coefficient of Thermal Expansion:** ~11.2 × 10⁻⁶/K (20-100°C) ### **Processing & Mechanical Data:** * **Solution Annealed Condition (Delivery):** ~30 HRC (285-320 HBW) * **Machining State:** All heavy machining, EDM, and texturing should be completed in the solution annealed condition. * **Aging Treatment:** 500-550°C (930-1020°F) for 4-8 hours (depending on section size), air cool. * **Final Hardness (Aged):** **40-44 HRC** (Typical operating range for optical applications) * **Tensile Strength:** ~1300-1400 MPa (after aging) * **Yield Strength (0.2%):** ~1100-1200 MPa (after aging) * **Impact Toughness:** Excellent, typically >40 J (Charpy V) * **Dimensional Change:** Typically +0.03% to +0.05% after aging --- ## **4. Primary Applications** M261 Extra is exclusively designed for the most demanding optical and high-surface-quality applications: * **Precision Optical Components:** * **Injection molds for camera lenses** (DSLR, smartphone, surveillance, medical imaging) * **VR/AR optical elements and waveguide molds** * **Projector lenses and micro-optics** * **Laser optics and light guide components** * **High-Definition Surface Applications:** * **OLED display covers and optical films** * **Precision optical gratings and diffractive elements** * **Medical diagnostic device windows** * **Aerospace transparent components** * **Master Models & Electrodes:** For producing ultra-precision EDM electrodes and replication masters. --- ## **5. Relevant International Standards & Comparable Grades** M261 Extra is a proprietary Böhler-Uddeholm grade with unique metallurgical characteristics: | Standard | Grade / Designation | Similarity / Key Difference | | :--- | :--- | :--- | | **Proprietary** | **BÖHLER M261 Extra** | Reference optical-grade precipitation hardening steel | | **AISI/UNS** | **Custom 630 (17-4PH)** | Similar precipitation hardening mechanism but different composition; M261 has optimized polishability | | **Japanese** | **NAK80** | Similar application area but different hardening mechanism (age-hardening vs. precipitation hardening) | | **European** | **1.2709** | Similar ultra-high polishability grade but different metallurgical approach | | **Other Optical Grades** | **M238 VMR®** | Conventional pre-hardened steel; M261 offers superior polishability through precipitation hardening | **Quality Distinction:** The "Extra" designation indicates premium quality with guaranteed optical performance characteristics not found in standard mold steels. --- ## **6. Processing & Fabrication Guidelines** ### **Machining & Fabrication:** 1. **Complete Machining:** Perform all machining, drilling, and EDM in solution annealed condition (~30 HRC) 2. **Aging Treatment:** Conduct aging ONLY after all machining operations are complete 3. **Final Finishing:** Execute polishing and ultra-fine finishing after aging treatment ### **Critical Processing Parameters:** * **Machining:** Use sharp carbide tools with positive rake angles * **EDM:** Standard parameters apply; fine-finish EDM recommended for optical surfaces * **Aging Cycle:** 520°C ±10°C for optimal results * **Polishing Protocol:** - Begin with #600 diamond stone - Progress through 15µm, 9µm, 3µm, 1µm diamond compounds - Final polish with 0.5µm or finer diamond suspension * **Cleaning:** Ultrasonic cleaning between polishing stages is essential * **Handling:** Use lint-free gloves and cleanroom protocols for final handling ### **Special Considerations:** * **Welding:** Excellent weldability using matching filler materials * **Stress Relieving:** Not required due to low-temperature aging process * **Storage:** Protect machined surfaces from corrosion during processing --- ## **7. Technical Advantages for Optical Applications** ### **Surface Quality Metrics:** * **Surface Roughness:** Capable of achieving Ra < 0.01 µm * **Waviness:** Minimal surface waviness due to homogeneous structure * **Defect Density:** Extremely low micro-pitting and inclusion-related defects ### **Optical Performance:** * **Light Scatter:** Minimal scattering due to surface perfection * **Image Distortion:** Negligible distortion from mold surface irregularities * **Consistency:** Uniform results across multiple cavities and production runs --- ## **8. Conclusion** **BÖHLER M261 Extra** represents the pinnacle of optical mold steel technology, specifically engineered to meet the exacting requirements of modern precision optics manufacturing. Its unique precipitation hardening mechanism, combined with exceptional microstructural homogeneity, provides mold makers with an unparalleled material for producing optical components with perfect surface characteristics. For applications where surface quality directly determines optical performance—such as smartphone camera lenses, AR/VR optics, and precision optical systems—M261 Extra offers a fundamental advantage over conventional mold steels. Its ability to achieve and maintain optical-grade surfaces through extended production runs makes it the material of choice for manufacturers seeking to push the boundaries of optical component quality and performance. The material's predictable behavior during processing, combined with its exceptional final properties, ensures that optical mold makers can achieve consistent, high-quality results while minimizing production risks and maximizing tool longevity. -:- For detailed product information, please contact sales. -: Bohler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel Specification Dimensions Size： Diameter 20-1000 mm Length <6890 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 M261 Extra Plastic Lens Mold Steel Properties -:- For detailed product information, please contact sales. -:

Applications of Bohler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel Sheet,Plate -:- For detailed product information, please contact sales. -: Chemical Identifiers Bohler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel Sheet,Plate -:- For detailed product information, please contact sales. -:

Packing of Bohler-Uddeholm BÖHLER M261 Extra Plastic Lens Mold Steel Sheet/Plate -:- 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 Sheet/Plate 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 3361 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