Bohler-Uddeholm,M238 VMR® P20 Plastic Lens Mold Steel Tube,Pipe

Bohler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel Tube Product Information -:- For detailed product information, please contact sales. -: Bohler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel Tube Synonyms -:- For detailed product information, please contact sales. -:

Bohler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel Product Information -:- For detailed product information, please contact sales. -: # **Böhler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel** ## **Product Overview** **Böhler-Uddeholm M238 VMR®** is a specialized **pre-hardened, chromium-nickel alloyed plastic mold steel** engineered specifically for the highest-demand optical applications, particularly **precision lens molds and components requiring exceptional surface finishes**. Supplied at a uniform pre-hardened state, this material combines the machinability advantages of P20-type steels with superior internal cleanliness and microstructure control achieved through **VMR® (Vacuum Melted and Remelted)** processing. Its optimized composition and advanced manufacturing ensure **outstanding polishability, excellent etching characteristics, and consistent isotropic properties** critical for producing optical-grade plastic components. --- ## **1. Key Characteristics & Advantages** * **Exceptional Polishability:** Capable of achieving ultra-high mirror finishes (SPI A-0/A-1, #0/#1 Diamond finish) without "orange peel" or pitting defects, essential for optical clarity. * **Superior Microstructural Cleanliness:** VMR® process ensures extremely low sulfur (<0.001%) and non-metallic inclusion content, directly translating to flawless polishing and etching performance. * **Excellent Photochemical Etching (Texturing) Performance:** The homogeneous, clean structure allows for precise, high-resolution texturing with sharp definition and consistency. * **Good Corrosion Resistance:** Provides adequate resistance to moisture and common coolants, protecting the mold surface during production and storage. * **Ready-to-Machine State:** Supplied pre-hardened (~30-33 HRC), eliminating heat treatment and associated distortion risks, while maintaining excellent machinability. * **High Dimensional Stability:** Excellent stability during machining and in service due to uniform properties and stress-relieved condition. * **Isotropic Properties:** Uniform behavior in all directions (longitudinal and transverse), ensuring predictable machining, polishing, and tool performance. --- ## **2. Typical Chemical Composition (Weight %)** | Element | Carbon (C) | Chromium (Cr) | Nickel (Ni) | Molybdenum (Mo) | Manganese (Mn) | Silicon (Si) | | :--- | :---: | :---: | :---: | :---: | :---: | :---: | | **Content** | **0.20 - 0.25** | **1.40 - 1.60** | **3.80 - 4.20** | **0.15 - 0.25** | **1.40 - 1.60** | **0.20 - 0.40** | **Alloying Rationale:** * **Nickel (4.0%):** The key differentiating element from standard P20. Promotes a tough, fine-grained microstructure with high impact strength and enhances polishability. * **Chromium (1.5%) & Molybdenum (0.2%):** Provide hardenability and strength in the pre-hardened state. * **Low Carbon (0.23%):** Optimized to balance machinability with sufficient hardness, while minimizing carbide banding that can interfere with polishing. * **VMR® Process:** Vacuum melting followed by vacuum arc remelting ensures exceptional purity, homogeneity, and a fine, uniform microstructure—the foundation of its optical-grade performance. --- ## **3. Physical & Mechanical Properties** ### **Physical Properties (at ~31 HRC):** * **Density:** ~7.85 g/cm³ * **Thermal Conductivity:** ~36 W/(m·K) at 20°C * **Modulus of Elasticity:** ~205 GPa * **Coefficient of Thermal Expansion:** ~12.8 x 10⁻⁶/K (20-100°C) ### **Mechanical Properties (Delivery Condition):** * **Hardness:** **290 - 330 HBW (30 - 34 HRC)** * **Tensile Strength:** ~1000 - 1150 MPa * **Yield Strength (0.2% offset):** ~850 - 950 MPa * **Elongation at Break:** ~12-15% * **Impact Strength (Charpy V):** **> 50 J** (Notably higher than standard P20 due to Ni content) * **Machinability Index:** ~85% (Excellent for its hardness level) --- ## **4. Primary Applications** M238 VMR® is exclusively designed for high-precision plastic molds where surface finish quality is paramount. * **Optical Component Molds:** * **Injection molds for precision lenses** (camera, smartphone, VR/AR, projector, microscope lenses). * **Light guides, diffusers, and reflectors** for LED lighting and displays. * **Transparent covers and windows** for medical devices and instruments. * **High-Gloss Surface Molds:** * **Consumer electronics housings** (laptops, tablets, televisions) requiring flawless Class-A surfaces. * **Automotive lens covers** (headlights, taillights, interior lighting). * **Cosmetic packaging** and premium consumer goods. * **Other Precision Components:** Master models, EDM electrodes for fine-featured cavities, and gauges requiring superior surface integrity. --- ## **5. Relevant International Standards & Comparable Grades** M238 is a proprietary Böhler-Uddeholm grade. Its composition aligns with a high-nickel variant within the P20 family but is distinguished by its VMR® quality level. | Standard | Grade / Designation | Country/Region | Similarity / Key Difference | | :--- | :--- | :--- | :--- | | **Proprietary (Böhler-Uddeholm)** | **M238 VMR®** | International | The reference optical-grade, Ni-alloyed P20 steel. | | **AISI / ASTM** | **P20+Ni (Modified)** | USA | Fits the "P20 Modified with Ni" category. M238 defines the premium standard within it. | | **DIN / Werkstoff** | **1.2738 (≈35CrNiMo6)** | Germany/EU | The common pre-hardened mold steel with Ni. M238 VMR® represents the highest quality tier of this classification with guaranteed optical properties. | | **JIS** | **PX5 / NAK55** | Japan | Japanese pre-hardened Ni-Cu-Al age-hardening steels. M238 is a through-hardening Cr-Ni-Mo steel with different metallurgy but similar application target (high polish). | | **Other Proprietary** | **IMPAX® Hi-Hard / SUPREME** | Uddeholm | Other premium pre-hardened steels; M238 is specifically optimized for optical polishability via its VMR® process and controlled chemistry. | **Critical Specification:** For optical applications, specifying **"M238 VMR®"** is essential to guarantee the material cleanliness and consistency required for defect-free high-polish results. --- ## **6. Processing & Fabrication Guidelines** * **Machining:** **Excellent machinability** in its pre-hardened state. Use sharp carbide tools. Its uniform structure provides predictable chip formation and good surface finishes directly from machining. * **Drilling & Tapping:** Performs very well. Standard practices apply. * **Grinding:** Straightforward. Use aluminum oxide wheels with standard parameters and adequate cooling. * **EDM (Sinker & Wire):** Performs exceptionally well due to its homogeneity. The fine, recast layer is typically easy to polish out. A light stress relief at 400-450°C post-EDM can be beneficial for critical optics. * **Polishing:** The core application strength. Begin with fine stone finishing (e.g., #600 grit) and progress systematically through diamond compounds (e.g., 15µm to 1µm or finer). The VMR® structure avoids the inclusion-related defects common in lower-grade steels. * **Photochemical Etching / Laser Texturing:** Delivers excellent, consistent results due to uniform material removal. * **Welding:** Good weldability for a pre-hardened steel. For repairs: * **Pre-heat:** 250 - 300°C. * **Filler Metal:** Use a soft, crack-resistant filler (e.g., AWS ER70S-6 or a proprietary mold repair wire). * **Post-Weld:** Temper immediately at 400 - 450°C and slow cool. * **Surface Hardening:** Can be nitrided to increase surface hardness (~700-900 HV) for enhanced wear resistance on parting lines or runner surfaces, though this is rarely needed for pure optical applications. --- ## **7. Conclusion** **Böhler-Uddeholm M238 VMR®** is not merely a mold steel; it is a **specialized optical manufacturing substrate**. Its development is focused on a single, critical outcome: enabling the production of plastic components with flawless optical surfaces. By integrating nickel alloying for toughness and, most importantly, the VMR® process for ultimate cleanliness, it solves the fundamental challenges of polishing and texturing high-precision molds. For molders of optical lenses, light guides, and any component where surface perfection directly defines product functionality and value, M238 VMR® is the definitive and necessary choice. It transforms the risk of polishing defects into a predictable, high-yield manufacturing process, ensuring that the mold material itself never limits the optical quality of the final part. -:- For detailed product information, please contact sales. -: Bohler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel Specification Dimensions Size： Diameter 20-1000 mm Length <6889 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 M238 VMR® P20 Plastic Lens Mold Steel Properties -:- For detailed product information, please contact sales. -:

Applications of Bohler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel Tube -:- For detailed product information, please contact sales. -: Chemical Identifiers Bohler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel Tube -:- For detailed product information, please contact sales. -:

Packing of Bohler-Uddeholm M238 VMR® P20 Plastic Lens Mold Steel Tube -:- 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 Tube 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 3360 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