JIS SKC31 Mold Steel Rod/Bar

JIS SKC31 Mold Steel Rod Product Information -:- For detailed product information, please contact sales. -: JIS SKC31 Mold Steel Rod Synonyms -:- For detailed product information, please contact sales. -:

JIS SKC31 Mold Steel Product Information -:- For detailed product information, please contact sales. -: ### **Product Technical Datasheet: JIS SKC31 Mold Steel** --- #### **1. Product Overview** **JIS SKC31** is a versatile **low-alloy, oil-hardening mold steel** specified under the Japanese Industrial Standard (JIS) G 4404. It is specifically formulated for the manufacture of **plastic injection molds, die-casting molds, and various cold-work tooling**. SKC31 offers an excellent balance of **good hardenability, moderate wear resistance, and superior machinability**, making it a highly cost-effective and popular choice for general-purpose mold applications. Its primary advantage lies in its ease of processing; it can be readily machined, polished, and heat-treated with standard workshop equipment, resulting in faster mold production cycles and lower overall manufacturing costs compared to high-alloy steels. --- #### **2. International Standard Cross-Reference** SKC31 is a widely recognized grade with direct or very close equivalents in most major international standards. | Standard System | Equivalent / Similar Grade | Note | | :--- | :--- | :--- | | **JIS G 4404 (Japan)** | **SKC31** | Defining Standard | | **AISI/SAE (USA)** | **P20** | The most common and direct equivalent for plastic mold applications. | | **DIN (Germany)** | **1.2311 / 40CrMnMo7** | Nearly identical composition and application. | | **BS (UK)** | **420M / 722M24** | Similar specification for mold steels. | | **ISO** | **35CrMo2 (Type 1)** | ISO designation for pre-hardened mold steel. | | **GB (China)** | **3Cr2Mo** | China's national equivalent to P20/SKC31. | --- #### **3. Chemical Composition (Typical, weight % per JIS G 4404)** The composition is characterized by a balanced addition of chromium, molybdenum, and manganese to ensure good hardenability and polishability. | Element | Carbon (C) | Silicon (Si) | Manganese (Mn) | Chromium (Cr) | Molybdenum (Mo) | Phosphorus (P) | Sulfur (S) | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | **Content (%)** | 0.28 - 0.40 | 0.20 - 0.40 | 1.30 - 1.70 | 1.40 - 1.80 | 0.30 - 0.50 | ≤ 0.030 | ≤ 0.030 | **Function of Key Alloying Elements:** * **Carbon (0.28-0.40%):** Provides a good balance of hardness and toughness in the quenched & tempered state. This medium-carbon level is ideal for mold cores and cavities. * **Chromium (1.40-1.80%):** Improves hardenability, contributes to wear resistance, and enhances corrosion resistance slightly. * **Molybdenum (0.30-0.50%):** Increases hardenability, reduces temper embrittlement, and promotes a fine grain structure for better toughness and polishability. * **Manganese (1.30-1.70%):** Primarily added to increase hardenability and ensure uniform through-hardening. --- #### **4. Physical & Mechanical Properties** * **Density:** ~7.85 g/cm³ * **Thermal Conductivity:** ~36-40 W/m·K (at 20°C). Moderate conductivity. * **Thermal Expansion Coefficient:** ~12.5 x 10⁻⁶ /K (20-200°C). * **Machinability (Pre-hardened State):** **Excellent.** SKC31/P20 is most commonly supplied **pre-hardened to ~290-330 HB (30-36 HRC)**, a condition ideal for direct machining of molds, eliminating the need for subsequent heat treatment by the mold maker. * **Hardenability:** **Very Good (Oil-Hardening).** Can be through-hardened in sections up to approximately 100mm. * **Polishing & Texturing:** **Very Good.** The homogeneous, fine-grained structure allows for superior surface finishes, essential for high-gloss plastic parts. * **Weldability:** **Good.** Can be repaired or modified using proper pre-heating and post-weld heat treatment procedures. * **Typical Hardness States:** * **Annealed:** ~ 200 HB Max * **Pre-hardened (Supplied Condition):** **30-36 HRC (290-330 HB)** * **Hardened & Tempered (Post-treatment):** Can be hardened to **50-55 HRC** for increased wear resistance if required. --- #### **5. Heat Treatment Guidelines** *Note: Most SKC31 is used in its supplied pre-hardened state. The following is for full heat treatment if required.* * **Forging:** Heat to 1100-900°C. Cool slowly. * **Annealing:** Heat to 780-820°C, slow furnace cool. Result: ≤ 200 HB. * **Hardening:** 1. **Preheat:** 650-700°C. 2. **Austenitizing:** **830-870°C.** 3. **Quench:** In **oil.** * **Tempering:** Temper immediately after quenching. The tempering temperature determines final hardness: * **For 50-55 HRC:** Temper at **400-500°C.** * **For 30-36 HRC (Typical Pre-hard):** Temper at **550-600°C.** --- #### **6. Product Applications** SKC31 (P20) is the **global industry standard** for a vast majority of plastic injection molds and many other tooling applications. * **Plastic Injection Molds:** **Cavities, cores, ejector pins, and mold bases** for manufacturing automotive parts, consumer goods, electronic housings, and general-purpose plastic components. * **Die-Casting Molds:** **Cavities and cores** for zinc, aluminum, and magnesium die-casting of non-severe applications. * **Compression & Transfer Molds:** For rubber and thermoset plastics. * **Master Models & Patterns:** For prototype development. * **General Tooling:** **Jigs, fixtures, and gauges** requiring good stability and machinability. * **Low-Stress Cold-Work Dies:** For bending and forming of sheet metal. --- #### **7. Advantages & Limitations** | Advantages | Limitations | | :--- | :--- | | • **Outstanding machinability** in pre-hardened state, reducing lead time and cost.
• **Excellent polishability and texturing capability** for high-surface-finish molds.
• **Good overall toughness** to withstand mold clamping forces and moderate impact.
• **Good weldability** for mold repairs and modifications.
• **Excellent dimensional stability** during and after machining.
• **Widely available** and cost-effective. | • **Moderate wear resistance** compared to high-hardness tool steels (e.g., D2, H13). Not suitable for highly abrasive plastics or long production runs without surface hardening.
• **Limited corrosion resistance** for processing PVC or other corrosive materials; often requires plating or use of corrosion-resistant grades (e.g., SUS420).
• **Moderate hot strength**; for high-temperature or high-cycle die-casting, hot-work steels (e.g., SKD61) are preferred. | --- #### **8. Selection Guidance** * **Choose SKC31/P20 when:** Manufacturing **general-purpose plastic injection molds** for commodities, engineering plastics (like ABS, PP, PE, PC), and where **fast machining, polishing, and cost-effectiveness** are primary drivers. * **Consider an upgrade when:** * **High Abrasion/Wear:** For glass-filled plastics or massive production → Use **hardened tool steels (SKS3, SKD11)** or apply **surface treatments** (nitriding) to SKC31. * **High Temperature/Cycling:** For hot-runner systems or die-casting → Use **hot-work steels (SKD61/H13).** * **Corrosion:** For PVC or acidic materials → Use **corrosion-resistant steels (SUS420J2/Stavax).** **Conclusion:** JIS SKC31 is the **cornerstone material of the global mold-making industry.** Its perfect balance of **processability, performance, and price** makes it the undisputed first choice for the majority of plastic injection molds. By being supplied in a readily machinable, pre-hardened condition, it enables efficient and predictable mold manufacturing. For any application where its wear and corrosion limits are not exceeded, SKC31 (P20) delivers **proven reliability, excellent surface quality, and optimal value**, solidifying its status as the workhorse of mold steels. -:- For detailed product information, please contact sales. -: JIS SKC31 Mold Steel Specification Dimensions Size： Diameter 20-1000 mm Length <6798 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. -: JIS SKC31 Mold Steel Properties -:- For detailed product information, please contact sales. -:

Applications of JIS SKC31 Mold Steel Rod -:- For detailed product information, please contact sales. -: Chemical Identifiers JIS SKC31 Mold Steel Rod -:- For detailed product information, please contact sales. -:

Packing of JIS SKC31 Mold 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 3269 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