JIS SKS7M Oil-Hardening Cold Work Tool Steel Rod/Bar

JIS SKS7M Oil-Hardening Cold Work Tool Steel Rod Product Information -:- For detailed product information, please contact sales. -: JIS SKS7M Oil-Hardening Cold Work Tool Steel Rod Synonyms -:- For detailed product information, please contact sales. -:

JIS SKS7M Oil-Hardening Cold Work Tool Steel Product Information -:- For detailed product information, please contact sales. -: # **JIS SKS7M Oil-Hardening Cold Work Tool Steel** **International Standard:** JIS G4404 (Japan Industrial Standard) - Tool Steels --- ## **1. Overview** JIS SKS7M is an **improved-machinability variant of the SKS7 oil-hardening cold work tool steel**, incorporating controlled sulfur addition to significantly enhance machining characteristics while retaining the core balanced properties of the base SKS7 grade. Characterized by its **excellent free-machining properties in the annealed state combined with the tungsten-enhanced wear resistance and dimensional stability of oil-hardening steel**, SKS7M is specifically engineered for manufacturing complex tooling components that require extensive machining operations prior to heat treatment. The "M" designation indicates enhanced machinability, making this steel particularly valuable for intricate dies, molds, and precision tools where machining efficiency and dimensional control are paramount. --- ## **2. Chemical Composition (Typical Weight %)** | Element | Content (%) | | :------ | :---------- | | C | 0.90–1.00 | | Si | 0.15–0.35 | | Mn | 0.90–1.20 | | Cr | 0.50–1.00 | | W | 1.00–1.50 | | V | 0.10–0.25 | | S | 0.08–0.15 | | Mo | ≤ 0.30 | | P (max) | 0.030 | | Ca (optional) | 0.001–0.005 | **Balance:** Iron (Fe). **Key Characteristics:** - **Controlled sulfur addition (0.08–0.15%)** creates manganese sulfide (MnS) inclusions that act as internal chip breakers - **Tungsten content (1.00–1.50%)** provides enhanced wear resistance through tungsten carbide formation - **Medium-high carbon (0.90–1.00%)** ensures good hardenability and wear resistance - **Balanced chromium (0.50–1.00%)** contributes to hardenability without compromising machinability excessively - **Vanadium (0.10–0.25%)** refines grain structure during heat treatment --- ## **3. Physical & Mechanical Properties** ### **Physical Properties** - **Density:** ~7.83 g/cm³ (slightly reduced due to sulfide inclusions) - **Thermal Conductivity:** ~41 W/m·K (at 20°C) - **Coefficient of Thermal Expansion:** ~12.3 ×10⁻⁶ /K (20–200°C) - **Specific Heat Capacity:** ~0.46 kJ/kg·K - **Modulus of Elasticity:** ~210 GPa (anisotropic: higher in longitudinal direction) - **Magnetic Properties:** Ferromagnetic ### **Mechanical Properties (Heat-Treated)** - **Annealed Hardness:** 192–229 HB (excellent for machining) - **Hardened & Tempered Hardness:** **58–62 HRC** (typical working range) - Can achieve 61–62 HRC with low-temperature tempering - Typically operated at 59–61 HRC for balanced performance - **Tensile Strength (Longitudinal):** ~1950–2200 MPa (at 60 HRC) - **Tensile Strength (Transverse):** 15–25% lower than longitudinal values - **Yield Strength:** ~1750–2000 MPa - **Elongation:** **Good** – 6–10% (longitudinal) - **Impact Toughness (Charpy, Longitudinal):** **Good** – Typically 12–20 J - **Impact Toughness (Transverse):** Reduced – Typically 6–12 J (50–60% of longitudinal) - **Wear Resistance:** **Very Good** – Tungsten carbides provide enhanced abrasion resistance - **Compressive Strength:** ~2500–2800 MPa - **Fatigue Strength:** Good – Suitable for cyclic loading (consider directional properties) - **Dimensional Stability:** **Excellent** – Minimal distortion during oil quenching ### **Machinability Characteristics** - **Machinability Rating:** 75–85% (compared to 1212 steel at 100%) - **Improvement over Standard SKS7:** 30–50% better machinability - **Chip Formation:** Short, broken chips – ideal for automated machining - **Surface Finish:** Good to very good with proper parameters - **Tool Life:** Significantly extended compared to non-free-machining grades - **Power Consumption:** Reduced during machining operations --- ## **4. Heat Treatment Specifications** ### **1. Annealing** - **Temperature:** 750–800°C - **Process:** Heat uniformly, hold for 2–4 hours, furnace cool slowly (≤ 20°C/h) to 550°C, then air cool - **Resulting Hardness:** 192–229 HB - **Spheroidize Annealing:** 760–780°C for 4–6 hours, slow cool to 600°C at 10°C/h (optimal for machining and cold work) ### **2. Stress Relieving** - **Temperature:** 600–650°C - **Hold Time:** 1–2 hours per 25mm thickness - **Purpose:** Critical after extensive machining operations to prevent distortion during hardening ### **3. Hardening (Quenching)** - **Preheating:** Recommended for complex shapes - **First Preheat:** 400–500°C (beneficial for uniform heating) - **Second Preheat:** 700–750°C (recommended) - **Austenitizing Temperature:** **790–850°C** (typically 810–830°C) - **Soaking Time:** 20–30 minutes per 25mm at temperature - **Quenching Medium:** **Oil** (40–80°C recommended for minimal distortion) - Warm oil reduces thermal shock and distortion - Vigorous agitation not typically required - **Quench Temperature:** Quench from austenitizing temperature to 50–70°C ### **4. Tempering** - **Immediate Tempering Required:** Begin when tool reaches 50–80°C - **Temperature Range:** - **Low Temperature (150–200°C):** For maximum hardness (61–62 HRC) – 1–2 hours - **Medium-Low (200–300°C):** For optimal balance (59–61 HRC) – 1–2 hours - **Medium (300–400°C):** For improved toughness (57–59 HRC) – 1–2 hours - **High (400–550°C):** For maximum toughness (54–57 HRC) – 1.5–2.5 hours - **Hold Time:** 1–2 hours per 25mm thickness, minimum 1 hour - **Cycles:** Single temper usually sufficient; double tempering improves dimensional stability - **Secondary Hardening:** Moderate – tungsten contributes to temper resistance ### **5. Special Considerations:** - **Decarburization Control:** Important during heating – protective atmosphere recommended - **Size Change Predictability:** Good – typically 0.10–0.15% expansion during hardening - **Anisotropic Considerations:** Account for directional properties in heat treatment planning - **Surface Integrity:** Sulfide inclusions may affect very high polish applications --- ## **5. Key Features & Advantages** 1. **Superior Machinability:** Primary advantage – enables complex machining with reduced time and cost 2. **Tungsten-Enhanced Wear Resistance:** Better abrasion resistance than standard free-machining grades 3. **Excellent Dimensional Stability:** Oil quenching provides predictable size changes and minimal distortion 4. **Good Through-Hardenability:** Can effectively harden moderate sections (up to 50mm) 5. **Balanced Properties:** Good compromise between wear resistance, toughness, and machinability 6. **Reduced Manufacturing Costs:** Faster machining, extended tool life, lower scrap rates 7. **Complex Geometry Capability:** Can produce intricate details before hardening 8. **Predictable Heat Treatment:** Consistent results with proper processing **Limitations:** - **Anisotropic Properties:** Reduced mechanical properties transverse to rolling direction - **Impact Toughness (Transverse):** Significantly reduced – not suitable for multi-directional impact - **High Polish Limitations:** Sulfide inclusions may be visible at very high polish levels - **Welding Difficulty:** Not recommended due to sulfur content - **Special Grinding Considerations:** May require adjusted parameters --- ## **6. Typical Applications** SKS7M is specifically designed for **complex tooling applications requiring extensive machining operations**, particularly where the balanced properties and tungsten-enhanced wear resistance of SKS7 are needed. ### **Mold & Die Manufacturing:** - **Plastic Injection Molds:** Complex cavity inserts, cores, hot runner components - **Die Casting Dies:** For aluminum, zinc alloys (non-abrasive applications) - **Rubber Molds:** For compression and transfer molding - **Glass Molds:** Precision molds requiring extensive machining - **Powder Metal Compaction Dies:** Intricate shapes requiring precision ### **Precision Stamping & Forming Tools:** - **Progressive Dies:** Multi-station dies with complex features - **Fine Blanking Tools:** For clean-edge blanking applications - **Forming Dies:** With intricate profiles and details - **Embossing Dies:** For decorative surface patterns - **Lamination Dies:** For electrical components ### **Precision Tooling & Fixtures:** - **Complex Gauges:** Inspection fixtures with intricate features - **Jigs and Fixtures:** Precision machining and assembly fixtures - **Machine Tool Components:** Complex gears, cams, guideways (aligned loading) - **Cutting Tools:** Special form tools, broaches (for non-ferrous materials) ### **Specialized Industrial Applications:** - **Textile Machine Parts:** Complex guides, cams, and forming tools - **Food Processing Equipment:** Molds and forming tools requiring frequent cleaning/machining - **Packaging Tooling:** Dies for complex packaging formations - **Automotive Tooling:** Precision dies for interior components ### **Application Guidelines:** - **Best for:** Complex shapes requiring extensive machining before hardening - **Ideal for:** Production tooling where dimensional stability and machinability are critical - **Suitable for:** Components with primary stresses aligned with rolling direction - **Avoid for:** Applications with significant multi-directional or impact loading - **Excellent for:** Tooling with intricate cooling channels or complex ejector systems --- ## **7. International Standard Equivalents** | Standard | Grade Designation | Notes | | :--------------- | :------------------ | :----------------------------------------- | | **JIS** | SKS7M | Original specification (JIS G4404) | | **AISI/SAE (USA)**| No direct equivalent | Similar to free-machining O1 with tungsten | | **Proprietary** | Various free-machining tool steels | With tungsten enhancement | | **DIN (Germany)** | Special treated grades | With machinability enhancement | | **Custom** | Modified tungsten oil-hardening grades | Engineered for specific needs | **Note:** The "M" suffix in JIS nomenclature consistently indicates improved machinability through sulfur addition. SKS7M represents a specialized combination of tungsten-enhanced wear resistance with free-machining characteristics. --- ## **8. Machining & Fabrication Guidelines** ### **Machining (In Annealed State):** - **Exceptional Machinability for Tungsten-Containing Steel:** 40–60% better than standard SKS7 - **Optimal Cutting Parameters:** - **Turning:** 60–85 m/min with HSS, 120–170 m/min with carbide - **Milling:** 30–45 m/min with HSS, 80–120 m/min with carbide - **Drilling:** 20–35 m/min with HSS, 50–75 m/min with carbide - **Feeds:** Can use more aggressive feeds than non-free-machining grades - **Tool Materials:** Carbide recommended for production, premium HSS suitable - **Chip Control:** Excellent – produces short, broken chips ideal for automation - **Coolant:** Highly recommended for best tool life and surface finish - **Surface Finish:** Can achieve Ra 0.8–1.6 μm with proper technique ### **Grinding:** - **Good Grindability:** Requires proper wheel selection due to sulfides - **Wheel Selection:** Aluminum oxide wheels (softer grade: H–J hardness) - **Coolant:** Essential to prevent wheel loading with sulfur compounds - **Parameters:** Light to moderate infeeds recommended (0.02–0.05 mm/pass) - **Surface Finish:** Can achieve good finishes with proper technique ### **Electrical Discharge Machining (EDM):** - **Excellent Candidate:** Performs very well in both sinking and wire EDM - **Material Removal Rate:** Good – comparable to standard tool steels - **Surface Finish:** Very good with proper finishing passes - **Post-EDM Processing:** Temper at 150–200°C to relieve white layer stresses - **Wire EDM:** Particularly effective for complex profiles ### **Welding:** - **Not Recommended:** High carbon + sulfur content creates extreme cracking risk - **If Absolutely Necessary:** - High preheat: 400–450°C minimum - Specialized low-hydrogen, low-sulfur electrodes - Controlled interpass temperatures - Immediate post-weld annealing - **Practical Approach:** Avoid welding – redesign as one-piece or use mechanical fastening ### **Orientation Control:** - **Critical Requirement:** Maintain and document material orientation throughout manufacturing - **Design Alignment:** Ensure primary load direction aligns with rolling direction - **Marking System:** Clear orientation marking from material receipt through final inspection - **Quality Verification:** Check orientation compliance at key manufacturing stages --- ## **9. Surface Treatment & Finishing** ### **1. Nitriding:** - **Highly Effective:** Creates extremely hard wear-resistant surface - **Process:** Plasma nitriding at 480–520°C recommended - **Case Depth:** 0.1–0.2 mm typical - **Surface Hardness:** 800–1000 HV - **Benefits:** Dramatically extends tool life in abrasive applications - **Consideration:** Temperature must remain below tempering temperature ### **2. PVD Coatings:** - **Excellent Results:** TiN, TiCN, TiAlN coatings adhere well - **Benefits:** Further enhance wear resistance, reduce friction, prevent galling - **Application Temperature:** 400–500°C - **Typical Thickness:** 2–5 μm ### **3. Polishing & Texturing:** - **Polishability:** Good to very good – can achieve #6–#8 mirror finish - **Limitation:** Sulfide inclusions may become visible at #8+ polish levels - **Texturing:** Excellent for chemical and laser texturing applications - **EDM Texturing:** Produces consistent, reproducible surface patterns ### **4. Traditional Finishes:** - **Black Oxide:** For corrosion protection and appearance - **Phosphate Coating:** For improved lubricity in forming applications - **Chromium Plating:** Decorative or hard chrome for specific applications --- ## **10. Performance Comparison** ### **Within Free-Machining Tool Steel Family:** | Property | SKS7M | SKS5M | SKS2M | Standard SKS7 | |-----------------------|---------------------|---------------------|---------------------|---------------------| | **Tungsten Content** | 1.00–1.50% | — | — | 1.00–1.50% | | **Carbon Content** | 0.90–1.00% | 1.20–1.30% | 0.95–1.10% | 0.90–1.00% | | **Sulfur Content** | 0.08–0.15% | 0.08–0.15% | 0.08–0.15% | ≤ 0.030% | | **Max Hardness** | 61–62 HRC | 63–64 HRC | 62–63 HRC | 61–62 HRC | | **Machinability** | **Excellent** | **Excellent** | **Excellent** | Good | | **Wear Resistance** | **Very Good** | **Excellent** | Good | **Very Good** | | **Toughness** | Good (longitudinal) | Moderate | Very Good | Good | | **Distortion Control**| Excellent | Excellent | Good | Excellent | ### **Economic Comparison in Tool Manufacturing:** | Manufacturing Stage | SKS7M Advantage vs Standard SKS7 | Economic Impact | |-----------------------|----------------------------------|----------------------------------| | **Material Cost** | 10–25% higher | Initial cost increase | | **Machining Time** | 30–50% reduction | Primary economic benefit | | **Tooling Cost** | 25–45% reduction | Longer tool life during machining| | **Scrap Rate** | Significant reduction | Fewer machining-related failures | | **Heat Treatment Success** | Similar or slightly better | More consistent results | | **Total Manufacturing Cost**| 20–40% lower | Despite higher material cost | --- ## **11. Design & Manufacturing Considerations** ### **Material Orientation Strategy:** - **Fundamental Principle:** Design for unidirectional loading aligned with rolling direction - **Design Documentation:** Include orientation requirements on all drawings - **Purchasing Specification:** Require certified orientation from material supplier - **Manufacturing Process Control:** Maintain orientation awareness through all operations ### **Section Size Optimization:** - **Oil Hardening Capability:** Good through-hardening up to 50mm - **Optimal Range:** 15–80 mm sections - **Large Components:** Suitable for moderate-sized mold bases and die sets - **Thin Sections:** Excellent dimensional control ### **Stress Concentration Management:** - **Increased Sensitivity:** To notches and sharp corners in transverse direction - **Design Enhancement Rules:** - Minimum radius: 1.5–2.0 mm (transverse stress areas) - Minimum radius: 1.0 mm (longitudinal stress areas) - Gradual section transitions (3:1 taper minimum) - **FEA Analysis:** Recommended for critical or highly stressed components ### **Heat Treatment Planning:** - **Minimal Fixturing:** Usually not required for oil quenching - **Size Change Prediction:** Highly predictable – typically 0.10–0.15% expansion - **Post-Hardening Machining:** Usually minimal – primarily polishing operations - **Finishing Allowance:** 0.05–0.15 mm per side typically sufficient ### **Tool Life Optimization Design:** - **Design for Re-sharpening/Refurbishment:** Where applicable - **Modular Design Approach:** For complex tools – replace worn components - **Surface Treatment Integration:** Plan for nitriding or coating from initial design - **Cooling System Design:** Critical for mold applications – complete before hardening --- ## **12. Quality Control & Inspection** ### **Material Certification & Verification:** - **Chemistry Analysis:** Verify sulfur (0.08–0.15%) and tungsten (1.00–1.50%) specifically - **Sulfide Inclusion Rating:** ASTM E45 Method – typically Type A, thin - **Ultrasonic Testing:** Establish baseline for normal sulfide stringer indications - **Orientation Verification:** Confirm and document rolling direction ### **Heat Treatment Validation:** - **Hardness Testing:** Multiple locations, different depths, both longitudinal and transverse - **Dimensional Verification:** Before/after heat treatment (predictable changes) - **Microstructure Examination:** Grain size, carbide distribution, sulfide alignment check - **Non-Destructive Testing:** Magnetic particle or dye penetrant for surface defects ### **Performance Testing Protocols:** - **Tool Life Testing:** For production tools – establish performance baselines - **Wear Testing:** For critical wear applications (consider directional effects) - **Dimensional Stability Testing:** For precision tooling applications - **Field Trials:** Most valuable for new applications or designs ### **Documentation Requirements:** - **Material Certificates:** Complete chemistry and physical properties - **Heat Treatment Records:** Complete cycle documentation - **Inspection Reports:** Dimensional, hardness, NDT results - **Orientation Documentation:** Throughout manufacturing process - **Performance Data Records:** Tool life, maintenance intervals, failure analysis --- ## **13. Summary & Selection Guidelines** JIS SKS7M represents a **strategically optimized combination of tungsten-enhanced wear resistance and free-machining characteristics** in an oil-hardening tool steel, specifically designed for complex tooling applications. ### **Select SKS7M When:** 1. **Complex tool geometries** require extensive machining operations 2. **Enhanced wear resistance** (via tungsten) is needed in service 3. **Excellent dimensional stability** during oil quenching is critical 4. **Manufacturing efficiency** and reduced machining time are priorities 5. **Balanced performance** (wear vs. toughness) is required 6. **Production tooling** with significant machining content is being manufactured 7. **Total cost optimization** justifies the material premium ### **Optimal Application Scenarios:** - **Complex injection molds** requiring tungsten-enhanced wear resistance - **Precision stamping and forming dies** with intricate features - **Production tooling** where machining time dominates manufacturing cost - **Prototype tooling** requiring quick turnaround of complex shapes - **Tooling for moderate-wear applications** needing good machinability - **Replacement components** for existing tungsten-containing tooling ### **Avoid SKS7M When:** 1. **Severe multi-directional impact loading** is anticipated 2. **Maximum transverse toughness** is critical to application success 3. **Ultra-high polish surfaces** (better than #6 mirror) are required 4. **Welding or major repair** is likely to be needed 5. **Material orientation** cannot be reliably controlled 6. **Simple shapes** make machinability advantages less valuable economically 7. **Extreme wear conditions** require maximum possible abrasion resistance ### **Economic Justification Analysis:** 1. **Calculate Machining Content:** Threshold typically >40% of total manufacturing time 2. **Compare Total Costs:** Include all value-added operations, not just material 3. **Consider Production Volume:** Higher volumes increase machining time savings value 4. **Evaluate Tool Performance:** Tungsten enhancement may provide longer service life 5. **Account for Risk Reduction:** Fewer machining failures and more predictable results ### **Implementation Strategy:** 1. **Pilot Application:** Start with less critical, complex tools 2. **Parameter Development:** Optimize machining for SKS7M's specific characteristics 3. **Quality System Enhancement:** Particularly for orientation control 4. **Personnel Training:** On unique aspects of free-machining tungsten steels 5. **Knowledge Building:** Document results and build application experience 6. **Gradual Expansion:** To more critical and complex applications ### **Industry-Specific Value Propositions:** - **Mold Making:** Complex molds needing wear resistance and machinability - **Precision Stamping:** Intricate dies requiring extensive machining - **Tool & Die Shops:** Diverse requirements benefiting from balanced properties - **Prototype Development:** Quick-turn tooling for product validation - **Maintenance & Repair:** Replacement parts for existing tungsten tooling ### **Technical Development Considerations:** - **Advanced Machining:** Excellent performance with high-speed and 5-axis machining - **Sustainability Benefits:** Reduced machining time = lower energy consumption - **Digital Manufacturing:** Predictable behavior supports simulation and optimization - **Lifecycle Management:** Enables more sophisticated tool maintenance strategies ### **Final Recommendation:** JIS SKS7M offers a **sophisticated engineering solution** that addresses the competing demands of modern tool manufacturing: complex geometries requiring extensive machining, need for enhanced wear resistance, and requirement for dimensional stability during heat treatment. By strategically combining tungsten-enhanced wear resistance with free-machining characteristics in an oil-hardening steel, it provides a **unique value proposition for specific applications**. For tooling applications where **machining complexity, wear performance, and dimensional control** must be balanced, SKS7M represents a **purpose-engineered solution** that can provide significant advantages over both standard oil-hardening steels and conventional free-machining grades. Its use should be considered as part of a **holistic approach to tool design and manufacturing optimization**, where total cost of ownership and manufacturing efficiency are key considerations. When applied with proper understanding of its anisotropic characteristics, appropriate design accommodations, and controlled manufacturing processes, SKS7M can deliver **substantial competitive advantages** through reduced manufacturing time and costs, while providing enhanced service performance compared to standard free-machining grades. It exemplifies the principle of **strategic material selection** – choosing not just a steel, but a manufacturing solution optimized for specific challenges and requirements. -:- For detailed product information, please contact sales. -: JIS SKS7M Oil-Hardening Cold Work Tool Steel Specification Dimensions Size： Diameter 20-1000 mm Length <6831 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 SKS7M Oil-Hardening Cold Work Tool Steel Properties -:- For detailed product information, please contact sales. -:

Applications of JIS SKS7M Oil-Hardening Cold Work Tool Steel Rod -:- For detailed product information, please contact sales. -: Chemical Identifiers JIS SKS7M Oil-Hardening Cold Work Tool Steel Rod -:- For detailed product information, please contact sales. -:

Packing of JIS SKS7M Oil-Hardening Cold Work Tool 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 3302 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