JIS SKS7 Oil-Hardening Cold Work Tool Steel Sheet,Plate

JIS SKS7 Oil-Hardening Cold Work Tool Steel Sheet/Plate Product Information -:- For detailed product information, please contact sales. -: JIS SKS7 Oil-Hardening Cold Work Tool Steel Sheet/Plate Synonyms -:- For detailed product information, please contact sales. -:

JIS SKS7 Oil-Hardening Cold Work Tool Steel Product Information -:- For detailed product information, please contact sales. -: # **JIS SKS7 Oil-Hardening Cold Work Tool Steel** **International Standard:** JIS G4404 (Japan Industrial Standard) - Tool Steels --- ## **1. Overview** JIS SKS7 is a **medium-carbon, low-alloy oil-hardening cold work tool steel** that occupies a unique position within the SKS series. Characterized by its **balanced composition with moderate tungsten content**, SKS7 offers a combination of good wear resistance, reasonable toughness, and excellent dimensional stability during oil quenching. This grade is specifically designed for applications requiring a reliable balance of properties for general-purpose cold work tooling, particularly where consistent performance and predictable heat treatment response are valued over extreme specialization. --- ## **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 | | Mo | ≤ 0.30 | | P (max) | 0.030 | | S (max) | 0.030 | **Balance:** Iron (Fe). **Key Characteristics:** SKS7 features a **distinctive tungsten addition (1.00–1.50%)** combined with moderate carbon (0.90–1.00%) and chromium (0.50–1.00%). This composition creates: - **Tungsten carbide formation** for improved wear resistance over plain carbon-oil hardening steels - **Good hardenability** through oil quenching with minimal distortion - **Balanced properties** that avoid the extremes of higher-alloy or water-hardening grades --- ## **3. Physical & Mechanical Properties** ### **Physical Properties** - **Density:** ~7.84 g/cm³ - **Thermal Conductivity:** ~42 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 - **Magnetic Properties:** Ferromagnetic ### **Mechanical Properties (Heat-Treated)** - **Annealed Hardness:** 192–229 HB - **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:** ~1950–2200 MPa (at 60 HRC) - **Yield Strength:** ~1750–2000 MPa - **Elongation:** **Good** – 6–10% - **Impact Toughness (Charpy):** **Good** – Typically 15–25 J - **Wear Resistance:** **Very Good** – Tungsten carbides provide enhanced abrasion resistance - **Compressive Strength:** ~2500–2800 MPa - **Fatigue Strength:** Good – Suitable for cyclic loading applications - **Transverse Strength:** Isotropic properties (unlike free-machining grades) ### **Hardenability Characteristics:** - **Critical Diameter (Oil Quench):** ~25–40 mm for 50% martensite at center - **Hardness Gradient:** Gradual – good through-hardening capability - **Full Hardening Depth:** Up to 50 mm diameter achievable - **Size Change Predictability:** Good – typically 0.08–0.15% expansion --- ## **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:** Essential for complex tools to minimize distortion ### **3. Hardening (Quenching)** - **Preheating:** Recommended for best results - **First Preheat:** 400–500°C (beneficial for complex shapes) - **Second Preheat:** 700–750°C (recommended for uniform heating) - **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 - **Agitation:** Moderate agitation recommended - **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 - **Grain Growth:** Moderate resistance – avoid excessive temperatures or times - **Size Change:** Predictable – typically 0.10–0.15% expansion during hardening - **Retained Austenite:** Typically low (<5%) with proper tempering --- ## **5. Key Features & Advantages** 1. **Balanced Performance:** Excellent compromise between wear resistance, toughness, and dimensional stability 2. **Tungsten-Enhanced Wear Resistance:** Better abrasion resistance than plain carbon oil-hardening grades 3. **Good Dimensional Control:** Oil quenching provides predictable size changes and minimal distortion 4. **Excellent Machinability:** In annealed state, comparable to other SKS grades 5. **Good Through-Hardenability:** Can effectively harden moderate sections 6. **Reliable Heat Treatment:** Forgiving processing characteristics 7. **Versatile Applications:** Suitable for wide range of cold work tooling 8. **Cost-Effective:** Provides good value for performance level **Limitations:** - **Moderate Maximum Hardness:** Cannot achieve the highest hardness levels of some specialized grades - **Limited Hot Hardness:** Not suitable for elevated temperature applications - **Moderate Wear Resistance:** Less than high-alloy or high-speed steels - **Not for Extreme Conditions:** Either wear or impact --- ## **6. Typical Applications** SKS7 is used for **general-purpose cold work tooling** where a balanced combination of properties is more valuable than specialization in one extreme. ### **Cutting & Shearing Tools:** - **Hand Tools:** Quality chisels, punches, screwdrivers - **Industrial Cutting Tools:** Machine knives for paper, textiles, plastics - **Shear Blades:** For metal cutting, particularly non-ferrous metals - **Woodworking Tools:** Planer blades, carving tools, router bits ### **Forming & Stamping Tools:** - **Punches and Dies:** For blanking, piercing, and forming of mild steels - **Bending Tools:** Press brake dies and punches - **Drawing Dies:** For shallow to medium drawing operations - **Thread Rolling Dies:** For softer materials ### **Measuring & Precision Tools:** - **Gauges:** Plug gauges, ring gauges, thread gauges - **Templates and Patterns:** For inspection and layout - **Machine Components:** Bushings, wear plates, guide pins ### **Mold & Die Applications:** - **Plastic Injection Mold Components:** Cavities, cores for non-abrasive plastics - **Die Casting Components:** Ejector pins, cores (for lower-temperature alloys) - **Rubber Molds:** For compression and transfer molding ### **Special Applications:** - **Lathe Tools:** For soft materials turning - **Knurling Tools:** For producing patterns on surfaces - **Marking Tools:** Scribers, center punches - **Spring Tools:** For spring forming and coiling ### **Application Guidelines:** - **Best for:** General-purpose tooling requiring balanced properties - **Ideal for:** Tools subject to both wear and moderate impact - **Suitable for:** Production environments needing reliable, predictable performance - **Avoid for:** Extreme wear, high impact, or elevated temperature applications --- ## **7. International Standard Equivalents** | Standard | Grade Designation | Notes | | :--------------- | :------------------ | :----------------------------------------- | | **JIS** | SKS7 | Original specification (JIS G4404) | | **AISI/SAE (USA)**| No direct equivalent | Similar to O1 with tungsten addition | | **DIN (Germany)** | 1.2510 mod | Modified with tungsten | | **ISO** | 95MnWCr2 | International designation | | **BS (UK)** | No direct equivalent | Similar to 01 tool steel | | **GB (China)** | 9CrWMn | Similar tungsten-bearing grade | | **Custom** | Various O1 modifications | With tungsten addition | **Note:** SKS7 is a distinctive Japanese grade with specific tungsten content that differentiates it from common international equivalents. Its properties place it between standard oil-hardening grades and more highly alloyed steels. --- ## **8. Machining & Fabrication Guidelines** ### **Machining (In Annealed State):** - **Excellent Machinability:** Comparable to other SKS grades - **Tooling:** High-speed steel tools work well; carbide for production - **Cutting Speeds:** 30–45 m/min for turning with HSS - **Feeds:** Moderate feeds with good chip control - **Chip Formation:** Discontinuous chips typical - **Surface Finish:** Produces good surface finishes - **Drilling and Tapping:** Good performance ### **Grinding:** - **Good Grindability:** Responds well to standard grinding operations - **Wheel Selection:** Aluminum oxide wheels (A46-JV or similar) - **Coolant:** Recommended for best results - **Parameters:** Standard grinding parameters suitable - **Surface Finish:** Can achieve excellent finishes ### **Electrical Discharge Machining (EDM):** - **Suitable:** Can be EDMed in hardened or annealed state - **Parameters:** Standard EDM settings generally suitable - **Post-EDM:** Temper at 150–200°C to relieve white layer stresses - **Surface Integrity:** Good with proper finishing passes ### **Welding:** - **Possible with Care:** Can be welded using appropriate techniques - **Preheat:** 200–300°C recommended - **Filler Material:** Use matching or similar composition filler - **Post-Weld:** Stress relieve at 600–650°C or re-harden for best results - **Techniques:** SMAW with low-hydrogen electrodes recommended ### **Forging:** - **Good Forgeability:** Can be forged with proper procedures - **Forging Temperature:** 1050–900°C - **Start:** 1050°C maximum - **Finish:** 900°C minimum - **Cooling:** Slow furnace cool after forging - **Annealing:** Always required after forging --- ## **9. Surface Treatment** ### **1. Nitriding:** - **Effective Treatment:** Improves surface hardness and wear resistance - **Process:** Gas or plasma nitriding at 500–550°C - **Case Depth:** 0.1–0.3 mm typical - **Surface Hardness:** 700–900 HV - **Benefits:** Extends tool life without affecting core toughness ### **2. Carburizing:** - **Occasionally Used:** For special applications requiring harder case - **Process:** Pack or gas carburizing - **Result:** Creates higher-carbon case on existing medium-carbon core ### **3. Coatings:** - **Phosphate Coating:** For corrosion resistance and lubricity - **Chrome Plating:** Hard chrome for wear resistance (0.01–0.05 mm) - **PVD Coatings:** TiN, TiCN for specialized applications ### **4. Traditional Finishes:** - **Black Oxide:** For corrosion protection and appearance - **Polishing:** Can achieve excellent surface finishes for mold applications --- ## **10. Performance Comparison** ### **Within Oil-Hardening Tool Steels:** | Property | SKS7 (W-bearing) | SKS2 (O1) | SKS3 (O2) | SKS21 (L6-type) | |-----------------------|---------------------|---------------------|---------------------|---------------------| | **Tungsten Content** | 1.00–1.50% | 0.50–1.00% | 0.50–1.00% | 0.50–1.00% | | **Carbon Content** | 0.90–1.00% | 0.95–1.10% | 0.85–0.95% | 0.70–0.80% | | **Typical Hardness** | 58–62 HRC | 57–62 HRC | 56–61 HRC | 54–59 HRC | | **Wear Resistance** | **Very Good** | Good | Good | Good | | **Impact Toughness** | Good | Good | Very Good | **Excellent** | | **Machinability** | Excellent | Excellent | Excellent | Excellent | | **Primary Advantage** | Balanced + Wear | General Purpose | Toughness Balance | Maximum Toughness | ### **Compared to Other Tool Steel Categories:** | Property | SKS7 (Oil-H, W) | A2 (Air-H) | D2 (High-Cr) | W1 (Water-H) | |-----------------------|---------------------|---------------------|---------------------|---------------------| | **Hardening Method** | Oil | Air | Air | Water | | **Max Hardness** | 62 HRC | 62 HRC | 62 HRC | 64 HRC | | **Distortion** | Low | Very Low | Very Low | Very High | | **Toughness** | Good | Good | Fair | Poor | | **Wear Resistance** | Very Good | Excellent | **Excellent** | Good (surface only) | | **Machinability** | Excellent | Good | Fair | Excellent | | **Cost** | Low-Medium | Medium | High | **Lowest** | --- ## **11. Design Considerations** ### **Section Size Capability:** - **Fully Hardenable:** Up to approximately 50 mm diameter/thickness - **Surface Hardening:** Effective for sections up to 100 mm - **Large Tools:** Consider for moderate-sized tooling applications - **Optimal Range:** 10–60 mm sections ### **Stress Management:** - **Radius Requirements:** Minimum 0.5 mm radius on all corners - **Uniform Sections:** Design for even wall thickness where possible - **Stress Relief:** Essential after rough machining of complex tools - **Gradual Transitions:** Use generous fillets and tapers ### **Hardness Selection Strategy:** - **For General Purpose:** Temper at 200–300°C (59–61 HRC) - **For Impact Resistance:** Temper at 350–450°C (57–59 HRC) - **For Maximum Wear Resistance:** Temper at 150–200°C (61–62 HRC) with possible surface treatment ### **Dimensional Changes:** - **During Hardening:** Typically 0.08–0.15% growth - **During Tempering:** Minimal change - **Predictability:** Good – consistent size changes with proper processing - **Machining Allowance:** 0.1–0.2 mm per side for finish grinding ### **Tool Design Philosophy:** - **Balanced Approach:** Neither extreme wear nor extreme toughness needed - **Reliability Focus:** Predictable performance over specialized extremes - **Manufacturing Efficiency:** Good machinability reduces production costs - **Maintenance Consideration:** Tools should accommodate resharpening --- ## **12. Quality Control** ### **Hardness Testing:** - **Surface Hardness:** Rockwell C scale (multiple locations) - **Core Hardness:** Important for thicker sections - **Hardness Uniformity:** Check across tool surfaces - **File Testing:** Quick verification method ### **Microstructure Examination:** - **Annealed Condition:** Spheroidized carbides in ferritic matrix - **Hardened Condition:** Tempered martensite with fine carbides - **Grain Size:** ASTM 8 or finer preferred - **Carbide Distribution:** Tungsten carbides should be fine and evenly distributed ### **Non-Destructive Testing:** - **Magnetic Particle Inspection:** For surface cracks after heat treatment - **Dye Penetrant:** Alternative for complex geometries - **Dimensional Verification:** Critical for precision tools - **Visual Inspection:** For surface defects and finish quality ### **Performance Testing:** - **Tool Life Testing:** For production applications - **Wear Testing:** For applications with specific requirements - **Field Trials:** Most valuable for new tool designs --- ## **13. Summary & Selection Guidelines** JIS SKS7 represents a **well-balanced, tungsten-enhanced oil-hardening tool steel** that offers reliable performance for a wide range of general-purpose cold work applications. ### **Select SKS7 When:** 1. A **balanced combination of properties** is more valuable than specialization 2. **Good wear resistance** is needed but extreme abrasion resistance is not required 3. **Reasonable toughness** is important for tool longevity 4. **Predictable heat treatment** with minimal distortion is desired 5. **Cost-effective performance** is a priority 6. **Good machinability** facilitates tool manufacturing 7. **General-purpose tooling** needs reliable, consistent performance ### **Optimal Application Examples:** - **General machine shop tooling** for varied applications - **Production tooling** where reliability trumps extreme performance - **Maintenance and repair tools** needing versatile performance - **Small to medium batch production** tooling - **Tooling for educational and training purposes** - **Prototype tooling** where requirements may evolve ### **Consider Alternatives When:** 1. **Extreme wear resistance** is the primary requirement (consider D2 or high-speed steels) 2. **Maximum toughness** is needed for severe impact (consider SKS21 or S41) 3. **Very high hardness** (>62 HRC) is necessary 4. **Elevated temperature operation** is involved 5. **Maximum dimensional stability** for complex geometries is critical (consider air-hardening grades) 6. **Cost must be absolutely minimized** (consider water-hardening grades for simple shapes) ### **Economic Advantages:** - **Competitive material cost** – good value for performance level - **Reduced machining costs** due to excellent machinability - **Lower heat treatment costs** compared to some specialized grades - **Good tool life** – balanced properties often yield longer overall life than specialized extremes - **Reduced downtime** – reliable performance means fewer unexpected failures ### **Heat Treatment Advantages:** - **Forgiving Process:** Tolerant of minor variations in time and temperature - **Predictable Results:** Consistent hardness and size changes - **Minimal Equipment Requirements:** Standard heat treatment facilities adequate - **Low Risk:** Reduced cracking and distortion compared to water hardening ### **Industry Preference:** SKS7 is particularly valued in: - **General tool and die shops** with varied requirements - **Maintenance departments** needing versatile tooling - **Small to medium manufacturers** with diverse production needs - **Educational institutions** teaching tool steel fundamentals - **Industries** where tooling requirements are not extreme in any direction ### **The "Balanced Approach" Philosophy:** SKS7 exemplifies the engineering principle that **optimal performance often comes from balance rather than extremes**. For many applications: - A steel with moderate wear resistance and moderate toughness outlasts a steel with extreme wear resistance but poor toughness - Predictable, consistent performance is more valuable than occasional exceptional performance with frequent failures - Total cost of ownership often favors balanced steels over specialized extremes ### **Final Recommendation:** JIS SKS7 is a **highly practical and versatile oil-hardening tool steel** that delivers reliable performance across a broad spectrum of cold work applications. Its tungsten-enhanced composition provides a meaningful improvement in wear resistance over plain carbon oil-hardening grades, while maintaining the processing advantages and balanced properties that make oil-hardening steels so valuable. For tool designers and manufacturers seeking a **dependable, cost-effective material** that performs well across many common cold work applications without excelling at any single extreme, SKS7 offers an excellent solution. Its combination of good machinability, predictable heat treatment response, balanced mechanical properties, and competitive cost ensures its continued relevance in toolrooms and manufacturing facilities worldwide. When tooling requirements are **well-defined but not extreme**, when **reliability and consistency are valued over peak performance**, or when a **single material must serve multiple purposes**, SKS7 represents a **smart, practical choice** that has stood the test of time in industrial applications. It may not be the "best" steel for any single application, but it is often the "right" steel for many applications – and in practical toolmaking, that distinction matters greatly. -:- For detailed product information, please contact sales. -: JIS SKS7 Oil-Hardening Cold Work Tool Steel Specification Dimensions Size： Diameter 20-1000 mm Length <6830 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 SKS7 Oil-Hardening Cold Work Tool Steel Properties -:- For detailed product information, please contact sales. -:

Applications of JIS SKS7 Oil-Hardening Cold Work Tool Steel Sheet,Plate -:- For detailed product information, please contact sales. -: Chemical Identifiers JIS SKS7 Oil-Hardening Cold Work Tool Steel Sheet,Plate -:- For detailed product information, please contact sales. -:

Packing of JIS SKS7 Oil-Hardening Cold Work Tool 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 3301 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