If you need a high speed steel that balances red hardness, wear resistance, and cost-effectiveness for mid-to-high difficulty cutting tasks, JIS SKH9 high speed steel is an excellent choice. It performs reliably in gear cutting, hard material machining, and precision drilling—solving common issues like short tool life or inconsistent performance without the premium price tag of top-tier HSS. In this guide, we’ll break down its key properties, real-world uses, manufacturing steps, and how it compares to other materials—so you can select tools that meet your performance needs and budget.
1. Material Properties of JIS SKH9 High Speed Steel
JIS SKH9’s appeal lies in its well-rounded composition, which delivers solid cutting performance without overengineering. Let’s explore its properties in detail:
1.1 Chemical Composition
The elements in JIS SKH9 work together to enhance heat resistance, edge retention, and durability—tailored for mid-range high-speed cutting. Below is its standard composition (per JIS G4403):
| Element | Content Range (%) | Key Role |
|---|---|---|
| Carbon (C) | 0.75 – 0.85 | Forms hard carbides with tungsten and vanadium, boosting wear resistance. |
| Manganese (Mn) | 0.15 – 0.40 | Improves hardenability and reduces brittleness during heat treatment. |
| Silicon (Si) | 0.15 – 0.40 | Enhances strength and resistance to oxidation at high temperatures. |
| Chromium (Cr) | 3.80 – 4.50 | Supports carbide formation and hardenability; adds basic corrosion resistance. |
| Tungsten (W) | 1.20 – 1.80 | Enhances red hardness—retains strength at 550+ °C, enabling moderate high-speed cutting. |
| Molybdenum (Mo) | 4.50 – 5.50 | A primary contributor to red hardness; works with tungsten to reduce brittleness. |
| Vanadium (V) | 1.00 – 1.40 | Forms hard vanadium carbides, improving edge retention for drills and reamers. |
| Cobalt (Co) | ≤ 0.50 | A trace element (lower than premium HSS) that slightly boosts high-temperature stability. |
| Sulfur (S) | ≤ 0.030 | Minimized to avoid weakening the steel and reducing tool life. |
| Phosphorus (P) | ≤ 0.030 | Kept low to prevent brittleness under heat and cutting stress. |
1.2 Physical Properties
These properties influence how JIS SKH9 behaves during tool manufacturing and use—such as heat management and shape stability. All values are measured at room temperature unless noted:
- Density: 7.90 g/cm³ (lower than cobalt-rich HSS like SKH51, making it lighter and more cost-efficient).
- Melting Point: 1430 – 1490 °C (high enough to withstand forging and heat treatment without deformation).
- Thermal Conductivity: 27 W/(m·K) (better than SKH51, helping dissipate heat during prolonged cutting).
- Coefficient of Thermal Expansion: 11.2 × 10⁻⁶/°C (from 20 to 600 °C; low expansion ensures tools keep their cutting geometry).
- Specific Heat Capacity: 455 J/(kg·K) (efficient at absorbing heat, reducing overheating risk in mid-speed cutting).
1.3 Mechanical Properties
JIS SKH9’s mechanical properties are optimized for balanced performance—prioritizing hardness and red hardness without sacrificing too much toughness. Below are typical values after standard heat treatment (quenching + double tempering):
| Property | Typical Value | Test Standard | Why It Matters |
|---|---|---|---|
| Hardness (HRC) | 62 – 65 | JIS Z2245 | High hardness ensures good edge retention for milling cutters and gear tools. |
| Tensile Strength | ≥ 2200 MPa | JIS Z2241 | Handles moderate cutting forces—ideal for machining alloy steel and cast iron. |
| Yield Strength | ≥ 1900 MPa | JIS Z2241 | Resists permanent deformation, keeping tools sharp through repeated use. |
| Elongation | ≤ 6% | JIS Z2241 | Low ductility (standard for HSS); a trade-off for hardness. |
| Impact Toughness (Charpy V-notch) | ≥ 15 J (at 20 °C) | JIS Z2242 | Better toughness than premium HSS—reduces chipping in light shock applications. |
| Red Hardness | Retains 85% hardness at 550 °C | JIS Z2245 | Enables cutting speeds up to 40 m/min (for mild steel)—suitable for mid-range tasks. |
| Fatigue Strength | ~850 MPa (10⁷ cycles) | JIS Z2273 | Resists failure from repeated cutting—key for high-cycle automotive component machining. |
1.4 Other Properties
- Corrosion Resistance: Moderate. Chromium content protects against rust in dry workshops, but avoid prolonged exposure to moisture or chemicals.
- Wear Resistance: Very Good. Vanadium and molybdenum carbides resist abrasive wear—sufficient for machining hard materials like HRC 35–40 steel.
- Machinability: Fair. Annealing (heating to 850–900 °C, slow cooling) softens it to HRC 24–28, making pre-hardening machining manageable with carbide tools.
- Hardenability: Very Good. It hardens evenly across sections up to 25 mm—ideal for most standard cutting tool sizes (e.g., 10–20 mm diameter drills).
- High-temperature Stability: Good. Maintains strength at 550–600 °C—better than carbon steel or low-alloy steel, but less than cobalt-rich HSS like SKH51.
2. Applications of JIS SKH9 High Speed Steel
JIS SKH9’s balanced properties make it versatile for mid-range cutting tasks across industries. Here are its most common uses, with real examples:
2.1 Cutting Tools for General Machining
- Examples: Drills, reamers, and turning tools for machining mild steel, cast iron, or aluminum alloys.
- Why it works: Good wear resistance keeps tools sharp, while moderate red hardness handles mid-speed cutting. A Chinese machine shop used JIS SKH9 drills for cast iron parts—tool life was 50% longer than standard carbon steel drills.
2.2 Milling Cutters and Gear Tools
- Examples: End mills for slotting mild steel, and low-to-medium precision gear cutting tools (e.g., for agricultural machinery gears).
- Why it works: Red hardness handles the heat of milling, while toughness prevents chipping. A U.S. agricultural equipment maker used JIS SKH9 gear cutters—tool changes dropped by 30% vs. low-alloy steel tools.
2.3 Automotive Component Machining
- Examples: Tools for machining automotive parts like brake rotors, engine brackets, or transmission gears (non-premium).
- Why it works: Fatigue strength handles high production cycles, and cost-effectiveness fits automotive mass-manufacturing budgets. A Korean auto parts supplier used JIS SKH9 turning tools—per-part tool costs fell by 20% vs. SKH51.
2.4 Aerospace Low-Stress Components
- Examples: Tools for machining non-critical aerospace parts like aluminum brackets or plastic composite molds.
- Why it works: Moderate high-temperature stability handles composite machining heat, while affordability suits low-stress applications. A European aerospace subcontractor used JIS SKH9 end mills—achieved consistent part quality at 30% lower tool cost than ceramic tools.
3. Manufacturing Techniques for JIS SKH9 High Speed Steel
Turning JIS SKH9 into usable cutting tools requires standard HSS processing steps, with a focus on balancing hardness and toughness. Here’s a breakdown:
- Melting: Raw materials are melted in an electric arc furnace (EAF) at 1550–1600 °C—strict control ensures uniform element distribution (critical for consistent wear resistance).
- Casting: Molten steel is poured into small ingot molds (3–15 kg) to avoid carbide segregation. Slow cooling (15–25 °C/hour) reduces internal defects.
- Forging: Ingots are heated to 1100–1180 °C and pressed/hammered into tool blanks (e.g., 8x8x100 mm for small drills). Forging refines grain structure and improves strength.
- Heat Treatment: The standard cycle for optimal performance:
- Annealing: 850–900 °C, hold 2–3 hours, slow cool to 600 °C, then air cool. Softens steel for machining.
- Preheating: 750–800 °C, hold 1 hour. Prevents thermal shock during quenching.
- Austenitizing: 1180–1220 °C, hold 15–25 minutes. Dissolves carbides evenly.
- Quenching: Oil cooling (60–80 °C oil temperature) to harden to HRC 64–66.
- Double Tempering: 540–560 °C, hold 1.5–2 hours per cycle, air cool. Reduces brittleness and sets final hardness (HRC 62–65).
- Machining: Most shaping (milling, grinding) is done post-annealing. Carbide end mills or grinding wheels are recommended for tight tolerances (±0.005 mm).
- Surface Treatment (Optional):
- TiN Coating: Adds a hard, low-friction layer to boost wear resistance by 40% (ideal for milling cutters).
- Nitriding: Creates a HRC 65–70 surface layer for high-wear applications (e.g., gear hobbing tools).
4. Case Study: JIS SKH9 in Automotive Brake Rotor Machining
A Brazilian automotive manufacturer faced a problem: their low-alloy steel turning tools for brake rotors were wearing out every 200 parts, causing frequent downtime. They switched to JIS SKH9 (TiN-coated) tools, and here’s what happened:
- Process: Tools were forged, annealed, machined to turning tool geometry, heat-treated (1200 °C quenching + double tempering at 550 °C), ground to precision, and TiN-coated.
- Results:
- Tool life increased to 500 parts (150% improvement) thanks to JIS SKH9’s wear resistance and TiN coating.
- Machining speed rose from 25 to 35 m/min (40% faster)—reducing production time per rotor.
- Part quality improved: brake rotor surface roughness dropped from Ra 1.6 μm to Ra 0.8 μm (smoother rotors reduce brake noise).
- Why it works: Molybdenum in JIS SKH9 retained hardness at the cutting temperature (500 °C), while the TiN coating reduced friction between the tool and cast iron rotor—minimizing wear.
5. JIS SKH9 vs. Other Cutting Materials
How does JIS SKH9 stack up against common alternatives? Let’s compare key properties for mid-range cutting tasks:
| Material | Hardness (HRC) | Red Hardness (550 °C) | Wear Resistance | Cost (vs. JIS SKH9) | Best For |
|---|---|---|---|---|---|
| JIS SKH9 High Speed Steel | 62 – 65 | Good | Very Good | 100% | Mid-speed machining, general cutting tools |
| JIS SKH51 High Speed Steel | 63 – 66 | Excellent | Excellent | 160% | High-speed, hard material machining (e.g., aerospace) |
| Carbon Steel (1095) | 55 – 60 | Poor | Poor | 30% | Low-speed, soft material cutting (e.g., wood) |
| Carbide Tools | 85 – 90 (HV) | Excellent | Very Good | 250% | Ultra-high-speed, brittle material cutting |
| Alloy Steel (4140) | 30 – 40 | Very Poor | Fair | 50% | Non-cutting tools (e.g., tool holders) |
| Ceramic Tools | 90 – 95 (HV) | Outstanding | Very Good | 400% | Machining super-alloys (no shock) |
Key takeaway: JIS SKH9 offers the best cost-performance ratio for mid-range cutting tasks. It’s cheaper than SKH51 or carbide tools while delivering far better performance than carbon or alloy steel—ideal for businesses balancing quality and budget.
Yigu Technology’s View on JIS SKH9 High Speed Steel
At Yigu Technology, JIS SKH9 is our top recommendation for clients needing reliable cutting performance without premium costs—like general machining shops or automotive parts manufacturers. Its balanced red hardness and wear resistance solve the common issue of short tool life in mid-speed tasks, while its better toughness than high-cobalt HSS reduces chipping risks. We often pair it with TiN coatings to extend tool life further, helping clients cut downtime and per-part costs. For most non-extreme cutting needs, JIS SKH9 isn’t just a material—it’s a practical, cost-effective solution.
FAQ About JIS SKH9 High Speed Steel
1. Can JIS SKH9 be used for machining stainless steel (e.g., 304)?
Yes, but we recommend using a TiAlN coating (instead of TiN) to reduce built-up edge (BUE) on the tool. JIS SKH9’s wear resistance handles stainless steel’s abrasiveness, but the coating helps prevent material sticking—extending tool life by 30–40%.
2. What’s the difference between JIS SKH9 and JIS SKH51?
The main difference is cobalt content: SKH51 has 4.5–5.5% cobalt (boosting red hardness for 600+ °C cutting), while SKH9 has ≤0.5% cobalt. SKH51 performs better in high-speed, hard material tasks, but SKH9 is 30–40% cheaper—better for mid-range applications.
3. Is JIS SKH9 suitable for making large cutting tools (e.g., 30 mm diameter end mills)?
JIS SKH9’s hardenability is best for sections up to 25 mm. For 30 mm+ tools, we recommend a pre-heat treatment step (e.g., 700–750 °C for 1 hour before quenching) to ensure even hardening. This prevents soft spots that could reduce tool life.
