Manufacturers categorize all tool steels into six core families based on metallurgical characteristics, heat treatment behavior and industrial application: water-hardening, cold-working, shock-resisting, high-speed, hot-working, and special-purpose plastic mold tool steel. Every grade family is engineered with unique alloy compositions and mechanical properties to fit specific manufacturing processes. For instance, H13 hot-work steel excels in automotive die casting production, while P20 plastic mold steel is widely adopted for injection molding dies. As a reliable tool steel supplier, NSPM supplies the full spectrum of these six tool steel grades and provides professional metallurgical consultation to manufacturers globally.
Key Takeaways
- Six core tool steel families cover all mainstream manufacturing scenarios, each optimized for distinct working conditions like high heat, heavy impact or long-cycle plastic molding.
- Low-cost water-hardening steel delivers sharp cutting edges and fits low-temperature, low-load simple hand tools.
- Cold-work tool steel features exceptional wear resistance and dimensional stability, ideal for room-temperature stamping, blanking and cutting dies.
- Shock-resisting steel prioritizes high toughness to withstand repeated heavy impacts for chisels, mining drill bits and pneumatic hammer tools.
- High-speed steel retains hardness and cutting performance under extreme frictional heat for high-speed machining cutters.
- Hot-working steel and plastic mold special-purpose steel are dedicated to high-temperature forming and precision plastic molding respectively.
Water-Hardening Tool Steel Grades
Core Properties
Water-hardening tool steel features high carbon content ranging from 0.50–1.4 wt%, which is the main contributor to surface hardness and wear resistance. Alloy additives including chromium, molybdenum, vanadium and nickel refine grain structure, improve hardenability and boost overall toughness.
After standard heat treatment (austenitized at 850°C, water quenched and double tempered at 200°C), this steel reaches 59–65 HRC, but it suffers poor heat resistance and high distortion risk during quenching. It stands out for its low material cost.
| Alloy Element | Content Range & Functional Effect |
|---|---|
| Carbon | 0.50–1.4 wt%: Boosts hardness and abrasive resistance |
| Chromium | 1.10–1.90 wt%: Enhances hardenability |
| Molybdenum | 0.10–0.50 wt%: Improves impact toughness |
| Nickel | 0.10–0.50 wt%: Refines internal grain structure |
| Vanadium | 1.0–1.5 wt%: Delivers secondary hardening performance |
Typical Applications
Water-hardening steel is only suitable for tools operating under low heat and light loads, including simple drill bits, small saw blades and basic hand cutting tools. It is widely used in small repair workshops due to its affordable price, but not recommended for precision molds or continuous high-load stamping work due to its high deformation tendency.
Cold-Work Tool Steel Grades
Core Properties
Cold-work tool steel is formulated with abundant hard carbide particles, achieving stable hardness of 60–62 HRC with outstanding anti-wear performance. MC-type carbides (vanadium, niobium alloyed) effectively resist abrasive wear; cryogenic post-treatment further optimizes dimensional stability and surface hardness. It accounts for roughly 28% of total tool steel consumption across manufacturing.
| Characteristic | Impact on Wear Resistance |
|---|---|
| Carbide Volume Fraction | Higher carbide content reduces abrasion loss |
| Matrix Hardness | Higher HRC rating extends service life |
| Carbide Morphology | Elongated thin carbides deliver superior wear protection |
| Cryogenic Treatment | Elevates hardness and long-term dimensional stability |
Typical Applications
Designed exclusively for room-temperature forming processes, common grades include A2, A6, A8, D2 and D3:
- A2: Bending dies, general plastic forming molds
- D2: High-wear burnishing tools, woodworking cutters Main products: Automotive stamping dies, sheet metal blanking punches, shear blades, drawing dies and precision gauges. Premature failure modes include abrasive wear, surface chipping and cracking; matching proper steel grade and standardized heat treatment can drastically extend tool service life.
Shock-Resisting Tool Steel Grades
Core Properties
Shock-resisting S-series steel balances medium carbon (0.5–0.6%) and 1.5–2.5% silicon to maximize impact toughness, with chromium, molybdenum and tungsten added to strengthen the matrix. Operating temperature caps at 600–700°F, far below hot-working steel thresholds. Air or oil quenching minimizes brittleness.
| Standard S-Grade Steel | Impact Resistance Level | Core Advantages |
|---|---|---|
| S7 | Excellent | Ultra-high toughness for heavy cyclic impact loads |
| S5 | Excellent | Heavy-duty industrial impact tools |
| High-carbon general tool steel | Low | Prone to cracking under sudden force |
Typical Applications
This grade serves construction, mining and automotive industries for tools enduring repeated impact: mining drill bits, chisels, jackhammer bits, heavy-duty impact punches and forming dies. High-carbon steels are unsuitable here as they crack easily under heavy shock.
High-Speed Tool Steel Grades
Core Properties
Alloyed with tungsten, molybdenum, chromium and vanadium, high-speed steel maintains stable hardness up to 65 HRC even under continuous cutting heat — a property known as red hardness. It avoids softening from frictional heat generated during high-speed machining and retains sharp cutting edges for long production runs.
Typical Applications
The primary material for all high-speed metal cutting equipment: twist drill bits, milling cutters, gear hobs, taps, saw blades and woodworking router bits. Its thermal stability allows uninterrupted high-volume machining and lowers overall production costs by reducing frequent tool replacement.
Hot-Work Tool Steel Grades
Core Properties
Hot-working steel relies on chromium, molybdenum and tungsten to form thermally stable carbides, resisting softening, oxidation and thermal fatigue under cyclic extreme heat. Bainite matrix variants deliver extra ductility to prevent thermal cracking under rapid temperature swings.
| Alloy Element | High-Temperature Performance Benefits |
|---|---|
| Chromium | Improves high-temp tensile strength, hardness and anti-scaling performance |
| Molybdenum | Boosts creep resistance, toughness and machinability at high heat |
| Tungsten | Reinforces hot hardness and long-term forming durability |
Typical Applications
Manufacturers select hot-work steel for processes combining extreme heat and mechanical pressure: hot forging dies, aluminum extrusion dies, hot stamping dies for auto & aerospace components and rolling mill rollers. H13 is the most widely used grade for high-pressure die casting mass production.
Special-Purpose Tool Steel (Plastic Mold Steel)
Core Properties
Customized for plastic injection molding, this steel prioritizes high polishability, corrosion resistance, dimensional stability and fatigue resistance. It avoids warpage during long molding cycles and supports mirror polishing for transparent optical and medical plastic parts.
| Key Mold Steel Property | Production Benefit |
|---|---|
| Thermal Shock Resistance | Prevents surface cracking from frequent heating & cooling cycles |
| Dimensional Stability | Eliminates part size deviation over thousands of molding shots |
| High Polishability | Achieves flawless mirror finish for transparent and cosmetic components |
| Corrosion Resistance | Compatible with PVC and acidic plastic raw materials |
Typical Applications
Main grades: P20, S7, H13 and 420 stainless mold steel
- P20: Medium-volume general injection molds
- 420 stainless: Corrosion-resistant molds for medical and food packaging
- S7: High-precision molds requiring mirror polishing Widely used in automotive plastic components, medical device molds, transparent optical parts and consumer household product molding.
Comparison of the Six Core Tool Steel Families
| Grade Family | Standout Advantage | Max Hardness (HRC) | Ideal Application Scenario |
|---|---|---|---|
| Water-Hardening | Low cost, easy edge sharpening | 65 | Low-load simple hand cutting tools |
| Cold-Work | Superior wear resistance | 63 | Room-temperature stamping, blanking dies |
| Shock-Resisting | Extreme impact toughness | 58 | Mining, construction impact tools |
| High-Speed | Outstanding red hardness | 65 | High-speed metal machining cutters |
| Hot-Work | Thermal fatigue resistance | 54 | Hot forging, die casting at high temperatures |
| Plastic Mold Special-Purpose | High polish & dimensional stability | 52 | Precision injection molds |
How to Select the Right Tool Steel
When sourcing tool steel, manufacturers need to evaluate six critical factors: working temperature, impact load, abrasion degree, dimensional precision requirements, material budget and machinability. Partnering with a professional supplier simplifies selection.
NSPM supplies the full lineup of all six tool steel grades and employs a team of metallurgy specialists to deliver customized material recommendations matching unique production processes, extending tool lifespan and cutting operational costs for factories worldwide.
FAQ
What differentiates air-hardening and oil-hardening cold-work tool steel?
Air-hardening steel cools naturally in ambient air after heating, resulting in minimal distortion and cracking risk, suitable for large-size precision dies. Oil-hardening steel uses oil quenching for deeper hardness penetration, better for small compact cutting tools. Both fall under the cold-work tool steel family among the six core grades.
What are high carbon-chromium cold-work steels used for?
High carbon-chromium steel (represented by D2) delivers top-tier wear resistance, making it ideal for long-run blanking punches, trimming dies and abrasive material cutting tools operating at room temperature.
Which of the six tool steel grades works best for high-temperature die casting?
Hot-working tool steel (H13 as the primary grade) is the optimal choice for die casting, as it retains hardness and resists thermal cracking under repeated molten metal contact.
Which grade is dedicated to transparent plastic part molds?
Special-purpose plastic mold steel (420 stainless or high-polish P20 variants) offers excellent mirror polish performance and dimensional stability, perfect for clear optical and cosmetic plastic components.
Can one tool steel grade cover multiple manufacturing processes?
Generally not. Each of the six core tool steel families is metallurgically optimized for a narrow working condition range. Cross-scenario use leads to premature wear, cracking or dimensional failure and raises long-term production expenses.