Tool Steel, D2/A2/H13/M2, Hardness, Wear Resistance, Heat Treatment, Machining

Explore comprehensive tool steel material properties with detailed grades, chemical composition, hardness, heat treatment, and application guides.

Quick Comparison Table: Top Tool Steel Grades

Here’s a snapshot of the most popular tool steel grades used across industries. This quick guide covers their key properties, typical hardness, and main applications—helping you pick the right material fast.

Grade (AISI)	Common Name	DIN/EN Equivalent	Key Properties	Typical Hardness (HRC)	Main Applications
D2	D2 (High Carbon, High Chromium)	1.2379	Excellent wear resistance, good toughness	58–62	Blanking, cold work dies, punches
A2	A2 (Air Hardening)	1.2363	Balanced toughness and wear resistance	56–60	Blanking, forming, medium-run tooling
O1	Oil Hardening	1.2510	Good machinability, decent wear resistance	55–62	Guards, jigs, cutting tools
H13	Hot Work Tool Steel	1.2344	Excellent thermal fatigue resistance, toughness	48–53	Hot forging dies, extrusion dies
M2	High-Speed Steel (HSS)	1.3343	High hardness, wear resistance, moderate toughness	62–67	Cutting tools, drills, milling cutters
S7	Shock-Resisting Tool Steel	1.2310	Superior impact resistance and toughness	54–60	Cold work tools, chisels, punches
P20	Plastic Mold Steel	1.2311	Good polishability, corrosion resistance	28–32 (pre-hardened)	Plastic injection moulds
1.2344	Tool Steel (Hot Work)	1.2344	Excellent hot hardness, wear resistance and thermal fatigue resistance	50–54	Hot stamping, die casting tools

This table provides a clear overview of common tool steels, helping you quickly assess which grade might suit your project needs. Each has well-documented properties according to international standards for reliable performance in United Kingdom manufacturing.

What Is Tool Steel?

Tool steel is a special type of steel designed to make tools that need to resist high wear and tear, maintain sharpness, and handle tough working conditions. Unlike regular steels, tool steels contain specific alloying elements such as carbon, chromium, vanadium, and molybdenum that enhance hardness, toughness, and heat resistance.

Tool Steel Classification

Tool steels are categorised into distinct groups based on their typical uses and properties:

Cold Work Tool Steel: Used for tools that operate at room temperature, such as punches, dies, and shear blades. These steels offer high hardness and wear resistance but are not intended for high heat.
Hot Work Tool Steel: Designed to withstand high temperatures without losing hardness. Commonly used in forging, extrusion, and die-casting tools. H13 is a popular hot work grade.
High-Speed Steel (HSS): Known for maintaining hardness even at red-hot cutting speeds. M2 is a classic high-speed steel grade used in cutting tools and drills.
Shock-Resisting Tool Steel: Constructed to handle impact and shock without cracking. S7 is a typical shock-resistant grade used in hammers and heavy-duty tools.
Plastic Mold Steel: Used to produce moulds for plastic injection moulding. These steels, such as P20, combine good machinability, hardness, and resistance to cracking.

Understanding these classifications helps you select the right steel for your application, whether you need wear resistance, heat tolerance, or impact strength. For more insights into machining and design, refer to our guide on helix angle for machining and gear design.

Key Mechanical & Physical Properties Explained

Understanding the key mechanical and physical properties of tool steel is vital to selecting the right grade for your application. Here’s a straightforward breakdown of what matters most:

Hardness & Wear Resistance

Hardness defines a tool steel’s ability to resist deformation and scratching. Grades like D2 and M2 are known for their high hardness (usually above 60 HRC), offering excellent wear resistance—ideal for cutting, punching, or forming tools that face constant abrasion.

Toughness & Impact Resistance

Toughness is about how well the steel handles shocks without cracking. Shock-resisting grades such as S7 excel here, providing durability under sudden impact, while hot work steels like H13 combine toughness with heat resistance, perfect for forging and extrusion dies.

Machinability

Some tool steels, like O1 and A2, are easier to machine in their annealed state, helping save time and costs during initial shaping. High-speed steels (M2) and air-hardening grades are typically tougher to machine but offer longer tool life after heat treatment.

Dimensional Stability after Heat Treatment

Tool steels must maintain shape and size after hardening to ensure precision. Grades like A2 and P20 are prized for their good dimensional stability, making them favourites for moulds and dies where tight tolerances are critical.

Thermal Fatigue Resistance

For tools exposed to repeated heating and cooling cycles, like hot work steels H13 and 1.2344, thermal fatigue resistance prevents cracks and extends tool life by enduring thermal shock stresses.

Corrosion Resistance

While many tool steels aren’t corrosion-resistant by default, some grades like modified 420 stainless steel, and D3 or D6, offer improved resistance to rust and oxidation, a must for tools exposed to moist or corrosive environments.

By balancing these properties with your specific needs—whether you need wear resistance, toughness, or corrosion protection—you can confidently choose the tool steel that delivers optimal performance. For detailed information on heat treatment and best machining practices of these steels, consider exploring our comprehensive tool steel heat treatment guide.

Detailed Grade-by-Grade Technical Data Sheets

When selecting tool steel, understanding detailed technical data for each grade is key. This includes international designations, chemical makeup, physical and mechanical properties, heat treatment guidelines, hardness ranges, and typical applications. We also stock large sizes and various forms like round bars, flats, plates, and blocks to suit your project needs.

International Designations

Grade (AISI)	DIN/EN	JIS	GB
D2	1.2379	SKD11	GCr12
A2	1.2363	SKD12	GCr12Mo
O1	1.2510	SKS3	9CrWMn
H13	1.2344	SKD61	CrMoV
M2	1.3343 / 1.3243	SKH51	W18Cr4V
S7	–	–	–
P20	1.2311	–	–

Chemical Composition Snapshot (%) — Example for D2 and H13

Element	D2	H13
C	1.5–1.6	0.32–0.45
Cr	11.5–13	4.75–5.5
Mo	0.7–1.2	1.1–1.75
V	0.9–1.4	0.8–1.2
Mn	0.3	0.2–0.5
Si	0.3	0.8–1.2

Physical Properties

Property	D2	H13
Density (g/cm³)	7.6	7.8
Thermal Conductivity (W/m·K)	19	28
Coefficient of Thermal Expansion (CTE, µm/m·°C)	11.3	12.3
Modulus of Elasticity (GPa)	210	205

Mechanical Properties (Typical)

Grade	Annealed Hardness (HRC)	Hardened Hardness (HRC)
D2	55	60-62
A2	55	58-60
O1	40	58-62
H13	25	48-52
M2	36	63-65
S7	28	50-56
P20	22	30-36

Recommended Heat Treatment

Step	D2 (°F)	H13 (°F)
Preheating	1100–1200	1475–1575
Austenitising	1850–1900	1900–2050
Quenching	Oil or Air	Air or Oil
Tempering	300–400 (3x)	900–1100 (2x)

Achievable Hardness Range

D2: 58-62 HRC (ideal for high wear resistance)
H13: 48-52 HRC (excellent for hot work applications)
M2: Up to 65 HRC (high-speed steel)
S7: 50-56 HRC (shock resistance)

Typical Applications + Industry Examples

D2: Cutting tools, dies for blanking, shear blades
A2: Punches, forming dies, gauges
O1: General-purpose tooling, jigs, dies
H13: Hot forging dies, extrusion tooling, die casting moulds
M2: High-speed drills, taps, milling cutters
S7: Impact tools, heavy-duty punches, cold chisels
P20: Plastic injection mould bases and cores

Stock Sizes & Forms

We supply wide ranges:

Round bars: Diameters from 1/4″ to 12″+
Flat bars: Thicknesses from 1/8″ to 4″+
Plates: Up to 6″ thick and large surface dimensions
Blocks: Custom cut sizes available

Our substantial inventory ensures quick turnaround for your tooling projects.

For additional insights into steel types used in tooling and their benefits, you might find helpful information in our guide comparing cast materials with aluminium alloys used in tooling applications.

This detailed grade-by-grade data will help you precisely match your project requirements with the right tool steel, verified by international standards and backed by tested mechanical and physical properties.

Tool Steel Selection Guide: Pick the Right Grade for Your Application

Choosing the right tool steel grade depends heavily on your specific application. Here’s a quick decision matrix to help you match the best steel type with common uses like blanking, forming, extrusion, injection moulding, and forging dies.

Application	Recommended Grades	Key Reasons
Blanking	D2, A2, O1	High wear resistance, good toughness
Forming	A2, O1, S7	Balanced hardness & toughness, shock resistant
Extrusion Dies	H13, 1.2344 (DIN), M2	Excellent thermal fatigue resistance, hot work capability
Injection Moulding	P20, 420 modified	Good machinability, corrosion resistance
Forging Dies	H13, S7, M2	High toughness, wear & heat resistance
Cutting Tools	M2, D2, A2	Superior hardness & wear resistance
Plastic Moulds	P20, 1.2311 (pre-hardened)	Easy to machine, consistent dimensional stability

How to Decide?

Wear Resistance Needed? Look at D2 or M2 for extremely hard, wear-resistant tools.
Impact & Shock Loads? Choose S7 or A2 for toughness to prevent cracking.
High Heat Applications? Go with H13 or M2, built to handle hot work & thermal fatigue.
Machinability & Surface Finish?P20 and 420 modified Offer good finishes for moulds with some corrosion resistance.
Dimensional stability after heat treatment? Consider 1.2311 pre-hardened steels for easier machining and minimal distortion.

This matrix helps simplify the complex selection process, but remember heat treatment and surface coatings will further influence tool performance. For injection moulding specifics, check out our detailed low volume injection moulding guide for best practices.

By matching tool steel grades to your needs, you’ll extend tool life and achieve better part quality with less downtime.

Heat treatment of tool steel – best practices

Heat treatment is key to unlocking the full potential of tool steel material properties. Properly done, it ensures ideal hardness, toughness, and wear resistance for your application. Here’s a straightforward guide to best practices, tempering curves, and common pitfalls to avoid.

Step-by-step heat treatment guidelines

Preheating: Heat the tool steel gradually to around 1,200°F–1,400°F (650°C–760°C) to reduce thermal shock and minimise distortion. Preheating helps prevent cracking during higher temperature treatments.
Austenitising (hardening): Raise the temperature to the steel’s austenitising range (typically 1,700°F–2,100°F or 925°C–1,150°C, depending on grade). Hold long enough for uniform heating—usually 20–40 minutes per inch of thickness. Use oil, air, or gas quenching based on the steel type (e.g., H13 is air-hardened; D2 requires oil quenching).
Quenching: Rapid cooling locks in the hard microstructure. The method varies:
- Oil quenching for grades like D2 and O1.
- Air quenching for air-hardening steels like A2 or H13.
- Gas or vacuum quenching for clean, distortion-free parts.
Tempering: Temper immediately after quenching to reduce brittleness. Tempering temperatures typically range from 350°F to 1,100°F (175°C to 600°C), depending on desired hardness and toughness. Repeat tempering (double or triple) is common for stable properties. Use tempering curves specific to the steel grade to target the right balance of hardness and toughness.

Understanding Tempering Curves

Tempering curves plot hardness against tempering temperature. They show how hardness drops as you increase heat, revealing a sweet spot where toughness improves without too much hardness loss. For example, D2 tool steel might drop from HRC 62 at low tempering to HRC 58 at moderate tempering—ideal for many die applications.

Common Heat Treatment Pitfalls to Avoid

Skipping Preheat: Leads to cracking and distortion.
Wrong Quench Medium: Using air instead of oil on steels needing oil quench can cause incomplete hardening.
Overheating During Austenitising: Excessive temperature causes grain growth, reducing toughness.
Insufficient Tempering: Leaves tools brittle, prone to cracking during use.
Tempering at Too High a Temperature: Causes excessive softening, reducing wear resistance.

Following these best practices ensures your tool steels deliver peak performance, long life, and reliable results. For tailored heat treatment advice on grades like H13 or M2, consulting a detailed tool steel heat treatment guide is highly recommended.

For machining and precision work, consider pairing heat-treated steels with advanced processes described in our mastering horizontal milling machines guide for precision and efficiency to achieve optimal final results.

Machining & Grinding Recommendations for Tool Steel

When working with tool steel, proper machining and grinding settings are crucial to avoid tool wear, maintain dimensional accuracy, and achieve a good surface finish. Here’s a quick guide covering cutting speeds, feeds, and EDM parameters for popular tool steels.

Cutting Speeds and Feeds

Grade	Cutting Speed (SFM)	Feed Rate (IPR)	Notes
D2	40 – 70	0.002 – 0.005	High wear resistance; use rigid setups
A2	60 – 90	0.003 – 0.006	Easier to machine than D2
O1	80 – 120	0.004 – 0.008	Good machinability
H13	80 – 150	0.004 – 0.010	Air-hardening; use coolant
M2	100 – 180	0.003 – 0.007	Requires sharp tools, coolant recommended
S7	70 – 110	0.003 – 0.006	Tough, shock-resistant
P20	90 – 130	0.004 – 0.008	Pre-hardened grade, easy to machine
1.2344 (H13 equivalent)	80 – 150	0.004 – 0.010	Widely used hot work steel

Note: Always use flooded coolant or appropriate lubrication to reduce heat and tool wear during machining.

Grinding Parameters

Grade	Wheel Type	Wheel Speed (RPM)	Downfeed (IPR)	Dressing Interval
D2	CBN (cubic boron nitride)	3000 – 3500	0.0002 – 0.0005	Frequent
A2	Aluminium Oxide	2500 – 3000	0.0003 – 0.0006	Moderate
O1	Aluminium Oxide	2500 – 3000	0.0004 – 0.0008	Moderate
H13	CBN / Aluminium Oxide	3000 – 3500	0.0003 – 0.0007	Frequent
M2	CBN	3000 – 3500	0.0002 – 0.0005	Frequent
S7	Aluminium Oxide	2500 – 3000	0.0003 – 0.0007	Moderate
P20	Aluminium Oxide	2500 – 3000	0.0004 – 0.0008	Moderate

Using CBN wheels is preferred for hard grades like D2 and M2 for faster removal and cooler grinding.

EDM Parameters (Electrical Discharge Machining)

Tool Electrode Materials: Copper or graphite, depending on precision and surface finish needed.
Pulse On Time: Short pulses (10-30 µs) for fine finishes; longer pulses (50–100 µs) for roughing.
Discharge Current: 3–15 amps for fine machining; up to 30 amps for rougher cuts.
Servo Feed Rate: Moderate to high feed rate to maintain spark gap; adjust to avoid arcing.
Dielectric Fluid: Use deionised water or specific EDM fluids for effective debris removal.

EDM is ideal for complex or hard-to-machine tool steel shapes, especially for hard grades like H13 and M2.

Optimising your cutting speeds, feeds, grinding setups, and EDM settings based on tool steel grade will extend tool life and improve efficiency. For practical machining insights, check our guide on CNC milling and precision machine processes.

Surface Treatments & Coatings for Extended Tool Life

To get the most out of your tool steel materials, surface treatments and coatings play a vital role in boosting durability and performance. These processes help reduce wear, improve hardness, and protect against corrosion or heat damage.

PVD Coatings (TiN, TiAlN, CrN)

Physical Vapour Deposition (PVD) coatings like Titanium Nitride (TiN), Titanium Aluminium Nitride (TiAlN), and Chromium Nitride (CrN) are popular options. They provide a hard, thin layer that:

Increases wear resistance
Reduces friction
Enhances heat resistance, especially important for high-speed steels like M2
Improves tool lifespan in demanding applications such as stamping, forming, and cutting

Nitriding

Nitriding is a heat treatment that diffuses nitrogen into the surface of the steel, forming a hard, wear-resistant layer without the need for further coating. It’s excellent for:

Improving surface hardness and fatigue resistance
Extending the life of dies and punches without sacrificing core toughness
Retaining dimensional stability

This method is often used for grades like H13 and S7 that work under repeated thermal and mechanical stress.

Diamond-Like Carbon (DLC)

DLC coatings are amorphous carbon layers that mimic diamond properties. Their benefits include:

Exceptional hardness with low friction
Resistance to wear and galling
Corrosion resistance, useful for tool steels exposed to harsh environments

DLC is especially useful for plastic mould steels like P20, where sticking and wear are concerns.

By choosing the right surface treatment or coating for your tool steel, you can significantly extend tool life, maintain precision, and reduce downtime. For details on dimensional stability and tolerance considerations when working with heat-treated steels, check out our detailed tolerance allowance explained guide.

Certifications & Quality Assurance

In the UK market, quality and consistency are key when choosing tool steel materials. That’s why reputable tool steel suppliers provide Mill Test Certificates (MTCs) with every batch. These certificates verify the chemical composition, mechanical properties, and heat treatment status, ensuring you get exactly what you ordered.

Most tool steel materials conform to ISO 9001 quality management standards, which means the manufacturing process follows strict guidelines for reliability and traceability. This helps reduce variability and boosts confidence in the product’s performance.

Compliance with ASTM and AISI standards is another critical factor. These standards define accepted chemical and mechanical properties for tool steel grades, making it easier for manufacturers and engineers to select the right material for specific applications — whether it’s cold work, hot work, or high-speed tool steel.

If you want peace of mind for your projects, always check for certified steel supplies that back their product with full mill test reports and meet these recognised standards. This approach helps you avoid surprises and ensures your production process runs smoothly.

Stock Availability & Custom Cutting Services

We keep a broad inventory of popular tool steel grades in various sizes ready for immediate delivery, providing you with quick turnaround times when you need it most. Whether you’re looking for round bars, flat bars, plates, or blocks, chances are we have the right size in stock.

Our custom cutting services include precise sawing, milling, and grinding to match your exact project requirements. This means you get clean, ready-to-use pieces that save you time and effort before machining or heat treatment.

Available Stock Sizes:

Round bars: typically from small diameters up to large-size stocks
Flat bars and plates: multiple thicknesses and widths
Blocks: for heavy-duty or prototype tooling

Custom Processing Services:

Sawing: Accurate sectional cuts with minimal burrs
Milling: Tight dimensional tolerances for complex shapes
Grinding: Surface finishes and precise thickness control

With our local cutting and processing options, you avoid shipping delays and get tailored tool steel materials quickly. This is especially important for time-sensitive tooling jobs or when working with high-demand grades like D2, H13, or M2.

If you want to optimise your machining setup, understanding different tooling types and heads can enhance productivity — check out our detailed guide on different types of drill bit heads to help plan your operations better.

We’re here to ensure your tool steel order fits your specifications perfectly and arrives promptly to keep your production moving.

FAQs About Tool Steel Properties

Here are answers to some common questions we get from users about tool steel properties to help you make the right choice.

Question	Answer
What’s the difference between D2 and A2?	D2 is higher in carbon and chromium, giving better wear resistance but less toughness than A2, which is easier to machine and more impact-resistant.
Is H13 air-hardening?	No, H13 is a hot work tool steel that typically requires oil or gas quenching. Air hardening is usually for grades like A2 or S7.
What’s the max working temperature for M2?	M2 can handle around 1100°F (593°C) before losing hardness, making it great for high-speed cutting tools.
Which grade offers the best toughness?	Shock-resisting steels like S7 have superior toughness to resist impact and shock loads.
Can D2 rust easily?	Yes, D2 has moderate corrosion resistance due to its high chromium but it can still rust if not maintained properly.
What is the typical hardness range for O1?	O1 usually achieves from 57 to 62 HRC after heat treatment.
Is P20 suitable for plastic moulds?	Yes, P20 is commonly used for plastic mould tooling due to good machinability and decent wear resistance.
How to choose between cold work and hot work tool steel?	Use cold work steels like D2 or A2 for room temperature tools, and hot work steels like H13 for high temperature applications.
Does the chemical composition affect machinability?	Absolutely, higher carbon and alloying elements typically reduce machinability but improve wear resistance.
What does “air hardening” tool steel mean?	It means the steel can reach full hardness just by cooling in air after heat treatment, simplifying the process.

If you want more detailed technical specs or help picking the right grade for your project, feel free to contact us via live chat or request a quote.

For a deeper breakdown on selecting the right tool steel and understanding fits and tolerances in your tooling, check our detailed engineering fit guide.

Related Products & Resources

For easy access to detailed tool steel information, we offer a Downloadable PDF Catalogue packed with technical specs, chemical compositions, mechanical properties, and heat treatment guidelines for all major grades. This comprehensive catalogue helps you quickly compare different materials and select the best grade for your application.

Additionally, our Hardness Conversion Table makes it simple to switch between common hardness scales (HRC, HRB, Vickers, Brinell), an essential tool when verifying material specifications or planning heat treatments.

We also provide a handy Tempering Parameter Calculator link, designed to help adjust tempering temperatures and times for optimal toughness and stability tailored to your specific tool steel grade.

These resources support informed decisions and maximise efficiency, ensuring you get the right tool steel with precise properties.

For more precise machining and preparation tips, check out our guide on how to measure a screw thread accurately with callipers and gauges to maintain quality standards throughout manufacturing.

Get Your Tool Steel Quote Today

Ready to find the perfect tool steel grade for your project? Request a fast, no-obligation quotation now! Whether you need D2, H13, M2, or any other popular grade, our team is here to help you choose the right material with the right specifications.

For instant material recommendations, you can also reach out via live chat, WhatsApp, or email. We’ll guide you through grades, heat treatment options, and delivery details so you get exactly what you need—on time and on budget.

Don’t wait—contact us now and get started with top-quality tool steel for your application!