In modern industries such as forging, die casting, and extrusion, tool steels play an essential role in achieving precision, durability, and efficiency. Among the various hot work tool steels, AISI H12 stands out as a material that combines strength, toughness, and thermal resistance—making it a top choice for high-temperature tooling.
This article will explore what makes AISI H12 Hot Work Tool Steel an ideal solution for forging and die casting applications, covering its composition, mechanical properties, heat treatment, and key advantages. We will also introduce why SAKYSTEEL is one of the leading suppliers of H12 steel worldwide.
AISI H12, also designated as UNS T20812 or DIN X35CrW5, is a chromium-molybdenum-tungsten alloyed hot work tool steel. It belongs to the H-series steels (H10–H13), which are specifically engineered for applications involving elevated temperatures and severe mechanical stress.
Hot work tool steels like H12 are designed to maintain hardness and resist thermal fatigue even under repeated heating and cooling cycles. This makes them suitable for molds, dies, and tools used in hot deformation processes.
AISI H12 / UNS T20812
Werkstoff Nr. 1.2605
DIN X35CrW5 / X35CrMoV5-1
JIS SKD6
AISI H12 sits between H11 and H13 in terms of composition and performance, providing a well-balanced mix of strength, toughness, and heat resistance.
The composition of AISI H12 provides a combination of mechanical robustness and thermal stability, ensuring reliability under high heat and pressure.
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.35 – 0.45 |
| Chromium (Cr) | 4.75 – 5.50 |
| Molybdenum (Mo) | 1.10 – 1.75 |
| Tungsten (W) | 1.00 – 1.75 |
| Vanadium (V) | 0.20 – 0.60 |
| Silicon (Si) | 0.80 – 1.20 |
| Manganese (Mn) | 0.25 – 0.50 |
| Nickel (Ni) | ≤ 0.3 |
| Sulfur + Phosphorus (S+P) | ≤ 0.03 |
Chromium (Cr): Increases wear resistance and corrosion resistance.
Tungsten (W): Improves red hardness at high temperatures.
Molybdenum (Mo): Enhances strength and reduces brittleness.
Vanadium (V): Refines grain structure and improves toughness.
This optimized alloy system gives AISI H12 its excellent balance of hardness, strength, and thermal stability—perfect for hot work applications.
After proper heat treatment, AISI H12 demonstrates outstanding mechanical performance, ensuring reliability even under extreme thermal cycling.
| Property | Typical Value |
|---|---|
| Density | 7.8 g/cm³ |
| Hardness (Annealed) | ≤ 229 HB |
| Hardness (Hardened & Tempered) | 44–52 HRC |
| Tensile Strength | 1500–1900 MPa |
| Yield Strength | Approx. 1200 MPa |
| Elongation | 10–15% |
| Impact Toughness | Excellent at high temperatures |
These properties allow AISI H12 tools to operate in aggressive environments such as hot forging dies and die-casting molds without premature wear or cracking.
To achieve optimal properties, AISI H12 must undergo a proper heat treatment sequence. This process enhances hardness, strength, and dimensional stability.
Heat to 850–900°C
Hold for 2–4 hours
Furnace cool to 600°C, then air cool
Result: Soft structure (≤229 HB) for easy machining.
Gradual preheating in two stages:
450–500°C
850–900°C
Austenitize at 1000–1050°C
Hold for 20–30 minutes
Air or oil quench
Result: Hardness up to 52 HRC.
Temper immediately after quenching.
Double tempering recommended at 500–650°C.
Final hardness adjusted to 44–52 HRC based on tool requirements.
Proper heat treatment ensures a fine microstructure, high strength, and resistance to thermal shock.
AISI H12 Hot Work Tool Steel offers several unique advantages that make it the preferred choice for tooling and die applications:
High Hot Strength
Retains mechanical integrity even above 600°C.
Excellent Thermal Fatigue Resistance
Resists heat checking and cracking during repeated heating cycles.
Superior Toughness
Outstanding shock and impact resistance under forging pressures.
Good Dimensional Stability
Minimal distortion after heat treatment.
Resistance to Softening
Maintains hardness at elevated temperatures.
Wear and Abrasion Resistance
Excellent performance in high-friction environments such as extrusion dies.
Extended Tool Life
Reduced downtime and cost per cycle for industrial users.
These advantages make AISI H12 an all-around solution for both precision and heavy-duty hot work tools.
AISI H12’s versatility extends across several critical industrial sectors, including forging, die casting, and extrusion.
Drop forging dies
Press forging dies
Hot trimming dies
Hammer dies
AISI H12 is particularly useful in heavy-duty forging operations, where die life and impact resistance are crucial.
Pressure die-casting molds
Core pins, inserts, and sleeves
Hot chamber and cold chamber dies
Its ability to resist thermal cracking makes it ideal for zinc, aluminum, and magnesium die casting molds.
Aluminum and copper extrusion dies
Container liners
Mandrels and stems
AISI H12 provides excellent wear resistance during the extrusion of non-ferrous metals.
Hot forming dies for exhaust manifolds
Turbine blade molds
Valve and injector components
Hot trimming knives
Shear blades for red-hot steel bars and billets
These applications demonstrate AISI H12’s performance versatility and long service life under demanding operating conditions.
Although H13 is often seen as the industry benchmark, H12 provides distinct advantages in specific use cases.
| Property | AISI H12 | AISI H13 |
|---|---|---|
| Carbon | 0.40% | 0.40% |
| Chromium | 5.25% | 5.25% |
| Molybdenum | 1.25% | 1.35% |
| Tungsten | 1.50% | — |
| Hot Strength | Excellent | Very Good |
| Toughness | Very High | High |
| Wear Resistance | High | Very High |
| Thermal Fatigue Resistance | Excellent | Excellent |
AISI H12 is typically chosen when impact strength and thermal fatigue resistance are more critical than surface wear. It is therefore preferred in heavy forging dies and large die-casting molds.
Machinability rating: ~75% of AISI 4140 steel.
Best machined in annealed condition using carbide tooling.
Proper coolant flow extends tool life and surface finish quality.
Preheat to 250–350°C.
Post-weld tempering required to relieve stress.
Recommended filler material: similar composition to base metal.
Nitriding enhances surface hardness and wear resistance.
PVD coatings improve performance for precision die-casting tools.
Such treatments extend the life of AISI H12 components significantly.
SAKYSTEEL supplies AISI H12 Hot Work Tool Steel in a variety of forms and delivery conditions to meet diverse customer needs:
| Form | Condition |
|---|---|
| Round Bars | Annealed / Hardened & Tempered |
| Flat Bars | Annealed / Pre-machined |
| Plates / Blocks | Annealed or Machined to Size |
| Forged Billets | Custom Dimensions Available |
All products come with EN 10204 3.1 Mill Test Certificates, confirming chemical composition and mechanical properties. Upon request, ultrasonic testing (UT) and hardness certification can be included.
At SAKYSTEEL, each batch of AISI H12 undergoes strict inspection to ensure it meets international standards such as:
ASTM A681 – Alloy Tool Steels
DIN EN ISO 4957 – Tool Steels
JIS G4404 – Alloy Tool Steels
Quality assurance includes:
Chemical analysis
Hardness and tensile testing
Ultrasonic flaw detection
Microstructure inspection
With advanced metallurgical control and precision forging facilities, SAKYSTEEL ensures that every AISI H12 product provides optimal performance and reliability.
When selecting hot work tool steel, material consistency and processing quality are key to performance.
Here’s why customers worldwide trust SAKYSTEEL:
Certified Production Sources – Fully traceable batches with ISO and ASTM certifications.
Tailored Heat Treatment – Controlled furnace processing to achieve precise hardness levels.
Extensive Inventory – Immediate supply of standard sizes for urgent tooling projects.
Custom Machining Service – CNC cutting, grinding, and pre-hardened blocks available.
Global Export Experience – Serving clients in automotive, aerospace, and toolmaking sectors across over 40 countries.
With a commitment to precision and quality, SAKYSTEEL has established itself as a reliable partner for tool steel solutions in demanding industries.
To extend tool life and maintain performance:
Always preheat tools before hot operations.
Avoid rapid temperature changes that cause heat checking.
Double temper to improve ductility.
Apply protective surface coatings for abrasive applications.
Monitor cooling systems during die-casting operations.
Following these best practices maximizes return on investment and minimizes downtime in production lines.
AISI H12 Hot Work Tool Steel is a superior material designed to withstand the intense heat, stress, and abrasion of forging and die-casting environments. With its exceptional combination of toughness, thermal fatigue resistance, and strength, it has become a cornerstone alloy for toolmakers worldwide.
As industries pursue higher productivity and longer tool life, SAKYSTEEL continues to provide premium-grade AISI H12 products backed by expert technical support, competitive pricing, and global delivery capability. Whether you require forged blocks, precision bars, or machined dies, SAKYSTEEL delivers consistent quality and performance every time.