Selecting the right tool steel is one of the most critical decisions in the design and performance of molds and dies used in high-temperature operations such as die casting, forging, and extrusion. Among the various grades available, AISI H12 and AISI H13 are two of the most popular choices in the hot work tool steel family.
Both steels are engineered for extreme heat resistance, strength, and toughness, but they possess distinct characteristics that make each suitable for specific applications. In this article, SAKYSTEEL analyzes the key differences between AISI H12 and H13, helping you make the right choice for your mold manufacturing and tooling requirements.
Hot work tool steels are designed to maintain mechanical strength and hardness even under the severe conditions of high temperature and cyclic thermal loading. In industries like die casting, hot forging, and extrusion, the wrong material selection can lead to cracking, premature wear, or dimensional distortion—resulting in costly downtime and mold failure.
Therefore, understanding the differences between AISI H12 and H13 is crucial for achieving the best balance between toughness, wear resistance, and thermal fatigue performance.
Both AISI H12 and AISI H13 belong to the AISI H-series of hot work tool steels, which are chromium-based steels known for their ability to resist softening at high temperatures.
AISI H12 (UNS T20812): A chromium-molybdenum-tungsten steel offering excellent thermal fatigue resistance and superior toughness.
AISI H13 (UNS T20813): A chromium-molybdenum-vanadium steel with higher wear resistance and good red hardness, often considered the industry standard for die-casting molds.
These steels are both widely used, but their specific alloying elements create differences in performance that make them better suited to different types of molds and operating conditions.
The primary difference between AISI H12 and H13 lies in their alloy composition, which directly influences hardness, toughness, and thermal resistance.
| Element | AISI H12 (%) | AISI H13 (%) | Effect on Performance |
|---|---|---|---|
| Carbon (C) | 0.35–0.45 | 0.35–0.40 | Controls hardness and wear resistance |
| Chromium (Cr) | 4.75–5.50 | 4.75–5.50 | Improves corrosion and oxidation resistance |
| Molybdenum (Mo) | 1.10–1.75 | 1.00–1.50 | Enhances hardenability and strength |
| Tungsten (W) | 1.00–1.75 | — | Boosts hot strength and red hardness |
| Vanadium (V) | 0.20–0.60 | 0.80–1.20 | Refines grain structure and increases wear resistance |
| Silicon (Si) | 0.80–1.20 | 1.00 | Improves oxidation resistance and hardness stability |
| Manganese (Mn) | 0.25–0.50 | 0.30–0.50 | Improves hardenability and toughness |
Key takeaway:
AISI H12 contains tungsten (W), which provides superior hot strength and toughness, while AISI H13 has a higher vanadium (V) content, improving wear resistance and hardness at high temperatures.
Both steels perform well under hot working conditions, but each excels in different mechanical aspects.
| Property | AISI H12 | AISI H13 |
|---|---|---|
| Density | 7.80 g/cm³ | 7.80 g/cm³ |
| Hardness (Annealed) | ≤ 229 HB | ≤ 229 HB |
| Hardness (After Hardening & Tempering) | 44–52 HRC | 46–54 HRC |
| Tensile Strength | 1500–1900 MPa | 1600–2000 MPa |
| Thermal Fatigue Resistance | Excellent | Excellent |
| Wear Resistance | High | Very High |
| Impact Toughness | Excellent | Very Good |
| Machinability | Good | Moderate |
AISI H12 offers better impact toughness and resistance to cracking, while AISI H13 provides superior surface wear resistance and slightly higher hardness retention during prolonged heat exposure.
Heat treatment plays a crucial role in determining the final performance of both steels.
Annealing: 850–900°C, slow furnace cooling
Hardening: 1000–1050°C, air or oil quench
Tempering: 500–650°C (double tempering recommended)
Annealing: 850–900°C, slow furnace cooling
Hardening: 1020–1040°C, air quench
Tempering: 520–620°C (double tempering for dimensional stability)
Summary:
H13 can withstand slightly higher hardening temperatures, achieving greater surface hardness. H12, however, offers superior thermal shock resistance and better dimensional stability in large tooling sections.
Ideal for forging dies, hot trimming tools, and extrusion molds that experience severe thermal cycling.
Performs exceptionally in conditions requiring repeated impact and high heat shock.
Preferred when toughness and crack resistance are more critical than maximum hardness.
Widely used in pressure die casting, plastic injection molds, and hot runner systems.
Excellent choice for tools requiring fine surface finish and high wear resistance.
Performs better under long exposure to molten aluminum or magnesium alloys.
In summary:
Choose H12 for heavy-duty, impact-prone operations.
Choose H13 for precision die casting requiring higher surface hardness.
Thermal fatigue, or “heat checking,” is a common failure mode in hot work tools.
Both AISI H12 and H13 resist this effectively, but the underlying mechanisms differ.
H12: Uses tungsten to resist structural softening and maintain stability under thermal cycling.
H13: Relies on vanadium carbides for surface stability and resistance to cracking.
For tools exposed to extreme temperature fluctuations, AISI H12 tends to outperform due to its toughness and lower sensitivity to rapid temperature changes.
AISI H13 forms fine vanadium carbides, giving it higher wear resistance during high-pressure metal flow, such as in die casting and extrusion dies.
AISI H12, while slightly softer, provides longer life in impact-heavy forging applications.
Both steels can be nitrided or PVD coated to extend service life.
Nitriding enhances surface hardness to over 1000 HV, providing excellent protection against erosion and adhesive wear.
| Aspect | AISI H12 | AISI H13 |
|---|---|---|
| Machinability | Easier to machine | Slightly harder to machine |
| Weldability | Excellent with preheat | Good with controlled heat |
| Preheat Temperature | 250–350°C | 250–400°C |
| Post-Weld Heat Treatment | Temper immediately | Temper immediately |
AISI H12’s structure allows smoother machining and repair welding, making it preferred when post-processing and mold repair frequency are high.
While both grades are similar in cost, AISI H12 is typically slightly more economical due to its lower vanadium content and simpler alloy design.
However, in applications where tool longevity and surface quality are more important than initial cost, AISI H13 may offer better long-term value.
Companies like SAKYSTEEL provide both grades in cost-effective supply forms—ensuring customers achieve the best performance-to-price ratio based on their production needs.
| Application | Recommended Steel | Reason |
|---|---|---|
| Drop forging dies | AISI H12 | High toughness, impact resistance |
| Aluminum die casting molds | AISI H13 | Superior wear resistance, surface finish |
| Hot trimming tools | AISI H12 | Shock resistance |
| Plastic injection molds | AISI H13 | Dimensional stability |
| Extrusion dies | AISI H12 or H13 | Based on pressure and temperature |
| Hot shear blades | AISI H12 | Crack resistance |
| Core pins and inserts | AISI H13 | Hardness and polishability |
SAKYSTEEL is a professional global supplier of high-quality hot work tool steels, including AISI H12 and H13. With advanced production, precision machining, and strict quality control, SAKYSTEEL ensures every product meets international standards such as ASTM A681, DIN EN ISO 4957, and JIS G4404.
Certified Quality – All materials are supplied with EN 10204 3.1 certificates.
Custom Processing – Machining, cutting, and heat treatment according to customer requirements.
Large Inventory – Ready-to-ship stock in various sizes and shapes.
Competitive Pricing – Factory-direct sales to reduce cost.
Global Support – Serving over 40 countries in tooling, die casting, and forging industries.
When it comes to performance and reliability, SAKYSTEEL provides the ideal combination of expertise and material quality to support your mold and die applications.
| Feature | AISI H12 | AISI H13 |
|---|---|---|
| Hot Strength | Excellent | Very Good |
| Toughness | Very High | High |
| Wear Resistance | High | Very High |
| Thermal Fatigue Resistance | Excellent | Excellent |
| Heat Checking Resistance | Excellent | Very Good |
| Machinability | Better | Moderate |
| Cost | Slightly Lower | Slightly Higher |
| Best Use | Forging Dies, Extrusion Tools | Die Casting Molds, Precision Molds |
When comparing AISI H12 vs H13, both steels deliver high performance under demanding hot work conditions, but the ideal choice depends on your application:
Choose AISI H12 if your process involves heavy impact, large dies, or frequent thermal cycling.
Choose AISI H13 if your focus is on wear resistance, fine surface finishes, and prolonged exposure to molten metals.
With deep metallurgical expertise and global supply capability, SAKYSTEEL offers both AISI H12 and H13 hot work tool steels in multiple forms—ensuring your molds, dies, and tooling systems achieve maximum efficiency, durability, and cost performance.