Thermodur® E40K Superclean: The Definitive Answer to Thermal Fatigue

We continue our column “Specialty as Normality” with a steel that has transformed the management of the number one criticality in the foundry: thermal fatigue (heat checking). We are talking about Thermodur® E40K Superclean. While standard steels like 1.2343 (H11) and 1.2344 (H13) have represented the backbone of die casting for decades, the evolution of processes and the demand for increasingly intensive cycles have made a leap in quality necessary. E40K was born precisely here: where standards reach their limit of thermal fatigue resistance.

The official technical datasheet of Thermodur® E40K Superclean.

Click here to download the full technical datasheet in PDF

Why consider E40K a necessary “normality” and not just a special steel? The answer lies in the direct comparison with the materials you use daily. Comparative tests, conducted both in research laboratories and in real applications (as documented in our scientific papers), show substantial differences:

• Compared to 1.2343 (H11): E40K offers superior hot strength while maintaining the high toughness that often makes H11 preferred for large dies.
• Compared to 1.2344 (H13): The performance leap is evident in the resistance to crack propagation. Where H13 begins to show the classic “crocodile skin” (heat checking), E40K resists longer, delaying initiation and slowing the growth of the cracks themselves.

In summary: E40K combines the toughness needed to avoid sudden breakage (catastrophic failure) with the thermal resistance essential for lasting over time.

The superiority of this material is the result of years of research and field tests, validated by the most important institutions in the sector.

We have collected the most relevant technical documentation for you to delve into every aspect:

Presented at the American congress last year, this study details E40K’s performance with real case studies on automotive and structural components.

An in-depth analysis (in Italian), curated by our technical department, analyzing resilience tests and tempering curves compared to grades 1.2343 and 1.2344.

Read the dedicated article on our blog:

👉 Thermal Fatigue Resistance: The Technical Analysis of Thermodur E40K Superclean

Switching from 1.2344 to E40K becomes strategic when:

• Die life is prematurely limited by thermal fatigue.
• Producing large castings with dies that require high toughness.
• You want to reduce the frequency of maintenance for polishing or die restoration.

Considering Thermodur® E40K Superclean only as a “special” steel means limiting your foundry’s potential. Today, for those seeking efficiency and durability, this material represents the new benchmark standard. Bonomi Acciai, partner of Swiss Steel Group, is at your disposal to analyze your application and evaluate the switch to new high-performance grades.