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Thermodur® E40K Superclean: Technical Analysis of Heat Checking Resistance for HPDC Dies
In the High-Pressure Die Casting (HPDC) sector, heat checking resistance is the most critical parameter determining the service life of a die. The continuous alternation of extreme thermal cycles inevitably leads to the formation of surface cracks, compromising the quality of the castings and increasing operating costs. To meet this challenge, Swiss Steel Group has developed the hot work tool steel Thermodur® E40K Superclean. This technical deep dive, based on the paper presented at the NADCA Die Casting Congress & Exposition 2024, analyzes the properties and industrial results of this innovative material.
The Official Abstract: Summary of the NADCA Research
Die casting applications require high-quality hot work tool steels that have the best property profile for the part to be produced. For steel producers, the requirements of the market are the most important starting point for further developments. The most critical parameter in die casting applications is heat checking resistance. To meet this requirement, Swiss Steel Group had developed Thermodur® E40K Superclean, which has been tested and approved by NADCA’s die material committee. Over the last several years, numerous field trials were completed and the feedback from the die casters confirmed our expectation of heat checking performance. In this paper we present a few of the most important field studies for Thermodur® E40K Superclean showing the benefit for the die casters.
Comparative Analysis: The Superior Performance of Thermodur® E40K Superclean
The development of Thermodur® E40K Superclean focused on optimizing toughness and, above all, resistance to thermal shock, which is responsible for 80% of die failures. Comparative analyses with standard steels like H13 ESR and 1.2367 ESR show a clear improvement in performance.
- Hot Mechanical Strength: Tensile tests at operating temperatures (between 500°C and 650°C) show that Thermodur® E40K Superclean has the best tensile and yield strength properties at all temperatures analyzed, with an advantage that increases as the temperature rises.
- Tempering Resistance: When exposed to typical die casting temperatures, steel loses hardness over time. In long-term tempering tests at 600°C, while H13 ESR steel shows a continuous and significant drop in hardness, Thermodur® E40K Superclean maintains a higher and more stable hardness level, similar to the 1.2367 ESR grade.
- Heat Checking Resistance: This is the most significant advantage. In experimental tests, steel samples were subjected to thousands of cycles of rapid heating to 600°C followed by quenching in 60°C water. After 8,000 cycles, Thermodur® E40K Superclean recorded a significantly lower maximum crack depth and total crack length compared to H11 ESR, H13 ESR, and 1.2367 ESR steels. Micrographs visually confirm the reduced crack propagation.
Field Results: Four Successful Case Studies
Laboratory tests have been validated by numerous industrial applications demonstrating the material’s effectiveness under real-world conditions.
- Automotive Component (Zamak) – Brazil: In the production of a Zamak keyring, the use of Thermodur® E40K Superclean increased the die life from 300,000 to over 700,000 shots, with a 233% increase in productivity compared to H13 ESR steel.
- Structural Component (Aluminum) – USA: For a structural ring in 380 aluminum, the H13 ESR die failed at 8,000 shots. Switching to Thermodur® E40K Superclean allowed them to consistently meet and exceed the target of 16,000 shots needed for the planned maintenance schedule.
- Water Pump for VW (Aluminum) – Brazil: In a mold for a water pump, the first thermal cracks on the standard material appeared after 5,000 cycles. With inserts made of Thermodur® E40K Superclean, the first signs only appeared after 25,000 cycles, raising the estimated service life from 100,000 to 150,000 shots.
- Lighting Fixture (Aluminum) – Italy: In the production of a street lighting module in 47100 aluminum alloy, the die life increased from 130,000 shots with H11 ESR to 208,000 shots with Thermodur® E40K Superclean, achieving a 60% improvement.
Heat Treatment Parameters
To achieve maximum performance, Thermodur® E40K Superclean requires specific heat treatment parameters: a slightly higher austenitizing temperature than H13 (1030-1040 °C) and tempering temperatures about 10-20°C higher to reach the desired working hardness.
Research in die casting requires technical knowledge, innovative materials, and the ability to translate results into concrete applications. The data and case studies presented confirm Thermodur® E40K Superclean as an excellent solution for maximizing heat checking resistance, extending die life, and improving the overall efficiency of die casting processes.
Bonomi Acciai, the Italian partner of Swiss Steel Group, continues to support die makers, designers, and foundries in developing high-performance solutions.
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