Preventing Heat Checking in H11 Die Casting Dies: Material Properties That Matter

Heat checking refers to thermal fatigue cracks that happen due to thermal cyclic stress in die casting dies. The cracks can vary from deep and sparse layers to fine, dense networks. Specific measures must be taken to counteract the heat checking impact in die casting dies. If you are currently in the lookout for an H11 steel supplier, you should pay attention to essential material properties that have a preventive impact on heat checking.

Critical Material Properties Imperative for H11 Dies

1. High-Temperature Yield Strength: By maintaining a high yield strength at elevated temperatures, you can retain the die surface in an elastic condition during the thermal cycles. This effectively delays the onset of plastic deformation and subsequent cracking of the dies. A good standard in this respect is to maintain a yield strength of 1400 MPa at 550°
2. High Temperature Resistance: One of the key priorities should be to resist softening of the dies when the temperature crosses the 600° C mark. This is because if the die surface softens, it yields under the compressive stress. This, in turn, results in a higher residual tensile stress during the cooling phase. Softening resistance is a key material property that should be considered.
3. High Thermal Conductivity: When you need to reduce the thermal gradient between the surface and the core, increasing the thermal conductivity can be the right option. This step effectively reduces the differential expansion driving tensile stress.
4. Impact Toughness: Achieving high hardness is critical. Sufficient impact toughness is necessary to prevent severe gross cracks.
5. Low Thermal Expansion: It is important to maintain a low coefficient of thermal expansion to minimize the physical volume change during the heating and cooling cycles. This method ensures a lowering of the cyclic stress magnitude, which prevents the formation of cracks in dies.

Prevention Summary Table

Best Practices in the Production Process

1. Effective Surface Treatments: The nitriding process using plasma or gas can create a hard surface layer with high thermal stability. It also results in adequate compressive residual stress that can, in turn, inhibit the initiation of fatigue cracks.
2. Choosing A Refined Microstructure: It is recommended that you use ESR h11 steel. Electro-Slag Remelted H11 can reduce the size and number of non-metallic inclusions that typically act as crack initiation sites in the dies. This selection can potentially enhance the life up to 10 times.
3. Maintaining Suitable Target Hardness: The steel is known to balance wear resistance if tempered at 47-52 HRC.

Selection is the Key

H11 is preferentially used in die casting because of its superior ability to withstand the intense thermal and mechanical stressors in the process. Since it contains less Vanadium compared to H13, H11 has a better impact toughness. This is one of the key reasons why it is used for dies with sharp corners or complex shapes, without chipping under pressure. Since it is an air-hardening steel, H11 undergoes minimal size and shape distortion during the heat treatment process. Select a reputed manufacturer like TGKSSL to get quality steel every time.