Stress in aluminium alloy die casting can be controlled through simulation optimization, reasonable gate and cooling design, and post-casting stress relief. Effective stress management can avoid warping, cracking, and mold fatigue, and reduce dimensional deviation and assembly scrap rate. The main factors affecting stress include filling speed, temperature gradient, wall thickness design, and material compatibility, which must be fully considered at the beginning of the design.
This article will cover stress sources, simulation control, impacts, material selection, design solutions, and stress control practices of CEX Casting. Read on to learn how to effectively manage internal stress in aluminium die casting components.
Types and Sources of Die Casting Stress
Thermal Stress
Thermal stress is caused by uneven temperature during mold filling and cooling.
Molten aluminum expands and contracts inconsistently during rapid thermal cycles, resulting in unbalanced forces in local areas and forming internal tension.
Residual Stress
Residual stress is the stress that remains in the casting after cooling and solidification.
It is usually caused by temperature gradients and uneven phase changes and is widely present in areas with drastic structural changes.
Mechanical Stress
Mechanical stress comes from the transient loads generated during injection, filling, holding, and demolding.
These loads are concentrated in complex geometric structures or where the wall thickness changes, resulting in stress accumulation.
Impacts of Uncontrolled Stress
Warping and Deformation
During demoulding or subsequent processing, the release of internal stress in the die casting parts may cause local or overall warping.
Resulting in structural deformation, uneven wall thickness, and geometric offset, which in turn affect the assembly accuracy and appearance consistency of the product.
Cracking and Fracture
When the stress accumulation in a local area exceeds the material’s bearing limit, it will induce microcracks or even fractures.
This type of damage is mostly concentrated in locations where stress is concentrated or thermal shock is frequent. In severe cases, it may cause the casting to be scrapped.
Dimensional Instability
The slight deformation during the stress release process will gradually accumulate in multiple process links and eventually manifest as a dimensional deviation of the finished product.
Such errors are unpredictable, especially in precision assembly scenarios.
Mold Stress and Fatigue
Long-term repeated heating and mechanical loads will form a stress alternating area inside the die casting mold.
This stress state will cause microcrack propagation, surface erosion, and local hardness reduction, reducing the mold life and increasing the maintenance frequency.
Stress Prediction and Control Through Simulation
Thermo-Mechanical Modeling
Finite element analysis (FEA) software can be used to simulate injection pressure and temperature distribution, and intuitively present the stress field distribution of die casting products at different stages.
This modeling method reveals stress concentration areas and potential deformation trends, and is a key means to identify high-risk areas in the early stages of design.
Flow and Solidification Analysis
Using professional casting simulation software such as ProCAST, the flow path, temperature distribution, and solidification sequence of molten metal can be simulated.
The system can generate flow front maps and solidification time maps in real time, revealing stress concentration areas caused by uneven filling, unbalanced cooling, or sudden changes in wall thickness.
Cooling System Optimization
Casting simulation software such as ProCAST can simulate mold temperature distribution and identify uneven cooling and hot spots.
By analyzing mold temperature cloud maps and heat flow paths, engineers can optimize cooling channel layout, improve cooling consistency, and reduce thermal stress concentration caused by local overheating.
Die Casting Stress Relief Methods
Annealing Treatment
Annealing is a low-temperature heat treatment method that is mainly used to release residual stress inside castings, improve dimensional stability, and reduce the risk of subsequent processing deformation.
Commonly used for aluminum parts with complex structures, uneven wall thickness, or subsequent precision machining.
Strengthening Heat Treatment
Through typical heat treatment processes such as T5 and T6, the metallographic structure of the alloy can be changed, the tensile strength and fatigue life can be improved, and the internal stress level can be reduced simultaneously.
The specific temperature and holding time need to be customized and controlled according to the alloy model and part function.
Shot Peening
Shot peening uses metal or ceramic media to apply a compressive stress layer to the surface of the casting, effectively offsetting the tensile stress, inhibiting the initiation and expansion of surface cracks, and improving fatigue life.
It is suitable for high-pressure die casting parts with high loads, thin walls, or high safety requirements.
The Impact of Material Selection on Stress Control
Thermal Expansion Matching
Different materials have different expansion rates when heated and cooled.
If the expansion coefficients of the aluminum alloy and the mold material do not match, additional stress is easily generated during the thermal cycle, affecting the size and molding stability of the casting.
Mechanical Strength Under Stress
The material needs to have sufficient toughness and fatigue resistance to withstand repeated thermal and mechanical stresses.
For example, ADC12 is strong but brittle, while A356 is more ductile and suitable for structures with large stress changes.
Different types of aluminum alloys should be used for different applications.
Stability of the Material Itself
If there are impurities, gas, or large grains in the aluminum liquid, the internal stress will be unevenly distributed, and deformation or stress accumulation will easily occur during production.
Choosing purer materials can help reduce unnecessary sources of stress.
Structural Design Methods to Reduce Stress
Wall Thickness Consistency
Partially too thick or too thin castings will lead to uneven cooling speeds, resulting in different shrinkage rates in different areas, thus forming internal stress at the junction.
Maintaining uniform wall thickness not only helps synchronize cooling but also reduces stress gradients and improves overall structural stability.
Fillets and Ribs
Sharp corners are the most common locations for stress concentration and are easily the starting point for stress superposition.
Using fillet design at turning points can make the stress transition smoother.
The ribs should be arranged reasonably to support the structure while avoiding the formation of heat concentration areas to prevent stress accumulation.
Gate and Runner Layout
Irrational gates and runners will lead to unbalanced metal flow during the filling process, causing stress to be concentrated at the end of filling or the sudden change of wall thickness.
By optimizing the gate position, size, and runner path through simulation analysis, the stress deviation caused by asymmetric filling can be effectively reduced.
Technical Solutions of CEX Casting in Stress Control
Integrated Stress Simulation Design
CEX introduced stress simulation analysis in the mold design stage and used professional software to predict metal flow, heat distribution, and cooling rate.
By optimizing the gate position, wall thickness transition, and overall geometric structure, high stress areas can be avoided in advance to improve molding quality.
Customized Cooling Channel Layout
We design special cooling solutions based on the shape and stress risk areas of each part.
For stress-sensitive areas such as thick walls and heavy bosses, local enhanced cooling methods are used to ensure uniform cooling and reduce thermal stress accumulation.
Precision Mold System
CEX has its internal mold workshop, using high-strength mold steel, modular inserts, and isothermal cooling systems to ensure that the mold can maintain a precise fit during long-term operation and reduce stress deviation caused by mold deformation.
In-house Heat Treatment
We have in-house heat treatment equipment to heat treat and anneal key parts.
By controlling the heating, insulation, and cooling processes, casting residual stress is released and dimensional stability is improved.
Conclusion
Effective stress control can reduce warping, cracking, and dimensional failure in the aluminum alloy die casting process, while extending mold life and improving processing consistency.
As an aluminum die casting manufacturer focusing on process optimization, CEX Casting provides simulation-driven stress analysis and heat treatment solutions to ensure stable, accurate, and reliable performance of aluminum die castings.
Contact us now to learn how we can help you solve the stress challenges of your next aluminum alloy die casting project.