There are various defects in die-casting parts, and the following are some common die-casting defects and their possible causes:
There are patterns or metal flow marks on the surface of the casting: this may be due to the shallow flow path leading to the inlet of the casting, or the high injection pressure causing the metal flow rate to be too high, causing splashing of the metal liquid.
There are small protrusions on the surface of the casting: this may be due to rough surface or foreign objects on the mold surface, which prevent the smooth flow of the molten metal during the cooling process.
Cracks or local deformations on the surface of castings: possible reasons may be uneven distribution or insufficient quantity of top rods, resulting in uneven stress distribution; The fixed plate of the push rod is skewed during operation, resulting in uneven force distribution; The casting wall is too thin and deforms after shrinkage.
There are pores on the surface of the die-casting parts: this may be due to excessive use of lubricants or incomplete gas discharge during the die-casting process.
The surface of the casting has shrinkage holes: this is usually due to the unreasonable processability of the die casting, and the large variation in wall thickness, which leads to uneven shrinkage of the metal during the cooling process.
The outer contour of the casting is unclear, unable to form a shape, and there is a local shortage of material: this may be due to insufficient pressure of the die-casting machine, too low injection pressure ratio, or too low metal liquid temperature and poor fluidity.
The casting part is not formed and the cavity is not fully filled: reasons may include low die casting mold temperature, low metal liquid temperature, low press pressure, insufficient metal liquid, high injection speed, and inability to discharge air.
Cold insulation: refers to the phenomenon where metal flows at lower temperatures are not fused together, resulting in gaps that may appear as blackening, accompanied by flow marks, or surface bubbles.
Scratches: Refers to the pulling marks on the surface of castings caused by metal adhesion along the demolding direction, and the small manufacturing slope of the mold, which can even lead to cracks in severe cases.
In addition, die-casting parts may also have other defects, such as poor fluidity caused by alloy composition not meeting standards, poor fusion of metal liquid splitting filling, and unreasonable and lengthy gating processes. These defects not only affect the appearance quality of die castings, but may also affect their performance and safety. Therefore, in the production process of die castings, it is necessary to strictly control various process parameters and operating procedures to ensure that the quality of the die castings meets the requirements.
To avoid defects in die castings, comprehensive control and management are needed from multiple aspects. Here are some key measures:
1. Raw material selection and processing:
--Choose high-quality aluminum alloys or other alloy raw materials to ensure their chemical composition meets standard requirements and avoid defects such as poor fluidity or shrinkage caused by raw material issues.
--Strictly screen and pretreat raw materials to remove impurities and foreign objects, ensuring the purity of the metal liquid.
2. Mold design and manufacturing:
-Optimize mold design to ensure uniform wall thickness, avoid areas that are too thin or too thick, and reduce shrinkage and cracks caused by uneven cooling.
-Improve the manufacturing accuracy and surface quality of molds, and reduce surface defects of castings caused by mold problems.
-Reasonably arrange the cooling water circuit to ensure uniform mold temperature and avoid casting defects caused by mold temperature being too high or too low.
3. Die casting process control:
-Strictly control the pressure and speed parameters of the die-casting machine to ensure that the metal liquid can flow uniformly when filling the mold cavity, avoiding defects such as porosity and shrinkage.
-Control the pouring temperature of the molten metal and the temperature of the mold to avoid problems such as poor fluidity caused by low temperature and mold sticking caused by high temperature.
-Reasonably arrange the use of exhaust ducts and coatings to ensure smooth gas discharge and prevent defects caused by gas retention.
4. Operation and maintenance:
-Regularly maintain and upkeep the die-casting machine and molds to ensure they are in good working condition and reduce casting defects caused by equipment issues.
-Strengthen employee training, improve the skill level and work responsibility of operators, and ensure the stability and reliability of the die-casting process.
5. Quality inspection and feedback:
-Establish a comprehensive quality inspection system, conduct comprehensive quality inspections on die-casting parts, and promptly identify and address potential defects.
-Analyze the causes of defects in castings, identify the root cause of the problem, and take corresponding measures for improvement and optimization.
In short, avoiding defects in die castings requires comprehensive management and control from multiple aspects such as raw materials, mold design, process control, operation and maintenance, and quality inspection. Only by ensuring effective control at every stage can we minimize the occurrence of defects in die castings and improve the quality and performance of castings.
Some specific improvement measures for improving defects in die-casting parts:
Optimize die-casting process parameters: Through experiments and simulation analysis, determine the optimal key parameters such as die-casting temperature, injection pressure, and injection speed to reduce product defects and improve production efficiency. At the same time, it is necessary to shorten the die-casting cycle time, including filling time, cooling time, and ejection time, in order to improve the machine's output rate.
Introducing vacuum die-casting technology: Vacuum die-casting technology can reduce the porosity and oxidation inclusions inside the die-casting parts, improve the density and mechanical properties of the products.
Reasonably select and use die-casting additives, such as die-casting coatings, release agents, granulating agents, etc., to improve filling performance, reduce mold sticking, and improve surface quality.
Mold design and runner system optimization: Design an efficient runner system, including the main runner, splitter, and gate, to achieve smooth flow and rapid filling of molten metal, reduce entrainment and cold shut. At the same time, optimize the layout and diameter of the cooling channels of the mold to ensure uniform cooling during operation, reduce thermal stress and deformation.
Targeted measures can be taken for specific defects: for example, for porosity defects, the gating and vent holes in the casting design can be increased, the pouring pressure and speed can be increased, and the heat dissipation ability of the mold can be improved to reduce the gas content of the alloy. For cold shut defects, mold design can be optimized, pouring temperature and pressure can be increased, and the fluidity of the molten metal can be improved.
Overall, improving defects in die castings requires comprehensive consideration and optimization from multiple aspects such as die casting process, mold design, and use of die casting additives. At the same time, for the defects that have already appeared, specific problems should be analyzed and corresponding repair measures should be taken. During the production process, it is also necessary to strictly control various process parameters and regularly inspect and maintain the molds to ensure the quality and performance of the die castings.
Kind reminder: The above suggestions cannot cover all possible defects and solutions of die-casting parts. Specific situations may need to be adjusted according to the actual production environment and product requirements.