Eight technical standards for die casting molds(part 2)
2024-03-04 08:00
Die Casting Mold Design and Manufacturing
Reasonable mold design is a crucial prerequisite for extending the service life of die casting molds. Proper wall thickness and cooling channel design can ensure mold strength and thermal balance. Stress concentration and severe wear areas should be particularly noted during mold design. Matching the precision of each part should be reasonable: excessive clearance leads to poor heat conduction, causing thermal fatigue damage; while insufficient clearance generates squeezing and tensile stresses. Internal stresses are easily generated during mold manufacturing, which significantly affects mold service life. Therefore, internal stresses should be avoided as much as possible during manufacturing, and timely stress relief should be performed after rough machining. Electric pulse technology can replace EDM to reduce surface tensile stress.
Die Casting Mold Surface Treatment Technology
By rigorously and reasonably treating the die casting mold surface, its performance and service life can be significantly improved. Die casting mold surface treatment technology can generally be divided into three categories: improvement of traditional heat treatment processes; surface modification technology, such as surface laser treatment technology; coating technology.
（1）Improvement of traditional heat treatment processes. The traditional die casting mold heat treatment process involves quenching and tempering. The improvement of traditional heat treatment processes combines quenching and tempering with advanced surface treatment technologies. For example, NQN (i.e., carburizing-nitriding-quenching-carburizing-nitriding composite reinforcement) results in higher mold surface hardness, increased internal strength, reasonable hardness gradient of the carburized layer, improved tempering stability and corrosion resistance, significantly enhancing comprehensive performance and service life.
Surface modification technology. Surface modification technology refers to changing the surface properties of molds using physical or chemical methods. Generally, there are two types: surface thermal, expansion, and penetration technology, and surface laser treatment technology.
（2）Surface thermal, expansion, and penetration technology include carburizing, nitriding, boriding, as well as carburizing-nitriding, sulfur-carbon-nitriding, etc. Carburizing helps strengthen the surface hardness of molds. Carburizing methods include solid powder carburizing, gas carburizing, vacuum carburizing, and ion carburizing. Vacuum and ion carburizing have fast penetration rates, uniform carburized layers, gentle carbon concentration gradients, and minimal workpiece deformation. Nitriding is convenient, and the mold nitrogenized layer has high hardness and good wear resistance, showing excellent anti-sticking mold performance. Boriding shows the most significant improvement in surface performance, with increased mold hardness, wear resistance, corrosion resistance, and anti-adhesion performance, but the process conditions are demanding.
Laser surface treatment of molds has emerged in the past three decades, enhancing mold surface performance in two ways. One method is to melt the mold surface with a laser and then combine it with processes such as carburizing, nitriding, or coating. The other method is to combine laser surface treatment technology with some metal additives with good physical properties, integrating them into the die casting mold surface.
（3）Coating technology. Coating technology involves applying a coating layer to the surface of the mold, acting as protective clothing for the mold. For example, polytetrafluoroethylene composite plating is mainly used to enhance mold wear resistance, corrosion resistance, and resistance to cold and heat.
Die Casting Mold Use
Selecting reasonable die casting processes and maintenance is crucial for the service life of molds. A significant portion of mold damage results from incorrect use and insufficient scientific maintenance. Firstly, special attention should be paid to temperature control of the mold. Preheating the mold before production and maintaining an appropriate temperature range during production can prevent surface cracks or even cracking caused by excessive temperature gradients inside and outside the cavity. Secondly, high-quality die casting release agents should be used, with moderate thickness uniformly applied to the mold surface, playing a crucial role in protecting mold materials. Finally, to reduce the accumulation of thermal stress and prevent die casting mold cracking, periodic stress relief using techniques such as tempering is necessary.
Conclusion
Die casting mold materials, mold design and manufacturing, mold surface treatment technology, and mold use comprehensively affect mold performance and service life. By considering these factors comprehensively and taking effective measures, die casting mold performance can be effectively improved, and die casting mold service life extended.
Get the latest price? We will reply as soon as possible (within 12 hours)