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New Technology of Die Casting

Clicks:483  time:2018/12/29 11:40:41

Die-casting die is one of the major types of dies. With the rapid development of China's automobile and motorcycle industry, die casting industry ushered in a new era of development. At the same time, it also puts forward higher requirements for comprehensive mechanical properties and service life of die casting die. In order to meet the increasing demand of service performance, it is still difficult to meet the demand only by the application of new die materials. It is necessary to apply various surface treatment technologies to the surface treatment of die-casting dies in order to achieve high efficiency, high precision and long life of die-casting dies. Among all kinds of dies, the working conditions of die casting dies are more stringent. Pressure casting is to make molten metal full of mould cavity at high pressure and high speed and die casting. It contacts with incandescent metal repeatedly in the working process. Therefore, it is required that die casting die has high thermal fatigue resistance, thermal conductivity, wear resistance, corrosion resistance, impact toughness, red hardness, good demoulding and so on. Therefore, the requirements for surface treatment technology of die-casting dies are higher. In recent years, various new technologies for surface treatment of die-casting dies have been emerging. Generally speaking, they can be divided into three categories: (1) improvement technology of traditional heat treatment process; (2) surface modification technology, including surface thermal diffusive treatment, surface phase transformation strengthening, spark strengthening technology; (3) coating technology, package technology, etc. Including electroless plating, etc.
The traditional heat treatment process of die casting die is quenching-tempering, and then surface treatment technology has been developed. Due to the variety of materials that can be used as die-casting dies, the same surface treatment technology and process will produce different effects on different materials. Schiff recently proposed the base material pretreatment technology for die base material and surface treatment technology. On the basis of traditional technology, he proposed suitable processing technology for different die materials, so as to improve the performance of the die and improve the life of the die. Another development direction of heat treatment technology improvement is to combine traditional heat treatment technology with advanced surface treatment technology to improve the service life of die casting die. For example, NQN (carbonitriding-quenching-carbonitriding) combined with conventional quenching and tempering process can not only obtain higher surface hardness, but also increase the depth of effective hardening layer, reasonable distribution of hardness gradient, tempering stability and corrosion resistance, so that the die casting die can obtain the same good core performance. At the same time, the surface quality and performance are greatly improved.
In recent years, the method of adding rare earth elements to die surface strengthening has been widely praised. This is because rare earth elements have many functions such as increasing the penetration rate, strengthening the surface and purifying the surface. It has great influence on improving the surface structure, physical, chemical and mechanical properties of the die surface. It can increase the penetration rate, strengthen the surface and generate rare earth compounds. At the same time, it can eliminate the harmful effect of trace impurities distributed on the grain boundary and play the role of strengthening and stabilizing the grain boundary on the surface of die cavity. In addition, rare earth elements interact with harmful elements in steel to form high melting point compounds, which can inhibit the segregation of harmful elements at grain boundaries, thus reducing deep brittleness. The addition of rare earth elements in the surface strengthening treatment process of die casting die can obviously increase the thickness of infiltration layer and surface hardness of various infiltration methods, and at the same time make the infiltration layer fine and disperse, the hardness gradient decrease, so that the wear resistance, cold resistance and thermal fatigue performance of die casting die can be significantly improved, thus greatly improving the life of die. At present, the treatment methods applied to die casting die cavity surface are rare earth carbonitriding, rare earth carbonitriding, rare earth boronizing, rare earth boronizing, rare earth boronizing, rare earth soft nitriding, rare earth sulphur nitriding and carbonitriding, etc.
Die pressure processing is an important part of mechanical manufacturing, and the level, quality and life of dies are closely related to the surface strengthening technology of dies. With the progress of science and technology, there has been great progress in various die surface treatment technologies in recent years. It can be shown as follows: 1) improvement of traditional heat treatment process and its combination with other new processes; 2) surface modification technology, including carburizing, low temperature thermal diffusing (various nitriding, carbonitriding, ion nitriding, ternary diffusing, salt bath thermal diffusing, boronizing, rare earth surface strengthening, laser surface treatment and spark deposition of cermet; 3) coating technology. However, for die-casting dies with extremely harsh working conditions, the existing new surface treatment technology can not meet the growing requirements. It can be expected that more advanced technology will also be applied to die-casting dies surface treatment. As surface treatment is one of the important means to improve the life of die casting die, surface treatment technology will play an important role in improving the overall level of die casting die production in China.

 
 
   

Nanjing Aspire Group

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