Detailed die-casting mold surface treatment
Die casting is a method of casting liquid forging is mold a categories. Die casting requires a higher heat fatigue, heat conductivity wear resistance, corrosion resistance, toughness, red hardness, good release and so on. Higher casting mold surface treatment technology requirements in recent years, a variety of die-casting mold surface treatment of new technologies are emerging, but in general it can be divided into the following three categories:
(1) the traditional heat treatment process improvement techniques;
(2) surface modification techniques, including surface thermal diffusion treatment, the surface phase transformation strengthening, strengthening EDM technology;
(3) coating techniques, including chemical plating and the like.
Traditional casting mold heat treatment process is hardening - tempering, and later developed a surface treatment technology. Since a variety of materials as die-casting mold, the same surface treatment technology and process applications on different materials will produce different results. Markov recent history of the base substrate pretreatment technology for mold and surface treatment technology in the traditional process on the basis of different mold materials proposed for the process, thereby improving tool performance, improve die life. Another heat treatment technology to improve the direction of development, is the traditional heat treatment process and advanced surface treatment technology combine to increase the life of the casting mold. As the method of chemical treatment of carbon and nitrogen permeation, and conventional quenching and tempering process of combining NQN (ie carbonitriding - quenching - Carbonitriding) composite strengthening, not only by high surface hardness and effective hardening layer depth increases, a reasonable layer hardness gradient distribution, tempering stability and improve corrosion resistance, so that the casting mold in the center portion for good performance, while greatly improved surface quality and performance.
This type include carburizing, nitriding, boronizing and carbonitriding, sulfur carbonitriding like.
Carburizing process used in cold and hot work and plastic mold surface strengthening, can improve die life. As 3Cr2W8V steel casting molds, first carburizing, and then by 1140 ~ 1150 ℃ quenching, 550 ℃ tempered twice, surface hardness up to HRC56 ~ 61, so that die-casting non-ferrous metals and their alloys die life increased by 1.8 to 3.0 times . Carburizing process, the main process methods are solid powder carburizing, gas carburizing and vacuum carburizing, ion carburizing and added nitrogen is formed in the atmosphere carburizing carbonitriding like. Among them, the vacuum carburizing and plasma carburizing are nearly 20 years developed technology, which has a penetration rate fast, uniform layer, the carbon concentration gradient gentle and characteristics of small deformation of the workpiece will be in the mold surface, especially precision mold play an increasingly important role in surface treatment.