Our company is the production roll forming machine.
Die casting mold is a major category. As China's automotive industry, the rapid development of motorcycle, die-casting industry has ushered in a new period of development. At the same time, die-casting molds for mechanical properties, such as life expectancy has put forward higher requirements. To meet the ever-increasing demand for the use of performance based only on the application of new mold materials is still difficult to meet, must be all kinds of surface treatment technology is applied to the surface of casting molds can be processed on the die-casting mold to achieve high efficiency, high precision and high life expectancy should be. In a variety of mold, die-casting mold is more of the working conditions harsh. Pressure casting molten metal is in the high-pressure, high-speed and under the mold cavity is full of die-casting molding, In the course of repeated contacts with the hot metal, die-casting mold therefore asked for a higher heat fatigue, heat resistance to abrasion, corrosion nature, impact toughness, red hardness, good mold release and so on. Therefore, the surface of the die-casting molds require a higher processing technology in recent years, a variety of die-casting mold surface treatment of new technologies continue to emerge, but on the whole can be divided into the following three broad categories: (1) Improvement of the traditional heat treatment process technology; (2) surface modification technology, including surface heat diffusion processing, the surface of phase-change enhancement techniques, such as enhanced EDM; (3) coating techniques, including electroless plating and so on.
1, the traditional heat treatment process to improve the technical
Die-casting mold of traditional heat treatment process is quenching - tempering, after surface treatment technology developed. As a result of die-casting mold can be used as a wide variety of materials, the same surface treatment technology and processes used in the different materials will produce different results. Markov recent history against the mold surface of the substrate and the substrate pretreatment processing technologies technology, based on the traditional crafts of different mold materials suitable processing technology in order to improve die performance, increase die life. Another heat treatment technology to improve the direction of development is to the traditional heat treatment process with advanced surface treatment technology combination to increase the service life of die-casting mold. If the chemical heat treatment method of carbonitriding with conventional quenching and tempering process of combining NQN (ie Carbonitriding - quenching - Carbonitriding) composite strengthening, not only had the higher surface hardness, and the effective hardening depth increased, the hardness gradient distribution layer reasonable and tempering to improve the stability and corrosion resistance, making die-casting mold in the center of a good performance at the same time, the surface of a substantial increase in quality and performance.
2 Surface Modification Technology
21 surface thermal diffusion technology
This type include carburizing, nitriding, and boronizing Carbonitriding, such as sulfur Carbonitriding.
211 carburizing and carbonitriding
Carburizing process used in cold and hot surface hardening in the plastic mold, can improve the die life. If the die-casting molds of steel 3Cr2W8V first carburization, and then by the 1140 ~ 1150 quenching, 550 tempered twice the surface hardness up to HRC56 ~ 61, so that non-ferrous metal and alloy die-casting die life increased by 1.8 ~ 3.0-fold. Carburization processing carried out, the main processes of the solid powder carburizing, gas carburizing and vacuum carburizing, ion carburizing and carburizing atmosphere formed by adding nitrogen and other carbonitriding. Among them, the vacuum carburizing and plasma carburizing are the last 20 years developed the technology, which has a percolation rate faster, uniform layer, the carbon concentration gradient of small flat, as well as features such as deformation of the workpiece, it will surface in the mold, especially precise mold surface treatment play an increasingly important role.
Nitriding and 212 low-temperature heat-related technology diffusion
This type include nitriding, ion nitriding, carbonitriding, oxygen permeation of nitrogen, N total carbon and nitrogen permeability as well as sulfur, oxygen permeation of nitrogen such as sulfur ternary method. Process of these methods is simple, adaptable, low penetration temperature (usually 480 ~ 600 ), the workpiece deformation small, in particular, to adapt to the surface of precision molds enhanced nitride layer and high hardness, wear resistance, and more good performance of anti-stick mode. 3Cr2W8V steel casting molds, after quenching and tempering, 520 ~ 540 nitride, the useful life of less nitrogen to increase the die 2 to 3 times. United States production of H13 die steel, and many have to carry out nitriding and nitriding in lieu of a temper, surface hardness up to HRC65 ~ 70, while the hardness of the center of the lower mold, toughness, and to obtain good comprehensive mechanical properties. Nitriding process is commonly used die-casting mold surface treatment process, but brittle nitride thin layer of white layer, could not resist alternating the role of thermal stress is very easy to produce micro-cracks, reducing thermal fatigue resistance. Therefore, in the process of nitriding, it is necessary to strictly control the process and avoid the emergence of brittle layer. Recently, the use of foreign countries and a series of secondary nitriding process. Nitriding repeated decomposition approach can be easily generated in the service process of micro-cracks in the white nitride layer to increase the nitriding layer thickness, and mold surface at the same time the existence of very thick layer of residual stress, so that mold can be markedly improved life expectancy. In addition, the use of salt bath salt bath carbonitriding and S-N-C co-diffusion and other methods.