Mold surface treatment technology
In the work of the mold, in addition to requiring the substrate to have a reasonable combination of high enough strength and toughness, its surface properties are critical to the work performance and service life of the mold. These surface properties refer to: wear resistance, corrosion resistance, friction coefficient, fatigue properties, and the like. The improvement of these properties depends on the improvement and improvement of the matrix material. It is very limited and uneconomical. However, surface treatment technology can often achieve a multiplier effect. This is the reason why the surface treatment technology has developed rapidly.
The surface treatment technology of the mold is a systematic project to change the morphology, chemical composition, structure and stress state of the mold surface to obtain the required surface properties through surface coating, surface modification or composite processing technology. From the surface treatment methods, it can be divided into: chemical methods, physical methods, physical and chemical methods and mechanical methods. Although new processing technologies aiming at improving the surface properties of molds are emerging, the major nitriding, carburizing, and hardened film depositions are applied in the mold manufacturing.
The nitriding process includes gas nitriding, ion nitriding and liquid nitriding. In each type of nitriding, there are several kinds of nitriding techniques that can adapt to the requirements of different steel types and different workpieces. Because the nitriding technology can form a surface with excellent performance, and the nitriding process has good coordination with the quenching process of the die steel, at the same time, the nitriding temperature is low, and after the nitriding without the need for intense cooling, the deformation of the die is minimal, therefore, the die The surface strengthening is the use of nitriding technology earlier, but also the most widely used.
The purpose of carburizing the mold is mainly to improve the overall toughness of the mold, that is, the working surface of the mold has high strength and wear resistance. The technical idea introduced hereby is to use lower grade materials, ie, carburizing and quenching to replace higher grade materials, thereby reducing manufacturing costs.
3, hardened film deposition
Hardened film deposition technology, which is currently more mature, is CVD and PVD. In order to increase the bonding strength between the film and the workpiece surface, various enhanced CVD and PVD technologies have now been developed.
The hardened film deposition technology was first applied to tools (tools, cutting tools, measuring tools, etc.), and the effect was excellent. A variety of tools had applied a cured film as a standard process.
Dies have been coated with hardened film technology since the 1980s. Under the current technical conditions, the cost of hardened film deposition technology (mainly equipment) is high, and it is still only applied to some precision and long-life molds. If the method of establishing a heat treatment center is adopted, the cost of coating hardened film will be greatly reduced. . More molds using this technology can improve the overall level of mold manufacturing in China.
Fourth, the pre-hardening technology of mold materials
In the manufacturing process of molds, heat treatment is a process that most molds use for a long time. Since the 70s of the last century, the idea of pre-hardening has been proposed internationally. However, due to the limitations of processing machine tool stiffness and cutting tools, the hardness of pre-hardening can not reach the hardness of the use of the mold. Therefore, the research and development of pre-hardening technology has little investment.
With the improvement of the performance of processing machine tools and cutting tools, the development speed of pre-hardening technology for mold materials has accelerated. By the 1980s, the proportion of pre-hardened modules used in plastic mold materials in industrial countries in the world had reached 30% (currently At over 60%, China began to use pre-hardened modules (mainly imported products) in the mid to late 1990s.
The pre-hardening technology of mold materials is mainly developed and implemented in mold material manufacturers. By adjusting the chemical composition of the steel and equipped with appropriate heat treatment equipment, mass-stable pre-hardened modules can be mass-produced. China's pre-hardening technology in mold materials, started late, small scale, can not meet the current domestic mold manufacturing requirements.
The use of pre-hardened mold materials can simplify the mold manufacturing process, shorten the manufacturing cycle of the mold, and improve the manufacturing precision of the mold. It is foreseeable that as the processing technology advances, pre-hardened mold materials will be used for more mold types.