Mold heat treatment is an important process to ensure mold performance. It has a direct impact on the following properties of the mold.
Mold manufacturing accuracy: uneven tissue transformation, incompleteness and excessive residual stress caused by heat treatment cause deformation of the mold after heat treatment, assembly and mold use, thereby reducing the accuracy of the mold and even scrapping.
Mold strength: improper heat treatment process, heat treatment operation is not standardized or the state of heat treatment equipment is not perfect, resulting in the strength (hardness) of the treated mold can not meet the design requirements.
The working life of the mold: the unreasonable structure caused by heat treatment, excessive grain size, etc., leading to the decline of main properties such as mold toughness, hot and cold fatigue performance, anti-wear performance, etc., affecting the working life of the mold.
Mold manufacturing cost: As the intermediate or final process of the mold manufacturing process, the cracking, deformation and poor performance caused by heat treatment will cause the mold to be scrapped in most cases, even if it can be used through repair, it will increase the working hours. , to extend the delivery time and increase the manufacturing cost of the mold.
It is the heat treatment technology that has a very close relationship with the quality of the mold, which makes these two technologies promote each other and improve together in the process of modernization. Since the 1980s, the field of rapid development of international mold heat treatment technology has been vacuum heat treatment technology, surface strengthening technology of molds and pre-hardening technology of mold materials.
Vacuum heat treatment technology for mold
Vacuum heat treatment technology is a new type of heat treatment technology developed in recent years. Its characteristics are urgently needed in mold manufacturing, such as preventing heating oxidation and non-decarburization, vacuum degassing or degassing, eliminating Hydrogen embrittlement improves the plasticity, toughness and fatigue strength of materials (parts). Factors such as slow vacuum heating and small temperature difference between the inside and outside of the part determine the small deformation of the parts caused by the vacuum heat treatment process.
According to the different cooling medium used, vacuum quenching can be divided into vacuum oil quenching, vacuum gas quenching, vacuum water quenching and vacuum nitrification. The main application of mold vacuum heat treatment is vacuum oil quenching, vacuum gas quenching and vacuum tempering. In order to maintain the excellent characteristics of vacuum heating of workpieces (such as molds), it is very important to select and formulate coolants and cooling processes. The mold quenching process mainly uses oil cooling and air cooling.
For the working face of the mold which is no longer machined after heat treatment, vacuum tempering is used as much as possible after quenching, especially vacuum hardened workpiece (mold), which can improve the mechanical properties related to surface quality, such as fatigue performance, surface brightness, Corrosive and so on.
The successful development and application of computer simulation technology (including tissue simulation and performance prediction technology) of the heat treatment process makes the intelligent heat treatment of the mold possible. Due to the small batch (even single piece) and multi-variety characteristics of the mold production, as well as the high requirements for heat treatment performance and the fact that waste products are not allowed, the intelligent heat treatment of the mold becomes a necessity. The intelligent heat treatment of the mold includes: clearing the structure of the mold, the material, the heat treatment performance, the temperature field of the mold heating process, the computer simulation of the stress field distribution, the temperature field of the mold cooling process, the phase change process and the stress field distribution of the computer simulation heating and cooling process The simulation of the quenching process develops automated control technology for the heat treatment equipment. Foreign industrial developed countries, such as the United States, Japan, etc., in the field of vacuum high pressure gas quenching, have carried out technical research and development in this area, mainly aimed at the mold.
In addition to the reasonable cooperation of the mold with sufficient strength and toughness, the surface properties of the mold are crucial to the working performance and service life of the mold. These surface properties are: abrasion resistance, corrosion resistance, friction coefficient, fatigue properties, and the like. These performance improvements, which rely solely on the improvement and improvement of the matrix material, are very limited and uneconomical, and surface treatment techniques can often achieve twice the result with half the effort, which is why surface treatment technology has developed rapidly.
The surface treatment technology of the mold is to systematically change the morphology, chemical composition, microstructure and stress state of the mold surface by surface coating, surface modification or composite treatment technology to obtain the desired surface properties. From the way of surface treatment, it can be divided into: chemical methods, physical methods, physical and chemical methods, and mechanical methods. Although new treatment technologies are being developed to improve the surface properties of molds, most of the applications in mold manufacturing are nitriding, carburizing and hardening film deposition.
The nitriding process has the methods of gas nitriding, ion nitriding, liquid nitriding, etc. In each nitriding mode, there are several kinds of nitriding techniques, which can adapt to the requirements of different workpieces of different steel types. 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, and the nitriding temperature is low, there is no need for intense cooling after nitriding, and the deformation of the mold is extremely small, so the mold is Surface strengthening is the earliest and most widely used nitriding technique.
The purpose of mold carburizing is mainly to improve the overall toughness of the mold, that is, the working surface of the mold has high strength and wear resistance, and the technical idea introduced is to use a lower grade material, that is, by carburizing and quenching. Instead of higher grade materials, it reduces manufacturing costs.
The most mature sclerosing film deposition technology is CVD and PVD. In order to increase the bonding strength of the surface of the film workpiece, various enhanced CVD and PVD technologies have been developed. The hardened film deposition technology was first applied to tools (tools, cutting tools, measuring tools, etc.), and the results were excellent. A variety of tools have been used as a standard process for coating hardened films. Molds 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 still 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 the cured film will be greatly reduced. If more molds adopt this technology, they can improve the overall level of mold manufacturing in China.
Pre-hardening technology for mold materials
The heat treatment of the mold in the manufacturing process is a process that most molds have been used for a long time. Since the 1970s, the idea of ​​pre-hardening has been proposed internationally, but due to the rigidity of the machine tool and the constraints of the cutting tool, the pre-hardening The hardness of the mold cannot reach the hardness of the mold, so the research and development of the pre-hardening technology is not large. With the improvement of the performance of machine tools and cutting tools, the development of pre-hardening technology for mold materials has accelerated. By the 1980s, the proportion of pre-hardened modules used in plastic molds in industrialized countries in the world has reached 30% (currently More than 60%). In the mid-to-late 1990s, China began to use pre-hardened modules (mainly imported products).
Pre-hardening technology for mold materials is mainly developed and implemented by mold material manufacturers. By adjusting the chemical composition of the steel and equipped with the corresponding heat treatment equipment, it is possible to mass produce pre-hardened modules of stable quality. In China, the pre-hardening technology of mold materials started late and has a small scale. At present, it cannot meet the requirements of domestic mold manufacturing.
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 processing technology advances, pre-hardened mold materials will be used for more mold types.
Concerned about surprises
Label: Current status of mold surface treatment technology
Previous: Door and window hardware can not be underestimated Next: Kitchen and bathroom hardware accessories common sense
Hospital Hermetic Door,Door For Hospital Rooms,Hermetic Sliding Door,Sliding Hermetic Door For Hospital Rooms
Caesar door control co.,ltd , https://www.caesar-door.com