Plastic molds need to improve mold heat treatment technology to improve quality

First, the relationship between heat treatment and mold quality

1. Manufacturing precision of the mold

Unevenness, incompleteness, and residual stress caused by heat treatment are too large, resulting in deformation of the mold after heat treatment, assembly, and mold use, thereby reducing the accuracy of the mold and even scrapping.

2, the strength of the mold

The heat treatment process is improperly formulated, the heat treatment operation is not standardized, or the state of the heat treatment equipment is not perfect, resulting in the strength (hardness) of the treated mold not meeting the design requirements.

3, the working life of the mold

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.

4, the manufacturing cost of the mold

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 and extend the delivery time. To 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. In recent years, the field of rapid development of mold heat treatment technology in the world is vacuum heat treatment technology, surface strengthening technology of molds and pre-hardening technology of mold materials.

Second, the vacuum heat treatment technology of the 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 oxidation and non-decarburization, vacuum degassing or degassing. Eliminates hydrogen embrittlement, thereby increasing 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 nitrate salt isothermal quenching. In vacuum heat treatment of molds, vacuum oil quenching, vacuum gas quenching and vacuum tempering are mainly used. 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 , corrosion resistance, etc.

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) of the mold production, the characteristics of many varieties, and the high requirements for heat treatment performance and the fact that waste products are not allowed, the intelligent processing of the mold becomes a necessity.

The intelligent heat treatment of the mold includes:

1. Defining the structure, materials and heat treatment performance requirements of the mold;

2. Computer simulation of temperature field and stress field distribution during mold heating process;

3. Computer simulation of temperature field, phase change process and stress field distribution in the mold cooling process;

4. Simulation of the heating and cooling process;

5. Formulation of quenching process;

6. Automatic control technology for 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.