Summary of surface strengthening technology of die casting die

Summary of surface strengthening technology of die casting die

The surface strengthening and modification technology of die casting die can design the die surface and matrix as a whole system, and make comprehensive use of surface strengthening modification technology and coating technology, so that the surface material itself is difficult to have but hopefully has a specific performance. The treatment technology that uses modern technology to change the composition, structure and performance of the material surface and sub-surface layer of the forging die is called surface modification technology, which mainly includes the following ten categories:

Electrochemical conversion

The technology of forming oxide film on the surface of parts under the action of electrolyte solution and external current is called electrochemical modification technology. In engineering, the electrochemical conversion modification technology is often called anodizing or anodizing. Recently, microarc plasma anodization is a major electrochemical conversion technology, which can significantly improve the surface hardness or form a new color decorative film, and has a good application in die casting industry.

The surface forms and intensifies

With shot peening, extrusion, laser shock, rolling, ultrasonic shock, vibration, high pressure jet technology methods, such as the elastic-plastic deformation caused the material surface layer, the introduction of the residual compressive stress and microstructure structure change, in order to improve the ability of material fatigue resistance and corrosion resistance, to improve the stability and durability of the parts.

Surface phase transformation enhancement

Electron beam and laser beam are used to heat the surface of the material rapidly, so that the surface and subsurface form new phase transition zone and surface strengthening amount, so as to get the special performance surface layer with fine structure and strengthening phase.

Ion implantation

The ionized ions from the vacuum system are accelerated under high voltage and injected directly into the surface of the die casting mold to form a very thin ion injection layer, which changes the composition and structure of the material surface and improves the surface properties of the material.

Organic and inorganic coating technology

Organic coating technology mainly refers to the use of coatings (paint, lacquer, pigment, thinning) to give die casting mold surface special protection, decoration, flame retardant, temperature and other functions.
Inorganic coating technology is to form an inorganic coating or surface film on the mold surface. The inorganic coating or surface film has specific chemical composition, structure and morphology, which can give new properties or functions to the substrate and coating system.

Surface alloying (diffusion infiltration)

The metal or non-metal is deposited on the surface of the die casting mold, which penetrates into the surface of the matrix material through diffusion, changes the chemical composition and phase structure of the material surface, and improves the service performance of the die surface.

Chemical conversion

In order to improve the performance of the die surface, the die parts are put into a certain chemical solution medium to form a blunt compound film on the surface. The blunt compound film commonly used in engineering mainly includes chromate passivation film, phosphate passivation film, oxalate passivation film, bluing on the surface of steel parts, etc. In addition, the surface roughness reduction process (polishing, polishing, rolling, etc.) and surface coloring are often attributed to the chemical transformation of this kind of surface modification process in engineering applications.

Metal electrochemical deposition technology

Metal electrochemical deposition refers to the technology of electrochemically depositing one or more layers of metal coating, alloy coating or composite coating on the surface of the die casting mold, also known as electroplating technology. Various coatings with different functions can be prepared on the surface of metal parts by electroplating.

Antirust technology

The chemical or electrochemical changes of metals under the action of environmental media are called metal corrosion, commonly known as rust or rust. Rust-proof metal is a technology to prevent corrosion of metal in the process of manufacturing, handling, transportation, storage and use.

Hot dip coating technology

Hot dip coating technology, also known as hot dip coating, is the gilded material immersed in other liquid metal or alloy with a lower melting point to form a coating process technology. Hot dip coating technology is characterized by the formation of an alloy layer between the base metal and the coating metal.

Development status of surface strengthening technology of die casting die

The technology types, basic principlesnand applications of surface strengthening treatment of die casting die are analyzed. The development status and applicability of various technologies are analyzed. Combined with the concept of “green manufacturing”, it is pointed out that surface treatment based on clean energy carriers such as plasma and laser will become an important direction in the future development of surface strengthening field.

Die casting is a kind of casting method in which molten alloy is injected into precision die casting die at high speed and high pressure under high temperature condition, and a large number of high-precision and fine casting surface are produced in a short time. It has the advantages of high production efficiency, small working area, high dimensional accuracy and small casting processing allowance. However, the life of die casting die has become a key factor restricting the benefit of die casting due to the extremely strict processing environment. Generally, the failure of die casting die starts from the surface failure. In the process of die casting, die casting die bears great clamping force, high pressure impact of liquid aluminum, injection reaction force and so on. The huge ground stress impact is easy to lead to the crack and failure of the surface of the die, especially the insert and sharp corner parts with small force area. Therefore, the surface of the die needs to have extremely high hardness and wear resistance.

The thermal environment in the die casting process is also extremely bad. The rapid heat and cold caused by the impact of high temperature liquid aluminum causes great alternating thermal stress on the die casting die surface. The die surface also needs to have high temperature resistance, thermal stability and thermal fatigue resistance. In order to achieve the above performance requirements, it is undoubtedly very uneconomical and difficult to proceed from the base material improvement alone. Therefore, surface strengthening technology becomes a powerful measure to solve this problem.

For the realization of the die surface strengthening, the most basic method is to use the mould manufacturing process quenching – tempering – polishing the traditional heat treatment process, this process is the basic of all die casting mould are used, but to the mold steel hardness, high temperature resistant performance is only a small rise, difficult to meet the demand of actual working condition, so still need to be more powerful surface strengthening technology.

The market has more stringent requirements on the performance of large precision die casting molds, and surface strengthening technology will also play a more important role. At the same time, with the requirements of “green manufacturing”, plasma and laser surface technology and other more energy saving and environmentally friendly surface treatment technology will usher in a broader development prospect. While each technology develops independently, it also appears the trend of cross development with the traditional strengthening technology, breaking through its applicable scope and practical restriction. For example, the ion beam assisted deposition (IBAD) technology and the surface nanometrization technology developed in recent years are complementary to each other and have achieved excellent surface treatment results. In order to meet the needs of modern industry and the rapid development of science and technology, it is reasonable to think that plasma and laser surface treatment will be an important pillar of the development of the whole surface strengthening technology.