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Classification of Surface Treatment Technologies for Metal Die Castings

2019/9/29 9:46:00 click:

Surface treatment is a very important step for metal die castings. today yixin precision metal and plastic ltd will explain the surface treatment method for metal die castings in detail.
Depending on the method used, surface treatment techniques can be divided into the following categories.
I. electrochemical methods
This method uses electrode reaction to form a coating on the surface of the workpiece. The main methods are:
(1) Electroplating
In electrolyte solution, the workpiece is the cathode, and the process of forming a coating on its surface under the action of external current is called electroplating. The plating layer may be metal, alloy, semiconductor or contain various solid particles, such as copper plating, nickel plating, etc.
(2) oxidation
In electrolyte solution, the workpiece is an anode, and the process of forming an oxide film on its surface under the action of external current is called anodic oxidation, such as anodic oxidation of aluminum alloy. The oxidation treatment of steel can be carried out by chemical or electrochemical methods. The chemical method is to put the workpiece into oxidation solution and form an oxidation film on the surface of the workpiece by chemical action, such as bluing of steel.
II. Chemical Methods
This method is to form a plating layer on the surface of the workpiece by using the interaction of chemical substances without current. The main methods are:
(1) chemical conversion membrane treatment
In electrolyte solution, the process of forming a coating on the surface of a metal workpiece by the interaction of chemical substances in the solution and the workpiece without external current is called chemical conversion film treatment. Such as bluing of metal surface, phosphating, passivation, chromium salt treatment, etc.
(2) Electroless plating
In the electrolyte solution, the surface of the workpiece is treated by catalysis without external current. In the solution, due to the reduction of chemical substances, some substances are deposited on the surface of the workpiece to form a coating. This process is called electroless plating, such as electroless nickel plating and electroless copper plating.
Three, hot processing method
This method is to order the material to melt or thermally diffuse under high temperature conditions to form a coating on the surface of the workpiece. The main method is as follows:
(1) Hot Dip Plating
The process of putting a metal workpiece into molten metal to form a coating on its surface is called hot dip plating, such as hot galvanizing, hot aluminizing, etc.
(2) thermal spraying
The process of atomizing and spraying molten metal on the surface of a workpiece to form a coating is called thermal spraying, such as thermal spraying of zinc, thermal spraying of aluminum, etc.
(3) Hot stamping
The process of heating and pressurizing a metal foil to cover the surface of a workpiece to form a coating layer is called hot stamping, such as hot stamping aluminum foil, etc.
(4) chemical heat treatment
The process of contacting and heating a workpiece with chemical substances and ordering certain elements to enter the surface of the workpiece at high temperature is called chemical heat treatment, such as nitriding and carburizing.
(5) surfacing welding
The process of forming a weld layer by stacking deposited metal on the surface of a workpiece by welding is called overlaying, such as overlaying wear-resistant alloy, etc.
IV. Vacuum Method
This method is a process of ordering materials to be gasified or ionized and deposited on the surface of a workpiece to form a plating layer in a high vacuum state. The main method is.
(I) physical vapor deposition (PVD)
Under vacuum conditions, metal is vaporized into atoms or molecules, or ionized into ions, which are directly deposited on the surface of the workpiece to form a coating. The process is called physical vapor deposition, and the deposited particle beam originates from non-chemical factors, such as evaporation, sputtering, ion plating, etc.
(2) Ion implantation
The process of surface modification by implanting different ions into the workpiece surface under high voltage is called ion implantation, such as boron injection, etc.
(3) chemical vapor deposition (CVD)
At low pressure (sometimes also at normal pressure), the process in which gaseous substances generate solid deposition layer on the surface of workpiece due to chemical reaction is called chemical vapor deposition, such as vapor deposition of silicon oxide, silicon nitride, etc.
V. other methods
Mainly mechanical, chemical, electrochemical and physical methods. The main method is.
(1) Painting
Idle spraying or brushing method, the process of coating (organic or inorganic) on the surface of a workpiece to form a coating, is called painting, such as painting, painting, etc.
(2) impact plating
The process of forming a coating on the surface of a workpiece by mechanical impact is called impact plating, such as impact galvanizing.
(3) laser surface treatment
The process of irradiating the workpiece surface with laser to change its structure is called laser surface treatment, such as laser quenching, laser remelting, etc.
(4) Superdural technique
The technology of preparing superhard film on the surface of workpiece by physical or chemical methods is called superhard film technology. Such as diamond film, cubic boron nitride film, etc.
(5) Electrophoresis and Electrostatic Spraying
1. Electrophoresis: The workpiece is put into conductive water-soluble or water-emulsified paint as one electrode to form a decoupling circuit with the other electrode in the paint. Under the action of electric field, the coating solution has dissociated into charged resin ions, cations move to the cathode and anions move to the anode. These charged resin ions, together with adsorbed pigment particles, are electrophoresed onto the surface of the workpiece to form a coating, a process called electrophoresis.
2, electrostatic spraying, under the action of DC high voltage electric field, atomized negatively charged paint particles are directed to the positively charged workpiece to obtain a paint film, which is called static spraying. Edit other classifications in this paragraph.
3. The common application of wire brushes is the cleaning of castings, including ferrous and non-ferrous ones. Splash and slag cleaning during welding; As long as the base material is strong enough to withstand brushing, dust, corrosion, and paint can be clearly identified. Wire brushes can produce a beautiful surface and can also be used to make decorative surfaces.
The division of all the above categories is not absolute. For example, surface treatment technology can also be divided into three major technologies: surface modification technology, thin film technology and coating technology. The significance of surface treatment: it can effectively improve the hardness and wear resistance of the workpiece surface.
Yixin Precision Metal and Plastic Ltd. has specialized in customizing various kinds of hardware injection molding precision parts for 15 years and has very rich experience. If you have any need, please feel free to contact us!
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