It is necessary to select high quality steel and apply corresponding surface treatment technology to improve the service life of the die. Die heat treatment and surface treatment are also the key links to determine the material properties of the final die steel.

Surface treatment is to form a layer of special properties on the surface of materials by physical or chemical methods. Surface treatment can improve the product appearance, texture, function and other aspects of performance.

The following is a detailed introduction of various surface treatment processes for metal 3D printing parts:

1.Anodic oxidation

Anodic oxidation is the electrochemical oxidation of metals or alloys. Metal or alloy parts are used as anode, and oxide film is formed on the surface by electrolysis. Metal oxide film changes the surface state and properties, such as surface coloring, improving corrosion resistance, enhancing wear resistance and hardness, protecting metal surface, etc. For example, anodization of aluminum, aluminum and its alloys are placed in the corresponding electrolyte (such as sulfuric acid, chromic acid, oxalic acid, etc.) as anode, and electrolysis is carried out under specific conditions and applied current. A thin layer of alumina is formed on the surface of anodized aluminum or its alloy, with a thickness of 5-20 μ m, and a hard anodized film of 60-200 μ M. The hardness and wear resistance of anodized aluminum or its alloy are improved, which can reach 250-500 kg/m2. It has good heat resistance. The melting point of hard anodized film is up to 2320k. It has excellent insulation. The breakdown voltage is up to 2000V, which enhances the corrosion resistance ω＝ 0.03 NaCl salt spray does not corrode after thousands of hours. There are a lot of micropores in the thin oxide film, which can absorb all kinds of lubricants and is suitable for manufacturing engine cylinders or other wear-resistant parts; The microporous membrane has strong adsorption capacity and can be colored into various beautiful colors.

Advantages of anodizing:

1). Anti static. 2). Surface magnesium. 3). Wear resistance.

Many small aluminum parts on semiconductor equipment need anodizing treatment, in order to increase hardness and reduce wear.

2. Phosphating treatment

Phosphating is a common pretreatment technology. In principle, it belongs to chemical conversion coating treatment. It is mainly used for phosphating steel surface, and non-ferrous metal parts (such as aluminum and zinc) can also be used for phosphating.

Phosphating is a process of chemical and electrochemical reaction to form phosphate chemical conversion film, which is called phosphating film. The main purpose of phosphating is to provide protection for the base metal and prevent the metal from being corroded to a certain extent; It is used for priming before painting to improve the adhesion and anti-corrosion ability of paint film; It plays the role of reducing friction and lubrication in metal cold working process.

Phosphating effect

1). Enhance the adhesion between coating (such as coating) and workpiece.

2.) Improve the corrosion resistance of the surface coating after coating.

3). Improve the decoration.

3. Blackening treatment

Blackening is a common method of chemical surface treatment. The principle is to produce a layer of oxide film on the metal surface to isolate the air and achieve the purpose of rust prevention.

There are two common methods of blackening: the traditional alkaline heating blackening and the later room temperature blackening. However, the effect of room temperature blackening process on low carbon steel is not very good. Alkaline blackening is subdivided into one blackening and two blackening. The main components of blackening liquor are sodium hydroxide and sodium nitrite. When blackening, the tolerance of temperature is relatively large, and a good surface can be obtained between 135-155 ℃, but the time required is only a little long.

4. Passivation treatment

The phenomenon that the corrosion rate of metal treated by oxidizing medium is significantly lower than that before treatment is called metal passivation. The passivation mechanism can be explained by the film theory, that is to say, passivation is due to the interaction between metal and oxidizing medium, which forms a very thin, dense, well covered passivation film on the metal surface and can be firmly attached to the metal surface. The film exists as an independent phase, usually a compound of oxygen and metal. It can completely separate the metal from the corrosive medium and prevent the metal from directly contacting with the corrosive medium, so that the metal can basically stop dissolving and form a passive state, so as to achieve the effect of preventing corrosion.

Passivation treatment is the last process step in chemical cleaning, and it is the key step. Its purpose is to protect the material from corrosion. Such as the boiler after pickling, water washing, rinsing, the metal surface is very clean, very activated, it is easy to suffer corrosion, so it must be passivated immediately, so that after cleaning the metal surface to form a protective film, slow down corrosion.

5. Radium carving

Radium carving, also known as laser carving or laser marking, is a surface treatment process based on optical principles. Radium carving is a marking method that uses high energy density laser to irradiate the workpiece locally, which makes the surface material vaporize or change color instantly, thus leaving a permanent mark. Radium engraving can produce all kinds of characters, symbols and patterns, and the size of characters can range from millimeter to micron. This technology can produce characters without any marks. The surface of the object is still smooth and the handwriting will not be worn.

6. Electrophoretic paint

The electrophoresis process is divided into anode electrophoresis and cathode electrophoresis. If the coating particles are negatively charged, the workpiece is the anode, and the coating particles deposit a film on the workpiece under the action of electric field force, which is called anodic electrophoresis; On the contrary, if the coating particles are positively charged, the workpiece is the cathode, and the coating particles deposit a film on the workpiece, which is called cathodic electrophoresis.

Electrophoretic application:

It can be divided into anode electrophoretic paint and cathode electrophoretic paint.

Among them, the anodic electrophoretic paint has anodic acrylic acid, which is mainly used in aluminum products. After aluminum is oxidized, it is protected by anodic electrophoretic paint. The gloss is between 50-90 degrees and the paint film is thin, so it is widely used in aluminum profile industry. Cathodic electrophoretic paint can be divided into epoxy electrophoretic paint, acrylic electrophoretic paint and polyurethane electrophoretic paint.

7. wire drawing

Wire drawing technology is a kind of metal processing technology. In metal pressure processing. Under the action of external force, the metal is forced through the die, the cross-sectional area of the metal is compressed, and the required cross-sectional area shape and size are obtained. Make it change shape. The size of the tool is called the drawing die. For example, in the cable industry, the 8mm copper rod is pulled into copper wire, such as 3.5mm, 2.0mm, through a group of (5 ~ 8) drawing dies from large to small.

Wire drawing is a method to improve the surface finish of the workpiece by using the reciprocating motion of the drawn cloth and rubbing it back and forth on the surface of the workpiece. The surface texture is linear. It can improve the surface quality and mask the slight scratch on the surface.

Function of wire drawing:

The surface of metal plate has anti rust, anti-oxidation, anti scratch, anti chemical agent and anti smoke properties. In terms of appearance, due to the special bright surface of the product itself, in order to avoid losing luster due to friction, it is recommended to apply it to the horizontal surface with less friction or the general vertical surface. In addition, it is recommended to use it in a dry place, or a place where it will not get wet frequently, and where the humidity is not too heavy, so as to maintain the stability of the product. Wire drawing on metal surface can well cover up the mechanical lines and mold closing defects in production.

8. CD pattern

CD pattern is a kind of effect similar to CD pattern, which is obtained by using precise CD pattern machine to remove materials on metal surface. The spacing of CD pattern is determined according to the appearance and size of the product. In the industry, it is generally recognized that CD pattern is a high-grade surface treatment process for metal surface.

High quality CD pattern processing must have the following five elements:

1. High precision CD texturing machine.

2. Scientific product processing fixture.

3. Well trained process operators.

4. Choose reasonable cutting tools.

5. Correct cooling scheme.