A method of special surface chemical treatment or zinc alloy surface treatment on the surface of aluminum alloy or zinc alloy. Surface treatment can improve the appearance, texture, function and other aspects of the product. 1. Surface treatment of zinc-aluminum alloy: Anodizing is mainly anodizing of aluminum alloy die-castings, and zinc-aluminum alloy die-castings cannot be surface treated due to technical reasons. A layer of aluminum oxide film is formed on the surface of aluminum alloy die castings using electrochemical principles. The oxide film has the characteristics of protection, decoration, insulation and wear resistance. Single color, gradient color: polishing/sandblasting/drawing→degreasing→anodic oxidation→neutralization→dyeing→sealing→drying two-color: ① polishing/sandblasting/drawing→degreasing→shielding→anodic oxidation 1→anodic oxidation 2→sealing → Drying ② Polishing/sandblasting/wire drawing → Degreasing → Anodizing 1 → Laser carving → Anodizing 2 → Sealing → Drying technical characteristics: 1. Strengthen the strength 2. Know any color other than white 3. Achieve nickel-free sealing, Technical difficulties and improvement points to meet the requirements of European and American countries: The yield of anodizing is related to the cost of the final product. The key to increasing the anodic oxidation rate is the proper amount of oxidant, proper temperature and current density, which requires continuous exploration and breakthroughs in the production process of aluminum alloy die-casting plants. 2. Electrophoresis can be used for stainless steel, aluminum alloy die-casting, zinc alloy die-casting, etc. It can make products show various colors, maintain metallic luster, improve surface performance, and have good corrosion resistance. Process flow: pretreatment → electrophoresis → drying Advantages: 1. Rich colors; 2. No metal texture, can be used with sandblasting, polishing, wire drawing, etc.; 3. Processing in a liquid environment can achieve surface treatment of complex structures; 4. , Can be used for mass production. Disadvantages: General defect coverage, high requirements for electrophoresis pretreatment of die castings. 3. Micro-arc oxidation In the electrolyte solution (usually a weak alkali solution), the ceramic surface film is formed by the action of high pressure, which is the result of the synergistic effect of physical discharge and electrochemical oxidation. Process flow: pretreatment→hot water washing→hair→drying Advantages: 1. Ceramic texture, dim appearance, no high-gloss products, fine hand feeling, anti-fingerprint; 2. A wide range of substrates: aluminum, titanium, zinc, zirconium, magnesium, Niobium and its alloys; 3. Simple pretreatment, good corrosion resistance, good weather resistance, and good heat dissipation performance. Disadvantages: At present, the colors are limited, only black and gray are mature. At present, bright colors are difficult to achieve; the cost is mainly affected by high consumption, which is a kind of surface treatment cost. 4. PVD vacuum electroplating, the full name of physical vapor deposition, is an industrial production process, mainly using physical process deposition film technology, various zinc alloy die castings, aluminum alloy die castings can use vacuum plating process. Process flow: cleaning before PVD→into the furnace vacuum→cleaning target and ions→coating→finishing, cooling outside the furnace→post-processing (polishing, AFP) Technical features: PVD (physical vapor deposition) can be used for high hardness and high wear resistance Coating on the metal surface 5. Electroplating zinc-aluminum alloy surface treatment technology is a technology that uses electrolysis to attach a metal film to the metal surface to prevent corrosion, improve wear resistance, conductivity, light reflection and improve appearance. Electroplating technology is widely used and can be used for a variety of zinc alloy die castings and aluminum alloy die castings. Process flow: pretreatment → cyanide-free alkaline copper → cyanide-free white copper tin → chromium plating Advantages: 1. The coating has high gloss and high-quality metal appearance; 2. The base material is SUS, Al, Zn, Mg, etc., and the cost is low于PVD. Disadvantages: poor environmental protection and high risk of environmental pollution. 6. Powder spraying. Powder spraying equipment (electrostatic spraying machine) is used to spray powder coating on the surface of zinc alloy die castings and aluminum alloy die castings. Under the action of static electricity, the powder is uniformly adsorbed on the surface of the casting to form a powder coating. The powder coating is dried, baked, leveled and cured at a high temperature, and finally coatings with different effects are obtained (the effects of powder coatings are different). Process flow: loading → electrostatic dust removal → spraying → low temperature leveling → baking Advantages: 1. Rich colors, high brightness, matte optional; 2. Low cost, suitable for building furniture products and radiator shells, etc.; 3. High utilization rate, 100% utilization, environmental protection; 4. Strong ability to shield defects; 5. Can imitate wood grain effect. Disadvantages: At present, it is less used in electronic products. 7. The formation of lines on the surface of zinc alloy die-casting parts by grinding products for metal drawing is a surface treatment method with decorative effect. According to the different patterns after painting, it can be divided into: straight line painting, random painting, wave painting and spiral pattern. Technical features: Wire drawing treatment can make the metal surface obtain a mirror-free metallic luster. At the same time, wire drawing treatment can also eliminate the small defects on the surface of zinc alloy die castings. 8. Sandblasting uses compressed air as power to form a high-speed jet stream, spraying the spraying material on the surface of the zinc alloy die casting at a high speed, thereby changing the appearance or shape of the outer surface of the zinc alloy die casting, so as to obtain a certain degree of cleanliness and different Roughness roughness process. Technical features: 1. Realize different reflection or matt. 2. It can remove microburrs on the surface of zinc alloy die castings, make the surface of zinc alloy die castings smoother, eliminate the hazards of burrs, and improve the grade of zinc alloy die castings. 3. Remove the dirt remaining in the pretreatment process, improve the smoothness of the zinc alloy die castings, make the zinc alloy die castings show a uniform metal color, and make the zinc alloy die castings more beautiful. 9. Polishing. Polishing media such as flexible polishing tools and abrasive particles are used to modify the surface of zinc alloy die castings. According to different polishing processes: rough polishing (basic polishing process), medium polishing (finishing process) and finishing polishing (polishing process) to select the appropriate polishing wheel can achieve the polishing effect and improve the polishing efficiency. Technical features: By improving the dimensional accuracy or geometric accuracy of zinc alloy die-casting parts, a smooth surface or mirror gloss can be obtained, and the gloss can be eliminated at the same time. X. Etching Generally speaking, etching is also called photochemical etching, which refers to removing the protective film of the etched area through exposure after plate making and development, and contacting chemical solutions during the etching process to achieve the effect of dissolving corrosion and forming bumps or voids. Exposure method: According to the drawings, this project provides the size of material preparation→material preparation→cleaning material→drying→coating or coating→drying→exposure→development→dry etching→peeling→OK. Screen printing method: cutting → cleaning plate (metal materials such as stainless steel) → screen printing → etching → peeling → OK Advantages: 1. The surface of zinc alloy die castings can be processed; 2. The special surface effects of zinc alloy die castings are given ; Disadvantages: Most etching solutions (acids, alkalis, etc.) are harmful to the environment.
Problems that should be paid attention to in the production of aluminum alloy die castings
Issues that need attention in the production of aluminum alloy die castings With the continuous expansion of the application range of aluminum alloy die casting products in the market, domestic aluminum alloy die casting has developed rapidly in recent years. In the current market situation, whether it will be restricted by some factors is also a question that many people in the industry are concerned about. Die-cast aluminum alloy is also a kind of die-casting. The knowledge introduced below is also about die-casting, so what is the specific introduction? 1. The control of alloy composition starts with the purchase of alloy ingots. The alloy ingot must be based on ultra-high-purity aluminum, plus alloy ingots made of ultra-high-purity aluminum, magnesium, and copper. The supplier has strict ingredient standards. High-quality aluminum alloy is the guarantee for the production of high-quality castings. 2. The purchased alloy ingots should have a clean and dry stacking area to avoid long-term damp and white rust, or pollution from factory dirt, increase slag output, and increase metal loss. A clean factory environment is very useful for effective control of alloy composition. 3. The ratio of new materials to water inlets and other recycled materials shall not exceed 50%. Usually, new material: old material = 70:30. The content of Al and Mg in the continuously remelted alloy gradually decreases. 4. When the nozzle material is remelted, the remelting temperature must be strictly controlled not to exceed 430℃ to avoid the loss of aluminum and magnesium. 5. When conditions permit, use a centralized smelting furnace to smelt aluminum alloys, so that the ratio of alloy ingots to recycled materials is uniform, the use of flux is more effective, and the alloy composition and temperature remain uniform and stable. Electroplating waste and fines should be smelted separately. In most cases, to manufacture high-quality aluminum alloy die castings, you do not need to pay attention to the above problems. If aluminum alloy die castings have the following defects, some treatment methods are provided below. Since each defect is caused by many different factors, this problem must be solved in actual production. Faced with many reasons, should we adjust the machine first, change the material first, or modify the mold first? It is recommended to deal with it according to the degree of difficulty. 1) Clean the parting surface, cavity and ejector rod; improve the coating and spraying process; increase the clamping force and the amount of pouring metal. These measures can be achieved through simple operations. 2) Adjust process parameters, injection force, injection speed, filling time, mold opening time, pouring temperature, mold temperature, etc. 3) In order to change the raw materials, select high-quality aluminum alloy ingots, change the ratio of new materials to recycled materials, and improve the smelting process. 4) Modify the mold, modify the gating system, add internal gates, increase overflow grooves, exhaust grooves, etc. For example, the reasons for flashing of die-casting parts are as follows: 1) Die-casting machine problem: the locking force is adjusted incorrectly. 2) Process problem: the injection speed is too high, and the pressure shock peak is too high. 3) Mold problems: deformation, debris on the parting surface, uneven wear of inserts and sliders, and insufficient template strength.
The main advantages and working temperature of aluminum alloy die casting
Aluminum alloy die casting occupies a very important position in today's industry. It has a very wide range of uses in many industries. With the continuous development of society, people's life needs are also increasing. In operation, the demand for aluminum alloy die-casting process is also increasing. 1. The main advantages of aluminum alloy die-casting 1. Aluminum alloy die-casting parts are beautiful in appearance and light in weight. It is easy to transport during operation. It is also a big advantage to use it in a car. 2. The density of aluminum alloy is significantly lower than that of cast iron and cast steel, but its strength and corrosion resistance are much higher. Therefore, under the same load weight, the use of aluminum alloy die-casting can greatly reduce the structural weight. 3. The aluminum alloy has good surface gloss and good casting performance. The mechanical properties and tensile strength of aluminum alloy die castings have great resistance during manufacture. To a certain extent, their elongation is a measure of the brittleness and plasticity of materials. Hardness refers to the resistance of the surface of a material to plastic deformation caused by the pressing or friction of hard materials. Aluminum alloy die castingThe working temperature and humidity of the workpiece, the medium and air tightness of the workpiece contact, and the accuracy and dimensional stability of the entire product. To a certain extent, the surface accuracy and surface roughness of aluminum alloy die castings will directly affect the working efficiency, energy consumption and cavitation development of the pump and hydraulic system. The strength and shock resistance of internal combustion engine cylinder blocks, cylinder heads, cylinder liners, piston rings and exhaust pipes directly affect the service life of the engine. Compared with other casting methods, sand casting has low cost, simple production process and short production cycle. It is aluminum alloy die casting. When the wet mold fails to meet the requirements, consider the use of clay sand dry sand molds, dry sand molds or other sand molds. The casting method of aluminum castings should be compatible with the production batch. Low pressure casting, die casting, centrifugal casting and other casting methods are only suitable for mass production due to the high cost of equipment and molds. Aluminum castings can be single-piece casting or mass production. 2. What causes the molten slag of aluminum alloy die-casting? According to the manufacturing process, aluminum alloy die-casting can be divided into two categories: cast-type zinc alloy die-casting and wrought zinc alloy die-casting. The output of cast zinc alloy is much larger than that of wrought zinc alloy. Listed below are the properties, properties and uses of several important zinc alloys. Cast zinc alloy; according to different casting methods, it is divided into pressure casting zinc alloy (solidified under the action of external pressure) and gravity casting zinc alloy (solidified only under the action of gravity). Die casting zinc alloy. Since this alloy was used in the automobile industry in 1940, the output has increased sharply. Among the total zinc consumption, about 25%, 0.004%, 0.003%, 0.02%, so zinc alloy die casting should be used High-purity zinc with a purity of 99.99% is used as a raw material. Gravity casting zinc alloy can be cast in sand molds, plaster molds or hard molds. This kind of zinc alloy not only has the characteristics of general zinc alloy die-casting, but also has high strength and good casting performance. The cooling rate has no obvious influence on the mechanical properties. The residues and scraps produced in the production of zinc alloy die-casting parts can be recycled and the gate is simple. It is not sensitive to overheating and remelting, has small shrinkage, less pores, can be electroplated, and can be finished by conventional methods. Wrought zinc alloy: In addition to traditional varieties of wrought zinc alloys used in industry, ZN-1CU-0.1TI and ZN-22AL alloys have appeared. After the former is rolled, because of the TIZN15 intermetallic compound dispersed particles arranged in rows along the rolling direction, it can hinder the movement of grain boundaries.