In the process of starting production of aluminum die-casting molds, the mold must be preheated to prevent the appearance of cracks caused by the sudden encounter of hot metal liquid in the cold mold. For more complex molds, blowtorch, liquefied gas, and good conditions With a mold temperature machine, relatively simple molds can be preheated by slow injection. If the mold is equipped with neutron control, pay attention to prohibit the signal line between the die-casting machine and the mold from having joints. The reason is very clear. In daily production, it is difficult to avoid water on the signal line, or the joints are easily broken. , resulting in a short circuit with the machine tool, if the signal is wrong, the alarm will automatically stop and delay the time, and the signal will be disordered and the mold will be damaged. cause unnecessary losses. Note that the travel switch is waterproof.
Analysis of crack failure causes of aluminum die-casting molds.
Through practice, it is found that there are uneven microstructures on the heat-treated substrate of the research object. By observing the research object under a low magnification microscope, we found that a large number of precipitated granular carbides are distributed on the matrix and have segregation. larger in size. Due to the excessive precipitation of carbides and alloyed carbides, the mold material loses a large amount of surrounding carbon and alloying elements. Under normal circumstances, the segregated carbides that occur when the mold is quenched and heated will not be easily dissolved. However, due to its lack of carbon and alloying elements, it is easy to change into a martensite structure under high temperature heating, thereby reducing the Tempered stars, and greatly reduce the strength and toughness of the steel, making it easy to break just now. By observing the steel in the annealed state before vacuum quenching with a metallographic low-power microscope, we found that the steel matrix also had segregation. The appearance of this phenomenon means that the steel raw material lacks uniformity.
And once the segregation phenomenon is not dealt with effectively, it will increase the risk of mold cracking and failure, and affect the final service life of the mold. Sanmen imported aluminum die-casting mold structure mold cooling water not only prolongs the service life of the mold under the condition of correct use, but also improves the production efficiency. The thickness of the aluminum die-casting mold wall directly affects the quality of the die-casting part. Due to the rapid cooling, the outer layer of the die-casting part has fine grains and fine arrangement, and its existence makes the die-casting part higher in strength. If the thick-walled die-casting parts are thick-walled, the grains in the middle layer of the precision die-casting parts are coarse, and defects such as shrinkage cavities and shrinkage porosity are prone to occur.
The mechanical properties of die castings will also decrease with the increase of wall thickness, and the amount of material and the weight of die castings are also increased. In order to facilitate the movement of the molten metal and the molding of the die-casting parts, and prevent the stress-concentration of the die-casting parts and the die-casting mold from causing cracks, the connection between the die-casting part and the wall generally adopts the rounded corners and corners recommended by domestic and foreign design standards to strengthen the sudden transition connection. The quality of the raw materials of the die-casting mold greatly affects the service life of the aluminum alloy die-casting mold.
Therefore, the staff needs to select the appropriate raw materials for the die-casting mold according to the actual needs. After determining the raw materials of the aluminum alloy die-casting mold, heat treatment needs to be carried out in time. At the same time, it is necessary to do a good job in the stress relief process in the production stage to prevent stress concentration, and to do a good job of R angle control. – Generally, when the aluminum alloy die-casting mold is used about 10,000 times, it needs to be tempered in time to relieve stress, so as to effectively prevent the cracking failure of the mold caused by stress concentration. In order to increase the service life of the mold as a whole, multiple tempering and stress relief methods can be used.
Scientifically and reasonably control the temperature in the production process of aluminum alloy die-casting molds
The production process of aluminum alloy die-casting molds presents high temperature and high pressure. Therefore, it is particularly important to scientifically and reasonably control the temperature in the production process. In the production process, the producer can use a suitable thermometer to measure the highest temperature in the die-casting process and take effective control measures to control the temperature within 650 degrees. The materials used in the machining of aluminum die-casting molds will affect the quality of the aluminum die-casting molds produced.
What are the advantages of die casting molds
- Die-casting parts can be treated with coating surface: due to the increasing use of die-casting parts, in order to meet the needs of use, the surface of die-casting parts can be coated and surfaced, such as electroplating, anodizing, polishing, organic maintenance coating. coating, painting, sandblasting, pickling, etc. Then comes the decorative or maintenance needs.
- The use of the insert casting method in the die-casting mold can save the installation process and simplify the production process: parts of other materials (such as steel, iron, copper, alloy, aluminum, etc.) can be embedded in the die-casting parts to save valuable materials. and machining man-hours, and can obtain parts with complex shapes and parts with excellent performance. 5. The die-casting parts are densely arranged and have high strength and hardness: because the liquid metal is rapidly cooled in the die. At the same time, it crystallizes under pressure, so the layer of metal grains near the surface of the die-casting part is finer and finely arranged. Improve surface hardness. The tensile strength of die castings can be 25%-30% greater than that of sand castings, but the elongation is reduced.
- The production efficiency of die-casting is very high: the production process of zinc-aluminum die-casting is easy to be mechanized and automated. Usually, the cold chamber die casting machine can die casting 600’I00 times every eight hours on average, while the hot chamber die casting machine can die casting 3000-TWO times every eight hours on average. Since the die-casting process is mainly completed on the die-casting machine, it is easy to automate the production process.
- Thin wall and shape of casting. Complex and clear summary: the smaller wall thickness of aluminum alloy die castings can be 0.3mm, the aluminum alloy die castings can be 4.5mm, the diameter of the smaller casting hole can be 0.7mm; the minimum pitch of the castable thread is 0.75mm because The production cycle is long, the investment is high and the manufacturing precision is high, so the cost is relatively high, and there are high requirements for the service life of the aluminum die.
During the die casting process, the molten metal enters the mold cavity, which will have a strong physical impact on the surface of the mold, as well as chemical corrosion.
The so-called thermal remelting zone means that the surface metal is melted by the high temperature released when it is discharged. Since the melt is not completely thrown out, and the retained melt solidifies with the cooling of the working fluid. The hot remelting zone is mostly distributed in the upper layer of the steel surface. Compared with the heat-affected layer in the thermal remelting zone, the metal material did not melt after being sintered at high temperature, but the metallographic structure of the material changed accordingly. Through a lot of practice, we found that the hot mold process will also increase the risk of mold crack failure in the thermal remelting zone and the heat affected zone. Although the metallographic structure of the aluminum alloy die-casting mold after EDM passes through the gas furnace, the metallographic structure of the mold does not change accordingly, but there will be slight cracks in the thermal remelting zone, and when the cracks extend to the thermal effect The range of micro-cracks will increase again after the zone, which in turn increases the degree of mold cracking failure. The die-casting machining industry has also obtained many development opportunities, especially aluminum die-casting parts are widely used. So what are the manufacturing processes of aluminum die-casting molds? What are the precautions in these processes?
Aluminum die-casting mold making process
- Design of aluminum die-casting mold: divided into product splitting, runner design, slider, thimble, exhaust, slag discharge design, etc.; this requires the mold designer to have sufficient working experience and familiarity with the product. The high-quality aluminum die-casting mold can have good results in terms of service life and die-casting products;
- Design drawing: draw the various parts and accessories of the aluminum die-casting mold one by one, the first is the 3D drawing, and the second is the 2D drawing. After drawing, the design must be reviewed first, followed by the director of the mold department, the project corresponding engineer, and the business plan. , to ensure the smooth production and production of aluminum die-casting molds;
- Aluminum die-casting mold machining: mold machining is divided into mold base machining, mold core (die core) machining, thimble, slider and other accessories machining, in addition to the need for spark machines, milling machines, grinders, CNC, heat treatment, etc. and other mold making equipment for machining;
- The assembly of aluminum die-casting molds: This section requires the previous processes to be successfully completed, and the various accessories are in place. Generally, the fitter responsible for this set of molds is responsible for this. This requires the fitter to be very familiar with this mold and have A certain experience, understanding of drawings, good assembly technology, and various mold making machinery, otherwise you cannot cope independently in the case of assembly. Master fitters with rich experience can often assemble a set of molds independently in the face of various problems.
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