Time：2019-08-24| Author：Admin
I. Die Casting Introduction Pressure casting is called die casting. It is a casting method in which a molten alloy liquid is poured into a pressure chamber to fill a cavity of a steel mold at a high speed, and the alloy liquid is solidified under pressure to form a casting. The main features of die casting that distinguish it from other casting methods are high pressure and high speed.
1 The molten metal fills the cavity under pressure and crystallizes and solidifies at a higher pressure. The common pressure is 15-100 MPa.
2 The metal liquid fills the cavity at high speed, usually at 10-50 m/s, and some can also exceed 80 m/s (the line speed of the cavity introduced into the cavity through the ingate), so the molten metal The filling time is extremely short, and the cavity can be filled within about 0.01-0.2 seconds (depending on the size of the casting). Die casting machines, die-casting alloys and die-casting molds are the three major elements of die-casting production and are indispensable. The so-called die-casting process is to organically combine these three elements to enable stable, rhythmic and efficient production of qualified castings, even high-quality castings, with the appearance, good internal quality, dimensional conforming to drawings or agreements.
1. Die-casting machine (1) Classification of die-casting machine The heating conditions of the pressing chamber of the die-casting machine can be divided into two categories: hot-pressing chamber and cold-pressing chamber. The cold chamber die casting machine can be divided into vertical, horizontal and full vertical die casting machines, which are different from the pressing chamber and the mold placement position. Hot chamber die casting machine Vertical cold chamber bedroom full vertical 2, die casting alloy die castings are mainly alloyed with non-ferrous alloys, as ferrous metals (steel, iron, etc.) are currently less used due to problems with mold materials. Among the non-ferrous alloy die-casting parts, aluminum alloy is widely used, and zinc alloy is second. The following is a brief introduction to the case of die-casting non-ferrous metals.
(1) Classification of die-casting non-ferrous alloys, shrinkage, shrinkage, shrinkage, shrinkage, free shrinkage, lead alloy-----0.2-0.3%, 0.3-0.4%, 0.4-0.5%, low-melting alloy, tin alloy, zinc alloy--------0.3 -0.4%0.4-0.6%0.6-0.8% aluminum silicon system--0.3-0.5%0.5-0.7%0.7-0.9% die-casting non-ferrous alloy aluminum alloy aluminum-copper aluminum-magnesium---0.5-0.7%0.7-0.9% 0.9-1.1% high melting point alloy aluminum-zinc-based magnesium alloy----------0.5-0.7%0.7-0.9%0.9-1.1% copper alloy
(2), various types of die casting alloy recommended casting temperature alloy type castings average wall thickness ≤ 3mm casting average wall thickness > 3mm structure simple structure complex structure simple structure complex aluminum alloy silicon 610-650 ° C 640-680 ° C60 die-casting mold Manufacture 0-620 ° C 610-650 ° C aluminum copper 630-660 ° C 660-700 ° C 600-640 ° C 630-660 ° C aluminum magnesium 640-680 ° C 660-700 ° C 640-670 ° C 650-690 ° C aluminum zinc system 590-620°C620-660°C580-620°C600-650°C zinc alloy 420-440°C430-450°C400-420°C420-440°C magnesium alloy 640-680°C660-700°C640-670°C650- 690 ° C copper alloy ordinary brass 910-930 ° C 940-980 ° C 900-930 ° C 900-950 ° C silicon brass 900-920 ° C 930-970 ° C 910-940 ° C 910-940 ° C Note: 1 casting temperature is generally The temperature of the molten metal of the holding furnace is measured. 2 The casting temperature of the zinc alloy should not exceed 450 ° C to avoid coarse grains.
II.Second, die-casting die-casting mold is one of the three major factors of die-casting production. The correct and reasonable mold is the prerequisite for the smooth progress of die-casting production, and plays an important role in ensuring the quality of castings. Due to the characteristics of the die-casting process, the correct selection of each process parameter is the decisive factor for obtaining high-quality castings, and the mold is the premise of being able to correctly select and adjust various process parameters. The mold design is essentially the prediction of various factors that may occur in the die-casting production. Comprehensive reflection. If the mold design is reasonable, there are fewer problems encountered in actual production, and the pass rate of the castings is high. On the contrary, the mold design is unreasonable. The casting force of the fixed mold is basically the same when the casting is designed. The casting system is mostly fixed in the mold, and it is produced on the Guannan die-casting machine where the punch cannot be fed after the shot, and it cannot be produced normally. The casting has been stuck to the fixed mold. Although the finish of the mold cavity is very light, due to the deep cavity, there is still a phenomenon of sticking to the fixed mold. Therefore, in the design of the mold, it is necessary to comprehensively analyze the structure of the casting, familiar with the operation process of the die-casting machine, to understand the possibility of adjustment of the die-casting machine and process parameters, to grasp the filling characteristics under different conditions, and to consider the method of drilling, drilling After the eye and the fixed form, it is possible to design a mold that is realistic and meets the production requirements. As mentioned at the beginning, the filling time of the molten metal is extremely short, and the specific pressure and flow rate of the molten metal are very high. This is extremely harsh in the working condition of the die-casting mold, coupled with the impact of the alternating stress of the chilling heat. The effect has a great influence on the service life of the mold. The service life of the mold usually refers to the modulus of die casting (including the natural damage caused by good maintenance under the conditions of normal use and the maintenance of the Chinese die-casting net under normal conditions of use, before being scrapped and scrapped (including The number of scraps in die casting production).
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