ईमेल प्रारूप त्रुटि
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In the whole process of aluminum alloy die-casting, aluminum alloy profiles can digest and absorb a lot of radon gas during smelting and pouring, and continue to dissolve due to the decrease of solubility during refrigeration. Some materials are introduced in detail. More hydrogen melts in the aluminum alloy profile, and its solubility expands with the increase of the temperature of the aluminum alloy liquid, and decreases with the decrease of the temperature. When the liquid is converted into a solid, the hydrogen is in the aluminum alloy profile. 19 times lower solubility. Therefore, in the whole process of condensation of aluminum alloy profile liquid, at a certain moment of hydrogen, the composition of hydrogen exceeds its solubility and dissolves in the form of bubbles. The radon bubbles generated by the dissolution of over-saturated hydrogen, which cannot be discharged in time for the upward adjustment, will produce fine and dispersed air vents during the whole process of condensation, which is commonly referred to as gasporosity.
The over-contrast achieved before radon bubbles are generated is a function of the number of radon bubbles nucleated, while metal oxides and other impurities play a key role in the formation of bubbles.
Under normal manufacturing standards, it is difficult to prevent pinholes, especially in thick sand castings. When smelting and pouring aluminum alloy profiles in an atmosphere with high air humidity, pinholes in castings are especially serious. This is why we are often puzzled by some people in the production process. The dry season is better than the rainy, wet and cold season. Aluminum alloy castings have fewer pinhole defects.
Generally speaking, for aluminum alloy profiles, if the crystal temperature range is large, the probability of causing pinholes in the network structure is also much larger. This is because under the general forging manufacturing standards, die-cast aluminum parts have a wide range of condensation temperature, which makes it very easy for aluminum alloy profiles to produce relatively developed network structure crystals. In the middle and late stage of condensation, the residual lithium bromide solution in part of the interstices of the network crystal structure will block each other, and each will be stored in a small closed indoor space, because they are subjected to the external atmospheric pressure and the negative pressure of the aluminum alloy liquid. When the residual lithium bromide solution is further refrigerated and folded, a certain level of vacuum pump will be generated (that is, the feeding safety channel is blocked), and then the over-saturated radon gas in the aluminum alloy will be dissolved, resulting in pinholes.
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