| Sharing the characteristics of low density, good ductility, high intensity and low earring rate, the wrought aluminum alloy 3104 is widely used in the production of cans; however, the scrap aluminum cans are often reclaimed by degrade. Therefore, in order to solve this problem, some of the key technologies in the Level-maintaining of 3104 aluminum alloy for cans are put forward in this paper, with an expectation of providing a reference for the re-production and further study on the aluminum alloy 3104.In specific, the law for the influence of the technologies of ultrasonic paint removing, melt purification, refinement with rare earth,modification by adjusting the content of Mn and composite thermal treatment on the micro organization of the reclaimed aluminum cans is mainly studied, the microstructure and mechanical properties of the regenerated 3104 are improved by controlling the process parameters. In addition, it can be found that the recovery of scrap aluminum, the basic theory for the aluminum melt treatment and the theory for the composite thermal treatment have a certain guiding significance to the development and amelioration of the avoid relegation reduction technology of the scrap aluminum cans. To be more specific, the content and the results of the study are:(1) The ultrasonic is used to remove the paint on the surface of the cans. According to the principle of ultrasonic cavitation, the law for the influence of cavitation bubbles with different initial radius, different ultrasonic powers and sound pressure amplitude on the dynamic property of the cavitation bubbles is discovered. That is, when the radius of the cavitation bubble R0 is 160μm, f is 20.5KHz, and the sound pressure amplitude is 0.5MPa, the expansion rate of the cavitation bubble is the biggest; the energy released is the greatest when the cavitation bubble is collapsed; the energy passed to the abrasive Al2O3 is the greatest; and the effect of paint removing is the best.(2) The metallurgical quality of the melt of the scrap aluminum cans is obviously ameliorated by the self-designed refinement technology of aluminum melt. Orthogonal experiment method is used to Study on the different flux formula and different spoiler width on melt impurity and gas removal effect. It is concluded that, at the melting temperature of 720℃, the refinement of the melt is made by adding 4% self-made refining agent, and it can be seen that the refinement effect of the aluminum melt is the best, the tensile strength and elongation of the sample can reach 193 MPa and 21.04% respectively; when the width of the spoiler is 15 mm, by adopting the degassing technology of water simulation spinning spraying, it can be found that the size of the cavitation bubble in the solution is the smallest and the most uniform; under the condition that the rotating speed and the size of the spoiler are fixed, when the spoiler is put in the middle and the bottom of the container, it can be seen that the size of the cavitation bubble is smaller and more uniform.(3) A kind of alloy refinement agent Al-5Ti-1B-Er is made by taking the powder of A1, Ti, B and Er as the raw material. Moreover, a study is made on the influence of the adding quantity of the rare earth Er on the alloy organization of Al-5Ti-1B-Er, and a kind of refinement agent Al-5Ti-1B-Er with the best performance is added into the aluminum alloy 3104, so as to test its refinement effect. After the alloy being refined, it is found that there are TiAl3, TiB2 and Ti2Al20 Er in the generated second phase. In addition, with the increase of the content of the rare earth, the size of the TiAl3 is reduced gradually. When the refinement is made, as the nucleation of the particle, Ti2Al20 Er is dissolved constantly, which can prolong the refinement time, thus, the long-term performance of the alloy is improved. Furthermore, with the adding of Er, the viscosity of the aluminum melt is increased, and the subsidence speed of the particles TiAl3, TiB2 and Ti2Al20 Er is made become lower, in this way, the segregation precipitation of TiB2 can be eliminated. In the condition of melting temperature of 750℃, Er addition 0.4wt.%, Al-5Ti-1B-0.4Er addition 1wt.%, the heat preservation time in the aluminum liquid 30 min, the refinement effect reaches the best; the measured size of the regeneration 3104 aluminum alloy is 159±59μm, 45% higher than that of AlTiB.(4) It is found in this study that, by adjusting the content of Mn, the microstructure and mechanical properties of 3104 aluminum alloy can be significantly influenced, when the content of Fe is more than 0.7, and the mass ratio of Mn/Fe is 1.5, the mechanical performance of the reclaimed aluminum alloy 3104 can be raised to the maximal value; when the mass ratio of Mn/Fe is beyond 1.5, the mechanical performance is decreased obviously. Specifically speaking, when the mass ratio of Mn/Fe is more than 1, it is in favor of the passivation, refinement or even the granulation of the AlMnFeMg phase in the organization of the reclaimed aluminum alloy 3104; however, when the mass ratio of Mn/Fe is more than 1.5, there will be existing more large and flaky AlMnFeMg phases, which will cause a deterioration in the mechanical performance.(5) The influence of the cryogenic treatment followed by homogenizing treatment is researched on the microstructure and mechanical properties of 3104 aluminum alloy. It is also found in this study that, there is a PLC effect in the stress-strain curve of the sample after homogenizing treatment, and there is no such effect in the stress-strain curve of the sample only after cryogenic treatment; after cryogenic treatment, the dispersed precipitation of the second phase of the aluminum alloy 3104 can be promoted by a further homogenizing treatment, and the dislocation pinning effect of the solute atoms can be strengthened by the large amount tiny and uniformly distributive precipitation phases, in this way, the critical strain value of the aluminum alloy 3014 can be improved. the sample after cryogenic treatment first and homogenizing treatment second shares a good comprehensive mechanical performance, and its tensile strength, yield strength and elongation can reach to 214 MPa, 105 MPa and 20.8% respectively, more 29%, 41% and 11% respectively than that of the sample processed only by the conventional homogenizing treatment.In conclusion, this study is not only good for deepening and expanding metal recycling technology, but also beneficial to gain a better comprehension to the surface-off-paint technology in its traditional sense and its related theories. At the same time, it is going to provide references for the popular technology research of metal relegation regeneration. The study on the key technologies during the course of 3104 aluminum alloy regeneration in this paper will provide an important theoretical basis and open up a new way to a complete technology industry for the green recycle of used cans. |
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