Results and Discussion
1. The influence of temperature
Temperature is an important guarantee for smelting process, which plays an important role in melting, burning loss and furnace age of metals. Due to the uniqueness of the new process, the alloy can be prepared below 600 ℃. Under the experimental conditions, the temperature has no significant effect on melting, but the comprehensive analysis shows that 570 ℃ melting alloy is more suitable for production.
2.Influence of covering agent
Theoretically, the addition of mulcher can reduce the oxidation, evaporation and inspiration of elements in the alloy. Therefore, charcoal was used as a covering agent. The results show that the suction tendency of zinc alloy is small, the gas precipitation is very little when the charcoal smelting is not used, and the burning loss of the alloy is small, and the addition of charcoal will bring inconvenience to the operation, and increase the amount of alloy liquid entraining in the slag. Considering the good sealing of power frequency coreless induction furnace, and its internal alloy liquid is automatically stirred by electromagnetic effect, so the production can be less or not add charcoal and other covering agent.
3.Influence of refiners
The refiner has a good effect on the degassing and slag removal of alloy liquid. It is reported that nearly 80% of the oxides and 70% of the intermetallic compounds in zinc alloy liquid can be removed by pressing ammonium chloride with bell jar at 450 ~ 470℃, so as to ensure the quality of the alloy. However, our experiments also found that the smelting rate of the alloy was increased by ammonium chloride refining (about 0.12% of the total weight of the metal), and a large amount of smoke and ammonia gas was produced during the process, which may worsen the operating environment. The alloy ingot with dense section structure and no slag and inclusions could be obtained by standing and clearing only. Therefore, production can be based on the amount of return charge to determine whether slagging operation and the amount of ammonium chloride needed to be added.
4.Al-Cu intermediate alloy preparation
The conventional two-step smelting process preforms the intermediate alloy first, mainly to facilitate the addition of copper with high melting point and shorten the melting time of zinc alloy. According to the phase diagram, the Al-Cu eutectic composition containing 33.2% Cuwas selected, and its melting point was 548℃, which could realize melting in zinc melt as soon as possible. It is observed that a large amount of gas precipitates when Al-Cu alloy is solidified at high temperature, and the amount of Al 2O3 suspended slag is large. The total melting loss rate of the alloy is up to about 7% on average, indicating that a large amount of metal (mainly Al) is lost during the process
Comparison of different process costs
Although the new smelting process takes about twice as long as the conventional two-step smelting process, the melting loss of the alloy does not increase much, and the total energy consumption of the old process is slightly higher than that of the new process or the two are almost equal because of the high temperature copper melting process. The average total melting loss rate of the new and old processes is about 1.35% and 1.12%, respectively, which can be used to calculate the metal loss cost of the two processes in alloy preparation. The new process has some advantages in economy. Obviously, when the annual output of alloy reaches 10,000 t, the new process can save about 189,000 yuan compared with the old process.
(1) The development and production of die-casting zinc alloy in zinc hydrometallurgy enterprises can avoid the secondary remelting of zinc ingot, which is conducive to saving energy and reducing the cost of alloy production.
(2) The new process uses the alloy melting of copper in zinc melt, so it can realize direct melting at low temperature, which overcomes the shortcomings of the conventional two-step smelting method, and has the advantages of economy, convenience and practicability.
(3) the choice of power frequency coreless induction furnace is appropriate for alloy making, because the furnace has good sealing property, less or no charcoal cover can be added in the process, and because the automatic mixing of melt can make the alloy composition uniform, good slagging effect, and can reduce labor intensity and conducive to operation.
(4) Adding refiner can obviously improve the quality of die-casting zinc alloy ingot, but at the same time, the melting loss rate of alloy also increases accordingly, so the amount of refiner added should be controlled in production