The distribution level of the nozzle determines the distribution effect of the aluminum melt in the cavity of the aluminium silicate caster tip, and plays a decisive role in the uniformity of the alloy chemical composition, flow field and temperature field in the nozzle. The 8079 aluminum alloy cast-rolled sheet has a large surface width, and the temperature field and flow field are very important for the uniform filling of the nozzle. Therefore, a three-stage distribution nozzle structure was selected for 8079 aluminum alloy cast-rolled plate production. Because the temperature, distribution and flow of molten aluminum in the nozzle cavity of the three-stage distribution nozzle are much more even than those of the first and second-stage distribution nozzles, the molten aluminum flowing into the nozzle cavity is almost the same static pressure. The flow rate is consistent, and the entire aluminium silicate caster tip can be filled quickly and evenly.
In order to ensure the fluidity of the melt in the casting nozzle cavity, a relatively high front box temperature should be selected, and it is more appropriate to control the front box temperature at 685 ~ 690 ℃. The front box temperature is affected by factors such as the temperature of the molten aluminum in the holding furnace, the length of the chute, the temperature performance of the chute and its preheating temperature. In order to ensure the temperature of the front box, in addition to controlling the temperature of the molten aluminum in the holding furnace to be 25 to 30 ℃ higher than the temperature of the front box, the chute insulation should also be strengthened, and the chute lining, degassing box lining and slagging box lining should be pre-processed in advance. Heat to maintain the melt temperature and its stability.
If the liquid level in the front tank is too high, the static pressure of the molten aluminum will increase, which can easily cause aluminum leakage and the formation of transverse ripple defects, and even cause the cast-rolled plate to break. If the temperature of the front box is too low, it will cause the static pressure of the molten aluminum to decrease and the filling of the nozzle to be difficult, and it is easy to produce defects such as hot strips. At the same time, it will also reduce the casting speed and affect the casting production. The main measures to ensure the liquid level and stability of the front tank: One is to install a 30 PPI ceramic foam filter plate in the chute, which can reduce the fluctuation of the aluminum liquid level in the chute, stabilize the liquid level of the front tank, and can also intercept the size Larger inclusions can improve the slag-retaining effect of the online filtering device; the second is to use a screw-type front box liquid level control device to accurately control the front box liquid level at 40 ± 0. 5 mm.