The hot top method uses the same level of casting to reduce the drop points of the distribution plate. At the same time, the exposed area of the upper part of the mold is small, and there is a “hot cap” for heat preservation, so the casting temperature is slightly lower than the ordinary method. However, if the casting temperature is too low, it will promote the formation of the cold barrier and increase its depth. If the casting temperature is too high, it is easy to produce lace structure in the ingot. It must be properly controlled.
As we all know, the liquid level of the liquid cavity in the mold is an important basis for judging the quality of round ingot casting. In the ordinary metal mold casting method, the liquid level of the mold cavity is about 50mm-80mm. When the molten metal passes through the crystallizer, the first solidified shell shrinks and separates from the working surface of the crystallizer, which creates a gap, which seriously hinders the continued cooling of the outer surface. Only after the surface of the ingot enters the direct water-cooling zone can a good cooling effect be obtained. Therefore, in order to minimize the segregation zone and the insufficient cooling area after solidification, and achieve the purpose of improving the structure and surface quality of the ingot, the hot top casting method will be more ideal. AdTech offers distributing launder, Ceramic Sprue Bush, Alumina Ceramic Ring, Hot Top Casting Cap, High Purity Graphite Ring, Hot Top Casting Cap for hot top casting. This is due to the low liquid level of its effective liquid cavity and precise adjustment, which makes the cross-sectional structure of the produced ingot more uniform.
In addition, the hot top method can achieve the same level of casting, it is convenient to use the melt purification treatment device, and can control the re-contamination of the melt during the casting. The oxide on the surface of the melt during the casting process is not easy to be involved in the melt. Stay on the gate. Since the floating funnel is not used, it is not easy to produce feather crystals at the corresponding part of the floating funnel. These advantages, for aviation and other important industrial sectors, require the provision of molds and forgings with low air content, no oxidation inclusions, and high structure performance, which will meet the satisfactory requirements. The online degassing system and produced by AdTech can effectively improve the quality of aluminum castings and is installed between the furnace and the casting platform.
At the same time, with the stability of the process, not only the production efficiency of the casting machine and the casting yield rate are improved. For the processing workshop, the homogenization time of the ingot is shortened, there is no edge segregation, and the dendrite network on the cross section is small, which greatly improves The extrusion speed and yield rate enable it to obtain greater economic benefits.
Of course, at present, the hot top method is widely used in the production of small diameter soft alloys at home and abroad, but the large diameter hard alloy has not yet received due attention. This is mainly due to the small diameter and fast casting speed, the small internal stress of the ingot during the casting process, and the low tendency to crack. The situation of large-diameter ingots is different, and the casting speed is severely limited by the tendency of cracks. In order to prevent cracks, it is necessary to reduce the casting speed. But the surface quality is not as smooth as the small diameter. But in the long run, it is not advisable to stay on the surface quality and ignore the improvement of the internal quality.