In the lost foam casting process, the entire process includes seven steps, each of which has a great influence on the quality of lost foam castings. Nanjing Kirin Scientific Instrument Group shares with you the entire lost foam casting process. It is a crucial part to master the precautions of the casting process. Strictly controlling every detail in the pouring process is the key to producing high quality lost foam castings.
1 pouring
Lost foam casting has certain specifications and requirements. The molding process must pay attention to the following aspects: In the case of lost foam casting, silica sand is generally used, and its silica content is required to be more than 85% and 90%. Considering the permeability and refractoriness, cast steel and iron castings generally use silica sand with a particle size of 0.850 to 0.300 mm. Firstly, a layer of dry sand with a thickness of about 100 mm is placed on the bottom cloth of the sand box. Then, the brushed EPS mold and the pouring head are placed in the center of the sand box, and sand edges are filled until the dry sand is about 50 mm away from the top of the sand box. Stop sanding and cover the dry sand with a plastic film. Place the sprue cup on the top of the sprue and remove a layer of sand on the film to prevent splashing of molten iron. Burn through the film and cause a gas leak. box.
In the lost foam casting process, the entire process includes seven steps, each of which has a great influence on the quality of lost foam castings. Of course, the pouring process is also a crucial part of the entire lost foam casting process. Pouring process considerations, strict control of every detail in the pouring process is the key to producing high quality lost foam castings.
The casting process of the lost foam casting is the process of molten steel filling and vaporization of the foam mold. The entire process needs to pay attention to:
(1) The sprue must be filled with molten steel from beginning to end. If it is not satisfied, due to the limited strength of the paint layer, it is easy to collapse the molding sand and air intake phenomenon, resulting in casting defects.
(2) Be sure to hold the molten steel and ensure it is stable, accurate, and fast. Fill the gating cup instantaneously, and do it quickly and continuously, with about a minute or so of molten steel. If the molten steel in the same box casting will be sucked into the air, it may cause sand-slug phenomenon or increase the porosity of the casting, resulting in the scrap casting.
(3) Lost foam casting uses negative pressure closure and must be closed below the gating cup. The molten steel enters the molding mold, which begins to liquefy and burn, and the gasification disappears. The front of the molten steel forms a temporary cavity for a short distance. Therefore, the speed of designing the molten steel and the disappearance of the foam model are approximately the same. In order to prevent molten steel from radiating at high temperatures and melting other models in the same box, the runners are farther away from the casting model. The position of the sprue is to choose the lowest position of the whole box casting. When pouring, attention should be paid to adjusting and controlling the negative pressure vacuum within a certain range. After the pouring is completed, it shall be maintained under a certain negative pressure for a period of time. The negative pressure shall be stopped and the molten steel shall be discharged out of the tank after condensation.
2 Prevent back spray
Lost foam casting is one of the casting processes. There are various casting defects in the casting process. This leads to defects in the castings, and lost foam casting is no exception. Re-injection is a phenomenon that often occurs in lost foam casting. When the back-injection is severe, the personal safety of the caster may be endangered and must be taken seriously. To reduce the spray phenomenon, the following measures can be taken:
In the entire lost foam casting process, the pouring process is one of the crucial links. The four factors of the casting system, the casting speed, the pouring temperature, and the pouring process are the key processes for improving the quality of castings. Only continuous improvement and continuous improvement can be achieved. Accurate and high quality castings.
The paint coating also has a great influence on the accuracy of the lost foam castings. The coating properties and coating thickness can affect the size of the pattern, which affects the dimensional accuracy of the casting. Therefore, in the lost foam casting, the coating should have good performance and sufficient strength. The paint coating operation process should be reasonable.
Nanjing Kirin Scientific Instrument Group Co., Ltd.
Testing Center
June 26, 2017
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