Effect Of Low-Pressure Casting Process On The Quality Of Aluminum Alloy Castings

Overview of aluminum alloy low-pressure casting aluminum is one of the familiar metals. Among many lightweight materials, aluminum alloy is one of the most important materials, and also a widely used lightweight material. Because aluminum has low melting point, good fluidity and good casting performance, it is easy to manufacture parts with complex shapes. Because of its low density and high specific strength, aluminum alloy has been widely used in mechanical industry, automobile industry, aerospace industry and other fields.

Low-pressure casting is a casting method between gravity casting and pressure casting. It uses gas pressure to hydraulically inject metal into the mold and make the casting crystallize and solidify under a certain pressure. Low-pressure casting has the advantages of high dimensional accuracy, smooth filling and easy to obtain high-quality castings. It has become an important process for producing automotive aluminum alloy castings.

Determination of process plan for aluminum alloy casting tank body 2.1 Analysis of aluminum alloy casting tank body The tank body is currently a product with high pressure rating * and has the world’s advanced level. This product puts forward higher requirements for the quality of aluminum alloy castings. Castings of this kind of products generally have the characteristics of larger overall dimensions, higher dimensional accuracy, more stringent requirements for air tightness and roughness, and batch use. How to meet the increasing quality requirements and batch production tasks under the existing production conditions has become our top priority.

In view of such problems, the research team gathered its wisdom, applied professional theory and practical experience, comprehensively analyzed several casting structures and technical requirements, conducted many demonstrations and studies on the production process of such castings, and decided to use resin sand molding for production of such castings. The use of resin sand molding production can not only ensure the surface roughness requirements of castings, but also achieve a new level of production rate and internal quality of castings, creating a precedent for the production of large size and high-precision castings.

Structural characteristics of aluminum alloy casting, See the blank casting of the tank body. The structure is relatively simple, but the size is large, the wall thickness is thin, and the flanges on both sides of the tank body have SF6 gas sealing requirements. The traditional sand molding process is more difficult to produce. After investigation and demonstration by the research team, it was decided to use resin sand molding technology for the production of this part, based on the experience of ABB casting technology.

The determination of the pouring system of RTVU. The horizontal molding method is adopted for the tank blank casting, and the pouring system adopts the ladle and four-riser gap gating system, see. The characteristics of this pouring system are that it can make the alloy liquid level of large-volume castings rise evenly and fill the mold smoothly during the pouring process, and it will not cause large drops of metal liquid level due to the high volume of castings, which will form high-speed splashing liquid into the mold cavity and cause defects in secondary slagging. The flange part of the end face of the part is thick. In order to ensure the formation of a dense structure, a circular chill is added here to prevent shrinkage. The production experience of ABB castings is used for reference in the design of the transverse runner. The upper and lower boxes are shaped separately, and the filter screen under the transverse runner is used to prevent inclusions from entering the mold cavity.

1.The feature of this scheme is that risers can be uniformly set on the circumference of the casting, which can not only meet the feeding function but also play the role of uniform stress to prevent deformation. However, there are many cylindrical risers, and it is difficult to clean and cut, the grinding amount is large, and the external surface roughness is difficult to meet the requirements.

2. The gating system in this scheme is composed of resin sand core, which ensures the roughness requirements of the outer surface of the casting, and reduces the size of the sand box, thus saving the use of resin sand and improving the process yield. Place cold iron on the circumference of the welding groove to make this part solidify first and form a dense structure with sufficient shrinkage to meet the production requirements of the next process.

The first process plan is the process plan that we adopted in the production of LW56-550 products, which has been verified by actual production and is feasible. However, the process yield is low, the grinding workload is large, and the shape roughness is not ideal. Process plan II is feasible in theory, but has not been verified by actual production. In order to improve the new process and improve the casting quality, we decided to boldly adopt the second production plan.

Pouring system scheme II Conclusion Three castings were tested and produced, and the above casting process was adopted in the production process, all of which were poured and formed at one time. After machining, the information feedback shows that the dimensional accuracy and internal quality of the casting indicate that the finish fully meets the machining requirements.

For the tank body with simple structure, large size, thin wall thickness and SF6 gas sealing requirements on both sides of the flange, the resin sand molding process, horizontal molding method, split ladle and four riser gap gating system can be used to cast aluminum alloy castings with quality requirements.