Which casting method is used in the production of ball valve castings

Sand Casting
Sand casting is one of the most widely used processes in ball valve casting production. This method uses refractory sand as the molding material. Through sand mix, binder addition, and compaction control, a mold cavity is formed that meets the design requirements. Molten metal is poured into the sand mold during pouring, and the casting is removed after cooling. Sand casting offers advantages in adaptability and relatively low cost, making it suitable for the production of large and medium-sized ball valve castings, and is particularly stable when producing low-pressure, large-diameter valve bodies. Improved sand casting processes, such as resin sand and coated sand, can effectively improve the surface quality and dimensional accuracy of castings.

Precision casting, also known as lost wax casting, is suitable for ball valve castings requiring high surface finish and dimensional accuracy. This method begins by replicating the precise shape of the ball valve casting using a wax pattern. The wax pattern is then repeatedly dipped in refractory coating and sprinkled with refractory sand to form a shell mold. After the wax pattern is removed, the shell mold is fired at high temperature, and the metal is poured. Ball valve castings produced by precision casting have low surface roughness and minimal machining allowance, reducing subsequent machining costs. They are commonly used for small stainless steel and alloy steel ball valves or valve body components requiring high sealing requirements.

Centrifugal Casting

Centrifugal casting utilizes the centrifugal force generated by a high-speed rotating metal mold to evenly distribute the molten metal along the mold wall and solidify it, resulting in ball valve castings with high density and fine metal structure. This process is suitable for producing tubular or annular valve body components, such as certain ball valve shells or liner components. Centrifugal casting reduces the incidence of defects such as shrinkage cavities and slag inclusions, making it suitable for the production of wear-resistant and corrosion-resistant alloy steels.

Low-Pressure Casting

Low-Pressure Casting involves pressurizing molten metal in a sealed crucible and steadily pouring it into the mold through a riser tube. This method provides a smooth pouring process, strong mold filling capability, and reduced turbulence and oxidation. Low-pressure casting is particularly effective in producing ball valve castings made of aluminum or copper alloys, ensuring a dense casting with uniform mechanical properties. Low-pressure casting is a high-quality option for non-ferrous metal ball valves requiring lightweight and excellent corrosion resistance.

Vacuum Casting
Vacuum casting involves pouring metal in a vacuum environment, effectively reducing casting defects such as porosity and slag inclusions, while improving the density and mechanical properties of the casting. When producing high-alloy ball valve castings, vacuum casting minimizes oxidation and maximizes alloy element retention, making it particularly suitable for ball valves used in highly corrosive environments such as offshore engineering and the chemical industry.

Lost Foam Casting
Lost foam casting involves embedding a polystyrene foam pattern in dry sand. During pouring, the high-temperature molten metal vaporizes and displaces the foam pattern, ultimately resulting in a ball valve casting that is identical to the foam pattern. This process reduces parting surfaces, improves the integrity and dimensional accuracy of the casting, and is suitable for the production of complex valve bodies. Lost foam casting shortens the process, reduces machining allowances, and improves production efficiency.

The Importance of Mold Material and Process Selection
In ball valve casting production, different casting methods require different mold material options. Sand casting typically uses quartz or zircon sand with a binder; precision casting utilizes high-purity refractory powder and multi-layer shell molds; centrifugal casting often utilizes high-temperature-resistant metal molds; and low-pressure and vacuum casting require metal molds with excellent sealing and heat resistance. Mold design directly impacts the dimensional accuracy, surface quality, and ease of subsequent processing of the casting.

Principles for Selecting Production Methods
The casting method for ball valve castings typically requires a comprehensive consideration of material properties, valve diameter, pressure rating, operating environment, and economic efficiency. For example, large-diameter, low-pressure carbon steel valve bodies tend to be sand cast; small and medium-diameter, high-precision stainless steel valve bodies are suitable for precision casting; valve components requiring high wear resistance can be centrifugal cast; and lightweight, corrosion-resistant non-ferrous metal valve bodies are often cast using low-pressure or vacuum casting. Choosing the right casting method can reduce production costs while ensuring the casting's comprehensive performance in terms of strength, toughness, and corrosion resistance.