March 29, 2025
Gravity casting of faucets is a common production process, especially suitable for copper alloy (such as brass) faucets with relatively complex structures and high surface quality requirements. The following is a detailed analysis of the process:
1. Basic principles of gravity casting
Definition: Pour molten metal (such as brass) into a steel mold (metal mold), naturally fill the cavity by gravity, cool down, and then open the mold to take out the part.
Core features:
The mold is made of steel and can be reused (with a lifespan of thousands to tens of thousands of times).
No external pressure, relying on the self weight flow of the molten metal.
The cooling rate is fast, and the casting structure is denser than sand casting.
2. Process flow
(1) Mold preparation
Material: The mold is usually made of heat-resistant alloy steel (such as H13), which needs to be preheated to 150-300 ℃ to avoid rapid cooling of the metal liquid.
Typing design: The mold is divided into upper and lower halves or multiple parts, taking into account the demolding slope (usually 1-3 °) and the position of the ejector pin.
(2) Melting and pouring
Material: Brass (such as HPb59-1, with lead content<1.8% to meet environmental standards).
Melting temperature: 1100~1200 ℃, strict control of zinc volatilization is required to prevent compositional deviation.
Pouring method: manual or mechanical tilting pouring, ensuring stability and speed to avoid oxidation and slag inclusion.
(3) Cooling and mold opening
Cooling time: Adjust according to the wall thickness (usually 30-120 seconds). If it is too long, it is easy to stick to the mold, and if it is too short, it is easy to deform.
Release agent: Spray graphite or water-based release agent to prevent adhesion between castings and molds.
(4) Post processing
Remove the sprue: saw or punch to remove excess metal.
Shot blasting/sandblasting: Clean the surface oxide layer.
Machining: Drilling and threading (such as valve core installation holes).
