Optimization of Gravity Casting Gate Basin Structure, Slag Pool Design, and Secondary Oxidation Control of Aluminum Liquid | Motorcycle Wheel Hub Casting Mold
The design defect of the gravity casting sprue basin resulted in the rolling of slag and secondary oxidation of 40% aluminum liquid before entering the mold, and the batch scrapping of castings with oxidation inclusions.
The liquid level of the sprue basin is 1.8 times lower than the cross-sectional area of the sprue. When the aluminum liquid flows in, the liquid level is disturbed violently, and the surface oxide scale is sucked up.
The distance between the entrance of the sprue and the bottom of the sprue is less than 12mm, and the sediment layer at the bottom is directly sucked into the mold cavity, increasing the risk of slag inclusion.
Lack of buffer weir and slag barrier, direct pouring of aluminum liquid into the sprue, turbulent flow rolling up the oxide film, and a 35% increase in the detection rate of oxide inclusions.
The roughness Ra of the inner wall of the sprue basin is greater than 2.5, and the oxide scale continues to adhere and accumulate, periodically falling off and entering the casting.
The insulation of the sprue basin is poor, and the temperature drop of the aluminum liquid in the basin exceeds 12 ℃, resulting in a decrease in fluidity and the formation of a large amount of cold slag.
Gravity casting molds are widely used in small and medium-sized wheel hub factories in South Asia and Africa, and the sprue basin is a key component of the entire set of fixtures; Low pressure die-casting molds (LPDC), reverse pressure casting molds (CPC), differential pressure casting molds for wheel hubs, and low-pressure casting molds for wheel hubs generally do not use open sprues. Structural component casting molds, aluminum alloy wheel hub molds, aluminum casting forming molds, low-pressure casting tooling molds, and many defects in gravity technology are not rooted in the mold cavity, but in the front-end pouring system. Zhejiang Xinfeng Machinery Optimization Plan: The height of the slag barrier is 6-8mm higher than the inlet of the sprue, and the buffer weir disperses the direct flow velocity; The sprue basin is lined with a fire-resistant coating to reduce heat dissipation. During the pouring of aluminum liquid, the liquid level should remain stable without interruption or surging. Many small factories simplify slag blocking structures in order to save refractory materials, seemingly saving costs, but the problem of slag inclusion remains high. The refractory layer of the sprue basin cracks and falls off, and debris enters the aluminum liquid, forming foreign inclusions. The refractory material is inspected and repaired every 700 molds.
FAQ
1. Question: What is the ratio of the liquid level of the sprue basin to the cross-section of the sprue?
Answer: The liquid level height should not be less than 1.8 times the gate section for stable flow and anti roll slag.
2. Question: What is the minimum distance between the entrance of the sprue and the bottom of the basin?
Answer: ≥ 12mm, avoid the bottom sediment area.
3. Question: How much is the recommended height of the slag barrier above the sprue?
Answer: The slag barrier is 6-8mm higher than the entrance of the sprue.
4. Question: How to control the roughness of the inner wall of the sprue basin?
Answer: Try to control within Ra2.5 to reduce the adhesion of oxide skin.
5. Question: What is the maintenance cycle for the refractory layer of the sprue basin?
Answer: About 700 cycles of inspection and repair to prevent coating detachment.
6. Question: Are low-pressure and CPC molds equipped with sprue basins?
Answer: LPDC and CPC are sealed and do not use open sprues.
