Pump valve casting in the production process of the annealing heat treatment is one of the methods in operation when annealing can be divided into graphitizing annealing and effective stress relieving, the former is the pump valve casting in graphitizing annealing is to reduce the hardness, improve the processing performance, plasticity and toughness of cast iron.If there is no eutectic cementite or its quantity in the castings, low temperature graphitizing annealing can be carried out, and high temperature graphitizing annealing should be done when the number of eutectic cementite in the castings is high.
Pump valve casting stress relieving in the process of operating mainly in order to eliminate the residual stress of castings, stabilize its geometrical size, reduce or eliminate machining to produce distortion, need to go to the casting stress annealing.The chemical composition of cast iron must be considered when determining the temperature of stress annealing.Ordinary valve castings when the temperature about 550 ℃, which may be part of the graphitizing and granulating of cementite , lower the strength and hardness.When containing alloy elements, the cementite starts to break down the temperature can be increased to around 650 ℃.
Process design of pump valve casting
1.Determination of shrinkage rate of pump valve casting.The castings are made of austenitic stainless steel, in the case of blocked contraction, with the shape of the casting structure, the outer cavity of the casting is 2.0%, and the inner cavity is reduced by 1.5%.
2. Parting face selection.The pump valve requires the Central Line of each pipe to be in the same plane, and each ring pipe is more difficult to make up. Therefore, the center of the three pipes is divided into two parts, and the casting is divided into two parts.
3. The parting surface selection through the center of the pump valve casting various nozzle, makes the parting surface is the largest section of a plane for the pump valve casting, guarantee each nozzle axial pump valve casting center line on the same plane, reduce the use of casting sand core, reduces the core box assembling deviation, avoid pouring seam, is formed after improving the pump valve casting parts relative size accuracy and surface quality, modelling is more convenient and simple.
4. The casting system of the pump valve is based on the bottom-injection casting system.The pouring system in the bottom pouring system is basically working under submerged condition, and the filling type is stable, which can prevent the metal liquid from splashing, oxidizing and forming the casting defect.No matter how big the gate ratio is, the basic work of the runner is in the full state, which is beneficial to the slag. The gas in the cavity is easily discharged in order.http://www.pump-casting.com/