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The requirements of the pouring temperature and the design of the gating system for the pump valve castings

Nov 20, 2017

The pouring temperature of the pump valve casting has a great relationship with the surface quality of the casting. In order to improve the rate of finished products of the pump valve castings, it is necessary to control the pouring temperature. When the pouring temperature of the product is 1460 ℃, the rate of spoiled products is 50 %. Therefore, the casting temperature should be controlled below 1420 ℃.

Requirements for pouring temperature of the pump valve castings

In the process of making the pump valve casting, if the pouring temperature is lower than 1380℃, the surface of the iron casting will find many monomer holes, the diameter of the hole is generally 1 ~ 3 mm, in some cases only 1 - 2 holes, and these holes will also appear with a small amount of liquid slag. The results show that this condition is mainly related to the pouring temperature. when the pouring temperature is higher than 1380 ℃, this situation will not occur in the pump valve casting.

The operational characteristic of the pump valve castings

1. The determination of shrinkage rate of pump valve castings. The CF8C material used in this casting is austenitic stainless steel. Under the condition of the hindered contraction, combined with the structure and shape of the casting, the external cavity scale is 2.0 % and the internal cavity scale is 1.5 %.

2. The selection of the joint face. The valve requires that each pipeline center line be in the same plane. Each annular pipeline is more difficult for feeding. Therefore, take the plane where centers of the three nozzles are as the joint face and divide the casting into the upper and lower halves. 

The selection of the face passes through the center of each nozzle of the pump valve casting, making the plane of the joint face as the maximum cross section of the valve casting, ensuring the axial centerline of the valve casting in the same plane, reducing the use of the cast core, reducing the assembly deviation of the lower core assembly, avoiding the formation of the fash after pouring, improving the relative dimensional accuracy and surface quality of the valve casting parts, and the modeling is convenient and simple.

The design of the gating system for the pump valve castings

The gating system of the pump valve casting adopts the bottom gating system. The ingate of the bottom pouring system is basically working under the engulfing pattern. And the filling is stable, so that the metal liquid splashing, oxidation and casting defects can be avoided. Regardless of the gating ratio, the basic work of the cross gate is in the full state, which is beneficial to resist theslag, and the gas in the cavity is easily discharged in sequence.