Casting method of thruster shroud with widely different wall thickness

Abstract

The invention provides a casting method of a propeller fairing with a great wall thickness difference. The casting method of the propeller fairing comprises the following steps that 1, mold manufacturing is carried out, specifically, a wooden mold is manufactured according to the shape and the inner cavity size of the fairing; 2, molding is carried out, specifically, a lower mold and a mold core are manufactured through the wooden mold, a sprue, cross pouring gates communicating with the sprue and gate risers are arranged in an upper mold, and inner sprues and inner pouring gates are arrangedin the lower mold; 3, mold closing is carried out, specifically, the mold core is installed in a mold cavity of the lower mold, and the upper mold is assembled on the lower mold; 4, smelting is carried out, specifically, raw materials for casting are smelted, and the brand of the casting materials is QT450-12; 5, inoculation is carried out, specifically, an inoculant is added to the bottom of a casting ladle before discharging, and the inoculant is added to a pouring basin for flow inoculation before pouring; 6, pouring is carried out, specifically, smelted and inoculated molten steel is poured into the sprue for pouring through a pouring cup; and 7, treatment is carried out, a pouring and riser system is cut off, the surface of a product is polished to be smooth and flat, and the size andsurface quality of the product are checked. The casting method can reduce distortion of graphite and improve the molding quality of a casting.

Description

technical field [0001] The invention relates to the field of casting, in particular to a casting method for propeller shrouds with widely different wall thicknesses. Background technique [0002] The shroud of the propeller is ellipsoidal, such as Figure 5~6 As shown, the maximum outer diameter: Ø1930mm, the height of the blank: 1432mm, the upper and lower wall thicknesses are very different, the maximum wall thickness is 107.5mm, and the minimum wall thickness is 12.7mm. It is an export product and requires high dimensional accuracy of castings (CT10--11). 100% surface magnetic particle inspection (level 2) and hydrostatic test (0.345MPa, 40min) are required. [0003] There are the following difficulties in the blank casting of the shroud: [0004] 1. The wall thickness of castings varies greatly, and it is difficult to guarantee the size of castings. [0005] 2. It is difficult to guarantee the filling capacity of molten iron. In order to improve the filling capacity in...

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Problems solved by technology

[0004] 1. The wall thickness of the castings varies greatly, and the size of the castings is difficult to guarantee

[0005] 2. It is difficult to ensure the filling capacity of molten iron. In order to improve the filling capacity in the foundry industry, it is generally achieved by increasing the carbon equivalent and increasing the pouring temperature. However, there are parts with large wall thickness in this casting, and graphite floating or graphite distortion is prone to occur in thick parts.

[0006] 3. The cooling speed of thin-walled ductile iron castings is fast, which easily leads to insufficient graphitization, and the feeding channel is easy to close, which affects the self-feeding effect of castings, and shrinkage cavities and shrinkage defects are prone to occur

In addition, the entry of slag and sand into the cavity can easily cause skin penetration at the thin wall, resulting in water pressure leakage

Therefore, it cannot meet the requirements of hydrostatic test

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