A low-cost pouring system for titanium alloy impeller castings

Abstract

The present invention discloses a low-cost pouring system for titanium alloy impeller castings, comprising a straight runner (1) and six cross runners (2) of an integrated structure, wherein the straight runner (1) is cylindrical, the six cross runners (2) are located at the bottom of the straight runner (1) and one end of each of the six cross runners is connected to the straight runner (1), the six cross runners (2) are located on the same horizontal plane and are evenly distributed in a radial shape, the other ends of the six cross runners (2) are forked structures, and a top pouring gate (3) and a bottom pouring gate (4) are respectively provided, the top pouring gate (3) corresponds to a molded top pouring impeller (6), and the bottom pouring gate (4) corresponds to a molded bottom pouring impeller (5), the pouring system enables the impeller pouring system to improve the utilization rate of the cross runner, greatly increases the number of impellers formed at one time, is conducive to greatly improving production efficiency, and solves the problem of low metal utilization rate of the existing impeller pouring system for casting titanium alloys.

Description

Technical Field

[0001] The invention discloses a low-cost pouring system for a titanium alloy impeller casting, and belongs to the technical field of casting. Background Art

[0002] With the development and application of titanium alloy casting technology, titanium alloy has been promoted from the high value-added aerospace field to the low-cost ground transportation field, and the ground transportation field has strict requirements on the cost performance of titanium alloy. In order to meet the needs of the market, breaking through the original high-cost pouring system design concept, improving the utilization rate of pouring metal, and reducing the alloy cost of castings is one of the development paths of titanium alloy casting technology.

[0003] Since titanium alloy has a very high chemical activity, its casting is usually smelted in a vacuum consumable shell furnace. The existing vacuum consumable shell furnace smelting uses the smelting conditions of a vacuum arc furnace, uses a tiltable water-cooled copper crucible, and controls the amount of cooling water to form a thin layer of "shell" in the crucible wall of the smelted metal, which isolates the smelted metal liquid from the crucible, thus avoiding the crucible from contaminating the active metal liquid; but at the same time, it also leads to the low superheat of titanium alloy smelting, which is only 60-100°C. Therefore, when the smelting is completed, it is necessary to pour as soon as possible to prevent the metal liquid from cooling and being unable to be poured out of the crucible. After the titanium liquid enters the pouring system, due to the low superheat, the metal liquid will have poor fluidity as it exchanges heat with the casting during the flow process. Therefore, the titanium alloy pouring system requires that the casting must be filled quickly, otherwise there will be defects such as under-pouring, cold shut and flow marks.

[0004] Titanium alloy casting usually requires that liquid titanium can quickly, smoothly and continuously fill the mold cavity from the bottom to the top in the same direction to avoid turbulence, splashing and interruption, prevent cold shut and flow marks, and allow the gas in the mold cavity to be smoothly discharged from the casting system. For this reason, titanium alloy castings usually use a bottom pouring system. Although the bottom pouring system is conducive to the smooth forming of castings, it also makes the metal amount of the titanium alloy casting pouring system usually much higher than the quality of the casting blank. The mass ratio of the bottom pouring system to the casting blank is usually 2:1 to 6:1, resulting in a low actual metal utilization rate of the pouring, only 14% to 33%, and thus a high casting alloy cost.

[0005] Titanium alloy impeller products have thin blades and the wall thickness of the blade edge is only about 1mm, which makes it difficult to fully form. In addition, the thickness difference between the blade and the hub is large, and large shrinkage holes are prone to appear inside the hub. Some literature reports use centrifugal casting solutions to achieve this, such as Figure 1 As shown, although centrifugal casting can achieve complete forming, its metal utilization rate is low; some literature reports use static casting, such as Figure 2As shown in the figure, the runner is designed as a main runner mold and six side runners with an integrated structure, which can form six impellers in one casting process. This casting system can improve the metal utilization rate, but when the casting titanium alloy impeller adopts this casting system, the impeller's internal shrinkage cavity deviates from the axis due to the influence of gravity during the solidification process. The closure of the shrinkage cavity after hot isostatic pressing of the casting will cause uneven deformation of the impeller, thereby affecting the subsequent dynamic balance of the impeller. Therefore, this method is not suitable for casting titanium alloy impellers. Summary of the invention

[0006] The present invention is designed to provide a low-cost pouring system for titanium alloy impeller castings in response to the above-mentioned existing technical conditions. Its purpose is to improve the utilization rate of the cross runner in the impeller pouring system, greatly increase the number of impellers formed at one time, which is conducive to greatly improving production efficiency and solving the problem of low metal utilization rate of the existing impeller pouring system for casting titanium alloys.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] The low-cost casting system of this titanium alloy impeller casting includes a straight runner 1 and six cross runners 2 with an integrated structure. The straight runner 1 is cylindrical. The six cross runners 2 are located at the bottom of the straight runner 1 and one end of each of the six cross runners 2 is connected to the straight runner 1. The six cross runners 2 are on the same horizontal plane and are radially evenly distributed. The other ends of the six cross runners 2 are forked structures, each of which is provided with a top pouring gate 3 and a bottom pouring gate 4. The top pouring gate 3 corresponds to the molded top pouring impeller 6, and the bottom pouring gate 4 corresponds to the molded bottom pouring impeller 5. After the titanium alloy casting melt enters the straight runner 1, it is diverted through the cross runner 2, and the filling of the lower layer's top pouring impeller 6 is completed through the top pouring gate 3, and then the filling of the upper layer's bottom pouring impeller 5 is completed through the bottom pouring gate 4.

[0009] The technology of the present invention is based on the size and structure characteristics of titanium alloy impeller castings, and designs a petal-shaped pouring system. Through a layer of runner, it integrates the two pouring methods of top pouring and bottom pouring. The mass ratio of the pouring system to the casting blank is only 0.5 to 1:1. While achieving complete forming of the casting, the actual metal utilization rate of the pouring is significantly improved, which can reach more than 50%.

[0010] The impeller casting system has a reasonable structure. Through the straight runner mold and six cross runners, two impellers of top casting and bottom casting are connected on each cross runner at the same time. 12 impellers can be formed in one casting process, which is beneficial to improve metal utilization and reduce alloy cost, and greatly improve production efficiency. Its advantages are as follows:

[0011] 1. The sprue and runner adopt a petal-shaped pouring system design method. The uniform distribution of the impeller can achieve consistency and high efficiency of impeller filling, which is conducive to the uniformity of the impeller forming size.

[0012] 2. According to the idea of ​​combining top injection and bottom injection, two kinds of gates, top injection and bottom injection, are designed on one runner at the same time, connecting two impellers respectively, which is convenient for the diversion and filling of the cross runner, realizing low-cost and high-efficiency casting of casting titanium alloy impeller.

[0013] 3. The gating system design is suitable for titanium alloy investment casting, graphite casting and sand casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a structural diagram of the existing impeller centrifugal casting system.

[0015] Figure 2 This is a schematic diagram of the structure of the existing impeller static casting system

[0016] Figure 3 The schematic diagram of the structure of the sprue and runner combination of the pouring system of the present invention is

[0017] Figure 4 Schematic diagram of the combined structure of the pouring system after forming the impeller of the present invention DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments:

[0019] See attached Figure 3 , 4 As shown, the low-cost pouring system of the titanium alloy impeller casting includes a straight runner 1 and six cross runners 2 of an integrated structure. The straight runner 1 is cylindrical. The six cross runners 2 are located at the bottom of the straight runner 1 and one end of each cross runner is connected to the straight runner 1. The cross section of the cross runner 2 is a quadrilateral or cylindrical shape. The six cross runners 2 are located on the same horizontal plane and are evenly distributed radially. The other ends of the six cross runners 2 are forked structures, and a top pouring gate 3 and a bottom pouring gate 4 are respectively provided. The bottom pouring gate 4 and the top pouring gate 3 is a circular structure, the top pouring gate 3 corresponds to the molding top pouring impeller 6, and the bottom pouring gate 4 corresponds to the molding bottom pouring impeller 5. When the pouring system is used for titanium alloy investment casting, graphite casting and sand casting, after the titanium alloy casting melt enters the straight runner 1, it is diverted through the cross runner 2, and the filling of the top pouring impeller 6 of the lower layer is completed through the top pouring gate 3, and then the filling of the bottom pouring impeller 5 of the upper layer is completed through the bottom pouring gate 4. This filling method is conducive to further improving the stability, orderliness and rapidity of the metal liquid filling.

Claims

1. A low-cost pouring system for titanium alloy impeller castings, characterized in that: The pouring system comprises a straight runner (1) and six cross runners (2) of an integrated structure. The straight runner (1) is cylindrical. The six cross runners (2) are located at the bottom of the straight runner (1) and one end of each of the six cross runners is connected to the straight runner (1). The six cross runners (2) are located on the same horizontal plane and are evenly distributed in a radial shape. The other ends of the six cross runners (2) are forked structures and are respectively provided with a top pouring gate (3) and a bottom pouring gate (4). The top pouring gate (3) corresponds to a molded top pouring impeller (6), and the bottom pouring gate (4) corresponds to a molded bottom pouring impeller (5). After the titanium alloy pouring melt enters the straight runner (1), it is diverted through the cross runner (2), and the top pouring gate (3) is first used to complete the filling of the top pouring impeller (6) of the lower layer, and then the bottom pouring gate (4) is used to complete the filling of the bottom pouring impeller (5) of the upper layer. The mass ratio of the pouring system to the casting blank is 0.5-1:

1.

2. The low-cost pouring system for titanium alloy impeller castings according to claim 1, characterized in that: The cross-sectional shape of the runner (2) is quadrilateral or cylindrical.

3. The low-cost pouring system for titanium alloy impeller castings according to claim 1, characterized in that: This gating system is used for titanium alloy investment casting, graphite casting and sand casting.

4. The low-cost pouring system for titanium alloy impeller castings according to claim 1, characterized in that: The bottom pouring gate (4) and the top pouring gate (3) of the pouring system are circular structures with petals.

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