A method for solving the problem of under-casting of large thin-walled outer ring castings

Abstract

The present invention discloses a method for solving the problem of undercasting of large thin-walled outer ring castings, including a molten metal filling step in which the molten metal is stably filled by distributed heat preservation at intervals. The heat of the front-end molten metal itself is more absorbed by the pouring basin and the sand mold shell at the pouring basin, forming heat preservation and reducing heat dissipation. When the rear-end molten metal is replenished and enters, the heat is directly transferred to the front-end molten metal, preventing the front-end molten metal from cooling and solidifying. The distributed pouring basins at intervals constitute distributed heat preservation at intervals, enabling the rear-end molten metal to supply heat to push the front-end molten metal for stable filling and complete filling, without the front-end molten metal dropping to the solidification temperature and stopping filling at local positions, thus solving the problem of large-area undercasting of the outer ring of the casting. Since the pouring basins are installed on the wax mold of the outer ring casting, compared with setting a hollow part and achieving a vacuum, the working environment is easier to maintain stability, and undercasting will not occur in the outer ring casting.

Description

Technical Field

[0001] The present invention relates to a method for solving the problem of under-casting of large thin-walled outer ring castings, belonging to the field of casting technology. Background Art

[0002] For the outer ring part of the integral casting of the high-temperature alloy rear casing, since this outer ring casting is used in civil aviation and requires high precision, it belongs to investment precision castings. Its outer ring wall thickness is 2mm, and the casting forming is extremely difficult. Due to the large annular size of the outer ring casting, especially the outer ring is the part of the integral casting farthest from the gate, the flow path of the molten metal to fill the outer ring casting is long, the temperature loss is large, and the heat dissipation condition of the outer ring of the casting is the best, and the temperature of the sand mold shell drops quickly. During the continuous filling process of the molten metal, the temperature of the front end of the molten metal has dropped to the solidification temperature, and the filling stops at local positions, resulting in the problem of large-area under-casting of the outer ring of the casting.

[0003] To solve the problem of under-casting of the above outer ring casting, a method for preparing a mold shell with controllable heat dissipation conditions disclosed in Chinese Patent Publication No. CN111957890B adopts the following technology: a hollow part is prepared in one layer of the mold shell, and the air in the hollow part flows out through the air flow channel to form a vacuum part, thereby reducing the thermal conductivity of the hollow part and slowing down the heat dissipation of the hollow part; although the problem of under-casting of the casting is solved by setting the hollow part to be evacuated to reduce heat dissipation, for the outer ring casting with a large annular size and a thin wall as a whole, setting multiple hollow parts and achieving a vacuum, since the sand mold shell needs to rotate centrifugally when pouring molten metal, there is a problem that the vacuum operation environment of the hollow part is unstable. Once air enters a certain hollow part of the outer ring casting, it will cause the entire outer ring casting to be scrapped. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for solving the under-casting of large thin-walled outer ring castings.

[0005] The present invention is achieved through the following technical solutions.

[0006] A method for solving the under-casting of large thin-walled outer ring castings provided by the present invention includes a molten metal filling step of stable flow and complete filling by distributed heat preservation of molten metal at intervals.

[0007] The specific steps of filling the molten metal are as follows: Pour the molten metal into the space for forming the outer ring casting through the gate. When the front-end molten metal passes through the position with the diversion plate, since the diversion plate thickens the outer ring casting at this position, more heat of the front-end molten metal is absorbed by the diversion plate and the sand mold shell at the position of the diversion plate, forming heat preservation and reducing heat dissipation. When the rear-end molten metal replenishes and enters, the heat is directly transferred to the front-end molten metal, preventing the front-end molten metal from cooling and solidifying. The spaced-apart diversion plates constitute spaced-apart distributed heat preservation, enabling the rear-end molten metal to supply heat and push the front-end molten metal to flow stably and completely fill the mold.

[0008] Before the step of filling the molten metal, there is also a step of forming the sand mold shell that is carried out first.

[0009] The step of forming the sand mold shell is as follows: Fix and wrap the outside of the wax mold of the outer ring casting to form the sand mold shell, melt and discharge the wax mold of the outer ring casting composed of wax material in the sand mold shell, so as to form a space in the sand mold shell for forming the outer ring casting. At this time, the diversion plate is inlaid and fixed on the sand mold shell.

[0010] Before the step of forming the sand mold shell, there is also a step of forming the wax mold that is carried out first.

[0011] The step of forming the wax mold is as follows: Using wax material to solidify and form the wax mold of the outer ring casting based on the shape of the outer ring casting, and paste and fix the diversion plate on the wax mold of the outer ring casting.

[0012] In the step of forming the wax mold, the position of the diversion plate on the wax mold of the outer ring casting is at a position that is convenient for subsequent processing operations of the outer ring casting or a position where the processing does not affect the shape accuracy.

[0013] In the step of forming the wax mold, the diversion plates are distributed and installed on the inner and outer sides of the wax mold of the outer ring casting.

[0014] In the step of forming the wax mold, there are multiple diversion plates on the same side of the wax mold of the outer ring casting, with an interval of 80 mm.

[0015] The beneficial effects of the present invention are as follows: More heat of the front-end molten metal is absorbed by the diversion plate and the sand mold shell at the position of the diversion plate, forming heat preservation and reducing heat dissipation. When the rear-end molten metal replenishes and enters, the heat is directly transferred to the front-end molten metal, preventing the front-end molten metal from cooling and solidifying. The spaced-apart diversion plates constitute spaced-apart distributed heat preservation, enabling the rear-end molten metal to supply heat and push the front-end molten metal to flow stably and completely fill the mold, without the situation that the front-end molten metal drops to the solidification temperature and stops filling at local positions, solving the problem of large-area undercasting of the outer ring of the casting. Since the diversion plate is installed on the wax mold of the outer ring casting, compared with setting a hollow part and achieving a vacuum, the working environment is easier to maintain stability, and undercasting of the outer ring casting will not occur. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the state of the wax mold of the outer ring casting of the present invention;

[0017] Figure 2 It is a schematic diagram of the start of metal liquid filling in the sand mold shell formed by sandblasting of the present invention;

[0018] Figure 3 It is a schematic diagram of the metal liquid entering the sand mold shell of the present invention;

[0019] In the figure: 1 - wax mold of outer ring casting; 2 - diversion plate; 3 - sand mold shell; 4 - outer ring casting; 51 - front-end metal liquid; 52 - rear-end metal liquid. Specific embodiments

[0020] The technical solution of the present invention will be further described below, but the scope of protection is not limited thereto.

[0021] As Figures 1 to 3 shown.

[0022] A method for solving the under-casting of large thin-walled outer ring castings in the present application includes the following steps:

[0023] Step 1, wax mold forming: Using the outer ring casting as the shape basis, a wax mold 1 of the outer ring casting is formed by curing wax material. A diversion plate 2 is fixedly installed on the wax mold 1 of the outer ring casting. The position of the diversion plate 2 on the wax mold 1 of the outer ring casting is a position that is convenient for later processing operations on the outer ring casting 4 or a position where the processing does not affect the shape accuracy, and is convenient for removing the diversion plate 2 later. The diversion plates 2 are distributed and installed on the inner and outer sides of the wax mold 1 of the outer ring casting, and multiple diversion plates 2 on the same side of the wax mold 1 of the outer ring casting are spaced at 80 mm intervals.

[0024] Step 2, sand mold shell forming: The outer ring casting wax mold 1 made of wax material in the sand mold shell 3 is melted into a liquid state and discharged by fixedly wrapping and forming the sand mold shell 3 outside the wax mold 1 of the outer ring casting, so as to form a space for the outer ring casting 4 to be formed in the sand mold shell 3. At this time, the diversion plate 2 is fixedly embedded in the sand mold shell 3.

[0025] Step 3, molten metal filling: Pour molten metal into the space for forming the outer-ring casting 4 through the gate. When the front-end molten metal 51 passes through the position with the flow guide plate 2, since the flow guide plate 2 thickens the outer-ring casting 4 at this position, more heat of the front-end molten metal 51 itself is absorbed by the flow guide plate 2 and the sand mold shell 3 at the position of the flow guide plate 2, forming heat preservation and reducing heat dissipation. When the rear-end molten metal 52 replenishes and enters, the heat is directly transferred to the front-end molten metal 51, preventing the front-end molten metal 51 from cooling and solidifying. The spaced-apart flow guide plates 2 constitute spaced-apart distributed heat preservation, enabling the rear-end molten metal 52 to supply heat and push the front-end molten metal 51 to flow stably and fill completely, without the situation that the front-end molten metal 51 drops to the solidification temperature and stops filling at local positions, solving the problem of large-area under-casting of the outer ring of the casting. Since the flow guide plate 2 is installed on the wax mold 1 of the outer-ring casting, compared with setting a hollow part and achieving vacuum, the working environment is easier to maintain stability, and under-casting will not occur in the outer-ring casting 4. After the molten metal solidifies, the outer-ring casting 4 is formed in the sand mold shell 3. The sand mold shell 3 is broken and the flow guide plate 2 is removed to obtain the finished product of the outer-ring casting 4.

[0026] The heat preservation formed by the spaced-apart flow guide plates 2 combined on the sand mold shell 3 has the following advantages compared with the overall heat preservation formed by completely wrapping the sand mold shell 3: After the molten metal completely fills, the heat dissipation condition becomes worse when the sand mold shell 3 is completely wrapped to form overall heat preservation, and the slow solidification of the molten metal leads to the formation of porosity defects in the outer-ring casting 4. However, the heat preservation formed by the spaced-apart flow guide plates 2 combined on the sand mold shell 3 satisfies the filling of the front-end molten metal 51 of the molten metal. After the rear-end molten metal 52 supplies heat and pushes the front-end molten metal 51 to flow stably and fill completely, the molten metal can dissipate heat through the part of the sand mold shell 3 without the flow guide plate 2, and there will be no situation where the heat dissipation condition becomes worse and the slow solidification of the molten metal leads to the formation of porosity defects in the outer-ring casting 4.

Claims

1. A method for solving the problem of under-casting of large thin-walled outer ring castings, characterized in that, A molten metal filling step including stable flow and complete filling by distributed heat preservation of molten metal intervals; The specific process of the molten metal filling step is as follows: Molten metal is filled into the space for forming the outer ring casting (4) through the gate. When the front-end molten metal (51) passes through the position with the flow guiding plate (2), since the flow guiding plate (2) thickens the outer ring casting (4) at this position, more heat of the front-end molten metal (51) itself is absorbed by the flow guiding plate (2) and the sand mold shell (3) at the position of the flow guiding plate (2), forming heat preservation and reducing heat dissipation. When the rear-end molten metal (52) replenishes and enters, heat is directly transferred to the front-end molten metal (51) so that the front-end molten metal (51) does not cool and solidify. The spaced-apart flow guiding plates (2) constitute distributed heat preservation at intervals, enabling the rear-end molten metal (52) to supply heat and push the front-end molten metal (51) to flow stably and fill completely; Before the molten metal filling step, there is also a sand mold shell forming step carried out first; The sand mold shell forming step is: The sand mold shell (3) is fixedly wrapped and formed outside the outer ring casting wax mold (1), and the outer ring casting wax mold (1) made of wax material in the sand mold shell (3) is melted into liquid and discharged, so that a space for forming the outer ring casting (4) is formed in the sand mold shell (3). At this time, the flow guiding plate (2) is inlaid and fixed on the sand mold shell (3); Before the sand mold shell forming step, there is also a wax mold forming step carried out first; The wax mold forming step is: Using wax material to solidify and form the outer ring casting wax mold (1) based on the shape of the outer ring casting, and fixedly installing the flow guiding plate (2) on the outer ring casting wax mold (1) by pasting; 2. The method for solving the problem of under-casting of large thin-walled outer ring castings as described in claim 1, wherein, In the wax mold forming step, the flow guiding plates (2) are distributed and installed on the inner and outer sides of the outer ring casting wax mold (1).

3. The method for solving the problem of under-casting of large thin-walled outer ring castings as claimed in claim 1, wherein: In the wax mold forming step, there are multiple flow guiding plates (2) on the same side of the outer ring casting wax mold (1) with an interval of 80 mm.

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