Bottom pouring type pouring device and pouring method for high-toughness aluminum alloy shell casting

Abstract

The invention discloses a bottom pouring type pouring device and method for a high-toughness aluminum alloy shell casting. The device comprises a water inlet, a cross gate, flow gates, a stand column, a connecting plate, risers and chilling blocks, the cross gate is composed of a shape follow-up section and a cross section, the flow gates are circumferentially distributed at the bottom of a casting, molten metal is stably filled from bottom to top, and the stand column is arranged at the cross point and communicated with the top riser to form an efficient feeding channel. The first chilling block, the second chilling block and the third chilling block are arranged on the flange edge and below the two auxiliary seats correspondingly and matched with the slag collecting spherical device, and sequential solidification and slag trapping are achieved. The method comprises the following steps: smelting a ZL205A alloy at 730-740 DEG C, and refining with argon; during pouring, the mold filling speed is controlled to be 5-10 cm / s, and argon stirring is conducted in multiple continuous pouring gaps; and in the solidification stage, sequential solidification is realized through chilling of a chilling block. According to the method, air holes, looseness and Cu segregation can be effectively restrained, and the internal quality and performance consistency of the casting are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy casting technology, and specifically to a bottom-pouring casting device and method for casting high-strength and high-toughness aluminum alloy shell castings. Background Technology

[0002] ZL205A alloy is a high-strength and high-toughness cast aluminum alloy with excellent comprehensive mechanical properties, making it promising for wide application in high-end manufacturing. However, this alloy exhibits a wide crystallization temperature range during solidification, displaying typical pasty solidification characteristics, which leads to poor casting performance and makes castings prone to defects such as porosity and hot cracking. Furthermore, copper (Cu) in ZL205A alloy is prone to macroscopic segregation during solidification, resulting in uneven composition in different areas of the casting, thus affecting the uniformity of the microstructure and the stability of mechanical properties.

[0003] To improve the forming quality of ZL205A alloy castings, various gating systems and melting processes have been proposed in the prior art. For example, Chinese invention publication CN119328104A discloses a slit gating system suitable for ZL205A alloy castings with regular and machinable outer surfaces, but it does not address the adaptability design for shell-type castings with unmachinable outer surfaces and complex structures. Another example is Chinese invention publication CN119525434A, which proposes a gating system including a sprue, runner, and ingate, mainly used in investment casting processes. This system is suitable for small ZL205A castings but cannot meet the filling and feeding requirements of large or complex shell castings under resin sand anti-gravity casting conditions. In addition, the invention patent with publication number CN119082517A discloses a smelting process for ZL205A alloy, which achieves composition homogenization by ultrasonic cleaning of furnace charge and electromagnetic stirring. Although this helps to reduce segregation, it requires special equipment, which is costly. Furthermore, it does not provide effective solutions to key issues such as mold filling stability, solidification sequence control, and casting defect suppression during the casting process.

[0004] Overall, existing technologies still have the following significant shortcomings when applied to ZL205A alloy shell castings (especially structures using resin sand anti-gravity casting with unmachinable outer surfaces):

[0005] (1) The design of the gating system failed to effectively ensure the smooth filling of the alloy liquid, which easily caused turbulence and air entrapment, resulting in defects such as porosity;

[0006] (2) The lack of effective means to control the temperature field of castings makes it difficult to achieve sequential solidification, which exacerbates shrinkage porosity and Cu element segregation.

[0007] (3) The feeding channel and riser structure are not optimized in coordination with the shell geometry (such as the seat and flange edge), resulting in insufficient feeding efficiency.

[0008] Therefore, there is an urgent need for a casting device and casting method suitable for ZL205A alloy shell castings, which can ensure stable filling while reasonably controlling the solidification sequence, effectively suppressing defects such as porosity, segregation and gas pores, thereby improving the internal quality and mechanical property consistency of the castings. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a bottom-pouring casting device and casting method for high-strength and high-toughness aluminum alloy shell castings.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A bottom-pouring casting device for a high-strength and tough aluminum alloy shell casting is characterized by comprising an inlet, a horizontal sprue, an ingate, a column, a connecting plate, a riser, and chills. The horizontal sprue includes a conformal horizontal sprue arranged around the flange contour of the shell casting and a cross-shaped horizontal sprue located between two supports at the top of the shell casting. The conformal horizontal sprue and the cross-shaped horizontal sprue are connected and have the same cross-sectional dimensions. The inlet is located directly below and connected to the intersection of the cross-shaped horizontal sprues. Multiple ingates are distributed circumferentially along the lower surface of the shell casting and are respectively connected to the conformal horizontal sprue. The horizontal runners are connected; the column is set at the intersection of the cross-shaped horizontal runners and is located above the center position of the shell casting attachment. The riser is set at the top of the shell casting corresponding to the attachment position. Its lower end is connected to the upper end of the column through the connecting plate, thus forming a feeding channel from the horizontal runner through the column and the connecting plate to the riser. The chills include chill one, chill two and chill three. Chill one is attached to the outside of the flange edge of the shell casting. Chill two and chill three are respectively attached to the bottom of the two attachments. A slag collection ball device is provided above the intersection of the cross-shaped horizontal runners.

[0012] Furthermore, the high-strength and high-toughness aluminum alloy is ZL205A alloy.

[0013] Furthermore, the arc length spacing L between adjacent ingates 内 The ingate is 140–180 mm thick, and its height H is 3–4 times the wall thickness of the casting in which it is located. The diameter D of the ingate is... 内 It is 0.5–0.75 times the height H.

[0014] Furthermore, the cross-section of the horizontal runner is trapezoidal, with a maximum width A at the top. 横 The width of the runner at the corresponding position is 1.5–3 times that of the casting, and the sidewalls of the runner are inclined at 3°–5° towards the bottom, with a height H. 横 The maximum width A of the horizontal runner 横 The radius of the fillet is 1–1.5 times the maximum width A of the runner. The intersection of the conformal runner and the cross-shaped runner uses a rounded transition, with the fillet radius being equal to the maximum width A of the runner. 横 0.2–0.5 times.

[0015] Furthermore, the column is cylindrical, with a diameter D. 柱 The maximum width A of the horizontal runner 横 0.5–0.9 times the height of the riser, with a spherical top, and the portion of the column extending above the top of the riser is equal to the column diameter D. 柱 1.2–1.5 times.

[0016] Furthermore, the riser is a necked riser, the width of which is 5–10 mm smaller than the corresponding part of the casting at the connection with the shell casting, the height of the necked section is 20–30 mm, and it expands upward at an angle of 15°–30°, the height of the non-necked section is 0.5–1 times the overall height of the casting, and it continues to expand at an angle of 5°–10°.

[0017] Furthermore, the slag-collecting spherical device has a hollow spherical crown structure, and its inner cavity diameter is the maximum width A of the horizontal runner. 横 It is 1.0–1.5 times larger than the previous size, with the bottom opening connected to the intersection of the cross-shaped horizontal runner, used to capture slag in the alloy liquid and guide it to remain in the ball cavity.

[0018] The method for casting high-strength and high-toughness aluminum alloy shell castings using the above-mentioned bottom-pouring casting device is characterized by comprising the following steps:

[0019] S1. The pretreated high-strength and high-toughness aluminum alloy ZL205A ingot is melted at 730–740℃ and refined and stirred by argon gas in a rotary spray to effectively remove gaseous and non-metallic inclusions.

[0020] S2. After adjusting the temperature of the molten alloy to the pouring temperature, hoist it into the low-pressure casting machine;

[0021] S3. Under pressure, the molten alloy enters the casting cavity from the inlet through the horizontal runner and the inlet, and rises to the riser through the column and connecting plate to achieve preheating and unobstructed flow of the feeding channel, thereby achieving stable filling from bottom to top.

[0022] S4. During the solidification stage, chills are used to rapidly cool the flange edge and the seat area, causing the casting to solidify sequentially from the thin-walled area to the thick seat.

[0023] S5. When multiple castings are poured in the same batch, the remaining alloy liquid should be stirred with argon gas again for 3–10 minutes during the pouring interval between adjacent castings.

[0024] Furthermore, in step S2, the pouring temperature is dynamically adjusted according to the casting wall thickness, ranging from 690 to 695℃.

[0025] Furthermore, during the filling process in step S3, the filling speed of the molten metal is controlled within the range of 5 cm / s to 10 cm / s by precisely adjusting the pressure parameters of the low-pressure casting machine. This ensures that the molten alloy rises steadily from the bottom of the casting, avoiding turbulence, splashing, and gas entrapment, thereby significantly reducing the risk of porosity defects.

[0026] Furthermore, when multiple shell castings are continuously poured from the same batch of molten alloy, the pouring temperature should be dynamically adjusted according to the differences in wall thickness of each casting. During the pouring interval between two adjacent castings, the molten alloy in the furnace should be stirred again with argon gas for 3-10 minutes (preferably 5-8 minutes) to maintain the uniform distribution of Cu element in the liquid phase and prevent macroscopic segregation caused by standing.

[0027] Furthermore, during the solidification stage, chills one located at the flange edge and chills two and three located below the two supports provide localized quenching to the thicker parts of the casting, accelerating its heat dissipation rate and promoting sequential solidification of the casting from the thin-walled region away from the riser towards the riser. This solidification mode not only effectively reduces shrinkage defects but also inhibits the enrichment of Cu elements in the final solidification region, thereby improving the uniformity of the casting's microstructure and the consistency of its mechanical properties.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention adopts a bottom-pouring casting structure. The molten metal rises synchronously and slowly from the bottom of the casting cavity through multiple circumferentially distributed ingates. With a controllable filling speed of 5–10 cm / s, it effectively avoids the turbulence, splashing and gas entrapment phenomena commonly found in traditional top-pouring or side-pouring methods, and significantly reduces the probability of porosity defects in ZL205A alloy shell castings.

[0030] (2) The slag collection spherical device set above the cross intersection of the horizontal sprue of the present invention utilizes its spherical crown cavity to form a local vortex retention zone, so that the low-density molten slag and non-metallic inclusions are effectively intercepted and collected in the spherical cavity before entering the column, preventing impurities from entering the mold cavity with the molten metal, and significantly improving the cleanliness of the casting.

[0031] (3) The present invention uses the vertical feeding path formed by the column, connecting plate and riser, combined with the directional cooling effect of the flange edge and the chiller below the seat, to make the casting solidify from the thin-walled area far away from the riser to the thick part (seat) last, realizing the sequential solidification mode from the outside to the inside, effectively reducing volume shrinkage defects such as shrinkage porosity and shrinkage cavity.

[0032] (4) In view of the characteristic that Cu segregation is easy to occur in ZL205A alloy, the present invention adopts argon gas rotary blowing and stirring process during the melting stage and the gap between continuous casting of multiple castings. This not only enhances the degassing and impurity removal effect, but also breaks the composition concentration gradient through forced convection. In particular, timely stirring after the first casting can effectively prevent Cu enrichment caused by static setting in subsequent castings, and ensure the consistency of composition and performance of batch castings.

[0033] (5) This invention deeply integrates structural design (bottom pouring system, slag collection device, chiller layout) with process control (speed-controlled filling, intermittent stirring, and sequential solidification), and is especially suitable for ZL205A shell castings whose outer surface cannot be machined under resin sand anti-gravity casting conditions. It solves the problem that existing technologies cannot take into account the stability of filling, feeding efficiency and composition uniformity in the forming of large and complex shells, significantly improves the first-pass yield, reduces rework and scrap costs, and has outstanding engineering application value. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the bottom-pouring gating system for a ZL205A alloy shell casting according to the present invention;

[0035] Figure 2 This is a schematic diagram of the column structure;

[0036] Figure 3 This is a schematic diagram of the connecting plate structure;

[0037] Figure 4 This is a schematic diagram of riser distribution;

[0038] Figure 5 This is a schematic diagram of the distribution of chilled iron.

[0039] Figure 6 This is a schematic diagram of the ingate structure;

[0040] Figure 7 This is a schematic diagram of the horizontal gating system.

[0041] Figure 8 This is a schematic diagram of the water inlet structure.

[0042] In the diagram: 1. Column, 2. Connecting plate, 3. Riser, 4. Chill, 401. Chill one, 402. Chill two, 403. Chill three, 5. Ingate, 6. Stream runner, 601. Slag collection ball device, 7. Water inlet. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings, but the present invention is not limited thereto.

[0044] like Figure 1-8As shown, the present invention includes a column 1, a connecting plate 2, a riser 3, a chill 4, an ingate 5, a runner 6, and a sprue 7. The runner 6 includes a conformal runner surrounding the flange contour of the shell casting and a cross-shaped runner located between two attachments at the top of the shell casting. The conformal runner and the cross-shaped runner are connected and have the same cross-sectional dimensions. The sprue 7 is located directly below and connected to the intersection of the cross-shaped runners. Multiple ingates 5 are distributed circumferentially along the lower surface of the shell casting and are connected to the conformal runners respectively. The column 1 is located at the intersection of the cross-shaped runners and above the center of the attachment of the shell casting. The riser 3 is located at the top of the shell casting corresponding to the attachment. The lower end of the seat is connected to the upper end of the column 1 via the connecting plate 2, thereby forming a feeding channel from the horizontal runner 6 through the column 1 and the connecting plate 2 to the riser 3. The chill 4 includes chill 1 401, chill 2 402 and chill 3 403. Chill 1 401 is attached to the outer side of the flange edge of the shell casting. Chill 2 402 and chill 3 403 are respectively attached to the lower part of the two seats. Chill 2 402 and chill 3 403 are perpendicular to the axis of the corresponding riser. A slag collecting ball device 601 is provided above the intersection of the cross-shaped horizontal runner. The bottom opening of the slag collecting ball device 601 is connected to the intersection of the cross-shaped horizontal runner to capture the slag in the alloy liquid and guide it to stay in the ball cavity.

[0045] Example 1: ZL205A alloy gear housing casting

[0046] Taking a ZL205A alloy gear housing casting for a certain weapon system as an example, its external dimensions are 600 mm × 450 mm × 150 mm, and its wall thickness ranges from 7 mm to 35 mm. Resin sand anti-gravity casting is performed using the bottom-pouring casting device described in this invention.

[0047] The specific structural parameters are as follows:

[0048] Column 1 is cylindrical with a diameter of 50 mm and a spherical top;

[0049] The connecting plate 2 is a rectangular cross-section plate structure with a width of 40 mm; the attachment consists of attachment one and attachment two, the height of the connecting plate connecting attachment one is 130 mm, and the height of the connecting plate connecting attachment two is 75 mm.

[0050] Riser 3 adopts a necking structure:

[0051] The riser corresponding to the first attachment is composed of two arcs. The radius of the first arc is 90 mm (R90), and the radius of the second arc is 100 mm (R100). The pitch angle is 90°. The height of the necked section is 20 mm, and it expands upward at a 20° angle. The height of the non-necked section is 130 mm, and it continues to expand at an 8° angle.

[0052] The riser radii corresponding to the second auxiliary seat are R70 and R90, with a pitch angle of 90°; the height of the necked section is 20 mm, with an inclination angle of 25°; the height of the non-necked section is 75 mm, with an inclination angle of 10°.

[0053] The chills include chill 1 401, chill 2 402 and chill 3 403, all with a thickness of 20 mm, and their shapes are consistent with the outline of the chilled areas of the flange edge and the two attachments, respectively.

[0054] The height of the ingate 5 is 70 mm, the maximum diameter is 50 mm, and it narrows inward at a 5° angle along the direction of molten metal flow.

[0055] The cross section of the horizontal pouring channel 6 is trapezoidal, with a maximum width of 60 mm and a maximum height of 50 mm. It narrows at a 3° angle towards the water inlet direction.

[0056] The inlet 7 has a maximum diameter of 100 mm and narrows at a 5° angle toward the horizontal runner.

[0057] The casting process is as follows:

[0058] The pretreated ZL205A alloy ingot was added to the melting furnace and heated to 730℃. Argon gas was used for rotary blowing refining for 15 minutes to thoroughly remove gases and inclusions. The alloy liquid temperature was then adjusted to 690℃ in preparation for pouring. The crucible containing the alloy liquid was hoisted into the low-pressure casting machine. Under pressure, the alloy liquid sequentially entered the casting cavity through the inlet 7, the horizontal sprue 6, and the ingate 5, while simultaneously rising through the column 1 and connecting plate 2 to the riser 3, forming a complete feeding channel. During the filling process, the liquid rising speed was controlled to maintain a stable metal front advance rate of 6 cm / s, achieving smooth filling.

[0059] Two castings were poured in this batch. Immediately after the first casting was poured, the remaining molten alloy was stirred with argon gas for 5 minutes to prevent macroscopic segregation of Cu due to settling. During solidification, chillers 401, 402, and 403 rapidly cooled the flange edge and the mounting area, and with riser feeding, the casting solidified sequentially from the thin-walled area to the thicker mounting area.

[0060] X-ray flaw detection and chemical composition analysis showed that the casting had no obvious defects such as porosity or cracks, the Cu element was evenly distributed and there was no macroscopic segregation, and the mechanical properties and dimensional accuracy met the design requirements.

[0061] Example 2: ZL205A alloy side deceleration housing casting

[0062] Taking a ZL205A alloy side deceleration shell casting for a certain weapon system as an example, its external dimensions are 700 mm × 400 mm × 240 mm, and the wall thickness ranges from 12 mm to 70 mm, which is a typical thick and complex shell. The bottom-pouring casting device of this invention is also used for resin sand anti-gravity casting.

[0063] The specific structural parameters are as follows:

[0064] Column 1 has a diameter of 60 mm and a spherical top;

[0065] The connecting plate 2 is 35 mm wide and 60 mm high;

[0066] Riser 3 has a necked structure with a bottom connection diameter of Φ230; the necked section is 20 mm high and expands in diameter at a 25° angle; the non-necked section is 150 mm high and continues to expand in diameter at an 8° angle.

[0067] The chill iron 4 is 30 mm thick and its shape perfectly matches the casting flange and thick-walled area.

[0068] Ingate 5 has a height of 90 mm, a maximum diameter of 65 mm, and narrows at a 5° angle along the flow direction.

[0069] The horizontal pouring channel 6 has a maximum width of 80 mm and a maximum height of 60 mm, and narrows towards the inlet at a 3° angle.

[0070] The inlet 7 has a maximum diameter of 100 mm and narrows at a 5° angle.

[0071] The casting process is as follows:

[0072] After pretreatment, ZL205A alloy ingots were melted at 730℃ and refined and stirred with argon rotary blowing for 15 minutes. The alloy liquid temperature was then controlled at 695℃ for pouring. In the low-pressure casting machine, the alloy liquid was steadily filled from the bottom at a filling speed of 7 cm / s. The path was as follows: the alloy liquid sequentially entered the casting cavity through the inlet 7, the horizontal runner 6, and the ingate 5, while simultaneously filling the riser 3 through the column 1 and the connecting plate 2.

[0073] Two castings were poured in this batch. After the first casting was poured, the remaining molten alloy was stirred with argon gas for 5 minutes to effectively maintain the uniformity of Cu. During the solidification stage, chills were used to strongly quench the thick-walled areas (up to 70 mm thick), combined with riser feeding, to ensure that the casting solidified sequentially from the thin-walled area at the edge to the thick-walled area at the center.

[0074] The final casting was tested and found to be internally dense, without shrinkage porosity, air holes or cracks, with uniform chemical composition, stable mechanical properties, and all indicators meeting the usage standards.

Claims

1. A bottom-pouring casting device for a high-strength and tough aluminum alloy shell casting, characterized in that, include The system includes an inlet, runner, sprues, columns, connecting plates, risers, and chills. The runner includes a conformal runner surrounding the flange contour of the shell casting and a cross-shaped runner located between two supports at the top of the shell casting. The conformal runner and the cross-shaped runner are connected and have the same cross-sectional dimensions. The inlet is located directly below and connected to the intersection of the cross-shaped runners. Multiple sprues are distributed circumferentially along the lower surface of the shell casting and are connected to the conformal runners. Columns are located at the intersection of the cross-shaped runners. At the intersection of the cross runners, and above the center of the shell casting attachment, the riser is set at the top of the shell casting corresponding to the attachment. Its lower end is connected to the upper end of the column through the connecting plate, thus forming a feeding channel from the runner through the column and connecting plate to the riser. The chills include chill one, chill two and chill three. Chill one is attached to the outside of the flange edge of the shell casting, and chill two and chill three are attached to the bottom of the two attachments respectively. A slag collection ball device is provided above the intersection of the cross runners.

2. The bottom-pouring casting device for high-strength and tough aluminum alloy shell castings as described in claim 1, characterized in that, The high-strength and high-toughness aluminum alloy is ZL205A.

3. The bottom-pouring casting device for high-strength and tough aluminum alloy shell castings as described in claim 1 or 2, characterized in that, The arc length distance L between adjacent ingates 内 The ingate is 140–180 mm thick, and its height H is 3–4 times the wall thickness of the casting in which it is located. The diameter D of the ingate is... 内 It is 0.5–0.75 times the height H.

4. The bottom-pouring casting device for high-strength and tough aluminum alloy shell castings as described in claim 1 or 2, characterized in that, The cross-section of the horizontal gating system is trapezoidal, with a maximum width A at the top. 横 The width of the runner at the corresponding position is 1.5–3 times that of the casting, and the sidewalls of the runner are inclined at 3°–5° towards the bottom, with a height H. 横 The maximum width A of the horizontal runner 横 The radius of the fillet is 1–1.5 times the maximum width A of the runner. The intersection of the conformal runner and the cross-shaped runner uses a rounded transition, with the fillet radius being equal to the maximum width A of the runner. 横 0.2–0.5 times.

5. The bottom-pouring casting device for high-strength and tough aluminum alloy shell castings as described in claim 1 or 2, characterized in that, The column is cylindrical with a diameter D. 柱 The maximum width A of the horizontal runner 横 0.5–0.9 times the height of the riser, with a spherical top, and the portion of the column extending above the top of the riser is equal to the column diameter D. 柱 1.2–1.5 times.

6. The bottom-pouring casting device for high-strength and tough aluminum alloy shell castings as described in claim 1 or 2, characterized in that, The riser is a necking riser, the width of which is 5–10 mm smaller than the corresponding part of the casting at the connection point with the shell casting. The height of the necking section is 20–30 mm, and it expands upward at an angle of 15°–30°. The height of the non-necking section is 0.5–1 times the overall height of the casting, and it continues to expand at an angle of 5°–10°.

7. The bottom-pouring casting device for high-strength and tough aluminum alloy shell castings as described in claim 1 or 2, characterized in that, The slag-collecting spherical device has a hollow spherical crown structure, and its inner cavity diameter is A, which is the maximum width of the horizontal pouring channel. 横 It is 1.0–1.5 times larger than the original size, and the bottom opening connects to the intersection of the cross-shaped horizontal runner.

8. A method for casting high-strength and tough aluminum alloy shell castings using the bottom-pouring casting apparatus according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. The pretreated high-strength and high-toughness aluminum alloy ZL205A ingot is melted at 730–740℃ and refined and stirred by argon gas in a rotary jet. S2. After adjusting the temperature of the molten alloy to the pouring temperature, hoist it into the low-pressure casting machine; S3. Under pressure, the molten alloy enters the casting cavity from the inlet through the horizontal runner and the inlet, and rises to the riser through the column and connecting plate to achieve stable filling from bottom to top. S4. During the solidification stage, chills are used to rapidly cool the flange edge and the seat area, causing the casting to solidify sequentially from the thin-walled area to the thick seat. S5. When multiple castings are poured in the same batch, the remaining alloy liquid should be stirred with argon gas again for 3–10 minutes during the pouring interval between adjacent castings.

9. The method according to claim 8, characterized in that, In step S2, the pouring temperature is dynamically adjusted according to the casting wall thickness, ranging from 690 to 695℃; in step S3, the filling speed is controlled between 5 cm / s and 10 cm / s.

10. The method according to claim 8, characterized in that, In step S5, argon stirring is performed immediately after the first casting is poured, and lasts for 5-8 minutes.

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