Manufacturing method of bearing seat investment casting

Abstract

The invention relates to the technical field of investment casting, in particular to a manufacturing method of a bearing seat investment casting, which comprises the following steps: S1, a ceramic core is manufactured, the ceramic core is of a cylindrical structure with an upper opening and a lower opening, an annular groove is formed in the inner wall of the ceramic core, a notch is formed in the top of the ceramic core, and the bottom of the notch is communicated with the top of the annular groove; s2, a ceramic core wax mold assembly is manufactured, the ceramic core wax mold assembly comprises a wax mold and the ceramic mold core, the ceramic mold core is embedded in the wax mold, and the lower portion of the ceramic mold core extends out of the lower end of the wax mold; s3, a notch of the ceramic core is filled with a wax block; s4, a feeding head is bonded to the top of the ceramic core wax mold assembly, and the feeding head is located over the notch; and S5, a shell is manufactured and poured, and a bearing seat investment casting is obtained. A feeding channel is formed through the notch in the ceramic core, and an inner cylinder on a bearing seat casting is fed through the feeding head to eliminate casting defects.

Description

Technical Field

[0001] The present invention relates to the technical field of investment casting, and particularly to a manufacturing method for an investment casting of a bearing seat. Background Art

[0002] As Figure 1 、 Figure 2 shown in the structural schematic diagram of the bearing seat, the bearing seat 100 is composed of an outer cylinder 101 and an inner cylinder 102 disposed inside the outer cylinder 101. There is a gap between the outer peripheral surface of the inner cylinder 102 and the inner wall surface of the outer cylinder 101. Three connecting blocks 103 are integrally formed between the inner wall of the outer cylinder 101 and the outer wall of the upper part of the inner cylinder 102. Since the gap between the inner cylinder 102 and the outer cylinder 101 is small, normal mold design is difficult to ensure dimensional accuracy, and it is difficult to remove the mold after the wax pattern is formed.

[0003] Generally, a ceramic core is used for molding to ensure dimensional accuracy. However, for the structure of the above-mentioned bearing seat 100, when using a ceramic core to manufacture an investment casting of the bearing seat, the following problems exist:

[0004] (1) After pouring, due to the cooling shrinkage of the inner cylinder 102, but since the inner cylinder 102 and the outer cylinder 101 are only connected by three connecting blocks 103, the feeding is not timely, which easily leads to defects such as shrinkage cavities and porosity in the internal window function of the cast inner cylinder 102.

[0005] (2) The ceramic core has good heat storage capacity and slow heat dissipation compared with the mold shell, resulting in a long solidification time of the alloy liquid and prone to defects such as superheat shrinkage cavities and porosity. Summary of the Invention

[0006] The main object of the present invention is to propose a manufacturing method for an investment casting of a bearing seat, aiming to solve the above technical problems.

[0007] To achieve the above object, the present invention proposes a manufacturing method for an investment casting of a bearing seat, including the following steps:

[0008] S1. Manufacture a ceramic core, which has a tubular structure with open upper and lower ends, an annular groove is formed on its inner wall, a notch is formed at the top, and the bottom of the notch is communicated with the top of the annular groove;

[0009] S2. Manufacture a ceramic core wax pattern assembly, the ceramic core wax pattern assembly includes a wax pattern and the ceramic core, the ceramic core is embedded in the wax pattern, and the lower part of the ceramic core extends out from the lower end of the wax pattern;

[0010] S3. Fill a wax block in the notch of the ceramic core;

[0011] S4. Bond a riser on the top of the ceramic core wax mold assembly, and the riser is located directly above the notch;

[0012] S5. Make a shell mold and pour molten metal to obtain a bearing housing investment casting.

[0013] Preferably, the size of the riser is determined according to the ratio of 1:3 of the hot spot.

[0014] Preferably, the wax mold includes a wax mold outer shell and a wax mold inner ring; the wax mold outer shell is sleeved outside the ceramic core and is used to form the outer cylinder on the bearing housing; the wax mold inner ring is embedded in the annular groove on the inner wall of the ceramic core and is used to form the inner cylinder on the bearing housing; the lower end surface of the wax block abuts against the top surface of the wax mold inner ring; holes are formed on the cylindrical wall of the ceramic core, and wax is filled in the holes to form the connecting block on the bearing housing.

[0015] Preferably, in step S4, a wax strip is bonded on the inner wall of the annular body at the mouth of the wax mold outer shell; the upper end of the wax strip is connected to the riser, and the lower end is connected to the wax block.

[0016] Preferably, the transition between the wax strip and the inner wall of the annular body at the mouth of the wax mold outer shell adopts a fillet with a radius of R3 - R5 for transition.

[0017] Preferably, in step S5, the making of the shell mold includes the following steps:

[0018] S501. Immerse the ceramic core wax mold assembly bonded with the riser in the coating to form a coating layer;

[0019] S502. Sprinkle sand grains on the coated ceramic core wax mold assembly to form a sand layer;

[0020] S503. Repeat steps S501 and S502 multiple times to form a multi-layer shell mold;

[0021] S504. Dewax the formed shell mold to obtain a cavity shell mold.

[0022] Preferably, in step S501, the coating used is a mixture of silica sol binder and refractory material, and the refractory material is quartz powder or corundum powder.

[0023] Preferably, in step S5, before pouring, the shell mold needs to be preheated by means of segmented heating up.

[0024] Preferably, the material of the ceramic core is alumina-based ceramic material, and its porosity is 15 - 25%.

[0025] Preferably, the height of the riser is 1.2 - 1.5 times the height of the casting.

[0026] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0027] (1) In the present invention, a notch is provided at the top of the ceramic core, and the bottom of the notch is communicated with the top of the annular groove. A wax block is filled in the notch of the ceramic core. In the prepared shell mold, a feeding channel is formed by the notch on the ceramic core, and the inner cylinder of the bearing seat casting is fed through a feeding riser, thereby eliminating shrinkage cavity and porosity defects in the inner cylinder part of the bearing seat casting.

[0028] (2) In the present invention, the lower part of the ceramic core extends out from the lower end of the wax mold. The functions include: First, the extended part can be embedded in the shell mold, which is beneficial to fixing the ceramic core. Second, it can increase the contact area between the ceramic core and the shell mold, promote heat exchange between the ceramic core and the mold shell, discharge the heat in the inner cavity, and accelerate the solidification and cooling rate of the casting. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0030] Figure 1 is a schematic structural diagram of the bearing seat;

[0031] Figure 2 is a sectional view of the bearing seat;

[0032] Figure 3 is a sectional view of the ceramic core in the present invention;

[0033] Figure 4 is a three-dimensional structural diagram of the ceramic core wax mold assembly in the present invention;

[0034] Figure 5 is a sectional view of the ceramic core wax mold assembly in the present invention;

[0035] Figure 6 is a sectional view of the ceramic core wax mold assembly after bonding the feeding riser in the present invention.

[0036] Explanation of the reference numerals in the drawings: 1, ceramic core; 1a, annular groove; 1b, notch; 1c, hole; 2, ceramic core wax mold assembly; 3, wax mold; 3a, wax mold outer shell; 3b, wax mold inner ring; 4, wax block; 5, feeding riser; 6, wax strip; 100, bearing seat; 101, outer cylinder; 102, inner cylinder; 103, connecting block. Detailed implementation mode

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0038] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0039] Combined with Figure 1 and Figure 2 As shown, the bearing seat 100 is composed of an outer cylinder 101 and an inner cylinder 102 disposed inside the outer cylinder 101. There is a gap between the outer peripheral surface of the inner cylinder 102 and the inner wall surface of the outer cylinder 101. Three connecting blocks 103 are integrally formed between the inner wall of the outer cylinder 101 and the outer wall of the upper part of the inner cylinder 102.

[0040] Combined with Figures 3 to 6 As shown, this embodiment provides a manufacturing method for a bearing seat investment casting, including the following steps:

[0041] S1. Manufacture a ceramic core 1, which is a tubular structure with open upper and lower ends. An annular groove 1a is opened on its inner wall, a notch 1b is opened at the top, and the bottom of the notch 1b communicates with the top of the annular groove 1a.

[0042] S2. Manufacture a ceramic core wax mold assembly 2, which includes a wax mold 3 and the ceramic core 1. The ceramic core 1 is embedded in the wax mold 3, and the lower part of the ceramic core 1 extends out from the lower end of the wax mold 3; specifically, the wax mold 3 includes a wax mold outer shell 3a and a wax mold inner ring 3b. The wax mold outer shell 3a is sleeved outside the ceramic core 1 and is used to form the outer cylinder 101 on the bearing seat 100; the wax mold inner ring 3b is embedded in the annular groove 1a on the inner wall of the ceramic core 1 and is used to form the inner cylinder 102 on the bearing seat 100; holes 1c are opened on the cylinder wall of the ceramic core 1, and wax material is filled in the holes 1c to form the connecting blocks 103 on the bearing seat 100.

[0043] S3. Fill a wax block 4 in the notch 1b of the ceramic core 1, and the lower end surface of the wax block 4 abuts against the top surface of the wax mold inner ring 3b.

[0044] S4. Bond a riser 5 to the top of the ceramic core wax mold assembly 2, and the riser 5 is located directly above the notch 1b.

[0045] S5. Make a shell mold and pour the molten metal to obtain a bearing housing investment casting. After making the shell mold, since the wax block 4 and the wax mold 3 have been melted, a feeding channel is formed at the notch 1b of the ceramic core 1. The inner cylinder of the bearing housing casting is fed through the riser 5, thereby eliminating shrinkage porosity and looseness defects in the inner cylinder part of the bearing housing casting.

[0046] In this embodiment, the size of the riser 5 is determined according to the ratio of the hot spot 1:3. Reasonably control the size of the riser 5 to ensure sufficient feeding during the solidification of the casting, and effectively prevent defects such as shrinkage porosity and looseness.

[0047] Combined Figure 6 As shown, in step S4, bond a wax strip 6 to the inner wall of the annular body at the mouth of the wax mold outer shell 3a; the upper end of the wax strip 6 is connected to the riser 5, and the lower end is connected to the wax block 4. In the shell mold, the melted part of the wax strip 6 forms an auxiliary feeding channel, further optimizing the metal liquid flow path and reducing the risk of shrinkage porosity.

[0048] At the transition between the wax strip 6 and the inner wall of the annular body at the mouth of the wax mold outer shell 3a, use a fillet with a radius of R3 - R5 for transition. The fillet transition reduces stress concentration, avoids crack generation, and at the same time improves the metal liquid flow and reduces inclusions caused by turbulence.

[0049] In this embodiment, the production of the shell mold in step S5 includes the following steps:

[0050] S501. Immerse the ceramic core wax mold assembly 2 bonded with the riser 5 into the coating material to form a coating layer;

[0051] S502. Sprinkle sand grains on the coated ceramic core wax mold assembly 2 to form a sand layer;

[0052] S503. Repeat steps S501 and S502 multiple times to form a multi-layer shell mold;

[0053] S504. Dewax the formed shell mold to obtain a cavity shell mold.

[0054] In step S501, the coating material used is a mixture of silica sol binder and refractory material, and the refractory material is quartz powder or corundum powder. The silica sol binder has the following advantages

[0055] (1) It has a high refractoriness. During the high-temperature pouring process, it enables the shell mold to remain stable without deformation or cracking, thus ensuring the dimensional accuracy and surface quality of the casting.

[0056] (2) It has a low coefficient of thermal expansion. At high temperatures, the size change of the mold shell is small, which can reduce the deformation and cracks of the casting caused by thermal expansion.

[0057] (3) It has high strength and toughness. The silica sol forms a hard silica network structure after drying, with high mechanical strength and toughness. The mold shell can withstand large mechanical stresses during handling and pouring, reducing the breakage and cracking of the mold shell.

[0058] (4) It has good air permeability. The mold shell formed by silica sol has a certain porosity and good air permeability. During pouring, the gas inside the mold shell can be discharged smoothly, reducing porosity and gas entrapment defects and improving the density of the casting.

[0059] (5) The surface of the mold shell formed by silica sol is smooth and has good demolding performance.

[0060] In the step S5, before pouring, the mold shell needs to be preheated by a segmented heating method. Segmented heating can ensure uniform thermal expansion of the mold shell during preheating, thereby improving the overall strength and stability of the mold shell. Uniform heating reduces the deformation of the mold shell and ensures good dimensional accuracy of the mold shell during pouring. The uniformly heated mold shell can better discharge the internal gas during pouring, reducing porosity and gas entrapment defects. The segmented heating includes the following three stages:

[0061] The first stage: low-temperature preheating stage. Temperature range: 100°C to 300°C. Purpose: Remove moisture and organic matter in the mold shell to ensure that the mold shell is dry before high-temperature preheating. Time: 1 to 2 hours.

[0062] The second stage: medium-temperature preheating stage. Temperature range 300°C to 600°C. Purpose: Further improve the strength of the mold shell to ensure that the mold shell can withstand greater thermal stress during high-temperature preheating. Time: 2 to 3 hours.

[0063] The third stage: high-temperature preheating stage. Temperature range: 600°C to 1000°C. Purpose: Make the mold shell reach the required temperature for pouring to ensure good strength and stability of the mold shell during pouring. Time: 2 to 4 hours.

[0064] In this embodiment, the material of the ceramic core 1 is an alumina-based ceramic material, and its porosity is 15 - 25%. Alumina-based ceramics have a high refractoriness and moderate air permeability, which can not only withstand the erosion of high-temperature molten metal but also promote the exhaust of the mold shell, reducing porosity defects.

[0065] In this embodiment, the height of the riser 5 is 1.2 - 1.5 times the height of the casting. Sufficient riser height provides sufficient feeding pressure to ensure the density inside the casting and reduce shrinkage cavity defects.

[0066] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields shall be included within the patent protection scope of the present invention.

Claims

1. A manufacturing method of an investment casting of a bearing housing, characterized in that, It includes the following steps: S1. Fabricate a ceramic core (1). The ceramic core (1) has a tubular structure with open upper and lower ends. An annular groove (1a) is formed on its inner wall, and a notch (1b) is formed at the top. The bottom of the notch (1b) communicates with the top of the annular groove (1a). S2. Fabricate a ceramic core wax mold assembly (2). The ceramic core wax mold assembly (2) includes a wax mold (3) and the ceramic core (1). The ceramic core (1) is embedded in the wax mold (3), and the lower part of the ceramic core (1) extends out from the lower end of the wax mold (3). S3. Fill a wax block (4) into the notch (1b) of the ceramic core (1). S4. Bond a feeder head (5) to the top of the ceramic core wax mold assembly (2). The feeder head (5) is located directly above the notch (1b). S5. Fabricate a mold shell and perform pouring to obtain a bearing housing investment casting.

2. The manufacturing method of a bearing housing investment casting as described in claim 1, characterized in that, The size of the feeder head (5) is determined according to the ratio of 1:3 of the hot spot.

3. The manufacturing method of a bearing housing investment casting as described in claim 1, characterized in that, The wax mold (3) includes a wax mold outer shell (3a) and a wax mold inner ring (3b). The wax mold outer shell (3a) is sleeved outside the ceramic core (1) and is used to form the outer cylinder (101) on the bearing housing (100). The wax mold inner ring (3b) is embedded in the annular groove (1a) on the inner wall of the ceramic core (1) and is used to form the inner cylinder (102) on the bearing housing (100). The lower end surface of the wax block (4) abuts against the top surface of the wax mold inner ring (3b). Holes (1c) are formed on the wall of the ceramic core (1), and wax is filled in the holes (1c) to form the connecting block (103) on the bearing housing (100).

4. The manufacturing method of a bearing housing investment casting as described in claim 3, characterized in that, In step S4, a wax strip (6) is bonded to the inner wall of the annular body at the mouth of the wax mold outer shell (3a). The upper end of the wax strip (6) is connected to the feeder head (5), and the lower end is connected to the wax block (4).

5. The manufacturing method of an investment casting for a bearing housing according to claim 4, wherein The transition between the wax strip (6) and the inner wall of the annular body at the mouth of the wax mold outer shell (3a) is made with a fillet of R3 - R5.

6. The manufacturing method of a bearing housing investment casting as described in claim 1, characterized in that, In step S5, the fabrication of the mold shell includes the following steps: S501. Immerse the ceramic core wax mold assembly (2) bonded with the feeder head (5) in a coating to form a coating layer. S502. Sprinkle sand grains on the coated ceramic core wax mold assembly (2) to form a sand layer. S503. Repeat steps S501 and S502 multiple times to form a multi-layer mold shell. S504. Perform dewaxing treatment on the formed mold shell to obtain a cavity mold shell.

7. The manufacturing method of a bearing housing investment casting as described in claim 6, characterized in that, In step S501, the coating used is a mixture of silica sol binder and refractory material, and the refractory material is quartz powder or corundum powder.

8. The manufacturing method of a bearing housing investment casting as described in claim 1, characterized in that, In step S5, before pouring, the mold shell needs to be preheated in a way of segmented temperature rise.

9. The manufacturing method of a bearing housing investment casting as described in claim 1, characterized in that The material of the ceramic core (1) is alumina-based ceramic material, and its porosity is 15 - 25%.

10. The manufacturing method of a bearing housing investment casting as described in claim 1, characterized in that, The height of the feeder head (5) is 1.2 - 1.5 times the height of the casting.

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