Method for controlling deformation of blades of impeller-type precision castings

Abstract

The method disclosed in the present invention for controlling the deformation of blades of impeller precision castings is specifically implemented according to the following steps: designing a preheating barrel for impeller casting based on the size of the impeller casting and the parameters of the mold shell; performing wax pressing, tree assembly, and shell making according to the traditional precision casting process to obtain an impeller mold shell with a wax mold; pre-baking after dewaxing; burying the baked mold shell in a designed preheating barrel and filling it with dry quartz sand; placing the preheating barrel containing the mold shell in a preheating furnace for preheating; removing the preheating barrel containing the mold shell from the preheating furnace and pouring molten metal into the preheating barrel; cooling the poured impeller casting and the preheating barrel together to below 200°C, removing the mold shell, and performing subsequent cooling and cleaning and finishing of the casting. The method for controlling the deformation of blades of impeller precision castings of the present invention requires little tooling investment and greatly improves the ability to control blade deformation of impeller castings without changing the current traditional precision casting method.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision casting, and in particular relates to a method for controlling the deformation of blades of impeller-type precision castings. Background Art

[0002] Impeller castings are mostly used in supercharger turbines, water jet propulsion rotors, gas turbine turbine disks and other key flow-through components and stress-bearing components for propulsion and supercharging. The structure of impeller castings is a thick hub in the center, surrounded by thin-walled blades distributed around the hub. The blades of this type of parts are open and evenly distributed. Due to the influence of propulsion efficiency or supercharging efficiency, high dimensional accuracy of the blades is required. Therefore, impeller castings are generally formed by precision casting to ensure the dimensional accuracy of the blades. However, due to the large variation in solidification rate, the shrinkage of the hub generally causes deformation of the blades, and the shrinkage is difficult to control. During the investment casting process, the blades are often scrapped due to deformation.

[0003] The traditional method generally adopts the reverse deformation design to ensure the dimensional accuracy of the impeller blades, but in the precision casting process, the shell thickness of the blade is generally only 6-8mm, which causes the blade to be in a suspended state. Due to the large thickness variation from the root to the tip of the blade and the distortion of the profile, it is generally difficult to achieve the required dimensional accuracy even after multiple reverse deformation compensations. Another method is to add tie rods to the tip of the blade to fix the deformation of the blade to ensure the dimensional accuracy of the blade, but this method is generally difficult to implement due to the thin tip of the blade. Even if it is implemented, it will cause inconsistent deformation in the width direction of the tip of the blade. In addition, due to the arrangement of tie rods, the difficulty of shell making is greatly increased, and the precision casting mold shell is prone to cracking during the production process. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for controlling the deformation of blades of impeller-type precision castings, which solves the problem of poor dimensional accuracy of impeller-type castings caused by blade deformation during the precision casting production process in the prior art.

[0005] The technical solution adopted by the present invention is a method for controlling the deformation of impeller blades of precision castings, which is specifically implemented according to the following steps:

[0006] Step 1: Design a preheating barrel for impeller casting based on the impeller casting size and mold shell parameters;

[0007] Step 2: According to the traditional precision casting process, wax pressing, tree assembly and shell making are performed to obtain the impeller shell with wax mold;

[0008] Step 3: dewaxing the impeller wax mold obtained in step 2 and then pre-baking it;

[0009] Step 4: bury the mold shell baked in step 3 into the designed preheating barrel and fill it with dry quartz sand;

[0010] Step 5: Place the preheating barrel with the mold shell in step 4 into the preheating furnace for preheating;

[0011] Step 6: Take out the preheating barrel with the mold shell from the preheating furnace and pour the molten metal into the preheating barrel;

[0012] Step 7: Cool the cast impeller casting to below 200°C along with the preheating barrel, remove the mold shell from the preheating barrel, and carry out subsequent cooling and cleaning and finishing of the casting.

[0013] The present invention is also characterized in that:

[0014] In step 1, the preheating barrel is a barrel-type tooling with a diameter 80mm-100mm larger than the diameter of the impeller mold shell, the height of the preheating barrel is 70mm-100mm higher than the height of the mold shell, and lifting ears are provided on both sides of the barrel-type tooling.

[0015] The barrel-shaped tooling is welded with heat-resistant stainless steel.

[0016] In step 3, the pre-baking temperature is 900° C.-1100° C.; and the pre-baking time is 1.5 h-3 h.

[0017] Step 4 is as follows: first fill quartz sand into the bottom of the preheating barrel, then place the mold shell baked in step 3 into the preheating barrel, and continue to fill quartz sand into the gap between the side of the mold shell and the inner wall of the preheating barrel until the horizontal height of the quartz sand is 10mm-20mm from the top of the mold shell, and then vibrate it.

[0018] The thickness of the quartz sand layer between the bottom of the mold shell and the sides of the mold shell and the preheating barrel is 30mm-50mm.

[0019] In step 4, the particle size of the quartz sand is 40 mesh to 100 mesh.

[0020] In step 5, the preheating temperature is 700° C.-950° C., and the preheating time is 2 h-3 h.

[0021] In step 7, when the temperature is cooled to below 200° C., the mold shell is taken out from the preheating barrel.

[0022] The beneficial effects of the present invention are:

[0023] The method for controlling the deformation of blades of impeller precision castings of the present invention comprises the following steps: placing an impeller casting mold shell formed by investment casting in a barrel-shaped tooling preheating barrel, then filling the preheating barrel with dry quartz sand, preheating it together with the mold shell, and directly pouring molten metal into the mold shell in the preheating barrel; during cooling, the filled quartz sand is used to control the deformation of the blades during solidification, thereby better controlling the dimensional accuracy of the blades; by controlling the deformation of the impeller blades during pouring and solidification, the problem of poor dimensional accuracy of impeller castings caused by blade deformation during precision casting production is solved; the tooling investment required is small, and on the basis of not changing the current traditional precision casting method, the deformation control capability of the impeller castings is greatly improved, the dimensional accuracy of the impeller castings can be greatly improved, and the trial production cost can be saved; at the same time, it is beneficial to the stability of the dimensional control of the impeller castings, and can be used for mass production of impeller parts, with significant economic benefits; BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a barrel-shaped tooling in a method for controlling blade deformation of an impeller-type precision casting according to the present invention;

[0025] Figure 2 It is a schematic diagram of sand filling in the method for controlling deformation of blades of impeller-type precision castings according to the present invention.

[0026] In the picture, 1. Preheating barrel, 2. Lifting lug, 3. Mould shell, 4. Quartz sand. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The method for controlling the deformation of impeller blades of precision castings of the present invention is specifically implemented according to the following steps:

[0029] Step 1: Design a preheating barrel 1 for impeller casting according to the size of the impeller casting and the parameters of the mold shell 3;

[0030] The preheating barrel 1 is a barrel-shaped fixture with a diameter 80mm-100mm larger than the diameter of the impeller mold. The height of the barrel-shaped fixture is 70mm-100mm higher than the height of the impeller mold 3. There are lifting ears 2 on both sides of the barrel-shaped fixture for lifting. Figure 1 As shown, the barrel-shaped tooling is formed by welding heat-resistant stainless steel.

[0031] Step 2: According to the traditional precision casting process, wax pressing, tree forming and shell making are performed to obtain the impeller shell 3 with wax mold;

[0032] Step 3: dewaxing the impeller mold shell 3 with wax mold obtained in step 2, and then pre-baking the dewaxed mold shell 3 at a pre-baking temperature of 900° C. to 1100° C. for a 1.5-3 h period.

[0033] Step 4: First fill quartz sand into the bottom of the preheating barrel 1. Put the mold shell 3 baked in step 3 into the preheating barrel 1 after passing the inspection, and continue to fill the gap between the side of the mold shell 3 and the inner wall of the preheating barrel 1 with dry 40-100 mesh quartz sand 4 until the horizontal height of the quartz sand 4 is 10mm-20mm away from the top of the mold shell 3. The thickness of the quartz sand layer between the bottom of the mold shell 3 and the preheating barrel 1 is 30mm-50mm, and the thickness of the quartz sand layer between the outer peripheral side of the maximum diameter of the mold shell 3 and the preheating barrel 1 is 30mm-50mm. After vibration compaction, it has good compactness, such as Figure 2 As shown;

[0034] Step 5: Place the preheating barrel with the mold shell in step 4 into a preheating furnace and preheat at 700°C-950°C for 2h-3h;

[0035] Step 6: Take out the preheating barrel with the mold shell from the preheating furnace and pour the molten metal into the preheating barrel;

[0036] Step 7: Cool the cast impeller casting along with the preheating barrel. When the temperature is less than 200°C, remove the mold shell from the preheating barrel for subsequent cooling and cleaning and finishing of the casting.

[0037] The present invention provides a method for controlling blade deformation in impeller precision castings. The method involves placing an impeller casting mold shell 3, formed by investment casting, in a barrel-shaped fixture. Dry quartz sand 4 is then filled into a preheating barrel 1, preheated together with the mold shell 3. Molten metal is then poured directly into the mold shell 3 within the preheating barrel 1. During cooling, the packed quartz sand 4 is used to control blade deformation during solidification, thereby effectively controlling blade dimensional accuracy. This method of controlling impeller blade deformation during pouring and solidification addresses the problem of poor dimensional accuracy of impeller castings caused by blade deformation during precision casting production.

[0038] Example 1:

[0039] Waterjet impeller stainless steel casting, size: The average thickness of the blade is 6mm, the minimum wall thickness is 1.5mm, and the diameter of the mold shell is The height is 280mm; if conventional investment casting is used, the blade deformation will reach more than 4mm, which is difficult to meet the use requirements.

[0040] According to the method for controlling the deformation of impeller-type precision casting blades, the following steps are adopted:

[0041] 1) Make the diameter size The 350mm high barrel-shaped fixture is made of 3mm thick 1Cr18Ni9 heat-resistant stainless steel plate and welded with lifting lugs;

[0042] 2) The impeller casting is waxed and assembled according to the traditional setting process. During the molding process, the wax mold is guaranteed not to be deformed, and a special mold is used to fix the blades;

[0043] 3) Make the shell of the wax pattern that has passed the inspection according to the investment casting process, ensure constant temperature during the shell making process, and appropriately reduce the drying speed;

[0044] 4) After dewaxing, pre-bake the mold shell at 900°C for 3 hours;

[0045] 5) After the baked mold shell passes the inspection, it is buried in the designed preheating barrel and filled with dry 40-100 mesh quartz sand. The thickness of the quartz sand layer between the bottom of the mold shell and the bottom of the preheating barrel is 30mm, the thickness of the quartz sand between the side of the mold shell and the inner wall of the preheating barrel is 44mm, and the horizontal height of the top quartz sand is 10mm from the height of the top gate position of the mold shell. After vibration and compaction, Figure 2 As shown;

[0046] 6) Place the assembled preheating barrel into the preheating furnace and preheat for 2 hours at 750°C.

[0047] 7) After the molten metal is melted, take out the preheating barrel with the mold shell from the preheating furnace and pour the molten metal into it;

[0048] 8) The cast impeller casting is cooled along with the preheating barrel. When the temperature is less than 200°C, the mold shell is removed from the preheating barrel for subsequent cooling and cleaning and finishing of the casting.

[0049] The impeller casting cast by the above method was inspected and the blade profile reached 1mm, meeting the design requirements.

[0050] Example 2:

[0051] K418B high temperature alloy turbocharger turbine casting, size: The minimum wall thickness of the blade is 1mm, and the diameter of the mold shell is The height is 220mm; the blade deformation of conventional investment casting is more than 2mm, which is difficult to meet the use requirements. According to the present invention, the following steps are adopted:

[0052] 1) Make the diameter size The 300mm high barrel-shaped fixture is made of 3mm thick Cr25Ni20 heat-resistant stainless steel plate and welded with lifting lugs;

[0053] 2) Wax and form the turbine casting according to the traditional setting process, and pay attention to controlling the deformation of the blades during the molding process;

[0054] 3) Make the shell of the wax pattern that has passed the inspection according to the investment casting process;

[0055] 4) After dewaxing, pre-baking the mold shell at 1000°C for 2 hours;

[0056] 5) After the baked mold shell passes the inspection, it is buried in the designed preheating barrel and filled with dry quartz sand with a particle size of 40-70 mesh. The thickness of the quartz sand layer between the bottom of the mold shell and the bottom of the preheating barrel is 40mm, and the thickness of the quartz sand between the side of the mold shell and the inner wall of the preheating barrel is 34mm. The gate part of the top of the mold shell is exposed to the quartz sand surface for 15mm. After vibration and compaction, if Figure 2 As shown;

[0057] 6) Place the assembled preheating barrel into the preheating furnace and preheat for 3 hours at 950°C.

[0058] 7) When smelting high-temperature alloys, first place the preheated preheating barrel with the mold shell into the single-chamber vacuum furnace, align the pouring position, start vacuuming and melt the high-temperature alloy liquid metal, and pour the high-temperature alloy liquid metal after it is melted;

[0059] 8) After pouring is completed, cool in the furnace for 2 minutes, remove the vacuum, take out the preheating barrel, and place it in the air to cool. When the temperature is less than 200°C, remove the mold shell from the preheating barrel for subsequent cooling and cleaning and finishing of the casting.

[0060] The impeller casting cast by the above method was tested and found that the blade profile reached 0.8mm, meeting the design requirements.

[0061] Example 3:

[0062] An engine turbine disk casting, size: The average thickness of the blade is 3mm, the minimum wall thickness is 1mm, and the diameter of the mold shell is The height is 280mm; if conventional investment casting is used, the blade deformation will reach more than 4mm, which is difficult to meet the use requirements.

[0063] According to the method for controlling the deformation of impeller-type precision casting blades, the following steps are adopted:

[0064] 1) Make the diameter size The barrel-shaped fixture is 380mm high and is made of 3mm thick 1Cr18Ni9 heat-resistant stainless steel plate with welded lifting lugs.

[0065] 2) The impeller casting is waxed and assembled according to the traditional setting process. During the molding process, the wax mold is guaranteed not to be deformed, and a special mold is used to fix the blades;

[0066] 3) Make the shell of the wax pattern that has passed the inspection according to the investment casting process, ensure constant temperature during the shell making process, and appropriately reduce the drying speed;

[0067] 4) After dewaxing, pre-baking the mold shell at 1100°C for 1.5 hours;

[0068] 5) After the fired mold shell passes the inspection, it is buried in the designed preheating barrel and filled with dry 70-100 mesh quartz sand. The thickness of the quartz sand layer between the bottom of the mold shell and the bottom of the preheating barrel is 50mm, the thickness of the quartz sand between the side of the mold shell and the inner wall of the preheating barrel is 38mm, and the height of the top quartz sand is 20mm from the height of the top gate position of the mold shell. It is vibrated and compacted;

[0069] 6) Place the assembled preheating barrel into the preheating furnace and preheat for 2.5 hours at a temperature of 825°C.

[0070] 7) After the molten metal is melted, take out the preheating barrel with the mold shell from the preheating furnace and pour the molten metal into it;

[0071] 8) The cast impeller casting is cooled along with the preheating barrel. When the temperature is less than 200°C, the mold shell is removed from the preheating barrel for subsequent cooling and cleaning and finishing of the casting.

[0072] The impeller casting cast by the above method was inspected and the blade profile reached 1mm, meeting the design requirements.

[0073] The method for controlling the deformation of blades of impeller-type precision castings of the present invention comprises the following steps: designing a stainless steel barrel-type tooling with earrings, placing an impeller-type casting mold shell formed by investment casting in the barrel-type tooling, then filling a preheating barrel with dry quartz sand having a sand intake of 30mm-50mm, and vibrating and enriching it to have good compactness; then, when the mold shell is preheated, the entire barrel-type tooling filled with dry sand and the impeller mold shell is placed in a preheating furnace, and preheating is designed according to the size of the impeller casting, with the preheating time controlled at 2h-3h; after the molten metal is smelted, it is taken out of the preheating furnace with a special sling, and the molten metal is directly poured into the mold shell in the preheating barrel; and the mold shell is taken out after cooling to a certain temperature. By adopting this method, the dimensional accuracy of the blades of the impeller-type casting can be better controlled. Compared with the existing technology, the required tooling investment is less, and the current traditional precision casting method is not changed. It greatly improves the blade deformation control ability of impeller castings, can greatly improve the dimensional accuracy of impeller castings, and save trial production costs; at the same time, it is beneficial to the stability of dimensional control of impeller castings, and can be used for mass production of impeller parts, with significant economic benefits.

Claims

1. A method for controlling the deformation of impeller blades, characterized in that: Please follow the steps below to implement it: Step 1: Design a preheating barrel (1) for impeller casting according to the size of the impeller casting and the parameters of the mold shell (3); Step 2: wax pressing, tree forming and shell making are performed according to the traditional precision casting process to obtain the impeller shell with wax mold (3); Step 3, dewaxing the impeller mold shell (3) with wax mold obtained in step 2, and then pre-baking it; Step 4: bury the mold shell (3) baked in step 3 into the designed preheating barrel (1) and fill it with dry quartz sand (4); Step 5: Place the preheating barrel (1) containing the mold shell (3) in step 4 into a preheating furnace for preheating; Step 6: Take out the preheating barrel (1) containing the mold shell (3) from the preheating furnace, and pour the molten metal into the preheating barrel (1); Step 7: Cool the cast impeller casting to below 200° C. along with the preheating barrel (1), remove the mold shell (3) from the preheating barrel, and carry out subsequent cooling and cleaning and finishing of the casting.

2. The method for controlling blade deformation of impeller precision castings according to claim 1, characterized in that: In step 1, the preheating barrel (1) is a barrel-shaped tooling with a diameter 80mm-100mm larger than the diameter of the impeller mold shell (3), the height of the preheating barrel (1) is 70mm-100mm higher than the height of the mold shell (3), and lifting ears (2) are provided on both sides of the barrel-shaped tooling.

3. The method for controlling the deformation of impeller blades according to claim 2, characterized in that: The barrel-shaped tooling is formed by welding heat-resistant stainless steel.

4. The method for controlling the deformation of impeller blades according to claim 1, wherein 5. The method for controlling blade deformation of impeller precision castings according to claim 1, characterized in that: The step 4 specifically comprises the following steps: first, filling quartz sand into the bottom of the preheating barrel (1), then placing the mold shell (3) baked in step 3 into the preheating barrel (1), and continuously filling quartz sand (4) into the gap between the side of the mold shell (3) and the inner wall of the preheating barrel (1) until the horizontal height of the quartz sand (4) is 10 mm to 20 mm from the top of the mold shell (3), and then vibrating the mold shell to compact the gap.

6. The method for controlling blade deformation of impeller precision castings according to claim 5, characterized in that: The thickness of the quartz sand layer between the bottom of the mold shell (3) and the side of the mold shell (3) and the preheating barrel (1) is 30mm-50mm.

7. The method for controlling blade deformation of impeller precision castings according to claim 1, characterized in that: In step 4, the particle size of the quartz sand (4) is 40 mesh to 100 mesh.

8. The method for controlling blade deformation of impeller precision castings according to claim 1, characterized in that: In step 5, the preheating temperature is 700° C.-950° C., and the preheating time is 2 h-3 h.

9. The method for controlling blade deformation of impeller precision castings according to claim 1, characterized in that: In step 7, when the temperature is cooled to below 200° C., the mold shell (3) is taken out from the preheating barrel.

Images