Heat treatment control method for large milled and welded impeller

Abstract

The present invention provides a large milling and welding impeller heat treatment control method, the steps of which include: performing a first solid solution treatment and a first aging treatment on a wheel cover and a wheel disc; performing a stress relief treatment after welding the wheel cover and the wheel disc into an impeller; performing an outer cylindrical machining on the impeller; performing a second solid solution treatment on the impeller; performing a rough machining on the impeller; placing the impeller on a tray for a second aging treatment; and performing a third aging treatment on the impeller. The large milling and welding impeller heat treatment control method provided by the present invention can ensure that the impeller reduces the deformation of the impeller during the heat treatment process while meeting the designed mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment, and in particular to a heat treatment control method for a large milled and welded impeller. Background Art

[0002] The impeller has a complex structure, especially when the flow channel is precision-machined. If the impeller is greatly deformed during the heat treatment process, it will not meet the design requirements and will be scrapped. In particular, as compressor structures continue to grow in size, the deformation of large impellers during heat treatment will often increase. Therefore, how to control the deformation of large milled and welded impellers during heat treatment is of great significance. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a heat treatment control method for a large milled welded impeller, so as to reduce the deformation of the impeller during the heat treatment process while satisfying the designed mechanical properties.

[0004] In order to solve the above technical problems, the present invention provides a large milling and welding impeller heat treatment control method, comprising the following steps:

[0005] Performing a first solution treatment and a first aging treatment on the wheel cover and the wheel disc;

[0006] After the wheel cover and wheel disc are welded into an impeller, stress relief treatment is performed;

[0007] Perform external machining on the impeller;

[0008] performing a second solution treatment on the impeller;

[0009] Rough machining of the impeller;

[0010] Place the impeller on a tray for the second aging treatment;

[0011] The impeller is subjected to a third aging treatment.

[0012] Furthermore, during the first solution treatment, the wheel cover and the wheel disc are heated to 800-900°C, kept warm for not less than 1 hour, and then heated to 1020-1060°C at a rate of ≤100°C / h, kept warm for not less than 2 hours, and then taken out of the furnace and cooled at a cooling rate not less than air cooling; during the first aging treatment, the wheel cover and the wheel disc are heated to 600-850°C, kept warm for not less than 4 hours, and then taken out of the furnace and cooled at a cooling rate not less than air cooling.

[0013] Furthermore, the wheel cover and the wheel disc may be subjected to repeated first aging treatment after the first solution treatment and the first aging treatment.

[0014] Furthermore, during the stress relief treatment, the impeller is heated to 600-660° C., kept warm for not less than 4 hours, and then cooled to room temperature in the furnace.

[0015] Furthermore, after the outer circle of the impeller is machined, a machining allowance of 10 to 20 mm is retained on the outer circle of the impeller.

[0016] Furthermore, during the second solution treatment of the impeller, the heat treatment equipment is evacuated, the impeller is heated to 800-900°C, 40Pa nitrogen is introduced, and after being kept warm for no less than 1h, it is heated to 1020-1060°C at a rate of ≤100°C / h, and after a holding time of 0.5-1h, it is cooled to 50-80°C with 1-2Bar nitrogen and then taken out of the furnace for air cooling.

[0017] Furthermore, after the impeller is roughly machined, a margin of 5 to 10 mm is reserved on the basis of the design size, and the thickness of the shaft disc side outlet is not less than 20 mm.

[0018] Furthermore, when the impeller is placed on a tray for the second aging treatment, the impeller is heated to 800-900° C. for a holding time of not less than 2 hours, and then cooled to room temperature at a cooling rate not less than air cooling after being taken out of the furnace.

[0019] Furthermore, the impeller is placed concentrically on the tray, the tray is placed in the center of the heat treatment equipment, the thickness of the tray is not less than 40 mm, the outer diameter of the tray is larger than the diameter of the impeller, and the tray has inner holes of φ80 mm evenly arranged on circles of different radii from the center within a diameter range of 900 mm.

[0020] Furthermore, during the third aging treatment of the impeller, the impeller is heated to 480-650° C., kept at this temperature for not less than 4 hours, and then taken out of the furnace and cooled to room temperature at a cooling rate not less than that of air cooling.

[0021] The present invention provides a large-scale milling and welding impeller heat treatment control method. Before the impeller is welded, the wheel cover and the wheel disc are first subjected to solution treatment and aging treatment, which can reduce the hardness of the wheel cover and the wheel disc, reduce the hardness of the material to 320HBW or even below 300HBW, improve the processing performance of the wheel cover and the wheel disc, improve their cutting ability, eliminate the internal stress of the wheel cover and the wheel disc, reduce the internal stress before the impeller is welded, and improve the welding effect of the impeller. In addition, since the impeller wheel cover and the wheel disc are pre-solution treated and aging treated, the insulation time of the impeller during the solution treatment of the performance heat treatment after welding only needs to ensure that the weld position meets the organizational transformation, which can effectively reduce its insulation time and only needs 0.5-1h. In this way, since the insulation time of the high-temperature solution treatment is shortened, the deformation of the impeller in this process can be effectively controlled. After the wheel cover and the wheel disc are welded into an impeller, the impeller is subjected to stress relief treatment, and then the outer circle of the impeller is processed, and then the impeller is subjected to solution treatment and rough processing. The aging treatment of the welded impeller can adjust the distribution of alloy elements in the steel, increase the phase transition temperature of martensite, obtain more martensite structure in the steel, and improve the strength and hardness of the impeller. And adding a rough processing process after this aging treatment can reduce the margin of the impeller heat treatment project, improve the material structure transformation effect, and obtain better material properties. Finally, the impeller is subjected to a performance heat treatment including high-temperature aging treatment and aging treatment. In addition, during this heat treatment process, a tray with an outer diameter larger than the impeller diameter is designed, and inner holes of φ80mm are evenly set on the circumference of different radii within 900mm of the tray diameter from its center. This can not only reduce the weight of the tray and facilitate the operator's use, but also enable the cooling medium to contact the impeller through the inner hole during the cooling process of the impeller, which is convenient for the impeller to cool. At the same time, since the outer circle side of the impeller is the weak link of the impeller during the heat treatment process and is very easy to deform during the heat treatment process, no inner hole is designed in the part outside the tray diameter of 900mm to improve the rigidity of the outer circle side of the impeller, so that the deformation of the impeller during the heat treatment process can be effectively controlled while ensuring the impeller performance during the heat treatment process.

[0022] Therefore, the heat treatment control method for a large milled and welded impeller provided by the present invention can effectively reduce the deformation of the impeller during the heat treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of a heat treatment control method for a large milled and welded impeller provided in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of processing the outer circle of a welded impeller after stress relief in a large-scale milled welded impeller heat treatment control method provided by an embodiment of the present invention;

[0025] Figure 3A schematic diagram of rough machining of a welded impeller after solution treatment in a heat treatment control method for a large milled welded impeller provided by an embodiment of the present invention;

[0026] Figure 4 A diagram showing the placement of a welding impeller in a heat treatment device in a large milling welding impeller heat treatment control method provided by an embodiment of the present invention;

[0027] Figure 5 A schematic diagram of a heat treatment tray for high temperature aging treatment and aging treatment of a welded impeller in a heat treatment control method for a large milled welded impeller provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] See also Figure 1 , a large milling and welding impeller heat treatment control method provided by an embodiment of the present invention comprises the following steps:

[0029] Step 1) The wheel cover and wheel disc are subjected to the first solution treatment and the first aging treatment. When the wheel cover and wheel disc are subjected to the solution treatment before welding, the wheel cover and wheel disc are first heated to 800-900°C, kept warm for at least 1 hour, and then heated to 1020-1060°C at a rate of ≤100°C / h, kept warm for at least 2 hours, and then taken out of the furnace to cool the wheel cover and wheel disc to room temperature at a cooling rate not less than air cooling. When the wheel cover and wheel disc are subjected to the aging treatment, the wheel cover and wheel disc are heated to 600-850°C, kept warm for at least 4 hours, and then taken out of the furnace to cool to room temperature at a cooling rate not less than air cooling.

[0030] If the impeller cover and impeller disc have difficulty in processing during the subsequent processing, they can be recycled for aging treatment after completing the solution treatment and aging treatment.

[0031] The large milling and welding impeller heat treatment control method provided by the present invention first performs solid solution treatment and aging treatment on the wheel cover and the wheel disc before the impeller is welded, which can reduce the hardness of the wheel cover and the wheel disc, and reduce the hardness of the material to 320HBW or even below 300HBW, which can improve its processing performance and cutting ability. It can also eliminate the internal stress of the wheel cover and the wheel disc, reduce the internal stress before the impeller is welded, and improve the welding effect of the impeller. At the same time, since the wheel cover and the wheel disc of the impeller have been solid solution treated and aging treated in advance, the insulation time of the solid solution treatment of the impeller for performance heat treatment after welding only needs to ensure that the weld position meets the structural transformation, which can effectively reduce the insulation time, generally only 0.5-1h is needed. Since the insulation time of the high-temperature solid solution treatment is shortened, the deformation of the impeller in this process can be effectively controlled.

[0032] Step 2) After the wheel cover and the wheel disc are welded into an impeller, a stress relief treatment is performed. When the impeller is subjected to stress relief treatment, the impeller is heated to 600-660° C., kept warm for not less than 4 hours, and then cooled to room temperature in a furnace.

[0033] Step 3) Process the outer diameter of the impeller. Process the outer diameter of the impeller after stress relief treatment. Figure 2 After machining the outer circle of the impeller, a machining allowance of 10 to 20 mm is retained on the outer circle of the impeller.

[0034] Step 4) Perform a second solution treatment on the impeller. When performing solution treatment on the impeller after external cylindrical processing, vacuum solution treatment is adopted, that is, after evacuating the heat treatment equipment, the impeller is heated to 800-900°C, 40Pa nitrogen is introduced, and after keeping the temperature for not less than 1h, it is heated to 1020-1060°C at a rate of ≤100°C / h, and after the temperature is kept for 0.5-1h, it is cooled to 50-80°C with 1-2Bar nitrogen and then taken out of the furnace for air cooling.

[0035] By subjecting the welded impeller to aging treatment again, the distribution of alloy elements in the steel can be adjusted, the phase transition temperature of martensite can be increased, more martensite structure can be obtained in the steel, and the strength and hardness of the impeller can be improved.

[0036] Step 5) Rough machining of the impeller. After the impeller after outer cylindrical machining is vacuum solution treated, the milled welded impeller is rough machined. Figure 3 After rough machining of impeller 1, a margin of 5 to 10 mm is reserved on the basis of the design size, and the thickness of the shaft disc side outlet is not less than 20 mm.

[0037] Adding a rough machining process here can reduce the allowance of the impeller heat treatment project, improve the material structure transformation effect, and obtain better material properties.

[0038] Step 6) Place the impeller on a tray for the second aging treatment. Figure 4 When the impeller is subjected to aging treatment after rough machining, the impeller 1 is first placed on the tray 2, while ensuring that the impeller 1 is concentric with the tray 2, and the outer diameter of the tray 2 is larger than the diameter of the impeller 1. Then the tray 2 is placed in the center of the heat treatment equipment to perform aging treatment on the impeller. The aging treatment of the impeller is a high-temperature aging treatment, that is, the impeller 1 is heated to 800-900℃, the heat preservation time is not less than 2 hours, and the impeller is cooled to room temperature at a cooling rate not less than air cooling after being taken out of the furnace.

[0039] See also Figure 5, the thickness of the tray 2 is not less than 40mm, and inner holes of φ80mm are evenly arranged on the circumference of the tray 2 at different radii from its center. This can not only reduce the weight of the tray 2, facilitate the operator to place it, and reduce the operating intensity, but also facilitate the flow of the cooling medium and the cooling of the impeller 1. At the same time, since the outer circle side of the impeller is the weak link of the impeller during the heat treatment process and is very easy to deform during the heat treatment process, the inner hole is not designed in the part outside the diameter of 900mm of the tray, so as to improve the rigidity of the outer circle side of the impeller, so that the deformation of the impeller during the heat treatment process can be effectively controlled while ensuring the impeller performance during the heat treatment process.

[0040] As a specific embodiment of the present invention, 6 inner holes of φ80 mm are evenly arranged on the circumference of the tray 2 with a diameter of 300 mm from the center thereof, 10 inner holes of φ80 mm are evenly arranged on the circumference of the tray 2 with a diameter of 600 mm from the center thereof, and 12 inner holes of φ80 mm are evenly arranged on the circumference of the tray 2 with a diameter of 900 mm from the center thereof.

[0041] Step 7) Perform a third aging treatment on the impeller. During the aging treatment, the impeller is heated to 480-650°C for a holding time of not less than 4 hours, and then taken out of the furnace and cooled to room temperature at a cooling rate not less than air cooling.

[0042] The large milled welded impeller heat treatment control method provided by the present invention optimizes the structural design of the impeller before heat treatment, designs a heat treatment tooling tray, and reasonably formulates the process parameters of the heat treatment, so that the deformation of the impeller during the heat treatment process is reduced while the designed mechanical properties of the impeller are met.

[0043] The heat treatment control method provided by the present invention is specifically described below by taking a large milled and welded impeller made of FV520B steel as an example.

[0044] Example 1

[0045] In the production of Φ1400mm impellers, the impeller cover and disc are subjected to solution treatment and aging treatment; after the impeller is welded and formed, it is subjected to stress relief treatment, the impeller outer circle is processed and the final performance heat treatment is carried out, and the performance heat treatment includes solution treatment, impeller rough processing, high temperature aging treatment and aging treatment.

[0046] (I) Preparatory heat treatment of impeller cover and impeller disc

[0047] Solution treatment: FV520B steel wheel cover and wheel disc are heated to 850℃, kept at this temperature for 2h, then heated to 1050℃ at 90℃ / h and kept at this temperature for 2.5h, and then taken out of the furnace and air-cooled.

[0048] Aging treatment: FV520B steel wheel cover and wheel disc are heated to 630℃, kept at this temperature for 5h, and then taken out of the furnace and air-cooled.

[0049] (II) After the impeller is welded, stress relief treatment is performed

[0050] Stress relief treatment: After welding with FV520B steel, the impeller is heated to 620℃, kept warm for 5h, and then furnace cooled to room temperature.

[0051] After stress relief, the impeller's outer diameter is machined to the designed diameter with a 10mm margin.

[0052] (III) The impeller undergoes performance heat treatment after processing

[0053] The solid solution treatment adopts vacuum heat treatment, that is, after the heat treatment equipment is evacuated, the FV520B steel is heated to 830℃, 40Pa nitrogen is introduced, and after keeping warm for 2h, it is heated to 1040℃ at 80℃ / h, and the holding time is 0.5h. Then, it is cooled to 50℃ with 1.5Bar nitrogen and air-cooled out of the furnace.

[0054] After solution treatment, the milled welded impeller is rough-machined, leaving a 5mm margin based on the design size, and the outlet thickness on the shaft disc side is 40mm.

[0055] Place a heat treatment tray with a thickness of 40 mm and an outer diameter of 1500 mm.

[0056] The rough-machined impeller is placed on a tray to ensure axial concentricity, and then subjected to high-temperature aging treatment. The FV520B steel is heated to 860°C for 2.5 hours and then air-cooled after being taken out of the furnace.

[0057] In the aging treatment, the FV520B steel was heated to 480°C and kept at this temperature for 5 hours, and then air-cooled.

[0058] After heat treatment, the mechanical properties of the impeller are shown in Table 1.

[0059] Table 1

[0060]

[0061] The changes in the coordinate dimensions of the impeller before and after heat treatment are shown in Table 2.

[0062] Table 2

[0063]

[0064] It can be seen from Table 1 and Table 2 that the heat treatment control method provided in the embodiment of the present invention can greatly reduce the deformation of the impeller during the heat treatment process while meeting the designed mechanical properties after heat treatment of the large milled and welded impeller.

[0065] Example 2

[0066] In the production of Φ1500mm impellers, the impeller cover and wheel disc are subjected to solid solution treatment, aging treatment and aging treatment; after the impeller is welded and formed, it is subjected to stress relief treatment, the impeller outer circle is processed and the final performance heat treatment is carried out, and the performance heat treatment includes solid solution treatment, impeller rough processing, high temperature aging treatment and aging treatment.

[0067] (I) Preparatory heat treatment of impeller cover and impeller disc

[0068] Solution treatment: FV520B steel wheel cover and wheel disc are heated to 850℃, kept at this temperature for 3h, then heated to 1050℃ at 90℃ / h and kept at this temperature for 7h, and then taken out of the furnace and air-cooled.

[0069] Aging treatment: FV520B steel wheel cover and wheel disc are heated to 625℃, kept warm for 20h, and then taken out of the furnace and oil cooled.

[0070] Aging treatment: FV520B steel wheel cover and wheel disc are heated to 620℃, kept at this temperature for 20h, and then taken out of the furnace and air-cooled.

[0071] (II) After the impeller is welded, stress relief treatment is performed

[0072] Stress relief treatment: After welding with FV520B steel, the impeller is heated to 660℃, kept warm for 6 hours, and then furnace cooled to room temperature.

[0073] After stress relief, the impeller's outer diameter is machined to the designed diameter with a 15mm margin.

[0074] (III) The impeller undergoes performance heat treatment after processing.

[0075] The solution treatment adopts vacuum heat treatment, that is, after the heat treatment equipment is evacuated, the FV520B steel is heated to 850℃, 40Pa nitrogen is introduced, and after keeping warm for 5h, it is heated to 1050℃ at 60℃ / h, kept warm for 1h, and then cooled to 60℃ with 2Bar nitrogen and air-cooled out of the furnace.

[0076] After solution treatment, the milled welded impeller is rough-machined, leaving a 7.5mm margin based on the design size, and the outlet thickness on the shaft disc side is 43mm.

[0077] Place the heat treatment tray, the tray thickness is 60mm and the tray outer diameter is 1800mm.

[0078] The rough-machined impeller is placed on a tray to ensure axial concentricity, and then subjected to high-temperature aging treatment. The FV520B steel is heated to 850°C for 3 hours and then air-cooled after being taken out of the furnace.

[0079] In the aging treatment, the FV520B steel was heated to 610℃ and kept at this temperature for 6 hours, and then air-cooled.

[0080] After heat treatment, the mechanical properties are shown in Table 3.

[0081] Table 3

[0082]

[0083] The changes in the coordinate dimensions of the impeller before and after heat treatment are shown in Table 4.

[0084] Table 4

[0085]

[0086] It can be seen from Tables 3 and 4 that the heat treatment control method provided in the embodiment of the present invention can greatly reduce the deformation of the impeller during the heat treatment process while satisfying the designed mechanical properties after heat treatment of the large milled and welded impeller.

[0087] The heat treatment control method for a large milled welded impeller provided by the present invention is not only applicable to the heat treatment of a large milled welded impeller made of FV520B steel, but can also be used for the heat treatment of a large milled welded impeller made of ASTM A705-630 steel, 17-4PH steel, S520B steel, etc. Moreover, the heat treatment method provided by the present invention can be used not only for the heat treatment of a milled welded impeller, but also for the heat treatment of other types of parts.

[0088] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A heat treatment control method for large milled and welded impellers. It is characterized in that The steps include: Performing a first solution treatment and a first aging treatment on the wheel cover and the wheel disc; After the wheel cover and wheel disc are welded into an impeller, stress relief treatment is performed; Perform external machining on the impeller; performing a second solution treatment on the impeller; Rough machining of the impeller; Place the impeller on a tray for the second aging treatment; Perform the third aging treatment on the impeller; During the second solution treatment of the impeller, the heat treatment equipment is evacuated, the impeller is heated to 800-900°C, 40Pa nitrogen is introduced, and after keeping the temperature for no less than 1h, it is heated to 1020-1060°C at a rate of ≤100°C / h. After the temperature is kept for 0.5-1h, it is cooled to 50-80°C with 1-2Bar nitrogen and then taken out of the furnace for air cooling; When the impeller is placed on a tray for the second aging treatment, the impeller and the tray are placed concentrically on the tray, the tray is placed at the center of the heat treatment equipment, the thickness of the tray is not less than 40 mm, the outer diameter of the tray is larger than the diameter of the impeller, and the tray is evenly provided with inner holes of φ80 mm on circles of different radii from the center within a diameter range of 900 mm.

2. The heat treatment control method for a large milled and welded impeller according to claim 1, Features: During the first solution treatment, the wheel cover and the wheel disc are heated to 800-900°C, kept warm for not less than 1 hour, and then heated to 1020-1060°C at a speed of ≤100°C / h, kept warm for not less than 2 hours, and then taken out of the furnace and cooled at a cooling rate not less than air cooling; during the first aging treatment, the wheel cover and the wheel disc are heated to 600-850°C, kept warm for not less than 4 hours, and then taken out of the furnace and cooled at a cooling rate not less than air cooling.

3. The heat treatment control method for a large milled and welded impeller according to claim 2, Features: The wheel cover and the wheel disc may be subjected to repeated first aging treatment after the first solution treatment and the first aging treatment.

4. The heat treatment control method for a large milled and welded impeller according to claim 1, Features: During the stress relief treatment, the impeller is heated to 600-660° C., kept at this temperature for not less than 4 hours, and then cooled to room temperature in the furnace.

5. The heat treatment control method for a large milled and welded impeller according to claim 1, Features: After the outer circle of the impeller is machined, a machining allowance of 10 to 20 mm is retained on the outer circle of the impeller.

6. The heat treatment control method for a large milled and welded impeller according to claim 1, Features: After the impeller is roughly machined, a margin of 5 to 10 mm is reserved on the basis of the design size, and the thickness of the shaft disc side outlet is not less than 20 mm.

7. The heat treatment control method for a large milled and welded impeller according to claim 1, Features: When the impeller is placed on a tray for the second aging treatment, the impeller is heated to 800-900° C. for a holding time of not less than 2 hours, and then cooled to room temperature at a cooling rate not less than air cooling after being taken out of the furnace.

8. The heat treatment control method for a large milled and welded impeller according to claim 1, Features: During the third aging treatment of the impeller, the impeller is heated to 480-650° C., kept at this temperature for not less than 4 hours, and then taken out of the furnace and cooled to room temperature at a cooling rate not less than that of air cooling.

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