A method of heat treating a heavy-duty gas turbine rotor

Abstract

The present application relates to a kind of heavy gas turbine rotor heat treatment method, belong to gas turbine technical field, solve the problem of different section performance difference of existing heavy gas turbine rotor.For the maximum flange of rotor, the outer diameter and length of well-type electric furnace are selected;The rotor is vertically placed on the base (or support) surface of well-type electric furnace, the center of rotor and the center of well-type furnace are coincided as far as possible, and the rotor is completely entered into the effective heating zone of well-type electric furnace;The rotor is heated in well-type electric furnace in stages and kept warm;The rotor is taken out of the furnace, immersed in water to control temperature, moved up and down in water, and taken out of water after the outer surface of the maximum flange of rotor is cooled to below 50℃;The rotor is returned to the furnace, the corresponding relationship between the placement position of each part of the rotor in the furnace and the electric furnace temperature control zone in well-type electric furnace is confirmed, the rotor is kept warm and heated to the first tempering temperature, the fine shaft neck part and large diameter part of the rotor are controlled in temperature, and the rotor is taken out of the furnace after being cooled to below 200℃.The performance difference of each part of the heavy gas turbine rotor is small.

Description

Technical Field

[0001] This invention belongs to the field of gas turbine technology, and particularly relates to a heat treatment method for a heavy-duty gas turbine rotor. Background Technology

[0002] A gas turbine is an internal combustion engine that uses a continuously flowing gas as its working fluid to drive a high-speed rotating impeller, converting the energy of fuel into useful work. It is a type of rotating impeller-type thermal engine. Gas turbines have advantages such as high thermal efficiency, low pollution, and low water consumption. Gas turbine units participating in combined cycle systems can achieve extremely high thermal efficiency and are widely used in thermal power generation, industrial applications, shipbuilding, railway transportation, military vehicles, and combined cooling, heating, and power (CCHP) systems.

[0003] Heavy-duty gas turbines are core power equipment for 21st-century energy efficiency conversion and clean utilization systems. Due to their extreme design and manufacturing complexity, they represent a concentrated reflection of a nation's industrial level, characterized by high technology intensity and a wide industrial impact. Heavy-duty gas turbine rotor forgings are the foundation and guarantee for advanced gas turbine design and manufacturing technologies. They need to meet requirements such as large diameter, minimal performance differences across different rotor cross-sections, and high strength. However, existing heat treatment processes for heavy-duty gas turbine rotor forgings result in uneven microstructure distribution and significant performance variations across different cross-sections, with some sections exhibiting weaker properties, failing to meet application requirements. Therefore, a new heat treatment method for heavy-duty gas turbine rotors is urgently needed to address the problem of significant performance differences across different cross-sections in existing heavy-duty gas turbine rotor forgings. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a heat treatment method for heavy-duty gas turbine rotors, solving the problems of large differences in the performance of different cross sections and weak overall performance of rotor forgings after heat treatment processes of existing heavy-duty gas turbine rotor forgings.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] On one hand, embodiments of the present invention provide a heat treatment method for a heavy-duty gas turbine rotor, comprising the following steps:

[0007] Step 1: Select a suitable pit furnace based on the outer diameter and length of the rotor's maximum flange;

[0008] Step 2: Loading the furnace: Place the rotor vertically on the base (or support) of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor must be fully inserted into the effective heating zone of the pit furnace;

[0009] Step 3: Heating: The rotor is heated and kept warm in stages in a pit furnace;

[0010] Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water for temperature control. The rotor moves up and down in the water to cool it down. After cooling, the outer diameter surface of the rotor's largest flange reaches below 50°C, and then it is taken out of the water.

[0011] Step 5: Tempering heat treatment: Return the rotor to the furnace, confirm the correspondence between the rotor's position in the furnace and the temperature control zone of the pit furnace, keep the rotor warm, heat to the first tempering temperature, control the temperature of the thin shaft neck and large diameter parts of the rotor in separate zones, and remove it from the furnace after cooling to below 200℃.

[0012] Further, in step 3, the staged heating and heat preservation includes: heating the rotor in a pit furnace from room temperature to 650±10℃ at a rate of 13-17℃ / h; heating the rotor in a pit furnace from 650±10℃ to 840±10℃ at a rate of 75-85℃ / h, and keeping it at that temperature for 15-17h.

[0013] Furthermore, in step 4, the water immersion temperature control ventilation includes: the rotor is completely immersed in water within 3-10 minutes after exiting the furnace, and the water temperature is controlled at 5-15℃.

[0014] Furthermore, in step 4, the up-and-down movement of the rotor in the water includes: within 30-40 minutes after the rotor is first immersed in water, the rotor is completely submerged in water and continuously moves up and down by 500-600 mm.

[0015] Furthermore, in step 4, the cooling rate is ≥1℃ / s, and the cooling time is 300-320min.

[0016] Furthermore, in step 5, the rotor insulation temperature is 100±20℃, and the insulation time is 5-6h.

[0017] Furthermore, in step 5, the heating rate is 25-30℃ / h.

[0018] Furthermore, in step 5, the first tempering temperature is 592±5℃.

[0019] Furthermore, in step 5, the temperature control of the rotor's thin neck section and large diameter section includes: controlling the temperature of the electric furnace temperature control zone corresponding to the rotor's thin neck section at 590℃±1℃ and holding it at that temperature for 30-35 hours; controlling the temperature of the electric furnace temperature control zone corresponding to the rotor's large diameter section at 587℃±1℃ and holding it at that temperature for 30-35 hours.

[0020] The present invention also provides a heavy-duty gas turbine rotor prepared according to the heat treatment method described above.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] 1. In the method of the present invention, after the rotor is taken out of the furnace, the rotor is quickly and completely immersed in water within 3-10 minutes. The water temperature is controlled at 10-15℃ and ventilation is carried out by air duct to ensure that the water in the water tank is fully flowing. Within 30-40 minutes of the start of immersion, the rotor is completely immersed in water and continuously moved up and down 500-600mm. This can make the cooling speed of each part of the rotor uniform and fast, and reduce the performance difference of each part of the rotor.

[0023] 2. In the heat treatment of rotor reflow, the present invention implements zoned temperature control for the tempering of the small diameter section and the large diameter section of the rotor. By controlling the temperature in zones, the strength difference between the large and small cross sections of the rotor is reduced, thereby improving the uniformity of the performance of each cross section of the rotor.

[0024] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from the description and drawings, which are particularly pointed out. Attached Figure Description

[0025] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0026] Figure 1 This is a heat treatment process diagram for the heavy-duty gas turbine rotor of the present invention;

[0027] Figure 2 This is a rough machining and sampling diagram of the heat treatment of the heavy-duty gas turbine rotor in Embodiment 1 of the present invention. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0029] This invention provides a heat treatment method for heavy-duty gas turbine rotors, comprising the following steps:

[0030] Step 1: Select a suitable pit furnace based on the outer diameter and length of the rotor's maximum flange;

[0031] Step 2: Loading the furnace: Place the rotor vertically on the base (or support) of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor must be fully inserted into the effective heating zone of the pit furnace;

[0032] Step 3: Heating: The rotor is heated and kept warm in stages in a pit furnace;

[0033] Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water for temperature control. The rotor moves up and down in the water to cool it down. After cooling, the outer diameter surface of the rotor's largest flange reaches below 50°C, and then it is taken out of the water.

[0034] Step 5: Tempering heat treatment: Return the rotor to the furnace, confirm the correspondence between the rotor's position in the furnace and the temperature control zone of the pit furnace, keep the rotor warm, heat to the first tempering temperature, control the temperature of the thin shaft neck and large diameter parts of the rotor in separate zones, and remove it from the furnace after cooling to below 200℃.

[0035] It should be noted that, as Figure 2 As shown, the thin journal of the rotor refers to the upper journal of the rotor's largest flange, the large diameter of the rotor refers to other parts of the rotor except for the upper diameter of the rotor's largest flange, and the electric furnace temperature control zone corresponding to the large diameter refers to the connection part of the two large flanges (including the flanges).

[0036] Existing heat treatment processes for heavy-duty gas turbine rotor forgings result in rotor forgings with uneven microstructure distribution across different cross-sections, leading to significant performance differences and weaker properties in some sections, failing to meet application requirements. The present invention addresses this by rapidly and completely immersing the rotor in water after it exits the furnace, controlling the water temperature, and using ductwork for ventilation and circulation to ensure sufficient water flow in the tank. Simultaneously, at the beginning of immersion, the rotor is continuously moved up and down to ensure uniform and rapid cooling of all parts, reducing performance differences between different sections. Furthermore, during the rotor's reheat heat treatment, the tempering of the smaller shaft diameter sections and the larger diameter sections is controlled by separate temperature zones. This zoned temperature control reduces the strength difference between the large and small cross-sections, improving the uniformity of performance across all rotor sections.

[0037] Specifically, in step 2, before loading the furnace, confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace. The thin neck of the rotor should be placed above the base of the pit furnace.

[0038] In step 3, the rotor is heated in stages in a pit furnace. The first stage heating process involves heating the rotor from room temperature to 650±10℃ at a rate of 13-17℃ / h. During this heating process, the rotor is in an elastic state. If the heating rate exceeds 17℃ / h, the rotor will experience significant stress and is prone to cracking. The second stage heating process involves heating the rotor from 650±10℃ to 840±10℃ at a rate of 75-85℃ / h and holding it at this temperature for 15-17 hours. During this process, the rotor is heated from the material's Ac1 temperature to its austenitizing temperature, which is beneficial for refining the rotor's grain size.

[0039] In step 4, the rotor is removed from the furnace and rapidly and completely immersed in water within 3-10 minutes. The water temperature is controlled at 5-15℃, and ventilation is provided using air ducts to ensure sufficient water flow in the tank. During the initial 30-40 minutes of immersion, the rotor must be completely submerged and continuously moved up and down 500-600mm to allow water flow between the rotor flanges, preventing the water temperature in this area from rising too quickly. This ensures a cooling rate ≥1℃ / s for the rotor. Within this cooling rate range, the rotor's microstructure transforms from austenite to lower bainite, with minimal differences in cooling rates across different parts, promoting uniform microstructure and properties. For rotors with perforated journals, the cooling chucks on the thinner journals are water-cooled for 150-160 minutes before being removed from the water. The principle for lifting the chucks is that the hole should just emerge from the water surface to prevent quenching cracks. For rotors without perforated journals, lifting the chucks is unnecessary. After 300-320 minutes of water cooling, when the outer surface temperature of the rotor's largest flange reaches below 50℃, the rotor is removed from the water and returned to the furnace.

[0040] Specifically, in step 5, before returning the rotor to the furnace, first confirm the correspondence between the rotor's placement in various parts of the furnace and the temperature control zones of the pit furnace. The thinner neck section should be placed above the base of the pit furnace. The rotor is held at 100±20℃ for 5-6 hours, then heated to 592±5℃ at a rate of 25-30℃ / h. The thinner neck section of the rotor corresponds to a temperature of 590±1℃ in the furnace temperature control zone, held for 30-35 hours. The larger diameter section of the rotor corresponds to a temperature of 587±1℃ in the furnace temperature control zone, held for 30-35 hours. It is then cooled to below 200℃ at a rate of 5-10℃ / h. Through tempering heat treatment, the microstructure of the rotor forging changes from lower bainite to tempered bainite. Figure 1 The diagram shows the heat treatment process of the heavy-duty gas turbine rotor of the present invention.

[0041] The heavy-duty gas turbine rotor that has undergone the above heat treatment has a yield strength (Rp0.2) of 850 MPa and a tensile strength of 950 MPa. The difference in yield strength (Rp0.2) between different parts of the rotor is ≤10 MPa and the difference in tensile strength is ≤10 MPa. Compared with heavy-duty gas turbine rotors prepared by existing methods, this reduces the performance differences between different parts of the rotor and improves the uniformity of the performance of different sections of the rotor.

[0042] The advantages of the heat treatment process and precise control of process parameters of the present invention will be demonstrated below with specific embodiments and comparative examples.

[0043] Example 1

[0044] Heat treatment is performed on the forged heavy-duty gas turbine rotor forgings, taking the heavy-duty gas turbine rotor used in a power plant as an example:

[0045] Material: 26Cr2Ni4MoV;

[0046] Rotor dimensions: outer diameters of the three flanges of the rotor. And thickness H are respectively 527mm; 431mm; 284mm; the upper end shaft diameter of the rotor's largest flange is equal to the outer diameter of the rotor's thin journal. Length L1867mm; Total rotor length 4749mm. Weight 23328KG.

[0047] The heat treatment process for the rotary engine rotor is as follows:

[0048] Step 1: Based on the outer diameter of the rotor's maximum flange With a total rotor length of 4749mm, the selected pit-type electric furnace size is...

[0049] Step 2: Loading the furnace: Place the rotor vertically on the base (or support) of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor fully entering the effective heating zone of the pit furnace; confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace, and place the thin shaft neck on top of the pit furnace.

[0050] Step 3: Heating: The rotor is heated in stages in a pit furnace. The first stage heating process is: the rotor is heated from room temperature to 650±10℃ in the pit furnace at a rate of 15℃ / h; the second stage heating process is: the rotor is heated from 650±10℃ to 840±10℃ in the pit furnace at a rate of 80℃ / h, and held at that temperature for 15h.

[0051] Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water within 10 minutes, with the water temperature controlled at 5-15℃ and ventilation provided by air ducts; within the first 30 minutes of immersion, the rotor must be fully immersed in water and continuously moved up and down 500-600mm; after cooling for 300 minutes, the outer surface temperature of the rotor's largest flange should reach below 50℃; the lifting chuck of the fine journal is water-cooled for 150 minutes and then removed from the water.

[0052] Step 5: Tempering heat treatment: Return the rotor to the furnace and confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace. The thin shaft neck should be placed on top of the pit furnace.

[0053] The rotor is kept at 100±20℃ for 5 hours; then heated to 590±5℃ at a rate of 30℃ / h, and the temperature of the thin-necked section is controlled at 590℃ in the electric furnace temperature control zone for 30 hours; the temperature of the other large-diameter sections is controlled at 587℃ in the electric furnace temperature control zone for 30 hours; and then cooled to below 200℃ at a rate of 10℃ / h before being removed from the furnace.

[0054] Step 6: Remove from the furnace. Lift the heat-treated rotor and take it out to complete the heat treatment process.

[0055] The heat-treated rotor was machined. Ultrasonic testing revealed no cracks, indicating the rotor met quality standards. Figure 2 As shown, samples were taken from radial specimen X1, radial specimen X2, longitudinal specimen L1, and longitudinal specimen L2 for performance testing. The performance tests were qualified, and the yield strength (Rp0.2) reached 850MPa. The performance test data are shown in Table 1.

[0056] Example 2

[0057] The rotor to be heat-treated in this embodiment is the same as in Embodiment 1. The heat treatment process for this rechargeable gas turbine rotor is as follows:

[0058] Step 1: Based on the outer diameter of the rotor's maximum flange (1776mm) and the total rotor length (4749mm), select the dimensions of the pit-type electric furnace as follows:

[0059] Step 2: Loading the furnace: Place the rotor vertically on the base (or support) of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor fully entering the effective heating zone of the pit furnace; confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace, and place the thin shaft neck on top of the pit furnace.

[0060] Step 3: Heating: The rotor is heated in stages in a pit furnace. The first stage heating process is: the rotor is heated from room temperature to 650±10℃ in the pit furnace at a rate of 17℃ / h; the second stage heating process is: the rotor is heated from 650±10℃ to 840±10℃ in the pit furnace at a rate of 75℃ / h, and held at that temperature for 17h.

[0061] Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water within 3 minutes, with the water temperature controlled at 5-15℃ and ventilation provided by air ducts; within 40 minutes of the start of immersion, the rotor must be fully immersed in water and continuously moved up and down 500-600mm; after 300 minutes of cooling, the outer surface temperature of the rotor's largest flange should reach below 50℃; the lifting chuck of the fine journal is water-cooled for 150 minutes and then removed from the water.

[0062] Step 5: Tempering heat treatment: Return the rotor to the furnace and confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace. The thin shaft neck should be placed on top of the pit furnace.

[0063] The rotor is kept at 100±20℃ for 6 hours; then heated to 590±5℃ at a rate of 25℃ / h, with the temperature of the thin-necked section corresponding to the electric furnace temperature control zone controlled at 591℃ for 32 hours; the temperature of the other large-diameter sections corresponding to the electric furnace temperature control zone controlled at 588℃ for 32 hours; and then cooled to below 200℃ at a rate of 5℃ / h before being removed from the furnace.

[0064] Step 6: Remove from the furnace. Lift the heat-treated rotor and take it out to complete the heat treatment process.

[0065] The heat-treated rotor was machined. Ultrasonic testing revealed no cracks, indicating the rotor met quality standards. Figure 2 As shown, samples were taken from radial specimen X1, radial specimen X2, longitudinal specimen L1, and longitudinal specimen L2 for performance testing. The performance tests were qualified, and the yield strength (Rp0.2) reached 850MPa. The performance test data are shown in Table 1.

[0066] Example 3

[0067] The rotor to be heat-treated in this embodiment is the same as in Embodiment 1. The heat treatment process for this rechargeable gas turbine rotor is as follows:

[0068] Step 1: Based on the outer diameter of the rotor's maximum flange (1776mm) and the total rotor length (4749mm), select the dimensions of the pit-type electric furnace as follows:

[0069] Step 2: Loading the furnace: Place the rotor vertically on the base (or support) of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor fully entering the effective heating zone of the pit furnace; confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace, and place the thin shaft neck on top of the pit furnace.

[0070] Step 3: Heating: The rotor is heated in stages in a pit furnace. The first stage of heating is as follows: the rotor is heated from room temperature to 650±10℃ in the pit furnace at a rate of 13℃ / h. The second stage of heating is as follows: the rotor is heated from 650±10℃ to 840±10℃ in the pit furnace at a rate of 85℃ / h, and held at that temperature for 16 hours.

[0071] Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water within 5 minutes, with the water temperature controlled at 5-15℃ and ventilation provided by air ducts; within 40 minutes of the start of immersion, the rotor must be fully immersed in water and continuously moved up and down 500-600mm; after 300 minutes of cooling, the outer surface temperature of the rotor's largest flange should reach below 50℃; the lifting chuck of the fine journal is water-cooled for 150 minutes and then removed from the water.

[0072] Step 5: Tempering heat treatment: Return the rotor to the furnace and confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace. The thin shaft neck should be placed on top of the pit furnace.

[0073] The rotor is kept at 100±20℃ for 6 hours; then heated to 590±5℃ at a rate of 28℃ / h, and the temperature of the thin-necked part is controlled at 589℃ in the electric furnace temperature control zone for 35 hours; the temperature of the other large-diameter parts is controlled at 586℃ in the electric furnace temperature control zone for 35 hours; and then cooled to below 200℃ at a rate of 8℃ / h before being removed from the furnace.

[0074] Step 6: Remove from the furnace. Lift the heat-treated rotor and take it out to complete the heat treatment process.

[0075] The heat-treated rotor was machined. Ultrasonic testing revealed no cracks, indicating the rotor met quality standards. Figure 2 As shown, samples were taken from radial specimen X1, radial specimen X2, longitudinal specimen L1, and longitudinal specimen L2 for performance testing. The performance tests were qualified, and the yield strength (Rp0.2) reached 850MPa. The performance test data are shown in Table 1.

[0076] Comparative Example 1

[0077] The rotor to be heat-treated in this comparative example is the same as that in Example 1. The heat treatment process for this rechargeable gas turbine rotor is as follows:

[0078] Step 1: Based on the outer diameter of the rotor's maximum flange (1776mm) and the total rotor length (4749mm), select the dimensions of the pit-type electric furnace as follows:

[0079] Step 2: Loading the furnace: Place the rotor vertically on the base (or support) of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor fully entering the effective heating zone of the pit furnace; confirm the correspondence between the placement of the rotor in various parts of the furnace and the temperature control zone of the pit furnace, and place the thin shaft neck on top of the pit furnace.

[0080] Step 3: Heating: The rotor is heated in stages in a pit furnace. The first stage heating process is: the rotor is heated from room temperature to 650±10℃ in the pit furnace at a rate of 10℃ / h; the second stage heating process is: the rotor is heated from 650±10℃ to 840±10℃ in the pit furnace at a rate of 60℃ / h, and held at that temperature for 13h.

[0081] Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water for 15 minutes, with the water temperature controlled at 5-15℃ and ventilation provided by air ducts; after cooling for 300 minutes, the outer surface temperature of the rotor's largest flange reaches below 50℃; the lifting chuck of the thin journal is water-cooled for 150 minutes and then removed from the water.

[0082] Step 5: Tempering heat treatment: The rotor is returned to the furnace and held at 100±20℃ for 4 hours; then heated to 590±5℃ at a rate of 20℃ / h and held for 30 hours; then cooled to below 200℃ at a rate of 10℃ / h before being removed from the furnace.

[0083] Step 6: Remove from the furnace. Lift the heat-treated rotor and take it out to complete the heat treatment process.

[0084] The heat-treated rotor was machined. Ultrasonic testing revealed no cracks, indicating the rotor was substandard. For example... Figure 2 As shown, samples were taken from radial specimen X1, radial specimen X2, longitudinal specimen L1, and longitudinal specimen L2 for performance testing. Some performance tests were unqualified, with the yield strength (Rp0.2) not reaching the 850MPa level. The yield strength (Rp0.2) at radial specimen X1 was 848MPa. The performance test data are shown in Table 1.

[0085] Comparative Example 2

[0086] The rotor to be heat-treated in this comparative example is the same as that in Example 1. The heat treatment process for this rechargeable gas turbine rotor is as follows:

[0087] Step 1: Based on the outer diameter of the rotor's maximum flange (1776mm) and the total rotor length (4749mm), select the dimensions of the pit-type electric furnace as follows:

[0088] Step 2: Loading the furnace: Place the rotor vertically on the base (or support) of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor fully enters the effective heating zone of the pit furnace;

[0089] Step 3: Heating: The rotor is heated in stages in a pit furnace. The first stage heating process is: the rotor is heated from room temperature to 650±10℃ in the pit furnace at a rate of 25℃ / h; the second stage heating process is: the rotor is heated from 650±10℃ to 840±10℃ in the pit furnace at a rate of 50℃ / h, and held at that temperature for 20h.

[0090] Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water within 5 minutes. The water temperature is controlled at 5-15℃ and ventilation is provided by air ducts. After the rotor is taken out of the furnace, it is completely immersed in water for cooling. Within 40 minutes of the start of immersion, the rotor must be completely immersed in water and continuously moved up and down 500-600mm. After 300 minutes of cooling, the maximum outer diameter surface temperature of the rotor reaches below 50℃. The chuck of the fine journal is water-cooled for 150 minutes and then removed from the water.

[0091] Step 5: Tempering heat treatment: The rotor is returned to the furnace and held at 100±20℃ for 4 hours; then heated to 590±5℃ at a rate of 30℃ / h and held for 37 hours; then cooled to below 200℃ at a rate of 10℃ / h and removed from the furnace.

[0092] Step 6: Remove from the furnace. Lift the heat-treated rotor and take it out to complete the heat treatment process.

[0093] The heat-treated rotor was machined. Ultrasonic testing revealed no cracks, indicating the rotor met quality standards. Figure 2 As shown, samples were taken from radial specimen X1, radial specimen X2, longitudinal specimen L1, and longitudinal specimen L2 for performance testing. The performance tests were satisfactory, with a yield strength (Rp0.2) reaching 850 MPa. However, the strength fluctuation values ​​at each sampling location exceeded 30 MPa, indicating large and uneven performance variations. The performance test data are shown in Table 1. The specific process parameters for the examples and comparative examples are shown in Table 2.

[0094] Table 1. Room temperature performance of the examples and comparative examples.

[0095]

[0096] Table 2. Specific process parameters for the examples and comparative examples.

[0097]

[0098]

[0099] As can be seen from Tables 1 and 2, the heavy-duty gas turbine rotor obtained by the heat treatment method of this invention achieves a yield strength (Rp0.2) of 850 MPa and a tensile strength of 950 MPa. In Comparative Example 1, some process parameters are not within the range required by this invention. During the water circulation cooling process, the operations required by this invention were not performed, nor was the tempering treatment with zoned temperature control for the rotor's thin journals and other large-diameter parts carried out. The performance testing of the final prepared heavy-duty gas turbine rotor showed that the yield strength (Rp0.2) in some areas did not reach the 850 MPa level, and the tensile strength did not reach the 950 MPa level. Furthermore, the fluctuation values ​​of the yield strength and tensile strength were significantly greater than those in the embodiment of this invention. Similarly, in Comparative Example 2, some process parameters are not within the range required by this invention. The tempering treatment with zoned temperature control for the rotor's thin journals and other large-diameter parts was not performed. Consequently, the tensile strength in some areas did not reach the 950 MPa level, and the fluctuation values ​​of the yield strength (Rp0.2) and tensile strength were significantly greater than those in the embodiment of this invention.

[0100] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat treatment method for a heavy-duty gas turbine rotor, characterized in that, Includes the following steps: Step 1: Select a suitable pit furnace based on the outer diameter and length of the rotor's maximum flange; Step 2: Loading the furnace: Place the rotor vertically on the base of the pit furnace, with the center of the rotor coinciding with the center of the pit furnace as much as possible, and the rotor must be fully inserted into the effective heating zone of the pit furnace; Step 3: Heating: The rotor is heated and kept warm in stages in a pit furnace; Step 4: Cooling: After the rotor is taken out of the furnace, it is immersed in water for temperature control. The rotor moves up and down in the water to cool it down. After cooling, the outer diameter surface of the rotor's largest flange reaches below 50°C, and then it is taken out of the water. Step 5: Tempering heat treatment: Return the rotor to the furnace, confirm the correspondence between the rotor's position in the furnace and the temperature control zone of the pit furnace, keep the rotor warm, heat to the first tempering temperature, control the temperature of the thin shaft neck and large diameter parts of the rotor in separate zones, and remove it from the furnace after cooling to below 200℃. In step 3, the staged heating and heat preservation includes: heating the rotor in a pit furnace from room temperature to 650±10℃ at a rate of 13-17℃ / h; heating the rotor in a pit furnace from 650±10℃ to 840±10℃ at a rate of 75-85℃ / h, and holding it at that temperature for 15-17h. In step 4, the water immersion temperature control includes: the rotor is completely immersed in water within 3-10 minutes after exiting the furnace, and the water temperature is controlled at 5-15℃; the rotor moving up and down in the water includes: within 30-40 minutes after the rotor is immersed in water, the rotor is completely submerged in water and moves up and down continuously for 500-600mm; the cooling rate is ≥1℃ / s, and the cooling time is 300-320min. In step 5, the temperature control of the rotor's thin neck and large diameter sections includes: controlling the temperature of the electric furnace temperature control zone corresponding to the rotor's thin neck section at 590℃±1℃ and holding it at that temperature for 30-35 hours; and controlling the temperature of the electric furnace temperature control zone corresponding to the rotor's large diameter section at 587℃±1℃ and holding it at that temperature for 30-35 hours. The heavy-duty gas turbine rotor is made of 26Cr2Ni4MoV material with a yield strength Rp. 0.2 The tensile strength reaches 850 MPa, the yield strength Rp of various parts of the rotor reaches 950 MPa. 0.2 The difference in strength fluctuation is ≤10MPa, and the difference in tensile strength fluctuation is ≤10MPa.

2. The heat treatment method according to claim 1, characterized in that, In step 3, the staged heating and heat preservation includes: heating the rotor in a pit furnace from room temperature to 650±10℃ at a rate of 15-17℃ / h; heating the rotor in a pit furnace from 650±10℃ to 840±10℃ at a rate of 75-80℃ / h, and keeping it at that temperature for 15-17h.

3. The heat treatment method according to claim 2, characterized in that, In step 5, the rotor is kept at a temperature of 100±20℃ for 5-6 hours.

4. The heat treatment method according to claim 3, characterized in that, In step 5, the heating rate is 25-30℃ / h.

5. The heat treatment method according to claim 4, characterized in that, In step 5, the first tempering temperature is 592±5℃.

6. The heat treatment method according to claim 5, characterized in that, In step 5, the temperature control of the rotor's thin neck section and large diameter section includes: controlling the temperature of the electric furnace temperature control zone corresponding to the rotor's thin neck section at 590℃±1℃ and holding it at that temperature for 30-32 hours; controlling the temperature of the electric furnace temperature control zone corresponding to the rotor's large diameter section at 587℃±1℃ and holding it at that temperature for 30-32 hours.

7. A heavy-duty gas turbine rotor prepared by the heat treatment method according to any one of claims 1-6.

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