Heat treatment method of 26NiCrMoV145 steel rotor forging
By adopting a multi-step process in the heat treatment of 26NiCrMoV145 steel rotor forging, including step heating and multiple forging, combined with preparatory heat and performance heat treatment, the problems of forging brittleness and uneven tissues are solved, and high performance and stability are achieved.
Patent Information
- Application Number
- CN202411892288.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-03-14
AI Technical Summary
26NiCrMoV145 steel rotor forgings are prone to tempering brittleness and tissue unevenness during hot processing, resulting in unstable performance and making manufacturing difficult.
Step-by-step heating treatment, controlled forging, furnace rehabilitation treatment, controlled forging and air-cooling treatment are adopted, combining preparatory heat treatment and performance heat treatment, including quenching, batch liquid cooling and tempering treatment, and optimized processes to control forging structure and reduce residual stress.
It realizes uniformity of forging structure and stability, improves toughness, strength and corrosion resistance, reduces the frequency of rework and production costs, and extends the service life of the rotor.
Smart Images
Figure CN119614812A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of heat treatment methods for steel parts, and relates to a heat treatment method for a steel rotor forging, and in particular to a heat treatment method for a 26NiCrMoV145 steel rotor forging. Background Art
[0002] With the rapid development of industrialization, generators are increasingly used in industry, national defense and science and technology. Large-scale generator sets are the basis for improving power generation efficiency. As the demand for the capacity of single generator sets increases, the size and weight of generator rotors are gradually required to be larger. As the most important component of power generation equipment, the generator rotor needs to have good comprehensive properties such as good toughness, strength and corrosion resistance under extreme service conditions of high weight and high speed.
[0003] 26NiCrMoV145 steel is a low carbon NiCrMoV steel. It can be used to manufacture turbine and generator rotor forgings because of its high strength and toughness, excellent tensile strength and yield strength, good elongation and impact work, low brittle transition temperature, high temperature durability and creep performance, good quenching performance and corrosion resistance.
[0004] Since the working conditions of rotor steel for generator sets are relatively extreme, rotor steel forgings need to have excellent comprehensive mechanical properties, so materials with high chemical purity and high homogeneity should be considered to ensure the refinement of forging structure. Since rotors are mostly heavy parts, their raw material specifications are large, but the larger the steel ingot, the more serious the segregation and the more internal defects. The production of forgings of such materials requires advanced technology and strict control methods.
[0005] However, 26NiCrMoV145 has a tendency to temper brittleness. The segregation of P and trace impurity elements such as Sn, As or Sb on the grain boundaries is the cause of embrittlement. During the hot working manufacturing process of the rotor, due to the strong inheritance of grains and grain boundaries, mixed crystals and coarse crystals are produced in the internal structure of the rotor, making the performance of the rotor product unstable and bringing great difficulties to the manufacture of rotor forgings. Analyzing and improving the process of such forgings is of great significance to improving the quality of the rotor. Summary of the invention
[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a heat treatment method for 26NiCrMoV145 steel rotor forgings, which realizes internal control of harmful elements in the forgings, and the forgings have a more uniform structure, which guarantees the first-time pass rate of the steel rotor forgings to a certain extent, reduces the frequency of rework, and is conducive to reducing production costs and reducing the labor intensity of workshop workers.
[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:
[0008] The present invention provides a heat treatment method for a 26NiCrMoV145 steel rotor forging, the heat treatment method comprising the following steps:
[0009] (1) A 26NiCrMoV145 steel ingot is subjected to step-wise heating treatment, controlled forging, remelting treatment, controlled shape forging and air cooling treatment in sequence to obtain a sintered billet;
[0010] (2) sequentially performing preliminary heat treatment, rough machining treatment and performance heat treatment on the calcined blank obtained in step (1);
[0011] The performance heat treatment includes quenching treatment, intermittent liquid cooling treatment and tempering treatment performed in sequence.
[0012] The purposes of the preliminary heat treatment described in the present invention are: (1) improving the structure: improving the structure of the forging, refining the grains, and solving the problem of grains and mixed crystals in the forging structure; (2) recrystallization: through the recrystallization process, the grains are refined, the structure is improved, and the performance is improved, and the defects detected by ultrasound are minimized; (3) dehydrogenation: ensuring the toughness of the forging and avoiding the generation of white spots; (4) eliminating thermal stress: reducing the surface hardness and improving the cold working performance;
[0013] The purpose of the performance heat treatment is to: minimize residual stress; avoid temper brittleness and prevent local segregation;
[0014] The present invention can ensure that the steel rotor forging has good comprehensive properties such as good toughness, strength and corrosion resistance by optimizing the post-forging preliminary heat treatment and performance heat treatment process, ensure the safety and reliability of the rotor under extreme working conditions, and extend the service life of the rotor.
[0015] As a preferred technical solution of the present invention, the step-by-step heating treatment in step (1) includes a first-stage heating treatment and a second-stage heating treatment performed sequentially.
[0016] Preferably, the temperature of the first heating treatment is 635-665°C, for example, it can be 635°C, 640°C, 645°C, 650°C, 655°C, 660°C or 665°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0017] Preferably, the insulation time per millimeter of effective thickness in the heating treatment is 0.3 to 0.4 min, for example, it can be 0.3 min, 0.32 min, 0.34 min, 0.36 min, 0.38 min or 0.4 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0018] Preferably, the temperature of the second stage heating treatment is 1235-1265°C, for example, it can be 1235°C, 1240°C, 1245°C, 1250°C, 1255°C, 1260°C or 1265°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0019] Preferably, the insulation time per millimeter of effective thickness in the heating treatment is 0.4 to 0.5 min, for example, it can be 0.4 min, 0.42 min, 0.44 min, 0.46 min, 0.48 min or 0.5 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0020] As a preferred technical solution of the present invention, the controlled forging in step (1) includes two upsetting operations and two drawing operations performed sequentially.
[0021] Preferably, the forging ratio of each controlled forging in step (1) is ≥2, for example, it can be 2, 2.1, 2.2, 2.3, 2.4 or 2.5, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0022] Preferably, the deformation amount of each controlled forging in step (1) is ≥50%, for example, it can be 50%, 52%, 54%, 56%, 58% or 60%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0023] Preferably, the final forging temperature of the controlled forging in step (1) is ≥900°C, for example, it can be 900°C, 910°C, 920°C, 930°C, 940°C, 950°C or 960°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0024] Preferably, the temperature of the remelting treatment in step (1) is 1185-1215°C, for example, it can be 1185°C, 1190°C, 1195°C, 1200°C, 1205°C, 1210°C or 1215°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0025] Preferably, the holding time per millimeter of effective thickness in the remelting treatment in step (1) is 0.2 to 0.3 min, for example, it can be 0.2 min, 0.22 min, 0.24 min, 0.26 min, 0.28 min or 0.3 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0026] Preferably, the shape-controlled forging in step (1) includes an upsetting process.
[0027] Preferably, the deformation amount of the upsetting treatment is 45-50%, for example, it can be 45%, 46%, 47%, 48%, 49% or 50%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0028] It is worth noting that the deformation amount of the controlled forging described in the present invention is greater than the deformation amount of the controlled forging described. Its purpose is to make the structure of the forging uniformly deformed, reduce the dead zone, transform the cast structure into the forged structure, refine the structure grains, and lay the foundation for subsequent heat treatment.
[0029] Preferably, the terminal temperature of the air cooling treatment in step (1) is ≥350°C, for example, it can be 350°C, 360°C, 370°C, 380°C, 390°C or 400°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0030] It is worth mentioning that due to the large volume of the 26NiCrMoV145 steel ingot being processed, a step-by-step heating treatment is adopted to allow the steel ingot to be heated through, further reducing the temperature difference between the surface and the core of the steel ingot, and preventing the surface from overheating while the core is not yet warm. If the surface is overheated or overburned, the ingot structure will be destroyed, and better performance cannot be obtained.
[0031] In addition, the present invention controls the temperature of the controlled forging (the initial forging temperature is 1235-1265°C, and the final forging temperature is ≥900°C) to prevent grain growth; the purpose of using two upsetting and two stretching in sequence during the controlled forging process is to ensure that the forging blank is fully deformed and improve the structure of the forging blank;
[0032] The present invention also prevents the growth of grains through controlled shape forging at low temperature (1185-1215° C.), which is beneficial to organizational improvement.
[0033] As a preferred technical solution of the present invention, the preliminary heat treatment in step (2) includes normalizing treatment, primary air cooling, material heat preservation treatment, complete annealing treatment, furnace cooling and secondary air cooling performed in sequence.
[0034] As a preferred technical solution of the present invention, the heating rate of the normalizing treatment is ≤120°C / h, for example, it can be 120°C / h, 115°C / h, 110°C / h, 105°C / h, 100°C / h or 95°C / h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0035] Preferably, the holding temperature of the normalizing treatment is 910-930°C, for example, it can be 910°C, 915°C, 920°C, 925°C or 930°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0036] Preferably, the holding time of the normalizing treatment is 0.5-0.7 min / mm×effective thickness+90 min, wherein the specific value of 0.5-0.7 min / mm can be, for example, 0.5 min / mm, 0.54 min / mm, 0.58 min / mm, 0.62 min / mm, 0.66 min / mm or 0.7 min / mm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0037] Preferably, the endpoint temperature of the primary air cooling is 190-210°C, for example, 190°C, 195°C, 200°C, 205°C or 210°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0038] Preferably, the insulation temperature of the material to be heat-insulated is 190-210°C, for example, it can be 190°C, 195°C, 200°C, 205°C or 210°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0039] Preferably, the insulation time of the material to be heat-insulated is 2 to 2.5 h, for example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0040] As a preferred technical solution of the present invention, the complete annealing treatment includes a first-stage annealing treatment, a second-stage annealing treatment and a third-stage annealing treatment performed sequentially.
[0041] Preferably, the heating rate of the annealing treatment is ≤50°C / h, for example, it can be 50°C / h, 48°C / h, 46°C / h, 44°C / h, 42°C / h or 40°C / h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0042] Preferably, the holding temperature of the annealing treatment is 630-650°C, for example, it can be 630°C, 634°C, 638°C, 642°C, 646°C or 650°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0043] Preferably, the holding time of the annealing treatment is 2 to 2.5 h, for example, 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0044] Preferably, the heating rate of the second-stage annealing treatment is ≤120°C / h, for example, it can be 120°C / h, 115°C / h, 110°C / h, 105°C / h, 100°C / h or 95°C / h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0045] Preferably, the holding temperature of the second-stage annealing treatment is 870-890°C, for example, it can be 870°C, 874°C, 878°C, 882°C, 886°C or 890°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0046] Preferably, the holding time of the second-stage annealing treatment is 0.5-0.7 min / mm×effective thickness+90 min, wherein the specific value of 0.5-0.7 min / mm can be, for example, 0.5 min / mm, 0.54 min / mm, 0.58 min / mm, 0.62 min / mm, 0.66 min / mm or 0.7 min / mm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0047] Preferably, the holding temperature of the three-stage annealing treatment is 670-690°C, for example, it can be 670°C, 674°C, 678°C, 682°C, 686°C or 690°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0048] Preferably, the holding time of the three-stage annealing treatment is 0.6-0.8 min / mm×effective thickness+120 min, and the specific value of 0.6-0.8 min / mm can be, for example, 0.6 min / mm, 0.64 min / mm, 0.68 min / mm, 0.72 min / mm, 0.76 min / mm or 0.8 min / mm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0049] As a preferred technical solution of the present invention, the terminal temperature of the furnace cooling is 340-360°C, for example, it can be 340°C, 344°C, 348°C, 352°C, 356°C or 360°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0050] Preferably, the terminal temperature of the secondary air cooling is 20-30°C, for example, it can be 20°C, 22°C, 24°C, 26°C, 28°C or 30°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0051] It is worth noting that the preliminary heat treatment described in the present invention can effectively improve the blank structure, refine the grains, solve the problem of grains and mixed crystals in the forging structure, reduce the genetic tendency of the raw material structure to a certain extent, and annealing can transform austenite into ferrite as soon as possible after forging, achieve the effect of dehydrogenation, avoid the generation of white spots, ensure the toughness of the forging, and lay the foundation for the stability of the rotor product performance.
[0052] In addition, the rough turning allowance in the rough machining process is determined according to the structural dimensions of the product, and the rough machining process can promote uniform performance heat treatment of the workpiece.
[0053] As a preferred technical solution of the present invention, the heating rate of the quenching treatment is ≤100°C / h, for example, it can be 100°C / h, 95°C / h, 90°C / h, 85°C / h, 80°C / h or 75°C / h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0054] Preferably, the holding temperature of the quenching treatment is 840-860°C, for example, it can be 840°C, 844°C, 848°C, 852°C, 856°C or 860°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0055] Preferably, the holding time of the quenching treatment is 0.5-0.7 min / mm×effective thickness+90 min, wherein the specific value of 0.5-0.7 min / mm can be, for example, 0.5 min / mm, 0.54 min / mm, 0.58 min / mm, 0.62 min / mm, 0.66 min / mm or 0.7 min / mm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0056] In the present invention, the temperature of the quenching treatment is 840-860°C. If the temperature is too high, the microstructure inside the material will change, the compound will partially dissolve, and the network will be disconnected, and the workpiece surface will be decarburized and the grains will be coarse. If the temperature is too low, it will lead to: austenite is not fully formed, and in addition to martensite, a small amount of ferrite remains in the structure, which will cause defects such as insufficient hardness, uneven structure, and soft spots. In addition, it will also cause the martensite structure after quenching to be coarse and brittle, thereby increasing the tendency of steel parts to crack and deform.
[0057] As a preferred technical solution of the present invention, the intermittent liquid cooling treatment includes a first liquid cooling, a first air cooling, and repeated second liquid cooling and second air cooling.
[0058] Preferably, the first liquid cooling time is 5 to 6 minutes, for example, 5 minutes, 5.2 minutes, 5.4 minutes, 5.6 minutes, 5.8 minutes or 6 minutes, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0059] Preferably, the first air-cooling endpoint temperature is 350-400°C, for example, it can be 350°C, 360°C, 370°C, 380°C, 390°C or 400°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0060] Preferably, the second liquid cooling time is 1 to 2 minutes, for example, 1 minute, 1.2 minutes, 1.4 minutes, 1.6 minutes, 1.8 minutes or 2 minutes, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0061] Preferably, the return time of the second air cooling is 2.5 to 3.5 min, for example, it can be 2.5 min, 2.7 min, 2.9 min, 3.1 min, 3.3 min or 3.5 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0062] Preferably, the endpoint of the intermittent liquid cooling treatment is: the surface and core temperatures of the steel rotor forging are both 100-200°C, for example, 100°C, 120°C, 140°C, 160°C, 180°C or 200°C, but are not limited to the listed values, and other values not listed within the numerical range are equally applicable; and the temperature difference between the surface and the core is ≤100°C, for example, 100°C, 95°C, 90°C, 85°C, 80°C, 75°C or 70°C, etc., but are not limited to the listed values, and other values not listed within the numerical range are equally applicable.
[0063] Preferably, the cooling liquid used in the intermittent liquid cooling treatment comprises a PAG solution.
[0064] Preferably, the concentration of the PAG solution is 6-10wt%, for example, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0065] It is worth noting that the intermittent liquid cooling treatment of the present invention can ensure that the residual stress is reduced to the maximum extent;
[0066] In addition, after quenching the billet, the tempered bainite structure can be obtained, which has the highest creep limit and endurance strength. Therefore, obtaining a uniform bainite structure after quenching is used as the main basis for formulating the performance heat treatment process.
[0067] As a preferred technical solution of the present invention, the heating rate of the tempering treatment is ≤120°C / h, for example, it can be 120°C / h, 115°C / h, 110°C / h, 105°C / h or 100°C / h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0068] Preferably, the holding temperature of the tempering treatment is ≥ 600°C, for example, it can be 600°C, 610°C, 620°C, 630°C, 640°C or 650°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0069] Preferably, the holding time of the tempering treatment is 0.6-0.8 min / mm×effective thickness+120 min, wherein the specific value of 0.6-0.8 min / mm can be, for example, 0.6 min / mm, 0.64 min / mm, 0.68 min / mm, 0.72 min / mm, 0.76 min / mm or 0.8 min / mm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0070] Preferably, the tempering treatment further includes air cooling treatment.
[0071] It is worth noting that the temperature in the tempering treatment of the present invention needs to avoid the temper brittleness region of the 26NiCrMoV145 material to prevent the carbide from precipitating too quickly and coarsening to cause local segregation;
[0072] In addition, air cooling after tempering can reduce the residual stress of the workpiece to a certain extent, laying the foundation for the high-intensity operation of the rotor.
[0073] The numerical range described in the present invention not only includes the point values listed above, but also includes any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.
[0074] Compared with the prior art, the present invention has the following beneficial effects:
[0075] (1) The heat treatment method provided by the present invention can achieve internal control of harmful elements, make the forging structure uniform, ensure the first-time pass rate of workpiece performance to a certain extent, reduce the frequency of rework, help reduce production costs, and reduce the labor intensity of workshop workers;
[0076] (2) The preliminary heat treatment process provided by the present invention adopts a normalizing + full annealing system, which is very effective in eliminating the structural inheritance of the steel grade and has guiding significance for the future production of such forgings;
[0077] (3) The quality of the forgings obtained by the heat treatment method provided by the present invention is stable, thereby increasing the first-time inspection rate of the products by 100%, avoiding the energy waste caused by rework and repair, and shortening the production cycle and manufacturing cost;
[0078] (4) The forgings obtained by the heat treatment method provided by the present invention have good comprehensive properties such as good toughness, strength and corrosion resistance, ensuring the safety and reliability of the rotor under extreme working conditions and extending the service life of the rotor. BRIEF DESCRIPTION OF THE DRAWINGS
[0079] Figure 1 A preliminary heat treatment process diagram provided by the present invention;
[0080] Figure 2 A quenching process diagram provided by the present invention;
[0081] Figure 3 A tempering process diagram provided by the present invention;
[0082] Figure 4 A cross-sectional view of a 26NiCrMoV145 steel rotor forging provided in step (1) of the present invention;
[0083] Figure 5 Schematic diagram of the grain structure of the 26NiCrMoV145 steel rotor forging provided in Example 1 of the present invention. DETAILED DESCRIPTION
[0084] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.
[0085] In a specific embodiment, the present invention provides a heat treatment method for a 26NiCrMoV145 steel rotor forging, comprising the following steps:
[0086] (1) a 26NiCrMoV145 steel ingot is subjected to step-wise heating treatment, controlled forging, remelting treatment, controlled shape forging and air cooling treatment in sequence until the final temperature is ≥350°C to obtain a calcined billet;
[0087] The step-type heating treatment includes a first-stage heating treatment and a second-stage heating treatment performed sequentially; the temperature of the first-stage heating treatment is 635-665°C, and the holding time per millimeter of effective thickness is 0.3-0.4 min; the temperature of the second-stage heating treatment is 1235-1265°C, and the holding time per millimeter of effective thickness is 0.4-0.5 min;
[0088] The controlled forging includes two upsetting operations and two stretching operations performed in sequence; the forging ratio of each controlled forging is ≥2, the deformation amount of each controlled forging is ≥50%, and the final forging temperature is ≥900°C;
[0089] The temperature of the remelting treatment is 1185-1215°C, and the holding time per millimeter of effective thickness is 0.2-0.3 minutes;
[0090] The controlled shape forging includes an upsetting process, and the deformation amount of the upsetting process is 45-50%;
[0091] (2) The calcined blank obtained in step (1) is subjected to the following steps: Figure 1 The preparatory heat treatment, rough machining treatment and performance heat treatment shown;
[0092] The preliminary heat treatment includes normalizing treatment, primary air cooling, material heat preservation treatment, complete annealing treatment, furnace cooling and secondary air cooling in sequence;
[0093] The normalizing treatment has a heating rate of ≤120°C / h, a holding temperature of 910-930°C, and a holding time of 0.5-0.7min / mm×effective thickness+90min;
[0094] The end point temperature of the primary air cooling is 190-210°C;
[0095] The heat preservation temperature of the material to be treated is 190-210°C, and the heat preservation time is 2-2.5h;
[0096] The complete annealing treatment includes a first-stage annealing treatment, a second-stage annealing treatment and a third-stage annealing treatment performed in sequence; the heating rate of the first-stage annealing treatment is ≤50°C / h, the holding temperature is 630-650°C, and the holding time is 2-2.5h; the heating rate of the second-stage annealing treatment is ≤120°C / h, the holding temperature is 870-890°C, and the holding time is 0.5-0.7min / mm×effective thickness+90min; the holding temperature of the third-stage annealing treatment is 670-690°C, and the holding time is 0.6-0.8min / mm×effective thickness+120min;
[0097] The terminal temperature of the furnace cooling is 340-360°C;
[0098] The end point temperature of the secondary air cooling is 20-30°C;
[0099] The performance heat treatment includes the following steps: Figure 2 The quenching treatment, intermittent liquid cooling treatment and Figure 3 Tempering treatment shown;
[0100] The heating rate of the quenching treatment is ≤100°C / h, the holding temperature is 840-860°C, and the holding time is 0.5-0.7min / mm×effective thickness+90min;
[0101] The intermittent liquid cooling treatment includes a first liquid cooling, a first air cooling, and a repeated second liquid cooling and a second air cooling; the first liquid cooling time is 5 to 6 minutes, the first air cooling end temperature is 350 to 400°C, the second liquid cooling time is 1 to 2 minutes, the second air cooling return time is 2.5 to 3.5 minutes, and the end point of the intermittent liquid cooling treatment is: the surface and core temperatures of the steel rotor forging are both 100 to 200°C, and the temperature difference between the surface and the core is ≤100°C; the coolant used in the intermittent liquid cooling treatment includes a PAG solution with a concentration of 6 to 10wt%;
[0102] The heating rate of the tempering treatment is ≤120°C / h, the holding temperature is ≥600°C, and the holding time is 0.6-0.8min / mm×effective thickness+120min.
[0103] Example 1
[0104] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging, the heat treatment method comprising the following steps:
[0105] (1) a 26NiCrMoV145 steel ingot is subjected to step-wise heating treatment, controlled forging, remelting treatment, controlled shape forging and air cooling treatment in sequence until the final temperature is ≥350°C to obtain a calcined billet;
[0106] The step-type heating treatment includes a first stage heating treatment and a second stage heating treatment performed sequentially; the temperature of the first stage heating treatment is 650°C, and the holding time per millimeter of effective thickness is 0.35min; the temperature of the second stage heating treatment is 1250°C, and the holding time per millimeter of effective thickness is 0.45min;
[0107] The controlled forging includes two upsetting operations and two stretching operations performed in sequence; the forging ratio of each controlled forging is 2.5, the deformation amount of each forging is 60%, and the final forging temperature is 950°C;
[0108] The temperature of the furnace treatment is 1200°C, and the holding time per millimeter of effective thickness is 0.25min;
[0109] The controlled shape forging includes an upsetting process, and the deformation amount of the upsetting process is 48%;
[0110] (2) sequentially performing preliminary heat treatment, rough machining treatment and performance heat treatment on the calcined blank obtained in step (1);
[0111] The preliminary heat treatment includes normalizing treatment, primary air cooling, material heat preservation treatment, complete annealing treatment, furnace cooling and secondary air cooling in sequence;
[0112] The normalizing treatment has a heating rate of 100°C / h, a holding temperature of 920°C, and a holding time of 0.6min / mm×effective thickness+90min;
[0113] The end point temperature of the primary air cooling is 200°C;
[0114] The insulation temperature of the material to be treated is 200°C and the insulation time is 2.25h;
[0115] The complete annealing treatment includes a first-stage annealing treatment, a second-stage annealing treatment and a third-stage annealing treatment performed in sequence; the first-stage annealing treatment has a heating rate of 45°C / h, a holding temperature of 640°C and a holding time of 2.25h; the second-stage annealing treatment has a heating rate of 100°C / h, a holding temperature of 880°C and a holding time of 0.6min / mm×effective thickness+90min; the third-stage annealing treatment has a holding temperature of 680°C and a holding time of 0.7min / mm×effective thickness+120min;
[0116] The final temperature of the furnace cooling is 350°C;
[0117] The endpoint temperature of the secondary air cooling is 25°C;
[0118] The performance heat treatment includes quenching treatment, intermittent liquid cooling treatment and tempering treatment performed in sequence;
[0119] The heating rate of the quenching treatment is 80°C / h, the holding temperature is 850°C, and the holding time is 0.6min / mm×effective thickness+90min;
[0120] The intermittent liquid cooling treatment includes a first liquid cooling, a first air cooling, and a repeated second liquid cooling and a second air cooling; the first liquid cooling time is 5 minutes, the first air cooling end temperature is 375°C, the second liquid cooling time is 1.5 minutes, the second air cooling return time is 3 minutes, and the end point of the intermittent liquid cooling treatment is: the surface and core temperatures of the steel rotor forging are both 100-200°C, and the temperature difference between the surface and the core is 60°C; the coolant used in the intermittent liquid cooling treatment includes a PAG solution with a concentration of 8wt%;
[0121] The heating rate of the tempering treatment is 100° C. / h, the holding temperature is 650° C., and the holding time is 0.7 min / mm×effective thickness+120 min.
[0122] The schematic diagram of the grain structure of the 26NiCrMoV145 steel rotor forging provided in this embodiment is as follows: Figure 5 As shown, according to Figure 5 It can be seen that the 26NiCrMoV145 steel rotor forging provided by the present invention has a uniform bainite structure.
[0123] Example 2
[0124] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging, the heat treatment method comprising the following steps:
[0125] (1) a 26NiCrMoV145 steel ingot is subjected to step-wise heating treatment, controlled forging, remelting treatment, controlled shape forging and air cooling treatment in sequence until the final temperature reaches 360° C. to obtain a calcined billet;
[0126] The step-wise heating treatment includes a first-stage heating treatment and a second-stage heating treatment performed sequentially; the temperature of the first-stage heating treatment is 635°C, and the holding time per millimeter of effective thickness is 0.4 min; the temperature of the second-stage heating treatment is 1235°C, and the holding time per millimeter of effective thickness is 0.5 min;
[0127] The controlled forging includes two upsetting operations and two drawing operations performed in sequence; the forging ratio of each controlled forging is 2.0, the deformation amount of each forging is 55%, and the final forging temperature is 950°C;
[0128] The temperature of the remelting treatment is 1185°C, and the holding time per millimeter of effective thickness is 0.3 min;
[0129] The controlled shape forging includes an upsetting process, and the deformation amount of the upsetting process is 50%;
[0130] (2) sequentially performing preliminary heat treatment, rough machining treatment and performance heat treatment on the calcined blank obtained in step (1);
[0131] The preliminary heat treatment includes normalizing treatment, primary air cooling, material heat preservation treatment, complete annealing treatment, furnace cooling and secondary air cooling in sequence;
[0132] The normalizing treatment has a heating rate of 110°C / h, a holding temperature of 910°C, and a holding time of 0.7min / mm×effective thickness+90min;
[0133] The end point temperature of the primary air cooling is 190°C;
[0134] The insulation temperature of the material to be treated is 190°C and the insulation time is 2.5h;
[0135] The complete annealing treatment includes a first-stage annealing treatment, a second-stage annealing treatment and a third-stage annealing treatment performed in sequence; the first-stage annealing treatment has a heating rate of 42°C / h, a holding temperature of 630°C and a holding time of 2.5h; the second-stage annealing treatment has a heating rate of 110°C / h, a holding temperature of 870°C and a holding time of 0.7min / mm×effective thickness+90min; the third-stage annealing treatment has a holding temperature of 670°C and a holding time of 0.8min / mm×effective thickness+120min;
[0136] The final temperature of the furnace cooling is 340°C;
[0137] The endpoint temperature of the secondary air cooling is 20°C;
[0138] The performance heat treatment includes quenching treatment, intermittent liquid cooling treatment and tempering treatment performed in sequence;
[0139] The heating rate of the quenching treatment is 90°C / h, the holding temperature is 840°C, and the holding time is 0.7min / mm×effective thickness+90min;
[0140] The intermittent liquid cooling treatment includes a first liquid cooling, a first air cooling, and a repeated second liquid cooling and a second air cooling; the first liquid cooling time is 5.2 minutes, the first air cooling end temperature is 400°C, the second liquid cooling time is 1 minute, the second air cooling return time is 2.5 minutes, and the end point of the intermittent liquid cooling treatment is: the surface and core temperatures of the steel rotor forging are both 120-160°C, and the temperature difference between the surface and the core is 20°C; the coolant used in the intermittent liquid cooling treatment includes a PAG solution with a concentration of 6wt%;
[0141] The heating rate of the tempering treatment is 100° C. / h, the holding temperature is 610° C., and the holding time is 0.6 min / mm×effective thickness+120 min.
[0142] Example 3
[0143] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging, the heat treatment method comprising the following steps:
[0144] (1) a 26NiCrMoV145 steel ingot is subjected to a stepwise heating treatment, a controlled forging, a remelting treatment, a controlled forging, and an air cooling treatment in sequence until the final temperature reaches 400° C. to obtain a sintered billet;
[0145] The step-wise heating treatment includes a first-stage heating treatment and a second-stage heating treatment performed sequentially; the temperature of the first-stage heating treatment is 665°C, and the holding time per millimeter of effective thickness is 0.3 min; the temperature of the second-stage heating treatment is 1265°C, and the holding time per millimeter of effective thickness is 0.4 min;
[0146] The controlled forging includes two upsetting operations and two stretching operations performed in sequence; the forging ratio of each controlled forging is 2.2, the deformation amount of each forging is 50%, and the final forging temperature is 900°C;
[0147] The temperature of the remelting treatment is 1235°C, and the holding time per millimeter of effective thickness is 0.2 min;
[0148] The controlled shape forging includes an upsetting process, and the deformation amount of the upsetting process is 45%;
[0149] (2) sequentially performing preliminary heat treatment, rough machining treatment and performance heat treatment on the calcined blank obtained in step (1);
[0150] The preliminary heat treatment includes normalizing treatment, primary air cooling, material heat preservation treatment, complete annealing treatment, furnace cooling and secondary air cooling in sequence;
[0151] The normalizing treatment has a heating rate of 120°C / h, a holding temperature of 930°C, and a holding time of 0.5min / mm×effective thickness+90min;
[0152] The end point temperature of the primary air cooling is 210°C;
[0153] The insulation temperature of the material to be treated is 210°C and the insulation time is 2h;
[0154] The complete annealing treatment includes a first-stage annealing treatment, a second-stage annealing treatment and a third-stage annealing treatment performed in sequence; the first-stage annealing treatment has a heating rate of 50°C / h, a holding temperature of 650°C and a holding time of 2h; the second-stage annealing treatment has a heating rate of 120°C / h, a holding temperature of 890°C and a holding time of 0.5min / mm×effective thickness+90min; the third-stage annealing treatment has a holding temperature of 690°C and a holding time of 0.6min / mm×effective thickness+120min;
[0155] The final temperature of the furnace cooling is 360°C;
[0156] The endpoint temperature of the secondary air cooling is 30°C;
[0157] The performance heat treatment includes quenching treatment, intermittent liquid cooling treatment and tempering treatment performed in sequence;
[0158] The heating rate of the quenching treatment is 100°C / h, the holding temperature is 860°C, and the holding time is 0.5min / mm×effective thickness+90min;
[0159] The intermittent liquid cooling treatment includes a first liquid cooling, a first air cooling, and a repeated second liquid cooling and a second air cooling; the first liquid cooling time is 6 minutes, the first air cooling end temperature is 350°C, the second liquid cooling time is 2 minutes, the second air cooling return time is 3.5 minutes, and the end point of the intermittent liquid cooling treatment is: the surface and core temperatures of the steel rotor forging are both 150-200°C, and the temperature difference between the surface and the core is 60°C; the coolant used in the intermittent liquid cooling treatment includes a PAG solution with a concentration of 10wt%;
[0160] The heating rate of the tempering treatment is 120° C. / h, the holding temperature is 600° C., and the holding time is 0.8 min / mm×effective thickness+120 min.
[0161] Example 4
[0162] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging. The heat treatment method is different from that of Embodiment 1 only in that:
[0163] In this embodiment, the complete annealing treatment in the preliminary heat treatment is adjusted to: heating to 880° C. at a heating rate of 50° C. / h, keeping the temperature for 25 hours, and then cooling to 350° C. in the furnace.
[0164] Example 5
[0165] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging. The heat treatment method is different from that of Embodiment 1 only in that:
[0166] In this embodiment, the holding temperature of the normalizing treatment in the preliminary heat treatment is adjusted to 900°C.
[0167] Example 6
[0168] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging. The heat treatment method is different from that of Embodiment 1 only in that:
[0169] In this embodiment, the holding temperature of the normalizing treatment in the preliminary heat treatment is adjusted to 950°C.
[0170] Example 7
[0171] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging. The heat treatment method is different from that of Embodiment 1 only in that:
[0172] In this embodiment, the holding temperature of the quenching treatment is adjusted to 800°C.
[0173] Example 8
[0174] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging. The heat treatment method is different from that of Embodiment 1 only in that:
[0175] In this embodiment, the holding temperature of the quenching treatment is adjusted to 880°C.
[0176] Example 9
[0177] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging. The heat treatment method is different from that of Embodiment 1 only in that:
[0178] In this embodiment, the holding temperature of the tempering treatment is adjusted to 500°C.
[0179] Example 10
[0180] This embodiment provides a heat treatment method for a 26NiCrMoV145 steel rotor forging. The heat treatment method is different from that of Embodiment 1 only in that:
[0181] In this embodiment, the deformation amount of the shape-controlled forging in step (1) is adjusted to 45%.
[0182] Comparative Example 1
[0183] This comparative example provides a heat treatment method for a 26NiCrMoV145 steel rotor forging, which differs from Example 1 only in that:
[0184] In this comparative example, one stage of the step-wise heating treatment in step (1) is omitted, that is, only two stages of heating treatment are performed.
[0185] Comparative Example 2
[0186] This comparative example provides a heat treatment method for a 26NiCrMoV145 steel rotor forging, which differs from Example 1 only in that:
[0187] In this comparative example, the intermittent liquid cooling treatment is adjusted to liquid cooling treatment, that is, the forging after quenching treatment is directly placed in a PAG solution with a concentration of 8wt% until the surface temperature of the forging is 100-200°C.
[0188] Performance testing:
[0189] The physical properties of the 26NiCrMoV145 steel rotor forging obtained by the heat treatment method provided in Example 1 were tested, and the results are shown in Table 1;
[0190] Physical properties of the outer ring of the 26NiCrMoV145 steel rotor forgings obtained by the heat treatment methods provided in Examples 2-10 and Comparative Examples 1-2 were tested in radial direction, and the results are shown in Table 2;
[0191] Among them, Figure 4 As shown, areas 1, 4, and 7 are the outer circle, areas 2, 5, and 6 are the middle circle, and areas 3, 6, and 9 are the inner circle;
[0192] The impact energy is the average value of three consecutive impact energies.
[0193] Table 1
[0194]
[0195]
[0196]
[0197] According to Table 1 and the above examples and comparative examples, the following points can be known:
[0198] (1) Comprehensive analysis of Examples 1-3 shows that the heat treatment method provided by the present invention can effectively improve the uniformity of the structure of the forging, enhance its strength, corrosion resistance and toughness, ensure the safety and reliability of the rotor under extreme working conditions, and extend the service life of the rotor;
[0199] More specifically, according to Table 1, the forgings obtained by the heat treatment method provided by the present invention have higher tensile, yield and impact in the upper and lower surface areas close to the outer diameter, lower radial and height directions, and the performance of area 4, i.e. the middle area of the outer diameter, is lower than that of the upper and lower surfaces. The closer to the inner diameter, the tangential performance gradually decreases; the overall tensile deviation of the tensile strength is 68.9 MPa, and the yield strength deviation is 84.2 MPa; further proves that it has excellent physical properties at any position, and further proves its uniformity of organization;
[0200] (2) Comprehensive analysis of Example 1 and Example 4 shows that adjusting the complete annealing process in the preliminary heat treatment process cannot improve the microstructure of the forging and does not have a good dehydrogenation effect;
[0201] (3) Comprehensive analysis of Example 1 and Examples 5-6 shows that adjusting the temperature of the normalizing treatment during the preliminary heat treatment will lead to changes in the physical properties of the resulting forgings;
[0202] When the temperature of the normalizing treatment is too high, the grain structure of the forging will become coarse, which will lead to a decrease in the strength and toughness of the material. In addition, too high a normalizing treatment temperature may cause overburning of the material, resulting in a decrease in the hardness of the material and poor wear resistance. When the temperature of the normalizing treatment is too low, the structural transformation may be incomplete, and the internal stress cannot be fully released. The hardness and strength cannot meet the requirements, affecting the performance of the product. In addition, the material may retain too much residual stress, increasing the risk of deformation of the material during use.
[0203] (4) Comprehensive analysis of Example 1 and Examples 7-8 shows that adjusting the temperature of the quenching treatment will lead to changes in the physical properties of the resulting forgings;
[0204] When the temperature of the quenching treatment is too high, the microstructure inside the material will change, the compound will partially dissolve, the network will be disconnected, and the surface of the workpiece will be decarburized and the grains will be coarse; when the temperature of the quenching treatment is too low, the austenite will not be fully formed, and in addition to the martensite, a small amount of ferrite will remain in the structure, resulting in shortcomings such as insufficient hardness, uneven structure, and soft spots; the austenite grains will grow, and the martensite structure after quenching will also be coarse, which will increase the brittleness of the steel and cause cracks and deformation of the steel parts;
[0205] (5) Comprehensive analysis of Example 1 and Examples 9-10 shows that adjusting the temperature of the tempering treatment will lead to changes in the physical properties of the resulting forgings;
[0206] When the temperature of the tempering treatment is too high, it will cause the hardness to decrease, cause non-uniform tempering and thermal cracks, soften the material and other disadvantages; when the temperature of the tempering treatment is too low, it will cause the brittleness to increase, the material will be too hard and other disadvantages;
[0207] (6) Comprehensive analysis of Example 1 and Comparative Example 1 shows that adjusting the step-type heating treatment process to a one-stage heating treatment will result in a larger forging volume, which will further result in the forging being heated unevenly. The surface reaches the temperature first, but there is still a large temperature difference between the core and the surface. It takes a long time for the core to be fully heated through, and too long a period of heat preservation will easily cause the surface to overheat and burn, resulting in reduced strength of the outer ring surface of the forging.
[0208] (7) Comprehensive analysis of Example 1 and Comparative Example 2 shows that adjusting the intermittent liquid cooling process will make the forgings cool evenly, that is, the cooling rate from the surface to the core can be consistent, avoiding the phenomenon that the surface cooling rate is too fast and the core cooling rate is too slow, and the temperature of the core has no time to be transferred, and the surface has been cooled completely, so that the forgings can obtain uniform structure, hardness and performance from the surface to the core.
[0209] In summary, the heat treatment method provided by the present invention realizes the internal control of harmful elements in the forgings, the forging structure is more uniform, and the good comprehensive properties of the obtained forgings such as toughness, strength and corrosion resistance are improved. To a certain extent, the first-time pass rate of steel rotor forgings is guaranteed, the frequency of rework is reduced, which is conducive to reducing production costs and extending the service life of the rotor.
[0210] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.
Claims
1. A heat treatment method for a 26NiCrMoV145 steel rotor forging, characterized in that: The heat treatment method comprises the following steps: (1) a 26NiCrMoV145 steel ingot is subjected to step-wise heating treatment, controlled forging, remelting treatment, controlled shape forging and air cooling treatment in sequence to obtain a sintered billet; (2) sequentially performing preliminary heat treatment, rough machining treatment and performance heat treatment on the calcined blank obtained in step (1); The performance heat treatment includes quenching treatment, intermittent liquid cooling treatment and tempering treatment performed in sequence.
2. The heat treatment method according to claim 1, characterized in that The step-wise heating treatment in step (1) includes a first-stage heating treatment and a second-stage heating treatment performed sequentially; Preferably, the temperature of the first stage of heating treatment is 635-665°C; Preferably, the holding time per millimeter of effective thickness in the heating treatment is 0.3 to 0.4 minutes; Preferably, the temperature of the second stage heating treatment is 1235-1265°C; Preferably, the heat preservation time per millimeter of effective thickness in the heating treatment is 0.4 to 0.5 min.
3. The heat treatment method according to claim 1 or 2, characterized in that: The controlled forging in step (1) includes two upsetting operations and two stretching operations performed sequentially; Preferably, the forging ratio of each controlled forging in step (1) is ≥ 2; Preferably, the deformation amount of each controlled forging in step (1) is ≥50%; Preferably, the final forging temperature of the controlled forging in step (1) is ≥ 900°C; Preferably, the temperature of the furnace treatment in step (1) is 1185-1215°C; Preferably, the holding time per millimeter of effective thickness in the remelting treatment in step (1) is 0.2 to 0.3 min; Preferably, the shape-controlled forging in step (1) includes upsetting treatment; Preferably, the deformation amount of the upsetting treatment is 45-50%; Preferably, the terminal temperature of the air cooling treatment in step (1) is ≥350°C.
4. The heat treatment method according to any one of claims 1 to 3, characterized in that: The preliminary heat treatment in step (2) includes normalizing treatment, primary air cooling, material heat preservation treatment, complete annealing treatment, furnace cooling and secondary air cooling.
5. The heat treatment method according to claim 4, characterized in that: The heating rate of the normalizing treatment is ≤120°C / h; Preferably, the holding temperature of the normalizing treatment is 910-930°C; Preferably, the holding time of the normalizing treatment is 0.5-0.7 min / mm×effective thickness+90 min; Preferably, the end temperature of the primary air cooling is 190-210°C; Preferably, the heat preservation temperature of the material to be treated is 190-210°C; Preferably, the heat preservation time of the material to be treated is 2 to 2.5 hours.
6. The heat treatment method according to claim 4, characterized in that: The complete annealing treatment includes a first-stage annealing treatment, a second-stage annealing treatment and a third-stage annealing treatment performed sequentially; Preferably, the heating rate of the first stage annealing treatment is ≤50°C / h; Preferably, the holding temperature of the first stage annealing treatment is 630-650°C; Preferably, the holding time of the annealing treatment is 2 to 2.5 hours; Preferably, the heating rate of the second-stage annealing treatment is ≤120°C / h; Preferably, the holding temperature of the second-stage annealing treatment is 870-890°C; Preferably, the holding time of the second-stage annealing treatment is 0.5-0.7 min / mm×effective thickness+90 min; Preferably, the holding temperature of the three-stage annealing treatment is 670-690°C; Preferably, the holding time of the three-stage annealing treatment is 0.6-0.8 min / mm×effective thickness+120 min.
7. The heat treatment method according to claim 4, characterized in that: The terminal temperature of the furnace cooling is 340-360°C; Preferably, the terminal temperature of the secondary air cooling is 20-30°C.
8. The heat treatment method according to any one of claims 1 to 7, characterized in that: The heating rate of the quenching treatment is ≤100°C / h; Preferably, the holding temperature of the quenching treatment is 840-860°C; Preferably, the holding time of the quenching treatment is 0.5-0.7 min / mm×effective thickness+90 min.
9. The heat treatment method according to any one of claims 1 to 8, characterized in that: The intermittent liquid cooling treatment includes a first liquid cooling, a first air cooling, and a repeated second liquid cooling and a second air cooling; Preferably, the first liquid cooling time is 5 to 6 minutes; Preferably, the first air cooling end point temperature is 350-400°C; Preferably, the second liquid cooling time is 1 to 2 minutes; Preferably, the second air cooling temperature return time is 2.5 to 3.5 minutes; Preferably, the end point of the intermittent liquid cooling treatment is: the surface and core temperatures of the steel rotor forging are both 100-200°C, and the temperature difference between the surface and the core is ≤100°C; Preferably, the coolant used in the intermittent liquid cooling treatment comprises a PAG solution; Preferably, the concentration of the PAG solution is 6-10 wt %.
10. The heat treatment method according to any one of claims 1 to 9, characterized in that: The heating rate of the tempering treatment is ≤120°C / h; Preferably, the holding temperature of the tempering treatment is ≥ 600°C; Preferably, the holding time of the tempering treatment is 0.6-0.8 min / mm×effective thickness+120 min; Preferably, the tempering treatment further includes air cooling treatment.