Method and system for predicting hardness and residual life of steel pipeline

Abstract

The invention provides a steel pipeline hardness and residual life prediction method and system.The method comprises the steps that T / P92 steel pipeline samples in different heat treatment states are obtained at different cooling speeds after austenitizing, and the room temperature hardness and microscopic structures of the T / P92 steel pipeline samples in different aging states are studied; establishing a mathematical relationship between the room temperature hardness and the cooling rate and aging function after austenitizing, further determining a mathematical model of the remaining life of the running T / P92 steel pipeline under the specific cooling rate after austenitizing by comparing the requirements of relevant standards on the hardness of the running T / P92 steel pipeline, and determining the remaining life of the running T / P92 steel pipeline through a nondestructive room temperature hardness test. And calculating the residual life of the T / P92 steel pipeline with the cooling rate after the specific austenitizing operation at the specific temperature. The method solves the technical problems that in the prior art, the prediction result of the remaining life of the T / P92 steel pipeline without considering the cooling speed after initial austenitizing is inaccurate, the prediction efficiency is low, shutdown is needed during conventional boiler inspection, and economic loss is caused by pipeline cutting.

Description

Technical Field

[0001] The present invention relates to the field of performance prediction and remaining life assessment of high-temperature components, and particularly relates to a method and system for predicting the hardness and remaining life of steel pipes. Background Art

[0002] Ultra (super) critical power generation can achieve the efficient utilization of fossil resources, effectively reduce the emissions of harmful gases such as CO2 and NOx, and the proportion in global thermal power generation is increasing. T / P92 (10Cr9MoW2VNbBN) steel is a new type of martensitic heat-resistant steel obtained by reducing the content of Mo element on the basis of T / P91 (10Cr9Mo1VNbN) steel, substituting W element, and adding N and B elements at the same time. It has excellent high-temperature creep strength, corrosion resistance, thermal fatigue resistance and high-temperature oxidation resistance. At the same time, it also has high thermal conductivity, low thermal expansion coefficient and easy processing performance, and is mainly used as high-temperature pipes and headers in ultra (super) critical units.

[0003] The designed life of ultra (super) critical units is usually 30 years or 200,000 hours. When operating in high-temperature and high-pressure environments, the microstructure of heat-resistant steel pipes will gradually age, and their mechanical properties will gradually degrade. It is necessary to regularly supervise and inspect the microstructure and properties to ensure the safe operation of the steel pipes. The reality is that due to loose control of the original pipe manufacturing process or over-temperature conditions during operation in some units, the actual operating life of heat-resistant steel pipes fails to reach the designed life. Therefore, it is extremely important to predict the degradation trend and life of heat-resistant steel microstructure and properties. Accurate prediction can ensure that high-temperature pipelines do not fail or burst during operation between regular inspections, guaranteeing the safe and stable operation of the units. In design or life assessment, the creep fracture of components is currently used as the end point of life. Therefore, high-temperature creep / rupture tests are required to simulate the operation of high-temperature components. Conducting life test experiments directly under actual operating conditions (temperature, stress) can directly obtain the specific life years, but it will take several years or even more than a decade. To shorten the process of life assessment, generally, the experimental stress or temperature is increased, that is, the accelerated experimental method is used, and then the extrapolation method is used to determine the operating life of heat-resistant steel pipes operating at high temperatures. Currently, the more widely used methods for predicting the remaining life of heat-resistant steel include: time-temperature parameter method (Larson-Miller parameter method), isothermal line extrapolation method, and least constraint method, etc. For example, the existing invention patent application document "Method for Predicting the Remaining Rupture Life of T / P91 Heat-Resistant Steel in Ultra-Supercritical Units Based on Room Temperature Brinell Hardness" with publication number CN107843510A provides a method for predicting the remaining life of T / P91 steel based on room temperature Brinell hardness. Through rupture tests, the rupture strength of T / P91 steel with different room temperature hardnesses is determined by the isothermal line extrapolation method, and the relationship between room temperature hardness and rupture strength is established to calculate the rupture life of T / P91 steel with specific hardness. And the existing invention patent application document "Method for Establishing an Extrapolation Function of the Rupture Curve of Low-Hardness P91 Pipe Fittings" with publication number CN 106769531 A. In this existing method, by correlating hardness with rupture performance, an extrapolation function of the rupture curve is established to achieve the prediction of the rupture life of low-hardness P91 steel. The existing invention patent application document "A Method for Predicting the Creep Life of P92 Main Steam Pipe Welded Joints" with publication number CN 116050228 A. In this existing method, by grading the microstructure state of P92 steel welded joints after operation and obtaining the rupture performance of different microstructure states through experiments, the maximum principal stress of the welded joints is calculated using finite element method, and the stress conditions calculated and the rupture performance of the corresponding microstructure states are used to calculate the life of the welded joints.

[0004] The above-mentioned existing solutions consider the remaining life of steel pipes under specific steam temperature, specific pressure operating conditions, or specific tissue states, but none of them consider the critical influencing factor of the cooling rate after austenitization in the heat treatment process during the manufacturing of T / P92 steel pipes, resulting in poor applicability to pipes from different sources (different manufacturers and batches). The basic manufacturing process of T / P92 steel includes: smelting → steel billet → piercing → hot rolling / hot extrusion → heat treatment → inspection and packaging, etc. Among them, heat treatment includes normalizing + tempering, which has a great influence on the final tissue state and mechanical properties of steel pipes. When normalizing T / P92 steel, martensite structure can be obtained within a wide range of cooling rates after austenitization, and qualified tempered martensite structure can be obtained after tempering. Therefore, the manufacturer's control of the austenitization cooling rate is relatively broad. However, recent research shows that the original metallographic structures of T / P92 steel obtained under different cooling rates after austenitization are all tempered martensite, but there are significant differences in their tissue stability after high-temperature operation. Even under the same operating conditions, the rates of tissue aging and performance deterioration are different, resulting in obvious differences in their remaining lives.

[0005] In addition, in the above-mentioned publicly disclosed patent documents, the creep rupture life is used as the judgment condition for the failure (end point of life) of high-temperature components. In the safety judgment of actual power plant high-temperature metal components, the hardness of the components usually needs to be considered. The standard DL / T 438-2023 stipulates that the hardness range of T / P92 steel pipes is 190-250 HBW. When the hardness is lower than the standard requirement, it can be considered that the life of the component is approaching expiration and treatment is required.

[0006] In summary, the existing technologies have technical problems such as low efficiency in estimating the remaining life of T / P92 steel pipes, narrow application range due to not considering the initial cooling rate after austenitization, inaccurate prediction results, the need to stop the machine during boiler inspection, and economic losses caused by pipeline cutting. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: how to solve the technical problems in the existing technology that the prediction results of the remaining life of T / P92 steel pipes without considering the initial cooling rate after austenitization are inaccurate, the prediction efficiency is low, the machine needs to be stopped during routine boiler inspection, and economic losses are caused by pipeline cutting.

[0008] The present invention solves the above technical problems by adopting the following technical solutions: A method for predicting the hardness and remaining life of a steel pipe includes:

[0009] S1. Prepare T / P92 steel pipe specimens with different cooling rates after austenitization, observe the martensite lath microstructure of the T / P92 steel pipe specimens, and test the room temperature hardness of the T / P92 steel pipe specimens;

[0010] S2. Perform artificial aging treatment on the T / P92 steel pipe specimens with different cooling rates (v) after austenitization in S1, observe the martensitic lath microstructure of the T / P92 steel pipe specimens, and test the room temperature hardness of the T / P92 steel pipe specimens;

[0011] S3. Combining the martensitic lath microstructure and room temperature hardness of T / P92 steel pipeline specimens in S1 and S2, a mathematical model of the corresponding relationship between the room temperature hardness of T / P92 steel, the cooling rate after austenitizing (v), and the aging function (P) is established. Through non-destructive room temperature hardness testing, the remaining life of T / P92 steel pipelines with a specific cooling rate after austenitizing under specific temperature operation is estimated.

[0012] Based on a simple, non-destructive room-temperature hardness test, the present invention rapidly and accurately estimates the remaining life of a T / P92 steel pipeline with a specific cooling rate after austenitization when operating at a specific temperature, and rapidly evaluates its operating status in real time. This can avoid the economic losses caused by shutdowns and pipeline cutting during routine boiler inspections, and provide effective technical support for metal supervision and operation management of ultra-supercritical units.

[0013] In a more specific technical solution, in S1, by wire cutting operation, the specification is At the middle position of the wall thickness of the supplied P92 steel pipe, cut along the axial line to obtain no less than two 220mm×40mm×25mm block samples.

[0014] In a more specific technical solution, in S1, the T / P92 steel pipe sample is completely austenitized at 1060°C × 1h in a box-type resistance furnace, the T / P92 steel pipe sample is cooled to room temperature at different cooling rates, and then subjected to high-temperature tempering at 760°C × 2h.

[0015] In a more specific technical solution, in S2, in a box-type resistance furnace, at an aging temperature of 650°C, T / P92 steel pipe samples with different cooling rates after austenitizing are aged, and aged P92 steel pipe samples with aging times of 0h, 500h, 1000h, 2000h, 3000h, and 4000h are prepared in sequence.

[0016] This study used T / P92 steel pipelines as the research object. Using heat treatment, T / P92 steel specimens were obtained at different post-austenitizing cooling rates. Long-term high-temperature aging experiments were then conducted at 650°C to simulate the aging process of T / P92 steel under actual operating conditions. The room-temperature hardness of the T / P92 steel specimens at different aging stages was measured. Finally, through data fitting, a mathematical relationship was derived between the room-temperature hardness of T / P92 steel and the post-austenitizing cooling rate (v) and the aging function (P). This model was then used to derive a remaining life prediction model for T / P92 steel pipelines at specific post-austenitizing cooling rates and operating temperatures.

[0017] In a more specific technical solution, in S2, according to the preset specimen size, hardness specimens and metallographic specimens are prepared for T / P92 steel pipe specimens with different cooling rates after austenitization and T / P92 steel pipe specimens after aging treatment for different durations.

[0018] For the hardness specimens and metallographic specimens of the aged P92 steel pipe specimens, they are polished successively with metallographic sandpapers, and then the hardness specimens and metallographic specimens are polished with 2.5μm diamond grinding paste. The hardness of the specimens is measured on an HBS-62.5Z type digital display small load Brinell hardness tester.

[0019] The metallographic specimens are corroded with an FeCl3-hydrochloric acid deionized aqueous solution corrosion agent to observe the martensite lath microstructure of the metallographic specimens.

[0020] The method for predicting the room temperature hardness and remaining life of T / P92 steel based on the initial austenitization cooling rate provided creatively by the present invention can predict the subsequent hardness changes and remaining life of T / P92 steel pipes from different sources (different manufacturers or different batches) during operation, and can provide technical support for the supervision and maintenance of high-temperature pipes in ultra (ultra)-critical units.

[0021] In a more specific technical solution, for the hardness specimens and metallographic specimens of the aged P92 steel pipe specimens, they are polished successively with metallographic sandpapers of 80, 400, 800, 1000, 1500, and 2000#.

[0022] In a more specific technical solution, the martensite lath microstructure of the metallographic specimens is observed under an MR 3000 type optical microscope and a JSM-6490 type scanning electron microscope (SEM).

[0023] In a more specific technical solution, in S3, based on the Larson-Miller formula: P = T(C + lgt), the aging function P of P9S steel specimens with different cooling rates after austenitization in different aging states is obtained.

[0024] Let the ternary linear function relationship among the room temperature Brinell hardness HBW of P92 steel, the cooling rate v (℃ / h) after different austenitizations, and the aging function P in different aging states be:

[0025] HBW = a×υ + b×P + c

[0026] A binary linear regression fitting is performed on the martensite lath microstructure and the room temperature hardness to obtain a mathematical model:

[0027] HBW = -1.27×10 -2 ·P + 0.98×10 -2 ·υ + 462.99 (1)

[0028] Based on the mathematical model of Equation (1), according to the known cooling rate v (°C / h) after austenitization and the operating temperature T of T / P92 steel, the hardness after a preset time is predicted; when the cooling rate v (°C / h) after austenitization of the original T / P92 steel cannot be determined, based on the existing operating temperature T and time t of the T / P92 steel pipeline, as well as the current room-temperature Brinell hardness HBW, the cooling rate v (°C / h) after the original austenitization can be inversely deduced, and then the hardness change of the T / P92 steel pipeline during subsequent operation can be accurately predicted.

[0029] Specifically, for T / P92 steel specimens with different cooling rates after austenitization, based on the Larson-Miller formula (P = T(C + lgt), where P is the aging function, T and t are the annealing (operating) temperature and time respectively, and C is a constant, C = 20), high-temperature aging is carried out to obtain T / P92 steel pipeline specimens in different aging states. The martensitic lath microstructure of the specimens is observed, and their room-temperature hardness is measured. Then, based on steps S1 and S2, a corresponding mathematical relationship between the room-temperature hardness and the cooling rate (v) after austenitization and the aging function (P) is established, and a remaining life prediction model for the T / P92 steel pipeline at a specific cooling rate after austenitization and operating temperature is deduced. This model can be used to guide the assessment of the operating aging state of the T / P92 steel pipeline, strengthen the supervision and maintenance of the pipelines in ultra (super)-critical units, and ensure the safe operation of the units.

[0030] In a more specific technical solution, according to GB / T 5310-2023, the lower limit of the room-temperature Brinell hardness of the T / P92 steel pipeline, 190 HBW, is substituted into Equation (1) to obtain the relationship between the aging function P and the austenitization cooling rate: P = 0.77υ + 21495.28. Then, the aging function of the T / P92 steel pipeline at a specific austenitization cooling rate is calculated, and after calculating the equivalent operating time at temperature T when it operates for t hours at the operating temperature T, the remaining life can be obtained by deducting it. That is, the calculation formula for the remaining life tr of a P92 steel pipeline with an original austenitization cooling rate of v and a current room-temperature Brinell hardness of HBW when operating at temperature T is:

[0031]

[0032] Based on Equation (2), according to the cooling rate v (°C / h) after austenitization of the T / P92 steel and the current room-temperature Brinell hardness HBW, the time (i.e., the remaining life) when the hardness of the T / P92 steel pipeline drops to the lower limit of the room-temperature Brinell hardness of 190 HBW at the operating temperature T is predicted.

[0033] In a more specific technical solution, a steel pipeline hardness and remaining life prediction system includes:

[0034] The test module for specimens with different cooling rates after austenitizing is used to prepare T / P92 steel pipe specimens with different cooling rates after austenitizing, observe the martensitic lath microstructure of T / P92 steel pipe specimens, and test the room temperature hardness of T / P92 steel pipe specimens;

[0035] An aging treatment sample test module is used to perform artificial aging treatment on T / P92 steel pipe samples with different cooling rates (v) after austenitization in S1, observe the martensitic lath microstructure of the T / P92 steel pipe samples, and test the room temperature hardness of the T / P92 steel pipe samples. The aging treatment sample test module is connected to the test modules for samples with different cooling rates after austenitization;

[0036] The steel pipeline life modeling and prediction module is used to combine the martensitic lath microstructure and room temperature hardness of the T / P92 steel pipeline specimens in S1 and S2 to establish a mathematical model for the corresponding relationship between the room temperature hardness of T / P92 steel, the cooling rate after austenitizing (v), and the aging function (P). Through non-destructive room temperature hardness testing, the remaining life of the T / P92 steel pipeline with a specific cooling rate after austenitizing under a specific temperature operation is estimated. The steel pipeline life modeling and prediction module is connected to the aging treatment specimen testing module and the cooling rate specimen testing module after austenitizing.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] Based on a simple, non-destructive room-temperature hardness test, the present invention rapidly and accurately estimates the remaining life of a T / P92 steel pipeline with a specific cooling rate after austenitization when operating at a specific temperature, and rapidly evaluates its operating status in real time. This can avoid the economic losses caused by shutdowns and pipeline cutting during routine boiler inspections, and provide effective technical support for metal supervision and operation management of ultra-supercritical units.

[0039] This study used T / P92 steel pipelines as the research object. Using heat treatment, T / P92 steel specimens were obtained at different post-austenitizing cooling rates. Long-term high-temperature aging experiments were then conducted at 650°C to simulate the aging process of T / P92 steel under actual operating conditions. The room-temperature hardness of the T / P92 steel specimens at different aging stages was measured. Finally, through data fitting, a mathematical relationship was derived between the room-temperature hardness of T / P92 steel and the post-austenitizing cooling rate (v) and the aging function (P). This model was then used to derive a remaining life prediction model for T / P92 steel pipelines at specific post-austenitizing cooling rates and operating temperatures.

[0040] The method creatively provided by the present invention for predicting the room temperature hardness and remaining life of T / P92 steel by considering the initial austenitization cooling rate can predict the subsequent hardness changes and remaining life of T / P92 steel pipelines from different sources (different manufacturers or different batches) during operation, and can provide technical support for the supervision and maintenance of high-temperature pipelines of ultra-supercritical units.

[0041] The present invention solves the technical problems in the prior art that the prediction result of the remaining life of T / P92 steel pipelines without considering the cooling rate after initial austenitization is inaccurate, the prediction efficiency is low, it is necessary to stop the machine during routine boiler inspections, and pipeline cutting causes economic losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the basic steps of a method for predicting the hardness and remaining life of a steel pipeline according to Embodiment 1 of the present invention;

[0043] Figure 2 Optical microscope photograph of the P92 steel specimen with a cooling rate of 2000 °C / h after austenitization and without aging according to Embodiment 1 of the present invention;

[0044] Figure 3 Optical microscope photograph of the P92 steel specimen with a cooling rate of 1440 °C / h after austenitization and without aging according to Embodiment 1 of the present invention;

[0045] Figure 4 Optical microscope photograph of the P92 steel specimen with a cooling rate of 360 °C / h after austenitization and without aging according to Embodiment 1 of the present invention;

[0046] Figure 5 Optical microscope photograph of the P92 steel specimen with a cooling rate of 2000 °C / h after austenitization and aged for 2000 h according to Embodiment 1 of the present invention;

[0047] Figure 6 Optical microscope photograph of the P92 steel specimen with a cooling rate of 1440 °C / h after austenitization and aged for 2000 h according to Embodiment 1 of the present invention;

[0048] Figure 7 Optical microscope photograph of the P92 steel specimen with a cooling rate of 360 °C / h after austenitization and aged for 2000 h according to Embodiment 1 of the present invention;

[0049] Figure 8 Graph of the change in the room temperature hardness of the aged P92 steel specimens with different cooling rates after austenitization according to Embodiment 1 of the present invention;

[0050] Figure 9 Graph of the corresponding relationship between the room temperature hardness of the P92 steel, the cooling rate v after austenitization, and the aging function P according to Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0052] Embodiment 1

[0053] As Figure 1 shown, a method for predicting the hardness and remaining life of a steel pipeline provided by the present invention includes the following basic steps:

[0054] S1. Prepare block-shaped T / P92 steel pipeline specimens with different cooling rates after austenitization, observe their martensite lath microstructures, and measure their room temperature hardness;

[0055] In this embodiment, use wire cutting to axially cut 3 block-shaped specimens of 220mm×40mm×25mm at the middle position of the wall thickness of the as-supplied P92 steel pipeline with a specification of ;

[0056] In this embodiment, after completely austenitizing the T / P92 steel specimens at 1060°C for 1 h in a box-type resistance furnace, cool them to room temperature at different cooling rates, and then perform high-temperature tempering at 760°C for 2 h.

[0057] In this embodiment, after completely austenitizing the P92 steel specimens at 1060°C for 1 h in a box-type resistance furnace, cool them to room temperature at cooling rates of 2000°C / h, 1440°C / h, and 360°C / h respectively, and then perform high-temperature tempering at 760°C for 2 h.

[0058] S2. For the T / P92 steel pipeline specimens with different cooling rates (v) after austenitization in step S1, perform artificial aging, observe their martensite lath microstructures, and measure the room temperature hardness of the T / P92 steel pipeline specimens;

[0059] In this embodiment, perform aging treatment on the T / P92 steel specimens with different cooling rates after austenitization in a box-type resistance furnace at an aging temperature of 650°C, and sequentially prepare aging P92 steel pipeline specimens with aging durations of 0 h, 500 h, 1000 h, 2000 h, 3000 h, and 4000 h;

[0060] In this embodiment, hardness and metallographic specimens are prepared for the T / P92 steel pipeline specimens with different cooling rates after austenitization and different aging durations, and the specimen size is 8mm×8mm×8mm;

[0061] In this embodiment, after removing the oxide scale of 0.5 mm on 6 surfaces of P92 steel specimens with different cooling rates after austenitization and different aging times, 3 hardness samples and 3 metallographic samples are cut out.

[0062] In this embodiment, the metallographic samples of the aforementioned hardness are polished successively with 80#, 400#, 800#, 1000#, 1500#, and 2000# metallographic sandpapers, and then the specimens are polished with 2.5 μm diamond grinding paste. The hardness of the specimens is measured on an HBS-62.5Z digital display small-load Brinell hardness tester. The hardness of 5 points of each specimen is measured, and the average value is taken.

[0063] In this embodiment, the aforementioned metallographic samples are polished successively with 80#, 400#, 800#, 1000#, 1500#, and 2000# metallographic sandpapers, then the specimens are polished with 2.5 μm diamond grinding paste, and then corroded with an FeCl3-hydrochloric acid deionized aqueous solution (prepared according to the ratio of 5 g FeCl3: 50 ml concentrated hydrochloric acid: 100 ml H2O) corrosion agent. The martensite lath microstructure is observed under an MR 3000 optical microscope and a JSM-6490 scanning electron microscope (SEM), as Figures 2 to 7 shown. To ensure the initial aging state, the microstructures of specimens with different cooling rates after austenitization are all martensite, meeting the requirements of national standard GB / T5310-2023.

[0064] S3. Combining steps S1 and S2, establish a mathematical model for the corresponding relationship between the room-temperature hardness of T / P92 steel, the cooling rate (v) after austenitization, and the aging function (P). Through non-destructive room-temperature hardness testing, estimate the remaining life of T / P92 steel pipelines with a specific cooling rate after austenitization operating at a specific temperature.

[0065] In this embodiment, the high-temperature aging hardness change curves of P92 steel specimens with different cooling rates after austenitization are as Figure 8 shown. Based on the Larson-Miller formula (P = T(C + lgt)), the aging function P of P92 steel specimens with different cooling rates after austenitization in different aging states is obtained. As Figure 8 shown, the corresponding relationship among the room-temperature Brinell hardness (HBW) of P92 steel, the cooling rate v (℃ / h) after different austenitizations, and the aging function P in different aging states is a ternary linear function. Let the ternary linear function relationship among the room-temperature Brinell hardness (HBW) of P92 steel, the cooling rate v (℃ / h) after different austenitizations, and the aging function P in different aging states be HBW = a×υ + b×P + c. By performing linear fitting on the experimental data, we can obtain:

[0066] HBW = -1.27×10 -2 ·P + 0.98×10 -2 ·υ + 462.99 (1)

[0067] In this embodiment, for the aforementioned formula (1), on the one hand, after knowing the cooling rate v (°C / h) and operating temperature T of a certain T / P92 steel after austenitization, the hardness after any time can be predicted; on the other hand, when the cooling rate v (°C / h) after austenitization of a certain T / P92 steel is uncertain, knowing its operating temperature T and time t, as well as the current room temperature Brinell hardness (HBW), the cooling rate v (°C / h) after austenitization can be inferred, and then the hardness change during its subsequent operation can be predicted.

[0068] In this embodiment, it is known from GB / T 5310-2023 that the lower limit of the room temperature Brinell hardness of the T / P92 steel pipeline is 190 HBW. Substituting HBW=190 into formula (1), we get P=0.77υ+21495.28. The remaining life tr of a P92 steel pipeline with a room temperature Brinell hardness of HBW after the T / P92 steel pipeline with a specific cooling rate after austenitization is operated for t hours can be calculated as follows:

[0069]

[0070] For the above formula (2), knowing the cooling rate v (℃ / h) of a certain T / P92 steel after austenitization and the current room temperature Brinell hardness (HBW) can predict how much time it will take for its hardness to drop to the standard lower limit of 190HBW at the operating temperature T (i.e. the remaining life).

[0071] In this example, a mathematical relationship is established between the room temperature hardness of a T / P92 steel sample and the cooling rate after austenitizing (v) and the aging function (P). A remaining life prediction model for T / P92 steel pipelines at specific cooling rates after austenitizing and operating temperatures is also derived.

[0072] In this embodiment, the remaining life calculation is performed with the end point of the life span when the room temperature hardness of T / P92 steel drops to the lower limit of the GB / T 5310-2023 standard. Both formulas (1) and (2) are only applicable to as-delivered T / P92 steel pipelines with a tempered martensite microstructure after heat treatment, which meets the requirements of GB / T 5310-2023. This requires the cooling rate v after austenitization to be greater than 90°C / h. In other words, the present invention is applicable to the hardness and remaining life prediction of T / P92 pipelines with a cooling rate v after austenitization greater than 90°C / h.

[0073] In this embodiment, for P92 steel with a cooling rate of 1440 °C / h after austenitization, after aging at 650 °C for 3358 h, its Brinell hardness is 199 HBW, which is consistent with the hardness of 199 HBW of P92 steel operating at 601 °C for 70,000 h. This shows that under the same P function, the aging degree of the aged state and the operating state of T / P92 steel is the same. From the aging experiments of the present invention, it can be seen that the variation laws of the room temperature hardness of P92 steel specimens with different cooling rates after austenitization with the aging time are basically the same. During the aging process, the martensite lath microstructure gradually ages and broadens. As the aging time prolongs, the lath martensite gradually transforms into tempered sorbite, and the precipitation and coarsening of the second phase become more and more serious. The corresponding relationship between the room temperature hardness HBW of the specimen, the cooling rate (v) after austenitization, and the aging function (P) is a ternary linear function relationship.

[0074] In summary, based on simple and non-destructive room temperature hardness testing, the present invention can quickly and accurately estimate the remaining life of T / P92 steel pipes with a specific cooling rate after austenitization under specific operating temperatures, and can rapidly evaluate its operating state in real time. It can avoid the economic losses caused by shutdown and pipe cutting during conventional boiler inspections, providing effective technical support for the metal supervision and operation management of ultra (super) critical units.

[0075] The present invention takes T / P92 steel pipes as the research object, obtains T / P92 steel specimens with different cooling rates after austenitization by heat treatment methods, and conducts high-temperature aging experiments at 650 °C for a long time to simulate the aging process of T / P92 steel under actual operating conditions and measure the room temperature hardness of T / P92 steel specimens at different aging stages. Finally, through data fitting, the corresponding mathematical relationship between the room temperature hardness of T / P92 steel, the cooling rate (v) after austenitization, and the aging function (P) is obtained, and the remaining life prediction model of T / P92 steel pipes under specific cooling rates after austenitization and operating temperatures is derived.

[0076] The method provided by the present invention for creatively predicting the room temperature hardness and remaining life of T / P92 steel considering the initial austenitization cooling rate can predict the subsequent hardness changes and remaining life of T / P92 steel pipes from different sources (different manufacturers or batches) during operation, providing technical support for the supervision and maintenance of high-temperature pipes in ultra (super) critical units.

[0077] The present invention solves the technical problems in the prior art that the prediction results of the remaining life of T / P92 steel pipes without considering the cooling rate after initial austenitization are inaccurate, the prediction efficiency is low, it is necessary to shut down during conventional boiler inspections, and pipe cutting causes economic losses.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for predicting the hardness and remaining life of a steel pipeline, characterized in that, The method includes the following steps: S1. Prepare T / P92 steel pipe specimens with different cooling rates after austenitization, observe the martensite lath microstructure of the T / P92 steel pipe specimens, and measure the room temperature hardness of the T / P92 steel pipe specimens; S2. For the T / P92 steel pipe specimens with different cooling rates (v) after austenitization in S1, conduct artificial aging treatment, observe the martensite lath microstructure of the T / P92 steel pipe specimens, and measure the room temperature hardness of the T / P92 steel pipe specimens; S3. Combine the martensite lath microstructure and the room temperature hardness of the T / P92 steel pipe specimens in S1 and S2 to establish a mathematical model of the corresponding relationship between the room temperature hardness, the cooling rate (v) after austenitization, and the aging function (P) of T / P92 steel. Through non-destructive room temperature hardness testing, estimate the remaining life of the T / P92 steel pipe with a specific cooling rate after austenitization under operation at a specific temperature.

2. The method for predicting the hardness and remaining life of a steel pipeline according to claim 1, wherein In S1, through wire cutting operation, at the middle position of the wall thickness of the as-supplied P92 steel pipe with a specification of , take no less than 2 block specimens of 220mm×40mm×25mm along the axial direction by wire cutting.

3. A method for predicting the hardness and remaining life of a steel pipeline according to claim 1, characterized in that, In S1, in a box-type resistance furnace, fully austenitize the T / P92 steel pipe specimens at 1060°C for 1 h, cool the T / P92 steel pipe specimens to room temperature at different cooling rates, and then conduct high-temperature tempering at 760°C for 2 h.

4. A method for predicting the hardness and remaining life of a steel pipeline according to claim 1, characterized in that, In S2, in a box-type resistance furnace, conduct the aging treatment on the T / P92 steel pipe specimens with different cooling rates after austenitization at an aging temperature of 650°C, and sequentially prepare aging P92 steel pipe specimens with aging durations of 0 h, 500 h, 1000 h, 2000 h, 3000 h, and 4000 h.

5. A method for predicting the hardness and remaining life of a steel pipeline according to claim 1, characterized in that, In S2, according to the preset specimen size, prepare hardness specimens and metallographic specimens for the T / P92 steel pipe specimens with different cooling rates after austenitization and the T / P92 steel pipe specimens after different durations of the aging treatment; For the hardness specimens and the metallographic specimens of the aging P92 steel pipe specimens, polish them successively with metallographic sandpaper, and then polish the hardness specimens and the metallographic specimens with 2.5-μm diamond grinding paste. Measure the hardness of the specimens on an HBS-62.5Z type digital display small-load Brinell hardness tester; Corrode the metallographic specimens with an FeCl3-hydrochloric acid deionized water solution corrosion agent, and observe the martensite lath microstructure of the metallographic specimens.

6. The method for predicting the hardness and remaining life of a steel pipeline according to claim 5, characterized in that, For the hardness specimens and the metallographic specimens of the aging P92 steel pipe specimens, polish them successively with metallographic sandpapers of 80, 400, 800, 1000, 1500, and 2000#; 7. A method for predicting the hardness and remaining life of a steel pipeline according to claim 5, characterized in that, Observe the martensite lath microstructure of the metallographic specimens under an MR3000 type optical microscope and a JSM-6490 type scanning electron microscope (SEM); 8. A method for predicting the hardness and remaining life of a steel pipeline according to claim 1, characterized in that, In S3, based on the Larson-Miller formula: P = T(C + lgt), calculate the aging function P of the P92 steel specimens with different cooling rates after austenitization in different aging states; Let the ternary linear function relationship between the room temperature Brinell hardness HBW of P92 steel, the different cooling rates v (°C / h) after austenitization, and the aging function P in different aging states be: HBW = a×v + b×P + c Perform binary linear regression fitting on the martensite lath microstructure and the room temperature hardness to obtain the mathematical model: HBW = -1.27×10 -2 ·P + 0.98×10 -2 ·v + 462.99 (1) Based on the mathematical model of Equation (1), predict the hardness after a preset time according to the cooling rate v (°C / h) after austenitization and the operating temperature T of the T / P92 steel; when the cooling rate v (°C / h) after austenitization of the original T / P92 steel cannot be determined, based on the existing operating temperature T and time t of the T / P92 steel pipeline, and the current room temperature Brinell hardness HBW, inversely deduce the cooling rate v (°C / h) after the original austenitization, and predict the hardness change of the T / P92 steel pipeline during subsequent operation.

9. A method for predicting the hardness and remaining life of a steel pipeline according to claim 1, characterized in that According to GB / T5310-2023, substitute the lower limit of the room temperature Brinell hardness of 190 HBW of the T / P92 steel pipeline into Equation (1) to obtain the relationship between the transformation function P and the austenitization cooling rate: P = 0.77v + 21495.28 Obtain the aging function of the T / P92 steel pipeline with a specific cooling rate after austenitization, and calculate the formula for the remaining life tr of the P92 steel pipeline corresponding to the room temperature Brinell hardness HBW after operating for t hours at the operating temperature T: Based on Equation (2), predict the time when the hardness of the T / P92 steel pipeline drops to the lower limit of the room temperature Brinell hardness of 190 HBW at the operating temperature T according to the cooling rate v (°C / h) after austenitization of the T / P92 steel and the current room temperature Brinell hardness HBW.

10. A steel pipe hardness and remaining life prediction system, characterized in that, The system includes: A test module for specimens with different cooling rates after austenitization, which is used to prepare specimens of the T / P92 steel pipeline with different cooling rates after austenitization, observe the martensite lath microstructure of the T / P92 steel pipeline specimens, and test the room temperature hardness of the T / P92 steel pipeline specimens; An aging treatment specimen test module, which is used to perform artificial aging treatment on the T / P92 steel pipeline specimens with different cooling rates (v) in S1, observe the martensite lath microstructure of the T / P92 steel pipeline specimens, and test the room temperature hardness of the T / P92 steel pipeline specimens. The aging treatment specimen test module is connected to the test module for specimens with different cooling rates after austenitization; A steel pipeline life modeling and prediction module, which is used to establish a mathematical model of the corresponding relationship between the room temperature hardness, the cooling rate (v) after austenitization, and the aging function (P) of the T / P92 steel by combining the martensite lath microstructure and the room temperature hardness of the T / P92 steel pipeline specimens in S1 and S2, and deduce the remaining life of the T / P92 steel pipeline with a specific cooling rate after austenitization operating at a specific temperature through non-destructive room temperature hardness testing. The steel pipeline life modeling and prediction module is connected to the aging treatment specimen test module and the test module for specimens with different cooling rates after austenitization.

Images