CN111141822A - HP type furnace tube high-temperature tissue degradation nondestructive evaluation method based on nonlinear torsional waves - Google Patents
HP type furnace tube high-temperature tissue degradation nondestructive evaluation method based on nonlinear torsional waves Download PDFInfo
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Abstract
A non-linear torsional wave based HP type furnace tube high-temperature tissue degradation nondestructive evaluation method belongs to the technical field of nondestructive evaluation. The method comprises the steps of selecting proper detection parameters and detection modes by using a nonlinear parameter measurement system, firstly measuring nonlinear parameters of furnace tube tissue degradation level samples in different service times in a laboratory, making a calibrated furnace tube tissue degradation level-nonlinear parameter relative relation graph, then selecting the detection parameters and the detection modes which are the same as those of the made calibration graph by using the nonlinear parameter measurement system, measuring nonlinear ultrasonic parameter values of a furnace tube to be evaluated, comparing the nonlinear ultrasonic parameter values with the calibration graph or inputting the nonlinear ultrasonic parameter values into an HP type furnace tube high-temperature tissue degradation evaluation system, and qualitatively evaluating the tissue degradation state of the furnace tube. The method can quickly and accurately evaluate the degradation state of the high-temperature structure of the HP type furnace tube in a nondestructive way within a large range without damaging the integrity of the furnace tube to be evaluated, and avoids the influence of human factors.
Description
Technical Field
The invention belongs to the technical field of nondestructive evaluation, and relates to tissue degradation of an HP type furnace tube in a high-temperature service process, in particular to a nondestructive evaluation method for high-temperature tissue degradation of the HP type furnace tube.
Background
The HP-series alloy is widely used at present, is an iron-based alloy with basic chemical components of 0.4 wt.% C, 25 wt.% Cr and 35 wt.% Ni, and sometimes alloy elements such as W, Mo, Nb and Re are added for improving the performance, the HP-type furnace tube is a furnace tube made of the HP-series alloy through centrifugal casting, is a key component of a hydrogen production furnace, a conversion furnace and a cracking furnace in the petrochemical industry, has a design life of 100000h generally, is poor in service condition, and generally bears the high temperature of about 1000 ℃ and the pressure of 2-5 MPa. Along with the increase of the service time of the furnace tube, the structure of the furnace tube is gradually degraded, and the expression form is that the aggregation and the growth of carbides gradually form a chain shape at a crystal boundary, so that the high-temperature mechanical performance indexes of the furnace tube, such as the lasting strength, the plasticity, the toughness and the like, are reduced, and the service safety of the furnace tube is seriously affected, therefore, the structure degradation degree of the HP type furnace tube in the high-temperature service process is quickly, effectively and accurately determined, and the method has a very important significance for guaranteeing the safety production.
The HP type furnace tube is manufactured by adopting a centrifugal casting method, if liquid molten steel is slowly cooled in the casting process, the microstructure at room temperature is austenite + eutectic (gamma + M)23C6) However, since the cooling rate of centrifugal casting is very high, solidification is an unbalanced process, so that M crystallized first7C3Late conversion of type carbide to M23C6Type carbide, so that the as-cast structure is supersaturated austenite + eutectic (gamma + M) at room temperature7C3) The eutectic carbide has two forms, skeleton and block, and the skeleton is distributed in the crystal boundary and the block is distributed between dendrites.
In the service process of the HP type furnace tube at high temperature, the M is in a framework shape7C3Type eutectic carbonizationThe product is unstable and gradually turns into M23C6Form carbides and accelerate with increasing temperature. Meanwhile, in the as-cast structure of the austenitic heat-resistant steel, austenite is a supersaturated solid solution, and secondary carbides are dispersed and precipitated from the austenite in the high-temperature service process. After long-term high-temperature service, eutectic carbide and secondary carbide gradually coarsen and are diffused to grain boundaries to be converted into a net chain shape, and the higher the operating temperature is, the longer the operating time is, the more obvious the furnace tube weaving net chain shape is, and the more serious the structure deterioration is.
Generally, the degradation degree of the high-temperature structure of the HP type furnace tube is classified into 5 grades, the structure characteristics are shown in table 1, and corresponding metallographic pictures are shown in fig. 1-5.
TABLE 1 HP-type furnace tube high-temperature texture degradation grade and texture characteristics
When the tissue deterioration of the furnace tube reaches 5 grades, the high-temperature endurance strength of the furnace tube material is seriously reduced, the brittleness is greatly increased, a serious potential safety hazard exists, and the furnace tube material needs to be replaced.
At present, the degradation degree of the high-temperature structure of the HP type furnace tube is judged by adopting a metallographic observation method, the furnace tube to be evaluated is observed under a metallographic microscope after being polished, corroded and coated, and the corresponding degradation grade is given according to the form change of carbide, so that the method has the following problems:
1. the procedure is tedious, the cycle is long: the metallurgical observation method is adopted to evaluate the structure degradation level of the furnace tube, the processes of grinding wheel coarse grinding, different types of abrasive paper fine grinding, polishing, corrosion, film coating, observation and the like are required to be carried out on the furnace tube to be evaluated, the period is longer, the implementation is not easy on site, and sometimes a sampling mode such as destructive cutting and the like is also required;
2. the evaluation range is small: the metallographic observation method can only carry out observation and evaluation on limited polished parts, can only be limited on the surface of the furnace tube, and cannot explain the tissue degradation conditions in the interior of the furnace tube and other parts;
3. the requirements on operators are high, and the evaluation results are greatly influenced by whether the fine grinding process, the polishing process, the corrosion process and the laminating process are proper or not, different understandings of different observers on metallographic maps and the like;
4. the grinding of the furnace tube is a destructive detection method, which affects the overall size of the furnace tube, thereby affecting the service strength of the furnace tube, and possibly causing other damages to the corrosion of the furnace tube.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a nondestructive evaluation method of HP type furnace tube high-temperature tissue degradation based on a nonlinear torsional wave technology, which does not need to polish, corrode, coat and observe a furnace tube to be evaluated, does not damage the integrity of the furnace tube to be evaluated, and determines the tissue degradation state of the furnace tube to be evaluated by measuring the nonlinear parameters of the furnace tube to be evaluated and comparing the nonlinear parameters with a laboratory-calibrated HP type furnace tube high-temperature tissue degradation level-nonlinear parameter relation diagram.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the traditional ultrasonic nondestructive detection technology is used for evaluating the damage inside a material based on the change of linear parameters such as the sound velocity, the attenuation coefficient and the like of the material, and can only evaluate the macroscopic defects of the material, while the nonlinear ultrasonic detection technology can evaluate the tiny damage, the tissue change, the early mechanical property degradation and the like in the material. Based on the basic theory of nonlinear ultrasound, the carbide morphological change can cause the nonlinear effect to occur in the process of the torsional wave propagating in the furnace tube wall, and higher harmonics are generated. The invention adopts a pair of frequency doubling ultrasonic transducers to determine proper detection parameters and detection modes, firstly measures nonlinear parameters of samples with different tissue degradation levels of the HP type furnace tube in a laboratory, makes a calibrated relative relationship diagram of the tissue degradation levels and the nonlinear parameters, then measures the nonlinear parameter value of the furnace tube to be evaluated by using a nonlinear parameter measuring system, compares the measured nonlinear parameter value with the calibrated relative relationship diagram of the tissue degradation levels and the nonlinear parameters or inputs the measured nonlinear parameter value into a high-temperature tissue degradation evaluation system of the HP type furnace tube, and then qualitatively evaluates the high-temperature tissue degradation state of the HP type furnace tube.
A non-linear torsional wave based HP type furnace tube high-temperature tissue deterioration nondestructive evaluation method specifically comprises the following steps:
1) building a nonlinear parameter measurement system, determining detection parameters and detection modes
Torsional waves are essentially guided ultrasonic waves. When ultrasonic waves propagate in a thin bar, a pipe or a thin plate, if the wall thickness (plate thickness) is close to the wavelength, longitudinal waves and transverse waves are affected by boundary conditions and cannot propagate in an initial waveform, but propagate in a specific form, and the structure for directionally guiding ultrasonic waves with specific frequencies is called a waveguide, i.e., a guided wave is an elastic wave propagating in the waveguide, and the propagation of the elastic wave in a medium depends on the geometric structure of the medium, and the elastic wave continuously reflects, refracts, interferes and converts the wave form on the interface of the medium to form a guided wave, for example, the elastic wave propagating in a pipeline exists in the form of a guided wave, as shown in fig. 6.
The main modes of ultrasonic guided wave applications include torsional and longitudinal waves, as shown in figure 7.
The torsional wave has the characteristics that the mass point vibrates along the circumferential direction of the pipe, the wave propagates along the axial direction of the pipe, the influence of the liquid in the pipe on the sound wave propagation process is small, the torsional wave can be used in a wide frequency range, the echo signal can contain the defect information in the pipe shaft direction, the clear echo signal can be obtained usually, and the signal identification is easy, so that the torsional wave is adopted for nondestructive evaluation of the high-temperature tissue degradation of the furnace pipe.
As shown in fig. 8, the HP-type furnace tube torsional wave nonlinear parameter measurement system determines the frequency of a transmitting/receiving ultrasonic transducer according to the tissue characteristics and acoustic parameters of the HP-type furnace tube, selects a detection mode according to the field working condition, and selects an appropriate excitation waveform, excitation string number and window function according to the size of a region to be evaluated.
The nonlinear parameter measuring system consists of a RAM-5000 type nonlinear ultrasonic detector, an attenuator, a low/high pass filter, an amplifier, an oscilloscope, a computer and a transmitting/receiving transducer. The oscilloscope is connected with the RAM-5000 type nonlinear ultrasonic detector and the computer, and the computer is connected with the RAM-5000 type nonlinear ultrasonic detector. The RAM-5000 type nonlinear ultrasonic detector transmits a finite amplitude ultrasonic pulse train as an excitation waveform, and the excitation waveform is adjusted by an attenuator and then transmitted to a transmitting transducer by a low-pass filter, wherein the attenuator prevents the excitation waveform from generating distortion, the low-pass filter allows a waveform signal lower than a cut-off frequency (generally set to be slightly higher than the frequency of the transmitting transducer) to pass through, and simultaneously filters a noise signal higher than the cut-off frequency. After the transmitting transducer receives the ultrasonic pulse train transmitted by the RAM-5000 type nonlinear ultrasonic detector, the transmitting transducer transmits a limited amplitude ultrasonic pulse train with single frequency into the furnace tube to be evaluated and receives the ultrasonic pulse train through the receiving transducer; the transmitting frequency of the transmitting transducer is set according to the acoustic characteristics of the furnace tube to be evaluated, the frequency of the receiving transducer is a multiple of the frequency of the transmitting transducer and can be determined by concerned higher harmonics, and if the 2 nd harmonic is concerned, the frequency of the receiving transducer is 2 times of the frequency of the transmitting transducer. The receiving signal of the receiving transducer enters the oscilloscope after passing through the high-pass filter and the amplifier in sequence; wherein the high pass filter passes waveform signals above a cut-off frequency (typically set slightly below the frequency of the receiving transducer), while filtering out noise signals below the cut-off frequency; the oscilloscope is used for displaying the transmitted and received waveform signals. The computer sets transmitting and receiving parameters through the RAM-5000 type nonlinear ultrasonic detector, acquires time domain waveform signals of the receiving transducer through the oscilloscope, performs Fourier transform on the time domain waveform signals to obtain an amplitude-frequency curve, and further obtains nonlinear parameter values.
During the propagation process of the torsional wave, if micro defects or uneven structures exist in the pipe wall range of the furnace pipe to be evaluated, for example, second phase particles with different forms, such as carbides, exist, a nonlinear effect is generated during the propagation process of the torsional wave, and the expression form of the nonlinear effect is that high-order harmonics are generated. The nonlinear effect of the torsional wave causes that the stress-strain relation no longer meets the commonly used Hooke's law, and a high-order elastic term needs to be introduced:
where σ is the stress, ε is the strain, E2And E3Second and third order elastic constants, respectively.
The one-dimensional nonlinear wave equation in the solid medium is as follows:
where u is the particle vibration displacement, t is the acoustic wave propagation time, ρ medium density, and x is the acoustic wave propagation distance.
Setting an incident initial sound wave equation as follows:
u(0,t)＝A1sinωt (3)
in the formula A1Is the fundamental amplitude, ω is the angular frequency, and t is the acoustic travel time.
Using a step-by-step approximation perturbation method, the solution of the nonlinear wave equation (2) can be obtained as:
wherein k is the wave number.
From the equation (4), the second harmonic amplitude
The following can be obtained:
β is called a second order non-linearity parameter.
When the incident acoustic frequency and the sample size are determined, the second order nonlinearity parameters can be simplified as:
the change of the nonlinear parameter is related to the form of carbide in the furnace tube, so that the form change of the carbide in the furnace tube can be qualitatively evaluated by measuring the value of the second-order nonlinear parameter β, and further the degradation state of the furnace tube structure can be evaluated.
2) Calibration graph making
In practice, even in the structure state of the HP-type furnace tube of the same degradation level, the carbide morphology is not completely the same, which causes the nonlinear parameter value of the furnace tube of the same degradation level to fluctuate within a certain range, so that it is necessary to make a furnace tube structure degradation level-nonlinear parameter relative diagram in a laboratory, which comprises the following specific processes: for each tissue degradation level, collecting a considerable number of furnace tube samples, adopting the nonlinear parameter measurement system and the detection parameters in the step 1), measuring n times of nonlinear parameters for each sample, averaging to obtain nonlinear parameters of all samples in the tissue degradation state of the level, and setting a rectangular range by taking the maximum value and the minimum value of the nonlinear parameters in the tissue degradation state of the level as boundaries to form a tissue degradation level-nonlinear parameter relative relation graph.
3) Measurement of non-linear parameters of furnace tube to be evaluated
And (2) measuring the nonlinear parameters of the actual furnace tube to be evaluated by adopting the nonlinear parameter measuring system and the detection parameters in the step 1), measuring each region to be evaluated at least 5 times, and taking the average value as the nonlinear parameter value of the furnace tube to be evaluated.
4) Determining the organization deterioration state of the furnace tube to be evaluated
Determining the structure deterioration state of the furnace tube to be evaluated by adopting the following two ways:
the first one is a manual evaluation mode, the service time of the furnace tube and the nonlinear parameter values of the furnace tube to be evaluated obtained in the step 3) are compared with the calibration graph obtained in the step 2), corresponding nonlinear parameter values are found in the graph by the ordinate, the tissue degradation level of the furnace tube to be evaluated corresponds to the abscissa, and due to the fact that the 5-level degradation is overlapped with the nonlinear parameter values of the 2-level degradation and the 3-level degradation, the judgment and the distinction can be carried out through the service time of the furnace tube, and the 5-level degradation can occur after the service time of the furnace tube is 80000h generally.
The second one is an intelligent evaluation mode, the nonlinear parameter values measured in each time in the step 3) are input into an HP type furnace tube high-temperature tissue degradation nondestructive evaluation system, the system is an intelligent evaluation system developed based on a Labview virtual instrument platform, and has the characteristics of friendly interface, clear module logic and strong data processing and analysis functions, the HP type furnace tube high-temperature tissue degradation nondestructive evaluation system is embedded into the nonlinear parameter value database corresponding to different tissue degradation levels obtained in the step 2) in advance, and the evaluation starting button is clicked according to the input furnace tube service time and the nonlinear parameter values measured in each time, so that the tissue degradation state of the furnace tube to be evaluated can be given. The system can be integrated into a computer operating system, automatically records the nonlinear parameter values of each measurement and gives an evaluation result, or can be used as an independent evaluation system to manually input the service time of the furnace tube and the corresponding nonlinear parameter values and give the evaluation result.
The method has the advantages that under the condition of not damaging the integrity of the furnace tube to be evaluated, the degradation state of the high-temperature tissue in a large range of the HP type furnace tube can be quickly and accurately evaluated in a nondestructive mode, and the defects that the existing evaluation method is complicated in procedure, multiple in artificial influence factor and small in coverage range are overcome.
Drawings
FIG. 1 is a metallographic photograph of an undegraded structure (grade 1) of an HP-type furnace tube.
Fig. 2 is a metallographic photograph of a slightly deteriorated structure (grade 2) of an HP-type furnace tube.
FIG. 3 is a metallographic photograph of a moderately deteriorated structure (grade 3) of an HP-type furnace tube.
FIG. 4 is a metallographic photograph of a highly deteriorated structure (grade 4) of an HP-type furnace tube.
Fig. 5 is a metallographic photograph of a HP-type furnace tube heavily deteriorated structure (grade 5).
Figure 6 is a schematic illustration of guided wave formation in a pipe.
Figure 7 is a wave pattern for which ultrasonic guided waves are primarily applied.
Fig. 8 is a block diagram of a torsional wave nonlinear parameter measurement system.
Fig. 9 is a schematic diagram of the evaluation process of the torsional wave single-sided transmission method.
Fig. 10 is a windowed sinusoidal burst waveform.
FIG. 11 is a laboratory calibrated furnace tube texture degradation level versus non-linear parameter.
FIG. 12 is a schematic representation of determining furnace tube texture degradation levels using calibration maps
FIG. 13 is a schematic diagram illustrating the determination of the degradation level of the furnace tube texture by using the HP-type furnace tube high-temperature texture degradation nondestructive evaluation system.
In fig. 9: 1 transmitting transducer, 2 couplant, 3 organic glass wedge block and 4 receiving transducer.
Detailed Description
The present invention is further illustrated by the following specific examples.
Determining proper detection parameters by using torsional waves, making a calibrated HP type furnace tube high-temperature tissue degradation level-nonlinear parameter relative relation graph in a laboratory, measuring a nonlinear ultrasonic parameter value of a furnace tube to be evaluated by using a nonlinear parameter measuring system, comparing the service time of the furnace tube and the nonlinear parameter value obtained by measurement with the calibrated HP type furnace tube high-temperature tissue degradation level-nonlinear parameter relative relation graph or inputting the result into the HP type furnace tube high-temperature tissue degradation evaluation system, and determining the tissue degradation state of the furnace tube to be evaluated. The method comprises the following specific steps:
1) building a nonlinear parameter measurement system, determining detection parameters and detection modes
The nonlinear parameter measuring system consists of an RAM-5000 type nonlinear ultrasonic detector, an attenuator, a low/high pass filter, an amplifier, an oscilloscope, a computer and a transmitting/receiving transducer, wherein the oscilloscope is connected with the RAM-5000 type nonlinear ultrasonic detector and the computer, and the computer is connected with the RAM-5000 type nonlinear ultrasonic detector. The RAM-5000 type nonlinear ultrasonic detector transmits a finite amplitude ultrasonic pulse train as an excitation waveform, and the excitation waveform is adjusted by an attenuator and then transmitted to a transmitting transducer by a low-pass filter. After receiving the ultrasonic pulse train transmitted by the RAM-5000 type nonlinear ultrasonic detector, the transmitting transducer 1 transmits a limited amplitude ultrasonic pulse train with single frequency into the furnace tube to be evaluated and receives the ultrasonic pulse train through the receiving transducer 4; the transmitting frequency of the transmitting transducer 1 is set according to the acoustic characteristics of the furnace tube to be evaluated, and the frequency of the receiving transducer 4 is a multiple of the frequency of the transmitting transducer. The receiving signal of the receiving transducer 4 enters an oscilloscope after passing through a high-pass filter and an amplifier in sequence; the oscilloscope is used for displaying the transmitted and received waveform signals. The computer sets transmitting and receiving parameters through the RAM-5000 type nonlinear ultrasonic detector, acquires time domain waveform signals of the receiving transducer 4 through the oscilloscope, performs Fourier transformation on the time domain waveform signals to obtain an amplitude-frequency curve, and further obtains nonlinear parameter values.
Further, after receiving the ultrasonic pulse train transmitted by the RAM-5000 type nonlinear ultrasonic detector, the transmitting transducer 1 transmits the finite amplitude ultrasonic pulse train with single frequency to the furnace tube to be evaluated through the coupling agent 2 and the organic glass wedge 3, the ultrasonic pulse train is transmitted in a torsional wave form in the tube wall of the furnace to be evaluated, and is received by the receiving transducer 4 after passing through the organic glass wedge 3 and the coupling agent 2, and the received waveform enters a computer for processing after passing through a high-pass filter, an amplifier and an oscilloscope. The couplant 2 is viscous fluid, so that the transmitting transducer 1 or the receiving transducer 4 can be subjected to angle fine adjustment within a certain range to ensure that the received waveform is clear, and the propagation area of the torsional wave in the pipe wall is an evaluable area.
The HP type furnace tube is a centrifugal casting tube, crystal grains are large, attenuation to ultrasonic waves is serious, and in order to enable torsional waves to propagate for a certain distance to ensure that a detection area has a certain coverage range, the frequency of the selected ultrasonic waves cannot be too high. The wall thickness of the HP type furnace tube is generally 8-12 mm, and in order to ensure that guided waves are formed in the tube wall, the ultrasonic wavelength and the wall thickness of the furnace tube are selected to be in the same order of magnitude. In this embodiment, focusing mainly on the 2 nd harmonic, the detection process should be convenient for field implementation, and considering comprehensively, in this embodiment, the frequency of the transmitting transducer is selected to be 0.5MHz, and the frequency of the receiving transducer is selected to be 1 MHz. The detection mode is selected as a single-sided transmission method, as shown in fig. 9. The excitation waveform is divided into continuous waves and pulse waves, and compared with the continuous waves, the pulse waves are high in axial resolution, higher waveform amplitude can be obtained, and the nonlinear effect is stronger, so that the excitation waveform is selected to be a sinusoidal pulse train. The area to be evaluated is determined to be 200mm each time, and in order to ensure that stronger nonlinear effect is generated, the number of pulse trains is selected to be 8. In order to suppress the leakage of the frequency-divided spectral components of the received signal after fourier transform, windowing processing needs to be performed on the signal, and in practice, commonly used window functions can be divided into three types, namely a power window, a trigonometric function window and an exponential window, wherein the trigonometric function window includes a hanning window, a hamming window and the like, the main lobe of the hanning window is wide, the side lobe is small, and the hanning window has a good effect in terms of reducing the spectral leakage, so that the hanning window is selected to process the signal in the embodiment, and the windowed waveform is as shown in fig. 10.
2) Making a calibration chart
The specific process comprises the following steps: collecting actual HP furnace tube samples with different service times and different tissue degradation states, and ensuring that the number of samples of each degradation level is not less than 50, otherwise, manufacturing artificial samples of corresponding degradation levels in a laboratory. By using the nonlinear parameter measurement system and the detection parameters described in step 1) of this embodiment, the nonlinear parameter values of all samples at each degradation level are measured, and averaged after at least 5 times to obtain the nonlinear parameters of each sample at the degradation state of the tissue at that level, and a rectangular range is set according to the maximum value and the minimum value of 50 sets of nonlinear parameter values at each level to form a furnace tube tissue degradation level-nonlinear parameter relative relationship diagram, as shown in fig. 11.
3) Measurement of non-linear parameters of furnace tube to be evaluated
The nonlinear parameter measurement system and the detection parameters in step 1) in this embodiment are used to measure the nonlinear parameters of the actual furnace tube to be evaluated, each region to be evaluated is measured at least 5 times, and the average value is taken as the nonlinear parameter value of the furnace tube to be evaluated. The selected furnace tube to be evaluated is an HP type hydrogen production furnace tube with the service time of 12000h in an oil refinery of a petrochemical company, and the measured nonlinear parameter values are shown in Table 2.
Table 2 measurement results of nonlinear parameter values of 12000h hydrogen production furnace tube in service
4) Determining the organization deterioration state of the furnace tube to be evaluated
The tissue deterioration state of the furnace tube to be evaluated can be determined in two ways:
the first is a manual evaluation mode, the service time of the furnace tube and the nonlinear parameter value obtained in step 3) in this embodiment are compared with the relative relationship graph of the tissue degradation level and the nonlinear parameter obtained in step 2) in this embodiment, a point with a value of β of 0.2324 is found on the ordinate, a straight line parallel to the abscissa axis is made to intersect with the rectangular frames of the level 2 degradation and the level 5 degradation, and since the service time of the furnace tube is less than 80000h, the tissue degradation level of the furnace tube group can be determined to be level 2, as shown in fig. 12.
The second is an intelligent evaluation mode, in which the measurement result of step 3) in this embodiment is input into the HP-type furnace tube high-temperature tissue degradation nondestructive evaluation system, the service time is input at the same time, the evaluation start button is clicked, and the tissue degradation state of the furnace tube to be evaluated is obtained, in this embodiment, the data input according to table 2 is used to obtain that the tissue degradation state of the furnace tube to be evaluated is level 2, as shown in fig. 13. It is worth noting that the degree of dispersion of the nonlinear parameters in the 5-level tissue degradation state is large, and covers the nonlinear parameter values of 3-level and part of 2-level, so that the judgment must be performed by inputting the service time, and generally, the furnace tube with the service time of more than 80000h may have 5-level degradation.
The above-mentioned embodiments only express the embodiments of the present invention, but not should be understood as the limitation of the patent scope of the present invention, it should be noted that, for those skilled in the art, many variations and modifications can be made without departing from the concept of the present invention, and these all fall into the protection scope of the present invention.
Claims (2)
1. A HP type boiler tube high temperature tissue deterioration nondestructive evaluation method based on nonlinear torsional wave is characterized in that a pair of frequency doubling ultrasonic transducers is adopted to determine appropriate detection parameters and detection modes, firstly nonlinear parameters of samples of different tissue deterioration levels of the HP type boiler tube are measured in a laboratory, a calibrated tissue deterioration level-nonlinear parameter relative relation graph is manufactured, then a nonlinear parameter measurement system is utilized to measure the nonlinear parameter value of the boiler tube to be evaluated, the measured nonlinear parameter value is compared with the calibrated tissue deterioration level-nonlinear parameter relative relation graph or input into the HP type boiler tube high temperature tissue deterioration evaluation system, and the HP type boiler tube high temperature tissue deterioration state can be qualitatively evaluated; the method comprises the following steps:
1) building a nonlinear parameter measurement system, determining detection parameters and detection modes
Based on the built nonlinear parameter measurement system, nondestructive evaluation of furnace tube high-temperature tissue degradation is carried out by utilizing torsional waves; the HP type furnace tube nonlinear parameter measuring system determines the frequency of a transmitting/receiving ultrasonic transducer according to the tissue characteristics and the acoustic parameters of the HP type furnace tube, selects a detection mode according to the on-site working condition, and selects a proper excitation waveform, excitation string number and window function according to the size of a region to be evaluated;
the nonlinear parameter measuring system comprises an RAM-5000 type nonlinear ultrasonic detector, an attenuator, a low/high pass filter, an amplifier, an oscilloscope, a computer and a transmitting/receiving transducer, wherein the oscilloscope is connected with the RAM-5000 type nonlinear ultrasonic detector and the computer, and the computer is connected with the RAM-5000 type nonlinear ultrasonic detector; the RAM-5000 type nonlinear ultrasonic detector transmits a finite amplitude ultrasonic pulse train as an excitation waveform, and the excitation waveform is adjusted by an attenuator and then transmitted to a transmitting transducer by a low-pass filter; after the transmitting transducer receives the ultrasonic pulse train transmitted by the RAM-5000 type nonlinear ultrasonic detector, the transmitting transducer transmits a limited amplitude ultrasonic pulse train with single frequency into the furnace tube to be evaluated and receives the ultrasonic pulse train through the receiving transducer; the receiving signal of the receiving transducer enters the oscilloscope after passing through the high-pass filter and the amplifier in sequence; the oscilloscope is used for displaying the transmitted and received waveform signals; the computer sets transmitting and receiving parameters through an RAM-5000 type nonlinear ultrasonic detector, acquires time domain waveform signals of the receiving transducer through an oscilloscope, performs Fourier transform on the time domain waveform signals to obtain an amplitude-frequency curve, and further obtains nonlinear parameter values;
when the incident acoustic frequency and the sample size are determined, obtaining nonlinear parameters of the furnace tube to be evaluated by measuring the amplitude of the second harmonic and the amplitude of the fundamental wave; the change of the nonlinear parameter is related to the form of the carbide in the furnace tube, so that the form change of the carbide in the furnace tube can be qualitatively evaluated by measuring a second-order nonlinear parameter value, and further the degradation state of the furnace tube structure can be evaluated;
2) calibration graph making
A furnace tube tissue degradation level-nonlinear parameter relative relation graph is manufactured in a laboratory, and the process is as follows: for each tissue degradation level, collecting furnace tube samples, measuring n times of nonlinear parameters of each sample by adopting the nonlinear parameter measuring system and the detection parameters in the step 1), averaging to obtain the nonlinear parameters of all samples in the tissue degradation state of the level, and setting a rectangular range by taking the maximum value and the minimum value of the nonlinear parameters in the tissue degradation state of the level as boundaries to form a tissue degradation level-nonlinear parameter relative relation graph;
3) measurement of non-linear parameters of furnace tube to be evaluated
Measuring the nonlinear parameters of the actual furnace tube to be evaluated by adopting the nonlinear parameter measuring system and the detection parameters in the step 1), measuring each region to be evaluated at least 5 times, and taking the average value as the nonlinear parameter value of the furnace tube to be evaluated;
4) determining the organization deterioration state of the furnace tube to be evaluated
Determining the structure deterioration state of the furnace tube to be evaluated by adopting the following two ways:
the first one is a manual evaluation mode, the service time of the furnace tube and the nonlinear parameter values of the furnace tube to be evaluated obtained in the step 3) are compared with the calibration graph obtained in the step 2), corresponding nonlinear parameter values are found in the graph by the ordinate, the tissue degradation level of the furnace tube to be evaluated corresponds to the abscissa, and since the 5-level degradation is overlapped with the nonlinear parameter values of the 2-level degradation and the 3-level degradation, the judgment is carried out according to the service time of the furnace tube, and the 5-level degradation occurs after the service time of the furnace tube is 80000 h;
and secondly, an intelligent evaluation mode is adopted, the nonlinear parameter values measured in each time in the step 3) are input into the HP type furnace tube high-temperature tissue degradation nondestructive evaluation system, the HP type furnace tube high-temperature tissue degradation nondestructive evaluation system is embedded into the nonlinear parameter value database corresponding to different tissue degradation levels obtained in the step 2) in advance, and the evaluation starting button is clicked according to the input furnace tube service time and the nonlinear parameter values measured in each time, so that the tissue degradation state of the furnace tube to be evaluated can be given.
2. The non-destructive evaluation method for the high-temperature tissue degradation of the HP type furnace tube based on the nonlinear torsional wave as claimed in claim 1, wherein the transmitting frequency of the transmitting transducer is set according to the acoustic characteristics of the furnace tube to be evaluated, and the frequency of the receiving transducer is a multiple of the frequency of the transmitting transducer; if the nth harmonic is of interest, the frequency of the receiving transducer is N times the frequency of the transmitting transducer, as determined by the higher harmonic of interest.
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