Nondestructive testing method for inner surface defects of bearing raw material seamless steel tube

Abstract

The invention discloses a nondestructive testing method for inner surface defects of a bearing raw material seamless steel tube. The nondestructive testing method comprises the following steps: S1, determining parameter indexes of a surface wave transducer; s2, designing a transducer array; s3, signal excitation and receiving are carried out through a transducer array; s4, quantifying the defect degree; and S5, defect imaging. The method solves the problem that eddy current detection and ultrasonic body wave detection hardware in the prior art are difficult to effectively detect pit defects on the inner surface of the seamless steel tube in principle, so that a detection method for high-precision detection of the bearing raw material seamless steel tube is lacked in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing methods, and particularly to a nondestructive testing method for inner surface defects of seamless steel pipes used as bearing raw materials. Background Art

[0002] Rolling bearings are widely used in industrial production, and their inner and outer rings are usually processed from seamless steel pipes made of bearing steel. During the production and transportation of seamless steel pipes, defects such as scratches, pits, rust, adhesion, and through-cracks are likely to occur. If the steel pipes with defects are not detected and flow into the subsequent processing links, it will affect the quality of the inner and outer rings of the bearings, increase the processing cost, and may also reduce the performance and service life of the ball bearings.

[0003] Currently, bearing companies mainly use methods such as eddy current testing, magnetic flux leakage testing, and ultrasonic body wave testing to detect seamless steel pipes. Although the detection speed of these methods can reach 0.5 - 1 m / s, there are many limitations. For example, the setting of detection parameters depends on the experience of operators, and the missed detection rate is relatively high. Especially for pit-like defects inside the pipeline, the missed detection situation is prominent. Among them, eddy current testing is sensitive to the thickness of the pipeline, and the detection frequency needs to be adjusted according to the thickness. The sensitivity to inner surface defects is low. Among them, point eddy current testing is sensitive to axial cracks, and through-type eddy current testing is sensitive to through-holes. For thick-walled steel pipes with a wall thickness greater than 5 mm, detection blind spots are likely to occur, resulting in missed detection of inner wall defects. And ultrasonic testing includes a thickness measurement channel and a flaw detection channel. The thickness measurement channel mainly measures the thickness of the pipeline and can occasionally detect large-area pits, but it is difficult to find small-area pits. The flaw detection channel is sensitive to axial cracks and has insufficient sensitivity to inner surface pits. Moreover, the rotation speed and feed speed of ultrasonic body wave testing need to be matched through a sample pipe. If not matched, detection blind spots will be generated. During the double inspection process, eddy current testing requires a faster feed speed, while ultrasonic testing requires a slower feed speed. When adjusting the feed rate to balance the efficiency of the two detection methods, the detection quality will decline. In summary, the existing detection technologies are difficult to effectively detect pit defects on the inner surface of seamless steel pipes in principle, which poses a challenge to the quality control of seamless steel pipes used as bearing raw materials. There is an urgent need to develop new detection methods to improve the detection accuracy and reduce the missed detection rate. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a nondestructive testing method for inner surface defects of seamless steel pipes used as bearing raw materials, in order to solve the problem that in the existing technology, eddy current testing and ultrasonic body wave testing hardware are difficult to effectively detect pit defects on the inner surface of seamless steel pipes, resulting in the lack of a detection method for high-precision detection of seamless steel pipes used as bearing raw materials in the existing technology.

[0005] To achieve the above object, the present invention provides a nondestructive testing method for inner surface defects of seamless steel pipes used as bearing raw materials, including the following steps: S1. Design the parameters of the ultrasonic guided wave surface wave transducer according to the size and material properties of the seamless steel pipe to be detected; S2. Build a test system, which includes a transducer array built on the inner surface of the seamless steel pipe to be detected; S3. The test system excites and receives ultrasonic guided wave surface waves of a specific mode through the water coupling method; S4. The test system uses the propagation characteristics of the guided wave to detect defects on the inner surface of the steel pipe, analyzes the defect characteristics of the echo signal, calculates the characteristic parameters based on the echo reflection coefficient formula derived from the elastic dynamics reciprocity theorem, and quantifies the defect degree; S5. The test system performs defect imaging through the delay - superposition reconstruction algorithm based on the wave velocity of a specific mode guided wave in the pipeline, and realizes the positioning and quantitative analysis of defects.

[0006] The present invention is further provided that: the transducer array works in the self - exciting self - checking or alternating excitation and receiving mode.

[0007] The present invention is further provided that: the test system further includes a signal generator, a power amplifier, an array control system, a pre - filter amplifier and a signal processing computer.

[0008] The present invention is further provided that: the number of transducers in the transducer array is a positive even number and the positions of every two transducers are symmetrically arranged.

[0009] The present invention is further provided that: water inlets are arranged on both sides of the transducers in the transducer array.

[0010] The advantages of adopting the above - mentioned technical solutions are as follows: compared with the existing eddy current detection and ultrasonic body wave detection in the production line, the present invention can detect defects on the inner surface of seamless steel pipes more accurately, effectively reduce the missed detection rate. At the same time, by adopting the water coupling detection method of the surface wave transducer, the detection efficiency is high, it can adapt to complex working environments, and is suitable for large - batch industrial detection. By applying the formula derived from the elastic dynamics reciprocity theorem, not only can the defect be located, but also the defect can be quantitatively detected to obtain information such as the damage size and depth. Description of the Drawings

[0011] Figure 1 It is a side schematic diagram of the working principle of the surface wave transducer used in the present invention; Figure 2 It is a front schematic diagram of the working principle of the surface wave transducer used in the present invention; Figure 3 It is a structural schematic diagram of the surface wave transducer array in the present invention; Figure 4 It is a schematic diagram of the principle of deriving the echo reflection coefficient formula from the elastic dynamics reciprocity theorem in the present invention; Figure 5It is the flowchart of signal processing and defect reconstruction calculation in the present invention; Figure 6 The center frequency of the surface wave transducer exemplified in the present invention satisfies the formula; Figure 7 It is the schematic diagram of the echo reflection coefficient formula derived based on the reciprocity theorem of elastodynamics in the present invention; Figure 8 It is Figure 7 The schematic diagram of the introduction of the meanings of some symbols in the formula shown; Figure 9 It is Figure 8 The schematic diagram of the introduction of the calculation formulas of some symbols derived from the formula shown; Figure 10 It is Figure 9 The schematic diagram of the introduction of the calculation formulas of some symbols in the formula shown; Figure 11 It is Figure 10 The schematic diagram of the introduction of the meanings of some symbols in the formula shown. Specific embodiments

[0012] The present invention provides a method for non-destructive detection of internal surface defects of seamless steel pipes for bearing raw materials, including the following steps: S1. Design the parameters of the ultrasonic guided wave surface wave transducer according to the size and material properties of the seamless steel pipe to be detected; S2. Build a test system, and the test system includes a transducer array built on the inner surface of the seamless steel pipe to be detected; S3. The test system excites and receives ultrasonic guided wave surface waves of a specific mode through the water coupling method; S4. The test system uses the propagation characteristics of the guided wave to detect the defects on the inner surface of the steel pipe, analyzes the defect characteristics of the echo signal, and calculates the characteristic parameters based on the echo reflection coefficient formula derived from the reciprocity theorem of elastodynamics to quantify the degree of the defect; S5. The test system performs defect imaging through the delay-superposition reconstruction algorithm based on the wave velocity of a specific mode guided wave in the pipeline to realize the positioning and quantitative analysis of the defect.

[0013] Furthermore: The transducer array works in the self-excitation self-test or alternate excitation and reception mode.

[0014] Furthermore: The test system further includes a signal generator, a power amplifier, an array control system, a pre-filter amplifier, and a signal processing computer.

[0015] Furthermore: The number of transducers in the transducer array is a positive even number, and the positions of every two transducers are symmetrically arranged.

[0016] Furthermore: water inlets are arranged on both sides of the transducers in the transducer array.

[0017] Based on the above document, the specific implementation process includes: S1. Determination of design parameters of surface wave transducer: According to the specific size and material of seamless steel pipe, design the curvature of the coupling surface of oblique incident transducer according to the inner diameter of the pipe to ensure the coupling effect. Determine the center frequency of the transducer according to the defect size to be detected. Taking 1mm deep pit as an example, the surface wave velocity is usually about 3000m / s. The center frequency of the surface wave transducer used should meet certain conditions (see the attached manual). Figure 6 ); S2. Transducer array design: Build a test system and transducer array. The test system is mainly composed of a signal generator, a power amplifier, a duplexer / transducer array control system, a transducer array, a pre-filter amplifier, and an oscilloscope / signal processing computer. If the transducer self-excitation self-test test method is adopted, a duplexer is selected at the corresponding position; if the array measurement point is alternately excited and received, a transducer array control system is designed at this position; the transducer array should be as densely distributed as possible while ensuring symmetry under the premise of size. 2, 4, or 8 transducers can be selected to form an array. During the test, the surface wave transducer is excited by a sinusoidal pulse signal modulated by a Hanning window to obtain the echo signal after the surface wave propagates on the inner wall of the seamless steel pipe, and the received signal is analyzed by the signal processing system; S3. Optimize the design of the surface wave transducer to excite the surface wave mode, select the transducer excitation and receiving mode according to the detection requirements, that is, adopt the self-excitation self-test detection method or the test method of alternating excitation and reception, design water inlets on both sides of the transducer coupling surface for water coupling, and improve the detection efficiency; S4. Calculate the damage degree based on the characteristics of the reflected wave signal: The pit defect on the material surface can be mathematically abstracted as a surface with a circular arc cross section for approximate calculation. The relevant formula is derived based on the dispersion theory of ultrasonic guided waves and the reciprocity theorem of elastic dynamics (see the original handover material for the specific formula). In actual measurement, based on the known incident surface wave amplitude and defect reflection wave amplitude, the pit defect depth, length and other dimensional parameters can be reversely evaluated to reflect the degree of the defect; S5. Defect analysis and imaging: After obtaining the time domain signals of the reflected echoes received by all transducers, the time domain signals are converted into damage degree-location distribution through the above algorithm. The delayed superposition method is applied to reconstruct defect images, and the detection signals are converted into intuitive imaging results of inner surface defects to achieve accurate defect positioning and size assessment.

[0018] In the above-mentioned technology, as shown in the attached drawings of the specification (4), the pit defects on the material surface can be abstracted mathematically as a surface with a cross-section of an arc for approximate calculation. For the surface pit defects with a circular arc shape, the calculation formula for the surface wave reflection amplitude can be found in the attached drawings of the specification (7). This formula is jointly derived from the dispersion theory of ultrasonic guided waves and the reciprocity theorem of elastodynamics. At the same time, the meanings represented by some symbols in this formula can be found in the attached drawings of the specification (8), and the formula meanings of some symbols derived from this formula can be found in the attached drawings of the specification (9). The attached drawings of the specification Figure 10 is a schematic diagram for introducing the calculation formulas of some symbols in the formula shown in the attached drawings of the specification; the attached drawings of the specification Figure 9 is shown; the attached drawings of the specification Figure 11 is the attached drawings of the specification Figure 10 is a schematic diagram for introducing the meanings represented by some symbols in the formula shown in the attached drawings of the specification; Based on the above formula, in actual measurement, on the basis of knowing the amplitude of the incident surface wave and the amplitude of the defect reflected wave, the size parameters such as the depth and length of the pit defect can be evaluated reversely, so as to reflect the degree of the defect.

[0019] In the above-mentioned attached drawings of the specification Figure 3 1 is marked as a signal generator, 2 is marked as a power amplifier, 3 is marked as a duplexer / transducer array control system, 4 is marked as a transducer array, 5 is marked as a pre-filter amplifier, and 6 is marked as an oscilloscope / signal processing computer.

[0020] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A method for nondestructive detection of inner surface defects of seamless steel pipes as bearing raw materials, characterized by: The following steps are involved: S1. Design the ultrasonic guided wave surface wave transducer parameters according to the size and material properties of the seamless steel pipe to be tested; S2. Building a test system, the test system comprising a transducer array built on the inner surface of the seamless steel pipe to be tested; S3, the test system excites and receives a specific mode of ultrasonic guided surface waves through water coupling; S4. The test system uses the propagation characteristics of the guide to detect defects on the inner surface of the steel pipe, analyzes the defect characteristics of the echo signal, calculates the characteristic parameters based on the echo reflection coefficient formula derived from the reciprocity theorem of elastic dynamics, and quantifies the degree of defects; S5. The test system uses a delay-superposition reconstruction algorithm to perform defect imaging based on the specific modal guided wave velocity in the pipeline to achieve defect location and quantitative analysis.

2. The method for nondestructive detection of inner surface defects of a seamless steel tube as a bearing raw material according to claim 1, characterized in that: The transducer array works in a self-excitation and self-detection mode or in an alternating excitation and reception mode.

3. The method for nondestructive detection of inner surface defects of a seamless steel tube as a bearing raw material according to claim 2, characterized in that: The test system also includes a signal generator, a power amplifier, an array control system, a pre-filter amplifier and a signal processing computer.

4. The method for nondestructive detection of inner surface defects of a seamless steel tube as a bearing raw material according to claim 1, characterized in that: The number of transducers in the transducer array is a positive even number and every two transducer positions are symmetrically arranged.

5. The method for nondestructive detection of inner surface defects of a seamless steel tube as a bearing raw material according to claim 1, characterized in that: Water inlets are arranged on both sides of the transducers in the transducer array.

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