WO2024000981A1 - 一种内穿式弱磁检测探头及其工作方法 - Google Patents

一种内穿式弱磁检测探头及其工作方法 Download PDF

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Publication number
WO2024000981A1
WO2024000981A1 PCT/CN2022/129558 CN2022129558W WO2024000981A1 WO 2024000981 A1 WO2024000981 A1 WO 2024000981A1 CN 2022129558 W CN2022129558 W CN 2022129558W WO 2024000981 A1 WO2024000981 A1 WO 2024000981A1
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weak magnetic
detection probe
magnetic detection
penetrating
probe according
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PCT/CN2022/129558
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English (en)
French (fr)
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殷尊
李佼佼
侯召堂
张红军
高磊
孟永乐
吕一楠
孙璞杰
高延忠
林琳
朱婷
吕游
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西安热工研究院有限公司
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Publication of WO2024000981A1 publication Critical patent/WO2024000981A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux

Definitions

  • This application belongs to the technical field of weak magnetic detection, and specifically relates to an internal penetrating weak magnetic detection probe and its working method.
  • the condenser is an important component of the steam power system. Its main function is to cool and condense the exhaust steam of the steam turbine, and together with the steam generator, form a steam-water energy cycle.
  • the condenser of the steam power system of a nuclear (thermal) power plant mostly adopts a surface heat exchange structure, in which cooling water and steam exchange heat through a solid surface.
  • the shell-and-tube condenser is the most commonly used.
  • the welded joints between the heat exchange tubes and the tube sheets of the condenser are prone to corrosion.
  • the corrosion of heat exchange tubes generally includes electrochemical corrosion, stress corrosion and erosion corrosion. Electrochemical corrosion is more common. In a humid environment, positive and negative electrode potentials will be formed, resulting in electrochemical corrosion.
  • the stress sources that cause stress corrosion include: working pressure caused by the difference in temperature between the inlet and outlet; residual stress generated during processing; structural stress generated during the manufacturing process due to structural design, etc. Erosion corrosion mostly occurs at the steam inlet. Fluid erosion will cause tube bundle vibration, and in severe cases may lead to damage to the heat exchange tubes.
  • stainless steel or metal materials such as copper and titanium as raw materials to process heat exchange tubes.
  • stainless steel is prone to intergranular corrosion; copper pipes are prone to electrochemical corrosion with circulating water.
  • major power plants generally inject ammonia or hydrazine into the circulating water to ensure a high pH value to ensure that the supercritical unit is put into use. This puts higher requirements on the corrosion resistance of the heat exchange tubes.
  • titanium heat exchange tubes are increasingly favored by major power plants.
  • titanium heat exchange tubes are widely used in condensers and other equipment under harsh conditions.
  • the key heat exchange components are Almost all tube bundle materials are titanium tubes. Because the heat exchange titanium tubes have been exposed to harsh working conditions such as mineral salt corrosion and seawater impact for a long time, they are susceptible to corrosion damage, resulting in titanium tube fracture and failure, seriously affecting the safe operation of the condenser.
  • Non-destructive testing methods for titanium heat exchange tubes usually include eddy current testing and ultrasonic testing.
  • Eddy current testing uses the principle of electromagnetic induction to have high detection sensitivity and fast detection speed for defects on the surface or near the surface of the inspected part.
  • eddy current is an induced current generated by an alternating magnetic field and is affected by the "skin effect"
  • ultrasonic testing is also widely used in the detection of pipeline materials and can locate and quantify defects.
  • ultrasonic flaw detection is not intuitive enough to display defects, is easily affected by subjective and objective factors, and relies heavily on the on-site experience of inspectors.
  • the purpose of this application is to provide an internally penetrating weak magnetic detection probe and its working method, which have a simple structure, reasonable design, easy operation, can accurately identify and quantitatively analyze defects, and have a wide range of applications. wide and does not depend on the operator's experience and skill level.
  • the present application discloses an internally penetrating weak magnetic detection probe, which includes a body; a signal line storage tube is provided in the front of the body and a number of weak magnetic sensor groups evenly distributed around the inner wall of the body; each weak magnetic sensor group includes 2 along the A weak magnetic sensor is arranged in the axis direction of the body.
  • the magnetically sensitive surface of the weak magnetic sensor is perpendicular to the wall of the body and faces outward.
  • the rear part of the body is equipped with a roller for driving the body to move linearly. The roller is connected to a motor.
  • the rear end of the rear part of the body is equipped with a Connection port; the signal wire of the weak magnetic sensor passes through the signal wire storage tube and is collected together with the motor's connection wire to the connection port.
  • the body includes a first body, an intermediate connector and a second body that are detachably connected in sequence; a signal wire storage tube and a number of weak magnetic sensors are arranged in the first body; the intermediate connector and the signal wire storage tube are It is connected to the inside of the second body, the roller is arranged on the second body, the motor is arranged inside the second body, and the connection port is arranged at the rear end of the second body.
  • the number of weak magnetic sensor groups is 6 to 12.
  • a distance measuring sensor is provided at the front end of the body, and the distance measuring sensor is connected to the connection port through a connecting wire.
  • ranging sensors are provided on both sides of the body, and the ranging sensors are connected to the connection port through a connecting wire.
  • the front end of the body is provided with an anti-collision contact.
  • the outer surface of the signal wire storage tube is covered with magnetic shielding material.
  • a counterweight is provided in the rear part of the body.
  • the working method of the above-mentioned internal penetrating weak magnetic detection probe disclosed in this application includes
  • connection ports are respectively connected to the weak magnetic flaw detector and the host computer, and the parameters of the probe are input into the host computer; the body is placed into the entrance of the condensation tube, and the motor drives the roller to rotate, thereby driving the entire body forward;
  • the two weak magnetic sensors in each weak magnetic sensor group are scanned in sequence.
  • the host computer displays the two magnetic induction intensity-time curves detected by each weak magnetic sensor group in real time to determine whether there is a defect and the specifications of the defect. .
  • This application discloses an internally penetrating weak magnetic detection probe that applies weak magnetic non-destructive testing technology to the defect detection of titanium heat exchange tubes.
  • Weak magnetic detection technology is a passive detection technology that does not require additional excitation sources. On the one hand, it can simplify the probe process design, and on the other hand, it also avoids the impact of the interference source field caused by the non-directional stress of the excitation source on the detection process.
  • the weak magnetic detection method is easy to learn and use, because weak magnetic detection does not require special treatment of the surface of the workpiece to be inspected, and there are no special requirements for the shape of the workpiece to be inspected. Neither coating detection nor non-contact detection affects the detection effect.
  • a high-precision weak magnetic sensor is used to scan the surface or near surface of the test piece, and the changes in magnetic induction intensity in different directions are collected to determine whether there is a magnetic anomaly in the detection area, and then the collected magnetic signals are analyzed. deal with.
  • the weak magnetic detection method is a comparative measurement method, which determines the type and quantification of defects by comparing the difference in signals between normal areas and magnetic abnormal areas.
  • an in-penetrating probe structure is designed for the characteristics of small diameter and thin wall thickness of the condenser heat exchange tube.
  • Several groups of weak magnetic sensors are evenly distributed in the circumferential direction of the front part of the probe. Each group of weak magnetic sensors consists of 2 weak magnetic sensors.
  • a roller device is set at the rear of the probe to facilitate the probe moving back and forth in the heat exchange pipe.
  • the probe body is made into a split structure, which is convenient for portability, storage, repair and maintenance.
  • the front end of the body is equipped with a distance measuring sensor, which can prevent collision damage caused by blockage of the heat exchange tube.
  • distance sensors are provided on both sides of the main body, which can promptly detect the narrowing of the internal diameter of the heat exchange tube.
  • the front end of the body is provided with an anti-collision contact to prevent the probe from being damaged by collision.
  • the outer surface of the signal line storage tube is covered with magnetic shielding material, which can prevent the leakage magnetic flux generated by the weak magnetic sensor coil from affecting the stability of the probe.
  • the working method of the above-mentioned internal penetrating weak magnetic detection probe disclosed in this application is easy to operate, has high detection efficiency and accurate results, and does not rely on the operator's experience and skill level.
  • Figure 1 is a schematic diagram of the overall structure of the probe of this application.
  • Figure 2 is a schematic diagram of a single magnetic measurement module inside the probe of this application.
  • FIG. 3 is a schematic diagram of the working status of the probe of this application.
  • Figure 4 is a schematic flow chart of the detection method of this application.
  • FIG. 5 is a schematic diagram of the detection principle of this application.
  • Figure 6a is a schematic diagram of feature value extraction of a single magnetic weakening curve
  • Figure 6b is a schematic diagram of the weak magnetic signals of two adjacent weak magnetic sensors scanning the same defect one after another;
  • Figure 7 shows the heat exchange tube processed with artificial inner wall thinning ring used in the testing example
  • Figure 8 is the original scanning curve chart of the detection example
  • Figure 9 is a differential curve diagram of a detection example.
  • 1 is the first body
  • 2 is the second body
  • 3 is the signal line storage tube
  • 4 is the weak magnetic sensor
  • 5 is the roller
  • 6 is the intermediate connector
  • 7 is the anti-collision contact
  • 8 is the condensation tube
  • 9 is the wire harness
  • 10 is the weak magnetic flaw detector.
  • an internally penetrating weak magnetic detection probe of the present application includes a signal line storage tube 3 in the front of the body and a number of weak magnetic sensor groups evenly distributed around the inner wall of the body.
  • Each weak magnetic sensor group includes 2
  • the magnetic sensing surface of the weak magnetic sensor 4 is perpendicular to the wall of the body and faces outward.
  • the back of the body is provided with a roller 5 for driving the body to move linearly.
  • the roller 5 is connected to a motor.
  • a connection port is provided at the rear end of the part; the signal wire of the weak magnetic sensor 4 passes through the signal wire storage tube 3 and is collected together with the connection wire of the motor to the connection port.
  • the body is made of ABS plastic as the tooling material, so that the tooling has good shock resistance and certain heat insulation properties.
  • the body includes a first body 1, an intermediate connector 6 and a second body 2 that are detachably connected in sequence; the signal line storage tube 3 and a number of weak magnetic sensor groups are located on the first In one body 1, the intermediate connecting body 6 is connected with the signal wire storage tube 3 and the second body 2.
  • the roller 5 is provided on the second body 2, the motor is provided in the second body 2, and the connection port is provided on The back end of the second body 2.
  • the number of weak magnetic sensor groups can be set to 6 to 12.
  • a ranging sensor is provided at the front end of the body, and the ranging sensor is connected to the connection port through a connecting wire.
  • ranging sensors are provided on both sides of the body, and the ranging sensors are connected to the connection port through a connecting wire.
  • an anti-collision contact 7 is provided at the front end of the body.
  • Magnetic shielding materials can be thin film materials processed from permalloy.
  • a counterweight is provided in the rear part of the body.
  • the working method of the above-mentioned internal penetrating weak magnetic detection probe includes:
  • connection ports are connected to the weak magnetic flaw detector 10 and the host computer respectively, and the parameters of the probe are input into the host computer; the body is placed into the entrance of the condensation tube 8, and the motor
  • the driving roller 5 rotates, thereby driving the entire body forward; during the detection process, the two weak magnetic sensors 4 in each weak magnetic sensor group scan in sequence, and the host computer displays in real time two magnetic induction intensities detected by each weak magnetic sensor group - Time curve to determine whether there is a defect and the specification of the defect.
  • differential processing is performed on the magnetic induction intensity-time curve to obtain the corresponding differential curve and a threshold line is set to intuitively respond to the mutation characteristics of the curve that exceed the threshold line range.
  • the magnetic permeability of the material being tested is ⁇
  • the magnetic permeability of the discontinuous area inside the workpiece is ⁇ '. If the relative magnetic permeability of the discontinuous area is greater than the relative magnetic permeability of the material being tested, that is, ⁇ '> ⁇ , then when the weak magnetic sensor passes through this area, the magnetic induction intensity curve will appear concave; if the relative magnetic permeability of the discontinuous area is less than the relative magnetic permeability of the material being tested, that is, ⁇ ' ⁇ , then when the weak magnetic field When the sensor passes through this area, the magnetic induction intensity curve will appear convex.
  • Weak magnetic detection technology uses high-precision magnetic sensors to detect abnormal signals of sudden changes in magnetic induction intensity, thereby characterizing material defects.
  • Titanium metal is a paramagnetic material. According to the principle of weak magnetic detection, use a weak magnetic probe to scan the titanium tube evenly. It is not difficult to find that the weak magnetic signal remains gentle at places without defects; at places close to defects, the weak magnetic signal begins to rise; Near the top of the defect, the weak magnetic signal will have a peak. In the quantitative study of defects, this application extracts the relevant characteristic values of the weak magnetic signals of the defects, and then calculates and inverts a large amount of data to achieve quantitative estimation of the defects.
  • the shape of the magnetic anomaly is closely related to the magnetic induction intensity curve caused by the defect.
  • the host computer software displays an approximately axially symmetrical figure in real time, as shown in Figure 6a.
  • the size data related to the magnetic induction intensity value is obtained.
  • ⁇ B1 be the difference between the maximum peak value of the defect signal and the minimum value at the left end
  • ⁇ L1 be the half-wave width on the left side of the defect signal
  • ⁇ B2 be the difference between the maximum peak value of the defect signal and the minimum value on the right end
  • ⁇ L2 be the half-wave width on the right side of the defect signal. It is easy to get the following formula:
  • ⁇ B is the average amplitude difference between the peak and trough of the defect signal
  • ⁇ L is the average half-wave width of the defect signal
  • the dotted line on the left and the solid line on the right are the magnetic weakening signals of two adjacent magnetic weak sensors scanning the same defect one after another.
  • ⁇ Bm is the peak value of the first magnetic weak sensor and the peak value of the second magnetic weak sensor.
  • ⁇ Bu be the amplitude difference obtained by the first weak magnetic sensor
  • B 1 be the average magnetic induction intensity value obtained by the first weak magnetic sensor
  • B 2 be the average magnetic induction intensity obtained by the second weak magnetic sensor. value
  • ⁇ S as the distance between the two weak magnetic sensors, taking a fixed value of 1mm. So we get the empirical formula:
  • K is the proportional adjustment coefficient
  • A1 and A2 are empirical coefficients related to the material's magnetic permeability
  • D is the defect depth.
  • a total of 6 pairs of weak magnetic sensor groups are arranged evenly distributed along the circumferential direction of the inner wall of the probe, and every two weak magnetic sensors are arranged side by side to form a pair of weak magnetic sensors.
  • the probe is connected to the weak magnetic flaw detector through the connection port.
  • One end of the weak magnetic flaw detector is connected to the probe, and the other end is connected to the host computer (notebook) through an Ethernet cable.
  • the host computer serves as the control terminal of the entire detection system.
  • the host computer software can perform real-time analysis of the weak magnetic signal and receive the signal at the same time.
  • the probe contacts and roller device transmit signals in real time and perform feedback operations on them.
  • two weak magnetic sensors arranged in parallel scan the area to be inspected in sequence.
  • the specific work flow is: 1. Connect the detection probe of this application to the weak magnetic flaw detector, and ensure that the collected weak magnetic signal can be presented in the host computer software interface in real time; 2. Place the detection probe at the entrance of the pipeline, and pass the upper The machine (control terminal) issues instructions to make the servo motor start working to ensure that the detection probe can advance and retreat normally in the pipeline; 3. Arrange a distance sensor directly in front of the probe contact. When the (measured) feedback distance data is less than the length of the heat exchange tube , it means that the pipeline is blocked and needs human intervention; distance sensors are also arranged on the left and right sides of the probe contact.
  • the detection probe When the measured data is larger than the diameter of the heat exchange tube or diverges directly, it means that there is a perforation defect in the inner wall of the pipeline at this location. Or the detection probe has moved out of the pipe mouth, and the servo motor automatically stops at this time; 4. Enter the K value, A1 value and A2 value suitable for the titanium pipe in the host computer software; 5. The detection starts, and the host computer software displays 6 in real time Group interface, each group of interfaces presents two magnetic induction intensity-time curves in real time. Then, the algorithm is used to accurately capture characteristic values such as amplitude and half-wave width. Based on the empirical formula obtained from many previous tests, it is judged whether there is a (corrosion) defect at the location and the degree of damage of the defect is estimated.
  • the steps include:

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Abstract

一种内穿式弱磁检测探头及其工作方法，属于弱磁检测技术领域。包括本体；本体前部内设有信号线收纳管（3）和若干环绕本体内壁均布的弱磁传感器组，每个弱磁传感器组包括2个沿本体轴线方向排布的弱磁传感器（4），弱磁传感器（4）的测磁敏感面垂直本体壁面向外；本体后部设有用于驱动本体直线移动的滚轮（5），滚轮（5）连接有电机；本体后部的后端设有连接端口；弱磁传感器（4）的信号线穿过信号线收纳管（3）与电机的连接线一同汇总至连接端口。内穿式弱磁检测探头结构简单、设计合理、操作方便，能够准确地对缺陷进行识别和定量分析，且应用范围广，不依赖操作者的经验和技能水平。

Description

一种内穿式弱磁检测探头及其工作方法
交叉引用
本申请要求在2022年6月29日提交中国国家知识产权局、申请号为202210753040.8、发明名称为“一种内穿式弱磁检测探头及其工作方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请属于弱磁检测技术领域，具体涉及一种内穿式弱磁检测探头及其工作方法。
背景技术
凝汽器是蒸汽动力系统的重要组成装置，其主要作用是对汽轮机的排汽过程进行冷却、凝结，与蒸汽发生器共同构成汽—水能量循环。核(热)电厂蒸汽动力系统的凝汽器多采用表面式换热结构，该结构中冷却水与蒸汽通过固体表面进行换热。目前使用最为普遍的管壳式凝汽器，在实际应用过程中，凝汽器的换热管与管板焊接接头是易发生腐蚀的部位。换热管受到的腐蚀一般有电化学腐蚀、应力腐蚀和冲刷腐蚀。电化学腐蚀较为常见，在潮湿的环境下会形成正负电极位，从而形成电化学腐蚀现象。产生应力腐蚀的应力来源有：进出口温差不同所产生的工作压力；加工过程中产生的残余应力；结构设计导致的在制造过程中产生的结构应力等。冲刷腐蚀大多发生在进汽口位置，流体冲刷会引起管束振动，严重时可能导致换热管的破损。
在生产过程中，制造厂一般采用不锈钢或者铜、钛等金属材料作为原材料加工换热管。在某些特殊的腐蚀环境，不锈钢容易发生晶间腐蚀；铜管容易与循环水发生电化学腐蚀。目前各大电厂普遍在循环水注入氨或联氨保证高PH值，以保证超临界机组投入使用，这对换热管的耐腐蚀性提出了更高的要求。钛作 为优质耐蚀材料，同时具有良好的塑性和韧性，易于焊接加工成型，因此钛材换热管越来越受到各大电厂的青睐。钛材换热管作为一种优异的耐腐蚀材料被广泛用于恶劣条件下的凝汽器等设备中，尤其在临海核电站，以海水作为循环冷却介质的凝汽器，其关键热交换部件的管束材料几乎全部采用钛管。由于换热钛管长期处于矿物盐侵蚀和海水冲击作用等恶劣工况下，容易受到腐蚀损伤，导致钛管断裂失效，严重影响凝汽器的安全运行。
钛材换热管的无损检测方式通常有涡流检测和超声波检测。涡流检测利用电磁感应原理，对被检测件表面或近表面的缺陷，有较高的检测灵敏度，而且检测速度快。但由于涡流是交变磁场产生的感应电流，且受到“趋肤效应”影响，其信号难以判断缺陷类型。超声波检测也是广泛运用到管道材料的检测中，并且能够对缺陷进行定位与定量，但是超声波探伤对缺陷的显示不够直观，容易受到主客观因素的影响，对检验人员的现场经验依赖较高。
发明内容
为了解决上述现有问题，本申请的目的在于提供一种内穿式弱磁检测探头及其工作方法，结构简单、设计合理、操作方便，能够准确地对缺陷进行识别和定量分析，且应用范围广，不依赖操作者的经验和技能水平。
本申请通过以下技术方案来实现：
本申请公开的一种内穿式弱磁检测探头，包括本体；本体前部内设有信号线收纳管和若干环绕本体内壁均布的弱磁传感器组，每个弱磁传感器组包括2个沿本体轴线方向排布的弱磁传感器，弱磁传感器的测磁敏感面垂直本体壁面向外；本体后部设有用于驱动本体直线移动的滚轮，滚轮连接有电机；本体后部的后端设有连接端口；弱磁传感器的信号线穿过信号线收纳管与电机的连接线一同汇总至连接端口。
可选地，所述本体包括依次可拆卸连接的第一本体、中间连接体和第二本体；信号线收纳管和若干弱磁传感器组设在第一本内，中间连接体与信号线收 纳管和第二本体内部贯通，滚轮设在第二本体上，所述电机设在第二本体内，所述连接端口设在第二本体的后端。
可选地，弱磁传感器组的数量为6～12。
可选地，所述本体的前端设有测距传感器，测距传感器通过连接线连接至所述连接端口。
可选地，所述本体的两侧设有测距传感器，测距传感器通过连接线连接至所述连接端口。
可选地，所述本体的前端设有防撞触头。
可选地，信号线收纳管外表面覆盖有磁屏蔽材料。
可选地，所述本体后部内设有配重块。
本申请公开的上述内穿式弱磁检测探头的工作方法，包括
通过所述连接端口分别与弱磁探伤仪和上位机连接，并在上位机中输入探头的参数；将所述本体置入冷凝管的入口，所述电机驱动滚轮转动，进而带动整个本体前进；检测过程中每组弱磁传感器组中的2个弱磁传感器依次扫查，上位机实时呈现每个弱磁传感器组检测得到的两条磁感应强度-时间曲线，判断是否存在缺陷以及该缺陷的规格。
可选地，对磁感应强度-时间曲线进行差分处理，得到相应的差分曲线并设置阈值线，对超过阈值线范围的曲线突变特征进行直观反应。
与现有技术相比，本申请具有以下有益的技术效果：
本申请公开的一种内穿式弱磁检测探头，将弱磁无损检测技术运用于钛材换热管的缺陷检测中。弱磁检测技术是一种被动式检测技术，无需额外的激励源，一方面可以简化探头工艺设计，另一方面也规避了由于激励源非指向性应激产生的干扰源场对检测过程的影响。同时弱磁检测手段易于学习上手，因为弱磁检测不需要对被检工件表面进行特殊处理，对检测工件的形状没有特殊要求，隔着涂层检测以及非接触式检测均不影响检测效果。在地磁场环境下，用 高精度的弱磁传感器在试件的表面或者近表面进行扫查，采集不同方向上磁感应强度的变化从而判断检测区域是否存在磁异常，然后对采集到的磁信号进行处理。弱磁检测方法属于比较测量方法，即通过对比正常区域与磁异常区域的信号的差异值来判断缺陷类型和定量。本申请针对凝汽器换热管管径小、壁厚薄的特点设计了内穿式的探头结构，探头前部内周向均布若干组弱磁传感器组，每组弱磁传感器组由2枚弱磁传感器组成；同时在探头后部设置滚轮装置，方便探头在换热管道内前后移动。通过基于弱磁检测原理的弱磁传感器组，实现对钛管的自动化扫查，从而对管道内壁减薄量、穿孔腐蚀等常见换热管缺陷进行智能识别，并对缺陷进行定量分析。
进一步地，探头本体制作成分体式结构，便于携带收纳和修理维护。
进一步地，本体的前端设有测距传感器，能够预防换热管堵塞造成的碰撞损坏。
进一步地，本体的所述本体的两侧设有测距传感器，能够及时检测换热管内部管径变窄的情况。
进一步地，本体的前端设有防撞触头，避免探头碰撞损坏。
进一步地，信号线收纳管外表面覆盖有磁屏蔽材料，能够防止弱磁传感器线圈产生的漏磁通对探头稳定性的影响。
进一步地，本体后部内设有配重块，能够使探头的中心集中在后部，从而避免前部下沉，使所有弱磁传感器组与换热管内壁的距离始终保持一致，提高检测的准确度。
本申请公开的上述内穿式弱磁检测探头的工作方法，操作方便，检测效率高、结果准确，不依赖操作者的经验和技能水平。
附图说明
图1为本申请的探头整体结构示意图；
图2为本申请的探头内部单一测磁模组检测示意图；
图3为本申请的探头工作状态示意图；
图4为本申请的检测方法流程示意图；
图5为本申请的检测原理示意图；
图6a为单一弱磁曲线特征值提取示意图；
图6b为两个相邻弱磁传感器相继扫查同一处缺陷的弱磁信号示意图；
图7为检测实例使用的加工有人工内壁减薄环的换热管；
图8为检测实例的扫查原始曲线图；
图9为检测实例的差分曲线图。
图中：1为第一本体，2为第二本体，3为信号线收纳管，4为弱磁传感器，5为滚轮，6为中间连接体，7为防撞触头，8为冷凝管，9为线束，10为弱磁探伤仪。
具体实施方式
下面结合附图和具体实施例对本申请做进一步详细描述，其内容是对本申请的解释而不是限定：
如图1，本申请的一种内穿式弱磁检测探头，包括本体前部内设有信号线收纳管3和若干环绕本体内壁均布的弱磁传感器组，每个弱磁传感器组包括2个沿本体轴线方向排布的弱磁传感器4，弱磁传感器4的测磁敏感面垂直本体壁面向外；本体后部设有用于驱动本体直线移动的滚轮5，滚轮5连接有电机；本体后部的后端设有连接端口；弱磁传感器4的信号线穿过信号线收纳管3与电机的连接线一同汇总至连接端口。
在本申请的一个较优的实施例中，所述本体采用ABS塑料作为工装材料，使得工装具备良好的抗震性以及一定的隔热性。
在本申请的一个较优的实施例中，所述本体包括依次可拆卸连接的第一本体1、中间连接体6和第二本体2；信号线收纳管3和若干弱磁传感器组设在第一本体1内，中间连接体6与信号线收纳管3和第二本体2内部贯通，滚轮5 设在第二本体2上，所述电机设在第二本体2内，所述连接端口设在第二本体2的后端。
在本申请的一个较优的实施例中，弱磁传感器组的数量可以设置为6～12。
在本申请的一个较优的实施例中，所述本体的前端设有测距传感器，测距传感器通过连接线连接至所述连接端口。
在本申请的一个较优的实施例中，所述本体的两侧设有测距传感器，测距传感器通过连接线连接至所述连接端口。
在本申请的一个较优的实施例中，所述本体的前端设有防撞触头7。
在本申请的一个较优的实施例中，信号线收纳管3外表面覆盖有磁屏蔽材料。磁屏蔽材料可以坡莫合金加工成的薄膜材料。
在本申请的一个较优的实施例中，所述本体后部内设有配重块。
上述内穿式弱磁检测探头的工作方法，包括：
如图2、3和4，通过所述连接端口分别与弱磁探伤仪10和上位机连接，并在上位机中输入探头的参数；将所述本体置入冷凝管8的入口，所述电机驱动滚轮5转动，进而带动整个本体前进；检测过程中每组弱磁传感器组中的2个弱磁传感器4依次扫查，上位机实时呈现每个弱磁传感器组检测得到的两条磁感应强度-时间曲线，判断是否存在缺陷以及该缺陷的规格。
在本申请的一个较优的实施例中，对磁感应强度-时间曲线进行差分处理，得到相应的差分曲线并设置阈值线，对超过阈值线范围的曲线突变特征进行直观反应。
本申请的理论基础和工作原理：
弱磁原理介绍
在应用弱磁探伤仪检测过程中，当待检工件在出现缺陷后，引起材料本身的应力变化，导致材料晶体内原子结构发生变化，从而自发产生异常磁场。若材料本身的相对磁导率大于材料中不连续缺陷出的相对磁导率，那么基于磁阻 与相对磁导率成反比的原因，在缺陷附近的局部区域中相应的磁阻将会增加，从而导致通过材料的磁力线弯曲，会绕过缺陷从其周边的材料中通过。弱磁检测原理示意图如图5所示。
假设被检材料本体的磁导率为μ，工件内部不连续区的磁导率为μ'，若是不连续区域的相对磁导率要大于被检材料的相对磁导率，即μ'>μ，那么在弱磁传感器通过该区域时，磁感应强度曲线会出现下凹现象；若是不连续区的相对磁导率要小于被检材料的相对磁导率，即μ'<μ，那么在弱磁传感器通过该区域时，磁感应强度曲线会出现上凸现象。弱磁检测技术正是利用高精度磁传感器检测到磁感应强度突变的异常信号，从而表征出材料的缺陷情况。
检测信号特征值计算：
钛金属是顺磁性材料，根据弱磁检测原理，用弱磁探头均匀扫查钛管，不难发现，在无缺陷处，弱磁信号保持平缓；在靠近缺陷处，弱磁信号开始上升；在缺陷的正上方附近，弱磁信号会出现波峰。在缺陷的定量研究中，本申请通过提取缺陷弱磁信号的相关特征值，再通过大量数据计算反演实现对缺陷的定量估计。
磁异常形态与由缺陷引发的磁感应强度曲线密切相关，尤其是当弱磁探头扫查经过缺陷上方，上位机软件实时呈现出一个近似轴对称的图形，如图6a所示。通过提取信号的幅值、宽度等特征值，并对它们进行公式化演算，得到与磁感应强度值相关的尺寸数据。记ΔB1为缺陷信号出波峰最大值与左端最小值的差值，ΔL1为缺陷信号左侧的半波占宽。记ΔB2为缺陷信号出波峰最大值与右端最小值的差值，ΔL2为缺陷信号右侧的半波占宽。易得下列公式：
△B＝(△B1+△B2)/2
△L＝(△L1+△L2)/2
Figure PCTCN2022129558-appb-000001
式中：ΔB为缺陷信号出现波峰与波谷的幅值差均值；ΔL为缺陷信号半波 占宽的平均值；
Figure PCTCN2022129558-appb-000002
为缺陷处的平均磁感应强度。
如图6b所示，左侧虚线部分和右侧实线部分别为两个相邻弱磁传感器相继扫查同一处缺陷的弱磁信号，ΔBm为第一个弱磁传感器波峰最大值与第二个弱磁传感器对应位置的磁感应强度的差值。进一步的，记ΔBu为第一个弱磁传感器得到的幅值差，记B 1为第一个弱磁传感器得到的平均磁感应强度值，记B 2为第二个弱磁传感器得到的平均磁感应强度值，另外记ΔS为两个弱磁传感器之间的距离，取固定值1mm。所以得到经验公式：
Figure PCTCN2022129558-appb-000003
其中，K为比例调节系数，A1与A2是与材料磁导率相关的经验系数，D为缺陷深度。
在一个具体实施例中，一共设置6对弱磁传感器组沿探头内壁周向均布，每两个弱磁传感器并排布置构成一对弱磁传感器。探头通过连接端口与弱磁探伤仪相连。弱磁探伤仪一端与探头相连，另一端通过以太网线与上位机(笔记本)相连，上位机(笔记本)作为整套检测系统的控制终端，通过上位机软件可以对弱磁信号进行实时分析，同时接收探头触头与滚轮装置实时传输的信号，并对它们进行反馈操作。在检测过程中，两个平行布置的弱磁传感器依次扫查待检区域，经上位机数据处理之后，实时呈现两条磁感应强度-时间曲线。再借助算法精确捕捉幅值、半波占宽等特征值，根据前期多次试验得到的经验公式，最终判断待检区域是否存在(腐蚀)缺陷，以及估算该缺陷的损伤程度。
具体工作流程为：1、将本申请的检测探头与弱磁探伤仪连通，并确保采集的弱磁信号能够实时呈现在上位机软件界面中；2、将检测探头放置在管道入口处，通过上位机(控制终端)下达指令使伺服电机开始工作，确保检测探头能够在管道内正常进退；3、探头触头正前方布置测距传感器，当(测出的)反馈的距离数据小于换热管长度，则说明此管道存在堵塞情况，需要人为干预处理； 探头触头左右两侧也分别布置测距传感器，当测出的数据大于换热管直径或者直接发散，则说明此位置管道内壁出现穿孔缺陷或者检测探头已驶出管道口，此时伺服电机自动停止；4、在上位机软件中输入适合该钛管对应的K值、A1值和A2值；5、检测开始，上位机软件实时呈现6组界面，每组界面上实时呈现两条磁感应强度-时间曲线。再借助算法精确捕捉幅值、半波占宽等特征值，根据前期多次试验得到的经验公式，判断该位置是否存在(腐蚀)缺陷，以及估算该缺陷的损伤程度。
在一个具体测试实施例中，步骤包括：
1、在尺寸为φ25×0.5mm的钛管上人工制作4处内壁减薄环，如图7，具体尺寸见表1。
2、将探头与弱磁探伤仪连通，并确保采集的弱磁信号能够实时呈现在上位机软件界面中。
3、在上位机软件中输入适合该钛管对应的K值、A1值和A2值。
4、固定钛管，然后将探头自左向右，匀速扫查经过预置的4处人工缺陷。扫查曲线如图8所示。对原始曲线进行差分处理，得到更为直观的差分曲线如图9所示。
5、扫查结束后，保存试验数据，并进行数据分析如表2所示，计算得到对应的缺陷信息。
表1
尺寸 第一处 第二处 第三处 第四处
壁厚/mm 1.2 1.4 1.6 1.8
宽度/mm 2 2 2 2
深度/mm 0.8 0.6 0.4 0.2
表2
尺寸 第一处 第二处 第三处 第四处
实际壁厚/mm 1.2 1.4 1.6 1.8
检测壁厚/mm 1.2355 1.4439 1.6472 1.8572
准确率/％ 97.04％ 96.86％ 97.05％ 96.82％
由表2可以看出，采用本申请的探头具有很高的准确率，能够满足实际检测需要。
以上所述仅为本申请实施例，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内可轻易想到的变化或者替换，或利用本申请说明书及附图内容所作的等效结构或者等效流程变换，或直接、间接运用在其他相关技术领域的情况，均应涵盖在本申请的保护范围之内。

Claims (10)

  1. 一种内穿式弱磁检测探头，其特征在于，包括本体；本体前部内设有信号线收纳管(3)和若干环绕本体内壁均布的弱磁传感器组，每个弱磁传感器组包括2个沿本体轴线方向排布的弱磁传感器(4)，弱磁传感器(4)的测磁敏感面垂直本体壁面向外；本体后部设有用于驱动本体直线移动的滚轮(5)，滚轮(5)连接有电机；本体后部的后端设有连接端口；弱磁传感器(4)的信号线穿过信号线收纳管(3)与电机的连接线一同汇总至连接端口。
  2. 根据权利要求1所述的内穿式弱磁检测探头，其特征在于，所述本体包括依次可拆卸连接的第一本体(1)、中间连接体(6)和第二本体(2)；信号线收纳管(3)和若干弱磁传感器组设在第一本体(1)内，中间连接体(6)与信号线收纳管(3)和第二本体(2)内部贯通，滚轮(5)设在第二本体(2)上，所述电机设在第二本体(2)内，所述连接端口设在第二本体(2)的后端。
  3. 根据权利要求1所述的内穿式弱磁检测探头，其特征在于，弱磁传感器组的数量为6～12。
  4. 根据权利要求1所述的内穿式弱磁检测探头，其特征在于，所述本体的前端设有测距传感器，测距传感器通过连接线连接至所述连接端口。
  5. 根据权利要求1所述的内穿式弱磁检测探头，其特征在于，所述本体的两侧设有测距传感器，测距传感器通过连接线连接至所述连接端口。
  6. 根据权利要求1所述的内穿式弱磁检测探头，其特征在于，所述本体的前端设有防撞触头(7)。
  7. 根据权利要求1所述的内穿式弱磁检测探头，其特征在于，信号线收纳管(3)外表面覆盖有磁屏蔽材料。
  8. 根据权利要求1所述的内穿式弱磁检测探头，其特征在于，所述本体后部内设有配重块。
  9. 权利要求1～8所述的内穿式弱磁检测探头的工作方法，其特征在于，包括：
    通过所述连接端口分别与弱磁探伤仪(10)和上位机连接，并在上位机中输入探头的参数；将所述本体置入冷凝管(8)的入口，所述电机驱动滚轮(5)转动，进而带动整个本体前进；检测过程中每组弱磁传感器组中的2个弱磁传感器(4)依次扫查，上位机实时呈现每个弱磁传感器组检测得到的两条磁感应强度-时间曲线，判断是否存在缺陷以及该缺陷的规格。
  10. 根据权利要求9所述的内穿式弱磁检测探头的工作方法，其特征在于，对磁感应强度-时间曲线进行差分处理，得到相应的差分曲线并设置阈值线，对超过阈值线范围的曲线突变特征进行直观反应。
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