阅读说明：本技术 一种孔内壁周向缺陷的磁粉检测方法 (magnetic powder detection method for circumferential defects of inner wall of hole ) 是由 胡德明 胡慧敏 曹传银 于 2019-09-17 设计创作，主要内容包括：本发明公开一种孔内壁周向缺陷的磁粉检测方法,它包括：清洁工件内孔表面,将影响磁粉集聚和载液流动的杂物清除；将一根高磁导率芯棒沿工件内孔的中心位置穿过,并将其置于磁化线圈中；磁化线圈中通以方向为周向的交流电,设置该交流电的电流值；对工件内孔壁进行预喷淋；先边喷淋边磁化工件,然后停止喷淋再磁化工件1-2次,每次磁化工件的时间为1-2s；在合适光照条件下观察工件内孔表面有无磁痕,按产品质量要求进行评定；评定完成后,进行交流电退磁和后续处理。本发明在工件内孔中穿入一根高磁导率芯棒,利用线圈磁化工件,有效实现了对内孔壁周向缺陷的磁粉检测,无需采用专用的磁粉探伤设备。(The invention discloses a magnetic powder detection method for circumferential defects of the inner wall of a hole, which comprises the following steps: cleaning the surface of an inner hole of a workpiece, and removing impurities which influence magnetic powder accumulation and carrier liquid flow; passing a high-permeability core rod along the central position of an inner hole of a workpiece and placing the core rod in a magnetizing coil; alternating current taking the direction as the circumferential direction is led into the magnetizing coil, and the current value of the alternating current is set; pre-spraying the inner hole wall of the workpiece; firstly, spraying and magnetizing the workpiece, then stopping spraying and magnetizing the workpiece for 1-2 times, wherein the time for magnetizing the workpiece every time is 1-2 s; observing whether the surface of the inner hole of the workpiece has magnetic marks or not under the proper illumination condition, and evaluating according to the product quality requirement; after the evaluation is finished, alternating current demagnetization and subsequent treatment are carried out. According to the invention, the high-permeability core rod penetrates into the inner hole of the workpiece, and the workpiece is magnetized by using the coil, so that the magnetic powder detection of circumferential defects of the inner hole wall is effectively realized, and a special magnetic powder inspection device is not required.)

1. a magnetic particle detection method for circumferential defects of the inner wall of a hole is characterized by comprising the following steps:

cleaning the surface of an inner hole of a workpiece (3) and removing impurities which influence magnetic powder accumulation and carrier liquid flow;

Secondly, a high-permeability core rod (2) penetrates through the center position of the inner hole of the workpiece (3) and is placed in the magnetizing coil (1);

Thirdly, alternating current taking the direction as the circumferential direction is introduced into the magnetizing coil (1), and the current value of the alternating current is set according to the inner diameter of the magnetizing coil (1), the material and the size of the high-permeability core rod (2) and the material and the size of the workpiece (3);

Fourthly, pre-spraying the inner hole wall of the workpiece (3);

Fifthly, spraying and magnetizing the workpiece (3) at first, then stopping spraying and magnetizing the workpiece (3) for 1-2 times, wherein the time for magnetizing the workpiece (3) every time is 1-2 s;

Step six, setting the ambient white light illumination of the detection area not more than 20lx and the ultraviolet light illumination of the detection area not less than 1000 muW/cm during fluorescent magnetic powder detection²(ii) a When non-fluorescent magnetic powder is detected, setting the white light illumination of a detection area to be not lower than 1000lx, observing whether the surface of the inner hole of the workpiece (3) has magnetic marks or not under the illumination condition, and evaluating according to the product quality requirement;

and seventhly, after the evaluation is finished, carrying out alternating current demagnetization and subsequent treatment.

2. the magnetic powder inspection method for circumferential defects of the inner wall of the hole according to claim 1, wherein in the seventh step, the workpiece (3) is placed at the position where the workpiece is magnetized when demagnetized, and then the workpiece (3) can be demagnetized by introducing gradually decreasing alternating current into the magnetizing coil (1).

3. The magnetic powder detection method for the circumferential defects of the inner wall of the hole according to claim 1, wherein the high-permeability core rod (2) in the second step is a silicon steel sheet core rod.

4. The magnetic particle inspection method for circumferential defects of the inner wall of the hole according to claim 1, wherein in the sixth step, if the observation is influenced by the high-permeability core rod (2), the high-permeability core rod (2) is taken out and then observed.

5. the magnetic powder detection method for circumferential defects of the inner wall of the hole according to claim 1, wherein in the seventh step, the high-permeability core rod (2) is positioned at the same or a similar position of the magnetized workpiece (3) during demagnetization.

Technical Field

the invention relates to a magnetic powder detection method for circumferential defects of an inner wall of a hole.

Background

The magnetic powder detection method can find defects which form a certain included angle with the direction of the magnetic field (when the defects are perpendicular to the direction of the magnetic field, the effect is optimal), and in order to find circumferential defects, a coil method or an induction current method is mostly adopted to magnetize the workpiece. However, when alternating current is applied in the coil method, due to the influence of the skin effect, the magnetic field of the inner wall of the workpiece hole is weak, effective magnetization cannot be obtained, and circumferential defects of the inner wall of the workpiece hole cannot be detected (except for thin-walled parts); when direct current is applied to the coil method, although circumferential defects of the inner wall of the hole can be detected, the workpiece is difficult to demagnetize, and the detection efficiency is low because several minutes or even dozens of minutes are needed; the induction current method is only suitable for thin-wall parts, and once the wall thickness of a workpiece is large, the difference of the magnetic field intensity of the inner wall and the outer wall is large (the magnetic field intensity of the inner wall is large), so that the sensitivity difference is large, and special magnetic powder inspection equipment is needed.

Disclosure of Invention

Aiming at the problems, the invention provides a magnetic powder detection method for circumferential defects of the inner wall of a hole.

in order to achieve the purpose, the invention adopts the following technical scheme:

A magnetic particle detection method for circumferential defects of the inner wall of a hole comprises the following steps:

cleaning the surface of an inner hole of a workpiece, and removing impurities which influence magnetic powder accumulation and carrier liquid flow;

Step two, passing a high-permeability core rod along the central position of the inner hole of the workpiece, and placing the core rod in a magnetizing coil;

Thirdly, alternating current taking the direction as the circumferential direction is introduced into the magnetizing coil, and the current value of the alternating current is set according to the inner diameter of the magnetizing coil, the material and the size of the high-permeability core rod and the material and the size of the workpiece;

fourthly, pre-spraying the inner hole wall of the workpiece;

fifthly, spraying and magnetizing the workpiece, stopping spraying and magnetizing the workpiece for 1-2 times, wherein the time for magnetizing the workpiece every time is 1-2 s;

step six, setting the ambient white light illumination of the detection area not more than 20lx and the ultraviolet light illumination of the detection area not less than 1000 muW/cm during fluorescent magnetic powder detection²(ii) a When non-fluorescent magnetic powder is detected, setting the white light illumination of a detection area to be not lower than 1000lx, observing whether the surface of an inner hole of a workpiece has magnetic marks or not under the illumination condition, and evaluating according to the product quality requirement;

And seventhly, after the evaluation is finished, carrying out alternating current demagnetization and subsequent treatment.

And step seven, when demagnetizing, firstly, placing the workpiece at the position where the workpiece is positioned when magnetizing, and then, introducing gradually-reduced alternating current into the magnetizing coil to demagnetize the workpiece.

and further, the high-permeability core rod in the step two is a silicon steel sheet core rod.

further, in the sixth step, if the observation is influenced by the high-permeability core rod during evaluation, the high-permeability core rod is taken out and then observed.

Further, in the seventh step, the high-permeability core rod is located at the same or a similar position of the magnetized workpiece during demagnetization.

Has the advantages that:

1. according to the invention, the high-permeability core rod penetrates into the inner hole of the workpiece, and the workpiece is magnetized by using the coil, so that the magnetic powder detection of circumferential defects of the inner hole wall is effectively realized, and a special magnetic powder inspection device is not required.

2. according to the invention, because the high-permeability core rod penetrates into the inner hole of the workpiece, induced current can be generated in the workpiece, and further a magnetic field can be generated on the wall of the inner hole of the workpiece, so that the circumferential defects of the wall of the inner hole can be detected.

3. the invention adopts alternating current magnetization, so that alternating current demagnetization can be directly adopted, thereby solving the problem of difficult workpiece demagnetization.

4. the invention is suitable for both thin-wall parts and thick-wall parts, and although the magnetic field generated by the induced current on the outer wall of the workpiece is smaller, the magnetic field of the magnetizing coil on the outer wall of the workpiece is larger, the two magnetic fields have the same direction and are mutually superposed, thereby realizing magnetic powder detection.

Drawings

FIG. 1 is a schematic diagram of the detection principle of the present invention;

In the figure: 1-a magnetizing coil; 2-a high magnetic permeability core rod; 3-a workpiece; 4-inner hole wall circumferential defect; 5-direction of magnetization current; 6-direction of magnetic force line in the high magnetic conductivity core rod; 7-inducing a current direction in the workpiece; 8-inducing current to generate magnetic field direction on the inner hole wall of the workpiece.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

The invention provides a magnetic powder detection method for circumferential defects of the inner wall of a hole, as shown in figure 1, on the basis of a general magnetic powder flaw detector, a high-permeability core rod 2 (a common silicon steel sheet core rod) is utilized to penetrate into an inner hole of a workpiece 3, and is arranged in a magnetizing coil 1, alternating current with the direction of 5 is conducted in the magnetizing coil 1, longitudinal magnetic lines of force are generated around the magnetizing coil 1, wherein a larger part of the magnetic flux passes through the high magnetic permeability core rod 2, the magnetic flux lines in the high magnetic permeability core rod 2 pass through the workpiece 3 along the direction 6, the magnetic lines of force are alternated, so that an induced current with the direction of 7 can be generated on the workpiece 3, the induced current then generates a magnetic field direction 8 which is parallel to the longitudinal direction on the inner hole wall of the workpiece 3, and then, a leakage magnetic field is formed at the circumferential defect 4 of the inner hole wall, and the existence of the circumferential defect of the inner hole wall can be judged through a conventional magnetic powder display mode. The method comprises the following specific steps:

Cleaning the surface of an inner hole of a workpiece 3, and removing impurities which influence magnetic powder accumulation and carrier liquid flow;

secondly, a high-permeability core rod 2 penetrates through the center position of the inner hole of the workpiece 3 to ensure that the magnetic field intensity of the inner hole wall of the workpiece 3 is uniform, and the core rod is placed in a magnetizing coil 1;

thirdly, alternating current taking the direction as the circumference is led into the magnetizing coil 1, the current value of the alternating current is set according to the inner diameter of the magnetizing coil 1, the material and the size of the high-permeability core rod 2 and the material and the size of the workpiece 3, and the current value of the alternating current can be specifically set and verified according to the method specified in GB/T15822.1 part 1-general rule of nondestructive testing magnetic powder testing;

Fourthly, pre-spraying the inner hole wall of the workpiece 3, wherein the conventional magnetic powder detection process can reduce the magnetization times and improve the magnetization efficiency;

Step five, spraying and magnetizing the workpiece 3, then stopping spraying and magnetizing the workpiece 31-2 times, wherein the time for magnetizing the workpiece 3 every time is 1-2s, and the conventional magnetic powder detection process needs enough time because the leakage magnetic field attracts magnetic powder to reach the defect, so that the magnetizing time cannot be too short, but the overlong magnetizing time can improve the requirement on the power supply of equipment and even damage the power supply; the formed magnetic traces can be prevented from being washed away by the magnetic suspension liquid by magnetization after the spraying is stopped;

Step six, setting the ambient white light illumination of the detection area not more than 20lx and the ultraviolet light illumination of the detection area not less than 1000 muW/cm during fluorescent magnetic powder detection²(ii) a During non-fluorescent magnetic powder detection, setting the white light illumination of a detection area to be not lower than 1000lx, specifically observing the conditions of nondestructive testing penetration testing and magnetic powder testing observation in ISO 3059-2012, observing whether the surface of an inner hole of a workpiece 3 has magnetic traces under the illumination condition, and evaluating according to the product quality requirement;

And seventhly, after the evaluation is finished, carrying out alternating current demagnetization and subsequent treatment. The alternating current demagnetization is to place the workpiece 3 at the position where the workpiece is magnetized, and then to energize the magnetizing coil 1 with decreasing alternating current to demagnetize the workpiece 3. When demagnetizing, the high magnetic conductivity core rod 2 should be in the same or similar position of the magnetized workpiece 3; when evaluating, if the observation is influenced by the high magnetic permeability core rod 2, the high magnetic permeability core rod 2 can be taken out and then observed.

The limitation of the protection scope of the present invention is understood by those skilled in the art, and various modifications or changes which can be made by those skilled in the art without inventive efforts based on the technical solution of the present invention are still within the protection scope of the present invention.