JB/T 5000.15-1988 General technical conditions for heavy machinery Non-destructive testing of forged steel parts
Some standard content:
JB/T5000.15-1998
Appendix A and Appendix B of this standard are both appendices of the standard. This standard is proposed and managed by the Technical Committee for Standardization of Metallurgical Machinery and Equipment of the Ministry of Machinery Industry. The responsible drafting unit of this standard is the Second Heavy Machinery Group Corporation. The participating drafting unit of this standard is the Xi'an Heavy Machinery Research Institute. The main drafters of this standard are Wang Guoyuan and Fan Lvhui. 1 Scopewww.bzxz.net
Machinery Industry Standards of the People's Republic of China
General Technical Conditions for Heavy Machinery
Non-destructive testing of forgings
The heavy mechanical general techniques and standardsNon-destructive testing of forging1.1 This standard specifies three non-destructive testing methods and quality grades: ultrasonic, magnetic powder and penetration. 1.2 The various non-destructive testing methods described in this standard are applicable to the testing of various types of ordinary forged steel parts. JB/T5000.15-1998
1.3 After selecting this standard, the type of flaw detection method, specific flaw detection location and quality acceptance level of different defect types must be indicated on the corresponding forging drawings. Quality acceptance levels can also be added separately. 1.4 Ultrasonic flaw detection in this standard is not applicable to longitudinal wave flaw detection of forgings with a radius of curvature less than 125mm and a detection thickness less than 50mm, and ultrasonic shear wave flaw detection of annular or cylindrical forgings with an inner and outer diameter ratio less than 75%. It is also not applicable to ultrasonic flaw detection of coarse-grained materials such as austenitic stainless steel.
1.5 This standard may involve hazardous materials, operations and equipment. The purpose of this standard is not to discuss safety issues related to use. Those who use this standard are responsible for formulating relevant safety protection and health implementation methods before use, and should determine the management regulations for the relevant application scope. 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB3721--83
GB5097-85
GB9445-88
Magnetic particle flaw detector
Indirect evaluation method of black light source
General rules for technical qualification appraisal of non-destructive testing personnel GB/T12604.1～12604.6-90 Non-destructive testing terminology ZBJ04001-87
ZBJ04003-87
ZBY230-84
ZBY231-84
ZBY232-84
3 Definitions
This standard adopts the following definitions.
3.1 Defects in dense areas
Test method for working performance of type A pulse reflection ultrasonic flaw detection system Method for controlling the quality of penetrant flaw detection materials
General technical conditions for type A pulse reflection ultrasonic flaw detector Performance test method for ultrasonic flaw detection probe
Technical conditions for No. 1 standard test block for ultrasonic flaw detection There are 5 or more defect reflection signals at the same time within the range of 50mm sound path on the fluorescent screen scanning line; or there are 5 or more defect reflection signals within the same depth range on the 50mm×50mm detection surface. The reflection amplitude is greater than the reference reflection amplitude of a certain equivalent defect.
3.2 Defect-induced bottom wave reduction BG/BF (dB) The ratio of the first bottom wave amplitude BG in the intact area near the defect to the first bottom wave amplitude BF in the defect area, expressed in sound pressure level (dB) value Approved by the State Bureau of Machinery Industry on September 30, 1998 and implemented on December 1, 1998
JB/T5000.15-1998
3.3 The rest of the definitions are in accordance with the provisions of GB/T12604.1~12604.6. 4 General requirements
4.1 Selection principles
4.1.1 The selection of test methods and quality acceptance levels shall be determined according to the specific use and type of forgings and shall comply with the requirements of the relevant technical documents.
4.1.2 For ferromagnetic forgings that require surface testing, magnetic particle testing should be used first. If magnetic particle testing cannot be used due to structural shape and other reasons, penetration testing shall be used.
4.2 Test files
4.2.1 When testing forgings in accordance with this standard, non-destructive testing procedures that meet the requirements of relevant specifications may be formulated in accordance with the provisions of this standard when necessary.
4.2.2 The test procedures and results shall be correct, complete and signed and approved by the corresponding responsible personnel. The retention period of test records and reports shall not be less than 5 years. After 5 years, if the user needs it, it can be transferred to the user for safekeeping. 4.2.3 In the inspection file, the corresponding qualification level and validity period of the inspection personnel who undertake the inspection items should be recorded. 4.2.4 The performance of the instruments and equipment used for inspection should be inspected regularly, and they can only be used after passing the inspection, and there should be inspection records. 4.3 Inspection personnel
4.3.1 All personnel engaged in non-destructive testing must undergo technical training and be assessed and identified in accordance with GB9445. 4.3.2 The technical levels of non-destructive testing personnel are divided into high, medium and primary. Personnel of each technical level who have obtained different non-destructive testing methods can only engage in non-destructive testing work corresponding to the level and bear corresponding technical responsibilities. 4.3.3 All personnel engaged in non-destructive testing, in addition to having good physical fitness, must meet the following requirements for vision: 4.3.3.1 Corrected vision must not be less than 1.0, and it must be checked once a year. 4.3.3.2 All personnel engaged in surface inspection must not be color blind or color weak. 5 Ultrasonic flaw detection and its quality level
5.1 Inspection basis
5.1.1 Whenever this standard is adopted, the user or design process department shall explain and provide the location range and quality acceptance level of ultrasonic flaw detection of forgings.
5.1.2 The method of establishing sensitivity, the selection of instruments and equipment, and the performance test shall be consistent with the provisions of this standard. 5.2 Instruments and equipment
5.2.1 Use a pulse reflection ultrasonic flaw detector with a frequency range of at least 1 to 5MHz. 5.2.1.1 The vertical linearity of the ultrasonic flaw detector shall be linearly displayed within at least 80% of the screen height, with an error within 5% and a horizontal linear error of ±2%. The linearity of the instrument shall be identified in accordance with the requirements of ZBY230. 5.2.1.2 The sensitivity margin of the instrument shall be above 30dB, and its determination method shall be carried out in accordance with the requirements of ZBJ04001. 5.3 Probes
5.3.1 Various probes should be used at the calibrated frequency. In principle, straight probes with a frequency of 2 to 2.5 MHz and a chip diameter of 20 to 30 mm should be used. 5.3.2 The main sound beam of the probe should not have obvious double peaks, and the sound beam line deflection should be less than 2°. 5.3.3 Various probes should have corresponding AVG curve charts. 5.3.4 Other probes can be replaced to evaluate defects and accurately locate defects. 5.3.5 See ZBY231 for the probe performance test method. 5.4 Coupling agent
5.4.1 The coupling agent should have good wettability. Engine oil, glycerin, paste or water can be used as a coupling agent. For finished forgings, it is recommended to use No. 30 engine oil as a coupling agent
JB/T5000.15-1998
5.4.2 Different coupling agents cannot be compared. Therefore, the performance test, sensitivity adjustment and calibration of the flaw detection system must be the same as the coupling agent used during flaw detection.
5.5 Test block
5.5.1 The test block shall be made of a material with the same or similar acoustic properties as the workpiece to be inspected. When the material is inspected with a straight probe, there shall be no defects greater than the equivalent diameter of a flat-bottomed hole of 2mm.
5.5.2 The calibration reflector may be a flat-bottomed hole or a V-groove. During calibration, the main sound beam of the probe shall be aligned with the reflector and perpendicular to the reflecting surface of the flat-bottomed hole and the axis of the V-groove. 5.5.3 The outer dimensions of the test block shall represent the characteristics of the workpiece to be inspected, and the thickness of the test block shall correspond to the thickness of the workpiece to be inspected. The error shall not exceed 10% of the detected thickness.
5.5.4 The manufacturing requirements of the test block shall comply with the provisions of ZBY232. 5.5.5 During on-site inspection, other types of equivalent test blocks may also be used. 5.6 Test of system combination performance see ZBJ04001. 5.7 Preparation of forgings before flaw detection
5.7.1 Unless otherwise specified at the time of ordering, the radial flaw detection of shaft forgings should be processed into a cylindrical surface; the two end faces should be processed into a plane perpendicular to the axis of the forging during axial flaw detection, and the surfaces of pie-shaped and rectangular forgings should be processed into planes. And parallel to each other. 5.7.2 Unless otherwise specified at the time of ordering, the roughness R of the forging surface shall not exceed 6.3um. 5.7.3 There should be no foreign matter on the flaw detection surface of the forging, such as oxide scale, paint, dirt, etc. 5.8 Flaw detection procedures
5.8.1 General rules
5.8.1.1Except for the case where the cross section and local shape of the forgings are changed due to rounding, drilling, etc. and it is impossible to perform flaw detection, ultrasonic flaw detection should be performed on the entire forgings as much as possible.
5.8.1.2Forgings should be ultrasonically tested after mechanical property heat treatment (excluding stress relief treatment) and before finishing. If the shape of the forgings after heat treatment cannot be fully tested, ultrasonic flaw detection is allowed before performance heat treatment. However, ultrasonic re-testing should be performed on the forgings as fully as possible after heat treatment. 5.8.1.3The probe should overlap at least 15% each time it moves to ensure that the entire forging can be completely scanned. Probe scanning speed: shall not exceed 150mm/s when operated manually; shall not exceed 1000mm/s when automatically detecting. 5.8.1.4All cross sections of the forgings should be scanned in two mutually perpendicular directions as much as possible. For pancake forgings, in addition to scanning from at least one plane, radial scanning should be performed from the circumference as much as possible. 5.8.1.5
When inspecting cylindrical solid or hollow forgings, in addition to scanning from the radial direction, auxiliary scanning should also be performed from the axial direction. 5.8.1.6
For the inspection of annular and cylindrical forgings, refer to Appendix A (Standard Appendix) at the same time. 5.8.1.7
When the manufacturer or user conducts a review or re-evaluation, comparable instruments, probes and coupling agents should be used as much as possible. 5.8.1.8
Forging inspection can be carried out in a static state or in a rotating state (using a lathe or a rotating tire). If the user does not specify, the manufacturer can choose arbitrarily.
5.8.1.10 When the thickness of the forging is greater than 400mm, the inspection should be carried out from the opposite parallel surfaces. 5.8.2 Flaw detection sensitivity
5.8.2.1 In principle, the AVG method is used to determine the flaw detection sensitivity. For forgings that are limited by their geometric shape and whose detection thickness is close to the length of the near-field zone, the test block comparison method is used.
5.8.2.2 The flaw detection sensitivity is based on the initial recorded equivalent value, and its reference wave height shall not be less than 40% of the full screen height. 5.8.2.3 When evaluating defects, the evaluation sensitivity should be adjusted at the intact part of the forging. 5.8.2.4 Recalibration of flaw detection sensitivity
a) The flaw detection sensitivity must be recalibrated in any of the following situations: - When any changes occur to the calibrated probe, coupling agent, instrument knob, etc.; when the external power supply voltage fluctuates greatly or the operator suspects that the flaw detection sensitivity has changed - when working continuously for 4 hours and at the end of work. JB/T5000.15-1998
b) When the flaw detection sensitivity decreases by more than 2dB, the forging should be fully re-tested; when it increases by more than 2dB, all recorded signals should be re-evaluated.
5.8.2.5 Method for adjusting flaw detection sensitivity
a) For solid cylindrical forgings and forgings with the flaw detection surface parallel to the reflecting surface, when the sound path is greater than 3 times the near field, the required increase in dB value should be calculated according to formula (1):
Where: S-sound path, mm;
λ-wavelength, mm;
Φ-equivalent diameter of flaw detection sensitivity, mm. dB= 20lg
b) For hollow cylindrical forgings, when the sound path is greater than 3 times the near field, the required additional dB value should be calculated according to formula (2): 2AS
±10 g
dB=20lg
Where: D-outer diameter of workpiece, mm
dinner diameter of workpiece, mm;
++inner hole detection, concave reflection;
radial detection of outer circle of workpiece, convex reflection. The remaining symbols are the same as 5.8.2.5a).
5.8.3 Determination of detectability of forgings
·(1)
·(2)
When the flaw detection sensitivity is determined, taking the flaw detection sensitivity as the benchmark, if the signal-to-noise ratio is greater than or equal to 6dB, the forging is considered to have sufficient detectability. Otherwise, it shall be handled by negotiation between the supply and demand parties. 5.8.4 Determination of material attenuation coefficient
5.8.4.1 When the sound path is greater than 3 times the near field, select at least three representative locations in the defect-free area of the forging to measure the dB difference of B,/B2, that is, the dB difference between the first bottom wave height B, and the second bottom wave height Bz. The material attenuation coefficient a (dB/mm) is calculated according to formula (3):
(B/B,)-6
Where: S sound path, mm.
5.8.4.2 When the material attenuation coefficient a exceeds 0.004dB/mm, the flaw detection results must be corrected. 5.8.5 Calculation of the sound beam diameter in the far field
The calculation of the 6dB sound beam diameter should be based on formula (4):as
Where: Ts chip diameter, mm;
d6——6dB sound beam diameter, mm.
The rest of the symbols are the same as those in 5.8.2.5a).
5.8.6 Determination of equivalent defect size
5.8.6.1 Quantification by AVG method
When the sound path is greater than 3 times the near field, the size of the equivalent defect diameter shall be calculated according to formula (5): B/B=20 lg +
+2a(rS)
Wherein: α—
-Material attenuation coefficient, dB/mm;
Defect depth
·(4)
d,--Equivalent defect diameter, mm;
JB/T5000.15-1998
B/B--Delta difference between the defect echo and the bottom wave, dB. The rest of the symbols are the same as those in 5.8.2.5a).
5.8.6.2 Quantitative determination by test block method
a) When the sound path is greater than 3 times the near field, the size of the defect equivalent diameter shall be calculated according to formula (6): +2ax-2a x
A=40lg@
Where: △-dB difference between the defect and the flat bottom hole of the test block, dB; r-depth of the flat bottom hole, mm;
a---material attenuation coefficient (comparison test block), dB/mm; ar--material attenuation coefficient at the defect, dB/mm. The remaining symbols are the same as those in 5.8.6.1.
b) When the sound path is less than 3 times the near field, the size of the defect equivalent diameter shall be determined by direct comparison with the test block or by using the measured AVG curve. 5.9 Classification of defects
5.9.1 Single defect
Defects with a spacing greater than 50mm and an equivalent diameter not less than the initial record equivalent. 5.9.2 Scattered defects
Defect spacing is less than or equal to 50mm, and there are 2 or more than 2 and less than 5 defects at the same time, and the equivalent diameter is not less than the initial record equivalent.
5.9.3 Defects in dense areas
According to 3.1.
5.9.4 Traveling signal
When the probe moves in a certain direction on the forging surface, the signal front continues to move more than 25mm deep. 5.9.5 Extensibility defect
The height of the continuous echo of the defect shall not be lower than the equivalent value of the initial record in at least one direction, and its extension length shall be greater than the maximum equivalent diameter allowed by the defect. The extension size of the extensibility defect is measured by the half-wave height method (6dB method). When measuring the extension size, the acoustic domain characteristics of the probe should be considered for correction.
5.9.6 The bottom wave reduction caused by the defect BG/BF (dB) is in accordance with 3.2.
5.10 Record of defects
5.10.1 Record defects with equivalent diameter not less than the starting record equivalent and their coordinate positions on the forging. 5.10.2 Record of defects in dense areas
5.10.2.1 Record the distribution range of dense areas. 5.10.2.2 Record the depth and equivalent of the defect with the maximum equivalent diameter in the dense area and its coordinate position on the forging. 5.10.3 Record of floating defect signals
Record the depth, length range, maximum equivalent and the coordinates of the starting and ending points of floating defect signals. 5.10.4 Record of ductility defects
Record the depth, length range, maximum equivalent and the coordinates of the starting and ending points of ductility defects. 5.10.5 Record of bottom wave reduction BG/BF (dB) caused by defects Record the dB difference between the first bottom wave amplitude BG in the intact area near the defect and the first bottom wave amplitude BF in the defect area when they reach the same reference wave height.
5.11 Quality grade
JB/T5000.15-1998
5.11.2 Any defects determined to be cracks, white spots, and shrinkage holes are not allowed to exist. If the floating defect signal can be determined as a non-hazardous defect, the quality grade shall be assessed according to the ductility defect; if it is determined to be a hazardous 5.11.3
defect, it shall be implemented in accordance with the provisions of 5.11.2. Except for the bottom wave attenuation caused by geometric reasons, any bottom wave attenuation is not allowed to exceed 26dB. 5.11.4
Table 1 gives the allowable values of the quality grade of different defect types in forged steel parts. Table 1 Classification of quality grades for different defect types Defect category
Starting record equivalent value Φ
Single defect
Maximum allowable equivalent value Φ
Maximum length of the defect
extending in any direction
Maximum allowable value of the bottom wave reduction at the defect
Maximum
Allowable range of defects in dense areas (×10°)
Not allowed
Not allowed
Not allowed
Not allowed
1 The quality grades of different defect types are independent of each other, and the quality grades of different defect types are specified by the design and other departments according to the actual situation of the workpiece. 2 The calculation of the defect range of the dense area is the maximum length range of the dense area × the maximum width range × the maximum depth range. The spacing between adjacent dense intervals shall not be less than 150mm. Otherwise, it should be regarded as a dense area. When there are multiple dense areas, the range of the dense areas should be calculated separately. Then the cumulative sum is calculated and evaluated according to the cumulative value. If the depth range of the dense area is less than or equal to 50mm, the depth range is calculated as 50mm; if the length range of the dense area is less than or equal to 50mm, the length range is calculated as 50mm. 3 Due to the limitations and shortcomings of ultrasonic flaw detection, in addition to estimating the nature of the defects from the production process, the location of the defects and their general direction and distribution, it is impossible to qualitatively characterize the defects purely from the ultrasonic flaw detection technology. Therefore, when using 5.11.2, it is best to use other effective methods to assist in the qualitative description of the defects, such as the defects have been exposed to the surface, metallographic inspection and other methods. 4 When the user has special requirements, the quality acceptance terms can also be specifically formulated by the supply and demand parties. 5.12 Ultrasonic inspection report
The ultrasonic inspection report should include the following: 5.12.1 The specifications and standards used for the inspection, the required quality acceptance level, the inspection method used, the specifications, frequency, flaw detection sensitivity and adjustment method of the probe used, the instrument model, the surface condition of the forging and the inspection period. 5.12.2 Manufacturer's mark number, product contract number, forging name, drawing number, material, furnace number, card number, etc. 5.12.3 A workpiece sketch should be drawn to indicate the actual external dimensions of the forging, the dimensions of the area not inspected due to factors such as geometric shape, and the origin of the defect location coordinates.
5.12.5 Evaluation of inspection results.
5.12.6 Inspection date and signature of the inspector. 6 Magnetic particle inspection and its quality level
6.1 Inspection basis
JB/T5000.15--1998
6.1.1 Whenever this method standard is adopted, the user or design process department shall explain and provide the scope of the forging magnetic particle inspection and the quality acceptance level.
6.1.2 The method for establishing sensitivity, the selection of instruments and equipment, the selection of magnetization methods, the requirements for magnetic field strength, etc. shall be consistent with this standard. 6.1.3 It should be stated whether there is a demagnetization requirement and the degree of demagnetization required. 6.2 Inspection surface requirements
6.2.1 The sensitivity of magnetic particle inspection is closely related to the surface condition of the inspected forging. If the irregular surface condition affects the display or evaluation of defects, the inspected surface must be processed by grinding, machining or other methods. 6.2.2 There should be no dirt, grease, cotton fiber, oxide scale or other foreign matter that affects magnetic particle inspection on the surface of the inspected area and within the adjacent 50mm range.
6.2.3 Any method that does not affect magnetic particle inspection can be used to remove foreign matter. 6.2.4 In order to detect small defects, the surface roughness R of the forging shall generally not be greater than 6.3um. 6.2.5 The temperature of the inspection surface: in the dry method, it should be less than 300℃; in the wet method, it should be less than 50℃. 6.3 Inspection period
6.3.1 Unless otherwise specified by the purchaser, the magnetic particle acceptance inspection shall be carried out after the forgings have been subjected to final heat treatment and fine machining. 6.3.2 When half-wave rectification, direct current and direct magnetization are used, the magnetic particle acceptance inspection can be carried out before fine machining. However, the machining allowance shall not exceed 3mm. 6.4 Equipment and magnetic powder
6.4.1 Magnetic particle flaw detection equipment and special types of equipment must comply with the requirements of GB3721. 6.4.2 Equipment calibration shall be carried out at least once a year in accordance with national standards. If it has been out of use for more than one year, it shall be calibrated before the first use. 6.4.3 Magnetic powder and magnetic suspension
6.4.3.1 Magnetic powder shall have high magnetic permeability and low residual magnetism, and there shall be no mutual attraction between magnetic powders. When inspected by magnetic particle weighing method, the weighing value shall be greater than 7g.
6.4.3.2 The particle size of magnetic powder should be uniform. The average particle size of magnetic powder for wet method is 2-10μm, and the maximum particle size should be less than 45μm; the average particle size of magnetic powder for dry method should be less than 90μm, and the maximum particle size should be less than 180um. 6.4.3.3 The color of magnetic powder can be red, yellow, blue, white, black, etc. The selection principle should be determined according to the surface of the workpiece, and it must have a high contrast with the color of the workpiece surface.
6.4.3.4 The wet powder method should use kerosene or water as the dispersion medium. When using water as the medium, appropriate rust inhibitors and surfactants should be added, and the viscosity of the magnetic suspension should be controlled within 5000-20000Pa·$ (25℃). 6.4.3.5 The concentration of magnetic suspension should be determined according to the type of magnetic powder, particle size, application method and time. Under normal circumstances, non-fluorescent: 10-25g/L; fluorescent: 1-3g/L, and its dispersion medium shall not have fluorescent characteristics. 6.4.3.6 For the magnetic suspension to be used in circulation, the concentration of the magnetic suspension should be measured regularly, and the suspension should be fully stirred before measurement (stirring time should be no less than 30 minutes). In general, the precipitation volume of non-fluorescent magnetic powder is required to be 1.2~2.4mL for every 100mL of magnetic suspension, and 0.1~0.5mL for fluorescent powder.
6.4.3.7 When using the fluorescence method for detection, the ultraviolet intensity of the ultraviolet lamp used on the workpiece surface should be no less than 1000μW/cm, and its wavelength should be within the range of 320~400nm. The indirect evaluation method is shown in GB5097. 6.4.4 Auxiliary equipment
To ensure the smooth progress of magnetic particle testing, the following auxiliary equipment should be available: a) magnetic field intensity meter;
c) magnetic suspension concentration measuring tube;
d) 210 times magnifying glass;
e) light meter;
f) ultraviolet lamp;
g) ultraviolet intensity meter.
6.5 Magnetization method
6.5.1 Method and materials
JB/T5000.15-1998
6.5.1.1 The ferromagnetic powder used as the test medium can be either dry or wet. And it can be fluorescent or non-fluorescent.
6.5.1.2 An electric current can be passed directly through the workpiece to magnetize the forging; or a central conductor or coil can be used to generate an induced magnetic field on the workpiece to magnetize the forging. To detect surface defects, alternating current can be used as a magnetizing power source, or direct current can be used as a magnetizing power source. In circumferential magnetization, since the "skin effect" of alternating current will reduce the maximum depth of defect detection, a direct current power source should be used when mainly detecting defects below the surface. 6.5.1.3 One or a combination of the following five magnetization methods can be used: a) contact method;
b) longitudinal magnetization method;
c) circumferential magnetization method;
d) yoke method;
e) multi-directional magnetization method.
6.5.2 Magnetic Particle Inspection Method
6.5.2.1 Continuous Method
While the magnetizing current is not interrupted and the external magnetic field is in effect, magnetic powder or magnetic suspension is applied to the surface of the forging to be inspected for inspection. When the continuous current is provided, the shortest duration of power-on should be 1/5 to 1/2s. 6.5.2.2 Fluctuation Method
This method is limited to the use of direct current. A higher magnetizing force is first applied, then the magnetizing force is reduced to a lower value, and magnetic powder or magnetic suspension is applied while maintaining this lower magnetizing force value. 6.5.2.3 Residual Magnetism Method
After the magnetizing current is cut off and the external magnetic field is removed, the inspection medium is applied, and the residual magnetism on the workpiece is used for inspection. This method is generally not used to inspect forgings. If it is to be used, the user's consent must be obtained. 6.5.3 Magnetization direction
Except for the multi-directional magnetization method, each inspection part shall be inspected at least twice, and the magnetization direction shall be roughly vertical. Magnetization in two or more directions at the same time is not allowed.
6.5.4 Magnetization type
6.5.4.1 Longitudinal magnetization
Magnetic lines are generally parallel to the axis of the forging and have definite magnetic poles. Magnetization is generally carried out using a solenoid (see Figure 1), a yoke (see Figure 2) or directly winding a cable (see Figure 3).
6.5.4.2 Circumferential magnetization
The magnetic lines of force are generally perpendicular to the axis of the forging, and there is no definite magnetic pole. Generally, magnetization is achieved by the workpiece direct current method (see Figure 4), the conductor induction method (see Figure 5), the wire penetration induction method (see Figure 6) or the contact method (see Figure 7). 6.6 Sensitivity test piece
6.6.1 Type A sensitivity test piece
Type A sensitivity test piece is only suitable for the continuous method to determine the effective magnetic field strength and direction of the surface of the inspected workpiece, the effective detection range, and whether the magnetization direction can effectively detect defects. The magnetization current should be able to clearly display the magnetic traces of the test piece. A-type sensitivity test piece is divided into three currents: high, medium and low
solenoid method
direct winding method
center conductor
conductor induction method
JB/T5000.151998
electrode contact
contact method
yoke method
direct current method
wire penetration induction method
A-15/100
A-30/100
A-6 0/100
JB/T5000.15-1998
Thickness 0.1
Artificial defects
Figure 8A-type sensitivity test piece
Table 2A-type sensitivity test piece
Relative groove depth
15/100
30/100
60/100
Sensitivity
Note: In the relative groove depth, the numerator indicates the groove depth and the denominator indicates the thickness of the test piece, in um. 6.6.2C-type sensitivity test piece
Ultra-high purity low carbon pure iron, c<0.03%,
H. <80A/m, annealed
Due to the size relationship, when the A-type sensitivity test piece is inconvenient to use, the C-type sensitivity test piece can be used. Its geometric dimensions are shown in Figure 9. The model and groove depth are shown in Table 3.
Dividing line
Artificial defect
C-type sensitivity test piece
C-type sensitivity test piece
6.6.3 Magnetic field indicator
Artificial defect depth
Ultra-high purity low-carbon pure iron, C<0.03%,
H<80A/m, after annealing
It can only roughly check the magnetic field direction, effective detection range and magnetization method of the workpiece surface. It cannot be used as a quantitative indicator of magnetic field intensity and its distribution. Its geometric dimensions are shown in Figure 10
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