JB/T 5442-1991 Magnetic particle inspection of important compressor parts
Some standard content:
Machinery Industry Standard of the People's Republic of China
Magnetic particle inspection of important parts of compressors
1 Subject content and applicable scope
JB 5442-91
This standard stipulates compression Dry and wet magnetic particle (including fluorescent and non-fluorescent) flaw detection methods and defect grade classification of important compressor parts. This standard is suitable for inspecting surface and near-surface defects of important compressor parts made of ferromagnetic materials (hereinafter referred to as "workpieces"). 2 Reference standards
GB3721 Magnetic particle flaw detector
Non-destructive testing terminology
JB3111:
3 Terminology
The terms and definitions of this standard are in accordance with the provisions of JB3111 . 4. Injury handling personnel
4.1 The flaw detection personnel should be those who have certain basic knowledge and flaw detection experience, and who have obtained qualification certificates recognized by relevant departments after examination. 4.2 Those who are color blind and whose corrected visual acuity at close range is below 1.0 are not allowed to participate in the magnetic particle inspection assessment. 4.3 Flaw detection personnel should be equipped with relevant protective equipment and operate in accordance with relevant operating procedures. 5 Timing of flaw detection
Unless otherwise required by the user, the workpiece should generally be carried out after final heat treatment and final finishing. 6 Flaw detection equipment
6.1 Magnetic particle detection equipment shall comply with the requirements in GB3721. 6.2 The flaw detection equipment should be able to safely and reliably magnetize the inspected workpiece, and facilitate magnetic powder application, observation and demagnetization operations. 6.3 The liquid tank of the wet powder method should be equipped with a stirrer to evenly distribute the magnetic powder. 6.4 The powder spraying device of the dry powder method should be able to keep the magnetic powder dry and make the magnetic powder form a uniform mist during powder spraying. 6.5 When fluorescent magnetic particle flaw detection is used, the ultraviolet lighting device used should be able to meet the flaw detection requirements, and the wavelength of ultraviolet light should be in the range of 0.32-0.40 μm.
6.6 The demagnetization device should be able to ensure that the surface magnetic field intensity of the workpiece after demagnetization is less than 160A/m. 7 Magnetic powder
7. 1 Magnetic powder should have high magnetic permeability and low residual magnetism. When inspected by magnetic weighing method, the weighing value should be greater than 7 people. 7.2 The particle size of the magnetic powder should be uniform, with an average particle size of 5~10 m and a maximum particle size of 50 μm. The particle size of fluorescent magnetic powder is 2 ~ 5 um7.3. The color of the magnetic powder should have a higher contrast than the workpiece being inspected. 7.4 The powder method should use kerosene or water as the dispersion medium. If water is used as the medium, appropriate rust inhibitors and surfactants should be added. The viscosity of the magnetic suspension should be controlled at 5000~20000Pas (25℃). The Ministry of Mechanical and Electronic Industry of the People's Republic of China approved the implementation on 1992-07-01 on July 22
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JB 5442-91
7.5 The concentration of magnetic suspension should be based on the type and particle size of the magnetic powder. And the application method and time to determine. Generally, the concentration of non-fluorescent magnetic powder is 9~20g/L, and the concentration of fluorescent magnetic powder is 0.52g/l.
8 Workpiece surface preparation
8.1 The surface roughness value of the inspected workpiece should be R.6.3μm. 8.2 There should be no grease or other substances that can adhere magnetic particles to the surface of the workpiece being inspected. 8.3 If it is difficult to remove magnetic particles from the oil holes and other pores of the inspected workpiece after flaw detection, they should be blocked with harmless substances before flaw detection. 8.4 In order to prevent the arc from burning the surface of the workpiece and improve the conductive performance, the contact part between the workpiece and the electrode must be cleaned, and a contact pad should be installed on the electrode if necessary.
9 Magnetization method
9.1 Longitudinal magnetization
When detecting defects that are perpendicular to the axis of the workpiece or at an angle greater than or equal to 45°, longitudinal magnetization should be used. Longitudinal magnetization can be obtained by the following method:
α. Coil method (Figure 1);
b. Magnetic yoke method (Figure 2).
Current
Fast trap
Coil
Current
9.2 Circumferential magnetization
Electric slip
Figure 1. Coil method
Core
Defects
Figure 2 Yoke method
When detecting defects that are parallel to the axis of the workpiece or at an angle less than 45°, the circumferential direction should be used magnetization. Circumferential magnetization can be obtained by:
a. Axial energization method (Figure 3):
h. Center conductor method (Figure 4):
c. Contact method (Figure 5),
Floor
G
Electricity
358
Defects
Figure 3 Axial energization method| |tt||Electric Games
Current
Work
Defects
Figure 4 Center Conductor Method
Center Conductor
Electricity|| tt | It can be divided into continuous method and residual magnet method. 9.3.1 When using the continuous method, the magnetic powder must be applied within the energization time, which is generally 0.5~3$. The magnetization can be stopped only after stopping the application of magnetic suspension for at least 1 s.
Continuous methods of energizing generally include: axial energizing method, central conductor method; contact method, coil method, yoke method, etc. 9.3.2 When using the residual magnet method, the magnetic powder should be applied after the end of power supply. The general power supply time is 0.25~1s. When using the AC residual magnetization method, a power-off phase controller must be equipped to ensure the magnetization effect of the workpiece. 9.4 Magnetized area
Each inspected area of ??the inspected workpiece should be inspected at least twice independently, and the directions of the magnetic lines of the two inspections should be roughly perpendicular to each other. When conditions permit, rotating magnetic fields and AC and DC composite magnetization can be used. 10 Magnetization Specifications
10.1 Sensitivity Test Piece
10.1.1A type sensitivity test piece is only suitable for the continuous method and is used for the effective magnetic field strength and direction of the surface of the workpiece to be inspected, the effective detection area and whether the flaw detection method is Correct measurement. The magnetizing current should be able to show clear magnetic marks on the test piece. 10.1.2A type sensitivity test piece has three levels of sensitivity: high, medium and low. Its dimensions are shown in Figure 6, and its model and groove depth are shown in Table 1. 6
Thickness 0.1
Deep 0.012
Figure 6 Type A test piece
359
Model
A:15/100
A-30/100
A -60/100
Relative groove depth
bag 1
am
%
1&
Go
Note: The relative groove depth expression of the test piece is medium and divided. JB5442-91
Type A sensitivity test piece
Tenderness
Shang
Low
Groove depth, the denominator is the thickness of the test piece
Miao
Loss
Ultra high purity low carbon pure iron (C0.03%
Hu80A/m) after annealing treatment| |tt|| - A type of sensitivity test strip, which functions as a type A sensitivity test strip. The geometric dimensions are shown in the picture. 10.1.3 | | tt | |tt||The thickness is 0.25
1t0.2 axial energization method
Picture? Magnetic field indicator
The magnetizing current during axial flux magnetization can be calculated as follows: Continuous method:
Residual magnetization method:
Wuzhong: 1-
Current value A
D
I 10 20D
1 -: 23 -~ 451
\I. Maximum size in diameter or cross section, mm10.3 Head method
When using the contact method, the local magnetization is large! When installing parts, see the table for magnetization specifications? . 10.3.1
Table 2 Contact method magnetizing current
Material thickness
nim
T≥20
0.025 steel skin
++ +++
......-++++.*++e..+++( I )
++++-+-+||tt ||Required current per unit thickness
A/min
(2)
10.3.2 When using the contact method, the electrode spacing should be controlled between 75 and 200) mm. The power-on time should not be too long. The contact between the electrode and the workpiece should be maintained well to avoid burning the workpiece. 10.4 Center conductor method
10.4.1. The magnetization of the inner surface of hollow or porous parts should use the center conductor method as much as possible. The material of the mandrel is preferably copper or aluminum. The diameter of the mandrel should be as large as possible. The mandrel can be placed in the center or eccentrically. When placed eccentrically, the effective detection area each time is about 4 times the diameter of the mandrel (see Figure 8) and there should be a certain overlap area and length of the overlap area Should be no less than 0.4d. 10.4.2 The magnetizing current value when the core diameter is 50mm is shown in Table 3. Table 3 Center conductor method magnetizing current value
wall thickness mm
>3~6
>6~g
>9~12
>12 ~15
Current value
A
1000
1250
1500
1750
When the wall thickness is greater than 15mm , for every 3mm increase in thickness, the current increases by 250A. When the core rod diameter increases or decreases by 1/4 compared to the specified value, the current value increases or decreases by 250A/mm accordingly. e
Figure 8 Effective area of ??central conductor detection
10.5 Yoke method
10.5.! When using the yoke method to magnetize a workpiece, the magnetizing current should be determined based on the sensitivity test piece or the lifting force test. When using the maximum pole spacing, the lifting force of the AC solenoid yoke should be at least 44N and the DC solenoid yoke force should be at least 177N. 10.5.2 The magnetic pole spacing of the yoke should be controlled between 50 and 200 mm, and the effective detection area is within a range of approximately 50 mm on both sides of the line connecting the two magnetic poles. The magnetized areas shall overlap by 25 mm at each time. 10.6 Coil method
10.6.1 When using the wire method to longitudinally magnetize the workpiece, the ampere-turns (IN) can be calculated as follows: IN
Where: I current value, A, | |tt||N-line diagram turns, t,
L workpiece length, mm;
45000
L/D
D---workpiece diameter or Maximum dimension in cross section, mm. The above formula does not apply to workpieces with an aspect ratio (L/D) less than 3. When L/D≥10, L/D in the formula is 10. (3)
10.6.2 For workpieces with an aspect ratio less than 3, if you want to use the coil method, you can use a magnetic pole extension block to increase the effective value of the aspect ratio or use a sensitivity test piece to measure the ampere-turn. Number(IN). 10.6.3 The effective magnetization area of ??the coil method is the range 0.5 times the diameter of the coil from the outside of the coil end. 10.6.4 When the total length of the inspected workpiece is too long, it can be magnetized in sections, but it should be ensured that all parts have a certain overlap area. The overlapping area should be no less than 361
10% of the segment detection length.
11 Application of magnetic powder
JB 5442-91
After the workpiece is properly magnetized, magnetic powder can be applied by any of the following methods. 11.1 Dry powder method
In the dry powder method, magnetic powder can be applied with a manual or electric duster and other suitable tools. Magnetic powder should be evenly sprinkled on the inspected surface of the workpiece. Magnetic powder should not be applied too much to avoid covering up defective magnetic marks. At the same time, when blowing off excess magnetic powder, defective magnetic marks should not be disturbed. 11.2 Wet powder method
11.2.1 When using the wet powder method, it should be confirmed that the entire flaw detection surface can be well wetted by the magnetic suspension before applying the magnetic suspension. 11.2.2 The magnetic suspension can be applied by pouring, dipping, etc., but brushing is not allowed. 12 Demagnetization
12.1 Under normal circumstances, demagnetization should be carried out after the flaw detection is completed. 12.2 If there are no special requirements for circumferentially magnetized parts and parts that need to be heated after flaw detection, they may not be demagnetized. 12.3 Demagnetization generally involves placing the workpiece into a magnetic field equal to or greater than the magnetized workpiece, and then continuously changing the direction of the magnetic field while gradually reducing the magnetic field to zero.
12.3.1 AC demagnetization method
Slowly withdraw the workpiece to be demagnetized from the energized magnetizing coil until the workpiece is more than 1m away from the coil and then cut off the current. Or place the workpiece into the energized magnetized coil and gradually reduce the current in the coil to zero. 12.3.2 DC demagnetization method
Place the workpiece to be demagnetized in a DC electromagnetic field, continuously change the direction of the current, and gradually reduce the current to zero. 12.3.3 Demagnetization of large workpieces
Large workpieces can be partially demagnetized using an AC electromagnetic yoke or segmented demagnetization using wound cable coils. 12.4 The degree of demagnetization of the workpiece can generally be measured with a residual magnetometer or magnetometer. 13 Evaluation of magnetic marks
13.1 Unless it can be determined that the magnetic marks are caused by uneven local magnetism of the workpiece material or improper operation, all other magnetic marks should be treated as defective magnetic marks.
13.2 Defect magnetic marks with a ratio of length to width greater than 3 shall be treated as linear defects, and defective magnetic marks with a ratio of length to width less than or equal to 3 shall be treated as circular defects.
13.3 When the angle between the magnetic defect mark and the workpiece axis or busbar is greater than or equal to 30°, it will be treated as a transverse defect, and other defects will be treated as a longitudinal defect. 13. When 42 defective magnetic marks are on the same connection line and the spacing is less than or equal to 3mm, they will be treated as one defect, and its length is the sum of the two defects plus the spacing.
13.5 Non-crack longitudinal defect magnetic marks with a length less than 1mm and non-crack transverse defects with a length less than 0.5mm are not included in the assessment.
13.6 According to the different stress conditions of each part of the workpiece, the surface of the workpiece can be divided into important areas (hereinafter referred to as area 1) and non-important areas (hereinafter referred to as area II).
13.6.1 The division of zone I and zone II of the crankshaft and connecting rod is shown in Figure 9 and Figure 10. 13.6.2 In other parts, the threaded area; mating surface; sealing surface; transition fillet; twice the width of the keyway , within 2 times the diameter of the oil hole and other stress concentration areas are all zone I, or divided according to the requirements of relevant technical documents, otherwise they are zone II. 13.6.3 If the defective magnetic mark is located at the junction of Zone I and Zone II of the workpiece, it will be counted as Zone I. 362
14 Defect level classification
t4.1 No defects allowed
14.1.1 Any cracks or white spots.
14.1.2 Any lateral defect magnetic marks,
(a/2)+
JB5442-91
Zone
Zone 1||tt| |a=D.1d and α≥25
Fig. 9 Crankshaft area division
H/2
(P/2)+
Net
Zone 1
North Zone
Figure 10 Connecting rod area division
14.1.3 There are 3 or more defective magnetic marks on any straight line and the edge distance is less than 5mm. 14.2 Linear defect grade classification
14.2.1 Linear defect grade classification according to Table 4. Linear defect grade classification
Table 4
Grade
2
6
Length 1. and quantity of linear defect magnetic marks
No Any defective magnetic marks are allowed to show
1 mm≤L<5mm, and no more than 1
1 mm≤L<5 mm, and no more than 3
1 mm ≤L<5mm, and no more than 5 strips
5mm≤L<8mm, and no more than 1 strip
5mm≤L<8mm, and no more than 3 strips
5mm≤L<8mm, and not more than 5 pieces
8mm≤L<10 mm, and not more than 1 piece
363
10
different|| tt||JB 5442--91
Table 4 (End)
Length L and quantity of linear defect magnetic marks
8 mm≤L<10 mm, and not more than 3 Article
Those greater than level 9
14.2.2 If the number of defective magnetic marks exceeds the requirements in Table 4, the level shall be reduced by 1 level for every 2 additional lines, and shall not exceed level 2 at most. Otherwise, the defects will be treated as not allowed.
14.2.3 The final grade of the workpiece shall be graded according to the lowest grade of defects. 14.3 Circular defect grade classification
14.3.1 Circular defect magnetic marks are carried out using an evaluation area, and the size of the evaluation area is a square of 15mm×15mm. The assessment area should be selected at the location with the most serious magnetic defects.
14.3.2
14.3.3
The maximum length of the magnetic marks of the defects participating in the assessment in the assessment area shall not be greater than 5mm, and those larger than 5m will be counted as linear defect magnetic marks. The round defect grade classification is according to Table 5.
Table 5
Levelbzxz.net
2
3
4
5
Circular defect grade classification||tt ||The number of circular defect magnetic marks in the evaluation area
1~~3
4-5
6-7
89
is greater than 5 Grader
14.3.4 In the same important area (I area), if there are defects of the same level with adjacent assessment areas and overlapping side lengths, the level will be reduced by one level. 14.4 Inspection after defect repair
After the defect is repaired, it should still be inspected and evaluated according to this standard. 15 Flaw detection report
The magnetic particle flaw detection report should at least include the following contents:. Name and serial number of the inspected workpiece;
b. Material, heat treatment status and surface condition of the inspected workpiece; C. Name, model and manufacturer name of the flaw detection equipment: d, magnetic powder type and magnetic suspension concentration; || tt||e. Method of applying magnetic powder;
t, magnetization method;
name. Flaw detection sensitivity calibration and test piece name; h. Defect record and workpiece sketch (or schematic diagram): i. Flaw detection results and grade classification;
]. Number of repairs, flaw detection results and grade classification after repairs; k. Signature of the flaw detector and responsible personnel;
1. Date of inspection.
Additional notes:
This standard was proposed by the National Compressor Standardization Technical Committee. This standard was recommended by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronic Industry and was responsible for drafting it. The main drafter of this standard is Liu Qing.
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