JB/T 9744-1999 This standard is a revision of NJ 320-84 "Magnetic Particle Inspection Method for Internal Combustion Engine Parts and Components". During the revision, only editorial changes were made according to relevant regulations, and the technical content has not changed. This standard specifies the terminology, inspection equipment, requirements for part surface, magnetization conditions, magnetization methods, magnetization specifications, precautions when magnetizing parts, inspection methods, requirements for magnetic powder and magnetic suspension, and demagnetization. This standard is applicable to the inspection of surface and near-surface defects of steel magnetic material products, semi-finished products and raw materials, and serves as the basis for formulating magnetic particle inspection operating procedures. This standard was first issued in 1984. JB/T 9744-1999 Magnetic Particle Inspection Method for Internal Combustion Engine Parts and Components JB/T9744-1999 Standard download decompression password: www.bzxz.net

JB/T 9744—1999
This standard is a revision of NJ320—84 Technical Conditions for Magnetic Particle Inspection of Internal Combustion Engine Parts and Components. During the revision, editorial changes were made to the original standard, and the main technical content remained unchanged. This standard replaces NJ320----84 from the date of implementation
Appendix A of this standard is the appendix of the standard.
This standard was proposed and managed by the National Technical Committee for Standardization of Internal Combustion Engines. The drafting unit of this standard: Shanghai Internal Combustion Engine Research Institute. The main drafters of this standard: Wang Haimin, Li Shaoqiu. This standard was first issued in 1984.
1 Scope
Machinery Industry Standard of the People's Republic of China
Internal combustion engines-Magnetic-particle inspection for parts and components
Internal combustion engines-Magnetic-particle inspection for parts and componentsJB/T 9744-1999
Replaces NJ320---84
This standard specifies the terminology, inspection equipment, requirements for part surface, magnetization conditions, magnetization methods, magnetization specifications, precautions when magnetizing parts, inspection methods, requirements for magnetic powder and magnetic suspension, and demagnetization for magnetic particle inspection for parts and components of internal combustion engines. This standard is applicable to the inspection of surface and near-surface defects of finished products, semi-finished products and raw materials made of iron and steel magnetic materials, and serves as the basis for formulating magnetic particle inspection operating procedures.
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 all valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest version of the following standards. GB/T12604.5-1990 Nondestructive testing terminology Magnetic particle testing GB/T15822--1995 Magnetic particle flaw detection method
3 Definitions
This standard adopts the definitions in GB/T12604.5. 4 Qualifications of flaw detection personnel
The qualifications of flaw detection personnel shall comply with the provisions of Chapter 4 of GB/T15822--1995. 5 Flaw detection equipment
5.1 The flaw detection equipment shall be able to perform effective flaw detection work with appropriate sensitivity according to the shape, size, surface condition of the material and the nature of the defects of the parts.
5.2 The flaw detection equipment should be able to magnetize the parts safely and reliably. The use, observation and demagnetization of magnetic powder should be simple and convenient. 5.3 The box containing magnetic suspension for mixed method inspection should be equipped with a stirrer to make the magnetic powder evenly distributed. The magnetic suspension should be able to be stably used on the parts and not interfere with the magnetic powder traces that have been generated.
5.4 The magnetic powder use device for dry method inspection should keep the magnetic powder dry, evenly distributed, and able to be stably used on the parts. 5.5 When using fluorescent magnetic powder for flaw detection, an ultraviolet irradiation device should be used. The wavelength of ultraviolet light should be between 3200×1010-~4000×10\m. When used, it should have an ultraviolet intensity that can clearly identify the fluorescent magnetic powder traces. 5.6 The demagnetization device should reduce the residual magnetism of the parts to 2×10-4T. 6 Requirements for the surface of the parts
6.1 The surface of the inspected parts should not have grease, metal chips, oxide scale, sticky sand and other substances that can adhere to magnetic powder. Magnetic particle inspection cannot be performed when there is a thick protective layer on the surface or the surface is seriously uneven enough to affect the detection effect. Approved by the State Bureau of Machinery Industry on September 17, 1999 528
Implemented on January 1, 2000
JB/T9744-1999
6.2 In order to prevent burns and improve the conductivity, the contact part between the parts and the electrode must be polished clean, and contact pads must be installed on the electrode if necessary.
6.3 Parts and welds that do not require processing can be subjected to magnetic particle inspection without processing under the condition that it does not affect the identification of magnetic particle traces. However, for parts with high requirements for detection sensitivity, when the surface state has a great influence on the detection sensitivity, the surface roughness Ra value is above 2.5. 6.4 When it is difficult to remove magnetic particles from oil holes and other pores after detection, they should be blocked with harmless substances before detection. 7 Magnetization conditions
7.1 The magnetization direction should be perpendicular to the direction where the defect occurs. 7.2 For some important parts, in order to fully display all the defects on their surface, magnetization should be carried out in two directions at right angles. Generally, longitudinal and circumferential magnetization are used, and composite magnetization can also be used. 7.3 During the magnetization operation, the magnetization method, type of magnetization current, power-on time, current value, and time of using magnetic powder or magnetic suspension should be selected according to the characteristics of the equipment, the magnetism, shape, size, and nature of the predicted defects (type, location, direction), etc. 8 Magnetization method
8.1 Circumferential magnetization
When current passes through the copper rod or cable in the part or the center hole, a magnetic field at right angles to the current is generated, and defects with an axial direction or an angle less than 45\ with the axial direction can be found.
8.1.1 Axial current method
Pass the current directly through the part itself (see Figure 1). 8.1.2 Center conductor method
Pass the current through the copper rod or cable in the hole of the part [see Figure 2a) and Figure 2b)]. 8.1.3 Support rod method
Use the contact electrode to make the current pass only through the part that needs to be inspected (see Figure 3). Test piece
Figure 1 Axial current method
Test piece (pipe)
Figure 2 Center conductor method
One defect
Test piece (pipe)
8.2 Longitudinal magnetization
JB/T9744—1999
Figure 3 Support rod method
Place the part in the magnetic field generated by the energized coil or electromagnet, and the transverse defects on the surface of the part or the defects with an angle of less than 45° with the direction of the magnetic field line can be found.
8.2.1 Coil method
Use a solenoid coil or a flexible cable wound around the workpiece to pass through the electromagnet (see Figure 4). 8.2.2 Inter-pole method
Place the part between the two poles of the electromagnet to form a closed loop (see Figure 5). Defects
Electromagnet
Figure 4 Coil method
8.3 Composite magnetization
Figure 5 Inter-pole method
It is used to find defects in any direction on the surface of the part. The method is to place the part in the magnetic field of the electromagnet or the solenoid coil with direct current, and the part itself is continuously passed through alternating current (see Figure 6). Electromagnet
Figure 6 Composite magnetization method
9 Magnetization specification
When different parts and materials are magnetized, the magnitude of the magnetic field strength should be determined based on the empirical formula, magnetic characteristic parameters (or application sensitivity test piece), and the test results of the magnetic measuring instrument. When different inspection methods and magnetization methods are selected, the magnetic properties of the parts in the final state after magnetization should ensure the following magnetic induction intensity: (3/5~~4/5)T for the continuous method and (4/5~1)T for the residual magnetism method. The magnetic induction intensity is measured by a Tesla meter. JB/T 9744—1999 9.1 Determination of the magnetizing current value during circumferential magnetization When a current is directly passed through a cylindrical (or approximately cylindrical) part for magnetization, the magnetizing current value is generally calculated according to formula (1) and formula (2): 9.1.1 Residual magnetism method: 1 (20~30)D Continuous method: 1 = (8~10)D Where: I Current value, A; D Part diameter, mm.
When the diameter is less than 20mm, 1=20D (continuous method). 9.1.2 When a flexible cable is used to magnetize a large workpiece through its inner hole, the magnetizing current is calculated according to formula (3) and formula (4): Residual magnetism method: I (20~30)D/N
Continuous method: 1 =(8~10)D/N
Where: N--
The number of cable coils passing through the inner hole of the workpiece.
The magnetization specifications for different parts during circumferential magnetization are shown in Table 19.1.3 When a large workpiece is partially magnetized using the support rod method, its magnetization specifications are shown in Table 2. Table 1 Circumferential magnetization specifications for different parts
Standard specifications
More stringent
More relaxed
Specifications for larger defects
Magnetization method
Suppression magnetization method
Continuous method
Residual magnetism method
Continuous method
Residual magnetism method
Residual magnetism method
Applicable parts
Defects that can be found
On the polished surface
High load of surface processing is used to find parts exposed on the surface
Defects, the depth exceeds
Springs, blades and similar parts
Highly stressed areas, wear and fatigue cracks or
0.05 mm cracks
! On the polished surface,
found
defects exposed on the surface, with a depth of 0.Defects within 05 mm Working under static load and repeated static load (tension, compression, longitudinal bending) Surface processed parts a) Working under static load and repeated static load (tension, compression, longitudinal bending) Surface rough processed parts h) Intermediate process inspection Magnetic field strength on the surface of parts (4) Magnetizing current of parts
Calculation formula
Cylindrical
6366-9349
1--25D
2387-3978
12732~15915l
4774-6366
Defective partSmall 4774~6366
Surface defect
Found to extend to the depth
Defects with a depth greater than 0.5
mm
Note: In the calculation formula, 1 is current, A; D is part diameter, mm: Width of S board, mm. Table 2
Span of support rods
Span of support rods and amperagebzxz.net
2387~3978
Magnetizing current
Cross-section thickness ≤20mm
>20～100
100～150
150~200
>200～300
>300～400
>400～600
Electricity passing along the board
Cross-section thickness ≥20mm||t t||>300~400
≥400～600
>600～800
『=30s
9.2 Determination of magnetic field strength during longitudinal magnetization
JB/T9744—1999
9.2.1: When using coils for longitudinal magnetization, the magnetic field strength should be selected according to the ratio of the length to the diameter of the workpiece (L/d). When magnetizing by continuous method, when parts are installed, the magnetic field strength of the effective magnetization area of ​​the coil is: Long parts with L/d≥10: 3978A/m; 2
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