JB/T 9743-1999 This standard is a revision of NJ 310-83 "Technical Conditions for Magnetic Particle Inspection of Connecting Rod Bolts for Internal Combustion Engines". In the evaluation method, different requirements are put forward for quenching cracks, forging cracks and hairline cracks. This standard specifies the technical requirements, inspection methods and evaluation methods for magnetic particle inspection of connecting rod bolts for internal combustion engines. This standard is applicable to the inspection of surface and near-surface defects of ferromagnetic material bolts of reciprocating internal combustion engines with a cylinder diameter less than or equal to 200mm. This standard was first issued on the date of year. JB/T 9743-1999 Technical Conditions for Magnetic Particle Inspection of Connecting Rod Bolts for Internal Combustion Engines JB/T9743-1999 Standard download decompression password: www.bzxz.net

JB/T9743—1999
This standard is a revision of NJ310--83 "Technical Conditions for Magnetic Particle Testing of Connecting Rod Bolts for Internal Combustion Engines". Compared with NI310--83, the main technical content of this standard has been changed as follows: In the evaluation method, different requirements are put forward for fire cracks, forging cracks and hairline cracks. This standard replaces NJ310-83 from the date of implementation. This standard is proposed and managed by the National Technical Committee for Standardization of Internal Combustion Engines. The responsible drafting units of this standard are: Shanghai Internal Combustion Engine Research Institute, Chuandong Zhucheng High Strength Fastener Co., Ltd., Jiangsu Wuxi Luoshe Standard Push Parts Factory, Nanjing Dongdian Flaw Detector Factory.
The main drafters of this standard are: Du Rong, Ma Naiguang, Zhang Wentian, Zeng Dewen. 523
1 Scope
Machinery Industry Standard of the People's Republic of China
Technical Conditions for Magnetic Particle Testing of Connecting Rod Bolts for Internal Combustion Engines
Technical Conditions for Magnetic Particle Testing of Connecting Rod Bolts for Internal Combustion Engines JB/T9743-1999
Replaces NJ310·83
This standard specifies the technical requirements, inspection methods and evaluation methods for magnetic particle testing of connecting rod bolts for internal combustion engines (hereinafter referred to as bolts). This standard is applicable to the inspection of surface and near-surface defects of ferromagnetic material bolts of reciprocating internal combustion engines with a cylinder diameter of less than or equal to 200mm.
2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T15822--1995 Magnetic particle inspection method
JB/T9744-1999 Magnetic particle inspection method for parts and components of internal combustion engines 3 Technical requirements
3.1 Requirements for bolt surface by magnetic particle inspection
3.1.1 The surface roughness of the bolt should be Ra value of 3.2μm. 3. 1.2
The bolt surface should not have grease, rust, scale and other substances that can adhere to magnetic powder. 3.1.3 Bolts should be subjected to magnetic particle inspection before surface treatment. If it must be carried out after surface treatment, the covering layer should not affect the inspection effect. 3.2 Inspection equipment
3.2.1 The inspection equipment should have the functions of safely and reliably completing magnetization, applying magnetic suspension, observing parts and demagnetizing the bolts. A stirrer should be installed in the box containing the magnetic suspension to ensure that the magnetic powder is evenly distributed. 3.2.2
When using fluorescent magnetic particle inspection, the ultraviolet irradiation device should have the ability to clearly identify the traces of fluorescent magnetic particles. 3.2.3
The demagnetization device should reduce the residual magnetism of the bolt to 2×10:4T. 3.2.4
3.3 Requirements for magnetic powder and magnetic suspension
3.3.1 The magnetic powder used for flaw detection is ferroferric oxide (FesO.), iron oxide (FeO:) or fluorescent magnetic powder. 3.3.2 The particle size of the magnetic powder should be uniform, with an average particle size of 5~10μm and a maximum particle size of 50μm. The particle size of fluorescent magnetic powder is 2~5um. 3.3.3 The magnetic suspension used for flaw detection is prepared from magnetic powder and liquid medium. The magnetic powder content in the magnetic suspension is 20~30g/L or 1~2g/L fluorescent magnetic powder, which should be stirred evenly and regularly added or replaced according to the usage. 4 Inspection methods
4.1 Flaw detection methods
4.1.1 Continuous method
Pour magnetic suspension on the bolt to make the whole bolt evenly wet, and continue to pour the magnetic suspension while continuously powering on for 1~35 seconds. After stopping pouring, power on several times, each time for 0.5~1S. Cut off the power supply and check the bolt defects. Alternating current is generally used for magnetization. 4.1.2 Residual magnetism method
Put the bolt on the magnet for an instant (no more than 0.5s) and pour the magnetic suspension 2~3 times after power off. The pressure of the magnetic suspension should be weak: or put the bolt in the magnetic suspension for 10~30s, slowly take it out, and check it after it is still for 1~2min. Direct current is generally used for magnetization. If alternating current is used, a power-off phase controller should be used.
4.2 Magnetization method
4.2.1 Longitudinal magnetization
Place the bolt in the magnetic field generated by the energized coil or electromagnet to produce longitudinal magnetization on the bolt surface, which is used to check for defects that are perpendicular or nearly perpendicular to the bolt surface and the axis.
4.2.2 Circumferential magnetization
Directly pass current through the bolt to generate circumferential magnetic lines of force, which are used to check for axial or nearly axial defects on the bolt surface. 4.2.3 Composite magnetization
Place the bolt in the magnetic field of an electromagnet or a solenoid coil with direct current, and at the same time, the bolt itself is continuously passed through alternating current to check for defects in any direction on the bolt surface.
4.3 Magnetization specification
4.3.1 When the continuous method is used for circumferential magnetization, the magnetization current is determined according to formula (1): I=Kdte
Wherein: -
Magnetization current, A;
K--coefficient, K=10～15 A/mm
d-bolt shank diameter, mm;
~maximum diagonal dimension of the hexagonal head of the bolt, mm. +++.-
4.3.2 Determination of magnetic field strength when using coil for longitudinal magnetization4.3.2.1 When the residual magnetism method is used, when the bolt to be inspected is installed, the central magnetic field strength H of the coil is generally specified as follows: When L/d>10, H is 12000A/m;
When 2L/d≤10, H is 19100A/m.
Note: L--Total length of bolt, mmsd-
Diameter of bolt shank, mm, bzxz.net
4.3.2.2 When using the continuous method, select one-third of the magnetic field strength of the residual magnetism method. 4.4 Verification of flaw detection sensitivity
(1)
4.4.1 Before flaw detection, the concentration of magnetic suspension and current must be verified by the continuous method with the standard test piece. During the verification, the notch must be clearly shown on the standard test piece.
2 This standard uses the A-15/100 standard test piece specified in GB/T15822-1995. 4.4.2
4.4.3 Since the A-type standard test piece is frequently used and easily damaged, the sample with natural defects can be used to verify the flaw detection sensitivity. However, the correct reliability of the sample sensitivity needs to be regularly verified by the standard test piece. 4.4.4 The standard test piece should be regularly inspected and verified to avoid failure. 4.5 Demagnetization
4.5.1 All bolts after flaw detection must be demagnetized. 4.5.2 After demagnetization, the residual magnetism of the bolt shall not exceed 4×10-*T, which can be measured by a magnetometer. 5 Evaluation method
5.1 No quenching cracks of any depth and length are allowed at any position of the bolt. 5.2 No transverse cracks are allowed at the fillet of the bearing surface of the bolt head, the rod and the threaded part. 5.3 Forging cracks with a length not exceeding 1d and a depth or width not exceeding 0.04d are allowed on the top surface of the bolt head (d is the major thread diameter).
5.4 One forging crack is allowed on the edge of the hexagonal head bolt, but it shall not extend to the top circle (chamfered circle) of the top surface of the head or the bearing surface under the head, and its depth and width shall be 0.025d+0.2mm; the width of the hexagonal head flange surface bolt on the circumference shall not exceed 0.08d. There shall not be more than one forging crack with a depth of not more than 0.04d (d is the major diameter of the thread, d. is the flange diameter). 5.5 One hairline parallel to the axis of the bolt is allowed, with a width of not more than 0.15mm and a depth of not more than 0.015l+0.1mm (the maximum value is 0.4mm: d is the major diameter of the thread).
5.6 Only one of the cracks in 5.3, 5.4 and 5.5 is allowed to exist, and they shall not appear at the same time. 5.7 Principles for distinguishing magnetic marks and judging defects
5.7.1 If magnetic marks appear on the surface of bolts, repeated flaw detection can be omitted. If the magnetic marks no longer appear in the original position, no defect treatment is performed. 5.7.2 If the angle between the magnetic mark and the axis is less than or equal to 30°, it is a longitudinal magnetic mark, and if it is greater than 30°, it is a transverse magnetic mark. 5.7.3
The judgment of defects shall be in accordance with the provisions of JB/T9744.
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