This standard specifies the magnetic particle inspection and evaluation method for the intake and exhaust valves of internal combustion engines. This standard is applicable to the inspection of surface and near-surface defects of ferromagnetic valves of reciprocating piston internal combustion engines with a cylinder diameter less than or equal to 200mm. JB/T 6719-1993 Magnetic particle inspection of intake and exhaust valves of internal combustion engines JB/T6719-1993 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Magnetic Particle Inspection of Intake and Exhaust Valves of Internal Combustion Engines
1 Subject Content and Applicable Model
JB/T 6719-93
This standard specifies the magnetic particle inspection and evaluation methods of intake and exhaust valves of internal combustion engines (hereinafter referred to as valves). This standard is applicable to the inspection of surface and near-surface defects of ferromagnetic valves of reciprocating piston internal combustion engines with a cylinder diameter less than or equal to 200mm.
2 Reference Standards
JB/T6012 Technical Conditions for Intake and Exhaust Valves of Internal Combustion Engines ZBJ04006 Magnetic Particle Inspection Method for Iron and Steel Materials NJ320 Magnetic Particle Inspection Method for Parts and Components of Internal Combustion Engines 3 Names of Various Parts of the Valve
The names of various parts of the valve are defined in accordance with the provisions of JB/T6012. 4 Requirements for Flaw Detection Equipment and Valve Surfaces
4.1 The flaw detection equipment should be able to ensure the sensitivity of valve flaw detection. 4.2 A stirrer should be installed in the box containing the magnetic suspension to ensure that the magnetic powder is evenly distributed. 4.3 The demagnetization device should be able to make the residual magnetism of the valve less than or equal to 0.3mT. 4.4 There should be no grease, gold dust, oxide scale or other substances that adhere to the magnetic powder on the surface of the inspected valve. 4.5 The valve surface roughness parameter R. value is 6.3μm. 5 Requirements for magnetic powder and magnetic suspension
5.1 The magnetic powder used for flaw detection is non-fluorescent black ferroferric oxide (Fe.O.) or reddish brown iron oxide (-Fe2O.) powder. 5.2 The magnetic powder should have high magnetic permeability and low coercive force. 5.3 The average particle size of the magnetic powder is 5-10um, the maximum particle size is 50μm, and the particle size of the magnetic powder should be uniform. When inspected by microscopy, it should comply with the provisions of ZBJ04006.
5.4 The magnetic suspension used for flaw detection is made of a mixture of magnetic powder and liquid medium. The content of magnetic powder in the magnetic suspension is 15-25g/L. Stir it evenly and replace it regularly according to the usage to keep the magnetic suspension clean. 5.5 The mixed oil is made of kerosene and transformer oil with a volume ratio of 3 to 1. 5.6 The kinematic viscosity of the magnetic liquid is controlled at 15×10-6～25×10-6m2/s at 20℃. 6 Evaluation method
6.1 Cracks and transverse defective magnetic marks are not allowed in any part. 6.2 The valve disc cone, neck, lock clamp groove, pin hole, retaining ring groove and rod end are not allowed to have defective magnetic marks. 6.3 The valve stem is allowed to have three non-crack defect magnetic marks, and their length and width shall comply with the provisions of the product drawings and technical documents. Approved by the Ministry of Machinery Industry of the People's Republic of China on July 29, 1993 and implemented on January 1, 1994
7 Inspection method
JB/T 6719--93
7.1 The continuous method is used for flaw detection, and the defects are displayed by magnetic suspension. 7.2 Magnetization method
7.2.1 The longitudinal magnetization method is used to check transverse defects. 7.2.2 The circumferential magnetization method is used to check longitudinal defects. 7.3 Magnetization specification
7.3.1 Longitudinal magnetization current
7.3.1.1 When the coil is longitudinally magnetized, the ampere-turns of the valve stem are determined according to formula (1). IN
Where: magnetizing current, A,
Number of turns of a line diagram, turns;
Valve stem diameter, mm;
Effective length of valve stem, mm.
7.3.1.2 The valve disc uses a sensitivity test piece to determine the ampere-turns. 7.3.2 The circumferential magnetizing current is determined according to formula (2). Where D--www.bzxz.net
Valve disc outer diameter, mm.
7.4 The power-on time is 0.5~3s.
I= (10 ～15)dD
7.5 Before and during the daily flaw detection, the sensitivity test piece should be used to verify the flaw detection sensitivity....( 1)
7.5.1 When verifying with the sensitivity test piece, it must be ensured that the position of the notch is clearly displayed on the sensitivity test piece. Otherwise, the flaw detector, magnetic suspension and current intensity should be checked to see if they are normal.
7.5.2 The sensitivity test piece adopts A-30/100 specified in ZBJ04006.7.6 The valve must be demagnetized after flaw detection, and its corners should not be able to attract a No. 2 pin. When precise measurement is required, the RC-1 type magnetometer can be used for measurement, and its residual magnetism is less than or equal to 0.3mT. 7.7 The finished valve should be 100% inspected by the circumferential magnetization method. The longitudinal magnetization method should be inspected according to the product drawing requirements. 8 Principles of magnetic thinness distinction and judgment of defects
8.1 If magnetic marks appear on the surface of the valve, repeated flaw detection can be avoided. If the magnetic marks no longer appear in the original position, no defect treatment will be made. 8.2 The angle between the magnetic mark and the axis is less than or equal to 30°, which is a longitudinal magnetic mark, and the angle greater than 30° is a transverse magnetic mark. The judgment of defects shall be in accordance with the provisions of NJ320.
Additional remarks:
This standard is proposed and managed by the Shanghai Internal Combustion Engine Research Institute of the Ministry of Machinery Industry. This standard was drafted by the Shanghai Internal Combustion Engine Research Institute of the Ministry of Machinery Industry. The main drafter of this standard is Zhao Minghao.
From the date of implementation of this standard, NJ43786 "Technical Conditions for Magnetic Particle Inspection of Intake and Exhaust Valves of Internal Combustion Engines" will be invalid.
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