This standard replaces NJ 317-84 and NJ 318-84. JB/T 6729-1993 Magnetic particle inspection of crankshafts and camshafts of internal combustion engines JB/T6729-1993 Standard download decompression password: www.bzxz.net

Machinery Industry Standards of the People's Republic of China
Magnetic Particle Flaw Inspection of Internal Combustion Engine Crankshafts and Camshafts
Subject Content and Scope of Application
This standard specifies the magnetic particle inspection and assessment methods for internal combustion engine crankshafts and camshafts. JB/T 6729--93
This standard is applicable to the inspection and evaluation of surface and near-surface defects of crankshafts and camshafts of reciprocating piston internal combustion engines with cylinder diameters less than or equal to 200mm. ] Division of magnetic particle inspection surface area 4.1 The division of crankshaft magnetic particle inspection surface area is as shown in Figure 1. A
A
B
Figure 1 Crankshaft surface partition
To: ①a=D.ld (d is the diameter of the main shaft diameter or connecting rod shaft diameter), b =2r (r is the radius of the fillet), d is the diameter of the oil hole. ②The area within 5mm of the edge of the flange, pin hole, screw hole and keyway is Zone I, 2d, the area is Zone I. The area of ??each journal fillet a within 120° is zone I, and the rest is zone II. 4.2 The camshaft magnetic particle inspection surface area is divided according to Figure 2. The Ministry of Machinery Industry of the People's Republic of China approved on 1993-07-29 and implemented on 1994-01-01
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Note: ABC surface and both sides are Zone I
JB/T 6729—93
Figure 2 Camshaft surface partitions
②Except for ①, the working surface and corresponding sides are Zone II; ③Except for ①, other surfaces are Zone III
5 Classification and Level of Defects
5.1 The classification of defect properties is shown in Table 1.
Table 1
Class
A
R
C
Speciality
Flake defect: Flake slag inclusion , dense defects Linear defects: nature of defects distributed along the rolling direction of the material
Process defects: including shear cracks, forging folding, braided cracks, grinding cracks, etc. AA
Note: Among defects A and B, if the magnetic traces are removed and observed with a magnifying glass of more than five times, the visible defects are called surface defects, and the invisible defects are called near-surface defects. 5.2 Levels of defects
5.2.1 Class A defects are divided into two levels, as specified in Table 2. Table 2 | |tt | No more than 15 defective magnetic marks greater than
1mml less than or equal to 5mm, no more than 10 in a square of 10 mm×10mm (one of which is greater than 5mm and less than or equal to 7mm is allowed) 5.2.2 Class B defects Divided into three levels, see Table 3 for specified levels
3
B
B
Speciality
Table 3
Defect magnetic mark length| |tt||A single defective magnetic mark less than or equal to 2mml is greater than 2mm, a single defective magnetic mark less than or equal to 5mm is greater than 5mm, a single defective magnetic mark less than or equal to 10mm 5.2.3 Class C defects are divided into two levels, see Table 4. . 408
Grade
C,
C2
JB/T 6729--93
Table 4
Defect magnetic mark length|| tt||A single defective magnetic mark less than or equal to 2mm
A single defective magnetic mark greater than 2 mm and less than or equal to 5mm 6 Allowable limit value of defective magnetic marks on the crankshaft
No defects are allowed in zone 6.11 exist.
6.21 In the 2d area around the oil removal hole on the entire crankshaft, except for one defective magnetic mark with a length of no more than 3mm, no other defects are allowed; for fillet quenching or nitrided crankshaft, each The area is also allowed to have near surface B and 1 defect, but the total number of defects allowed in the entire crankshaft: 1 for a single-cylinder engine and 3 for a multi-cylinder engine.
6.3 In zone III, defective magnetic marks of A, A2, B, and Bz are allowed in each area. A total of 2 defective magnetic marks are allowed on the connecting rod journal and 3 on the main journal, but the entire The total number of allowable defects on a crankshaft: 2 for single-cylinder engines and 4 for multi-cylinder engines. 6.4 In zone IV, defective magnetic marks of CI, C2, A1, A2, B, B, and B are allowed to exist. The entire crankshaft is allowed to have 2 defective magnetic marks of CI, C., and A, Az (or B, Bz , B.) There are 3 defective magnetic marks in total, but the total number of allowed defects on the entire crankshaft is: 3 for single-cylinder engines and 5 for multi-cylinder engines. 7 Allowable limit value of defective magnetic marks on camshaft
7.11 In the area, each area is allowed to have one defective magnetic mark near surface A, A (or near surface BI, B,), and the entire camshaft is allowed to have defects. Total number: 1 for single-cylinder machines and 2 for multi-cylinder machines. 7.2 In Zone II, each area is allowed to have 1 magnetic defect mark B (or A,) or 2 magnetic defect marks near surface B (or near surface A2) or 1 magnetic defect mark near surface B (or near surface A3). , Near surface B. The distance between two defective magnetic marks is not less than 1.6mm. The total number of allowed defects in the entire camshaft: 2 for single-cylinder engines and 3 for multi-cylinder engines.
7.3 In zone III, each area is allowed AI, A2 (or BI, B2) defective magnetic marks, near-surface B defective magnetic marks, Ci, C2 defective magnetic marks, a total of 3 + allowed defects on the entire camshaft Total number: 3 for single-cylinder machines and 4 for multi-cylinder machines. 8 Class B and Class C defective magnetic marks are not allowed to exist in the lateral direction. 9 Determination of magnetic marks
9.1 When the angle between the defective magnetic marks and the axis is greater than 30°, it is treated as a lateral defect. 9.2 Magnetic defect marks with a length more than three times the width shall be treated as linear defects; magnetic marks with more than 10 in a square area of ??10 mm × 10 mm and a single defect length not exceeding 5 mm shall be treated as flake defects. 9.3 Magnetic marks less than 0.5mm in length will not be treated as defects. 10. After magnetic particle inspection, it should be demagnetized, and the residual magnetic intensity should not be greater than 2×10~4T. 11 When the crankshaft journal is larger than 75mm, the length values ??of various defective magnetic marks specified in Table 2, Table 3 and Table 4 should be multiplied by the coefficient K and calculated according to the following formula:
Where: K - coefficient; | |tt||d--crankshaft journal diameter size, mm.
K=
d
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JB/T6729--93
This standard is approved by the Ministry of Machinery Industry Shanghai Proposed and managed by the Institute of Internal Combustion Engines. This standard is drafted by the Shanghai Internal Combustion Engine Research Institute of the Ministry of Machinery Industry. The main drafters of this standard are Weng Zuliang and Chen Jiansheng. From the date of implementation of this standard, NJ317-84 "Technical Conditions for Magnetic Particle Flaw Inspection of Diesel Engine Forged Steel Crankshafts and Camshafts" and NJ318-84 "Technical Conditions for Magnetic Particle Flaw Inspection of Diesel Engine Ductile Iron Crankshafts and Camshafts" are invalid. 410
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