This standard specifies the metallographic inspection and evaluation methods for ductile iron piston rings for internal combustion engines. JB/T 6724-1993 Metallographic inspection of ductile iron piston rings for internal combustion engines JB/T6724-1993 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T6724-93
Metallographic Inspection of Ductile Iron Piston Rings for Internal Combustion EnginesPublished on 1993-07-29
Ministry of Machinery Industry of the People's Republic of China
Implementation on 1994-01-01
Metallographic Inspection of Ductile Iron Piston Rings for Internal Combustion Engines1 Subject Content and Scope of Application
This standard specifies the metallographic inspection method and evaluation method for ductile iron piston rings for internal combustion engines. JB/T6724-93
This standard is applicable to the inspection of the metallographic structure of ductile iron piston rings for reciprocating piston internal combustion engines with a cylinder diameter less than or equal to 16 cm.
2 Reference standards
GB9441 Metallographic inspection of ductile iron castings
3 Technical requirements
3.1 Graphite
3.1.1 Graphite morphology and spheroidization rate
Graphite should be spherical and agglomerated, with a small amount of agglomerated floccules and worms allowed, evenly distributed, and the graphite spheroidization rate should be greater than or equal to 75%, and evaluated according to the first level diagram: 1 to 4 levels are qualified.
3.1.2 Graphite size (graphite spheroid diameter size) Graphite spheroid diameter should be less than or equal to 50μm, and evaluated according to the second level diagram: 1 to 3 levels are qualified. 3.2 Matrix structure
The matrix structures are lamellar pearlite, tempered troostite, tempered martensite or bainite, etc. 3.2.1 Free ferrite
For cast or normalized piston rings, the amount of free ferrite should be less than or equal to 15% of the viewing area. For quenched-tempered piston rings, the amount of free ferrite (broken ferrite) should be less than or equal to 5%. Evaluated according to the third level diagram: cast, normalized, 1 to 4 levels qualified: quenched-tempered, 1 to 2 levels qualified. 3.2.2 Disc eutectic
Phosphorus eutectic should be in small pieces or discontinuous networks, and its amount should be less than or equal to 1%. Evaluated according to GB9441: Figure 34~Figure 35 qualified. 3.2.3 Carbide
Carbide should be in the form of dots, small strips, small pieces, and evenly distributed. Its amount should be less than or equal to 3%. Evaluated according to GB9441: Figure 39~Figure 41 qualified.
4 Inspection method
Sampling location
The sample should be cut within 1cm on the left and right of the ring opening, and its cross section should be used as the metallographic grinding surface. Note: The centrifugal casting piston ring can be cut on the cross section of any part of the ring. 4.2 Evaluation method
4.2.1 The graphite spheroidization rate should be evaluated by selecting the worst field of view on the entire grinding surface. If three fields of view are unqualified, it is unqualified. 4.2.2 Evaluation of graphite size
The size of the graphite spheroid diameter should be evaluated by selecting the worst three fields of view on the entire grinding surface (three graphites exceeding the specified size are not allowed in each field of view). If three fields of view are unqualified, it is unqualified. Approved by the Ministry of Machinery Industry on July 29, 1993
Implemented on January 1, 1994
4.2.3 Evaluation of matrix structure
JB/T6724-93Www.bzxZ.net
The matrix structure is etched with 2% to 5% nitric acid alcohol solution or 4% picric acid solution. Pearlite, ferrite, cementite, and phosphorus eutectic are evaluated by selecting the worst field of view on the entire grinding surface. If three fields of view are unqualified, it is unqualified. 4.2.4 The image size of this standard is 70mm in diameter. 5
Grading of metallographic structure
Grading of graphite
The rating of graphite spheroidization rate is evaluated according to the first level map at 100 times magnification. The description of each level is shown in Table 1. Table 1
Grading of graphite size
Spheroidization rate
Graphite size is evaluated according to the second level diagram at 100 times magnification, and the description of each level is shown in Table 2. Table 2
Grading of matrix structure
5.2.1 Grading of free ferrite
Graphite size is evaluated according to the third level diagram at 100 times magnification, and the description of each level is shown in Table 3. Table 3
Ferrite content
Figure 33 level
JB/T 6724-93
First level diagram (100 times)
Diagram 55 level
Diagram 22 level
Diagram 61 level
Diagram 83 level
Diagram 101 level
JB/T6724-93
Second level diagram (100 times)
Third level diagram (100 times)
Diagram 72 level
Diagram 94 level
Diagram 112 level
Additional instructions:
Diagram 123 level
JB/T6724-93
Diagram 145 level
This standard is proposed and managed by the Shanghai Internal Combustion Engine Research Institute of the Ministry of Machinery Industry. This standard is drafted by the Shanghai Internal Combustion Engine Research Institute of the Ministry of Machinery Industry. The main drafter of this standard is Zhao Shiqun.
Figure 134
People's Republic of China
Mechanical Industry Standard
Metallographic Inspection of Ductile Iron Piston Rings for Internal Combustion Engines JB/T6724-93
Published and distributed by the Machinery Standardization Research Institute of the Ministry of Machinery Industry Printed by the Machinery Standardization Research Institute of the Ministry of Machinery Industry (PO Box 8144, Beijing 100081)
Copyright reserved
Reproduction prohibited
Format 880×12301/16 Printing sheet 5/8 Number of characters 10000First printing in December 1993
First edition in December 1993
Price 8.00 yuan
Printing 00,001-500
Number 1250
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