JB/T 9745-1999 This standard is a revision of NJ 325-84 "Metallographic Inspection of Boron Cast Iron Monomer Cast Piston Rings for Internal Combustion Engines". During the revision, only the necessary editorial changes were made according to relevant regulations, and the main technical content remained unchanged. This standard specifies the technical requirements, inspection rules and rating standards for the metallographic structure of boron cast iron monomer cast piston rings for internal combustion engines. This standard is applicable to the metallographic structure inspection and rating of boron cast iron monomer cast piston rings for internal combustion engines with a cylinder diameter of less than 160mm. This standard was first issued in 1984. JB/T 9745-1999 Metallographic Inspection of Boron Cast Iron Monomer Cast Piston Rings for Internal Combustion Engines JB/T9745-1999 Standard download decompression password: www.bzxz.net

ICS 27.020
Machinery Industry Standard of the People's Republic of China
JB/T9745—1999
Internal cornbustion engines--Individually cast rings with boron-Metallographicexamination
1999-09-17 Issued
Issued by the State Bureau of Machinery Industry
Implemented on 2000-01-01
JB/T9745-1999
This standard is a revision of EN 325-84 "Metallographic Examination Standard for Individual Cast Iron Piston Rings for Internal Combustion Engines". Editorial changes were made to the standard during the revision, and the main technical content remained unchanged. This standard replaces NJ 325—84a from the date of implementation. This standard is proposed and managed by the National Technical Committee for Standardization of Internal Combustion Engines. The drafting unit of this standard is Shanghai Internal Combustion Engine Research Institute. The main drafter of this standard is Su Qinghua.
This standard was first issued on September 12, 1984. 1
Machinery Industry Standard of the People's Republic of China
Internal combustion engines--Individually cast rings with boronMetallographic examination
JB 9745—1999
Replaces NI 325—84
This standard specifies the technical requirements, inspection rules and rating standards for the metallographic structure of boron cast iron monolithic cast piston rings for internal combustion engines. This standard applies to the inspection and rating of the metallographic structure of boron cast iron monolithic cast piston rings for internal combustion engines with a cylinder diameter of less than 160mm. Technical requirements
2.1 Graphite
2.1.1 Graphite should be evenly distributed F type, A type or B type. D and E type graphite are allowed, and the number shall not exceed 30% of the field area, of which E type graphite shall not exceed 10% of the field area. The concentrated distribution of F type graphite shall not exceed 35% of the field area. Its level shall be evaluated according to the first level diagram of this standard. When the section coefficient of the piston ring is less than or equal to 0.8, grades 1-4 are qualified; when the section coefficient of the piston ring is greater than 0.8, grades 1~5 are qualified.
2.1.2 Graphite length: It is evaluated in four grades according to the section coefficient of the piston ring. In the section coefficient,
> 0.8~1.1
Note: The section coefficient refers to the ratio of the cross-sectional area to the circumference of the finished ring. 2.2 Matrix structure
2.2.1 Hard phase containing graphite
Graphite length (μ)
2.2.1.1 Composition of hard phase containing graphite: It should be boron carbide or boron composite. It is allowed to have phosphorus eutectic distributed separately, but the sum of the area of ​​phosphorus eutectic in boron composite and phosphorus eutectic distributed separately shall not exceed 40% of the total area of ​​hard phase in the field of view. Its level shall be evaluated according to the second level diagram of this standard, and 1-2 levels are qualified.
2.2.1.2 Distribution of hard phase containing graphite: It should be discontinuous network or dispersed distribution, and some distribution in aggregate is allowed. 2.2.1.2.1 Discontinuous network distribution of hard phase containing graphite: Its level shall be evaluated according to the third level diagram of this standard. When the section coefficient of the piston ring is less than or equal to 1.1, the average diameter of the mesh is not more than 0.2 mm, and the 1-3 grades are qualified; when the section coefficient of the piston ring is greater than 1.1, the average diameter of the mesh is not more than 0.25 mm, and the 1-4 grades are qualified. Note: The average true diameter of the mesh refers to the arithmetic mean of the major diameter and the minor diameter of the mesh. Approved by the National Machinery Industry High Commission on September 17, 1999 and implemented on January 1, 2000
JB/T 9745-1999
2.2.1.2.2 The hard phase containing boron is distributed in clusters: the cluster area is not more than 15000um. Its level is evaluated according to the fourth level diagram of this standard: 1 grade is qualified.
2.2.1.3 The number of hard phases containing boron: not less than 4% of the field of view area. The grade is evaluated according to the fifth level diagram of this standard, and the grade 1~2 is qualified. 2.2.1.4 Block size of boron-containing hard phase: The single block area of ​​boron-containing hard phase is not more than 1000μm. The grade is evaluated according to the sixth level diagram of this standard, and the grade 1~2 is qualified.
2.2.2 Free iron violet body: The quantity is not more than 3% of the viewing area. The grade is evaluated according to the seventh level diagram of this standard, and the grade 1~2 is qualified. 2.2.3 Pearlite should be lamellar, and granular is not allowed. Needle-shaped structure is allowed, but ledeburite is not allowed (except for reverse white mouth). 3 Inspection rules
3.1 Sample location
Should be taken within the range of 5mm on the left and right opposite to the center of the free opening of the ring, and this section shall be used as the metallographic grinding surface. 3.2 Inspection location
3.2.1 Graphite distribution, graphite length, free ferrite and pearlite shall be inspected in the entire grinding surface. Among them, D, E type graphite and ledeburite should be inspected in the area of ​​1mm from the outer cylindrical surface of the ring and 0.7mm on the upper and lower sides. 3.2.2 The composition of the boron-containing hard phase, the distribution and quantity of the boron-containing selenite phase and the block size of the boron-containing hard phase should be inspected in the area of ​​1mm from the outer cylindrical surface of the ring and 0.7mm on the upper and lower sides.
3.3 Rating method
3.3.1 The distribution of graphite is evaluated according to the majority of the fields on the grinding surface. The length of the right graphite is calculated as the straight line length between the two ends. If the length of 3 graphite lines on the grinding surface exceeds the specified value, it is unqualified. If one field of view exceeds the specified value for D, E type graphite and F type graphite with aggregate distribution exceeds the specified value, it is unqualified.
3.3.2 For the evaluation of the composition of the boron-containing hard phase, take 5 fields of view from the worst part of the inspection area. If the phosphorus eutectic area of ​​3 fields exceeds the specified value, it is unqualified.
3.3.3 Distribution and quantity of boron-containing hard phases shall be evaluated according to the majority of the inspection areas. Five fields of view shall be taken from the worst part. If the average diameter or number of mesh holes in three fields of view exceeds the specified value, it shall be deemed unqualified. 3.3.4 If the distribution of boron-containing hard phases in aggregate and the blockiness of boron-containing hard phases exceed the specified value in one field of view, it shall be deemed unqualified. If the number of free iron decay bodies exceeds the specified value in three fields of view, it shall be deemed unqualified. 3.3.5
3.3.6 The matrix structure shall be etched with 2%~5% nitric acid alcohol solution. 3.3.7 All kinds of structures shall be evaluated under a field of view with a diameter of 70mm. 4 Metallographic structure rating standard
4.1 Graphite rating standard
Graphite shall be evaluated according to the first-level diagram (Figure 1-Figure 8) at a magnification of 100 times. The rating instructions are shown in Table 1. Grade
JB/T 9745-1999
Characteristics of graphite distribution
Fine F-type graphite, evenly distributed
A+F-type graphite, evenly distributed
B graphite, evenly distributed
D, E-type graphite <30%
Large F-type graphite, evenly distributed
Coarse F-type graphite
D, E-type graphite>30%
Agglomerated F-type graphite>35%
Drawing No. National
4.2 Rating Standard for Boron-Containing Hard Phase Composition
JBT9745—1999www.bzxz.net
The boron-containing hard phase composition is evaluated according to the second level diagram (Figure 9~Figure 11) under a magnification of 500 times. The rating instructions are shown in Table 2. Table 2
Composition of the hard phase
Contains carbide
Phosphorus eutectic area in the abrasive composite ≤40%
Euctectonic area in the abrasive composite>40%
4.3 Boron-containing hard phase intermittent network fast distribution rating standard 3B 9745—1999
The mesh size is evaluated according to the third level diagram (Figure 12~Figure 16) under a magnification of 100 times. The rating instructions are shown in Table 3. Table 3
Mesh distribution of hard phase
Fine mesh
Small mesh
Medium mesh
Large mesh
Large mesh
Average mesh diameter
JB/T9745-1999
4.4 Rating standard for clustered distribution of boron-containing hard phase JB/T9745-1999
The distribution area of ​​boron-containing hard phase clusters is evaluated according to the fourth level diagram (Figure 17~Figure 18) under magnification of 100, and the rating description is shown in Table 4. Table 4
4.5 Rating standards for the number of hard phases
Area size of boron-containing hard phases
Agglomeration area greater than 15 000 μm
Neck area>15 000 μm
The number of boron-containing hard phases is evaluated according to the fifth level diagram (Figures 19 to 21) under a magnification of 100 times. The rating instructions are shown in Table 5. Qiu 5
Number of ketone-containing hard phase%
Number of phosphorus-containing hard phase> 6
Number of ground hard phase2 4
Number of ground hard phase> 4
4.6 Rating standard for blockiness of boron-containing hard phase
JB/T 9745-1999
The blockiness of boron-containing phase is rated according to the sixth level (Figure 22-Figure 24) under a magnification of 500 times. The rating instructions are shown in Table 6. Table 6
Containing hard phase block area
Small block area μm
Medium block area 1000um
Large block area>1000μm
4. Rating standard for free ferrite quantity
The free ferrite quantity is rated according to the seventh level diagram (Figure 25-Figure 27) under magnification of 200, and its rating description is shown in Table 7. Table 7
Free ferrite quantity%
Free ferrite quantity more than 1
Free ferrite quantity less than 3
Free ferrite quantity>3
IB/T 9745-1999
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