JB/T 2798-1999 This standard is a revision of JB 2798-81 "Metallographic Standard for Iron-based Powder Metallurgy Sintered Products". This standard specifies the quantitative evaluation grade of pearlite and cementite in the metallographic structure of iron-based powder metallurgy sintered products. This standard is applicable to the evaluation of the metallographic structure of medium and high density iron-based powder metallurgy sintered products with a density of not less than 6.0g/cm3. This standard was first issued in July 1981. JB/T 2798-1999 Metallographic Standard for Iron-based Powder Metallurgy Sintered Products JB/T2798-1999 Standard Download Decompression Password: www.bzxz.net

ICS77.160
Machinery Industry Standard of the People's Republic of China
JB/T2798—1999
Metallographestandard specifications for powdermetallurgyiron-basedsinteringproducts1999-08-06Published
National Bureau of Machinery Industry
2000-01-01Implementation
JB/T2798—1999
This standard is a revision of JB2798—81 "Metallographe Standard for Iron-based Powder Metallurgy Sintering Products". During the revision, only editorial changes were made to the original standard, and the main technical content remained unchanged. This standard replaces JB2798—81 from the date of implementation. This standard is proposed and managed by the Technical Committee for Standardization of Powder Metallurgy Products. The drafting unit of this standard: Shanghai Materials Research Institute. The main drafters of this standard are Zhang Deming, Chen Shanzhu and Zhong Shouliang. This standard was first issued in July 1981.
1 Scope
Standards of the Machinery Industry of the People's Republic of China
Metallographestandard specifications for powder metallurgy iron-based sintering productsMetallographestandard specifications for powder metallurgy iron-based sintering productsJB/T2798-1999
Replaces JB2798-81
This standard specifies the quantitative evaluation grade of pearlite and cementite in the metallographic structure of iron-based powder metallurgy sintering products. This standard is applicable to the evaluation of the metallographic structure of medium and high density iron-based powder metallurgy sintering products with a density of not less than 6.0g/cm2. 2 Sample preparation and metallographic examination
2.1 Sampling
2.1.1 The sampling part should be the surface perpendicular to the pressing direction of the part as the metallographic grinding surface. 2.1.2 Parts immersed in oil must be degreased with carbon tetrachloride, ether, etc. before inspection. 2.2 To check pearlite and cementite structures, use 4% picric acid alcohol solution plus 0.5% nitric acid alcohol solution, or 2% nitric acid alcohol solution.
2.3 Magnification when evaluating various structures
2.3.1 When evaluating pearlite and cementite, 250 times is often used, and 300 times can also be used. 2.3.2 When evaluating porosity, use 100 times.
2.4 The number of various structures is evaluated with the field area as 100%. 2.5 When evaluating the number of pearlite, at least five fields of view should be observed before evaluation. When the difference between the pearlite number and the comparison evaluation is not more than 20%, the result is taken as the average value. When the difference between the pearlite number and the comparison evaluation is more than 20%, it should be explained in detail in the test report. 2.6 The evaluation of cementite quantity shall be conducted in at least five viewing fields, and the field with the largest number shall be used for judgment. 2.7 The evaluation of pores shall be conducted directly on the polished and uncorroded specimen. The number, size, shape and distribution of pores shall be used as a reference for metallographic analysis, not as a basis for acceptance. 3 Metallographic Structure
3.1 Pearlite
3.1.1 The number of pearlite is divided into nine levels by percentage. According to the coarseness of pearlite in the product, it is divided into Group A (coarse) and Group B (fine).
3.1.2 The number level of pearlite shall be evaluated according to Table 1 and Figures 1A to 9A, 1B to 9B. 3.2 Cementite
3.2.1 The number of cementite shall be divided into six levels according to the percentage requirements specified in the technical conditions for powder metallurgy products. 3.2.2 The number level of cementite shall be evaluated according to Table 2 and Figures 1 to 6. Table 1
Approved by the State Machinery Industry Bureau on 1999-08-06
Pearlite content
Implementation on 2000-01-01
JB/T2798-1999
Pearlite quantity level diagram (magnification: 250 times) Group A (fine)
Cementite quantity
Figure 1A bead 10
Figure 3A bead 30
JB/T2798—1999
Figure 4A bead 40
Figure 5A bead 50
Figure 7 A bead 70
JB/T27981999
Figure 6A bead 60
Figure 8A bead 80
Figure 1B bead 10
JB/T2798—1999
Figure 9A bead 90
Group B (rough)
Figure 2B bead 20
Figure 3B bead 30
Figure 5B bead 50
JB/T2798-1999
Figure 4B bead 40
Figure 7B bead 70bzxz.net
JB/T2798 -1999
Figure 9B bead 90
Cementite quantity level diagram (magnification: 250 times)Figure 1 Cementite 1
Figure 3 Cementite 5
JB/T27981999
Figure 2 Cementite 3
Figure 4 Cementite 7
Figure 5 Cementite 10
JB/T2798—1999
Figure 6 Cementite 13
Mechanical Industry Standard
Metallographic Standard of Iron-based Powder Metallurgy Sintered ProductsJB/T2798—1999
Mechanical Science Research Institute Published and distributed
Printed by the China Academy of Mechanical Science
(No. 2, Shouti South Road, Beijing, zip code 100044)*
Format 880×12301/16 Printing sheet 3/4
4 Word count 20000
First printing in March 2000
First edition in March 2000
Print run 1-500
Price 2000 yuan
99-1183
Mechanical Industry Standards Service Network: http/vwwJB.ac.cn66686
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