GB/T 2688-1981 Technical requirements for sliding bearings - powder metallurgy bearings
Some standard content:
National Standard of the People's Republic of China
Sliding Bearings
Technical Conditions for Powder Metallurgy Bearings
GB2688—81
This standard applies to powder metallurgy iron-based and copper-based bearings (hereinafter referred to as bearings) specified in GB2685-81 "Types, Dimensions and Tolerances of Powder Metallurgy Cylindrical Bearings", GB2686--81 "Types, Dimensions and Tolerances of Powder Metallurgy Rib Cylindrical Bearings" and GB2687—81 "Types, Dimensions and Tolerances of Powder Metallurgy Spherical Bearings". 1 Technical Requirements
1.1 The materials of the bearings are classified according to the alloy composition and density as specified in Table 1. Class
Material grade marking example
Alloy composition
Iron-carbon
Iron-carbon-copper
Iron-pot
Copper-tin-zinc-lead
Copper-tin
Copper-tin-lead
Grade marking
FZ1160
FZ1165
FZ1260
FZ1265
FZ1360
FZ1365
FZ1460bZxz.net
FZ1465
FZ2170
FZ 2175
FZ2265
FZ2270
FZ2365
Iron-based Class 1 Powder Metallurgy Bearing Material with Oil Density of 5.7~6.2g/cm° Marking: Fz
GB 2688--81
Oil Density
-Iron-based
Powder Metallurgy Bearing
Bureau Issued
The First Machinery Industry Ministry of the People's Republic of China proposed Table 1
Implemented on January 1, 1982
Beijing Powder Metallurgy Research Institute.
Shanghai Textile Bearing Factory No. 1, etc.
GB 268881
1.2 The chemical composition and physical and mechanical properties of the bearing shall comply with the provisions of Table 2. Brand
jo.250.601.0
0.250.601.0
6～10
Note: ① The chemical composition of various iron-based bearings is allowed to contain less than 1% sulfur. ② The combined carbon content is allowed to be evaluated by metallographic method. Zn
③ The total carbon in the chemical composition of various copper-based bearings refers to free graphite. ④ The fluctuation range of the hardness values at three points on the same test piece shall not exceed 15 Brinell units. Others
Physical-Mechanical Properties
Oil Content
Radial Compression
Strength
Apparent Hardness
kgf/mm2
50~100
60~110
60~110
70~120
50~100
60~110
1.3 The structural type, size and tolerance of the bearing shall comply with the provisions of GB2685-81, GB2686--81 and GB2687-81. 1.4 The appearance of the bearing shall have a uniform metallic luster, and no defects such as cracks, inclusions and rust are allowed. 1.5 The finished bearing shall be impregnated with lubricating oil. Generally, the bearings are immersed in the HJ-~20 brand mechanical oil specified in GB443-64 (iron-based bearings are allowed to add rust inhibitors). If there are other requirements for the impregnated lubricating oil, they should be put forward when ordering. 1.6 The bearings should have good surface porosity. 1.7 Special technical requirements not specified in this standard should be put forward when ordering. 2 Acceptance rules
2.1 The finished bearings should be inspected and qualified by the manufacturer according to this standard, and can only be shipped with the product certificate attached. 2.2 The finished bearings should be delivered and inspected in batches. The batch size should be indicated when ordering. If not indicated, it shall be determined by the manufacturer. 2.3 If necessary, the ordering unit may sample and inspect the finished products delivered by the manufacturer in batches. The method is as follows: 2.3.1 Take 2% of each batch of finished bearings, but not less than 5 pieces and not more than 50 pieces, and check the appearance quality with the naked eye according to the provisions of this standard. 2.3.2 Take 2% of each batch of finished bearings, but not less than 5 pieces and not more than 50 pieces, and check the size and tolerance according to the provisions of this standard. 2.3.3 Take at least 2 samples from each batch of finished bearings, and after degreasing, obtain samples of no less than 50 grams, and analyze the chemical composition according to the provisions of Table 2.
2.3.4 Take 5 to 10 pieces (or agreed by both parties) from each batch of finished bearings, and check the physical and mechanical properties according to the provisions of Table 2. 296
GB2688-81
2.3.5 If there is one unqualified piece in the results of various sampling tests, double the number of finished products for the unqualified items will be sampled for re-inspection. If there are still unqualified pieces, they will not be accepted.
2.4 Finished bearings shall be inspected according to the following methods. 2.4.1 Coaxiality and circular runout tolerances shall be inspected in accordance with GB1958--80 "Shape and Position Tolerance Inspection Regulations". 2.4.2 The chemical composition shall be analyzed according to the following methods: GB223-63 "Methods for Chemical Analysis of Iron and Steel": JB2245-77 "Test Methods for Reduced Iron Powder": YB493--64 "Methods for Chemical Analysis of Tin Bronze". 2.4.3 The density shall be tested according to JB2869-81 "Determination of Density of Sintered Metal Materials (Except Cemented Carbide)". 2.4.4 The oil content shall be tested according to JB2870-81 "Determination of Open Porosity (Oil Content) of Sintered Metal Materials and Products". 2.4.5 The radial crushing strength shall be tested according to JB 2871-81 "Determination of Radial Crushing Strength of Sintered Metal Bushings". Spherical bearings and simple bearings with a diameter deformation of more than 10% before the specimen breaks shall be tested according to the breaking load agreed upon by the supply and demand parties. 2.4.6 The hardness shall be tested according to JB2867-81 "Determination of Apparent Hardness of Sintered Metal Materials (Except Cemented Carbide)". When the bearing length is more than 20mm, the apparent hardness value of the test piece at 1/6 of each end and at each measuring point in the middle; when the bearing length is less than or equal to 20mm, the number and position of the points for measuring the apparent hardness value shall be agreed upon by both parties. 2.4.7 The surface porosity test method is to heat the test piece to no more than 80℃ and keep it for 5 minutes, and use the naked eye to determine whether there is oil seepage on the inner diameter surface of the bearing.
3 Packaging and marking
3.1 The finished bearings shall be properly packaged to ensure that they will not be damaged under normal transportation conditions and will not rust within half a year from the date of leaving the factory under normal storage and preservation conditions.
3.2 The total weight of each packaging box shall not exceed 40 kg 3.3 The packaging box, box (or bag) shall be accompanied by a product inspection certificate or mark. 3.4 The following marks shall be clearly marked on the packaging: a. Product name;
b. Marking of type, size specification and material; c. Manufacturing batch number;
d. Quantity;
e. Net weight and gross weight:
f. Manufacturer name:
g. Manufacturing date;
h. Date of production.
GB 2688-81
Appendix 1
The bearing surface and body have pores, which can be immersed in a certain amount of lubricating oil, have a high surface finish and form a hardened layer after shaping, have a low apparent hardness (the microhardness of the matrix structure components is basically the same as that of the corresponding material), and have a certain deformation and shrinkage after being pressed into the seat hole. In processing, installation, use and maintenance, full attention should be paid to these characteristics to ensure the good performance of the bearing.
1 The working surface of the finished bearing should generally not be cut as much as possible. 2 After the bearing is pressed into the seat hole, if the inner diameter is deformed and shrunk too much, it can be expanded by non-cutting methods such as smooth shaft, steel ball, toothless reamer, toothless pusher, etc. If the inner diameter must be cut, it is advisable to use turning, boring and other methods, rather than grinding and other methods, so as to avoid fine chips blocking the pores and reducing the oil supply capacity.
3 The non-working surface of the bearing can be cut when necessary: 4 After cutting, the bearing should be cleaned and oiled. 5 Before assembly, the bearing can be placed in the 1st.5. Soak and clean in the oil specified in Article 5. But it must not be cleaned with kerosene, gasoline or other solvents that can dissolve the impregnated lubricating oil. 6. When assembling, the bearing surface must be kept clean, and dust and impurities should be prevented from falling on the bearing surface, blocking the pores or scratching the working surface, affecting the performance.
The dimensional tolerance of the bearing seat hole is in accordance with GB1800--79 "Tolerances and Fits". 8. When installing 7, 8, 9 grade cylindrical and ribbed cylindrical bearings, the recommended seat hole dimensional tolerance and the recommended shaft dimensional tolerance are listed in Appendix 1.
Appendix 1
Inner diameter tolerance
Bearing grade
Outer diameter tolerance
Recommended
Recommended shaft tolerance
When the bearing is pressed into the seat hole, the inner diameter shrinks by 0 of the interference drawing
Bearing seat hole tolerance
Shrinkage is 50~ of the interference amount
9For installing spherical bearings of grade 7 and 8, the seat hole size tolerance is recommended to be G10. e
10When the installation batch of bearings is large or the installation accuracy requirements are high, special machines such as presses and installation mandrels should be used for assembly. 11The surface finish of the bearing shaft should not be less than √7. The hardness value is recommended to be not less than HB250.12The appropriate operating clearance between the bearing and the shaft should be determined according to the use conditions. The recommended minimum clearance value is listed in Appendix 2. um
Appendix 2
Shaft diameter
>6～10
>10~18
Recommended minimum clearance
Shaft diameter
>18～30
>30～50
>50~60
Recommended minimum clearance
GB 2688-81
13The allowable load of bearings at different speeds is affected by many factors such as starting and loading methods, lubrication conditions, assembly level, structural conditions, and shaft material and surface conditions. Under the assumption that the steel shaft has been ground, the recommended values of the allowable load of the bearing are listed in the following Appendix 3. When designing and selecting, necessary corrections should be made to the allowable load according to different use conditions. Appendix 3
Slow and intermittent
>15~30
>30~40
>40~60
kgf/cm2
P-1050
14. Lubricating oil has a direct impact on the starting, noise, service life, power loss, etc. of the bearing. It should be appropriately selected according to the operation room, load, speed, working environment and refueling conditions. 15 Refueling can extend the service life of the bearing. The appropriate refueling method and refueling cycle should be determined according to the use conditions.
16 It is best to refuel by circulating or pressure supply. It is also possible to use the characteristics of the connected pores in the bearing body to set up an "oil depot" on the non-working surface of the bearing or install oil felt and oil cups, etc., to penetrate and replenish oil through the non-working surface. 17 In the case of a large amount of lubricating oil required, when the lubricating oil impregnated in the bearing body is not enough, you can also drill oil holes or open oil grooves on the bearing to allow the lubricating oil to flow directly into the running surface. 18 The operating temperature of the bearing is closely related to the lubricating oil. It is generally recommended that the temperature rise of the bearing should not exceed 50°C. 19 During the storage and transportation of the bearing, attention should be paid to moisture-proof, rust-proof and bruise-proof. 20 If the storage time of the bearing exceeds the anti-rust period, it should be checked for rust and re-immersed in oil by vacuum immersion, heated immersion or room temperature immersion according to regulations.
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