JB/T 7021.3-1993 Block brake pad JB/T7021.3-1993 Standard download and decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Block Brake
1 Subject Content and Scope of Application
Brake Pad
JB/T7021.3-93
This standard specifies the type and size, technical requirements, test methods, inspection rules, etc. of brake pads for block brakes (hereinafter referred to as brake pads).
This standard applies to brake pads for brake shoes of block brakes. 2 Reference standards
GB1036
Method for determining linear expansion coefficient of plastics
GB1041
Method for testing compression of plastics
GB/T1804 General tolerances for linear dimensions without tolerance GB5766 Method for determining Rockwell hardness of friction materials JB/T7021.2 Block brakes Brake pads 3 Types and dimensions
3.1 Types
Brake pads are classified according to the connection method with the brake pads: a. Bonded brake pads, code E1 b. Riveted brake pads, code E2 c. Assembled brake pads, code E3. 3.2 Dimensions
3.2.1 The dimensions of the brake pads shall comply with the requirements of Figure 1 and Table 1. Figure 1
Approved by the Ministry of Machinery Industry of the People's Republic of China on September 21, 199317.4
Implementation on July 1, 1994
Basic size
160
200
250
315
400
500
630
710
800
D
Limit deviation
+2
0
+3
0
+4
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Note: There is no deviation requirement for L for E1 and E2 types. 5
JB/T 7021.3—93
Table 1
C
Basic dimensions
65
90
110
140
180
225
255
280
Basic dimensions
6
8
10
12
15
Limit deviation
±0.2
±0.25
±:0.3
3.2.2 The types and dimensions of the rivet holes for E2 brake pads and brake shoes are shown in Figure 2 and Table 2. Brake shoe
Figure 2
Table 2
D
C
C2
160
6
200
8
2
250
8
2
315
10
400
10
Note: Rivet holes are processed according to the assembly dimensions of B-type riveted brake shoes in JB/T7021.2. 3.2.3 The tolerance of unmarked dimensions shall comply with the m grade in GB/T1804. 3.3 Model and marking
3.3.1 Model indication
500
12
3
Brake wheel diameter D, mm
Product code
Basic size
105
132
162
204
256
320
400
452
507
630||tt| |12
3
710
15
3
mm
Limit deviation
+1
0
+1.2
+1.4
0
+1.6
0
1-1.8
0
mm
800
15
3
1
JB/T 7021.3-- 93
3.3.2 Marking example
The brake pad with quick connection to the brake shoe is bonding, and the brake wheel diameter D=200mm is marked as: Brake Pad E-200JB/T7021.3
4 Technical requirements
4.1 Friction performance
4.1.1 The maximum thermal equilibrium temperature of the brake pad is 250℃. 4.1.2 Friction coefficient μ of the brake pad: The dynamic friction coefficient relative to the brake wheel made of cast iron and cast steel materials should be not less than 0.35. 4.1.3 Wear rate q of the brake pad: The ratio of the wear mass of the brake pad to the mass before wear should not be greater than 2% after 2000 consecutive brakings on the brake inertia test bench.
4.1.4 The thermal recovery of the brake pad should meet the requirements of Articles 4.1.2 and 4.1.3. 4.2 Materials
4.2.1 The mechanical properties of the materials shall comply with the requirements of Table 3. Table 3
Name
Linear expansion coefficient.1/C
Compressive strength.N/mm2
Rockwell hardness
Index
3×10-
40
Standard
Measured according to P, M, L scale, the HR value is between 50 and 1154.2.2 The material size of the brake pad shall be uniform and shall not contain impurities that may damage the brake wheel. 4.3 Appearance
4.3.1 The surface of the brake pad shall be uniform in texture and free of defects such as cracks, air bubbles and interlayers. 4.3.2 The surface of the brake pad shall not be contaminated with impurities such as oil, dirt and water. 5 Test method
5.1
5.1.1
General requirements
The measuring tools and instruments used for the test shall comply with the relevant national metrological verification regulations. 5.1.2 The simulated brake inertia test bench shall be approved by the technical supervision and inspection department. 5.2 Friction performance
Determination of friction coefficient
5.2.1
According to the actual operating range of the brake, the five balanced temperature sections of 50, 100, 150, 200, and 250C are divided. On the brake inertia test bench, from low temperature to high temperature and then from high temperature to low temperature, the following procedures are used for determination; 2. Install the brake that meets the standards on the brake inertia test bench according to the product use requirements: Measure M, N, and D respectively according to the friction coefficient formula (1): b.
M
μLi
Where M - braking torque. N·m·
N---positive pressure, N;
D brake wheel diameter, m.
(1)
c. Calculate the maximum value max·minimum in each equilibrium temperature section, and the average value m (the amount of data collected to calculate the average value should be no less than 50), where the minimum value μmm should be no less than 80% of the average value m. 5.2.2 Determination of wear rate α
a. Measure the mass of the brake pad under test with an electronic balance; 176
JB/T 7021.3-93
b. Adjust the brake inertia test bench according to the brake wheel speed of 15m/s, equilibrium temperature of 150C, and brake pad specific pressure of 0.2N/mm2; c. Brake continuously for 2000 times, then measure the mass of the brake pad and calculate it according to formula (2). 9192×100%
Where:
The mass of the brake pad before the test, kg;
-The mass of the brake pad after the test, kg.
5.3 Determination of mechanical properties of materials
5.3.1 The linear expansion coefficient of the material shall be tested according to the test method specified in GB1036. 5.3.2 The compressive strength of the material shall be tested according to the test method specified in GB1041. 5.3.3 The Rockwell hardness of the material shall be tested in accordance with the test method specified in GB5766. 6 Inspection rules
6.1 Factory inspection
(2)
Each brake pad shall be inspected by the quality inspection department of the manufacturer in accordance with this standard. It may be shipped only after passing the inspection and accompanied by a product certificate.
6.1.1 Use general measuring tools and fixtures to routinely inspect the dimensions and deviations of the brake pads. 6.1.2 Use visual inspection and tapping methods to inspect the appearance quality specified in Article 4.3. 6.1.3 All factory inspection items must be qualified. 6.2 Type inspection
6.2.1 Type inspection shall be carried out in any of the following situations: a.
b.
When new products are trial-produced or old products are transferred to the factory for finalization and identification; when there are major changes in the formula of friction materials and the manufacturing process of brake pads, which may affect product performance; when the product has been suspended for more than one year and is resumed. ;During the normal production process of the product, type inspection should be carried out once a year; d.
e.
When the national quality supervision agency puts forward the requirement for type inspection 6.2.2 Inspection items
a ,"'inspect various countries;
b. The friction properties are tested according to Article 5.2; the mechanical properties of the materials are tested according to Article 5.3. c,
6.2.3 Sampling method for type inspection, randomly select 3 pairs of one specification for each type as inspection samples. 6.2.4 Judgment rules
The products or samples extracted for inspection must all be qualified according to the test items. If there are unqualified items, double sampling inspection is allowed, and all re-inspection items must be qualified.
Additional notes:
This standard is proposed and administered by the Beijing Hoisting and Transport Machinery Research Institute of the Ministry of Machinery Industry. This standard is drafted by Jiaozuo Brake Factory. The main drafters of this standard are Duan Jingli, Guo Yachun, Wang Zhifang, Wang Zhi, and Pan Shaofeng. 177
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