This standard specifies the hardness measurement method for wire used in rivet contacts. This standard is applicable to various wires used in rivet contacts processed by various methods, and also to other wires used in contacts. JB/T 7780.2-1995 Mechanical and physical properties test of wire used in rivet contacts JB/T7780.2-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Test Methods for Mechanical and Physical Properties of Wire for Rivet Contacts Hardness Measurement Method for Wire for Rivet Contacts
Subject Content and Scope of Application
This standard specifies the hardness measurement method for wire for rivet contacts. JB/T 7780.2—1995
This standard applies to various types of wire for rivet contacts processed by various methods, and also to other wires for contacts. 2 Reference Standards
GB5030 Small Load Vickers Hardness Test Method for Metals 3 Principle
The principle of Vickers hardness measurement is to press a regular tetrahedral diamond indenter with an angle of 136° between two opposite faces into the cross section of the sample with a specified load, keep it for a specified time, remove the load, measure the length of the two diagonals of the indentation, and obtain the hardness value by calculation or table lookup. Calculate using the following formula:
HV=1.8544 F/d2
Wherein, HV-Vickers hardness, MPa
F-load applied to the surface of the sample by the indenter, Nd-arithmetic mean of the two diagonals of the indentation, mm. 4 Specimen
4.1 Cut a small section of wire not less than 2mm from each of the two ends and the three middle parts of the sample to be inspected, and mount it in the cross section (see Figure 1 (a)). If the diameter of the wire is less than or equal to 1mm, two small sections can be taken from each of the above three parts (see Figure 1 (b)). Specimen
Figure 1 Mounting diagram
4.2 The wire is mounted, ground and polished to make a specimen. The mounting method shall not affect the mechanical properties of the wire. 4.3 The surface roughness Ra of the specimen shall not be greater than 0.1 μm. 5 Test InstrumentsbzxZ.net
Approved by the Ministry of Machinery Industry on October 9, 1995
Implemented on January 1, 1996
JB/T 7780.2-1995
5.1 The hardness tester should be placed on a stable foundation and adjusted to a horizontal level. 5.2 The central part of 60% of the field diameter of the microscope used to measure the diagonal length of the indentation is the effective use range. Within this range, the image quality should be clear, the edge should be obvious, the shape of the indentation can be clearly observed, and the diagonal length of the indentation can be accurately measured. 5.3 The requirements for the hardness tester must be consistent with those specified in GB5030. 5.4 The hardness tester should be calibrated regularly by the national metrology department. 6 Test
6.1 The room should be clean, free of corrosive atmosphere and vibration, and the room temperature is generally 10 to 35°C. 6.2 The Vickers hardness adopts a test force of 2.9S42N. 6.3 The test surface of the specimen should be perpendicular to the axis of the indenter. 6.4 The application and removal of the load should be slow and steady. There should be no impact or vibration during the test. The time for applying the full test force should not exceed 10s, and the holding time should be 30±2s. After removing the load, measure the length of the two diagonals of the indentation. The difference in length should not exceed 5% of the length of the short diagonal.
6.5 Calculate or look up the table using the average value of the indentation diagonal. 6.6 The distance from the center of the indentation to the edge of the specimen and the distance between the centers of two adjacent indentations should be at least 5 times the average length of the two diagonals of the indentation. 6.7 Measure the Vickers hardness on the processed specimen, measure 2 to 3 hardness values ​​on each section of the specimen, measure one point at the center of each section, and measure 1 to 2 hardness values ​​at the edge if 6.5 is met (see Figure 2). If the wire diameter is less than 1mm, measure 1 point at the center of one section and 1 to 2 hardness values ​​at the edge of the other section (see Figure 3). Figure 2 Test specimen
Figure 3 Test specimen
6.8 Before testing a large number of specimens or when replacing the indenter, use the corresponding standard small-load Vickers hardness block for daily calibration. 7 Test results
The test results give the hardness values ​​or average values ​​of each point at the center and edge of each section. Additional notes:
This standard was proposed and coordinated by the Guilin Electric Science Research Institute of the Ministry of Machinery Industry. This standard was drafted by the Guilin Electric Science Research Institute. The main drafter of this standard is Wang Liping
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