This standard specifies the technical requirements, test methods, inspection rules, packaging and storage of resistance strain gauge pressure sensors. This standard applies to resistance strain gauge pressure sensors (hereinafter referred to as sensors) whose sensitive parts are strain gauge tubes or strain gauge diaphragms. JB/T 5493-1991 Resistance strain gauge pressure sensor JB/T5493-1991 Standard download decompression password: www.bzxz.net

Aviation Industry Standard of the Ministry of Aerospace Industry of the People's Republic of China
HB5493-91
Carburizing, carbonitriding,
Determination method of carburizing depth of aviation steel parts
Published on April 15, 1992
Implemented on May 1, 1992
Approved by the Ministry of Aerospace Industry of the People's Republic of China
Aviation Industry Standard of the Ministry of Aerospace Industry of the People's Republic of ChinaDetermination method of carburizing depth of aviation steel parts
1 Subject content and scope of application
This standard specifies the determination method of carburizing depth of aviation steel parts. HB5493-91
This standard is applicable to the inspection of carburizing depth of aviation products and carbonitriding depth of aviation products specified in HB/Z159. 2 Reference standards
HB/Z159
Instructions for gas carburizing and carbonitriding process of aviation steelHB5172www.bzxz.net
GB9451
3 Test specimens
Metal Rockwell hardness test method
The test specimen for the determination of the total hardened layer depth or effective hardened layer depth on the thin surface of steel parts should be cut from the carburized or carbonitrided parts. It is allowed to use the same grade and furnace carburized or carbonitrided test specimens as the parts. The measurement surface must be perpendicular to the working surface of carburizing or carbonitriding or the approximate working surface (except when the Vickers hardness method is used to measure the thin carburized layer with a depth equal to or less than 0.3mm). 4 Determination method
The methods for measuring the depth of carburized layer include Vickers hardness determination method, high-power structure determination method, low-power structure determination method and fracture determination method. Among them, Vickers hardness determination method is the recommended method and arbitration method, and low-power structure determination method and fracture determination method are only used for pre-furnace inspection. 5 Vickers hardness determination method
5.1 For carburizing and carbonitriding, the effective hardened layer depth (DC) is greater than 0.3mm, and the hardness of the part three times the effective hardened layer from the surface is less than 450HV after heat treatment to the final hardness value, the effective hardened layer depth is determined according to the following method. For parts with a hardness greater than or equal to 450HV at a distance of three times the effective hardened layer from the surface, the effective hardened layer depth is determined by agreement between the relevant parties. The effective hardened layer depth can be determined by a limit value greater than 550HV (with 25HV as one level). 5.1.1 Effective hardened layer depth: Generally, it is specified that after quenching and tempering of carburizing or carbonitriding, the vertical distance from the surface of the part to the Vickers hardness value of 550HV. The test force used to determine the hardness is 9.807N. In special cases, with the agreement of the relevant parties, a test force ranging from 3.923N to 49.030N or a surface Rockwell hardness tester can also be used. The Rockwell hardness determination method is implemented in accordance with HB5172. The effective hardened layer depth is represented by the letter DC, the unit is millimeter, and the effective digit is two decimal places. If other test forces or limit values ​​are used, they should be specified after the letter DC. For example, DC49.03/575 means that the test force of 49.03N is used for determination, and the limit hardness value is 575HV. 5.1.2 The measurement of the effective hardened layer depth should be carried out at the specified position according to the requirements of the drawings. The test surface of the specimen is required to be parallel to the hardness test bench and to be ground and polished. Various measures should be taken during this process to avoid overheating or changes in the edge angle of the test surface. 5.1.3 The hardness indentation should be carried out within the specified width (W) of 1.5mm along one or more parallel lines perpendicular to the surface (see Figure 1). The distance (S) between two adjacent indentations should not be less than 2.5 times the diagonal of the indentation. The distance difference from the surface to the center of each successive indentation should not exceed 0.1mm (for example, d2-d, less than or equal to 0.1mm). The accuracy of the cumulative distance from the measuring surface to each indentation is ±25um, and the measurement accuracy of the diagonal of each indentation is ±0.5um. w
Figure 1 Hardness pressure position
Except for special agreements between the two parties concerned, the indentation should generally be made under a test force of 9.807N and measured with an optical instrument with a magnification of about 400 times. The measurement position should be determined by consultation between the parties concerned and carried out within two bands on the polished test surface. A hardness change curve relative to the surface distance should be drawn for the measurement results of each position. According to each curve drawn above, the vertical distance from the surface of the part to the hardness value of 550HV is measured respectively. If the difference between these two values ​​is less than or equal to 0.1mm, take their average value as the effective hardened layer depth; if the difference is greater than 0.1mm, the test should be repeated until it is confirmed that there is no problem with the test, and then the test value is given truthfully. 5.1.4 When the effective hardened layer depth has been roughly determined, the following interpolation method can be used as a conventional effective hardened layer depth measurement method:
On a vertical section of the part, at a distance of d, and d, from the surface, at least five indentations are made. d, and d2 are respectively greater than and less than the determined effective hardened layer depth (see Figure 2). The value of (d, - d,) should not exceed 0.3mm. The effective hardened layer depth is given by the following formula:
DC = d, + (d:- d,) (H - Hs)H,-H2
Where: H: Determined hardness value:
H,, H2---The arithmetic mean of the hardness measurement values ​​at d:, d2 (see Figure 3). 2
HB5493-91
Position of hardness measurement point
Distance to surface, mm
Figure 3 Mathematical diagram of effective hardened layer depth
5.2 For parts with effective hardened layer depth less than or equal to 0.3mm, the relevant provisions of GB9451 shall apply. 6 High-power structure determination method
6.1 After carburizing and carbonitriding of low-carbon steel and low-carbon alloy steel, the specimens in air cooling, quenching and tempering, incomplete annealing or annealing can be used. After polishing, they are generally corroded in 3% to 5% nitric acid alcohol for 15 to 25s and measured under a microscope with a magnification of 100 times. The depth of the layer is equivalent to the sum of the hypereutectoid plus the eutectoid plus the half transition zone of the structure in the equilibrium state. 3
HB5493-91
Low-carbon steel and low-alloy steel are generally measured in the annealed state. For example: 12CrNi3A, 12Cr2Ni4A carburized parts are kept at 850±10℃ for 20~60min, and then cooled to below 400℃. Typical pictures are shown in Figures 4~5. 18Cr2Ni4WA steel is generally measured in the isothermal quenching state. The isothermal quenching specification is heating at 860±10℃, isothermal at 280±5℃, isothermal time is 5~10min, and immediately water-cooled. The half transition zone is equivalent to 50% isothermal martensite. Typical pictures are shown in Figure 6.
Carburized layer
HB5493—91
Carburized layer
HB5493—91
Carburized layer
c) Quenching and tempering
12CrNi3A steel typical picture of carburized layer depth measurement under different conditions Figure 4
HB5493-91
Carburized layer
Carburized layer
HB5493-91
HB549391
Carburized layer
c) Quenching + tempering × 100
Figure 512Cr2Ni4A steel typical picture of carburized layer depth measurement under different conditions 9
HB5493-91
Carburized layer
Isothermal quenching
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