JB/T 9219-1999 Method for determination of ultrasonic sound velocity of ductile iron
Some standard content:
JB/T9219—1999
This standard is a revision of JB/Z265--86 "Method for determination of ultrasonic velocity of ductile iron". During the revision, editorial changes were made to the original standard, and the main technical content remained unchanged. This standard replaces JB/Z265-86 from the date of implementation. Appendix A and Appendix B of this standard are both standard appendices. This standard is proposed and managed by the National Casting Standardization Technical Committee. This standard was drafted by: Shenyang Foundry Research Institute. The main drafters of this standard are: Xia Renkai and He Houyue. 17
1 Scope
Machinery Industry Standard of the People's Republic of China
Test method of ultrasonic sound velocity for spheroidal graphite cast ironsJB/T 9219.- . 1999
Replaces J13/Z26586
This standard specifies the method for measuring the ultrasonic propagation velocity (hereinafter referred to as the speed of sound) in ductile iron using the ultrasonic pulse method and contact manual operation.
This standard is applicable to the determination of ultrasonic sound velocity of ductile iron. Other cast irons can also be used for reference. 2 Referenced standards
The provisions contained in the following standards constitute provisions of this standard by being quoted in this standard. When this standard is published. The version shown is valid. All standards are subject to revision and parties using this standard should explore the possibility of using the latest version of the standard listed below. YB/T5148--1993 Metal average grain size determination method 3... General provisions
3.1 This standard uses the pulse reflection or penetration method to measure the propagation time of ultrasonic longitudinal waves in the specimen (referred to as acoustic time). Principle, industrial test method to determine the speed of sound.
3.2 The thickness of the test part of the test piece should be measured correctly. The test surface should be flat and free of burrs, scale, sticky sand, paint, etc. that would affect the nose test results. The parallelism of the two opposite planes of the test part should not be greater than 3°. . 3.3 In addition to being familiar with the performance of instruments and equipment and being able to adjust and use them correctly, operators should have general knowledge of ductile iron. 4 Instruments
4.1 Depending on the specific situation, ultrasonic sound velocity measuring instruments, ultrasonic thickness gauges and Equipment used in connection with ultrasonic flaw detectors and time measuring devices, etc., but should meet the following requirements:
a) The operating frequency is in the range of 1 ~ 5MHz; b) The time resolution is not less than 0.01us, or the measurement time resolution is not less than 0.01us. The thickness resolution is not less than 0.01mm; c) The instability of the instrument when working at room temperature is less than 0.2%, and the measurement nonlinearity is not more than 0.2%. 5 Adjustment of the instrument
5.1 This measurement method is based on comparing the unknown sound speed of the tested piece with the known sound speed of the steel calibration test block or water. Therefore, calibration must be performed before each test. Test blocks or water calibration instruments should be calibrated regularly when used continuously. 5.1.1 The calibration test block is made of rolled or drawn medium carbon steel. It has been heat treated to make the metal structure uniform. The grain size is above level five according to YB/T5148. The surface roughness Ra should not be greater than 2.5um. The length is recommended to be 50 or 100mm, the sound velocity of the steel test block should be corrected by the standard water sound velocity.
5.1.2 The standard sound speed of distilled water is shown in Appendix A (standard appendix). 5.2 Instruments that use synchronized pulses as the door opening signal of the timing device will cause noise due to the delay in signal conversion and transmission. National Machinery Industry Bureau 1999-06-24 Approved 418
2000-01- 01Implementation
JB/T 9219--1999
The error between the indicated value and the true value on the instrument, therefore, zero calibration must be performed first. 5.2.1 For instruments equipped with a zeroing device, the zeroing method can be obtained from the instrument’s instruction manual. 5.2.2 For instruments without zero calibration device, see Appendix B (standard appendix) for adjustment methods. 6 Method
6.1 Depending on the shape, thickness, etc. of the test piece, the pulse reflection method or the penetration method can be used for measurement. 6.2. Pulse reflection method
propagation time.
Use a single probe to transmit and receive ultrasonic waves, and use a display to display the round-trip of ultrasonic waves in the material. 6.2.1 For instruments with a device for displaying sound duration, adjust the instrument according to Chapter 3 to measure the sound in the test piece. The time interval between two adjacent back-surface echoes. After measuring the thickness of the measurement part, calculate the sound velocity according to formula (1): V-2H
where: Vi.--ultrasonic longitudinal wave speed, m/s; H--thickness of the tested part of the test piece, mm ;
1——The time interval between two adjacent bottom echoes·ps. 103 | When testing, two calibration test blocks should be used first, - the thickness of the block is smaller than the thickness of the test part of the test piece: - the thickness of the block is greater than the thickness of the test part of the test piece, to calibrate the linearity of the instrument. When the thickness display on the instrument is consistent with the actual thickness of the two calibration test blocks, then measure the displayed thickness and the actual thickness of the test piece, and calculate the sound speed according to formula (2): Vi
- in the test piece Ultrasonic longitudinal wave velocity, m/s; where.V.- --
Known ultrasonic longitudinal wave velocity of Vi correction test block, m/sH—actual thickness of the measurement part of the specimen, mm; H'|| tt||Thickness of the measurement part of the specimen displayed on the instrument, nm. (2)bZxz.net
6.3 Penetration method - Place the two probes that emit and receive ultrasonic waves on the planes on both sides of the measurement part of the specimen, and make the axes of the two probes coincide with each other to measure the penetration of ultrasonic waves. Penetration time, after measuring the thickness between the two detection surfaces, calculate the sound velocity according to equation (3): Vi.=
where V. The ultrasonic longitudinal wave speed of the specimen, m/s; H—the detection location of the specimen The actual thickness, mm; 1--the sound time penetrating the detection part of the specimen, μs. 7 Application of sound velocity measurement in castings
7.1 Ductile iron is a rigid material that can propagate ultrasonic waves (longitudinal waves, transverse waves, surface waves). Among them, the longitudinal wave propagation speed follows the expression in an infinite solid medium. See Formula (4): E
Where: Vi..-ultrasonic longitudinal wave velocity, m/s; E-Young's elastic modulus, N/m;
0—-material density.kg /m\;
Poisson's ratio (ratio of transverse and longitudinal deformation). 1-a
(1-α)(1=2)
There is free graphite in ductile iron, which has a certain influence on the physical quantities in formula (4) (4)|| tt | The production process is relatively stable 7.2.2 In the application, the corresponding relationship between the sound speed, mechanical properties and the degree of spheroidization is established according to the production conditions. 7.2.3 The degree of spheroidization and mechanical properties can only be evaluated when the matrix is similar. 8 Application Guidance
It is recommended to use instruments with wide-band amplification and narrow pulse probes. When such instruments are not available, it is recommended to use the penetration method for testing as much as possible. When the thickness of the low specimen 8.1
is less than 30mm, it should be used Reflection detection. 8.1.1 When using the penetration method for detection, the front edge of the received ultrasonic pulse should be saturated as much as possible. 8.1.2 When the pulse reflection method is used to detect thin parts with a thickness less than 15 mm, the multiple reflection method can be used to calculate the sound speed by taking the arithmetic mean of the round-trip propagation time of the ultrasonic wave in the specimen. 8.2 Since the error of the sound velocity value depends on the measurement error of thickness and sound time, thin parts should be avoided from testing on the rough surface. 8.3 The thickness measurement of the specimen should ensure that the relative error of thickness measurement is less than 0.5%. 8.4 When testing on solid castings, representative parts should be selected for fixed-point testing. 8.5 When using the reflection method to test on an instrument without an oscilloscope monitoring device, if abnormal display values are found, try to verify 8.6 During the test, the temperature difference between the calibration test block and the traced test piece should not exceed 30°C. 420
JB/T 9219
Appendix A
(standard appendix)
Standard speed of sound for distilled water
Appendix B
(standard Appendix)
Measurement of post-belt time
1491,1
This appendix is suitable for the timing device of the A-type pulse reflection ultrasonic flaw detector with alarm door. Determination of lag time during use.
The connection and use of the flaw detector and the time measuring device should be carried out according to the instrument instructions. B1
B2 uses the synchronous pulse of the ultrasonic flaw detector directly as the door opening signal of the time measuring device, and uses the interwave signal (ultrasonic video pulse) reported by the flaw detector to gate the gate as the closing signal of the time measuring device. time, the measured sound time of ultrasonic wave propagation in the test piece will be greater than the actual sound time, B3 measurement method
B3.1 Pulse reflection method
B3.1.1. When the probe and calibration test block (3.1.1) are well coupled, adjust the relevant knobs of the flaw detector so that the oscilloscope screen 1: displays more than two clear echoes, and the first echo B reaches an amplitude of more than 80% of the vertical display limit of the oscilloscope screen. B3.1.2 Adjust the position of the alarm gate of the flaw detector so that B2 falls into the gate and measure the time interval t between the initial wave TB1. B3.1.3 Adjust the gain of the flaw detector so that the amplitude of the second echo Bz is the same as 13, and move the gate position backward so that B falls into the gate. +m121
JB/T9219-1999
Measure the time interval t between the initial wave T and B2, see Figure B1. Assume that the lag time is △t, after measuring t1, and t2 respectively, then: At 2ti
Lag time, ps:
Where: ——
t——the time interval between the initial wave and the second echo, μus; the time interval between the initial wave and the second echo, us. B3.2 Penetration method
（B1）
B3.2.1 Place two probes with separate ultrasonic transmission and reception functions on two opposite planes of the calibration test block, adjust the relevant knobs of the flaw detector, and make two clear penetrating wave waveforms appear on the oscilloscope screen, then increase the output and gain to saturate the front edge of the ultrasonic pulse as much as possible without instrument noise.
B3.2.2 Adjust the gate position so that the first penetrating wave P. falls within the gate range, and measure the time interval t1 between the initial wave T and P. Then, move the gate position so that the second penetrating wave P. falls within the gate range, and measure t, see Figure B2. Since t is the propagation time of the ultrasonic wave through three times the thickness of the test block, the lag time △ is: At
Where: At---lag time μs;
t\-time interval between the initial wave and the first penetrating wave, μs; time interval between the initial wave and the second penetrating wave, μs. P
B3.2.3 It is also possible to use two test blocks of the same material with an integral multiple of thickness to test separately and obtain △t. B4 Since the performance of the probes is not consistent, the probes used should be measured separately. B5 The sound time operation method of the actual test piece is the same as that of Chapter B3, and the sound speed should be calculated after deducting the lag time 422
(B2)
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