GOST 21120-75
GOST 21120−75 Bars and billets round and rectangular section. Methods of ultrasonic flaw detection (with Amendments No. 1, 2)
GOST 21120−75*
Group B09
STATE STANDARD OF THE USSR
RODS AND BILLET ROUND AND RECTANGULAR
Methods of ultrasonic flaw detection
Round and rectangular bars and billets. Ultrasonic testing
Date of introduction 1977−01−01
The decision of the State Committee of standards of Ministerial Council of the USSR of August 29, 1975 N 2282 the introduction installed from 01.01.77
Proven in 1986 by Decree of the state standard from
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** Expiration removed by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS No. 5/6, 1993). — Note the manufacturer’s database.
* REISSUE (December 1988) with Amendments No. 1, 2 approved in November 1981, July 1986 (IUS 2−82, 10−86).
This standard applies to rolled round bars and square cross section, compressed ingots, billets for pipes and for roll diameter or a side of the square from 30 to 300 mm of carbon, alloy and high-alloy steels and alloys and sets the pulse-echo, shadow and mirror-shadow methods of ultrasonic inspection of metal, or a combination to identify internal defects within the sensitivity of the method.
General requirements for methods of ultrasonic testing — according to GOST and GOST 12503−75 20415−82.
Terms and definitions — according to GOST 23829−85 and reference application.
1. SAMPLING METHOD
1.1. A control sample to adjust the sensitivity of the detector is made of a piece of billet, not from defects in the ultrasonic inspection results. A control sample is produced in the cross section is equal to or less than ± 10% of the amount of controlled products, and the configuration, structure and surface quality similar to controlled products.
1.2. To adjust the sensitivity of the instrument under ultrasound control with the help of direct converters used control samples with artificial reflectors which is the lateral surface (Fig.1 and 3) or flat bottom (Fig.2 and 4) of the hole.
The diameter of the hole , if it is not specified in the standards or technical conditions, the reflection of ultrasonic waves from the lateral surface of the hole should be no more than 2.5 mm from the flat bottom holes greater than 3.0 mm. drilling Depth for the case when the artificial reflector is a lateral surface of the hole must be at least 50 mm.
1.3. The diameters of the artificial reflectors to be selected from a number of: 1; 1,5; 2; 2,5; 3; 3,5; 4; 5; 6; 7; 8 mm.
Damn.1
Damn.2
Damn.3
Damn.4
1.4. The depth of artificial reflectors from the surface of input of ultrasonic vibrations should be ¾ of the diameter or thickness of the controlled metal, unless described in the normative-technical documentation.
1.5. Accuracy and the technology of artificial reflectors in the control samples for the direct Converter — GOST 21397−81, for an angle beam transducer — according to GOST 14782−86.
Sec. 1. (Changed edition, Rev. N 2).
2. PREPARATION FOR TESTING
2.1. On the surface of the rental should be free of dirt, loose scale, captured and molten metal splashes. The surface quality must meet regulatory and technical documentation on controlled metal.
2.2. Sensitivity setting of the ultrasonic flaw detector is made on the control sample. Adjust the sensitivity of the automated ultrasonic setup is performed 5-fold by passing the control sample through the installation. This should be 100% registration of artificial reflectors.
Setting the sensitivity of the detector when using angle beam transducers are manufactured in accordance with GOST 14782−86.
Sec. 2. (Changed edition, Rev. N 2).
3. TESTING
3.1. Control is carried out by longitudinal and (or) transverse waves. The entering of ultrasonic vibrations into the metal is contactless, contact, immersion, or slit methods.
3.2. When control of circular cross section blanks or slotted pin methods, the working surface of the Converter must be identical to the shape of the surface of the workpiece. Use nozzles and supports under the control of blanks of circular cross-section transducer with a flat working surface.
3.3. The sounding scheme of workpieces is set in such a way that was controlled the entire volume of the metal, except in uncontrolled areas, inherent in the ultrasonic method of control. The billet of square section prosvechivayut with two mutually perpendicular faces, round billet — forming. When using the angle beam transducers scan performed in two directions perpendicular to the generatrix of the circular workpiece and the length of the rectangular.
3.4. The way the relative movement of the seeker and a controlled metal surface (scan) must provide detection of defects specified in the standards and technical conditions for products, and the scan rate — fixing these defects.
3.5. The main measured characteristics of these defects is the amplitude of the signal from an artificial reflector in the test sample.
3.6. With the sensitivity setting flaw signal amplitude reflected from an artificial reflector in test sample, should be at least ½ the height of the screen of a cathode-ray tube flaw detector.
3.7. The recommended frequency of ultrasonic vibrations is set from 0.5 to 5 MHz.
3.8. When using manual and mechanized methods of control set a search sensitivity of the detector and the level of fixation. Fixing level corresponds to the amplitude of the signal reflected from the artificial reflector in test sample, the size and location of which is indicated in the normative-technical documentation approved in the established order. Search sensitivity level is set 6 dB above the level of fixation. Using the automatic method of control only to establish the level of fixation.
3.9. Defects produced on the search sensitivity, and commit subject areas of the workpiece in which there is at least one of the following defect:
the reflected signal, the amplitude of which is equal to or greater than the level of fixing;
the weakening of the signal or attenuation of the previous signal or below the level of fixation.
3.10. Verifying the configuration of the instrument is made of control samples not less than 4 hours of work.
3.11. The boundaries of the defective areas determined by the position of the transducer. Conditional length of the defect is determined by the amount of displacement of the transducer, within which the perceived flaw signal at a predetermined sensitivity of the detector.
3.12. Method, key parameters, circuit converters, input method, ultrasonic oscillations, a scheme of scan methods of separation of false signals and signals from defects are established in the normative-technical documentation for specific products.
3.13. It is allowed to join the echo-pulse and mirror-shadow methods of control, if the amplitude of the bottom signal in areas that do not contain discontinuities that exceed the amplitude of the echo signal from the reflector a control sample not less than 6 dB.
Sec. 3. (Changed edition, Rev. N 2).
4. PROCESSING OF THE RESULTS
4.1. Affected controlled metal internal defects at a given sensitivity control is characterized by the groups in accordance with the table.
| The quality group |
Conditional length of discontinuities, mm |
| 1 |
Not more than 20 |
| 2 |
Not more than 50 |
| 3 |
Not more than 100 |
| 4 |
From 100 to 300 |
Note. If the distance between the boundaries of the identified defective areas not exceeding 15 mm, the standard length of stack and defect refers to the appropriate quality group.
(Changed edition, Rev. N 2).
4.1 a. Acceptance criterion for all groups-quality control by different methods are the following parameters set in the normative and technical documentation:
when the pulse-echo method — the amplitude of the signal reflected from the discontinuity is equal to or more than the amplitude of the signal from the reference reflector;
when the ultrasonic mirror-shadow method is the amount of attenuation of the amplitude of the bottom signal;
the shadow method is the amount of attenuation of the amplitude of the transmitted signal.
(Added, Rev. N 2).
4.2. Acceptable quality group and the control sensitivity of the metal depends on its purpose and specified in standards and technical regulations or other normative and technical documentation for the products.
(Changed edition, Rev. N 2).
4.3. Registration and registration of inspection results are conducted according to GOST 12503−75.
APPLICATION (reference). Explanation of terms used in the standard
APP
Reference
| The term |
Explanation |
| A control sample. |
Means for setting the sensitivity of the detector, made of a defect-free phase-controlled workpiece having artificial reflector and certified in the prescribed manner |
(Added, Rev. N 2).
The electronic text of the document
prepared by JSC «Code» and checked by:
the official publication of the
M.: Publishing house of standards, 1989
