GOST 28831-90

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  ГОСТ 28831-90

GOST 28831−90 the plates. Methods of ultrasonic testing

GOST 28831−90
Group B09

INTERSTATE STANDARD

THE PLATES

Methods of ultrasonic testing

Rolled plates. Ultrasonic test methods

AXTU 0909

Date of introduction 1992−07−01

INFORMATION DATA

1. DEVELOPED AND SUBMITTED by Mineralogii of the USSR, USSR Minsudprom, Intimacies of the USSR, USSR

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from 29.12.90 N 3475

3. INTRODUCED FOR THE FIRST TIME

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Limitation of actions taken by Protocol No. 5−94 of the Interstate Council for standardization, Metrology and certification (ICS 11−95)

6. REISSUE


This standard specifies the echo method in combination with a mirror-shadow and echo-through method in combination with the shadow methods of ultrasonic inspection of rolled plates of carbon, low alloy and alloy steel thickness in excess of 200 to 450 mm, used for detection of discontinuity flaws of metal and the determination of their conditional dimensions and classes of the continuity of rental without recognition of types, orientations, and other valid characteristics of defects.

Terms used in this standard, and their explanations are given in Appendix 1.

Characteristics of methods of ultrasonic testing are given in Appendix 2.

1. EQUIPMENT

1.1. Ultrasonic flaw detectors, equipped with piezoelectric transducers, and other means of ultrasonic testing, certified in the prescribed manner.

1.2. Control samples in accordance with Annex 3.

1.3. DGS diagrams.

1.4. Assistive devices for compliance with the parameters of scan and determine characteristics of the identified discontinuities.

2. PREPARATION FOR CONTROL

2.1. In the preparation of rent control to perform the following operations:

estimate visually the surface condition of the rental;

verify that the rental standards and specifications the dimensions and form;

to implement a given testing sensitivity depending on the surface quality of the rolled spend the partial or complete surface treatment of the rental;

check for partial surface treatment of the rental to the magnitude of the local slope was less than 2% when the length of the stripped area of 50 mm.

2.2. Kind of surface treatment products (shot-blasting, abrasion, chemical or others) set in the normative-technical documentation on products or ordering.

2.3. In the preparation of equipment to control, perform the following operations:

check the functioning of the means of automation and mechanization;

set the operating frequency of ultrasonic oscillations and the sensitivity of the control;

estimate the size of the zones of uncertain detection of discontinuities in thickness and the perimeter of the rental;

install the zone control on the thickness of the hire.

3. CONTROL

3.1. Monitoring is carried out according to the technical documentation developed under shot 20415.

3.2. When control sheet is scanning one or more transducers. The scanning parameters indicated in the technical documentation for the control.

When moving the transducer manually, and to determine the characteristics of the identified discontinuities are allowed to use equipment without auxiliary devices intended for compliance with the scan settings.

3.3. Under the control of the echo method in combination with a mirror-shadow method in a given time interval to register one or more echo signals from discontinuities, the amplitude of at least one of which is equal to or exceeds a level corresponding to a predetermined sensitivity, and (or) decreasing the amplitude of the bottom signal (below) the specified level.

3.4. Under the control of the echo end-to-end in combination with the shadow method in a given time interval to register one or more echo signals from discontinuities, the amplitude of at least one of which is equal to or exceeds a level corresponding to a predetermined sensitivity, and (or) reduction of the amplitude transmitted through the sheet pulse to (below) the specified level.

3.5. The parameters of the discontinuities is determined based on the depth of their occurrence.

3.6. Permitted by agreement with the consumer, to monitor leaves the echo method on the two surfaces with the mandatory turning over of the leaves.

4. EVALUATION OF THE RESULTS

4.1. Key controlled features:

the sensitivity of the control in accordance with Annex 2;

the conditional area of each defect (cm);

total conditional area of discontinuities on any square meter of the sheet surface (cm);

conditional length of individual discontinuities (mm);

total conventional length of discontinuities in any meter length of sheet (mm).

4.2. Characteristics of discontinuities in the form of conditional extensions is used for discrete linear scanning of the surfaces of the sheet.

Allowed to apply the characteristics of discontinuities in the form of a conditional space in automated discrete linear scanning of the sheet surface if the instrument displays the results of the control in square units or in equivalent standard units.

4.3. In the control account shall be subject to all defect sizes calculated by one of the formulas

or ,

where  — the minimum area value in the measurement of the conditional square cm;

 — the minimum value of the length when measuring conditional length;

and the values of continuity, is given in Appendix 4.

Allowed in control to take account of discontinuities and having a conventional square less than 0.2and 0.5, if such possibility is provided in the technical specifications of the apparatus used

.

4.4. Located in one or more planes according to the thickness of the hire of discontinuities and combine into one if the distance between their conventional boundaries less than the specified regulatory and technical documentation for specific products and in the absence of guidance in the normative-technical documentation — if it is less than 30 mm.

4.5. With automatic control units, providing a continuous surface scan of sheet metal and the registration of discontinuities in the form of defects recording for the conditional area of the discontinuities of the metal are taking the area of the relevant entries in the defects recording obtained for a given sensitivity control.

4.6. Depending on the item controlled by the characteristics of the rental is divided into category 1C-3C in accordance with the table.1.

Table 1

Note. The «+" sign means that the feature control, the sign «— «is not in control.

4.7. Continuity of hire, depending on the sensitivity of the control is evaluated by four classes, having designations 01; 0; 1; 2.

4.8. Depending on the maximum allowable values of characteristics of discontinuities rental classes continuity 1 and 2 are divided into three groups of continuity A, B, V.

4.9. The limit values (norms) characteristics of the discontinuities according to the classes of the continuity of the products (, , , ) is given in Appendix 4.

4.10. Class, group and category point of continuity in the normative and technical documentation in order.

Integrity rental classes 0−2 indicate the order in the form of a cipher.

For example, code UT-2A-3C means that the consumer ordered rental with ultrasound control, class 2 continuity, group continuity And category continuity 3C. If ordered rental class 0 continuity, group continuity is not indicated.

4.11. Allowed for class continuity 01 to introduce an additional controlled characteristics, for example the minimum distance between the boundaries of the individual discontinuities number of discontinuities per 1 mof the sheet surface or some part that should be specified in the order by agreement between the consumer and the manufacturer.

4.12. Defect fixed in defectogram, records or control logs.

4.13. In defectogram, records or control logs indicate the cipher normative-technical documentation for metal products, the characteristic of the controlled object, the value of the indexes of continuity, the name or index of the operator who carried out the monitoring, control parameters.

5. SAFETY REQUIREMENTS

5.1. When carrying out ultrasonic testing of sheet metal, you must follow the rules of technical operation of electrical installations and safety rules for electrical installations according to GOST 12.1.001, GOST 12.2.003.

5.2. When performing control should comply with sanitary norms approved by the USSR Ministry of health, and safety requirements set out in the technical documentation for applicable equipment.

5.3. Noise levels in the workplace inspector must not exceed dopustimykh 12.1.003.

5.4. In the organization of control should comply with fire safety requirements according to GOST 12.1.004.

ANNEX 1 (reference). TERMS USED IN THIS STANDARD, AND THEIR EXPLANATIONS

ANNEX 1
Reference

Table 2

ANNEX 2 (mandatory). CHARACTERISTICS OF THE METHODS OF ULTRASONIC TESTING

ANNEX 2
Mandatory

1. The main characteristics of the method of control are:

the method for setting sensitivity;

method sensitivity settings;

registration settings sensitivity;

maximum deviations of registration parameters sensitivity.

1.1. When specifying and setting up the sensitivity for the initial level is the amplitude:

first bottom of the first or the last signal on sections of sheet metal that does not contain discontinuities at the control of all methods, except for the echo end-to-end;

the first echo-signal from artificial reflector control sample when controlling echo method;

the first of the last (through) signal to an arbitrary area of the sheet or no sheet at the control echo-through method;

1.2. Methods of specification and sensitivity settings and notation the characteristics of the control methods shown in table.3.

Table 3

Note. Permitted subject to the approval of normative-technical documentation on the rolled sheet to apply different values of sensitivity.

1.3. To control used ultrasonic vibrations at a frequency from 0.5% to 2.5 MHz. Operating frequency of ultrasonic vibrations stipulate in the technical documentation for the control.

1.4. The values for uncontrolled areas along the thickness and the perimeter of the sheet set in the technical documentation for the equipment, and in the absence of documentation on equipment — in technical documentation for the control or normative-technical documentation for the products.

1.5. Rental see fit to control if the amplitude of signal from defect to be recorded exceeds the level of structural noise is not less than 6 dB.

APPENDIX 3 (obligatory). THE REQUIREMENTS FOR CONTROL SAMPLES (KO)

APPENDIX 3
Mandatory

TO used to adjust the sensitivity in the control of sheet metal echo method.

1. TO produce from sheets of the same steel grade, heat treatment and thickness and the same surface condition, and controlled products.

2. TO produce rental speed. TO speed can be manufactured in a single unit or in separate steps. The height of the first stage and the difference in heights of the two adjacent treads shall be not more than 50 mm. Height of the last stage equal TO the thickness of the controlled rental.

Permitted difference between the height of the last stage TO and thickness of the controlled rent is not more than 10 mm.

3. In KO must be absent of discontinuities detected by ultrasonic testing with a sensitivity twice higher than the sensitivity level is customizable to this TO.

4. Allowed TO use other grades of steel and different surface condition than a controlled product, if the mean value of the amplitude of the bottom signal TO equal the amplitude of the corresponding signal in a controlled rent of the same thickness or less than the value of not more than 6 dB.

5. In each stage TO perform artificial reflectors to establish a predetermined sensitivity of control.

Artificial reflectors represent a flat-bottomed hole, located perpendicular to the surface of the tread TO the side which the input / reception of ultrasound. Accuracy and the technology of artificial reflectors according to GOST 21397.

6. Distance from the bottom surface of each stage to the flat bottom of the reflector must be not more than 25 mm and not less than half the height of the first stage.

The distance between the axis of the flat-bottomed hole, and closest to her TO reflective surfaces must be not less than the value , in mm, calculated by the formula

,

where is the step height, mm;

 — the radius of the active element of the transducer, mm;

is the ultrasound frequency, MHz.

7. In the first and the last stage should be provided additional artificial reflector to check uncontrolled areas on the thickness of the hire specified in the technical documentation for the control or means of control.

8. Everyone should have the marks containing the number, grade of steel and thickness of hire, from which it is made.

If I consists of separate stages, each stage optionally specify its number.

9. Each should be certified by metrological service of the enterprise, carrying out ultrasound control.

ANNEX 4 (required). RULES OF THE CONTINUITY PLATE

ANNEX 4
Mandatory

Table 4

Note. The sensitivity of the shadow and mirror-shadow methods for control of a combined echo and echo-through methods for a specific product established by the manufacturer in accordance with Annex 2, and the values of controlled characteristics for categories 1C-3C in accordance with this table.