GOST 24507-80

Group B09

STATE STANDARD OF THE UNION OF THE SSR

NON-DESTRUCTIVE CONTROL.
FORGINGS FROM FERROUS AND NON-FERROUS METALS

Methods of ultrasonic flaw detection

Non-destructive testing.
Forgings from ferrous and non-ferrous metals.
Ultrasonic methods of slow defection

Introduction date 1982-01-01

APPROVED AND INTRODUCED BY Decree of the USSR State Committee for Standards dated December 30, 1980 No. 6178

REPUBLICATION (March 1993) with Amendment No. 1 approved in May 1986 (IUS 8-86).


This standard applies to forgings made of ferrous and non-ferrous metals with a thickness of 10 mm or more and establishes methods for ultrasonic flaw detection of metal continuity, which ensure the detection of defects such as shells, sunsets, cracks, flocks, delaminations, non-metallic inclusions without determining their nature and actual sizes.

The need for ultrasonic testing, its scope and norms of unacceptable defects should be established in the technical documentation for forgings.

General requirements for ultrasonic testing methods - according to GOST 20415-82.

The terms used in the standard are given in the appendix.

1. APPARATUS AND TEST SPECIMENS

1.1. During the control, the following should be used: ultrasonic pulsed flaw detector, transducers, test or standard samples or DGS diagrams, auxiliary devices and devices to ensure constant control parameters and registration of results.

1.2. During the control, flaw detectors and transducers that have passed certification, state tests and periodic verification in the prescribed manner are used.

1.3. During contact testing of cylindrical forgings with a diameter of 150 mm and less with inclined transducers in the direction perpendicular to the generatrix, the working surface of the transducer is rubbed on the surface of the forging.

When inspecting forgings with a diameter of more than 150 mm, nozzles and supports can be used to fix the entry angle.

1.4. Test and standard samples are used in large-scale production of forgings that are homogeneous in terms of attenuation of ultrasound, when the amplitude fluctuations of the bottom signal inside individual forgings do not exceed 4 dB, and from forging to forging - 6 dB (with equal thicknesses and the same surface treatment).

1.5. DGS diagrams are used in small-scale production or in the control of large-sized forgings, as well as in the case when the fluctuations of the bottom signal exceed the values ​​specified in clause 1.4.

1.6. DGS diagrams are used for testing on flat surfaces, on concave cylindrical surfaces with a diameter of 1 m or more, and on convex cylindrical surfaces with a diameter of 500 mm or more - for a direct probe, and with a diameter of 150 mm or more - for an inclined probe.

1.7. The test specimens shall be made of metal of the same grade and structure and have the same surface finish as the inspected forgings. The test specimens shall be free from defects detectable by ultrasonic testing.

1.8. The amplitude of the back signal in the test specimen shall not be less than the amplitude of the back signal in the forging (with equal thicknesses and equal surface finish) and shall not exceed it by more than 6 dB.

1.9. It is allowed to use test specimens from similar types of alloys (for example, from carbon steel of various grades) provided that the requirements of clause 1.8 are met.

1.10. The shape and dimensions of the control reflectors in the samples are indicated in the regulatory and technical documentation. It is recommended to use reflectors in the form of flat-bottomed holes oriented along the axis of the ultrasonic beam.

1.11. The set of reflectors in the test specimens shall consist of reflectors made at different depths, of which the minimum shall be equal to the "dead" zone of the applied finder, and the maximum shall be equal to the maximum thickness of the forgings to be tested.

1.12. The depth steps should be such that the ratio of the amplitudes of the signals from the same control reflectors located at the nearest depths is in the range of 2-4 dB.

1.13. At each depth step in the test sample, reference reflectors shall be made to determine the level of fixation and the level of rejection. It is allowed to manufacture control reflectors of other sizes, but at the same time, the ratio of the amplitudes from the two closest reflectors in size should not be less than 2 dB.

1.14. The distance between reference reflectors in the test pieces shall be such that the effect of adjacent reflectors on the echo amplitude does not exceed 1 dB.

1.15. The distance from the reference reflector to the wall of the test sample must satisfy the condition:

where is the distance along the beam from the input point to the reflecting surface of the control reflector, mm;

- wavelength ultrasonic vibrations, mm.

1.16. The areas of flat-bottomed reflectors should be selected from the following range (corresponding hole diameters are indicated in brackets): 1 (1.1); 2 (1.6); 3 (1.9); 5 (2.5); 7(3); 10 (3.6); 15 (4.3); 20(5); 30 (6.2); 40 (7.2); 50 (8); 70 (9.6) mm.

1.17. The depths of flat-bottomed reflectors (distances from their ends to the input surface) should be selected from the range: 2, 5, 10, 20, 50, 75, 100, 150, 200, 250, 325, 400, 500 mm and then after 100 mm with an error of no more than ±2 mm.

1.18. Test specimens for the control of aluminum forgings are made in accordance with GOST 21397-81. It is allowed to use analogue test specimens made of D16T aluminum alloy for testing other materials using calculators.

1.19. Accuracy and manufacturing technology of control reflectors for a direct transducer - according to GOST 21397-81, for an inclined transducer - according to GOST 14782-76.

1.20. The radius of the test specimen shall be equal to , where is the radius of the forging.

It is allowed to use test specimens of a different radius when the ratio is 0.9<<1,2.

1.21. The use of test specimens with a flat input surface is allowed when testing cylindrical products with a diameter of more than 500 mm with a direct combined transducer and when testing cylindrical products with a diameter of more than 150 mm with a straight double-combined transducer or an inclined probe.

1.22. DGS-diagrams or calculating devices must meet the following requirements:

the division value of the "Signal amplitude" scale should be no more than 2 dB;

the scale division value "Depth of occurrence" should be no more than 10 mm;

the distance along the ordinate axis between the curves corresponding to different sizes of control reflectors should be no more than 6 dB and no less than 2 dB.

2. PREPARATION FOR CONTROL

2.1. During the general technological preparation of production for forgings subject to ultrasonic testing, technological charts of ultrasonic testing are compiled.

2.2. A technological map is compiled for each standard size of a forging. The map contains the following information:

basic forging data (drawing, alloy grade, if necessary - sound speed and attenuation coefficient);

scope of control;

surface treatment and allowances (if necessary, indicate on the sketch);

basic control parameters (sound scheme, transducer types, input angles and operating frequencies, control sensitivity, scanning speed and step);

quality requirements for forgings.

It is allowed to draw up standard control charts combined with one or more of the listed parameters.

2.3. The control flow chart should provide for the control at that stage technological process when the forging has the simplest geometric shape and the largest allowance. Control without allowance is allowed if full sounding of the entire volume of metal is ensured. It is recommended to carry out control after heat treatment of the forging.

2.4. Before testing, the surfaces of the forgings from which sounding is carried out (input surfaces) must be machined and have a surface roughness parameter<10 мкм по ГОСТ 2789-73 .

The surfaces of forgings parallel to the input surfaces (bottom surfaces) must have a roughness parameter of 40 µm according to GOST 2789-73.

It is allowed to reduce the requirements for surface roughness, provided that unacceptable defects are detected.

3. CONTROL

3.1. The control of forgings is carried out by the echo method and the mirror-shadow method.

Other methods may be used provided unacceptable defects are identified. Control by the mirror-shadow method is carried out by observing the attenuation of the amplitude of the bottom signal.

3.2. Sounding schemes for forgings of various geometric shapes are established by the technical documentation for testing.

3.3. The scheme of sounding forgings in full is set in such a way that each elementary volume of metal is sounded in three mutually perpendicular directions or close to them. In this case, forgings of rectangular section are sounded by a direct transducer from three perpendicular faces. Cylindrical forgings are sounded by a direct transducer from the end and side surfaces, as well as by an inclined transducer from the side surface in two directions perpendicular to the generatrix (chordal sounding).

3.4. If one of the dimensions of the forging exceeds the other dimension by a factor or more, then the direct transducer is replaced by an inclined transducer. In this case, inclined transducers with the largest possible input angle are used, and sounding is carried out along the largest dimension in two opposite directions.

The value is determined by the expression

where is the diameter of the transducer piezoelectric plate, mm;

- frequency of ultrasound, MHz;

- speed of longitudinal ultrasonic vibrations in the given metal, m/s.

(Revised edition, Rev. No. 1).

3.5. The drawing shows examples of sounding schemes in full forgings of a simple geometric shape, the sign indicates the direction of radiation of the direct finder, the sign indicates the direction of movement and the orientation of the inclined finder.

Examples of sounding forgings of a simple form

3.6. The control is carried out by scanning the surfaces of the forgings, determined by the given scheme of sounding, by the transducer.

The scanning speed and step are set by the technical documentation for control, based on the reliable detection of unacceptable defects.

3.7. The frequency of ultrasound is indicated in the technical documentation for the control. Massive and coarse-grained forgings are recommended to be sounded at frequencies of 0.5-2.0 MHz, thin forgings with a fine-grained structure - at frequencies of 2.0-5.0 MHz.

3.8. The level of fixation and the rejection level must correspond to the levels established by the technical documentation for forgings, with an error of no more than ±2 dB.

3.9. The search for defects is carried out on the search sensitivity, which is set:

with manual control - 6 dB above the fixation level;

with automatic control - such that the defect to be fixed is detected at least 9 times out of 10 experimental soundings.

3.10. During the control, areas are fixed in which at least one of the following signs of defects is observed:

reflected signal, the amplitude of which is equal to or exceeds the specified fixation level;

attenuation of the bottom signal or attenuation of the transmitted signal to or below a given fixation level.

4. PROCESSING AND FORMULATION OF THE RESULTS OF CONTROL

4.1. When defects are detected, their main characteristics are evaluated:

distance to the transducer;

equivalent size or area;

conditional boundaries and (or) conditional length.

If necessary, the defects are classified into extended and non-extended ones and their spatial location is determined.

4.2. The results of the control are recorded in the forging certificate and entered in a special journal, which is drawn up in accordance with GOST 12503-75 with the following additional details:

fixation level;

control dates;

surname or signature of the operator.

If defects are found in the log, their main characteristics are recorded in accordance with clause 4.1 and (or) defectograms.

4.3. Based on the comparison of the results of the control with the requirements of the normative and technical documentation, a conclusion is made about the suitability or rejection of the forging.

4.4. In the normative and technical documentation for forgings subject to ultrasonic testing, the following must be indicated:

fixation level, unacceptable level of bottom signal attenuation and parameters of unacceptable defects (minimum equivalent size or area, minimum conditional length, minimum number of defects in a certain volume), for example:

Defects of an equivalent area or more are subject to fixation.

Defects of an equivalent area or more are not allowed.

Defects of nominal length and more are not allowed.

Defects are not allowed that cause, when controlled by a direct transducer, the back- ground signal is weakened to a level or lower.

Non-extended defects with an equivalent area from to are not allowed if they form an accumulation of or more defects with a spatial distance between the most remote defects equal to or less than the thickness of the forging.

Indicators of technical requirements for forgings based on the results of ultrasonic testing

Direct converter

Angle transducer

Specific

pa-chest-

density of defects in

cluster

4.5. When writing normative requirements for the quality of forgings, it is recommended to indicate the quality group of forgings in accordance with the table. The table shows the values ​​that are used to calculate the unacceptable number of defects in a cluster of sizes according to the formula

When calculating, round down to the nearest whole number.

(Revised edition, Rev. No. 1).

4.6. In forgings assigned to groups 1, 2 and 3, not a single extended defect and not a single defect of an equivalent area or more is allowed. Such a condition is usually satisfied by vacuum melting metals. In forgings assigned to groups 2, 3 and 4, small non-extended defects are allowed (for example, non-metallic inclusions found in some open-hearth steels). In forgings assigned to group 4, some extended defects are allowed, the nominal length of which is less than 1.5.

5. SAFETY REQUIREMENTS

5.1. Ultrasonic flaw detectors are portable electrical receivers, therefore, when using them, safety and industrial hygiene requirements must be met in accordance with the "Rules for the technical operation of consumer electrical installations" and "Safety regulations for the operation of consumer electrical installations", approved by the State Energy Supervision Authority in 1969 with additions and changes in 1971 .

5.2. Persons who have passed the knowledge test of the "Rules for the technical operation of consumer electrical installations" are allowed to work with ultrasonic devices. If necessary, the qualification group of flaw detectorists is established by the company conducting the control, depending on the working conditions.

5.3. Fire safety measures are carried out in accordance with the requirements of the "Model Fire Safety Rules for Industrial Enterprises" approved by the GUPO of the USSR Ministry of Internal Affairs in 1975 and GOST 12.1.004-91.

5.4. The control area must comply with the requirements of SN 245-71, approved by the USSR Gosstroy, as well as GOST 12.1.005-88.

5.5. When using lifting mechanisms at the control site, the requirements of the "Rules for the Design and Safe Operation of Hoist Cranes", approved by the USSR Gosgortekhnadzor in 1969, must be taken into account.

5.6. Additional safety requirements are specified in the technical documentation that defines the technology for testing specific forgings and approved in the prescribed manner.

5.7. During the control, the requirements of GOST 12.3.002-75 and GOST 12.1.003-83 must be observed.

APPENDIX (reference). TERMS USED IN THE STANDARD

APPENDIX
Reference

	Explanation
equivalent size	The size (or dimensions) of a control reflector of a given shape, located in the test sample at a depth closest to the depth of the defect, and giving an echo signal equal in amplitude to the signal from the defect
Equivalent defect area	The area of ​​the end face of a flat-bottomed drilling located in the test sample at a depth closest to the depth of the defect and giving an echo signal equal in amplitude to the signal from the defect
Fixation level	The amplitude level of the echo signal from the control reflector, specified by the normative and technical documentation for forgings, which serves as the basis for fixing the defect:
	by exceeding this level by the signal during the control by the echo method;
	by attenuation of the bottom signal to this level when controlled by the mirror-shadow method
Rejection level (applies only to echo testing)	The amplitude level of the echo signal from the control reflector, specified by the normative and technical documentation for forgings, the excess of which by a signal from a defect serves as the basis for rejecting the forging
Conditional defect boundary	The locus of the positions of the center of the forward transducer or the entry point of the inclined transducer on the input surface, at which the amplitude of the echo signal from the defect or the amplitude of the back-wall signal (when controlled by the direct transducer) is equal to the specified fixation level
Conditional defect length	The maximum distance (in a given direction) between two points located on the conditional boundary of the defect.
	Note. Designated, mm. The conditional length of the control reflector, equivalent in amplitude to this defect, is denoted , mm.
	It is allowed to define the value as a conditional length of the control reflector that determines the rejection level
Extended defect	A defect that satisfies the condition >.
Non-extended defect	A defect that satisfies the condition .
Scan speed	The speed of movement of the transducer along a given trajectory along the input surface.
Scan step	Distance between adjacent transducer paths, e.g. between rows in progressive scanning or between helical turns in helical scanning
ARD diagram	A system of graphs relating the amplitude of the echo signal with the distance to the defect and its equivalent area

The text of the document is verified by:
official publication
M.: Publishing house of standards, 1993

Shortcut http://bibt.ru

Forging control methods

Methods of control of forgings are selected depending on the requirements that apply to the part during its operation. All forgings must be subjected to external inspection and measurement. At the same time, the quality of the surface, the presence of surface defects - hairlines, cracks, captivity, etc., and the correspondence of the size of the forging to the drawing are checked.

In some cases, external defects can be removed by punching, grinding, etc. In this case, it is necessary to establish the possibility of obtaining a good product from the workpiece after removing the defect.

After preliminary heat treatment, annealing and normalization, the hardness of the forgings is measured. The measurement is carried out on a Brinell or Rockwell press and makes it possible to judge the correctness of the heat treatment mode and the mechanical properties of the part. When forging critical products, the mechanical properties of the metal of the forging are monitored by tensile testing of samples cut from the forging places located at the most critical part of the part.

In some cases (forging of critical parts, the introduction of a new technological regime, etc.), the structure of the metal in forgings is determined. The structure of a previously ground and etched sample can be determined with the naked eye (macrostructure check) or with a microscope (microstructure check). In the first case, metallurgical defects can be detected - bubbles, shells, non-metallic inclusions, etc. Under the microscope, the presence of structural components in steel (ferrite, pearlite, martensite), the size and uniformity of inclusions and grains are determined.

These studies, however, do not always make it possible to identify all defects - hairlines, cracks, delaminations, slag inclusions, etc., since they can be located in the depth of the forging.

Laboratory non-destructive testing Trade House "Spetssplav" is pleased to offer you our services for ultrasonic testing of the quality of forgings and rolled metal products.

The ultrasonic method is based on the ability of ultrasonic vibrations to be reflected from the surfaces of internal defects of the metal.
With the help of ultrasound, shells, cracks, strata, fistulas and ripples are detected, which lie at a depth, in the thickness of the metal, which are not detected by magnetic and luminescent methods and are not always detected by X-rays. Having reached the opposite face of the product (to the “bottom”), the ultrasonic beam is reflected, hits a special seeker, which converts it into an alternating voltage supplied to the amplifier input, and then to the oscilloscope tube crane in the form of a peak (bottom signal). If there is a defect in the thickness of the metal, the beam is also reflected from it, and a defective signal will appear on the side of the bottom signal (the location of the defective and bottom signals on the screen is predetermined by the device of the oscilloscope).

Our laboratory is equipped with the most modern equipment, which allows you to work with various steel grades and detect hidden defects of any size. In addition, our staff consists of certified specialists who have undergone specialized training and have a confirmed qualification from Rostekhnadzor. Thanks to this, we can carry out high-quality ultrasonic testing of forgings in accordance with all requirements of the customer's technical documentation.

Some manufacturers, for the sake of economy or incompetence, ignore non-destructive testing of products or remember about it only at the last stage - immediately before the delivery of products (and this leads to additional loss of time and unforeseen costs, sometimes very significant), when the control is technically unfeasible. Such an attitude to quality control most often leads to emergency situations during the operation of finished products.

Quality control of forgings is an obligatory part production process. All control equipment, tools, fixtures must be prepared simultaneously with the main technological equipment and rigging.

Applies raw material control, inter-operational control and control finished products. The source material is controlled for compliance with the parameters of the specifications. Interoperational control in the conditions of large-scale and mass production is necessary to prevent marriage by adjusting the installation of dies and other tools, the operation of equipment. The control of finished products is varied and comes down to determining whether dimensions, structure and hardness meet the specifications, the presence of cracks and other external defects.

A forging that deviates from the technical specifications for its manufacture is called defective, and a forging that cannot be corrected is considered a defect. Marriage can be obtained:

When using defective source material;

When cutting workpieces;

When heated;

When stamping and trimming flash;

During heat treatment;

When cleaning from scale.

The defects of the source material include:

Hairline - thin cracks that occur during rolling;

Sunsets - burrs rolled up in the form of diametrically opposite longitudinal folds;

Captivity - splashes of liquid metal frozen on the surface of the ingot, rolled out during rolling;

Delaminations - a shrinkage cavity or friability that opens during the forging and stamping process; non-metallic inclusions of slag, sand, refractories that enter the metal during melting, pouring and are revealed during the machining of forgings;

Flocks are accumulations of the smallest cracks visible on the sections of steel in the form of white spots or flakes, the cause of which is the presence of hydrogen gas in the steel.

The presence of flakes leads to a decrease in mechanical properties, forgings tend to form cracks during hardening.

Marriage when cutting the source material includes: an oblique or rough cut, depending on the quality of the knives and the correctness of their installation; end cracks that occur when cutting large profiles of alloyed and high-carbon steels (especially at low temperatures); mismatch of workpieces in length due to incorrect installation of stops.

Overheating and burnout of workpieces as a result of a violation of temperature regime; excessive scale formation due to the long stay of the workpieces in the furnace.

Marriage during stamping and trimming of flash include:

Dents, which are traces of stamped scale up to 2 mm deep;

Nicks - various kinds of mechanical damage to a forging that occurs during the transfer or extraction of forgings;

Understamping - an increase in all dimensions in height;

Skew - transverse or longitudinal displacement of a part of the forging in the plane of the die parting;

Clamps - stamped folds, which are obtained due to improper flow of metal in the stamp or improper laying of the workpiece in the stamp;

Curvature - deviation of the axes or planes of the forging from the given directions; deviation from the specified dimensions due to excessive scale, die wear or improper manufacture;

Non-filling of the figure due to the wrong size of the workpiece, a faulty stamp, uneven temperature distribution over the cross section.

Marriage during heat treatment: insufficient or increased hardness against the stipulated in specifications; hardening cracks due to improper heat treatment.

Marriage during descaling: scale residues, overetching, nicks and dents.

Marriage detected after machining: blackness due to insufficient allowance, curvature, incompleteness of the forging figure; dents; thin walls in forgings with distortions, curvature or deviations in length. Usually, after machining, various internal defects are also detected.

To prevent marriage, it is necessary to strictly observe the technological process. The main means of detecting and preventing marriage is proper organization end-to-end control at all stages of forging production. In workshops of mass and large-scale production operations technical control are elements of the technological process and are included in the operational flow charts.