GOST 22848-77
GOST 22848−77 Metals. Test method for impact strength at temperatures from minus 100 to minus 269 °C (Change No. 1)
GOST 22848−77
Group B09
INTERSTATE STANDARD
METALS
Test method for impact strength at temperatures from minus 100 to minus 269 °C
Metals. Method for testing the impact strength at temperature from -100 up to -269 °C
AXTU 1909
Date of introduction 1979−01−01
INFORMATION DATA
1. DEVELOPED by the Central research Institute of ferrous metallurgy them. I. P. Bardin (TSNIICHM), Central research Institute of machine building (TSNIIMASH), Central research Institute of materials science (CNIIMF), Institute of problems of strength, Academy of Sciences of the Ukrainian SSR (IPP an UkrSSR), the State Institute of applied chemistry (gipkh), all-Union scientific-research Institute of cryogenic engineering (VNIEKIEM)
INTRODUCED by the Ministry of ferrous metallurgy of the USSR
2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from
3. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
Section number, paragraph |
| GOST 9.301−86 |
3.2 |
| GOST 334−73 |
4.2.1 |
| GOST 4543−71 |
5.3 |
| GOST 9293−74 |
2 |
| GOST 9454−78 |
1.1; 3.1; 5.1 |
| GOST 10708−82 |
2 |
4. Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)
5. EDITION (may 2001) with amendment No. 1, approved in April 1988 (I & C 7−88)
This standard applies to metals and alloys and their products and establishes a method of testing the impact strength of the samples at temperatures from minus 100 to minus 269 °C.
When testing determined the following characteristics:
the work spent on the destruction of the sample;
toughness equal to the ratio of the value of the work of impact to the initial cross sectional area of the specimen at the point of impact;
the percentage of the viscous component in the fractured sample is destroyed in impact bending.
(Changed edition, Rev. N 1).
1. SAMPLING METHOD
1.1. Sampling method and size shall conform to the requirements of GOST 9454.
It is permitted to use specimens of other sizes.
Size requirements samples establish normative-technical documentation for specific types of products.
1.2. The cutting blanks for the samples from welded joints, specimen preparation, choice of application incision should be given in the normative-technical documentation for specific products.
1.1, 1.2. (Changed edition, Rev. N 1).
2. EQUIPMENT
For testing the impact strength at temperatures down to minus 253 °C is used pendulum copra according to GOST 10708, and for testing at minus 269 °C — special copra.
Scheme of copra is given in Appendix 1.
Copra should be equipped with sensors to measure dynamic loads and specimen deflection and registering equipment for automatic recording of the diagrams of deformation (see Annex 2).
When tested in the temperature range from minus 100 to minus 196 °C, copra must be equipped with templates for mounting the cut sample in the middle of the span of the pendulum; when tested at a temperature of minus 253 °C should be used a mechanical limiter which should not hinder the deformation of the specimen.
The inspection of copra should be NTD or other technical documentation approved in the established order.
To measure the temperature of samples should be used instruments that provide accuracy of ±1 °C.
As the refrigerant used liquid nitrogen with oxygen content not more than 10% (GOST 9293), liquid hydrogen and helium.
Liquid oxygen and liquid air as a refrigerant is prohibited to take.
(Changed edition, Rev. N 1).
3. PREPARING FOR THE TEST
3.1. The ambient temperature, the position of the sample on the supports, check the pointer of the free fall of the pendulum, the number of test specimens shall conform to the requirements of GOST 9454.
3.2. Samples of steels and alloys, excluding copper, aluminum and stainless steels of austenitic class intended for tests in liquid hydrogen, to prevent sparking when struck with a knife of the pendulum copra, cover with a layer of copper of thickness 9−12 µm after application of the notch.
Copper plating of samples according to GOST 9.301.
4. TESTING
4.1. Testing at temperatures from minus 100 to minus 196 °C
4.1.1. The temperature at which shall be tested samples, is indicated in the technical documentation.
Testing the impact strength is recommended at temperatures of minus 100, 110, 120, 130, 140, 150, 160, 170 and 180 °and the boiling point of liquid nitrogen — minus 196 °C. it is allowed to conduct tests at intermediate temperatures.
4.1.2. Test temperature — the temperature at the surface of the bottom of the incision at the time of impact of the pendulum with the sample. The test temperature should not deviate from the specified by more than ±3 °C.
4.1.3. The samples are cooled to the desired temperature, but not below 180 °C, is recommended in refrigerating chambers by the speed of circulation of liquid nitrogen.
4.1.4. Samples should be placed on a special rack in the refrigerating chamber at intervals separately for each test temperature. The exposure time at a given temperature taking into account the subcooling should be 5−10 min.
Note. In cases where the supercooling of the samples below the required temperature does not cause changes in the structure of the metal, allowed to lay in the cooling chamber, the samples to be tested at several temperatures. Test this when you start with a lower temperature, gradually moving from one temperature to the adjacent.
(Changed edition, Rev. N 1).
4.1.5. The temperature measured on the control samples, laid simultaneously with the samples intended for testing. The specimen temperature must be below the specified test temperature by an amount dependent on the difference between the room temperature and cooling temperature, speed of transfer and other particular test conditions. Required amount of subcooling needs for specific cases to be determined empirically. The time of installation of the cooled sample on copra from the moment of extraction from the cooling chamber to the stroke of the pendulum must not exceed 5 s.
4.1.6. For testing the impact strength at the temperature of boiling of liquid nitrogen in the container must be filled with liquid nitrogen so that the samples all the time was immersed in the liquid. Samples in liquid nitrogen should be maintained after the cessation of rapid boil for at least 5 min. the temperature of the cooling liquid nitrogen or sample is not measured.
4.1.7. Forceps or other tools to extract the samples must be cooled simultaneously with sample.
4.2. Test at a temperature of minus 253 °C
4.2.1. For testing the impact strength at the boiling point of liquid hydrogen (minus 253 °C) the sample is placed in a container made of graph paper according to GOST 334. At the top of the container has a slot in it to fill it with liquid hydrogen (Fig.1).
1 — slot Bay liquid hydrogen
Damn.1
The dotted line on the scan of the container depicts the fold line (Fig.2).
Damn.2
4.2.2. The connection of the sample container is sealed with silicate cement. Drips of glue on the supporting planes of the samples are not allowed.
4.2.3. When gluing the sample, you must pay attention to the fact that the mark or stamp of the sample were at the position of the container shown in hell.3.
1 — slit; 2 — the reference plane; 3 — string; 4 — mark
Damn.3
4.2.4. The container with the sample placed in a cryostat filled with liquid hydrogen. After the cessation of intensive boiling of the hydrogen container with the sample held for 5−10 minutes, then remove from the cryostat and mounted on support copra.
4.2.5. The installation time of the container with the specimen on the supports of copra, starting from the moment of extraction from the cryostat to the knife of the pendulum must not exceed 5 s.
4.2.6. The use of liquid hydrogen as a refrigerant requires strict adherence to safety rules.
4.3. Test at a temperature of minus 269 °C
4.3.1. Testing the impact strength at a temperature of minus 269 °C (the boiling point of liquid helium) is carried out in special coprah.
5. PROCESSING OF THE RESULTS
5.1. The test results are processed and made according to GOST 9454.
5.2. In the presence of derricks, equipped with the recording equipment, the work spent on the destruction of the sample, determined by the strain diagram, the method of treatment which is given in the mandatory Annex 3.
5.3. The percentage of the viscous component of the fracture surface is determined according to the method specified in Annex 3 to GOST 4543.
5.4. The test results obtained on any sample type, should be compared only with the test results obtained on samples of the same type.
ANNEX 1 (recommended). THE COPRA SCHEME FOR TESTING IN LIQUID HELIUM
ANNEX 1
Recommended
1 — base copra; 2 — bellows; 3 — the volume of the fill liquid refrigerant; 4 — rod; 5 — hammer; 6 — cylinder; 7 — rod; 8 — ball lock; 9 — shutter; 10 — sensor; 11 — sample; 12 — anvil; 13 — dynamometer
APPENDIX 2 (recommended). THE METHOD OF DETERMINING THE FORCES APPLIED TO THE SAMPLE, AND THE DEFLECTION OF THE SAMPLE WITH THE REGISTRATION OF THE DIAGRAMS OF DEFORMATION
ANNEX 2
Recommended
Diagram of the system measuring the force applied to the sample, and the deflection of the sample with the registration of the diagram of deformation in coordinates of the force-deflection, force-time, when tested on a pendulum coprah shown in Fig.
1 — the supports of pendulum; 2 — sample; 3 — knife hammer; 4 — strain gages;
5 — shutter; 6 — illuminator; 7 — sensor; 8, 9 — amps; 10 — oscilloscope
Upon impact, the sensor signals of the load and the deflection is proportional to applied to the specimen stress and the deflection of the sample at the respective measurement channels received on the vertical and horizontal inputs of an electronic oscilloscope. Curves recorded from the oscilloscope screen on a highly sensitive photographic film.
For registration of the diagram of deformation in coordinates of the force-deflection can be used various types of oscilloscopes, allows you to record on-screen position of the light beam by the static calibration (loading of the load sensor using the load cell in the vertical direction and moving from the solar cell in the horizontal), for example, oscilloscope S1−34.
To register diagrams in the coordinates of the force-time signal from the load cell is fed to the vertical input of the oscilloscope. The beam sweep is a sweep generator, operating in standby mode. This can be used oscilloscopes of various types, allowing you to capture the movement of the beam when a static calibration of the load sensors.
The force applied to the specimen during impact is measured using wire strain gauges, for example, type PKB-10−200 (base 10 mm, resistance 200 Ohm) mounted on the supports copra. The glue BF-2 and its polymerization produced according to the standard technique.
In the measuring circuit include strain gages in bridge circuit. The measuring bridge is powered with alternating current frequency of about 50 kHz or DC voltage of 6 V.
Specimen deflection is measured with fotobelka consisting of a photocell SCV-51 and illuminator of the OS that is attached near the pillars of copra. The illuminator provides uniform light output that illuminates the photocell through a curved slot in its body. Moving the hammer shutter, which is movably mounted thereon, overlaps the light output. When you change the illumination of the photocell changes its resistance. In this case the output signal proportional to the deflection of the sample, is fed to the input of the oscilloscope, performing the scan signal of the load horizontally.
System to measure the specimen deflection shall be calibrated using a micrometer device, which moves the hammer in the work area. Change the waveform on the oscilloscope is controlled through the 0.1 mm (0.5 mm) move the blind hammer. When the calibration according to the change of the light flux on the photocell, due to the shape of the slot, to achieve a linear dependence of the signal fotobelka when you move the hammer throughout the working area.
APPENDIX 3 (obligatory). THE METHODS OF PROCESSING DIAGRAMS OF DEFORMATION
APPENDIX 3
Mandatory
Before testing, samples from oscilloscope screen pictures of the movement of the beam of the oscilloscope (in one frame) corresponding to known values of the load
(e.g. 1000 kg), and moving the beam of the oscilloscope
(on another frame) corresponding to a known amount of deflection
(e.g. 0.001 m).
The strain diagram when testing each sample is photographed from the oscilloscope screen and transferred to paper by means of a photographic enlarger. The zoom scale of the diagram must match the scale of the calibration marks and
.
Processing chart is as follows:
a) determine the area of the rectangle in mm
, the sides of which are respectively
and
in mm. the Area
corresponds with the value of work
, for example 10 j (1Kgs·m) equals
to
(see drawing);
b) planimetering determine the total area of the curves , in mm
;
C) area curves define the job
in j (kgf·m) expended in the destruction of the sample by the formula
Notes:
1. The work of crack initiation and development of cracks
in the diagrams of deformation is determined in the same way as General work
. In the formula (1) is
to substitute for the value of the square of the curves before and after maximum load, respectively,
or
(see drawing).
2. On diagrams of strains and establish the maximum load () in N (kgf) and the deflection of the specimen until fracture (
) in meters, and characterizes the dynamic strength and ductility of materials under impact bending. These quantities are calculated by the formulas:
where is the maximum impact loading, N (kgf);
where is the maximum deflection, mm.
APPENDIX 3. (Changed edition, Rev. N 1).
The electronic text of the document
prepared by JSC «Code» and checked by:
the official publication of the
M.: IPK Publishing house of standards, 2001
