GOST 7268-82
GOST 7268−82 Steel. The method of determining the propensity to mechanical aging test the impact strength (with Change No. 1)
GOST 7268−82*
Group B09
INTERSTATE STANDARD
STEEL
The method of determining the propensity to mechanical aging test the impact strength
Steel. Method for determination of ability to mechanical ageing by impact bend testing
AXTU 1909
Date of introduction 1983−01−01
The decision of the State Committee USSR on standards on September 3, 1982 N 3519 date of introduction is established 01.01.83
Limitation of actions taken by Protocol No. 4−93 of the Interstate Council for standardization, Metrology and certification (ICS 4−94)
REPLACE GOST 7268−67
* PUBLICATION (February 2002) with amendment No. 1, approved in November 1986 (IUS 2−87).
This standard specifies a method for determining the propensity to mechanical aging test the impact strength of sheet and strip steel products with thickness not less than 5 mm, and shaped and rolled.
The method consists in determination of the impact or notch toughness of steel subjected to cold plastic deformation and artificial aging, or comparing these values with the operation of the shock or impact toughness of steel in the initial state with the determination of increased propensity to aging.
The standard fully complies ST SEV 1957−79.
1. SAMPLING
1.1. Sampling — according to GOST 7564−97, if regulatory and technical documentation for metal products is not available in other guidelines.
The definition of a measure of tendency to mechanical aging of samples cut out two blanks: one to hold the strain and making samples in a deformed state, the second for fabrication of specimens in the initial state.
If in the normative and technical documentation for metal products is not specified the definition of the measure of the tendency to mechanical aging, then cut only one workpiece.
1.2. Hire a nominal thickness of 12 mm or more cut the workpiece with a size of 12 x 12 mm and a length of not less than 250 mm of rolled nominal thickness less than 12 mm size x 12 mm and a length of not less than 250 mm (
the actual thickness of the rolled).
It is also possible to cut workpieces with a size of 12 x 30 mm x 30 mm and a length of not less than 250 mm.
Blanks cut from rolled nominal thickness over 12 mm shall have one laminated surface (except blanks cut from a sheet of a thickness of > 40 mm and long products).
Blanks cut from rolled steel of thickness 12 mm and less, have to keep the two laminated surfaces.
Note. With a nominal plate thickness of over 12 mm are permitted deformation on the billets untreated with two laminated surfaces.
(Changed edition, Rev. N 1).
1.3. The type of test specimen the impact strength is specified in normative and technical documentation for metal products. If such instructions are not available, then, depending on the thickness of the rolled test carried out on samples of type 1, 2 or 3 according to GOST 9454−78.
When the thickness of the deformed workpiece is less than 5 mm the sample is made with two laminated surfaces when the specimen thickness equal to the thickness of the deformed workpiece.
1.4. The number of samples for testing the impact strength after aging sets in normative-technical documentation for metal products. If instructions are not available, the test shall be conducted not less than three samples.
The indicator of the tendency of steel to mechanical aging (p. 5.2) the test is conducted not less than six samples: three intact and three after aging.
Samples must be of the same type according to GOST 9454−78.
2. EQUIPMENT
2.1. Tensile and universal testing machines and presses to deform the workpieces must meet the requirements of GOST 28840−90.
2.2. The heating device must provide uniform heating of the sample to the set temperature aging and the maintenance of a constant temperature within the required holding time.
2.3. Primary thermoelectric converters (thermocouples) must meet the requirements of GOST 6616−94, GOST 3044−84*.
________________
* In the Russian Federation GOST R 8.585−2001.
2.4. The regulating and measuring instruments shall comply with the requirements of GOST 7164−78, 9245−79 GOST, GOST 9736−91 and have an accuracy class not less than 0.5.
2.5. The differences in the assessment of the quality of the metal used, the device with automatic temperature recording.
2.6. Impact testing machine should conform to GOST 10708−82.
Sec. 2. (Changed edition, Rev. N 1).
3. PREPARING FOR THE TEST
3.1. The workpiece coated with her design length 120, 160 mm or more is subjected to tensile strain from the calculation of receipt of (10±0,5)% residual elongation.
Distance from the capture machine before the start of the estimated length of the billet must be at least 10 mm.
In the presence of normative-technical documentation for metal products instructions carrying out deformation of the billet samples for testing the impact strength thickness (b) of size b x 12 x 57 mm. In the residual deformation after compression needs to be (7±0,7)%.
Allowed other strain, if so specified in the normative-technical documentation for metal products.
3.2. Deformation of the workpieces is carried out at a temperature of (20)°C.
3.3. Of the workpiece, subjected to deformation, produce samples for testing the impact strength in accordance with GOST 9454−78.
Place cutting blanks for the samples under tensile strain must be within the estimated length of the deformed workpiece.
3.4. Samples for testing the impact strength made of pre-deformed billet is subjected to heating (artificial aging) at a temperature of (250±10)°C with exposure for 1 h at this temperature and subsequent cooling on the air, if regulatory and technical documentation for metal products is not available in other guidelines.
Allowed artificial aging conducted on the pre-deformed workpieces.
4. TESTING
4.1. Test for impact strength — according to GOST 9454−78.
4.2. Test temperature specified in normative and technical documentation for metal products. In the absence of such instructions the test is performed at a temperature of (20)°C.
5. PROCESSING OF THE RESULTS
5.1. Job impact or impact strength is calculated according to GOST 9454−78.
5.2. The increased tendency of steel to mechanical aging (C) in percent is calculated according to the formula
where — the average arithmetic value of impact toughness of steel in the initial state, j/cm
;
— the arithmetic average of the toughness of the steel after aging j/cm
.
5.3. The comparison shall be only those test results that are obtained with the same method, deformation of blanks on the same type of specimens.
6. TEST REPORT
In the test report indicate:
coded sample;
type and size of the sample;
the method of conducting deformation;
the degree of deformation;
the heating temperature and holding time during the aging of the sample, if they differ from those established in this standard;
the amount of work strike or toughness after aging;
the value of the indicator of the tendency of steel to mechanical aging, if it is regulated in the normative-technical documentation for metal products.
(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, 2002
