This standard is applicable to the determination of ferrite grain size of cold-rolled low-carbon steel sheets with a carbon content of less than 0.2% under a microscope. The ferrite grain size of low-carbon low-alloy steel sheets can also be evaluated with reference to this standard. GB/T 4335-1984 Method for determination of ferrite grain size of cold-rolled low-carbon steel sheets GB/T4335-1984 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Cold rolled low-carbon steel sheet
Method for determination of ferrite grain size
Cold rolled low-carbon steel sheet-Ferritegrain sze--TestmethodsUDC 669.15-194
620.186.8
GB 4335-84
This standard is applicable to the determination of ferrite grain size of cold rolled low-carbon steel sheet with carbon content less than 0.2% under microscope. The ferrite grain size of low-carbon low-alloy steel sheet can also be evaluated with reference to this standard. Definition
The size of the grain is expressed by the grain size grade. 1.2 Grain size grade-based on the average size of the grain, divided into grades according to the provisions of Table 1. 1
Grain size
Number of grains per half square meter section
National Bureau of Standards1984-04-09
Flat section area, square meter"
0,0p0122
1110 times 625 mm (|inch1)
Average number of grains on section
1985-03-01
1.9 Grain elongation
武 e-
2 Sample
GB4385-84
-When ferrite grains are in an elongated shape, their elongation can be determined by the following formula degree. t
Grain elongation,
The number of grains cut by a cutting line of a fixed length that is parallel to the direction of the grain's elongation, and the number of grains cut by a cutting line of the same length that is parallel to the direction of the grain's elongation. 2.1 Sampling section
Sampling is conducted at 1/2 of the width of the steel plate. If necessary, sampling can be conducted at about 50 mm on the other side or in accordance with relevant standards, but it must be stated in the test results.
2.2 Test size
The grinding surface dimension of the test specimen is the thickness of the steel plate, and the length is about 20 mm. 2.3 Sampling method
The specimen is generally cut by cold working methods such as punching, shearing, and sawing. 2.4 Grinding surface universal
Special specifications The grinding surface of the sample should be parallel to the rolling direction of the steel plate. 2.5 Sample preparation
The sample undergoes coarse grinding, fine grinding, polishing, corrosion and other procedures. The cold working hardened layer produced during sampling should be removed by coarse grinding. The sample should be prevented from being over-cooked during grinding. The corrosive liquid generally uses a 1% nitric acid alcohol solution. The corrosion time is about 15 to 20 seconds. 3 Determination method
There are two methods for determining the grain size of the product: the comparison method and the cutting method. The comparison method is generally used for production inspection. 3.1 Comparison method
After the sample is prepared, the grain size is measured under a 100 mm microscope. The on-site diameter is 0.80 mm. During the measurement, first observe the sample comprehensively under a microscope, and then select the sample with the highest grain size. The field of view of the chemical table is compared with the ferrite grain size rating chart of low carbon steel cold rolled thin plate in this standard.
3.1.1 The first standard level chart in the ferrite grain size rating chart of low carbon steel cold rolled thin plate is a chart with an elongation of approximately 1, the second standard level chart is a chart with an elongation of approximately 2, and the third standard level chart is a chart with an elongation of approximately 4. Use 1, II, and III to represent it respectively. When evaluating, the chart and the grain size grade should be recorded. For example, when the quality of the observed sample is equivalent to grade 6 of the first standard level chart, t! III6, indicating an elongation of approximately 4 and a grain size of grade 6. If the grain elongation is between the two charts, it can be expressed as ~.
3.1.2 If the observed grain size is between two grain size grades, it can be expressed as a half grade. 3.1.3 If it is difficult to evaluate with 100 times, it can be evaluated with 50 times, 200 times, 300 times or 400 times, and then converted into the standard grade with 2. Table 2
Number of people
GB 4835-84
3.1.1 If the sample is found to have uneven grains, after comprehensive observation, if it is an individual phenomenon, and the dominant grain size occupies not less than 90% of the field of view, the grade of the dominant grain size can be recorded as the evaluation result. If the uneven phenomenon is more common, it can be expressed in the grade frequency sequence according to the size of the area occupied by the grains of each grade in the field of view. s.2 Kevlar
After the sample is prepared, observe it with a microscope or take a photo with a microscope, and count the number of ferrite grains cut by two sets of mutually perpendicular cutting lines of a certain length, so as to calculate the grain size grade. 3.2.1 If both grains at the two ends of the cutting line are partially cut, only one shall be counted; if only one is partially cut, it shall not be counted.
3.2.2 The total number of grains cut by the cutting line in one direction shall not be less than 50. If necessary, several fields of view may be measured. 3.2.3 When measuring by the cutting method, calculate according to the following formula. N
Where. N
Grain size grade (keep one decimal place)
When the microscope magnification is 100 times, the number of grains on each 625 mm2 (1 in2) section. 3.2.4 The number of grains n in formula (2) is calculated by the formula below. M)+x(
n = 500(-
(L,×L)
wherein, M is the magnification of the microscope,
L is the sum of the lengths of the cut lines in one direction on mutually perpendicular cutting lines, and L is the sum of the lengths of the cut lines in two directions on mutually perpendicular cutting lines.
is the total number of grains cut by the cutting line length, and
is the total number of grains cut by the cutting line length. (2)wwW.bzxz.Net
(3)
0B438584
Grain size rating chart of ferrite product of low carbon steel cold rolled sheet, the first standard male grade chart (magnification 100 times)
GB 4335—84
GB 4335--84
GB4335-84
Third standard level diagram (magnified 100 times)
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