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2012
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3. Each element of the standard series is a monodisperse system
of spheres of an equal diameter
4. To harmonise the numeric series of the new standard with the
functioning standards, volumes of the monodisperse system
spheres are taken equal to the volumes of the corresponding
elements of the cubic model, ie the principle of geometric
progression is preserved in the standard series
5. To determine the value of the structural 3D objects, structure
reconstruction is made over the planar section and its initial
data is distribution of chords in disperse intervals of the
standard series obtained by any known quantitative method.
The initial data are obtained in a planar section (microsection)
by determination of chord dimensions in two mutually transverse
directions
6. The structure reconstruction ismade using softwareSTRUCTURE
2001
[7]
or other software used for the reconstruction of the
spherical model of the equiaxial grain structure. The requirement
of reconstruction is obtaining of distribution of standard sphere
diameters (grain numbers) in a 3D space and numerical
characteristics of this distribution the number of independent
monodisperse spheres in a volume, average value of their
diameters, deviations from the average value and variation
coefficient determining grain anisotropy in the studied object in
the space
Table 3 shows data for assessment of grain size and anisotropy
by the new standard in accordance with standards АSТМ Е112,
DIN 50601 and GОSТ 5639. Figures 1 and 2 show examples of
assessment of a homogeneous and anisotropy structures in the
specimens taken from cold-worked tubes of АSТМ316L steel type
after rapid and furnace heating at 1150°C.
As the above figures show, Coefficient of variation shows clearly
anisotropy of the tube metal. It should be pointed out that the
average value of diameters are determined in a volume, in a plane
and in a chord, not only in a plane as the existing standards specify.
The index of anisotropy
r
attitude of variation real structure (figure1,
2) can serve as toward the variation of flat cut of monodispersible
spherical model (table 3).
This method of assessment was used in
[7]
in the analysis of
influence of the heating parameters on the grain size and structural
anisotropy in cold-worked tubes made of corrosion-resistant steel of
Kh18Н10Т, Kh17Н14МZB type and alloy Kh15N35МBТUR.
Analysis of a great number of experimental data
[1, 8-10]
shows a high
level of grain anisotropy in above Cr-Ni steels and other (16-15;
18-12; Х15Н35, Х25Н45 type) steels and alloys. It leads to the
appearance of a significant unhomogeneity of physical-mechanical
properties and can result in undesired consequences during service
of the products from such materials.
Analysis of these data makes it possible to draw the following
conclusions:
1. Relative level of grain anisotropy for all studied materials
subjected to isothermal heat treatment is higher
(1.5 ≤
r
≤ 2.5)
than during anisothermal heat treatment
(1.52 ≤
r
≤ 1.8)
Grain number, G according to…
Parameters for the determination of grain size and grain anisotropy
GОSТ 5639 ASTM E112 DIN 50601
Number of
grains in
1mm
2
In a volume
In a plane
In a line
Diameter, D,
μm
Coefficient
of variation
Diameter,
d, μm
Coefficient of
variation
Chord,
l, μm
Coefficient
of variation
-3
-3
1
1240.7
0
974.4
0.2842
815.1
0.36
-2
-2
2
877.3
0
689.0
0.2842
576.4
0.36
-1
00
-1
4
620.4
0
487.2
0.2842
407.6
0.36
0
0
0
8
438.7
0
344.5
0.2842
288.2
0.36
1
1
1
16
310.2
0
243.6
0.2842
23.8
0.36
2
2
2
32
219.3
0
172.3
0.2842
144.1
0.36
3
3
3
64
155.1
0
121.8
0.2842
101.9
0.36
4
4
4
128
109.7
0
86.1
0.2842
72.1
0.36
5
5
5
256
77.5
0
60.9
0.2842
50.9
0.36
6
6
6
512
54.8
0
43.1
0.2842
36.0
0.36
7
7
7
1024
38.8
0
30.5
0.2842
25.5
0.36
8
8
8
2048
27.4
0
21.5
0.2842
18.0
0.36
9
9
9
4096
19.4
0
15.2
0.2842
12.7
0.36
10
10
10
8192
13.7
0
10.8
0.2842
9.0
0.36
11
11
11
16384
9.7
0
7.6
0.2842
6.4
0.36
12
12
12
32768
6.9
0
5.4
0.2842
4.5
0.36
13
13
13
65536
4.8
0
3.8
0.2842
3.2
0.36
14
14
14
131072
3.4
0
2.7
0.2842
2.2
0.36
Table 3
:
Parameters of grain structure according to the new standard