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GB/T 13299-1991 (GBT13299-1991)

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BASIC DATA
Standard ID GB/T 13299-1991 (GB/T13299-1991)
Description (Translated English) Steel. Determination of microstructure
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard H24
Classification of International Standard 77.040.30
Word Count Estimation 19,145
Date of Issue 1991/12/13
Date of Implementation 1992/10/1
Quoted Standard GB/T 13298
Drafting Organization Taiyuan Iron and Steel Company
Proposing organization Ministry of Metallurgical Industry of the People Republic of China
Issuing agency(ies) State Bureau of Technical Supervision
Summary This standard specifies the metallurgical evaluation method free cementite steel, low carbon steel deformed pearlite banded structure and widmanstatten, evaluation principles and organizational characteristics. This standard applies to low-carbon, medium carbon steel, steel and profiles of microstructure evaluation; other steel grades according to the relevant standards or protocols, may refer to the standard assessment.

Standards related to: GB/T 13299-1991

GB/T 13299-1991
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC 669.14: 620.186
H 24
GB/T 13299-91
Steel - Determination of microstructure
ISSUED ON: DECEMBER 13, 1991
IMPLEMENTED ON: OCTOBER 01, 1992
Issued by: Administration of Technical Supervision of the People’s
Republic of China
Table of Contents
1 Subject content and scope of application ... 3
2 Reference ... 3
3 Cutting and preparation of specimens ... 3
4 Determination method of microstructure ... 3
5 Determination principles of microstructure ... 4
6 Test record ... 8
Annex A Standard rating diagrams (supplement) ... 9
Additional information: ... 14
Steel - Determination of microstructure
1 Subject content and scope of application
This Standard specifies the metallographic determination method,
determination principles and structural characteristics of free cementite, pearlite
of low-carbon deformed steels, banded structure and Widmannstatten structure
of steels.
This Standard applies to the determination of microstructure of steel plates,
steel strips and sections of low-carbon and medium-carbon steels. Other steel
types can be determined with reference to this Standard according to relevant
standards or agreements.
2 Reference
GB/T 13298 Inspection methods of microstructure for metals
3 Cutting and preparation of specimens
The cutting and preparation of specimens shall be carried out in accordance
with the relevant provisions of GB/T 13298.
4 Determination method of microstructure
4.1 The magnification for determination of free cementite and pearlite is 400×
(360 ~ 450× is allowed). The magnification for determination of banded
structure and Widmannstatten structure is 100× (95 ~ 110× is allowed).
4.2 The standard field of view diameter is 80 mm.
4.3 The determination is carried out by comparison with the corresponding
standard rating diagrams.
4.4 The two surface layers with a depth of approximately 10 % of the thickness
of the steel plate are not inspected.
4.5 When rating, it shall select the highest level in each field of view on the
grinding surface for determination.
4.6 The determination results are expressed by levels. If the level
characteristics are between the adjacent 2 levels, a half level can be attached.
If necessary, the series letter shall be marked, such as 1A, 3B.
5 Determination principles of microstructure
5.1 Free cementite (rating diagrams are shown in Annex A1)
For the determination of free cementite of low-carbon annealed steels with a
carbon content of less than or equal to 0.15 %, it is determined based on the
shape, distribution and size characteristics of cementite.
Table 1 is the description of the structural characteristics of which the rating
diagrams are shown in Annex A1. It consists of each 6 levels in 3 series.
A series: It is determined according to the principle of forming cementite
networks at grain boundaries. The ratio of the part surrounded by cementite
networks at the periphery of individual ferrite grains is used as the determination
principle.
B series: It is determined according to the principle of free cementite granules
constituting single-layer, double-layer and multi-layer chains of different lengths
and increase in granule size.
C series: It is determined according to the principle of transition from evenly
distributed dotted cementite to uneven banded structure.
5.2 Pearlite of low-carbon deformed steels (rating diagrams are shown in
Annex A2)
For the determination of pearlite of low-carbon deformed steels with a carbon
content of 0.10 % to 0.30 %, it is determined according to the structure (granular,
fine granular pearlite colony or lamellar), quantity and distribution
characteristics of pearlite.
Table 2 is the description of the structural characteristics of which the rating
diagrams are shown in Annex A2. It consists of each 6 levels in 3 series.
A series: It is designated for the rating of granular pearlite of cold-rolled steels
with a carbon content of 0.10 % to 0.20 %. As the level increases, cementite
granules aggregate and tend to form bands.
B series: It is designated for the rating of fine granular pearlite colonies of hot-
rolled steels with a carbon content of 0.1 % to 0.20 %. As the level increases,
granular pearlite transitions to lamellar pearlite that forms deformation bands
(and forms split bands).
C series: It is designated for the rating of pearlite of hot-rolled steels with a
carbon content of 0.21 % to 0.30 %. As the level increases, fine lamellar pearlite
transitions from uneven-size and evenly distributed colony structure to uneven
banded structure. At this time, it must be determined based on the width of the
continuous band composed of aggregated pearlite.
5.3 Banded structure (rating diagrams are shown in Annex A3)
For the determination of banded structure of pearlitic steels, it is determined
according to the increase in the quantity of banded ferrites, considering the
degree and continuity of banded structure that passes through the field of view,
and the quantity of deformed ferrite grains.
Table 3 is the description of the structural characteristics of which the rating
diagrams are shown in A3. It consists of each 6 levels in 3 series.
A series: It is designated for the rating of banded structure of steels with a
carbon content of 0.15 % or less.
B series: It is designated for the rating of banded structure of steels with a
carbon content of 0.16 % to 0.30 %.
C series: It is designated for the rating of banded structure of steels with a
carbon content of 0.31 % to 0.50 %.
5.4 Widmannstatten structure (rating diagrams are shown in Annex A4)
For the determination of Widmannstatten structure of pearlitic steels after
overheating, it is determined according to the quantity and size of acicular ferrite
precipitated and the size of austenite grains determined by ferrite networks.
Table 4 is the description of the structural characteristics of which the rating
diagrams are shown in Annex A4. It consists of each 6 levels in 2 series.
A series: It is designated for the rating of Widmannstatten structure of steels
with a carbon content of 0.15 % to 0.30 %.
B series: It is designated for the rating of Widmannstatten structure of steels
with a carbon content of 0.31 % to 0.50 %.
Table 1 -- Free cementite
Level Structural characteristics A series B series C series
Free cementite is granular
with a size of ≤ 2 mm,
evenly distributed
Free cementite is dotted or
small granular, tending to
constitute single-layer
chains
Free cementite is dotted or
small granules, evenly
distributed, slightly oriented
in the deformation direction
...