YB/T 4003-2016 English PDF (YBT4003-2016)

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YB/T 4003-2016: Standard diagrams for macrostructure and defect in continuous casting slab
YB/T 4003-2016
YB
FERROUS METALLURGY INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
H 24
Replacing YB/T 4003-1997
Standard diagrams for macrostructure and defect in
continuous casting slab
ISSUED ON: OCTOBER 22, 2016
IMPLEMENTED ON: APRIL 01, 2017
Issued by: Ministry of Industry and Information Technology of the People’s
Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Sampling and sample corrosion methods ... 4
4 Defect classification and evaluation ... 4
5 Inspection report ... 8
Appendix A (Informative) Evaluation details for macrostructure and defect in
continuous casting slab ... 10
Appendix B (Normative) Standard diagrams for macrostructure and defect in
continuous casting slab by etching ... 12
Appendix C (Normative) Standard diagrams for macrostructure and defect in
continuous casting slab by sulphur print ... 41
Standard diagrams for macrostructure and defect in
continuous casting slab
1 Scope
This Standard specifies the samples used in the testing of macrostructure and defect in
continuous casting slab by etching and sulfur print, as well as the morphological
characteristics, cause and evaluation principle of defects.
This Standard applies to the evaluation for macrostructure and defect in slabs such as
carbon steel and alloy steel produced by continuous casting process.
The qualification grade of various defects in this Standard and the defects that are not
allowed to exist shall be stipulated in the corresponding technical conditions and the
agreement between the two parties.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
GB/T 226, Test method for macrostructure and defect of steel by etching
GB/T 4236, Steel examination by sulphur print (Baumann method)
3 Sampling and sample corrosion methods
The sample cut-out and display methods shall comply with the provisions of GB/T 226
or GB/T 4236.
4 Defect classification and evaluation
4.1 Morphological characteristics, cause and evaluation principle of various
defects
4.1.1 Center segregation
The morphological characteristics, cause and evaluation principle of center segregation
are as follows:
a) Morphological characteristics: deep corroded dark spots or bands in the central
area of the acid-etched test surface of the continuous casting slab; brown spots or
concentrated brown bands of different colors in the central area of the sulfur print.
The segregated bands are distributed continuously, discontinuously or dispersedly.
Type A segregation is a continuously distributed band, type B segregation is a
discontinuously distributed band, and type C segregation is a band formed by
discontinuous aggregation of spots of different sizes;
b) Cause: formed during the solidification process of molten steel, when elements
such as sulfur and phosphorus with low melting points are pushed to the center
of the continuous casting slab due to the result of fractional crystallization;
c) Evaluation principle: evaluate by segregation type, segregated band thickness or
segregated spot size; see A.1 for evaluation details.
4.1.2 Center porosity
The morphological characteristics, cause and evaluation principle of center porosity are
as follows:
a) Morphological characteristics: many small dark spots or voids in the central area
of the acid-etched test surface of the continuous casting slab;
b) Cause: many micropores formed due to volume shrinkage – during casting and
solidification of molten steel – without sufficient molten steel supplementation,
and lack of compact structure in the central area resulted from gas precipitation
and impurity accumulation during final solidification;
c) Evaluation principle: evaluate according to the quantity and density of dark spots
or voids.
4.1.3 Intermediate crack
The morphological characteristics, cause and evaluation principle of intermediate crack
are as follows:
a) Morphological characteristics: linear defects appearing in the columnar area on
the acid-etched test surface or sulfur print of the continuous casting slab;
h) Cause: cracks – expanding along the columnar crystal – caused by the uneven
cooling in the secondary cooling zone, and thermal stress resulted from rising
surface temperature;
c) Evaluation principle: evaluate according to the length, opening width and quantity
of cracks; see A.2 for evaluation details.
4.1.4 Corner crack
The morphological characteristics, cause and evaluation principle of pinhole bubbles
are as follows:
a) Morphological characteristics: pinhole-like circular holes appearing on the acid-
etched test surface or sulfur print of the continuous casting slab, separated by a
clear boundary with the steel substrate;
b) Cause: formed by molten steel peroxidation or gas trapped;
c) Evaluation principle: evaluate according to the size, quantity and distribution of
bubbles; see A.3 for evaluation details.
4.1.8 Honeycomb bubbles
The morphological characteristics, cause and evaluation principle of honeycomb
bubbles are as follows:
a) Morphological characteristics: strip-shaped, oval-shaped or circular holes
perpendicular to the surface of the slab appearing on the acid-etched surface or
sulfur print of the continuous casting slab;
b) Cause: formed due to poor deoxidation of molten steel, damp casting system or
gas trapped during argon blowing;
c) Evaluation principle: evaluate according to the size, quantity and distribution of
bubbles; see A.3 for evaluation details.
4.1.9 Silicate inclusions
The morphological characteristics, cause and evaluation principle of silicate inclusions
are as follows:
a) Morphological characteristics: dark-gray spherical or oval particles with smooth
edges appearing on the acid-etched test surface of the continuous casting slab;
h) Cause: formed when refractories or dirt from smelting or pouring systems enter
and remain in molten steel;
c) Evaluation principle: record only the size and data of inclusions; do not evaluate
the grade.
4.1.10 White bands
The morphological characteristics, cause and evaluation principle of white bands are as
follows:
a) Morphological characteristics: white bands with strong corrosion resistance and
dense structure appearing on the acid-etched test surface or sulfur print of the
continuous casting slab;
b) Cause: formed along the solute-enriched molten steel of small temperature
gradient before solidification, due to improper electromagnetic stirring, fast
moving speed of molten steel;
c) Evaluation principle: record only the distance from the edge and the width of the
band; do not evaluate the grade.
4.2 Standard diagrams
4.2.1 This Standard includes the following two sets of standard diagrams:
a) Macrostructure diagram of continuous casting slab by etching (see Appendix B);
b) Sulfur print standard diagrams (see Appendix C).
Note: The defect in the standard diagram is taken from the 210 mm × 1300 mm
continuous casting slab. When evaluating the defect grade of continuous casting
slabs of other specifications, the standard diagrams can be zoomed out or
zoomed in in proportion.
4.2.2 All types of standard diagrams for defect are composed of 6 grades ...