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GB/T 37598-2019 (GBT37598-2019)

GB/T 37598-2019_English: PDF (GBT 37598-2019, GBT37598-2019)
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Standard ID GB/T 37598-2019 (GB/T37598-2019)
Description (Translated English) Inspection of non-metallic inclusions in steel -- Blue fracture test method
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard H24
Classification of International Standard 77.040.99
Word Count Estimation 6,689
Date of Issue 2019-06-04
Date of Implementation 2020-05-01
Drafting Organization Northeast Special Steel Group Co., Ltd., Metallurgical Industry Information Standards Research Institute
Administrative Organization National Steel Standardization Technical Committee (SAC/TC 183)
Proposing organization China Iron and Steel Association
Issuing agency(ies) State Administration for Market Regulation, China National Standardization Administration

Standards related to: GB/T 37598-2019

GB/T 37598-2019
ICS 77.040.99
H 24
Inspection of non-metallic inclusions in steel -
Blue fracture test method
ISSUED ON: JUNE 04, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Principle ... 5 
5 Sample preparation ... 5 
6 Inspection method ... 6 
7 Inspection result ... 7 
8 Inspection report ... 7 
Annex A (informative) Record of original inspection results of blue fracture ... 8 
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard was proposed by China Iron and Steel Association.
This Standard shall be under the jurisdiction of National Technical Committee
on Steels of Standardization Administration of China (SAC/TC 183).
The drafting organizations of this Standard: Northeast Special Steel Group Co.,
Ltd., Metallurgical Industry Information Standards Institute.
Main drafters of this Standard: Kang Ge, Cheng Lijie, Yan Chengming, Liu
Yanjun, Wen Zhengmao, Cheng Yu.
Inspection of non-metallic inclusions in steel -
Blue fracture test method
1 Scope
This Standard specifies to use blue fracture test method to inspect macro non-
metallic inclusions in steel, including sample preparation, inspection method,
inspection result and inspection report.
This Standard is applicable to inspect macro non-metallic inclusions in steel, of
which length is not less than 1mm, width is not less than 0.1mm.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 8170, Rules of rounding off for numerical values & expression and
judgement of limiting values
GB/T 30067, Standard Terminology Relating to Metallography
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T
30067 as well as followings apply.
3.1 macro non-metallic inclusion
Strip-shaped non-metallic inclusion that is visible by using visual inspection or
magnification device not more than 10 times
3.2 bluing
Heat treatment method that heat steel to a proper temperature to make it
produce a very thin blue oxide film on its surface
4 Principle
Under blue brittle temperature, make fractured metal substrate produce blue
metal oxide film while non-metallic inclusion is not oxidized. Keep its original
color. It usually is a gray, light yellow or yellowish green non-crystalline strip.
Use visual inspection or a magnification device of no more than 10 times to
observe the size, number and distribution of strip-shaped non-metallic
inclusions visible on longitudinal fracture.
5 Sample preparation
5.1 Sampling method
Cut a transverse steel sample. It may use hot-sawing, cold-sawing, flame
sawing and cutting to cut. Sample thickness is 15mm~20mm. See Figure 1 for
fracture sampling diagram. It shall ensure that deformation and heat-affected
zone caused by sampling outside the fracture. On centerline of cross section of
sample, inscribe V-groove through shaft. Groove depth shall make remaining
sample thickness not less than 10mm.
1 - Slotting;
2 - Rolling direction;
3 - Slice.
Figure 1 -- Fracture sampling diagram
5.2 Sampling quantity
Sampling quantity and sampling site shall be specified in product standard or
agreed by supplier and purchaser. If not specified, it shall extract two samples
on steel.
5.3 Sample preparation
5.3.1 When preparing fracture, place sample face down on fracturing machine
(or pressure testing machine) support table. Ensure that impact knife edge
matches centerline of fracture sample groove. Then, under impact load (or
pressure), break fracture sample once. Repeated stamping is prohibited. In
order to ensure that the fracture is flush, it shall preheat sample.
5.3.2 In order to display non-metallic inclusion, perform bluing to sample
according to one of the following methods:
a) Heat sample in furnace to blue brittle temperature (300°C ~ 350°C). Take
it out and quickly break it off to make sample at break at blue brittle
b) Heat broken sample to blue brittle temperature (300°C ~ 350°C), so as to
make the fracture blue.
NOTE: For high-alloy steel, it may appropriately increase blue brittle temperature. But it
shall not exceed 530°C.
6 Inspection method
6.1 On a fracture surface of dual fracture (usually selecting severe surface of
defect), visually inspect or use a magnification device not more than 10 times
to observe the seize, quantity or distribution of non-metallic inclusion.
6.2 Equally divide fracture surface into three zones: surface zone, middle zone,
central zone. Respectively use S, M, C to represent. See Figure 2 for fracture
surface division.
1 - Notch;
2 - Fracture;
3 - Rolling direction;
S - Surface zone;
M - Middle zone;
C - Central zone.
Figure 2 -- Fracture surface division
6.3 Determine fracture area. Measure length of each inclusion and inclusion
quantity of each zone. Ferritic strips, carbide strips, segregation lines or loose
lines are easily confused with non-metallic inclusions. Pay attention to
7 Inspection result
7.1 Record length of each inclusion of each sample in different zone. Calculate
the sum of lengths of inclusions on inspection area, that is, total length.
Calculate ratio of total length to inspection area, i.e., average length. For
inclusions of which length is less than 1.0mm, width is less than 0.1mm, record
quantity in original record. Do not participate in calculating ratio of total length
to inspection area. Refer to Annex A for record of original inspection results.
7.2 According to requirements of product’s standard, record lengths, quantity of
non-metallic inclusions or maximum length of non-metallic inclusion of each
7.3 Testing and inspection results shall comply with provisions of GB/T 8170.
Round values off to 0.1mm.
8 Inspection report
Inspection report shall contain the following information:
a) reference to this Standard;
b) steel number, furnace number, specification and sample number;
c) inspection result;
d) number, date of inspection report as well as inspector.
Annex A
Record of original inspection results of blue fracture
See Table A.1 for record of original inspection results of blue fracture.
Table A.1 -- Record of original inspection results of blue fracture
n area
Inclusion size / mm
number of
mm/dm2 S M C
__________ END __________