GB/T 15711-2018 English PDF (GBT15711-2018)

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GB/T 15711-2018: Inspection of non-metallic inclusions of steel -- Etching test method of tower samples
GB/T 15711-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
H 24
Replacing GB/T 15711-1995
Inspection of non-metallic inclusions of steel -
Etching test method of tower samples
ISSUED ON. MAY 14, 2018
IMPLEMENTED ON. FEBRUARY 1, 2019
Issued by. State Administration for Market Regulation;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions ... 5 
4 Selection and preparation of samples ... 5 
5 Hairline inspection method ... 8 
6 Representation and assessment of inspection results ... 8 
7 Test report ... 9 
Inspection of non-metallic inclusions of steel -
Etching test method of tower samples
1 Scope
This Standard specifies the selection and preparation of samples, hairline
inspection method, representation and assessment of inspection results, and
test report, etc. for the use of etching test method of tower samples for
inspection of non-metallic inclusions of steel.
This Standard is applicable to the inspection of the number, length, and
distribution of hairlines in steel by etching test of tower samples of steel with a
diameter, side length, or thickness of 16 mm ~ 150 mm. Other products or
specifications may refer to.
2 Normative references
The following documents are indispensable for the application of this document.
For the dated references, only the versions with the dates indicated are
applicable to this document. For the undated references, the latest version
(including all the amendments) are applicable to this document.
GB/T 226 Test method for macrostructure and defect of steel by etching
GB/T 8170 Rules of rounding off for numerical values and expression and
judgement of limiting values
3 Terms and definitions
The following terms and definitions are applicable to this document.
3.1 Hairlines
The streaks formed by the non-metallic inclusions in steel extending in the
forging-rolling direction during processing and deformation.
4 Selection and preparation of samples
4.1 Sampling method
Table 1 (continued) (in millimeters)
Step No. Dimensions of each step, Di (Ti) Length, L
3 0.60D (0.60T) 50
Note. D - Diameter of round steel, side length of square steel; T - Thickness of flat steel
or steel plate.
a Through the negotiation between the supplier and the buyer, it can be sampled
according to the step length of L1=60 mm, L2=72 mm, and L3=90 mm.
4.3.3 The sample processing shall adopt a reasonable cutting process, to
prevent overheating. The surface roughness Ra of the sample after processing
shall be ≤1.6 μm.
4.3.4 The surface etching of the sample shall be in accordance with the
provisions of GB/T 226.
5 Hairline inspection method
5.1 The number, length, and distribution of hairlines on the entire surface of
each step are observed and inspected with the naked eye, and if necessary, a
magnifying glass of not more than 10 times can be used for inspection.
Note. It shall be noted that, during the inspection, the hairline is a non-metallic inclusion
streak, which shall be separated from the segregation line and the loose stripe zone
after etching. The latter is not included in the inspection results.
5.2 The test and inspection results shall comply with the provisions of GB/T
8170. The numerical values shall be rounded to single digit.
6 Representation and assessment of inspection results
6.1 The inspection results of hairlines shall include.
a) Number of hairlines on each step;
b) The total length of the hairline on each step, in millimeters (mm);
c) The total number of hairlines on each sample;
d) The total length of the hairline on each sample, in millimeters (mm);
e) The maximum length of the hairline on each sample, in millimeters (mm).
6.2 The starting-calculation length of the hairline shall comply with the