GB/T 15711-1995

Steel Products — Method for Etch Test of Tower Sample

(neq ISO 3763:1976)

Issued: 1995-10-10  |  Implemented: 1996-03-01

Proposed by: National Technical Committee on Steel Standardization

Drafting Units: Dalian Steel Works, Information and Standards Research Institute, Ministry of Metallurgical Industry

Main Drafters: Zhang Shumin, Liu Zhaohui

Foreword

This standard is developed on the basis of YB 47-64, with non-equivalent adoption of ISO 3763:1976 “Forged steel products — Macroscopic method for the assessment of non-metallic inclusion content.”

This standard retains the scientifically sound and reasonable content from the original YB 47-64 standard that ensures the continuity of inspection standards and product standards, and can correctly display and inspect hairline cracks. On the tower-shaped specimen, the l/D ratio coefficient specified in ISO 3763 is adopted non-equivalently, representing a significant modification from the original YB 47-64 standard. This standard also revises the measurement method for the distance between two hairline cracks on the same straight line of the specimen inspection surface, and removes the “magnetic flaw detection method.”

This standard is implemented from March 1, 1996. From the date of implementation, the original YB 47-64 “Tower-shaped Turning Hairline Inspection Method” is invalidated.

1 Scope

This standard specifies the selection and preparation of tower-shaped specimens for inspecting hairline cracks in steel products, the inspection method, the representation and evaluation of inspection results, and the inspection report.

This standard is applicable to the etch test method using tower-shaped specimens to inspect the quantity, length, and distribution of hairline cracks in steel products.

2 Referenced Standards

The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest editions of the standards listed below.

GB 226-91 — Test method for macrostructure and defect etching of steel

3 Selection and Preparation of Specimens

3.1 Sampling Method

This standard employs tower-shaped specimens. Unless otherwise specified by product standards or special agreements, the applicable dimensions for tower-shaped hairline inspection of steel products (or steel billets) range from φ16 to φ150 mm.

Specimens are cut from steel products (or steel billets) in the delivered condition.

Specimens shall be cut by mechanical means in a cold state. If gas cutting or hot cutting methods are used, the melted zone, plastically deformed zone, and heat-affected zone must be completely removed.

3.2 Sampling Quantity and Location

The sampling quantity and location shall be as specified by the corresponding product standards or special agreements. If there are no explicit provisions, it is recommended to take three specimens.

3.3 Specimen Preparation

3.3.1 For square or round steel specimens, the inspection surface consists of three concentric cylindrical surfaces parallel to the axis of the steel product (or steel billet) (see Figure 1); for flat steel specimens, the inspection surface is the longitudinal section parallel to the axis of the steel product (or steel billet) (see Figure 2).

D — Steel diameter or side length

Figure 1 — Tower-shaped specimen for square or round steel

Figure 2 — Tower-shaped specimen for flat steel

3.3.2 The dimensions of tower-shaped specimens are shown in Table 1.

Table 1 — Tower-shaped Specimen Dimensions (mm)

Note: D — Steel diameter or side length

3.3.3 During specimen processing, reasonable cutting techniques should be used to prevent overheating. The processed specimen surface shall be smooth, with a surface roughness Ra value of 1.6 μm after processing.

3.3.4 Acid etching of the specimen surface shall be performed in accordance with GB 226.

4 Inspection Method

4.1 Observe with the naked eye and inspect the quantity, length, and distribution of hairline cracks on the entire surface of each step. If necessary, a magnifying glass of no more than 10× magnification may be used for inspection.

5 Representation and Evaluation of Inspection Results

5.1 The inspection results of hairline cracks shall include:

a) Number of hairline cracks on each step;

b) Total length of hairline cracks on each step, in mm;

c) Total number of hairline cracks on each specimen;

d) Total length of hairline cracks on each specimen, in mm;

e) Maximum length of hairline cracks on each specimen, in mm.

5.2 The starting length for counting hairline cracks shall be as specified by the corresponding product standards or special agreements.

Note: If two hairline cracks exist on the same straight line of the specimen inspection surface, and the distance between them is less than the starting length, they shall be counted as one hairline crack, with the hairline crack length including the distance between them.

5.3 The acceptance limits for hairline cracks in steel products shall be as specified by the corresponding product standards or special agreements.

6 Inspection Report

The inspection report shall include the following items:

a) This standard number;

b) Steel grade, heat number, specification, and specimen number;

c) Inspection results;

d) Inspection report number, date, and inspector.

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