GB/T 226-2015Test method for macrostructure and defect of steel by etching (English PDF)

GB/T 226-2015 is the English-translated version of 钢的低倍组织及缺陷酸蚀检验法.

GB/T 226-2015 sets out the etching tests that reveal the macrostructure and defects of steel.

Clause 1 states that the standard specifies the hot acid etching method, the cold acid etching method, including the dendrite corrosion method, and the electrolytic etching method which test the macrostructure and defect of steel, that it is applicable to the acid etching test of the macrostructure and defect of steel, and that the acid etching test of other materials can be implemented according to it.

The contents list clause 3 Specimen, clause 4 Test Method, clause 5 Test Results, clause 6 Specimen Retention, clause 7 Lab Environment Safety and clause 8 Test Report.

Clause 3 covers specimen cutting, machining and dimension: the specimen may be cut by hot saw, cold saw, flame cutting, shearing or other methods and the deformation or heat affected zone caused by sampling has to be removed during machining, the reference dimension from the test surface to the cutting surface and the test surface roughness Ra after machining are both provided for, and the specimen thickness is generally about 20 mm to 30 mm while a longitudinal specimen is generally about 1.5 times the edge or diameter in length.

Clause 4 recommends the hot acid etching method for arbitration inspection where the technical conditions make no special provision, selects the acid liquid for hot acid etching according to the steel type, has the test surface reprocessed to a depth of 1 mm or more and re-etched if over corrosion occurs in cold acid etching, and splits electrolytic etching into an AC and a DC method, the DC method working at room temperature with an acid solution of 100 mL of water plus 6 mL to 12 mL of hydrochloric acid for a specimen area below 130 cm2 and of 100 mL of water plus 6 mL of hydrochloric acid and 1 g of boric acid above it.

Clause 5 allows the macrostructure and defect shapes displayed by the hot acid, routine cold acid and electrolytic etching methods to be obtained by photo-optical or digital imaging, clause 6 recommends methods for keeping the specimen for a certain period, and clause 7 requires the residual waste acid left after etching to be treated according to the discharge provision for second pollutants in 4.2.1.2 of GB 8978-1996, which clause 2 cites.

The foreword records the changes against the 1991 edition, among them the modified specimen cutting provision, the modified reference dimension from the test surface to the cutting surface, the new requirement on test surface roughness after machining, the added dendrite corrosion and cold acid etching method, the modified ingredients, etching time and temperature of some hot and cold acid etching methods, the added DC electrolytic corrosion method, the new way of expressing test results, the removal of the evaluation provision for test results and the new provision on lab environment safety; it also records that the standard was proposed by the China Iron and Steel Industry Association and is under the jurisdiction of SAC/TC 183.

It replaces GB/T 226-1991, was issued on 11 September 2015 and has applied since 1 June 2016.

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.

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