Superseding
Chinese Name	�ṹ�ֵͱ���֯ȱ������ͼ
English Name
Chinese Standard Classification
Professional Classification
ICS Classification
Issued on	2001-1-2
Implemented on	2002-5-1
Abolished on
Issued by	AQSIQ
Chinese Pages
Word Count	4000 words

1 Scope
This national standard specifies and describes classification, characteristics, causes and evaluation principles of the acid pickling macrostructure and defect of structural steels, and also the classification, application scope, evaluation methods and survey reports of standard diagrams.
This standard is applicable to evaluate allowable and unallowable defect of acid pickling macrostructure in the cross section of carbon construction steel, alloy constructional steel, spring steels (forged and rolled steels). According to mutual agreement between the supply and demand sides, it also may be used to evaluate the defect of steel-type macrostructure.
2 Normative references
The following standard contains provisions which, through reference in the following text, constitute provisions of this standard. For dated reference, subsequent amendments (excluding correction) to, or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. For undated references, the latest edition of the normative document referred to applies. For undated references, the latest edition of the normative document referred to applies.
GB/T 226 Etch Test for Macrostructure and Defect of Steels
3 Sample interception and display methods
Sample interception and display methods shall comply with those specified in GB/T 226. Other sample display methods also may be adopted according to mutual agreement between supply and demand sides.
4 Classification, characteristics, causes and evaluate principles of the defect
4.1 General porosity
Characteristic: the test plate shows with loose tissues which distribute over dark spots and interspace in the whole section. Dark spots mainly show in a circle or oval. The interspace shows with anomalous blow holes or round pinholes through observing with the magnifier. These dark spots and interspace usually exist between primary axis and secondary axis of the thick branched crystallization. The porosity region is dark and the axial region is bright. Steel pit will not occur provided that there is no great difference between the corrosiveness of light region and dark region.
Causes: each crystallization core usually grows up in the branched crystallization form when the molten steel freezing. Microvoid generates from the freezing molten steel exist between the primary axis and each secondary axis of branched crystallization; some low melting components, gasses and non-metallic inclusions gather there. These microvoid and gathered inclusions will show in porotic tissue after acid corrosion.
Evaluation principle: the quantity, size and distribution state of dark spots and interspace distributed over the whole section, and the thickness degree of branched crystallization.
4.2 Central porosity