GB/T 26656-2023 Metallographic test for compacted (vermicular) graphite cast irons
1 Scope
This document specifies the preparation, inspection items and grading of metallographic specimens of vermicular graphite cast irons.
This document is applicable to the identification of graphite forms in sand casting vermicular cast iron, as well as the assessment of vermicularity, pearlite, phosphorus eutectic, and carbide content and their grading.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions 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 13298 Inspection methods of microstructure for metals
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
maximum Féret diameter
lm
maximum straight line distance between any two points on the outer edge profile of graphite particles
3.2
particle roundness
ρ
area of the graphite particle divided by the area of the circle with the diameter equal to the maximum Féret diameter of that graphite particle
4 Preparation of metallographic specimens
4.1 The metallographic specimen shall be taken from test blocks or castings, and the test surface shall not be taken from the casting surface.
4.2 The metallographic specimen shall be prepared in accordance with the requirements of GB/T 13298. During the process of cutting and preparing the metallographic specimen, measures shall be taken to prevent changes in the microstructure, graphite peeling, and graphite dragging. The surface of the specimen shall be smooth and free from coarse scratches.
5 Test items and grading
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Preparation of metallographic specimens
5 Test items and grading
Annex A (Informative) Graphite classification
Annex B (Informative) Vermicular graphite form
Annex C (Informative) Determination of creep rate of vermicular cast iron
Bibliography
