High manganese steel casting structure&flash& Flash; Metallographic map

    The purpose of metallographic sample preparation is to display the true microstructure of the sample. So, in order to achieve such sample preparation results, we must meet some conditions: for example, because the damage layer generated during the cutting, embedding, and polishing processes must be removed (very small scratches left during the polishing process are allowed to exist), and for very small scratches generated during the polishing process, they can be removed through corrosion solution corrosion. During the sample preparation process, it is necessary to avoid the occurrence of false images during other sample preparation processes such as detachment of the second phase, pits, rupture of the hard second phase, and plastic deformation of the sample. During the sample preparation process, it is necessary to choose suitable pulse metallographic polishing machines and metallographic sample preparation consumables to avoid causing uneven surface of the sample (such as surface height changes caused by hardness differences between different components in the alloy material). This situation must be reduced to a lower ratio, otherwise it will not be able to focus well when observed under the microscope. After each step of the sample cutting, embedding, polishing, and corrosion process, cleaning, cleaning, and drying work must be carried out to effectively avoid sample damage and oxidation. The last point is to choose the most suitable corrosion solution to obtain an ideal phase or grain boundary with clear contrast.

    The selection of samples should be based on the purpose of the inspection. Traditional steel selection generally follows these principles: 1) When observing surface defects, such as grinding cracks, heat treatment cracks, etc., select the outer surface of steel or steel products for metallographic preparation; 2) During sampling inspection, samples should be cut from both ends of the steel separately; 3) When analyzing and inspecting ingots and billets, one longitudinal plane and two or three (both ends or upper, middle, and lower) cross sections should be selected. For example, defects such as white spots, segregation, subcutaneous bubbles, porosity, residual shrinkage pores, and intergranular cracks along the axis in steel can be observed on the cross-section; The strip structure in steel can be observed on longitudinal specimens. 4) The samples for failure analysis and defect detection should not only be sampled at the defect location, but also in the normal area for comparison. During this rough sampling process, it is important to be careful not to cause changes in the metallographic structure of the area to be tested, such as extrusion deformation, grain growth, and cracks, due to overheating during the cutting process. The traditional reference distance between the test surface and the cutting surface during sample cutting is: not less than 20mm during thermal cutting; Not less than 10mm during cold cutting; When burning and cutting, it should not be less than 40mm. When sampling horizontally, the sample thickness is generally 20mm, and the test surface should be perpendicular to the longitudinal axis of the steel (billet) (the plane for metallographic examination should be perpendicular to the deformation direction).

    The above is a sharing from QMAXIS metallographic sample preparation experts in the United States, hoping to provide you with some reference.