Study of the anisotropy of carbon steel sheet by the tensile test

In test laboratories, the characteristics of the sheets shall be determined by the tensile test on specimens taken in the direction perpendicular to the rolling direction, and these characteristics shall be used as the date of entry into the process of calculating the parts made of the sheet. In the case of parts with special characteristics such as safety parts in the automotive industry, or for mechanically stressed parts in a certain direction, it is important to know precisely the values of the mechanical characteristics of the sheet in relation to the rolling direction, so as to ensure the required resistance. Also, in the case of stamped parts, their quality is all the better the lower the anisotropy. The paper presents the results of experimental research on the mechanical characteristics of the sheet DC04 with a thickness of 0,65 mm, determined by tensile testing on sets of 7 test specimens, taken every 15 degrees from the rolling direction.

Experimental study on tensile deformation process of graphitized high carbon steel sheet

As the object for the study, graphitized high-carbon steel sheet with a carbon content of 0.66 % was used, the tensile test of this sheet using a universal testing (breaking) machine was performed; as well as in-situ observation of the microstructure in the process of tensile deformation of this sheet using in-situ technology of scanning electron microscopy (SEM) was made. The test results show that the main mechanical properties in different directions of tested graphitized high-carbon steel sheet are relatively the same, that is, for a tensile sample of different directions, the ratio of the yield strength σ0,2 to the tensile strength σв is approximately 0.73; the strain hardening index n is approximately 0.24; the plastic deformation coefficient r is approximately 0.83. This indicates that this sheet did not exhibit significant anisotropy. In the process of tensile, deformation of the specimen is mainly developed from local plastic deformation of the graphite inclusions to the total deformation in the deformation zone of the sample; with the increase of displacement, micro-gap between the graphite inclusion and ferrite grain along the direction of the axis of tensile gradually formed and propagated along the direction perpendicular to the axis of tensile; number of slip lines in the ferrite matrix gradually increased, and the distance between them gradually decreases; when the sample breaks, in the fracture large dimple with the core of graphite inclusion and small dimples in the ferrite appears. And the ferrite matrix near the fracture is covered with slip lines, this shows that the ferritic matrix underwent severe plastic deformation before breaking.