TECHNOLOGIES

Development of a new technology for carbon steel bars processing

  • 1 Karaganda Industrial University, Temirtau, Kazakhstan

Abstract

In this paper, bars from carbon steel grade 45 deformed by a new technology are studied. This technology consists in drawing bars from medium carbon steel on a radial-shift rolling mill and subsequent drawing. As a result of deformation, bars with gradient microstructure were obtained. The surface zone of the bar is significantly crushed, the average ferrite size is 0.5 μm. In the neutral zone the deformation is not large enough, so the structure is not so strongly crushed, the ferrite grains are reduced to 2 microns. In the central zone, the microstructure consists of large grains with an average size of 7 μm. The quantitative ratio of large-angle boundaries in the surface zone is much higher than the central zone. To understand the relationship between strength and microstructure, the microhardness of the bar was determined. Thus for three deformation cycles the average value of microhardness in the central zone was 2085 MPa, in the neutral zone – 2505 MPa, and in the surface zone – 2915 MPa. As it can be seen, the hardness decreases as we move away from the surface zone to the central zone, this can be explained in terms of dislocation and boundary hardening.

Keywords

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