Peculiarities of steel hardening under deformation conditions with external influence of a magnetic field

Abstract

The strain resistance of a metal, its intensity of hardening, directly depends on the evolution of defects in the crystal lattice. The positive influence of a magnetic field (MF) on the movement of dislocations and their interaction with stoppers (magnetoplastic effect) is known. For the practical use of MF in forging technologies, generalized data on the strengthening of metals during plastic deformation are required. The results of using a constant MF with induction up to 1,2 T in the processes of testing samples for tension and compression were studied. Tensile tests were carried out on samples of steels St3, 20, U8, 40Cr, 09Cr16Ni4Nb, X10CrNiTi18-10, copper M3 and compression tests on steels St3, 09Cr16Ni4Nb, X10CrNiTi18-10, copper M3. Curves of metal hardening during deformation are plotted in the coordinates flow stress – logarithmic strain. The flow stress is determined by the ratio of the load to the cross-sectional area of the sample valid for a given moment of testing under uniform deformation. The change in flow stress of metals is described by the power function of the Ludwik-Hollomon equation. In tension and compression of ferromagnetic steels St3, 20, 40Cr, U8 and 09Cr16Ni4Nb, the impact of MF leads to an increase in the intensity of their hardening. This is most evident in hardened or high-strength steels. But for St3 steel softened by annealing, the effect is the opposite - in MF the intensity of hardening is somewhat less. Tension in MF of paramagnetic steel X10CrNiTi18-10 showed an increase in the intensity of hardening, but compression showed its decrease. Tension and compression of M3 copper in MF occur with a slight decrease in the intensity of hardening. The experiments carried out revealed the main effect of MF at the initial stage of deformation. The hardening curves were divided into straight and parabolic sections with the hardening coefficients determined for each of them. The main effect of MT on the primary stage of linear hardening has been revealed, where a decrease in the intensity of hardening (St3, 40Cr, X10CrNiTi18-10, M3), an increase (St3 and X10CrNiTi18-10) or a reduction (St3 annealed) in the duration of this stage is observed. Keywords: magnetoplasticity, tension, compression, hardening, stress, strain.