METHOD AND DEVICE FOR CONTINUOUS EVALUATION OF MECHANICAL AND MICROSTRUCTURAL PROPERTIES OF METAL MATERIAL, IN PARTICULAR STEEL, DURING COLD DEFORMATION

摘要

A method is described for continuously evaluating mechanical and micro structural properties of a rolled metallic material (L) in a cold deformation process, subjected to combinations of deformation forces selected among compression forces, traction forces and bending moment applied at low deformation speed in a range comprised between 1*10−4 and 10*10−4 s−1 which corresponds to laboratory static conditions and at high deformation speed in a range comprised between 0.1 and 10 s−1 which corresponds to dynamic pp conditions, the method comprising the step of: —measuring characteristic parameters of the cold deformation process under dynamic conditions, comprising at least one value of temperature (T), deformation (ε) and deformation speed ({acute over (ε)}) of the rolled sheet (L); characterized in that it further comprises the steps of: —calculating the traction yield strength at high deformation speed (σYD) according to equation (I), being: σc a compression strength of the rolled sheet (L) when a compression force (Fc) is applied thereon; σt a traction strength of the rolled sheet (L) when traction forces (Tin, Tout) are applied thereon; σbend a strength due to the bending of the rolled sheet (L) when a bending moment is applied thereon; and m, n, p are a first, a second and a third parameter respectively being a function of continuously-measured operating conditions of the cold deformation process and being a function of the rolled sheet (L) in terms of chemical composition and of preceding operating conditions of a hot deformation process, in terms of hot-rolling start and end temperature, winding temperature and grain size; calculating the traction yield strength at low deformation speed (σYS) according to equation (II), being: σYD the traction yield strength at high deformation speed; f a statistical optimization factor between data measured at low deformation speed and at high deformation speed; α a first characteristic parameter of the rolled sheet (L) being a function of a chemical composition of the rolled sheet (L) and of operating conditions of a hot deformation process of the rolled sheet (L); and β a second characteristic parameter of the rolled sheet (L) being a function of the cold deformation process calculated as (III), being {acute over (ε)} the deformation speed, Q an activation energy of the deformation of the rolled sheet (L) evaluated through laboratory tests, R the Boltzmann constant of ideal gases, and T the temperature of the rolled sheet (L).