The effect of heating rate and soaking time on microstructure of an advanced high strength steel

Abstract

This work focuses on the effect of soaking time on the microstructure during ultrafast heat treatment of a 50% cold rolled low carbon steel with initial ferritic-pearlitic microstructure.Dilatometry analysis was used to estimate the effect of heating rate on the phase transformation temperatures and to select an appropriate inter-critical temperature for final heat treatments. A thorough qualitative and quantitative microstructural characterization of the heat treated samples is performed using a wide range of characterization techniques. A complex multiphase, hierarchical microstructure consisting of ferritic matrix with embedded martensite and retained austenite is formed after all applied heat treatments. In turn, the ferritic matrix contains recrystallized and non-recrystallized grains. It is demonstrated that the ultrafast heating generally results in finer microstructure compared to the conventional heating independently on the soaking time. There is a significant effect of the soaking time on the volume fraction of martensite of the ultrafast heated material, while in the samples heated with conventional heating rate it remains relatively unchanged during soaking.Recrystallization, recovery and phase transformations occurring during soaking are discussed with respect to the applied heating rate.

Optimization of heat treatment parameters of medium carbon steel quenched in different media using Taguchi method and grey relational analysis

“…An increase in soaking time yielded an increase in tensile strength. This agrees with the study of Valdes-Tabernero et al. (2019) .…”

“…The results in the present study affirm the report of Singh et al (2013) on the effect of soaking time on the behaviour of carburized mild steel, where it was stated that soaking time increment has a direct influence on the hardness value increment of the mild steel used. It was similarly reported by Valdes-Tabernero et al (2019) that fraction of the recrystallization ferritic matrix with embedded martensitic and retained austenite grains generally tends to increase with increasing soaking time, thus, the tendency of an increased hardness in mild carbon steel. Therefore, an increase in soaking time above all other process parameters during heat treatment of MCS has the largest impact on its hardness.…”

The Performance of CR180IF and DP600 Laser Welded Steel Sheets under Different Strain Rates

“…A specific heat treatment achieves this microstructure. The steel is first intercritically annealed in the range of recrystallization temperatures Ac1 and Ac3 [ 14 ], while austenite and ferrite are transformed in the stable phase [ 15 , 16 ]. The process follows with hardening, in which the material cools very rapidly, which results in the conversion of austenite to martensite [ 17 , 18 ].…”

Mechanical stability of retained austenite in aluminum-containing medium-Mn steel deformed at different temperatures

“…The retained austenite characterized by very high stability is not able to transform into strain-induced martensite, and as a result such steel sheets show the low plasticity [4]. Retained austenite with low stability transforms into martensite rapidly at small strains [5]; thus, the steel cannot achieve the satisfactory work hardening rate [6]. Therefore, research efforts are focused on designing the chemical composition and processing parameters which allow producing the optimal microstructure with a volume fraction of retained austenite characterized by the tailored stability [7].…”