Grain Refinement and Improved Mechanical Properties of EUROFER97 by Thermo-Mechanical Treatments

Abstract

EUROFER97 steel plates for nuclear fusion applications are usually manufactured by hot rolling and subsequent heat treatments: (1) austenitization at 980 °C for 30 min, (2) rapid cooling and (3) tempering at 760 °C for 90 min. An extended experimental campaign was carried out with the scope of improving the strength of the steel without a loss of ductility. Forty groups of samples were prepared by combining cold rolling with five cold reduction ratios (20, 40, 50, 60 and 80%) and heat treatments at eight different temperatures in the range 400–750 °C (steps of 50 °C). This work reports preliminary results regarding the microstructure and mechanical properties of all the cold-rolled samples and the effects of heat treatments on the samples deformed with the greater CR ratio (80%). The strength of deformed samples decreased as heat treatment temperature increased and the change was more pronounced in the samples cold-rolled with greater CR ratios. After heat treatments at temperature up to 600 °C yield stress (YS) and ultimate tensile strength (UTS) of samples deformed with CR ratio of 80% were significantly larger than those of standard EUROFER97 but ductility was lower. On the contrary, the treatment at 650 °C produced a fully recrystallized structure with sub-micrometric grains which guarantees higher strength and comparable ductility. The work demonstrated that EUROFER97 steel can be strengthened without compromising its ductility; the most effective process parameters will be identified by completing the analyses on all the prepared samples.

Effect of Ultrafast Heating on Aisi 441 Ferritic Stainless Steel

“…It is also successfully applied after cold rolling to promote grain refinement [27,28], leading to an increase in tensile properties [29][30][31]. It is reported that the application of UFH inhibits the dislocation re-organization which is typical of recovery [32][33][34][35]. Hence recrystallization process occurs in direct competition with austenitization [36][37][38].…”

Recrystallization and Grain Growth of AISI 904L Super-Austenitic Stainless Steel: A Multivariate Regression Approach

“…During the subsequent annealing heat treatment, following the work-hardening induced by the deformation process, primary recrystallization and grain growth phenomena occur, depending on the heat treatment temperature and soaking time [51,52]. The grain growth phenomena typically act in two modes: (I) normal grain growth (NGG) with a uniform increase in grain size, based on grain boundary migration and annihilation of slam grains; (II) abnormal grain growth (AGG) or secondary recrystallization, characterized by the rapid growth of some grains at the expense of neighboring ones (e.g., [53,54]).…”

Vanadium Alloying in S355 Structural Steel: Effect on Residual Austenite Formation in Welded Joints Heat Affected Zone

“…The development of high strength materials for oil and gas and energy application has been driven in last times by customer requests to combine high tensile properties, impact resistance and good weldability on industrial scale at prices responding to market requests [1][2][3][4][5]. A comparable figure is met in different market sectors of structural steels (for example offshore metallic structures or ships, with broadly similar aims).…”