Microstructure-Mechanical Property Relation of Cold-rolled Low Carbon Steel under Electropulsing Treatment (EPT)

The main purpose of this research is the investigation of the hardness-microstructure relation under electropulsing treatment (EPT) and the feasibility of hardness improvement in the sheets use in AEM’s (Abrah Ettesal-e-Mehr) (steel joints and valves producer) production line. In this regard, cold-rolled low carbon steel sheets with mm thickness deformed by 16 and 33 percentages and reached 2.5 and mm, respectively. Steel specimen were applied under EPT for 20, 30, 40, 45, 50, 60, 70, 105 and 140 seconds. Hardness measurement done after each experiment in the AEM laboratory and in order to evaluate microstructural evolution, as-received specimen and specimen that undergo 20 and 140 seconds of EPT were investigated by FESEM. It observed that by increasing the total EPT time up to 20 seconds, finer grains which located in short distances obtained, this could be owe to increasing nucleation kinetic, decreasing precipitate growth kinetic and anisotropic protective layer formation. As result, hardness improvement appeared. In the following, by continuing EPT process up to 140 seconds, coarser precipitates obtained which could be due to increasing precipitate growth kinetic and also forming precipitate free zones (PFZ), therefore, hardness drops. It can be concluded from the outcomes that by applying EPT for 20 seconds finest precipitates and highest hardness achieve. According to our findings, the most optimum state in order to obtain finest microstructure and highest hardness in shortest time is applying EPT for 20 seconds with the treated time of 0.5 second on 16% deformed specimen.

کلیدواژه ها:

Electropulsing ، low carbon steel ، rolling ، microstructure ، hardness ، electron microscope