Estudo sobre a transformação martensítica em aços com efeito TRIP sob temperaturas sub-zero

Abstract

The work was developed on TRIP steels, whose microconstituents are a ferritic matrix with islands of retained austenite, bainite and martensite. This type of steel undergoes mechanical conformation, causing the retained austenite to transform into martensite, thus increasing its hardness and modifying its initial properties. Due to this characteristic of phase change, TRIP steel is widely used in the automotive industry, revealing great value as a high-strength steel that increases passenger safety in the event of an accident, however, due to its high production value, find new processing routes in order to maintain the initial properties reducing the associated cost. One of the proposed ways is the use of cryogenic punching for drilling, however, as is known, this process faces challenges regarding the appearance of defects and changes in the microstructure of the material due to the deformation inflicted on the material and the transformation energy with the consequent increase in temperature. Thus, the study of temperature in TRIP steels aims to understand the behavior of the microstructure at specific temperatures, verifying its behavior in different working ranges, especially at cryogenic temperatures, and thus support a future study on how the processing will be used. by mechanical punching. The microstructural analysis was carried out with the support of the microscopy technique via EBSD and aims to identify significant changes in the material at four temperatures, namely: room temperature, 0ºC, -80ºC and -196.15°C. Such temperatures were achieved using atmospheric air, water on ice, isopropyl alcohol under refrigeration and with liquid nitrogen, respectively. With the results obtained, it is possible, in future research, to evaluate the result of mechanical punching in TRIP steel sheets.