Influência do tamanho de grão da austenita prévia nas propriedades magnéticas dos aços maraging 300.

Abstract

Maraging steels are Ni-Co-Mo-Ti quaternary alloys developed by Clarence Bieber that have a martensitic (mar) microstructure and are hardened by aging heat treatment. These are steels that have an excellent combination of ultra high strength and toughness, which places them in an advantageous position when compared to other steels used in nuclear, military, aeronautical and pressure vessel industries. The present work aims to relate the grain size of maraging 300 steel with the magnetic properties of the material that will have final application in high-speed centrifuge rotors. The solution annealing heat treatment was carried out at four temperatures for 1 h, these were 840 °C, 950 °C, 1050 °C and 1150 °C and it was noted that the grain grew exponentially with the increase in temperature. With the subsequent aging in two conditions, 480 °C for 3 h and 560 °C for 1 h, there was no grain growth. The samples were submitted to XRD measurements for visualization of martensite and reverse austenite peaks, Vibrant Sample Magnetometer (VSM) and Barkhausen magnetic noise (RMS) to study the variation of magnetic properties with the increase of grain size. Reverse austenite is believed to influence directly in the magnetic properties of maraging 300 steel.