Abstract: The surface hardness and mechanical properties of steel materials are both improved by means of scanning electron beam. The influence of electron-beam scanning on the transformation hardening of 45 steel is studied in this work. The effects of electron beam parameters, such as electron beam power, scanning speed and so on, on the microstructure and mechanical properties are discussed. The microstructure of the 45 steel electron beam surface hardened layers is analyzed by using scanning electron microscope, and the hardness is measured by microhardness tester. The experimental results show that the microstructures of hardened layers of 45 steel is needle and lath martensite after electron beam scanning, and is more uniform and compact than those which are treated by quenching and tempering . The surface hardness of hardened layers reach to 58 HRC, which is harder than that treated with quenching and low temperature tempering of 3～5 HRC, and is about as two times as that treated by quenching and tempering, the hardness is declined gradually alone the deep section from the treated surface. The hardened layer microstructure and mechanical properties are great influenced with electron beam parameters. The width and depth of the hardened layer and the max hardness of the hardened layer are increased greatly with electron beam power increasing, declined with scanning speed increasing.

Key words: 45 steel, Electron beam scanning, Hardness, Microstructure