Tempered tool steel 5Cr15MoV was normalized at different temperatures followed by air-cooling.It is found that the hardness increases with the increment of a normalizing temperature from 950℃ to 1 150℃,and it then decreases with the temperature getting higher.The Thermo-calc calculation reveales that the mole fraction of carbides decreases when the normalizing temperature increases,which indicates that more carbon dissolved in the matrix enhances the hardness of the steel.However,the existence of retained austenite causes hardness reduction when the normalizing temperature is over 1 150℃.The salt spray test shows that the steel possesses poor corrosion resistance when it is normalized at a temperature above 1 100℃.The precipitation of the carbides in the cooling process creates a number of chromium-depleted zones,making the steel vulnerable to corrosives.In the present work,an appropriate normalizing temperature is suggested.
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