Abstract
To optimize the properties of the new corrosion resisting steel 3CR12 the microstructure has been studied as a function heat treatment. The kinetics of both the decomposition of austenite and the reaustenization reactions have been investigated using a series of isothermal anneals. The steel has a dual phase ferrite–austenite structure between 800 and 1350°C and the amount of austenite is maximum at about 1050°C. At this temperature a higher nickel version of the alloy is fully austenite. On cooling to ambient temperature, the austenite transforms to a lath-type martensite. Heat treatments at temperatures up to 800°C cause the slow tempering of the martensite, the recovery and recrystallization of original ferrite regions, and the nucleation and growth of newly formed ferrite. The growth of ferrite requires the concomitant precipitation of carbides and nitride particles from the austenite or martensite and these particles mark the stepwise movement of the interface. In contrast the reaustenization does not require any immediate redistribution of elements. Consequently, the hardness of the resulting martensite is a function of both the temperature and time of the austenization treatment. These findings can be used to advantage by the producers, fabricators, and end users of the steel since variations in thermomechanical treatments promote differences in formability, strength, and toughness.
MST/493
Get full access to this article
View all access options for this article.