EFFECT OF RARE EARTH ADDITION ON PROPERTIES OF CONTROLLED ROLLING LOW CARBON MnMoNb FERRITE STEEL

A study was made of the effect of rare earth (RE) addition on the microstructure and fractograph of the controlled rolling low carbon MnMoNb ferrite steel. Further refinement of grains as well as the decrement and refinement of bainite and martensite, hence, a mixed structure of equiaxial and acicular ferrite in the steel may be achieved by RE addition. The ultrairdcrostructural RE inclusion, which is able to contribute RE-containing steel for refinement of grains in the process of controlled rolling, is observed on the fracture surface. Therefore, a satisfactory combination of mechanical properties, such as improved strength and impact toughness, may be approached for the steel containing RE addi(?)ion.