Effects of rare earth addition on microstructure of C–Mn steel

Abstract

The microstructures were observed in C–Mn steel and statistical analysis of the inclusions produced when trace amounts of rare earth were added to the steel. The results show that the content of intragranular acicular ferrite decreased in the order of being treated with La+Ce/La/Ce in C–Mn steel after the treatment of different kinds of rare earths. The optimum mass ratio of La and Ce for La+Ce combined treatment is 3:1.The best incubation time after Le+Ce (3:1) treatment is 5 min. The size of inclusion nuclei favouring intragranular acicular ferrite nucleation concentrates in the range of 1–4 μm. The disregistries between rare earth inclusions and α-Fe are small, which plays an important role in rare earth inclusions inducing intragranular acicular ferrite nucleation.

Keywords:

• Trace rare earth treatment
• Microstructure
• Intragranular acicular ferrite
• Inclusion
• Heterogeneous nucleation