Microalloying and Precipitation in Cr-V Rail Steels
Abstract:
A STUDY OF ALLOYING EFFECTS in Cr-V rail steels has been carried out to determine the microstructural strengthening mechanisms. The laboratory steels investigated were based on the commercial 1% Cr rail steel chemistry (0.75C - 0.8Mn - l.25Cr - 0.30Si), and represented two levels of nitrogen (nominally 0.007 and 0.015 wt %), and two types of deoxidation practice. It is found that vanadium microalloying produces a yield stress increment of approximately 90 MPa for low nitrogen steels and 140 MPa for high nitrogen steels. This strengthening effect appears to saturate at approximately 0.15 wt % vanadium, with no further strength increase for higher vanadium concentration. The hardness and UTS exhibit the same variation with vanadium content as the yield stress. There is no consistent effect of aluminum content (deoxidation practice). Several distinct precipitate morphologies, a wide range of precipitate sizes and a non-homogeneous distribution of precipitates are observed. There is also significant partitioning of V, Cr and Mn to cementite. It is suggested that an increase in the amount of coarse austenite- nucleated V(C,N) and possibly other coarse precipitate modes is responsible for the saturation of the vanadium strengthening effect.
Keywords:
vanadium, rail steel.
Author:
D. E. Parsons. T. F. Malis, J. D. Boyd
Affiiation
PMRL, CANMET, Energy Mines and Resources, Ottawa, Canada
PDF:
Source:
Vanadium Structural Steels - Reprint of papers on vanadium steel from the proceedings of “ASM HSLA Steels Technology and Applications Conference, Philadelphia, USA, Oct., 1983, pp.249-256
PDF Preview:
