Effect of Titanium Addition on As Cast Structure and Macrosegregation of High-Carbon High-Chromium Steel

摘要

In casting heavy ingots of high-chromium high-carbon cold work steels, macrosegregation develops in the center of the ingot, causing difficulties during subsequent hot working. Heat transfer and solidification of an industrial scale high-carbon high-chromium steel ingot was simulated and thereafter a laboratory scale representative ingot was designed to model the solidification of the industrial scale ingot. Titanium in the range of 0.3-1% was added to the high-chromium high-carbon (12%Cr-2%C) steel during melting process. Microstructures, macrosegregation and phase formations were studied using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, wave dispersive X-ray spectrometry, optical emission spectroscopy, and X-ray diffraction. Addition of 0.3% titanium was sufficient to diminish the macrosegregation; however it did not have a significant effect on the grain size. Addition of 0.7 and 1% titanium had a substantial effect on grain size in the longitudinal direction and refined the primary carbides structure. The formation of small TiC carbides that precipitated before solidification of liquid iron acted as nuclei for primary pro-eutectic austenite grains.