制御圧延材で析出する Nb 化合物とその組成に及ぼす鋼の化学成分の影響

概要

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The effects of C, N and Nb contents and processing variables on the chemical compositions of Nb compounds formed in controlled rolled HSLA steel plates were systematically investigated. Identification of Nb compounds and determination of X and Y values in NbCxNy were performed by chemical analysis and X-ray diffraction on the precipitates extracted by electro-chemical method. Nb compound formed in commercial HSLA steels was δ phase of NbCx or NbCxNy. NbCx with X value of 0.84 to 0.86 was formed in the steels with the very low N content or with the addition of small amount of Ti. X+Y value in NbCxNy was almost constant in around 0.83 to 0.86, while X or Y value was widely varied depending on N content in steel. The δ′ phase of NbN was formed exceptionally in the high N-Nb steel containing an extreamly low carbon content less than 0.003%. The reduction of slab reheating temperature in controlled rolling or post heat treatment increased the amount of AlN precipitates, resulting in the decrease of N content in NbCxNy. The map describing formation of various Nb compounds and their chemical compositions was drawn based on C/Nb and N^*/Nb mole ratio in steel, where N^* was free nitrogen not combined with Al or Ti.
社団法人日本鉄鋼協会の論文
1987-05-01