Ni含有鋼の冷却特性に及ぼす酸化スケールの影響
1997 年 83 巻 10 号 p. 611-616
詳細
1997 年 83 巻 10 号 p. 611-616
The effect of surface oxidation on heat transfer of a low-alloy steel with Ni of 0-4.9mass% was investigated. Cooling curves were obtained by means of 10mm thick plate heated and oxidized by induction heating in air at 1473K for 300 sec. The results obtained are summarized as follows.
Heat transfer properties change noticeably depending on Ni content. As the Ni content increases, transition boiling begins at higher temperature. At temperatures below the breakdown temperature of film boiling, i.e. the lower limit temperature of film boiling, the heat transfer coefficient has risen with Ni increase, while above that temperature it is independent of Ni content.
During the heating and cooling scale layer adheres to Ni bearing steel surface. The adherent scale layer becomes thicker with increase in Ni content.
The scale layer consists of oxide and Ni enriched metal, and seems to be a subscale peculiar to Ni bearing steel. Change of the heat transfer properties depending on Ni content is due to the adherent scale layer. The scale layer has low effective thermal conductivity, and produces a steep temperature gradient in it during cooling. As a result true surface temperature is lowered, and transition boiling begins at higher temperature.
