Showing papers in "Tetsu To Hagane-journal of The Iron and Steel Institute of Japan in 1970"

Structure of Grain Boundary

Abstract: 金属材料は単結晶で利 用 され る場合 と多結晶 で用い ら れ る場合の2つ がある.単 結晶 として実用 され るものは 磁性材料,半 導体材料,ウ ィス カーなどの特殊材料が近 年著 しく発展 して きているが,こ れ らについては結晶粒 界がないので,結 晶 粒界の構造は問題 とな らない.し か し一般 の工業材料はほ とん ど多結晶体 として利用 され る ので,結 晶粒界はそ の材料の性質 に大 きな影響を及ぼす ものであ る.特 に塑性加工に よる粒界の変化,そ の後の 焼鈍 による再結晶 ならびに結晶成長,こ れに伴 う集合組 織お よび機械的性 質,物 理的性 質の変化は,金 属 物性上 もまた実用材料 の観点か らも重要 であって,こ れ は帰 す るところ結晶粒界の問題である.こ の結晶粒界の問題 も その内容は多方 面にわた るのであるが,今 回は結晶粒界 の構造に主眼 をおいて解説 を試み ることとしよう. つ ぎに結晶粒 界の話に入る前 に,結 晶粒界が全般の結 晶界面の中での位置づけを把握 してお く必要があ る.結 晶界面 とは結晶の一部分 と他の部分 とが,2次 元的に何 らかの性 質において異 なる部分に分け られ るとき,そ の 境界を結晶界面 と称するものであ る.他 方結晶欠陥の立 場において,大 きな分類 として点欠陥,線 欠陥,面 欠陥 の3種 類があ るが,結 晶 界面はその内の面欠陥に属す る もので ある.こ の ような結晶界面は,具 体的にはつ ぎに 示 すよ うに多 くの種類 が あ り,そ れぞれ特徴を有 してい る. (a) 隣接相の結晶構造が異な る場合 (i) 整合界面(coherent boundary)隣 接相の結晶方 位が一定の関係 にある. (ii) 非整合界面(incohercnt boundary)隣 接相の結 晶方位が無関係 (b) 隣接相が同一結晶であ る場合 (i) 小 傾角粒界(low angle grain boundary)亜 粒 界(subgrain boundary)隣 接相の結 晶方位差が僅少 であ る結晶粒界,通 常 θ<15 (ii) 大傾角粒界(high angle grain boundary)隣 接 相 の結 晶方位差が大 きい結晶粒 界 (iii) 双晶界面(twin boundary)隣 接結晶が特定の対 称関係を満 足す る. (iv) 積層欠陥(stacking fault)隣 接結晶が方位は同 一で あるが,原 子の積み重ね順が異 なる. そ の他結晶の表面その ものは気体 と結晶 との界面であ り,ま た結 晶的 には全 く同一であるが磁化の方向の異な るような界面すなわち磁壁な ども結晶界面の特別な場合 として考 える.

The Role of Rust Layers on the Corrosion Process of Steels in the Atmosphere

Abstract: The Role of Rust Layers on the Corrosion Process of Steels in the Atmosphere Hideya OKADA, Yuzo Hosor, and Hiramitsu NAITO Synopsis: An electrochemical investigation has been made of the corrosion process of the steels rusted in the atmos— phere, in order to reveal the role of the rust in the atmospheric corrosion. The cathodic reaction of the rusted steel is found to be mainly consisted of the reduction of FeOOH (brown rust) to Fe3O4 rather than the reduction of dissolved oxygen, and the anodic reaction is the dissolution, of iron. In the case of low alloy steels alloyed suitably for atmospheric corrosion resistance, both anodic and cathodic reactions are remarkably suppressed by the formation of protective rust layer after exposure to the atmosphere for more than about 3.5 years. Ancdic reaction is prevented due to masking of active sites on the steel surface by the formaticn of dense arnorplicus iron oxide layer and cathodic reaction is suppressed by increasing difficulty in the reduction of FeOOH. (Received July 31, 1969)

Simulation Experiment on Gas Flow Patterns in the Reheating Furnace

Abstract: Simulation Experiment on Gas Flow Patterns in the Reheating Furnace Bunsho HIRAOKA Synopsis: Lots of simulation have been applied to the iron and steel making processes and especially fluid flow models are helpful in investigating the gas flow in the furnace. The reconstruction of the three zone pusher furnace was planned to increase its heating capacity. Enlargement of the combustion space was aimed by raising the furnace roof and this also made it necessary to pursuit the most suitable position and direction of burners in each zone. In addition, the roof height at the nose of soaking zone and the preheating zone was discussed and the effect of piling up of scale on the gas flow was also considered. Then gas flow patterns in the furnace were examined under these various conditions. These tests resulted in the most desirable design of the furnace in its line and burner setting. The furnace was reconstructed satisfactorily according to these results. (Received Mar. 25, 1970)

Fundamental Study on the Viscosity Measurement of Molten Metals by Oscillating Crucible Method

Abstract: Synopsis: Knowledge of viscosity of liquid metals and alloys is valuable pratically and theoretically, and accurate data should be particularly important on the consideration of the structure of liquid metals and alloys. An accurate measurement of viscosity, however, especially on high temperature such as on liquid iron is quite difficult and most of the data having been obtained may be dcubtful in their reliability. For the purpose of carrying out precise measurement of viscosity of liquid metals and alloys at high temperature an improved apparatus for viscosity measurement by oscillating crucible method was made, and through the experiments using this apparatus some fundamental problems on the viscosity measurement were analytically examined and discussed. The main results obtained are summarized as follows: ( 1 ) From an analysis of the oscillation modes on distilled water, n-heptane and liquid mercury, it was concluded that oscillation periods shorter than about 4 seconds should not be employed for the measurement because of the occurrence of the irregular flow in liquid. The most reliable result was obtained at the periods of about 7 seconds on present apparatus. ( 2 ) The atmosphere used in the viscosity measurement is very important factor affecting the accuracy of the measurement especially at high temperature. Although Ar was inadequate for this purpose on account of its large disturbing effects on the oscillation, in He atmosphere these effects were remarkably small. Therefore, the use of He was considered to be preferable. ( 3 ) From a series of experimental analysis, it was confirmed that under the suitable experimental condition it was possible to measure the viscosity of liquid metals and alloys at high temperature with sufficient accuracy using the apparatus presented in this paper. (Received Mar. 19, 1970)