軟鋼電弧熔接部に表れる線状組織の研究(第 1 報) : 線状組織の性質と生成に及ぼす冷速却度の影響

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Arc welding technique has reached a considerable stage of development and is now extensively utilized. However even at present certain defects are found in the process. In order to increase the reliability of the arc welding process, we must make an effort to eliminate these defects and reduce their effects as much as possible by thorough and careful study. The occurrence of ice flower like structure is one of the serious defects which are apt to be found in welded parts. Particularly, it often appears in the welded part of thick plate. Ice flower like structure may be defined as follows : Ice flower like structure is formed by very fine columnar crystals, standing side by side, similar to ice flower in earth crevices, and it usually contains many micro-blow holes and fine particles of refractory material between the crystals. Ice flower like structure is often found in the fracture of deposited metal. Ice fllower like structure is generally formed by almost fin columnar crystals, having micro-blow holes and refractory oxide particles between their boundaries. An example is shown in Fig. 1. When the deposited metal is rapidly cooled, the fine columnar crystals are formed side by side, and the micro-blow holes are formed by the gas evolved from the deposited metal during solidification. The dispersed oxide particles in ice flower like structure are mostly refractory deoxidation products. From these facts, it is considered that the period of formation of ice flower like structure is during the solldification process of deposited metal. On cooling from molten state, the separation of gas and formation of stress of ice flower like structure are similar to white spot formation in ingot. But there is remarkable difference between the periods of their formation and the characteristics of their shapes. Ice flower like structure is different from fish eye in such points as the period of formation, location and shapes. The cooling velocity is closely connected with the volume of the deposited metals, which in urn is closely related with the formation of the ice flower like structure. when plenty of metal is deposited, the cooling velocity becomes comparatively low, accordingly ice flower like structure is not formed. On the other hand, when less metal is deposited, the cooling velocity becomes comparatively high, therefore ice flower like structure is formed. We examined the formation of ice flower like structure by the various experiments. As a result, we pointed out the fact that the cooling velocity is one of the factors of its formation.
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軟鋼電弧熔接部に表れる線状組織の研究(第 1 報) : 線状組織の性質と生成に及ぼす冷速却度の影響

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