高張力鋼熱影響部 微視組織의 類別 = Classification of Microstructure in HAZ of Low Alloy Steel

다국어 초록 (Multilingual Abstract)

The assessment of the toe HAZ fracture toughness is one of the most troublesome problems to resolve because the fracture toughness depends to a large extent upon microstructural gradients such as variations of the microstructure and the grain size in the HAZ and because such microstructural characteristics are directly influenced by the thermal cycle during welding.
The aim of the present study is to classify metallurgically the distribution of the constituents of microstructure in the HAZ by measuring Vickers microhardness.
The metallurgical observation and microhardness measurement for the toe HAZ of 60㎏/㎟ low alloy steel, which was submerged are welded as bead-on-plate, were carried out.
The experimental results were summarized as follows;
There is a linear relationship between the ratio of hardness Hv/(Hv)_M (Hv:Vickers hardness, (Hv)_M : Vickers hardness of 100% martensite) and the area percentage of their structural constituents, and it is independent on chemical composition of materials.
It was concluded, consequently, that the transformation behavior for the structure of other 60㎏/㎟ low alloy steel in the HAZ and the ratio of mixture of structural constituents in its every position can be quantitatively classified by the ratio of microhardness Hv/(Hv)_M.