The weld deposit metal is formed by a complicated process. Assuming the carbon content of the deposit metal to be about 0.15%, the weld molten metal solidifies in peritectic reaction, and it transforms into austenite. Then, the ferrite grain precipitates at the austenite grain boundary. Therefore, there are relations between the primary structure and the secondary structure.
Authors already reported about the relation between the heat input and the primary structure. This time, they researched the relation between the primary structure and the austenite grains and the ferrite grains. Besides, the influence upon the mechanical property was investigated.
The conclusions are summarized as follows;
(1) The precipitation of the austenite grain is controlled by the primary structure, hence it forms a counter cone like a cellular structure.
(2) Austenite grain growth mainly occurs at above 1200°C.
(3) The ferrite grain precipitates at the austenite grain boundary. So, it can be said that the weld deposit metal is the assembly of a counter cone surrounded by the ferrite grains.
(4) When the mass of the deposit metal is large, it exhibits mechanical anisotropy in the Charpy inpact test.
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