Welding Inspection & Metallurgy API ICP Self Study Notes

The metallurgy of each weld area is related to the base and weld metal
compositions, the welding process and procedures used. Most typical weld
metals are rapidly solidified and, like the structure of a casting described
earlier, usually solidify in the same manner as a casting and have a fine grain
dendritic microstructure. The solidified weld metal is a mixture of melted base
metal and deposited weld filler metal, if used. In most welds, there will also be
segregation of alloy elements. The amount of segregation is determined by
the chemical composition of the weld and the base metal. Consequently, the
weld will be less homogenous than the base metal, which can affect the
mechanical properties of the weld.