PURPOSE: To improve the reliability of welding at a part where a packing member is hardly removed, by using a thin packing member which melts into a connection weld zone to form one body and then refins the melt-stuck metal.

CONSTITUTION: A thin packing member 8 is positioned to surround the connecting part of an incorporated pipe-plate. the packing member 8 is a ring of an about 1mm thickness and about 3mm breadth. When incorporated with melt-attached metal, such components for enhancint the connection strength as C, Si, and Mn are used as compounding materials. In this case, when the welding is worked from inside the pipe, the packing member 8 is molten into said metal. The packing member 8 is able to be positioned inside the pipe to weld from outside.