PURPOSE: To manufacture the branch pipe in uniform thickness
with a high branch pipe part by pulling a burring punch out of a
prepared hole by heating the whole pipe blank and passing the
mandrel for straightening to the inner part by reheating the
pipe blank on the deformation of the pipe blank. CONSTITUTION:
In the case of forming the branch pipe part of H/d≥0.5 by taking
the height of the branch pipe part as H and the outer diameter
as (d), the oblong hole becoming a prepared hole is pierced at
the specified position of a pipe blank 2 to insert a burring
punch 3 into the inner part of the pipe blank 2. The part shown
by an alternate long and two short dashes line is then heated to
a work temp. and the branch pipe part 1 is formed by performing
burring by loading a specific work force on the burring punch 3
by an actuator, etc. In order to straighten the deformed pipe
blank 2 the mandrel 4 for straightening in complete roundness is
inserted into the pipe blank 2. The part shown by an alternate
long and two