delimited, pointed and long.
The ratio (width of wedge base line to wedge height) in the web should
be 1:3. The wedge height, depending on the extent of deformation,
should be selected in such a way that the wedge tip only just exceeds
the neutral axis of the profile. In this way, the stiffness of non-heated
material zones is used as a means of restricting expansion. If a greater
deformation is required, the wedge shape is drawn further across the
neutral axis. The width-height ratio remains 1:3. In this case, additional
restriction of the expansion process would favour deformation.
The shape of the heat wedge must be drawn on both sides of the
component to ensure, as far as possible, that both sides of the wedge
volume are heated exactly opposite each other
If heating is displaced, a wedge-shaped heating zone cannot be
achieved, only an undefined heated workpiece area. This, in turn, does
not lead to the desired straightening result.
The procedure for profiles is the same. The heat wedge is drawn on
the component. Heating begins in the web from the fillet towards the
wedge tip. The dwell time for heating the wedge tip must be very brief
so that the heat cannot spread too much, in contrast to the fillet. The
wedge base line determines the width of flange heating. The fillet area
of profiles, the area in which the most material accumulates, is heated
most effectively from the top side of the flange (Figure 17).
To prevent steps between the heated flange zone and the non-heated
flange areas, it is recommended that the flame temperature be kept
somewhat lower in the edge zone of the heated flange.

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