(57) 1. Method for making an expansion formed at the end of metal bars (1) of steel, such
as a conical expansion (10) formed at the end of concrete anchors, in which method
- the end portion (4) of a bar (1) is heated in a controlled manner by starting the
heating from a point (6) of said portion (4) opposite to the bar end (5) and increasing
the heating to a temperature rising towards the end (5) of the bar, and
- the heated bar (1) is locked immovably in place and it is compressed from the bar
end (5) disposed at a distance from a mould/boss (2), starting with a press plate
(3) or a similar pressing element towards the mould/boss (2), thus causing, due to
the temperature differences occurring between different parts (5, 6) of the end portion
of the bar, an upsetting process to begin from the hotter end (5) of the bar (1) and
to advance towards the bar portion (6) of falling temperature, especially creating
conditions for optimal shaping of the end portion (4) of the bar.
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