| The
process commences with the formation of
welded mother tube on the tube mill from
imported and tested prime quality stainless
steel strips. The latest TIG multi electrode
welding technique is employed for superior
weld quality and 100% Fusion, with argon
purging, No filler metal added.
These mother tubes
are solution annealed at 1060 D. 1100 D.
C in continuous annealing furnace followed
by immediate quenching to prevent chromium
carbide precipitation.
Annealling of mother tuber ensures:
A) Removal of stress induced during tube
forming and cold drawing:
B) Sufficient ductility and softness for
cold drawing:
C) Transformation of the weld zone to austentic
nature,
D) Re crystallization of metallic grains
to original form and thereby improving corrosion
resistance.
During annealing, scales are formed on
the surface of the tubes. In order to remove
these, the tubes are pickled by immersing
into hot pickling solution made of nitric
acid, sulphuric acid and hydrofluric acid.
The tubes are then coated with proper lubricant
and then cold drawn over a drew bench:
1) To vary the metallurgical structure and
restore the properties to the parent material:
2) To achieve a tube having closer dimensional
tolerances:
3) To achieve a tube having closer dimensional
tolerances:
4) To produce tubing of smaller size and
wall thickness.
5) To reorient the grain structure of weld
portion with that of the parent material
and
6) To remove/minimize the internal bead.
Drawing is followed by subsequent annealing
and pickling to restore the properties of
the entire tube to that of the parent material.
The tubes are then passiated to impart extra
corrosion resistance. Thereafter every tube
is electrically marked with material grade,
size and manufacturing standard. |
Manufacturing Process