86
TUBE PRODUCTS INTERNATIONAL March 2014
7-11 April 2014
For TIG/plasma applications, in-line
control of penetration is possible.
Unsymmetrical penetration is detected,
which can also be caused by arc
deviations.
The optics developed for laser welding
processes allow the recognition of pores
and ‘out-of-positions’ of 5/100mm
only from the temperature field. All
systems evaluate the welding quality
automatically and enable universal
documentation of the temperature
fields.
Hoesch Schwerter Profile GmbH
Germany
3G25
Hoesch Schwerter Profile develops
products in collaboration with specific
fields of industry and customers.
Modern power stations and industrial
plants are two areas where special steel
solutions are used that are required to
withstand extreme loads.
Extruded tubing with internal and external
layer
The classic seamless steel tube for
pressure vessels represents a key
construction element in the building of
thermal plants. The requirements for
boiler construction steels become more
exacting if, instead of conventional
boiler fuels such as coal, oil or gas,
other sources of energy are used that
result in strongly corrosive combustion
products. For instance, boiler tubes
in a waste incineration plant are not
only exposed to thermal loads, but
are also subject to corrosive attack,
fundamentally triggered by the chemical
element chlorine.
For this specific application, the
conventional boiler tube used in plant
construction with its proven component
strength was equipped with a ‘coating’
using a corrosion-resistant austenitic
material. The intention behind this
combination of materials is to allow
the carbon steel to handle the thermal-
mechanical load on the tube, while
the austenite provides protection
against corrosion from the prevailing
environment.
Clad pipes (where the corrosion-
resistant layer is applied to the tube
body by welding) have one or two layers
of corrosion-resistant outer covering,
approximately 2.5mm thick. This is
applied using fusion welding, which
creates overlapping welding beads.
During welding, there is an intermixing
of a few tenths of a millimetre between
the carbon steel and the austenite. In
metallurgical terms this is equivalent to a
‘dilution’ of the high-alloy layer material.
Since it is obtained via the liquid phase,
the layer material is characterised by a
casting structure typical of welding.
The development of composite tubing
pursued by Hoesch Schwerter Profile
GmbH was undertaken with the aim of
overcoming the known disadvantages
particular to clad pipes. The carbon
steel component and austenitic layer
of the extrusion billet are manufactured
in a common hot forming process at
around 1,150-1,250°C. The metallurgical
connection between the two materials
is achieved in the solid state using
pressure-accelerated solid state
diffusion. A diffusion zone approximately
10µm thick forms between the
materials, which is responsible for a
high-strength, oxide-free metallurgical
bond of materials.
The fine microstructure configuration
of the layer and base material is
preserved, with no variation in the
alloy concentration. Smooth surface
structures avoid deposition of corrosion-
promoting ash and salt particles from
the flue gas.
Special cross-section forms such as fin
tubes, omega tubes or double omega
tubes are possible. Cold bending is also
possible, since there is no cast structure
created by cladding.
HUS Ltd
Bulgaria
7C28
HUS Ltd, a Bulgarian steel products
manufacturer and distributor, is
launching a new steel tubes and
hollow sections production facility. The
factory spreads out over more than
200,000m
2
, with 60,000m
2
covered halls
for industrial production, heavy-lifting
cranes, administrative building and
other assets.
The initial tube products range from 10
to 219mm for round pipes; from 10x20
to 100x200mm for rectangular tubes;
and from 15 to 150mm for square tubes,
with thicknesses of up to 8mm.
Production capacity will be up to
12,000mt per month, planned to be
implemented in stages. The production
lines and machines are brand new,
corresponding to the latest technological
standards, and the welding equipment
is provided by EFD Induction.
The company was founded in 1990
and has experience in steel processing,
including electro-welded steel tube
manufacturing.
The establishment of the tube factory
is a logical course of action, expressing
• Alloy 200/201
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