special - ALUMINIUM-Nachrichten – ALU-WEB.DE

ALUMINIUM SMELTING INDUSTRY
The specimens show the homogeneous welding
attainable and how tight the two parts are pressed
together. This improves the electric conductivity,
and it transfers heat better then than other joints
available on the market today.
studs, the anode yoke and rod is directed to
the automatic welding station. If the welding
station is occupied, the anode yokes and rod
wait at the intermediate storage zone. While
one robot handles the new stud, checks and
prepares it for a correct replacement and welding,
the other two robots execute the welding
operation simultaneously from both sides.
Then the already repaired anode yoke and
rod is returned into the system for rodding.
Safety system: The whole of HMR’s ASRL
is surrounded by a safety fence. Each robot
station has an additional safety fence. If anyone
opens a door in the fences, the system
stops robot movements momentarily. A separate,
moveable safety catch is placed around
the chain centrifugal blast cleaning station.
Samples of the stud bar cut by the saw. The quality
of the cut is very good and can be systematically
tested.
the saw cutting / welding area.
Saw: Thereafter the anode yoke and rod is
transported to the automatic saw station. Data
from the measuring station is transferred to
the cutting station, which performs cutting according
to the given information.
Welding station: After removal of a stud or
The photo shows two sliced part cut in the exact same cut
before welding. Second cut 10 mm below welding.
Performance, capacity and quality
HMR’s ASRL brings the studs distinctively to
the same condition as on a new anode yoke.
The operation provided by ASRL ensures in
a low electrical resistance of the joint thanks
to optimised cutting and welding procedures
developed by HMR and executed
reliably by the automated robotic
line.
The system has a repeatability
of < 0,1 mm (NB. depending on
anode rod condition) and a productive
capacity of ≤ 6 min. (NB.
depends on groove weld design,
number of studs per anode rod
and on conveyor speed). The
welding time is about four minutes
per stud.
It is quite important that the
cutting and welding area is kept
clean of bath, rust and iron scale contamination.
That is why a chain centrifugal blast cleaning
is a part of the ASRL system. This device prevents
bath, rust and iron scale from interfering
with welding, and it prolongs the life of saw
blades (40% alumina content in bath causes
rapid wear of saw blades). This cleaning allows
up to 800-1,000 studs cut to be obtained from
recommended saw blades.
However, one must bear in mind that the
quality of weld provided by ASRL depends
also upon external conditions. The most important
of these is that joint surfaces must be
clean and accurately machined. The studs cut
by the saw have a bright steel surface, which
is preferred for welding.
Author
Italo Dal Porto is senior engineer at HMR Hydeq
AS, based in Årdal, Norway.
Channel-type versus coreless induction furnaces
W. Spitz and C. Eckenbach, Marx GmbH & Co. KG
The company Marx gives an overview of
the different types of induction heating
units for melting, holding and holding/
casting furnaces. This paper focuses on
coreless inductors and on their advantages
over channel type inductors when
it comes to holding /casting of special
aluminium alloys. It illustrates and explains
this comparison for the case of a
holding/casting furnace in an aluminium
semi-fabrication plant in Europe which
was modified from a channel-type furnace
to a furnace with coreless inductor
technology. The paper gives technical
information comparing in detail the new
benefits, such as an increased service life
of the furnace of up to three years with
the crucible inductor. Specifically, this revamp
and upgrade of a 28 tonnes holding
and casting furnace with a power of 200
kW converted it to 40 tonnes and 450
kW, as demonstrated by construction and
field results.
Basically two different kinds of induction furnaces
are used for melting, holding and cast-
ing of metals: the channel-type induction furnace
and the coreless type induction furnace.
The channel-type induction furnace consists
of a refractory lined furnace body made
of steel to which one or several channel-type
inductors are flanged for heating the metal.
Due to effects like thermal conductivity and
buoyancy of the hot melt, in most cases the
channel-type inductor is flanged at the bottom
of the channel type furnace body. This results
in the typical design of a small to mediumsized
channel-type melting furnace like that
shown in Fig. 1.
46 ALUMINIUM · 1-2/2013