Operation
43
6.7
Connecting the earth cable.
Warning!
Chapter 6.2; Electrical Hazard. Ensure that the welding current cannot
flow through chains of lifting appliances, crane cables or other electrically
conductive components.
Chapter 6.2, Electrical Hazard. Ensure that the earth cable is connected
to the workpiece as close as possible to the welding position. Earth
connections that are at a distance to the welding operation reduce
effectiveness, and increase the risk of electric shocks and stray currents.
6.8
Practical hints for use.
Practical hints for use listed below are only able to portray an overview of the
various applications of REHM
TIG welding units. In the event of questions
concerning special welding jobs, materials, inert gases or welding equipment,
please refer to appropriate technical literature or manufacturer’s
recommendations.
For TIG welding, a distinction is drawn between materials that can be welded
using DC and those which can be welded using AC. DC can be used to weld
Copper, Nickel, Titanium and their alloys as well as mild steel, low and high-
alloyed. AC is generally used to weld Aluminium and its alloys.
Various tungsten electrodes are offered and used for TIG welding. The difference
lies in the level of oxide additions and in the oxides used. The compositions are
listed in EN 26848 and generally consist of Thorium oxide, Cerium oxide,
Zirconium oxide, or Lanthanum oxide. Advantages of oxide-enriched tungsten
electrodes have:
Improved ignition properties.
A more stable arc.
Higher current-carrying capacity.
Longer lifetime.
The relevant literature provides details of the most common electrode diameters
and their current-carrying capacity. Please note that the values given in this
literature have usually been established using machines that fall well short of the
balance range of the REHM TIG welding units. A suitable guideline is that for a
given electrode the current is too high if it forms droplets or assumes a broom
type structure. You can then choose between reducing the current or, in the AC
mode, increase the negative proportion of the wave balance.
When DC welding, the tip of the electrode should be a point.
With the REHM TIG welding units, a pointed electrode may also be used in AC
mode with balance settings in the minus range. This has the advantage that the
arc becomes even more concentrated and effective. In most cases, the welding
speed is increased as a result.
Special care and attention should be taken when grinding tungsten electrodes,
always use a protective mask and eye shields. In addition a suitable dust
extraction unit must also be used to protect the operator for the grinding dust,
which are dangerous if inhaled.
Weldable materials
Tungsten
electrodes
