FastROOT - Kemppi

Program
Fe -group
Wire (mm) Material Shielding gas Backing
903 1 Fe Ar+18%-25% CO2 904 1,2 Fe Ar+18%-25% CO2 913
Ss -group
1 Fe CO2 923 1 SS-316 Ar+2%CO2 Ar
924 1,2 SS-316 Ar+2%CO2 Ar
933 1 SS-316 Ar+30%He+1%02 Ar
934 1,2 SS-316 Ar+30%He+1%02 Ar
Figure 7.
Synergic curves included in a standard delivery.
6
Kemppi ProNews 2 • 2006
Figure 8.
T-joint, 1/2V-groove 45 o , root run welded in PG
position and fill-up run in PF position, air gap 5 - 6
mm, welding current 146A, voltage 16V, speed 100
mm/min, energy E=1.4 kJ/mm and heat input Q=1.1
kJ/mm
Figure 9.
Butt joint, V-groove 60 o , root run welded in PG
position and fill-up run in PF position, air gap 3 - 4
mm, welding current 130A, voltage 16V, speed 138
mm/min, energy E=0.9 kJ/mm and heat input Q=0.72
kJ/mm
Figure 10.
Butt joint, V-groove 60 o , root run welded in PE
position and fill-up run in PE position, air gap 3 - 4
mm, welding current 110A, voltage 14V, speed 76
mm/min, energy E=1.3 kJ/mm and heat input Q=1.0
kJ/mm
Various techniques can be used when welding
the root pass. The FastROOT process allows for welding
the pipe in the downward direction from 12 o’clock
to 6 o’clock or from 12 o’clock to 9 o’clock, while a regular
short-arc process allows for upward welding from 6
o’clock to 9 o’clock (see Figure 4). In the right-hand side
of the fi gure, the FastROOT process is used for welding
from 12 o’clock to 6 o’clock by moving the torch at
a 10–15-degree angle. In the left-hand side of the fi gure,
the FastROOT process is used for welding from 12
o’clock to 9 o’clock and a normal short arc is used for
welding from 6 o’clock to 9 o’clock. The welding machine
also allows for welding so that the pipe is rotating
and the torch remains, for example, at 2 o’clock.
The most important objective in the motion technique is
to maintain the arc on top of the weld pool and not on its
side (see Figure 6). There is suffi cient power in the arc
to make the fi ller wire push through the weld pool at the
sides, causing root-side spatter. The arc must be kept on
top of the weld pool during the oscillation. The welder
should not wait at the sides; instead, the direction of motion
must be changed immediately after the oscillation
ends. The oscillation is faster than in regular vertical up
short-arc welding. The FastROOT process allows for
welding without the oscillation. This increases the travel
speed but the weld run surface will not have as smooth a
shape as with the oscillation technique.
Applications of the process
The FastROOT process has been developed particularly
for root pass welding but can also be used for thin
sheet welding. The most commonly welded materials
are structural and stainless steels. Figure 7 lists the
synergic curves included in a standard FastMig Synergic
welding machine delivery. In addition to these, it
is possible to create customer-specifi c curves designed
for various production needs in the machines. The fi rst
customer-specifi c curves have been created for ferritic
stainless steel EN 10088 1.4539 -904 L and EN 10088
1.4464 – 22%Cr duplex steel. In addition to these, there
are stainless steel welding curves designed for various
shielding gas mixtures.
The fi rst users of the FastROOT process include Norwegian
companies in the offshore industry. The customers
have characterised the process as easy to use and
adjust. The spatter-free results in welding pipe steel has
also received praise. The process is currently in daily use
in the Ormen Lange project in Norway. It is the secondlargest
marine gas fi eld project with the greatest demand
for pipelines in the world.
Offshore customers had welding tests carried out on
the process using different types of joints and welding
parameters. The test results and welding parameters are
presented in fi gures 8-10.