3.3 Alloyed steel
TIG welding may be used for welding alloy steels
but because deposition rates are low, it is usually
only used for welding sheet and thin sections
for high quality applications, small components,
and root passes of multipass butt joints in plate
and pipe.
Standard DC TIG equipment is normally suitable
and DCEN polarity is usually chosen to provide
good workpiece heating. Tungsten electrodes
with additions of thorium oxide, cerium oxide, or
lanthanum oxide are used for welding steel and
they give good arc stability.
Only inert or reducing gases should be used for TIG
welding and pure argon is normally recommended
as the shielding gas for welding alloy steel.
Filler rods are usually selected to match the
chemical composition and the mechanical
properties of the parent plate. The weldability of
the steel may impose restrictions on the choice of
filler rod.
Alloy steels with high carbon equivalents are
hardenable, and fast cooling will produce a hard
HAZ and this is liable to result in hydrogen cracking.
This form of cracking can be prevented by use of
preheat and suitable welding procedures.
General welding parameters
Plate thickness
(mm)
Tungsten
electrode (mm)
Gas flow
(l/min)
Current (A)
Consumable
size (mm)
1.0
1.0
3 – 4
30 – 60
1.0
1.5
1.6
3 – 4
70 – 100
1.5
2.0
1.6
4
90 – 110
1.5 – 2.0
3.0
1.6 – 2.4
4 – 5
120 – 150
2.0 – 3.0
5.0
2.4 – 3.2
4 – 6
190 – 250
3.0 – 4.0
6.0
3.2 – 4.0
5 – 6
220 – 340
4.0 – 6.0
8.0
4.0
5 – 6
300 – 360
4.0 – 6.0
12.0
4.8 – 6.4
5 – 7
350 – 450
4.0 – 6.0
Polarity: DC –
3.0 TIG Welding of Materials
Plate
thickness
(mm)
Joint
type
Number
of passes
Tungsten
electrode
size (mm)
Consumable
size (mm)
Current (A)
Welding
travel
speed
(cm/min)
Gasflow
(l/min)
0.8
Fillet
1
1.6
1.5
70
30
5
1.0
Fillet
1
1.6
1.5
90
30
5
1.5
Fillet
1
1.6
2.0
110
30
6
2.0
Fillet
1
2.4
2.5
130
25
6
1.0
Butt
1
1.6
1.5
80
20
6
1.5
Butt
1
1.6
2.0
120
20
7
2.0
Butt
1
2.4
2.5
140
20
7
Shielding gas: Argon, Consumable ER70S-6, Position: Downhand, Polarity: DC–
3.2 C-Mn steel
TIG welding may be used for welding carbon steel
but because deposition rates are low, it is usually
only used for welding sheet and thin sections
for high quality applications, small components,
and root passes of multipass butt joints in plate
and pipe.
Standard DC TIG equipment is normally suitable and
DCEN polarity is usually chosen to provide good
workpiece heating.
Only inert or reducing gases should be used for TIG
welding and pure argon is normally recommended
as the shielding gas for steel.
Filler rods are usually selected to match the
chemical composition and the mechanical
properties of the parent plate. The weldability of
the steel may impose restrictions on the choice of
filler rod.
Steels with carbon contents above about 0.3% are
hardenable, and fast cooling will produce a hard
HAZ and this is liable to result in hydrogen cracking.
This form of cracking can be prevented by use of
preheat and suitable welding procedures.
3.1 Application summary
Material
Type of current
Polarity
C-Mn steel
Direct current (-)
DC negative
Alloyed steel
Direct current (-)
DC negative
Copper and Cu alloys
Direct current (-)
DC negative
Nickel and Ni alloys
Direct current (-)
DC negative
Titanium and Ti alloys
Direct current (-)
DC negative
BOC Smootharc TIG 185 Operating Manual
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BOC Smootharc TIG 185 Operating Manual
Содержание Smootharc TIG 185 DC
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