DAIDO STEEL
G-coat
Titanium and Titanium Alloy Welding Wire for
Gas Metal Arc Welding
G-coat - Titanium and Titanium Alloy Welding Wire for GMAW*
Introduction
The use of lightweight titanium parts in automobile and motorcycle exhaust systems is rapidly expanding in
order to meet the growing demand for improved fuel efficiency and design flexibility.
Welding of titanium and titanium alloy parts usually employs TIG (Tungsten Inert Gas) welding although low
throughput of TIG welding results in higher costs of such assemblies. A more desirable option is higher
efficiency MIG (Metal Inert Gas) welding. However, the addition of a small amount of oxygen into argon gas is
necessary in order to stabilize the welding arc and the oxygen reacts with the titanium to form hard and brittle
oxides that deteriorate the welded joint integrity.
Daido Steel has solved this problem with the development of a new class of welding wires, “G-coat”, which
enables high efficiency MIG welding of titanium and titanium alloy parts using inert gas only (Ar or He),
without the addition of oxygen.
“G-coat” titanium and titanium alloy welding wire, with its special coating , exhibits many positive qualities.
Some of these qualities are outlines below.
(1) The most suitable for GMAW
(2) Excellent arc stability in inert shielding gas (Pure Ar or He)
(3) Good wire feedability
(4) Smooth and uniform surface weld bead
(5) Low spatter
(6) Provides good mechanical properties in the Welded joints comparable with the base metal
Table 1 SPECIFICATION OF PRODUCTS
Chemical Composition (mass%)
Equivalent Standards
Trade Name
O
H
N
C
Fe
Al
V
Ti
AWS
JIS
WT1G
≦ 0.10
≦ 0.008
≦ 0.02
≦ 0.02
≦ 0.20
---
---
Bal.
ERTi-1
YTW270
WT2G
≦ 0.15
≦ 0.008
≦ 0.02
≦ 0.02
≦ 0.20
---
---
Bal.
ERTi-2
YTW340
WT3G
≦ 0.25
≦ 0.008
≦ 0.02
≦ 0.02
≦ 0.30
---
---
Bal.
ERTi-3
YTW480
WAT5G
≦ 0.20 ≦ 0.0125 ≦ 0.05
≦ 0.10
≦ 0.30
5.50~
6.75
3.50~
4.50
Bal.
ERTi-5
YTAW6400
WAT5EG
≦ 0.13 ≦ 0.0125 ≦ 0.05
≦ 0.08
≦ 0.25
5.50~
6.50
3.50~
4.50
Bal.
ERTi-23
YTAW6400E
* GMAW: Gas Metal Arc Welding also known as MIG (Metal Inert Gas) Welding
1. Weld Bead (Bead on Plate)
Smooth and uniform surface weld beads can be obtained using G-coat.
G-coat
20mm
Conventional
20mm
Fig.1 Weld Beads
Table 2 Welding Conditions
Wire
Diameter
AWS
JIS
1.0mm
ERTi-2
equiv.
YTW340
equiv.
Welding
Arc
Current Voltage
100A
20V
Welding
Speed
Shielding
Gas
60cm/min
Pure Ar
Base metal
ASTM
JIS
Thickness
B265 Grade2
equiv.
TP340
1.5mm
2. Wire Feedability
Required feeding load of G-coat is extremely low and stable even with metal conduits.
Feeding Load (N)
G-coat
Feeding time (sec)
Feeding Load (N)
Conventional
Feeding time (sec)
Fig.2 Wire Feeding Load
Table 3 Test Conditions
Wire
Diameter
AWS
JIS
1.0mm
ERTi-2
equiv.
YTW340
equiv.
Wire Feeding Rate
Arc
Metal Conduit
4.5m/min
None
2.0m Length (for steel wire)
3. Tensile Properties of Deposited Metal
Deposited metal with G-coat wire has the same tensile strength as that with
conventional MIG wire or TIG welding, as does the base metal.
Table 4 Welding Conditions
Wire
Sample
Diameter AWS
JIS
ERTi-1
equiv.
G-coat
Welding Arc
Welding Shielding
Current Voltage Speed
Gas
YTW270
equiv.
1.0mm
Conventional
150A
Base Metal
ASTM
JIS
B265 Grade1
equiv.
TP270
22-23V 40cm/min Pure Ar
12mm
ERTi-5 YTAW6400
equiv.
equiv.
B265 Grade5
TAP6400
equiv.
ERTi-1
equiv.
B265 Grade1
equiv.
YTW270
equiv.
1.0mm
150A
TP270
22-23V 40cm/min Pure Ar
ERTi-5 YTAW6400
equiv.
equiv.
12mm
B265 Grade5
TAP6400
equiv.
Test Piece
12mm
60°
4mm
(*) 8 Layer 21 Pass Welded
10mm
500
1000
Gco
at
MI
G
MI
G
e
Ba
s
TI
G
Co
nv
en
ti
on
MI
G
Me
ta
l
0
we
ld
in
g
0
al
200
Gco
at
100
ERTｉ-1
ERTｉ-5
Fig.4 Tensile Strength of Deposited Metal
Me
ta
l
400
Ba
se
200
600
we
ld
in
g
300
800
TI
G
400
Co
nv
en
ti
on
al
Tensile Strength (MPa)
1200
MI
G
Tensile Strength
(MPa)
Fig.3 Position of Tensile Test Piece sampled from Deposited Metal
600
Thickness
4. Mechanical Properties of Butt Joint in Thin Plates
Butt joint with G-coat has good mechanical properties comparable to the base metal.
Table 6 Welding Conditions
Wire
Diameter
Welding
Arc
Current Voltage
AWS
JIS
ERTi-1
equiv.
YTW280
equiv.
ERTi-5
equiv.
YTAW6400e
quiv.
1.0mm
100A
20V
Welding
Speed
60cm/min
Base Metal
Shielding
Gas
ASTM
JIS
B265 Grade1
equiv.
TP270
Pure Ar
Thickness
1.5mm
B265 Grade5
equiv.
TAP6400
Table 7 Results of Tensile Test and Face Bend Test of Welded Joint
Tensile Test
Face Bend Test
Sample
Tensile Strength
Fractured Portion
R=2t (3mm), 180°Bend
ERTi-1
406MPa
Base Metal
No Cracks Observed
B265 Grade1
390MPa
-
No Cracks Observed
ERTi-5
1074MPa
Heat Affected Zone
-
B265 Grade5
1071MPa
-
-
Weld Metal
Penetrant Testing
20mm
5mm
Fig.5 Appearances of Tensile Test Piece and Face Bend Test Piece of Welded Joint (ERTi-1)
( Note: Excess weld metal removed by grinding)
5. Microstructure of Weld Metal
Microstructures of weld metal with G-coat show close similarities to those with conventional wire.
Conventional
Center
Surface
G-coat
200µm
Fig.6 Microstructures of Weld Metal (ERTi-1)
6. Hardness of Weld Metal
Hardness of weld metal is no difference when comparing G-coat and conventional wire.
○
□
●
■
ERTi-1
ERTi-5
V direction
G-coat
Conventional
H direction
G-coat
Conventional
Direction of Measurement
500
500
H direction
450
400
400
350
350
300
Base
250 Metal
200
Base
Metal
Weld Metal
150
Hardness（HV）
Hardness（Hv）
450
300
250
200
150
100
100
50
50
0
-4.0
V direction
0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
Distance from center of weld bead(mm)
4.0
0
0.5
1
1.5
2
2.5
3
Distance from surface of weld bead(mm)
Fig.7 Hardness Distribution of Weld Metal
3.5
4
7. Application Examples
Sound and deep-penetrated weld bead is possible when using G-coat.
5mm
10mm
Fig.8 Fillet Welded Joint of Thick Plates
Table 8 Welding Conditions
Wire
Base Metal
Welding Current
Diameter
AWS
JIS
1.2mm
ERTi-2
equiv.
YTW340
equiv.
Arc Voltage
Welding Speed
ASTM
230A
21V
30cm/min
B265 Grade2
equiv.
20mm
JIS
Thickness
TP340
16mm
2mm
Fig.9 Weld Joint of Tube and Flange
Table 9 Welding Conditions
Wire
Base Metal
Welding Current
Diameter
AWS
JIS
1.2mm
ERTi-2
equiv.
YTW340
equiv.
Arc Voltage
Welding Speed
ASTM
150A
22V
30cm/min
8. Patent
Patents pending (JPN,Others)
B265 Grade2
equiv.
JIS
Thickness
TP340
Tube: 4mm
Flange: 10mm