1. [ Hot wire - narrow gap welding ]
Z.I. du Bois Briand
2, rue Paul Beaupère
F NANTES
FRANCE
[ Hot wire - narrow gap welding ]
Hot wire rev 3

2. Hot wire narrow gap welding
Hot wire welding with narrow gap preparation permits :
Increase of productivity up to a factor of 9 compared to standard TIG welding
Maintain the best affordable quality produced by the TIG process

3. Hot wire narrow gap welding
Other advantages of the TIG hot wire process:
Can be used on root, filling and finish passes
As the TIG process, the TIG HW offers the great advantage to control separately the energy in the arc and the quantity of metal in the weld pool:
easy to control the starting and down slope stages
control of welding energy permits to weld delicate materials as duplex, super duplex, titanium…
fusion operations for repair are simplified

4. Hot wire welding principle
Hot wire technique
Hot wire welding principle

5. Welding deposit rates for TIG cold and hotwire
Narrow gap technique
Welding deposit rates for TIG cold and hotwire
Wide bevel /Building up
Position
Narrow gap 1G 2G
3G1
5GT (4G, 3G2)
TIG Cold Wire
(Kg/h)
TIG Hold Wire
0.5 to 1.0
0.5 to 0.7
3.5
2.5
1 to 1.5
0.3 to 0.4
0.5
0.4
2 to 2.5
1.5 to 2.0

6. Narrow gap technique
Influence of the variation of stick-out on the theoretical heating length of filler wire L1
L1.3
L1.2 H1
L set
Wire speed (m/mn)
HW current
(A)

7. Influencing parameters of TIG hot wire welding Influencing parameters:
Narrow gap technique
Influencing parameters of TIG hot wire welding
Influencing parameters:
(Except Vs = constant) h
Wire angle L1
Torche inclinaison angle
I arc
h (electrode/work piece)
gas (type)
Hot wire current, Wire speed and associated L1
Torch inclination angle
Filler wire / torch angle
Welding direction
Length h and L1 correspond to theoretical adjustment made before welding. Their adjustments characterise the mechanical parameters directly associated to the welding parameters

8. Hot wire Narrow gap technique Different type of narrow gap technique
Advantages
Disadvantages
Welding with tungsten oscillation
Welding with two passes per layer
Welding with one pass per layer
Good torch accessibility
Easy for wide range
Lower productivity
Sophisticated torch
Less side wall penetration
Two positions for the tungsten
Problem for AVC
Difficult in orbital configuration
High productivity
Easy to operate
Good side penetration
Less tolerance for the prep.
Sophisticated weld procedure
POLYSOUDE’S
SOLUTION

9. Surface comparisons between std and narrow gap bevel
Narrow gap technique
Surface comparisons between std and narrow gap bevel
60 mm 6°
Narrow gap bevel 6°
SNG = 1617 mm²
37°+10°
Compound bevel 37°+10°
SCB = 498 mm²
SNG
SCB
= 3.2

10. Welding procedure for hot wire narrow gap
Hot wire Narrow gap technique
Welding procedure for hot wire narrow gap
Base material
Weld material
Shrinkage
Operating weldability
Weld position
Joint configuration
(un-restrained shrinkage ?)
Groove design
(shape and tolerances)
Weld parameters
(for each sequence)
Groove width control (LB)
Pass thickness control
Weld configuration result
Weld test objective
Weld procedure

11. Definition of the bevel design
Narrow gap technique
Definition of the bevel design LB LB LB
 “LB” must be constant for the complete weld
 For orbital and fixed station welding: mm < LB < 10 mm
The groove angle is adjusted according to thickness, material and welding parameters

12. Definition of the bevel design (cont.)
Narrow gap technique
Definition of the bevel design (cont.) Th
 “Th” must be constant for the complete weld
 For orbital welding: mm < Th < 2.5 mm
 For fixed station welding: mm < Th < 3.5 mm
The wire preheating and wire speed is adjusted for a constant heat input (+/- 10%)

13. Different type of welding torches
Narrow gap technique
Different type of welding torches
PIPE THICKNESS
< 40 mm
> 40 mm
< 70 mm
> 70 mm
WP27 Weldcraft torch
WP27 Weldcraft torch with the narrow gap nozzle
Narrow gap toch (150mm & 200 mm)

14. Welding sequences Narrow gap technique S4: Cap sequence
S1a: Root
S1b: Root reinforcing (1 or 3 passes)
S2: Filler passes with high productivity
S3: Final passes
S4: Cap sequence
Cooling of side walls is lower (edge effect cooling), therefore heat input will be less
For reinforcement and cosmetic appearance
Each filler pass in the same condition
S5: Weld programs for repair according to the requirements of each sequences

15. Working scope of the camera
Welding cycle comparison
Welding cycle compari mm pipeson between TIG cold wire and TIG hot wire for 168 mm pipe :
Filler wire: 0.8 mm
Time for preflow of shielding gas, arc time and maintenance of shielding gas after a weld pass are taken into consideration. Time to re-coil hoses, to change electrode and to respect interpasses temperature (when applied) are not considered.
Working scope of the camera

16. Working scope of the camera
Hot wire welding procedure example
Working scope of the camera

17. Working scope of the camera
Narrow gap TIG welding
Application examples
Working scope of the camera

18. Working scope of the camera
Narrow gap TIG welding
Orbital TIG Hot wire welding Narrow gap (5GT)
TOSHIBA on site
Carbon steel STPG38
508 x 50 mm
356 x 54 mm
24 layers
Working scope of the camera

19. Working scope of the camera
Narrow gap TIG welding
TOSHIBA on site (cont.)
Working scope of the camera

20. Working scope of the camera
Narrow gap TIG welding
Orbital TIG Hot wire welding Narrow gap (5GT)
TODEN - Japan
508 x 70 mm
Working scope of the camera

21. Working scope of the camera
Narrow gap TIG welding
Fix station TIG Hot wire welding Narrow gap
HOLMING WORKS FINLAND
Carbon steel
280 x 100 mm
460 x 85 mm
Working scope of the camera

22. Working scope of the camera
Narrow gap TIG welding
Orbital TIG Hot wire welding Narrow gap
Application: 250 bars / 600°C
SIEMENS KWU
180 mm
X10CrMoVNb91
700 mm x 180 mm
Position 5GT
Total arc time: 40 hours
Working scope of the camera

23. Working scope of the camera
Narrow gap TIG welding
SIEMENS KWU (cont.)
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24. Working scope of the camera
Narrow gap TIG welding
SCHWING - Austria
Welding of Cardan shafts for concrete mixing vehicles
Material:
carbon steel / St 690.
Dimensions:
O.D.: mm
Wall thickness: mm
Length: mm
Equipment:
Power source: 600 PC TIG hot wire
Precision TIG Welding Lathe with AVC (control distance: 350 mm) with motorized, programmable AVC-slide running gear for the complete length.
Working scope of the camera

25. Narrow gap hot wire TIG welding: The solution for the best Quality with the highest productivity level !