Titanium is difficult to weld due to its high reactivity, which can cause embrittlement. It requires shielding with an inert gas like argon to protect the weld area from oxygen and nitrogen in the atmosphere. Large assemblies may be welded out of chamber, but this requires careful shielding and protection from drafts. The document describes an automatic tube to tube sheet welding machine that welds titanium tubes to a tubesheet. It welds without filler wire inside a dust free enclosure, using a water-cooled welding head and power supply to provide inert gas shielding during the welding process. Testing of the welds includes visual examination, fluorescent penetrant testing, and vacuum testing.

1. 1
Welding of Titanium
- 4th most abundant metal & 9th industrial metal
- Excellent resistance to chlorine environment
Reactive metal;
- Oxidation temp. ~ 420 oC
- Requires shielding until weld metal temp. down to 420 oC
- Embrittlement due to Ti-carbide / Ti-nitride
- Corrosion due to Ti-oxide (atmospheric contamination)
“Titanium – Easiest metal to weld if earth atmosphere is ARGON”

2. 2
Cleaning;
- Acetone
- SS or Ti wire brush
Shielding;
- Ultra high pure argon (99.9998%)
- Weld metal sensitive to wind draft / atmospheric gases (O2, N2)
Welding can be done;
- In-chamber
- Out-of-chamber
Welding of Titanium

3. 3
Excellent Welds can be obtained in chamber
High reactivity to O2 and N2 makes Ti embrittled
Not always possible
→ limitation on visibility,
movement, accessibility
For large assemblies,
→ movement of job & re-purging
→ time consuming & expensive
Welding in chamber

4. 4
Ensure adequate shielding in Weld and HAZ
Trailing shield - required
Protection against drafts
Preferably; DUST FREE ENCLOSURE (DFE)
Out-of-chamber Welding

5. 5
Automatic Tube to Tube sheet Welding Machine
Machine supplier: Arc Machines Inc. (AMI)
Power Supply
Water Cooler
Welding Head
Welding set-up inside Dust Free Enclosure (DFE)

6. 6
Details of T # TS welding
Tubesheet - SB 265 Gr. 1
Tubes - SB 338 Gr. 2
Tube hole size - 22.53 mm
∆ pitch - 28.58 mm
Tube OD - 22.23 mm
Tube thk. - 0.51 mm
- 0.89 mm
No. of holes per Job = 38542
Welding without filler wire
AMI - Model 96 welding head + M207 Power supply
Gas chamber

7. 7
Features of Automatic Welding Machine
Power Supply – M207
Programmable and operational functions;
Pre-purge time 10 – 999 sec.
Post-purge time 0 – 999 sec.
Upslopw time 0 – 99.9 sec.
Downslope time 0 – 99.9 sec.
Primary current 3 – 150 Amps
Background time 3 – 150 Amps
Rotation start delay 0 – 99.9 sec.
Pulse mode setting On - Off
Primary pulse time 0 – 9.99 sec.
Background pulse time 0 – 9.99 sec.
Levels 1 – 99
Water Cooler
Power Supply

8. 8
Conti…
Weld Head – Model 96
(without the provision of filler wire)
- Can weld 12.5 mm to 50 mm tube OD
- Tubes can be Flush, slightly Underflush or Slightly projected
Purge chamber:
1) Weld head housing at the top
2) Clear (opaque) chamber at sides
3) Nose ring at the bottom
Forms enclosed space to provide inert
gas atmosphere to protect weld from
atmosphere during welding
2
3
1

9. 9
Welding in progress

10. 10
Testing requirement
- Visual examination
- Flouroscent penetrant examination
- Vacuum test

11. 11
Visual of Weld

12. 12
Colour identification for Visual examination of weld

13. 13
Flouroscent Penetrant Test