A TIG welded tube mill (Tungsten Inert Gas welded tube mill) is used for producing precision stainless steel tubes, especially for industries that demand high-quality welds, such as food processing, pharmaceuticals, instrumentation, and heat exchangers.
Unlike ERW mills that use high-frequency electric current, TIG welding uses a tungsten electrode and inert gas (argon) to form a clean, stable arc - ideal for thin-walled or small-diameter tubes, especially in stainless steel and non-ferrous alloys.
Step-by-Step
1. Raw Material: Stainless Steel Coil
Stainless grades: 304, 316, 321, etc.
Supplied as cold-rolled coil with precise surface and edge quality.
2. Uncoiling and Strip Feeding
Coil is fed into the tube mill via a decoiler.
A pinch roll feeder and leveler flatten the strip.
3. Strip Joining (Optional)
End shear and butt-weld join coils for continuous production.
Required when using an accumulator or looping pit.
4. Edge Trimming / Deburring (Optional)
Ensures smooth edges for better weld quality.
Important for thin-walled or food-grade tubes.
5. Forming Section
Strip passes through forming rolls to gradually bend it into a round tube.
Precise roll design avoids deformation and misalignment of the edges.
6. TIG Welding
The core step in this process.
Uses:
Non-consumable tungsten electrode for arc generation.
Argon or argon-helium gas as a shielding atmosphere to protect the weld.
Automatic TIG welding heads are mounted to ensure consistent heat and arc.
Welds are usually autogenous (no filler wire), especially for thin walls.
Key Features of TIG Welding in Tube Mills:
Low heat input → Minimal distortion.
Excellent weld quality and corrosion resistance.
No spatter, no oxide contamination.
Slow process compared to ERW but higher weld purity.
7. Weld Bead Control (Optional)
External weld bead can be ground off using bead grinders.
Internal bead removal is common in sanitary tubing.
8. Weld Cooling
Welded area is cooled using water jets or air blowers.
Ensures microstructure stabilization and avoids distortion.
9. Sizing and Straightening
The tube enters the sizing section:
Refines the outer diameter.
Improves roundness and dimensional tolerance.
For square/rectangular tubes: reshaped after round forming.
Turk's head rolls or straightening units adjust tube straightness.
10. Non-Destructive Testing (NDT)
Eddy current testing, laser alignment, or X-ray inspection ensures:
No pinholes, inclusions, or undercuts.
Seam is centered and sound.
11. Cutting to Length
Tubes are cut using:
Flying cold saws or
Offline orbital cutters (for thin, precision tubes).
12. End Finishing
Depending on application:
Deburring
Chamfering
Facing
Threading (if needed)
13. Final Inspection and Packaging
Tubes undergo:
Dimensional check
Visual surface inspection
Weld quality verification
Tubes are bundled or packed in plastic sleeves, paper wraps, or wooden crates, often with clean-room packaging for sanitary use.
Common Applications of TIG Welded Tubes
| Industry | Use Examples |
|---|---|
| Food & Beverage | Sanitary process lines, dairy, brewing |
| Medical | Hypodermic needles, surgical tubing |
| Pharmaceutical | Cleanroom piping, sterile systems |
| Heat Exchangers | U-bend tubes, thin-walled stainless coils |
| Aerospace | Hydraulic lines, fuel systems |
| Instrumentation | Small-diameter stainless tubes |
