Research On TIG Welding Process And Quality Control Technology Of Titanium Alloy

Tungsten Inert Gas (TIG) welding boasts stable electric arc, controllable heat input, small welding deformation and reliable shielding effect, thus becoming the dominant welding method for titanium alloys.

1.Core Process Characteristics

Titanium alloy manual/automatic TIG suits thin-wall (≤3mm) and precision parts. Argon shielding blocks air; concentrated heat narrows HAZ, eases molten pool control to cut deformation and grain coarsening.

Spatter-free smooth welds need no grinding, retaining base metal strength and corrosion resistance for high-reliability precision workpieces.

2. Main Welding Difficulties

Titanium absorbs hydrogen at 250°C, nitrogen at 400°C, and undergoes severe oxidation at 600°C. The generated brittle compounds reduce the plasticity and toughness of welds and lead to brittle fracture.

Grains in welds and heat-affected zones grow coarsely, lowering the fatigue strength of joints.

Improper welding parameters easily induce hidden defects including pores, incomplete penetration and crater cracks, which are hard to detect.

1.Pre-welding Preparation

Material cleaning: Grind off oxide scales on the groove and areas within 20 mm on both sides mechanically, then wipe with anhydrous ethanol or acetone and air-dry. Welding shall be performed within 4 hours after cleaning to avoid secondary contamination that causes pores and inclusions.

• Welding filler wire: Select matching titanium filler wire based on the equal-strength and homogeneous material principle. If special filler wire is unavailable, cut strips from the same batch of base metal; mixing dissimilar filler wires is prohibited.
• Shielding gas: High-purity argon with purity ≥99.995% is adopted, equipped with a trailing shield to provide full protection for the electric arc, molten pool and high-temperature zone, preventing oxidation embrittlement of high-temperature titanium.
• Tooling equipment: Debug high-frequency arc striking DC TIG welding machines. Fasten workpieces with tooling to strictly control butt clearance and misalignment; rigidly fix thin-walled parts to minimize deformation.

2.Control of Welding Process Parameters

• Current and voltage: For thin plates of 0.5–2 mm, low current of 30–100 A and short arc voltage of 8–12 V are adopted to reduce air intrusion.
• Welding speed and wire feeding: Weld at a constant speed of 80–150 mm/min; feed filler wire steadily at an included angle of 10°–15° with the workpiece, and keep the wire tip inside the argon shielding zone at all times.
• Gas flow rate: Front shielding gas flow rate: 8–15 L/min; back shielding gas flow rate: 6–10 L/min. Improper flow rate leads to shielding failure.
• Interlayer temperature: Control interlayer temperature below 100°C to prevent heat accumulation from deteriorating joint toughness.

3. Post-weld Crater Treatment and Cooling

Adopt current decay method to fill craters fully during arc termination to avoid crater cracks and shrinkage cavities. Maintain argon supply after arc breaking until the weld cools down below 200°C before cutting off gas. Cool workpieces naturally to room temperature; water cooling and forced air cooling are strictly forbidden to prevent internal stress and microcracks.

1.Oxidation discoloration

Cause: Impure argon, poor shielding, dirty parts, early gas cut-off

Effect: Reduced toughness & corrosion resistance

Fix: 99.995%+ pure argon, trailing shields, pre-clean parts, extended post-weld gas

2.Pores

Cause: Oil/moisture, unstable gas flow, fast welding speed

Effect: Low density & load capacity

Fix: Dry clean materials, steady argon flow, slower travel speed

3.Weld cracks

Cause: Unfilled craters, over heat input & interpass temp

Effect: Risk of part breakage

Fix: Current ramp-down for craters, controlled heat/temp, symmetrical welding, preheat thick plates

4.Incomplete penetration & slag inclusions

Cause: Low current, fast speed, bad groove/gap, unsteady wire feed, residual slag

Effect: Sharp drop in weld strength

Fix: Optimize parameters, standardize groove/gap, steady wire feed, timely slag removal

1. Pre-Weld

• Verify material certifications & sample test materials; discard defective stock.
• Regularly calibrate welders; check gas equipment airtightness.
• Qualify welding procedures by thickness and make standard operating docs.
• Weld indoors at ≥5°C, dry, clean & windless; no outdoor dusty/windy work.

2. Welding Process

• Certified welders follow fixed parameters strictly with real-time monitoring.
• Stop work to fix oxidation or gas supply failures immediately.
• Clean interlayer slag and control interpass temperature.
• Keep full records for quality traceability.

3. Post-Weld Acceptance

• Welds must be smooth, crack/oxidation/burn-through/undercut-free and dimensionally compliant.
• Standard UT & RT inspection; add PT for high-precision parts.
• Run tensile, bend and impact tests to check joint mechanical performanc

Ruihang, as a direct manufacturer of titanium products, supply optimal quality raw materials for your precision components production. If you have any purchasing needs for titanium alloy products, please feel free to contact us via email: Sam.Rui@bjrh-titanium.com