A Comprehensive Guide: Mastering the Art of Titanium Welding

Embarking on the journey of welding titanium requires precision, knowledge, and a keen understanding of this metal. Titanium, renowned for its lightweight, corrosion resistance, and remarkable strength, is a prized material in industries such as aerospace and marine. This comprehensive guide will equip you with the skills to weld titanium like a professional, ensuring success in repairing valuable components for high-end applications.

Understanding Titanium Properties and Welding Challenges:

Titanium, being over 50% lighter than stainless steel and twice as strong, boasts an exceptional strength-to-weight ratio. However, its high melting point and affinity for oxygen creates challenges during the welding process. Rapid oxidation, susceptibility to contamination, and the risk of brittleness require extreme attention to detail. Recognizing severe titanium oxidation is crucial. 

Recognizing Severe Titanium Oxidation 

Like stainless steel, titanium will tell you if it became too oxidised during the welding process. However, titanium has different rules than stainless steel. The weld and HAZ surfaces will change colours ranging from silver, straw-yellow, blue, and white. These colours indicate the level of titanium oxides that were formed as a result of welding. 

Here is a brief colour guide to recognizing the titanium weld quality:

Unlike stainless steel, titanium surface oxides don’t turn black at the final, unacceptable weld oxide stage. Instead, titanium oxide buildup that’s excessively white is a clear sign that the weld picked up too many oxides and is likely weak and unreliable. 

However, here is an important note:

Just because the weld is clear from surface oxide, doesn’t mean that the weld is safe for critical applications! This is just a simple visual way to evaluate the weld quality. But, titanium can easily pick up oxygen and other contaminants deep within the weld metal. So, you shouldn’t rely on visual confirmation alone.

Important Safety Notes on Titanium:

It is vital that you prioritise safety when working with titanium. Titanium dust is flammable and can spontaneously combust. So, ensure that you don’t have any flammable items in the nearby vicinity of the work area before you grind or otherwise shape titanium joints. In addition, sweep the titanium dust from the work area before welding to prevent any sparks from igniting the titanium dust and shavings.

Don’t use water to fight titanium-induced flames because it may explode! Instead, ensure that you have a working Class D fire extinguisher. They are designed for fighting fires from combustible metals like sodium, magnesium, and of course, titanium. 

Preparing Titanium for Welding:

Preparing the titanium joint for welding is crucial for a successful weld! You must clean the metal perfectly and shape the joint without smearing the material.

Wear nitrile gloves to prevent moisture and oils from your skin from contaminating the weld joint. Titanium requires avoiding skin-to-joint contact. You can never be too clean with this material.

Use acetone or methyl ethyl ketone and a brand new, clean, lint-free cloth to wipe the titanium joint clean from any oils, grease, dust, and other hydrocarbons. DON‘T use Chlorinated Fluoro Carbon (CFC) or other chlorides to clean titanium. They can lead to stress-corrosion cracking after the welded piece is heated above 430°C during welding.

Next, you need to remove the titanium oxide layer that formed naturally on the surface. You can use a file or a stainless steel wire brush if it’s a small joint. You can also use a flap wheel or grinding wheel for titanium. However, if you use a grinder, avoid concentrating too much pressure in one area and grind slowly to avoid localised heat buildup. Wipe clean the joint again after grinding off the titanium oxide.

If using carbide burrs, stainless brushes, and other tools, make sure they are dedicated to titanium only. Inclusions from carbon steel and other metals can contaminate titanium and weaken the weld.Clean the titanium filler metal wire from oxides as well. We’ll get to wire selection soon.. It’s also recommended to clip the end of the filler wire just before welding to expose the pure titanium underneath.

Purging the Weld:

Because titanium is very reactive with oxygen and susceptible to contamination from hydrogen and nitrogen,, purging the weld is essential for the best results. You must purge the underside of the weld with a non-reactive gas like argon. While the shielding gas from MIG or TIG welding process will protect the weld from above, the back side of the weld will get oxidated, lose corrosion resistance, and become brittle unless you purge the air and replace it with argon. This is especially important when welding titanium pipes. 

You can make a DIY purging solution by plugging both sides of the pipe shut with tape. Then, poke a hole in one end and stick an argon gas hose through it to force the air outside and replace the inside atmosphere with argon. As always, there are commercial products for professional pipe purging, but you may be able to get a good purge with a little bit of a DIY.

Here is a purging tip for you: If you have multiple joints on a pipe system, like a motorcycle or sports car exhaust pipe system, tape the joints at the bottom and keep those higher joints loose. Argon is heavier than air, so you want to push the argon through the system starting from the lowest point of the pipe system all the way to the highest point.

Welding Process Selection:

We highly recommend sticking to TIG to weld titanium. The TIG welding process provides excellent precision and lets you carefully direct the shielding gas using a wide cup and gas lens setup . While MIG welding is possible, TIG welding ensures superior weld quality by avoiding excessive heat and spatter. However, fluxed welding and oxy-fuel welding are NOT recommended to weld titanium or titanium alloys. 

TIG Welding Titanium:

The TIG welding process uses a non-consumable tungsten electrode to transfer an electrical and inert shielding gas to protect the weld puddle from atmospheric contamination. 

You need to use Direct Current Electrode Negative (DCEN) TIG welding polarity to weld titanium. While it’s necessary to use AC TIG to weld aluminium or magnesium, titanium doesn’t require AC TIG output.

However, you don’t want to use just any plain DC TIG welder, either. Your TIG machine should be equipped with a high-frequency arc start to prevent the tungsten electrode from contaminating the titanium. In addition, pulsed TIG welding is a welcome feature to prevent excessive heat input and improve weld penetration. Equipment with high-frequency arc start and pulsed TIG welding capabilities enhances the process. Consistent shielding gas coverage, large nozzles, and welding in the flat position contribute to successful titanium TIG welding.

When TIG welding titanium, you’ll notice that its weld pool behaves quite similarly to stainless steel or nickel alloys. So, if you’ve had previous experiences with those materials, you won’t have many issues. 

However, titanium requires extra shielding gas protection. Therefore, you need to ensure no wind drafts in the area where you are welding. In addition, it’s probably better to use gas lens for titanium because of a more consistent shielding gas coverage. You should also use a large nozzle/cup to prevent the heated parts from coming in contact with the air. A larger TIG cup will provide a broader shielding gas coverage and better protect the sensitive, heated titanium. TIG welding titanium works best when performed in the flat position. Vertical or out of position welding can negatively impact the shielding gas coverage, which can have devastating consequences for titanium. 

Shielding Gas and Tungsten Electrode Selection:

To TIG weld titanium, we recommend using 100% argon. But you can add helium to the mix as well. Still, helium is unnecessary for titanium, and it’s more expensive than argon. So, there aren’t many reasons to stray from welders’ favourite — straight argon shielding gas.

It’s extremely important to get a high quality argon shielding gas tank. The higher the purity of the argon tank, the better the weld will be. Many welders experience weld discoloration (oxidation) when welding titanium and can’t seem to find the culprit. If the gas tank has air and moisture inside, you can experience weld oxides. The only solution to this problem is to get a better quality argon tank.

Tungsten Electrode Selection:

Most welders use thoriated and lanthanated tungsten electrodes to weld titanium. However, you can also use ceriated tungsten if welding thin sections at low amps — ceriated, grey tungsten works well for low amps applications across the board.  

Grind your tungsten electrode sharply to a point, but be careful not to touch the titanium at any moment. Pointy tungsten can erode and contaminate the weld pool and cause embrittlement. Your tungsten electrode stickout should be as limited as possible, but don’t compromise your weld pool visibility either. 

Filler Metal Selection:

You should strive to match the filler metal alloy to the titanium alloy you are welding. Unalloyed titanium filler metals are suitable for commercially pure titanium, with ERTi-2, ERTi-3, and ERTi-4 being common choices. This is because it can tolerate atmospheric contamination well, without a significant ductility loss of the weld metal.  You can also use unalloyed titanium filler wire to weld some specialty titanium alloys to improve ductility at some loss of strength, but this requires a very dedicated approach. Consult the engineer if welding specialty alloys like alpha base titanium.

Post Weld Shielding Gas Flow:

Its vital to maintain a post-weld shielding gas flow until the weld cools below 430°C to prevent rapid oxidation. Consider using a trailing shielding gas fixture for automated welding. You can try making a short weld on a scrap piece without providing a post-shielding gas flow and see just how quickly the weld will start to oxidise.

Use post-welding gas flow of at least the 20s. Sometimes you may even require more, depending on the titanium’s thickness. If your welder doesn’t support a higher setting than the 20s for post flow. Lightly press on your TIG foot pedal to initiate a small arc for just a fraction of a second as you are holding the torch over the completed weld and the welder will release another 20s of gas.

Sometimes it’s also necessary to use a trailing shielding gas fixture. This allows you to shield the weld bead as you move along the joint. However, this is not always required for manual welding. It’s usually used for fast, automated welding of titanium.

TIG325X AC/DC TIG Welder With Foot Pedal

Final Thoughts:

Mastering titanium welding requires attention to cleanliness and shielding gas protection. Armed with these fundamental principles, you can elevate your titanium welding skills, ensuring success in handling valuable components for diverse applications.

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