Titanium welding is a specialty within a specialty. This remarkable metal has unusual properties and offers unique benefits — especially for critical-use aerospace and marine applications.
But titanium also presents unique challenges.
Working with titanium is not like working with any of the other more common metals, and before a contractor hires a supplier for a titanium-based project, that contractor should make sure the vendor has a history of success working with this incredible, but challenging metal.
Titanium: Strong, Light and Durable
Titanium is the go-to metal for marine and aerospace applications — and for good reason. It has a very high strength-to-weight ratio, which means it's strong, yet light. Since they don't require as much mass or material density, titanium parts can achieve comparable strength with thinner sections.
It is also highly resistant to corrosion, like the kind that is typical in marine environments.
The Challenges of Working With Titanium
At a glance, titanium welding looks similar to steel welding. Welders familiar with other metals often assume that since they're skilled and experienced, they will be able to figure out titanium as they go.
The unique challenge with titanium welding, however, is oxygen embrittlement. When the material is heated during welding, oxygen — like that found in ambient air — can infiltrate and corrupt the weld. This makes the metal brittle and prone to cracking or premature fracture in service, which is clearly unacceptable in critical-use applications. Titanium welders must master the techniques and tools required to shield welds from oxygen. This requires the use of inert gas, which could be helium, but is usually argon. Titanium welders have to shield not just the liquid weld pool, but also the surrounding metal. This is an exceptional challenge that is not familiar to even the most skilled nontitanium welders.
It requires close control over the quality of the argon, as well as a mastery of specialized tools like trailing shields and purge dams. During manual welding, the welder must possess a remarkable level of hand-eye coordination to make sure their movements don't disturb the shielding gas and create entry points for oxygen, which could corrupt the weld.
The Titanium Color Scale and Traits of an Expert Supplier
Properly welded titanium looks bright, shiny and silver as soon as it is complete. Any discoloration is an indication that something went wrong. Certain colors — such as blue, purple and brown — are telltale signs of a serious problem and a low-quality weld, which is likely to result in embrittlement and product failure. Titanium welders use a color scale to determine the effectiveness of their shielding. It moves from light straw to darker straw to green to purple to blue to gray to chalky white. This scale lets them know if there is simply room for improvement, or if the weld went catastrophically wrong.
The problem is that other metals — such as stainless steel and nickel-based alloys — often produce discolored welds without any negative impact. Skilled stainless steel welders frequently create welds that are tinted with blue, purple or green, and the discolored portion can simply be wire-brushed away without affecting performance. These welders are unfamiliar with the dangers associated with discoloration in titanium welding, and don't have processes in place to prevent it from happening or to react to it after the fact. They run the risk of conducting a bad weld without even realizing it, and simply moving on.
Contractors, therefore, should only consider vendors with a proven track record of working with titanium. They should carefully vet the supplier by asking the following questions:
- Is every member of the workforce skilled and experienced in the use of titanium specifically?
- Have they proven that they can work with a variety of shapes, sizes, orientations and plates?
- Do they know how to pre-clean the joints?
- How do they keep filler metals clean?
- Are they trained in designing and using trailing shields to fit weld joints in a way that will keep oxygen out?
- How do they ensure the metals are clean before welding?
- What steps do they take to ensure clean welds?
- What is their contamination/cross-contamination protocol to ensure the cleanliness of everything that could potentially contact the metal?
- Is everything in the room clean, and are grinding processes conducted away from welding operations?
Titanium is a remarkable material that offers incredible benefits to projects that demand strong, light metal with anti-corrosion properties. Titanium welding, however, is not like welding other materials. It requires a mastery and experience that even great welders can not learn on the fly or ad lib if they don't have a proven track record with this unique, but difficult, material.