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A lot of welders have little or no experience in welding titanium. It’s not an everyday metal you see in workshops. However, it is used in building aircrafts, ships, process equipment, cars, bicycles, and utensils. So if you’re a professional welder, you’ll eventually come across this material.
The properties of this metal create a challenging welding situation for inexperienced and even some professional welders. Titanium is one of the strongest metals, but it’s also highly reactive. This reactivity is one reason welders only work with this material in sealed chambers to reduce risk of contamination. Nonetheless, it’s worth noting that with the right technique, this metal is as weldable as steel or aluminum. It’s also not as elastic and ductile as other metals. Despite all these properties, titanium can be welded on. In fact, you can weld on it as easily as you can weld on steel as long as you know what you’re doing.
Preparing the Titanium Workpiece
There are a few things that you need to do before you start welding. Pre-welding preparations ensure your weld is as strong as possible.
Cleaning is an essential aspect of preparing titanium for welding. Although you can get away with certain welding techniques that don’t require cleaning beforehand for some metals, cleaning is essential when welding titanium. Oil, dirt, or paint on the titanium surface creates a feeble joint. Hence, removing all these surface contaminants is necessary for a strong weld.
It’s not just your workpiece that needs cleaning. You also need a clean work area as well as filler rods. Anything that contaminates the surface of the metal affects the quality of the weld. You can steam clean your work surfaces and disinfect the area further with a dilute solution of sodium hydroxide. Do not use chlorine-based cleaners, because chlorine corrodes titanium.
The workspace should be free from moisture. You can wipe surfaces dry or use a hot air blower to dry surfaces, but make sure you don’t aim the blow on any volatile chemicals. Also, make sure you’re wearing nitrile gloves when handling titanium.
Your Shielding Gas Matters
TIG welding is preferred for titanium. With titanium, you’ll have to be more worried about oxygen in the air. The presence of even the tiniest bit of oxygen can ruin your weld. This is why pure argon is typically the shielding gas used for welding titanium.
When we say pure, we mean 99.999 percent pure argon. It shouldn’t be any less pure than that. Even trace impurities can cause yellowish discoloration on your welds. You can tell whether the shielding gas you’re using isn’t the purest quality because you’ll see blue streaks on the surface of titanium on both sides of the weld joint. You may also notice mottling.
Applying Argon Properly
It’s not just the quality of argon that matters. How the shielding gas is applied also affects the quality of the weld. A common practice is to start the argon flowing for a few seconds before striking an arc. When enough argon is flowing while you’re welding, there should be no to minimal discoloration. It’s not just inadequate flowing shielding gas that’s a potential problem. Too much shielding gas can also cause mottling or swirling patterns around the weld.
Because of the nature of titanium, you have to ensure that the front and the back are not exposed to ambient oxygen, especially when you’re subjecting the metal to high temperatures. This makes welding titanium more difficult. The tougher shielding requirements for welding titanium include primary and secondary shielding as well as backup shielding. The welding torch provides the primary shielding, while the trailing shield attached to the tip of the torch provides secondary shielding.
There are different ways to ensure sufficient gas coverage. One useful tool for providing an even argon coverage to your workpiece is the copper purge block. Purge blocks aren’t applicable in all situations, but there are other ways to protect your workpiece. Small pieces can be fitted into an argon purge box for adequate shielding. Special polyethylene plastic bags are used for welding large titanium pieces that can’t fit into small purge devices.
Let the gas flow into the purge box or compartment before you start welding, just as you want to start your primary shielding gas flowing beforehand. Ideal gas flow for purge blocks is 10 cubic feet per hour. A purge monitor helps you determine whether you have pure argon flowing into the compartment.
There are other considerations to take into account with TIG welding titanium. One is you have to use a wide gas lens for improved gas coverage and, thus, longer welds. You should be looking at diameters of 0.75-1 inch. Gas lenses are necessary in welding stainless steel, titanium, and aluminum, because they reduce shielding gas turbulence, hence providing gas coverage that effectively keeps oxygen from contaminating the weld. Your TIG welding torch usually comes with the standard nozzle and the collet body. Remove the nozzle and the collet body and replace them with a gas lens.
A purge monitor helps you determine whether you have pure argon flowing into the compartment.
Choosing Your Filler Rods
Ceriated tungsten electrodes are commonly used for welding titanium. How thick the rods are depends on your working amperage. Thin rods 1/16” or smaller are used for welding below 125 amps, while those 1/16”-3/32” rods are for 125-200 amps. If you’re working above 200 amps, consider a 1/8″ rod.
While tungsten rods are typically used for TIG welding, titanium TIG rods may be used in many cases. Titanium filler rods come in different grades for different applications (1).
The Bottom Line
You can weld on titanium, and you have to in many circumstances. There’s no other way to fuse titanium pipes but to weld on them. Titanium is an expensive metal, so you have to be careful, unless you want to waste resources. Also, the reason strict measures are followed when welding titanium is to preserve the excellent properties of the metal. What’s the point in having a strong metal with brittle joints?
You’re probably wondering whether you can MIG weld titanium. You certainly can. But the reason welders prefer TIG for titanium is because MIG can burn through titanium plates.
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