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As with most metals, Titanium can be welded. For a long time, metal fabricators have tried to achieve clean titanium welds with difficulties, leaving many people to conclude that it is impossible.
However, these difficulties arose from inadequate knowledge about the properties and behavior of the metal. It was only welded in tightly sealed chambers.
These exotic metals offer many benefits, including high strength and corrosion resistance. In fact, a clean weld should appear like frozen mercury, with a shiny and reflective appearance. But its reactive nature makes attaining this difficult. So if you have tried or just wondering if welding titanium can be done, let’s run through this together.
Distinct Properties Of Titanium
As a transition metal, Titanium shares similar properties with metals in its period. However, it has unique properties that affect how it behaves, which should be taken in when considering welding.
For one, it is very reactive, meaning it readily forms compounds with available elements such as oxygen under the proper condition. Many times, these compounds have very undesirable properties.
High Strength To Weight Ratio
Titanium is famous for having a very high strength-to-weight ratio and low electrical and thermal conductivity.
Compared to most metals, Titanium has a very low density.
High Melting Point
A higher melting point than many metals is another characteristic feature of this metal.
Low elasticity when compared to other metals.
As a metal, it is also ductile but not as flexible as stainless steel.
Making Welding Preparations
Having identified that Titanium readily reacts with other elements to give products with very undesirable properties, you should make adequate preparations before you begin welding. One of such preparations is proper cleaning.
Titanium is a highly reactive metal, and cleaning is as vital as with any other welding job. The surface to be welded, the workspace, and the filler rod to be used should be free from dust, oil, grease, rust, paint, or even cutting fluid. The presence of this can result in a weld failure. Wipe down all the equipment and tools to be used beforehand.
Fabricators that work with several metals may find it challenging to create an immaculate workspace. To achieve this, you could use dilute sodium hydroxide to clean out impurities. You could also use a steam cleaner to ensure a thoroughly cleaned space. When you use moisture, try using a hot air blower to dry up the moisture from the area.
With a clean workspace, the next focus of the welder is how to prevent the Titanium from getting contaminated by atmospheric gases. That is why a shielding gas is needed. The shielding gas offers protection to the metal during the welding and as it cools down.
Argon is the most popular shielding gas option when it comes to titanium welding. But you would have to ensure that it is at least 99.9% pure, as anything less can result in contamination of the metal. For total protection, you would need to supply the gas at three stages;
Shielding of the molten weld puddle is referred to as the primary shielding. As known of Titanium, shielding, especially at this stage, is crucial. Usually, this protection is provided by using the appropriate welding torch.
Water-cooled welding torches are preferable. But you should ensure that the cup is broad with glass lenses. The broad cup allows adequate coverage while the glass allows the gas to flow in a moderate pattern.
Although argon is most preferable, you could use a mixture of argon-helium if you are welding at a high voltage or aiming to attain greater penetration. Remember to continue to supply the gas even after the puddle is formed and until the weld cools.
The trailing shield provides secondary shielding. These shields come custom-fit for individual torches and specific operations. This is important to protect the titanium weld and the heat-affected areas as it solidifies or reaches 800oF.
Back-up shields look similar to the trailing shields. Unlike the trailing shields, these do not come fit for a torch. Instead, they are held in position by hand while working or using a clamp. The essence of having a back-up shielding is to provide gas to the roots of the weld and the other heat-affected areas.
Filler Metal To Be Used
When welding Titanium or Titanium alloy, you should select filler wires whose metals have similar properties as the Titanium, thus noting its properties. Your filler wire should have similar strength or at least one grade below it. This is to ensure uniformity first in the melting and cooling times.
Usually, it is advised that you get a filler wire with a yield strength slightly lower than that of Titanium. For special welding conditions, you could use a different grade of filler wire. Ensure that the filler wire has a low percentage of other elements such as oxygen, hydrogen, nitrogen, and carbon.
Unalloyed wires could also be used as filler wires. Whatever you choose, filler wires for titanium welding are required to be within the specification AWS A5.16-70.
Titanium Welding Process
There are several welding methods you can employ when welding titanium.
Gas Tungsten Welding (GTAW) or Tungsten Inert Gas (TIG) Welding
GTA or TIG welding is a popular welding process for Titanium and its alloy. This is done by the current sent from the tungsten electrode welding rod in the welding torch. You might not need a filler material when welding base metals of up to 2.5mm for this welding process. However, you would need a filler material for thicker sheets. TIG welding can be used on many types of joints, including relatively thin ones, and on all metals including:
- Stainless steel
The electron beam welding involves fusing two metals using a high-velocity electron beam. As the beam of electrons is focused on the metals, they heat up, melt, and fuse to form one piece. This method is effective for metals of between 6mm and 76mm. Electron beam welding is also well regarded because it produces high-quality welds.
Similar to electron beam welding, this also involves the fusion of the two metals. This fusion results in the creation of a firm and durable piece. Many welders tend to use the laser beam rather than the electron beam for titanium welding because it removes the need for a vacuum chamber. The marked difference is that laser beam welding cannot work for more than 13mm thick metals.
Gas-Metal Arc Welding or Metal Inert Gas (MIG) Welding
Several welders favor the GMA or the MIG welding process because it is highly productive. In this method, the filler metal is heated and supplied continuously till the Titanium or the metals are joined. Caution has to be employed in this process to ensure that the melt puddle does not get contaminated.
Resistance Welding (RW)
Resistance welding can be used for joining Titanium or its alloys at a spot. This works by passing a controlled amount of current through the plates for a period. The good thing about this method is that the current is restricted to the area being worked on. It can also be used when joining Titanium and other metals.
Plasma Arc Welding and Friction Welding
Plasma Arc welding is more suitable for thicker titanium plates. This process works mid-way of the tungsten and the electrode welding.
Friction welding is a solid-state method of joining two metals together. Friction is applied to join the Titanium to the other metal with a reduced risk of contamination.
Getting It Right
A colored weld joint in Titanium indicates the presence of impurities and a poor weld. In order To avoid this, you should take the following steps through the welding process
- Setting up the workspace. Remember that the area has to be very clean. An excellent way to get ready for welding titanium would be to ensure a clean space.
- You must wear nitrile gloves when working with Titanium to avoid contamination from your hands.
- In preparing the Titanium, remember to break the oxide layer around it. This you can do by using a grinder or a steel brush to scrape around the Titanium. You should also be careful that whatever grinder you use for Titanium should not be used for another metal to avoid contamination.
- Always maintain the shielding gas flow from the beginning of the process till the temperature drops below 800oF
- The filler metal to be used should be in line with specifications and should be well cleaned before using it. After use, you should neatly store it away.
To Wrap Up
Despite myths and fears, Titanium can be welded. Titanium is a very reactive metal, so to create neat and durable welds, you have to ensure no contamination on the metal or the work area. Clean weld titanium looks like frozen mercury and should not have bluish or purplish coloration. In order to achieve this, the metal must be appropriately shielded all through.
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