In this article, we will learn all about titanium welding, how to weld it, process, different types, etc. A weld is a fabrication process that involves the joining of two or more parts by means of heat, pressure, or both, forming a joining that will remain after the parts have cooled down. Generally, welding is used to attach metals and thermoplastics together, but it can also be used to attach wood together. Weldment is the term used to describe the completed welded joint.
What is Titanium Welding? Basics
What is Titanium?
The fact that titanium is a light, strong, corrosion-resistant metal makes it considered as an exotic metal. In the past, however, it was believed that only sealed chambers were capable of performing the welding of titanium to the highest degree. In addition to its corrosion resistance, the metal also has the highest strength-to-density ratio of any metallic element, making it a versatile metal.
Benefits of Titanium
There is a possibility that it can become contaminated by atmospheric gases since it is a reactive metal. Although titanium is a difficult metal to weld, most welders do not think it is as challenging as they think. During welding, you will only need to maintain proper gas shielding during the process, the rest of the process will be very similar to welding other types of metal.
The strength-to-weight ratio of titanium as a metal has been recognized as one of its advantages. A relatively high melting point of 1,668 °C or 3,034 °F, combined with ductility, especially in an oxygen-free environment, makes it suitable for use as a refractory metal due to its strength and low density. It is lustrous in appearance and metallic-white in color.
Differences between Titanium and Steel or Nickel-Base Alloys
We need to recognize that titanium has significant differences from steels or alloys of nickel-base that are made from steel. As a result, we have the following:
- Compared to other metals, titanium is less dense
- Due to its lower modulus of elasticity, titanium is more brittle
- Compared to other metals, titanium has a higher melting point
- When it comes to welding titanium, it is very sensitive to contamination
- A characteristic of titanium that makes it prone to galling is its hardness
- The lower ductility of titanium
What is Titanium Welding?
The majority of titanium and its alloys are welded using the gas tungsten arc (GTA) and gas metal arc (GMA) welding processes in order to prevent cracking from occurring. To a limited extent, titanium is also welded with resistance welding, plasma arc welding, electron beam welding, and friction welding. There are advantages to each of these processes based on the specific situation to that they are applied.
A wide range of welding processes is available for the welding of titanium and most titanium alloys. When a weld is made correctly, the resulting weld is ductile and corrosion resistant in most environments. This means that the weld is as durable as the base metal in its as-welded condition. In contrast, improperly welded welds may be embrittled, and the welds may be less corrosion-resistant than the base metal it is welded to.
Factors about Welding Titanium
Welding titanium uses the same techniques and equipment as welding stainless steel or nickel-based alloys, which are both high-performance materials that are often used in aerospace applications. As opposed to these materials, titanium needs to be kept as clean as possible and it must be shielded by an additional inert gas in addition to this.
- It is extremely imperative to protect titanium welding metal from air contamination while it is in molten form. There is also a necessity to shield hot heat-affected zones and the root side of titanium welds until the temperature drops below 800°F (427°C).
- In most cases, the alloys of titanium form brittle compounds when they are exposed to air, moisture, grease, dirt, and most other metals. In order to weld titanium, it must be exposed to gases and fluxes that react with it, which makes common welding processes such as gas welding, shielded metal arc welding, flux-cored arc welding, and submerged arc welding unsuitable.
- In addition, titanium cannot be welded to most dissimilar metals, including titanium itself, simply because titanium forms brittle compounds when combined with most other metals, but it can be welded to zirconium, tantalum, and niobium, for example.
- There are many fabricators that routinely and economically weld titanium, regardless of the precautions that need to be taken, making ductile, sound welds at comparable rates as many other high-performance materials are being welded on a daily basis.
- A major advantage of welding commercial grade titanium is the fact that these grades are over 99 percent pure titanium and there is no concern for segregation as a result of welding. A similarly high-quality weld wire or rod in commercially pure grades can be used to make the same type of weld.
Welding Titanium Presents a Number of Challenges
Titanium is a metallic alloy characterized by a very high strength-to-weight ratio and excellent corrosion resistance. This combination of properties makes titanium a very desirable material for difficult applications in extremely demanding environments, because of its high strength-to-weight ratio.
This is why titanium is often used in aerospace and medical applications. For medical purposes, titanium is ideal, such as to be used in artificial joints or to be incorporated into implanted devices. As a result, it is light and strong, and the compounds within the human body are incapable of bonding or reacting with it thanks to its properties.
Other Complications in Welding Titanium
It is very difficult to weld titanium to any other metal since titanium is basically non-reactive to most materials, which means that it does not easily alloy with other metals. Due to its high reactivity to oxygen, titanium is very difficult to weld unless those conditions are tightly controlled, which is the result of its high reactivity to oxygen.
- It has been found that titanium begins to form a microscopic layer of oxides when it is exposed to oxygen, and these oxides inhibit chemical reactions between titanium and other chemicals. During the process of heating titanium towards its melting point (3,034°F / 1,668°C), oxides are formed even more rapidly as the metal is heated.
- As welding involves melting the materials to be welded, it is normal for oxides to form quickly in the weld pool. When the oxides dissolve, they contaminate the weld pool, resulting in a weak, poor-quality weld.
- Hence, titanium is difficult, if not impossible, to weld in the open air due to the fact that either a cover gas must be used or a vacuum must be created in order for the metal to be welded.
Cleaning before Welding Titanium
In order to properly weld titanium, it is imperative that weld joints and weld wire be free of mill scale, dirt, dust, grease, oil, moisture, and other contaminants, before welding titanium. There is a possibility that the inclusion of these foreign substances could degrade the properties and corrosion resistance of titanium welding metal.
The wire is clean and ready to use when it comes in the packaging provided by the manufacturer. Before using wire, clean it with a non-chlorinated solvent if it appears dirty. There may be a need for acid cleaning in severe cases.
Steps to remember
You should follow the three Cs for ensuring a successful and durable weld:
- Clean filler rod
- Clean Workspace
- Clean surface
Having even one of these surfaces that is not clean can lead to contamination of your workpiece if even one of them is unclean. As a piece of advice, we recommend that you use a chemical cleaner specifically designed for titanium surfaces in order to remove all the unwanted particles from them.
If you wish to remove all the contaminants from the work surface, you should use a steam cleaner and a diluted solution of sodium hydroxide to do so. In order to remove all moisture from the workspace, you should use a hot air blower to remove the moisture. Before using any piece of equipment, make sure it has been cleaned and wiped dry. As with the workstation, you can use the same solution for the tools as you did for the workstation.
In order to keep titanium in good condition, it is important to ensure that the cleaner is not based on chlorine, as titanium doesn’t react well with chlorine. There is also chlorine in rubber gloves, so it would be better if you used cotton or plastic gloves rather than rubber gloves.
Choosing the Right Tungsten for Titanium Welding
Chemical element tungsten (W), often known as wolfram, is a Group 6 (VIb) refractory metal that is incredibly strong. It is used in lamp filaments and steel to boost its strength and hardness.
- In order to choose the best tungsten for titanium welding, one must take into consideration the need to maintain a consistently high level of heat on the weld in order to keep the heat-affected zone as narrow as possible.
- A tungsten electrode is one of the most important considerations when choosing the best tungsten electrode to weld titanium since it must be able to withstand the high heat required.
- In order to weld titanium properly, it is imperative to use an electrode made from tungsten that is resilient to the high heat necessary to weld titanium without melting or spitting tungsten into the molten metal, which will cause weld defects during the welding process.
- The tungsten you should choose should be alloyed with another component in order to be able to withstand higher temperatures a little better. Because titanium is usually welded with direct current (DC) and not alternating current (AC), it is only possible to use tungsten electrodes that can handle DC current, so there is only a limited range of electrodes that can be used.
Perimeters and other functions of Titanium Welding
Environment for Welding
While chamber welding still occurs in limited quantities, most titanium welding today takes place in open fabrication shops. It is common to perform welding in the field. Welding titanium requires a clean environment, regardless of where it is performed.
Welding titanium is done in a separate area, specifically designated for titanium welding. The area should not be used for grinder operations, torch cutting, or painting. Moreover, air drafts should be avoided in the welding area, and humidity should be controlled.
The preparation for the weld
A quality titanium weld depends heavily on the preparation of the weld, which plays a key role in determining the quality of the weld. The process for the preparation is explained in brief as follows
- If the titanium surface is dirty, oil, grease, or dirt can be removed by cleaning it with a soft cloth to remove any impurities. When it comes to cleaning titanium, it is best to use chemicals that are designed specifically for this purpose. Whenever you are creating a weld out of titanium, keep in mind that the cleaner the titanium is, the stronger it will be. You can use chemicals that are designed specifically for this purpose. You should keep in mind that the cleaner the titanium is, the stronger the weld that you will create.
- A steam cleaner or diluted sodium hydroxide solution can be used in order to remove the contaminants from the carpet.
- If you need to remove any moisture from the surface, you can blow it away using a small hot-air blower. Make sure, however, that you do not use it on any solvents that are flammable so that you don’t damage the product.
- It is also important to make sure that all welding parts are clean, dry, and free of debris.
- On titanium, you should never use any cleaning solution that contains chlorine.
- There are many sources of contamination that can be found in the environment, including your hands. If you do not want to use rubber gloves, you may want to opt for plastic or cotton gloves instead, because rubber gloves can contain chlorine.
- Ensure that the cleaning solvent with which you were cleaning the surface has fully evaporated before striking the arc, as they usually have a low flash point and should not be used to strike the arc.
Also Read: Weld Porosity
Choosing the Right Shielding Gas
When it comes to welding titanium, using the right shield gas is essential when it relates to ensuring that you end up with a strong weld. This is because titanium reacts readily with air, oil, dirt, moisture, and other metals to create brittle compounds. Usually, when welders do this process, they use 99.999% pure Argon for the purpose of welding. There is no substitute for truly pure Argon and Helium when it comes to providing optimal protection from the atmosphere.
The shield gas you purchase for your welding project should only be purchased from reputable suppliers if you intend to use this gas for your welding project. A slightly less pure Argon can result in discoloration even if it is a little less pure than the required amount. There is a chance that you will end up with a weld that is yellowish-tinged, which is something that is not desirable. Blue tinting and mottling can also be caused by impure gas or incomplete coverage.
Some other things to keep in mind are
Choosing titanium means that it has to be protected as much as possible from the atmosphere both on the front as well as on the back. In the presence of oxygen, any area that is affected by heat will show a negative reaction as soon as it comes into contact with it.
If you need to protect smaller parts, you can use enclosed compartments made from glove boxes filled with shielding gas that have been made out of glove boxes. There are even special polyethylene purge gas chambers available on the market that can be used in combination with a purge monitor. Using them, you can make sure that there is enough Argon in the chamber for it to provide the best level of protection. Also Read: Welding to Galvanized Steel
Shielding for primary use
A welder’s torch is usually equipped with a molten weld protection shield that provides primary coverage for a molten weld puddle and is usually mounted directly on the torch. As an alternative, you can use a water-cooled torch that has a ceramic cup and gas lenses and that is equipped with a water-cooled system. The best choice for you would be to choose a torch with a broader cup to ensure that you are covered from all directions.
Shielding for secondary use
Secondary protection is provided by trailing shields. Generally speaking, they are attached to the end of most welding torches to ensure that the heat-affected areas are kept clean and free from contamination at all times.
Shielding for backup
It is true that these devices look like trailing shields and serve a similar purpose as well. Either they are handheld devices or they are taped into place to hold them in place. Rarely do they ever come pre-fitted into the welding torch when they are purchased. Also Read: Tips for Best Aluminium Welding
How to Choose the Right Filler Wire for Titanium Welding?
We suggest that if you are choosing the filler metal to weld titanium and its alloys, you should select a filler wire that primarily has the same properties as the base material you are welding. In addition to this, you are also able to choose a wire whose strength is categorized in a grade that is one grade below the grade of the base metal. The welder may even use a different category of filler wire altogether depending on the circumstances of the welding process.
Choosing the right filler wire for your joint will depend on the properties of the joint, as well as the combination of the joints. The following steps can be taken to improve the ductility of joints:
- Use a filler metal that has a lower yield strength than the base metal when welding unalloyed titanium of higher strength.
- If you are welding titanium under the classification Ti-5A1-2.5Sn or Ti-6A1-4V, you can use unalloyed filler material as the welding filler material.
- In addition, there is an option of using filler metals that contain lower concentrations of oxygen, nitrogen, hydrogen, carbon, and other alloying elements than the base metal.
The Power Supply
The use of a conventional power supply, connected to a D.C. supply with a straight polarity (DCSP), is used in GTA welding of titanium in which a conventional power supply is used. The GMA welding of titanium is performed with reverse polarity (DCRP).
A remote-controlled contactor allows the arc to be broken without having to remove the torch from the cooling weld metal, thus ensuring that the inert gas shielding remains intact. In addition, there are a number of other desirable features included in the shielding gas starters such as foot-operated contactor and current control. Also Read: Ultrasonic Welding
An open flame, which is powered by gas fuels and oxygen, is used by a welding torch to fuse two pieces of metal together, in order to melt them together, causing a tight seam to form. Various industries and purposes use this torch and it is used in a wide range of applications. Welders that work with either metal inert gas (MIG) or tungsten inert gas (TIG) are two of the most common types.
In the welding of titanium
In order to perform GTA welding of titanium, it is recommended to use a water-cooled welding torch, equipped with a 3/4-inch ceramic cup and a gas lens. In order to be able to perform GMA welding, you will need a cup that measures one inch.
GTA welding of titanium should be carried out with a thoriated tungsten electrode usually 2 percent of thorium. In order to control the characteristics of the arc, pointed electrodes should be used. In order to ensure that the required current can be carried by the electrode, it should have the smallest diameter possible.
Processes for Welding that Can Be Used
There are several welding procedures that can be used when welding titanium and titanium alloys, including:
- Tungsten Inert Gas Welding(TIG) or Gas-tungsten arc welding (GTAW)
- Laser beam welding (LBW)
- Electron beam welding (EBW)
- Plasma arc welding (PAW)
- Friction Welding (FRW)
- Metal Inert Gas (MIG) or Gas- metal arc welding (GMAW)
- Resistance welding (RW)
Also Read: Underwater Welding
Tungsten Inert Gas Welding (TIG) or Gas-tungsten arc welding (GTAW)
Welding with tungsten inert gas (TIG), also referred to as Gas Tungsten Arc Welding (GTAW), is a process of welding that uses a non-consumable tungsten electrode to produce the welded product.
As part of the TIG or GTA welding processes, a non-consumable tungsten electrode is used to transfer current to the welding arc. Welding puddles require shielding gas to prevent external contamination from entering the weld puddle, which can result in weak and low-quality welds. For the weld joint to be properly formed, a filler metal or wire needs to be used.
In the welding of Titanium
Welding titanium and its alloys is a widely used method of joining titanium. TIG joints with square butt grooves can be welded without the use of filler material on base metals with a thickness of up to 2.5 mm. Generally speaking, if you are welding thicker sheets, you should use filler metal in order to ensure that the weld joint will last for a long time
Laser Beam Welding (LBW)
During Laser Beam Welding, two metal pieces are joined together by using a laser beam in order to fuse them together as a single piece. There is a cavity between the two metal pieces that have to be joined, and the laser beams are focused on it.
Having sufficient energy, the laser beams strike the metal pieces with enough force, and heat is produced as a result. As a result, the material melts from the two metal pieces and fills the cavity that the laser beams have struck. The two pieces of metal are welded together after they are cooled to form a strong bond.
As a welding process, it is very efficient and can be automated with robotic machinery very easily as it is a very efficient welding process. It is mainly used in the automotive industry that this welding technique is used.
In the welding of Titanium
There is a growing trend among welders to weld titanium with laser beams as there is no need for a vacuum chamber when laser beam welding is done. The use of shielding gas, however, is still a must in order to avoid contamination because the risk of contamination remains constant.
Despite the fact that both a laser beam and an electron beam can be used for fusion welding, the scope of the former is more limited than the latter. If your titanium plates are larger than 13 mm in thickness, you would not be able to use the process effectively. Also Read: Plasma Cutting
Electron Beam Welding (EBW)
Electron beam welding (EBW) involves regenerating electrons from an electron gun and accelerating them to high speeds through electrical fields in order to create a fusion welding process.
Through the use of magnetic fields, this high-speed stream of electrons is tightly focused and is applied to the materials that need to be joined in order to complete the bond. As an electron beam impacts on the components of the workpiece, it generates kinetic heat which causes the components to melt and form a strong bond as a result.
In the welding of Titanium
Depending on the size of the plate, you can use the electron beam welding procedure to weld plates ranging from 6mm to 76mm. As the process is carried out in a high vacuum atmosphere with the aim of generating highly reliable welds with minimal contamination levels, the process produces very high-quality welds.
Plasma Arc Welding (PAW)
A plasma arc welding process (PAW) is essentially the same as a gas tungsten arc welding process (GTAW) in that it uses an arc welding process. Between the electrode and the workpiece, an electric arc is formed between the electrode which is usually made from sintered tungsten but is not always the case and the workpiece.
In the welding of Titanium
It can be used on almost all titanium classifications, and even on heavier sheets of metal, it performs well, even if they are thicker in thickness. In addition to being able to use it on a one-pass plate that is up to 13 mm thick using the keyhole technique.
Friction Welding (FRW)
The friction welding (FRW) procedure is a solid-state welding process that creates heat by using mechanical friction between work-pieces moving in relative motions to each other while adding a lateral force known as an “upset” that displaces and, in turn, fuses the materials together.
Friction welding does not involve melting, so it is not a fusion welding process, but rather a solid-state welding technique that is more like forge welding since there is no melting involved. There are a variety of applications in the aviation and automotive industries that use friction welding to bind metals and thermoplastics together.
In the welding of Titanium
As one of the most preferred methods of joining titanium alloys with other metals, friction welding is preferred over other methods due to its many advantages including low energy consumption, high productivity, the absence of smoke and welding dust, the absence of fill material, and the lack of external heat source, as compared to other methods of welding.
Metal Inert Gas (MIG) or Gas-Metal Arc Welding (GMAW)
It is a welding technique that uses a solid filler metal wire that is constantly heated and is fed through a welding gun with a constant current. As a result of the nature of the welding process, it is necessary to use a shielding gas in order to prevent contamination of the weld puddle. The high metal deposition rate and productivity rates of GMAW are significant reasons why many welders prefer it.
In the welding of Titanium
The titanium weld process can also be used on plates that are thicker than 3mm in order to weld titanium. In order to produce high-quality welds, it is necessary to implement the pulsed current technique. Compared to other methods, it proves to be less costly, especially for use on titanium plates that are thicker than 13mm and is more efficient.