Titanium is a highly lightweight metal with a very high melting point. It is often used in medical equipment, aerospace applications, and other places where lightweight and high performance are essential. Long ago, titanium was considered one of the most challenging metals to weld. However, many fabricators learned how to weld titanium with time. They gradually realized that it could be soldered easily like other high-performance metals. Although, it’s pertinent to mention that titanium is a demanding metal to work with. It’s hard to weld, sensitive to heat, and prone to cracking.
You must know how to handle it, mainly if you use it for your projects. Below are some of the tips and guidelines on how to weld titanium.
Let’s begin with the properties of this distinctive metal (titanium).
Contents
Properties of Titanium
You should know about titanium’s distinctive properties, which could be vital for welding titanium projects.
- Titanium is a highly reactive metal.
- It has the same strength as steel yet half of its weight.
- It is less ductile than stainless steel.
- Other metals are more elastic than titanium.
- It has a high melting point with a low density.
- It has good creep resistance.
- Titanium remains sturdy up to the temperature of -196 ⁰C.
- Good corrosion resistance, especially in chloride-containing surroundings.
Welding Titanium: A Quick walkthrough
For its excellent properties, titanium is heavily used in marine, aerospace, sports, automotive, and medical applications. It is a perfect weldable metal regardless of the fundamental problem of welding titanium is eradicating atmospheric contamination.
The oxide layer formed on its surface makes it corrosion resistant. This happens because it is a reactive metal that reacts promptly with oxygen and nitrogen. However, this oxide layer protects it from corrosion in many conditions, particularly in chloride-containing environments. The oxide layer must be removed before welding because its melting point is higher than the base metal.
Thus, it is good to use shielding gas all around the weld to prevent it from absorbing oxides because its surroundings could contaminate it and can weaken the weld. The tough oxide layer which protects it also makes it difficult to weld. Hence, it is challenging for the welder to select the correct welding filler wire and shielding gas to get the perfect weldment.
Cleaning Procedure
Cleanliness is the key to getting the desired result. Oxygen and nitrogen diffuse into titanium at temperatures above 400°C, boosting the tensile strength while rendering oxidation of the metal. The maximum forgiving amount of oxygen in the weld metal is 0.30%, while nitrogen reaches only 0.15%, and hydrogen is restricted even further to 150 parts per million. This is the reason cleanliness plays a crucial role in welding titanium.
Years before, many fabricators used to weld titanium in confined sealed chambers because of its highly reactive property. However, today most titanium welding is done in an open workplace, but they are designated to weld titanium alloys only to get a good quality weld. The area must be clean and free from dirt, oil, grease, rust, paint, moisture, and other contaminants.
Cleaning Of A Workplace And Base Metal
When preparing titanium for welding, Wear nitrile or cotton gloves. You must first remove any oxides that may be present on the surface. To do this, use a grinder or file to smooth down the inner and outer surface of the pipe and 1 inch away from the joint. Be careful not to overheat the titanium while you’re working.
Your workplace must be neat and free from any contaminants. You can use a diluted sodium hydroxide solution or acetone or methyl ethyl ketone (MEK) to clean the surface. Similarly, you can clean the base metal, filler metal, and all the equipment with the same solution to remove any contamination before welding.
However, ensure that you do not use flammable or chlorine base cleaning agents. Do not use steel wool or erode for cleaning, as these things can be hazardous or contaminate the base metal.
Selection Of Gas Shielding
The welding of titanium can be done like aluminum, stainless steel, or other metals. Although, as we discussed earlier, it is a highly reactive metal. Thus the selection of the inert gas plays a crucial role in welding. Covering the surrounding with inert gas is recommended to save the workpiece from contamination; otherwise, you’ll end up with brittle weldment.
The inert surrounding is essential for solidification and when the weld and heat-affected zone cools below 520˚C. However, the inert atmosphere is suggested to be kept as late as the base metal cooled below 400˚C. Hence, welding the small workpiece inside an inert gas chamber is better, and the enclosure must be filled entirely with gas.
The experts suggest using pure argon shielding for this purpose. Many professionals also use helium and a mixture of argon and helium to increase the penetration and fluidity of the weld pool. Although, purity of the argon gas is a must. Please do not use any active gas for shielding. Otherwise, it’ll react with the titanium and cause oxidation.
If you want to know more about welding gas, read our article Types of welding gases.
Selection Of Filler Wire
When selecting a filler wire for welding titanium, try to choose a welding wire covered by the AWS A5.16-70 specification. Try to pick a wire that complements the properties and composition of titanium base metal grade.
However, many welders also use different filler wires for some situations to achieve the desired combination of joint properties. Always clean the filler metal and keep it in a package to avoid contamination before welding.
Selection of Welding Procedure
There are many ways to weld titanium, but the two most common are gas tungsten-arc (GTAW or TIG) and gas metal-arc (GMA or MIG) welding. Other methods include:
- Resistance welding
- Laser-beam welding
- Plasma arc welding
- Electron-beam welding
- Friction welding
In general, TIG and MIG welding is the most versatile and recommended by many professionals. They can be used in various situations and produce a professional weld appearance.
Tungsten-Inert Gas Arc Welding (TIG) Or (GTAW)
TIG welding is a widely used method, particularly for welding titanium and its alloys. The size of the electrode is essential in TIG. It should be big enough to carry the welding current but not so big that cumbersome.
The best size to use is the smallest size that will still carry the specified current. This electrode is used to transfer current to the welding arc, which helps shield the weld puddle from any external contamination.
It’s also possible to use TIG without filler material, though this is only recommended for square groove joints that are not thicker than 1\8- inches. If you’re working with thicker sheets, you’ll need filler metal and grooved joints to get a strong and long-lasting weld joint.
Gas-Metal Arc Welding (GMAW) Or (MIG) Metal Inert Gas
GMA welding is more reasonable for units heavier than about 1\2 inches. It is a prime choice while welding large and thick material. GTAW welding uses a consumable wire that serves the purpose of electrode and filler metal. A tungsten electrode can be of either the 2% ceriated type containing a minimum of 97.30% tungsten and 1.80 to 2.20% cerium or the thoriated type.
MIG welding uses a solid metal wire as a filler material continuously heated and fed into the weld pool from a welding gun. To protect the weld puddle from contamination, it is essential to use a shielding gas. Many welders prefer GMAW for its high metal deposition and productivity rates. You can also use the pulsed current technique for MIG welding to produce high-quality welds on titanium plates that are more than 3mm thick.
FAQ’s
1- What type of welding is used for titanium?
You can weld titanium with various welding techniques like gas tungsten-arc welding (GTAW or TIG) and gas metal-arc (GMAW or MIG) welding, resistance welding, plasma arc welding, electron beam welding, and friction welding.
However, titanium is a highly reactive metal, so it is essential to maintain an inert gas atmosphere to prevent the weld from being contaminated. This is why the American Welding Society. AWS recommends practices for Gas Tungsten Arc Welding of Titanium Piping and Tubing (Miami American Welding Society, 2000), and many professionals also prefer gas tungsten-arc (GTA or TIG) and gas metal-arc (GMA or MIG) for welding titanium. These two techniques use inert gas for shielding and give you a solid weld without contamination.
2- Is welding titanium difficult?
Titanium is simple to weld. You can weld it just like nickel alloys and stainless steel. All you need to do is to keep its distinctive properties in mind. By doing so, you can quickly fabricate titanium in any shape.
It is a highly reactive metal requiring proper cleaning of the surface, base metal, filler wires, and removing the oxide layer before welding. You can use industrial cleaning agents for this purpose but make sure that they must be chlorine-free and inflammable.
It also requires to maintain an inert gas atmosphere to prevent the weld from contamination. So, it is better to use cambers for welding a small piece of titanium for best results.
3- Do titanium welds crack?
Due to its reactive nature, titanium weld tends to crack. In order to ensure that your welds are of the highest quality, it is essential to clean your tubes both inside and out before welding. This will remove any oxide build-up that could cause problems during the welding process.
It is also essential to keep any surfaces exceeding 800F during the welding process inert and free of contaminants. This will prevent those contaminants from being drawn into the weld and potentially causing problems.
Trailing gas shields protect the weld side, and argon backups cover the back side of the plate and pipe. These measures are necessary to prevent the heat-affected zone from potential damage. (Source)
Ending Notes
Titanium is as strongest as steel yet half of its weight. It is also corrosion-resistant and has a high melting point. These unique properties make titanium the prime choice for fabricating critical aeronautical components in aviation and other high-tech industries.
In welding titanium, your success depends mainly on selecting the right tools and the appropriate welding process and knowledge to execute the job. This is the reason that there are only a few businesses that have truly mastered the craft.