Welding Talk – How to Weld Titanium
This week we look at welding one of the most challenging materials you’re likely to meet. Titanium has a well-deserved reputation for testing even experienced TIG welders who’ve mastered stainless steel and aluminium. In this introductory article, how to weld titanium, we offer some important advice. With the right approach to cleanliness, costs and set-up, you too can weld this specialised material with confidence …
As Chinese military strategist Sun Tzu (545 BC–470 BC) said, ‘If you know the enemy and know yourself, you need not fear the result of a hundred battles.’ Let’s get to know our ‘opponent’ – in this case, titanium and titanium alloy.
Even better, let’s see how, with the right mind-set, equipment and consumables, we can make a powerful friend of this metal. OK, so at the very highest levels of aerospace and Formula 1 engineering, welding wizards may have moved on to the even-lighter, more heat-resistant Inconel, but titanium still has an important role in fields such as chemical processing, aerospace and automotive engineering – including super-trick, high-end custom exhausts for cars and motorcycles.
What is titanium and why is it so challenging to weld?
Titanium, the chemical element with the symbol Ti, is one of the so-called transition metals. It typically comes in two different crystalline forms, the occurrence of which depends on temperature and chemical composition. The result is a metal with impressive corrosion resistance, excellent strength-to-density ratio, high melting point combined with the light weight that so endears it to engineers.
A wide range of titanium and alloys
The different forms of titanium and their combination with other elements such as aluminium and vanadium, give a wide range of titanium and titanium alloys – well over 30. It’s titanium alloy (often referred to simply as ‘titanium’) that industrial welders are most likely to come across. The most often encountered are commercially pure grades of unalloyed titanium and variants of the 6% aluminium and 4% vanadium alloy. As we’ll see later, this means it’s vital to match TIG filler rods to the grade of titanium we use.
Titanium’s susceptibility to contamination
At the heart of the challenge facing titanium welders is the susceptibility of titanium to contamination. It’s not a case of maybe it will contaminate, get it wrong and it is guaranteed! Titanium is a reactive metal with a strong affinity for oxygen. It burns in pure oxygen at 600°C (1112°F) and in nitrogen around 800°C (1472°F). And when it’s heated, titanium’s reactivity increases significantly and it then readily reacts with, not only oxygen, but nitrogen, hydrogen and carbon, to form undesirable oxides. It’s the various thicknesses of these oxides that give titanium its renowned colours.
Because titanium reacts so readily, it’s important to keep your weld zone bathed in inert gas during the whole weld process. Pre-flow, proper control of the gas pocket during welding, and post flow gas afterwards to allow the titanium to cool to around 400°C (800°F) are all required. This is typically done with argon of at least 99.995% purity.
Be generous with the argon
We’re not talking half-hearted use of gas either. When welding titanium, whether it’s an open joint or within a tube or pipe, hyper-sanitisation of the heated zone is critical; it’s no place to be sparing with gas. Incidentally, the same sanitisation applies to handling and preparing your titanium-welding consumables and accessories.
Repeat after us and commit to memory the three ‘Cs’ of titanium welding: cleanliness; cleanliness; and cleanliness.
What this means for welders
With titanium, the colouring given by oxide formation is the key indicator of weld quality. With materials such as stainless steel or aluminium, a little ‘exotic’ colouring may be allowed, and for some processes, where welds aren’t structurally critical, colours may even be deemed attractive.
Colours indicate weld quality
Not so with titanium, where the difference between satisfactory and unsatisfactory welds is marked by specific colours. A quick online search will soon find websites (such as this one) that include visual guides to acceptable and unacceptable titanium weld colouring. As a rule of thumb, ‘light silver’, ‘bright straw’ and ‘dark straw’ indicate acceptable welds. There are no ifs or buts; anything else, including blue, violet, grey, green, white and darker browns don’t make the grade. When you consider the applications where titanium gets used, whether it be for performance or safety reasons, based on its thermal, weight and strength characteristics, weld failure simply mustn’t happen. Colouring is the key indicator of titanium weld quality.
Cleanliness, cleanliness, and cleanliness
When it comes to cleanliness and rigid adherence to strict process, titanium is as demanding as stainless steel – and then some. This focus on cleanliness starts with removing the titanium dioxide (Ti02) that forms at room temperature. It’s this layer that gives titanium its renowned corrosion resistance. However, if left on the workpiece during welding it can contribute to poor weld quality.
No room for poor cleanliness
From ensuring a clean working area and cleaning the metal, to handling filler rods and preserving integrity of an argon gas bath, there’s no room for poor cleanliness.
It’s not just about the criticality of the weld. The high cost of titanium and time needed to weld it properly, means every failed weld is expensive. As Daz Higgs, our operations manager, reminds: ‘When you weld titanium, cleanliness isn’t just key, it’s the Holy Grail.’
Relative material cost of titanium
For a moment, let’s consider material cost alone. The price per kilogramme of titanium is many times that of a similar weight of aluminium or stainless steel. We asked Brindley Metals, a leading UK metal dealer, for typical prices. With the qualification that these are influenced by many variables, as a very rough guide in late 2019, general grade aluminium 6082 (in 1 tonne lots) costs around £4.50/kg, while stainless steel 303 free-machining is around £3–£4/kg. Compare this to £30–£40/kg for widely-used Grade 5 titanium 6al 4v!
Translated into retail pricing of a product such as a motorbike exhaust end cap, think (very roughly) of £190 for stainless steel and, maybe, £800 for titanium. Okay, so we should allow for the perceived value of titanium in retail pricing, but you get the picture. Titanium is expensive and you won’t want to waste it. You’re welding titanium to make money and gain satisfaction with a great join at the pinnacle of TIG welding. We can’t overemphasise the importance of being super-cautious with material, planning, cleanliness and precise set-up.
What machine for welding titanium?
We mentioned earlier that titanium is mainly TIG welded. Yes, in theory, you can MIG-weld titanium, but it doesn’t happen, and there are also Plasma and Friction Stir welding options, but they are very much a minority.
You’re joining the elite welders
For welding likely to be done by ambitious DIYers or most small commercial welders, the process of interest is DC-TIG. Be aware, if you can nail this discipline, you’ll be joining an elite two-to-three percent of the mainstream welding industry. Titanium welding, in case you hadn’t realised, is seriously specialised.
So, which R-tech welding machine do we recommend for TIG welding titanium? First off, whatever machine you choose, we always recommend digital welders over analogue welding machines. That’s because of digital welders’ precision when inputting set-up parameters and making fine adjustments, which is absolutely the way for such tricky material.
So, if you are looking to weld steels alongside titanium, take a look at our capable TIG160PD-D DC Digital 160Amp, 240V machine with its all-important digital panel, true 4-way latching with pre/post gas and handy nine-memory store. Alternatively, our TIG210EXT Digital AC/DC 210Amp, 240V welder will add in the capability of also welding aluminium. Its functions include four AC waveforms, nine-job memory store, true 4-way latching with pre/post gas and a massive 60% duty cycle.
Call or email the team for more information and advice – it’s what we’re here for. And please remember that we’ll never try to sell you anything that you don’t need.
Weigh up the costs
Here’s something else to bear in mind when you’re looking at prices of suitable welding machines for titanium. The titanium welding process is inherently more complex and costly than standard TIG welding. For starters, there’s the expensive parent material and cost of specialised filler rods. Next, factor in the more-sophisticated torch and gas cup set-up and much larger gas volumes needed. And, of course, the cost of other accessories such as trailing shields, purge blocks and perforated welding benches. There’s also the cost of your time – you’ll need to allow more of it, particularly as you start climbing the steep titanium-welding learning-curve. Given all this cost, the extra investment in a decent welding machine – one that’s suitable for titanium work – suddenly forms a much smaller part of your ongoing costs.
This leads neatly to the main accessories needed for welding titanium. The most important ones are large diameter TIG cups (use the biggest-possible ceramic shroud) and gas lenses. We talked about TIG cups in an earlier Welding Talk article titled ‘TIG Cups – Ceramic or Glass?’ When working with titanium, controlling air-reaction and avoiding overheating is critical. It’s largely determined by how we control the size and reach of the gas pocket – with those super-sized TIG cups.
Back purging with argon
There’s more too, given that you’ll need to thoroughly back purge the back of your weld with inert argon. This may be achieved with ‘staging’ to support the weld and allow access to a secondary gas line fed through a two-way Y-splitter (see our November 2019 article on gas purging). If you gas purge regularly, you might also want to consider using a perforated welding bench that helps with accurate placement of purge-gas lines to the back of your workpiece.
Purging enclosed spaces
When welding a pipe such as a motorcycle exhaust, you must also consider purging the enclosed part of the work. In high-end production engineering, this is often done with pressurised argon baths or freestanding ‘glove boxes’ that allow handling of the welding torch, filler rod and workpiece within a controlled argon-filled chamber. Even if your titanium welding doesn’t justify the expense and complexity of such equipment, you may need to improvise a suitable sealing system for the inside volume of that pipe. If you’ll repeat the operation often, it could make sense to fabricate a more-permanent purpose-made system to maintain positive argon pressure.
Another potential solution is presented by the use of back purge bungs, providing a fully sealed interior to any pipes or chambers being welded, with the facility to completely fill the void internally with argon. This ensures the back purge side is dealt with, but there is still the issue of looking after the front.
You won’t be surprised to learn there is an accessory for that as well! Take a look at adding a trailing shield (also referred to as a ‘trailing cup’, ‘trail cup’, ‘purge shield’ or ‘auxiliary shield’). Typically, this is shaped to closely follow the lines of the workpiece. It moves in formation with the TIG torch and supplementary gas outlet to protect the cooling weld as you progress along the joint.
Be careful with power tools
Be aware of the potential for air-powered tools to introduce contamination during wire brushing or weld preparation. The Welding Institute (TWI) recommends using only electric tools after degreasing an item for welding. Even if hand tools are used, it’s vital to match the material of brushes and grinders to the titanium. And make sure the tools are only used with titanium.
Filler rods for TIG welding titanium
Along with lots of gas, filler rods are the main consumable for TIG welding titanium. As ever, quality matters. We’re not only talking about the rod’s inherent quality, but the quality of its packaging, storage and handling from factory to welding bench. Whatever the required filler rod specification, cleanliness and avoiding contamination is essential. Be cautious if sourcing a few filler rods from suppliers that break bulk. We’ll come to the price of titanium filler rods later, but first, a word about their specification.
Different kinds of titanium filler rods
One of the questions we’re often asked by first-time titanium welders is about the filler rod to use. Our response is to ask what grade of titanium they plan to weld. This is because you can get different rods to match the main grades of commercially pure titanium (CP) and titanium alloys. Of the latter, the most widely commercially available is Titanium Grade 5 (Titanium 6Al-4V), an alloy of titanium, aluminium and vanadium.
What grade of titanium are you using?
Having found out which grade of titanium you’re welding, we can then advise on a suitable rod. Be warned that, compared to ‘standard’ rods for TIG welding steel or aluminium, rods for titanium welding are much more expensive. For instance, compare the price of high-end 1.6mm 308L Stainless Steel TIG Filler Rods (£25.80 incl. VAT per kilogramme at the time of writing) with retail prices for 1.6mm titanium TIG welding rods. The latter can easily cost between £170 and £500/Kg. Enough said, particularly when the kicker is that they may only be available in 2.5kg packs!
Buy the best filler rods you can
For the same reasons that we don’t support cutting corners with welding equipment, we always recommend buying the best filler rods that you can. Daz Higgs again: ‘Buy the right consumables for the job, accept that high filler rod prices go with the territory, and remember the likely cost of wasting expensive titanium if you use cheap consumables.
As ever, the nature of parent material dictates the quality of every other aspect of your welding. Cutting corners when sourcing rods never makes sense.’
You’ll notice that we don’t list TIG filler rods for titanium welding on our website. This is because we sell relatively small quantities and prefer to order fresh stocks from wholesalers when rods are needed. For quality reasons we prefer not to ‘break bulk’ and sell rods in small quantities. That said, if you need filler rods for TIG welding and can afford full packs, please contact us because we can source them competitively – typically within 24–48 hours.
Buying one or two filler rods?
Alternatively, if you only need a couple of rods, we recommend searching online to find suppliers prepared to break bulk and sell very small quantities. Of course, TIG rods for titanium welding are very susceptible to contamination from skin oils during handling. Because of this, please confirm that the rods have been protected in storage and will be suitably protected in transit.
Handling filler rods
On receipt, we recommend handling them with nitrile rubber or cotton gloves and storage in clean, dry conditions. Before use, clean them with a lint-free cloth and degrease with a suitable solvent before use. Of course, the importance of thorough degreasing also applies to titanium workpieces – followed by airtight packaging in sealed plastic bags until you weld them.
Cotton or nitrile rubber gloves?
Good titanium welding practice dictates wearing clean protective gloves whenever you handle titanium filler rods. If the current and temperatures involved in the welding process allow (e.g., low-current detail work), a cotton glove will give better feeding than nitrile rubber. Of course, you’ll wear a normal TIG glove on your ‘torch’ hand.
If it’s not practical to wear a rubber or cotton glove, you’ll need to persevere with a good pair of TIG welding gloves. Even when facing the challenge of welding titanium, there’s no place for compromising safety.
What does titanium ‘feel’ like during welding?
As said before, you’ll be using the DC-TIG process for this. In some ways it’s like working with stainless steel, albeit with a slightly ‘stickier’ feel and much less ‘liquid’ than welding aluminium. If you’ve worked with stainless steel, you’ll appreciate how heat sensitive that material is. Compared to stainless, titanium is much less tolerant of overheating – to be blunt, it isn’t tolerant of overheating, as your weld colouring will quickly reveal.
Cleanliness, good equipment and colour
We’ll say it again: when working with titanium, cleanliness is king, overheating is a guaranteed project-killer and you must avoid lack of gas in the weld zone at all costs. This explains the importance of pre-flow, high gas-flow during welding, back purging and maintaining gas-flow as the weld cools. Planning your weld carefully with this in mind, and painstaking set-up are essential – before you even strike an arc.
Don’t skimp on equipment and consumables
As ever, invest in the best – correct – equipment, accessories and consumables that you can afford. They’ll reward you over and over as you refine your titanium welding skills. The best welding machines for titanium, such as the machines mentioned earlier, may not be the cheapest. But they’re built to last and designed with replaceable parts for a long, rewarding, service life.
Lastly, remember that the colour of your weld is the most important sign of weld integrity. And that wrong colours mean failed welds with potential safety and performance consequences. Review titanium welding colour comparisons regularly, compare them with your work and remember that they’re signposts to be obeyed. The quality of your work, your reputation as a welder and people’s safety rely on it.
Talk titanium with our team
Many welders go through their careers without ever welding titanium. Others learn to love titanium and make a living specialising in welding it.
Maybe you’ve just been asked to weld titanium for the first time and want to invest in a ‘titanium-capable’ digital welder. Or, perhaps, you’re an experienced titanium welder seeking more filler rods and accessories such as Y-splitters. Whatever titanium welding means to you, we’re here to help.
Let’s talk titanium. Send us an email or call us sometime!