Welding Stainless Steel

There’s knowing how to weld steel and there’s knowing how to weld stainless steel. The latter, renowned for its corrosion resistance and use where hygiene is essential, distorts easily when heated. However, its lower thermal conductivity means heat energy isn’t dispersed from the welding zone so fast, which helps during welding. Overall, it’s easy to work with, but with the help of the following tips and advice, you should soon be on the way to stainless mastery… 

Can you weld stainless steel?

Yes, absolutely. And you can do it with the MIG welding process, TIG welding or MMA (stick welding). Whether you’re a newcomer to welding or a seasoned professional, it’s probable that welding stainless steel will eventually find its way into your welding skill set.

Is welding stainless steel difficult?

As with all weldable metals, stainless steel comes with its own peculiarities and behaviours under the arc. Getting the best from this alloy (also called inox steel or inox), with its minimum 10.5% Chromium content, can take a lifetime. Along with aluminium, it’s undoubtedly one of the more challenging materials to weld.

However, whether you’re just starting out or work regularly with this material, a few tips will serve as a valuable learning aid – or a helpful reminder…

Which welding is best for stainless steel?

In this article, we draw on the expertise of the R-Tech team to assemble a selection of tips and advice relating to three common methods for welding stainless steel: MIG welding; TIG welding; and manual metal arc welding (MMA). Which is best for welding stainless steel? Choosing the best process really does come down to the specifics of the task – and the qualities required from the finished weld. If cost is the key factor it could be MMA; but for precision with thin materials, it’s probably going to be TIG. Let’s explore the three processes. But first, here’s an important reminder about safety when welding stainless steel.

Is welding stainless steel harmful to your health?

The short answer is that stainless steel welding comes with potentially severe health risks – not least from Cadmium and Chromium (Vi) fume. Suitable safety measures, including local exhaust ventilation (LEV) and welders’ personal protective equipment (PPE) such as air-fed welding masks are therefore essential.

MIG welding stainless steel

Can you MIG weld stainless steel?

Again, yes you can. Firstly, as with any welding process, make sure your MIG welding machine is set up correctly for welding stainless steel.

We recommend that you always fit a Teflon wire liner; this will ensure good wire feed as well as preventing wire contamination. Stainless steel may be highly corrosion resistant, but it’s also susceptible to contamination. When welding stainless steel with MIG, any ferrous material (including contamination by a steel liner) in the weld pool can easily cause rust spots on finished work.

• Naturally, you’ll also make sure your MIG torch is in good condition before starting to weld. As with welding aluminium, it may also make sense to buy a torch sized larger than you’d use for normal steel. Because, welding stainless steel produces more heat, the larger torch will carry higher amperages better.
• Reverting to contamination, it’s vital to use only stainless steel wire brushes and grinding/cutting discs whenever working with stainless steel.
• As well as the vulnerability of stainless steel to ferrous contamination, you need to ensure that your working area is free from iron or steel dust, or any ferrous oxides. This may sound trivial, but it’s vital. Cleanliness of materials and workspaces is always important for good welding. With stainless steel, avoiding even the tiniest particulate contamination is critical.
• Next comes that old favourite: correct wire type and diameter. As ever this is project specific, so seek advice.
• More advice shared with aluminium welding is the importance of clamping and tack welding your workpiece to avoid movement and distortion through cracking. Mike Gadsby, one of R-Tech Welding Equipment’s sales advisors (and an experienced welder) says:

‘Think about staggering your stainless steel welds to mitigate the risk of heat distortion caused by the material’s thermal properties.’ 

What gas do you use for MIG welding stainless steel?

As ever, correct gas choice matters when MIG welding stainless steel. You may be using pure argon or a blend of argon and minor gases to improve starting. Or maybe even a specialist stainless gas mix (such as BOC’s Stainshield range of argon, helium and carbon dioxide), especially for more-exotic stainless steels such as Inconel, Hastelloy or Monel alloys. With stainless MIG welding, you’ll use a slightly higher gas-flow rate of around 14–16 LPM. We recommend contacting gas suppliers to discuss gas requirements for your specific project. 

TIG welding stainless steel

For TIG welding stainless steel, you can use a DC-only machine or AC/DC TIG welding machines in DC-mode. Importantly, make sure your machine has sufficient power to weld stainless steel. Whether you’re unsure about your existing machine’s capability, or buying a machine for stainless steel welding, ask the machine’s supplier for help – including advice on TIG welding stainless steel settings.

• Yet again, cleanliness is everything when you TIG weld stainless steel. Clean the workspace and material thoroughly. As with MIG, if it’s dirty, use a stainless-steel wire brush that’s only used for stainless steel. And if it’s oily, always degrease it thoroughly. Because of the risk of ferrous contamination, you can’t be too clean or too careful.
• Get your TIG torch set-up for stainless. In particular, make sure the torch has the appropriate duty cycle for the amperage being run. Never cut corners; if the torch isn’t up to the task, invest in one that is.
• Don’t overlook all-important torch consumables either. Paying attention to having the appropriate gas cup, selecting your tungsten type correctly, and getting the electrode diameter just right are vital. Because stainless steel benefits from generous gas coverage, use a slightly larger diameter gas cup than usual. Better still, fit a gas lens (such as the TIG Zone eVo-FLO cover kit) to boost gas flow over the weld, keep it cool and provide extra shielding for the weld pool.
• As ever, make sure to choose the correct rod for the grade of stainless steel that you’ll be welding (widely-used grades include 316, 308 and 312 stainless). Correct rod thickness is also essential: thinner stainless steel demands thinner rods to deliver required deposition rates. Again, this is job-specific, so seek advice from your TIG filler rod supplier or rod manufacturer. And while we’re discussing filler rods, make sure to wipe your filler rod clean to remove any oily residue. It’s that cleanliness and contamination thing again… And of course, when you weld, do wait for the weld puddle to pool before you introduce the rod.
• Just as for TIG welding aluminium, control is everything. For optimum control and precision, use a TIG foot pedal or a TIG torch with variable amperage control.
• Consider pulse welding thinner stainless steel. Welding the face of a plate can be very different to welding, say, the edge of the same piece. When TIG welding stainless steel, pulse welding helps reduce distortion by minimising the heat going into the weld – while simultaneously optimising penetration. If this is a consideration, make sure your TIG welding machine has pulse welding capability. All R-Tech TIG machines do – covering the range 0.5–50 Hz. 

MMA welding stainless steel

We’ve looked at MIG and TIG welding. Now we’ll touch briefly on MMA arc welding of stainless steel. It’s the simplest of the three processes to set up (most importantly, choose the right electrode for the weld). It’s also the cheapest way to weld stainless alloys. Assuming that you have a welding machine with stick welding capability, all you really need to start are some suitable rods. There’s no gas, torch, foot pedals or torch consumables…It’s welding at its simplest.

• Stainless steel moves on welding tables, so make sure you clamp or tack weld it to your workpiece.
• Choose the correct electrode for the workpiece (again, 316, 308 or 312 grade are typical).
• Remember that you won’t be able to weld thin sheets of stainless steel. Many welders struggle with stainless sheet less than 2mm thick. It’s all down to the lower controllability of MMA arc welding for such applications.
• Thin sheet may be a struggle. But in comparison, welding mild steel to stainless steels or high-carbon tool steels really plays to MMA’s strengths.
• Pre-heating often helps with some stainless steels. That’s because it can help prevent cracking. Pre-heating is typically done with a blow torch, or with an oxy acetylene or oxy propane torch.

Get more advice on welding stainless steel

Whether it’s MIG, TIG or MMA welding of stainless steel, your work will benefit from consistent application of helpful tips such as the ones above. Add quality consumables and (as appropriate) some well-chosen accessories, then practise, practise, practise. You’ll soon be on your way to mastering stainless steel welding. If you’re a professional who’s already there, you know what we mean.

Let’s talk stainless steel welding

Having mastered the basics of welding stainless steel, perhaps you’ll extend your skills to the special challenges of welding stainless to mild steel (carbon steel) – or even more specialised applications.

Whatever you are welding with stainless steel, remember that the R-Tech team is here for you. Of course they’ll help you choose anything from a single gas lense or a set of stainless steel filler rods to a MIG welding machine. But they also like sharing valuable advice based on decades of experience – or simply talking stainless steel welding.