Metal Casting

Welding Stainless Steel: A Guide

Sparks fly as a welder works on stainless steel piping

Corrosion-resistant stainless steel is prized for durability, but this multi-purpose metal can be tricky to weld

Stainless steel tubes glint in the sun
Stainless steel is sought after for its strength and resistance to rust, but this sleek, modern metal can be tricky to weld.

First created in 1913 to solve the problem of rusting gun barrels, stainless steel is the metal of choice for engineers, architects, and industrial designers everywhere. Stainless steel is part of our everyday life, used for everything from cookware, kitchen appliances, and cutlery to skyscrapers, bridges, and aircraft.

This versatile ferrous alloy of iron and carbon mixed with chromium is strong, flexible, and rust-resistant, characteristics sought after by civil engineers and designers. Urban planners and municipal developers love stainless steel for sleek, modern public amenities and traffic management solutions, such as bollards and bike racks.

Demand for stainless steel is only expected to grow, especially in Asia where new and existing cities continue to expand and steel production continues to rise. China dominates today’s market, producing over half of the world’s stainless steel.

What makes stainless steel stainless?

Stainless steel’s magic ingredient is the addition of at least 10.5% chromium which hardens the metals’ surface and makes it rust resistant. Oxygen reacts with iron to produce rust in a process known as oxidization. When chromium reacts with oxygen, it forms a tough top layer which protects the alloy from corrosion, making it a metal of choice in construction, engineering, architecture, and manufacturing.

There’s just one catch: this do-it-all metal is difficult to weld. Due to its excellent heat retention and the need to preserve its anti-corrosive top layer, welding stainless steel can be extremely tricky, even for an experienced welder.

Rusty chains
Chromium gives stainless steel its prized rust-resistant properties, adding a protective layer of chromium oxide to the alloy and preventing corrosion.

Why is welding stainless steel tricky?

The first problem you’ll encounter when welding stainless steel is that this popular alloy retains heat very efficiently. This means that if you use too much heat stainless steel will warp during welding or distort or crack during the cooling process.

Additionally, stainless steel will easily show weld imperfections, making it an unforgiving material for decorative or aesthetic projects.

Sparks fly as a welder works on stainless steel piping
Welding stainless steel requires meticulous preparation to avoid contamination with other metals.

Ensuring that the metal retains its rust-resistant chrome oxide film is possibly the most important part of welding stainless steel. Heat tinting or “blueing” during the weld process is a clear sign that the stainless steel’s protective chromium layer has become depleted, reducing its corrosion resistance and leaving your weld susceptible to rust.

Welding stainless steel also requires making sure the material does not become contaminated with carbon steel residue left behind on other tools; this will introduce iron into the weld, leading to corrosion over time. Both the preparation and the final finishing stage of a stainless steel weld must be completed with great care, including ensuring you’re the material and your work area are meticulously clean and that the finished product is properly cleaned. When welding stainless steel it is best to use separately labelled tools, brushes and grinders to prevent cross-contamination.

What’s the best method for welding stainless steel?

Welding stainless steel can be done using a variety of methods, including TIG, MIG, and spot and stick welding. As with any welding job, the materials and tools required will depend on the type of stainless steel you’re working with. Be sure to check the unique requirements for your stainless steel weld based on the thickness and composition of your metal and the specifications of the job. Make sure you’ve correctly identified the grade of the stainless steel you’re working with.

TIG welding a stainless steel exhaust pipe
TIG welding is slow and requires a high degree of skill but produces a beautiful finish.

TIG (Tungsten Inert Gas) welding is arguably the best choice for welding stainless steel as it is a lower heat weld, offering better control and precision, and a finished look to the job. TIG welding uses a tungsten electrode combined with a shielding gas to produce a beautiful weld finish sometimes known as “stacking” or “laying dimes.”  TIG welding is done by hand and requires a high degree of skill. Because it can’t be automated, it’s a slower option for welding stainless steel. TIG welding’s clean, polished finish making it perfect for decorative or aesthetic stainless steel welding projects. ­­­

Welding sparks in a dark factory
Metal Inert Gas (MIG) welding creates solid welds without producing a lot of spatter.

MIG (Metal Inert Gas) welding, or gas metal arc welding, uses a wire electrode to run an electrical current onto a metal surface, producing strong welds. MIG welding also requires the use of a shielding gas. MIG welding is a good choice for welding stainless steel because it doesn’t produce spatters and is a faster option than TIG welding. It works well on particularly thick pieces—creating solid, robust welds.

Robotic spot welding in a factory
Spot welding can be automated making it a good choice for fast, high-speed welds.

Resistance or spot welding is another good option for welding stainless steel. This method involves using two electrodes to pass an electric current through two connected pieces of metal to melt and join them. Spot welding can be automated for manufacturing for fast-moving assembly lines and doesn’t require the use of filler. Because of its electrical resistance and heat retention properties, spot welding stainless steel can be completed very quickly.

a worker welds in a factory
Stick welding is perfect for welding stainless steel outdoors in poor weather conditions.

Stick welding , or shielded metal arc welding, is a good choice if the appearance of the weld isn’t a concern. Stick welding is one of the oldest and most cost-effective forms of welding, and is a good choice for welding stainless steel outdoors or in bad weather because there’s no gas shielding required. Stick welding relies on an electrode with an electric current to melt metal and filler for the weld joint. Unfortunately, stick welding does produce a lot of spatter.

Metalworking and stainless steel

Stainless steel is more often worked than cast, as steel casting requires very high temperatures and careful pattern design to get a good pour. Welding is therefore a very important part of stainless-steel manufacturing.

Our stainless products, produced in 316 alloy for outdoor use, may have welded components, as seen in our bollard manufacturing tour. The contemporary look of stainless steel married to its corrosion resistance make stainless bollards and bike racks increasingly popular with site managers.