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Welding Stainless Steel

• Stainless steel is a family of iron-based alloys that contain a minimum of approximately 11% chromium

• The chromium oxide layer creates resistance to corrosion and staining, as well as providing heat-resistant properties.

• As stainless steel is hygienic, low maintenance and has aesthetic appeal it is rarely coated.

• Different types of stainless steel include the elements carbon, nitrogen, aluminium, silicon, titanium, nickel, copper, selenium, niobium, and molybdenum.

• There are four categories of stainless steel:

• Austenitic stainless steel

• Ferritic stainless steel

• Martenitic stainless steel

• Duplex stainless steel

• Typical applications range from installations in the pharma/chemical industries to offshore and from food applications to road tankers and more.

Download Maxx® Weld Process Gases brochure

What welding gas is required for welding stainless steel?

Pure argon or argon/carbon dioxide mixtures are commonly used for MIG/MAG welding stainless steel.  Additional benefits can be gained from the inclusion of helium into the mixture.  For TIG welding stainless steel a small addition of hydrogen reduces surface oxidisation.  Use our interactive welding gas selector to identify the most suitable gas for your welding application.

How to MIG weld stainless steel?

There are some core materials required to MIG weld – welding machine, filler wire, welding gas and PPE.  There are also some core safety rules that need to be observed and surface preparation required before welding can commence.

In summary, an electric motor continuously feeds consumable filler wire through the welding torch into the arc, and the power source keeps the arc length at a pre-set value. This allows the welder to concentrate on ensuring a complete fusion of the joint. Most power sources for MIG/MAG welding processes are known as constant voltage machines.

Stainless steel can be difficult to weld as the metal conducts heat slower than carbon steel increasing the risk of distortion, burn-through and oxidisation.  A clean workplace is essential as stainless steel is vulnerable to ferrous contamination.  Likewise, spatter should be kept to a minimum to avoid damaging the protective chromium oxide layer.

What is the best gas for MIG/MAG welding stainless steel?

Inert gases such as argon or helium can be used for welding stainless steel.  However, argon mix gases provide optimal weldability and weld quality.  If you are looking for an ideal all-rounder for MIG/ MAG welding stainless steel, Inomaxx® 2 welding gas with 2% oxygen in argon, provides optimal heat, even with thin materials, to prevent burn-through.  It is suitable for pulsed arc transfer and offers superior mechanical properties. 

Stainless steel can be sluggish to weld – for increased weldability there is Inomaxx® Plus with 35% helium and 2% carbon dioxide in argon.  The low addition of carbon dioxide eliminates the risk of carbonisation and any mechanical property interference and the optimum helium addition allows for faster weld travel speeds and better control.

How to TIG weld stainless steel?

One of the advantages of TIG welding is that it allows you to weld a wide range of materials. Modern power sources combine constant current and constant voltage characteristics and deliver excellent arc stability. Machines ranging from 5A (micro-TIG) to over 500A are available.

In manual welding the operator points the electrode in the direction of welding and uses the arc to melt the metal at the joint. Arc length is controlled by the welder and is usually between 2mm and 5mm.  Note – stainless steel is vulnerable to ferrous contamination so it is important that the workspace is clean.

Filler metal is added to the leading edge of the weld pool.  Travel speed is adjusted to match the time needed to melt the joint and keep a constant weld pool size. Stainless steel can be sluggish as it conducts heat slower than carbon steel so welder needs to be mindful of oxidisation and/or burn-through.


What is the best gas for TIG welding stainless steel?

Often the gas is argon, but helium by itself, or mixed with argon, may be used for special applications. Argon-hydrogen mixtures can be used for exceptional results when welding austenitic stainless steel.

Air Products recommends Inomaxx® TIG welding gas (2% hydrogen in argon) for TIG welding stainless steel as the hydrogen reduces surface oxidisation which reduces the post-weld cleaning as well as reducing the amount of ozone produced in the fume.

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"What is spatter"

Spatter is made up of many thousands of droplets of molten filler metal that escape from the weld pool and are scattered around the work area during welding. These small, round balls of molten metal can fall on the welder, workpiece, the floor and surrounds. Sometimes they stick and are difficult to remove, sometimes they cool and form tiny balls of metal.


What causes Spatter?

Causes of spatter include:

  • Poor base material surface conditions; joint faces and the weld area need to be clean and free from contamination such as oil, paint, scale and rust. 
  • Use of welding equipment in poor working order. 
  • Sub-optimal shielding gas selection; for instance, when MAG welding carbon steel, argon/carbon dioxide mixtures generate more spatter than argon/carbon dioxide/oxygen gas mixtures such as one of the Ferromaxx® gases from Air Products.


How to reduce spatter when welding?

Spatter can be removed either using hand tools (such as a grinder or chisel) or via a chemical process. In some instances, anti-spatter wipes can be applied to the workpiece, prior to welding, to ease the removal of spatter. However, any method to remove spatter will require some manual input. From a visual perspective, it is well understood why it is undesirable to have spatter on the workpiece, as it negatively impacts the finish of the product. Due to the uneven surface and poor adhesion of the spatter, paint finishes will have imperfections and offer poor protection. This, in turn, can shorten the life cycle of the final product. However, there are several other key reasons to eliminate spatter that are sometimes overlooked. These are all cost-related:

  • Spatter is a waste of wire. On the face of it a reduction in spatter on a weld may seem insignificant and not worth the effort to resolve. However, filler wire is expensive, and the melting of spatter uses valuable electricity, up to 20% of filler wire can be wasted in spatter if not controlled properly. In addition, spatter can stick to gas nozzles and contact tips blocking the flow of gas and causing porosity. 
  • Spatter increases material costs. Anti-spatter, grinding wheels, chemicals, power – the more spatter there is to remove, the more these costs increase.
  • Spatter incurs labour costs to remove. This is lost production time. Welders are skilled labour. Any time spent removing spatter is time that could have been spent in a more productive way.

There is a compelling case to minimise spatter. Air Products can work with you to achieve this goal. All our Maxx® weld process gases have been designed to minimise spatter, saving you time and money.


Why is Shielding Gas Used in Welding?

Shielding gas acts as a blanket that sits over the weld pool protecting it from atmospheric contamination. If moisture, nitrogen or oxygen enter the weld pool then this weakens the weld quality leading to defects and potentially rejects. Welding gas is inert or semi-inert so that it does not interact with the weld process. The most common element in welding gas is Argon. Many modern welding gases are mixtures; some may contain reactive elements, such as hydrogen, however these are smaller constituents in the mixture.


What is Weld Porosity?

One example of a welding defect caused by contamination is porosity. Porosity is caused by absorption of gas in the weld pool, that is released as solidification takes place to become trapped in the weld. Gases like hydrogen, oxygen and nitrogen have a larger solubility in molten metal than in the solid phase. Therefore, as a weld cools, gases are expelled from the solidifying melt and can become trapped as pores if solidification occurs before they reach the surface.

Welder's Handbook

Request a download of our industry-leading comprehensive guide to gas shielded arc welding and oxy-fuel cutting.


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