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Welding Carbon Steel

Carbon steel is by far the most common metal that is welded. Chosen for its relatively low-cost, it is easily cut, formed and welded. It is primarily chosen for its strength and versatility, although normally it needs to be coated, whether with paint, powder coating or by galvanising.

Carbon steel is available with varying levels of carbon content; these are grouped as per the following:

  • Low (or mild) carbon steel
  • Medium carbon steel
  • High carbon steel
  • Ultra-high

Carbon steel, with a low carbon content, is by far the most common variant and therefore, for this reason, carbon steel is often referred to as mild steel even when it has a higher carbon content.

The applications for carbon steel spans all applications, ranging from small items such as chairs through to cars, bridges or ships.

The Ferromaxx® weld process gases range has been purpose-designed for MAG welding carbon, carbon manganese and low alloy steels.

Download Welder's Handbook

How to MIG-MAG weld carbon steel?

There are some basic materials required to MIG/MAG 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. 

Carbon steel is relatively easy to weld -the lower the carbon content, the easier to weld.  Defects are generally a result of poor welding practice, rather than the base metal.  It is important, therefore, that the metal is clean and prepared to achieve the best quality weld.

Expect more from your Welding Gas

Welding gas should do more than just shield the weld pool – it should contribute to improving weldability, increasing productivity and maximising profitability through improved efficiencies.

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Supply Options

Air Products can help you determine the most economical supply option for your particular application and geographic location. Industrial gases are typically provided in gaseous and liquid form through a variety of supply systems.

Cylinders & Hard Goods

The traditional solution for low-volume gas supply. Cylinders can be supplied in a full range of sizes, pressures and gas purities for a range of gases and gas mixtures. Search our extensive network of distributors in the U.S. and parts of Canada for your cylinder and hard goods supply needs.

Welding Cutting Gases

A range of gases, technologies and services for metal fabrication, whether you are welding, cutting, thermal spraying, brazing or gouging.


"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.