Steel welding

Challenge of steel welding

Not all steel is the same: depending on the alloy and heat treatment, the properties can vary considerably – from high strength and good toughness to excellent corrosion and heat resistance. The challenge is to preserve these advantageous characteristics as much as possible after welding. To achieve this, it is crucial to select the appropriate welding process and precisely adjust the stretch energy.

Interesting facts about steel

Steel is primarily composed of iron and a maximum of 2.06% carbon. Alloys with a higher proportion of carbon are known as cast iron. If the proportion of sulfur and phosphorus accompanying iron is less than 0.025%, it is called stainless steel.

Not every steel can also be welded: only pure steels, i.e. alloys with a carbon content of less than 0.22%, are suitable for this process. As a rule, the more impure the alloy, the harder it is to weld the steel.

Of particular importance are high-strength and super-high-strength steels. They are used, for example, in lightweight construction in the automotive industry, as well as in mobile cranes, concrete pumps, and agricultural and forestry machinery. Processing them is more demanding than with conventional steel alloys, so it is essential to follow the manufacturer's instructions.

Steel exists in a wide range of forms:

Flat steel
Round steel
Profile pipes
Square pipes

This is how to prepare steel for welding

Select suitable seam finishing
Depending on the welding task, single-sided or double-sided preparation is recommended to ensure reliable penetration welding – for example, by milling, grinding, or cutting. Important: The surface should be bare before welding.
Remove rust
Remove rusty areas in the parent material before welding so that no bonding flaws occur in the weld metal.
Remove oil or grease
Oily parent material makes the welding process more difficult and may, among other things, cause poor results. You should therefore remove the oil from the steel before welding.
Preheat
In case of higher material thicknesses, you should preheat the part before welding to slow down the cooling time. This prevents a high degree of hardness in the microstructure and significantly reduces the risk of cracking.

Advantages

Simple and secure fusion welding connection
Wide range of applications
High strength of the connection
High toughness depending on the choice of material

Disadvantages

Delay due to shrinkage
Necessary corrosion protection
Structural changes in the heat-affected zone (e.g. hardening)

Welding process for steel

In principle, all welding processes are suitable for joining steel. However, the MIG/MAG process is primarily used because this allows for the highest welding speeds.