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At first glance, welding steel may seem to be a fairly simple and straightforward proceedure for an experienced welder. And it usually is. But also be aware that there are a number of considerations that need to be taking into account before welding steel, and under some circumstances it might not be easy or even possible.
The first consideration is the type of steel to be welded. Steels are typically classified according to hardness and application. The majority of common steel are weldable, but there are other steels like bearing steel or tool steel that are not.
An alloy that consists primarily of iron, most steel has a carbon content of 0.2 to 2.0 percent. As the carbon content increases, the steel becomes harder - but also more brittle. You’ll need to determine the composition of the steel in question before any attempts at welding.
In general, steels with fewer alloys are softer, and more weldable. The carbon content of the steel will have the largest effect as far as its weldability (less carbon = more weldable) but also be aware that other alloys like vanadium and chromium will decrease weldability as well.
As a rule, low carbon steels (those having a carbon content of less than .25%, and a phosphorus and sulfur content of less than .05%) are fairly easy to weld. A lot of the steel you see in building construction projects are of this type, and
can be stick welded in the field without any special precautions.
Welding steel is a balancing act between weldabilty and strength. If you can, use low-alloy, high strength steel that’s been designed for welding. This might not always be possible, of course, but it will make your job a whole lot easier. Also keep in mind that tempered and hardened low-alloy steels are more prone to losing some of their hardness and strength, and may even crack, when welded.
Stainless steels can also be welded, but with a greater degree of difficulty. This is not a weld you should attempt unless you’re a fairly experienced and competent welder. The most weldable forms of stainless steel are the austenitic grades of steel. But be aware that these steels are prone to high thermal expansion, and may distort when welded. Also use an electrode that limits that amount of ferrite in the weld, as this can lead to hot cracking with austenitic steels.
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