Steel: As with stainless steels, there are far too many alloys and properties to cover here. But four important issues to consider are:
Steels generally cost less than stainless steels and superalloys
In the presence of air and humidity, all steels corrode
Most steels are quite machinable, with the exception of some tool steels
The lower the carbon content, the less hard steels can be made (indicated by the alloy’s first two digits, as in 1018, 4340, or 8620, three common selections). That said, steel, and its cousin iron, are by far the most commonly used of all metals, with aluminum coming in a close second.
