Ferrous and Non-Ferrous Metals – All You need to know
As a general rule, ferrous materials are distinguished from non-ferrous materials by the fact that they contain iron and non-ferrous materials do not. “Ferrous” is derived from the Latin word “iron” (ferrum), which is also responsible for the chemical element symbol Fe.
Technically, this means that non-ferrous materials are also materials such as polyethylene, plant fibers and wood. However, this terminology is usually only applied to the field of metallurgy in order to distinguish between metals that contain iron and those that do not. In this article, we explore the major differences in terms of mechanical properties, price and other factors.
Iron itself is, by mass, the most common element on earth. Our planet’s crust contains 5% of iron content, while scientists suspect that the outer and inner core is molten iron alloyed with little amounts of nickel. Elemental iron does not occur naturally on Earth, but can be found in meteorites and reacts to oxygen and water. Iron metal is one of the most important material in human history as it was used to weld weapons, tools and even buildings. Chemically, the metal is a powerhouse because it’s reactive to many elements and can form alloys to achieve better properties. Even in biology, it is extremely important because it is used to form complexes with oxygen in blood.
Properties of ferrous materials
All ferrous materials contain iron in some form or another. The most common ferrous metal is steel. Due to its excellent ability to form alloys, there is a large steel variety, with more than a thousand different types of steel. Furthermore, it is widely used in the construction and manufacturing industry. The most widely known grades and groups of steel are: mild steel, stainless steel, tool steel, HSLA steel, alloy steel and carbon steel.
A widely spread misconception about ferrous metals is that they are all defined by their magnetic properties. However, there are many steel types that are not ferromagnetic, since ferromagnetism is not necessarily defined by iron itself but by its elemental structure. To cut a long story short: Ferrous materials are not necessarily ferromagnetic. After all, one of the most widely spread steel types are non-magnetic or show very little ferromagnetism. Plus, there are ferromagnetic materials that do not contain any iron, such as cobalt and nickel.
So if not magnetism, what other defining properties are there for ferrous metals? Since there are so many types of ferrous metals, it’s hard to find common ground other than the fact that they contain iron. However, ferrous metals are generally heavier than non-ferrous metals, as the density of iron is high. Majority of ferrous metals can form iron oxides when exposed to oxygen. Even so, this can be prevented by alloying elements such as chromium and nickel. Furthermore, ferrous metals generally have relatively high yield and tensile strength as well as high hardness.
Common applications for such metals are railroad tracks, shipping containers and automobiles.
Properties of non-ferrous materials
Non-ferrous metal contains no or very little amounts of iron. On average, non-ferrous metal is more expensive than ferrous metal, as it is generally rarer. Common non-ferrous metals include precious metals, such as gold, silver and platinum and others, such as aluminum, copper, nickel, zinc, titanium and many more. Most of these metals can be alloyed with iron, usually forming a stronger and harder material.
Due to their diversity, it is hard to make general statements regarding mechanical properties of nonferrous metals. They are not generally harder or softer than ferrous metals – non-ferrous titanium for instance is one of the hardest elements on earth, while gold is very soft. Non-ferrous metal can be both more expensive and more affordable than ferrous metals as well, depending on which material.
Other differences between ferrous and non-ferrous materials
While ferrous metals offer a great variety, there are many cases where non-ferrous metal is preferred. For instance, aircraft and car bodies would benefit from the excellent corrosion and wear resistance of stainless steel (especially when it has been hardened), but due to costs and weight, aluminum is a better choice. It doesn’t form “rust” in the traditional sense, but creates a protective layer of aluminum oxides that forms once exposed to our atmosphere. While there are steel types that operate with a similar concept, for example weathering steels, they are more expensive and weigh much more.
Nonferrous metals can also be found in expensive jewelry, while metals containing iron are usually used for low-cost jewelry. And that’s not only because of higher material value. Ferrous metals are not suitable for jewelry production because they can rust and wear. Adding nickel and chromium can improve the material, but nickel is extremely allergenic and chromium makes steel hard to work with.
In conclusion, there are many types of metals which can very roughly be divided into the two categories, ferrous and non-ferrous metals. However, taking a closer look into these categories shows that there is a vast diversity of metals, and it is almost impossible to make generalizing statements about one group.
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