Ferrous vs Non-Ferrous Metals: What Is the Difference?

Introduction

In simple terms, ferrous metals are metals with iron as the main element, while non-ferrous metals do not contain iron. This is their most basic and significant difference. This basic difference also makes ferrous metals and non-ferrous metals have many differences in performance, use, processing technology, physical properties, etc. Understanding these differences will enable us to choose the right metal materials in the project and conceive solutions that take into account both project operation efficiency and cost-effectiveness. This article will compare the differences between ferrous metals and nonferrous metals from multiple dimensions to help newcomers in the metallurgical industry acquire basic knowledge and provide new perspectives and thinking for professionals in manufacturing, engineering, construction and other industries.

Examples of Ferrous Metals and Non-Ferrous Metals

Before comparing ferrous metals and nonferrous metals, we must first understand examples of common ferrous metals and nonferrous metals

Ferrous Metals

Ferrous metals mainly refer to iron and iron alloys, and iron alloys are divided into cast iron and steel.

Cast iron

Gray cast iron

Ductile cast iron

Malleable cast iron

White cast iron

Alloy cast iron

Wrought iron

Steel

Non-alloy steel =  (low/medium/high) carbon steel

Alloy steel/stainless steel

Non-Ferrous Metals

Aluminum

Brass

Bronze

Copper

Lead

Zinc

Tin

Gold

Silver

Titanium

Nickel

What’s the Difference Between Ferrous Metals and Non-Ferrous Metals?

Next, we will compare ferrous and non-ferrous metals in detail from multiple perspectives. A simplified table is attached at the end of the article for your convenience.

Appearance

Appearance of Ferrous Metals

Cast Iron

Cast iron is a ferrous metal produced by a casting process. Among them, carbon usually exists in the form of graphite. There are two more common types of cast iron, namely gray iron and ductile iron.

Gray Cast Iron

Gray cast iron has a matte dark gray (most common) to black appearance. The dark appearance of gray cast iron is mainly due to its large amount of flake graphite. After oxidation, the surface of gray cast iron will show reddish-brown rust. The surface of gray cast iron is generally rough and uneven, mainly because the flake graphite in its microstructure is mainly distributed irregularly in a network and layered manner, which makes the surface of gray cast iron look uneven from a macroscopic perspective. In addition, gray cast iron is usually cast in sand molds, which is prone to various defects (such as pores). In the production of large castings, the surface roughness caused by these gaps is more intuitive.

Ductile Cast Iron

Unlike gray cast iron, the spherical graphite structure of ductile iron is more regularly distributed than the flake graphite structure of gray cast iron, so the surface of ductile iron is smooth and delicate, bright dark gray or silver gray. Ductile cast iron, compared with gray cast iron, has good toughness and ductility, so it is stronger and can withstand greater impact.

Wrought Iron

Wrought iron is another black metal produced by forging. Wrought iron is silver-gray or dark gray overall. Similar to cast iron, after oxidation, a layer of reddish-brown rust will form on the surface. Since forging is a process of forming iron by forging, hammering, etc., the surface of forged iron presents a fibrous texture, and it also retains some forging marks such as hammer marks, which is relatively smooth overall.

Non-Alloy Steel/Low/Medium/High Carbon Steel

Carbon steel, also known as non-alloy steel, is an alloy composed of iron and carbon. According to the carbon content, it is divided into low carbon steel, medium carbon steel, and high carbon steel, and their respective appearance characteristics are different.

Low carbon steel

The carbon content of low carbon steel is 0.05 to 0.15%. The surface of low carbon steel is light gray or silver gray. Because of the low carbon content, the hardness is low and it is easy to process. Therefore, after low carbon steel is processed, its surface is often smooth and delicate.

Medium carbon steel

The carbon content of medium carbon steel is 0.3–0.5%. The surface of medium carbon steel is metallic gray. Its appearance is not as bright as that of low carbon steel, and it mainly presents a low gloss, matte texture.

High Carbon Steel

The carbon content of high carbon steel is 0.6 to 1.0%. The color of high carbon steel is mainly metallic gray or dark gray. Its high carbon content makes it have a higher hardness, but it is also easy to produce many small bumps and scratches during processing, which makes the surface of high carbon steel uneven and shows a completely matte texture.

Alloy Steel/Stainless Steel

Alloy steel is another main type of ferrous metal. The so-called alloy steel is a type of steel obtained by mixing alloy elements such as chromium, nickel, silicon, copper, titanium and iron. These alloy elements also give alloy steel a good surface.

Stainless steel is the most common alloy steel. The basic component of stainless steel is still iron, followed by chromium, and then other alloy elements such as nickel, molybdenum, titanium, etc. The surface of stainless steel materials is generally smooth, showing silver white, gray white, or close to mirror reflection. And stainless steel materials can be subjected to a variety of surface treatment processes, such as polishing, brushing, etc., so that stainless steel materials have a better appearance and are more suitable for application scenarios that require a modern appearance.

Appearance of Non-Ferrous metals

Non-ferrous metals have a variety of metallic colors under normal conditions.

Aluminum

Under normal conditions, aluminum has a visually similar appearance to silver, with a silvery gray metallic appearance. Aluminum has a smooth surface that reflects visible light like a mirror. Aluminum alloys have a silvery-white metallic sheen when smooth and a dark gray when rough.

Brass

Brass is an alloy of copper and zinc. Brass has a bright golden appearance and is a popular material for many aesthetically pleasing applications. Brass with a higher copper content is softer and more golden in color; conversely, brass with a lower copper content and a higher zinc content is harder and more silver in color.

Bronze

Bronze is an alloy composed primarily of copper and tin. The tin content is generally 12-12.5%, and other metals are often added. Bronze products have a golden-brown color when freshly made and a bluish-gray color when oxidized.

Copper

Copper is a soft metal. New, pure copper metal has a pinkish-orange metallic sheen.

Lead

Lead is a soft metal. When lead metal is cut, its cross section will show a slightly bluish silver color. After being exposed to the air for a period of time, the cross section will lose its luster and turn into dark gray.

Zinc

Zinc is a hard and brittle substance at room temperature, showing a bluish-white color and a metallic luster.

Tin

Tin is a soft silver-white metal.

Gold

Gold has a bright metallic luster at room temperature, showing a yellowish-red color, and the overall texture of gold is soft.

Silver

At room temperature, silver is a soft metal with a white luster.

Titanium

The surface of titanium has a silver metallic luster, and the surface is smooth and hard.

Nickel

Nickel is a solid with a silvery-white metallic luster at room temperature, and its silver-white color is mixed with some light gold, and it is relatively hard.

Summary

Through the above content, we can find the following rules. Most ferrous metals are dark gray and dark black, with low gloss and a rough surface. A few have a bright metallic color. The colors of non-ferrous metals are richer, covering gold, silver, red, turquoise, etc. At the same time, they have higher brightness and the surfaces of most metals are smoother.

Chemical Composition

Ferrous Metals

Ferrous metals are mainly steel and cast iron. The basic components of these two types of metals are mainly iron and carbon, supplemented by other small amounts of elements;

Non-Ferrous Metals

The main components of non-ferrous metals are metals other than iron, including aluminum, copper, gold, silver, nickel, etc.;

Magnetic

Ferrous metals are magnetic and can be attracted by magnets;

Most non-ferrous metals are non-magnetic and cannot be attracted by magnets.

However, some alloys of non-ferrous metals will show magnetism. For example, brass will also show magnetism if some aluminum, iron and other elements are added;

Corrosion Susceptibility

Ferrous metals are prone to corrosion and rust.

Because the main component of ferrous metals is iron, they will easily rust and corrode when exposed to air and humid environments. By mixing alloy elements such as nickel and chromium, stainless steel, a ferrous metal, can cope with this corrosion challenge;

Non-ferrous metals usually have strong corrosion resistance and are often used in some highly corrosive working environments;

Density

The density of ferrous metals is generally larger than that of non-ferrous metals.

Taking stainless steel as an example, the density of common 304 stainless steel is 7.9 g/cm³, and the density of low carbon steel is about 7.85 g/cm³;

The density of non-ferrous metals is usually lower than that of ferrous metals.

The densities of common non-ferrous metals are aluminum (2.7 g/cm³), titanium (4.5 g/cm³), magnesium (1.737 g/cm³), etc.

Strength and Durability

Ferrous metals, especially steel, generally show high strength.

By mixing alloy elements, the mechanical strength and mechanical properties of steel can be improved. However, steel has low corrosion resistance and is easily corroded, so its service life is often limited. Only through special surface treatment or adding some elements during the production process, such as chromium, nickel, and titanium, can the corrosion resistance of steel in some extreme environments be improved, and its service life be increased;

The strength of non-ferrous metals is generally lower than that of ferrous metals.

Titanium is an exception. Titanium is a non-ferrous metal with a very high strength-to-weight ratio. In high-demand applications such as aerospace, titanium is more suitable than steel. Most non-ferrous metals, such as aluminum and magnesium, require alloying to improve their strength; non-ferrous metals generally have good corrosion resistance, which can ensure the long-term operation of facilities in marine environments and high-temperature applications;

Electrical Conductivity

Ferrous metals are mainly iron and iron alloys, and their electrical conductivity is generally low.

Due to the crystal structure and electronic arrangement of iron, the electrical conductivity of iron is low. At 20℃, the electrical conductivity of iron is about 1.00×10⁷σ (S/m). At 20℃, the electrical conductivity of carbon steel is 1.43×10⁻⁷σ (S/m), and the electrical conductivity of stainless steel is 1.45×10⁶σ (S/m);

Nonferrous metals are generally more conductive than ferrous metals.

The electrical conductivity of copper is 5.96×10⁷σ (S/m), the electrical conductivity of silver is the highest among all metals, about 6.30×10⁷σ (S/m), and the electrical conductivity of aluminum is about 3.5×10⁷σ (S/m). Therefore, nonferrous metals are more widely used in industries such as electricity, energy, and electronic components;

Thermal Conductivity

The thermal conductivity of ferrous metals is generally low.

Iron has a low thermal conductivity of about 80 W/m·K, and the crystal structure of steel obtained by mixing iron with other elements becomes more complex and the thermal conductivity is also reduced. The thermal conductivity of stainless steel is 15-30 W/m·K, while the thermal conductivity of carbon steel is 45-58 W/m·K, the thermal conductivity of wrought iron is 59 W/m·K, and the thermal conductivity of ordinary gray cast iron is about 40 W/m·K;

The thermal conductivity of non-ferrous metals is generally higher than that of ferrous metals.

The thermal conductivity of copper is 401 W/m·K, which is almost 8 times that of iron, while the thermal conductivity of silver is higher than that of copper, at 429 W/m·K. Therefore, non-ferrous metals are more suitable for applications such as heat exchange.

Plasticity

The plasticity of ferrous metals is generally low, and the specific plasticity depends on the alloy composition and heat treatment.

Generally speaking, steel with a lower carbon content has better plasticity, but as the carbon content increases, the hardness and strength of high carbon steel increase, but the plasticity will deteriorate. High carbon steel tends to become brittle during cold and hot working. In cast iron, the graphite of gray cast iron is distributed in flakes, with poor plasticity and toughness, while the spherical graphite in ductile iron improves the plasticity of the cast iron itself, showing better plasticity than gray cast iron. Through annealing, normalizing, quenching, tempering and other heat treatment methods, the structure of the metal can be significantly changed and the plasticity of the metal can be improved.

Nonferrous metals generally have higher plasticity.

For example, common aluminum, copper, nickel, zinc, and titanium are relatively soft at room temperature relative to ferrous metals, have better ductility, and therefore have higher plasticity.

Processability

At room temperature, the processability of ferrous metals is poor.

Carbon steel, alloy steel and other steels among ferrous metals have added a lot of other elements. The strength and hardness of the steel itself are high, but at the same time, the steel becomes harder and more brittle, which is prone to tool wear and surface cracks, increasing the difficulty of processing. It is often necessary to use high-performance processing tools, or use appropriate heat treatment methods to reduce the brittleness of the material and reduce the difficulty of processing;

At room temperature, non-ferrous metals have good processability.

Most non-ferrous metals at room temperature have good ductility and are relatively soft. Most pure non-ferrous metals have good cutting performance and less tool wear; however, the alloy products of non-ferrous metals, such as titanium alloys, are also relatively difficult to process;

Cost

The cost of ferrous metals is low.

Ferrous metals are mainly iron and steel. The costs mentioned here are mainly the cost of obtaining raw materials, production costs and energy consumption in the production process. Thanks to the abundant iron reserves and mature smelting and processing technology, the overall cost of ferrous metals is relatively low.

The cost of non-ferrous metals is high.

Nonferrous metals include copper, aluminum, zinc, lead, nickel, etc. Some of these metals have low reserves and are more dispersed. The transportation cost of metals is high. At the same time, the smelting and processing of nonferrous metals are more difficult and the process is more complicated, so the overall cost is also high;

Recycling

The recycling difficulty of ferrous metals is relatively low. Ferrous metals have recycling value.

Metal recycling involves recycling difficulty, cost, source and value. The recycling history of ferrous metals is very long. With the application of new equipment and new technologies, the recycling technology of ferrous metals has been very mature, and the recycling cost is relatively low. At the same time, ferrous metals are widely used in our daily life and industrial life. Construction waste, automobiles and home appliances are the main sources of ferrous metals, so the resources of ferrous metal waste are very sufficient. At the same time, the market demand for ferrous metals is also very high, and the recycling value of ferrous metals is particularly prominent.

The recycling difficulty of nonferrous metals is relatively high. Non-ferrous metals also have recycling value.

First of all, the chemical and physical properties of nonferrous metals are quite different, so the recycling methods of nonferrous metals are very different. For example, copper is recycled through a series of steps such as melting, desulfurization, and deoxidation by smelting; while zinc needs to be recycled through electrolytic smelting technology, which can improve the degree of zinc refining. Therefore, the recycling cost of non-ferrous metals is also an issue that cannot be ignored. From the source of non-ferrous metal waste, most of the application products of non-ferrous metals have a long service life, and compared with ferrous metals, non-ferrous metal waste is relatively less. Although the difficulty and cost of recycling non-ferrous metals are relatively high, and the sources of waste are relatively few, they also have great recycling value.

Conclusion

In the above chapters, we first learned what are the common ferrous metals and non-ferrous metals, and then we compared the chemical and physical properties of ferrous metals and non-ferrous metals through multiple dimensions. The advantages of ferrous metals and non-ferrous metals allow them to be widely used in various industries and play an important role in today’s daily life and industrial production. At the same time, understanding their respective shortcomings also allows us to think more carefully when formulating solutions for the challenges in the project. I hope this article can bring you new thinking and value. HYT will also continue to provide you with more valuable content related to metals.

Simplified Table of Differences Between Ferrous Metals and Non-Ferrous Metals

HYT Ferrous Metals and Non-Ferrous Metals

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Reference

List of thermal conductivities

Table of Electrical Resistivity and Conductivity

Best Heat Conductive Metals

Metals, Metallic Elements and Alloys – Thermal Conductivities

Comparing the Thermal Conductivity of Different Metals