What are the differences between iron and steel?
Iron vs. steel. Cast iron vs. carbon steel. The simple fact is, steel is unlike iron. But how? We’ve put together this guide to explain their properties, how they’re made, and what components you can find them in. We’ll cover:
What is iron?
Iron is the fourth most abundant element by mass in the Earth’s crust. The other elements that precede iron are oxygen, silicon and aluminium. Of course, the periodic table classifies iron as a metal. As you can see below, the atomic number is 26, which tells us the number of protons in the nucleus of its atoms. That, in turn, tells us the element to which the atom belongs.
Iron is a ferromagnetic metal, which means it's attracted to magnetic fields. Iron is used to create electromagnets, which is why iron is used in motors, generators, and transformers. It’s also ideal for magnetic storage devices, magnetic separation, and magnetic resonance imaging (MRI) machines.
What are the properties of iron?
Strong and tough, pure iron is a shiny, dense, silver-white metal. When light weight is critical to the application, you should consider different metals.
Chemically, pure iron is incredibly reactive, forming compounds with elements such as oxygen and sulphur. This is also why it will rust easily in moist environments, which can weaken the material's magnetic properties and reduce its effectiveness for magnetic applications. Strong external magnetic fields or high temperatures can cause iron to lose its magnetic properties, a process known as demagnetisation.
With a melting point around 1,537°C, iron is malleable and ductile, so it can be moulded in different shapes.
At room temperature, it’s a solid material. At high temperatures, it can transition to a liquid state, and at very high temperatures, it can exist as a gas. Of course, the phase of any material depends on its temperature and pressure.
Iron is also a good conductor of heat. It can transfer heat efficiently, so it’s often used for heat exchangers and boilers. As a metal, it can conduct electricity, but it has a high resistivity, so it’s not the best metal for the job. For conducting electricity, aluminium or copper are used. Their excellent performance – especially that of copper – comes down to having lower resistivity.
How is iron created?
To produce iron on an industrial scale requires the smelting process, which takes place in a blast furnace. This involves extracting iron from its ore through an oxidation-reduction reaction. An example of an iron ore is haematite, which contains iron (III) oxide, Fe2O3. The oxygen must be removed from the iron oxide.
As the ore decomposes, unwanted elements in the form of gases and slag escape, leaving the desired iron behind. (Slag is calcium silicate, an abrasive material.) Other materials necessary to produce this reaction are coke, which contains carbon, limestone, and air, which enables the coke to burn, generating the necessary heat. The result is pig iron, with about 3% carbon content.
Cast iron vs. wrought iron
Cast iron is a ferrous alloy consisting of 2% – 4% carbon. It’s made through the process of casting. Molten pig iron is mixed with carbon and other alloying elements, such as silicon. The solution made from mixing iron is then transferred into moulds into the desired shape. When the iron cools, the cast iron is removed.
Wrought iron is another story, consisting mostly of iron with 1% to 2% slag. It’s produced by heating and bending multiple times using a hammer. The iron is reheated and reworked several times to produce the final product.
Cast iron is less time-consuming and easier to produce, but wrought iron is stronger. Each time wrought iron is heated and worked, its strength increases. Yet despite this strength, cast iron is harder. Cast iron resists deformation under pressure or stress much easier than wrought iron.
What is steel?
Technically, all steels are alloy steels. Alloys are metals made by combining two metals, or rather, two or more metallic elements. Some occur naturally – electrum, an alloy of gold and silver, is an example – while the first man-made alloy combined tin and copper to make bronze.
The main component of steel is iron, with a carbon content that varies, but typically includes less than 2%, with 1% manganese and small amounts of silicon, phosphorus, sulphur and oxygen. It’s the addition of carbon with multiple-mixed elements that increases strength, resistance, and even variability of alloy steel.
Carbon steel generally contains from 0.1% to 2% carbon by weight. The specific amount of carbon in a carbon steel alloy determines its properties and the specific use of the steel. You can control the amount of carbon by adjusting the composition of the raw materials and the manufacturing process.
Low-carbon steel
This contains between 0.05% to 0.3% carbon and is typically used for applications that require good formability and weldability. Body panels in automotive and components for machinery are often made of low-carbon steel. Mild steel is a type of low-carbon steel, offering a good combination of strength and ductility.
High-carbon steel
Contains between 0.6% to 2% carbon and is used for applications that require high strength and hardness, such as springs, tools, and high-strength wires.
Stainless steel
Carbon is not the main alloying element for some steels, such as stainless. Stainless steel contains a minimum of 10.5% chromium, which is what makes this steel corrosion resistant.
You can learn more in our guide, Understanding stainless steel grades.
What are the properties of steel?
Properties vary according to the type of steel, but generally, you can expect good hardness and wear resistance. This is why it’s popular for applications that need wear resistance, such as machine parts and making tools.
Steel has excellent toughness and can absorb a good amount of energy before it breaks. Its iron content makes it extremely magnetic and a good conductor of heat and electricity. For that purpose, it’s used in electrical wiring and heat exchangers.
Like all metals, steel is 100% recyclable. It can be melted down and reused, retaining all of its properties each time.
How is steel created?
Steel is made by refining pig iron and melting it into a liquid. The liquid steel is then poured into moulds and cooled to form solid steel. Additional elements are added during the process to produce different grades of steel with specific properties. This process can be done through basic oxygen furnace (BOF) or electric arc furnace (EAF) methods.
- BOF process: pig iron, scrap metal and other alloys are melted in a refractory-lined vessel. Impurities burn off when oxygen is blown into the liquid metal. The result leaves behind purer steel.
- EAF process: An electric current is passed through electrodes, which heats scrap and your choice of alloy to melting point. The resistance of the scrap to the electric current generates enough heat to melt the metal. The liquid steel is then poured into moulds to make ingots. The EAF process is regarded as more flexible, as it allows the production of steel from a wider range of materials and in smaller quantities.
Which one is stronger? Iron vs. steel
We’ve already hinted at the answer, so the question is really, what makes steel stronger?
Steel vs. iron strength is a contest between materials. Both iron and steel are strong, but iron is brittle. The primary difference between the two is that steel is made stronger by adding carbon, and various other metals and compounds.
Steel has a lower melting point at 1,371°C, compared to iron’s 1,537°C, but steel is also able to withstand wide temperature ranges. This makes it better suited for structural applications. On the issue of strength, carbon steel vs cast iron puts steel on top.
Cast steel vs. cast iron
You can achieve a high level of detail through metal casting, which can eliminate the need for additional fabrication or assembly. As a process, casting iron is less expensive than steel. It’s easier, making it less time intensive, and involves Iower material and energy costs.
Iron pours out quite easily, nor does it shrink as much as steel. It has excellent flowability, which again points to iron being easier to work with when casting.
How to tell the difference between iron and steel
Steel vs. iron. If you’re trying to differentiate between the two to determine the material of a component, there are several options.
Having the component analysed for its chemical composition is the sure method. Others include feel. Most of the steel around us is mild steel, which has a smooth appearance and some flexibility. Iron, on the other hand, tends to be cast with a rough surface. If feeling the materials doesn’t help, and you don’t mind the possibility of leaving an indentation on the component, your last resort is to use a ball-peen hammer. Hit the component and if it doesn’t bend, you’ve got iron. If an indentation is left, you’ve got mild steel.
Steel vs cast iron
Here’s a summary of how they compare:
| Steel | Cast iron | |
|---|---|---|
| Carbon content | Less than 2% | 2% – 4% |
| Melting point | 1,371°C | 1,537°C |
| Strength | More compressive strength | More tensile strength |
| Castability | Easy due to low shrinkage and good flowability | Not as easy due to low flowability and more shrinkage |
| Corrosion resistance | Less corrosion resistance | More corrosion resistance |
| Impact resistance | Less impact resistance | More impact resistance |
| Applications | Pipe fittings, washers, equipment, machine parts, hand tools and electrical fittings | Infrastructure, vehicles, electrical appliances, masking hooks and tools |
Examples of iron and steel in components
How are these two materials used in manufacturing industrial components? Below shows you just a few examples.
These versatile steel lift-off hinges provide a compact and strong method to attach metal doors to metal frames.
- Ideal choice for narrow frames where other hinge types take up too much space
- Stylish, yet robust
Clamps made of steel with PVC coating for user comfort.
- Adjustable to suit a range of bundle diameters
- Incredibly flexible
- Secure cable mounting solution
- Screw mounted
Made of cold-drawn steel, which is processed at room temperature to make thin shapes.
- Supports hanging loads during paint finishing, surface treatments, and material handling
- S shape is ideal for wider parts or multiple styles of parts with varying thicknesses
- Also available in iron
Round inserts and glides steel base
Steel-threaded inserts with HDPE glides.
- Ideal for use with adjustable feet, tilt glides and castors
- Metal thread provides a smooth repeatable adjustment
Cable conduit
Developed and tested in demanding quality standards and awarded quality approvals and compliance worldwide.
- Available in steel, nylon and flexible LDPE
- Typical applications include general factory wiring and connections to machines
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