Carbon Steel vs Iron

The difference between carbon steel and iron is the carbon content. Steel is a general term for ferroalloys with a carbon content of 0.02% to 2.04%. The chemical composition of steel varies widely. Steel containing only carbon elements is called carbon steel or ordinary steel; in actual production, steel often contains different alloying elements, such as manganese, nickel, vanadium, etc., according to different uses.

What Is Carbon Steel?

In fact, carbon steel (CS/MS seamless pipe) refers to the carbon content in the steel, on which its mechanical properties depend. Generally, steel without alloying elements is also called plain carbon steel or carbon steel, which refers to iron-carbon alloys with a carbon content of less than 2%, while carbon steel also contains a small amount of silicon, manganese, sulfur and in addition to carbon, there are phosphorus. Generally speaking, carbon steel with higher carbon content has higher hardness and strength, but lower ductility.

Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel according to the carbon content:

Low carbon steel: the carbon content is generally less than 0.25% (mass fraction);

Medium carbon steel: the carbon content is generally 0.25%~0.60% (mass fraction);

High carbon steel: the carbon content is generally higher than 0.60% (mass fraction).

What Is Iron?

At room temperature, iron is not easy to react with non-metallic elements such as oxygen, sulfur and chlorine in dry air, but it reacts violently at high temperature.

Iron is divided into pig iron and wrought iron. Both are iron-carbon alloys distinguished by their carbon content:

Generally, iron with a carbon content of less than 0.2% is called wrought iron or pure iron, while iron with a carbon content greater than 1.7% is called pig iron.

Wrought iron is soft, malleable, and easily deformed, with low strength and hardness, making it less widely used.

Pig iron, with a high carbon content, is hard, brittle, and has almost no plasticity.

Carbon Steel vs Iron: Composition

1. Pure Iron

Contains ≤0.02% carbon (by mass) and contains virtually no other alloying elements. It is soft and commonly used in electromagnetic components (such as transformer cores).

2. Carbon Steel

An alloy of iron and carbon, containing 0.02%-2.1% carbon. Elements such as manganese and silicon may be added to enhance performance. For example, low-carbon steel (<0.25% carbon) is used in automotive sheet metal, while high-carbon steel (>0.6% carbon) is used in cutting tools. Carbon steel pipe contains 0.12%-2.1% carbon (ASTM A53 standard), along with trace amounts of manganese, phosphorus, and sulfur.

Carbon Steel vs Iron: Manufacturing Process

1. Carbon Steel

Carbon steel is typically produced through processes such as heating, forging, and rolling. After heating, the billet is forged or rolled to produce carbon steel products in various shapes. For example, carbon steel pipes are typically formed through cold or hot rolling.

2. Iron

Iron is typically produced through ironmaking. During the ironmaking process, ore and coke react at high temperatures to produce molten iron and slag. After purification and tempering, the molten iron is purified and refined to produce pure iron.

Carbon Steel vs Iron: Performance

1. Hardness And Wear Resistance

Pure iron is relatively soft, with a hardness of around HV 120, and is not very wear-resistant.

The hardness of carbon steel increases with carbon content: low carbon steel has a HV of 150-250, medium carbon steel has a HV of 300-500, and high carbon steel can reach HV 600. Every 0.1% increase in carbon increases the hardness by approximately 15 HV.

2. Toughness And Deformability

Pure iron has excellent toughness, an elongation of 28%, and can withstand significant deformation. The toughness of carbon steel increases as its carbon content decreases: low-carbon steel has an elongation of 25%, medium-carbon steel has an elongation of 15%-20%, and high-carbon steel has an elongation of less than 12%.

3. Corrosion Resistance

Carbon steel is more corrosion-resistant than iron. Certain alloying elements in carbon steel can make it even more corrosion-resistant, allowing it to maintain its strength and integrity in humid or harsh environments.

For example, ordinary carbon steel pipes have a lifespan of approximately 20-30 years in mildly corrosive environments, while cast iron pipes are susceptible to rust in humid environments and, without corrosion protection, have a lifespan of only 10-15 years.

Carbon Steel vs Iron: Price

1. Carbon Steel Price

Due to its superior properties and higher manufacturing costs, carbon steel is generally more expensive than iron.

The price of carbon steel is influenced by several factors.

First, its price is related to its carbon content; higher carbon content carbon steel is generally more expensive.

Second, the addition of alloying elements and other additives also increases the cost. These additives enhance carbon steel's strength, wear resistance, and corrosion resistance.

In addition, the production process and manufacturing costs are also important factors in determining price.

2. Iron Price

Iron's price is relatively low, primarily due to its wide range of uses and abundant reserves.

However, different types of iron, such as pig iron and wrought iron, have different prices.

Pig iron is an iron alloy with a carbon content of 2% to 4.5%. It is commonly used in the manufacture of heavy equipment and building structures.

Wrought iron is a further processed form of iron with a lower carbon content and a relatively higher price.

Carbon Steel vs Iron: Typical Application

1. Large Deformation Requirements

Pure iron is suitable for applications requiring large deformation, such as bridge castings and building buffers.

Carbon steel is prone to stress concentration during large deformation, and high-carbon steel is more prone to cracking, making it unsuitable for parts that are prone to frequent bending.

2. High Strength And Wear Resistance

Carbon steel is suitable for high-load, high-wear environments: low-carbon steel is used for building steel structures, medium-carbon steel is used for gear shafts, and high-carbon steel is used for tool molds.

Pure iron lacks strength and cannot be used for high-load components such as drive shafts and tools.

FAQ

1. Which Is Lighter, Carbon Steel Or Iron?

Iron is a metallic element, so for the same volume, iron weighs more than the same volume of carbon steel.

However, for the same weight, carbon steel is harder and stronger than iron.

2. Carbon Steel Vs. Cast Iron: Which One Should I Choose?

Carbon steel has better machinability and processability, making it more suitable for manufacturing mechanical parts.

Cast iron, on the other hand, is more suitable for manufacturing parts requiring high hardness and wear resistance.

Read more: Carbon Steel Pipe vs. Black Iron Pipe or Seamless Black Steel Pipe vs. Black Iron Pipe