Carbon Steel vs Stainless Steel

by AMC


Posted on January 30, 2023 at 12:05 PM

Carbon Steel vs Stainless Steel

Steel is a popular material used in construction, manufacturing, and everyday tools. Two common types are carbon steel and stainless steel, each with unique qualities. While both are made from iron and carbon, their differences in composition affect their strength, durability, and resistance to rust. In this blog, we’ll explain these differences in simple terms and help you decide which type of steel is right for your needs. Let’s get started!

What is Carbon Steel?

Carbon steel is a common type of steel made by mixing iron and carbon. It has more carbon, a lower melting point, and lasts longer compared to stainless steel.

Carbon steel has a high amount of carbon, usually up to 2.1% of its total weight. The American Iron and Steel Institute (ASISI) says the following things about carbon steel:

  • There is no minimum amount of chromium, cobalt, nickel, titanium, tungsten, vanadium, or other metals that resist corrosion that must be used.
  • Copper content must be at least 0.40% but no more than that.
  • Manganese can't be more than 1.65% of the total amount.
  • Copper cannot have more than 0.6% of it.
  • The most silicon that can be in a product is 0.6%.
So, what are the benefits of carbon steel?

When there is a lot of carbon in steel, it changes how it works. In particular, it gets stronger and tougher. This is why high-carbon steel is used to make a lot of swords, knives, and other weapons with blades. In feudal Japan, swordsmiths were the first to use tamahagane, which is a type of high-carbon steel, to make weapons like the katana.

Does carbon steel rust?

Yes, carbon steel does rust because it doesn't have the same properties as stainless steel that keep it from rusting. Carbon steel is stronger and lasts longer than stainless steel, but it can rust and corrode if it gets wet. Carbon steel can rust if it gets wet, even if it's just a little bit. This includes moisture vapor in the air. Carbon steel is also harder to bend than stainless steel.

Carbon Steel Composition

Carbon steel is composed of iron and between 0.12% and 2.00% carbon. In the broader definition, alloy steels are also included, which can have up to 10.5% alloy content. Even within a range of less than 2% carbon, there are huge differences in physical properties, especially hardness.

Types of Carbon Steel

The different kinds of carbon steel can be put into the following groups:

Low-carbon steel: This is the most common type. It has less than 0.25 percent carbon. This type of carbon steel is weaker and softer than most, but it is more flexible and easy to weld, so it is used for machining and welding at a low cost.

Medium-carbon steel:
This type usually has between 0.25 and 0.6% carbon and between 0.6 and 1.65% manganese. It can be made better by heating it. But this can only be done on very thin pieces of metal if no alloying elements are added. It is stronger than low-carbon steel, but it is not as easy to bend.

High-carbon steel:
This is the type of carbon steel that is the hardest and toughest. It is the least flexible and wears down the least slowly. The amount of carbon in it ranges from 0.6% to 1.25 %, and the amount of manganese is between 0.3% and 0.9%.


What is Stainless Steel?

Stainless steel is an iron alloy that doesn't rust or break down easily. It has at least 11% chromium and may also have carbon, other nonmetals, and metals to get other properties. The chromium in stainless steel makes it resistant to corrosion. The chromium forms a passive film that can protect the material and heal itself when oxygen is present.

Stainless steel, which is also called inox steel (from the French word inoxydable, which means "not oxidized"), lives up to its name by being very resistant to corrosion stains. When iron-based metals like steel are exposed to oxygen, they usually go through a chemical change called "oxidation" that changes how they behave. The iron oxidizes, which turns the hard iron into a metal with a reddish-brown color (iron oxide). At some point, the iron oxide will become so oxidized that it will break up completely.

Stainless steel is made to keep things from rusting. It has at least 10.5% of its weight in chromium. This is important because, unlike iron, chromium doesn't easily rust. Chromium doesn't rust or corrode when it's exposed to oxygen, which makes it an important part of making stainless steel. Stainless steel has a layer of chromium that protects it from corrosion. This layer acts as a barrier between the oxygen in the air and the iron in the metal.

Composition of Stainless Steel
Carbon and iron are mixed together to make steel. Stainless steels have at least 10.5% chromium, less than 1.2% carbon, and other elements that make them stronger. Other elements, like nickel, molybdenum, titanium, niobium, manganese, etc., can be added to stainless steel to improve its resistance to corrosion and its mechanical properties.

Types of Stainless Steel

The following are the types of stainless steel with different properties:

Austenitic: This is the most common type of stainless steel. It has a low yield strength but is resistant to heat and corrosion. It is often used to make home goods, pipes and vessels for industry, buildings, and facades.

Ferritic: This type of stainless steel doesn't usually have nickel in it. But this type promises better resistance to corrosion, heat, and cracks than most other types. This type of stainless steel is often used in washing machines, boilers, and the construction of buildings inside.

Martensitic: This type of stainless steel is usually magnetic and doesn't resist corrosion as well as other types of stainless steel because it doesn't have as much chromium in it. It is also very strong, which is why knives and turbine blades are made from it.

Duplex: This is the combination of austenitic and ferritic steels that is both strong and flexible. It has twice the yield strength of austenitic stainless steel and is used a lot in industries like paper, pulp, shipbuilding, and petrochemicals.

Precipitation: This type of stainless steel is just as resistant to corrosion as austenitic metals, but it can be made even stronger by adding things like aluminum, copper, and niobium.

Feature

Stainless Steel

Carbon Steel

Composition

High Chromium content

High Carbon content

Corrosion Resistance

Highly resistant to corrosion and rust

High risk of corrosion and rust

Appearance

Visually appealing

Not very visually appealing

Cost

High cost

Low cost

Thermal Conductivity

Lower Thermal Conductivity

High Thermal Conductivity

Surface

Superior surface with Lustrous Finish

Dull Matte Finish

Alloying Elements

Includes various alloying elements

Alloying elements available in very low quantity

Applications

Wider applications due to high weldability

Limited usage due to poor weldability

Grades

Available in various types of Grades

Available in two main groups: Mild Steel and High Carbon Steel

Can Stainless Steel Be Welded to Carbon Steel?

While it is technically possible to weld stainless steel to carbon steel, it is generally not recommended. The primary challenge lies in their differing electrical conductivity levels. Carbon steel is more electrically conductive and heats up slower than stainless steel during resistance welding, often requiring preheating. This makes achieving the correct weld temperature and a strong bond difficult. For better results and reduced complications, it is advisable to weld steels of similar types rather than combining dissimilar metals like carbon and stainless steel.

Carbon Steel vs Stainless Steel: Which Material Fits Your Application?

Aspect

Carbon Steel Applications

Stainless Steel Applications

Automotive

Low-carbon steel is used for automobile body components and pipes.

Used for exhaust systems, grills, trims, and structural components.

Construction

Low-carbon steel is used for bridges and construction materials.

Common in architecture due to its strength, resistance, and aesthetics, e.g., Helix Bridge in Singapore.

Railway Industry

Medium-carbon steel is used for railway tracks, train wheels, and crankshafts.

Rarely used for railway components; primarily serves other purposes.

Industrial Tools

High-carbon steel is used for cutting tools, springs, and dies.

Less ductile grades are used for knives, while more ductile grades are used for grills and sinks.

Chemical Industry

Limited use due to lower corrosion resistance.

Preferred for chemical transport and sterile environments due to high corrosion resistance.

Medical Technology

Rarely used in medical applications.

Common in medical equipment and tools due to its hygienic and corrosion-resistant properties.

Food & Catering

Low-carbon steel is used for food cans.

Widely used in cookware, cutlery, kitchen accessories, and appliances.

Aerospace

Rarely used in aerospace applications.

Used in airplane frames, jet engines, and landing gear due to its strength and corrosion resistance.

Should I Pick Carbon Steel or Stainless Steel?

Carbon steel and stainless steel are not the same, but that doesn't mean that one is better than the other. It depends on what is going on. Each material has its own pros and cons. The key is to find the right steel for the job.

High Carbon Steel

  • Vulnerable to rust
  • Brittle
  • Wear-resistant
Stainless Steel

  • Resistant to rust
  • Less brittle
  • Less wear-resistant
Contact us if you want to know more about carbon steel or stainless steel, or if you want a quote for a custom project.

FAQs

1. Which is better carbon steel or stainless steel?

Compared to low-carbon steel, stainless steel offers a massive upgrade in strength, hardness, and most importantly corrosion resistance. High carbon steel offers strength rivaling and sometimes exceeding stainless steel but is largely a niche material in the manufacturing world.

2. Does carbon steel rust easily?

Yes. As already mentioned, high-carbon steels are more corrosion-resistant than low-carbon-content steels. However, even high-carbon steels will still rust if exposed to moisture over time.

3. Is stainless steel rust-proof?

Stainless steel is naturally corrosion-resistant, but it is not immune to rust. While it is less prone to rusting than conventional steels, exposure to damaging chemicals, saline, grease, moisture, or heat for extended periods can cause corrosion.