by AMC
Posted on January 30, 2023 at 12:05 PM
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!
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:
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%.
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.
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 |
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.
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. |
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
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.
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.
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.