Carbon Steel vs Stainless Steel: What is the Difference?

Introduction

Steel is an immensely important metal seen everywhere, but did you know it is an alloy? What is more, all kinds of steel contain carbon. How confusing, especially given the popularity of the terms carbon steel and stainless steel. If both contain iron and carbon, then what is the difference between them? Do they differ in their mechanical or chemical properties? Are you debating which type of steel is suitable for you? Don’t worry! We will lift your doubts about carbon and stainless steel for good. 

What is Carbon Steel?

As we have mentioned, all forms of steel contain iron and carbon. Other metals are added to steel in order to impart unique properties to it. However, that is not the case with carbon steel. It is made from iron and carbon. Iron makes up the majority of metal, coming in at around 98%. The amount of carbon varies between 0.12 to 2% of the steel by weight.

You might think that 2% of carbon can’t affect the steel by much, but that’s wrong. It can change the metal’s physical properties immensely. Steels with high amounts of carbon are known to be harder and wear-resistant. However, their high strength can also make them tougher to bend and prone to cracking. Carbon steel is also susceptible to corrosion and rust, unlike stainless steel.

Carbon steel is categorized based on the percentage of carbon. Let’s discuss the physical properties of different carbon steels.

Low-Carbon Steel

If pure iron and carbon steel have less than 0.25% carbon, it’s known as low-carbon steel. This steel does not have the hardness that is characteristic of high-carbon steels, but it has excellent malleability and ductility. Automobile parts, construction materials, and machine tools are all made from carbon steel. Low-carbon steel has great welding ability. 

Medium-Carbon Steel

Steel with a carbon percentage falling between 0.25 and 0.6% is known as medium-carbon steel. It also contains 0.6 to 1.65% manganese by mass. Medium-carbon steel has a greater hardness than low-carbon steel and offers good tensile strength. Quenching and tempering can increase its strength and hardness. While it is tough to bend, its ductility can be increased through annealing.

High-Carbon Steel

High-carbon steel is renowned for its exceptional hardness and robustness. It has carbon content ranging from 0.6 to 1.25% and manganese content between 0.3 to 0.9%. It has the greatest tensile strength among carbon steels. It can match and sometimes even exceed the strength of stainless steel. Due to its extreme hardness, it has very poor ductility. It is also not suitable for welding. Cutting tools, drills, knives, and swords are made from high-carbon steel.

For more information on carbon steel grades, forms, and availability, visit our website. 

What is Stainless Steel?

Stainless steel is an alloy that has great corrosion resistance. It contains iron and carbon like all steel. Additionally, it contains a significant amount of chromium. It consists of 10.5 to 30% chromium by weight. The chromium imparts stainless steel with its characteristic resistance to corrosion and rusting. Chromium forms an inert layer at the surface of the steel, preventing further oxidation and damage. Other metals like nickel, molybdenum, and titanium are often added to stainless steel to give it special properties.

Stainless steel is an important metal because of its resistance to rusting. It is highly advantageous in applications that expose steel to heat, water, and humidity. The strength of corrosion resistance depends upon the amount of chromium added. Stainless steel comes in many grades. The different grades of stainless steel have different properties: corrosion resistance to a specific environment, oxidation resistance, or special characteristics. Let’s dive deeper into the kinds of stainless steel. 

Austenitic

Austenitic steel is composed of 16 to 26% chromium and as much as 35% nickel by weight. It offers the highest resistance to rusting and corrosion. Austenitic steel is the most commonly available form of stainless steel. It makes homeware, cookware, pipes, containers, and structural components. Austenitic steel is not fit for hardening through heat treatment. It is non-magnetic. 

Ferritic

Standard ferritic steel consists of iron, carbon, and chromium. However, it is free of nickel. It contains chromium in the 10.5 to 27% range. Due to the low-carbon percentage, it cannot be hardened further by heat treatment. It has high corrosion and temperature tolerance. Homeware appliances like washing machines and boilers use ferritic steel. It constitutes indoor and outdoor architectural elements. 

Martensitic

Martensitic stainless steel is hard and strong due to its high carbon content. They can be further hardened through quenching. Due to a low chromium content of around 11.5 to 18%, they are moderately corrosion-resistant. Due to the hardness and tensile strength of martensitic steel, they make kitchenware, turbines, wrenches, and surgical instruments. 

Duplex

Duplex stainless steel is a mixture of austenitic and ferritic steel in the same quantity. It contains around 21 to 27% chromium, molybdenum, copper, and nickel. It is superior to austenitic and ferritic steel, having greater tensile strength and corrosion resistance. Storage vessels, chemical vessels, and ship sections use duplex steel. 

Precipitation

When stainless steel undergoes precipitation hardening its strength and hardness increase. The process involves adding aluminum, niobium, and copper precipitates.  Its corrosion resistance is in the same bracket as austenitic steel. It contains about 15 to 17.5% chromium. It also contains nickel and copper in the range of 3 to 5%. Precipitation-hardening steel has excellent strength. Structural components and construction materials employ this steel.

Do you want to know everything about stainless steel? Are you looking for high-quality steel suppliers? We have much more information available on this blog. 

Carbon Steel and Stainless Steel Compared

Composition

Iron and carbon are fundamental constituents of steel. Other metals are mixed in the alloy to impart certain abilities.

Carbon steel has iron as the main component. Carbon is present in the range of 0.12 to 2% by mass. Other constituents like copper, silicon, or manganese may be present.

The special ingredient in stainless steel is chromium. This is what imparts corrosion resistance to the steel. Stainless steel contains between 10.5 and 30% chromium by mass. Nickel, molybdenum, aluminum, or copper are some other metals that may be present. 

Cost

Steel price is affected by several factors like type, grade, quantity, etc. Stainless steel is hard to make and has high demand in several industries. It is generally costly as compared to carbon steel. However, ultra-high carbon steel (containing 3% carbon) can be equally or even more expensive than stainless steel. 

Corrosion Resistance

Stainless steel is highly corrosion-resistant because it contains chromium. Chromium reacts with atmospheric oxygen to produce a layer of chromium oxide. It is a passive layer that protects the rest of the steel and prevents rusting. Carbon steel has many beneficial qualities; however, it is not corrosion-resistant. It can decompose and lose strength if exposed to humidity or water. 

Tensile and Yield Strength

Carbon steel has great yield strength but average tensile strength. It can withstand huge weights but breaks rather than deforms upon overloading. Carbon steel is unsuitable for applications that involve great load stress. Stainless steel has good yield and tensile strength. It doesn’t have the hardness of high-carbon steel, but it can deform and bend. Stainless steel structures are less susceptible to collapse. 

Machining and Welding

Carbon steel is suitable for welding. It can be bent and shaped easily. It is highly machinable and is used to make small and large objects. Low-carbon steel is available in several forms: sheets, rolls, wires, shafts, etc.

Stainless steel is a challenging alloy to shape and bend. Its high tensile strength and thermal resistance mean that only specialized tools can cut it. 

Appearance

The appearance of metal can impact your project. Carbon steel has a dark matte finish. It is also susceptible to discoloration and rusting due to corrosion. Carbon steel requires regular care, cleaning, and oiling.

Stainless steel is bright and silvery in appearance. Its smooth and shiny surface is appealing to the eye. It requires less maintenance due to its natural resistance to rusting. 

Heat Resistance

As mentioned earlier, stainless steel has excellent heat resistance. Some stainless grades, like 310 and 309, can withstand more than 1000 degrees Celsius. For this reason, they often make kitchenware, appliances, boilers, chemical apparatus, etc. Their high resistance causes cutting and drilling tools to heat up. For this reason, it is difficult to shape stainless steel.

Carbon steel has a lower heat tolerance than stainless steel. Pipes made of low or medium-carbon steel can endure temperatures to 750 degrees Celsius. While high-carbon steel has greater heat tolerance, its extreme hardness is not suitable for making versatile objects. It makes high-performing cutting and drilling tools that can withstand extreme heat. 

Conclusion

One thing is clear: carbon steel and stainless steel excel in their ways. When comparing them, there is no clear-cut winner. Only you can decide the winner of this race. Based on your needs, one of these metals will prove superior.

Stainless steel is good-looking, strong, rust-free, and long-lasting. It can fulfill many requirements for you. However, its weak machinability and high cost mean that you will be limited to certain applications and products. Carbon steel is hard, strong, wear-resistant, and cheap. It is available in all shapes and sizes, making it highly adaptable. However, maintaining it will be expensive due to a lack of corrosion resistance.

We hope that this blog provides you with a comprehensive understanding of stainless steel and carbon steel. For an expert consultation, contact our professional team. We would be happy to assist you in selecting the best possible metal for your needs!