Steel, an alloy of iron and carbon, is one of the most widely used materials in various industries due to its strength, durability, and versatility. Among the different types of steel, carbon steel and stainless steel are the most common and serve a plethora of applications. While both types of steel have their unique advantages, they also come with their specific drawbacks.
This article provides a detailed comparison between carbon steel and stainless steel, covering their composition, properties, applications, and other key differences.
What is Carbon Steel?
Carbon steel refers to steel mainly composed of iron and carbon, the carbon content is generally between 0.05% and 2.0%. Carbon steel is the most common type of steel in the steel industry and is widely used in construction, manufacturing, machinery and other engineering fields. The properties and uses of carbon steel mainly depend on its carbon content and the addition of other trace elements.
Carbon Steel Type
Carbon steel primarily consists of iron and carbon. The carbon content typically ranges from 0.05% to 2.1% by weight, and it is the primary element that dictates the steel’s hardness, strength, and ductility. Depending on the carbon content, carbon steels are classified into three categories:
- Low Carbon Steel (Mild Steel): 0.05%-0.25% carbon
- Medium Carbon Steel: 0.26%-0.60% carbon
- High Carbon Steel: 0.61%-2.1% carbon
Additional elements like manganese, silicon, and copper are often present in minor amounts to improve properties like strength and hardness.
What Makes Carbon Steel So Hard?
Carbon steel is hard, mainly due to its specific composition and processing process. With the increase of carbon content, the solid solution strengthening effect of carbon atom in iron atom lattice is enhanced, resulting in lattice distortion and hardness enhancement. In particular, the quenching process, by heating steel to the right temperature and then cooling it quickly, can transform its structure into a harder martensitic structure.
In addition, in carbon steel, ferrite and cementite are the main organizational components. As the carbon content increases, the amount of cementite increases and the amount of ferrite decreases, which results in an increase in the hardness of carbon steel. During processing, carbon steel also undergoes the phenomenon of work hardening. Plastic deformation leads to grain refinement, lattice distortion and dislocation increase inside the material, and these microstructure changes make the hardness of carbon steel further increase.
Advantages of Carbon Steel
Carbon steel is a widely used material with many advantages that make it suitable for use in all walks of life. Here are some of the main advantages of carbon steel:
- Carbon steel can be welded by a variety of welding methods (such as arc welding, gas welding, laser welding, etc.), and the welding process is relatively simple and easy to operate.
- Carbon steel can maintain high fatigue strength under repeated loading, reduce fatigue cracks and extend service life. Due to its excellent fatigue resistance, carbon steel is widely used in structures and components that need to withstand dynamic loads, such as Bridges, cranes, automotive suspension systems, etc.
- When subjected to sudden impact, carbon steel can effectively absorb impact energy and reduce the risk of fracture of the material. When carbon steel is stretched or bent, it can undergo large plastic deformation without breaking immediately.
- Iron and carbon are very abundant elements in the Earth’s crust, and extraction and smelting costs are low. Carbon steel production process has been very mature, high industrial production efficiency, low cost.
- Low carbon steel and medium carbon steel have good plasticity and can form complex shapes in the forging process. Through appropriate heat treatment (such as quenching and tempering), the hardness and toughness of carbon steel can be adjusted to meet different performance requirements.
- The surface of carbon steel can be polished, polished and other methods to achieve the required finish and precision. The surface of the polished carbon steel is smooth and smooth, which is conducive to the subsequent surface treatment process such as coating and electroplating, and further improves the corrosion resistance and beauty of the product.
Disadvantages of Carbon Steel
Carbon steel as a commonly used metal material, although it has a wide range of applications in many fields, but there are also some shortcomings.
- Carbon steel contains higher carbon elements, which is easy to produce oxidation in a humid environment, resulting in rust. This rust will continue to erode outward, causing the material to fracture, failure, etc. Therefore, carbon steel in the need for high corrosion resistance occasions, such as chemical, Marine engineering and other fields, may need additional anti-corrosion measures.
- During the heat treatment of carbon steel, parameters such as temperature, time and cooling rate need to be strictly controlled. Improper heat treatment will lead to a decline in the performance of steel, such as low hardenability, low strength and yield ratio, poor tempering stability.
- The surface of carbon steel is prone to rust and rust, which will affect its appearance. In some cases where high appearance requirements are required, carbon steel may need to be surface treated (such as spraying, coating, etc.) to improve its aesthetics.
Application of Carbon Steel
Despite some shortcomings, carbon steel is still widely used in many fields because of its excellent properties and cost effectiveness. Here are some of the main applications of carbon steel:
- Construction industry: such as steel beams, steel columns and rebar, used in the construction of Bridges, buildings and other large structures.
- Mechanical manufacturing: High carbon steel because of its high strength and wear resistance, suitable for manufacturing gears, bearings, hammers, wrenches, molds and other tools.
- Automotive industry: Low carbon steel because of its good ductility and welding performance, often used in the manufacture of automobile frame, body, crankshaft, connecting rod and other high-strength parts.
- Tools and cutters: Blades and scissors made of high carbon steel are sharp and durable for a variety of cutting tasks. Hand tools, such as hammers, wrenches, pliers, etc., have become the preferred material for hand tool manufacturing due to the high strength and durability of carbon steel.
What is Stainless Steel?
Stainless steel is a kind of stainless steel with stainless steel and corrosion resistance as the main characteristics, with a chromium content of at least 10.5% and a maximum carbon content of no more than 1.2%. This kind of steel is resistant to weak corrosive media such as air, steam and water, and is widely used in many fields. The “rust” and “corrosion resistance” characteristics of stainless steel mainly come from its alloy composition, especially the content of chromium.
Stainless Steel Type
There are many types of stainless steel, which are mainly divided into the following types according to the organizational structure:
Austenitic stainless steel:
The structure is austenitic, with good corrosion resistance and plasticity. Commonly used models are 304, 316, 321 and so on. Among them, 304 stainless steel is the most common one, with good corrosion resistance and weldability, widely used in furniture, kitchenware, containers and equipment and other fields.
Austenitic stainless steel contains more than 18% chromium, and about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements.
Ferritic stainless steel:
The structure is ferrite, with good heat resistance and corrosion resistance. Commonly used models are 430, 446 and so on. 430 stainless steel is often used in kitchen equipment, automotive exhaust pipes and other fields, while 446 stainless steel is often used in high temperature furnace equipment, gas pipelines and other fields.
Martensitic stainless steel:
The structure is martensite, with high hardness and strength, but poor corrosion resistance. Commonly used models are 410, 420, 440C and so on. The carbon content of martensitic stainless steel and the content of other hardeners are higher than that of ferrite, so its strength and hardness are higher.
Duplex Stainless Steel:
The structure is biphase structure, with both austenitic and ferritic properties, with good strength and corrosion resistance.
Commonly used models are 2205, 2507 and so on. Duplex stainless steel is widely used in chemical, Marine and pulp manufacturing fields.
Precipitation (precipitation hardening) stainless steel:
Is a kind of stainless steel material with a special hardening mechanism, through the appropriate heat treatment process, so that the formation of a dispersed precipitation phase in the solid solution state of the crystal, thereby obtaining excellent hardness and strength. The common precipitation-hardened stainless steel grades are 17-4PH, 15-5PH, etc., which are widely used in aerospace, petrochemical, ocean engineering and other fields.
Advantages of Stainless Steel
Stainless steel has the advantages of strong corrosion resistance, good heat resistance, low maintenance cost, high aesthetics, high strength, environmental protection and health.
- Stainless steel is mainly composed of chromium, nickel and other elements, these elements can form a dense oxide film to prevent further oxidation of metal ions on the surface of the steel, stainless steel corrosion resistance makes it can be used in a variety of harsh environmental conditions for a long time, not easy to rust or corrosion.
- Stainless steel has good high temperature resistance, its high temperature resistance can reach 1000-1200 degrees Celsius, in the high temperature environment, stainless steel is not easy to deformation or oxidation, which makes it widely used in high temperature equipment such as stoves, engines, heat exchangers.
- Stainless steel has a high surface finish and is not easy to absorb dust and dirt, so it is easy to clean and maintain. For example, in the school water supply system, stainless steel water pipes reduce the school’s operating costs due to their good corrosion resistance, sealing and long life.
- Stainless steel has a silver-white appearance and gloss, with high decorative, can meet the appearance of higher requirements of the occasion. At the same time, its surface is flat, easy to clean, and can maintain long-term beauty and durability.
- Stainless steel has high strength and hardness, can withstand greater external pressure and impact load, is not easy to deformation or damage. This makes stainless steel in the structural parts, mechanical parts and other fields have important application value.
- Stainless steel is an environmentally friendly and healthy material, does not contain heavy metal elements harmful to the human body, will not release toxic gases or volatile organic compounds, harmless to human health.
Disadvantages of Stainless Steel
Stainless steel disadvantages may limit its use in some applications. Here are a few main disadvantages of stainless steel:
- The main components of stainless steel include chromium, nickel and molybdenum, and the cost of these elements is relatively high, resulting in the price of stainless steel is much higher than carbon steel.
- Stainless steel can be forged at high temperatures, and high temperature processing requires special equipment and technology, which increases the difficulty and cost of production. Moreover, the processing process of stainless steel is complex, including heat treatment and cooling steps, which must be precisely controlled to avoid degradation or deformation of material properties.
- The lower toughness is more obvious in some stainless steel types, especially martensitic stainless steel. Some types of stainless steel, such as high-carbon martensitic stainless steel, despite their high hardness, have low toughness and are prone to brittle breaks under impact or bending loads.
- The high hardness of stainless steel makes the grinding and polishing process more difficult, requiring higher quality abrasive tools and longer processing times. Some stainless steel after grinding, the blade retention is not as good as high carbon steel, need frequent grinding and maintenance.
What Makes Stainless Steel Rust Resistant?
The reason why stainless steel can prevent rust is mainly due to its special alloy composition and surface treatment process. The content of chromium in stainless steel usually exceeds 10.5%. When the stainless steel surface is damaged or exposed to air, the chromium element combines with oxygen to quickly form a dense oxide film. This layer of oxide film can isolate the direct contact between the metal surface and air, water and other substances, thereby preventing further oxidation and corrosion of the metal.
In addition to the alloy composition, the rust resistance of stainless steel is also affected by its surface treatment process. The common anti-rust methods include passivation treatment, coating anti-rust coating, forming anti-rust oil film and so on.
Related resources: When is Passivation of Stainless Steel Required?
What is the Carbon Content of Stainless Steel?
According to the definition in GB/T20878-2007, the maximum carbon content of stainless steel does not exceed 1.2%, but usually the carbon content of stainless steel will be lower than this upper limit.
- Low carbon stainless steel: less than 0.03%.
- Medium carbon stainless steel: 0.03% to 0.08%.
- High carbon stainless steel: greater than 0.08%.
Application of Stainless Steel
Stainless steel is widely used in many fields because of its excellent characteristics:
- Food and beverage industry: Stainless steel has good corrosion resistance and antibacterial properties, and is mainly used in the food and beverage industry to manufacture equipment, containers and pipes. Including tableware, cookware and kitchen countertops, due to their easy cleaning and beautiful appearance.
- Medical equipment: Stainless steel is also widely used in the medical industry. Such as scalpel, scissors, pliers, etc., because of its high strength, corrosion resistance and easy disinfection characteristics. Including operating table, hospital bed and various diagnosis and treatment equipment.
- Construction and decoration: Stainless steel sheets are often used for the exterior walls and roofs of buildings because of their corrosion resistance and beautiful appearance. Including stair railings, doorknobs and interior decoration strips, due to its bright surface and modern appearance.
- Automotive industry: Stainless steel is often used in the manufacture of automotive exhaust systems because of its high temperature and corrosion resistance. Some high-end car body parts and trim are also made of stainless steel to enhance appearance and durability.
Carbon Steel vs. Stainless Steel
There are significant differences between Carbon Steel and Stainless Steel in several aspects, and the following is a detailed comparison of the two steels:
Chemical Composition
Below is a table comparing the chemical compositions of general steel, carbon steel, and stainless steel:
| Element | General Steel | Carbon Steel | Stainless Steel |
|---|---|---|---|
| Carbon (C) | 0.08-0.15% | 0.02-2.0% | 0.03-1.2% |
| Manganese (Mn) | 0.25-0.50% | 0.3-1.5% | 1.0-2.0% |
| Silicon (Si) | 0.10-0.35% | 0.1-0.4% | 0.5-1.0% |
| Sulfur (S) | ≤ 0.050% | ≤ 0.05% | ≤ 0.03% |
| Phosphorus (P) | ≤ 0.045% | ≤ 0.04% | ≤ 0.045% |
| Chromium (Cr) | – | – | 10.5-30% |
| Nickel (Ni) | – | – | 0-35% |
| Molybdenum (Mo) | – | – | 0-3% |
| Other Elements | May contain trace elements like Titanium (Ti), Vanadium (V) | May contain trace elements like Chromium (Cr), Nickel (Ni) | May contain trace elements like Titanium (Ti), Niobium (Nb) |
Cost
The price of stainless steel is usually higher than that of carbon steel, mainly due to the need to add a large number of alloying elements (such as chromium, nickel, etc.) in the production process of stainless steel, resulting in its higher cost. Carbon steel, on the other hand, is relatively simple, mainly composed of iron and carbon, and has a lower cost. Therefore, in terms of price, carbon steel has a certain advantage.
| Type of Steel | Price Range (USD per ton) |
|---|---|
| Low-Carbon Steel | $600 – $800 |
| Medium-Carbon Steel | $700 – $1,000 |
| High-Carbon Steel | $900 – $1,200 |
| Stainless Steel (304) | $2,000 – $3,000 |
| Stainless Steel (316) | $2,500 – $3,500 |
| Stainless Steel (430) | $1,500 – $2,000 |
Weight
Carbon steel density approximately 7.85 g/cm³. Carbon steel is relatively heavy due to its high density, which contributes to its strength. Stainless steel density approximately 7.75 to 8.0 g/cm³, slightly higher than carbon steel. stainless steel is generally heavier than carbon steel, depending on the specific alloy composition, which includes elements like chromium and nickel.
Corrosion Resistance
Carbon steel corrosion resistance low. Carbon steel is prone to rust and corrosion when exposed to moisture and oxygen. It requires protective coatings or treatments to prevent corrosion. Stainless steel corrosion resistance high. Stainless steel contains chromium (at least 10.5%), which forms a passive layer of chromium oxide on the surface, preventing further corrosion. This makes it suitable for environments exposed to moisture, acids, and other corrosive substances.
Strength and Hardness
Carbon steel generally offers higher tensile strength and hardness compared to stainless steel. The higher the carbon content, the stronger and harder the steel becomes, though it also becomes less ductile. This makes high carbon steel suitable for cutting tools and heavy-duty construction materials.
Stainless steel, while also strong, offers a balance between strength, toughness, and ductility. Its strength can be enhanced through alloying and heat treatment, particularly in martensitic and precipitation-hardened grades.
Tensile and Yield Strength
Carbon steel’s tensile strength typically ranges from 400 to 550 MPa for low-carbon steel and can reach up to 2000 MPa for high-carbon steel. Its yield strength generally ranges from 250 to 600 MPa, depending on the carbon content and heat treatment.
Stainless steel, particularly austenitic grades like 304 and 316, has a tensile strength ranging from 485 to 620 MPa, with higher strengths achievable in other types like martensitic or duplex stainless steels. The yield strength of stainless steel is generally lower, between 200 and 300 MPa for austenitic grades, but can be higher in other types, such as duplex stainless steels, which have yield strengths around 450 MPa.
Machinability and Weldability
Machinability and weldability are also important considerations. Carbon steel is generally easier to machine, especially low and medium carbon steels. High-carbon steel, due to its hardness, can be more challenging to machine. Carbon steel is also easy to weld, although high-carbon steels require preheating and post-weld heat treatment to avoid cracking.
Stainless steel is more challenging to machine due to its hardness and tendency to work harden, requiring specialized tools and techniques. Its weldability is generally good, but it requires careful attention to detail, especially for non-austenitic grades, to avoid issues like cracking and corrosion at the welds.
Appearance
In terms of appearance, carbon steel is typically dull and prone to rusting. It often requires painting or coating for a better appearance and corrosion protection. Its surface is usually matte or rough unless polished or coated. Stainless steel, however, is naturally bright and shiny, resistant to tarnishing and rust. It can be polished to a mirror-like finish and is available in various finishes, including brushed, satin, and mirror, making it aesthetically pleasing for decorative and architectural applications.
Thermal and Electrical Conductivity
Carbon steel has higher thermal and electrical conductivity than stainless steel, making it suitable for applications where heat dissipation is crucial, such as in radiators and heat exchangers.
Stainless steel, with lower conductivity, is often used where thermal insulation is beneficial or where electrical conductivity needs to be minimized.
Heat Resistance
Heat resistance is another crucial factor. Carbon steel can withstand high temperatures but may oxidize and scale at elevated temperatures. High-carbon steels can lose hardness when exposed to high heat, making carbon steel suitable for applications where extreme heat resistance is not critical. On the other hand, stainless steel, particularly austenitic grades like 304 and 316, maintains strength and resists oxidation at high temperatures. This makes stainless steel ideal for high-temperature environments such as heat exchangers, boilers, and kitchen appliances.
Physical Properties
Below is a table comparing the key physical properties of carbon steel and stainless steel:
| Property | Carbon Steel | Stainless Steel |
|---|---|---|
| Thermal Conductivity | 45-60 W/m·K | 15-25 W/m·K |
| Electrical Conductivity | 6-15 MS/m | 1.4-1.6 MS/m |
| Thermal Expansion Coefficient | 11-16 µm/m·K | 16-18 µm/m·K |
| Hardness (Brinell) | 120-500 HB (varies with carbon content) | 150-200 HB (austenitic grades) |
| Modulus of Elasticity | 200 GPa | 190-200 GPa |
| Magnetic Permeability | High (ferritic and martensitic) | Variable (high in ferritic and martensitic, low in austenitic) |
| Melting Point | 1425-1540 °C | 1375-1530 °C |
Sustainability
Both types of steel are recyclable, but stainless steel’s longer lifespan and resistance to corrosion contribute to lower environmental impact over time. The production processes for both types are energy-intensive, but advancements in recycling technologies help mitigate some environmental concerns.
Choosing Between Carbon Steel and Stainless Steel
Selecting the appropriate material between carbon steel and stainless steel depends on various factors specific to your application. Below is a comparison table summarizing the key considerations to help you make an informed decision.
| Criteria | Carbon Steel | Stainless Steel |
|---|---|---|
| Corrosion Resistance | Low, requires protective coatings | High, natural resistance due to chromium |
| Strength | High tensile and yield strength, varies with carbon content | High tensile strength, slightly lower yield strength for austenitic grades |
| Cost | Generally lower | Higher due to alloying elements |
| Weight | Slightly lighter | Slightly heavier |
| Machinability | Good, better for low and medium carbon steel | More challenging, requires special tools |
| Weldability | Good, special care for high-carbon steel | Good, specific procedures for certain grades |
| Appearance | Dull, prone to rust | Bright, shiny, various finishes available |
| Heat Resistance | Moderate | High, suitable for high-temperature applications |
| Thermal Conductivity | Higher | Lower |
| Electrical Conductivity | Higher | Lower |
| Thermal Expansion | Lower | Higher |
| Hardness | Variable (120-500 HB) | Moderate (150-200 HB for austenitic) |
| Magnetic Properties | High (ferritic and martensitic) | Variable (high in ferritic/martensitic, low in austenitic) |
| Melting Point | 1425-1540 °C | 1375-1530 °C |
| Typical Applications | Structural, automotive parts, tools | Kitchenware, medical instruments, marine environments |
Can Stainless Steel Be Welded to Carbon Steel?
Stainless steel can be welded with carbon steel, but attention should be paid to the differences in material properties between the two to avoid possible welding defects and corrosion issues. Normally, welding rods or wires that match stainless steel materials should be selected for welding. For example, for stainless steel materials such as 0Cr18Ni10Ti (i.e. American standard 321 stainless steel), stainless steel welding rods such as A302, A312, etc. should be used for welding. Therefore, although technically feasible, caution should be exercised in evaluating requirements and risks in practical applications.
Conclusion
Both carbon steel and stainless steel have their unique properties and advantages, making them suitable for different applications. Understanding the specific requirements of your application will help you choose the appropriate type of steel, ensuring the best performance and longevity of your products.
Choose BOYI professional, reliable, and efficient CNC machining services for carbon steel and stainless steel materials. Let us be the strong support behind your success, contact our team for more information and pricing details.
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FAQ
Stainless steel can replace carbon steel in some cases, but not in all cases. The cost of stainless steel is usually higher than that of carbon steel, and in some applications, the strength and toughness of carbon steel may be more suitable. Therefore, when selecting materials, it is necessary to weigh the specific application requirements and cost-effectiveness.
The main difference between stainless steel and carbon steel lies in their chemical composition and properties. Stainless steel contains a high amount of chromium and usually also alloy elements such as nickel and molybdenum, thus possessing excellent corrosion resistance and oxidation resistance. Carbon steel is mainly composed of iron and carbon, with high mechanical properties but relatively poor corrosion resistance.
Catalog: Materials Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
