Steel is undoubtedly one of the most important materials in modern society. Its remarkable strength and versatility make it crucial in many buildings, industrial machinery, and significant engineering projects worldwide.
Steel comes in various alloys, with carbon steel and stainless steel being the most common and widely used. While both alloys share certain features that make them suitable for different applications, they also have notable differences in structure and performance.
This article will explore the differences between carbon steel and stainless steel in multiple aspects.
Chemical Composition：Carbon Steel VS Stainless Steel
Element | Carbon Steel | Stainless Steel |
Carbon (C) | 0.05% – 2.1% | 0.03% – 1.2% |
Chromium (Cr) | ≤ 0.5% | 10.5% – 30% |
Nickel (Ni) | ≤ 0.4% | 8% – 35% |
Manganese (Mn) | 0.3% – 1.0% | 0.5% – 2.0% |
Silicon (Si) | 0.1% – 0.5% | 0.2% – 1.0% |
Phosphorus (P) | ≤ 0.04% | ≤ 0.04% |
Sulfur (S) | ≤ 0.05% | ≤ 0.03% |
Molybdenum (Mo) | ≤ 0.1% | 2% – 3% |
Titanium (Ti) | ≤ 0.1% | 0.1% – 0.6% |
Carbon steel contains a higher carbon content, typically between 0.05% and 2.1%. Carbon is the key element that determines the hardness and strength of steel. High-carbon steel has higher hardness but poorer toughness.
In contrast, stainless steel contains higher amounts of various metals:
- Stainless steel contains at least 10.5% chromium. Chromium forms a protective oxide layer, significantly enhancing the steel’s corrosion resistance.
- The addition of nickel in stainless steel greatly improves its corrosion resistance, ductility, and toughness, especially in high-temperature environments.
- Silicon in stainless steel primarily strengthens its oxidation resistance and helps maintain stability at high temperatures.
- Stainless steel often has higher molybdenum content, especially in high-grade alloys like 316. Molybdenum enhances corrosion resistance, particularly in marine or chemical environments.
Mechanical Properties：Carbon Steel VS Stainless Steel
Mechanical Properties | Carbon Steel | Stainless Steel |
Yield Strength | 250 – 600 MPa | 250 – 450 MPa |
Tensile Strength | 400 – 700 MPa | 500 – 800 MPa |
Elongation | 20% – 40% | 40% – 60% |
Hardness | 80 – 100 HRB / 40 – 60 HRC | 70 – 95 HRB / 30 – 40 HRC |
Impact Toughness | Lower (depends on carbon content) | Higher (especially in low-temp environments) |
Fatigue Strength | 200 – 400 MPa | 300 – 500 MPa |
Physical Properties：Carbon Steel VS Stainless Steel
| Physical Properties | Carbon Steel | Stainless Steel |
| Density | 7.85 g/cm³ | 7.75 – 8.05 g/cm³ |
| Melting Point | 1425 – 1540°C | 1375 – 1530°C |
| Thermal Conductivity | 50 – 60 W/m·K | 15 – 25 W/m·K |
| Specific Heat Capacity | 460 – 500 J/kg·K | 500 – 600 J/kg·K |
| Thermal Expansion Coefficient | 11 – 13 × 10⁻⁶/°C | 16 – 18 × 10⁻⁶/°C |
| Magnetic Property | Strongly magnetic | Non-magnetic or weakly magnetic (depends on composition) |
| Electrical Resistivity | 50 – 60 × 10⁻⁶ Ω·m | 70 – 75 × 10⁻⁶ Ω·m |
Manufacturing Process：Carbon Steel VS Stainless Steel
Casting
Due to the distinct compositions of stainless steel and carbon steel, there are many differences in their casting processes.
When melting metal, stainless steel requires vacuum or inert gas protection to prevent oxidation, with temperatures exceeding 1600°C. Carbon steel, composed mainly of carbon and iron, can be melted using a conventional electric arc furnace at a temperature of around 1500–1550°C, making the process simpler.
Stainless steel, due to its high alloy content, has poor fluidity. Therefore, it requires larger gate designs and bottom-pour systems to reduce oxidation, and it has a higher shrinkage rate (2.5%–3.0%). Multiple risers and chilled iron are needed to compensate for shrinkage. Carbon steel, with better fluidity and lower shrinkage (1.8%–2.2%), needs simpler molds and natural cooling.
For example, when casting flanges, the volume of risers in stainless steel casting accounts for 15%–20% of the total casting weight, while for carbon steel flanges, it only accounts for 8%–12%.
Carbon steel has a simple chemical composition, mainly composed of iron and carbon, with fewer alloying elements. Its stable structure and excellent physical properties make it easy to machine. Carbon steel has moderate hardness, low work-hardening tendency, and generates less tool wear. Additionally, chips break easily, and less heat accumulates, significantly improving machining efficiency.
In contrast, stainless steel contains many alloying elements (such as chromium, nickel, and molybdenum), resulting in high hardness, toughness, and low thermal conductivity. As a result, machining stainless steel is more difficult. It tends to work-harden, generate heat, and wear tools quickly.
To machine stainless steel, specialized hard alloy or coated tools must be used. The cutting speed should be lowered, feed rates increased, and sufficient coolant should be used to help with heat dissipation and lubrication. Appropriate parameters must also be used during milling, turning, or drilling stainless steel.
Welding
Carbon steel has good welding properties, especially low-carbon steel, which is suitable for various welding methods (such as arc welding and gas welding). The process is simple and cost-effective. However, high-carbon steel requires preheating and post-weld heat treatment to avoid cracking and brittleness. Overall, welding carbon steel is relatively easy and suitable for most common applications.
The welding properties of stainless steel vary by type. Austenitic stainless steel (such as 304 and 316) has good weldability but requires attention to the corrosion resistance of the heat-affected zone and potential hot cracking. Martensitic and ferritic stainless steels have poor weldability and require preheating and post-weld heat treatment. Welding stainless steel generally requires specialized methods (such as TIG welding), and the technical requirements are higher. It is ideal for applications that demand corrosion resistance and aesthetic appearance.
Cost Comparison：Carbon Steel VS Stainless Steel
Carbon steel has a significant advantage in cost, especially in terms of raw materials, production processes, and machining costs. Its raw materials, mainly iron and carbon, are inexpensive and readily available. The production process is simple and mature, with low equipment investment and maintenance costs.
Additionally, carbon steel is easy to cut, weld, and shape. Its machining efficiency is high, with minimal tool wear and low heat generation, further reducing machining costs. These features make carbon steel an ideal choice for projects with limited budgets and low corrosion resistance requirements.
However, carbon steel has higher maintenance costs because it is prone to rusting. Regular surface treatments, such as painting or galvanizing, are needed to prevent corrosion.
In contrast, while stainless steel has higher raw material, production, and machining costs, its excellent corrosion resistance means it requires little additional maintenance, resulting in lower long-term maintenance costs.
Carbon steel is suitable for scenarios with limited initial budgets and low corrosion resistance requirements. Although stainless steel has higher initial costs, its low maintenance costs and superior corrosion resistance make it more cost-effective in the long run, especially for projects with higher performance demands. When choosing between them, the specific needs and budget should be considered.
Corrosion Resistance：Carbon Steel VS Stainless Steel
Carbon steel has poor corrosion resistance because it lacks an effective protective mechanism. It easily reacts with water and oxygen to form iron oxide (rust), corroding faster in humid, acidic, or alkaline environments.
To improve corrosion resistance, carbon steel often requires surface treatments, such as galvanizing, painting, or electroplating. However, these treatments add cost and maintenance complexity. Even with treatment, carbon steel may still corrode over time and needs regular maintenance.
In contrast, stainless steel has excellent corrosion resistance, mainly due to the chromium it contains. Chromium reacts with oxygen to form a dense oxide layer (passivation film) that effectively prevents further corrosion.
Stainless steel performs well in most environments, especially in oxidative environments like air and fresh water, and usually does not require additional surface treatments. Even in harsh environments, such as seawater or acidic media, stainless steel’s corrosion resistance is much better than carbon steel, although pitting or crevice corrosion may occur in extreme conditions.
Carbon steel is suitable for scenarios where corrosion resistance is not a primary concern, but it requires additional surface treatments and regular maintenance. Stainless steel, with its excellent corrosion resistance and low maintenance costs, is better suited for long-term applications, especially in harsh environments. The specific environmental needs and economic considerations should guide the choice.
Application Comparison：Carbon Steel VS Stainless Steel
Applications of Carbon Steel
Construction and Structural Engineering:
Carbon steel is widely used in large structures like buildings, bridges, and railways due to its high tensile strength and hardness. Its low cost and high strength make it ideal for load-bearing components, such as steel beams and columns.
Automobile Manufacturing:
In the automotive industry, carbon steel is often used to make body frames, chassis, and rims. Its strength and wear resistance make it suitable for withstanding shocks and friction during vehicle operation.
Machining:
Carbon steel performs well in manufacturing gears, bearings, tools, and other mechanical parts due to its excellent hardness and strength. Its good machinability and low cost make it widely used in machine tool and equipment manufacturing.
Oil and Gas Industry:
Due to its strength and high-temperature resistance, carbon steel is widely used in oil drilling, pipelines, and pressure vessels. However, its poor corrosion resistance often requires additional protective coatings.
Shipbuilding and Aerospace Industry:
While carbon steel is used in shipbuilding and aerospace applications, it often requires protective coatings or low-alloy steel due to its poor performance in corrosive environments.
Applications of Stainless Steel
Medical Equipment and Instruments:
Stainless steel is widely used in the medical industry due to its excellent corrosion resistance and biocompatibility. It is commonly found in surgical instruments, implants (such as artificial joints, dental implants), and medical equipment (such as hospital beds and device casings).
Food and Beverage Industry:
Due to its corrosion resistance and oxidation resistance, stainless steel is widely used in food processing equipment, beverage containers, and kitchen utensils. It does not react with food, making it ideal for manufacturing food processing machinery and storage containers.
Chemical and Petrochemical Industry:
Stainless steel is commonly used in pipelines, containers, and reactors in chemical, petroleum, and natural gas industries. Its corrosion resistance ensures long-term use in harsh chemical environments.
Marine Engineering:
Stainless steel’s corrosion resistance makes it widely used in marine environments, such as offshore platforms, ships, diving equipment, and marine pipelines.
Aerospace and High-Temperature Environments:
Stainless steel’s high-temperature resistance makes it suitable for aerospace applications, especially for engine components and external structures that must withstand high temperatures and pressure.
Architectural Decoration and Furniture:
Stainless steel is also used in architectural decoration and furniture due to its aesthetic and durability. For example, it is commonly used for exterior wall decoration, stair railings, and bathroom fittings, offering both high decorative value and durability.
Carbon steel is often used in applications that require high strength, hardness, and wear resistance, particularly in construction, manufacturing, and the automotive industry, where heavy loads or impact forces are common.
Stainless steel is more suitable for environments that require corrosion resistance, high-temperature resistance, or chemical resistance, especially in industries like healthcare, food processing, chemicals, and marine engineering.
How Can Manek Help
At Manek, we offer our clients a series of customized services specifically for stainless steel and carbon steel, including investment casting, sand casting, die casting, CNC machining, sheet metal fabrication as well as various surface treatments.
We also provide a variety of other manufacturing capabilities. You can get quotations for free, such as 3D printing, plastic injection molding and powder coating.
