Carbon steel and stainless steel share the same iron and carbon constituents. Carbon steel has less than 10.5% alloy, whereas stainless steel must include at least 10.5% chromium. This fundamental distinction gives carbon steel and stainless steel their unique physical properties.
The primary distinction between stainless steel and carbon steel is their corrosion resistance. Stainless steel is designed to be resistant to rust and corrosion. Stainless Steel has a higher corrosion resistance than Carbon Steel. In stainless steel, a large quantity of chromium is added to form a chromium oxide coating that prevents corrosion. On the other hand, carbon steel lacks sufficient chromium to form such a coating and is therefore susceptible to corrosion and rusting.
Carbon steel and stainless steel have different physical properties. The parameters are shown in the table below.
| Physical parameter | Carbon Steel | Stainless Steel |
|---|---|---|
| Average Density | The average Density of Carbon Steel is 7850 Kg/m3 | The average Density of Stainless Steel is 8000 Kg/m3. So Stainless Steel is slightly heavier than Carbon Steel |
| Co-efficient of Linear Thermal Expansion | The thermal expansion coefficient for Carbon Steel is usually less than that of stainless steel and varies in the range of (10.8 – 12.5) X 10-6 m/(m °C) | The expansion coefficient of Stainless Steel is comparatively more than that of Carbon Steel. Depending on grade, the coefficient varies in the range of (10-17.3) X10-6 m/(m °C). So, the thermal growth of Stainless Steel is more than Carbon Steel material. |
| Melting Point | The melting point of Carbon Steel is more than Stainless Steel. Typically Low Carbon Steel has a melting point of 1410°C. The melting point of high Carbon steel ranges between 1425-1540°C. | The melting point of stainless steel varies between 1375 to 1530 °C. |
Ductility: Austenitic stainless steel grades have more ductility than carbon steel grades. Martensitic stainless steel grades, on the other hand, are brittle stainless steel grades that may be more brittle than carbon steel.
Mechanical Strength: Because of the lower carbon content, stainless steel is often softer and weaker in strength. The following table compares the mechanical characteristics of carbon steel with stainless steel:
| Mechanical properties | Carbon Steel | Stainless Steel |
|---|---|---|
| Yield Strength | Low-carbon Steel: 180 to 260 MPa; High carbon Steel: 325 to 440 Mpa. | Ferritic Steel: 280 Mpa; Austenitic Steel: 230 MPA; Martensitic Steel: 480 MPA |
| Tensile Strength | Low-carbon Steel: 325 to 485 MPa; High carbon Steel: 460 to 924 Mpa. | Ferritic Steel: 450 Mpa; Austenitic Steel: 540 MPA; Martensitic Steel: 660 MPA |
| Elastic Modulus | 2100000 Mpa | 1900000 MPa |
| Shear Modulus | 81000 Mpa | 740000 MPa |
| Poisson’s Ratio | 0.3 | 0.27 |
Carbon steel is readily machined and has high welding capabilities. Stainless steel, on the other hand, necessitates specialist welding and machining techniques. Stainless steel is harder than carbon steel for machine tools.
Stainless steel is capable of containing fluids with temperatures over 426°C. In contrast, graphitization begins around 426°C for carbon steel. Stainless steel is renowned for its superior heat resistance.
Regular carbon steel should not be used at temperatures below -46°C. Below -46°C, a unique LTCS material is employed. On the other hand, stainless steel may be utilized at considerably lower temperatures.
In terms of aesthetic appeal, stainless steel is far superior to carbon steel. Stainless steel looks excellent as is. However, carbon steel surfaces must be painted to prevent rusting.
One of the most significant considerations for carbon steel and stainless steel products is their cost. Stainless steel is often more expensive than carbon steel. However, prices vary according to the grades of the material. The cost of stainless steel rises due to particular alloy additives such as chromium, nickel, and so on, as well as the production processes involved with it.
Carbon steel and stainless steel both have advantages and disadvantages in terms of application, characteristics, and cost. As a result, the choice between stainless steel and carbon steel must always be made depending on the application. Suppose cost is not an issue, and the application demands high temperature (or cryogenic temperature) as well as corrosion resistance. In that case, stainless steel is always the best choice. On the other hand, carbon steel is adequate for regular, non-corrosive conditions.
Carbon steel and stainless steel also differ in other ways, such as thermal conductivity, wear resistance, heat treatment, etc. They are compared as follows:
| Stainless Steel | Carbon Steel |
|---|---|
| Thermal conductivity is comparatively lower. | Higher thermal conductivity. |
| Excellent wear resistance. | Poor wear resistance. |
| Heat treatment of Stainless steel is difficult. | Carbon Steel can easily undergo heat treatment. |
| Stainless Steel is easily cleanable. | The cleanability of carbon steel is less than stainless steel. |
Compared to low-carbon steel, stainless steel significantly improves strength, hardness, and, most critically, corrosion resistance. High-carbon steel rivals and occasionally surpasses stainless steel in terms of strength. Yet, it is primarily a niche production material in the manufacturing sector. Unlike carbon steel, stainless steel can live and thrive in corrosive or humid situations without oxidizing. However, carbon steel is significantly less expensive than stainless steel and more suitable for major structural components such as tubes, beams, and rolled sheet steel.
