As two popular steel grades, our team of steel experts at Capital Steel receives many questions regarding the properties of 1045 steel and 4140 steel. Each grade has distinct chemical and mechanical characteristics, which make it valuable for different applications. Let’s dive into the key differences, so you can better understand which steel grade may be better for your project.
Chemical Properties of 1045 Steel & 4140 Steel
Regardless of whether 1045 steel and 4140 steel are hot rolled or cold drawn, their chemical composition remains consistent. Reference the chart below to see the individual chemical properties of each grade.
| Element | 1045 Steel | 4140 Steel |
| Iron, Fe | 98.51-98.98% | 96.79-97.78% |
| Carbon, C | 0.45% | 0.40% |
| Manganese, Mn | 0.60-0.90% | 0.75-1.00% |
| Phosphorus, P (max) | 0.04% | 0.035% |
| Sulfur, S (max) | 0.05% | 0.040% |
The chemical properties of a steel grade determine its name. The carbon content of both 1045 and 4140 determines the last two digits of their grade number. The carbon content of 1040 steel is 0.40%, while that of 1045 is 0.45%. The first digit “1” identifies that they are both carbon steels, and the second digit “0” identifies that there were no modifications to the alloy.
Mechanical Properties of 1045 Steel & 4140 Steel
The mechanical properties of steel significantly shift depending on how the steel is manufactured. In general, steel that is cold drawn is typically more robust than it otherwise would be in a hot rolled state. For better clarity, there are two comparison charts below to break down the mechanical properties of these steel grades in both hot rolled and cold drawn forms.
Here is a comparison chart of 1045 and 4140 hot rolled steel mechanical properties:
| Mechanical Property | 1045 Hot Rolled Steel | 4140 Hot Rolled Steel |
| Tensile Strength | 82,000 psi | 90,000 psi |
| Yield Strength | 45,000 psi | 65,000 psi |
| Elongation in 2″ | 16% | 35% |
| Reduction in Area | 40% | 40% |
| Brinell Hardness | 163 | 25 |
Here is a comparison chart of 1045 and 4140 cold drawn steel mechanical properties:
| Mechanical Property | 1045 Cold Drawn Steel | 4140 Cold Drawn Steel |
| Tensile Strength | 91,000 psi | 95,000 psi |
| Yield Strength | 77,000 psi | 60,200 psi |
| Elongation in 2″ | 12% | 25% |
| Reduction in Area | 35% | 35% |
| Brinell Hardness | 179 | 197 |
Applications of 1045 Steel & 4140 Steel
1045 steel has a nice balance of strength, toughness, and machinability, which allows it to be used across a wide variety of applications. Its versatility and cost-effectiveness make it a popular choice for high quantity projects. Some common uses of 1045 steel include automotive parts and bolts in construction. Conversely, 4140 steel is praised for its superior strength and wear resistance. It’s ideal for applications that involve high amounts of stress or impact. For instance, landing gear for planes is typically made using 4140 steel.
Choose Capital Steel for Your Steel Needs
With over 20 years of experience in the steel industry, Capital Steel & Wire has the expertise and resources to help you accomplish your project. Our team is ready and eager to assist you with any questions related to steel.
