Steel is still one of the most important materials used in various industries today. This metal has several properties that lead many project managers and manufacturers to choose it for their projects. Two of the types of steel used today are 1018 steel and 4140 steel. Although they share some similarities, there are many points comparing 1018 steel to 4140 steel.
When selecting types of steel materials for your project, you need to understand the differences between their properties. See how to find out which one best suits your project. Therefore, this article explains the different properties of 1018 steel and 4140 steel. This will give you a clearer idea of where these types of steel are good and where they should not be used.
What is 1018 steel?
1018 steel is a medium to low carbon steel. Thanks to its low manganese content, this steel is known for its excellent combination of strength, hardness and ductility. Although some other types of steel may exceed its mechanical properties, 1018 steel is easy to machine and heat treatable. This reduces costs and makes it ideal for a wide range of components.
Advantages and Disadvantages of 1018 Steel
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- Easy to machine, shape, weld and fabricate.
- You can easily weld this steel without preheating or postheating.
- Suitable for cold forming techniques including bending, crimping and forging.
- It can be hardened by carburizing or carbonitriding.
Disadvantages
- Low corrosion resistance.
- Its yield strength and low ductility can affect edge strength.
What is 4140 steel?
4140 steel is a chromium-molybdenum steel alloy with increased strength and hardness. Its chromium content provides excellent hardness penetration, while molybdenum guarantees high strength and uniform hardness. Therefore, this type of steel has high fatigue resistance, torsion resistance and impact resistance.
Other desirable properties of 4140 steel include good ductility, superior toughness, and excellent wear resistance in both tempered and quenched states. Additionally, 4140 steel can be hardened using several methods, including cold working or heating and quenching. Few types of steel can match the utility and versatility of 4140.
Advantages and Disadvantages of 4140 Steel
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- It has excellent toughness and high fatigue resistance.
- It also has good corrosion resistance.
- Heat-treated 4140 has good strength, excellent comprehensive mechanical properties and high yield strength.
Disadvantages
- Requires special care during welding.
Differences Between 1018 and 4140 Steel: A Detailed Comparison
Now that we have an overview of the two types of steel, we need to look at the main differences between 1018 steel and 4140 steel. Therefore, we will compare them based on the following content:
Chemical composition (alloy composition)
You can already see the first difference between 1018 steel and 4140 steel in the four numbers. The first digit indicates what type of steel it is, while the second digit indicates whether there are any changes in the alloys. The last two digits indicate the carbon content of the finished steel.
From this you can conclude that 1018 steel is carbon steel without any modifications. It also contains about 0.18% carbon. 4140 steel is molybdenum steel with modifications (additions of chromium). It also contains about 0.40% carbon. The table below shows the details of the chemical composition of steels 4140 and 1018.
| Chemical elements | 1018 steel | 4140 steel |
| Carbon (C) | 0.0018 | 0.004 |
| Manganese (Mn) | 0.60% to 0.90% | 0.75% to 1.00% |
| Sulfur (S) | 0.0005 | 0.0004 |
| Phosphorus (S) | 0.0004 | 0.00035 |
| molybdenum | – | 0.15% to 0.25% |
| chrome | – | 0.80% to 1.10% |
| silicon | – | 0.15% to 0.30% |
| iron | 98.81% to 99.26% | 96.79% to 97.78% |
Mechanical properties
Stretch Limit
4140 steel has a higher yield strength of 60,200 PSI (415 MPa) than 1018 steel at 53,700 PSI (370 MPa). Therefore, 4140 steel can withstand more impact and pressure without deforming. Its greater yield limit is a result of its chemical composition. However, 1018 steel also has a relatively high yield point, meaning it is not a weak metal.
elasticity
This property is a means of understanding the elasticity and resistance to deformation of a material. Elasticity is also related to the rigidity of the metal. 1018 steel has an elastic modulus of 205 GPa, while 4140 steel is between 190 and 210 GPa. This shows that both types of steel respond similarly to elastic deformation.
Material hardness
The hardness of a material indicates its ability to resist deformation by penetration, indentation, or other means. 4140 steel has a Brinell hardness of 200, while 1018 steel has a hardness of 130 to 140. This shows that the former is much harder than the latter. However, both steel materials are hard enough to withstand pressure without deforming.
Corrosion resistance
4140 steel is more resistant to corrosion than 1018 thanks to the chromium content. This is one of the properties of 4140 steel that makes it most useful for outdoor applications. Manufacturers often choose this steel material to produce components that may come into contact with corrosive materials.
Thermal and electrical properties
Temperature resistance
We compared the temperature resistance of 1018 and 4140 steels by analyzing their melting points. Both types of steel have the same melting point of 1420°C to 1460°C. Therefore, both alloys can withstand high temperatures and respond excellently to heat treatment. Therefore, there is an excellent distribution of elements within the metals.
Thermal conductivity
Steel materials are generally poor conductors of heat. However, 1018 steel has a higher thermal conductivity than 4140 steel. This is due to the different chemical compositions. The thermal conductivity of 1018 is 52 W/mK while that of 4140 is 43 W/mK.
Electric conductivity
Despite their low thermal conductivity, steel materials are relatively good conductors of electricity. Therefore, they are an excellent option for high temperature environments. Although the difference in electrical conductivity is small, 4140 steel is a better conductor of electricity than 1018.
Manufacturing and heat treatment
Machinability
4140 alloy steel is very easy to machine when annealed. Its high ductility facilitates molding using traditional techniques. However, due to its toughness, it requires greater pressure and force for sufficient shaping.
Likewise, cold-rolled 1018 steel bars are easy to machine, shape, weld and fabricate. The machinist will have no problem getting exactly what is written in his blueprint. You can even weld this type of steel without any pre- or post-heat treatment. Plus, it works well with any traditional welding process. However, it may not be a good idea to weld carbonitrided or carburized 1018 steel.
Heat treatment
AISI 4140 steel resists heat treatments without deforming. It can be heated to 845°C and then quenched in oil. Some manufacturers also heat it to 913°C before air cooling and hardening. In general, this steel material can withstand the following heat treatments:
- Forge
- Hot forming
- Cold work
- Shine
- Temperament
- Hardening
Steel 1018 or 4140: Which is best for you?
Choosing between different types of metal can be easy. However, deciding between alloys of the same metal can be quite complicated. In this case, the type of steel you choose will depend on your desired applications and specifications. Here are the main factors you should consider to make the best decisions:
Strength
The tensile strength of steel is a crucial factor to consider, especially if its components are used in high stress environments. This ensures that the material can withstand tension without deforming.
4140 steel has a higher tensile strength of 655 MPa than 1018 steel at 440 MPa. Therefore, grade 4140 can withstand more pressure and impact than grade 1018. Therefore, it is a better choice for applications that require high impact frequency.
Machinability properties
The machinability of steel types largely depends on their ability to be modified. Both AISI 4140 and 1018 steel are easy to machine, fabricate, shape and weld when annealed. However, the 4140 variant contains a higher carbon content.
Therefore, appropriate precautions must be taken during welding to avoid cracking. While 1018 steel is easily machined and weldable, 4140 steel may require preheat and postheat treatment to prevent cracking.
Corrosion resistance
Before choosing a steel grade, you should also consider the operating environment of the desired product. External influences can seriously affect component performance. 4140 steel offers better corrosion resistance due to its chemical composition. Its chromium and molybdenum content provides notable resistance to corrosive environments. Therefore, it is a reliable material for external components exposed to corrosive media.
Heat Treatment Options
Not all types of steel can be heat treated, which makes this an important factor to consider before making your decision. Fortunately, both 1018 and 4140 steel can be easily heat treated, resulting in increased tensile strength and excellent hardness. Heat treatment processes also provide materials with resistance to abrasion and wear without compromising their ductility and toughness.
1018 Steel vs. 4140: Applications
1018 steel has a wide range of applications and is useful for components that require cold forming. It is also suitable for carbureted components including gears, pins, ratchets, pins, tool holders and other machine parts. Other examples include fasteners, pins, axles, ratchets, spindles, etc. 1018 steel is also used to manufacture consumer products such as anchor bolts, gaskets and shafts. Some manufacturers also use this type of steel for structural applications.
On the other hand, 4140 steel is suitable for producing high-strength forgings due to its strength, hardness and temperature resistance. It has numerous applications in the automotive industry and is used by manufacturers for drive wheels, drive gears, rear axles, spring clamps, etc. Other typical components made from 4140 steel include shafts, bolts and nuts, jigs, gears, brackets, etc.
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Material selection and selection is an extremely important aspect of product development. Steel alloys are commonly used in metal fabrication projects. Choosing the right alloy ensures you get the most out of your project. In this article, we compare 1018 and 4140 steels based on several parameters. If you want to use any of these materials in your project, you must observe their properties and choose the ideal material.
Common questions
Is 4140 a carbon steel?
4140 steel is a low alloy steel or carbon steel. The addition of molybdenum and chromium makes it one of the most common alloy steels. Molybdenum increases its toughness while chromium increases its corrosion resistance.
Is 1018 steel ductile or brittle?
The chemical composition of 1018 steel results in a strong, ductile material with relatively lower hardness and toughness than other alloys.
What do steel type numbers say?
The first digit indicates what type of steel it is, while the second digit indicates whether there are any changes in the alloys. The last two digits indicate the carbon content of the finished steel.
