What is the Difference Between S235JR and S355JR?

Steel is one of the most important components in the construction industry. It is the component that provides both strength and durability, which is a necessity for structures like buildings and bridges. Among the available grades in the global market, S235JR and S355JR are the two that are the most commonly used structural steels. Although they may seem similar based on their names, the differences come from their strength, chemical composition, and applications. If you want to know more, read on and be informed about the key differences between S235JR and S355JR, determine what sets them apart, and learn how each type is best utilized in projects.

What is S235JR?

S235JR is a non-alloy steel grade. The “S” stands for suitability for load-bearing application. This steel grade possesses a yield strength of 235 MPa (thickness up to 16 mm). Keep in mind that as the thickness increases, yield strength will decrease. The “JR” in the name signifies that the material has passed a Charpy V-notch impact test at room temperature (20°C). The impact test has a minimum impact energy of 27 Joules, and bypassing such tests, the material demonstrates its ability to withstand sudden impacts while resisting brittle fracture.

What is S355JR?

The two steel grades, S235JR and S355JR, possess the same characteristics as non-alloy structural steel. Both adhere to EN 10025-2 European standards. What sets them apart, however, is that S355JR offers greater strength. S355JR offers 355 MPa yield strength compared to the 235 MPa provided by S235JR, both for thicknesses up to 16 mm. This better and higher yield strength makes it the ideal choice for projects where tougher and more durable materials are crucial.

Key Differences Between S235JR and S355JR

1. Minimum Yield Strength

S235JR Steel Grade

As specified earlier in this article, S235JR possesses a minimum yield strength of 235 MPa, which decreases as the thickness increases. This is something to keep in mind on projects where strength matters because as the thickness of steel increases, it is more prone to stress and environmental conditions.

S355JR steel grade

S355JR steel grade has a minimum yield strength of 355 MPa compared to S235JR. The yield strength also decreases as the thickness increases, but it makes up for it by offering a higher minimum yield strength. This is the ideal and reliable choice for projects needing high performance and durability in structural applications.

2. Tensile Strength

S235JR

The tensile strength of this grade ranges between 360 MPa and 510 MPa, which varies depending on the thickness of the steel.

S355JR

The tensile strength of this grade ranges between 470 MPa and 630 MPa, which also varies depending on the steel’s thickness, but S355JR possesses greater tensile strength than S235JR.

3.  Chemical Composition

Both S235JR and S355JR are non-alloy structural steels. They are both made of iron and carbon; the difference, however, is that S355JR is composed of slightly higher levels of carbon and manganese. This difference in composition gives S355JR a distinct advantage because it is tougher and applicable for demanding applications.

4. Weldability

S235JR

This steel grade has excellent weldability because of its lower carbon content. This allows it for less demanding preheating procedures, specifically for thinner sections, and can be welded using standard techniques. Due to this, it is a better choice for welding in construction and fabrication applications. 

S355JR

S355JR also has good weldability, but due to its higher carbon content, additional precautions should be considered. Preheating should be considered for thicker sections to help reduce the occurrence of hydrogen-induced cracking. 

5. Distinction in their Applications

S235JR

S235JR steel is the best option for projects that need reliable performance without the necessity for maximum strength. This type of steel grade is the ideal choice for low-rise buildings, in general construction, and the fabrication of machine parts. It is reliable, easy to work with, and budget-friendly.

S355JR

S355JR is the best choice for more demanding structural applications that require both strength and higher load-bearing capacity. This steel grade is designed for heavy-duty applications such as bridges, skyscrapers, large machinery, and transportation systems. With its superior strength and higher load-bearing capability, the S355JR is the most reliable choice for projects where both performance and durability are essential.

6. Cost

Between S355JR and S235JR, S355JR comes at a higher price point. This is due to its superior strength, higher durability, better load-bearing capability, and more complex manufacturing processes. When choosing, weigh the pros and cons. Check if the higher cost of S355JR is valid given the advantages it offers. For applications that demand structural integrity, opting for the higher strength grade may be essential, despite the higher material costs. To ensure you get the best deal, it’s advisable to obtain multiple quotes from local suppliers.

S235JR and S355JR Equivalent Grade

Conclusion:

In conclusion, both S235JR and S355JR are the most popular and commonly used structural steels, but they are used for different applications. S355JR is better both in yield strength and tensile strength, which is ideal for heavier and more demanding constructions, while S235JR is more economical and well-suited for lighter construction projects. Both materials have good weldability and are easy to work with, though S235JR tends to bend more easily in cold conditions. Both are good choices, so choose based on your project’s requirements and budget, and do not forget to consult your supplier for the best match.