One of the most important choices when starting a construction task is defining the steel grade used on the project. The selection of steel plays a very important role in the stability, longevity, and cost-efficient nature of your edifice. Out of the many choices, Fe500 and Fe550 TMT bars are among the common options available because of their ability to withstand diverse forces easily. This article by Brick & Bolt will focus on the main characteristics of Fe500 and Fe550 steel grades, the benefits, and limitations of each, and which is best for your construction project. This article will be able to highlight the differences as well as the similarities between these steel grades. Resultantly, there will be clarity on the project and its implications in context to its success.
Steel Grade 500 and 550
With the leapfrog in modern critical infrastructures, the FE500 and 550 TMT bars have become more appropriate for the increasing need for vital infrastructure projects and high-rise construction. TMT bars are used extensively in the construction of engineering structures and are classified into four based on the size and strength of the building variations. Among the four types of TMT, the Fe500 and Fe550 are the popular choices as they offer greater seismic stability and ductility. Here, “Fe” stands for iron, and numbers “500 and 550” imply the minimum yield stress in MPa (megapascal), which is a unit of pressure or tension. “D” means the ductility of the steel bars. The TMT stands for ‘Thermonuclear Mechanical Treatment’ also known as the metallurgical process, manufactured under the Indian Standards. Increasing infrastructural developments such as skyscrapers, stadiums, fly-overs, airports, malls, multiplexes, dams, etc, demand the inclusion of “D” grade TMT bars. Specific properties of Fe500 and Fe550 grade TMT bars, such as resistance to earthquakes, flexibility and bending capacity of the bars, high elongation property, resistance to corrosion and rust, fire resistance, fatigue resistance, and weldability make these types preferable to other types.
Key Difference Between Fe500 and Fe550
| Fe500 | Fe550 | |
| Strength | Yield strength of 500 MPa | Yield strength of 550 MPa |
| Ductility | Balanced ductility suitable for various constructions | Increased ductility, better deformation resistance |
| Elongation (%) | 18% | 20% |
| Tensile Strength | 8% | 6% |
| Weldability | Higher carbon content (0.30%) reduces weldability | Lower carbon content (0.25%) increases weldability |
| Chemical Composition | Carbon: 0.3%, Phosphorus: 0.055%, Sulphur: 0.055%, Manganese: ≥0.60% | Carbon: 0.25%, Phosphorus: 0.04%, Sulphur: 0.04%, Manganese: ≥0.60% |
| Durability | Suitable for general construction, less durable | More durable due to higher tensile strength |
| Applications | Standard in multi-storey buildings and commercial projects | Preferred for high-rise buildings, bridges, and industrial complexes |
| Cost | Generally less expensive | Typically more expensive, but cost-effective over the long term due to durability |
Strength
The key difference between Fe500 and Fe550 is determined by the strength of the material. Yield strength and ductility are the deciding factors that determine the preferability of TMTs to meet constructional requirements. Fe500D is more apt for a range of constructional applications due to its striking balance between strength and flexibility. Whereas, Fe550D is well-known for its increased ductility. This gives them an edge over withstanding higher levels of deformation without compromising their inherent strength.
Properties
In terms of their chemical composition and mechanical properties, the manufacturers of these two TMT bars stringently adhere to the standards of core elements such as carbon, sulphur, and phosphorus to attain the desired attributes. The presence of a low amount of Sulphur and Phosphorus makes the TMT Fe500 and Fe550 grades highly acceptable for all construction purposes. As we all know, the higher presence of these two elements makes the material prone to fire and fatigue. The mechanical properties of Fe500 vary from Fe550D as the figure in the name does. Fe500 TMT bars provide a yield strength of around 500 MPa. On the other hand, besides providing enhanced ductility, Fe550D provides a higher yield strength of 550 MPa. These differences in their mechanical properties make them exclusive to their requirements.
Weldability
When it comes to the weldability of TMT bars, it is the carbon content that determines the result. The lesser carbon content increases the weldability of steel bars. In terms of chemical composition, the carbon content in Fe500 is 0.30% which is higher in comparison to that of Fe550D’s 0.25%.
Elongation
Usually, the elongation and the strength of the rods on applying tension/force are higher in D variant rods. In terms of percentage, the elongation of Fe500 is 18% and Fe550D is 20%. Their high elongation property provides them the resistance to withstand earthquakes. They can even elongate up to 50% without compromising on the measurements.
Composition
The chemical composition of Fe500 incorporates 0.3% of Carbon, 0.055% of Phosphorus, 0.055% of Sulphur, >=0.60% of Manganese. Whereas, Fe550 incorporates 0.25% of Carbon, 0.04% of Phosphorus, 0.04% of Sulphur, >=0.60% of Manganese.
Durability Comparison
The durability of the Fe500 and Fe550 TMT is determined based on the strength of the material. As we discussed above, the Fe500 TMT bar is designed to withstand a minimum strength of 500 MPa. While Fe550 TMT is designed to withstand a minimum strength of 550 MPa. When it comes to tensile strength, Fe500 TMT Grade Bar is 8% more than 0.2% PS but not less than 545.0 N/mm2, whereas, the tensile strength of Fe550 TMT Grade Bar is 6% more but not less than 585.0 N/mm2. Resultant of the difference in values, Fe550 is more durable than Fe500.
Cost Differences
Most commonly, Fe550 steel is more expensive than Fe500 steel due to its strength properties and better durability performance. This may change with the purpose for which we use them because the durability property of Fe550 decreases the cost needed to be spent in maintenance and repair over the life of the structure. This factor makes Fe550 more affordable and cost-effective in the long run. It is imperative to consider factors such as the grade of steel, the manufacturing process and the supplier’s location to ensure the quality of steel.
Application and Usages of Fe550 Grade Bars
- As the tensile strength of Fe550 Grade bars is much greater, they are often found suitable for construction projects with more arenas.
- They can also be used for mechanical undertakings, scaffolds, and other structures that need to withstand a lot of weight.
- These types of bars are the most preferred for underground construction projects, marine projects, beachfront properties, and more.
- Fe550D is more suitable for projects demanding exceptional structural needs, such as high-rise buildings, bridges, and industrial complexes.
Application and Usages of Fe500 Grade Bars
- Fe500 is standard in the market across many types of construction projects. Despite their reduced ductility, Fe500 has good stability and security in terms of earthquake resistance. They are mainly preferred in the construction of multi-storeyed buildings, business complexes, and private ventures.
- Fe500D, with its properties, is suitable for conventional construction needs such as residential buildings and low-rise structures.
Advantages and Disadvantages of TMT Bars
In general, TMT bars are resilient and ideal to use with concrete to make buildings stronger. The ribbed pattern of the steel bar provides better conglomeration with the concrete. Its ductile property allows it to withstand shocks without any cracks or deformity. Their thermal stability doubles the capacity of a building to remain intact even during a fire. The withstanding capacity against that of fire ranges between 400 to 600 degrees centigrade. However, the transportation of bars is challenging and expensive due to its weight and transportation time. Even though bars can withstand fire, they may start melting at very high temperatures and lose their shape if welded.
Advantages and Disadvantages of Fe500 and Fe550 Grade Bars
Advantages of Using Fe500 Grade Bars
- Fe500 TMT bar is highly ductile with an elasticity of around 12% to 18%, minimising the risk of concrete cracking, and ensuring safer and more durable structures.
- Malleable and resilient physical properties of Fe500 can withstand stress due to variations in temperature and adverse weather conditions.
- Fe500 grades are highly preferable in seismic zones 3, 4, and 5 as they can endure reactive and seismic stress.
Disadvantages of Using Fe500 Grade Bars
- While Fe500 TMT Grade bars are cost-effective, it is inappropriate to use them in projects requiring extremely high strength.
- When we say, Fe500 provides a good balance of strength and ductility, we must ensure structural integrity is not compromised by adding excessive load.
Advantages of Using Fe 550 Grade Bars
- The yield and tensile strength of Fe 550 make it apt for huge constructions like towers, dams, flyovers etc.
- It can withstand corrosion and has an amazing weldability feature.
- Low content of sulphur, phosphorus, and carbon increases the resilience of bars to tolerate fluctuating temperatures, improving the durability of the building.
Disadvantages of Using Fe 550 Grade Bars
- Fe550 TMT bars affordability compared to Fe500 makes it less suitable for small-scale projects.
- Its high strength requires specialised handling equipment and techniques during transportation, storage, and fabrication.
Manufacturing Process of Fe500 and Fe550
The manufacturing process of Fe500 and Fe550 includes a comprehensive manufacturing process. The first process incorporates the processing of iron ore, where the raw material is processed in the furnace. The impurities are tackled through beneficiation. Pre-treatment and ladle heating convert them into steel. Then, the molten steel is heated at 1200 degrees Celsius. When it comes to this heat treatment, Fe500 undergoes standard heat treatment. Meanwhile, Fe550 is subjected to a modified heat treatment process. The additional heat treatment of Fe550 makes it suitable for structures requiring high load-bearing capacity. Following this, thermos-mechanical treatment starts and water is sprayed onto the hot bars. This process toughens the outer layer of the bar, while the core remains smooth. The transfer of heat from the core to the surface strengthens the bar. The cooling process for Fe500 and Fe550 steel is a bit different. For Fe500, the steel bars are cooled quickly by quenching (fast cooling) right after rolling, which makes the outer part hard but leaves the inside softer. Fe550 bars also go through quenching, but they may include extra temperature control during the self-tempering stage to make them tougher.
Which Steel Grade is Better
When it comes to construction, both Fe500 and Fe550 have their merits and demerits. While Fe500 is mostly used for residential buildings, Fe550 is widely used for projects that demand additional strength and structural robustness to ensure buildings withstand unprecedented challenges over time. While both variants offer better tensile strength, yield strength and elongation, the 550 is far better when we compare both. Selecting any one out of the two depends on the building project. Fe550 are preferred for structures that need to bear a higher amount of load.
Conclusion
Finally, it is quite evident that Fe500 and Fe550 are similar in properties, and the differentiating factor between these two is the presence of ductility. The buyer needs to choose a suitable grade of steel depending on the kind of structure.