A Comprehensive Guide to Steel Grades IS 2062, Impact Testing, and De-Oxidation Modes

Introduction

In the world of steel, grades play a crucial role in determining the quality and performance of the material. Steel grades are used to classify different types of steel based on their composition, properties, and intended use. In this blog post, we will explore the nine grades of steel and their sub-qualities, as well as the impact test requirements and modes of de-oxidation associated with each grade.

Steel is an alloy composed primarily of iron and carbon, with other elements such as manganese, silicon, and trace amounts of other elements added to enhance its properties. The composition of these elements determines the grade of steel and its suitability for various applications.

The nine grades of steel that we will be discussing are commonly used in industries such as construction, automotive, manufacturing, and oil and gas. Each grade has its own unique set of properties and characteristics, making it suitable for specific purposes.

One of the key factors that differentiate the grades of steel is the carbon content. Low carbon steel, also known as mild steel, contains a carbon content of up to 0.25%. It is easy to work with and is commonly used in applications that require low strength and good formability. Medium carbon steel, on the other hand, contains a carbon content between 0.25% and 0.60%. It offers higher strength and hardness compared to low carbon steel, making it suitable for applications such as axles, gears, and shafts.

High carbon steel, with a carbon content ranging from 0.60% to 1.0%, is known for its exceptional hardness and wear resistance. It is commonly used in applications that require cutting tools, springs, and high-strength wires. However, high carbon steel is more brittle and less ductile compared to low and medium carbon steels.

In addition to carbon content, other elements such as manganese, silicon, and phosphorus are also important in determining the properties of steel. Manganese, for example, is commonly added to improve the strength and hardenability of steel. Silicon helps in deoxidizing the steel and improves its resistance to oxidation and scaling at high temperatures. Phosphorus, on the other hand, is added in small amounts to improve machinability and enhance the strength of steel.

Another important aspect of steel grades is the impact test requirements. The impact test measures the ability of a material to absorb energy during fracture. It is conducted by subjecting a notched specimen to an impact force and measuring the amount of energy absorbed. The impact test requirements vary depending on the grade of steel and its intended use. For example, steel used in structural applications such as buildings and bridges must meet specific impact test requirements to ensure its structural integrity.

The mode of de-oxidation is another factor that distinguishes the grades of steel. De-oxidation is the process of removing oxygen from the steel during its production. There are three main modes of de-oxidation: killed steel, semi-killed steel, and rimmed steel. Killed steel is fully de-oxidized, resulting in a more uniform and fine-grained structure. Semi-killed steel is partially de-oxidized, while rimmed steel is not de-oxidized at all. Each mode of de-oxidation has its own advantages and disadvantages, and the choice of de-oxidation mode depends on the desired properties of the steel.

In conclusion, understanding the different grades of steel is essential for selecting the right material for a specific application. The composition, properties, impact test requirements, and mode of de-oxidation are all important factors to consider when choosing a grade of steel. By understanding these factors, engineers and manufacturers can ensure that they are using the most suitable grade of steel for their needs, resulting in high-quality and reliable products.

Grades

For grades E 650 to E 900, there are three sub-qualities: A, BR, and C. These sub-qualities have similar impact test requirements and modes of de-oxidation as the previous grades.

Sub-Quality A

Sub-quality A does not require an impact test and is categorized as semi-killed or killed steel.

Sub-Quality BR

Sub-quality BR has an optional impact test requirement, conducted at room temperature. It is also classified as semi-killed or killed steel.

Sub-Quality C

Sub-quality C requires an impact test at -40°C and is classified as killed steel. The impact test at lower temperatures ensures that the steel can withstand extremely cold conditions and maintain its structural integrity.

These nine grades of steel provide a wide range of options for various applications. The choice of grade depends on the specific requirements of the project, such as the desired strength, toughness, and resistance to corrosion. The different sub-qualities within each grade offer further customization based on the need for impact testing and the mode of de-oxidation. It is important for engineers and manufacturers to carefully consider these factors when selecting the appropriate grade of steel for their applications.

Importance of Impact Testing

Impact testing is a critical aspect of assessing the toughness and resistance of steel. It measures the ability of a material to absorb energy during sudden loading or impact, such as in structural applications or under extreme conditions.

The impact test helps determine the behavior of steel when subjected to dynamic loads or sudden impacts. It provides valuable information about the material's ability to resist fracture and deformation, ensuring its suitability for specific applications.

By categorizing steel grades based on impact test requirements, manufacturers and users can select the appropriate grade for their intended use. The impact test results provide insights into the steel's performance under different conditions, allowing for informed decision-making.

One of the main reasons why impact testing is crucial is its role in ensuring the safety and reliability of structures and components. For example, in the construction industry, buildings and bridges are subjected to various forms of dynamic loading, such as earthquakes, heavy winds, and vehicular impact. Without proper impact testing, the structural integrity of these constructions could be compromised, leading to catastrophic failures.

Additionally, impact testing plays a significant role in the automotive industry. Vehicles are exposed to various impacts, such as collisions and accidents. The ability of the steel used in the car's frame to absorb and dissipate energy is vital for the safety of the occupants. Impact testing helps ensure that the steel used in car manufacturing meets the necessary standards and can withstand the forces experienced during accidents.

Furthermore, impact testing is essential in industries where materials are exposed to extreme conditions, such as aerospace and defense. Components used in aircraft and military equipment must be able to withstand sudden impacts and high-stress situations. Impact testing allows manufacturers to evaluate the performance of different materials and select those that can withstand the demanding requirements of these industries.

Moreover, impact testing also aids in research and development efforts. Scientists and engineers can use the results of impact tests to improve the design and performance of materials. By understanding how different steel grades behave under impact, they can develop innovative materials that are stronger, more durable, and safer.

In conclusion, impact testing is of utmost importance in assessing the toughness and resistance of steel. It ensures the safety and reliability of structures, components, and vehicles by providing valuable insights into the material's behavior under dynamic loads and sudden impacts. It also plays a vital role in industries where materials are exposed to extreme conditions and aids in research and development efforts to enhance the performance of materials.

Modes of De-Oxidation

The mode of de-oxidation refers to the process used during steel manufacturing to remove oxygen and other impurities. This process plays a crucial role in enhancing the properties and performance of the steel.

In the context of the nine grades of steel, the modes of de-oxidation are categorized as semi-killed and killed steel:

Semi-Killed Steel

Semi-killed steel is partially de-oxidized during the manufacturing process. This mode of de-oxidation helps improve the steel's properties, such as its ductility, toughness, and weldability. Semi-killed steel is commonly used in applications where a balance between strength and formability is required.

During the semi-killed steel manufacturing process, a controlled amount of oxygen is left in the steel. This controlled amount of oxygen allows for the formation of small, dispersed gas bubbles within the steel matrix. These gas bubbles act as nucleation sites for the formation of fine-grained structures in the steel, which enhances its mechanical properties. The presence of oxygen also helps in reducing the risk of hot cracking during solidification.

Semi-killed steel is often used in the production of structural components, such as beams, columns, and plates. It is also commonly employed in the manufacturing of pipes, tubes, and automotive parts. The combination of improved formability and mechanical properties makes semi-killed steel a versatile choice for various applications.

Killed Steel

Killed steel is fully de-oxidized during the manufacturing process. This mode of de-oxidation ensures a higher level of purity and removes all oxygen from the steel. Killed steel exhibits excellent properties, including superior strength, uniformity, and resistance to cracking. It is often used in critical applications where consistency and reliability are paramount.

During the manufacturing of killed steel, a strong de-oxidizing agent, such as silicon or aluminum, is added to the molten steel. This de-oxidizing agent reacts with the oxygen present in the steel, forming stable oxides that float to the surface and are subsequently removed. By eliminating all traces of oxygen, killed steel achieves a high level of cleanliness and minimizes the risk of impurities and defects.

Killed steel is commonly employed in the production of high-strength structural components, such as bridges, buildings, and offshore platforms. It is also used in the manufacturing of pressure vessels, shipbuilding, and oil and gas pipelines. The exceptional mechanical properties and reliability of killed steel make it suitable for demanding applications that require superior performance and durability.