Steel is the top choice in construction thanks to its optimal cost, outstanding flexibility and long-term durability. Understanding steel materials not only helps improve construction efficiency but also ensures the quality and suitability of each project. This article will analyze in detail the lines of structural steel materials, outstanding features and scope of application of each type.
1. Classification by chemical composition
Structural steel materials are divided into several groups based on their chemical composition, including the carbon content (low, medium, high carbon steels), the combination with alloying elements (alloy steels), or the characteristic chromium content (stainless steels).
Carbon steel:
Considered the main steel in the construction industry, carbon steel is mainly composed of iron and carbon, with minimal amounts of other elements. This type of steel is known for its superior strength and flexible weldability.
Based on the carbon content, carbon steels are divided into three main groups:
- Low carbon steel (≤ 0,25% carbon): Tough, easy to process.
- Medium carbon steel (0,25% – 0,60% carbon): Balance between strength and ductility.
- High carbon steel (≥ 0,60% carbon): High hardness, good strength.
Carbon steel is widely used in large structures such as high-rise building frames, bridges, and transportation infrastructure due to its high efficiency and economy.
Stainless Steel:
Stainless steel is an alloy containing at least 10,5% chromium, providing superior corrosion resistance. With its high durability, shiny appearance and low maintenance requirements, this type of steel is popular in both construction and industry.
In construction, stainless steel appears in architectural details such as facades, railings, or decorative parts. In addition, thanks to its hygienic properties and chemical resistance, it is also the first choice for the food processing, pharmaceutical and chemical industries.
Alloy steel:
Alloy steel is created by adding elements such as manganese, nickel, chromium, or molybdenum to steel to improve properties such as hardness, strength, or corrosion resistance. Depending on the alloy composition, steel can be optimized for specific purposes.
This type of steel is often used in applications that require high strength and toughness, such as the manufacture of industrial machinery, automotive parts, or specialized engineering equipment.
2. Classification by surface processing
Structural steel materials can be classified based on the surface treatment technique in the finishing stage, including main types such as hot rolled steel, cold rolled steel and cold worked steel.
Hot rolled steel:
Hot rolled steel is produced by heating steel billets at temperatures above 1.000°C, then passing them through a roller system to shape and adjust the thickness. This type of steel is often used for products such as shaped steel (H, I, U), steel plates or large-sized steel pipes. The distinguishing feature of hot rolled steel is that the surface has an oxide layer (rolling scale) due to the impact of high temperatures, suitable for projects that do not require high aesthetic finishing such as factory frames, steel bridges or infrastructure structures.
Cold rolled steel:
Cold rolled steel is produced from hot rolled steel, which undergoes further rolling at room temperature to achieve a thinner profile and improved surface quality. The result is a product with a smooth surface, precise dimensions with tight tolerances, and increased strength and hardness. This type of steel is ideal for applications requiring precision, such as car bodies, electronic components, or machine parts that require aesthetics and high precision.
Cold worked steel:
Cold-worked steel is processed through methods such as drawing, grinding or peeling to produce steel bars, steel wire or steel pipes with optimum precision and super-smooth surfaces. This process usually involves drawing the steel through specialized dies or using machine tools to precisely shape it, which significantly improves mechanical properties such as tensile strength and hardness. Cold-worked steel is used in products that require a high degree of finish, such as drive shafts, engineering accessories or complex machine parts.
3. Classification by production technology
Structural steel materials can be divided into many types based on the production process, including major groups such as blast furnace steel, electric arc furnace steel and continuous casting steel.
Blast furnace steel is produced through a traditional smelting process using iron ore, coke and limestone as the main raw materials. In the blast furnace, the extremely high temperatures from the coke combustion reaction melt the iron ore, creating molten pig iron that accumulates at the bottom of the furnace. This pig iron is then refined through additional processes to remove impurities and adjust the composition, resulting in quality steel. This type of steel is often used in large structural applications such as industrial steel frames and transportation infrastructure.
Electric arc furnace steel:
The electric arc furnace (EAF) process uses a high-voltage electric current to create an arc, melting scrap steel or additional alloys. Scrap steel is fed into the furnace, and an electric arc between electrodes and metals generates high temperatures, turning the raw material into liquid steel. This method is notable for its flexibility, allowing the chemical composition to be adjusted to produce specific grades of steel. EAF steel is widely used in steel recycling and manufacturing products such as alloy steel or high-tech steel.
Continuous casting steel:
Continuous casting is a modern technology in which molten steel is poured into a water-cooled mold to form shapes such as square billets, slabs or blooms. The process is continuous, with the solidified steel being drawn out, cooled and cut into standard sizes. This method offers high efficiency, reduces production costs and ensures consistent quality, making it ideal for making steel products for construction, machinery manufacturing and other industries.
4. Additional classification methods
In addition to the main criteria, structural steel materials are also classified according to a number of other technical characteristics, including mechanical strength, deoxidation process and heat treatment method.
According to mechanical strength:
Steel can be classified based on mechanical parameters according to ASTM (American Society for Testing and Materials) standards, such as yield strength, tensile strength, and tensile strength. These properties determine the suitability of steel for specific applications, from factory structures to bridges or heavy industrial equipment.
According to the deoxidation process:
The deoxidation process in steelmaking directly affects the quality and microstructure of steel. Based on the degree of oxygen removal from the molten steel, steel is divided into:
- Fully de-annealed steel: Oxygen is completely removed, creating steel with a uniform structure, suitable for products requiring high durability.
- Semi-reduced steel: Partially reduced oxygen content, often used for applications that do not require too strict quality requirements.
This method affects the purity and mechanical properties of steel, meeting diverse production needs.
By heat treatment:
Heat treatment is a technique for changing the properties of steel through controlled cycles of heating and cooling. Some common methods include:
- Annealing: Soften steel, increase toughness, easy to process.
- Quenching and Tempering: Increase hardness and durability, suitable for steel with heavy load capacity.
These processes optimize steel for specific purposes, from pre-engineered steel frames to machine components.
The article has summarized 4 ways to classify structural steel materials, from chemical composition, surface processing, manufacturing technology to additional properties. Understanding these methods helps you choose the right type of steel for each construction or manufacturing project.
With more than 25 years of experience in the field of manufacturing and installing steel structures, choosing Hai Long Construction will help you design and construct industrial factories with steel structures to ensure safety and efficiency.
