Hollow section steel is a term for square and rectangular steel tubes, which refers to steel tubes with equal and unequal side lengths. It is made by rolling strip steel after process processing. Generally, the strip steel is unpacked, flattened, curled, and welded to form a round tube, which is then rolled into a square tube and cut into the required length.
Types of Hollow Section Steel by Production Method
Hollow structural sections are categorized into seamless and welded types and come in three main shapes: rectangular (RHS), square (SHS), and circular (CHS), each with distinct advantages, properties, and applications.Hollow section steel is classified into different categories based on the production process. The main types include:
1. Welded Hollow Section Steel
Welded hollow section steel is made by forming steel strips into a circular shape, welding the edges together, and then shaping them into square or rectangular sections. This type is cost-effective and widely used in construction and mechanical applications. Common welded varieties include:
ERW (Electric Resistance Welded) Hollow Section Steel: Manufactured through high-frequency electrical resistance welding, suitable for structural uses.
SSAW (Spiral Submerged Arc Welded) Hollow Section Steel: Produced by spiral welding, commonly used in pipelines.
2. Seamless Hollow Section Steel
Unlike welded pipes, seamless hollow section steel is produced without welding seams. It is made by perforating solid steel billets and then rolling them into the desired shape. Key types include:
Hot-Rolled Seamless Hollow Section Steel: Manufactured using high temperatures, providing better mechanical properties.
Cold-Drawn Seamless Hollow Section Steel: Produced at lower temperatures for precise dimensions and higher strength.
Extruded Seamless Hollow Section Steel: Created by forcing heated steel through a die, resulting in uniform thickness.
3.Square Hollow Section Pipes
Square Hollow Section (SHS) pipes represent a crucial form of steel pipe, distinguished by their unique blend of durability, aesthetic charm, and structural integrity. These pipes, characterized by their square cross-section, provide a versatile solution across a broad spectrum of applications, particularly in the construction and manufacturing sectors. SHS pipes are renowned for their strength and durability, qualities stemming from the manufacturing process and the material's inherent attributes.
4.Rectangular Hollow Section Pipes
When considering the design and application of rectangular hollow section (RHS) pipes for your engineering projects, grasping their unique characteristics is crucial. RHS pipes, with their flat surfaces and rectangular cross-section, provide a blend of strength, efficiency, and aesthetic appeal that can be pivotal across a wide range of applications. RHS pipes find diverse applications, ranging from structural to aesthetic.
In construction, they are frequently used in frames and columns, where their shape allows for easy connection and load distribution. The ease of joining and welding RHS pipes also makes them suitable for architectural designs, where clean lines and modern aesthetics are desired. Additionally, their robustness and ability to withstand high temperatures and pressures render them ideal for infrastructure projects, including bridges and platforms. For engineers, the choice of RHS pipes can significantly influence the success of a project.
5.Circular Hollow Section
One of the most typical hollow sections is the circular hollow section (CHS) used in construction, mechanical and structural projects. They have a smooth surface, no sharp or protruding edges, so they have high aesthetic value. Similar to SHS and RHS, CHS products are durable, strong, easy to shape, suitable to be used as materials for projects requiring low temperature.
Classification by Material Composition
Hollow section steel is available in various material compositions, depending on strength, corrosion resistance, and application requirements. The main categories are:
1. Carbon Steel Hollow Section Steel
Carbon steel hollow sections are the most common, offering excellent strength and affordability. They are used in construction, automotive, and agricultural industries.
2. Low-Alloy Hollow Section Steel
Low-alloy steel contains elements like manganese, vanadium, or chromium, enhancing strength, toughness, and corrosion resistance. These are often used in heavy-duty structures.
3. Galvanized Hollow Section Steel
To improve corrosion resistance, hollow section steel can undergo surface treatments like galvanization. Two common types include:
Hot-Dip Galvanized Hollow Section Steel: Immersed in molten zinc for superior protection.
Electro-Galvanized Hollow Section Steel: Coated through electroplating for a thinner zinc layer.
Classification by Industry Standards
Hollow section steel is manufactured according to different international standards to meet specific industry requirements. The main standards include:
GB (Chinese Standard): Widely used in domestic construction and infrastructure.
ASTM (American Standard): Includes ASTM A500 for structural applications.
JIS (Japanese Standard): Follows JIS G3466 for hollow structural sections.
BS (British Standard): Covers BS EN 10219 and BS EN 10210 for cold-formed and hot-finished sections.
EN (European Standard): Used across the EU, focusing on structural performance.
Non-Standard Hollow Section Steel: Custom-produced sections for specific applications.
Hollow section steel is also called square and rectangular cold-bent hollow steel, referred to as square tube and rectangular tube, with codes F and J respectively.
The allowable deviation of the wall thickness of hollow section steel shall not exceed plus or minus 10% of the nominal wall thickness when the wall thickness is not more than 10 mm, and plus or minus 8% of the wall thickness when the wall thickness is greater than 10 mm, excluding the wall thickness of the bend and weld area.
The usual delivery length of hollow section steel is 4,000 mm - 12,000 mm, with 6,000 mm and 12,000 mm being more common. Hollow section steel is allowed to deliver short-length and non-fixed-length products of not less than 2,000 mm, and can also be delivered in the form of interface tubes, but the purchaser should cut off the interface tubes when using them. The weight of short-length and non-fixed-length products shall not exceed 5% of the total delivery volume. For hollow section steel with a theoretical weight greater than 20 kg/m, it shall not exceed 10% of the total delivery volume.
The curvature of hollow section steel shall not exceed 2 mm per meter, and the total curvature shall not exceed 0.2% of the total length.
Conclusion
Hollow section steel plays a crucial role in modern industries, offering durability, cost efficiency, and adaptability. It is classified based on production methods, materials, and industry standards, ensuring suitability for various applications. Whether used in construction, manufacturing, or transportation, hollow section steel continues to be an essential material for structural engineering.
At BAOWI Steel, we provide premium hollow section steel solutions, delivering high-quality CHS, RHS, SHS, and seamless pipes for the most demanding engineering projects. Our commitment to excellence ensures that every product meets the highest industry standards, offering durability, strength, and precision.
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