Before purchasing large-diameter spiral steel pipe, purchase according to pre-designed specifications, length, material, wall thickness, welding standards, and weld requirements, ensuring thorough pre-purchase communication.

First, consider the standard. For example, 800mm is also known as DN800, and also includes 820mm and 813mm in the A and B series. Alternatively, the outer diameter of 800mm should be clearly indicated to avoid unnecessary losses.

The wall thickness requirement for large-diameter straight seam steel pipe is 16mm. The actual thickness of the raw material may vary between 15.75mm and 16.2mm, with some fluctuation. These fluctuations are normal. Since straight seam steel pipe is priced by tonnage, prior communication is necessary to avoid weight discrepancies.

The standard length of large-diameter straight seam steel pipe is 12 meters. If a custom length is required, it is recommended to communicate in advance, as the price of custom lengths will be relatively higher. If no prior communication is made, the typical length is 9.87 meters, and the manufacturer will generally provide 9.9 meters directly. 

 When purchasing large-diameter straight seam steel pipe, ensure thorough communication with the supplier to ensure that the materials used are not OEM products. A raw material list from the steel mill must be provided to verify the authenticity of the materials. Any material issues will result in a return and compensation.

Welding standards during production and processing must comply with the requirements of Automatic Submerged Arc Welding (LSAW) GB/T3091-2015, and a product quality certificate must be provided. If these standards are not met, the product will be deemed unqualified.

When purchasing large-diameter straight seam steel pipe, be sure to confirm weld inspection requirements in advance, as this testing incurs additional costs.

In addition, large-diameter straight seam steel pipe over 1020 mm may have two welds. Many projects do not allow the use of two welds without prior consultation, and this will be considered a defective pipe.

Thus, prior consultation is crucial before purchasing any steel pipe to avoid unnecessary disputes and financial losses.

Square tubes are a type of square-shaped tubular material, specifically steel tubes with equal side lengths. They are manufactured by rolling steel strips through a specialized process. Steel tubes have become an indispensable material in construction and interior decoration. Square tubes are also widely used in interior decoration, but it is important to first understand the dimensions of square tubes and familiarize yourself with the common sizes available, as this will assist you in making an informed purchase.

What are square tubes?

Square tubes, as their name suggests, are tubular structures with square cross-sections. Various materials can be used to form square tubes, depending on their intended use and application. Most square tubes are made from steel tubes, which are first unpacked, flattened, rolled, and welded into round tubes. These round tubes are then rolled into square tubes and cut to the required length. Generally, there are 50 pieces per package. In terms of stock availability, larger sizes are more common, ranging from 10x10x0.8-1.5 to 500x500x10-25. Square tubes are categorized by application into structural square tubes, decorative square tubes, construction square tubes, and mechanical square tubes, among others.

A square tube is a lightweight, thin-walled steel tube with a hollow square cross-section, also known as steel cold-formed profiles. It is manufactured by cold-bending and welding Q235 hot-rolled or cold-rolled steel strips or coils into a square cross-section shape, followed by high-frequency welding. For hot-rolled thick-walled square tubes, except for increased wall thickness, the corner dimensions and edge straightness meet or exceed the standards of resistance-welded cold-formed square tubes.

Features and Applications of Square Tubes

1. Square Tube Product Description

Square tubes are hollow square-section lightweight thin-walled steel tubes, also known as steel cold-formed profiles. They are manufactured using Q235 hot-rolled or cold-rolled steel strips or coils as raw material, which are cold-bent into shape and then welded using high-frequency welding to form square-section steel with specified dimensions. Except for the increased wall thickness, the corner dimensions and edge straightness of hot-rolled thick-walled square tubes meet or even exceed the standards of resistance-welded cold-formed square tubes. They have excellent comprehensive mechanical properties, weldability, cold and hot processing performance, corrosion resistance, and good low-temperature toughness.

1. Applications of square tubes

Square tubes are used in various projects such as construction, mechanical manufacturing, steel construction, shipbuilding, solar power generation supports, steel structure engineering, power engineering, power plants, agricultural and chemical machinery, glass curtain walls, automobile chassis, airports, boiler construction, highway guardrails, building construction, pressure vessels, oil storage tanks, bridges, power plant equipment, lifting and transportation machinery, and other welded structural components with higher load requirements.

Methods for Identifying Square Tubes

With the development of the economy, counterfeit products have become increasingly prevalent in society. To avoid being deceived when purchasing square tubes, it is essential to understand how to distinguish between genuine and counterfeit products: We can assess the quality of square tubes by observing their surface smoothness and flatness. If the surface is relatively flat, it indicates that the tube is of good quality. Conversely, if the surface is uneven and the dimensions and thickness are irregular, it suggests that the tube is of poor quality."

Square Tube Weight Calculation Formulas

Square tube weight calculation formula: 4 × wall thickness × (side length – wall thickness) × 0.00785

Circular Tube Weight Calculation Formula: {(Circumference ÷ 3.14) - Wall Thickness} × Wall Thickness × 0.02466

(Note: The units above are kg/m, where wall thickness and side length are measured in millimeters (mm).)

Structurally, a ringlock scaffold primarily consists of vertical posts, horizontal posts, diagonal posts, and discs. The discs are attached to the vertical posts, while the horizontal and diagonal posts connect to the discs via plugs, providing a simple and stable connection.

A cuplock scaffold, on the other hand, consists of vertical posts, horizontal posts, and bowl-type joints. The joints are cuplock scaffold, with the plugs at each end of the horizontal posts inserted into the bowls and tightened by twisting.

In terms of mechanical performance, the ringlock scaffold, due to its node connection method, has virtually no eccentricity between the members, resulting in better load-bearing performance, capable of withstanding large vertical and horizontal loads, and offering high stability.

While the nodes of a cuplock scaffold may experience some eccentricity, its overall stability is slightly lower. However, with proper design and normal use, it can still meet the load-bearing requirements of most construction projects.

In terms of construction efficiency, a ringlock scaffold with a ringlock scaffold is faster to erect. The latch-type connection allows for quick installation and dismantling. During installation, the cuplock scaffold requires tightening the cups one by one. Disassembly requires removing the stop pins and lifting the cups, resulting in more steps and lower efficiency.

In terms of material costs, the ringlock scaffold requires precision casting of the disc-lock nodes, which increases the steel consumption and leads to higher initial procurement costs, but reduces labor costs for assembly and disassembly.
The disc-lock scaffolding has fewer components (vertical poles, horizontal poles, and cuplock scaffold), but the cups require additional processing, resulting in a more moderate material cost.