Direct Square Forming and Sizing Section

Productio Range

Line Specification

1. Technical Overview

Direct square forming (also known as direct forming to square or rectangular tube) is a tube mill process in which flat steel strip is directly formed into square or rectangular shapes without first forming into a round pipe. The entire shaping takes place in the form-and-size section, enabling a more efficient, accurate, and material-saving production for hollow structural sections (HSS).

2. Process Flow

Coil → Uncoiler → Leveling → Shearing & Welding → Accumulator → Forming Section (Direct Square) → HF Welding → Burr Removal → Cooling → Sizing Section → Flying Saw → Stacking

🔧 Detailed Steps:

1. Material Entry: Steel strip is leveled and joined via shear & welder.

2. Forming Section: Gradual deformation of flat strip into square/rectangular shape through roll forming – no round stage involved.

3. High-Frequency Welding: Weld seam generated along one edge (typically inner corner).

4. Weld Bead Removal: Internal and/or external trimming as required.

5. Cooling System: Water spray cooling to stabilize tube shape and microstructure.

6. Sizing Section: Final shaping and dimension correction; ensures angle sharpness and wall flatness.

7. Flying Saw Cutting: Length-wise cutting according to user-set lengths.

8. Output Table / Auto Stacker: Pipe collection and automatic alignment.

3. Technical Parameters  

Note: Larger sizes (up to 250×250 mm or more) available on request using modular mill setups.

4. Advantages of Direct Square Technology

✅ Efficiency & Material Saving

• Avoids round pre-forming, reducing tooling steps and energy consumption.

• Saves up to 2–3% material by reducing corner stretching and less reshaping.

✅ High Product Accuracy

• Achieves precise outer dimensions, excellent flatness of sides, and sharp corners.

• Stable weld seam location along corner (more uniform structure).

✅ Tooling Flexibility

• Fewer forming stands required.

• Standardized roll sets can be reused across similar profiles (only fine adjustment needed).

✅ Reduced Maintenance & Wear

• Less deformation per stand → lower roll wear.

• Simplified structure → easier roll replacement and alignment.

5. Application Scope

This technology is suitable for manufacturers focusing on:

• Hollow Structural Sections (HSS)

• Mechanical & Automotive Frames

• Steel Furniture Tubes

• Scaffold Tubes / Guard Rails

• Solar Panel Mounting Structures

• Greenhouse & Agricultural Frames

Especially advantageous when production is focused on square/rectangular tubes only and requires high output, repeatability, and low running cost.

6. Frequently Asked Questions (FAQ)

Q1: Is direct square forming better than round-to-square?
A: For dedicated square/rectangular tube production, yes. It eliminates redundant forming stages and provides better efficiency. However, if the mill needs to produce both round and square tubes, round-to-square offers more flexibility.

Q2: Can this process handle high-strength or galvanized steel?
A: Yes. As long as the line is equipped with proper roll material (D2, Cr12MoV, or carbide), and forming passes are adjusted accordingly, direct square forming can handle Q345/S355, galvanized coils, and even certain AHSS grades.

Q3: What are the limitations of this process?
A: It’s not ideal for very small tubes (e.g., <20×20 mm) or extremely thin walls (<1.2 mm), as the corner formability and weld control become difficult without round shaping.

Q4: How is weld seam quality ensured without round pre-forming?
A: Through precise edge positioning before welding, and using automatic seam tracking systems with real-time correction. The weld seam is located along a corner, where stress distribution is relatively favorable.

Q5: What’s the typical tooling changeover time for a new size?
A: With manual roll change: 3–5 hours.
With quick-change cassette type: 30–60 minutes.

✅ Summary

Direct square forming is a highly efficient, cost-effective solution for large-volume production of square and rectangular tubes, delivering improved yield, precision, and structural consistency — especially when integrated with automatic control systems and modular tooling design.

Forming section（Flattening unit +Main driving unit +Forming unit +Guide unit +squeeze roller）+ De-burr frame →→Cooling unit →→ Sizing unit and straightener