1. Technical Overview: Round-to-Square Forming Process
In ERW tube production, the round-to-square forming process is a key technique for manufacturing square and rectangular pipes. It involves reshaping a fully welded round tube into a square or rectangular section through a series of precision sizing and forming rolls under cold forming conditions.
Process Flow:
Raw material → Forming → HF Welding → Burr Removal → Cooling → Round-to-Square → Sizing → Flying Saw → Finished Pipe
Key Features and Technical Notes:
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Stepwise Deformation: The tube undergoes three stages: pre-forming, transitional forming, and final shaping, progressively transforming the round section into a square.
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Cold Bending Principle: The shaping relies on plastic deformation across multiple roll passes to gradually modify the profile.
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Precision Control: Equipped with CNC adjustments and inline measuring systems to ensure dimensional accuracy and edge/angle precision.
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Flexible Tooling: Only the final forming and sizing rolls need to be replaced for different specifications, allowing fast product changeovers.
Technical Advantages:
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High dimensional accuracy and straight edges with clean corners
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Centralized weld seam, ensuring better structural performance
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Reduced energy consumption and tooling wear compared to direct square forming
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Widely used in construction, mechanical frames, furniture tubing, and automotive profiles
2. BASIC DESIGN DATA
Taklif etilayotgan liniyaning dizayni quyidagi spetsifikatsiyalarga asoslanadi:
Xom ashyo spetsifikatsiyasi
Raw Material Feeding
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CR bright tube with oiled, Galvanized steel, HR coil
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Material Tensile Strength
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Max 517MPa (75,000 psi max)
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Material Yield Strength
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Max 460MPa (67,000 psi max)
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Bobin OD
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1200mm to 2000mm
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Bobin identifikatori
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508mm&610mm (customer order)
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Bobinning og'irligi
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Max 7000 kg
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Chiziq kengligi
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Min 240mm, Max520mm
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Chiziq qalinligi
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Min2.0mm Max6.35mm
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Ishlab chiqarish diapazoni
Ishlab chiqarish turi
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▪Round Tubes
▪Kvadrat va to'rtburchaklar bo'shliq bo'laklar
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Round Tube OD
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Min 76mm, Max 165mm
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Round Tube Thickness
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Min 2.0mm, Max 6.35mm
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Kvadrat ichi bo'sh qism
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Min 60x60mm, Max 130x130mm
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To'rtburchaklar ichi bo'sh qism
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Min 80x40mm, Max 100X160mm
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Square and rectangle Tube Thickness
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Min2.0mm, Max 5.0mm
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Quvurni kesish uzunligi
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Min 6 meter, Max 12 meter
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Line Specification
Forming Section
Shaft material:
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40Cr, HF tempering quenching
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Material of bevel gear:
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20CrMnTi
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Driven stand
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7 sets
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Idle stand
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8 sets
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Vites qutisi
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7 sets
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Sizing Section
Shaft material:
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40Cr,HF tempering quenching
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Material of bevel gear:
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20CrMnTi
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Driven stand
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5 sets
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Idle stand
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5 sets
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Vites qutisi
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5 sets
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The Flow of the Production Line
Forming section(Flattening unit +Main driving unit +Forming unit +Guide unit +squeeze roller)+ De-burr frame →→Cooling unit →→ Sizing unit and straightener

2. Frequently Asked Questions (FAQ)
Q1: Why choose the round-to-square process instead of direct square forming?
A: The round-to-square method ensures better weld seam alignment, stronger structural integrity, and greater tooling flexibility, especially for mid-to-thick wall and high-strength materials.
Q2: How is the corner quality controlled? What are the common issues?
A: Corners are formed through gradual pressing in multiple roll passes. Issues like cracking, over-rounded corners, or misalignment can be resolved by optimizing roll design and adjusting pressure settings.
Q3: How to prevent weld seam misalignment during forming?
A: Keep the weld seam centered after welding and ensure symmetrical roll forces during forming. Optional weld seam tracking systems can further stabilize seam position.
Q4: Do we need to replace the entire roll set when changing specifications?
A: No. Only the round-to-square and sizing sections need to be changed, significantly reducing downtime and tooling costs.
Q5: What causes edge waviness or "bamboo-like" defects?
A: These are typically due to excessive deformation per pass or improper roll design. Adjusting the deformation rate and optimizing pressure balance in the sizing unit can solve this.
Q6: Is round-to-square suitable for small-size thin-wall tubes?
A: Generally not. Thin-wall small tubes are prone to instability or cracking during transformation. Direct square forming is more appropriate for such sizes.