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:
-
Stepwise Deformation: The tube undergoes three stages: pre-forming, transitional forming, and final shaping, progressively transforming the round section into a square.
-
Cold Bending Principle: The shaping relies on plastic deformation across multiple roll passes to gradually modify the profile.
-
Precision Control: Equipped with CNC adjustments and inline measuring systems to ensure dimensional accuracy and edge/angle precision.
-
Flexible Tooling: Only the final forming and sizing rolls need to be replaced for different specifications, allowing fast product changeovers.
Technical Advantages:
-
High dimensional accuracy and straight edges with clean corners
-
Centralized weld seam, ensuring better structural performance
-
Reduced energy consumption and tooling wear compared to direct square forming
-
Widely used in construction, mechanical frames, furniture tubing, and automotive profiles
2. BASIC DESIGN DATA
Önerilen hattın tasarımı aşağıdaki özelliklere dayanmaktadır:
Hammadde Spesifikasyonu
Raw Material Feeding
|
CR bright tube with oiled, Galvanized steel, HR coil
|
Malzeme Çekme Dayanımı
|
Maksimum 517MPa (maksimum 75.000 psi)
|
Malzemenin Akma Mukavemeti
|
Maksimum 460MPa (maksimum 67.000 psi)
|
Bobin OD
|
1200mm ila 2000mm
|
Bobin kimliği
|
508mm&610mm (customer order)
|
Bobin Ağırlığı
|
Maksimum 7000 kg
|
Şerit Genişliği
|
Min 240mm, Max520mm
|
Şerit Kalınlığı
|
Min2.0mm Max6.35mm
|
Üretim Aralığı
Üretim türü
|
▪Yuvarlak Borular
▪Kare ve Dikdörtgen Boş Kesitler
|
Yuvarlak Boru OD
|
Min 76mm, Max 165mm
|
Yuvarlak Boru Kalınlığı
|
Min 2.0mm, Max 6.35mm
|
Kare Boş Kesit
|
En az 60x60mm, En fazla 130x130mm
|
Dikdörtgen içi boş kesit
|
En az 80x40mm, En fazla 100X160mm
|
Kare ve dikdörtgen boru kalınlığı
|
Min2.0mm, Max 5.0mm
|
Tüp Kesim Uzunluğu
|
Min 6 meter, Max 12 meter
|
Hat Spesifikasyonu
Forming Section
Mil malzemesi:
|
40Cr, HF tempering quenching
|
Konik dişli malzemesi:
|
20CrMnTi
|
Sürülen stand
|
7 set
|
Boşta durma
|
8 set
|
Vites kutusu
|
7 set
|
Sizing Section
Mil malzemesi:
|
40Cr,HF temperleme söndürme
|
Konik dişli malzemesi:
|
20CrMnTi
|
Sürülen stand
|
5 set
|
Boşta durma
|
5 set
|
Vites kutusu
|
5 set
|
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.