ERW Pipe Production Process and Rolling Groove Processing Principle

ERW Pipe Production Process and Pipe End Grooving Process Principle:

1. Overview of ERW Production Process
Currently, most ordinary longitudinal seam welded pipes on the market are produced using high-frequency resistance welding. Its characteristics include high production efficiency and a small heat-affected zone in the weld. This process requires extremely high forming precision; any fluctuation in the "V"-shaped opening angle and shape formed by the steel strip before entering the welding station can lead to quality problems such as incomplete fusion or inclusions in the weld.

2. Pipe End Grooving Process Principle
Grooving (also known as grooving) is a pre-treatment process for pipe ends used in grooved pipe fitting connections. Its principle is: using a grooving machine to drive the pipe to rotate, while simultaneously applying radial pressure to the pipe wall through rollers, causing the pipe to undergo cold plastic deformation at a predetermined position, thereby forming an annular groove for installing clamps. This is a purely physical cold forming process and does not involve welding.

3. Root Cause Analysis of Grooving Cracking
"Grooving cracking" is a stringent test for evaluating the comprehensive performance of the weld. The direct manifestation is cracking, but the root cause is not the processing itself, but rather insufficient strength or plasticity in the weld area. The severe radial deformation caused by grooving will cause stress concentration in defective weld areas, ultimately leading to tearing.

4. The Influence of Raw Materials on Weld Quality
The chemical composition and internal structure of the raw materials are fundamental to weld quality:

● Chemical Composition: Excessive sulfur (S) and phosphorus (P) content easily causes crystal segregation; excessive carbon content or carbon equivalent promotes the formation of brittle and hard phases such as martensite, leading to weld embrittlement.
● Internal Defects: Non-metallic inclusions, delamination, banded structures, and dimensional fluctuations can all become crack initiation points, significantly reducing the weld's crack resistance during grooving.

5. Reasonable Setting of Welding Process Parameters
Key parameters for ERW welding include: input power, welding speed, V-notch angle, welding pressure, induction coil position, and impedance device position. Improper parameter settings are a major cause of insufficient weld strength (leading to cracking during grooving):

● Improper heat input: Insufficient power input or excessive speed results in insufficient heat and incomplete fusion ("cold weld"); conversely, excessive heat causes spatter or overheating.

● Improper welding pressure: Insufficient pressure leads to poor fusion on both sides of the metal flow lines, resulting in low strength; excessive pressure results in excessively high internal burrs and a steep flow line angle. Only when the pressure is moderate, keeping the metal flow line angle within the ideal range of 45°-60° and forming a clear, distortion-free fusion line, can the weld possess sufficient strength and ductility to pass the subsequent grooving test.

Read more: ERW Pipe Size Chart