Comprehensive Analysis of Steel Pipe End Treatment
Date:2025-11-04
I. Core Purpose of End Treatment
Before categorizing, we first need to understand the goals of end treatment:
Ensuring Connection Quality: Providing a smooth, clean, and dimensionally accurate interface for welding, threaded connections, or mechanical connections.
Improving Safety: Eliminating burrs and flash at the ends to prevent injuries or damage to seals.
Enhancing Sealing: Providing a smooth sealing surface for flanged or socket connections.
Optimizing Fluid Dynamics: Reducing flow resistance of the medium within the pipe, preventing eddies and corrosion.
Improving Corrosion Resistance: Protecting cut surfaces and compensating for coatings or plating lost during cutting.
II. Detailed Classification of Steel Pipe End Treatment
Based on the processing technology and final form, steel pipe end treatment can be mainly divided into the following categories:
1. Beveling
This is the most common pretreatment before welding, aimed at ensuring penetration and forming a good weld bead.
Type I Beveling (Flat): Suitable for butt welding of thin-walled steel pipes, typically with a wall thickness of less than 6mm.
V-groove: The most commonly used groove type. A single-sided V-shaped bevel is machined by turning or grinding, leaving a blunt edge to prevent burn-through.
X-groove (Double V-groove): Suitable for thick-walled steel pipes. The groove is machined simultaneously from both the inner and outer sides of the pipe, reducing welding stress and deformation, and saving welding material.
U-groove: Also used for thick-walled pipes, it is machined into a U-shaped groove. It reduces welding material consumption even more than the V-groove, but the processing cost is higher.
J-groove: A variation of the U-groove, typically used for special requirements.
Processing methods: Beveling machine, lathe, flame cutting, plasma cutting followed by grinding.
2. Thread Machining
Mainly used for threaded connections, commonly found in oil pipes, water pipes, drill pipes, etc.
Tapered Pipe Threads: Such as NPT, PT, BSPT, etc. Their characteristic is that the thread has a taper, relying on the engagement of the thread itself to achieve a seal. Commonly used in medium and low pressure systems.
Straight Pipe Threads: Such as BSPP, G series. The thread itself is cylindrical, and sealing relies on end-face sealing rings or packing.
Special Threads: In the oil and gas industry, there are many high-performance special threads (such as VAM, BTC, etc.). They have more complex tooth profiles, sealing surfaces, and torque shoulders, and can withstand high pressure, high temperature, and combined loads.
Machining Methods: Specialized pipe threading lathes, comb-cut dies.
3. Port Forming and Finishing This type of treatment does not change the connection method but optimizes the shape and performance of the port itself.
Chamfering/Deburring: The most basic and necessary treatment. Removes sharp edges and burrs from the inside and outside of the port, facilitating installation and ensuring safety.
Port Flattening (Fixed-Length Cutting): Ensures accurate steel pipe length and perpendicularity of the port to the axis, providing a reference surface for subsequent connections.
Port Inner Wall Treatment:
Internal Chamfering: Machining a small-angle bevel on the inner edge of the port greatly reduces fluid resistance and is standard in high-performance hydraulic systems.
Polishing/Mirror Finish: For industries such as food, pharmaceuticals, and high-purity chemicals, the inner wall of the port needs to be polished to achieve specific roughness requirements, preventing media residue and bacterial growth.
Processing Methods: Chamfering machine, end milling machine, specialized internal chamfering cutter, polishing machine.
4. Port Strengthening and Corrosion Protection Protecting the exposed metal surface after port cutting is crucial for extending the lifespan of the steel pipe.
Spraying/Coating: Spraying epoxy resin, zinc-rich primer, or other anti-corrosion coatings onto the port to match the anti-corrosion layer of the pipe body.
Platinum: Localized electroplating (e.g., galvanizing) of the port restores its corrosion resistance.
Installing Port Protectors: Before transporting, storing, and installing the steel pipe, cover the port with plastic or metal protective caps/rings to prevent impacts, dirt, and moisture intrusion.
III. How to Choose the Appropriate Port Treatment Method? The choice of port treatment method is not arbitrary, but determined by several key factors:
Connection Method
Welding: Beveling and deburring are required.
Threaded Connection: Precise thread machining is required.
Flanged Connection: Ensures port flatness and perpendicularity, and deburrs on bolt holes.
Socket Connection: Requires chamfering for easy insertion.
Application Areas and Media
Oil and Natural Gas: Thick-walled pipes commonly use X-type or U-type beveling; drill pipes and casings use high-performance special threads.
Hydraulic Systems: Internal chamfering is required to ensure seal safety and system cleanliness.
Food and Pharmaceutical Industries: Port polishing is required.
Construction Scaffolding: Usually only simple port flatness and deburring are needed.
Steel Pipe Specifications
Wall Thickness: Determines the type of beveling (I-type, V-type, X-type).
Material: Affects processing difficulty and process selection (e.g., high-hardness steel pipes require more wear-resistant tools).
Cost and Efficiency
Manual beveling machines are inexpensive but slow, suitable for small batches and maintenance applications.
Fully automatic CNC beveling production lines are highly efficient and suitable for large-scale production.
