ERW steel pipe (straight seam electric resistance welded pipe) is a longitudinal welded steel pipe manufactured by high-frequency resistance welding process. Its core characteristics and applications are as follows:
Definition and process principle
Manufacturing process
The hot-rolled coil is used as the raw material. The edge of the tube is heated to a molten state through the skin effect and proximity effect generated by high-frequency current (usually ≥70kHz), and then pressurized and welded by extrusion rollers.
After welding, heat treatment can be performed to eliminate stress, achieve physical seamlessness of the weld, and improve mechanical properties.
Technical classification
According to the current type: divided into AC welding (including low frequency/medium frequency/high frequency) and DC welding, high-frequency welding (contact welding/induction welding) is suitable for thin-walled or conventional wall thickness pipes.
High-frequency resistance welding (HFW) is an advanced subclass of ERW, with a welding frequency of ≥70kHz, used in high-demand fields.
Applications
Energy transmission system
Oil and gas pipelines: oil/natural gas transmission branch lines (applicable pressure ≤25MPa), replacing some seamless pipe scenarios; Heat network: building HVAC, boiler supporting pipelines (long-term temperature resistance ≤350℃).
Industrial and building structures
Power casing, chemical equipment bracket (cathodic protection design life 50 years);
Roof trusses of large venues, bridge support structures (rectangular cross-section specifications up to 1200×1200mm).
Mechanical manufacturing
Engineering machinery hydraulic oil pipe (surface galvanized salt spray resistance >3000 hours);
Automobile chassis structural parts (lightweight design weight reduction 15%–20%).
Technical limitations
Corrosive environment: Strong acidic media (such as pH <2) need to add 3PE anti-corrosion layer; High-pressure scenario: Ultra-high pressure transmission (>25MPa) still requires seamless pipes; Special media: Wet acidic natural gas requires special anti-corrosion treatment
