Welded steel pipe refers strip or plate bending round
Welded steel pipe refers strip or plate bending round, square and other shapes and then welded into the surface jointed pipe. Welded steel pipes used in billet steel sheet or strip.
By welding methods classification

Can be divided into spiral welded steel pipe, welded steel pipe, stove pipe.
Spiral welded steel pipe: according to different welding methods can be divided arc welded pipe, high-frequency or low frequency electric resistance welded pipe, gas pipe, stove pipe, Bundy tubes.
Welded steel pipe: for oil drilling and machinery manufacturing.
hydrostatic test should be done each pipe hydrostatic test without leakage, pressure test press Calculate P = 2ST / D where S- hydrostatic test stress test Mpa, hydrostatic test stress test according to the corresponding steel with standard of minimum specified yield (Q235 is 235Mpa) 60% of the selection. Regulators time: D <508 test pressure holding time less than 5 seconds; D≥508 test pressure holding time less than 10 seconds 4 NDT pipe welding seam, strip end weld and circumferential joints should be X-ray or ultrasonic inspection. For ordinary combustible fluid transport spiral steel to weld should be 100% SX-ray or ultrasound test, used for water, sewage, air, heating steam and other general transmission fluid with spiral weld steel pipe should be X-rays or ultrasonic inspection checks (20%).
defect treatment
1. Available defective wheel rubbed off, but the remaining wall thickness must be within an allowable range
2. A minimum length of welding seam 50mm; shall not exceed 1.5mm base metal to be welded after grinding
3. Within the allowable length of the defective tube resection
4. As unqualified