Spiral steel pipe is a kind of spiral steel pipe, which is made of strip coil as raw material and is often extruded at high temperature. It is welded by automatic double-wire submerged arc welding process.
(1) Raw materials are strip coil, welding wire and flux. Strict physical and chemical tests are required before investment.
(2) Submerged arc welding with single or double wires is used for butt joint of strip head and tail, and automatic submerged arc welding is used for repair welding after coiling into steel pipe.
(3) Before forming, the strip is leveled, trimmed and planed, and the surface is cleaned, conveyed and bent.
(4) Using electric contact pressure gauge to control the pressure of the cylinder on both sides of the conveyor to ensure the smooth conveying of strip steel.
(5) Externally or internally controlled roll forming.
(6) Weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, offset and weld gap are strictly controlled.
(7) Both internal welding and external welding are performed by single-wire or double-wire submerged arc welding with Lincoln Welding Machine, USA, so as to obtain stable welding specifications. (8) The welds after welding are inspected by on-line continuous ultrasonic automatic damage instrument, which ensures 100% non-destructive detection coverage of spiral welds. If there are defects, alarm automatically and spray marking, production workers can adjust the process parameters at any time to eliminate defects in time. (9) Air plasma cutting machine is used to cut the steel pipe into single pieces.
(10) After cutting into a single steel pipe, each batch of steel pipes must undergo a strict first inspection system to check the mechanical properties of welds, chemical composition, dissolution status, surface quality of steel pipes and non-destructive testing to ensure that the pipe-making process is qualified before being put into production. (11) Where there is a continuous acoustic flaw detection mark on the weld seam, after manual ultrasonic and X-ray inspection, if there is a defect, after repair, the defect is subjected to non-destructive inspection again until it is confirmed that the defect has been eliminated.
(12) The tube where the butt weld of strip steel and the T-joint intersect with the spiral weld are all inspected by X-ray television or photography. (13) After hydrostatic test, the pressure of each steel pipe is sealed radially. The test pressure and time are strictly controlled by the micro-computer detection device of steel pipe hydraulic pressure. The test parameters are printed and recorded automatically.
(14) The end of the pipe is machined so that the verticality, groove angle and blunt edge of the end face can be accurately controlled.