Spiral steel pipe production process
(1) Raw materials include steel strip coil, welding wire, and flux. They must undergo strict physical and chemical inspections before being put into use.
(2) The head and tail of the steel strip are butt-jointed using single-wire or double-wire submerged arc welding. After being rolled into a steel pipe, automatic submerged arc welding is used for repair welding.
(3) Before forming, the strip steel is leveled, trimmed, planed, surface cleaned, transported, and pre-bent.
(4) Electric contact pressure gauges are used to control the pressure of the cylinders on both sides of the conveyor to ensure smooth transportation of the strip.
(5) Adopt external control or internal control roller forming.
(6) A weld gap control device is used to ensure that the weld gap meets the welding requirements. The pipe diameter, offset amount, and weld gap are all strictly controlled.
(7) Both internal and external welding use American Lincoln electric welding machines for single-wire or double-wire submerged arc welding to obtain stable welding quality.
(8) All completed welds have been inspected by an online continuous ultrasonic automatic flaw detector, ensuring 100% non-destructive testing coverage of spiral welds. If there is a defect, it will automatically alarm and spray mark, so that production workers can adjust the process parameters at any time to eliminate defects in time.
(9) Use an air plasma cutting machine to cut the steel pipe into individual pieces.
(10) After cutting into individual steel pipes, each batch of steel pipes must undergo a strict first inspection system to check the mechanical properties, chemical composition, fusion status of the welds, the surface quality of the steel pipes, and non-destructive testing to ensure that the pipe making process is qualified. Only then can it be officially put into production.
(11) The areas with continuous sonic flaw detection marks on the welds will undergo manual ultrasonic and X-ray re-examination. If there are indeed defects, they will be repaired and then undergo non-destructive inspection again until it is confirmed that the defects have been eliminated.
(12) The pipes where the strip butt welds and the T-shaped joints intersecting the spiral welds are located must be inspected by X-ray television or film.
(13) Each steel pipe has undergone a hydrostatic pressure test, and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. Test parameters are automatically printed and recorded.
(14) The pipe end is machined to accurately control the end face verticality, bevel angle, and blunt edge.
Welding seam treatment of spiral steel pipe
The spiral steel pipe feeds the strip into the welded pipe unit. After being rolled by multiple rollers, the strip is gradually rolled up to form a circular tube blank with an opening gap. Adjust the reduction amount of the extrusion roller to control the weld gap between 1~ 3mm, and make both ends of the welding joint flush.
1. If the gap is too large, the proximity effect will be reduced, the eddy current heat will be insufficient, and the inter-crystal bonding of the weld will be poor, resulting in a lack of fusion or cracking.
2. If the gap is too small, the proximity effect will increase and the welding heat will be too high, causing the weld to burn out; or the weld will form a deep pit after being extruded and rolled, affecting the surface quality of the weld.
After the two edges of the tube blank are heated to the welding temperature, under the squeeze of the extrusion roller, common metal grains are formed to penetrate and crystallize with each other and finally form a strong weld. If the extrusion force of the spiral steel pipe is too small, the number of common crystals formed will be small, the strength of the weld metal will decrease, and cracking will occur after stress; if the extrusion force is too large, the molten metal will be squeezed out of the weld, It not only reduces the strength of the weld, but also produces a large number of internal and external burrs, and even causes defects such as welding laps.
Process characteristics of spiral steel pipe
a. During the forming process, the steel plate deforms evenly, has small residual stress, and does not produce scratches on the surface. The processed spiral steel pipe has greater flexibility in the size range of diameter and wall thickness, especially in the production of high-grade thick-walled pipes, especially small and medium-diameter thick-walled pipes. It has advantages that other processes cannot match, and can satisfy users’ requirements in terms of spiral steel pipe specifications.
b. Using the advanced double-sided submerged arc welding process, welding can be achieved at the right position, and defects such as wrong edges, welding deviations, and incomplete penetration are less likely to occur, and the welding quality can be easily controlled.
c. Conduct 100% quality inspection on steel pipes so that the entire process of steel pipe production is under effective detection and monitoring, effectively ensuring product quality.
d. All equipment in the entire production line has the function of networking with the computer data collection system to realize real-time transmission of data, and the central control room monitors the technical parameters in the production process.
Post time: Dec-25-2023