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The spiral steel pipe feeds the strip steel into the welded pipe unit. After rolling by multiple rollers, the strip steel is gradually rolled up to form a round tube blank with an open gap. The reduction of the squeeze roller is adjusted to control the weld gap at 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 weld will have poor intercrystalline joints, resulting in non-fusion or cracking.
2. If the gap is too small, the proximity effect will increase, and the welding heat will be too large, causing the weld to burn; or the weld will form a deep pit after being extruded and rolled, which will affect the surface quality of the weld.
After heating the two edges of the tube blank to the welding temperature, under the squeezing of the squeeze roller, a common metal crystal grain is formed to infiltrate and crystallize each other, and finally, a firm weld is formed. If the extrusion force of the spiral steel pipe is too small, the number of common crystals formed will be small, and the weld metal strength will decrease, and cracks will occur after the force is applied; if the extrusion force is too large, the molten metal will be squeezed out of the weld. 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 weld overlap.
Main technological characteristics of spiral steel pipe:
A. During the forming process, the steel plate deforms uniformly, the residual stress is small, and the surface does not produce scratches. The processed spiral steel pipe has greater flexibility in the size and specification range of diameter and wall thickness, especially in the production of high-grade steel-grade thick-walled pipes, especially small and medium-diameter thick-walled pipes. It has advantages that other processes cannot match, and can satisfy users. More requirements on spiral steel pipe specifications.
B. Adopting advanced double-sided submerged arc welding technology, welding can be realized in the best position, and it is not easy to have defects such as wrong edge, welding deviation, and incomplete penetration, and it is easy to control the welding quality.
C. Perform 100% quality inspection on steel pipes, so that the entire process of steel pipe production is under effective inspection and monitoring, effectively ensuring product quality.
D. All equipment of the entire production line has the function of networking with the computer data acquisition system to realize the instant data transmission, and the central control room will control the technical parameters in the production process.