ERW steel pipe and spiral submerged arc welded pipe is able to better meet the oil, natural gas pipeline.
Characteristics of ERW Pipe
(1) ERW steel pipe welding mechanism made gratifying achievements, and to the theory as a guide for the optimization of the welding process, all optimized parameters, the computer control, to mention Song of weld quality.
(2) weld annealing using fluorescence line positioning technology, so that annealing strictly specified site, so that weld quality further improved.
(3) early ERW pipe weld zone the ductile-brittle turn temperature FATT value is much higher than the base metal, the maximum difference of 40-50 degrees. Metallurgical and technological progress, the FATT the value of the pipe base metal can be as low as about -70-80 degrees, so even if the two have some difference, able to meet user requirements.
(4) the application of the technology of automated ultrasonic testing, ultrasonic automatic tracking online detection can be achieved, so that the weld formed to further reduce the probability of missing hidden due to undetected.
ERW steel tube and spiral welded pipe characteristics
ERW steel tube and spiral submerged arc welded pipe in the process of tube forming, welding and process the two kinds of steel pipe and there are some differences in performance.
(1) ERW steel pipe surface quality is superior to spiral submerged arc welded pipe, ERW steel pipe surface is smooth, smooth, beautiful, spiral submerged arc welded pipe inside and outside weld reinforcement.
(2) ERW steel pipe welds than the spiral submerged arc welded pipe is short, as long as the length of ERW steel pipe welds and steel, spiral submerged arc welded pipe weld length 1.4-1.7 times that of steel pipe length. Weld the longer, the higher the chance of weld defects.
(3) The standard requirements are basically the same geometric dimensions, but in-kind, ERW steel pipe sizing, straightening process, therefore, the geometric dimensions higher than the accuracy of spiral submerged arc welded pipe.
(4) ERW steel pipe weld defect types spiral submerged arc welded pipe. The dissolved deposition welding of spiral submerged arc welded pipe, the type of defect is more, in addition to volume defects, as well as wire line trap. ERW pipe weld line only line defects and weld flat, easy to track the inspection process, and defects at the maximum reflection, once missing hidden, ultrasound reflects the strong, easy to detect.
(5)ERW steel pipe residual stress is lower than the spiral submerged arc welded pipe. ERW pipe deformation in the deformation process more fully, coupled with subsequent sizing flat ellipsoid, vertical ellipsoid change and reducing the residual stress of ERW pipe smaller. The physical test showed that the same specifications, the same material, ERW steel pipe cut along the axis of the axial and transverse incision after displacement than the spiral submerged arc welded pipe is small.
(6) ERW steel pipes and the overall performance of the same, when the steel tube defects, pipe sentenced to waste, Allow welding. Spiral submerged arc welded pipe allows welding, welding performance and pipe the overall performance is inconsistent, the the patching Department prone to stress corrosion cracking. Experimental results show that the ERW pipe stress corrosion fatigue experiment life than the spiral submerged arc welded pipe.
(7) ERW steel pipe coating quality than the spiral submerged arc welded pipe. Investment ERW production units, processes, and relatively high cost of processing steel pipe. ERW pipe welding, does not allow the head tube, the relative timber low. Therefore, the direct of ERW steel pipe prices than the spiral submerged arc welded steel pipe is about 300 yuan / T Does not increase the overall cost of the pipeline construction scoreboard. First, ERW pipe of good quality and long life; ERW pipe surface quality, coating evenly, saving a large number of coating materials, pipe coating and low cost; high geometric dimensional accuracy of ERW pipe butt welding speed, on-site construction high efficiency, low spin-staff costs.