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How to distinguish between spiral steel pipe and straight seam steel pipe?

Jan. 02, 2020

Spiral steel pipe is produced from hot rolled coil, and LSAW pipe is produced from steel plate. The rolling process of the hot-rolled strip mill has a series of advantages, and it has the metallurgical process ability to produce high-quality pipeline steel. For example, a water cooling system is installed on the output rack to accelerate cooling, which allows the use of low alloy components to achieve special strength levels and low temperature toughness, thereby improving the weldability of the steel. However, this system is basically absent in special design steel pipe factorys. The alloy content (carbon equivalent) of coils is often lower than that of similar grades of steel, which also improves the weldability of spiral steel pipes. There is no corresponding production standard for straight seam welded pipes.

Generally, the spiral steel pipe unit adopts an online continuous inspection method to ensure the welding quality of the weld. This is another important feature of the production of spiral welded pipes different from the production of straight seam welded pipes. Continuous inspection is conducive to the monitoring of welding defects, the stability of welding quality, and the guarantee of welding level.

In terms of welding process, the welding method of spiral steel pipe and straight seam steel pipe is the same, but there are inevitably many T-shaped seams in straight seam steel pipes, so the probability of welding defects is also greatly improved, and the welding residue at T-shaped seams The stress is large, and the weld metal is often in a three-way stress state, which increases the possibility of cracks.

The quality of the spiral steel pipe can be judged based on the external dimensions and the length and appearance of the spiral steel pipe. When the sprial steel pipe is blasted, because the normal stress and the combined stress of the weld are relatively small, the blast mouth generally does not originate at the spiral weld, and its safety is higher than that of the straight welded pipe. When there is a defect parallel to the spiral weld near the spiral weld, the risk of expansion is not as great as that of the straight weld because the spiral weld has less force. Since the radial stress is the maximum stress existing on the steel tube, the maximum load is applied when the weld is in the direction of vertical stress. That is, the straight seam bears the largest load, the hoop weld carries the smallest load, and the spiral seam is somewhere in between. It is easy to judge the material you want to buy from the material and appearance of the spiral steel pipe.

Sprial Steel Pipe

Sprial Steel Pipe

How to increase the stable performance of spiral steel pipes

(1) Small and medium-sized steel, wire rods, rebars, medium-caliber steel pipes, steel wires, and wire ropes can be stored in well-ventilated sheds, but they must be placed on top of each other.

(2) Some small steels, thin steel plates, steel strips, silicon steel sheets, small-caliber or thin-walled seamless carbon steel pipes, various cold-rolled and cold-drawn steels, and expensive and easily corroded metal products can be stored in the warehouse.

(3) The site or warehouse where the spiral steel pipe products are stored should be selected in a clean and well-drained place, away from factories and mines that produce harmful gas or dust. Weeds and all debris should be removed on the site, and the steel should be kept clean.

(4) Large sections, steel rails, steel plates, large-diameter steel pipes, forgings, etc. can be stacked in the open air.

(5) Do not stack in the warehouse with materials that are corrosive to steel such as acid, alkali, salt, and cement. Different types of steel should be stacked separately to prevent confusion and prevent contact corrosion.