It is used for welding with double-sided submerged arc welding and is mainly used for spiral seam welded steel pipe devices for pressure fluid transportation. The ability of the steel pipe to withstand pressure is strong and the welding performance is also very good. After a variety of rigorous scientific inspections and tests, the use situation is relatively safe and reliable. The solid diameter of the steel pipe is large, the transmission efficiency is also high, and it can effectively save the investment of laying pipelines. It is mainly used for pipelines that transport oil and natural gas.2.General low-pressure fluid transport is mainly hot-rolled steel coiled tube blanks, often temperature spiral molding, using high-frequency lap welding Color Coated Steel Sheets method for general low-pressure fluid conveying spiral seam high-frequency welded steel pipe.
Welding steel with spiral welds.3. the hot rolled steel strip is used as the tube blank, which is often formed by spiral molding and is made of double-sided submerged arc welding or high-frequency welded steel pipe. It is used for the foundation pile steel pipe for civil building structures, wharves, and bridges.4.the general low-pressure fluid transport is hot rolled steel strip coiled tube, regular temperature spiral molding, using double-sided automatic submerged arc welding or single-sided welding method for water, gas, air and steam and other general low-pressure fluid transport Submerged arc welded steel pipe. The5.the pressure fluid transport is based on the hot-rolled steel strip for tube blanks, regular temperature spiral molding, high-frequency lap welding method used for pressure fluid transmission spiral seam high-frequency welding steel pipe device.
The qualification rate of the steel plate that meets the technical requirements is relatively low. According to the weight of the coil and the actual length of the measured coil unit length, the length of the rolled steel coil is calculated, and the qualified steel plate with the full cutting length and the number of sheets is determined; Head and tail end defects, real-time shearing and take-up boards that are severely excessive in straightness, and shearing; for heads and reels that have large straightness exceeding the standard, the amount of milling is increased. Since the coils have not been slit, the edges of the coils are prone to rolling defects and deficiencies such as heavy skins, folding, scabs, crushing, scratches, etc., and manual inspections have been intensified for the first time on the steel plate. In addition, since steel billets are hot-rolled into steel plates in steel mills and then coiled into steel coils, the coiling temperature is 500-600 degrees Celsius. Therefore, UT stratification cannot be performed at the steel works, and coil quality cannot be guaranteed.
Therefore, the technical conditions for steel pipes require that “all steel plates must be 100% layered and 100% scanned”. Domestic steel pipe mills are equipped with ultrasonic stratified flaw detection procedures on the feeding production line, so online stratified flaw detection can be realized, but the scanning area is different, and the general scanning area can reach more than 25%. In order to improve the scanning coverage rate, the linear movement of the group probe is changed to a slow-speed reciprocating swing scan, which can increase the scanning area to more than 40% to ensure the intrinsic quality of the online steel plate.