In general, the straightness of the edge of the coil head and coil end is easily exceeded, and defects and defects such as heavy skin, folding, scab, crushing, scratching, etc. are prone to occur, and thus the appearance and geometry after cutting into a steel plate are opened and flattened. 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.
After edge milling and forming, in the pre-welding and internal and external welding, strengthening the weld and weld edge inspection is also the best way to eliminate edge defects. When the steel tube welds are subjected to X-ray industrial television or X-ray film inspection, the inspection of the 20-50mm base material on both edges of the weld is strengthened. When the steel tube weld is subjected to automatic UT inspection, the weld edge marginal base material layered flaw detection inspection can be performed. To ensure the quality of the weld seam of the steel pipe. Strengthen the appearance inspection of steel pipes and timely handle the defects found.
The production of lsaw steel pipe by coil plate is faced with low plate rate after Kaiping. The performance of steel pipe at the head, middle and tail is different. The coil plate has no defects after slitting, and the UT stratification cannot be performed at the rolling mill. The Bauschinger effect has unknown changes and other issues. Through the tensile test and fracture toughness test of the coil head, the coil and the coiled end plate and its steel tube, the performance of the steel plate and the steel pipe in the coil is relatively weak. Therefore, it is recommended to measure the performance of the steel pipe that is rolled into the middle position, which is the most representative of the performance of this pipe and the furnace than the steel pipe.
In order to improve the coverage of stratified flaw detection on the steel plate, the straight-line walking of the group probe is changed to a slow-moving reciprocating swing scan, which can increase the scanning area to more than 40% and ensure the intrinsic quality of the online steel plate. The coil is made of JCOE steel pipe. The yield strength of the steel pipe is about 30 MPa higher than the average of the steel plate, and the yield ratio is increased by about 0.02 on average. This shows that the SAG steel pipe produced by adopting the JCOE process for this size coil has a smaller SHENGGE effect. , far less than the deformation during the molding process to strengthen, mainly to strengthen the material deformation.
The steel plate made of UOE process is used for the coiled plate. The horizontal baggage effect of the steel pipe parent metal is obvious, with an average of 24 MPa. The longitudinal baggage application effect of the steel pipe parent metal is not obvious. The main performance is that the longitudinal yield strength is 36 MPa higher than the steel plate on average. It is also caused by deformation of the material.