Improvement of Billet and Wire Rod Inspection System of POSCO Wire Rod Mill

摘要

In these days, the user's need for surface flaw is getting severe and the importance of surface inspection system is also increasing. Under this trend, many wire-rod making mills have been developing their own surface inspection system and POSCO also making efforts in that area. In this paper, the development cases in the inspection process are introduced. The billet inspection machines work in a very restricted temperature under 50 degrees Celsius. So, billet-cooling system is installed in the billeting mill. The billet surface temperature is 400 degrees celsius at the beginning and the billet is cooled by 90 degrees Celsius in 5 minutes. By using cooling system, the inspection efficiency is increased. The detection capacity of DDU (Defect Detecting Unit of billet surface) was 0.6mm D X 10.0mm L. We change the magnetic particle from dry type to the wetted fluorescence magnetic particle type and the particle size is reduced from 50 mu m to 10 mu m. As result of improvement, the defect of 0.2mmD X 5.0mmL can be detected. The new inspection system using CCD Camera after DDU process is developed to improve the inspection ability and monitor the billet surface quality. The detection results are recognized by the computer and displayed to the workers who are working in grinding room or control room. The all information is saved in the quality data sever and is used as referance of billet surface quality improvememt. New ECT inspection system is developed to chect the hot wire rod surface. At the beginnig, the sensivity and nosise was problem. The interval of exciting coil is reduced to improve sensivity and the detecting coil diameter is enlarged to minimize the heat effect and the sleeve material is exchanged form stainless to titanium to reduce the magnetic field of hot coil. As a result of these kinds of improvements, we canremarkably increse the detectibility and minize the noise effect.