The hot-strip mill generally doesn't produce enough roll marks or other surface defects to justify such a system's expense. It can detect microscopic flaws in the surface of hot-dip galvanized sheet and mark them automatically. It also can be used for electroplated and cold-rolled sheet. The NKK system has three cameras and can detect the smallest defects in the surface with almost 100-percent accuracy, the company says. This enables sheet to be rolled into larger coils, reducing handling at automakers and other manufacturing plants.
Workers usually check sheet used for auto bodies after stamping.
But because this system detects flaws ahead of time, it reduces the amount of inspection work, the steelmaker says. Toyota and other automakers are studying the system. The first unit in commercial operation is at NKK's Fukuyama Works in Japan. NKK has applied for 50 patents regarding the new system. Detecting a flaw is just the first step in a process.