The ultrasonic testing is usually used for inspection of internal defects of steel billets and bars. The former has advantage of reduction of materials for inspection, and disadvantage of difficulties of inspection for bend, twist, bur and hair crack of material. In the latter case it is inverse, so we inspect billets for detection of serious defects (ex. primary pipe) and bars for detection of minute defects (ex. secondary pipe, nonmetallic inclusion, hair crack). This is the reason why we need the automatic ultrasonic inspection system of immersion method. The system is composed of two lines and dual-scanning for one line.
The inspection rate is 480 pieces/hour at the scanning speed of 30m/min for hot rolled round bars of 34∼75mm diameter. In practical operation, the defect over F 30% at the gain of STB V15-1.4F 80% and over 8mm to 50mm in length can be detected at the reliability of over 90% and error marking for noise is less than 2% without descaling.
Now, with double inspecting methed for billets and bars our products are guaranteed to over 99.99% for harmful internal defects.