Method and apparatus for detecting flaws in strip, method of manufacturing cold-rolled steel sheet and pickling equipment for hot-rolled steel strip

An apparatus for continuously testing for defects in a continuously carried strip, comprising:

• a liquid;
• at least one carrying roll through which the strip is introduced to pass the strip through the liquid such that the strip is fully immersed in the liquid;
• an ultrasonic testing apparatus that tests a portion of the strip that is fully immersed in the liquid;
• and
• a device that inhibits the formation of air bubbles in the liquid during carrying of the strip through the liquid by preventing liquid that adheres to the strip and that is carried from the liquid to above the liquid surface from dropping back onto the liquid surface.

An apparatus for continuously testing for defects in a continuously carried strip, comprising:

• a liquid;
• at least one carrying roll through which the strip is introduced to cause the strip to pass through the liquid such that the strip is fully immersed in the liquid;
• an ultrasonic testing apparatus that tests a portion of the strip that is fully immersed in the liquid;
• wherein each of the at least one carrying roll that is in contact with the liquid is fully immersed in the liquid;
• and
• a device that prevents the liquid that adheres to the strip and that is carried from the liquid to above the liquid surface from dropping back onto the liquid surface.

An apparatus for continuously testing for defects in a continuously carried strip, comprising:

• a liquid;
• at least one carrying roll through which the strip is introduced to cause the strip to pass through the liquid such that the strip is fully immersed in the liquid;
• an ultrasonic testing apparatus for testing a portion of the strip that is fully immersed in the liquid;
• wherein each of the at least one carrying roll that is in contact with the liquid is fully immersed in the liquid;
• a device that catches the liquid that drops from a portion of the strip located above the liquid surface to prevent the liquid from dropping back onto the liquid surface;
• and
• a device disposed near the liquid surface that removes the liquid that adheres to the portion of the strip that has moved from the liquid to above the liquid surface.

A method of detecting defects in a strip, comprising;

• continuously testing a strip by use of ultrasound as the strip is carried continuously through a liquid in which the strip is fully immersed, the ultrasonic testing comprising:
• arranging a transmitting probe and a receiving probe face to face in the thickness direction of the strip with the strip between the transmitting probe and receiving probe;
• transmitting a line-focused ultrasonic beam with the transmitting probe;
• and
• receiving an ultrasound reflected at an internal flaw in the strip with the receiving probe, thereby detecting the internal flaw in the strip;
• and
• inhibiting the formation of air bubbles in the liquid during carrying of the strip through the liquid.