Abstract
Laboratory tests were conducted in order to quantify the cooling performance of intensive inter-pass water cooling, which was introduced as an effective method for increasing productivity in the manufacture of high strength steel plates.
The range of flow rates was extended to 0.17-0.39 m3/m2 s. Pipe nozzles with inner diameters of 3 mm or 6 mm were used in addition to the original hole-type nozzle. The influences on cooling performance on the type of nozzle, nozzle pitch and injection distance were investigated. In the water cooling tests with the φ6 pipe nozzles, temperature drop in the specimens increased with higher water flow rates. The upper limit of cooling performance was found to be around 0.25 m3/m2 s in upper side cooling, whereas an upper limit was not seen in lower side cooling. In tests with the φ3 hole nozzles, temperature drop decreased with longer injection distance, and that tendency is larger in lower side cooling. A nozzle arrangement with a shorter installation pitch results in higher cooling performance. The influence of the inner diameter of the pipe nozzles on cooling performance is small.
After water cooling, controlled rolling of specimens of Si-Mn steel, which is used widely as high tensile steel, was performed with a laboratory mill. As a result, it was found that total rolling time can be reduced with inter-pass water cooling, and water cooling does not affect the microstructure nor mechanical properties.
Intensive inter-pass cooling, which has high cooling performance, has the potential to realize efficient production of high strength steel plates in controlled rolling.