Abstract: The effects of water temperature(15~35℃) and roll speed(1.0~3.0m/min) on the thickness cooling rate of jet impingement quenching for ultra heavy steel plate are experimentally investigated. The temperature decrease，temperature gradient and the factors of cooling rate along thickness direction in difference sections of the plate are analyzed. Using the inverse heat conduction method to solve the differential equation of heat conduction， the quenching temperature field and cooling rate of the plate can be calculated. The results indicate that the cooling rate of the 160mm steel core is greater than 1.2℃/s under the jet impingement quenching， and water temperature and roll speed affect not only the average heat transfer coefficient and the type of heat transfer near the plate surface， but also the thickness cooling rate by changing temperature gradient distribution. The thickness cooling rate decreases when water temperature and roll speed increase， and the decreasing range of cooling rate depends on cooling intensity， quenching time and thermal conductivity of the plate.

Key words: ultra heavy plate, roller quenching, thickness cooling rate, temperature gradient, jet heat transfer