1984 Volume 70 Issue 1 Pages 89-95
The plate mill on-line accelerated cooling (OLAC) process is a controlled cooling process characterized by interrupted accelerated cooling in the transformation temperature range after hot-rolling, and subsequent air cooling to room temperature. To optimize production conditions, the effects of rolling conditions, cooling conditions and chemical composition on the mechanical properties of the controlled cooled plates were studied in comparison with controlled rolled (CR) plates. The controlled cooling process could increase strength withont sacrificing toughness, resulting in improved weldability because of decrease in carbon and alloying elements. The beneficial effect was attributed to the fine ferrite and finely dispersed bainite microstructure. The toughness and strength of the controlled cooled plates were determined by the CR conditions before cooling, and the subsequent cooling conditions, respectively. The optimum cooling conditions were as follows : the initial cooling temperature above Ar3, the final cooling temperature ranging from 500 to 600°C, and the cooling rate from 3 to 15°C/s. The controlled cooled plates produced under the optimum conditions had good mechanical properties, equal or superior to those of the CR plates finish-rolled in the (γ+ α) regions, even with the remarkably reduced separation. The production results are also described herein.
