| 摘要 |
<p>A hot rolled steel sheet and a high strength pipe having superior continuous furnace normalizing characteristics and a method of manufacturing the same are provided to reduce precipitates, to contribute to generation of bainite, and to increase hardenability of the steel plate after heat treatment by adding V, N, Cr, And Nb to a medium carbon steel. A method of manufacturing a hot rolled steel sheet having high frequency normalizing characteristics comprises the steps of: re-heating a slab consisting of, by weight%, C:0.25~0.45%, Si:0.20~0.60%, Mn:1.4~2.2%, P: less than 0.02%, S: less than 0.01%, Ti:0.005~0.03%, Nb: less than 0.005%, Ca:0.001~0.006%, Al:0.01~0.06%, N: less than 0.008%, O: less than 0.006%, V:0.15~0.25%, Cr:0.30~0.50%, and the remainder Fe, and other unavoidable impurities; finishing-mill the slab at 800~900°C; and cooling the rolled steel sheet up to 550~700°C at 10~20°C/sec and then coiling the steel sheet. The structure of the steel sheet contains 30~50% of bainite, and the remainder ferrite, and pearlite.</p> |
