The L450M pipeline steel (/% ：0. 06C

1.52Mn

0. 19Si

0. 017Ti

0.048Nb

0. 028Als) has obtained good strength and toughness by control of compression ratio

reduction ratio and rolling temperature. The results reveal that the high reduction rate of more than 20% in the last three passes of 200 mm slab rough rolling and the first three passes of finish rolling can make the 12 mm steel plate to form fine micron grain during the subsequent cooling process. The grain size is basically below 10μm

and some grains can be refined to below 2 μm. The yield strength of pipeline steel can reach above 500 MPa and the transverse impact energy at -15 ℃ can reach over 300 J by the compression ratio of finishing rolling 3.5

finishing rolling starting temperature at 930 ~ 950 ℃ and finishing temperature at 810 ~ 830 ℃. The yield ratio of steel can be effectively reduced by increasing rough rolling temperature to ≥1 040 ℃

reducing compression ratio to ≤ 3.8 and increasing finish rolling temperature to ≥800℃ etc.