The effect of cleanliness and rolling process of two heats of 20R steel-0. 15C

0.008P

0.008S

0.06Mo and 0. 18C

0.009P

0.004S

0.01Mo on low temperature impact energy of steel has been rescarched by 200 kg vacuum induction furnace and 500 mm mill in laboratory.Results showed that the low temperature impact toughness of steel was obviously improved by decreasing S content and inclusion; with steel1180 ℃ heating

1020 ℃ beginning rolling and 800 ℃ finishing rolling

the longitudinal

cross impact energy at -40℃ of0.008% S steel by hot rolled air cooling and hot rolled + 880 ℃ normalizing were respectively  14.7J

10J and 13J

9J

and inclusion rating in steel was A- 1.5 and B- 1.5; the longitudinal

cross impact energy at -40℃ of 0.004% S steel by hot rolled air cooling were 180J

98 J

and inclusion rating in steel was D-0.5;The longitudinal and cross impact energy at -40℃ of0.004% S steel by hot rolled and control cooling(water cooling)increased respectively to 210 J and 146 J with improved bending structure.