The Φ 110 〜260 mm products of steel AISI4145HM (/% : 0.44 -0.46C

0. 21 〜0. 23Si

1. 32 ~ 1.33Mn

1. 18-1.20Cr

0. 30 ~0. 31 Mo

0.16 ~0.17Ni

≤ 0.012P

≤ 0.004S

≤ 0.05Cu

0. 15 ~0. 35Als) is produced by hot-metal + scrap- 100 t EAF-LF-VD-0500

600 mm round bloom casting-walking beam reheating furnace- 950mm rolling mill- slow cooling- annealing flowsheet

in the special steel division new district of Laiwu steel. With the process measures including controlling EAF end [C

]

≥0.15% and [P

]

≤0.008%

pre-deoxidation and alloying in tapping

using LF high aluminium refining slag (30% ~40% Al

2

O

3

) and feeding 0. 45 kg/t calcium wire

gradient soft blowin

g after VD

controlling overheating extent of liquid in tundish 12 - 25℃ ，casting speed 0. 25 〜0. 35 m/min

whole course shielding casting

using M-EMS and F-EMS

slow cooling after rolling and annealing

the macro structure of produced casting bloom is better with center porosity and center line shrinkage ≤ rating 1.0

crack and subskin blowhole rating 0

each inclusion rating ≤ 1. 5

total inclusions rating ≤ 7. 0

the each index of steel products all meets the requirement of specification.