The Φ600 mm cast bloom of 4130X steel ( /% ：0. 31C

0. 26Si

0. 80Mn

0. 008P

0. 003S

0. 99Cr

0. 21Mo

0.005Ti

0.023Al) is produced by the technological route of umolten iron→vanadium extraction converter→pretreatment desulfurization→70 t converter→LF→VD→Ground bloom continuous casting→slow cooling". By control [ P

]

≤ 0. 140%

[ S

]

≤0.070% in hot metal; KR pretreatment after vanadium extraction in converter

KR stirring speed 80 r/min for 15 min

and KR end [ S

]

w0. 005% ; converter end point 0. 06% ~0. 10% C

end point [ P

]

≤0.008%

tapping steel temperature m 1 620 ℃

and using slide plate slag blocking technology; LF using high Al refining slag system

with the initial slag 40% ～45%( CaO )

10% ～15%( SiO

2

)

the final slag 35% ～40%( Al

2

O

3

)

50% ～55%( CaO )

5% ~15%( SiO

2

)；VD Ca treated to control 0. 000 5% ~ 0. 001 0% [ Ca

]

the vacuum degree less than 67 Pa for ≥18 min

and the soft blowing time ≥20 min; in the process of continuous casting

using the mould ( 200 A/2. 0 Hz ) + solidification end electromagnetic stirring ( 900 A/6. 0 Hz ) combined stirring mode

the superheat 20 ～30 °C

the constant drawing speed 0. 21 m/min

and the secondary cooling specific water volume 0. 08 L/kg

the Φ600 mm casting bloom of 4310X steel for large volume seamless gas cylinder is successfully developed with class A and class D inclusions in steel ≤1. 0 grade

class B and class C inclusions 0

class Ds ≤l. 5 grade

and all the indicators to meet the requirements of users.