US 11,732,337 B2 · Method for producing high nitrogen steel by duplex melting process of pressurized ladle refining and pressurized electroslag remelting

Abstract

The present disclosure provides a method for producing a high nitrogen steel by a duplex melting process of a pressurized ladle refining and a pressurized electroslag remelting, which relates to the technical field of high nitrogen steel melting. In the present disclosure, the molten steel is subjected in sequence to a nitrogen alloying, a deep deoxidation and a deep desulfurization by adding a nickel-magnesium alloy and rare earth in the pressurized ladle furnace, and a combination of a blowing nitrogen from the bottom of the pressurized ladle and a pressurized nitriding at the interface of gas and the molten steel is used to achieve a high-efficiency nitrogen alloying, a uniform nitrogen distribution, and a decreased impurity content in the ingot; then the ingot is subjected to a pressurized electroslag remelting to obtain a high nitrogen steel.

A method for producing a high nitrogen steel by a duplex melting process of pressurized ladle refining and a pressurized electroslag remelting, comprising the following steps:

(1) subjecting a molten steel to a nitrogen alloying in a pressurized ladle furnace to obtain a nitrogen-alloyed molten steel,
then subjecting the nitrogen-alloyed molten steel to a deep deoxidation to obtain a deeply deoxidized product,
subjecting the deeply deoxidized product to a deep desulfurization to obtain a deeply desulfurized product, and
finally casting the deeply desulfurized product, to obtain a high nitrogen steel ingot,
wherein the nitrogen alloying comprises blowing nitrogen from the bottom of the pressurized ladle and nitriding at the interface of gas and the molten steel under pressure;
and the deep deoxidation and deep desulfurization are achieved by adding a nickel-magnesium alloy and rare earth to the nitrogen-alloyed molten steel;
and
(2) subjecting the high nitrogen steel ingot obtained in step (1) to a pressurized electroslag remelting, to obtain a high nitrogen steel electroslag remelting ingot;
wherein a gas nitriding pressure p1 during the nitriding at the interface of gas and the molten steel in step (1) is calculated according to Formula I:
1
⁢
g
⁡
[
%
⁢
⁢
N
]
=
1
2
⁢
1
⁢
g
⁡
(
p
1
⁢
/
⁢
p
θ
)
-
188
T
-
1.17
-
{
(
3280
T
-
0.75
)
⁢
(
0.13
⁡
[
%
⁢
⁢
N
]
+
0.118
⁡
[
%
⁢
⁢
C
]
+
0.043
⁡
[
%
⁢
⁢
Si
]
+
0.011
⁡
[
%
⁢
⁢
Ni
]
+
3.5
×
10
-
5
⁡
[
%
⁢
⁢
Ni
]
2
-
0.024
⁡
[
%
⁢
⁢
Mn
]
+
3.2
×
10
-
5
⁡
[
%
⁢
⁢
Mn
]
2
-
0.01
⁡
[
%
⁢
⁢
Mo
]
+
7.9
×
10
-
5
⁡
[
%
⁢
⁢
Mo
]
2
-
0.048
⁡
[
%
⁢
⁢
Cr
]
+
3.5
×
10
-
4
⁡
[
%
⁢
⁢
Cr
]
2
)
-
0.098
⁡
[
%
⁢
⁢
V
]
+
0.061
⁢
⁢
g
⁢
p
1
⁢
/
⁢
p
θ
}
,
Formula
⁢
⁢
I
in which p1 represents the gas nitriding pressure in MPa;
pθ represents a standard atmospheric pressure, which is 0.101325 MPa;
and T represents a melting temperature in K;
wherein a bottom blowing pressure p2 during blowing nitrogen from the bottom of the pressurized ladle in step (1) is calculated according to Formula II:
p2=1.1(p1+ρsteelgh+ploss) Formula II,
in which p2 represents the bottom blowing pressure in MPa;
p1 represents the gas nitriding pressure in MPa;
ρsteel represents a density of the molten steel in kg/m3;
g represents gravitational acceleration, which is 9.8 m/s2;
h represents a depth of the molten steel in the ladle, in m;
and ploss represents a pressure loss in pipelines and permeable bricks, which is in a range of 0.30 MPa to 0.50 MPa;
wherein the high nitrogen steel is a high nitrogen stainless steel, and the high nitrogen stainless steel is a high nitrogen austenitic stainless steel or a high nitrogen martensitic stainless steel;
under the condition that the high nitrogen steel is the high nitrogen austenitic stainless steel, a casting pressure p3 in step (1) is calculated according to Formula III:
p3=[(0.30 to 0.40)p1/pθ+(0.50 to 0.60)] Formula III,
in which p3 represents the casting pressure in MPa;
pθ represents the standard atmospheric pressure in MPa;
and
a remelting pressure p4 for the pressurized electroslag remelting in step (2) is calculated according to Formula IV:
p4=[p3+(0.30 to 0.40)] Formula IV,
in which p4 represents the remelting pressure in MPa;
and
under the condition that the high nitrogen steel is the high nitrogen martensitic stainless steel, a casting pressure p5 in step (1) is calculated according to Formula V:
p5=[(0.15 to 0.20)p1/pθ+(0.45 to 0.60)] Formula V;
in which p5 represents the casting pressure in MPa;
pθ represents the standard atmospheric pressure in MPa;
and
a remelting pressure p6 for the pressurized electroslag remelting in step (2) is calculated according to Formula VI:
p6=[p5+(0.30 to 0.40)] Formula VI,
in which p6 represents the remelting pressure in MPa.

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Method for producing high nitrogen steel by duplex melting process of pressurized ladle refining and pressurized electroslag remelting

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Method for producing high nitrogen steel by duplex melting process of pressurized ladle refining and pressurized electroslag remelting

Life of this patent

Abstract

Claims5