CN102277467A - Method for denitrifying molten steel in tapping process of converter - Google Patents

Abstract

The invention relates to a method for denitrifying molten steel in a tapping process of a converter, and the method is characterized by comprising the following steps: in the tapping process of the converter, successively adding carbonate, coke and metallic aluminium into a steel ladle; and decomposing or causing all components to react with oxygen in the molten steel under the dynamics and the thermodynamics action of the molten steel during tapping to generate CO2 or CO bubbles, wherein because [N] in the molten steel easily adsorbs on the surface of the bubbles, [N] is removed along with the upward floating of the CO2 or CO bubbles, and each component is successively added at the mass ratio. The method has the beneficial effects that the boiling state of the molten steel in the steel ladle is controlled by metallic aluminium in the later stage of tapping to accurately judge that the steel ladle is freely clear; ingredients, such as Mn, Cr and the like can be alloyed at any moment before tapping ends as required; lime granules used for modifying steel ladle slag can be added before adding metallic aluminium as required to obviously lower nitrogen content in the molten steel; and after tapping ends, the ratio that the nitrogen content in the molten steel is less than 20ppm can be 100%.

Description

The method of a kind of converter tapping process molten steel denitrogenation

Technical field

The present invention relates to the denitrogenation field of molten steel, relate in particular to the method for a kind of converter tapping process molten steel denitrogenation.

Background technology

At present, the automobile that requires utmost point low-carbon (LC) and low nitrogen with the non orientating silicon steel of IF steel and low nitrogen generally be the molten iron of melting in the blast furnace is smelted into molten steel in converter after, at the RH de-gassing vessel molten steel is carried out secondary treatment, pour into strand by continuous caster then.Whole smelting process mainly relies on the decarburizing reaction in the converter to carry out denitrogenation, can obtain 40 * 10 ^-6Following low nitrogen steel water, though the RH device is in reduced atmosphere, owing to influenced by the restriction of vacuum chamber seal degree and lower molten steel nitrogen content, denitrification reaction can not carry out substantially, therefore after the converter smelting endpoint nitrogen content exceeds standard, can't effectively remove in later process.

In the existing denitride technology, having a kind of is to have invented a kind of a refining unit, by vacuum system, direct current pulse power source, working gas and glow plasma generation systems are formed, rely on the DC pulse electric field above molten steel, to form the glow plasma of argon-hydrogen mixed gas, nitrogen in the molten steel and glow plasma effect, the nitrogen of effusion ionic state also reacts with working gas, thereby form nitrogen and ammonia at last and reach the purpose of denitrogenation by the vacuum system withdrawing device, this technical deficiency part is to transform RH equal vacuum system device, could realize the purpose of denitrogenation.

Summary of the invention

The method that the purpose of this invention is to provide the denitrogenation of a kind of converter tapping process molten steel by in the converter tapping process molten steel being carried out denitrogenation processing, reduces the nitrogen content in the molten steel, improves the quality of products.

For solving the problems of the technologies described above, technical scheme of the present invention is:

The method of a kind of converter tapping process molten steel denitrogenation, successively in ladle, add carbonate, coke and metallic aluminium in the converter tapping process, when utilizing tapping the kinetics of molten steel and thermodynamics effect with its decomposition or impel it with molten steel in oxygen react generation CO ₂Or the CO bubble, because [N] in the molten steel easily is adsorbed on bubble surface, along with CO ₂Or the come-up of CO bubble discharges [N] removed, and its each component is interpolation successively by weight proportion, and its step is as follows:

1) in 0～20% process of total steel amount of tapping, adds carbonate, addition 0.5～15kg/ ton steel;

2) in 15～35% processes of total steel amount of tapping, add coke, its granularity 5～50mm, carbon content is more than 97%, addition 0～5kg/ ton steel;

3) in 65～80% processes of total steel amount of tapping, add metallic aluminium, addition 0～1kg/ ton steel;

Above-mentioned carbonate is CaCO ₃, NaCO ₃, MgCO ₃, CaCO wherein ₃Be purified Wingdale, effective content is greater than 90%; MgCO ₃Be wagnerite, effective content is greater than 90%; Na ₂CO3 is a soda powder, and effective content is greater than 95%, granularity 5～50mm;

Above-mentioned metallic aluminium is taken from aluminium ferromanganese or spherical Al slag, granularity 8～150mm, and wherein aluminium ferromanganese contains Al more than 55%, and spherical Al slag contains Al more than 45%, contains CaO more than 25%.

Compared with prior art, the invention has the beneficial effects as follows: adopt metallic aluminium can control the boiling state of molten steel in the ladle in the tapping later stage, guarantee carrying out smoothly of tapping steel, and judge the free headroom of ladle accurately, if need the alloying of compositions such as manganese chromium, can be before tapping finishes any time carry out, if need to add ladle slag upgrading lime granule, can before adding metallic aluminium, add, the present invention can significantly reduce the nitrogen content in the molten steel, and nitrogen content can reach 100% less than the ratio of 20ppm in the molten steel of tapping end back.

Embodiment

The invention will be further described below in conjunction with embodiment:

Embodiment one

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.029	0.0988	0.0027			185
CaCO3				Add ladle bottom before the tapping	0.80
							Coke				Tapping to 40 ton adding	0.50
The lime granule				Tapping to 120 ton adding	1.80
							Spherical Al slag				Tapping to 150 ton adding	1.10
In the ladle bag	0.021	0.0685	0.0014

Embodiment two

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.034	0.0835	0.0025			183
MgCO3				Tapping to 20 ton adding	0.65
							High carbon ferromanganese				Tapping to 50 ton adding	2.50
Spherical Al slag				Tapping to 150 ton adding	1.50
							In the ladle bag	0.026	0.0640	0.0014

Embodiment three

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.042	0.0786	0.0024			187
Na 2CO3				Tapping to 30 ton adding	0.45
							High carbon ferro-chrome				Tapping to 60 ton adding	1.5
Aluminium ferromanganese				Tapping to 130 ton adding	0.65
							In the ladle bag	0.035	0.0456	0.0013

Embodiment four

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.038	0.0827	0.0025			186
Na 2CO3				Tapping to 20 ton adding	1.0
							Aluminium ferromanganese				Tapping to 140 ton adding	0.55
In the ladle bag	0.032	0.0687	0.0011

Embodiment five

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.024	0.0998	0.0023			185
Ca 2CO3				Add in the ladle before the tapping	15.0
							Mid-carbon fe-mn				The preceding 80 tons of addings of tapping	2.5
Aluminium ferromanganese				Tapping to 140 ton adding	0.65
							In the ladle bag	0.021	0.0464	0.0011

Embodiment six

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.035	0.0856	0.0026			182
Mg 2CO3				Add in the ladle before the tapping	10.0
							The lime granule				Tapping to 100 ton adding	2.80
Spherical Al slag				Tapping to 140 ton adding	1.50
							In the ladle bag	0.033	0.0462	0.0017

Embodiment seven

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.070	0.0430	0.0026			184
Ca 2CO3				Add in the ladle before the tapping	0.50
							High carbon ferromanganese				Tapping to 30 ton adding	10
Coke				Tapping to 30 ton adding	4.2
							Aluminium ferromanganese				Tapping to 140 ton adding	1.10
In the ladle bag	0.726	0.0026	0.0018

Embodiment eight

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.026	0.0936	0.0031			184
Mg 2CO3				Add in the ladle before the tapping	0.80
							Na 2CO3				Tapping to 20 ton adding	0.50
Coke				Tapping to 30 ton adding	0.35
							Spherical Al slag				Tapping to 130 ton adding	0.80
In the ladle bag	0.021	0.0574	0.0015

Do not adopt contrast heat of the present invention

	C，％	O，％	N，％	Adding mode and time	Add-on kilogram/ton steel	Tap, ton
							Converter terminal	0.028	0.0964	0.0023			184
Aluminium ferromanganese				Tapping to 30 ton adding	1.10
							The lime granule				Tapping to 140 ton adding	2.70
In the ladle bag	0.026	0.0732	0.0028

In the foregoing description, CaCO ₃Be purified Wingdale, granularity 5～50mm; MgCO ₃Be wagnerite, granularity 5～50mm; Na ₂CO3 is a soda powder, and effective content is adjusted addition according to steel grade to the requirement of oxygen level in the jar greater than 90%; The coke carbon containing is more than 97%, granularity 5～50mm; Aluminium ferromanganese contains Al more than 55%, and it is more than 45% that spherical Al slag contains Al, and containing CaO is more than 25%.Carbonate and coke can independently use, but also arbitrary combination is used, and carbonate and coke are used in combination under the situation of tapping carbon content lower (≤0.30%), and under the situation of tapping carbon content higher (＞0.30%), carbonate uses separately.

Above-mentioned metallic aluminium is taken from aluminium-containing substances such as aluminium ferromanganese, aluminium manganese ferrotianium, aluminium ingot, aluminum magnesium alloy, spherical Al slag, wherein preferred aluminium ferromanganese, spherical Al slag, and its granularity need be controlled at 8～150mm, can adjust addition to the requirement of oxygen level in the jar according to steel grade.Add the small amount of aluminum alloy or contain Al properties-correcting agent in the tapping later stage, its objective is the boiling state of molten steel in the control ladle, guarantee carrying out smoothly of tapping steel, thereby judge the free headroom of ladle accurately.

Above-mentioned denitrogenation method is applicable to the molten steel that converter is produced, the denitrogenation of the molten steel of boiling tapping is adopted in preferred converter, as production requirement nitrogen less than 0.0020% household electrical appliances steel, nitrogen is less than 0.0020% 70# high carbon steel, nitrogen is during less than 0.0020% IF steel, with 180 tons of converters is example, it is≤0.050% that technological process requires the interior carbon control criterion of ladle, oxygen is controlled at 0.055%～0.075% in the ladle, adopt the present invention and the effect comparison that does not adopt the present invention to reach, the present invention can significantly reduce the nitrogen content in the molten steel, and nitrogen content can reach 100% less than the ratio of 20ppm in the molten steel of tapping end back.

If need produce the alloying molten steel of being with compositions such as manganese chromium, can before finishing, tapping any time interpolation contain the aluminium ferromanganese of Al more than 55%; Carbon containing 7%, the high carbon ferromanganese of manganese more than 66%; Carbon containing is less than 1.5%, the mid-carbon fe-mn of manganese more than 80%; Carbon containing 9.5%, the high carbon ferro-chrome of chromium more than 65% if need to add ladle slag upgrading lime granule, then can add before adding aluminium alloy, all do not clash with the present invention.

Claims (1)

1. the method for converter tapping process molten steel denitrogenation, it is characterized in that, successively in ladle, add carbonate, coke and metallic aluminium in the converter tapping process, when utilizing tapping the kinetics of molten steel and thermodynamics effect with its decomposition or impel it with molten steel in oxygen react generation CO ₂Or the CO bubble, because [N] in the molten steel easily is adsorbed on bubble surface, along with CO ₂Or the come-up of CO bubble discharges [N] removed, and its each component is interpolation successively by weight proportion, and its step is as follows:

1) in 0～20% process of total steel amount of tapping, adds carbonate, addition 0.5～15kg/ ton steel;

2) in 15～35% processes of total steel amount of tapping, add coke, its granularity 5～50mm, carbon content is more than 97%, addition 0～5kg/ ton steel;

3) in 65～80% processes of total steel amount of tapping, add metallic aluminium, addition 0～1kg/ ton steel;

Above-mentioned carbonate is CaCO ₃, NaCO ₃, MgCO ₃, CaCO wherein ₃Be purified Wingdale, effective content is greater than 90%; MgCO ₃Be wagnerite, effective content is greater than 90%; Na ₂CO3 is a soda powder, and effective content is greater than 95%, granularity 5～50mm;

Above-mentioned metallic aluminium is taken from aluminium ferromanganese or spherical Al slag, granularity 8～150mm, and wherein aluminium ferromanganese contains Al more than 55%, and spherical Al slag contains Al more than 45%, contains CaO more than 25%.