CN119162506A

CN119162506A - A method for producing interstitial-free atomic steel using all-scrap steel + electric arc furnace process

Info

Publication number: CN119162506A
Application number: CN202411310959.5A
Authority: CN
Inventors: 马有光; 刘轶良; 付培茂; 元鹏飞; 刘涛; 孙少南; 赵海明
Original assignee: Shanxi Taigang Stainless Steel Co Ltd
Current assignee: Shanxi Taigang Stainless Steel Co Ltd
Priority date: 2024-09-20
Filing date: 2024-09-20
Publication date: 2024-12-20
Anticipated expiration: 2044-09-20
Also published as: CN119162506B

Abstract

本发明公开了一种采用全废钢+电弧炉工艺生产无间隙原子钢的方法，包括废钢配比、电弧炉炼钢、LF精炼、RH精炼、板坯连铸，以短流程工艺实现了C≤0.0025％、N≤0.005％、O≤0.004％的高等级、低碳排放无间隙原子钢的工业化批量生产，成品具备较好的强度和成型性能，解决电弧炉生产超低碳钢、超低氮钢的技术难题，填补了本领域的技术空白，相较于常规的高炉+转炉的长流程冶炼方法，本发明的方法大幅降低了无间隙原子钢生产过程中的碳排放，具备明显的环境效益。The invention discloses a method for producing interstitial-free steel by adopting a full scrap steel + electric arc furnace process, comprising scrap steel proportioning, electric arc furnace steelmaking, LF refining, RH refining, and slab continuous casting, and a short-process process is used to realize industrialized mass production of high-grade, low-carbon emission interstitial-free steel with C≤0.0025%, N≤0.005%, and O≤0.004%. The finished product has good strength and forming performance, solves the technical problem of producing ultra-low carbon steel and ultra-low nitrogen steel by electric arc furnace, and fills the technical gap in this field. Compared with the conventional blast furnace + converter long-process smelting method, the method of the invention greatly reduces the carbon emission in the production process of interstitial-free steel, and has obvious environmental benefits.

Description

Method for producing gapless atomic steel by adopting full scrap steel and electric arc furnace process

Technical Field

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for producing gapless atomic steel by adopting a full scrap steel and electric arc furnace process.

Background

The Interstitial Free (IF) steel is developed by controlling interstitial C, N and impurity elements in the steel, which seriously deteriorate deep drawing performance, at a level as low as possible and eliminating interstitial atoms in ferrite through alloying of Nb or Ti elements, thereby obtaining ultra deep drawing performance, is a new generation of deep drawing steel which is a first generation boiling steel and a second generation aluminum killed steel, has very excellent deep drawing performance, and is widely used as a raw material of stamping parts of automobile plates, home appliance plates, and the like.

At present, the IF steel is mainly produced by adopting a conventional long-flow mode of a blast furnace and a converter at home and abroad, and main working procedures comprise iron ore sintering, pelletizing, blast furnace ironmaking, oxygen converter steelmaking and the like, and the production flow is very long from iron ore to qualified continuous casting blank of the IF steel, and relates to numerous working procedures, high carbon emission and environment friendliness.

With the continuous promotion of 'carbon peak, carbon neutralization', the steel industry is faced with huge low-carbon transformation pressure, and the effective reduction of carbon emission in the steel production process has become a serious problem to be solved by the steel industry and even the country. Compared with the long process of a blast furnace and a converter, the short process of full scrap steel and an electric arc furnace is adopted for steelmaking, the energy consumption per ton of steel is reduced by about 50%, and the carbon emission is reduced by about 70%. Therefore, the development of the whole scrap steel and the short-flow steelmaking of the electric arc furnace is one of the great trends of the future development of the steel industry in China.

However, compared with oxygen converter steelmaking, electric arc furnace steelmaking inevitably ionizes nitrogen in the air due to the heating of scrap steel by electric arc, resulting in an increase in N in molten steel, and thus it is difficult to produce ultra-low nitrogen steel, particularly IF steel. At present, no related technology for producing IF steel by adopting scrap steel and an arc furnace is yet seen at home and abroad. Therefore, researches are conducted on the steel making process of the scrap steel and the electric arc furnace, and a method for producing the IF steel by adopting the process of the scrap steel and the electric arc furnace is developed so as to reduce the dependence on the flow of a blast furnace and a converter and reduce the carbon emission, and the method is a technical problem which is urgently needed to be solved in the field.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a method for producing gapless atomic steel by adopting a full scrap steel and electric arc furnace process, which comprises the following steps:

(1) Scrap steel proportion

The adding amount of the scrap steel is controlled to ensure that the mass percentage of chemical components in molten steel after the arc furnace is cleared reaches the following requirements ：P≤0.015％、S≤0.015％、Al≤0.08％、Cr≤0.05％、Ni≤0.05％、Mo≤0.03％、Cu≤0.05％、N≤0.010％、B≤0.0005％、Sn≤0.01％、Nb≤0.01％、V≤0.01％、Ti≤0.01％;

(2) Steelmaking by electric arc furnace

Putting the proportioned scrap steel into an electric arc furnace, electrifying and heating, performing slag stopping operation in the tapping process, controlling the slag thickness to be less than or equal to 40mm, and controlling the tapping components of the electric arc furnace to be:

C

Si

Mn

P

S

Al

Cr

≤0.04

≤0.10

≤0.013

≤0.015

≤0.07

≤0.05

Ni

Mo

Cu

N

B

Sn

≤0.05

≤0.03

≤0.05

≤0.010

≤0.0005

≤0.010

(3) LF refining

Feeding a ladle into an LF station, carrying out power transmission and heating, adding a slag former in the heating process to carry out slag formation, adding an aluminum wire or aluminum particles in molten steel to carry out pre-deoxidation, wherein the addition amount of the aluminum wire or the aluminum particles is required to ensure that the O content in the molten steel is 600-700 ppm, stirring the molten steel by adopting bottom blowing argon in the whole LF refining process, uniformly adding an aluminum-containing premelted steel slag modifier on the slag surface of the top slag of the ladle before the LF is discharged, and discharging after the addition of the aluminum-containing premelted steel slag modifier and the weak stirring of the bottom blowing argon for 1-2 minutes;

(4) RH refining

The steel ladle enters an RH station, is vacuumized, performs molten steel circulation and decarburization operation, adds Al alloy and electrolytic manganese, ferrotitanium and ferroniobium alloy into the molten steel to perform alloying after decarburization is completed, continues circulation for more than or equal to 20 minutes after alloying is completed, performs a breaking operation after circulation is completed, and discharges the molten steel after blowing argon gas and weak stirring after RH breaking, wherein the RH tapping component is controlled as follows:

C

Si

Mn

P

S

Al

Ti

Cr

≤0.0015

≤0.03

0.10~0.20

≤0.013

≤0.015

0.04~0.06

0.04~0.08

≤0.05

Ni

Mo

Cu

N

B

Sn

Nb

V

≤0.05

≤0.005

≤0.0005

≤0.01

(5) Continuous casting of slabs

The continuous casting tundish adopts an ultralow-carbon covering agent with the total carbon content less than or equal to 1.5%, the crystallizer covering slag adopts an ultralow-carbon covering slag with the total carbon content less than or equal to 2.0%, the continuous casting ladle is subjected to protection casting in the casting process, the superheat degree of the continuous casting tundish is controlled to be 20-30 ℃, and the continuous casting drawing speed is controlled to be 1.10-1.15 m/min.

Preferably, in the slab continuous casting process, the 1 st furnace of the tundish uses other ultra-low carbon steel with C less than or equal to 0.0050 percent for casting, and the 2 nd furnace of the tundish and subsequent heats use molten steel prepared by the scrap steel proportioning, electric arc furnace steelmaking, LF refining and RH refining processes for casting.

As a specific embodiment, in the method for producing the gapless atomic steel by adopting the full scrap steel and electric arc furnace process, in the scrap steel proportioning procedure, the proportion of scrap steel in all smelting raw materials is more than or equal to 95 percent, wherein the scrap steel comprises 45 percent by weight or more of cold plate pressed scrap steel, 30 percent by weight or more of special broken materials and/or 10 percent by weight or more of pure iron scrap steel, and the proportion of the scrap steel is required to satisfy the requirement of characteristic elements in molten steel after electric arc furnace smelting ：P≤0.015％、S≤0.015％、Al≤0.08％、Cr≤0.05％、Ni≤0.05％、Mo≤0.03％、Cu≤0.05％、N≤0.010％、B≤0.0005％、Sn≤0.01％、Nb≤0.01％、V≤0.01％、Ti≤0.01％.

In the method for producing the interstitial free steel by adopting the scrap steel and electric arc furnace process, lime, fluorite and red mud balls are added in the smelting process in the electric arc furnace steelmaking process to form slag, coke, ferrosilicon and silicon carbide slag are added in the smelting process, after power transmission, temperature rising and melting clearing are carried out, small gear power transmission is carried out, oxygen is blown into an oxygen stirring molten pool, lime and fluorite are added again to improve slag alkalinity, oxygen blowing and dephosphorization are carried out, and tapping is carried out after slag discharge.

In the method for producing the interstitial free steel by adopting the scrap steel and the arc furnace process, 800-1000 kg of lime and 200-400 kg of fluorite are added in the heating process in the LF refining process, slag conditions are adjusted, 150-300 m of aluminum wires are added for pre-deoxidation, the total flow of bottom blowing argon is 100-500 NL/min, and the temperature of molten steel at an LF outlet is controlled to be 1660-1670 ℃.

Further, in the above method for producing interstitial free steel using the scrap+arc furnace process, in the RH refining process:

the ladle enters an RH station, vacuumizing is started, molten steel circulation is carried out, timing is started when the vacuum degree is less than or equal to 150Pa, and decarburization operation is carried out in the vacuum circulation for 6-10 minutes;

Sampling and analyzing the molten steel components after decarburization is finished, when the mass percent content of C in the molten steel is less than or equal to 0.0015%, performing oxygen determination operation by adopting a high-precision oxygen determination instrument to determine the O content in the molten steel, calculating the Al content required by deoxidization and alloying according to the O content, adding the required amount of Al alloy into the molten steel, and then circulating for 3-6 minutes;

According to the target components of the interstitial-free steel, adding electrolytic manganese, ferrotitanium and ferroniobium for alloying, circulating for 3-4 minutes, sampling and analyzing the components of the molten steel, and fine-adjusting the components of the steel based on the target components of the interstitial-free steel;

after alloying is completed, when the vacuum degree is less than or equal to 150Pa, continuing to circulate for more than or equal to 20 minutes, and carrying out a breaking operation after circulation is completed, wherein in the breaking operation process, when the vacuum tank leaves the liquid surface of the steel, a proper amount of aluminum-containing steel slag modifier is rapidly added to the liquid surface of the steel;

the temperature of molten steel at an RH outlet is controlled to be 1595-1610 ℃.

Further, in the above method for producing interstitial free steel using the scrap+arc furnace process, in the slab continuous casting process:

On-line baking is carried out on the tundish and the water gap before continuous casting, the baking time is 2 hours, the longest time is not more than 4 hours, and the steel ladle fork arm calm time is controlled to be more than or equal to 5 minutes;

The fluctuation of the liquid level of the crystallizer is required to be +/-5 mm, the flow rate of stopper rod argon is controlled to be less than or equal to 10NL/min, a dynamic light reduction process parameter is that the reduction is applied in the area of 50-95% of the solid phase rate of a two-phase area, the total reduction is 3.2mm, and the dynamic light reduction and a roller type electromagnetic stirrer are put into the crystallizer to control center loosening and center segregation, and the technological parameters of the roller type electromagnetic stirrer are 300A, 6Hz and no reversing.

In addition, the invention also provides the interstitial free steel, which comprises the following chemical components in percentage by mass ：C≤0.0025％、Si≤0.03％、Mn≤0.25％、P≤0.015％、S≤0.015％、Al≤0.08％、Ti：0.03～0.10％、Cr≤0.05％、Ni≤0.05％、Mo≤0.03％、Cu≤0.05％、N≤0.005％、B≤0.0005％、Sn≤0.01％、Nb≤0.01％、V≤0.01％, and the balance of Fe and unavoidable impurities.

The method for producing Interstitial Free (IF) steel by adopting the full scrap steel and electric arc furnace process has the advantages and beneficial effects that the batch production of high-grade low-carbon-emission IF steel with C less than or equal to 0.0025%, N less than or equal to 0.005% and O less than or equal to 0.004% is realized by adopting a short-flow process, the finished product has better strength and forming property, the technical problem of producing ultra-low carbon steel and ultra-low nitrogen steel by adopting an electric arc furnace is solved, the technical blank in the field is filled, and compared with the conventional long-flow smelting method of a blast furnace and a converter, the method greatly reduces the carbon emission in the IF steel production process and has obvious environmental benefit.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below in connection with specific embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The invention aims to develop an industrial smelting method for producing high-grade low-carbon emission interstitial free steel by adopting a full scrap steel and arc furnace process, realize batch production of high-grade IF steel with C less than or equal to 0.0025%, N less than or equal to 0.005% and O less than or equal to 0.004%, solve the technical problem of producing ultra-low carbon steel and ultra-low nitrogen steel by an arc furnace, and greatly reduce carbon emission in the IF steel production process.

In the method for producing the gapless atomic steel by adopting the full scrap steel and electric arc furnace process, the full scrap steel refers to scrap steel with the proportion of more than or equal to 95 percent in all smelting raw materials, and the scrap steel comprises, but is not limited to, cold plate pressed scrap steel, superfine broken materials, pure iron scrap steel and silicon steel scrap steel.

Specifically, the method for producing the gapless atomic steel by adopting the full scrap steel and electric arc furnace process comprises the following steps of:

(1) Scrap steel proportion

The adding amount of the scrap steel is controlled to ensure that the mass percentage of chemical components in molten steel after the arc furnace is cleared reaches the following requirements ：P≤0.015％、S≤0.015％、Al≤0.08％、Cr≤0.05％、Ni≤0.05％、Mo≤0.03％、Cu≤0.05％、N≤0.010％、B≤0.0005％、Sn≤0.01％、Nb≤0.01％、V≤0.01％、Ti≤0.01％.

(2) Steelmaking by electric arc furnace

The proportioned scrap steel is put into an electric arc furnace, an electrode is lowered, the electric arc furnace is electrified to heat, a proper amount of auxiliary materials such as limestone, coke and the like can be added into the electric arc furnace in an auxiliary manner in the steelmaking process of the electric arc furnace, and a proper amount of oxygen is introduced to assist in heating and melting. Slag stopping operation is carried out in the tapping process, slag discharging is avoided as much as possible, and the slag thickness is controlled to be less than or equal to 40mm. And deoxidization and alloying operations are not performed in the tapping process, so that the tapping back phosphorus is avoided.

The tapping composition of the electric arc furnace was controlled as shown in table 1 below:

TABLE 1 tapping composition of electric arc furnace (mass percent, balance Fe and unavoidable impurities)

C

Si

Mn

P

S

Al

Cr

≤0.04

≤0.10

≤0.013

≤0.015

≤0.07

≤0.05

Ni

Mo

Cu

N

B

Sn

≤0.05

≤0.03

≤0.05

≤0.010

≤0.0005

≤0.010

(3) LF refining

And (3) feeding the ladle into an LF station for temperature measurement, adopting an electrode to transmit power for temperature rise according to the temperature of molten steel, and adding a proper amount of slag formers such as lime, fluorite and the like for slag formation in the temperature rise process. Proper amount of aluminum wires or aluminum particles can be added into the molten steel for pre-deoxidation, but the O content in the molten steel is 600-700 ppm for RH decarburization. And in the whole LF refining process, bottom argon blowing is adopted to stir molten steel. Before the LF is discharged, a proper amount of aluminum-containing premelted steel slag modifier is uniformly added on the slag surface of the top slag of the steel ladle, and after the aluminum-containing premelted steel slag modifier is added, argon is blown into the steel ladle, the steel ladle is discharged after being weakly stirred for 1-2 minutes. The temperature of molten steel at the LF outlet is 1660-1670 ℃. The molten steel only carries out heating and slagging operations in the LF procedure, and does not carry out desulfurization and alloying.

(4) RH refining

And (3) feeding the ladle into an RH station for temperature measurement, vacuumizing, and performing molten steel circulation and decarburization operation. After decarburization is completed, adding Al alloy, electrolytic manganese, ferrotitanium, ferroniobium and other alloys into molten steel according to the target components of the IF steel to carry out alloying. And continuing to circulate for more than or equal to 20 minutes after alloying is completed. And (5) carrying out a breaking operation after the circulation is completed. The temperature of the molten steel at the RH outlet is 1595-1610 ℃.

In the RH refining process, the vacuum lifting gas is argon, and the lifting gas flow is 90-100% of the limiting flow. The RH tapping composition was controlled as shown in Table 2 below:

TABLE 2RH tapping component (mass percent, balance Fe and unavoidable impurities)

C

Si

Mn

P

S

Al

Ti

Cr

≤0.0015

≤0.03

0.10~0.20

≤0.013

≤0.015

0.04~0.06

0.04~0.08

≤0.05

Ni

Mo

Cu

N

B

Sn

Nb

V

≤0.05

≤0.03

≤0.05

≤0.005

≤0.0005

≤0.01

(5) Continuous casting of slabs

The continuous casting tundish adopts an ultralow-carbon covering agent with the total carbon content less than or equal to 1.5%, the crystallizer covering slag adopts an ultralow-carbon covering slag with the total carbon content less than or equal to 2.0%, the continuous casting ladle is subjected to protective casting in the casting process, and the N and C increase are strictly controlled. And the superheat degree of the continuous casting tundish is executed according to 20-30 ℃. The continuous casting and drawing speed of the double-flow continuous casting machine is controlled according to 1.10-1.15 m/min.

Particularly, as the molten steel can be in direct contact with various carbon-containing raw and auxiliary materials in a tundish and a crystallizer, such as a tundish covering agent, a tundish coating material, a crystallizer casting powder and the like, the carbon-containing raw and auxiliary materials can inevitably transfer mass into the molten steel, so that the molten steel is increased in C. Generally, the C increment of the furnace 1 of the tundish in the continuous casting process is obvious, and is usually 7-12 ppm, and the C increment is obviously reduced from the furnace 2. The C increment of 7-12 ppm in furnace 1 of the tundish is likely to cause the molten steel C of the final smelting analysis to exceed 0.0025 percent. Therefore, in order to ensure that the high-grade interstitial free steel is smelted, C is not increased or is increased little in the continuous casting process, when the slab is continuously cast, the 1 st furnace of the tundish uses other ultra-low carbon steel with C less than or equal to 0.0050 percent for casting, and the 2 nd furnace of the tundish and subsequent heats use molten steel prepared through the scrap steel proportioning, electric arc furnace steelmaking, LF refining and RH refining processes for casting.

In the slab continuous casting process, when the residual weight of molten steel in a continuous casting ladle is 40-60% of the total weight of molten steel in the ladle, sampling the chemical components of the produced IF steel in a tundish, wherein the chemical components are obtained as shown in the following Table 3:

TABLE 3 chemical composition of IF steel (mass percent, balance Fe and unavoidable impurities)

C

Si

Mn

P

S

Al

Ti

Cr

≤0.0025

≤0.03

≤0.25

≤0.015

≤0.08

0.03~0.10

≤0.05

Ni

Mo

Cu

N

B

Sn

Nb

V

≤0.05

≤0.03

≤0.05

≤0.005

≤0.0005

≤0.01

The method for producing interstitial free steel by using the full scrap steel+electric arc furnace process according to the present invention will be described below with reference to examples 1 and 2, and the method for producing interstitial free steel by using the full scrap steel+electric arc furnace process according to examples 1 and 2 according to the present invention is performed according to the foregoing scrap ratio, electric arc furnace steelmaking, LF refining, RH refining, slab continuous casting, etc., and the specific implementation procedures are as follows:

In the scrap blending step, the scrap blending cases of example 1 and example 2 are shown in table 4 below:

Table 4 proportion of scrap steel of examples 1 and 2

In the steelmaking process of the electric arc furnace, the prepared scrap steel is filled into the electric arc furnace by adopting a material basket, an electrode is lowered, the electric current is increased in temperature, auxiliary materials such as lime, fluorite, red mud balls and the like are added in the smelting process to form slag, coke, ferrosilicon and silicon carbide slags are added in the smelting process, after the electric current is fed in temperature, molten and clear, small gear power is fed in, oxygen is blown into an oxygen stirring molten pool in proper amount, the temperature in the furnace is uniform and no steel is adhered, proper lime and fluorite are added again to improve the slag alkalinity, oxygen blowing dephosphorization is carried out, and tapping is carried out after slag discharge. And deoxidization and alloying operations are not performed in the tapping process, so that the tapping back phosphorus is avoided. Slag stopping operation is carried out in the tapping process, slag discharging is avoided as much as possible, and the slag thickness is controlled to be less than or equal to 40mm. If slag blocking fails in the tapping process, the slag discharging amount is large, slag skimming operation can be performed in the tapping process, and the slag thickness after slag skimming is required to be less than or equal to 40mm.

The composition of the tapping of the electric arc furnace was controlled as shown in the following table 5:

TABLE 5 tapping composition of electric arc furnace (mass percent, balance Fe and unavoidable impurities)

In the LF refining process, the temperature of a steel ladle entering an LF station is measured, according to the temperature of molten steel, power is transmitted by an electrode to raise the temperature, 800-1000 kg of lime and 200-400 kg of fluorite are added in the temperature raising process to adjust the slag condition, 150-300 m of aluminum wire is added to conduct pre-deoxidation, 600-700 ppm of oxygen is reserved in the molten steel for subsequent RH decarburization, bottom blowing argon is adopted in the whole LF refining process to stir the molten steel, the total flow of the argon is 100-500 NL/min, a proper amount of aluminum-containing premelted steel slag modifier is uniformly added on the slag surface of the top slag of the steel ladle before the LF is discharged, after the addition, the bottom blowing argon is weakly stirred for 1-2 minutes, the molten steel is discharged, and the temperature of the molten steel at the LF discharge station is 1660-1670 ℃.

In the RH refining process, the steel ladle enters an RH station for measuring temperature, vacuumizing is started, molten steel circulation is carried out, when the vacuum degree is less than or equal to 150Pa, timing is started, and decarburization operation is carried out in the vacuum circulation for 6-10 minutes. And after decarburization is finished, sampling and analyzing the molten steel component, when the mass percent content of C in the molten steel is less than or equal to 0.0015%, performing oxygen determination operation by adopting a high-precision oxygen determination instrument to determine the O content in the molten steel, calculating the Al content required by deoxidization and alloying according to the O content, adding the required amount of Al alloy into the molten steel, and then circulating for 3-6 minutes. And adding a proper amount of electrolytic manganese, ferrotitanium, ferroniobium and other alloys according to the target components of the IF steel for alloying, circulating for 3-4 minutes, sampling and analyzing the molten steel components, and fine-tuning the steel components based on the target components of the IF steel. After alloying is completed, when the vacuum degree is less than or equal to 150Pa, the circulation is continued for more than or equal to 20 minutes. And (3) carrying out a breaking operation after the circulation is completed, wherein in the breaking operation process, when the vacuum tank leaves the liquid surface of the steel, a proper amount of aluminum-containing steel slag modifier is rapidly added to the liquid surface of the steel so as to improve the oxidizing property of steel slag in direct contact with the steel liquid and reduce the TFe content in the slag. The temperature of the molten steel at the RH outlet is 1595-1610 ℃.

The RH tapping composition was controlled as shown in Table 6 below:

TABLE 6RH tapping component (mass percent, balance Fe and unavoidable impurities)

In the slab continuous casting process, an intermediate ladle and a water gap are baked on line before continuous casting, the baking time is 2h, the maximum time is not more than 4h, the rest time of a ladle fork arm is more than or equal to 5 minutes, the continuous casting intermediate ladle adopts an ultralow carbon covering agent with the total carbon content of less than or equal to 1.5%, the crystallizer covering slag adopts ultralow carbon covering slag with the total carbon content of less than or equal to 2.0%, the continuous casting ladle casting process is implemented for protection casting, the N and C increase are strictly controlled, the superheat degree of the continuous casting intermediate ladle is controlled to be 20-30 ℃, the continuous casting drawing speed of a double-flow continuous casting machine is controlled to be 1.10-1.15 m/min, the fluctuation of the liquid level of the crystallizer is required to be +/-5 mm, the flow rate of stopper argon is less than or equal to 10NL/min so as to reduce the disturbance of argon to the liquid level of the crystallizer, the dynamic light reduction and the roller electromagnetic stirrer are input so as to control center loosening and center segregation, and the dynamic light reduction process parameters are that the pressure is applied within a range of 50-95% of the solid phase region, the total pressure is 3.2mm, and the roller electromagnetic stirring process parameters are 300A and 6Hz and the non-reversing.

In addition, during slab continuous casting, the 1 st furnace of the tundish uses other ultra-low carbon steel with C less than or equal to 0.0050 percent for casting, and the 2 nd furnace and subsequent heats of the tundish use molten steel prepared through the steps of scrap steel proportioning, electric arc furnace steelmaking, LF refining and RH refining for casting.

When the residual molten steel in the ladle is 90-120 tons, a smelting analysis sample is taken in a tundish, and the chemical components of the produced IF steel can be obtained, and the chemical components are shown in the following table 7:

TABLE 7 chemical composition of IF steel (mass percent, balance Fe and unavoidable impurities)

In summary, the invention provides an industrialized smelting method for producing high-grade low-carbon emission interstitial free steel by adopting a full scrap steel and arc furnace process, which mainly comprises a scrap steel proportioning process, an arc furnace steelmaking process, an LF refining process, an RH refining process and a slab continuous casting process, wherein the batch production of high-grade IF steel with C less than or equal to 0.0025%, N less than or equal to 0.005% and O less than or equal to 0.004% is realized by a short process, the finished product has better strength and formability, the technical problem of producing ultra-low carbon steel and ultra-low nitrogen steel by an arc furnace is solved, the technical blank in the field is filled, and compared with the conventional long process smelting method of a blast furnace and a converter, the carbon emission in the IF steel production process is greatly reduced, and the method has obvious environmental benefit.

It should be noted that, in this document, the term "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus.

It should be further noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the technical solution described in the above-mentioned embodiments may be modified or some technical features may be equivalently replaced, and these modifications or substitutions do not deviate from the essence of the corresponding technical solution from the scope of the present invention.

Claims

1. An interstitial-free steel, characterized in that the chemical composition of the interstitial-free steel is as follows by mass percentage: C≤0.0025%, Si≤0.03%, Mn≤0.25%, P≤0.015%, S≤0.015%, Al≤0.08%, Ti: 0.03-0.10%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.005%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, and the remainder is Fe and unavoidable impurities.

2. A method for producing interstitial-free steel using a full scrap steel + electric arc furnace process, characterized in that the method comprises the following steps:

(1) Scrap steel ratio

The amount of scrap steel added is controlled to ensure that the mass percentage of the chemical composition in the molten steel after the electric arc furnace is melted and cleared meets the following requirements: P≤0.015%, S≤0.015%, Al≤0.08%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.010%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, Ti≤0.01%;

(2) Electric Arc Furnace Steelmaking

The scrap steel with good proportion is loaded into the electric arc furnace, and the power is turned on to increase the temperature. The slag blocking operation is carried out during the steel tapping process to control the slag thickness to ≤40mm. The composition of the steel tapped from the electric arc furnace is controlled as follows:

C Si Mn P S Al Cr ≤0.04 ≤0.04 ≤0.10 ≤0.013 ≤0.015 ≤0.07 ≤0.05 Ni Mo Cu N B Sn ≤0.05 ≤0.03 ≤0.05 ≤0.010 ≤0.0005 ≤0.010

(3) LF refining

The ladle enters the LF station, and is powered on for heating. During the heating process, slag-forming agent is added to form slag. Aluminum wire or aluminum particles are added to the molten steel for pre-deoxidation. The amount of aluminum wire or aluminum particles added must ensure that the O content in the molten steel is 600-700ppm. Bottom-blown argon is used to stir the molten steel throughout the LF refining process. Before the LF leaves the station, aluminum-containing pre-melted steel slag modifier is evenly added to the slag surface on the top of the ladle. After adding, argon is blown from the bottom for weak stirring for 1-2 minutes before leaving the station.

(4) RH refining

The ladle enters the RH station, evacuates, and performs molten steel circulation and decarburization operations. After decarburization, Al alloy, electrolytic manganese, ferrotitanium, and ferroniobium alloy are added to the molten steel for alloying. After alloying, the deep vacuum condition is maintained for circulation for ≥ 20 minutes. After the circulation is completed, the air breaking operation is performed. After the RH air breaking, the molten steel is blown with argon gas for weak stirring and then discharged from the station. The RH steel composition is controlled as follows:

C Si Mn P S Al Ti Cr ≤0.0015 ≤0.03 0.10～0.20 ≤0.013 ≤0.015 0.04～0.06 0.04～0.08 ≤0.05 Ni Mo Cu N B Sn Nb V ≤0.05 ≤0.05 ≤0.05 ≤0.005 ≤0.0005 ≤0.01 ≤0.01 ≤0.01

(5) Slab continuous casting

The continuous casting tundish uses an ultra-low carbon covering agent with a total carbon content of ≤1.5%, and the crystallizer protective slag uses an ultra-low carbon protective slag with a total carbon content of ≤2.0%. Protective casting is implemented during the continuous casting ladle pouring process. The superheat of the continuous casting tundish is controlled at 20-30°C, and the continuous casting drawing speed is controlled at 1.10-1.15m/min.

3. The method for producing interstitial-free steel by using all-scrap steel + electric arc furnace process according to claim 2, characterized in that, in the scrap steel proportioning process, the scrap steel accounts for ≥95% of all smelting raw materials, wherein the scrap steel includes cold plate briquette scrap steel with a weight percentage of ≥45%, and/or special grade crushed material with a weight percentage of ≥30%, and/or pure iron scrap steel with a weight percentage of ≥10%, and the proportion of the scrap steel should meet the characteristic elements in the molten steel after electric arc furnace smelting: P≤0.015%, S≤0.015%, Al≤0.08%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.010%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, Ti≤0.01%.

4. The method for producing interstitial-free atomic steel using all-scrap steel + electric arc furnace process according to claim 2 is characterized in that in the electric arc furnace steelmaking process, lime, fluorite and red mud balls are added during the smelting process to form slag, coke, ferrosilicon and silicon carbide are added during the smelting process to form slag, and after power is supplied to increase the temperature and melt, power is supplied at a low gear and oxygen is blown into the molten pool to stir the molten pool, lime and fluorite are added again to increase the slag basicity, oxygen is blown to dephosphorize, and the steel is tapped after the slag is discharged.

5. The method for producing interstitial-free steel by using all-scrap steel + electric arc furnace process according to claim 2 is characterized in that, in the LF refining process, 800-1000 kg of lime and 200-400 kg of fluorite are added during the heating process to adjust the slag condition, 150-300 m of aluminum wire is added for pre-deoxidation, the total flow rate of bottom blowing argon is 100-500 NL/min, and the temperature of the molten steel at the LF outlet is controlled to be 1660-1670°C.

6. The method for producing interstitial-free steel using all-scrap steel + electric arc furnace process according to claim 2, characterized in that in the RH refining step:

The ladle enters the RH station, starts to evacuate and circulate the liquid steel. When the vacuum degree reaches ≤150Pa, start timing, and the vacuum circulation lasts for 6 to 10 minutes for decarburization operation.

After decarburization is completed, the steel liquid is sampled and analyzed for composition. When the mass percentage of C in the steel liquid is ≤0.0015%, a high-precision oxygen meter is used to determine the oxygen content in the steel liquid. The Al content required for deoxidation and alloying is calculated based on the O content, and the required amount of Al alloy is added to the steel liquid, and then circulated for 3 to 6 minutes.

According to the interstitial atomic steel target composition, electrolytic manganese, ferrotitanium and ferroniobium alloys are added for alloying, and after circulating for 3 to 4 minutes, the steel liquid composition is sampled and analyzed, and the steel composition is fine-tuned based on the interstitial atomic steel target composition;

After alloying is completed, when the vacuum degree reaches ≤150Pa, continue to circulate for ≥20 minutes. After the cycle is completed, perform the air-breaking operation. During the air-breaking operation, when the vacuum tank leaves the molten steel surface, quickly add an appropriate amount of aluminum-containing steel slag modifier to the molten steel surface;

The outlet temperature of molten steel at RH is controlled at 1595～1610℃.

7. The method for producing interstitial-free atomic steel using the all-scrap steel + electric arc furnace process according to claim 2 is characterized in that in the slab continuous casting process, the first tundish furnace uses other ultra-low carbon steel with C≤0.0050% for casting, and the second tundish furnace and subsequent furnaces use molten steel produced by the scrap steel proportioning, electric arc furnace steelmaking, LF refining, and RH refining processes for casting.

8. The method for producing interstitial-free steel using all-scrap steel + electric arc furnace process according to claim 2, characterized in that in the slab continuous casting process:

Before continuous casting, the tundish and nozzle are baked online for 2 hours and no longer than 4 hours. The cooling time of the ladle fork arm is controlled to be ≥5 minutes.

The crystallizer liquid level fluctuation requirement is ±5mm, the stopper argon flow rate is controlled to ≤10NL/min, dynamic light pressure and roller electromagnetic stirrer are used to control center loosening and center segregation. The dynamic light pressure process parameters are: pressure is applied in the range of 50-95% solid phase ratio in the two-phase zone, the total pressure reduction is 3.2mm, and the roller electromagnetic stirring process parameters are: 300A, 6Hz, no reversing.