阅读说明：本技术 一种超低铝极低硫无取向硅钢的冶炼方法 (Smelting method of ultralow-aluminum-content low-sulfur non-oriented silicon steel ) 是由 廖明 张创举 文敏 何洪霞 孙彤彤 刘晓峰 陈露涛 赵启帆 唐志刚 杨华 于 2021-09-24 设计创作，主要内容包括：本发明属于钢铁冶炼技术领域,涉及一种超低铝极低硫无取向硅钢的冶炼方法,包括如下步骤：KR铁水预处理→BOF复吹转炉冶炼→RH真空炉精炼→LF精炼→连铸；采用本发明中的冶炼方法,铁水脱后硫可以适当放宽,转炉出钢温度可以适当降低,RH工序无需采用OB法升温,也无需RH顶枪喷粉或者加入合成渣脱硫,LF只需实现微调成分、调节温度、平衡炉机节奏以及适当脱硫。此种冶炼方法充分利用并发挥了各工序优势,避免了在某一工序完成所有冶炼任务,一旦发生事故,容易造成生产中断,产品质量难以保证。(The invention belongs to the technical field of steel smelting, and relates to a smelting method of ultralow-aluminum-content low-sulfur non-oriented silicon steel, which comprises the following steps: KR molten iron pretreatment → BOF combined blown converter smelting → RH vacuum furnace refining → LF refining → continuous casting; by adopting the smelting method, the sulfur of molten iron can be properly relaxed after the molten iron is desulfurized, the tapping temperature of the converter can be properly reduced, the RH process does not need to adopt an OB method for heating, RH top lance powder injection or synthetic slag addition for desulfurization, and the LF only needs to realize component fine adjustment, temperature adjustment, balance furnace rhythm and proper desulfurization. The smelting method fully utilizes and exerts the advantages of each process, avoids the problems that all smelting tasks are finished in a certain process, production interruption is easy to cause once an accident occurs, and the product quality is difficult to ensure.)

1. A smelting method of ultralow-aluminum-content and extremely low-sulfur non-oriented silicon steel is characterized by comprising the following steps:

(1) KR molten iron pretreatment: controlling the temperature of molten iron to a KR desulfurization station to be more than or equal to 1320 ℃, controlling the S of molten iron desulfurization to be less than or equal to 0.010 percent, and controlling the bright surface of an iron ladle to be more than or equal to 95 percent;

(2) and (3) smelting by using a BOF combined blown converter: the converter end point temperature is controlled as follows: 1635-1660 ℃, and controlling the chemical components of the molten iron to have a weight end point C element content of less than or equal to 0.05% and an oxygen content of 500-850 ppm;

(3) and (3) refining in an RH vacuum furnace: controlling the inbound oxygen content to be 300-700 ppm; controlling the ultimate vacuum degree to be less than or equal to 273Pa in the refining process, controlling the net circulation time of the molten steel to be 6-10 min under the ultimate vacuum degree, controlling the total RH refining time to be 40-50 min/furnace, and after refining and re-pressing, not blowing argon and stirring the steel ladle and not carrying out calcium treatment;

(4) LF refining: heating molten steel when the molten steel enters a station, adding lime into the molten steel, adding 2.2-3.6 kg of lime into the lime per ton of steel, and adding bauxite according to the requirement;

(5) continuous casting: the molten steel on the continuous casting platform is calmed for more than or equal to 5min, the continuous casting pouring period is controlled according to 43min, a tundish sample is taken after pouring is started for 10min, and simultaneously the oxygen content in the molten steel is monitored; controlling the temperature of the tundish molten steel at 1549-1563 ℃; and argon is blown by a stopper rod, and the flow of the argon is controlled to be less than or equal to 3L/min.

2. The method for smelting ultra-low aluminum ultra-low sulfur non-oriented silicon steel according to claim 1, wherein: the ultralow-aluminum-content and extremely-low-sulfur non-oriented silicon steel comprises the following chemical components in percentage by weight: c is less than or equal to 0.005%, Si: 0.35-1.20%, Mn: 0.15% -0.55%, P: 0.02-0.06 percent, less than or equal to 0.005 percent of S, less than or equal to 0.005 percent of Als, and the balance of Fe and inevitable impurities.

3. The method for smelting ultra-low aluminum ultra-low sulfur non-oriented silicon steel according to claim 1, wherein: in the step (2), the slag discharging amount is strictly controlled during converter tapping, and refined lime, a slag thickening agent and low-carbon ferromanganese are added during tapping; controlling the argon blowing flow to be 10-15 Nm in the tapping process³And h, after tapping, adding a slag surface deoxidizing agent into the steel ladle to adjust slag, wherein the adding amount of the slag surface deoxidizing agent is 60-120 Kg per furnace.

4. The method for smelting ultra-low aluminum ultra-low sulfur non-oriented silicon steel according to claim 1, wherein: in the step (3), after RH decarburization is finished, adding a proper amount of metal aluminum pills, micro-carbon ferrosilicon and metal manganese for deoxidation alloying, wherein the cycle time is not less than 3min after the alloying is finished.

5. The method for smelting ultra-low aluminum ultra-low sulfur non-oriented silicon steel according to claim 1, wherein: in the step (4), a reducing agent is manually added into the steel ladle in the temperature rising process; the flow of the argon blowing flow of the ladle in the whole LF refining process is controlled to be 10-15 Nm³H; before the molten steel is refined in LF, no calcium treatment is carried out, and the soft argon blowing time is more than or equal to 5 min.

6. The method for smelting ultra-low aluminum ultra-low sulfur non-oriented silicon steel according to claim 1, wherein: in the step (5), the tundish uses a carbon-free heat preservation agent, and the crystallizer uses non-oriented silicon steel special-purpose covering slag.

Technical Field

The invention belongs to the technical field of steel smelting, and relates to a smelting method of ultralow-aluminum-content low-sulfur non-oriented silicon steel.

Background

The ultra-low aluminum-pole low-sulfur non-oriented silicon steel is a soft magnetic alloy, is an indispensable energy-saving functional material in the national power, electronic and military industries, is mainly applied to iron cores of various household motors, micromotors, small motors, compressors, generators, ballasts and transformers, plays a role in electromagnetic energy conversion medium, plays an important role in energy conservation and consumption reduction, and is closely related to national economic development and people life. The conventional smelting process flow of the non-oriented silicon steel at present comprises the following steps: KR molten iron pretreatment → BOF combined blown converter smelting → RH vacuum furnace refining → continuous casting. The process route has simple manufacturing process, low manufacturing cost and wide application, but has extremely strict requirements on molten iron desulphurization depth, clean desulphurization slag, scrap steel quality, tapping temperature and furnace protection process, and continuous casting break or component yield can be caused by a little carelessness in a certain link. In order to optimize the product structure and enhance the profitability of the product, a production process suitable for the equipment characteristics of the enterprise is urgently needed to be developed so as to stably and smoothly produce the steel grade.

In the prior art, for example, a single RH process production method is provided in Chinese patent CN112921237A entitled smelting method of silicon-manganese killed non-oriented silicon steel, which has the advantages of short process flow and the like, but has high requirements on molten iron desulphurization, slag skimming and tapping temperature, and large temperature drop because synthetic slag is added in the RH process.

Also, for example, chinese patent No. CN104017929A, "a method for increasing the percent of pass of carbon and sulfur components in non-oriented silicon steel", provides a production method using processes of RH first and LF second, but has very strict requirements on parameters of each process, the content of sulfur after removal does not exceed 0.002%, the tapping temperature is more than 1710 ℃, the types of slag added in LF are many, the amount is large, the percent of pass of carbon and sulfur components is only more than 95%, quality control is unstable, and production cost is still high.

Disclosure of Invention

In view of the above, the invention aims to solve the defects in the prior art and provide a method for smelting ultra-low aluminum ultra-low sulfur non-oriented silicon steel.

In order to achieve the purpose, the invention provides the following technical scheme:

a smelting method of ultralow-aluminum-content and extremely low-sulfur non-oriented silicon steel comprises the following steps:

(1) KR molten iron pretreatment: controlling the temperature of molten iron to a KR desulfurization station to be more than or equal to 1320 ℃, controlling the S of molten iron desulfurization to be less than or equal to 0.010 percent, and controlling the bright surface of an iron ladle to be more than or equal to 95 percent;

(2) and (3) smelting by using a BOF combined blown converter: the converter end point temperature is controlled as follows: 1635-1660 ℃, and controlling the chemical components of the molten iron to have a weight end point C element content of less than or equal to 0.05% and an oxygen content of 500-850 ppm;

(3) and (3) refining in an RH vacuum furnace: controlling the inbound oxygen content to be 300-700 ppm; controlling the ultimate vacuum degree to be less than or equal to 273Pa in the refining process, controlling the net circulation time of the molten steel to be 6-10 min under the ultimate vacuum degree, controlling the total RH refining time to be 40-50 min/furnace, and after refining and re-pressing, not blowing argon and stirring the steel ladle and not carrying out calcium treatment;

(4) LF refining: heating molten steel when the molten steel enters a station, adding lime into the molten steel, adding 2.2-3.6 kg of lime into the lime per ton of steel, and adding bauxite according to the requirement;

(5) continuous casting: the molten steel on the continuous casting platform is calmed for more than or equal to 5min, the continuous casting pouring period is controlled according to 43min, a tundish sample is taken after pouring is started for 10min, and simultaneously the oxygen content in the molten steel is monitored; controlling the temperature of the tundish molten steel at 1549-1563 ℃; and argon is blown by a stopper rod, and the flow of the argon is controlled to be less than or equal to 3L/min.

Further, the chemical components of the ultralow-aluminum extremely-low-sulfur non-oriented silicon steel are as follows by weight percent: c is less than or equal to 0.005%, Si: 0.35-1.20%, Mn: 0.15% -0.55%, P: 0.02-0.06 percent, less than or equal to 0.005 percent of S, less than or equal to 0.005 percent of Als, and the balance of Fe and inevitable impurities.

Further, in the step (2), the slag discharging amount is strictly controlled during converter tapping, and refined lime, a thick slag agent and low-carbon ferromanganese are added during tapping; controlling the argon blowing flow to be 10-15 Nm in the tapping process³And h, after tapping, adding a slag surface deoxidizing agent into the steel ladle to adjust slag, wherein the adding amount of the slag surface deoxidizing agent is 60-120 Kg per furnace.

Further, in the step (3), after RH decarburization is finished, adding a proper amount of metal aluminum pills, micro-carbon ferrosilicon and metal manganese for deoxidation alloying, wherein the cycle time is not less than 3min after the alloying is finished.

Further, in the step (4), a reducing agent is manually added into the steel ladle in the temperature rising process; the flow of the argon blowing flow of the ladle in the whole LF refining process is controlled to be 10-15 Nm³H; before the molten steel is refined in LF, no calcium treatment is carried out, and the soft argon blowing time is more than or equal to 5 min.

Further, in the step (5), the tundish uses a carbon-free heat preservation agent, and the crystallizer uses non-oriented silicon steel special-purpose covering slag.

The invention has the beneficial effects that:

by adopting the smelting method, the sulfur content of molten iron after being removed can be properly relaxed, the tapping temperature of the converter can be properly reduced, the RH process does not need to adopt an OB method for heating, RH top lance powder injection or synthetic slag addition for desulfurization, and the LF only needs to realize component fine adjustment, temperature adjustment, furnace balance rhythm and proper desulfurization.

The smelting method has the advantages of smooth production process, easy control of rhythm, accurate control of components, good castability of molten steel, complete control of product quality and the like, fully utilizes and exerts the advantages of all working procedures, avoids the completion of all smelting tasks in a certain working procedure, is easy to cause production interruption once an accident occurs, and has difficulty in ensuring the product quality.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

A smelting method of ultra-low aluminum electrode low-sulfur non-oriented silicon steel comprises the following chemical components in percentage by weight: c is less than or equal to 0.005%, Si: 0.35-1.20%, Mn: 0.15% -0.55%, P: 0.02-0.06 percent, less than or equal to 0.005 percent of S, less than or equal to 0.005 percent of Als, and the balance of Fe and inevitable impurities; the method comprises the following implementation steps:

(1) KR molten iron pretreatment: controlling the temperature of molten iron to a KR desulfurization station to be more than or equal to 1320 ℃, controlling the S of molten iron desulfurization to be less than or equal to 0.010 percent, and controlling the bright surface of an iron ladle to be more than or equal to 95 percent;

(2) and (3) smelting by using a BOF combined blown converter: a210-ton converter is adopted, and the end point temperature of the converter is controlled as follows: 1635-1660 ℃, and controlling the chemical components of the molten iron to have a weight end point C element content of less than or equal to 0.05% and an oxygen content of 500-850 ppm; the slag discharge amount of converter tapping is strictly controlled, and refined lime, a thick slag agent and low-carbon ferromanganese are added in the tapping process; the argon blowing flow rate is controlled to be 10 to15Nm³And h, after tapping, adding a slag surface deoxidizing agent into the steel ladle to adjust slag, wherein the adding amount of the slag surface deoxidizing agent is 60-120 Kg per furnace.

(3) And (3) refining in an RH vacuum furnace: controlling the inbound oxygen content to be 300-700 ppm; controlling the ultimate vacuum degree to be less than or equal to 273Pa in the refining process, controlling the net circulation time of the molten steel to be 6-10 min under the ultimate vacuum degree, controlling the total RH refining time to be 40-50 min/furnace, and after refining and re-pressing, not blowing argon and stirring the steel ladle and not carrying out calcium treatment; after RH decarburization is finished, adding a proper amount of metal aluminum pills, micro-carbon ferrosilicon and metal manganese for deoxidation alloying, and after the alloy is added, the cycle time is not less than 3 min.

(4) LF refining: heating molten steel when the molten steel enters a station, adding lime into the molten steel, adding 2.2-3.6 kg of lime into the lime per ton of steel, and adding bauxite according to the requirement; in the temperature rising process, a reducing agent is manually added into the steel ladle; controlling the flow rate of ladle argon blowing in the whole LF refining process to be 10-15 Nm 3/h; before the molten steel is refined in LF, no calcium treatment is carried out, and the soft argon blowing time is more than or equal to 5 min.

(5) Continuous casting: the molten steel on the continuous casting platform is calmed for more than or equal to 5min, the continuous casting pouring period is controlled according to 43min, a tundish sample is taken after pouring is started for 10min, and simultaneously the oxygen content in the molten steel is monitored; controlling the temperature of the tundish molten steel at 1549-1563 ℃; argon is blown by a stopper rod, and the flow of the argon is controlled to be less than or equal to 3L/min; the tundish uses a carbon-free heat preservation agent, and the crystallizer uses non-oriented silicon steel special-purpose covering slag.

In the present example, the process was carried out three times with the furnace numbers 1, 2 and 3 according to the above method, and the process control parameters are shown in tables 1 to 12.

Wherein, KR molten iron pretreatment is controlled as shown in Table 1:

TABLE 1 molten iron composition, temperature and charging of iron and steel materials

Wherein, BOF combined blown converter smelting is controlled according to the following table 2-4:

TABLE 2 converter smelting Process control parameters

TABLE 3 converter slag charge and steel tapping alloying (Kg/t steel)

TABLE 4 CAS composition and oxygen determination (%)

Wherein, RH vacuum furnace refining is controlled according to the following table 5-8:

TABLE 5 RH Process parameter control

TABLE 6RH Process molten Steel oxygen content Change (ppm)

TABLE 7 RH alloy consumption (Kg/furnace)

Furnace number	Amount of aluminum supplement	Manganese metal	Silicon iron
				1	46	319	1500
2	48	300	1623
				3	80	159	1500

TABLE 8 composition change of molten steel in RH Process

Wherein the LF refining process is controlled according to the following table 9-11:

TABLE 9 LF Process parameter control case

TABLE 10 LF slag charge and alloy consumption (Kg/t steel)

TABLE 11 LF Process molten Steel composition Change (%)

The continuous casting process was controlled as per table 12:

TABLE 12 Process control parameters for continuous casting machines (230 mm. times.1270 mm)

The final product composition control results are shown in table 13:

TABLE 13 Final ingredients (%)

Furnace number	Carbon (C)	Silicon	Manganese oxide	Phosphorus (P)	Sulfur	Als
							1	0.0033	0.56	0.26	0.025	0.0056	0.005
2	0.0035	0.54	0.33	0.022	0.0049	0.004
							3	0.0026	0.60	0.35	0.030	0.0060	0.005

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.