阅读说明：本技术 一种改质重轨钢复合夹杂物的控制方法 (Control method for modified heavy rail steel composite inclusions ) 是由 谌智勇 刘南 翁举 王文义 高博 杨乐 高勇 于 2020-05-12 设计创作，主要内容包括：本发明公开了一种改质重轨钢复合夹杂物的控制方法,包括：采用稀土铈铁合金对夹杂物进行变质处理,铈铁合金按质量百分比Ce:10-30％,O％≤0.005％；在保持原生产工艺的基础上,采用稀土铈铁合金在LF离位前加入,Ce加入量0.03-0.05kg/t；3)加入前要求钢液O％≤0.002％、S％≤0.02％；加入过程中调节钢包吹氩流量,将钢包表面渣面吹开直径小于500mm的范围；将夹杂空脱气工艺按照原有工艺进行,VD后软吹要求≥20min；软吹后上铸机浇注。本发明的目的是克服重轨钢VD真空脱气的工艺下所形成的多相复合夹杂物不易去除的问题。(The invention discloses a control method for modifying composite inclusions of heavy rail steel, which comprises the following steps: modifying the impurities by adopting rare earth cerium-iron alloy, wherein the cerium-iron alloy comprises, by mass, 10-30% of Ce and less than or equal to 0.005% of O; on the basis of keeping the original production process, rare earth cerium-iron alloy is added before LF dislocation, and the addition amount of Ce is 0.03-0.05 kg/t; 3) before adding, the O percent of the molten steel is required to be less than or equal to 0.002 percent, and the S percent is required to be less than or equal to 0.02 percent; adjusting the flow rate of argon blowing of the steel ladle in the adding process, and blowing off the slag surface on the surface of the steel ladle within the range of less than 500mm in diameter; degassing the inclusion air according to the original process, wherein the soft blowing requirement after VD is more than or equal to 20 min; and pouring in a casting machine after soft blowing. The invention aims to solve the problem that multiphase composite inclusions formed under the heavy rail steel VD vacuum degassing process are not easy to remove.)

1. A control method for modifying composite inclusions in heavy rail steel is characterized by comprising the following steps: the method comprises the following steps:

1) modifying the impurities by adopting rare earth cerium-iron alloy, wherein the cerium-iron alloy comprises, by mass, 10-30% of Ce and less than or equal to 0.005% of O;

2) on the basis of keeping the original production process, rare earth cerium-iron alloy is added before LF dislocation, and the addition amount of Ce is 0.03-0.05 kg/t;

3) the adding method comprises the following steps: before adding, the O percent of the molten steel is required to be less than or equal to 0.002 percent, and the S percent is required to be less than or equal to 0.02 percent; adjusting the flow rate of argon blowing of the steel ladle in the adding process, and blowing off the slag surface on the surface of the steel ladle within the range of less than 500mm in diameter;

4) subsequent VD deep vacuum

Degassing the inclusion air according to the original process, wherein the soft blowing requirement after VD is more than or equal to 20 min; and pouring in a casting machine after soft blowing.

2. The method of controlling a modified heavy rail steel composite inclusion according to claim 1, wherein: the converter adopts a double-slag method 'high-tension blowing-in' process, silicon, calcium and barium are used for deoxidation, the deoxidation strength is 3 kg/ton steel, the terminal C% is controlled to be more than or equal to 0.010%, the P% is controlled to be less than or equal to 0.020%, and the tapping temperature is 1620-.

3. The method of controlling a modified heavy rail steel composite inclusion according to claim 1, wherein: and 3), after the argon is added, adjusting the argon blowing of the steel ladle to the soft blowing flow rate, avoiding the contact of the molten steel and the air, and keeping the temperature for 10 min.

4. The method of controlling a modified heavy rail steel composite inclusion according to claim 1, wherein: and 3) rapidly adding the sealed and stored rare earth cerium-iron alloy to avoid contact reaction between the rare earth alloy and the slag.

Technical Field

The invention relates to the technical field of steel-making refining processes, in particular to a control method for modified heavy rail steel composite inclusions.

Background

The precondition of realizing high speed and heavy load of the railway is the service life of the steel rail, and the cleanliness of the steel rail is one of the main factors influencing the service life of the steel rail. The technical conditions of TB/T3276-2011 'high-speed railway steel rail' require that the class A of the inclusions is less than or equal to 2.0, the class B of the inclusions is less than or equal to 1.0, the class C of the inclusions is less than or equal to 1.0, and the class D of the inclusions is less than or equal to 1.0. The domestic steel rail production plants all adopt an aluminum-free deoxidation process for production, and the process flow is as follows: BOF converter, LF refining, VD or RH vacuum degassing, CC bloom casting machine. The VD vacuum degassing process is adopted, and because the steel slag fully reacts under the VD vacuum condition, the inclusion is a multiphase composite inclusion, the type of inclusion has low melting point and large size, is liquid at high temperature, is not easy to remove, is easy to aggregate and grow at the center of a casting blank, finally causes the defects of inclusion, looseness, segregation and the like of the rail web of the steel rail, and obviously influences the service performance of the steel rail.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a control method for modifying heavy rail steel composite inclusions, which solves the problem that multiphase composite inclusions formed in the heavy rail steel are difficult to remove in a VD (vacuum degassing) process.

In order to solve the technical problems, the invention adopts the following technical scheme:

a control method for modifying composite inclusions in heavy rail steel comprises the following steps:

1) modifying the impurities by adopting rare earth cerium-iron alloy, wherein the cerium-iron alloy comprises, by mass, 10-30% of Ce and less than or equal to 0.005% of O;

2) on the basis of keeping the original production process, rare earth cerium-iron alloy is added before LF dislocation, and the addition amount of Ce is 0.03-0.05 kg/t;

3) the adding method comprises the following steps: before adding, the O percent of the molten steel is required to be less than or equal to 0.002 percent, and the S percent is required to be less than or equal to 0.02 percent; during the adding process, the argon blowing flow of the steel ladle is adjusted, the slag surface on the surface of the steel ladle is blown to a diameter smaller than 500mm, and the sealed and stored rare earth cerium iron alloy is rapidly added from the steel ladle, so that the contact reaction of the rare earth alloy and the slag is avoided;

4) subsequent VD deep vacuum

Degassing the inclusion air according to the original process, wherein the soft blowing requirement after VD is more than or equal to 20 min; and pouring in a casting machine after soft blowing.

Further, in the step 1), the converter adopts a double-slag method 'high-tension combined blowing' process, silicon, calcium and barium are used for deoxidation, the deoxidation strength is 3 kg/ton steel, the end point C% is controlled to be more than or equal to 0.010%, the P% is controlled to be less than or equal to 0.020%, and the tapping temperature is 1620-.

And furthermore, in the step 3), the argon blowing of the steel ladle is adjusted to the soft blowing flow after the argon blowing is added, so that the contact between the molten steel and air is avoided, and the molten steel is kept for 10 min.

Compared with the prior art, the invention has the beneficial technical effects that:

1) the number density and the area fraction of the inclusions are reduced by more than 85% by the implementation of the method;

2) the method quantifies the key technical requirements, so the method is easy to popularize and implement and can ensure the implementation effect;

3) the method can be popularized and applied to the removal of the composite inclusion of the aluminum-free deoxidized steel.

Detailed Description

Case 1:

in the embodiment, the method is used for producing the 3-furnace high-strength steel rail U20MN2 SICRIMO in a 150-ton converter, and the chemical components are shown in Table 1.

TABLE 1U 20MN2 SICRIMO chemical composition/%

The production process route is as follows: KR molten iron pretreatment desulfurization, top and bottom combined blown converter, LF refining, VD refining and large square billet continuous casting with the diameter of 280 multiplied by 380 mm.

Wherein:

the rare earth alloy is cerium-iron alloy, 10% of Ce and 10% of O: 0.0034%;

the adding amount of the cerium-iron alloy is 45 kg/furnace, and the adding amount is 0.03kg/t in terms of Ce%;

the molten iron is pretreated by KR molten iron, and the components and temperature control conditions before entering the furnace are shown in the following table 2:

TABLE 2

The converter adopts a double-slag method 'high-tension reblowing' process, silicon, calcium and barium are used for deoxidation, the deoxidation strength is 3 kg/ton steel, the control terminal point C% is more than or equal to 0.010%, the P% is less than or equal to 0.020%, the tapping temperature is 1620-1650 ℃, and the actual control conditions are shown in the following table 3:

TABLE 3

Thereafter, the steel is subjected to LF refining treatment to adjust the temperature and composition of molten steel, thereby adjusting the physical properties of slag. The silicon-calcium-barium reduced slag is used, the viscosity and the color of the white slag are observed through dipping a slag sample to form 'white slag', the deoxidation strength is 1 kg/ton steel, and the oxygen activity of the molten steel is further reduced through diffusion deoxidation. Adding rare earth before LF dislocation, detecting the oxygen activity of molten steel by using an oxygen determinator before adding, sampling and detecting molten steel components, wherein the actual conditions are shown in the following table 4:

TABLE 3

And hoisting the sealed rare earth alloy by using a crane, adjusting the argon blowing flow of the steel ladle, blowing the slag surface on the surface of the steel ladle to a range with the diameter less than 500mm, and quickly adding the sealed rare earth cerium-iron alloy to avoid the contact reaction of the rare earth alloy and the slag. After the addition, the argon blowing of the steel ladle is adjusted to the soft blowing flow rate, so that the contact of the molten steel and the air is avoided, and the operation is kept for 10 min.

Thereafter, the VD processing is performed. The treatment process is shown in table 5 below:

TABLE 5

After VD vacuum treatment, soft blowing is carried out for more than 20min in order to promote floating of inclusions.

And then pouring by using a casting machine.

By implementing the method, the inspection indexes of the produced 3-furnace steel inclusion are shown in the following table 6:

TABLE 6

As can be seen from the above table, the number density of inclusions is from 44.22/mm²Reduced to 4.65 pieces/mm²The area fraction of the inclusions is sharply reduced from 119.43 × 10-6 to 16.03 × 10-6, and is reduced by 86.6 percent.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.