CN110592325B

CN110592325B - RH deep decarburization method of molten steel

Info

Publication number: CN110592325B
Application number: CN201911045003.6A
Authority: CN
Inventors: 李龙; 王建
Original assignee: Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
Current assignee: Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
Priority date: 2019-10-30
Filing date: 2019-10-30
Publication date: 2021-06-22
Anticipated expiration: 2039-10-30
Also published as: CN110592325A

Abstract

The invention discloses steelA method for RH deep decarburization of water, comprising the steps of: a1) CO supply is arranged on RH vacuum treatment equipment₂-an argon blowing tube of Ar gas mixture; a2) inserting RH vacuum treatment equipment into a ladle filled with molten steel, starting a vacuum pump to ensure that the vacuum of the RH vacuum treatment equipment is pumped to be less than a first pressure, and starting blowing CO₂-Ar gas mixture circulating molten steel; a3) the vacuum pump makes the RH vacuum processing equipment vacuumized to be less than the second pressure, and then the CO supply is stopped₂-Ar mixed gas and the argon blowing tube starts supplying the first gas so that molten steel circulates; a4) and when the vacuum of the RH vacuum processing equipment is pumped to be lower than the third pressure by the vacuum pump, continuously supplying the first gas for 4-6 min. The RH deep decarburization method of the molten steel can realize the end point carbon content of 13-17ppm or 12-14ppm when the gas is sprayed by the oxygen-free gun, and the smelting time is shortened by 2-3 min.

Description

RH deep decarburization method of molten steel

Technical Field

The present invention relates to the field of metallurgy, and more particularly, to a method of RH deep decarburization of molten steel.

Background

In recent years, RH vacuum degassing equipment, and RH functions and steel types for refining have been expanded, and a multifunctional vacuum refining technology has been developed, and has been dominant in external refining. Most steel mills are provided with RH refining equipment, so that the high-efficiency and low-cost production of high-quality steel is realized.

Along with the requirement of the market on the carbon content of various steels, particularly the carbon content of finished products is within 15ppm or even 10ppm, in order to meet the requirement, RH adopts oxygen blowing to perform forced decarburization, the oxygen supply time needs to be prolonged, so that the oxygen activity of molten steel is higher, and the cleanliness of the molten steel is not favorable.

In the prior art, through holes are arranged on the lower pipe wall of an RH ascending/descending pipe, and CO is blown into molten steel through a spray pipe during RH refining₂Blowing CaCO into molten steel by using gas, or gas of nitrogen, argon, carbon dioxide or carbon monoxide as carrier₃、BaCO₃、MgCO₃、NaCO₃、FeO、Fe₂O₃Or one or more than one powder in MnO, the decarburization reaction efficiency is promoted, and the carbon content in the molten steel is further reduced. The adoption of blowing/adding of oxidizing powder can easily cause larger temperature drop of molten steel, and on the other hand, the change of top slag composition can influence the cleanliness of molten steel.

In the prior art, a heating agent (metal Al/Si) is added in the vacuum decarburization process, and oxygen is supplied by a top lance to heat molten steel and accelerate the decarburization speed. However, this increases the Al/Si consumption, which is not good for reducing the production cost.

Therefore, there is still a need for a method of decarburization at a low cost, quickly and efficiently.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a method for RH deep decarburization of molten steel.

Based on the purpose, the following technical scheme is adopted:

according to the present invention, there is provided a method for RH deep decarburization of molten steel, comprising the steps of:

a1) CO supply is arranged on RH vacuum treatment equipment₂-an argon blowing tube of Ar gas mixture;

a2) inserting RH vacuum treatment equipment into a ladle filled with molten steel, starting a vacuum pump to ensure that the vacuum of the RH vacuum treatment equipment is pumped to be less than a first pressure, and starting blowing CO₂-Ar gas mixture circulating molten steel;

a3) the vacuum pump makes the RH vacuum processing equipment vacuumized to be less than the second pressure, and then the CO supply is stopped₂-Ar mixed gas and the argon blowing tube starts supplying the first gas so that molten steel circulates;

a4) and when the vacuum of the RH vacuum processing equipment is pumped to be lower than the third pressure by the vacuum pump, continuously supplying the first gas for 4-6 min.

Further, the first gas is Ar-H₂Mixed gas or Ar gas.

Further, Ar-H₂H in the mixed gas₂55 to 70 weight percent of Ar-H₂The air supply flow of the mixed gas is 0.7-1.2Nm³/h·t。

Further, the carbon content of the molten steel before treatment is 0.0035 to 0.045 weight percent, the oxygen content is 0.025 to 0.040 weight percent, and the temperature is 1650-1710 ℃.

Further, CO₂CO in-Ar gas mixture₂50-65 wt% of CO₂The flow rate of the-Ar mixture is 0.7-1.2Nm³/h·t。

Further, the first pressure was 17 kPa.

Further, the second pressure is 300 Pa.

Further, the second pressure is 100 Pa.

The invention has the beneficial effects that:

the RH deep decarburization method of molten steel can realize 12-14ppm of end point carbon content (the first gas is Ar-H) when the gas is injected by an oxygen-free gun₂Mixed gas) or 13-17ppm (the first gas is Ar gas), the smelting time is shortened by 2-3 min; the good decarburization effect can be achieved and the smelting time is shortened under the condition of only adopting the argon blowing pipe for air intake; and only the argon blowing pipe is used for air inlet, so that the cost is further reduced.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some implementation examples of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a schematic view of an RH vacuum processing apparatus according to embodiments 1 to 4 of the present invention;

FIG. 2 is a schematic view of an argon blowing tube according to an embodiment of the present invention;

FIG. 3 is a schematic view of the projection of the argon blowing tube and the rising pipe to the horizontal plane according to the embodiment of the present invention.

List of reference numerals

1-steel ladle 2-vacuum degassing tank 3-tank body 4-downcomer 5-riser 8-argon blowing pipe 81-main pipe 82-first branch pipe 83-second branch pipe

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention are described in further detail with reference to the accompanying drawings.

Examples 1 to 4 the RH vacuum processing apparatus used in examples 1 to 4 is shown in fig. 1, 2 and 3 and includes:

the device comprises a steel ladle 1, a vacuum degassing tank 2 inserted into the steel ladle 1, an argon blowing pipe 8 and an air exhaust through hole for vacuumizing the vacuum degassing tank 2;

the vacuum degassing tank 2 comprises a tank body 3, a downcomer 4 and an ascending pipe 5, wherein the downcomer 4 and the ascending pipe 5 are arranged at the bottom of the tank body 3 and are communicated with the tank body 3; the downcomer 4 and the riser 5 are arranged side by side.

The argon blowing pipe 8 is arranged on the ascending pipe 5 and is communicated with the ascending pipe 5;

wherein, the argon blowing pipe 8 comprises a main pipe 81, a first branch pipe 82 and a second branch pipe 83 which are divided into two paths at the tail end of the main pipe 81; the first branch pipe 82 and the second branch pipe 83 communicate with the rising pipe 5. The first branch pipe 82 and the second branch pipe 83 are arranged offset, and the second branch pipe 83 is located below the first branch pipe 82. In the projection shown in fig. 3, the angle R between the first branch pipe 82 and the second branch pipe 83 is 10-25 degrees, and the angle R is the angle formed by the connection line of the first branch pipe 82 and the second branch pipe 83 with the center O of the rising pipe 5. As shown in the schematic view of the argon blowing tube shown in fig. 2, a horizontal direction (indicated by an arrow) is defined, and the second branch tube 82 is inclined downward at an angle of 5 to 15 degrees from the horizontal direction. Therefore, gas blown out of the argon blowing pipe 8 is disturbed from the bottom end of the ascending pipe 5, so that the disturbance of the gas on the molten steel is more sufficient, and the second branch pipe 82 is inclined downwards at an angle of only 5-15 degrees from the horizontal direction, so that the gas cannot be excessively blown downwards, and the disturbance strength is ensured.

The second branch pipe is arranged at one quarter of the distance from the bottom end of the ascending pipe.

The argon blowing pipe 8 is a stainless steel pipe.

Example 1

The molten steel to be treated meets the following requirements: the carbon content is 0.035 to 0.045 weight percent, the oxygen content is 0.025 to 0.040 weight percent, and the temperature is 1650 and 1710 ℃.

When the ladle is placed at the RH treatment station, the dip pipe is inserted into the molten steel of the ladle, and the vacuum pump is started to pump air. When the pressure in the vacuum degassing tank is less than 17kPa, CO is supplied through the argon blowing pipe₂The mixed gas of-Ar is used as circulating gas and reaction medium, and CO is contained in the mixed gas₂65wt% of the content and 0.7Nm of the strength of gas supply³T, using CO at high temperature₂Weak oxidation of the gas, reaction occurs: c + CO ₂2 CO. On the one hand, direct decarbonization of CO₂Reduction of CO partial pressure by the mixed gas of-Ar to promote the reactionThe process is carried out. On the other hand, twice of CO is generated, and the circulation flow is increased to accelerate the decarburization. When the pressure in the vacuum degassing tank is less than 300Pa, the operation is switched to Ar gas drive, and the gas supply intensity is 1.2Nm³H.t. The pressure in the vacuum degassing tank is less than 100Pa for further decarburization for 4 min. The end point carbon content can be realized to be 17ppm, and the smelting time is shortened by 3 min.

Example 2

When the ladle is placed at the RH treatment station, the dip pipe is inserted into the molten steel of the ladle, and the vacuum pump is started to pump air. When the pressure in the vacuum degassing tank is less than 17kPa, CO is supplied through the argon blowing pipe₂The mixed gas of-Ar is used as circulating gas and reaction medium, and CO is contained in the mixed gas₂The content is 50wt%, and the gas supply intensity is 1.2Nm³T, using CO at high temperature₂Weak oxidation of the gas, reaction occurs: c + CO ₂2 CO. On the one hand, direct decarbonization of CO₂The reaction is promoted by reducing the partial pressure of CO in the Ar-mixed gas. On the other hand, twice of CO is generated, and the circulation flow is increased to accelerate the decarburization. When the pressure in the vacuum degassing tank is less than 300Pa, the operation is switched to Ar gas drive, and the gas supply intensity is 0.7Nm³H.t. And further decarbonizing for 5min under the pressure of less than 100Pa in the vacuum degassing tank. The end point carbon content can be 13ppm, and the smelting time is shortened by 2 min.

Example 3

When the ladle is placed at the RH treatment station, the dip pipe is inserted into the molten steel of the ladle, and the vacuum pump is started to pump air. When the pressure in the vacuum degassing tank is less than 17kPa, CO is supplied through the argon blowing pipe₂The mixed gas of-Ar is used as circulating gas and reaction medium, and CO is contained in the mixed gas₂The content is 50wt%, and the gas supply intensity is 1.2Nm³T, using CO at high temperature₂Weak oxidation of the gas, reaction occurs: [ C ]]+CO ₂2 CO. On the one hand, direct decarbonization of CO₂Reduction of CO partial pressure by the mixed gas of-Ar to promote the reactionThe process is carried out. On the other hand, twice of CO is generated, and the circulation flow is increased to accelerate the decarburization. When the pressure in the vacuum degassing tank is less than 300Pa, switching to Ar-H₂Driven by mixed gas, H in the mixed gas₂The content is 55wt%, and the gas supply intensity is 0.7Nm³H.t. The pressure in the vacuum degassing tank is less than 100Pa for further decarburization for 4 min. The end point carbon content can be 14ppm, and the smelting time is shortened by 3 min.

Example 4

When the ladle is placed at the RH treatment station, the dip pipe is inserted into the molten steel of the ladle, and the vacuum pump is started to pump air. When the pressure in the vacuum degassing tank is less than 17kPa, CO is supplied through the argon blowing pipe₂The mixed gas of-Ar is used as circulating gas and reaction medium, and CO is contained in the mixed gas₂The content is 60 wt%, and the gas supply intensity is 0.8Nm³T, using CO at high temperature₂Weak oxidation of the gas, reaction occurs: [ C ]]+CO ₂2 CO. On the one hand, direct decarbonization of CO₂The reaction is promoted by reducing the partial pressure of CO in the Ar-mixed gas. On the other hand, twice of CO is generated, and the circulation flow is increased to accelerate the decarburization. When the pressure in the vacuum degassing tank is less than 300Pa, switching to Ar-H₂Driven by mixed gas, H in the mixed gas₂The content is 70wt%, and the gas supply intensity is 1.2Nm³H.t. And further decarbonizing for 6min under the pressure of less than 100Pa in the vacuum degassing tank. The end point carbon content can be 12ppm, and the smelting time is shortened by 2 min.

The foregoing is an exemplary embodiment of the present disclosure, but it should be noted that various changes and modifications could be made herein without departing from the scope of the present disclosure as defined by the appended claims. Furthermore, although elements of the disclosed embodiments of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

It should be understood that, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly supports the exception. It should also be understood that "and/or" as used herein is meant to include any and all possible combinations of one or more of the associated listed items.

The numbers of the embodiments disclosed in the embodiments of the present invention are merely for description, and do not represent the merits of the embodiments.

Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, of embodiments of the invention is limited to these examples; within the idea of an embodiment of the invention, also technical features in the above embodiment or in different embodiments may be combined and there are many other variations of the different aspects of an embodiment of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of the embodiments of the present invention are intended to be included within the scope of the embodiments of the present invention.

Claims

1. A method for RH deep decarburization of molten steel is characterized by comprising the following steps:

a4) when the vacuum of the RH vacuum processing equipment is pumped to be lower than the third pressure by the vacuum pump, continuously supplying the first gas for 4-6 min;

wherein the first gas is Ar-H₂Mixed gas or Ar gas;

the argon blowing pipe comprises a main pipe, a first branch pipe and a second branch pipe, wherein the first branch pipe and the second branch pipe are divided into two paths at the tail end of the main pipe; the first branch pipe and the second branch pipe are arranged in a staggered mode, and the second branch pipe is located below the first branch pipe; the included angle between the first branch pipe and the second branch pipe is 10-25 degrees; the second branch pipe is inclined downwards by 5-15 degrees from the horizontal direction;

wherein the first pressure is 17kPa, the second pressure is 300Pa and the third pressure is 100 Pa.

2. The method for RH deep decarburization of molten steel of claim 1, wherein Ar-H₂H in the mixed gas₂55 to 70 weight percent of Ar-H₂The air supply flow of the mixed gas is 0.7-1.2Nm³/h·t。

3. The method for RH deep decarburization of a molten steel as recited in claim 1, wherein the molten steel before being treated has a carbon content of 0.0035 wt.% to 0.045 wt.%, an oxygen content of 0.025 wt.% to 0.040 wt.%, and a temperature of 1650-1710 ℃.

4. The method for RH deep decarburization of molten steel of claim 1, wherein CO is introduced into the molten steel₂CO in-Ar gas mixture₂50-65 wt% of CO₂The flow rate of the-Ar mixture is 0.7-1.2Nm³/h·t。