CN110218841B - Method for producing ultra-low phosphorus steel by converter - Google Patents
Method for producing ultra-low phosphorus steel by converter Download PDFInfo
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- CN110218841B CN110218841B CN201910568664.0A CN201910568664A CN110218841B CN 110218841 B CN110218841 B CN 110218841B CN 201910568664 A CN201910568664 A CN 201910568664A CN 110218841 B CN110218841 B CN 110218841B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
- C21C5/32—Blowing from above
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
Abstract
The invention discloses a method for producing ultra-low phosphorus steel by a converter, belongs to the field of steel, and particularly relates to a method for producing ultra-low phosphorus steel by adopting a nitrogen stirring process at the last stage of blowing of a 120-ton converter, which comprises the following process flow design: the oxygen converting process of the converter adopts a single slag method for dephosphorization, gas medium is switched into nitrogen after a gun is lifted at the end point, the nitrogen is inserted into molten steel for stirring, slagging is carried out during the stirring process, slag is poured out for tapping, and the phosphorus content at the end point of the converter tapping is less than or equal to 0.005 percent.
Description
Technical Field
The invention belongs to the field of pretreatment of molten iron in ferrous metallurgy, and particularly relates to a process method for smelting ultra-low phosphorus steel by adopting nitrogen stirring and deep dephosphorization on the basis of producing low phosphorus steel.
Background
For most steels, phosphorus is a fairly harmful element in the steel, the lower the requirement the better. The oxygen converter has the main function of dephosphorization, and the reaction formula of the converter dephosphorization is as follows:
2[P]+5(FeO)+3(CaO)＝(3CaO·P205)+5[Fe] (1)
Lg((P)％/[P]％)＝22350/T-24.0+7lg(CaO)％+2.5lg(FeO)％ (2)
from the analysis of the formula (2), it is found that the lower the bath temperature, the higher the content of (FeO) and (CaO) in the slag, the higher the distribution ratio of P (P)%/[ P ])% is, and the more favorable the thermodynamic and kinetic conditions for dephosphorization are.
At present, the main methods for producing converter low-phosphorus steel at home and abroad comprise converter blowing dephosphorization, double-slag dephosphorization and double-slag dephosphorization. The double-slag method improves the effect of blowing dephosphorization in the early stage, the dephosphorization slag is poured out of the converter after the blowing in the early stage, the phosphorus content of the whole converter system is reduced, and further dephosphorization is carried out in the later stage of decarburization blowing to achieve the aim of producing low-phosphorus steel; the duplex method adopts two oxygen lances of dephosphorization and decarburization, and molten steel dephosphorized by a first converter is added into a second converter for decarburization.
The oxygen converting converter has the measures of improving the early dephosphorization efficiency, improving the oxidability of slag, reducing the tapping temperature and the like, the domestic converter adopts a duplex method, a double slag method and the like to control the tapping phosphorus within 0.005 percent, adopts a single slag method to stably control the tapping phosphorus within 0.015 percent, and has larger difficulty in controlling the tapping phosphorus below 0.005 percent.
Disclosure of Invention
Based on the defects of the prior art, the invention aims to provide a method for producing ultra-low phosphorus steel by adopting a nitrogen stirring process in the final stage of converter single-slag blowing, wherein the phosphorus discharged from a converter is stably controlled within 0.005%.
In order to solve the technical problem, the invention provides a method for producing ultra-low phosphorus steel by a converter, which is characterized in that on the basis that the P content of oxygen converting tapping is less than or equal to 0.010 percent, a nitrogen stirring process is added, deep dephosphorization is continued, and the P content of tapping is reduced to be less than or equal to 0.005 percent.
Preferably, the method for producing ultra-low phosphorus steel by using the converter further comprises part or all of the following technical characteristics:
as an improvement of the above technical solution, the method comprises the steps of:
firstly, adopting a single slag method for blowing in a converter;
secondly, pouring off the slag at the end point of oxygen converting, measuring the temperature, and switching a gas medium into nitrogen;
the third step, the oxygen lance is lowered to the blowing point, the nitrogen flow rate is 20000-3Stirring at the gun position of 130 +/-50 cm, synchronously adding iron sheets according to the temperature measured by slag pouring in the second step, and adjusting the temperature, the oxidability and the alkalinity of molten slag according to the light burning addition amount;
and fourthly, pouring slag again, finishing the slag blocking work of the steel tapping hole at the end point, and splashing slag to protect the furnace.
And (5) slag splashing and furnace protection. Reducing the slag discharging probability in the tapping process and stabilizing the rephosphorization value. During nitrogen stirring, because slag has strong oxidizability, the slag is seriously washed and eroded on the converter lining, and in order to ensure the continuity of smelting the ultra-low phosphorus steel, a slag splashing furnace protection method is required to be adopted, and the furnace protection effect is improved by adding magnesium balls, adjusting the slag splashing gun position and flow, hanging slag on the furnace wall and the like.
As an improvement of the technical scheme, in the first step, the alkalinity of the slag is controlled to be more than or equal to 3.0, the tapping temperature is controlled to be less than or equal to 1640 ℃, the content of P in the molten steel is controlled to be less than or equal to 0.010 percent, and the content of C in the molten steel is controlled to be less than or equal to 0.07 percent.
As an improvement of the technical scheme, in the first step, dephosphorization is carried out by adopting a single slag method, lime is added in the blowing process for 40-60 kg/ton steel, 15-25 kg/ton steel, 10-30 kg/ton steel of ore or iron sheet are lightly burned, and the flow of an oxygen lance is 18000-23000Nm3/h。
The early-stage slagging adopts high-lance-position large oxygen amount to increase the stirring strength of a molten pool, and the cooling material is added to reduce the temperature of the molten pool and improve the oxidability, based on the activity of slag. The oxygen flow is reduced to 18000-20000Nm in the middle period3And h, adjusting the lance position of the oxygen lance according to the slag, reducing the lance position to 1.6-2.0m when the furnace mouth is active, increasing the lance position to 2.0-2.2m when the dry-back phenomenon appears, and adding a small amount of lime and ore to assist in slag regulation. The pressure in the later stage of the converting is reduced to 1.4-1.6m, the oxygen flow is 22000-3H is used as the reference value. The converter temperature is targeted 1640, the carbon content is less than or equal to 0.07 percent, and the phosphorus content is less than or equal to 0.010 percent.
As an improvement of the technical scheme, in the second step, the dephosphorization residues in the oxygen converting stage are removed as much as possible, and the deslagging process is subject to the condition that molten steel does not flow out.
As an improvement of the technical scheme, in the second step, the temperature obtained by measuring the temperature is T1, the higher the temperature T1 is, the longer the stirring time in the third step is, and the adding amount of the light burning and the iron sheet is controlled to be lower than 1620 ℃.
And step two, pouring the end slag and measuring the temperature. The method aims to pour the dephosphorized slag in the oxygen converting stage as much as possible, and the slag pouring process is based on that the molten steel does not flow out. If the oxidability of the slag is high and the deslagging amount is small, adding 100-200kg of light burning, and deslagging again after deslagging. The purpose of temperature measurement is to control the addition of light burning and iron sheet in the nitrogen stirring stage, so that the temperature is lower than 1620 ℃.
As an improvement of the technical scheme, the third step is carried out again for slagging, the stirring time is 1-3min, and the tapping temperature is less than or equal to 1620 ℃.
Creates strong oxidizing property, low temperature, high alkalinity and strong stirring condition for dephosphorization, and takes the FeO content of the slag of more than or equal to 15 percent, the alkalinity of more than 2.0 and the temperature T of less than or equal to 1620 ℃ as the standard. Adding 2-5kg of iron sheet per ton of steel, 2-5kg of light burned steel and 3-7kg of lime per ton of steel, according to the dephosphorization theory, in the present stage, the lower the temperature is, the higher the dephosphorization efficiency is, i.e. the larger the temperature drop during nitrogen stirring is, the better the nitrogen flow rate is, 20000-rich 30000Nm3The stirring time slightly fluctuates according to the temperature T1, and the higher the temperature T1, the longer the stirring time. In order to ensure smooth production and reduce the heating time of the LF furnace, the stirring time is preferably less than or equal to 3min
As an improvement of the technical scheme, in the third step, the FeO content of the slag is more than or equal to 15 percent, the alkalinity is more than 2.0, and the T is less than or equal to 1620 ℃.
As an improvement of the technical scheme, in the third step, 2-5kg of iron sheet per ton of steel, 2-5kg of light burned steel and 3-7kg of lime per ton of steel are added according to the temperature measured by deslagging in the second step
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1) the phosphorus tapping of the converter is stably controlled within 0.005 percent.
2) Compared with the prior converter 'point blowing' process, the 'nitrogen stirring' process is adopted to reduce the oxidability of molten steel, but is not suitable for low-nitrogen steel grades.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the contents of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following detailed description is given in conjunction with the preferred embodiments.
Detailed Description
Other aspects, features and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.
Examples
The technical scheme of the invention is implemented in a certain steel mill, and the 14-furnace ultra-low phosphorus steel is produced according to the process, and the process comprises converter blowing, deslagging, slag mixing, nitrogen stirring, deslagging and steel tapping. The specific process control comprises four steps:
firstly, adopting a single slag method for blowing in a converter;
secondly, pouring off the slag at the end point of oxygen converting, measuring the temperature, and switching a gas medium into nitrogen;
the third step, the oxygen lance is lowered to the blowing point, the nitrogen flow rate is 20000-3Stirring at the gun position of 130 +/-50 cm, synchronously adding iron sheets according to the temperature measured by slag pouring in the second step, and adjusting the temperature, the oxidability and the alkalinity of molten slag according to the light burning addition amount;
and fourthly, pouring slag again, finishing the slag blocking work of the steel tapping hole at the end point, and splashing slag to protect the furnace.
The detailed process parameters of each step are shown in the table below.
TABLE 1 Process parameters and test values
In the embodiment, the process is implemented, and the proportion of the phosphorus at the end point of the converter is less than or equal to 0.005 percent and reaches 85.7 percent.
The invention discloses a method for producing ultra-low phosphorus steel by a converter, belongs to the field of steel, and particularly relates to a method for producing ultra-low phosphorus steel by adopting a nitrogen stirring process at the last stage of blowing of a 120-ton converter, which comprises the following process flow design: the oxygen converting process of the converter adopts a single slag method for dephosphorization, gas medium is switched into nitrogen after a gun is lifted at the end point, the nitrogen is inserted into molten steel for stirring, slagging is carried out during the stirring process, slag is poured out for tapping, and the phosphorus content at the end point of the converter tapping is less than or equal to 0.005 percent.
The raw materials listed in the invention, the upper and lower limits and interval values of the raw materials of the invention, and the upper and lower limits and interval values of the process parameters (such as temperature, time and the like) can all realize the invention, and the examples are not listed.
While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (8)
1. A method for producing ultra-low phosphorus steel by a converter is characterized by comprising the following steps: on the basis that P in oxygen converting tapping is less than or equal to 0.010 percent, a nitrogen stirring process is added, deep dephosphorization is continued, and the phosphorus in tapping is reduced to be less than or equal to 0.005 percent; the method comprises the following steps:
firstly, adopting a single slag method for blowing in a converter;
secondly, pouring off the slag at the end point of oxygen converting, measuring the temperature, and switching a gas medium into nitrogen;
the third step, the oxygen lance is lowered to the blowing point, the nitrogen flow rate is 20000-3Stirring at the gun position of 130 +/-50 cm, synchronously adding iron sheet according to the temperature measured by slag pouring in the second step, regulating the temperature by light burning, and regulating the oxidability and alkalinity of molten slag;
and fourthly, pouring slag again, finishing the slag blocking work of the steel tapping hole at the end point, and splashing slag to protect the furnace.
2. A method for producing ultra-low phosphorous steel in a converter as claimed in claim 1, wherein: in the first step, the alkalinity of the slag is controlled to be more than or equal to 3.0, the tapping temperature is controlled to be less than or equal to 1640 ℃, the content of P in the molten steel is controlled to be less than or equal to 0.010 percent, and the content of C in the molten steel is controlled to be less than or equal to 0.07 percent.
3. A method for producing ultra-low phosphorous steel in a converter as claimed in claim 1, wherein: in the first step, dephosphorization is carried out by adopting a single slag method, lime is added in the blowing process at 40-60 kg/ton steel, light burning is carried out at 15-25 kg/ton steel, ore or iron sheet is added in the blowing process at 10-30 kg/ton steel, and the flow of an oxygen lance is 18000-23000Nm3/h。
4. A method for producing ultra-low phosphorous steel in a converter as claimed in claim 1, wherein: in the second step, the dephosphorization slag in the oxygen converting stage is removed as much as possible, and the deslagging process is subject to the condition that the molten steel does not flow out.
5. A method for producing ultra-low phosphorous steel in a converter as claimed in claim 1, wherein: in the second step, the temperature obtained by temperature measurement is T1，T1The higher the temperature is, the longer the stirring time in the third step is, and the adding amount of the light burning and the iron sheet is controlled to ensure that the temperature is less than or equal to 1620 ℃.
6. A method for producing ultra-low phosphorous steel in a converter as claimed in claim 1, wherein: and in the third step, slagging is carried out again, the stirring time is 1-3min, and the tapping temperature is less than or equal to 1620 ℃.
7. A method for producing ultra-low phosphorous steel in a converter as claimed in claim 1, wherein: in the third step, the FeO content of the slag is more than or equal to 15 percent, the alkalinity is more than 2.0, and the T is less than or equal to 1620 ℃.
8. A method for producing ultra-low phosphorous steel in a converter as claimed in claim 1, wherein: in the third step, 2-5kg of iron sheet per ton of steel, 2-5kg of light burning per ton of steel and 3-7kg of lime per ton of steel are added according to the temperature measured by deslagging in the second step.
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| CN201910568664.0A CN110218841B (en) | 2019-06-27 | 2019-06-27 | Method for producing ultra-low phosphorus steel by converter |
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| CN201910568664.0A CN110218841B (en) | 2019-06-27 | 2019-06-27 | Method for producing ultra-low phosphorus steel by converter |
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| CN110218841B true CN110218841B (en) | 2021-07-30 |
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| CN112342340A (en) * | 2020-10-14 | 2021-02-09 | 石横特钢集团有限公司 | Nitrogen supplementary blowing dephosphorization process for converter |
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| US6500224B1 (en) * | 2001-10-11 | 2002-12-31 | Bethlehem Steel Corporation | Method for operating a steelmaking furnace during a steelmaking process |
| CN102220448A (en) * | 2011-06-02 | 2011-10-19 | 首钢总公司 | Method for smelting uniform end-point molten steel composition with converter |
| CN102925629A (en) * | 2012-11-12 | 2013-02-13 | 武汉钢铁(集团)公司 | Induction furnace dephosphorization method adopting top and bottom blowing |
| CN104928432A (en) * | 2015-06-11 | 2015-09-23 | 江苏永钢集团有限公司 | Method for removing phosphorus in converter through blowing nitrogen |
| CN105950816A (en) * | 2016-05-25 | 2016-09-21 | 河北钢铁股份有限公司承德分公司 | Combined blowing dephosphorization method of converter |
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