阅读说明：本技术 一种能缩短Consteel电炉冶炼周期的冶炼方法 (smelting method capable of shortening smelting period of Consteel electric furnace ) 是由 谈彪 袁成文 张伯影 苗红生 赵海东 尚大军 李明林 张旭 姜新岩 熊皓 曹小军 于 2019-09-28 设计创作，主要内容包括：本发明公开了一种能缩短Consteel电炉冶炼周期的冶炼方法,该方法是将冶炼过程分为化渣期、脱磷期、吹碳升温期,并且在化渣期和吹碳升温期利用不同的渣系成分对冶炼过程脱磷率进行影响,其中：化渣期温度从1300℃开始,匀速升至1520℃,当炉内温度达到1450℃时添加渣料I,使脱磷期目标渣系成分为FeO含量≤25wt％、MgO含量4～5wt％、炉渣碱度R＝2.5～3.0；脱磷期温度从1520℃开始,匀速升至1580℃,当钢样的成分满足碳＞0.35wt％、磷＜0.030wt％时进入吹碳升温期；吹碳升温期温度从1580℃开始,匀速升至1650℃,一开始即添加渣料II,使吹碳升温期目标渣系的成分为FeO含量15～20wt％、MgO含量4～5wt％、炉渣碱度R＝3.0～3.5。本发明的有益之处在于：利用不同的渣系成分对电炉冶炼过程脱磷率进行影响,从而缩短了冶炼周期。(The invention discloses a smelting method capable of shortening smelting period of a Consteel electric furnace, which comprises the following steps of dividing the smelting process into a slagging period, a dephosphorization period and a carbon blowing temperature rise period, and influencing the dephosphorization rate of the smelting process by utilizing different slag system components in the slagging period and the carbon blowing temperature rise period, wherein: the temperature in the slagging stage is increased from 1300 ℃ to 1520 ℃ at a constant speed, and when the temperature in the furnace reaches 1450 ℃, slag charge I is added, so that the components of the target slag system in the dephosphorization stage are less than or equal to 25 wt% of FeO, 4-5 wt% of MgO and 2.5-3.0 of slag alkalinity R; the temperature of the dephosphorization period is increased to 1580 ℃ from 1520 ℃ at a constant speed, and when the components of the steel sample meet the requirements that carbon is more than 0.35 wt% and phosphorus is less than 0.030 wt%, the steel sample enters a carbon blowing temperature rise period; and (3) starting the temperature of the carbon blowing temperature rise period from 1580 ℃, raising the temperature to 1650 ℃ at a constant speed, and adding the slag II at the beginning to ensure that the components of the target slag system in the carbon blowing temperature rise period comprise 15-20 wt% of FeO, 4-5 wt% of MgO and 3.0-3.5 of slag alkalinity R. The invention has the advantages that: different slag system components are utilized to influence the dephosphorization rate in the electric furnace smelting process, thereby shortening the smelting period.)

1. the utility model provides a can shorten smelting method of Consteel electric stove smelting cycle which characterized in that, divide into slagging stage, dephosphorization phase, the three stage of carbon blowing intensification phase with whole smelting process in proper order, adopt stage type accuse temperature to utilize different slag system compositions to influence the electric stove smelting process dephosphorization rate in slagging stage and carbon blowing intensification phase, wherein:

The temperature of the slagging stage is increased to 1520 ℃ from 1300 ℃ at the speed of 7-10 ℃/min, when the temperature in the furnace reaches 1450 ℃, slag I is added into the Consteel electric furnace, the slag I is composed of dolomite and lime, and the slag I is used for influencing the dephosphorization rate of the electric furnace smelting process, so that the target slag system in the dephosphorization stage comprises the following components: the FeO content is less than or equal to 25 wt%, the MgO content is 4-5 wt%, and the slag alkalinity R is 2.5-3.0;

The temperature of the dephosphorization period is increased to 1580 ℃ from 1520 ℃ at the speed of 3-4 ℃/min, when the components of the steel sample meet the requirements that the carbon is more than 0.35 wt% and the phosphorus is less than 0.030 wt%, the steel sample enters a carbon blowing heating period, otherwise, the dephosphorization operation is prolonged, and secondary dephosphorization is carried out;

The temperature of the carbon blowing temperature rise period is increased to 1650 ℃ from 1580 ℃ at the speed of 7-10 ℃/min, slag II is added into the Consteel electric furnace at the beginning of the carbon blowing temperature rise period, the slag II is also composed of dolomite and lime, the dephosphorization rate of the electric furnace smelting process is influenced by the slag II, and the components of a target slag system in the carbon blowing temperature rise period are as follows: 15-20 wt% of FeO, 4-5 wt% of MgO and 3.0-3.5 of slag alkalinity R.

2. The smelting method according to claim 1, wherein the temperature of the Consteel electric furnace is adjusted to 1600 ℃ in advance according to the tapping temperature of the upper furnace during the slagging period.

3. the smelting method according to claim 1, wherein in the slagging stage, oxygen supply modes of the 1 ^# oxygen lance and the 2 ^# oxygen lance of the Consteel electric furnace are set in advance, and oxygen is supplied to the Consteel electric furnace at an oxygen flow rate of 1500Nm ³/min to 2500Nm ³/min.

4. The smelting method capable of shortening the smelting period of the Consteel electric furnace as claimed in claim 1, wherein the mass ratio of dolomite to lime in the slag I is 8:15, 800kg of dolomite and 1500kg of lime are added to each 72 t-74 t of furnace burden, the dolomite is added in two batches, and the lime is added in three batches.

5. The method according to claim 1, wherein the oxygen supply mode of the 1 ^# lance and the 2 ^# lance of the Consteel furnace is adjusted so that the oxygen flow rate of the 1 Nm ³/min to the 800Nm ³/min is controlled to supply oxygen to the Consteel furnace during the dephosphorization period.

6. The smelting method according to claim 1, wherein in the carbon blowing temperature raising period, the oxygen supply modes of the 1 ^# lance and the 2 ^# lance of the Consteel electric furnace are adjusted so that the oxygen flows of the 1 Nm ^#/mi lance and the 2 Nm ^# lance of the Consteel electric furnace are supplied to the Consteel electric furnace at the oxygen flow rate of 800Nm ³/mi to 2000Nm ³/min.

7. The smelting method capable of shortening the smelting period of the Consteel electric furnace as claimed in claim 1, wherein the mass ratio of dolomite to lime in the slag II is 2-3: 5-10, and 200 kg-300 kg of dolomite and 500 kg-1000 kg of lime are added into every 72 t-74 t of furnace burden.

8. a smelting process according to claim 1, which is characterized in that the total content of dolomite and lime used in the two times of smelting in the slag I and slag II is controlled within the following range: the total amount of dolomite is 1000 kg-1100 kg, and the total amount of lime is 2000 kg-2500 kg.

Technical Field

The invention relates to a smelting method, in particular to a smelting method capable of shortening the smelting period of a Consteel electric furnace, and belongs to the technical field of metallurgy.

Background

at present, the smelting method adopted by the Consteel electric furnace for smelting special steel in our company is the traditional Consteel electric furnace smelting method, and the method comprises the following specific steps:

1. adding molten iron at the beginning of smelting, wherein the adding amount is 60-90% of the total loading amount;

2. After molten iron is mixed into 2/3, the oxygen lance starts to blow oxygen and raise the temperature, the flow rate is 2500Nm ³/min-3000 Nm ³/min, and slag charge adding operation is carried out after oxygen blowing is carried out for 10 min;

3. slag materials are added randomly according to the slag conditions in the furnace, 500kg of lime and 500kg of limestone are added in each batch, and the total ash amount is controlled to be 2500kg of lime and 2000kg of limestone;

4. Adding scrap steel after smelting for 15min until the adding is finished;

5. Sampling is carried out when the smelting reaches about 50min, and whether tapping operation is carried out or not is determined according to the components of molten steel.

statistics shows that when the smelting method is used for smelting special steel, the smelting period is 58min, the smelting period is long, and the main reasons are as follows:

(1) the addition of the waste steel is lagged, a large amount of oxygen is supplied in the early stage of smelting, so that the local temperature in the furnace is high, the content of FeO in slag is high, the carbon-oxygen reaction is severe, a large amount of slag in the furnace overflows from a furnace door, the slag is added and dispersed, the slag such as CaO added in the early stage does not completely form slag, the slag flows out along with the slag from the furnace door, the slag cannot follow up in the later stage, the content of FeO and SiO ₂ in the slag is low, the slag forming in the smelting process is slow, and the fluidity and the foamability of the slag are poor;

(2) in the middle stage of smelting, high temperature is generated in the furnace, thermodynamic conditions of dephosphorization cannot be met, and dephosphorization is difficult in the smelting process;

(3) When the carbon content in steel is low at the smelting end point, the molten steel is over oxidized, the FeO content in slag is higher, rephosphorization is easily generated in the molten steel at high temperature before tapping, dephosphorization operation needs to be carried out again, and the smelting period is prolonged.

The smelting period of the Consteel electric furnace is relatively long, so that the running cost of the Consteel electric furnace is increased.

in addition, at the end of smelting, when the carbon content in steel is low, the molten steel is seriously oxidized, so that the smelting cost and the operation difficulty of a subsequent refining furnace are increased.

Disclosure of Invention

In order to solve the defects of the prior art, the invention aims to provide a smelting method for smelting special steel by using a Consteel electric furnace, which can shorten the smelting period and simultaneously avoid the peroxidation of molten steel at the smelting end point.

In order to achieve the above object, the present invention adopts the following technical solutions:

the utility model provides a can shorten smelting method of Consteel electric stove smelting cycle which characterized in that, divide into slagging stage, dephosphorization phase, the three stage of carbon blowing intensification phase with whole smelting process in proper order, adopt stage type accuse temperature to utilize different slag system compositions to influence the electric stove smelting process dephosphorization rate in slagging stage and carbon blowing intensification phase, wherein:

The temperature of the slagging stage is increased to 1520 ℃ from 1300 ℃ at the speed of 7-10 ℃/min, when the temperature in the furnace reaches 1450 ℃, slag I is added into the Consteel electric furnace, the slag I is composed of dolomite and lime, and the slag I is used for influencing the dephosphorization rate of the electric furnace smelting process, so that the target slag system in the dephosphorization stage comprises the following components: the FeO content is less than or equal to 25 wt%, the MgO content is 4-5 wt%, and the slag alkalinity R is 2.5-3.0;

The temperature of the dephosphorization period is increased to 1580 ℃ from 1520 ℃ at the speed of 3-4 ℃/min, when the components of the steel sample meet the requirements that the carbon is more than 0.35 wt% and the phosphorus is less than 0.030 wt%, the steel sample enters a carbon blowing heating period, otherwise, the dephosphorization operation is prolonged, and secondary dephosphorization is carried out;

The temperature of the carbon blowing temperature rise period is increased to 1650 ℃ from 1580 ℃ at the speed of 7-10 ℃/min, slag II is added into the Consteel electric furnace at the beginning of the carbon blowing temperature rise period, the slag II is also composed of dolomite and lime, the dephosphorization rate of the electric furnace smelting process is influenced by the slag II, and the components of a target slag system in the carbon blowing temperature rise period are as follows: 15-20 wt% of FeO, 4-5 wt% of MgO and 3.0-3.5 of slag alkalinity R.

The smelting method capable of shortening the smelting period of the Consteel electric furnace is characterized in that the temperature in the Consteel electric furnace is adjusted to 1600 ℃ in advance according to the tapping temperature of the upper furnace in the slagging period.

The smelting method capable of shortening the smelting period of the Consteel electric furnace is characterized in that in the slagging period, an oxygen supply mode of a 1 ^# oxygen lance and an oxygen supply mode of a 2 ^# oxygen lance of the Consteel electric furnace are set in advance, and oxygen is supplied to the Consteel electric furnace at an oxygen flow rate of 1500Nm ³/min-2500 Nm ³/min.

the smelting method capable of shortening the smelting period of the Consteel electric furnace is characterized in that the mass ratio of dolomite to lime in the slag I is 8:15, 800kg of dolomite and 1500kg of lime are added into 72-74 t of furnace burden, the dolomite is added in two batches, and the lime is added in three batches.

The smelting method capable of shortening the smelting period of the Consteel electric furnace is characterized in that in the dephosphorization period, the oxygen supply modes of a 1 ^# oxygen lance and a 2 ^# oxygen lance of the Consteel electric furnace are adjusted so that the oxygen and the oxygen are supplied to the Consteel electric furnace at the oxygen flow rate of 500Nm ³/min-800 Nm ³/min.

the smelting method capable of shortening the smelting period of the Consteel electric furnace is characterized in that in the carbon blowing temperature rise period, the oxygen supply modes of the 1 ^# oxygen lance and the 2 ^# oxygen lance of the Consteel electric furnace are adjusted, and oxygen is supplied to the Consteel electric furnace at the oxygen flow rate of 800Nm ³/mi-2000 Nm ³/min.

The smelting method capable of shortening the smelting period of the Consteel electric furnace is characterized in that the mass ratio of dolomite to lime in the slag II is 2-3: 5-10, and 200 kg-300 kg of dolomite and 500 kg-1000 kg of lime are added into every 72 t-74 t of furnace burden.

The smelting method capable of shortening the smelting period of the Consteel electric furnace is characterized in that the total amount of dolomite and lime used twice is controlled within the following range: the total amount of dolomite is 1000 kg-1100 kg, and the total amount of lime is 2000 kg-2500 kg.

The invention has the advantages that:

(1) According to the characteristics of the structure and the feeding characteristics of furnace burden of a Consteel electric furnace, the control of an oxygen lance on the furnace wall, the influence of the temperature in the furnace and the slag condition on the components of molten steel, the whole smelting process is divided into three stages of a slagging stage, a dephosphorization stage and a carbon blowing and temperature rising stage according to the principles of early slagging, dephosphorization and decarburization, so that the fine control is realized, and the quality problem is ensured not to occur in the whole smelting process easily;

(2) In the early smelting period (namely, slagging period) and the later smelting period (namely, carbon blowing and temperature rising period), different slag system components are utilized to influence the dephosphorization rate in the electric furnace smelting process, so that the dephosphorization capability is improved at low temperature, and the rephosphorization is prevented at high temperature, so that the smelting speed of a Consteel electric furnace is effectively improved, the smelting period is shortened, and the operation cost is reduced;

(3) The smelting process adopts stage temperature control, the redox reaction in the furnace is controlled through the flow of an oxygen lance, the temperature of the whole smelting process is controlled according to three-stage smelting, the temperature of a slagging stage is 1300-1520 ℃, the temperature of a dephosphorization stage is 1520-1580 ℃, the temperature of a carbon blowing heating stage is 1580-1650 ℃, the smelting is started, the temperature in the furnace before the carbon blowing heating stage (namely the end of the dephosphorization stage) is controlled at 1580 ℃ or below by utilizing the characteristics of low-temperature dephosphorization and oxidative decarburization, and the furnace directly enters the carbon blowing heating stage to carry out carbon drawing and steel tapping after the dephosphorization is finished, so that various consumptions (including ash consumption, oxygen consumption and steel material unit consumption) in the smelting process are effectively reduced;

(4) in the carbon blowing and temperature rising period, the oxygen lance is controlled according to the principle of dephosphorization and carbon protection, so that the carbon of the medium-high carbon steel tapping is increased to more than 0.10 percent, the molten steel peroxidation at the smelting end point is effectively avoided, and the smelting cost and the operation difficulty of a subsequent refining furnace are further reduced.

Drawings

FIG. 1 is a schematic view of the control of the temperature in the furnace throughout a smelting process;

FIG. 2 is a graph showing the influence of slag basicity R and FeO content on Lp;

FIG. 3 is a graph showing the relationship between the furnace temperature and the phosphorus distribution ratio.

Detailed Description

The invention is described in detail below with reference to the figures and the embodiments.

electric furnace: a 110t Consteel electric furnace.

The furnace charge structure: the burden consisted of molten iron and steel (pig iron + scrap) in the proportions given in Table 1.

TABLE 1 furnace burden structure

In order to solve the problem of molten steel peroxidation at the smelting end point, the whole smelting process is divided into three stages according to the principle of early slagging, dephosphorization firstly and decarburization secondly, according to the characteristics of the burden structure and the feeding of a Consteel electric furnace, the control of an oxygen lance on a furnace wall, the influence of the temperature in the furnace and the slag condition on the components of the molten steel: a slagging period, a dephosphorization period and a carbon blowing and heating period.

first, slagging stage

the furnace temperature of the Consteel electric furnace was adjusted to 1600 ℃ according to the tapping temperature of the upper furnace.

The oxygen supply modes of the 1 ^# oxygen lance and the 2 ^# oxygen lance of the Consteel electric furnace are set in advance, and the oxygen supply modes are enabled to supply oxygen to the Consteel electric furnace at oxygen flow rates of 1500Nm ³/min to 2500Nm ³/min, when the proportion of coke in charging materials is more, the oxygen flow rates of the 1 ^# oxygen lance and the 2 ^# oxygen lance can be lower, and vice versa, according to the first behavior example in the table 1, the usage amounts of coke are respectively 1t, 0.8t, 0.5t, 0.3t, 0.03t, 0t, 1 ^# and 2 ^# oxygen flow rates of the 1 Nm ³/min, 1500Nm ³/min, 2000Nm ³/min, 2000Nm ³/min, 2500Nm ³/min and 2500Nm ³/min.

After the iron adding is finished, feeding into a Consteel electric furnace, and finishing feeding before the P removing period. Starting a gun, namely entering a slagging period, in the slagging period, raising the temperature in the Consteel electric furnace to 1520 ℃ at a speed of 7-10 ℃/min, adding slag I into the Consteel electric furnace when the temperature in the furnace reaches 1450 ℃, and influencing the dephosphorization rate in the electric furnace smelting process by utilizing the slag I so as to ensure that the target slag system in the dephosphorization period comprises the following components: the FeO content is less than or equal to 25 wt%, the MgO content is 4-5 wt%, and the slag alkalinity R is 2.5-3.0.

The composition and amount of slag I are shown in Table 2.

TABLE 2 composition and amount of slag I

composition of	Dolomite	Lime
			Added amount/kg	800	1500

Wherein, the dolomite is added in two batches, each batch is 400kg, and the total time is 5 min; lime is added in three batches, the addition amount of each batch is 300 kg-800 kg, and the total time is also 5 min.

Second, dephosphorization period

When the temperature in the Consteel electric furnace rises to 1520 ℃, the slagging period is finished and the dephosphorization period is started.

the oxygen supply modes of the 1 ^# oxygen lance and the 2 ^# oxygen lance of the Consteel electric furnace are adjusted, and the oxygen flow rate is reduced, so that the oxygen flow rate of the 1 ^# oxygen lance and the oxygen flow rate of the 2 Nm ³ oxygen lance of the Consteel electric furnace are adjusted to supply oxygen to the Consteel electric furnace at the oxygen flow rate of 500Nm ³/min-800 Nm ³.

The temperature in the Consteel electric furnace is increased from 1520 ℃ to 1580 ℃ at a speed of 3 ℃/min to 4 ℃/min.

At the end of the dephosphorization period, the components of the steel sample (namely the first sample of the electric furnace) need to meet the requirements of more than 0.35 wt% of carbon and less than 0.030 wt% of phosphorus, when the components of the steel sample meet the requirements, the steel sample enters a carbon blowing heating period to prepare for heating and tapping, and when the components of the steel sample do not meet the requirements, the dephosphorization operation needs to be prolonged to carry out secondary dephosphorization.

third, carbon blowing temperature rising period

When the temperature in the Consteel electric furnace rises to 1580 ℃, the dephosphorization period is finished, and the carbon blowing temperature rise period is started.

According to the principle of dephosphorization and carbon protection, the oxygen supply modes of a 1 ^# oxygen lance and a 2 ^# oxygen lance of a Consteel electric furnace are adjusted, the oxygen flow is increased, so that the oxygen flow is supplied to the Consteel electric furnace at the oxygen flow of 800Nm ³/mi-2000 Nm ³/min, and as in the slagging period, when the proportion of coke in furnace burden is more, the oxygen flow of the 1 ^# oxygen lance and the oxygen flow of the 2 ^# oxygen lance can be lower, and vice versa, the oxygen flow is higher.

Adding a slag material II into a Consteel electric furnace, and utilizing the slag material II to influence the dephosphorization rate of the electric furnace smelting process, so that the target slag system in the carbon blowing and temperature rising period comprises the following components: 15-20 wt% of FeO, 4-5 wt% of MgO and 3.0-3.5 of slag alkalinity R.

The composition and amount of slag II are shown in table 3.

TABLE 3 composition and amount of slag II

Composition of	dolomite	Lime
			Added amount/kg	200～300	500～1000

The slag I is used in the slagging period, the slag II is used in the carbon blowing and temperature rising period, and the total amount of the slag dolomite and the lime used in the two times is controlled in the following range:

The total amount of dolomite is 1000 kg-1100 kg, and the total amount of lime is 2000 kg-2500 kg.

The temperature in the Consteel electric furnace is increased from 1580 ℃ to 1650 ℃ at the speed of 7 ℃/min to 10 ℃/min.

And when the temperature in the Consteel electric furnace reaches 1650 ℃, and the components of the target slag system meet the requirements of FeO content of 15-20 wt%, MgO content of 4-5 wt% and slag alkalinity R of 3.0-3.5, ending the carbon blowing temperature rise period, namely ending the smelting process of the Consteel electric furnace, and then carrying out the subsequent refining furnace smelting.

Until now, from 2 months in 2019, by adopting the smelting method (marked as implementation), about 3000 furnaces of special steel are smelted by using a 110t Consteel electric furnace, and through statistics, the smelting period, various consumptions, tapping conditions, the service life of a furnace shell and the like, compared with the traditional Consteel electric furnace smelting method (marked as implementation) mentioned in the background art, the smelting method provided by the invention has the following remarkable improvements:

TABLE 4 comparison of smelting results

From the above table, when the smelting method provided by the invention is used for smelting special steel:

(1) The smelting period is shortened from 58min of the original one furnace to 52min of the original one furnace, each furnace is shortened by 6min, at least two more furnaces can be produced in one day, and the operation cost of the Consteel electric furnace is greatly reduced;

(2) The ash consumption, the oxygen consumption and the unit consumption of steel materials are all reduced, so that the smelting cost of steel is greatly reduced;

(3) the component qualification rate and the slag condition qualification rate of the refining furnace are improved, the steel tapping temperature qualification rate is equal to that before the implementation, and the smelting quality of a Consteel electric furnace is improved;

(4) The service life of the furnace shell is nearly 3 times of the original service life, and the economic benefit is greatly improved.

Before the above-mentioned smelting method provided by the present invention was confirmed, we made a lot of studies and experiments on dephosphorization, decarburization and smelting temperature.

The activity of CaO in the slag is increased, which is not only beneficial to dephosphorization, but also can prevent rephosphorization because Ca ²⁺ is an ion which can be really stably associated with PO ₄ ^3- , so that PO ₄ ^3- can stably exist in the slag, and the activity of FeO in the slag is increased, thereby not only oxidizing phosphorus in molten steel into P ₂ O ₅, but also accelerating the dissolution of lime and simultaneously promoting the improvement of the fluidity of the slag.

In order to effectively control the dephosphorization reaction in the furnace, systematic research needs to be carried out on the contents of different slag basicities R (R is CaO/SiO ₂) and FeO, therefore, the influence of the slag basicity R, FeO content in the electric furnace smelting process on the dephosphorization distribution ratio Lp (Lp can show the dephosphorization capability of the slag) is analyzed, wherein the influence of the slag basicity R and the FeO content on the Lp is shown in a figure 2, and according to the analysis result, the following double-slag method is finally determined:

(1) Smelting earlier stage (slagging stage): when the temperature in the furnace reaches 1450 ℃, 1500kg of lime and 800kg of dolomite are added to carry out advanced slagging operation, early slagging and fast dephosphorization P are realized when the dephosphorization period is started, the slag alkalinity R is controlled to be 2.5-3.0, and the FeO content is controlled to be within 25 wt%.

(2) And in the later smelting period (carbon blowing and temperature rising period), when the temperature reaches 1580 ℃, discharging high-phosphorus slag from the interior of the furnace, adding 500-1000 kg of lime and 200-300 kg of dolomite, controlling the alkalinity R at 3.0-3.5, and controlling the FeO content to be 15-20 wt% (in the later smelting period, the low FeO content and the high alkalinity can effectively prevent P ₂ O ₅ in the slag from being decomposed and entering steel).

The double-slag method provided by the inventor prevents rephosphorization while efficiently dephosphorizing, so that the smelting rate of a Consteel electric furnace can be effectively improved, the smelting period is shortened, and the operation cost is reduced.

In order to systematically control the decarburization and dephosphorization reactions at different temperatures in the smelting process, the relationship between the oxidation decarburization and the reduction decarburization in furnaces at different temperatures and the temperature and the phosphorus in slag needs to be analyzed.

(1) Oxidation and decarbonization

In order to obtain the reaction mechanism of oxidation and decarburization in the electric furnace smelting process, the influence of the oxygen supply intensity on the decarburization rate in the smelting process is studied, and the research result is shown in Table 5.

TABLE 5 relationship between oxygen supply intensity and decarburization Rate

From the above table, it can be seen that:

(a) The lower the temperature in the furnace is, the lower the carbon blowing rate is;

(b) When the oxygen flow rate of the 1 ^# oxygen lance and the 2 ^# oxygen lance is 2500Nm ³/min, the original temperature T1 in the furnace is 1574 ℃, the decarburization rate is 0.05%/min, and when the oxygen flow rate of the 1 ^# oxygen lance and the 2 ^# oxygen lance is 2500Nm ³/min, the temperature T1 in the furnace is 1523 ℃, the decarburization rate is 0.011%/min, which shows that the temperature has great influence on the decarburization rate.

In conclusion, in the slagging stage, the oxidation decarburization reaction can be effectively prevented only by avoiding the high temperature phenomenon in the furnace (the temperature in the furnace is less than 1575 ℃).

(2) Reduction decarburization

when molten steel in the furnace is seriously oxidized, the reaction of reducing FeO by carbon can occur in the early stage of smelting, the phenomenon of slag overflow is also accompanied while decarburization is caused, and the slag can not meet the requirements of dephosphorization slag systems.

In order to prevent the carbon reduction reaction in the smelting process, the relationship between the FeO content in the slag in the smelting process and the decarburization rate is studied, and the research results are shown in Table 6.

TABLE 6 relationship between FeO content in slag and decarburization rate

In the smelting process, the control of the slag alkalinity R and the FeO content in the slag:

when the temperature is 1520-1580 ℃, the slag alkalinity R is controlled to be 2.5-3.0, and the FeO content in the slag is controlled to be 20-25%;

When the temperature is 1580-1650 ℃, the alkalinity R of the slag is controlled to be 3.0-3.5, and the content of FeO in the slag is controlled to be 15-20%.

From the above table, it can be seen that: in the electric furnace smelting process, the reduction reaction of carbon and FeO can be carried out at low temperature, and when the content of FeO is more than 20%, the reaction rate is accelerated, namely, the carbon reduction reaction in the early stage of smelting can be effectively reduced by reducing the content of FeO in the final slag of the electric furnace.

(3) temperature dependence of phosphorus in slag

Dephosphorization is a strong exothermic reaction, the lower smelting temperature is favorable for dephosphorization of molten steel, and the excessive temperature can inhibit the dephosphorization reaction; however, the temperature is too low, which is not beneficial to the melting of lime in the furnace and influences the fluidity of the slag. It is generally considered that "three high and one low", i.e., large amount of slag, high FeO, high basicity and low temperature, are considered for the dephosphorization reaction, while taking into consideration the melting and fluidity of the slag in the furnace.

In order to study the relationship between the temperature and the phosphorus in the slag, the relationship between the temperature in the furnace and the distribution ratio of the phosphorus was investigated, and the investigation result is shown in FIG. 3.

Based on fig. 3, the temperature of the whole smelting process is controlled according to three-stage smelting, and the method comprises the following steps of:

(a) And (3) slagging stage: the temperature is controlled between 1300 ℃ and 1520 ℃;

(b) a dephosphorization period: the temperature is controlled to be 1520 ℃ to 1580 ℃ (1520 ℃ to 1550 ℃ is the low-temperature dephosphorization period and is also the optimal dephosphorization period;

(c) Carbon blowing and temperature rising period: the temperature is controlled at 1580-1650 ℃.

It should be noted that the above-mentioned embodiments do not limit the present invention in any way, and all technical solutions obtained by using equivalent alternatives or equivalent variations fall within the protection scope of the present invention.