阅读说明：本技术 一种lf精炼过程钢水脱磷的方法 (Method for dephosphorizing molten steel in LF refining process ) 是由 王腾飞 麻衡 任继银 于 2021-08-17 设计创作，主要内容包括：本发明公开一种LF精炼过程钢水脱磷的方法,钢水进入LF精炼炉后,加石灰2.8～3.2kg/t,吹氧3～4分钟,氧气流量240～260NL/min；钢水温度提升至1590～1600℃,保持此温度7～9分钟,此期间不添加任何脱氧合金材料；LF精炼13～15分钟后,通过电弧加热,在120s内将温度快速提升至1617～1622℃,保持此温度3～5分钟,完成LF炉内脱磷。采用本发明方法生产低磷钢时,使用的铁水P上限可提升至0.160％,铁水条件基本不影响生产；转炉冶炼周期基本在35分钟左右,大幅提升了生产效率；LF冶炼过程,磷元素的脱除率在50％以上,对生产低磷钢产品起到重大促进作用。(The invention discloses a method for dephosphorizing molten steel in an LF refining process, wherein after the molten steel enters an LF refining furnace, 2.8-3.2 kg/t of lime is added, oxygen is blown for 3-4 minutes, and the oxygen flow is 240-260 NL/min; raising the temperature of the molten steel to 1590-1600 ℃, and keeping the temperature for 7-9 minutes, wherein no deoxidized alloy material is added in the period; and after LF refining is carried out for 13-15 minutes, rapidly raising the temperature to 1617-1622 ℃ within 120 seconds through electric arc heating, and keeping the temperature for 3-5 minutes to complete dephosphorization in the LF furnace. When the method is adopted to produce the low-phosphorus steel, the upper limit of the used molten iron P can be increased to 0.160 percent, and the production is basically not influenced by the molten iron condition; the smelting period of the converter is basically about 35 minutes, so that the production efficiency is greatly improved; in the LF smelting process, the removal rate of the phosphorus element is over 50 percent, and the method plays a great role in promoting the production of low-phosphorus steel products.)

1. A method for dephosphorizing molten steel in an LF refining process is characterized in that,

after molten steel enters an LF refining furnace, adding 2.8-3.2 kg/t of lime, blowing oxygen for 3-4 minutes, and controlling the oxygen flow rate to be 240-260 NL/min; raising the temperature of the molten steel to 1590-1600 ℃, and keeping the temperature for 7-9 minutes, wherein no deoxidized alloy material is added in the period;

and after LF refining is carried out for 13-15 minutes, rapidly raising the temperature to 1617-1622 ℃ within 120 seconds through electric arc heating, and keeping the temperature for 3-5 minutes to complete dephosphorization in the LF furnace.

2. The method according to claim 1, wherein the molten iron raw material comprises the following components: 3.5-5.0%, Mn: 0.15-0.30%, Si: 0.18-0.32%, P: 0.130-0.160%, S: 0.015-0.025%, and the balance of Fe and inevitable impurities.

3. The method of claim 1, wherein the molten steel before refining in the LF furnace comprises the following components: c: 0.070-0.160%, Mn: 0.85 to 1.60%, Si: 0.10-0.40%, P: 0.011-0.018%, S: 0.009-0.013%, Nb: 0.005-0.060%, V: 0.005% -0.070%, Ni: 0.010-0.500 percent, and the balance of Fe and inevitable impurities.

4. The method of claim 1, wherein 1.9-2.1 kg/t deoxidizer is added after dephosphorization of molten steel in an LF furnace, LF refining treatment is carried out for 18-23 minutes, and a proper amount of alloy is added for fine adjustment of components according to steel components; then feeding a calcium silicate wire of 160-200m, soft blowing for 15min, and controlling the temperature of the molten steel at the LF outlet station to be 1600-1610 ℃.

5. The method according to claim 4, wherein the deoxidizer is an aluminum magnesium calcium complex deoxidizer.

6. The method of claim 1, wherein the LF outbound molten steel composition is: c: 0.080-0.200%, Mn: 0.90-1.70%, Si: 0.15-0.55%, S is less than or equal to 0.005%, P is less than or equal to 0.007%, Nb: 0.005-0.060%, V: 0.005% -0.070%, Ni: 0.010-0.500%, Ti: 0.005-0.020%, Ca: 0.005-0.010% and the balance of Fe and inevitable impurities, which are mass percent.

Technical Field

The invention belongs to the field of steelmaking, and relates to a method for dephosphorizing molten steel in an LF refining process.

Background

Phosphorus is a harmful element in steel, can improve the strength of the steel in a small amount, but greatly reduces the plasticity and toughness of the steel and increases the sensitivity of welding cracks. Meanwhile, phosphorus is easy to segregate, so that the banded structure of steel is aggravated, and the influence on the performance of the steel is great, so that the lower the phosphorus content is, the better the phosphorus content is, in the smelting process of most of steel, but P in molten steel is difficult to effectively remove due to the restriction of various factors in the smelting process. According to the statistics of relevant data, the content of phosphorus in molten steel is difficult to remove to be less than 100ppm in most cases, and the low-temperature performance yield of steel products with high requirements on low-temperature toughness is seriously influenced. At present, most iron and steel enterprises dephosphorize in the converter process, LF refining mainly has the functions of molten steel temperature rise, desulfurization, component fine adjustment and molten steel cleanliness improvement, and phosphorus content in the LF refining process cannot be removed and is partially increased.

Chinese patent document CN 112195309A (202010870303.4) discloses an LF furnace smelting process with a deep dephosphorization function. The patent mainly controls the oxygen partial pressure of the steel slag interface and P in molten steel by adding a reduction dephosphorization agent and utilizing LF reducing atmosphere³⁺Further deep threshing. The patent adopts reductive dephosphorization, and has high cost and difficult operation. In addition, according to the descriptions of the patent examples 1 to 3, the method further performs LF reduction deep dephosphorization after the depp treatment and RH treatment just before the converter is taken out, has complex process and high cost, and is not suitable for popularization and application in common steel smelting.

Chinese patent document CN105039647A (201510348833.1) discloses a dephosphorization refining method of LF furnace, which comprises the following steps: (1) after molten steel enters the LF furnace, a ladle bottom blowing pipe and an external oxygen source are connected, bottom blowing oxygen is switched to an argon source after 40-42 s, and argon is bottom blown in the whole refining process; (2) power transmission and slagging: adding the following slag making materials before power transmission: 9-10 Kg/t of converter particle steel, 1.5-2.8 Kg/t of ore and 2Kg/t of fluorite are conveyed to the furnace slag for thorough melting; the converter granular steel is crushed particles after converter end-point slag returns to natural cooling, and comprises the main components of 45-49% of CaO, 14-20% of FeO and the balance of impurities in percentage by mass; (3) after slag is completely melted, power is cut off, the flow of bottom blowing argon is increased to 800-850 NL/min, the gas is adopted for stirring for 10-15 min, 1-1.5 Kg/t of converter particle steel, 1-1.5 Kg/t of ore and 1Kg/t of fluorite powder are added in the stirring process and spread to a slag layer for dephosphorization; (4) after dephosphorization is finished, 1.5-2 Kg/t of lime is added to prevent rephosphorization. However, the method of controlling dephosphorization by changing the slagging method is poor in operability and low in dephosphorization rate which is only 16%.

Disclosure of Invention

The invention provides a novel molten steel dephosphorization method in an LF refining process, aiming at the problem of difficult dephosphorization in the LF refining process in the prior art. The method is reasonable, the production process is simple to control, the dephosphorization efficiency is high, the effect is good, and the product quality is stable.

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

a method for dephosphorizing molten steel in an LF refining process is characterized in that,

after molten steel enters an LF refining furnace, adding 2.8-3.2 kg/t of lime, blowing oxygen for 3-4 minutes, and controlling the oxygen flow rate to be 240-260 NL/min; raising the temperature of the molten steel to 1590-1600 ℃, and keeping the temperature for 7-9 minutes, wherein no deoxidized alloy material is added in the period;

and after 13-15 minutes of LF refining (the LF refining time is calculated from the beginning of oxygen blowing), rapidly raising the temperature to 1617-1622 ℃ within 120 seconds by arc heating, and keeping the temperature for 3-5 minutes to complete dephosphorization in the LF furnace.

Preferably, in the above method, the molten iron raw material used comprises the following components: 3.5-5.0%, Mn: 0.15-0.30%, Si: 0.18-0.32%, P: 0.130-0.160%, S: 0.015-0.025%, and the balance of Fe and inevitable impurities.

Preferably, the molten steel before refining in the LF furnace (namely, the molten steel after smelting in the converter) comprises the following components: c: 0.070-0.160%, Mn: 0.85 to 1.60%, Si: 0.10-0.40%, P: 0.011-0.018%, S: 0.009-0.013%, Nb: 0.005-0.060%, V: 0.005% -0.070%, Ni: 0.010-0.500 percent, and the balance of Fe and inevitable impurities.

Preferably, after molten steel is dephosphorized in an LF furnace, 1.9-2.1 kg/t of deoxidizer is added, LF refining treatment is carried out for 18-23 minutes, and a proper amount of alloy is added for component fine adjustment according to the component requirement of the steel; then feeding a calcium silicate wire of 160-200m, soft blowing for 15min, and controlling the temperature of the molten steel at the LF outlet station to be 1600-1610 ℃.

More preferably, the deoxidizer is an aluminum-magnesium-calcium composite deoxidizer.

Further preferably, the LF outbound molten steel comprises the following components: c: 0.080-0.200%, Mn: 0.90-1.70%, Si: 0.15-0.55%, S is less than or equal to 0.005%, P is less than or equal to 0.007%, Nb: 0.005-0.060%, V: 0.005% -0.070%, Ni: 0.010-0.500%, Ti: 0.005-0.020%, Ca: 0.005-0.010% and the balance of Fe and inevitable impurities, which are mass percent.

According to the method, the step (1) not only completes dephosphorization operation, but also the step (2) is normal LF refining treatment, the operation is simple, the dephosphorization operation in the LF refining process can be realized only by controlling factors such as oxygen blowing flow, time, molten steel temperature and the like, and the method is convenient, simple and convenient.

The method has the advantages of reasonableness, simple control of production process, high dephosphorization efficiency, good effect, stable control of P content within 70ppm and stable product quality.

The invention has at least the following beneficial effects:

(1) in the prior art, when the steel with P less than or equal to 0.010 percent is produced, the content of P in molten iron is required to be controlled within 0.130 percent; compared with the conventional smelting production process, the method increases the early-stage dephosphorization process of the LF, so that the upper limit of the used molten iron P can be increased to 0.160 percent when the low-phosphorus steel is produced, and the production is basically not influenced by the molten iron conditions;

(2) the production pressure of the converter is reduced, the smelting time for smelting the low-phosphorus steel by the converter is generally over 45 minutes before the method is adopted, and the smelting period of the converter is basically about 35 minutes after the method is adopted, so that the production efficiency is greatly improved;

(3) before the method is adopted, the phosphorus content in the LF smelting process can not be controlled, even can be increased to a certain extent, and after the method is adopted, the removal rate of phosphorus elements in the LF smelting process is over 50 percent, so that the method plays a great role in promoting the production of low-phosphorus steel products.

Detailed Description

The technical solution of the present invention is further explained by the following examples.

Example 1

A method for dephosphorizing molten steel in an LF refining process comprises the following steps:

(1) raw material composition of molten iron

4.2 percent of C, 0.26 percent of Mn, 0.24 percent of Si, 0.153 percent of P, 0.019 percent of S, and the balance of Fe and inevitable impurities;

(2) molten steel composition after converter smelting

0.120% of C, 1.41% of Mn, 0.31% of Si, 0.016% of P, 0.010% of S, Nb: 0.028%, V: 0.026%, Ni: 0.17 percent, the balance of Fe and inevitable impurities, and the converter tapping amount is 137 tons;

(3) LF refining process

Adding 411kg of lime into a steel ladle when the steel ladle enters a station, blowing oxygen for 3.5 minutes, wherein the oxygen flow is as follows: 250 NL/min; raising the temperature to 1595 ℃, and keeping the temperature for 7 minutes, wherein no deoxidized alloy material is added in the period; carrying out LF smelting for 14 minutes, rapidly raising the temperature to 1620 ℃, keeping the temperature for 4 minutes, then adding 274kg of aluminum-magnesium-calcium composite deoxidizer, 50kg of silicon-manganese alloy, 15kg of Nb iron and 300m of Ti wire, carrying out LF refining treatment for 21 minutes, feeding 200m of silicon-calcium wire, carrying out soft blowing for 15 minutes, and carrying out LF outlet molten steel temperature of 1607 ℃;

the LF outlet molten steel comprises the following components in percentage by mass: 0.135%, Mn: 1.42%, Si: 0.32%, S: 0.003%, P: 0.007%, Nb: 0.029%, V: 0.026%, Ni: 0.17%, Ti: 0.013%, Ca: 0.006%, and the balance Fe and inevitable impurities.

The calculation shows that the dephosphorization rate of LF refining is 56.25%.

Example 2

A method for dephosphorizing molten steel in an LF refining process comprises the following steps:

(1) raw material composition of molten iron

4.17 percent of C, 0.29 percent of Mn, 0.22 percent of Si, 0.145 percent of P, 0.017 percent of S and the balance of Fe and inevitable impurities;

(2) molten steel composition after converter smelting

0.131% of C, 1.37% of Mn, 0.29% of Si, 0.013% of P, 0.011% of S, Nb: 0.030%, V: 0.024%, Ni: 0.15 percent, the balance of Fe and inevitable impurities, and the converter tapping amount is 135 tons;

(3) LF refining

Adding 405kg of lime into a steel ladle when the steel ladle enters a station, blowing oxygen for 3 minutes, wherein the oxygen flow rate is as follows: 250 NL/min; raising the temperature to 1595 ℃, keeping the temperature for 8 minutes, and not adding any deoxidation alloy material in the period; LF smelting is carried out for 13 minutes, the temperature is quickly raised to 1620 ℃, the temperature is kept for 3 minutes, then 270kg of aluminum-magnesium-calcium composite deoxidizer, 70kg of silicon-manganese alloy, 12kg of ferroniobium, 20kg of ferrovanadium and 300m of titanium wire are added, LF refining treatment is carried out for 19 minutes, 200m of silicon-calcium wire is fed, soft blowing is carried out for 15 minutes, and the temperature of LF outgoing molten steel is as follows: 1610 ℃;

the LF outlet molten steel comprises the following components in percentage by mass: 0.134%, Mn: 1.40%, Si: 0.30%, S: 0.002%, P: 0.005%, Nb: 0.031%, V: 0.026%, Ni: 0.15%, Ti: 0.014%, Ca: 0.005% and the balance of Fe and inevitable impurities;

calculated, the dephosphorization rate of LF refining is 61.54%.

Example 3

A method for dephosphorizing molten steel in an LF refining process comprises the following steps:

(1) raw material composition of molten iron

3.95 percent of C, 0.26 percent of Mn, 0.20 percent of Si, 0.160 percent of P, 0.020 percent of S and the balance of Fe and inevitable impurities;

(2) molten steel composition after converter smelting

0.140% of C, 1.43% of Mn, 0.33% of Si, 0.017% of P, 0.012% of S, Nb: 0.025%, V: 0.030%, Ni: 0.18 percent, the balance of Fe and inevitable impurities, and 139 tons of converter tapping amount;

(3) LF refining

417kg of high-quality lime is added when the steel ladle enters the station, oxygen blowing is carried out for 4 minutes, and the oxygen flow is as follows: 250 NL/min; raising the temperature to 1595 ℃, keeping the temperature for 9 minutes, and not adding any deoxidation alloy material in the period; LF smelting is carried out for 15 minutes, the temperature is quickly raised to 1620 ℃, the temperature is kept for 3 minutes, then 278kg of aluminum-magnesium-calcium composite deoxidizer, 30kg of Nb iron and 330m of Ti wire are added, LF refining treatment is carried out for 23 minutes, 200m of silicon-calcium wire is fed, soft blowing is carried out for 15 minutes, and the temperature of LF outgoing molten steel is as follows: 1605 deg.C;

the LF outlet molten steel comprises the following components in percentage by mass: 0.143%, Mn: 1.43%, Si: 0.33%, S: 0.001%, P: 0.007%, Nb: 0.028%, V: 0.030%, Ni: 0.18%, Ti: 0.015%, Ca: 0.008% and the balance of Fe and inevitable impurities;

the calculation shows that the dephosphorization rate of LF refining is 58.82%.

Comparative example 1

A method for dephosphorizing molten steel in an LF refining process comprises the following steps:

(1) raw material composition of molten iron

4.0 percent of C, 0.25 percent of Mn, 0.27 percent of Si, 0.152 percent of P, 0.017 percent of S and the balance of Fe and inevitable impurities; (2) molten steel composition after converter smelting

0.116% of C, 1.39% of Mn, 0.30% of Si, 0.017% of P, 0.009% of S, Nb: 0.027%, V: 0.028%, Ni: 0.18 percent, the balance of Fe and inevitable impurities, and the converter tapping amount is 138 tons;

(3) LF refining

417kg of high-quality lime is added when the steel ladle enters a station, oxygen blowing is carried out for 2.5 minutes, and the oxygen flow is as follows: 250 NL/min; raising the temperature to 1595 ℃, and keeping the temperature for 7 minutes, wherein no deoxidized alloy material is added in the period; carrying out LF smelting for 14 minutes, rapidly raising the temperature to 1620 ℃, keeping the temperature for 4 minutes, then adding 276kg of aluminum-magnesium-calcium composite deoxidizer, 90kg of silicon-manganese alloy, 14kg of Nb iron and 310m of Ti wire, carrying out LF refining treatment for 21 minutes, feeding 200m of silicon-calcium wire, carrying out soft blowing for 15 minutes, and carrying out LF outlet molten steel temperature at 1608 ℃;

the LF outlet molten steel comprises the following components in percentage by mass: 0.125%, Mn: 1.43%, Si: 0.31%, S: 0.003%, P: 0.016%, Nb: 0.028%, V: 0.028%, Ni: 0.18%, Ti: 0.014%, Ca: 0.005% and the balance of Fe and inevitable impurities;

the calculation shows that the dephosphorization rate of LF refining is 5.88%.

Comparative example 2

A method for dephosphorizing molten steel in an LF refining process comprises the following steps:

(1) raw material composition of molten iron

(1) Raw material composition of molten iron

4.21 percent of C, 0.28 percent of Mn, 0.23 percent of Si, 0.146 percent of P, 0.015 percent of S and the balance of Fe and inevitable impurities;

(2) molten steel composition after converter smelting

0.133% of C, 1.38% of Mn, 0.27% of Si, 0.013% of P, 0.010% of S, Nb: 0.030%, V: 0.025%, Ni: 0.15 percent, the balance of Fe and inevitable impurities, and the converter tapping amount is 135 tons;

(3) LF refining

Adding 405kg of high-quality lime into a steel ladle when the steel ladle enters a station, blowing oxygen for 3.3 minutes, wherein the oxygen flow rate is as follows: 230 NL/min; raising the temperature to 1595 ℃, keeping the temperature for 8 minutes, and not adding any deoxidation alloy material in the period; carrying out LF smelting for 13 minutes, rapidly raising the temperature to 1620 ℃, keeping the temperature for 3 minutes, then adding 270kg of an aluminum-magnesium-calcium composite deoxidizer, 90kg of a silicon-manganese alloy, 29kg of ferrovanadium, 290m of a Ti wire, carrying out LF refining treatment for 19 minutes, feeding 200m of a silicon-calcium wire, carrying out soft blowing for 15min, and carrying out LF outlet molten steel temperature: 1610 ℃;

the LF outlet molten steel comprises the following components in percentage by mass: 0.133%, Mn: 1.41%, Si: 0.30%, S: 0.002%, P: 0.012%, Nb: 0.030%, V: 0.027%, Ni: 0.15%, Ti: 0.013%, Ca: 0.006% of Fe and the balance of inevitable impurities;

the calculation shows that the dephosphorization rate of LF refining is 7.70%.

Comparative example 3

A method for dephosphorizing molten steel in an LF refining process comprises the following steps:

(1) raw material composition of molten iron

3.97 percent of C, 0.26 percent of Mn, 0.21 percent of Si, 0.159 percent of P, 0.018 percent of S and the balance of Fe and inevitable impurities;

(2) molten steel composition after converter smelting

0.141% of C, 1.44% of Mn, 0.32% of Si, 0.017% of P, 0.011% of S, Nb: 0.025%, V: 0.029%, Ni: 0.18 percent, the balance of Fe and inevitable impurities, and the converter tapping amount is 140 tons;

(3) LF refining

Adding 422kg of high-quality lime when a steel ladle enters a station, blowing oxygen for 4 minutes, wherein the oxygen flow is as follows: 250 NL/min; raising the temperature to 1585 ℃, and keeping the temperature for 9 minutes, wherein no deoxidizing alloy material is added in the period; and (2) LF smelting is carried out for 15 minutes, the temperature is quickly raised to 1620 ℃, the temperature is kept for 3 minutes, then 280kg of aluminum-magnesium-calcium composite deoxidizer, 28kg of Nb iron and 320m of Ti wire are added, LF refining treatment is carried out for 22 minutes, 200m of silicon-calcium wire is fed, soft blowing is carried out for 15 minutes, and the temperature of LF outlet molten steel is as follows: 1605 deg.C;

the LF outlet molten steel comprises the following components in percentage by mass: 0.142%, Mn: 1.44%, Si: 0.32%, S: 0.001%, P: 0.016%, Nb: 0.028%, V: 0.029%, Ni: 0.18%, Ti: 0.014%, Ca: 0.007% and the balance of Fe and inevitable impurities;

the calculation shows that the dephosphorization rate of LF refining is 5.88%.

Comparative example 4

A method for dephosphorizing molten steel in an LF refining process comprises the following steps:

(1) raw material composition of molten iron

3.99 percent of C, 0.26 percent of Mn, 0.22 percent of Si, 0.160 percent of P, 0.017 percent of S and the balance of Fe and inevitable impurities;

(2) molten steel composition after converter smelting

0.140% of C, 1.44% of Mn, 0.33% of Si, 0.018% of P, 0.014% of S, Nb: 0.027%, V: 0.029%, Ni: 0.17 percent, the balance of Fe and inevitable impurities, and 139 tons of converter tapping amount;

(3) LF refining

417kg of high-quality lime is added when the steel ladle enters the station, oxygen blowing is carried out for 4 minutes, and the oxygen flow is as follows: 250 NL/min; raising the temperature to 1595 ℃, and keeping the temperature for 5 minutes, wherein no deoxidized alloy material is added in the period; LF smelting is carried out for 15 minutes, the temperature is quickly raised to 1620 ℃, the temperature is kept for 3 minutes, then 278kg of aluminum-magnesium-calcium composite deoxidizer, 25kg of silicon-manganese alloy, 25kg of Nb iron, 12kg of vanadium iron and 300m of Ti wire are added, LF refining treatment is carried out for 22 minutes, 200m of silicon-calcium wire is fed, soft blowing is carried out for 15 minutes, and the temperature of LF outgoing molten steel is as follows: 1605 deg.C;

the LF outlet molten steel comprises the following components in percentage by mass: 0.141%, Mn: 1.45%, Si: 0.33%, S: 0.002%, P: 0.016%, Nb: 0.029%, V: 0.030%, Ni: 0.17%, Ti: 0.013%, Ca: 0.006% of Fe and the balance of inevitable impurities;

the calculation shows that the dephosphorization rate of LF refining is 11.11%.

According to the method for dephosphorizing molten steel in the LF refining process, factors such as oxygen blowing time, oxygen flow, temperature after oxygen blowing, temperature maintaining time and the like are controlled, so that O, Ca and P are controlled to react to generate calcium and phosphorus oxides, [ O ] + [ Ga ] + [ P ] → CaPxOy, and the density of the products is less than that of the molten steel and can float upwards to be absorbed by a slag layer on the surface of a steel ladle. The molten steel dephosphorization method in the refining process can be realized, molten iron with the phosphorus content of 0.130-0.160% can be used for smelting steel with the phosphorus content of less than 0.007%, the production pressure of a converter is reduced, the production efficiency is improved, and the product quality is improved.