阅读说明：本技术 提高pc钢钢水流动性的炼钢方法 (Steelmaking method for improving fluidity of molten PC steel ) 是由 宋依新 肖步庆 杨之俊 杨海滨 杨森 王玉刚 徐学良 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种提高PC钢钢水流动性的炼钢方法,包括转炉冶炼和LF精炼过程；所述LF精炼的中后期进行变渣操作,向钢包中加入硅灰石或石英砂,控制精炼渣碱度R=1.5～2.5。本方法在LF精炼后期对精炼渣进行改质,通过对PC钢钢水在LF精炼过程的成分进行特殊控制,大幅提升了小方坯连铸机生产PC钢的全流拉钢率,实现与其它钢种同等的生产效率,平均连拉炉数由原来的6炉提高到16炉,从而实现小方坯连铸机顺利生产PC钢；适宜于生产30MnSi、35Si2Mn等低锰硅比钢种；方法简单、操作性强、效果显著,可以实现连铸生产PC钢的顺利开浇,全流生产,减少浸入水口结瘤,保证了炼钢厂的正常生产,降低了生产成本。(The invention discloses a steelmaking method for improving the fluidity of molten PC steel, which comprises the processes of converter smelting and LF refining; and performing slag changing operation in the middle and later stages of LF refining, adding wollastonite or quartz sand into a ladle, and controlling the alkalinity R = 1.5-2.5 of refining slag. The method modifies the refining slag at the later stage of LF refining, and by specially controlling the components of the molten PC steel in the LF refining process, the full-flow steel drawing rate of the PC steel produced by the billet continuous casting machine is greatly improved, the production efficiency equal to that of other steel types is realized, the average continuous drawing furnace number is increased from 6 furnaces to 16 furnaces, and the smooth production of the PC steel by the billet continuous casting machine is realized; is suitable for producing steel grades with low manganese-silicon ratio such as 30MnSi, 35Si2Mn and the like; the method is simple, strong in operability and remarkable in effect, can realize smooth casting and full-flow production of continuous casting production of PC steel, reduces the nodulation of the water immersion port, ensures the normal production of a steel plant, and reduces the production cost.)

1. A steelmaking method for improving the fluidity of molten PC steel is characterized by comprising the following steps: comprises converter smelting and LF refining processes; and performing slag changing operation in the middle and later stages of LF refining, adding wollastonite or quartz sand into a ladle, and controlling the alkalinity R = 1.5-2.5 of refining slag.

2. The steelmaking method for improving the fluidity of molten PC steel according to claim 1, wherein: wollastonite of 2-4 kg/t steel or quartz sand of 1-2 kg/t steel is added into the steel ladle.

3. The steelmaking method for improving the fluidity of molten PC steel according to claim 1, wherein: and in the converter smelting and LF refining processes, ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy materials.

4. A steel-making method for improving fluidity of molten PC steel according to claim 1, 2 or 3, characterized in that: and adjusting the components of the molten steel in the middle and early stages of LF refining.

Technical Field

The invention relates to a smelting method, in particular to a steelmaking method for improving the fluidity of molten PC steel.

Background

The Steel Bar for Prestressed Concrete (PC Steel Bar for short) belongs to the middle strength level in the prestress strength level; the high-strength prestressed concrete centrifugal pipe pile has the characteristics of high strength and toughness, low relaxation, strong bond stress with concrete, good weldability, upsetting property, material saving and the like, is widely applied to prestressed members such as high-strength prestressed concrete centrifugal pipe piles, electric poles, overhead piers, railway sleepers and the like abroad, and has a very wide market in the world, particularly Asia.

The main raw material of the PC steel bar is a twist-free controlled cold and hot rolled wire rod, and the raw material for producing the PC steel hot rolled wire rod is a small square billet continuous casting billet. And the small square billet continuous casting machine for producing the PC steel has higher requirements on the quality of molten steel.

The steel type of the PC steel bar is silicon killed steel, the castability of molten steel is poor, the molten steel has poor fluidity in the continuous casting process, and nozzle nodulation is easily caused, so that accidents such as casting stop of a continuous casting machine, molten steel remelting or falling to the ground are caused, normal production of steelmaking is influenced, the production cost is improved, and the enterprise benefit is reduced. The inner diameter of the billet continuous casting water inlet is small, so that the blockage is easy to occur, and the phenomenon is more prominent in billet continuous casting. How to solve the problem of the blockage of a PC molten steel pouring nozzle in the continuous casting production of small square billets becomes a technical problem to be solved urgently by steelmaking technicians.

Disclosure of Invention

The invention aims to solve the technical problem of providing a steelmaking method for improving the fluidity of molten PC steel so as to solve the problem of blockage of a pouring nozzle of the molten PC steel.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: comprises converter smelting and LF refining processes; and performing slag changing operation in the middle and later stages of LF refining, adding wollastonite or quartz sand into a ladle, and controlling the alkalinity R of refining slag to be 1.5-2.5.

Wollastonite of 2-4 kg/t steel or quartz sand of 1-2 kg/t steel is added into the steel ladle.

In the converter smelting and LF refining process, ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy materials.

In the invention, the molten steel components are adjusted in the middle and early stages of LF refining.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the invention, the refining slag is modified at the later stage of LF refining, the full-flow steel drawing rate of PC steel produced by the billet continuous casting machine is greatly improved by specially controlling the components of the molten PC steel in the LF refining process, the production efficiency equal to that of other steel types is realized, the average continuous drawing furnace number is increased from 6 furnaces to 16 furnaces, and thus the billet continuous casting machine can smoothly produce the PC steel; is suitable for producing steel grades with low manganese-silicon ratio such as 30MnSi, 35Si2Mn and the like. The method is simple, strong in operability and remarkable in effect, solves the technical problems that the continuous casting machine is easy to block the soaking port to cause the accident of stopping casting of the continuous casting machine and the return of molten steel to the furnace or the landing of molten steel and the like in the production of low manganese-silicon ratio steel by the small square billet continuous casting machine, can realize the smooth casting and the full-flow production of continuous casting production of PC steel, reduces the nodulation of the soaking port, ensures the normal production of a steel mill, reduces the production cost, improves the benefit of enterprises, and has excellent popularization and application values in the industry.

The invention can use ferrosilicon, ferromanganese and ferrosilicon-ferromanganese for the alloy added in the converter and the refining without using low-aluminum ferrosilicon, thus reducing the alloy production cost; meanwhile, the time for refining white slag of molten steel is not required, and particularly, after the molten steel with long refining time is treated by the method for accident steel pressing, continuous casting and pouring are smooth.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

FIG. 1 shows MnO-SiO₂-Al₂O₃A ternary phase diagram;

FIG. 2 is an equilibrium diagram of Fe-Al-Si-1% Mn inclusions at 1600 ℃.

Detailed Description

The steelmaking method for improving the fluidity of the molten PC steel is suitable for steel grades with main grades of 30MnSi and 35Si2Mn, and adopts the following process and principle:

(1) the composition requirements of 30MnSi and 35Si2Mn are as follows: the chemical composition requirements of the steel grade 30MnSi are shown in Table 1; the chemical composition requirements of the steel grade 35Si2Mn are shown in table 2.

Table 1: the chemical composition requirement of the steel grade 30MnSi

Table 2: the chemical composition requirement of the steel grade 35Si2Mn

(2) The method comprises the following steps: comprises converter smelting and LF refining processes. And in the converter smelting, ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy materials, and low-aluminum ferrosilicon is not needed. In the LF refining, ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy materials, and low-aluminum ferrosilicon is not needed; slagging and heating at the early stage in LF refining, adjusting the components of molten steel to meet the outbound requirement, and enabling the temperature of the molten steel to reach the outbound temperature +/-20 ℃; and (3) carrying out slag changing operation in the middle and later stages of LF refining, adding 2-4 kg/t of wollastonite steel or 1-2 kg/t of quartz sand steel into a ladle, and controlling the alkalinity R of refining slag to be 1.5-2.5.

(3) The principle of the method is as follows:

the inclusions generated by the silicon killed steel are as follows: pure SiO₂(solid), MnO. SiO₂(liquid), MnO. FeO (solid solution), and Al₂O₃Similar to composite inclusion. In the prior art, the fluidity of molten steel is generally improved by adjusting the manganese-silicon ratio of the molten steel to be more than 2.5. While the high-time formation of Mn and Si is typicalMnO·SiO₂And the impurities are easy to float upwards.

And (II) in the production of PC steel, ferrosilicon (PG FeSi72Al2.5) is used for deoxidation alloying, and the addition amount is large. The Al content in the ferrosilicon is 1.5-2.5 wt%. Al produced during production₂O₃The deoxidation product enters the slag and the deoxidation product formed may be: [ solution ] Rose spodumene (2MnO 2 Al)₂O₃·5SiO₂) (ii) a ② manganese aluminum garnet (3 MnO. Al)₂O₃·3SiO₂) (ii) a ③ pure (Al)₂O₃25%). If the components of the inclusion are controlled in the shadow area of the manganese aluminum garnet in the phase diagram shown in figure 1, the melting point of the inclusion is low (1400 ℃), and the sphere is easy to float; and no separate Al₂O₃The molten steel has good castability and does not block the water gap. The inclusion is controlled in the shadow region by controlling Al of the molten steel to be less than or equal to 50ppm and the free oxygen content to be 10-20 ppm.

And (III) wollastonite is added in the middle and later stages of LF refining to reduce the alkalinity of refining slag, wherein R is 1.5-2.5, so that the types of impurities in molten steel can be changed, and the fluidity of the molten steel is improved. Al in steel slag₂O₃Under the condition of basically fixed content, the content of SiO in the steel slag is changed₂The content is improved, so that the content of Al in the molten steel can be effectively reduced; the alkalinity of the refining slag is reduced, and Al in the slag can be reduced₂O₃The reduction of the inclusion is represented by the following reaction formula (A).

[Si]+(Al₂O₃)＝[Al]+(SiO₂) (A)

[Al]+(SiO₂)＝(Al₂O₃)+[Si] (B)

As shown in FIG. 2, the reduction of the Al content in the molten steel makes the inclusions in the molten steel liquid, and reduces the above-mentioned reaction (B) of the molten steel during the continuous casting, and Al₂O₃The generation of impurities and Al₂O₃Blocking the water gap.

(4) In the production process of silicon killed steel, the white slag time is long, so that the free oxygen content in molten steel is very low, and when the free oxygen content in the molten steel is less than 10ppm, MnO-Al is caused₂O₃Generation of inclusions such thatThe probability of the nozzle being blocked is greatly increased. In the prior art, low-aluminum ferrosilicon is mostly adopted in the production of PC steel, and the Al content in molten steel is controlled to reduce Al₂O₃The amount of impurities is reduced by controlling the time of refining white slag₂O₃And (4) inclusion.

In the method, low-aluminum ferrosilicon is not added in the converter smelting and LF refining processes, but low-alkalinity slag is adopted, so that SiO in the slag is improved₂Activity; can well improve the oxygen content in molten steel and reduce the high melting point MnO.Al₂O₃The generation of inclusions (as shown in fig. 1) makes the castability of molten steel good. The method can avoid the blockage of the soaking water inlet when the small square billet continuous casting machine produces the PC steel, greatly improve the number of continuous drawing furnaces, reduce production accidents and ensure normal production.

Example 1: the steel-making method for improving the fluidity of the molten PC steel adopts the following specific process.

(1) Smelting in a converter: producing 30MnSi steel; ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy material, and low-aluminum ferrosilicon is not used.

(2) LF refining: and (3) measuring the temperature of molten steel in the first furnace at 1540 ℃ in a certain pouring time, adding lime in batches for slagging, transmitting power, heating for 15min, and sampling and testing after white slag is formed. A first sample of a refining furnace; then the power is supplied again to heat for 5min, alloy components are added according to the molten steel components of the first sample, the second sample is taken, the temperature is measured at 1615 ℃, and the assay components meet the requirements; at this time, the refining time was 30min in total, and 2kg/t wollastonite was added to the ladle. And (3) electrifying for the third time to increase the temperature, measuring the temperature at 1620 ℃ when the refining time is accumulated to 50min, and taking out the molten steel after soft blowing for 5 min. The refining time of the molten steel in the furnace is accumulated for 60 min. The composition of each of the above sampled molten steels is shown in Table 3 below.

Table 3: composition of each sampled molten steel in LF process

(3) The compositions of the furnace slag sample are shown in the following table 4, and the basicity R of the slag is 2.4.

Table 4: slag sample composition

(4) The continuous casting of the furnace square billet is smoothly carried out.

Example 2: the steel-making method for improving the fluidity of the molten PC steel adopts the following specific process.

(1) Smelting in a converter: producing 30MnSi steel; ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy material, and low-aluminum ferrosilicon is not used.

(2) LF refining: and (3) measuring the temperature of molten steel in the 5 th furnace at 1560 ℃ in a certain casting time, adding lime in batches for slagging, transmitting power and heating for 12min, and sampling and testing after white slag is formed. A first sample of a refining furnace; then the power is supplied again to heat for 3min, alloy components are added according to the molten steel components of the first sample, the second sample is taken, the temperature is measured for 1600 ℃, and the assay components meet the requirements; at this time, the refining time was 29min in total, and 4kg/t wollastonite was added to the ladle. And (3) supplying power for the third time to increase the temperature, measuring the temperature by 1580 ℃ when the refining time is accumulated to 46min, and discharging the molten steel after the molten steel is softly blown for 5 min. The refining time of the molten steel in the furnace is accumulated for 55 min. The composition of each of the above sampled molten steels is shown in Table 5 below.

Table 5: composition of each sampled molten steel in LF process

(3) The compositions of the furnace slag sample are shown in the following table 6, and the basicity R of the slag is 1.8.

Table 6: slag sample composition

(4) The continuous casting of the furnace square billet is smoothly carried out.

Example 3: the steel-making method for improving the fluidity of the molten PC steel adopts the following specific process.

(1) Smelting in a converter: producing 30MnSi steel; ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy material, and low-aluminum ferrosilicon is not used.

(2) LF refining: and (3) measuring the temperature of the 15 th furnace molten steel entering the station at 1519 ℃ in a certain pouring time, adding lime in batches for slagging, transmitting power and heating for 15min, and sampling and testing after white slag is formed. A first sample of a refining furnace; then the power is supplied again to heat for 8min, alloy components are added according to the molten steel components of the first sample, the second sample is taken, the temperature is measured for 1555 ℃, and the assay components meet the requirements; at this time, the refining time was 30min in total, and 3.7kg/t wollastonite was added to the ladle. And (3) electrifying for the third time to increase the temperature, measuring the temperature by 1575 ℃ when the refining time is accumulated to 43min, and taking out the molten steel after soft blowing for 4 min. The refining time of the molten steel in the furnace is accumulated for 54 min. The composition of each of the above sampled molten steels is shown in Table 7 below.

Table 7: composition of each sampled molten steel in LF process

(3) The compositions of the furnace slag sample are shown in the following table 8, and the basicity R of the slag is 1.5.

Table 8: slag sample composition

(4) The continuous casting of the furnace square billet is smoothly carried out.

Example 4: the steel-making method for improving the fluidity of the molten PC steel adopts the following specific process.

(1) Smelting in a converter: producing 30MnSi steel; ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy material, and low-aluminum ferrosilicon is not used.

(2) LF refining: and (3) measuring the temperature of 17 th molten steel entering the station by 1535 ℃ in a certain pouring time, adding lime in batches for slagging, transmitting power and heating for 14min, and sampling and testing after white slag is formed. A first sample of a refining furnace; powering on again to raise the temperature for 5min, adding alloy components according to the molten steel components of the first sample, taking the second sample, measuring the temperature at 1566 ℃, and testing the components to meet the requirements; at this time, the refining time was accumulated for 32min, and 1.0kg/t of silica sand was added to the ladle. And (3) electrifying for the third time to increase the temperature, measuring the temperature at 1577 ℃ when the refining time is accumulated to 40min, and taking out the molten steel after soft blowing for 6 min. The refining time of the molten steel in the furnace is accumulated for 50 min. The composition of each of the above sampled molten steels is shown in Table 9 below.

Table 9: composition of each sampled molten steel in LF process

(3) The compositions of the furnace slag sample are shown in the following table 10, and the basicity R of the slag is 2.5.

Table 10: slag sample composition

(4) The continuous casting of the furnace square billet is smoothly carried out.

Example 5: the steel-making method for improving the fluidity of the molten PC steel adopts the following specific process.

(1) Smelting in a converter: producing 35Si2Mn steel; ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy material, and low-aluminum ferrosilicon is not used.

(2) LF refining: and (3) measuring the temperature of molten steel entering the station of the 2 nd furnace at 1522 ℃ in a certain casting time, adding lime in batches for slagging, transmitting power and heating for 12min, and sampling and testing after white slag is formed. A first sample of a refining furnace; then the power is supplied again to heat for 7min, alloy components are added according to the molten steel components of the first sample, the second sample is taken, the temperature is measured for 1555 ℃, and the assay components meet the requirements; at this time, the refining time was 30min in total, and 2kg/t wollastonite was added to the ladle. And (3) electrifying for the third time to increase the temperature, measuring the temperature by 1570 ℃ when the refining time is accumulated to 43min, taking out the sample from the station, and taking out the sample after the molten steel is softly blown for 5 min. The refining time of the molten steel in the furnace is accumulated for 57 min. The composition of each of the above sampled molten steels is shown in Table 11 below.

Table 11: composition of each sampled molten steel in LF process

(3) The compositions of the furnace slag sample are shown in the following table 12, and the basicity R of the slag is 1.9.

Table 12: slag sample composition

(4) The continuous casting of the furnace square billet is smoothly carried out.

Example 6: the steel-making method for improving the fluidity of the molten PC steel adopts the following specific process.

(1) Smelting in a converter: producing 35Si2Mn steel; ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy material, and low-aluminum ferrosilicon is not used.

(2) LF refining: and (3) measuring the temperature of the 7 th molten steel entering the station by 1518 ℃ in a certain pouring time, adding lime in batches for slagging, transmitting power and heating for 13min, and sampling and testing after white slag is formed. A first sample of a refining furnace; transmitting electricity again to heat for 6min, adding alloy components according to the molten steel components of the first sample, taking the second sample, measuring the temperature of 1580 ℃, and testing the components to meet the requirements; at this time, the refining time was integrated for 27min, and 2kg/t of silica sand was added to the ladle. And (3) supplying power for the third time to increase the temperature, measuring the temperature at 1560 ℃ when the refining time is accumulated to 43min, and discharging the molten steel after the molten steel is soft-blown for 5 min. The refining time of the molten steel in the furnace is accumulated for 50 min. The composition of each of the above sampled molten steels is shown in Table 13 below.

Table 13: composition of each sampled molten steel in LF process

(3) The compositions of the furnace slag sample are shown in the following table 14, and the basicity R of the slag is 1.5.

Table 14: slag sample composition

(4) The continuous casting of the furnace square billet is smoothly carried out.

Example 7: the steel-making method for improving the fluidity of the molten PC steel adopts the following specific process.

(1) Smelting in a converter: producing 35Si2Mn steel; ferrosilicon, ferromanganese and/or ferromanganese are/is used as alloy material, and low-aluminum ferrosilicon is not used.

(2) LF refining: and (3) measuring the temperature of 16 th furnace molten steel entering a station at 1530 ℃ in a certain pouring time, adding lime in batches for slagging, transmitting power and heating for 10min, and sampling and testing after white slag is formed. A first sample of a refining furnace; then the power is supplied again to heat for 6min, alloy components are added according to the molten steel components of the first sample, the second sample is taken, the temperature is measured at 1565 ℃, and the assay components meet the requirements; at this time, the refining time was 25min in total, and 2.6kg/t wollastonite was added to the ladle. And (3) electrifying for the third time to increase the temperature, measuring the temperature of 1555 ℃ when the refining time is accumulated to 40min, and taking out the molten steel after soft blowing for 4 min. The refining time of the molten steel in the furnace is accumulated for 45 min. The composition of each of the above sampled molten steels is shown in Table 15 below.

Table 15: composition of each sampled molten steel in LF process

(3) The compositions of the furnace slag sample are shown in the following table 16, and the basicity R of the slag is 2.5.

Table 16: slag sample composition

(4) The continuous casting of the furnace square billet is smoothly carried out.