CN113564297B

CN113564297B - Method for reducing content of manganese oxide in slag

Info

Publication number: CN113564297B
Application number: CN202110864202.0A
Authority: CN
Inventors: 梁森泉; 徐友顺; 江育明; 胡现锋; 张建平; 肖双林; 陈兵
Original assignee: SGIS Songshan Co Ltd
Current assignee: SGIS Songshan Co Ltd
Priority date: 2021-07-29
Filing date: 2021-07-29
Publication date: 2022-06-21
Anticipated expiration: 2041-07-29
Also published as: CN113564297A

Abstract

A method for reducing the content of manganese oxide in slag, belonging to the technical field of metal smelting. The method comprises blast furnace tapping, converter smelting and LF refining, and is characterized in that a slag agent is added in the LF refining process to carry out power transmission slagging, after the power transmission slagging is finished, MnO in the refining slag is controlled to a first threshold value after argon gas is blown softly for a set time, the alkalinity of the refining slag is adjusted to a second threshold value, a first molten steel sample, slag bonding, temperature measurement and oxygen determination are taken, ferromanganese, ferrosilicon and lime are sequentially added, the MnO in the refining slag is controlled to a third threshold value, and the alkalinity of the refining slag is adjusted to a fourth threshold value, wherein the Si content in steel is adjusted by adding the ferrosilicon according to the silicon content of the first molten steel sample, the first threshold value is larger than the third threshold value, and the second threshold value is smaller than the fourth threshold value. The method has the advantages of realizing easier operation of the process of controlling free oxygen by silicon, simplifying the process, reducing the oxygen control steps in the process, reducing the proportion of converting Mn into slag and returning the slag into steel, reducing the consumption of Mn raw materials and greatly improving the quality of casting blanks.

Description

Method for reducing content of manganese oxide in slag

Technical Field

The application relates to the technical field of metal smelting, in particular to a method for reducing the content of manganese oxide in slag.

Background

The first prior art is as follows: patent application No. CN200910062748.3 (the patent of this invention is granted to be effective). The invention relates to a production process method of low-carbon high-sulfur free-cutting steel, which is characterized by comprising the following steps: 1) oxygen blowing smelting is carried out by adopting an electric furnace under the condition of no power supply, the ratio of hot molten iron and scrap steel of the electric furnace reaches 7.0: 1.0-3.0, and a carbon-oxygen gun of a furnace door and a coal-oxygen sublance of a furnace wall alternately feed into the furnaceOxygen blowing and carbon-rich smelting; 2) steel is left at the eccentric furnace bottom, slag is left for tapping, pre-deoxidation is carried out after the furnace, and then slag is formed; 3) the low-alkalinity slag is manufactured by a refining furnace, and the refining slag comprises the following components in percentage by weight: CaO: 40 to 50% of SiO₂：15～30％，Al₂O₃: 20-35%, MgO: 5-15%; after the chemical components of all elements in the steel meet the required requirements and the temperature reaches 1580-1600 ℃, feeding Ca wires or Ca-Si wires into a refining furnace, and carrying out pit forming and ladle transferring on a continuous casting platform for soft blowing for 8-15 min; 4) continuous casting adopts a four-flow arc continuous casting machine, and adopts long-nozzle argon seam sealing protection and tundish argon blowing protection casting; the secondary cooling adopts a weak cooling process, the crystallizer adopts electromagnetic stirring, the current is 600-700A, and the frequency is 4-5 Hz.

The second prior art is: patent application No. CN201210184463.9 (the patent of this invention is granted to be effective). The invention relates to a low-carbon high-sulfur free-cutting steel with excellent cutting performance and a production method thereof, and the low-carbon high-sulfur free-cutting steel is characterized by being recorded in a specification: the free-cutting steel comprises the following components in percentage by mass: c: 0.05-0.2%, Mn: 0.6-2.0%, P: 0.04-0.1%, S: 0.2-0.45%, O: 0.005-0.02%, N is less than or equal to 0.02%, Si is less than or equal to 0.005%, and Al is less than or equal to 0.001%, wherein the generated MnS inclusion has the following properties: (1) more than 95 percent of MnS inclusions in the as-cast steel are I-class MnS, and the proportion of single-phase MnS inclusions is more than or equal to 80 percent; (2) at least 70 percent of MnS inclusions in the rolling direction have the length more than or equal to 5 microns and the length-width ratio less than or equal to 6; (3) the average area of MnS inclusions in the area of 2mm in the rolling direction is not less than 50 mu m 2. The deoxidation is carried out by adopting C, the cooling rate of the cast ingot is controlled to be 2-4 mm/min, the initial rolling temperature is controlled to be 1200-1250 ℃, and the final rolling temperature is controlled to be not less than 1050 ℃. The steel has excellent cutting performance, the surface of a part after cutting has better finish, the total level is close to or reaches the level of lead-containing low-carbon free-cutting steel, and the steel is suitable for high-speed cutting.

The prior art is three: patent application No. CN201410178495.7 (the patent of this invention is granted to be effective). The invention relates to a production method of low-carbon high-sulfur free-cutting steel with excellent sulfide form, which is characterized by comprising the following steps: (1) controlling the end point carbon content of the electric furnace to be 0.03-0.05%, and controlling the tapping temperature to be 1610-1640 ℃; slag-remaining tapping is adopted, 1.5-2.5 kg/t of silicomanganese, 10-15 kg/t of low-carbon ferromanganese, 10-13 kg/t of pyrite and 1-2 kg/t of phosphosiderite are added in sequence in the tapping process for alloying, and 6-8 kg/t of special synthetic slag and 1-2 kg/t of lime slagging are added; (2) the TFe content in the refining slag is 3-5%, and 80-100 m sulfur core-spun yarns are fed into molten steel in the later stage of refining; the free oxygen content in molten steel before tapping is controlled to be 50-100 ppm, and the temperature of the tapped molten steel is 1560-1590 ℃; (3) the continuous casting adopts the special covering slag for free-cutting steel, the water flow of a crystallizer is 1700-1900L/min, the secondary cooling zone adopts spray cooling, the specific water amount is 0.7-0.9L/kg, and the pulling speed is 2.0-2.6 m/min; (4) the temperature of the heating furnace is 1230-1280 ℃, and the temperature is kept for 0.5-1.5 h; the initial rolling temperature is 1100-1130 ℃, the final rolling temperature is 1050-1120 ℃, and the stelmor linear cooling speed is 0.5-1.5K/s.

The three patent applications of the invention all relate to the oxygen content control of low-carbon high-sulfur free-cutting steel, wherein the patent application number is CN200910062748.3, and the oxygen content control method comprises the following steps: when the steel tapping amount reaches 1/3, adding steel core aluminum and a composite refining deoxidizer into the ladle at 0.5 kg/t; the refining furnace produces low-alkalinity slag, and Ca wires or Ca-Si wires are fed before the refining is out of the station. Aluminum is used for deoxidation, and Ca lines or Ca-Si lines are used for accurately controlling the oxygen content, but Al and Ca in molten steel are easily high, and formed oxide particles are easy to fall off to form surface pits during cutting in a post process. Patent application No. CN201210184463.9 relates to die cast steel, and the oxygen content control method comprises the following steps: and Al and Si are not used for deoxidation in the deoxidation process, C is used for deoxidation, and the oxygen content in the steel is controlled within the range of 0.005-0.02%. The patent application number CN201210184463.9 relates to electric furnace steel, and the oxygen content control method comprises the following steps: controlling the end point carbon and the tapping temperature, and adding 1.5-2.5 kg/t of silicomanganese, 10-15 kg/t of low-carbon ferromanganese, 10-13 kg/t of pyrite and 1-2 kg/t of phosphosiderite to carry out alloying in the tapping process; controlling the TFe content in the refining slag to be 3-5%, and controlling the free oxygen content in the molten steel at the end of refining to be 50-100 ppm. The above patent does not pay attention to the control of the manganese oxide content in the slag while paying attention to the control of the oxygen content of the low-carbon high-sulfur free-cutting steel, and does not pay attention to how to reduce the control of the manganese oxide content in the slag, and does not relate to the control of the manganese oxide content in the slag in the LF refining process, the adding time of raw materials, argon blowing, slag control in the refining process and the like, so that the problems that according to the method disclosed by the above patent, the oxygen content of the low-carbon high-sulfur free-cutting steel is unstable, the oxygen content of part of the furnace is over-standard, the consumption of manganese raw materials is large and the like are caused.

The prior art is four: CN201911084949.3 discloses a molten steel refining and continuous casting method for reducing subcutaneous bubbles of low-silicon low-aluminum oxygen-containing steel casting blanks, which adopts a step control method to control the content of dissolved oxygen and Si in molten steel and the content of MnO in refining slag, and specifically comprises the following steps: controlling the Si content in molten steel at the early stage of LF refining to be 0.04-0.06%; before LF refining is finished, adding ferrosilicon to increase the Si content in the molten steel to 0.015-0.035%; after LF refining is finished, the dissolved oxygen in the molten steel is 35-60 ppm, the Si content is 0.015-0.035%, and the MnO content in the refining slag is less than 10%. The method mainly relates to the step-by-step control of the oxygen content in molten steel, the control of the Si content in the molten steel at the early stage of LF refining, and the early addition of ferrosilicon to deoxidize the molten steel in advance, so that the purposes of improving the alkalinity in slag and reducing the manganese oxide in the slag are facilitated.

In addition, if ferrosilicon is added in the late stage of refining, the reaction time is easy to be insufficient, deoxidation is insufficient, and in the case that molten steel contains oxygen and silicon, oxidation reaction of silicon occurs slowly to continuously generate inclusions, and during continuous casting and steel drawing, the inclusions are easy to aggregate or peel off, and liquid level fluctuation is caused.

According to the problems, the method for simultaneously controlling the content of manganese oxide in slag during molten steel deoxidation needs to be improved urgently so as to realize easier operation of the silicon-controlled free oxygen process, simplify the process, reduce the oxygen control steps in the process, reduce the proportion of Mn converted into slag and returned into steel, reduce the consumption of Mn raw materials and greatly improve the quality of casting blanks.

Disclosure of Invention

The embodiment of the application aims to provide a method for reducing the content of manganese oxide in slag, which can realize easier operation of a silicon-controlled free oxygen process, simplify the process, reduce the oxygen control steps of the process, reduce the proportion of Mn converted into slag and then returned into steel, reduce the consumption of Mn raw materials and greatly improve the quality of a casting blank.

The application is realized as follows:

the example of this application provides a method of manganese oxide content in reduction sediment, including blast furnace tapping, the converter is smelted, the LF is concise, and the LF refining process adds the slag agent and carries out the power transmission slagging, after the power transmission slagging is ended, MnO control to threshold value one in will refining the sediment after to more than the settlement time of soft argon gas that blows, and refining sediment basicity is adjusted threshold value two, gets molten steel sample one, glues the sediment, temperature measurement, decide oxygen, later add ferromanganese, ferrosilicon, lime in proper order, MnO control to threshold value three in will refining the sediment, and refining sediment basicity is adjusted to threshold value four, and wherein, Si content basis in the steel the silicon content of molten steel sample one is joined in marriage with the ferrosilicon and is adjusted, threshold value one is greater than threshold value three, threshold value two is less than threshold value four.

In some examples, MnO in the refining slag is controlled to be 17wt% -20 wt% of the first threshold, and the alkalinity of the refining slag is adjusted to be 1.9-2.1 of the second threshold; and controlling MnO in the refining slag to 10-13.5 wt% of the threshold III, and adjusting the alkalinity of the refining slag to 2.3-2.6 of the threshold IV.

In some examples, the argon is soft-blown to the set time of 1 minute;

in some examples, the LF arrival temperature is measured first, and oxygen is not determined when the temperature is lower than 1530 ℃.

In some examples, after the electric slagging is finished, soft argon blowing is carried out to ensure that the diameter of a bright ring of an argon port on the liquid surface is within 20cm, and the argon flow is 3.5-6.5 NM³/h。

In some examples, the Si content in the steel is adjusted to 0.36wt% to 0.44wt% by adding ferrosilicon according to the silicon content of the first steel liquid sample.

In some examples, the Si content in the steel is adjusted according to the silicon content of the first steel liquid sample, ferrosilicon is added, then lime is added after the argon blowing stirring interval is 260-300 s, and the adding amount of the lime is 2.7-3.3 times of the adding amount of the ferrosilicon.

In some examples, when ferromanganese, ferrosilicon and lime are added in sequence, the diameter of argon gas blown is more than 50mm, and the flow rate of argon gas is 50NM³/h～70NM³H, uniformly adding lime for 2.7-3.3 minutes, taking a molten steel sample II, weakly blowing argon, wherein the argon blowing diameter is 20mm, the liquid level is still, and the argon flow is 3.5NM³/h-6.5NM³/h。

In some examples, a liquid steel sample is taken to be secondarily oxygenated, ferrosilicon powder is added according to the oxygen content of the liquid steel for deoxidation, the free oxygen content of the liquid steel is accurately adjusted to 35 ppm-65 ppm, the ferrosilicon powder is added by hand for deoxidation, scattered black spots are formed on the slag surface after the deoxidizer is added by hand until the black spots are not seen, then oxygen is determined, lime is supplemented according to the oxygen content of the liquid steel, and the ferrosilicon powder is supplemented by oxygen.

In some examples, the converter smelting process only heats up for decarburization, the end point carbon content is controlled to be 0.03-0.06 wt%, the end point temperature is 1650-1680 ℃, and the end point [ O ]: 600ppm to 800ppm, respectively adding 13kg/t to 14kg/t of low-carbon ferromanganese, 2.3kg/t to 2.6kg/t of silicon-manganese alloy and 0.7kg/t to 2.3kg/t of ferrophosphorus in the tapping process in sequence, and controlling the free oxygen content in the molten steel to be 90ppm to 200 ppm.

The beneficial effect of this application includes:

after a slag agent is added in the LF refining process to carry out power transmission slagging, a molten steel sample I, slag adhering, temperature measuring and oxygen determining are taken, ferromanganese, ferrosilicon and lime are sequentially added, the taken molten steel sample I is taken as the optimal time for controlling the content of manganese oxide, the content of Si in steel is adjusted by adding the ferrosilicon according to the content of silicon in the molten steel sample I, therefore, before the sample I, silicon is not added for deoxidation treatment, the ferromanganese is added for manganese preparation, the deoxidation effect of the ferromanganese is also utilized to reduce the burden of Si deoxidation, the Si deoxidation time is delayed to the middle time of LF refining, at the moment, the free oxygen in the molten steel and the oxygen in the slag are uniformly mixed, the steel and the slag are fully mixed by utilizing big argon gas for stirring, the reduction of the manganese oxide in the slag is facilitated, the free oxygen in the molten steel is easy to accurately controlled, in addition, the argon blowing oxygenation time can be reduced for at least 20-30 minutes, and the increase of manganese oxide caused by ferromanganese and silicon deoxidation in the early stage of LF refining is avoided, the problems of excessively high MnO content in the slag process and the like are facilitated, manganese oxide in the slag is reduced, Mn and Fe are firstly blended for alloying, then Si is reduced, lime is added, the adverse effect of low alkalinity in the slag on reduction of manganese oxide can be avoided, the alkalinity is improved, the feeding step is tightly matched, the time interval is short, the manganese oxide in the slag is transferred to the slag after the manganese component is oxidized in a reducing mode, the problem of excessively high manganese oxide in the slag is caused, and the control to the lower degree of the MnO content in the slag is facilitated.

The adding mode can fully deoxidize, simultaneously reduces manganese in slag to the maximum extent, achieves the effects of reducing manganese oxide and saving ferromanganese, can realize easier operation of a silicon controlled free oxygen process, simplifies the process, reduces the process oxygen control steps, reduces the proportion of converting Mn into slag and returning the slag into steel, greatly improves the casting blank quality, ensures the total oxygen content of 130-180 ppm in finished product (steel) steel, and meets the cutting performance requirements of steel grades such as low-carbon high-sulfur free-cutting steel and the like. After the technology is implemented, the defect of bubbles on the surface of a casting blank is obviously improved, the accident of warping quality of the surface of a rolled wire rod is reduced, the pinhole rate of the surface of a processed polished rod is reduced to an acceptable range, and the product quality is greatly improved.

Drawings

To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

FIG. 1 is a diagram of a slag surface with black spots after a deoxidizer is thrown by hands.

Detailed Description

1215MS of the low-carbon high-sulfur free-cutting steel has the following process flow: blast furnace molten iron → blast furnace mixer → 120t converter smelting → LF furnace refining → 2# continuous casting → casting blank stacking and cooling → blank inspection, cleaning → heating of billet cold charging and heating furnace → mill plant-high line controlled rolling and cooling → finishing → inspection → packing → weighing → warehousing. Through research and demonstration, the process requirement is continuously improved, the oxygen discharged from the refining furnace can reach a target value of +/-10 ppm, and the total oxygen content on the material is 130-180 ppm; meanwhile, the surface quality of the casting blank is also considered (the oxygen content is high, a large number of air holes exist on the surface of the casting blank, the defects of scabbing, warping and the like on the surface of a wire rod can be caused, and the oxygen content needs to be controlled to a lower level).

A method for reducing the content of manganese oxide in slag is provided based on the deoxidation control requirement of 1215MS of low-carbon high-sulfur free-cutting steel, and the steps of the smelting method for reducing the content of manganese oxide in slag in the embodiment of the application are described in detail below.

In order to accurately adjust the free oxygen content of molten steel after LF refining to 35 ppm-65 ppm, the method adopts the following smelting method:

(1) the converter smelting process is characterized in that only temperature rise and decarburization are carried out in the converter smelting process, the end point carbon content is controlled to be 0.03wt% -0.06 wt%, optionally 0.03wt%, 0.04 wt%, 0.05 wt%, 0.06wt% and the like, the end point temperature is 1650-1680 ℃, optionally 1650 ℃, 1660 ℃, 1670 ℃, 1680 ℃ and the like, and the end point [ O ]: 600 ppm-800 ppm, optionally 600ppm, 610ppm, 620ppm, 630ppm, 650ppm, 660ppm, 670ppm, 690ppm, 700ppm, 710ppm, 720ppm, 740ppm, 750ppm, 770ppm, 780ppm, 790ppm, 800ppm and the like, 13 kg/t-14 kg/t of low-carbon ferromanganese is added in the tapping process, optionally 13kg/t, 13.3kg/t, 13.5kg/t, 13.6kg/t, 13.7kg/t, 13.8kg/t, 13.9kg/t, 14kg/t and the like; 2.3 kg/t-2.6 kg/t silicon-manganese alloy, which can be selected from 2.3kg/t, 2.4kg/t, 2.5kg/t, 2.6kg/t, etc.; 0.7kg/t to 2.3kg/t ferrophosphorus, optionally 0.7kg/t, 0.8kg/t, 0.9kg/t, 1.0kg/t, 1.3kg/t, 1.5kg/t, 1.6kg/t, 1.7kg/t, 1.8kg/t, 1.9kg/t, 2.0kg/t, 2.1kg/t, 2.2kg/t, 2.3kg/t, etc., wherein the free oxygen content in the molten steel is controlled to be 90ppm to 200ppm, optionally 90ppm, 93ppm, 95ppm, 99ppm, 100ppm, 110ppm, 120ppm, 130ppm, 140ppm, 150ppm, 160ppm, 170ppm, 180ppm, 200ppm, etc. The mass percentage of the manganese content in 1215MS steel is 1.10-1.35%, because the MnO content needs to be reduced in the converter tapping, and the manganese can be reduced to molten steel after the subsequent refining deoxidation, most of low-carbon ferromanganese and silicomanganese need to be added in the converter smelting, and fine adjustment is performed in the refining process, so that the control of the manganese component is more stable. The end point carbon content, the end point oxygen content and the end point temperature are controlled during the tapping of the converter, manganese alloy is added in sequence in the tapping process, the oxygen content in steel is reduced, the Mn alloying in the steel is ensured, the oxygen content control of molten steel before LF refining is ensured, the subsequent manganese oxidation can be reduced, the MnO generation in the tapping process is reduced, the MnO content in slag is reduced, and good conditions are created for the subsequent LF refining control.

(2) LF refining

And (4) measuring the temperature at the LF arrival station, and determining the oxygen when the temperature is lower than 1530 ℃. When the temperature of molten steel is less than 1520 ℃ or close temperature, only the temperature is needed, no oxygen value exists, even if oxygen can be determined, the oxygen value is inaccurate and can be too high, the deoxidation control of operators is influenced, and the deoxidation is insufficient to cause high manganese oxide in slag, so that LF refining is adopted to measure temperature first when arriving at a station, oxygen is not determined when the temperature is lower than 1530 ℃, and oxygen is not determined, or the oxygen value of oxygen is not determined, and the oxygen determination couple is wasted. At this time, the operation of heating up and slagging can be directly adopted, and the oxygen is determined after the temperature of the molten steel is raised.

In the early stage of LF refining, in order to ensure that the alkalinity is not too low after molten steel deoxidation and ensure that manganese oxide in slag does not exceed the standard, 40-60 kg of aluminum slag and 360-440 kg of lime are sequentially added into the molten steel in the refining process, preferably, 50 kg of aluminum slag and 400 kg of lime are sequentially added into the molten steel in the refining process, a slag agent is added for electrically-conveying slagging, argon is softly blown after the electrically-conveying slagging is finished, the diameter of an argon hole bright ring at the liquid level is ensured to be within 20cm (optionally 16cm, 17cm, 18cm, 19cm, 20cm and the like), and the argon flow is 3.5-6.5 NM³H, optionally 3.5NM³/h、3.6NM³/h、3.7NM³/h、3.8NM³/h、3.9NM³/h、4.1NM³/h、4.3NM³/h、4.5NM³/h、4.7NM³/h、4.9NM³/h、5.0NM³/h、5.2NM³/h、5.4NM³/h、5.7NM³/h、5.9NM³/h、6.1NM³/h、6.3NM³/h、6.5NM³And/h, soft blowing argon for more than 1 minute, wherein the bright ring of the argon port on the small liquid level, the flow and the time of the argon can ensure that the liquid steel level is calm down, the liquid steel and the steel slag are completely separated, carbon contained in the electrode is avoided, and the electrode has a certain deoxidation function to cause fixationThe oxygen content is low, and the molten steel is excessively oxidized. Therefore, MnO in the refining slag is controlled to be 17wt% -20 wt%, and 17wt%, 18 wt%, 19 wt%, 20wt% and the like can be selected, and the alkalinity of the refining slag is adjusted to be 1.9-2.1, and 1.9, 2.0, 2.1 and the like can be selected. The electric slagging process is carried out without deoxidation to a lower level, the high oxidability and low alkalinity of the slag are maintained, the subsequent oxygenation problem caused by deoxidation in the early stage of refining can be reduced, and early slagging is facilitated. The inventor finds that the slag alkalinity control range and the MnO control range create favorable conditions for subsequent deoxidation and reduction of MnO in the slag.

Taking a molten steel sample I, sticking slag, measuring temperature and determining oxygen, wherein the oxygen is determined at the moment, the molten steel and the steel slag are completely separated, the problems that the oxygen determination value is lower and the molten steel is excessively oxidized and the like caused by carbon containing and certain deoxidation function of an electrode are avoided, and the accuracy of the oxygen determination value is ensured.

Adding ferromanganese, ferrosilicon and lime in sequence after oxygen determination, blowing argon gas with diameter of 50mm or more, optionally 50mm, 53mm, 55mm, 60mm, etc. with argon gas flow of 50NM³/h～70NM³H, optionally 50NM³/h、53NM³/h、57NM³/h、61NM³/h、64NM³/h、67NM³/h、69NM³/h、70NM³And/h, controlling MnO in the refining slag to be 10wt% -13.5 wt%, optionally 10wt%, 11 wt%, 12 wt%, 13.5wt%, and the like, adjusting the alkalinity of the refining slag to be 2.3-2.6, optionally 2.3, 2.4, 2.5, 2.6, and the like, wherein the Si content in the steel is adjusted to be 0.36wt% -0.44 wt%, optionally 0.36wt%, 0.37 wt%, 0.38 wt%, 0.39 wt%, 0.40 wt%, 0.41 wt%, 0.42 wt%, 0.43 wt%, 0.44wt%, and the like according to the silicon content of the first molten steel sample.

If add ferrosilicon deoxidization then carry out manganese alloying in LF refining earlier stage, there is 55 minutes argon blowing process after LF earlier stage, argon blowing process must increase manganese oxidation, MnO content is very high in the slag in the result of LF refining process, reductant such as more ferrosilicon need be adopted in the later stage with it reduction to the steel in, it leads to the fact the raw materials extravagant while to lead to Mn0 content to reduce difficult the realization, MnO content too high phenomenon in the slag appears in partial heat, therefore, do not carry out before the molten steel appearance oneAnd silicon deoxidation treatment is matched, when a molten steel sample is obtained, ferromanganese is firstly added for alloying, ferrosilicon is then added, the Si deoxidation time is delayed until the middle time of LF refining, the total length of argon blowing oxygenation time is reduced by at least 20-30 minutes, the increase of manganese oxidation in the argon blowing process is reduced, the problem of overhigh MnO content in the slag process is avoided, manganese oxide in the slag is reduced, Mn iron is firstly matched for alloying and then Si is reduced, lime is added, the alkalinity is improved, the feeding step is closely matched, the time interval is short, the transfer of manganese components after oxidation to the slag can be reduced, the problem of manganese oxide in the slag is increased, and the control of the MnO content in the slag to a reduction degree is facilitated. The inventor finds that the MnO control target and the alkalinity control target in the slag are realized, deoxidation can be realized, and the manganese in the molten steel can be returned in all the furnace times, namely, the reduction of the manganese oxide in the slag can be reflected in different degrees, namely, the reduction target of the manganese oxide in the slag is realized. The diameter of the argon blowing is more than 50mm, the flow of the argon is 50-70 NM³And h, the diameter of the large argon gas and the argon blowing flow enable ferromanganese, ferrosilicon, lime and the like added to react quickly, instant slag foams, and manganese oxide in the slag can be reduced rapidly.

After the ferrosilicon is added, argon is blown, the stirring interval is 260-300 s (optional 260s, 270s, 280s, 290s, 300s and the like), then lime is added, the stirring time is short, silicon in steel does not react completely, the deoxidation is insufficient, and the determined oxygen value is higher; however, if the stirring time is too long, silicon in the steel is completely oxidized, oxygen is absorbed by the molten steel, and manganese oxide in the slag is higher. The adding amount of lime is 2.7-3.3 times of the adding amount of silicon and iron, and can be selected from 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3 and the like, and the preferable adding amount of lime is 3 times of the adding amount of silicon and iron. In order to avoid the disadvantage that the low alkalinity in the slag is harmful to the reduction of manganese oxide, lime needs to be added after the ferrosilicon or ferrosilicon powder is added, the alkalinity of the slag is supplemented, and the adding amount of the lime is calculated according to 2.7-3.3 times of the adding amount of the ferrosilicon. The addition amount is small, the slag surface looks slightly dilute, the alkalinity in the slag is not enough, the manganese return of the molten steel is not obvious, and the manganese oxide in the slag is slightly high; however, if the amount of the manganese oxide is increased, the slag is too thick, the fluidity is poor, the steel-slag reaction is not facilitated, and the phenomena of high alkalinity and high manganese oxide in the slag can occur.

Uniformly adding lime, uniformly stirring for 2.7-3.3 minutes, taking a molten steel sample II, and weakly blowing argon with the diameter of 20mm or moreThe liquid level is still and the argon flow is 3.5NM³/h-6.5NM³H is used as the reference value. Taking a molten steel sample, determining oxygen, adding ferrosilicon powder according to the oxygen content of the molten steel for deoxidation, accurately adjusting the free oxygen content of the molten steel to 35-65 ppm, wherein the adding mode is that the ferrosilicon powder is manually added for deoxidation, scattered black points are formed on the slag surface after a deoxidizer is manually added until the black points cannot be seen, then determining oxygen, supplementing lime according to the oxygen content of the molten steel, and determining oxygen and supplementing ferrosilicon powder. After the deoxidizer is thrown by hand, scattered black spots are formed on the slag surface, a certain argon blowing amount or argon blowing time is needed to enable the deoxidizer to be completely reacted with slag or molten steel until the black spots cannot be seen, and then oxygen is determined, wherein the oxygen determination can ensure that the result is accurate.

The features and properties of the present application are described in further detail below with reference to examples:

example one

Deoxygenation smelting of 1215MS of the low-carbon high-sulfur free-cutting steel, a converter smelting process, only heating and decarbonization in the converter smelting process, controlling the end point carbon content to be 0.04 wt%, controlling the end point temperature to be 1660 ℃, and controlling the end point [ O ] to be [ O ]]: 610ppm, respectively adding 13.3kg/t of low-carbon ferromanganese, 2.5kg/t of silicon-manganese alloy and 0.9kg/t of ferrophosphorus in the tapping process in sequence, and controlling the free oxygen content in the molten steel to be 110 ppm. In LF refining, 50 kg of aluminum slag and 400 kg of lime are added into molten steel in sequence in the refining process, a slag agent is added to carry out electric slagging, and after the electric slagging is finished, argon is blown softly to ensure that the diameter of a bright ring at an argon port on a liquid surface is 20cm, and the argon flow is 3.9NM³And/h, soft blowing argon for more than 1 minute, controlling MnO in the refining slag to be 18 wt%, and adjusting the alkalinity of the refining slag to be 1.9. Taking a molten steel sample I, sticking slag, measuring temperature, determining oxygen, sequentially adding ferromanganese, ferrosilicon and lime after determining the oxygen, and blowing argon gas with the diameter of 53mm and the argon gas flow of 53NM when the ferromanganese, the ferrosilicon and the lime are sequentially added³And h, controlling MnO in the refining slag to be 11 wt%, and adjusting the alkalinity of the refining slag to be 2.6, wherein the Si content in the steel is adjusted to be 0.41 wt% by adding ferrosilicon according to the silicon content of the first steel liquid sample. Adding lime after blowing argon and stirring for 260s after adding ferrosilicon, wherein the adding amount of lime is calculated according to 3 times of the adding amount of ferrosilicon, 3 minutes after adding lime, taking a molten steel sample II, blowing argon weakly, blowing argon with the diameter of 20mm, keeping the liquid level still, and controlling the argon flow to be 3.5NM³H is used as the reference value. Taking a molten steel sample, determining oxygen, adding ferrosilicon powder according to the oxygen content of the molten steel for deoxidation, and accurately adjusting the free oxygen content of the molten steel to 38 ppm. The detected content of the first manganese in the steel liquid sample is 1.219 wt%, the content of the second manganese in the steel liquid sample is 1.36 wt%, the theoretical manganese is increased by 0.045 wt%, the actual manganese is increased by 0.141 wt%, and the manganese in the slag is returned by 0.096 wt%, which reflects that the content of the manganese oxide in the slag is reduced.

Example two

Deoxygenation smelting of 1215MS of low-carbon high-sulfur free-cutting steel, a converter smelting process, only heating and decarbonization in the converter smelting process, controlling the end point carbon content to be 0.05 wt%, the end point temperature to be 1671 ℃, and the end point [ O ] O]: 670ppm, respectively adding 13.2kg/t of low-carbon ferromanganese, 2.4kg/t of silicon-manganese alloy and 2.1kg/t of ferrophosphorus in the tapping process in sequence, and controlling the free oxygen content in the molten steel to 170 ppm. In LF refining, 55 kg of aluminum slag and 430 kg of lime are added into molten steel in sequence in the refining process, a slag agent is added for power transmission slagging, argon is blown softly after the power transmission slagging is finished, the diameter of a bright ring at an argon port on the liquid surface is ensured to be 20cm, and the argon flow is 5.2NM³And/h, soft blowing argon for more than 1 minute, controlling MnO in the refining slag to be 16.5 wt%, and adjusting the alkalinity of the refining slag to be 1.85. Taking a molten steel sample I, sticking slag, measuring temperature, determining oxygen, sequentially adding ferromanganese, ferrosilicon and lime after determining the oxygen, and when the ferromanganese, the ferrosilicon and the lime are sequentially added, blowing argon gas with the diameter of 54mm and the argon gas flow of 63NM³And h, controlling MnO in the refining slag to be 12 wt%, and adjusting the alkalinity of the refining slag to be 2.5, wherein the Si content in the steel is adjusted to be 0.43 wt% by adding ferrosilicon according to the silicon content of the first steel liquid sample. Adding lime after the ferrosilicon is added and argon blowing stirring is carried out for 290s, wherein the adding amount of the lime is calculated according to 3.1 times of the adding amount of the ferrosilicon, 3 minutes after the lime is added, taking a molten steel sample II, blowing argon weakly, blowing argon with the diameter of 20mm, keeping the liquid level still, and controlling the argon flow to be 3.5NM³H is used as the reference value. Taking a molten steel sample, determining oxygen, adding ferrosilicon powder according to the oxygen content of the molten steel for deoxidation, and accurately adjusting the free oxygen content of the molten steel to 41 ppm. The detected content of the first manganese in the steel liquid sample is 1.221 wt%, the content of the second manganese in the steel liquid sample is 1.304 wt%, the theoretical manganese is increased by 0.041 wt%, the actual manganese is increased by 0.083 wt%, and the manganese in the slag is returned by 0.042 wt%, which reflects that the content of the manganese oxide in the slag is reduced.

EXAMPLE III

Deoxygenation smelting of 1215MS of low-carbon high-sulfur free-cutting steel, converter smelting process, only heating for decarbonization in the converter smelting process, controlling the end point carbon content to be 0.03wt%, the end point temperature to be 1659 ℃, and the end point [ O ] O]: 723ppm, respectively adding 13.2kg/t of low-carbon ferromanganese, 2.51kg/t of silicon-manganese alloy and 1.75kg/t of ferrophosphorus in the tapping process in sequence, and controlling the free oxygen content in the molten steel to be 135 ppm. In LF refining, 43 kg of aluminum slag and 385 kg of lime are added into molten steel in the refining process in sequence, a slag agent is added to carry out power transmission slagging, argon is blown softly after the power transmission slagging is finished, the diameter of a bright ring at an argon port on the liquid surface is ensured to be 19cm, and the argon flow is 4.2NM³And/h, soft blowing argon for more than 1 minute, controlling MnO in the refining slag to be 18.5 wt%, and adjusting the alkalinity of the refining slag to be 2.05. Taking a molten steel sample I, sticking slag, measuring temperature, determining oxygen, sequentially adding ferromanganese, ferrosilicon and lime after determining the oxygen, and when the ferromanganese, the ferrosilicon and the lime are sequentially added, blowing argon gas with the diameter of 52mm and the argon gas flow of 56NM³And h, controlling MnO in the refining slag to be 13 wt%, and adjusting the alkalinity of the refining slag to be 2.2, wherein the Si content in the steel is adjusted to be 0.44wt% by adding ferrosilicon according to the silicon content of the first steel liquid sample. Adding lime after blowing argon and stirring for 285s after adding ferrosilicon, wherein the adding amount of lime is calculated according to 2.6 times of the adding amount of ferrosilicon, 3 minutes after adding lime, taking a molten steel sample II, blowing argon gas weakly, blowing argon gas with diameter of 20mm, keeping the liquid level still, and controlling the argon gas flow to be 3.5NM³H is used as the reference value. Taking a molten steel sample, determining oxygen, adding ferrosilicon powder according to the oxygen content of the molten steel for deoxidation, and accurately adjusting the free oxygen content of the molten steel to 43 ppm. The detected content of manganese I in the steel liquid sample is 1.257 wt%, the content of manganese II in the steel liquid sample is 1.315 wt%, the theoretical manganese content is increased by 0.035 wt%, the actual manganese content is increased by 0.058 wt%, and the content of manganese oxide in slag is reduced by 0.023 wt%.

Example four

Deoxygenation smelting of 1215MS of low-carbon high-sulfur free-cutting steel, a converter smelting process, only heating and decarbonization in the converter smelting process, controlling the end point carbon content to be 0.06wt%, the end point temperature to be 1676 ℃, and the end point [ O ] O]: 636ppm, respectively adding 13.9kg/t low-carbon ferromanganese, 2.33kg/t silicon-manganese alloy and 0.86kg/t ferrophosphorus in the tapping process in sequence, and controlling the free oxygen content in the molten steel to be 96 ppm. In LF refining, 48 kg of aluminum slag and 423 kg of stone are added into molten steel in sequence in the refining processAsh, adding slag agent to carry out electric slagging, and after the electric slagging is finished, soft blowing argon to ensure that the diameter of a bright ring of an argon port on the liquid surface is 18cm, and the argon flow is 3.9NM³And/h, soft blowing argon for more than 1 minute, controlling MnO in the refining slag to be 20.5 wt%, and adjusting the alkalinity of the refining slag to be 2.15. Taking a molten steel sample I, sticking slag, measuring temperature, determining oxygen, sequentially adding ferromanganese, ferrosilicon and lime after determining the oxygen, and when the ferromanganese, the ferrosilicon and the lime are sequentially added, blowing argon with the diameter of 51mm and the argon flow of 53NM³And h, controlling MnO in the refining slag to be 13.5wt%, and adjusting the alkalinity of the refining slag to be 2.7, wherein the Si content in the steel is adjusted to be 0.40 wt% by adding ferrosilicon according to the silicon content of the first steel liquid sample. Adding lime after adding ferrosilicon and blowing argon for stirring at an interval of 283s, wherein the adding amount of lime is calculated according to 3.4 times of the adding amount of ferrosilicon, taking a molten steel sample II 3 minutes after adding lime, blowing argon weakly, blowing argon with the diameter of 20mm, keeping the liquid level still, and controlling the argon flow to be 3.5NM³H is used as the reference value. Taking a molten steel sample, determining oxygen, adding ferrosilicon powder according to the oxygen content of the molten steel for deoxidation, and accurately adjusting the free oxygen content of the molten steel to 44 ppm. The detected content of the first manganese in the steel liquid sample is 1.234 wt%, the content of the second manganese in the steel liquid sample is 1.287 wt%, the theoretical manganese is increased by 0.036 wt%, the actual manganese is increased by 0.053 wt%, and the manganese in the slag is returned by 0.017 wt%, which reflects the reduction of the content of the manganese oxide in the slag.

Comparative example 1

The converter smelting process of the 1215MS of the low-carbon high-sulfur free-cutting steel is basically the same as that of the example 1. In LF refining, molten steel adds 50 kilograms of aluminium sediment, 400 kilograms lime in proper order at the refining process, and LF refining earlier stage, the sample is molten steel appearance one, according to the silicon of argon station appearance, joins in 0.04% silicon, replenishes lime simultaneously, and the lime addition is 1: and 4, adding 10 kg of ferrosilicon to supplement 40 kg of lime, and taking a molten steel sample II.

The detected content of the first manganese in the steel liquid sample is 1.19 wt%, the content of the second manganese in the steel liquid sample is 1.235 wt%, the theoretical manganese is increased by 0.035 wt%, the actual manganese is increased by 0.045 wt%, and the manganese in the slag is returned by 0.01 wt%, which reflects that the content of the manganese oxide in the slag is not obviously reduced.

By the smelting method for reducing the content of the manganese oxide in the slag, the qualification rate (less than 13.5 wt%) of the manganese oxide in the slag is stabilized at 100%, and compared with the qualification rate (less than 13.5 wt%) of the manganese oxide in the average slag in one month in a silicon adding mode at the early stage of refining, the qualification rate (less than 13.5 wt%) of the manganese oxide in the slag is greatly improved by about 60%. The process of controlling free oxygen by silicon is easier to operate, the process is simplified, the oxygen control steps in the process are reduced, the proportion of converting Mn into slag and returning the slag into steel is reduced, the consumption of Mn raw materials is reduced, and the quality of casting blanks is greatly improved.

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are clearly and completely described above. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. The above detailed description of embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the present application, all the embodiments, implementations, and features of the present application may be combined with each other without contradiction or conflict. In the present application, conventional equipment, devices, components, etc. are either commercially available or self-made in accordance with the present disclosure. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In this application, some conventional operations and devices, apparatuses, components are omitted or only briefly described in order to highlight the importance of the present application.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for reducing the content of manganese oxide in slag comprises blast furnace tapping, converter smelting and LF refining, and is characterized in that a slag agent is added in the LF refining process to carry out power transmission and slagging, after the power transmission and slagging are finished, argon gas is blown softly for more than set time, MnO in the refining slag is controlled to be a first threshold value, the alkalinity of the refining slag is adjusted to be a second threshold value, a first molten steel sample is taken, slag is adhered, temperature measurement and oxygen determination are carried out, ferromanganese, ferrosilicon and lime are sequentially added, the MnO in the refining slag is controlled to be a third threshold value, and the alkalinity of the refining slag is adjusted to be a fourth threshold value, wherein the content of Si in steel is adjusted according to the content of silicon in the first molten steel sample by adding ferrosilicon, the first threshold value is larger than the third threshold value, and the second threshold value is smaller than the fourth threshold value;

controlling MnO in the refining slag to be 17-20 wt% of the first threshold value, and adjusting the alkalinity of the refining slag to be 1.9-2.1 of the second threshold value; and controlling MnO in the refining slag to 10-13.5 wt% of the threshold III, and adjusting the alkalinity of the refining slag to 2.3-2.6 of the threshold IV.

2. The method for reducing the content of manganese oxide in slag according to claim 1, wherein argon is soft-blown for the set time of 1 minute.

3. The method for reducing the content of manganese oxide in slag according to claim 1, wherein the LF arrival station is firstly subjected to temperature measurement, and oxygen is not determined when the temperature is lower than 1530 ℃.

4. The method for reducing the content of manganese oxide in slag according to claim 1, wherein after the electric slagging is finished, soft argon blowing is carried out to ensure that the diameter of a bright ring of an argon port on a liquid surface is within 20cm, and the flow of the argon is 3.5-6.5 NM³/h。

5. The method for reducing the content of manganese oxide in slag according to claim 1, wherein the Si content in the steel is adjusted to 0.36wt% -0.44 wt% by adding ferrosilicon according to the silicon content of the first steel liquid sample.

6. The method for reducing the content of manganese oxide in slag according to claim 1, wherein the content of Si in steel is adjusted by adding ferrosilicon according to the silicon content of the first steel liquid sample, then lime is added after the argon blowing stirring interval is 260-300 s, and the addition amount of lime is calculated by 2.7-3.3 times of the addition amount of ferrosilicon.

7. The method for reducing the content of manganese oxide in slag according to claim 1, wherein when ferromanganese, ferrosilicon and lime are added in sequence, the diameter of argon gas blown is 50mm or more, and the flow rate of argon gas is 50NM³/h～70NM³H, uniformly adding lime for 2.7-3.3 minutes, taking a molten steel sample II, blowing argon weakly, wherein the argon blowing diameter is 20mm, the liquid level is still, and the argon flow is 3.5NM³/h-6.5NM³/h。

8. The method for reducing the content of manganese oxide in slag according to claim 7, wherein a steel liquid sample is taken to be secondarily oxidized, ferrosilicon powder is added for deoxidation according to the oxygen content of the molten steel, the free oxygen content of the molten steel is accurately adjusted to 35 ppm-65 ppm, the ferrosilicon powder is added by hand for deoxidation, after the deoxidizer is added by hand, scattered black spots are formed on the slag surface until the black spots cannot be seen, then oxygen is determined, lime is supplemented according to the oxygen content of the molten steel, and the ferrosilicon powder is supplemented by oxygen.

9. The method for reducing the content of manganese oxide in slag according to claim 1, wherein the converter smelting process is only heated for decarburization, the end point carbon content is controlled to be 0.03wt% -0.06 wt%, the end point temperature is 1650 ℃ -1680 ℃, and the end point [ O ]: 600 ppm-800 ppm, respectively adding 13 kg/t-14 kg/t low-carbon ferromanganese, 2.3 kg/t-2.6 kg/t silicon-manganese alloy and 0.7 kg/t-2.3 kg/t ferrophosphorus in the tapping process in sequence, and controlling the free oxygen content in the molten steel at 90 ppm-200 ppm.