LF refining method for 1215MS high-sulfur free-cutting steel

Abstract

The application discloses a LF refining method of 1215MS high-sulfur free-cutting steel. The LF refining method of the 1215MS high-sulfur free-cutting steel provided by the application calculates the addition amount of the deoxidizer according to the oxygen content sampled at an argon station, the oxygen content sampled at an LF inlet station and the oxygen content sampled at the LF, and precisely controls the oxygen content in the LF refining process of the 1215MS high-sulfur free-cutting steel. Meanwhile, the addition amount of lime and fluorite is calculated according to the oxygen content sampled at the argon station and the oxygen content sampled at the LF inlet station, the slag basicity in the LF refining process of the 1215MS high-sulfur free-cutting steel is precisely controlled, and finally the stable control of the free oxygen content of the molten steel and the final refining slag basicity is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, in particular to a LF refining method of 1215MS high-sulfur free-cutting steel. BACKGROUND

[0002] 1215MS belongs to high-sulfur free-cutting steel, and the cutting performance elements of the steel are improved by adding sulfur and phosphorus into the steel, and the inclusion form in the steel is controlled as spindle as far as possible, so that the cutting resistance of the steel is reduced, and the steel also plays a role of lubricating the cutting tool. The steel is mainly used for manufacturing instrument and meter parts, watch parts, automobiles, machine tools and other machines, and the market demand is large for standard parts such as gears, shafts, bolts, valves, bushings, pins, pipe joints, spring seats, machine tool screws, plastic forming molds, surgical and dental instruments, etc., which have strict requirements on size accuracy and smoothness, and relatively low requirements on mechanical properties.

[0003] The production process of the high-sulfur free-cutting steel 1215MS provided by the related art is as follows: high-temperature molten iron of a blast furnace→120t converter smelting→LF refining→billet continuous casting. The smelting process card stipulates that the C range is 0.03%-0.08%, the Si range is ≤0.08%, the Mn range is 1.10%-1.45%, the P range is 0.04%-0.09%, the S range is 0.26%-0.40%, and the O range is 35-65ppm. The C internal control is 0.04%-0.075%, the Si internal control is ≤0.06%, the Mn internal control is 1.25%-1.38%, the P internal control is 0.04%-0.09%, the S internal control is 0.30%-0.38%, and the O internal control is 40-55ppm. The C target is 0.050%, the Si target is ≤0.06%, the Mn target is 1.30%, the P target is 0.07%, the S target is 0.34%, and the O target is 45ppm. The converter tapping alloying and slag washing: 10.1-10.7kg low-carbon ferromanganese per ton of steel, 6.9-7.5kg silicon manganese per ton of steel, 8.1-8.7kg ferrous sulfide per ton of steel, and 3.7-4.3kg lime per ton of steel are added at 1 / 3 of tapping. The LF slag forming material is 2.9-3.5kg lime per ton of steel and 0.37-0.43kg aluminum slag ball per ton of steel. The LF slag material is 3.0-3.4kg lime per ton of steel, and the deoxidizing material is 0.38-0.42kg aluminum slag ball per ton of steel or 0-1.5kg silicon iron powder per ton of steel or 0-0.8kg silicon iron. The refining final slag MnO≤13.5%, TFe≤5%, and the basicity R is 2.0-3.5.

[0004] The basicity of the converter tapping alloying and slag washing material, the LF slag material, the deoxidizing material and the refining final slag is not matched, which causes the unstable control of the basicity of the refining final slag. SUMMARY

[0005] The present application aims to provide a LF refining method for 1215MS high-sulfur free-cutting steel to overcome the defects of the prior art.

[0006] The present application solves the technical problems by the following technical solutions.

[0007] The present application provides a LF refining method for 1215MS high-sulfur free-cutting steel, comprising the following steps:

[0008] S1: converter tapping for deoxidizing and alloying of molten steel and slag washing;

[0009] S2: argon station sampling to determine W[O] 氩站 , and the silicon-iron alloy addition amount is determined according to W[O] 氩站 ;

[0010] S3: LF refining to the station, temperature measurement to obtain T 进站 , and when T 进站 > grade liquidus temperature + 30℃, W[O] LF进站 is measured, and the addition amounts of lime, fluorite, aluminum slag ball, silicon-iron powder and silicon-iron alloy are determined according to W[O] LF进站 ;

[0011] S4: LF sampling 1 to determine W[C] 样1 %, W[Mn] 样1 %, W[S] 样1 %, W[P] 样1 %, W[O] 样1 %, and the silicon-iron powder addition amount is determined according to W[O] 样1 ;

[0012] S5: according to the results of LF sampling 1, the C, Mn, S and P contents in the molten steel are adjusted;

[0013] S6: after the temperature is raised to the target temperature required before soft blowing, the temperature is measured, the oxygen is determined, the sampling and the slag adhesion observation are performed, the molten steel composition, the oxygen content, the temperature and the final slag composition all meet the requirements, and the LF molten steel leaves the station.

[0014] The present application has the following beneficial effects:

[0015] The present application provides a LF refining method for 1215MS high-sulfur free-cutting steel. According to the oxygen content of argon station sampling, the oxygen content of LF inlet station sampling and the oxygen content of LF sampling 1, the addition amounts of lime, fluorite and deoxidizer are calculated, the target of accurately controlling the slag basicity and free oxygen content in the LF refining process of 1215MS high-sulfur free-cutting steel is achieved, and the molten steel smelting quality is improved. DETAILED DESCRIPTION

[0016] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not specified in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not specified, the conventional products that can be purchased in the market are adopted.

[0017] The LF refining method of the 1215MS high-sulfur free-cutting steel provided by the embodiments of the present application will be described in detail below.

[0018] S1: The end-point C of the converter is controlled at 0.03%-0.04%, the end-point O is controlled at 600-700 ppm, the P is controlled at 0.05%-0.06%, and the tapping temperature is controlled at 1620±20℃.

[0019] S2: The converter tapping alloying and slag washing are performed.

[0020] The alloying adding time: 6.9-7.2 kg of silicon manganese per ton of steel, 9.8-10.1 kg of low-carbon ferromanganese per ton of steel, and 8.1-8.4 kg of ferrous sulfide per ton of steel are added at 1 / 6 of the tapping.

[0021] The slag washing material adding time: 6.8-7.3 kg of lime per ton of steel, preferably 7 kg of lime per ton of steel, and 0.77-0.81 kg of fluorite per ton of steel, preferably 0.79 kg of fluorite per ton of steel are added at 1 / 2 of the tapping.

[0022] It is worth mentioning that: the silicon manganese is added first, and then the low-carbon ferromanganese and ferrous sulfide are added during the alloying, so as to reduce the formation of MnO in the slag. During the alloying and slag washing, the argon is introduced at 60 Nm 3 / h, and after completion, it is adjusted to 20 Nm 3 / h, so as to ensure good melting effect.

[0023] When the tapping C is lower than 0.03%, 0.12-0.15 kg of carbon powder per ton of steel is manually added for pre-deoxidization and exhaust, and at the same time, the carbon is increased, so as to ensure that the C of the LF station reaches 0.03%-0.04%, preferably 0.04%.G 碳粉 =0.2×[(0.04%-W[C] 出钢 )÷0.01%] kg / ton of steel. In the production practice, it is found that the carbon powder yield is about 40%, that is, 60% is used for deoxidization and exhaust, and 40% is used for carbon increase.

[0024] S3: After the tapping is completed, the argon flow is adjusted to the soft blowing state at 5-10 Nm 3 / h, so as to make the molten steel not exposed.

[0025] The argon station is used to determine the oxygen and sampling, and W[O] 氩站 ppm and W 氩站[Si]%. W[O] 氩站 When the concentration of ferrosilicon alloy is >50ppm, the amount of ferrosilicon alloy added (G) 氩站硅铁合金 =0.008×(W[O]) 氩站 -50)+80×(0.04%-W[C] 出钢 %) kg / ton of steel, of which W[O] 氩站 -50≥0、[C] 出钢 % < 0.04%. W[O] 氩站 When <50ppm, the amount of ferrosilicon alloy added G 氩站硅铁合金 =80×(0.04%-W[C]) 出钢 %) kg / ton of steel, of which [C] 出钢 % < 0.04%. It should be noted that W[O] in the formula... 氩站 The target value is controlled at 50 ± 5 ppm (preferably 50 ppm), while W[C] 出钢 When the peroxide content is less than 0.04%, ferrosilicon should be added for deoxidation correction. 出钢 If % > 0.04%, then no ferrosilicon is added for deoxidation correction.

[0026] S4: Perform LF refining, including the following steps:

[0027] S41: Temperature measurement upon entry, T is obtained. 进站 When T 进站 When the temperature exceeds 1545℃ (the liquidus temperature of the steel grade + 30℃), the oxygen content is determined, and W[O] is obtained. LF进站 When T 进站 When the temperature is below 1545℃ (liquidotherm temperature of the steel grade + 30℃), oxygen determination should not be performed initially. Oxygen determination should only be conducted after the power supply temperature rises above 1545℃. Performing oxygen determination at a low inlet temperature will affect the accuracy of the determined oxygen value, rendering it useless as a reference.

[0028] S42:W[O] LF进站 When ≤30ppm or from W[Si] in step S3 氩站 When the content of free silicon in the steel is greater than 0.05% (using the principle of deoxidation based on the free silicon content in the liquid), no deoxidizer is added. Argon gas is introduced at a rate of 60 Nm³. 3 / h, adding lime and fluorite slag directly for power supply and heating. Lime amount added: G LF石灰 =3.3+G 氩站硅铁 ×6 (kg / ton of steel), of which the lime content is 3.3 kg / ton of steel as the base value, i.e., G 氩站硅铁 When no additives are added; G 氩站硅铁 ×6 (kg / ton of steel) is the correction for lime addition. According to G 氩站硅铁 The larger the lime content, the higher the SiO2 content in the slag and the lower the alkalinity. Production trials have shown that the amount of lime added (G)... LF石灰 =3.3+G 氩站硅铁×6(kg / ton steel), which can increase the CaO content in the slag, and G 氩站硅铁 The SiO2 content in the slag increases synchronously after the addition, thereby ensuring that the slag basicity R is in the process range of 2.0-3.5. The amount of added fluorite G LF萤石 = [3.3 + G 氩站硅铁 ×6] ÷ 5 (kg / ton steel), that is, G LF石灰 : G LF萤石 = 5:1, the slag fluidity is better.

[0029] S43: W[O] LF进站 > 30 ppm, argon is introduced at 60 Nm 3 / h, G LF铝渣球 0.3 kg / ton steel and G LF硅铁粉 0.24 kg / ton steel, and the deoxidation yield into the steel liquid is 60%, that is, the amount of ferrosilicon added after the addition of ferrosilicon is converted into G LF硅铁粉 = 0.24 × 60% = 0.144 kg / ton steel. The amount of ferrosilicon added before LF sample 1 G LF硅铁 = 0.008 × (W[O] LF进站 - 45) × W[Si] LF损失 % - GLF ferrosilicon powder conversion (kg / ton steel), wherein W[O] LF进站 > 45 ppm, when W[O] LF进站 ≤ 45 ppm, 0.008 × (W[O] LF进站 - 45) in the formula is 0. G LF硅铁粉折算 = 0.144 (kg / ton steel). 0.008 × (W[O] LF进站 - 45) is a basic value of the amount of ferrosilicon required for deoxidation to 45 ppm before LF sample 1, W[Si] LF损失 % × 0.008 × (W[O] LF进站 - 45) is the silicon loss in the steel liquid caused by the argon blowing process. When Q 吹氩流量 = 35-38 Nm 3 / h, preferably 35 Nm 3 / h, the silicon loss W[Si] LF损失 % = 0.01% per 5 minutes of power supply heating, Q 吹氩流量 is greater, S 吹氩时间 is greater, the secondary oxidation of the steel liquid is more serious, and W[Si] LF损失 % is greater. Therefore, W[Si] LF损失 % is closely related to Q 吹氩流量 , S 吹氩时间 . When Q 吹氩流量 = 35 Nm 3 / h, S 吹氩时间 = 5 (min), the silicon loss W LF损失[Si] % = 0.01 %, W[Si] LF每分钟损失 % = W[Si] LF损失 % ÷ S 吹氩时间 = 0.01 % ÷ 5 = 0.002 %, further, when Q 吹氩流量 = 35 Nm 3 / h, the silicon loss rate W 3 = 0.002 % ÷ 35 = 0.00057 %. Therefore, further, W[Si] LF每分钟损失 % = W[Si] LF损失 % × Q LF每分钟损失 × S 吹氩流量 . In summary, the amount of ferrosilicon G 吹氩时间 added before LF sample 1 is G LF硅铁 = 0.008 × (W[O] LF进站 - 45) × W[Si] LF每分钟损失 % × Q 吹氩流量 × S 吹氩时间 = 0.144 (kg / ton of steel). It is worth mentioning that Q 吹氩流量 can be adjusted at will according to the actual needs of the current smelting, and the correction of silicon loss in the LF smelting process can keep the oxygen in the molten steel stable at a certain level.

[0030] S44: After the step of S43, argon gas is passed at a flow rate of 60 Nm 3 / h, and lime and fluorite are added as two kinds of slag to directly supply power and heat. The amount of lime added G LF石灰 = 3.3 + (G 氩站硅铁 + G LF硅铁 ) × 6 (kg / ton of steel), wherein the lime amount of 3.3 kg / ton of steel is the basic value, and (G 氩站硅铁 + G LF硅铁 ) × 6 (kg / ton of steel) is the correction of the amount of lime added. According to (G 氩站硅铁 + G LF硅铁 ), the higher the SiO2 in the slag, the lower the basicity. In production, it is found that (the principle is the same as that in S42 step), the amount of lime added G LF石灰 = 3.3 + (G 氩站硅铁 + G LF硅铁 ) × 6 (kg / ton of steel) can increase the CaO content in the slag, which is synchronized with the increase of SiO2 in the slag after (G 氩站硅铁 + G LF硅铁 ) is added. Thus, the slag basicity R is ensured to be in the process interval of 2.0-3.5. The amount of fluorite added G LF萤石 = [3.3 + (G 氩站硅铁 + G LF硅铁 ) × 6] ÷ 5 (kg / ton of steel), that is, G LF石灰 : G LF萤石=5:1, the slag fluidity is better (same as the principle of S42 step).

[0031] S45: After adding the two slag materials of lime and fluorite, aluminum slag ball, silicon-iron powder deoxidizer and silicon-iron, a transformer with 11 levels (preheating gear) is used, argon gas is passed at 35-38 Nm 3 / h (preferably 35 cm Nm 3 / h) to conduct slagging for 5 minutes, then switch to a 4-gear transformer level, continue to pass electricity, and conduct main heating to raise the temperature. When the temperature is raised to T 样1 > 1575℃ (liquidus temperature of steel grade + 50℃), argon gas is passed at 60 Nm 3 / h to conduct power stirring to promote the steel slag interface reaction and uniform steel liquid composition temperature. After stirring for 2 minutes, sampling, oxygen determination, temperature measurement and slag sticking are performed to obtain W[C] 样1 %, W[Mn] 样1 %, W[S] 样1 %, W[P] 样1 %, W[O] 样1 %.

[0032] S46: When W[O] 样1 < 40ppm, no silicon-iron powder is added (to avoid low oxygen content of the steel liquid), and natural oxygen return is used by argon blowing to the target value of 45ppm. In production practice, it is found that the larger Q 吹氩流量1 (>10 Nm 3 / h), the more serious the oxygen return of the steel liquid. When Q 吹氩流量1 <10 Nm 3 / h, the argon blowing intensity is small, and the surface of the steel liquid is not exposed, so there is no oxygen return. When Q 吹氩流量1 =60 Nm 3 / h, about 2ppm of oxygen is returned per minute, i.e. 0.04×(60-10) =0.04ppm of oxygen return value for 1 Nm 3 / h argon blowing flow, so the relationship W[O] 样1后回氧 =0.04×Q 吹氩流量1 ×S 吹氩时间1 is obtained, where Q 吹氩流量1 >10 Nm 3 / h.

[0033] When 40ppm < W[O] 样1 ≤45ppm, according to the calculation of 0.013 kg / ton of silicon-iron powder to remove 1ppm of oxygen, continue to remove to 40ppm of oxygen. The relationship of adding silicon-iron powder to remove oxygen to 40ppm is obtained: the amount of silicon-iron powder added G LF硅铁粉1 =0.013×(W[O] 样1 -40) kg / ton of steel. After removing to 40ppm of oxygen, the oxygen return relationship (W[O] 样1后回氧= 0.04 x Q 吹氩流量1 x S 吹氩时间1 , wherein Q 吹氩流量1 > 10 Nm 3 / h) to calculate the argon flow rate and argon blowing time for returning oxygen to the target value of 45 ppm.

[0034] W[O] 样1 > 45 ppm, 1 ppm of oxygen is removed by adding 0.008 kg of ferrosilicon per ton of steel, and the deoxidization continues until the oxygen content is 45 ppm. The total relationship for continuing deoxidization to 45 ppm of oxygen after argon blowing and returning oxygen is derived as follows: the amount of ferrosilicon powder G LF硅铁粉2 = 0.013 x [(W[O] 样1 - 45) + W[O] 样1后回氧 ] = 0.013 x [(W[O] 样1 - 45) + 0.04 x Q 吹氩流量1 x S 吹氩时间1 ] kg / ton of steel, and the amount of ferrosilicon alloy G LF硅铁合金2 = 0.008 x [(W[O] 样1 - 45) + W[O] 样1后回氧 ] = 0.008 x [(W[O] 样1 - 45) + 0.04 x Q 吹氩流量1 x S 吹氩时间1 ] kg / ton of steel, wherein Q 吹氩流量1 > 10 Nm 3 / h. After deoxidization to 45 ppm of oxygen by ferrosilicon, it is considered that returning oxygen will occur subsequently, so the deoxidization to 40 ppm of oxygen by ferrosilicon powder is continued, and 1 ppm of oxygen is removed by ferrosilicon powder at a rate of 0.013 kg / ton of steel to correct the deoxidization to 40 ppm of oxygen. The relationship for deoxidization to 40 ppm of oxygen by ferrosilicon powder is derived as follows: the amount of ferrosilicon powder G LF硅铁粉1 = 0.013 x (W[O] 样1 - 40) kg / ton of steel.

[0035] S47: continue to pass argon at a flow rate of 35 Nm 3 / h (the argon flow rate can be adjusted according to the need for returning oxygen), and supply power to heat to the target temperature required before soft blowing. The components of W[C] 样1 %, W[Mn] 样1 %, W[S] 样1 %, and W[P] 样1 % are added according to the test results of sample 1. W[C] 样1 %, W[S] 样1 %, and W[P] 样1 % are respectively adjusted to the process target values by the conventional method. Among them, W[Mn] 样1 % needs to be referred to W[O] 样1Composition was added, and samples were taken 1 when the free oxygen level in the molten steel was high and 1 when the free oxygen level in the molten steel was low, W[Mn] 样1 The results are different. In production practice, it was found that for every 4 ppm increase in free oxygen in molten steel above a predetermined value, [Mn] decreases by 0.01%, and for every 4 ppm decrease in free oxygen in molten steel below a predetermined value, [Mn] increases by 0.01%. That is, W[O] 样1 >45ppm or W[O] 样1 <45ppm with W[O] 样1 =45ppm sample 1 W sample 1 [Mn]% results are different.

[0036] Therefore, the target oxygen value W[O] for process control is taken. 样2 =45ppm is the precise value for W[Mn] 样1 By adding ingredients, we obtain the following relationship ①: W[O] 样1 When W[Mn] > 45 ppm 样2 % = [W[Mn] 工艺目标 %-(W[O] 样1 -45)÷4×0.01%-W[Mn] 样1 %], where W[Mn] 样2 The percentage represents the desired addition of [Mn]%, W[Mn]% 工艺目标 % represents the process target control value (or required setpoint), (W[O]) 样1 -45)÷4×0.01% represents the percentage of [Mn] lost after reoxygenation (i.e., it should be replenished). Further, to achieve W[Mn] 样2 The required amount of low-carbon ferromanganese to be added at % is: G LF低碳锰铁 =[W[Mn] 工艺目标 %-(W[O] 样1 -45)÷4×0.01%-W[Mn] 样1 [%] × 0.12 kg / ton of steel. This leads to equation ②: W[O] 样1 When W[Mn] is <45ppm, 样2 % = [W[Mn] 工艺目标 %+(45-W[O]) 样1 )÷4×0.01%-W[Mn] 样1 %]×0.12, where W[Mn] 样2 The percentage represents the desired addition of [Mn]%, W[Mn]% 工艺目标 % represents the process target control value (or required setpoint), (45-W[O]) 样1 ) ÷ 4 represents the increase in [Mn]% after deoxygenation (i.e., the addition should be reduced). Further, to achieve W[Mn] 样2 The required amount of low-carbon ferromanganese to be added at % is: G LF低碳锰铁 =[W[Mn]工艺目标 % + (45 - W[O] 样1 ) ÷ 4 x 0.01% - W[Mn] 样1 %] x 0.12 kg / ton steel.

[0037] S48: After the power supply is heated to the target temperature required before soft blowing, power off, and 25 Nm 3 / h of argon is introduced for weak stirring for 3 minutes, 10 Nm 3 / h of soft blowing argon is introduced, sampling, oxygen determination, temperature measurement, and slag color observation are performed. W[C] 样2 %, W[Mn] 样2 %, W[S] 样2 %, W[P] 样2 %, W[O] Sample 2, respectively reaches the process target value.

[0038] In combination with the foregoing step operation, the sticky slag is preferably thin and light yellow or yellow-brown. The LF final slag is CaO: 42%-45%, SiO2: 16%-19%, Al2O3: 6%-9%, TFe: 2%-4%, MnO: 8%-13%, S: 3%-4%, MgO: 4%-7%, P2O5: 0.04%-0.07%, R: 2.2-2.8, the free oxygen content of the steel liquid and the deoxidation effect of the slag are optimal.

[0039] S49: 10 Nm 3 / h of soft blowing argon is introduced, and the steel liquid is discharged.

[0040] The application will be further described below in combination with examples.

[0041] Example 1

[0042] S1: The converter endpoint C: 0.03% control, endpoint O: 660 ppm control, P: 0.055%, and the tapping temperature is 1630°C.

[0043] S2: The converter tapping alloying and slag washing treatment are performed.

[0044] The alloying addition timing: 6.9 kg of silicon manganese per ton of steel, 9.8 kg of low-carbon ferromanganese per ton of steel, and 8.2 kg of ferrous sulfide per ton of steel are added at 1 / 6 of the tapping time.

[0045] The slag washing material addition timing: 7 kg of lime per ton of steel and 0.79 kg of fluorite per ton of steel are added at 1 / 2 of the tapping time.

[0046] The silicon manganese is added first, and then the low-carbon ferromanganese and ferrous sulfide are added during alloying to reduce the formation of MnO in the slag. During alloying and slag washing, 60 Nm 3 / h of argon is introduced, and after completion, it is adjusted to 20 Nm3 / h, to ensure good melting effect.

[0047] Steel tapping C: 0.02%, manually added carbon powder for pre-deoxidation and venting, while simultaneously increasing carbon content to ensure that the C at the LF station reaches 0.03%-0.04%, preferably 0.04%. G 碳粉 = 0.2 × [(0.04% - W[C]] 出钢 [(0.04% - 0.02%) ÷ 0.01%] = 0.2 × [(0.04% - 0.02%) ÷ 0.01%] = 0.4 kg / ton of steel. In production practice, it has been found that the carbon powder recovery rate is around 40%, meaning 60% is used for deoxidation and exhaust, and 40% is used for carbon addition.

[0048] S3: After tapping the steel, reduce the argon gas flow rate to a soft blowing state of 5-10 Nm. 3 / h, to prevent the molten steel from being exposed.

[0049] Oxygen was determined and samples were taken at the argon station to obtain W[O]. 氩站 ppm: 60ppm, W 氩站 [Si]%: 0.001%. W[O] 氩站 When the concentration is >50 ppm, the amount of ferrosilicon alloy added is G. 氩站硅铁合金 =0.008×(W[O]) 氩站 -50)+80×(0.04%-W[C] 出钢 %)=0.008×(60-50)+80×(0.04%-0.02%)=0.096kg / ton of steel, of which W[O] 氩站 -50≥0、W[C] 出钢 % < 0.04%. It should be noted that W[O] in the formula... 氩站 The target value is controlled at 50 ± 5 ppm (50 ppm is preferred), while W[C] 出钢 When the peroxide content is less than 0.04%, ferrosilicon should be added for deoxidation correction. 出钢 If % > 0.04%, then no ferrosilicon is added for deoxidation correction.

[0050] S4: Perform LF refining, including the following steps:

[0051] S41: Temperature measurement upon entry, T is obtained. 进站 1572℃. When T 进站 When the temperature exceeds 1545℃ (the liquidus temperature of the steel grade + 30℃), the oxygen content is determined, and W[O] is obtained. LF进站 48ppm, when T 进站 When the temperature is below 1545℃ (liquidotherm temperature of the steel grade + 30℃), oxygen determination should not be performed initially. Oxygen determination should only be conducted after the power supply temperature rises above 1545℃. Performing oxygen determination at a low inlet temperature will affect the accuracy of the determined oxygen value, rendering it useless as a reference.

[0052] S42:W[O] LF进站 When ≤30ppm or from W[Si] in step S3 氩站 When the free silicon content in the molten steel is greater than 0.05% (using the free silicon content of the molten steel for initial deoxidation), no deoxidizer is added. Argon gas is introduced at a rate of 60 Nm³. 3 / h, adding lime and fluorite slag directly for power supply and heating. Lime amount added: G LF石灰 =3.3+G 氩站硅铁 ×6=3.3+0.096×6=3.88(kg / ton of steel), fluorite addition amount G LF萤石 =[3.3+G 氩站硅铁 ×6]÷5=[3.3+0.096×6]÷5=0.78(kg / ton of steel), that is, G LF石灰 :G LF萤石 When the ratio is 5:1, the slag has better fluidity, thus ensuring that the slag basicity R is within the process range of 2.0-3.5.

[0053] S43: W[O] LF进站 When the concentration is >30 ppm, introduce 60 Nm of argon gas. 3 / h is 3min, add G LF铝渣球 0.3kg / ton steel and G LF硅铁粉 0.24 kg / ton of steel, with a deoxidation yield of 60% after adding ferrosilicon powder, is calculated as the amount of ferrosilicon added (G). LF硅铁粉 Conversion = 0.24 × 60% = 0.144 kg / ton of steel. LF Sample 1: Amount of ferrosilicon added (G) LF硅铁 =0.008×(W[O]) LF进站 -45)×W[Si] LF每分钟损失 %×Q 吹氩流量 ×S 吹氩时间 -0.144 = 0.008 × (48-45) × 0.00057% × 60 × 3 - 0.144 = 0.12 (kg / ton of steel). Where W[O] LF进站 -45 > 0, W[O] LF进站 No ferrosilicon is added when -45 ≤ 0.

[0054] S44: After step S43, introduce 60 Nm of argon gas. 3 / h, adding lime and fluorite slag directly for power supply and heating. Lime amount added: G LF石灰 =3.3+(G 氩站硅铁 +G LF硅铁 )×6=3.3+(0.096+0.12)×6=4.59(kg / ton steel)(kg / ton steel), Fluorite addition amount G LF萤石 =[3.3+(G 氩站硅铁 +G LF硅铁) x 6] ÷ 5 (= [3.3 + 0.096 x 6] ÷ 5 = 0.92 kg / ton steel), i.e. G LF石灰 : G LF萤石 = 5:1, the slag fluidity is better. Thus, the slag basicity R is ensured to be in the process interval 2.0-3.5.

[0055] S45: After adding the two slag materials of lime and fluorite, the aluminum slag ball, the silicon-iron powder deoxidizer and the silicon-iron, the transformer is used in 11 stages (preheating gear), argon gas is passed in at 35-38 Nm 3 / h (preferably 35 cm Nm 3 / h), power is supplied for 5 minutes to make slag, 5 minutes later, the transformer is switched to 4 gears, power supply is continued, and main heating is performed. When the temperature is raised to T 样1 > 1575 ℃ (steel grade liquidus temperature + 50 ℃), argon gas is passed in at 60 Nm 3 / h to perform dynamic stirring to promote the steel slag interface reaction and uniform steel liquid composition and temperature. After stirring for 2 minutes, sampling, oxygen determination, temperature measurement and slag sticking are performed to obtain W[C] 样1 %: 0.039%, W[Si] 样1 %: 0.002%, W[Mn] 样1 %: 1.05%, W[S] 样1 %: 0.295%, W[P] 样1 %: 0.055%, W[O] 样1 ppm: 43 ppm.

[0056] S46: When W[O] 样1 ≤ 40 ppm, no silicon-iron powder is added (to avoid low oxygen content of the steel liquid), and natural oxygen return to the target value 45 ppm is performed by argon blowing. In the production practice, it is found that the larger Q 吹氩流量1 (> 10 Nm 3 / h), the more serious the oxygen return of the steel liquid is. When Q 吹氩流量1 < 10 Nm 3 / h, since the argon blowing intensity is small, the surface of the steel liquid is not exposed, so there is no oxygen return. When Q 吹氩流量1 = 60 Nm 3 / h, about 2 ppm of oxygen is returned per minute, i.e. 0.04 x (60-10) = 0.04 ppm of oxygen is returned per minute by 1 Nm 3 / h argon blowing flow, thus the relationship W[O] 样1后回氧 = Q 1Nm 3 / h argon blowing 流量回氧 x Q 吹氩流量1 x S 吹氩时间1 = 0.04 x Q 吹氩流量1 x S 吹氩时间1 , wherein Q 吹氩流量1 > 10 Nm 3 / h.

[0057] When 40ppm < W[O] 样1 When the oxygen content is ≤45ppm, based on the calculation of removing 1ppm of oxygen from 0.013kg / ton of steel ferrosilicon powder, continue deoxidation until the oxygen content reaches 40ppm. The formula for deoxidizing ferrosilicon powder to 40ppm is derived as: Ferrosilicon powder added G LF硅铁粉1 =0.013×(W[O]) 样1 -40)=0.013×(43-40)=0.039kg / ton of steel. After removing oxygen to 40ppm, the oxygen return relationship (W[O]) is used. 样1后回氧 =0.04×Q 吹氩流量1 ×S 吹氩时间1 Q 吹氩流量1 >10Nm 3 / h) Re-oxygenate to the target value of 45ppm.

[0058] W[O] 样1 When the oxygen content is >45 ppm, remove 1 ppm of oxygen at a rate of 0.008 kg / ton of ferrosilicon steel, and continue deoxidation until the oxygen content reaches 45 ppm. From the above argon blowing and oxygen return relationship W[O]... 样1后回氧 =0.04×Q 吹氩流量1 ×S 吹氩时间1 (where Q) 吹氩流量1 >10Nm 3 / h) The overall formula for deoxygenation to 45ppm after argon blowing and oxygen re-oxygenation: Amount of ferrosilicon powder added G LF硅铁粉2 =0.013×[(W[O] 样1 -45)+W[O) 样1后回氧 ]=0.013×[(W[O] 样1 -45)+0.04×Q 吹氩流量1 ×S 吹氩时间1 kg / ton of steel, or the amount of ferrosilicon alloy added (G) LF硅铁合金2 =0.008×[(W[O] 样1 -45)+W[O) 样1后回氧 ]=0.008×[(W[O] 样1 -45)+0.04×Q 吹氩流量1 ×S 吹氩时间1 kg / ton of steel, of which Q 吹氩流量1 >10Nm 3 / h. After deoxidizing ferrosilicon to 45ppm, calculate based on removing 1ppm of oxygen per 0.013kg / ton of steel ferrosilicon powder, and continue deoxidizing to 40ppm for correction. The relationship for deoxidizing ferrosilicon powder to 40ppm is derived as: Ferrosilicon powder added G LF硅铁粉1 =0.013×(W[O]) 样1 -40)kg / ton of steel.

[0059] S47: Continue to introduce argon gas at 15 Nm.3 / h, the argon blowing time is 10 min (the argon flow rate and the argon blowing time are adjusted according to the oxygen recovery requirement), and the power is supplied to warm up to the target temperature required before soft blowing. The W[C] 样1 %, W[Mn] 样1 %, W[S] 样1 %, W[P] 样1 % are added according to the test results of Sample 1. The W[C] 样1 %, W[S] 样1 %, W[P] 样1 % are respectively adjusted to the process target value according to the conventional method. The W[O] 样1 > 45 ppm, the W[Mn] 样2 % required to be added is: G LF低碳锰铁 = [W[Mn] 工艺目标 % - (W[O] 样1 - 45) ÷ 4 × 0.01% - W[Mn] 样1 %] × 0.12 kg / ton of steel. The W[O] 样1 < 45 ppm, the W[Mn] 样2 % required to be added is: G LF低碳锰铁 = [W[Mn] 工艺目标 % + (45 - W[O] 样1 ) ÷ 4 × 0.01% - W[Mn] 样1 %] × 0.12 kg / ton of steel = [1.30% + (45 - 43) ÷ 4 × 0.01% - 1.05%] × 0.12 = 3.21 kg / ton of steel.

[0060] W[O] 样1后回氧 = Q 吹氩流量1Nm 3 / h × Q 吹氩流量1 × S 吹氩时间1 , wherein Q 吹氩流量1 > 10 Nm 3 / h.

[0061] W[O] 样1后回氧 = 45 - W[O] 样1 = 2 ppm (the oxygen recovery amount required when the oxygen is less than 45 ppm), so W[O] 样1后回氧 = 0.04 × Q 吹氩流量1 × S 吹氩时间1 = 2, and Q 吹氩流量1 = W[O] 样1后回氧 ÷ 0.04 ÷ S 吹氩时间1 = 0.04 × 0.04 ÷ 10 = 5, and Q 吹氩流量1 > 10 Nm 3 / h (≤ 10 Nm3 / h without reoxygenation, so Q 吹氩流量1 = 10 + 5 = 15 (Nm 3 / h).

[0062] S48: After the power supply temperature reaches the target temperature required before soft blowing, power off, and 25 Nm 3 / h of argon gas is introduced for 3 minutes of weak stirring, 10 Nm 3 / h of soft blowing argon gas is introduced, sampling, oxygen determination, temperature measurement, and slag color observation are performed. The W[C] 样2 %: 0.05%, W[Mn] 样2 %: 1.30%, W[S] 样2 %: 0.34%, W[P] 样2 %: 0.069%, W[O] Sample 2: 45 ppm, respectively reaching the process target value.

[0063] In combination with the foregoing steps, the slag is preferably thin, light yellow or yellow-brown. The LF final slag is CaO: 43%, SiO2: 17%, Al2O3: 6.8%, TFe: 3.5%, MnO: 11.2%, S: 3.3%, MgO: 5.5%, P2O5: 0.05%, R: 2.53, the free oxygen content of the steel liquid and the deoxidation effect of the slag are best.

[0064] S49: 10 Nm 3 / h of soft blowing argon gas is introduced, and the temperature is measured. The molten steel is discharged.

[0065] Example 2

[0066] S1: Converter endpoint C: 0.035% control, endpoint O: 680 ppm control, P: 0.052%, tapping temperature 1633°C.

[0067] S2: Converter tapping alloying and slag washing treatment are performed.

[0068] Alloying addition timing: 7.1 kg of silicon manganese per ton of steel, 9.9 kg of low-carbon ferromanganese per ton of steel, and 8.1 kg of ferrosulfur per ton of steel are added at 1 / 6 of tapping.

[0069] Slag washing material addition timing: 7 kg of lime per ton of steel and 0.79 kg of fluorite per ton of steel are added at 1 / 2 of tapping.

[0070] During alloying, silicon manganese is added first, followed by low-carbon ferromanganese and ferrosulfur to reduce the formation of MnO in the slag. During alloying and slag washing, 60 Nm 3 / h of argon gas is introduced, and after completion, it is adjusted to 20 Nm 3 / h to ensure good melting effect.

[0071] Tapping C: 0.025%, manual carbon powder pre-deoxidation exhaust, at the same time carbon enrichment, ensure that the LF to station C reaches 0.03%-0.04%, preferably 0.04%. G 碳粉 = 0.2 x [(0.04%-W[C] 出钢 ) ÷ 0.01%] = 0.2 x [(0.04%-0.025%) ÷ 0.01%] = 0.3 kg / ton steel. In production practice, it is found that the carbon powder yield is about 40%, i.e. 60% for deoxidation exhaust and 40% for carbon enrichment.

[0072] S3: After tapping, the argon flow is adjusted to a soft blowing state of 5-10 Nm 3 / h, so that the molten steel is not exposed.

[0073] Oxygen is determined at the argon station, and sampling is performed to obtain W[O] 氩站 ppm: 50 ppm, W 氩站 [Si] %: 0.018%. When W[O] 氩站 > 50 ppm, the amount of ferrosilicon alloy G 氩站硅铁合金 = 0.008 x (W[O] 氩站 - 50) + 80 x (0.04%-W[C] 出钢 %) = 0.008 x (50-50) + 80 x (0.04%-0.025%) = 0.012 kg / ton steel, wherein W[O] 氩站 - 50 ≥ 0, W[C] 出钢 % < 0.04%. When W[O] 氩站 < 50 ppm, the amount of ferrosilicon alloy G 氩站硅铁合金 = 80 x (0.04%-W[C] 出钢 %) kg / ton steel, wherein W[C] 出钢 % < 0.04%. It should be noted that the target value of W[O] 氩站 is controlled at 50 ± 5 ppm (preferably 50 ppm), and at the same time, W[C] 出钢 % < 0.04% when the oxygen is over-oxidized, additional ferrosilicon is added for deoxidation correction, and W[C] 出钢 % > 0.04%, then no ferrosilicon is added for deoxidation correction.

[0074] S4: LF refining is performed, including the following steps:

[0075] S41: temperature measurement upon entry to obtain T 进站 : 1561°C. When T 进站 > 1545°C (liquidus temperature of the steel grade + 30°C), oxygen is determined to obtain W[O] LF进站 : 35 ppm, and when T 进站<1545℃(steel grade liquidus temperature + 30℃) first not oxygen, after the power supply to 1545 ℃ or more to oxygen. Low temperature into the station oxygen, will affect the accuracy of the oxygen value, no reference value.

[0076] S42: W[O] LF进站 ≤30ppm or by S3 step W[Si] 氩站 > 0.05% (using the free silicon content of the liquid steel first deoxidation), do not add any deoxidizer. Argon 60 Nm 3 / h, adding lime, fluorite two kinds of slag directly power supply heating. Add lime amount G LF石灰 = 3.3 + G 氩站硅铁 × 6 = 3.3 + 0.012 × 6 = 3.37 (kg / ton steel), adding fluorite amount G LF萤石 = [3.3 + G 氩站硅铁 × 6] ÷ 5 = [3.3 + 0.012 × 6] ÷ 5 = 0.67 (kg / ton steel), that is, G LF石灰 : G LF萤石 = 5:1, the slag fluidity is better, so as to ensure the slag basicity R in the process interval 2.0-3.5.

[0077] S43: W[O] LF进站 > 30ppm, argon 60 Nm 3 / h for 4 min, adding G LF铝渣球 0.3 kg / ton steel and G LF硅铁粉 0.24 kg / ton steel, its into the liquid steel deoxidation yield is 60%, that is, the amount of ferrosilicon added after conversion G LF硅铁粉 = 0.24 × 60% = 0.144 kg / ton steel. LF sample 1 before adding ferrosilicon amount G LF硅铁 = 0.008 × (W[O] LF进站 -45) × W[Si] LF每分钟损失 % × Q 吹氩流量 × S 吹氩时间 -0.144. Wherein W[O] LF进站 -45 > 0, W[O] LF进站 -45 ≤ 0 do not add ferrosilicon.

[0078] S44: by S43 step after argon 60 Nm 3 / h, adding lime, fluorite two kinds of slag directly power supply heating. Add lime amount G LF石灰 = 3.3 + (G 氩站硅铁 + G LF硅铁 ) × 6 = 3.3 + (0.012 + 0) × 6 = 3.37 (kg / ton steel) (kg / ton steel), adding fluorite amount G LF萤石 = [3.3 + (G氩站硅铁 +G LF硅铁 [3.3 + (0.012 + 0) × 6] ÷ 5 (= [3.3 + (0.012 + 0) × 6] ÷ 5 = 0.73 kg / ton of steel), that is, G LF石灰 :G LF萤石 When the ratio is 5:1, the slag fluidity is better. This ensures that the slag basicity R is within the process range of 2.0-3.5.

[0079] S45: After adding lime, fluorite, aluminum slag balls, ferrosilicon powder deoxidizer, and ferrosilicon, use a transformer with 11 poles (preheating setting) and introduce argon gas at 35-38 Nm. 3 / h (preferably 35cmNm) 3 (h) Power is applied for 5 minutes to form slag. After 5 minutes, the transformer is switched to level 4 and power is continued for main heating. The temperature is raised to T. 样1 When the temperature exceeds 1575℃ (liquidotherm temperature of the steel grade + 50℃), 60 Nm of argon gas is introduced. 3 The mixture is stirred at a rate of / h to promote the interfacial reaction between the steel and slag and to homogenize the composition and temperature of the molten steel. After stirring for 2 minutes, samples are taken, oxygen levels are determined, temperature is measured, and slag adhesion is investigated to obtain W[C]. 样1 %: 0.041%, W[Si] 样1 %: 0.008%, W[Mn] 样1 %: 1.12%, W[S] 样1 %: 0.31%, W[P] 样1 %: 0.056%, W[O] 样1 ppm: 40ppm.

[0080] S46: When W[O] 样1 When the oxygen content is ≤40ppm, no ferrosilicon powder is added (to avoid excessively low oxygen content in the molten steel), and argon blowing is used to naturally re-oxygenate the steel to the target value of 45ppm. In production practice, it has been found that Q... 吹氩流量1 The larger (>10Nm) 3 The more severe the reoxidation of molten steel (at / h), the more serious the reoxidation. Q 吹氩流量1 <10Nm 3 At / h, due to the low argon blowing force, the surface of the molten steel is not exposed, so oxygen does not return. When Q 吹氩流量1 =60Nm 3 At a rate of / h, approximately 2ppm of oxygen is returned per minute, which is equivalent to 1Nm³. 3 / h Argon blowing flow rate and oxygen return Q 吹氩流量1Nm 3 / h The value is 0.04 × (60 - 10) = 0.04 ppm, therefore the relationship W[O] is derived. 样1后回氧 =Q 吹氩流量1Nm 3 / h ×Q 吹氩流量1 ×S 吹氩时间1= 0.04 x Q 吹氩流量1 x S 吹氩时间1 , where Q 吹氩流量1 > 10 Nm 3 / h.

[0081] When 40 ppm < W[O] 样1 ≤ 45 ppm, continue to remove to 40 ppm oxygen according to 0.013 kg / ton of steel of silicon iron powder to remove 1 ppm oxygen, and derive the relationship of silicon iron powder deoxidization to 40 ppm: the amount of silicon iron powder added G LF硅铁粉1 = 0.013 x (W[O] 样1 - 40) = 0.013 x (43 - 40) = 0.039 kg / ton of steel. After deoxidization to 40 ppm oxygen, reoxygenation is performed to the target value of 45 ppm using the reoxygenation relationship (W[O] 样1后回氧 = 0.04 x Q 吹氩流量1 x S 吹氩时间1 , where Q 吹氩流量1 > 10 Nm 3 / h.

[0082] When W[O] 样1 > 45 ppm, continue to deoxidize to 45 ppm according to 0.008 kg / ton of steel of silicon iron to remove 1 ppm oxygen, and derive the total relationship of continued deoxidization to 45 ppm after argon blowing reoxygenation: the amount of silicon iron powder added G LF硅铁粉2 = 0.013 x [(W[O] 样1 - 45) + W[O] 样1后回氧 ] = 0.013 x [(W[O] 样1 - 45) + 0.04 x Q 吹氩流量1 x S 吹氩时间1 ] kg / ton of steel, or the amount of silicon iron alloy added G LF硅铁合金2 = 0.008 x [(W[O] 样1 - 45) + W[O] 样1后回氧 ] = 0.008 x [(W[O] 样1 - 45) + 0.04 x Q 吹氩流量1 x S 吹氩时间1 ] kg / ton of steel, where Q 吹氩流量1 > 10 Nm 3 / h. After deoxidization of silicon iron to 45 ppm, continue to deoxidize to 40 ppm oxygen for correction according to 0.013 kg / ton of steel of silicon iron powder to remove 1 ppm oxygen. Derive the relationship of silicon iron powder deoxidization to 40 ppm: the amount of silicon iron powder added G LF硅铁粉1 = 0.013 x (W[O] 样1 - 40) kg / ton of steel.

[0083] S47: continue to pass argon gas 12.5 Nm 3 / h, the argon purging time is 10 min (the argon flow rate and the argon purging time are adjusted according to the oxygen recovery requirement), and the power is supplied to warm up to the target temperature required before soft blowing. The components are added according to the test results of Sample 1. W[C] 样1 %, W[Mn] 样1 %, W[S] 样1 %, W[P] 样1 % are adjusted to the process target value by the conventional method. W[O] 样1 %, W[S] 样1 %, W[P] 样1 % are adjusted to the process target value by the conventional method. W[O] 样1 > 45 ppm, the amount of low-carbon ferromanganese required to reach W[Mn] 样2 % is: W[O] 样1 > 45 ppm, the amount of low-carbon ferromanganese required to reach W[Mn] 样2 % is: G LF低碳锰铁 = [W[Mn] 工艺目标 % - (W[O] 样1 - 45) ÷ 4 × 0.01% - W[Mn] 样1 %] × 0.12 kg / ton of steel. W[O] 样1 < 45 ppm, the amount of low-carbon ferromanganese required to reach W[Mn] 样2 % is: G LF低碳锰铁 = [W[Mn] 工艺目标 % + (45 - W[O] 样1 ) ÷ 4 × 0.01% - W[Mn] 样1 %] × 0.12 = [1.30% + (45 - 40) ÷ 4 × 0.01% - 1.12%] × 0.12 = 2.31 kg / ton of steel. W[O] 样1后回氧 = Q 吹氩流量1Nm 3 / h × Q 吹氩流量1 × S 吹氩时间1 , wherein Q 吹氩流量1 > 10 Nm 3 / h.

[0084] W[O] 样1后回氧 = 45 - W[O] 样1 = 5 ppm (the amount of oxygen recovery required when the oxygen is lower than 45 ppm), so W[O] 样1后回氧 = 0.04 × Q 吹氩流量1 × S 吹氩时间1 = 5, and Q 吹氩流量1 = W[O] 样1后回氧 ÷ 0.04 ÷ S 吹氩时间1 = 5 ÷ 0.04 ÷ 10 = 12.5, and Q 吹氩流量1 > 10 Nm3 / h (≤10 Nm 3 / h no reoxygenation), thus Q 吹氩流量1 = 10 + 12.5 = 22.5 (Nm 3 / h).

[0085] S48: After the power supply is warmed up to the target temperature required before soft blowing, power is cut off, argon is introduced at 25 Nm 3 / h weak stirring for 3 min, soft blowing argon is introduced at 10 Nm 3 / h, sampling, oxygen determination, temperature measurement, and slag color observation are performed. The results are as follows: W[C] 样2 %: 0.05%, W[Mn] 样2 %: 1.31%, W[S] 样2 %: 0.34%, W[P] 样2 %: 0.070%, W[O] sample 2: 45 ppm, which respectively reaches the process target value.

[0086] In combination with the foregoing steps, the slag is preferably thin, light yellow or yellow-brown. The LF final slag is as follows: CaO: 44%, SiO2: 16%, Al2O3: 7.3%, TFe: 3.1%, MnO: 10.3%, S: 3.8%, MgO: 6.1%, P2O5: 0.04%, R: 2.75, the free oxygen content of the molten steel and the deoxidation effect of the slag are optimal.

[0087] S49: Soft blowing argon is introduced at 10 Nm 3 / h, and husks are added for heat preservation. Soft blowing is performed for 10-20 min, and sampling and temperature measurement are performed. The molten steel is discharged.

[0088] Example 3

[0089] S1: The converter endpoint C is controlled at 0.04%, the endpoint O is controlled at 600 ppm, P is 0.054%, and the tapping temperature is 1605°C.

[0090] S2: Converter tapping alloying and slag washing are performed.

[0091] Alloying addition timing: 7.2 kg of silicon manganese per ton of steel, 10.1 kg of low-carbon ferromanganese per ton of steel, and 8.3 kg of ferrosulfur per ton of steel are added at 1 / 6 of the tapping time.

[0092] Slag washing material addition timing: 7 kg of lime per ton of steel and 0.79 kg of fluorite per ton of steel are added at 1 / 2 of the tapping time.

[0093] Silicon manganese is added first during alloying, followed by low-carbon ferromanganese and ferrosulfur, so as to reduce the formation of MnO in the slag. During alloying and slag washing, argon is introduced at 60 Nm 3 / h, and after completion, it is adjusted to 20 Nm 3 / h to ensure good melting effect.

[0094] The carbon content of the tapped steel is 0.042%, eliminating the need for manual carbon powder addition for pre-deoxidation, venting, and carbon enrichment.

[0095] S3: After tapping the steel, reduce the argon gas flow rate to a soft blowing state of 5-10 Nm. 3 / h, to prevent the molten steel from being exposed.

[0096] Oxygen was determined and samples were taken at the argon station to obtain W[O]. 氩站 ppm: 56ppm, W 氩站 [Si]%: 0.052%. W[O] 氩站 When the concentration is >50 ppm, the amount of ferrosilicon alloy added is G. 氩站硅铁合金 =0.008×(W[O]) 氩站 -50)=0.008×(56-50)=0.048kg / ton of steel, where W[O] 氩站 -50≥0、W[C] 出钢 % < 0.04%. W[O] 氩站 When <50ppm, the amount of ferrosilicon alloy added G 氩站硅铁合金 =80×(0.04%-W[C]) 出钢 %) kg / ton of steel, of which [C] 出钢 % < 0.04%. It should be noted that W[O] in the formula... 氩站 The target value is controlled at 50 ± 5 ppm (preferably 50 ppm), while W[C] 出钢 When the peroxide content is less than 0.04%, ferrosilicon should be added for deoxidation correction. 出钢 If % > 0.04%, then no ferrosilicon is added for deoxidation correction.

[0097] S4: Perform LF refining, including the following steps:

[0098] S41: Temperature measurement upon entry, T is obtained. 进站 1546℃. When T 进站 When the temperature exceeds 1545℃ (the liquidus temperature of the steel grade + 30℃), the oxygen content is determined, and W[O] is obtained. LF进站 38ppm, when T 进站 When the temperature is below 1545℃ (liquidotherm temperature of the steel grade + 30℃), oxygen determination should not be performed initially. Oxygen determination should only be conducted after the power supply temperature rises above 1545℃. Performing oxygen determination at a low inlet temperature will affect the accuracy of the determined oxygen value, rendering it useless as a reference.

[0099] S42:W[O] LF进站 ≤30ppm or from W[Si] in step S3 氩站 When the free silicon content in the molten steel is greater than 0.05% (using the free silicon content of the molten steel for initial deoxidation), no deoxidizer is added. Argon gas is introduced at a rate of 60 Nm³. 3 / h, lime and fluorite slag are added to directly heat by power supply. Lime addition G LF石灰 = 3.3 + G 氩站硅铁 × 6 = 3.3 + 0.048 × 6 = 3.59 (kg / ton of steel), fluorite addition G LF萤石 = [3.3 + G 氩站硅铁 × 6] ÷ 5 = [3.3 + 0.048 × 6] ÷ 5 = 0.72 (kg / ton of steel), i.e. G LF石灰 : G LF萤石 = 5:1, the slag fluidity is better, thereby ensuring the slag basicity R in the process interval 2.0-3.5.

[0100] S43: W[O] LF进站 > 30 ppm, argon is passed 60 Nm 3 / h for 5 min, G LF铝渣球 0.3 kg / ton of steel and G LF硅铁粉 0.24 kg / ton of steel, and the entering steel liquid deoxidation yield is 60%, i.e. the silicon iron powder after addition is converted into silicon iron addition G LF硅铁粉 = 0.24 × 60% = 0.144 kg / ton of steel. LF sample 1 before silicon iron addition G LF硅铁 = 0.008 × (W[O] LF进站 - 45) × W[Si] LF每分钟损失 % × Q 吹氩流量 × S 吹氩时间 - 0.144. Wherein W[O] LF进站 - 45 > 0, W[O] LF进站 - 45 ≤ 0, no silicon iron is added.

[0101] S44: After S43 step, argon is passed 60 Nm 3 / h, lime and fluorite slag are added to directly heat by power supply. Lime addition G LF石灰 = 3.3 + (G 氩站硅铁 + G LF硅铁 ) × 6 = 3.3 + (0.048 + 0) × 6 = 3.59 (kg / ton of steel) (kg / ton of steel), fluorite addition G LF萤石 = [3.3 + (G 氩站硅铁 + G LF硅铁 ) × 6] ÷ 5 (= [3.3 + (0.048 + 0) × 6] ÷ 5 = 0.72 kg / ton of steel), i.e. G LF石灰 : G LF萤石 = 5:1, the slag fluidity is better. Thereby ensuring the slag basicity R in the process interval 2.0-3.5.

[0102] S45: After adding lime, fluorite slag, aluminum slag ball, silicon-iron powder deoxidizer and silicon-iron, use transformer series of 11 stages (preheating gear), and pass in argon 35-38 Nm 3 / h (preferably 35 cm Nm 3 / h) to conduct slagging for 5 minutes, then switch to 4-gear transformer series, continue to pass in electricity, and conduct main heating to raise temperature. When the temperature is raised to T 样1 > 1575 ℃ (steel grade liquidus temperature + 50 ℃), pass in argon 60 Nm 3 / h to conduct power stirring to promote steel slag interface reaction and uniform steel liquid composition and temperature. After stirring for 2 minutes, take sample, determine oxygen, measure temperature, and conduct slag sticking operation to obtain W[C] 样1 %: 0.046%, W[Si] 样1 %: 0.015%, W[Mn] 样1 %: 1.14%, W[S] 样1 %: 0.002%, W[P] 样1 %: 0.055%, W[O] 样1 ppm: 50 ppm.

[0103] S46: When W[O] 样1 ≤ 40 ppm, do not add silicon-iron powder (to avoid low oxygen content of steel liquid), and use argon blowing to naturally return oxygen to 45 ppm target value. In production practice, it is found that the greater Q 吹氩流量1 (> 10 Nm 3 / h), the more serious the return of oxygen of steel liquid. When Q 吹氩流量1 < 10 Nm 3 / h, because the argon blowing intensity is small, the surface of steel liquid is not exposed, so there is no return of oxygen. When Q 吹氩流量1 = 60 Nm 3 / h, about 2 ppm of oxygen is returned per minute, that is, 0.04×(60-10) = 0.04 ppm of oxygen is returned per minute by 1 Nm 3 / h argon blowing flow, so the relationship W[O] 样1后回氧 = Q 1Nm3 / h吹氩流量回氧 × Q 吹氩流量1 × S 吹氩时间1 = 0.04×Q 吹氩流量1 × S 吹氩时间1 , wherein Q 吹氩流量1 > 10 Nm 3 / h.

[0104] When 40 ppm < W[O] 样1 ≤ 45 ppm, continue to deoxidize to 40 ppm according to 0.013 kg / ton steel silicon-iron powder to remove 1 ppm oxygen. Obtain the relationship of silicon-iron powder deoxidization to 40 ppm: the amount of silicon-iron powder added G LF硅铁粉1 = 0.013×(W[O]样1 -40) kg / ton steel. After deoxidizing to 40 ppm oxygen, re-oxygenation is carried out using the re-oxygenation relationship (W[O] 样1后回氧 = 0.04 x Q 吹氩流量1 x S 吹氩时间1 , wherein Q 吹氩流量1 > 10 Nm 3 / h) to the target value of 45 ppm.

[0105] W[O] 样1 > 45 ppm, 1 ppm oxygen is removed by ferrosilicon at 0.008 kg / ton steel, and deoxidization is continued to 45 ppm. The total relationship of continuing deoxidization to 45 ppm oxygen after argon blowing and re-oxygenation is derived: the amount of ferrosilicon powder added G LF硅铁粉2 = 0.013 x [(W[O] 样1 - 45) + W[O] 样1后回氧 ] = 0.013 x [(W[O] 样1 - 45) + 0.04 x Q 吹氩流量1 x S 吹氩时间1 ] = 0.013 x [(50 - 45) + 0.04 x 15 x 10] = 1.38 kg / ton steel, or the amount of ferrosilicon alloy added G LF硅铁合金2 = 0.008 x [(W[O] 样1 - 45) + W[O] 样1后回氧 ] = 0.008 x [(W[O] 样1 - 45) + 0.04 x Q 吹氩流量1 x S 吹氩时间1 ] = 0.008 x [(50 - 45) + 0.04 x 15 x 10] = 0.088 kg / ton steel, wherein Q 吹氩流量1 > 10 Nm 3 / h (i.e. when Q 吹氩流量1 = 15 Nm 3 / h, the actual adjusting flow rate is 25 Nm 3 / h). After deoxidization to 45 ppm by ferrosilicon, 1 ppm oxygen is removed by ferrosilicon powder at 0.013 kg / ton steel, and deoxidization is continued to 40 ppm oxygen for correction. The relationship of deoxidization to 40 ppm by ferrosilicon powder is derived: the amount of ferrosilicon powder added G LF硅铁粉1 = 0.013 x (W[O] 样1 - 40) = 0.013 x (45 - 40) = 0.065 kg / ton steel.

[0106] S47: continue to pass argon at 25 Nm 3 / h, the argon passing time is 10 min (the argon flow rate and the argon blowing time are adjusted according to the re-oxygenation requirement), and the power is supplied to heat to the target temperature required before soft blowing. According to the test results of sample 1, W[C] 样1 %, W[Mn] 样1%, W[S] 样1 %, W[P] 样1 % to add ingredients. W[C] 样1 %, W[S] 样1 %, W[P] 样1 % respectively adjusted to the process target value by the conventional method. W[O] 样1 > 45 ppm, W[Mn] 样2 % required to add low-carbon ferromanganese is: G LF低碳锰铁 = [W[Mn] 工艺目标 % - (W[O] 样1 - 45) ÷ 4 x 0.01% - W[Mn] 样1 %] x 0.12 = [1.30% - (50 - 45) ÷ 4 x 0.01% - 1.14%] x 0.12 = 1.77 kg / ton of steel. W[O] 样1 < 45 ppm, W[Mn] 样2 % required to add low-carbon ferromanganese is: G LF低碳锰铁 = [W[Mn] 工艺目标 % + (W[O] 样1 - 45) ÷ 4 x 0.01% - W[Mn] 样1 %] x 0.12 kg / ton of steel.

[0107] W[O] 样1后回氧 = Q 吹氩流量1Nm3 / h x Q 吹氩流量1 x S 吹氩时间1 , wherein Q 吹氩流量1 > 10 Nm 3 / h.

[0108] W[O] 样1后回氧 = 45 - W[O] 样1 = 5 ppm (required oxygen back to oxygen below 45 ppm), so W[O] 样1后回氧 = 0.04 x Q 吹氩流量1 x S 吹氩时间1 = 5, Q 吹氩流量1 = W[O] 样1后回氧 ÷ 0.04 ÷ S 吹氩时间1 = 5 ÷ 0.04 ÷ 10 = 12.5, and Q 吹氩流量1 > 10 Nm 3 / h (≤ 10 Nm 3 / h not oxygen back), so Q 吹氩流量1 = 10 + 12.5 = 22.5 (Nm 3 / h).

[0109] S48: power supply is turned off after the target temperature required before soft blowing is reached, argon is introduced at 25 Nm 3 / h, soft blowing argon 10 Nm 3 / h, sampling, oxygen determination, temperature measurement, and slag color observation. The W[C] is obtained 样2 %: 0.05%, W[Mn] 样2 %: 1.30%, W[S] 样2 %: 0.33%, W[P] 样2 %: 0.071%, W[O] Sample 2 ppm: 45 ppm, respectively reaching the process target value.

[0110] In combination with the foregoing step operation, the sticky slag is thin yellow or yellow-brown slag S49: soft blowing argon 10 Nm 3 / h, add heat hulls, soft blowing 10-20 min, preferably. The LF final slag is CaO: 45%, SiO2: 18%, Al2O3: 8.2%, TFe: 2.2%, MnO: 10.7%, S: 3.9%, MgO: 6.8%, P2O5: 0.06%, R: 2.5, the free oxygen content of the molten steel and the deoxidation effect of the slag are best.

[0111] Sampling, temperature measurement. Molten steel out of station.

[0112] Comparative Example 1

[0113] After the molten steel is discharged, it is directly subjected to LF refining without argon station treatment.

[0114] The lime amount G LF石灰 added in the LF refining is 3.3 kg / ton of steel, and the fluorite amount G LF萤石 added is 0.66 kg / ton of steel.

[0115] The LF final slag is CaO: 37%, SiO2: 18%, Al2O3: 6.9%, TFe: 3.7%, MnO: 12.2%, S: 3.1%, MgO: 5.2%, P2O5: 0.06%, R: 2.06.

[0116] Similar to the steps of Example 1, the only difference is that the argon station is not oxygen-determined and silicon iron is added for deoxidation, and the lime and fluorite are not supplemented according to the amount of silicon iron in Sample 1 during the refining process, resulting in an alkalinity R lower than 2.2 (2.2-2.8), which is 2.06.

[0117] Comparative Example 2

[0118] W[O] 样1 ppm: 40 ppm.

[0119] Argon 35 Nm 3 / h, power supply to the required target temperature before soft blowing.

[0120] Power supply is stopped after the temperature reaches the target temperature before soft blowing, and argon is introduced at 25 Nm 3 / h, and soft blowing argon is introduced at 10 Nm 3 / h, sampling, oxygen determination, temperature measurement, and slag color observation. The W[O] 样2 : 51 ppm.

[0121] The final LF slag is CaO: 44%, SiO2: 16%, Al2O3: 7.3%, TFe: 3.1%, MnO: 14.3%, S: 3.8%, MgO: 6.1%, P2O5: 0.04%, and R: 2.75.

[0122] Similar to the steps of Example 2, except that silicon-iron alloy or silicon-iron powder is not added according to the argon blowing oxygen return amount during refining, resulting in W[O] 样2 higher than 45 ppm, and MnO in the slag higher than 13%, with results of W[O] 样2 : 51 ppm, and MnO: 14.3%.

[0123] Comparative Example 3

[0124] W[Mn] 样1 : 1.14%, W[O] 样1 : 50 ppm.

[0125] According to the conventional method, W[Mn] 样1 is added. The amount of low-carbon manganese iron required when W[Mn] 样2 is 1.30% is G LF低碳锰铁 = (W[Mn] 工艺目标 -W[Mn] 样1 ) x 0.12 = (1.30%-1.14%) x 0.12 = 1.92 kg / ton of steel. When W[Mn] 样2 : 1.313%.

[0126] Similar to the steps of Example 3, except that low-carbon manganese iron is not added to adjust the composition when the free oxygen in the steel liquid is higher than the specified value of 4 ppm by 0.01%[Mn] during refining, resulting in W[Mn] 样2 higher than the target value of 1.30%, and the amount of low-carbon manganese iron higher than 1.77 kg / ton of steel, with results of W[Mn] 样2 : 1.313%, and G LF低碳锰铁 : 1.92 kg / ton of steel.

[0127] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. 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 refining 1215MS high-sulfur free-cutting steel using the LF process, characterized in that, Includes the following steps: S1: The molten steel is deoxidized, alloyed, and slag washed during the converter tapping process; S2: Sampling and determination of W[O] at the argon station 氩站 According to W[O] 氩站 Determine the amount of ferrosilicon alloy to be added; S3: LF refining arrives at the station, temperature measurement yields T. 进站 When T 进站 >Measure W[O] at the liquidus temperature of the steel grade +30℃. LF进站 According to W[O] LF进站 Determine the amount of lime, fluorite, aluminum slag balls, ferrosilicon powder, and ferrosilicon alloy to be added; S4: LF sample 1, W[C] measured. 样1 %, W[Mn] 样1 %, W[S] 样1 %, W[P] 样1 %, W[O] 样1 ppm, and according to W[O] 样1 Determine the amount of ferrosilicon powder to be added; S5: Adjust the C, Mn, S and P content in the molten steel based on the results of LF sampling 1; S6: After the temperature rises to the target temperature required before soft blowing, temperature measurement, oxygen determination, sampling, and slag adhesion observation are performed. The steel composition, oxygen content, temperature, and final slag composition all meet the requirements. LF molten steel exits the station, including: Step S2 includes: sampling at the argon station and determining W[O]. 氩站 ppm, W[Si] 氩站 %, when W[O] 氩站 When ppm > 50 ppm, ferrosilicon alloy is added for deoxidation correction. The amount of ferrosilicon alloy added is G. 氩站硅铁合金 =0.008×(W[O]) 氩站 -50)+80×(0.04%-W[C] 出钢 %) kg / ton of steel, of which W[C] 出钢 % < 0.04%; Step S3 includes: LF refining at the station, and measuring W[O]. LF进站 , when W[O] LF进站 ppm ≤ 30ppm or W[Si] 氩站 When % > 0.05%, 60 Nm of argon gas is introduced. 3 / h, lime addition amount G LF石灰 =3.3+G 氩站硅铁 ×6, Unit: kg / ton of steel, The mass ratio of lime to fluorite is 5:

1. The addition of lime and fluorite controls the slag basicity R at 2.0-3.

5. When W[O] LF进站 When ppm > 30ppm, argon gas is introduced at 60Nm. 3 / h, Aluminum slag ball addition amount G LF铝渣球 The addition amount of 0.3 kg / ton of steel and ferrosilicon powder is G. LF硅铁粉 The amount of ferrosilicon alloy added is 0.24 kg / ton of steel. LF硅铁合金 =0.008×(W[O]) LF进站 -45)×W[Si] LF每分钟损失 %×Q 吹氩流量 ×S 吹氩时间 -0.144, unit: kg / ton of steel; after deoxidation, continue to introduce 60 Nm of argon gas. 3 / h, lime addition amount G LF石灰 =3.3+(G 氩站硅铁 +G LF硅铁 )×6, unit: kg / ton of steel, the mass ratio of lime to fluorite is 5:1, and the addition of lime and fluorite controls the slag basicity R at 2.0-3.5; Step S4 includes: When W[O] 样1 When ppm < 40ppm, no ferrosilicon powder is added; oxygen is naturally restored to the target value of 45ppm using argon blowing. W[O] 样1后回氧 ppm = 0.04ppm × Q 吹氩流量1 ×S 吹氩时间1 Q 吹氩流量1 >10Nm 3 / h,S 吹氩时间1 The unit is minutes; When 40ppm < W[O] 样1 When ppm ≤ 45ppm, based on the calculation of removing 1ppm of oxygen with 0.013kg / ton of steel ferrosilicon powder, to reduce the oxygen in the molten steel to 40ppm, the amount of ferrosilicon powder added, G LF硅铁粉1 =0.013×(W[O]) 样1 -40) kg / ton of steel, deoxidized to 40 ppm, then reoxidized using the formula W[O) 样1后回氧 ppm = 0.04ppm × Q 吹氩流量1 ×S 吹氩时间1 Q 吹氩流量 1 > 10 Nm 3 / h, argon is blown to restore oxygen to the target value of 45ppm in the molten steel, S 吹氩时间 The unit of 1 is minutes; When W[O] 样1 When ppm > 45ppm, remove 1ppm of oxygen by adding 0.013kg / ton of ferrosilicon powder to the steel. The oxygen content in the molten steel is reduced to 45ppm by adding ferrosilicon powder. The amount of ferrosilicon powder added is G. LF硅铁粉2 =0.013×[(W[O] 样1 -45)+W[O) 样1后回氧 ]=0.013×[(W[O] 样1 -45)+0.04×Q 吹氩流量1 ×S 吹氩时间1 kg / ton of steel, of which Q 吹氩流量 1 > 10 Nm 3 / h, or remove 1ppm oxygen by adding ferrosilicon alloy at a rate of 0.008kg / ton of steel. Adding ferrosilicon alloy reduces the oxygen in the molten steel to 45ppm. The amount of ferrosilicon alloy added is G. LF硅铁合金2 =0.008×[(W[O] 样1 -45)+0.04×Q 吹氩流量1 ×S 吹氩时间1 kg / ton of steel, of which Q 吹氩流量1 >10Nm 3 / h, after deoxidizing ferrosilicon to 45ppm, then calculate based on 0.013kg / ton of steel ferrosilicon powder removing 1ppm of oxygen, continue adding carbon powder to deoxidize to 40ppm for correction, the amount of ferrosilicon powder added is G LF硅铁粉1 =0.013×(W[O]) 样1 -40)kg / ton of steel.

2. The LF refining method according to claim 1, characterized in that, Step S1 includes: converter smelting, converter tapping alloying, slag washing and carbonization treatment.

3. The LF refining method according to claim 2, characterized in that, Converter smelting includes: The converter's final concentration of carbon is controlled at 0.03%-0.04%, oxygen at 600-700ppm, and phosphorus at 0.05%-0.06%, while the tapping temperature is controlled at 1620±20℃.

4. The LF refining method according to claim 2, characterized in that, The alloying and slag washing processes during converter tapping include: adding 6.9-7.2 kg ferrosilicon / ton of steel, 9.8-10.1 kg low-carbon ferromanganese / ton of steel, and 8.1-8.4 kg ferrosulfite / ton of steel at 1 / 6 of the tapping stage; adding 6.8-7.3 kg lime / ton of steel and 0.77-0.81 kg fluorite / ton of steel at 1 / 2 of the tapping stage; and introducing 60 Nm³ of argon gas during alloying and slag washing. 3 / h, after steel tapping is completed, adjust to 20Nm 3 / h.

5. The LF refining method according to claim 2, characterized in that, The carbon enrichment process includes: when the carbon content of the tapped steel is below 0.03%, 0.12-0.15 kg / ton of steel is manually added to perform pre-deoxidation and exhaust, while simultaneously increasing the carbon content to bring the carbon content of the LF to 0.03%-0.04%.

6. The LF refining method according to claim 1, characterized in that, Step S4 includes: adding lime and fluorite to control the slag basicity R at 2.0-3.5, then preheating at setting 11 with an argon flow rate of 35-38 Nm. 3 / h power on for 5 minutes to form slag, then switch to 4 for main heating and temperature rise to T. 样1 >When the liquidus temperature of the steel is +50℃, 60 Nm of argon gas is introduced. 3 After stirring for 2 minutes per hour, sample 1 was taken, oxygen was determined, temperature was measured, and slag adhesion was investigated to obtain W[C]. 样1 %, W[Mn] 样1 %, W[S] 样1 %, W[P] 样1 %, W[O] 样1 ppm.

7. The LF refining method according to claim 1, characterized in that, Step S5 includes: adjusting the oxygen content of the molten steel after LF sampling 1 to the target value, and then continuing to introduce argon gas at 35 Nm³. 3 / h, power supply heats up to the target temperature required before soft blowing, and W[C] is tested according to the results of sample 1. 样1 %, W[S] 样1 %, W[P] 样1 Adjust % to the process target value, where W[Mn] 样1 %Reference W[O] 样1 and W[Mn] 样1 Make adjustments; When W[O] 样1 When ppm > 45 ppm, W[Mn] is achieved. 样2 The amount of low-carbon ferromanganese required to be added at % is: G LF低碳锰铁 =[W[Mn] 工艺目标 %-(W[O] 样1 -45)÷4×0.01%-W[Mn] 样1 [%] × 0.12 kg / ton of steel, of which W[Mn] 工艺目标 %=1.30%; when W[O] 样1 When ppm < 45ppm, W is achieved. 样2 The amount of low-carbon ferromanganese required to be added when [Mn]% is: G LF低碳锰铁 =[W[Mn] 工艺目标 %+(45-W[O]) 样1 )÷4×0.01%-W[Mn] 样1 [%] × 0.12 kg / ton of steel, of which W[Mn] 工艺目标 % = 1.30%.

8. The LF refining method according to claim 1, characterized in that, Step S6 includes: after the power supply is turned on and the temperature reaches the target temperature required before soft blowing, the power is turned off and 25 Nm of argon gas is introduced. 3 Weakly stir for 3 minutes per hour, then gently purge with 10 Nm of argon gas. 3 / h, sampling, oxygen determination, and temperature measurement are performed; slag adhesion is observed for color change, and W[C] is obtained. 样2 %, W[Mn] 样2 %, W[S] 样2 %, W[P] 样2 %, W[O] 样2 ppm, respectively, achieving the process target values; The slag should be thin, light yellow or yellowish-brown. The final LF slag should contain: CaO: 42%-45%, SiO2: 16%-19%, Al2O3: 6%-9%, TFe: 2%-4%, MnO: 8%-13%, S: 3%-4%, MgO: 4%-7%, P2O5: 0.04%-0.07%, and R: 2.2-2.

8.

9. The LF refining method according to claim 1, characterized in that, Step S6 includes: after the slag adhesion and sampling are completed, 10 Nm of soft-blown argon gas is introduced. 3 / h, add insulated rice husks, soft blow for 10-20 minutes, take samples, measure temperature, and LF molten steel exits the station.