CN102816979B - Production method of low-carbon sulfur series free-cutting steel continuous casting billet - Google Patents
Production method of low-carbon sulfur series free-cutting steel continuous casting billet Download PDFInfo
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Abstract
The invention relates to a production method of a low-carbon sulfur series free-cutting steel continuous casting billet. The method comprises the steps of: first placing scrap steel into a converter, then loading liquid iron into the converter; conducting top-bottom combined blowing; carrying out tapping; performing deoxygenation and alloying; implementing argon blowing treatment; conducting soft argon blowing after alloy fine adjustment; adding carbonized rice hulls into a steel ladle when the argon blowing is over; starting continuous casting when the molten steel temperature reaches 1530-1570DEG C; and employing a continuous casting process of tundish treatment, crystallizer control, secondary cooling, straightening and cutting. The invention has the characteristics that: the smelting is free of desulfurization, LF refining treatment and other processes, no steel breakout phenomenon exists in casting, the composition control is stable, the yields of S and Mn elements are both above 90%, the cutting-tool wear can be reduced during processing so as to improve the service life, the tundish has a high utilization rate, the continuous casting billet has no subcutaneous bubble, heart crack, surface crack and other defects, and is free of composition segregation, and the inclusions in the casting billet are thick, big and in a spherical shape, thus being in favor of shape control of the rolled inclusions and improvement of the steel cutting performance.
Description
Technical field
The present invention relates to the production method of free-cutting steel, specifically belong to the production method of low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom.
Background technology
In recent years, machinery manufacturing industry is towards high speed, precise treatment and automation direction development, in order to reduce the machining cost and to enhance productivity, improve quality product, increasing to the resulfurizing series free cutting steel with excellent cutting performance.Sulphur is that free-cutting steel is the steel grade that in current free-cutting steel, kind is maximum, output is maximum, accounts for 70% of free-cutting steel ultimate production, resulfurizing series free cutting steel seriation, stdn that developed country produces.Take cutting ability as main sulphur and the compound free-cutting steel of sulphur, and sulphur content generally, between 0.20%-0.40%, is up to 0.60%; Take mechanical property as main, and cutting ability is auxiliary free-cutting steel, and sulphur content, at 0.04-0.07%, 0.08%-0.13%, is done more important member.MnS inclusion in resulfurizing series free cutting steel has cut off the continuity of matrix and has made the car bits easily broken, lubricate and reduce the wearing and tearing of cutter again simultaneously, thereby improved the cutting ability of steel, yet MnS extends along rolling direction in course of hot rolling, make the transverse mechanical performance of sulphur free-cutting steel significantly reduce, aggravated the steel anisotropy.In order to suppress this harmful effect, can in steel, add appropriate alloying element as selenium, tellurium, zirconium, calcium, titanium, rare earth element etc., form new on-deformable inclusion as MnTe, Mn (SSe) etc., be distributed in MnS around, or form inclusion that (MeMn) S hardness is higher etc., restriction MnS distortion, also can make in steel to form (Mn by controlling deoxygenation conditions (oxygen amount in steel), Fe) (S, O) oxysulfide, due to dissolving in of oxygen, significantly reduce the deformability of MnS, the inclusion long-width ratio is little, be spherical or spindle shape, be conducive to improve the cutting ability of steel.
The low-carbon (LC) resulfurizing series free cutting steel is as U.S.'s trade mark 1213 and 1215, Japan trade mark SUM22, SUM23 and SUM25, the steel such as Germany trade mark 11SMn30 and 11SMn37, be mainly used in making stressed less and size and smooth finish are had to the machined parts such as the production such as strict household electrical appliances, instrument, office automation, IT and lathe, this class steel grade has lower cutting force and cutting temperature, easily chip breaking in cutting process, workpiece surface finish is high and cutter life high excellence cutting ability.The composition characteristic of low-carbon (LC) resulfurizing series free cutting steel is to have added S, P element in steel, S element in steel and Mn element interaction form manganese sulfide inclusion, utilize the manganese sulfide inclusion thing to stress concentration in working angles and be conducive to the effect such as crack propagation, improving the cutting ability of steel; P element in steel, improve ferrite intensity, thereby the embrittlement matrix improves cutting ability.
S in the low-carbon (LC) resulfurizing series free cutting steel, O content are high, are similar to semikilled steel, rimming steel.This type of steel grade mainly adopts the mode of production of " arc melting+die casting " at the invention initial stage, along with the development of steel-making continuous casting technology, by the mode of production of " electric arc furnace/converter melting+LF secondary refining+continuous casting process ", replaced gradually.The production difficulty of this type of steel grade is large, particularly, when continuous casting is produced, following problem usually occurs: greatly, Composition Control is very unstable for (1) Mn, the fluctuation of S elemental composition, and the Si and Al deoxidation product is many, and these brittle inclusions have reduced the cutting rolled steel performance; (2) yield of alloy is low, smelts and adopts Si-Mn, the deoxidation of Mn alloy, and the Mn recovery rate is generally below 85%, and the S recovery rate is not high yet, generally below 80%; (3) continuous casting process difficulty, often occur that slag, castability are poor, bleed-out, connect the problems such as the stove number is few of watering, and continuous casting is controlled bad, and strand is easy to produce the problems such as serious subsurface bubble, component segregation, heart check, surface crack.
Through preliminary search, Japanese Patent JP19940117455, JP2005363816A mention the low-carbon (LC) resulfurizing series free cutting steel, and it discloses employing nitrogen pick-up mode and has been produced, the deficiency of its existence: the one, greatly increase a nitrogen content in steel, easily form bubble, cause slab quality not high; The 2nd, production efficiency is low, cost is high.
China Patent No. is the CN200510024205.4 patent documentation, and it discloses the production method of a kind of low carbon high sulfur (sulphur phosphorus) easy-to-cut structural steel continuous casting billet, i.e. the processing method of " electric furnace/converter+LF processing+continuous casting ".The deficiency of its existence is that the steel-making cycle is long, production efficiency is low, connects and water the shortcomings such as the stove number is few.
The present invention adopts the technology pattern of " converter+Argon+continuous casting ", and optimized production process, enhances productivity, and reduces production costs, and final production goes out the low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom of high-quality.
Summary of the invention
The present invention is directed to and exist at present operational path long, continuous casting process often occurs that slag, castability are poor, bleed-out, connect and water the more deficiency of rigid oxide content that the stove number is few, affect cutting ability, provide a kind of blast-melted need to process through desulfurization, the rear converter of directly packing into of skimming, continuous casting process is stable, can not produce bleed-out, improve connect and to water the stove number, the production method of the low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom that the good rigid oxide content of continuous casting billet quality is few.
Realize the measure of above-mentioned purpose:
A kind of production method of low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom, its step:
1) existing steel scrap is packed in converter, then molten iron is directly packed in converter, the ratio control of packing into of molten iron and steel scrap is in 10:1～3;
2) carry out top bottom blowing: before oxygen blast, first carry out the nitrogen that supplies of 2 minutes, then oxygen blast is until finish;
3) tapping: control tapping temperature at 1650～1720 ℃, the oxygen activity in steel is 500～900ppm;
4) deoxidation and alloying: when tap to the molten steel total amount 20～40% the time, add the Si-Al-Mn alloy according to 0.05 ~ 0.50 kilogram/ppm * oxygen activity; When tap to the molten steel total amount 41～70% the time, according to the steel grades design requirements, add successively ferromanganese, Iron sulfuret and ferrophosphorus to carry out alloying; When tap to the molten steel total amount 80～95% the time, add refining slag according to 4～7 kg/tonnes of steel, the CaO/SiO in refining slag
2it is 1.0～2.0 that ratio is controlled;
5) carry out the Argon processing: liquid steel temperature carries out the alloy fine setting in the time of 1590 ~ 1610 ℃;
6) the alloy fine setting is carried out the soft blow argon after finishing, and the time is 4～15 minutes;
7) Argon finishes, and according to 1.15 ~ 1.55 kg/tonnes of steel, in ladle, adds charring rice husk;
8), when liquid steel temperature reaches 1530～1570 ℃, start continuous casting;
9) continuous casting process: tundish processing → crystallizer → bis-are cold → aligning → cutting; In continuous casting process and control following parameter:
A) adopt long nozzle argon envelope and the cast of tundish blowing argon, tundish molten steel face adds the low-carbon (LC) insulating covering agent according to 0.60 ~ 0.79 kg/tonne of steel;
B) liquid level of crystallization control device is 80～85% of crystallizer total height, and carries out induction stirring, and electromagnetic stirrer coil center molten steel velocity of flow is controlled at 0.4 ~ 1.0 meter per second;
C) control the casting speed of strand at 0.9～1.5 m/min;
D) control of the add-on of crystallizer protecting residue is 0.3 ~ 0.5 kg/tonne of steel;
E) crystallization control device cooling water flow is at 2000 ~ 3500 liter/mins;
F) specific water of secondary cooling zone is controlled at 0.40 ~ 0.80 liter of/kilogram steel, and continuously cast bloom is controlled at 0.2 ~ 1.0 ℃/sec at the average cooling rate of secondary cooling zone;
G) straightening temperature is controlled at 900 ~ 970 ℃.
It is characterized in that: the chemical composition of Si-Al-Mn alloy and weight percent content are: Si:10 ~ 17%, Al:10 ~ 18%, Mn:67 ~ 75%.
It is characterized in that: the chemical composition of refining slag finishing slag and weight percent content are: 35 ~ 49%CaO, 20 ~ 45%SiO
2, 5 ~ 25%Al
2o
3, 8 ~ 20%MgO.
It is characterized in that: before rising and winching to continuous casting platform, concentration of oxygen in molten steel is controlled at 81 ~ 150ppm.
It is characterized in that: the degree of depth that submerged nozzle inserts crystallizer is 120～180 millimeters.
It is characterized in that: the CaO/SiO of low-carbon (LC) insulating covering agent
2it is 0.8 ~ 0.95 that ratio is controlled.
It is characterized in that: the viscosity of crystallizer protecting residue is 0.50 ~ 0.85 pool under 1300 ℃ of conditions, CaO/SiO
2ratio is 0.68 ~ 0.84.
Control the reason of some main technologic parameters in the present invention:
Tapping temperature: why tapping temperature is controlled at 1650 ~ 1720 ℃, is because when tapping temperature during higher than 1720 ℃, will greatly increase to smelt to consume and easily make the concentration of oxygen in molten steel rising; When tapping temperature is less than 1650 ℃, again less than heat supplement, after molten steel temperature reduces gradually, affect follow-up alloying and gon technics after tapping, pouring practice also can't direct motion.
Tapping oxygen activity: tapping oxygen activity is controlled at below 900ppm, is because the molten steel oxygen activity is too high, can make the ladle erosion degree strengthen, and reduces ladle work-ing life, also increases the deoxidation cost simultaneously; Tapping oxygen activity, more than 500ppm, is because need to retain a part of oxygen and better control steel inclusion in steel, avoids subsequent technique to cause in molten steel oxygen level too low.
Adopt the deoxidation of SiAlMn alloy, deoxidation products easily floats, and greatly improves and the recovery rate of stable Mn, S, P alloying element, and controls as requested the add-on of SiAlMn alloy, guarantees that molten steel has suitable oxygen concn.
Before rising and winching to continuous casting platform, concentration of oxygen in molten steel is controlled at 81 ~ 150ppm, be because in molten steel hyperoxia concentration be conducive to form thick spherical, roll the sulfide inclusion that after strain is little, thereby improve the cutting ability of steel, but too high oxygen concn causes very large difficulty can to the continuous casting operation, the problems such as strand subsurface bubble, heart check easily occur, reduce slab quality, so the molten steel oxygen concn should be controlled at 81 ~ 150ppm.
The degree of depth that submerged nozzle inserts crystallizer is 120～180 millimeters, be because the mouth of a river was inserted shallowly, from the molten steel of tapping hole, mouth of a river outflow, easily make the steel liquid fluctuating large, affect the normal inflow of molten mold flux, also have influence on lubricating between base shell and crystallizer wall, easily cause bleed-out, slag; The mouth of a river is inserted too dark, flows out the shortage of heat that molten steel takes the molten steel face to from tapping hole, the mouth of a river, makes the crystallizer protecting residue fusing bad, and the melt cinder flowed between base shell and crystallizer wall is less, can not evenly lubricate the base shell, affects slab quality and even causes bleed-out.Therefore the degree of depth of submerged nozzle insertion crystallizer is set as 120～180 millimeters.
The specific water of secondary cooling zone is controlled at 0.40 ~ 0.80 liter of/kilogram steel, continuously cast bloom is controlled at 0.2 ~ 1.0 ℃/sec at the average cooling rate of secondary cooling zone, because two cold-zone cooling intensity are too small, should cause continuously cast bloom to produce the problems such as bulge and bleedout, cooling intensity is excessive, and the defects such as seriously loosening easily appears in continuously cast bloom heart section, shrinkage cavity, heart check cause straightening temperature to reduce simultaneously, the strand high-temp plastic reduces, and easily forms the aligning crackle.
Controlling electromagnetic stirrer coil center molten steel velocity of flow and be controlled at 0.4 ~ 1.0 meter per second, is because suitable Molten Steel Flow speed is conducive to interrupt column crystal, improves the strand equiaxial crystal ratio, makes molten steel component even, avoids occurring the subsurface bubble defect; Too high velocity of flow easily makes liquid fluctuating excessive, may form the even problem such as bleed-out of slag, therefore, should control Molten Steel Flow speed at 0.4 ~ 1.0 meter per second.
Straightening temperature is controlled at 900 ~ 970 ℃, be because the low-carbon (LC) resulfurizing series free cutting steel 800 ~ be no more than between 900 ℃ and have high-temperature brittleness, straightening temperature is too low, easily produces the aligning crackle; Straightening temperature is too high, and secondary cooling zone is controlled and required too harshness, easily makes continuously cast bloom form heart defect, even causes the industrial accidents such as bleed-out.
Compared with prior art, its characteristics are in the present invention: (1) smelting technology is simple, on-the-spot workable; (2) continuous casting is without bleed-out, and industrial accident is few; (3) due to without operations such as desulfurization, LF refining treatment, reduce energy consumption; (4) Composition Control is stable, and S, Mn element recovery rate are high, all can reach more than 90%; Owing to making Si<0.02%, Al<0.003%, therefore make the Si and Al deoxidation product few, reduce tool wear and improve cutter life; (5) connect and to water more than the stove number can reach 7 stoves, thereby improved the tundish utilization ratio, reduce refractory consumption, production efficiency is improved; (6) continuously cast bloom is without defects such as subsurface bubble, heart check, surface cracks, and the strand composition is even simultaneously, and without component segregation, cc billet surface quality is good; (7) in strand, inclusion is thick is spherical, is conducive to roll rear inclusion morphology control, improves the cutting rolled steel performance.
Embodiment
Below the present invention is described in detail: table 1 is the list of various embodiments of the present invention Performance Detection situation;
Embodiment 1
Test conditions: adopting process: converter melting → argon station Argon → curved type continuous caster continuous casting, the production cross dimensions is 200 * 200mm
2, the step of U.S.'s trade mark 1215 low-carbon (LC) resulfurizing series free cutting steel continuously cast blooms is as follows:
1) existing steel scrap is packed in converter, then molten iron is directly packed in converter, the ratio control of packing into of molten iron and steel scrap is at 10:1.5;
2) carry out top bottom blowing: before oxygen blast, first carry out the nitrogen that supplies of 2 minutes, then oxygen blast is until finish;
3) tapping: control tapping temperature at 1685 ~ 1690 ℃, the oxygen activity in steel is 800ppm;
4) when tap to the molten steel total amount 20% the time, add 280 kilograms of Si-Al-Mn alloys according to 0.35 kilogram/ppm * 800ppm (tapping oxygen activity), the chemical composition of Si-Al-Mn alloy and weight percent content are: Si:10%, Al:15%, Mn:75%; When tap to the molten steel total amount be 55% the time, according to steel grades, add successively ferromanganese, Iron sulfuret and ferrophosphorus to carry out alloying; When tap to the molten steel total amount 82% the time, add refining slag according to 4Kg/ ton steel, the chemical composition of refining slag finishing slag and weight percent content are: 37.5%CaO, 25%SiO
2, 22.5%Al
2o
3, 15%MgO, the CaO/SiO of refining slag
2ratio is 1.5;
5) carry out the Argon processing: liquid steel temperature carries out the alloy fine setting in the time of 1590 ~ 1595 ℃;
6) the alloy fine setting is carried out the soft blow argon after finishing, and the time is 4.5 minutes;
7) Argon finishes, and according to 1.2 kg/tonnes of steel, adds charring rice husk; Before rising and winching to continuous casting platform, concentration of oxygen in molten steel is 98ppm;
8), when liquid steel temperature reaches 1537～1547 ℃, start to carry out continuous casting; Even watering the stove number reaches 9 stoves;
9) continuous casting process: tundish processing → crystallizer → bis-are cold → aligning → cutting; In continuous casting process and control following parameter:
A) adopt long nozzle argon envelope and the cast of tundish blowing argon, tundish molten steel face adds CaO/SiO according to 0.61 kg/tonne of steel
2the low-carbon (LC) insulating covering agent that ratio is 0.92;
B) liquid level of crystallization control device is 80% of crystallizer total height, and carries out induction stirring, and hub of a spool Molten Steel Flow speed control is at 0.6 meter per second;
C) control the casting speed of strand at 1.2 m/mins;
D) adopting viscosity is 0.85 pool, CaO/SiO
2the crystallizer protecting residue that ratio is 0.8, the add-on of covering slag is 0.4kg/ ton steel;
E) the crystallizer cooling water flow is controlled at 3000 liter/mins; The degree of depth that submerged nozzle inserts crystallizer is 125 millimeters;
F) specific water of secondary cooling zone is controlled at 0.40 liter/kilogram, and continuously cast bloom is controlled at 0.22 ℃/sec at the average cooling rate of secondary cooling zone;
G) aligned, straightening temperature is 965 ℃.
Embodiment 2
Test conditions: adopting process: converter melting → argon station Argon → curved type continuous caster continuous casting, the production cross dimensions is 150 * 150mm
2, the step of Japanese trade mark SUM22 low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom is as follows:
1) existing steel scrap is packed in converter, then molten iron is directly packed in converter, the ratio control of packing into of molten iron and steel scrap is at 10:2;
2) carry out top bottom blowing: before oxygen blast, first carry out the nitrogen that supplies of 2 minutes, then oxygen blast is until finish;
3) tapping: control tapping temperature at 1715 ~ 1720 ℃, the oxygen activity in steel is 800ppm;
4) when tap to the molten steel total amount 20% the time, add 44.88 kilograms of Si-Al-Mn alloys according to 0.051 kilogram/ppm * 800ppm (tapping oxygen activity), the chemical composition of Si-Al-Mn alloy and weight percent content are: Si: 14%, Al: 16%, Mn:70%; When tap to the molten steel total amount 60% the time, according to steel grades, add successively ferromanganese, Iron sulfuret and ferrophosphorus to carry out alloying; When tap to the molten steel total amount 90% the time, add refining slag according to 7Kg/ ton steel, the chemical composition of refining slag finishing slag and weight percent content are: 49%CaO, 25%SiO
2, 6%Al
2o
3, 20%MgO, the CaO/SiO of refining slag
2ratio is 1.96;
5) carry out the Argon processing: liquid steel temperature carries out the alloy fine setting in the time of 1595 ~ 1600 ℃;
6) the alloy fine setting is carried out the soft blow argon after finishing, and the time is 9 minutes;
7) Argon finishes, and according to 1.5 kg/tonnes of steel, adds charring rice husk; Before rising and winching to continuous casting platform, concentration of oxygen in molten steel is 135ppm;
8), when liquid steel temperature reaches 1540～1550 ℃, start to carry out continuous casting; Even watering the stove number reaches 8 stoves;
9) continuous casting process: tundish processing → crystallizer → bis-are cold → aligning → cutting; In continuous casting process and control following parameter:
A) adopt long nozzle argon envelope and the cast of tundish blowing argon, tundish molten steel face adds CaO/SiO according to 0.73 kilogram
2the low-carbon (LC) insulating covering agent that ratio is 0.90;
B) liquid level of crystallization control device is 80% of crystallizer total height, and carries out induction stirring, and hub of a spool Molten Steel Flow speed control is at 1.0 meter per seconds;
C) control the casting speed of strand at 1.5 m/mins;
D) adopting viscosity is 0.55 pool, CaO/SiO
2the crystallizer protecting residue that ratio is 0.7, the add-on of covering slag is 0.3kg/ ton steel;
E) the crystallizer cooling water flow is controlled at 3000 liter/mins; The degree of depth that submerged nozzle inserts crystallizer is 170 millimeters;
F) specific water of secondary cooling zone is controlled at 0.6 liter/kilogram, and the average cooling rate of continuously cast bloom in two cold-zones is controlled at 0.65 ℃/sec;
G) aligned 930 ℃ of straightening temperatures.
Embodiment 3
Test conditions: adopting process: converter melting → argon station Argon → curved type continuous caster continuous casting, the production cross dimensions is 220 * 220mm
2, the step of German trade mark 11SMn37 low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom is as follows:
1) existing steel scrap is packed in converter, then molten iron is directly packed in converter, the ratio control of packing into of molten iron and steel scrap is at 10:3;
2) carry out top bottom blowing: before oxygen blast, first carry out the nitrogen that supplies of 2 minutes, then oxygen blast is until finish;
3) tapping: control tapping temperature at 1660 ~ 1665 ℃, the oxygen activity in steel is 600ppm;
4) when tap to the molten steel total amount 20% the time, add 270 kilograms of Si-Al-Mn alloys according to 0.45 kilogram/ppm * 600ppm (tapping oxygen activity), the chemical composition of Si-Al-Mn alloy and weight percent content are: Si: 15%, Al: 14%, Mn:71%; When tap to the molten steel total amount be 68% the time, according to steel grades, add successively ferromanganese, Iron sulfuret and ferrophosphorus to carry out alloying; When tap to the molten steel total amount 93% the time, add refining slag according to 5Kg/ ton steel, the chemical composition of refining slag finishing slag and weight percent content are: 44%CaO, 40%SiO
2, 6%Al
2o
3, 10%MgO, the CaO/SiO of refining slag
2ratio is 1.1;
5) carry out the Argon processing: liquid steel temperature carries out the alloy fine setting in the time of 1605 ~ 1610 ℃;
6) the alloy fine setting is carried out the soft blow argon after finishing, and the time is 15 minutes;
7) Argon finishes, and according to 1.3 kg/tonnes of steel, adds charring rice husk; Before rising and winching to continuous casting platform, concentration of oxygen in molten steel is 85ppm;
8), when liquid steel temperature reaches 1560～1570 ℃, start to carry out continuous casting; Even watering the stove number reaches 10 stoves;
9) continuous casting process: tundish processing → crystallizer → bis-are cold → aligning → cutting; In continuous casting process and control following parameter:
A) adopt long nozzle argon envelope and the cast of tundish blowing argon, tundish molten steel face adds CaO/SiO according to 0.79 kg/tonne of steel
2the low-carbon (LC) insulating covering agent that ratio is 0.80;
B) liquid level of crystallization control device is 80% of crystallizer total height, and carries out induction stirring, and hub of a spool Molten Steel Flow speed control is at 0.4 meter per second;
C) control the casting speed of strand at 1.0 m/mins;
D) adopting viscosity is the crystallizer protecting residue that 0.75 pool, basicity are 0.75, and the add-on of covering slag is 0.5kg/ ton steel;
E) the crystallizer cooling water flow is controlled at 3000 liter/mins; The degree of depth that submerged nozzle inserts crystallizer is 140 millimeters;
F) specific water of secondary cooling zone is controlled at 0.80 liter/kilogram, and continuously cast bloom is controlled at 1 ℃/sec at the average cooling rate of secondary cooling zone;
G) adopt withdrawal straightening machine to be aligned continuously cast bloom, 910 ℃ of straightening temperatures.
9 stove steel interalloy recovery rates and Si, Al content in table 1 embodiment 1
| Connect and water the stove sequence number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| The Mn add-on, % | 0.892 | 0.914 | 0.886 | 0.924 | 0.915 | 0.893 | 0.904 | 0.889 | 0.916 |
| The Mn quantities received, % | 0.836 | 0.842 | 0.831 | 0.882 | 0.872 | 0.856 | 0.854 | 0.837 | 0.904 |
| The Mn recovery rate, % | 94 | 92 | 94 | 95 | 95 | 96 | 94 | 94 | 99 |
| The S add-on, % | 0.281 | 0.272 | 0.285 | 0.266 | 0.257 | 0.273 | 0.264 | 0.282 | 0.274 |
| The S quantities received, % | 0.276 | 0.256 | 0.271 | 0.249 | 0.238 | 0.254 | 0.240 | 0.260 | 0.258 |
| The S recovery rate, % | 98 | 94 | 95 | 94 | 93 | 93 | 91 | 92 | 94 |
| The P add-on, % | 0.051 | 0.054 | 0.048 | 0.057 | 0.046 | 0.054 | 0.056 | 0.050 | 0.053 |
| The P quantities received, % | 0.050 | 0.053 | 0.048 | 0.058 | 0.047 | 0.053 | 0.057 | 0.049 | 0.055 |
| The P recovery rate, % | 98 | 98 | 100 | 102 | 102 | 98 | 102 | 98 | 104 |
| Si content, % | 0.009 | 0.008 | 0.011 | 0.007 | 0.008 | 0.014 | 0.008 | 0.012 | 0.010 |
| Al content, % | 0.001 | 0.002 | 0.001 | 0.002 | 0.001 | 0.002 | 0.002 | 0.001 | 0.002 |
8 stove steel interalloy recovery rates and Si, Al content in table 2 embodiment 2
| Connect and water the stove sequence number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| The Mn add-on, % | 0.854 | 0.829 | 0.822 | 0.864 | 0.880 | 0.865 | 0.835 | 0.813 |
| The Mn quantities received, % | 0.811 | 0.796 | 0.773 | 0.795 | 0.801 | 0.813 | 0.802 | 0.756 |
| The Mn recovery rate, % | 95 | 96 | 94 | 92 | 91 | 94 | 96 | 93 |
| The S add-on, % | 0.273 | 0.279 | 0.273 | 0.257 | 0.259 | 0.309 | 0.300 | 0.289 |
| The S quantities received, % | 0.251 | 0.262 | 0.248 | 0.239 | 0.246 | 0.281 | 0.276 | 0.263 |
| The S recovery rate, % | 92 | 94 | 91 | 93 | 95 | 91 | 92 | 91 |
| The P add-on, % | 0.084 | 0.079 | 0.065 | 0.068 | 0.082 | 0.094 | 0.093 | 0.082 |
| The P quantities received, % | 0.081 | 0.076 | 0.064 | 0.068 | 0.083 | 0.09 | 0.091 | 0.081 |
| The P recovery rate, % | 97 | 96 | 98 | 100 | 101 | 96 | 98 | 99 |
| Si content, % | 0.009 | 0.012 | 0.013 | 0.016 | 0.010 | 0.011 | 0.008 | 0.009 |
| Al content, % | 0.002 | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.002 | 0.001 |
10 stove steel interalloy recovery rates and Si, Al content in table 3 embodiment 3
| Connect and water the stove sequence number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| The Mn add-on, % | 1.339 | 1.420 | 1.443 | 1.379 | 1.541 | 1.264 | 1.350 | 1.376 | 1.396 | 1.459 |
| The Mn quantities received, % | 1.245 | 1.306 | 1.356 | 1.324 | 1.402 | 1.226 | 1.269 | 1.252 | 1.298 | 1.357 |
| The Mn recovery rate, % | 93 | 92 | 94 | 96 | 91 | 97 | 94 | 91 | 93 | 93 |
| The S add-on, % | 0.366 | 0.360 | 0.392 | 0.371 | 0.372 | 0.383 | 0.391 | 0.376 | 0.374 | 0.371 |
| The S quantities received, % | 0.351 | 0.342 | 0.361 | 0.338 | 0.342 | 0.356 | 0.368 | 0.357 | 0.348 | 0.341 |
| The S recovery rate, % | 96 | 95 | 92 | 91 | 92 | 93 | 94 | 95 | 93 | 92 |
| The P add-on, % | 0.066 | 0.057 | 0.066 | 0.066 | 0.078 | 0.072 | 0.059 | 0.067 | 0.061 | 0.072 |
| The P quantities received, % | 0.063 | 0.056 | 0.067 | 0.064 | 0.075 | 0.068 | 0.056 | 0.062 | 0.059 | 0.071 |
| The P recovery rate, % | 96 | 98 | 102 | 97 | 96 | 94 | 95 | 93 | 96 | 98 |
| Si content, % | 0.010 | 0.015 | 0.009 | 0.015 | 0.012 | 0.013 | 0.012 | 0.011 | 0.008 | 0.011 |
| Al content, % | 0.001 | 0.001 | 0.001 | 0.001 | 0.002 | 0.001 | 0.001 | 0.002 | 0.002 | 0.001 |
From table 1 ~ 3, can find out, the strand Composition Control is stable, and S, Mn, P element recovery rate are high, and make Si<0.02%, and Al<0.003, make the Si and Al deoxidation product few.Continuously cast bloom is without defects such as subsurface bubble, heart check, surface cracks, and the strand composition is even simultaneously, the segregation-free problem, and excellent surface quality, connect and water more than the stove number reaches 7 stoves.In continuously cast bloom, inclusion particle is thick is spherical, is evenly distributed, and rolls in rear steel manganese sulfide inclusion thing long-width ratio little, the cutting rolled steel excellent property.
Above-described embodiment only exemplifies for the best, and is not the restriction to embodiments of the present invention.
Claims (6)
1. the production method of a low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom, its step:
1) first steel scrap is packed in converter, then molten iron is directly packed in converter, the ratio control of packing into of molten iron and steel scrap is in 10:1～3;
2) carry out top bottom blowing: before oxygen blast, first carry out the nitrogen that supplies of 2 minutes, then oxygen blast is until finish;
3) tapping: control tapping temperature at 1650～1720 ℃, the oxygen activity in steel is 500～900ppm;
4) deoxidation and alloying: when tap to the molten steel total amount 20～40% the time, add the Si-Al-Mn alloy according to 0.05 ~ 0.50 kilogram/ppm * oxygen activity; When tap to the molten steel total amount 41～70% the time, according to the steel grades design requirements, add successively ferromanganese, Iron sulfuret and ferrophosphorus to carry out alloying; When tap to the molten steel total amount 80～95% the time, add refining slag according to 4～7 kg/tonnes of steel, the CaO/SiO in refining slag
2it is 1.0～2.0 that ratio is controlled;
5) carry out the Argon processing: liquid steel temperature carries out the alloy fine setting in the time of 1590 ~ 1610 ℃;
6) the alloy fine setting is carried out the soft blow argon after finishing, and the time is 4～15 minutes;
7) Argon finishes, and according to 1.15 ~ 1.55 kg/tonnes of steel, in ladle, adds charring rice husk;
8), when liquid steel temperature reaches 1530～1570 ℃, start continuous casting;
9) continuous casting process: tundish processing → crystallizer → bis-are cold → aligning → cutting; In continuous casting process and control following parameter:
A) adopt long nozzle argon envelope and the cast of tundish blowing argon, tundish molten steel face adds the low-carbon (LC) insulating covering agent according to 0.60 ~ 0.79 kg/tonne of steel;
B) liquid level of crystallization control device is 80～85% of crystallizer total height, and carries out induction stirring, and electromagnetic stirrer coil center molten steel velocity of flow is controlled at 0.4 ~ 1.0 meter per second;
C) control the casting speed of strand at 0.9～1.5 m/min;
D) control of the add-on of crystallizer protecting residue is 0.3 ~ 0.5 kg/tonne of steel;
E) crystallization control device cooling water flow is at 2000 ~ 3500 liter/mins;
F) specific water of secondary cooling zone is controlled at 0.40 ~ 0.80 liter of/kilogram steel, and continuously cast bloom is controlled at 0.2 ~ 1.0 ℃/sec at the average cooling rate of secondary cooling zone;
G) straightening temperature is controlled at 900 ~ 970 ℃.
2. the production method of a kind of low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom as claimed in claim 1, it is characterized in that: the chemical composition of Si-Al-Mn alloy and weight percent content are: Si:10 ~ 17%, Al:10 ~ 18%, Mn:67 ~ 75%.
3. the production method of a kind of low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom as claimed in claim 1, it is characterized in that: the chemical composition of refining slag finishing slag and weight percent content are: 35 ~ 49%CaO, 20 ~ 45%SiO
2, 5 ~ 25%Al
2o
3, 8 ~ 20%MgO.
4. the production method of a kind of low-carbon (LC) resulfurizing series free cutting steel continuously cast bloom as claimed in claim 1 is characterized in that: before rising and winching to continuous casting platform, concentration of oxygen in molten steel is controlled at 81 ~ 150ppm.
5. the production method of the continuously cast bloom of a kind of low-carbon (LC) resulfurizing series free cutting steel as claimed in claim 1 is characterized in that: the degree of depth that submerged nozzle inserts crystallizer is 120～180 millimeters.
6. the production method of the continuously cast bloom of a kind of low-carbon (LC) resulfurizing series free cutting steel as claimed in claim 1, is characterized in that: the CaO/SiO of low-carbon (LC) insulating covering agent
2it is 0.8 ~ 0.95 that ratio is controlled.
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| CN114433807A (en) * | 2022-01-26 | 2022-05-06 | 南京钢铁股份有限公司 | Continuous casting process for producing free-cutting steel by converter |
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