CN102816979A - 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 working method of free-cutting steel, specifically belong to the working method of low carbon-sulfur 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, and is in order to reduce the cut cost and to enhance productivity, improve quality product, increasing to the resulfurizing series free cutting steel with excellent in machinability ability.Sulphur is that free-cutting steel is the steel grade that kind is maximum in the current free-cutting steel, output is maximum, accounts for 70% of free-cutting steel ultimate production, resulfurizing series free cutting steel seriation, stdn that developed country produces.With the cutting ability is main sulphur and the compound free-cutting steel of sulphur, and sulphur content generally between 0.20%-0.40%, is up to 0.60%; With mechanical property is main, and cutting ability is the free-cutting steel of assisting, and sulphur content is done more important member at 0.04-0.07%, 0.08%-0.13%.MnS inclusion in the 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 along the rolling direction elongation, makes the transverse mechanical performance of sulphur free-cutting steel significantly reduce in course of hot rolling, has aggravated the steel anisotropy.In order to suppress this harmful effect, can in steel, add an amount of alloying element such as selenium, tellurium, zirconium, calcium, titanium, REE etc., form new on-deformable inclusion such as MnTe; Mn (SSe) etc., be distributed in MnS around, or form the higher inclusion of (MeMn) S hardness etc.; Restriction MnS distortion also can make through control deoxygenation conditions (oxygen amount in the steel) and form (Mn, Fe) (S in the steel; O) oxysulfide is because dissolving in of oxygen significantly reduces the deformability of MnS; The inclusion long-width ratio is little, is spherical or the spindle shape, helps improving the cutting ability of steel.
Low carbon-sulfur series free-cutting steel such as U.S.'s trade mark 1213 and 1215; Japan trade mark SUM22, SUM23 and SUM25; Steel such as Germany trade mark 11SMn30 and 11SMn37; Be mainly used in make stressed less and size and smooth finish had machining component such as production such as strict household electrical appliances, instrument, office automation, IT and lathe, this type steel grade in cutting process, have lower cutting force and cutting temperature, easy chip breaking, workpiece surface finish height and cutter life high excellence cutting ability.The composition characteristic of low carbon-sulfur series free-cutting steel is in steel, to have added S, P element; S element in the steel and Mn element interaction form manganese sulfide inclusion; Utilize the manganese sulfide inclusion thing to stress concentration in the working angles and help effect such as crack propagation, improve the cutting ability of steel; P element in the steel improves ferritic intensity, thereby the embrittlement matrix improves cutting ability.
S, O content height are similar to semikilled steel, rimming steel in the low carbon-sulfur series free-cutting steel.This type of steel grade mainly adopts the mode of production of " arc melting+die casting " at the invention initial stage, and the development along with the steel-making continuous casting technology is replaced by the mode of production of " electric arc furnace/converter melting+LF secondary refining+continuous casting process " gradually.The production difficulty of this type of steel grade is big, particularly when continuous casting is produced, following problem usually occurs: the fluctuation of (1) Mn, S elemental composition is big, and Composition Control is very unstable, and silicon, aluminium deoxidation product are 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 yield is generally below 85%, and the S yield is not high yet, generally below 80%; (3) continuous casting process difficulty often occurs that volume slag, watering property are poor, bleed-out, connects the problems such as the stove number is few of watering, and continuous casting control is bad, and strand is easy to produce problems such as serious subsurface bubble, component segregation, heart check, surface crack.
Through preliminary search; Japanese Patent JP19940117455, JP2005363816A mention the low carbon-sulfur series free-cutting steel, and it discloses employing nitrogen pick-up mode and has produced, the deficiency of its existence: the one, increase a nitrogen content in the steel greatly; Be prone to form bubble, cause slab quality not high; The 2nd, production efficiency is low, cost is high.
Chinese patent number is the CN200510024205.4 patent documentation, and it discloses the working method of a kind of low carbon high sulfur (sulphur phosphorus) easy-to-cut structural steel continuous casting billet, i.e. the process method of " electric furnace/converter+LF processing+continuous casting ".The deficiency of its existence be the steel-making cycle long, production efficiency is low, connect and to water shortcomings such as the stove number is few.
The present invention adopts the technology pattern of " converter+Argon+continuous casting ", and optimization production technology, enhances productivity, and reduces production costs, and final production goes out fine low carbon-sulfur series free-cutting steel continuously cast bloom.
Summary of the invention
The present invention is directed to and exist operational path long at present; Continuous casting process often occurs rolling up that slag, watering property are poor, bleed-out, connect and water the more deficiency of rigid oxide content that the stove number is few, influence cutting ability, and a kind of blast-melted need through desulfurization processing, the converter of directly packing into after skimming is provided; Continuous casting process is stable; Can not produce bleed-out, improve connect and to water the stove number, the working method of the low carbon-sulfur 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 working method of low carbon-sulfur series free-cutting steel continuously cast bloom, its step:
1) existing steel scrap is packed in the converter, molten iron is directly packed in the converter again, 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, carry out 2 minutes confession nitrogen earlier, oxygen blast is up to end then;
3) tapping: the control tapping temperature is at 1650～1720 ℃, and the oxygen activity in the 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, add ferromanganese, Iron sulfuret and ferrophosphorus successively according to the steel grades design requirements and carry out alloying; When tap to the molten steel total amount 80～95% the time, add refining slags, the CaO/SiO in the refining slag according to 4～7 kilograms of/ton steel
2Ratio is controlled to be 1.0～2.0;
5) carrying out Argon handles: liquid steel temperature carries out the alloy fine setting in the time of 1590 ~ 1610 ℃;
6) carry out the soft blow argon after the alloy fine setting finishes, the time is 4～15 minutes;
7) Argon finishes, and in ladle, adds charring rice husk according to 1.15 ~ 1.55 kilograms of/ton steel;
8) when liquid steel temperature reaches 1530～1570 ℃, the beginning continuous casting;
9) continuous casting process: tundish processing → mold → two 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 kilogram of/ton steel;
B) liquid level of crystallization control device is 80～85% of a mold total height, and carries out induction stirring, and electromagnetic stirrer coil center Molten Steel Flow speed control is at 0.4 ~ 1.0 meter per second;
C) casting speed of control strand is at 0.9～1.5 meter/minute;
D) add-on of crystallizer protecting residue is controlled to be 0.3 ~ 0.5 kilogram of/ton steel;
E) crystallization control device cooling water flow is at 2000 ~ 3500 liters/minute;
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 ℃/second 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: rise winch to continuous casting platform before, oxygen concn is controlled at 81 ~ 150ppm in the molten steel.
It is characterized in that: the degree of depth that submerged nozzle inserts mold is 120～180 millimeters.
It is characterized in that: the CaO/SiO of low-carbon (LC) insulating covering agent
2Ratio is controlled to be 0.8 ~ 0.95.
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.
The reason of some main technologic parameters of control among the present invention:
Tapping temperature: why tapping temperature is controlled at 1650 ~ 1720 ℃, is because when tapping temperature is higher than 1720 ℃, will increase greatly to smelt to consume and make easily oxygen concn rising in the molten steel; When tapping temperature during less than 1650 ℃, again less than heat supplement, after molten steel temperature reduces gradually, influence follow-up alloying and Argon technology after the tapping, pouring practice also can't direct motion.
Tapping oxygen activity: tapping oxygen activity is controlled at below the 900ppm, is because the molten steel oxygen activity is too high, and the ladle erosion degree is strengthened, and reduces ladle work-ing life, also increases the deoxidation cost simultaneously; Tapping oxygen activity is to come better control steel inclusion because need to keep a part of oxygen in the steel more than 500ppm, avoids subsequent technique to cause in the molten steel oxygen level low excessively.
Adopt the deoxidation of SiAlMn alloy, deoxidation products floats easily, and improves greatly and the yield of stable Mn, S, P alloying element, and controls the add-on of SiAlMn alloy as requested, guarantees that molten steel has suitable oxygen concn.
Rise winch to continuous casting platform before; Oxygen concn is controlled at 81 ~ 150ppm in the molten steel, be because in the molten steel hyperoxia concentration help forming thick spherical, roll the little sulfide inclusion of after strain, thereby improve the cutting ability of steel; But too high oxygen concn causes very big difficulty can for the continuous casting operation; Occur problems such as strand subsurface bubble, heart check easily, reduce slab quality, so the molten steel oxygen concn should be controlled at 81 ~ 150ppm.
The degree of depth that submerged nozzle inserts mold is 120～180 millimeters; Be that effusive molten steel makes the molten steel ground roll greatly moving easily from mouth of a river tapping hole, influences the normal inflow of molten mold flux because the mouth of a river was inserted shallowly; Also have influence on lubricating between base shell and the mould wall, be prone to cause bleed-out, volume slag; The mouth of a river is inserted too dark, and the tapping orifice flow goes out the shortage of heat that molten steel takes the molten steel face to from the mouth of a river, makes the crystallizer protecting residue fusing bad, and the melt cinder that flows between base shell and the mould wall is less, can not evenly lubricate the base shell, influences slab quality even causes bleed-out.Therefore the degree of depth of submerged nozzle insertion mold is set at 120～180 millimeters.
The 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 ℃/second at the average cooling rate of secondary cooling zone, is because two cold-zone cooling intensity are too small; Should cause continuously cast bloom to produce problems such as bulge and bleedout; Cooling intensity is excessive, and defectives such as seriously loosening appears in continuously cast bloom heart portion easily, shrinkage cavity, heart check cause straightening temperature to reduce simultaneously; The strand high-temp plastic reduces, and forms the aligning crackle easily.
Control electromagnetic stirrer coil center Molten Steel Flow speed control is because suitable Molten Steel Flow speed helps interrupting column crystal at 0.4 ~ 1.0 meter per second, improves the strand equiaxial crystal ratio, makes molten steel component even, avoids occurring the subsurface bubble defective; Too high velocity of flow makes liquid fluctuating excessive easily, possibly form problems such as volume slag even bleed-out, 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-sulfur series free-cutting steel 800 ~ be no more than between 900 ℃ and have high-temperature brittleness, straightening temperature is low excessively, is easy to generate the aligning crackle; Straightening temperature is too high, secondary cooling zone control is required too harsh, is prone to make continuously cast bloom to form heart defect, even causes industrial accident such as bleed-out.
The present invention compared with prior art, its characteristics are: (1) smelting technology is simple, and is on-the-spot workable; (2) continuous casting does not have bleed-out, and industrial accident is few; (3) owing to, cut down the consumption of energy without operations such as desulfurization, LF refining treatment; (4) Composition Control is stable, and S, Mn element yield height all can reach more than 90%; Owing to can make Si＜0.02%, Al＜0.003% so make silicon, aluminium deoxidation product few, reduces tool wear raising cutter life; (5) even water the stove number and can reach more than 7 stoves, thereby improved the tundish utilization ratio, reduce refractory consumption, production efficiency is improved; (6) continuously cast bloom does not have defectives such as subsurface bubble, heart check, surface crack, and the strand composition is even simultaneously, no component segregation, and cc billet surface quality is good; (7) inclusion is thick in the strand is spherical, helps rolling back inclusion morphology control, improves the cutting rolled steel performance.
Embodiment
Describe in detail in the face of the present invention down: table 1 is the tabulation 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-sulfur series free-cutting steel continuously cast blooms is following:
1) existing steel scrap is packed in the converter, molten iron is directly packed in the converter again, 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, carry out 2 minutes confession nitrogen earlier, oxygen blast is up to end then;
3) tapping: the control tapping temperature is at 1685 ~ 1690 ℃, and the oxygen activity in the 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, add ferromanganese, Iron sulfuret and ferrophosphorus successively according to steel grades and 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) carrying out Argon handles: liquid steel temperature carries out the alloy fine setting in the time of 1590 ~ 1595 ℃;
6) carry out the soft blow argon after the alloy fine setting finishes, the time is 4.5 minutes;
7) Argon finishes, and adds charring rice husk according to 1.2 kilograms of/ton steel; Rise winch to continuous casting platform before, oxygen concn is 98ppm in the molten steel;
8) when liquid steel temperature reaches 1537～1547 ℃, begin to carry out continuous casting; Even watering the stove number reaches 9 stoves;
9) continuous casting process: tundish processing → mold → two 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 kilogram of/ton steel
2Ratio is 0.92 low-carbon (LC) insulating covering agent;
B) liquid level of crystallization control device is 80% of a mold 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) casting speed of control strand is at 1.2 meters/minute;
D) adopting viscosity is 0.85 pool, CaO/SiO
2Ratio is 0.8 crystallizer protecting residue, and the add-on of covering slag is a 0.4kg/ ton steel;
E) the mold cooling water flow is controlled at 3000 liters/minute; The degree of depth that submerged nozzle inserts mold 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 ℃/second at the average cooling rate of secondary cooling zone;
G) align, 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-sulfur series free-cutting steel continuously cast bloom is following:
1) existing steel scrap is packed in the converter, molten iron is directly packed in the converter again, 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, carry out 2 minutes confession nitrogen earlier, oxygen blast is up to end then;
3) tapping: the control tapping temperature is at 1715 ~ 1720 ℃, and the oxygen activity in the 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: Al 14%: Mn:70% 16%; When tap to the molten steel total amount 60% the time, add ferromanganese, Iron sulfuret and ferrophosphorus successively according to steel grades and 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) carrying out Argon handles: liquid steel temperature carries out the alloy fine setting in the time of 1595 ~ 1600 ℃;
6) carry out the soft blow argon after the alloy fine setting finishes, the time is 9 minutes;
7) Argon finishes, and adds charring rice husk according to 1.5 kilograms of/ton steel; Rise winch to continuous casting platform before, oxygen concn is 135ppm in the molten steel;
8) when liquid steel temperature reaches 1540～1550 ℃, begin to carry out continuous casting; Even watering the stove number reaches 8 stoves;
9) continuous casting process: tundish processing → mold → two 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
2Ratio is 0.90 low-carbon (LC) insulating covering agent;
B) liquid level of crystallization control device is 80% of a mold 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) casting speed of control strand is at 1.5 meters/minute;
D) adopting viscosity is 0.55 pool, CaO/SiO
2Ratio is 0.7 crystallizer protecting residue, and the add-on of covering slag is a 0.3kg/ ton steel;
E) the mold cooling water flow is controlled at 3000 liters/minute; The degree of depth that submerged nozzle inserts mold 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 ℃/second;
G) align 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-sulfur series free-cutting steel continuously cast bloom is following:
1) existing steel scrap is packed in the converter, molten iron is directly packed in the converter again, 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, carry out 2 minutes confession nitrogen earlier, oxygen blast is up to end then;
3) tapping: the control tapping temperature is at 1660 ~ 1665 ℃, and the oxygen activity in the 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: Al 15%: Mn:71% 14%; When tap to the molten steel total amount be 68% the time, add ferromanganese, Iron sulfuret and ferrophosphorus successively according to steel grades and 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) carrying out Argon handles: liquid steel temperature carries out the alloy fine setting in the time of 1605 ~ 1610 ℃;
6) carry out the soft blow argon after the alloy fine setting finishes, the time is 15 minutes;
7) Argon finishes, and adds charring rice husk according to 1.3 kilograms of/ton steel; Rise winch to continuous casting platform before, oxygen concn is 85ppm in the molten steel;
8) when liquid steel temperature reaches 1560～1570 ℃, begin to carry out continuous casting; Even watering the stove number reaches 10 stoves;
9) continuous casting process: tundish processing → mold → two 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 kilogram of/ton steel
2Ratio is 0.80 low-carbon (LC) insulating covering agent;
B) liquid level of crystallization control device is 80% of a mold 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) casting speed of control strand is at 1.0 meters/minute;
D) adopting viscosity is that 0.75 pool, basicity are 0.75 crystallizer protecting residue, and the add-on of covering slag is a 0.5kg/ ton steel;
E) the mold cooling water flow is controlled at 3000 liters/minute; The degree of depth that submerged nozzle inserts mold 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 ℃/second at the average cooling rate of secondary cooling zone;
G) adopt the straightening machine continuously cast bloom to be aligned 910 ℃ of straightening temperatures.
9 stove steel interalloy yields and Si, Al content among 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 yield, % | 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 yield, % | 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 yield, % | 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 yields and Si, Al content among 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 yield, % | 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 yield, % | 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 yield, % | 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 yields and Si, Al content among 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 yield, % | 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 yield, % | 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 yield, % | 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 |
Can find out that from table 1 ~ 3 the strand Composition Control is stable, S, Mn, P element yield are high, and make Si＜0.02%, and Al＜0.003 makes silicon, aluminium deoxidation product few.Continuously cast bloom does not have defectives such as subsurface bubble, heart check, surface crack, and the strand composition is even simultaneously, the segregation-free problem, and surface quality is good, even waters the stove number and reaches more than 7 stoves.Inclusion particle is thick in the continuously cast bloom is spherical, is evenly distributed, roll the back steel in manganese sulfide inclusion thing long-width ratio little, the cutting rolled steel excellent property.
The foregoing description is merely the best and gives an example, and is not to be the qualification to embodiment of the present invention.
Claims (7)
1. the working method of a low carbon-sulfur series free-cutting steel continuously cast bloom, its step:
1) earlier steel scrap is packed in the converter, molten iron is directly packed in the converter again, 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, carry out 2 minutes confession nitrogen earlier, oxygen blast is up to end then;
3) tapping: the control tapping temperature is at 1650～1720 ℃, and the oxygen activity in the 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, add ferromanganese, Iron sulfuret and ferrophosphorus successively according to the steel grades design requirements and carry out alloying; When tap to the molten steel total amount 80～95% the time, add refining slags, the CaO/SiO in the refining slag according to 4～7 kilograms of/ton steel
2Ratio is controlled to be 1.0～2.0;
5) carrying out Argon handles: liquid steel temperature carries out the alloy fine setting in the time of 1590 ~ 1610 ℃;
6) carry out the soft blow argon after the alloy fine setting finishes, the time is 4～15 minutes;
7) Argon finishes, and in ladle, adds charring rice husk according to 1.15 ~ 1.55 kilograms of/ton steel;
8) when liquid steel temperature reaches 1530～1570 ℃, the beginning continuous casting;
9) continuous casting process: tundish processing → mold → two 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 kilogram of/ton steel;
B) liquid level of crystallization control device is 80～85% of a mold total height, and carries out induction stirring, and electromagnetic stirrer coil center Molten Steel Flow speed control is at 0.4 ~ 1.0 meter per second;
C) casting speed of control strand is at 0.9～1.5 meter/minute;
D) add-on of crystallizer protecting residue is controlled to be 0.3 ~ 0.5 kilogram of/ton steel;
E) crystallization control device cooling water flow is at 2000 ~ 3500 liters/minute;
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 ℃/second at the average cooling rate of secondary cooling zone;
G) straightening temperature is controlled at 900 ~ 970 ℃.
2. the working method of a kind of low carbon-sulfur series free-cutting steel continuously cast bloom as claimed in claim 1 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 working method of a kind of low carbon-sulfur series free-cutting steel continuously cast bloom as claimed in claim 1 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 working method of a kind of low carbon-sulfur series free-cutting steel continuously cast bloom as claimed in claim 1 is characterized in that: rise winch to continuous casting platform before, oxygen concn is controlled at 81 ~ 150ppm in the molten steel.
5. the working method of the continuously cast bloom of a kind of low carbon-sulfur series free-cutting steel as claimed in claim 1 is characterized in that: the degree of depth that submerged nozzle inserts mold is 120～180 millimeters.
6. the working method of the continuously cast bloom of a kind of low carbon-sulfur series free-cutting steel as claimed in claim 1 is characterized in that: the CaO/SiO of low-carbon (LC) insulating covering agent
2Ratio is controlled to be 0.8 ~ 0.95.
7. the working method of a kind of low carbon-sulfur series free-cutting steel continuously cast bloom as claimed in claim 1 is characterized in that: the viscosity of crystallizer protecting residue is 0.50 ~ 0.85 pascal second under 1300 ℃ of conditions, CaO/SiO
2Ratio is 0.68 ~ 0.84.
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