CN115287401B - Smelting method for controlling silicate inclusions in axle steel - Google Patents
Smelting method for controlling silicate inclusions in axle steel Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 159
- 239000010959 steel Substances 0.000 title claims abstract description 159
- 238000000034 method Methods 0.000 title claims abstract description 32
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 title claims abstract description 30
- 238000003723 Smelting Methods 0.000 title claims abstract description 30
- 239000002893 slag Substances 0.000 claims abstract description 65
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 52
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 42
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 38
- 238000007670 refining Methods 0.000 claims abstract description 28
- 239000010703 silicon Substances 0.000 claims abstract description 28
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 21
- 239000001301 oxygen Substances 0.000 claims abstract description 21
- 238000010079 rubber tapping Methods 0.000 claims abstract description 21
- 238000005275 alloying Methods 0.000 claims abstract description 20
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims abstract description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 28
- 238000009749 continuous casting Methods 0.000 claims description 23
- 239000008188 pellet Substances 0.000 claims description 20
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 18
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 18
- 239000004571 lime Substances 0.000 claims description 18
- 238000003756 stirring Methods 0.000 claims description 15
- 229910052786 argon Inorganic materials 0.000 claims description 14
- 230000001276 controlling effect Effects 0.000 claims description 13
- 238000009489 vacuum treatment Methods 0.000 claims description 12
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 10
- 238000007664 blowing Methods 0.000 claims description 9
- 239000000126 substance Substances 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 8
- 229910000914 Mn alloy Inorganic materials 0.000 claims description 7
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 7
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 238000004458 analytical method Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 229910008455 Si—Ca Inorganic materials 0.000 claims description 5
- 230000005540 biological transmission Effects 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 5
- 239000010459 dolomite Substances 0.000 claims description 5
- 229910000514 dolomite Inorganic materials 0.000 claims description 5
- 238000005096 rolling process Methods 0.000 claims description 5
- 239000005997 Calcium carbide Substances 0.000 claims description 4
- 229910001208 Crucible steel Inorganic materials 0.000 claims description 4
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 4
- 229910000628 Ferrovanadium Inorganic materials 0.000 claims description 4
- 238000009529 body temperature measurement Methods 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 239000010436 fluorite Substances 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- PNXOJQQRXBVKEX-UHFFFAOYSA-N iron vanadium Chemical compound [V].[Fe] PNXOJQQRXBVKEX-UHFFFAOYSA-N 0.000 claims description 4
- 238000005086 pumping Methods 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 4
- 229910052717 sulfur Inorganic materials 0.000 claims description 4
- CLZWAWBPWVRRGI-UHFFFAOYSA-N tert-butyl 2-[2-[2-[2-[bis[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]amino]-5-bromophenoxy]ethoxy]-4-methyl-n-[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]anilino]acetate Chemical compound CC1=CC=C(N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)C(OCCOC=2C(=CC=C(Br)C=2)N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)=C1 CLZWAWBPWVRRGI-UHFFFAOYSA-N 0.000 claims description 4
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
- 239000006187 pill Substances 0.000 claims description 2
- 229910004261 CaF 2 Inorganic materials 0.000 claims 1
- 239000004411 aluminium Substances 0.000 claims 1
- 230000005611 electricity Effects 0.000 claims 1
- 230000005764 inhibitory process Effects 0.000 claims 1
- 230000003647 oxidation Effects 0.000 abstract description 6
- 238000007254 oxidation reaction Methods 0.000 abstract description 6
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 abstract description 2
- 230000007774 longterm Effects 0.000 abstract description 2
- 238000005457 optimization Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910000720 Silicomanganese Inorganic materials 0.000 description 2
- XFWJKVMFIVXPKK-UHFFFAOYSA-N calcium;oxido(oxo)alumane Chemical compound [Ca+2].[O-][Al]=O.[O-][Al]=O XFWJKVMFIVXPKK-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000004925 denaturation Methods 0.000 description 1
- 230000036425 denaturation Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- PYLLWONICXJARP-UHFFFAOYSA-N manganese silicon Chemical compound [Si].[Mn] PYLLWONICXJARP-UHFFFAOYSA-N 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention discloses a smelting method for controlling silicate inclusions in axle steel, which adopts tapping full aluminum deoxidization, refining and slag system adjustment, aluminum-silicon content control and alloying sequence optimization to reduce the oxidation of silicon elements in the steel, thereby reducing the silicate inclusions in the axle steel. Firstly, controlling the addition of aluminum in the tapping stage and the refining stage, so as to inhibit the oxidation of silicon element in steel; the combination of the fluorine-free high-alkalinity slag system (Al 2 O 3 :22-35%, R is more than or equal to 8), and under the low oxygen atmosphere, thereby controlling the generation of brittle silicate with larger harm in the axle steel, improving the steel purity of the axle steel, checking that the silicate inclusion (C class) in the axle steel is below 0.5 level, mainly taking D class or Ds class inclusion as the main, and improving the long-term service safety of the train axle.
Description
Technical Field
The invention relates to a smelting production technology of pure axle steel, in particular to a smelting method for controlling silicate inclusions in the axle steel, and belongs to the field of steel smelting.
Background
Axles are one of the important load bearing members of railroad trains. The train axle has long service time, generally more than twenty years; the service environment is bad, and various complex stresses such as fatigue, bending, torsion, stretching, impact and the like are born. Therefore, axle quality reliability is directly related to the driving safety of the railway train.
The safety performance of the axle is closely related to the purity of the material used for manufacturing the axle, besides the components and the performance of the axle. Studies have shown that the main cause of axle failure is the formation of fatigue cracks in the vicinity of inclusions, especially brittle inclusions in steel.
The silicate inclusions in the axle steel are mainly SiO formed in the steel 2 The deoxidized product is formed by combining with metal oxide in the steel. Silicate inclusions in axle steel belong to brittle inclusions, most of the inclusions are spherical or irregular, the shapes of the inclusions are basically unchanged during forging and rolling deformation of the steel, microcracks are formed at the interface between the inclusions and a steel matrix, and the existence of the microcracks has a great hidden trouble on the safe operation of the axle.
Therefore, silicate inclusions in steel should be reduced or removed in the process of smelting the axle steel, which is important to improve the quality of safe operation of the axle.
Disclosure of Invention
The invention aims to provide a smelting method for controlling silicate inclusion in axle steel, which improves the purity of the steel of the axle steel by controlling silicate brittle inclusion with larger harm in the steel, and meets the quality requirement of train safe operation on the axle material with high standard.
The smelting method for controlling silicate inclusions in the axle steel adopts the scheme of 'using aluminum to inhibit silicon', and controls the addition of aluminum in the tapping stage and the refining stage, thereby inhibiting the oxidation of silicon element in the steel. And is used in combination with a fluorine-free high-alkalinity slag system (Al) 2 O 3 :22-35%, R is more than or equal to 8) (R is alkalinity, caO/SiO 2 The value of (2) and the alloying measure of the silicon component under the low-oxygen atmosphere, thereby controlling the generation of brittle silicate with larger harm in the axle steel, improving the steel purity of the axle steel, checking that the silicate inclusion (C type) in the axle steel is below 0.5 level and mainly takes D type or Ds type inclusion as the main material, and further improving the long-term service safety of the train axle.
The invention adopts tapping full aluminum deoxidization, refining and slag system adjustment, aluminum-silicon content control and alloying sequence optimization to reduce the oxidation of silicon element in steel, thereby reducing silicate inclusion in axle steel.
The invention provides a smelting method for controlling silicate inclusions in axle steel, which comprises the following steps:
(1) Adopting an eccentric bottom electric furnace for smelting, tapping to control the flow of oxidizing slag into a ladle, adding aluminum pellets along with the flow of steel, wherein the adding amount of the aluminum pellets is 1.8-2.5 kg/ton of steel.
(2) The aluminum deoxidization adopts a control scheme of 'suppressing silicon by aluminum'. When the content of dissolved oxygen in molten steel is less than 4X 10 -6 Then alloying silicon element.
(3) Fluorine-free high-alkalinity low-silicon component (mass percent) refining slag system: caO: 45-56%, mgO:8 to 12 percent of Al 2 O 3 ：22～35%，SiO 2 : 2-8%, and slag system binary alkalinity R (CaO/SiO) 2 ) And is more than or equal to 8. The proportion of the alkalinity R is CaO and SiO 2 The mass ratio of the two.
Preferably: al (Al) 2 O 3 : 22-30%, and slag system binary alkalinity R (CaO/SiO) 2 ) 8-15.
(4) After LF (ladle) refining is finished, the [%Al ]/[%Si ] (mass ratio) in molten steel is kept at 15% -20%. After the VD vacuum treatment is finished, the [%Al ]/[%Si ] in the steel is kept at 5% -15%.
The smelting method for controlling silicate inclusions in the axle steel specifically comprises the following steps:
(1) EBT-EAF (eccentric bottom electric furnace) charging;
(2) Oxygen is blown to the side wall of the electric furnace in the smelting process, lime is added into the electric furnace for smelting in two batches, so that P, S, si and other elements in steel are removed;
(3) Tapping in an electric furnace, and measuring the temperature and chemical components of molten steel; the tapping amount of molten steel is 80-90 tons;
(4) And adding 300-400kg of lime, 200-300kg of dolomite, 300-400kg of synthetic slag and 150-200kg of aluminum pellets into the steel along with the steel flow during tapping to initially finish the alloying and deoxidization of the components in the steel ladle. Adding 145-200kg of aluminum pellets into molten steel, wherein the ratio of the amount of the added aluminum pellets to the molten steel is 1.8-2.5kg/t of steel.
(5) When tapping, steel and slag are reserved, and oxygen-enriched oxidizing slag in the electric furnace is controlled to flow into a ladle by utilizing the eccentric bottom characteristic of the electric furnace;
(6) Feeding the materials into an LF station for temperature measurement, adding 120-150kg of calcium carbide, and carrying out power transmission and temperature rise for 10+/-2 minutes. Heating to 1570+ -10deg.C, adding 180-200kg lime, 30-60kg aluminum pellet, and 40-60kg ferrovanadium for regulating the first component and slag system.
(7) And then 10 seeds are fed, the temperature is raised, slag is dissolved, 180-200kg of lime is added, and the secondary slag system and component adjustment are carried out. When the oxygen content in the molten steel is detected to be less than 4ppm, alloying silicon components, adding 30-50kg of ferrosilicon and 40-60kg of high manganese alloy, and adding 10-15kg of aluminum pellets. Argon is blown at the bottom of the whole process, and the flow is 1000-1100NL/min.
(8) The refining process does not add fluorite (CaF) 2 ) The refining slag is prepared by adjusting the components of CaO: 45-56%, mgO:8 to 12 percent of Al 2 O 3 ：22～35%，SiO 2 : 2-8%, slag system alkalinity R (CaO/SiO) 2 ) And (8) or more, forming a fluorine-free high-alkalinity low-silicon slag system.
(9) After alloying is completed, carrying out third power transmission heating to the LF outlet temperature of 1650-1670 ℃, wherein the Si and Al components in the steel during outlet are as follows: si=0.20-0.45%, al=0.050-0.065%. The Al/Si in the molten steel is kept to be more than or equal to 15 percent when the ladle refining station is used.
(10) And (3) feeding the material into a VD station, and measuring the temperature to 1650-1660 ℃. Vacuum pumping is carried out on the movable VD sealing cover, the holding time is 20-25 minutes under the high vacuum degree (less than or equal to 67 pa), and argon is blown in the whole process, and the flow is 1000-1100NL/min.
(11) After the vacuum treatment is completed, the Si-Ca wire is fed for 120-150 m.
(12) And adding a heat-insulating covering agent. And (3) soft stirring by bottom blowing Ar gas, wherein the flow is 50-60NL/min, and the time is 15-20 minutes.
(13) And (3) taking the VD out of the station, and measuring the temperature by 1572 ℃. After the VD vacuum treatment is finished, the chemical components of Si and Al in the molten steel are as follows: si=0.25-0.40%, al=0.020-0.035%, al/si=10-20% in molten steel.
(14) And (5) operating the ladle to the cast steel platform. And (3) pre-burning the middle ladle in continuous casting for 4+/-1 hours on a casting platform. After the arm fork is cast on the ladle, the baked tundish is moved to a continuous casting position, the submerged nozzle is centered, argon blowing operation is carried out on the tundish, and air in the ladle is removed.
(15) And rotating the steel ladle to the upper part of the middle ladle, and carrying out continuous casting production, wherein the continuous casting adopts crystallizer electromagnetic stirring (M-EMS), secondary cooling electromagnetic stirring (S-EMS) and terminal electromagnetic stirring (F-EMS) to produce continuous casting blanks.
(16) Rolling the continuous casting blank into a shaft blank with the square specification of 250mm, and taking an inclusion analysis sample at 1/2 side length of the shaft blank.
In the invention, the technical conception of controlling silicate inclusions in axle steel in the smelting process is as follows:
firstly, utilizing the characteristic of eccentric bottom of smelting electric furnace, controlling the electric furnace to be rich in SiO during tapping of the electric furnace 2 The slag flows into a ladle, lime, synthetic slag and silicon-manganese alloy are added along with the steel flow to carry out coarse adjustment on the molten steel components, and meanwhile, a certain amount of aluminum balls are added to carry out aluminum precipitation deoxidization after the furnace. The adding amount of the aluminum pellets is a control link, and the adding amount of the aluminum pellets is controlled to be 1.5-2.3 kg/ton of steel. If the addition amount is small, the oxidation of the silicon component in the coarse adjustment of the component cannot be sufficiently restrained; excessive addition amount can cause Al in steel 2 O 3 The number of inclusions increases.
And secondly, preparing fluorine-free high-alkalinity reducing slag in a refining stage, and deoxidizing the whole aluminum in a smelting process. The components of the refining slag system are as follows: caO: 45-56%, mgO:8 to 12 percent of Al 2 O 3 ：22～35%，SiO 2 : 2-8%, and slag system binary alkalinity R (CaO/SiO) 2 ) And is more than or equal to 8. Two points in the control link are required to be controlled with emphasis: (1) al in slag system 2 O 3 The content of Al in the slag system is controlled to be less than or equal to 35 percent, preferably 22 to 30 percent 2 O 3 The excessive content can lead to the increase of the number of D-type or Ds-type inclusions in the steel; al in slag system 2 O 3 If the content is too low, the viscosity of the slag is high, which is unfavorable for the slag to adsorb the floating inclusion in the steel. (2) Slag system basicity R (CaO/SiO) 2 ) More than or equal to 8, and the alkalinity R is preferably 8-15, so as to be favorable for fully absorbing a small amount of SiO produced in steel by CaO 2 。
Thirdly, the alloying sequence of the silicon element and the content ratio of aluminum to silicon are controlled. In the LF ladle refining stage, after the molten steel is fully deoxidized by aluminum, when the free oxygen content in the molten steel is less than 4 multiplied by 10 -6 Then go throughAlloying silicon element. At this time, the molten steel has a low free oxygen content and a certain aluminum content, and oxidation of silicon during component adjustment can be suppressed, thereby avoiding silicate production. Control [%Al in molten steel at this stage] / [%Si]The content is kept at 15-20%.
Fourthly, the molten steel is subjected to VD vacuum treatment, argon soft stirring is required for more than 20 minutes, and inclusions in the molten steel are promoted to float upwards and are adsorbed by slag. After smelting, the [%Al ]/[%Si ] in the molten steel is kept at 5% -15%.
Due to the adoption of aluminum deoxidation, in order to avoid Al in the steel 2 O 3 The inclusions are aggregated to form large-particle inclusions, and the inclusions must be treated with a calcium wire to form Al in the steel 2 O 3 The dispersion and denaturation treatment are carried out to convert the calcium aluminate into small-sized and spherical calcium aluminate inclusions with low melting point.
The invention has the beneficial effects that:
(1) The invention mainly adopts an eccentric bottom electric furnace for smelting, can prevent oxidizing slag in molten steel in the electric furnace from flowing into a ladle during tapping, adds a strong deoxidizer aluminum pill along with the steel flow for deoxidizing during tapping, and adds a certain amount of lime, dolomite and synthetic slag into the ladle for secondary slagging.
(2) During ladle refining, a fluorine-free high-alkalinity refining slag system is adopted, the aluminum content in steel is controlled to be about 0.060%, the dissolved oxygen in steel is about 0.0004%, and at the moment, silicon component adjustment is carried out; has good adsorption effect on SiO2 deoxidized products in steel.
(3) The invention adopts technical measures such as tapping operation, refining slag system control, optimized alloying sequence, al-Si content control and the like, controls the generation of silicate with larger harm in the axle steel, improves the steel purity of the axle steel, and tests that the silicate inclusion (C type) in the axle steel is below 0.5 level, and mainly takes D type or Ds type inclusion with smaller harm as a main part.
Drawings
FIG. 1 is a schematic diagram of class C silicate inclusions found in the original axle steel test in example 1.
FIG. 2 is a schematic diagram of Ds inclusion present in the treated axle steel of example 1.
FIG. 3 is a schematic view showing the class D inclusions in the treated axle steel of example 1.
Detailed Description
The present invention is further illustrated by, but not limited to, the following examples.
Example 1:
taking an example of production of subway axle steel EA1N by an eccentric bottom electric furnace, the main components are as follows in Table 1:
TABLE 1 chemical composition Range (wt%) of subway axle Steel EA1N
The specific implementation steps are as follows:
(1) EBT-EAF (eccentric bottom electric furnace) charge: 13.5 tons of scrap steel and 76 tons of molten iron.
(2) Oxygen is blown on the side wall of the electric furnace in the smelting process, 3800kg of lime is added into the electric furnace in two batches for electric furnace smelting, so as to remove P, S, si and other elements in the steel.
(3) Tapping in an electric furnace, and measuring the temperature of molten steel: 1650 ℃, chemical composition: c=0.26%, si=0.036%, mn=0.109%, p=0.006%, s=0.026%, ni=0.007%, cr=0.057%, cu=0.007%, mo=0.005%, and molten steel content 85 tons.
(4) 400kg of lime, 300kg of dolomite, 400kg of synthetic slag, 150kg of aluminum pellets and 800kg of silicomanganese are added into the steel along with the steel flow, and the alloying and deoxidization of the components in the steel ladle are primarily completed. 156kg of aluminum pellets in molten steel are added, and the ratio of the amount of the added aluminum pellets to the molten steel is 1.84kg/t steel.
(5) The steel and slag are left during tapping, and the oxygen-enriched oxidizing slag in the electric furnace is controlled to flow into the steel ladle by utilizing the eccentric bottom characteristic of the electric furnace.
(6) The temperature measurement at the LF station is 1550 ℃, 150kg of calcium carbide is added, and the power is transmitted to heat for 10 minutes. The temperature was raised to 1570 ℃ and first component and slag system adjustments were made by adding 200kg lime, 116kg high manganese alloy, 50kg aluminum pellets, 52kg ferrovanadium.
(7) And then 10 kinds of power are transmitted, the temperature is raised, slags are melted, 200kg of lime is added, and the secondary slag system and component adjustment are carried out. When the oxygen content in the molten steel is detected to be less than 4ppm, alloying silicon components, adding 40kg of ferrosilicon and 50kg of high manganese alloy, and adding 10kg of aluminum pellets. Argon is blown at the bottom of the whole process, and the flow is 1100NL/min.
(8) The refining process does not add fluorite (CaF) 2 ) The refining slag is prepared by adjusting the components of CaO:50%, mgO:9%, al 2 O 3 ：27%，SiO 2 :5.5%, other: 8.5% of slag system alkalinity R (CaO/SiO) 2 ) =9.1, forming a fluorine-free high alkalinity low silicon slag system.
(9) After alloying is completed, carrying out third power transmission and heating to LF outlet temperature of 1660 ℃, wherein the components during outlet are as follows: c=0.33%, si=0.27%, mn=0.93%, p=0.008%, s=0.001%, cr=0.05%, ni=0.02%, mo=0.006%, al=0.055%, v=0.03%. The Al/Si in the molten steel is kept to be more than or equal to 15 percent when the ladle refining station is used.
(10) And (3) feeding the material into a VD station, and measuring the temperature to 1652 ℃. Vacuum pumping is carried out by moving the VD sealing cover, the holding time is 25 minutes under the high vacuum degree (less than or equal to 67 pa), and argon is blown out from the bottom in the whole process, and the flow is 1100NL/min.
(11) After the vacuum treatment, the temperature of molten steel is 1598 ℃, and Si-Ca wires are fed for 150 meters.
(12) And adding a heat-insulating covering agent. And (3) soft stirring is carried out by bottom blowing Ar gas, the flow is 60NL/min, and the time is more than 15 minutes.
(13) And (3) taking the VD out of the station, and measuring the temperature by 1572 ℃. After the VD vacuum treatment is finished, the chemical components of molten steel are as follows: c=0.34%, si=0.28%, mn=0.90%, p=0.007%, s=0.001%, cr=0.04%, ni=0.02%, mo=0.006%, al=0.030%, v=0.03%. Al/si=10.7% in the molten steel.
(14) And (5) operating the ladle to the cast steel platform. In the casting platform, the continuous casting middle ladle is pre-burned for 4 hours. After the arm fork is cast on the ladle, the baked tundish is moved to a continuous casting position, the submerged nozzle is centered, argon blowing operation is carried out on the tundish, and air in the ladle is removed.
(15) The ladle rotates to the upper part of the tundish, a sealed long nozzle is assembled, a sliding nozzle is opened, and molten steel starts to flow into the tundish from the ladle.
(16) The specification of the crystallizer is phi 690mm, and the specific water quantity of the secondary cooling is 0.11L/kg. Argon is introduced all the way from the ladle to the ladle and the ladle is covered with asbestos at Fang Kongxi. The weight of molten steel in the tundish is 37.8 tons, the stopper rod is regulated to start casting, and at the moment, the temperature of the tundish is measured to 1520 ℃, the superheat degree is 18 ℃, and the continuous casting pulling speed is 0.22m/min.
(17) The continuous casting adopts crystallizer electromagnetic stirring (M-EMS), secondary cooling electromagnetic stirring (S-EMS) and terminal electromagnetic stirring (F-EMS) to produce the continuous casting blank with the diameter of 690 mm.
(18) The continuous casting blank was rolled into a 250mm square shaft blank, and an inclusion analysis sample was taken at 1/2 side length of the shaft blank, the analysis surface was equal to the rolling direction, and the inclusion test results were as follows.
Table 2 inspection of axle blanks for inclusions
After implementation, the strip-shaped C-type brittle silicate inclusions in the axle steel are effectively controlled, and the inclusions in the steel are mainly composed of small-size spherical D-type inclusions and Ds-type inclusions.
As shown in FIGS. 1-3, FIG. 1 is a class C silicate inclusion, grade 2, found in axle steel testing prior to implementation. Fig. 2 and 3 show the types of main inclusions existing in the steel for the axle after the implementation, mainly including D-type inclusions and Ds-type inclusions. It can be seen that by adopting the method, the inclusion of C-type brittle silicate in the axle steel is effectively controlled.
Example 2:
taking smelting LZ50 axle steel as an example
TABLE 3 axle Steel LZ50 chemical composition Range (wt%)
(1) EBT-EAF (eccentric bottom electric furnace) charge: 15 tons of scrap steel and 74 tons of molten iron.
(2) And (3) blowing oxygen on the side wall of the electric furnace in the smelting process, and adding 4000kg of lime into the electric furnace in two batches to perform electric furnace smelting so as to remove P, S, si and other elements in the steel.
(3) Tapping in an electric furnace, and measuring the temperature of molten steel: 1660 ℃, carbon content: 0.28 percent, the molten steel amount is 84 tons,
(4) 403kg of lime, 350kg of dolomite, 398kg of synthetic slag, 180kg of aluminum pellets and 650kg of silicomanganese are added into the steel along with the steel flow, and the alloying and deoxidization of the components in the steel ladle are primarily completed. 180kg of aluminum pellets in molten steel are added, and the ratio of the amount of the added aluminum pellets to the molten steel is 2.14kg/t steel.
(5) The steel and slag are left during tapping, and the oxygen-enriched oxidizing slag in the electric furnace is controlled to flow into the steel ladle by utilizing the eccentric bottom characteristic of the electric furnace.
(6) The temperature measurement at the LF station is 1555 ℃, 140kg of calcium carbide is added, and the power is transmitted and the temperature is raised for 10 minutes. The temperature was raised to 1567 c and first component and slag system adjustments were made by adding 170kg lime, 120kg high manganese alloy, 45kg aluminum pellets, 50kg ferrovanadium.
(7) And then 10 seeds are fed, the temperature is raised, slags are melted, 190kg lime is added, and the secondary slag system and component adjustment are carried out. The content of dissolved oxygen in the molten steel was detected to be 3.4ppm on line, alloying of the silicon component was performed, 50kg of ferrosilicon and 40kg of a high manganese alloy were added, and 15kg of aluminum pellets were added concomitantly. Argon is blown at the bottom of the whole process, and the flow is 1100NL/min.
(8) The refining process does not add fluorite (CaF) 2 ) The refining slag is prepared by adjusting the components of CaO:54%, mgO:8%, al 2 O 3 ：27.5%，SiO 2 :6.5%, other: 4%, slag system basicity R (CaO/SiO) 2 ) =8.31, forming a fluorine-free high alkalinity low silicon slag system.
(9) After alloying is completed, carrying out third power transmission and heating to LF outlet temperature of 1660 ℃, wherein the components during outlet are as follows: c=0.49%, si=0.25%, mn=0.78%, p=0.007%, s=0.001%, cr=0.07%, ni=0.01%, mo=0.005%, al=0.047%, v=0.03%. Al/si=18.8% in the molten steel is maintained at the ladle refining station.
(10) And (3) feeding the material into a VD station, and measuring the temperature to 1650 ℃. Vacuum pumping is carried out by moving the VD sealing cover, the holding time is 25 minutes under the high vacuum degree (less than or equal to 67 pa), and argon is blown out from the bottom in the whole process, and the flow is 1100NL/min.
(11) After the vacuum treatment, the temperature of molten steel is 1590 ℃, and Si-Ca wires are fed for 160 meters.
(12) And adding a heat-insulating covering agent. And (3) soft stirring is carried out by bottom blowing Ar gas, the flow is 60NL/min, and the time is more than 15 minutes.
(13) And (3) taking the sample out of the station by VD, and measuring the temperature by 1559 ℃. After the VD vacuum treatment is finished, the chemical components of molten steel are as follows: c=0.51%, si=0.24%, mn=0.75%, p=0.007%, s=0.002%, cr=0.05%, ni=0.02%, mo=0.005%, al=0.025%, v=0.03%. Al/si=10.42% in the molten steel.
(14) And (5) operating the ladle to the cast steel platform. In the casting platform, the continuous casting middle ladle is pre-burned for 4 hours. After the arm fork is cast on the ladle, the baked tundish is moved to a continuous casting position, the submerged nozzle is centered, argon blowing operation is carried out on the tundish, and air in the ladle is removed.
(15) The ladle rotates to the upper part of the tundish, and a three-section electromagnetic stirring large round billet continuous casting machine process is adopted to produce phi 690mm continuous casting billets.
(18) The continuous casting blank was rolled into a 250mm square shaft blank, and an inclusion analysis sample was taken at 1/2 side length of the shaft blank, the analysis surface was equal to the rolling direction, and the inclusion test results were as follows.
Table 4 inspection of axle blank inclusions
After implementation, the strip-shaped C-type brittle silicate inclusions in the axle steel are effectively controlled, and the inclusions in the steel are mainly composed of small-size spherical D-type inclusions and Ds-type inclusions.
Claims (3)
1. A smelting method for controlling silicate inclusions in axle steel is characterized by comprising the following steps:
(1) Adopting an eccentric bottom electric furnace for smelting, tapping to control the flow of oxidizing slag into a ladle, adding aluminum balls along with the flow of steel, wherein the adding amount of the aluminum balls is 1.8-2.5 kg/ton of steel;
(2) When the content of dissolved oxygen in molten steel is less than 4X 10 -6 Then alloying silicon element:
by "aluminiumControl scheme of silicon inhibition, LF ladle refining stage, after fully aluminium deoxidizing molten steel, when free oxygen content in molten steel is less than 4×10 -6 Then alloying silicon element;
(3) The fluorine-free high-alkalinity low-silicon component refining slag system comprises the following components in percentage by mass: caO: 45-56%, mgO:8 to 12 percent of Al 2 O 3 ：22～35%，SiO 2 : 2-8%, wherein the binary basicity R of the slag system is more than or equal to 8; the proportion of the alkalinity R is CaO and SiO 2 The mass ratio of the two;
(4) After LF refining is finished, the mass ratio of [%Al ]/[%Si ] in molten steel is kept between 15 and 20 percent; after the vacuum treatment is finished, feeding Si-Ca wires for 120-150 m; the mass ratio of [%Al ]/[%Si ] in the steel after the VD vacuum treatment is finished is kept between 5 and 15 percent.
2. The method for controlling the smelting of silicate inclusions in axle steel according to claim 1, wherein: in the step (3), al is contained in the fluorine-free high-alkalinity low-silicon component refining slag system 2 O 3 : 22-30%, and the binary basicity R of the slag system is 8-15.
3. The method for controlling the smelting of silicate inclusions in axle steel according to claim 1 or 2, characterized by comprising the steps of:
(1) Charging by an eccentric bottom electric furnace;
(2) Oxygen is blown to the side wall of the electric furnace in the smelting process, lime is added into the electric furnace for smelting in two batches, so as to remove P, S, si element in steel;
(3) Tapping in an electric furnace, and measuring the temperature and chemical components of molten steel; the tapping amount of molten steel is 80-90 tons;
(4) Adding 300-400kg of lime, 200-300kg of dolomite, 300-400kg of synthetic slag and 150-200kg of aluminum balls into steel along with steel flow, and primarily completing alloying and deoxidizing of components in a steel ladle; adding steel with the ratio of the aluminum pill amount to the molten steel of 1.8-2.5 kg/t;
(5) When tapping, steel and slag are reserved, and oxygen-enriched oxidizing slag in the electric furnace is controlled to flow into a ladle by utilizing the eccentric bottom characteristic of the electric furnace;
(6) Feeding the materials into an LF station for temperature measurement, adding 120-150kg of calcium carbide, and feeding electricity for temperature rise for 10+/-2 minutes; heating to 1570+ -10deg.C, adding 180-200kg lime, 30-60kg aluminum pellet, 40-60kg ferrovanadium for regulating the first component and slag system;
(7) Delivering power for 10 minutes, heating, melting slag, adding 180-200kg lime, and adjusting slag system and components for the second time; detecting the content of dissolved oxygen in molten steel on line, and alloying silicon components when the content of oxygen in the molten steel is detected to be less than 4ppm, adding 30-50kg of ferrosilicon and 40-60kg of high manganese alloy, and adding 10-15kg of aluminum balls; argon is blown at the bottom of the whole process, and the flow is 1000-1100NL/min;
(8) The refining process does not add fluorite CaF 2 The refining slag is prepared by adjusting the components of CaO: 45-56%, mgO:8 to 12 percent of Al 2 O 3 ：22～35%，SiO 2 : 2-8%, wherein the slag system alkalinity R is more than or equal to 8, and a fluorine-free high-alkalinity low-silicon slag system is formed;
(9) After alloying is completed, carrying out third power transmission heating to the LF outlet temperature of 1650-1670 ℃, wherein the Si and Al components in the steel during outlet are as follows: si=0.20-0.45%, al=0.050-0.065%; the Al/Si mass ratio in the molten steel is kept to be 15-20% during the ladle refining station;
(10) Feeding into a VD station, and measuring the temperature to 1650-1660 ℃; vacuum pumping is carried out by moving the VD sealing cover, the holding time is 20-25 minutes under the high vacuum degree, argon is blown in the whole process, and the flow is 1000-1100NL/min;
(11) After the vacuum treatment is finished, feeding Si-Ca wires for 120-150 m;
(12) Adding a heat-insulating covering agent; bottom blowing Ar gas for soft stirring at the flow rate of 50-60NL/min for 15-20 min;
(13) And (3) when the VD comes out and the VD vacuum treatment is finished, the chemical components of Si and Al in the molten steel are as follows: si=0.25-0.40%, al=0.020-0.035%, the mass ratio of Al/Si in molten steel is 5% -15%;
(14) Operating the steel ladle to a cast steel platform; pre-burning a middle ladle in continuous casting for 4+/-1 hours on a casting platform; after the arm fork is cast on the ladle, moving the baked tundish to a continuous casting position, centering the submerged nozzle, blowing argon into the tundish, and removing air in the ladle;
(15) Rotating the ladle to the upper part of the tundish, and carrying out continuous casting production, wherein the continuous casting adopts crystallizer electromagnetic stirring, secondary cooling electromagnetic stirring and terminal electromagnetic stirring to produce a continuous casting blank;
(16) Rolling the continuous casting blank into a shaft blank with the square specification of 250mm, and taking an inclusion analysis sample at 1/2 side length of the shaft blank.
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