CN117512262A - LF refining rapid slag method - Google Patents
LF refining rapid slag method Download PDFInfo
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- CN117512262A CN117512262A CN202311548260.8A CN202311548260A CN117512262A CN 117512262 A CN117512262 A CN 117512262A CN 202311548260 A CN202311548260 A CN 202311548260A CN 117512262 A CN117512262 A CN 117512262A
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- 239000002893 slag Substances 0.000 title claims abstract description 139
- 238000007670 refining Methods 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims abstract description 37
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 120
- 239000010959 steel Substances 0.000 claims abstract description 120
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 34
- 239000000292 calcium oxide Substances 0.000 claims abstract description 33
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 33
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims abstract description 28
- 238000002844 melting Methods 0.000 claims abstract description 28
- 230000008018 melting Effects 0.000 claims abstract description 28
- 238000010079 rubber tapping Methods 0.000 claims abstract description 28
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 17
- 230000008569 process Effects 0.000 claims abstract description 16
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims abstract description 15
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910001634 calcium fluoride Inorganic materials 0.000 claims abstract description 12
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910001947 lithium oxide Inorganic materials 0.000 claims abstract description 12
- 239000000395 magnesium oxide Substances 0.000 claims abstract description 11
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims abstract description 8
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims abstract description 7
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 22
- 230000004907 flux Effects 0.000 claims description 19
- 229910052782 aluminium Inorganic materials 0.000 claims description 18
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 18
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 17
- 229910052760 oxygen Inorganic materials 0.000 claims description 17
- 239000001301 oxygen Substances 0.000 claims description 17
- 238000003756 stirring Methods 0.000 claims description 16
- 239000002245 particle Substances 0.000 claims description 14
- 238000002347 injection Methods 0.000 claims description 12
- 239000007924 injection Substances 0.000 claims description 12
- 229910052786 argon Inorganic materials 0.000 claims description 11
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 9
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 9
- 239000004571 lime Substances 0.000 claims description 9
- 238000007664 blowing Methods 0.000 claims description 5
- 230000001737 promoting effect Effects 0.000 claims description 3
- 239000004411 aluminium Substances 0.000 claims description 2
- 239000008187 granular material Substances 0.000 claims description 2
- 238000009847 ladle furnace Methods 0.000 abstract description 29
- 238000003723 Smelting Methods 0.000 abstract description 9
- 239000000463 material Substances 0.000 abstract description 6
- 238000009628 steelmaking Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 19
- 239000011574 phosphorus Substances 0.000 description 19
- 229910052698 phosphorus Inorganic materials 0.000 description 19
- 238000006477 desulfuration reaction Methods 0.000 description 13
- 230000023556 desulfurization Effects 0.000 description 13
- 230000000694 effects Effects 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 8
- 238000001179 sorption measurement Methods 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000003749 cleanliness Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 238000005189 flocculation Methods 0.000 description 5
- 230000016615 flocculation Effects 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000010436 fluorite Substances 0.000 description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000011449 brick Substances 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010891 electric arc Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 241001417490 Sillaginidae Species 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000378 calcium silicate Substances 0.000 description 1
- 229910052918 calcium silicate Inorganic materials 0.000 description 1
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 230000003313 weakening effect Effects 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
- C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
-
- 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
- C21C5/28—Manufacture of steel in the converter
-
- 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
- C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
-
- 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
- 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
- C21C7/064—Dephosphorising; Desulfurising
- C21C7/0645—Agents used for dephosphorising or desulfurising
-
- 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
- C21C2300/00—Process aspects
- C21C2300/02—Foam creation
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Analytical Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention belongs to the technical field of converter steelmaking, and provides a quick slag refining method in LF (ladle furnace), which comprises the following steps of: 60-70% of calcium oxide, 4-7% of lithium oxide, 3-6% of silicon dioxide, 5-10% of calcium fluoride, 4-8% of magnesium oxide and 10-15% of aluminum oxide, and by adding the preflux in the tapping process, the slag alkalinity is improved, the slag melting point is effectively reduced, the rapid melting of slag is promoted, the slag melting time of LF refining entering a station is shortened, the occurrence of rephosphorization is inhibited, the LF refining smelting time is reduced, and good guarantee is provided for the quality of rolled materials. The application of the invention can provide a reliable high-quality steel smelting method for improving the production efficiency for operators, can effectively reduce the production cost and ensures the purity of molten steel.
Description
Technical Field
The invention belongs to the technical field of converter steelmaking, and particularly relates to a quick slag refining method for LF (ladle furnace).
Background
With the continuous development of iron and steel enterprises, the requirements of the market on the cleanliness of molten steel are higher and higher, and especially, the harmful elements such as phosphorus, inclusions and the like in the steel are as few as possible. In the steelmaking process, slag entering a ladle from a converter contains a large amount of harmful element phosphorus, and if the slag is not treated, the phosphorus content of molten steel is high, so that the slag is forced to be changed or judged to be wasted. If the phosphorus is to be removed effectively, a slag removing mode is adopted, but the time and the labor are wasted, the slag is required to be formed again, and the cost is increased; or the alkalinity and the oxidability of the slag are improved, but the viscosity and the melting point of the slag are increased, so that the deoxidization amount and the alloy amount are increased, the oxygen content of molten steel is increased due to the high oxidability of the slag, and the cleanliness of the molten steel is reduced. Therefore, for high quality steel, the aim is to avoid the increase of phosphorus in the molten steel after tapping in a converter, reduce the cost as much as possible and avoid the decrease of the cleanliness of the molten steel.
Chinese patent document CN101058838A (CN 200710099032.1) discloses a method for pre-refining molten steel in the tapping process, in which aluminum and refining flux are added to molten steel in a ladle, and the molten steel is desulfurized, deoxidized, transformed and removed by the strong stirring effect of "flushing" the molten steel into the ladle in the tapping process, so that the method has good desulfurization, deoxidization and inclusion control effects. However, the preflux used in the above patent contains 85-95% of calcium oxide, 5-15% of calcium fluoride, and too high of calcium oxide, the slag melting time required for refining is too long, which is unfavorable for continuous control of inclusions, and the prefinishing process cannot ensure effective control of phosphorus content.
Disclosure of Invention
Aiming at the problems, the invention provides the LF refining rapid slag method, which can ensure the fluidity and alkalinity of slag and reduce the rephosphorization of molten steel by adding the preflux in the tapping process on the basis of the existing conditions, thereby ensuring the cleanliness of molten steel and further providing raw material guarantee for the quality of rolled materials.
The technical problems to be solved by the invention are realized by adopting the following technical scheme: an LF refining rapid slag method comprises the following steps:
s1, adding a preflux along with molten steel injection in the tapping process of a converter;
the components of the pre-flux are as follows according to mass percent: 60-70% of calcium oxide, 4-7% of lithium oxide, 3-6% of silicon dioxide, 5-10% of calcium fluoride, 4-8% of magnesium oxide and 10-15% of aluminum oxide;
when the molten steel flows out to two thirds of the total amount, 500-800kg of pre-flux is added along with molten steel injection, and the adding speed is controlled to be 30-50kg/s;
s2, closing a steel tapping hole of the converter when the converter slag tapping is detected;
s3, conveying the ladle to LF refining, measuring the oxygen content of molten steel, opening a bottom blowing argon valve immediately, opening argon to 800-1200L/min, stirring for 30-60S, ensuring that the molten steel is turned to a height of 20-50cm under the stirring of gas, adding 10-50Kg of aluminum particles into slag in the stirring process, adding 50-150Kg of lime after stirring, and electrifying to adjust the slag and the temperature.
The technical scheme of the invention is as follows: in the step S1, 30 seconds before tapping is finished, no pre-flux is added, so that the accuracy of slag detection equipment is not affected.
The technical scheme of the invention is as follows: in the step S3, if the oxygen content of the molten steel is more than 50ppm, adding 30-50kg of aluminum particles;
if the oxygen content of molten steel is less than 20ppm and less than 50ppm, adding 10-30kg of aluminum particles;
if the oxygen content is < 20ppm, 10kg of aluminium granulate are added.
The technical scheme of the invention is as follows: in step S1, the preflux is pressed intoIs used after being spherical. By pressing the preflux into +.>Is convenient to add and avoids dust pollution.
The technical scheme of the invention is as follows: in the step S1, the pre-flux adding point is aimed at the pouring point position of molten steel poured into a ladle at any time, so that the pre-flux is ensured to be melted rapidly under the impact of molten steel pouring flow in time.
The technical scheme of the invention is as follows: if the preflux is not well melted, namely, lump formation occurs around the impact area of molten steel, when the lump formation diameter is less than 30cm, the adding speed of the preflux is adjusted to 15-25kg/s, a ladle is adjusted, the impact lump formation position of molten steel injection is ensured, and the rapid melting is promoted to be complete;
stopping adding the preflux when the diameter of the lump is smaller than 30cm and smaller than 50cm, adjusting the ladle to enable molten steel to flow to impact the lump position, and ensuring that the preflux is added according to the initial adding speed after the lump is completely melted;
when 50cm is smaller than the diameter of the lump, stopping adding the preflux, adjusting the ladle, and ensuring that molten steel flows to impact the position of the lump until tapping is finished.
The invention is characterized in that: calcium oxide is an indispensable material for slagging, dephosphorization and desulfurization in metallurgy, and is one of main components in various slag systems; typically, the basicity in slag is achieved by adjustment of calcium oxide and silica, i.e. basicity = calcium oxide/silica, typically in the suitable range of 2.5-8 basicities, typically higher 5-8 basicities for aluminum-containing steels, and lower 2.5-3 basicities for non-aluminum-containing steels. Examples: if the calcium oxide in the slag is 55% and the silica is 18%, the alkalinity is 3.05. It can be seen that the higher the calcium oxide, the lower the silica, the higher the alkalinity. And vice versa.
However, the higher the slag basicity is, the better, but the higher the slag basicity is, the more disadvantageous. Because the higher the alkalinity of the slag is, the more viscous the slag is, the mobility of the slag is reduced, and the desulfurization, dephosphorization and inclusion adsorption are not facilitated; too low slag alkali makes the slag too dilute, while good in fluidity, also unfavorable for desulfurization, dephosphorization and inclusion adsorption, and meanwhile, unfavorable for LF refining to stabilize electric arc. The slag basicity must therefore not be too high or too low and must be controlled in a suitable range. Also, if the slag basicity is controlled, the contents of calcium oxide and silica must be adjusted separately.
Furthermore, the earlier the slag is, the more advantageous. The good slag can promote dephosphorization, desulfurization, inclusion adsorption and stable electric arc to facilitate rapid temperature rise, and the slag can promote better improvement of molten steel quality, improve molten steel purity and reach required molten steel temperature more quickly, thereby shortening refining time and providing high-quality molten steel. Therefore, it is a goal of the skilled person to ensure that the LF refining smelts molten steel with high crystallinity and few inclusions in a short time.
In general, the amount of silica in the slag (mainly the converter carry-over) is relatively stable without other sources. The alkalinity is mainly adjusted by adjusting the amount of calcium oxide, and when the total amount of calcium oxide is low, the calcium oxide needs to be added. Therefore, the calcium oxide content in the preflux is set to 60-70%, and the total amount of calcium oxide is sufficient for most heats calculated in combination with the addition amount. If not enough, the proper alkalinity can be achieved only by a small increase, and the method provides convenience for LF refining operation.
Lithium oxide has good propertiesThe dephosphorization and desulfurization effects of the slag are achieved, and meanwhile, the melting point of the formed slag is low, so that slag melting is facilitated; adding 4-7% of lithium oxide, which is the same family as calcium oxide, with the alkalinity being higher than that of calcium oxide, and the metal cation pair O 2- Is less attractive and causes O in slag 2- Activity is improved, P in slag is promoted 2 O 5 With O 2- Conversion of binding to PO 3- 4 And exist stably. In addition, lithium oxide, calcium oxide, silicon dioxide and calcium silicate can generate low-melting-point compounds which are far lower than 2CaO.SiO 2 Thereby causing a reduction in the melting point of the slag, increasing the basicity of the slag while avoiding an increase in the melting point due to excess CaO.
In calculating alkalinity, lithium oxide needs to be considered for ingress, i.e.: alkalinity= (calcium oxide + lithium oxide)/silica, so it helps to increase alkalinity. According to dephosphorization reaction, dephosphorization needs higher slag alkalinity and oxygen potential, and after lithium oxide is added, the slag alkalinity and oxygen potential are increased, so that dephosphorization dynamic conditions are improved, and dephosphorization is promoted.
The addition of lithium oxide increases the basicity of the slag and is also beneficial to promoting the desulfurization of calcium oxide. Sulfur is present in the form of FeS and can be removed when there is sufficient CaO in the slag, as follows: feS+CaO- & gtCaS+FeO, the generated CaS is not dissolved in the molten steel, and slag is formed to float on the surface of the molten steel.
Silica has a certain fluxing effect; silica is an important component of alkalinity, and typically, silica in LF refining slag flows into the ladle as molten steel flows into the top slag during tapping after the converter is finished. The same reason is that 3-6% is added here, so that the fluxing effect of the slag is increased, and the slag is melted more quickly. However, the silicon dioxide cannot be excessive, which would greatly reduce the alkalinity of the slag, resulting in serious dilution of the slag.
The calcium fluoride can obviously reduce the viscosity of the slag and promote the improvement of the fluidity of the slag; calcium fluoride is a slag melting flux accepted by metallurgical enterprises, and is added by 5-10% to promote the melting of calcium oxide, but the calcium fluoride is not easy to be added too much due to the fact that the calcium fluoride is high in price and generates fluoride to pollute the environment. And too much calcium fluoride can cause too thin slag.
The magnesia has certain desulfurization capability and also has the function of protecting furnace lining bricks; the magnesium oxide can assist in adjusting slag to form CaO-MgO-Al 2 O 3 The ternary slag system further promotes the desulfurization effect of slag; meanwhile, the magnesia has the characteristic of high melting point, and after the magnesia is added, the corrosion of furnace lining bricks by slag can be reduced (in order to contain molten steel, the converter and the ladle are all required to be paved with refractory materials such as furnace lining bricks and the like in a steel shell so as to isolate the corrosion of high-temperature molten steel and slag). However, magnesium oxide cannot be excessive, slag is easy to be sticky and not easy to melt, and 4-8% of magnesium oxide is added.
The aluminum oxide can promote the reduction of the viscosity of slag, promote the reaction of the slag and is beneficial to desulfurization. Aluminum oxide is an important component of slag, typically CaO, siO 2 、Al 2 O 3 Can form a ternary slag system CaO, mgO, al 2 O 3 The slag can form a ternary slag system and the like, and the formation of the slag system has the characteristics of low oxygen potential, low melting point, low viscosity, easy absorption of impurities generated by deoxidization and the like, can promote the reaction of steel slag, is favorable for desulfurization, and simultaneously provides favorable conditions for other various chemical reactions. The proportion of 10-15% also considers the characteristics of the ternary slag system and the proportion of each element, if too little is unfavorable for forming the optimal slag with the characteristics, and if too much is too thin, the slag needs to be blended, and is unfavorable for adsorbing the inclusions.
After the preflux is added, the molten steel is gradually melted along with stirring, and the density is usually 2.4-3.0g/cm due to small density 3 Far less than 7.8g/cm of molten steel density 3 The slag floats on the surface of molten steel to form complex compounds together with slag entering a converter in the later stage of tapping, and the complex compounds gradually undergo mutual fusion change in the process of transporting to LF refining, so that the slag with LF refining characteristics is finally formed (good refined slag has low melting point, proper viscosity, good fluidity, good inclusion adsorption, good desulfurization capability, good foaming, good energizing heat-insulation effect and the like).
Compared with the prior art, the invention has the beneficial effects that:
the invention adds pre-flux along with molten steel injection in the converter tapping process, and the pre-flux comprises the following components in percentage by mass: 60-70% of calcium oxide, 4-7% of lithium oxide, 3-6% of silicon dioxide, 5-10% of calcium fluoride, 4-8% of magnesium oxide and 10-15% of aluminum oxide, and by adding the preflux in the tapping process, the slag alkalinity is improved, the slag melting point is effectively reduced, the rapid melting of slag is promoted, the slag melting time of LF refining entering a station is shortened, the occurrence of rephosphorization is inhibited, the LF refining smelting time is reduced, and good guarantee is provided for the quality of rolled materials.
The invention has simple operation, convenient execution and good use effect. The method can be applied to any steel mill producing similar steel grades (all aluminum-containing steel), and has the advantages of wide application range, high popularization value and the like.
Detailed Description
Embodiments of the present invention are described in further detail below with reference to examples. The following examples are illustrative of the invention but are not intended to limit the scope of the invention.
Example 1
Taking a 120-ton top-bottom combined blown converter of a mountain steel stock steelworks as an example, the following details of the embodiments of the present invention.
The invention provides an LF refining rapid slag method, which comprises the following steps:
s1, after the converter smelting is finished and detected, the molten steel components meet the tapping requirement, the converter is rotated, and molten steel flows out of the tapping hole to a ladle from the tapping hole. And adding a pre-flux along with molten steel injection in the tapping process of the converter, and adding the pre-flux into a bin behind the converter in advance for standby.
The components of the pre-flux are as follows according to mass percent: 65% of calcium oxide, 6% of lithium oxide, 4% of silicon dioxide, 8% of calcium fluoride, 5% of magnesium oxide and 12% of aluminum oxide, and is prepared by pressingIs used after being spherical.
When the molten steel flows out to two thirds of the total amount, 500-800kg of pre-flux is added along with the molten steel injection flow, the adding speed is controlled to be 30-50kg/s, and the adding point is aimed at the position of the pouring point of the molten steel injected into the ladle at any time, so that the pre-flux is ensured to melt rapidly under the impact of the molten steel injection flow in time.
If the preflux is not well melted (namely, lump formation occurs around the impact area of molten steel), when the diameter of the lump formation is less than 30cm, adjusting the adding speed to 15-25kg/s, adjusting a ladle, ensuring the impact position of molten steel injection on the lump formation, and promoting the rapid melting of the molten steel;
stopping adding the preflux when the diameter of the lump is smaller than 30cm and smaller than 50cm, adjusting the ladle to enable molten steel to flow to impact the lump position, and ensuring that the preflux is added according to the initial adding speed after the lump is completely melted;
when 50cm is smaller than the diameter of the lump, stopping adding the preflux, adjusting the ladle, and ensuring that molten steel flows to impact the position of the lump until tapping is finished.
In any case, 30 seconds before tapping is finished, no pre-flux is added, so that the accuracy of slag detection equipment is not affected.
S2, when slag is detected, the control valve is closed in time, and the slag is not discharged from the steel outlet.
S3, the steel ladle is filled with molten steel, and is conveyed to an appointed LF for refining under the lifting of the crown block, so that deep treatment is carried out. After the ladle containing molten steel enters LF refining, measuring the oxygen content of the molten steel, opening a bottom blowing argon valve, opening argon to 800-1200L/min (the molten steel is stirred by gas to ensure the rising height of the molten steel to be 20-50 cm), stirring for 30-60S, adding 10-50kg of aluminum particles (99% AL) into slag in the stirring process, (if the oxygen content of the molten steel is more than 50ppm, adding 30-50kg of aluminum particles, if the oxygen content of the molten steel is less than 20ppm and less than 50ppm, adding 10-30kg of aluminum particles, and if the oxygen content is less than 20ppm, adding 10kg of aluminum particles) and weakening the oxidization of slag by adding the aluminum particles. After stirring, adding lime of 50-150Kg, and electrifying to adjust the temperature of slag and molten steel.
Comparative example 1
The converter adopts a traditional tapping mode to produce the same steel grade as in comparative example 1, and takes a 120 ton converter of a mountain steel group steel mill as an example, the specific operation steps are as follows:
step 1) adding premelting slag into a bin behind a furnace in advance for standby.
The premelting slag is one of slag-forming materials widely used by metallurgical enterprises and is generally added into a ladle to improve the melting point of slag and the fluidity of slag, and the premelting slag comprises the following active ingredients in percentage by mass: al (Al) 2 O 3 ：20-30％，SiO 2 :20-30%, mgO:5-10%, caO:7-10% of calcium fluoride and 20-30%.
And 2) after the converter smelting is finished and detected, the molten steel components meet the tapping requirement.
And 3) rotating the converter, and discharging molten steel from the tapping hole to the ladle.
And 4) adding 500-800kg of premelted slag along with molten steel injection when the molten steel flows out to three fourths of the total amount, wherein the adding point is aimed at the pouring point position of the molten steel injected into the ladle at any time.
And 5) when the slag is detected, closing the control valve in time, wherein the slag is not discharged from the steel outlet.
And 6) the steel ladle is filled with molten steel, and is conveyed to a designated LF for refining under the lifting of a crown block for deep treatment.
And 7) after the ladle filled with molten steel enters LF refining, measuring the oxygen content of the molten steel, immediately opening a bottom blowing argon valve, opening argon to 1200-1500L/min (molten steel is stirred under gas to ensure that the rising height of the molten steel exceeds 50 cm), stirring for 1 min, adding 50Kg of aluminum particles (99% AL) into slag to reduce the oxidizing property of the slag in the stirring process, and adding 500-600Kg of lime and 0-100Kg of fluorite in 3 batches for assisting slag melting. In order to reduce the melting point of slag, improve the fluidity of slag, the CaO content in premelted slag is lower, although melting is very fast, the alkalinity is low, the slag is thin, the electrifying arc stabilization and the heating are not facilitated, and impurities cannot be effectively adsorbed, a large amount of lime is required to be additionally added to adjust the slag, fluorite is required to be added to promote the melting of lime, and after stirring is completed, electrifying is performed to adjust the slag and the temperature, so that LF refining time is increased.
Compared with the embodiment 1, the calcium oxide content in the comparative example 1 is only 7-10%, the combination of the addition amount is obviously insufficient, the calcium oxide gap is more, 500-600kg of calcium oxide is needed to be added in 2-3 batches, each time of adding calcium oxide needs to be electrified to remove slag, one batch can be added after the other batch is removed, the refining and slagging time is prolonged, the slagging time is delayed, the desulfurization, dephosphorization, inclusion adsorption and rapid heating are all unfavorable, more time is needed for treatment if high-quality molten steel is required to be smelted, the electricity consumption and refining time are increased, and adverse effects are brought to cost reduction and period matching.
Example 1 was compared with comparative example 1 and the corresponding results are shown in table 1:
TABLE 1
The lower the phosphorus content in molten steel is, the better, but the dephosphorization rate under the condition of a steelmaking converter is usually 85-95% (if the dephosphorization rate is to be improved again, the difficulty and the cost are increased greatly), namely when the initial phosphorus content of molten iron is 0.150%, the final phosphorus content of the converter is usually about 0.015%, after refining smelting, the back phosphorus content is about 0.016% (the greater back phosphorus content leads to the exceeding of the standard and the waste of the component phosphorus), and the phosphorus content of the finished product of many steel types is not higher than 0.015%. Therefore, molten steel smelted by the converter is reduced or prevented from returning phosphorus (phosphorus is a harmful element in the steel, and causes the problems of phosphorus brittle cracks and the like), and the higher the phosphorus is, the more serious the problems are, but after the converter is smelted, the phosphorus content of the molten steel gradually increases along with the refining smelting process, namely, the so-called 'returning phosphorus'. To reduce refined rephosphorization, the skilled man is also researching a number of methods, but good methods have drawbacks (increased costs, increased time, etc.). From the data in table 1, it can be seen that with the method of the present application, the amount of rephosphorization during the LF refining stage is significantly reduced compared to comparative example 1.
In addition, as mentioned above, refining is required to have a certain smelting time, and in a limited time, the earlier and better the refining and slagging time is, the longer and better the maintaining time is. Once the good slag is formed, the slag can be desulfurized, avoid rephosphorization, adsorb more impurities and Al 2 O 3 I.e. inclusions ofOne of the materials. During refining, argon is blown into the bottom of the ladle at any time, and under the stirring of the argon, the impurities collide and grow up to form large-particle impurities which circulate in molten steel, and if the adsorption effect of refined slag is poor, al is contained in the molten steel 2 O 3 Will circulate continuously in the molten steel until the good slag is formed and will not float up gradually to be captured by the slag. Therefore, al in molten steel 2 O 3 At a fixed total amount, al 2 O 3 The earlier the molten steel is removed, the higher the purity of the molten steel is, the flocculation phenomenon of the continuous casting nozzle can not occur. Conversely, al 2 O 3 The later is removed, al remaining in the molten steel 2 O 3 The more the purity of the molten steel is relatively low, the refining total time is limited, and when the ladle is required to be transported to continuous casting, the blowing of argon is stopped, so Al remained in the molten steel 2 O 3 No longer adsorbed by slag, and accumulated at the nozzle to form a flocculation flow during casting, specifically, during casting, al 2 O 3 The large-particle inclusions stay at the water gap of the tundish and gather and grow up to form larger-size inclusions, and the inclusions are not easy to melt at the casting temperature (1500 ℃) because the melting point of the inclusions is higher than 1600 ℃, so that a hard bell mouth shape is formed, the water gap with the original size diameter is blocked into the water gap with the smaller diameter, so that molten steel passing through the water gap is reduced, and the phenomenon of water gap flocculation is shown. The flocculation flow often occurs along with changes in smelting environment, such as excessive backward delay of refining slag formation time and too short time for adsorbing inclusions. Therefore, the slag forming time can be greatly advanced, the maintaining time is longer, the floating of the inclusion is promoted, the cleanliness of molten steel is greatly improved, and the flocculation problem is avoided as shown in the table 1.
After the preflux is added, the purpose of the invention is to form slag with LF refining slag characteristics close to or directly, and after the slag enters LF refining, the slag melting and slagging can be completed without adding lime or adding lime and fluorite in a small amount on the basis of rapid melting of the slag, thereby reducing the burden of LF refining and reducing slag forming time; the existing premelting slag is different, the purpose is to remove slag, lime and fluxing agent-fluorite are additionally added after the premelting slag enters LF refining, and the slag is further adjusted to meet the refining requirement, so that the removal of inclusions is not facilitated.
Claims (6)
1. An LF refining rapid slag method is characterized by comprising the following steps:
s1, adding a preflux along with molten steel injection in the tapping process of a converter;
the components of the pre-flux are as follows according to mass percent: 60-70% of calcium oxide, 4-7% of lithium oxide, 3-6% of silicon dioxide, 5-10% of calcium fluoride, 4-8% of magnesium oxide and 10-15% of aluminum oxide;
when the molten steel flows out to two thirds of the total amount, 500-800kg of pre-flux is added along with molten steel injection, and the adding speed is controlled to be 30-50kg/s;
s2, closing a steel tapping hole of the converter when the converter slag tapping is detected;
s3, conveying the steel ladle to LF refining, measuring the oxygen content of molten steel, opening a bottom blowing argon valve immediately, stirring for 30-60S until the argon is opened to 800-1200L/min, adding 10-50Kg of aluminum particles into the slag in the stirring process, adding 50-150Kg of lime after stirring, and electrifying to adjust the slag and the temperature.
2. The LF refining rapid slag method of claim 1, wherein: in step S1, 30 seconds before tapping is finished, no pre-flux is added.
3. The LF refining rapid slag method of claim 1, wherein: in the step S3, if the oxygen content of the molten steel is more than 50ppm, adding 30-50kg of aluminum particles;
if the oxygen content of molten steel is less than 20ppm and less than 50ppm, adding 10-30kg of aluminum particles;
if the oxygen content is < 20ppm, 10kg of aluminium granulate are added.
4. The LF refining rapid slag method of claim 1, wherein: in the step S1, the pre-flux is pressed into a sphere with the diameter of 80-120mm for use.
5. The LF refining rapid slag method of claim 1, wherein: in step S1, the preflux adding point is aligned with the pouring point of molten steel into the ladle.
6. The LF refining rapid slag method of claim 1, wherein: in the step S1, if the preflux forms a lump around the impact area of molten steel, when the diameter of the lump is less than 30cm, adjusting the adding speed of the preflux to 15-25kg/S, adjusting a ladle, ensuring the impact position of the molten steel injection flow on the lump, and promoting the rapid melting of the molten steel;
stopping adding the preflux when the diameter of the lump is smaller than 30cm and smaller than 50cm, adjusting the ladle to enable molten steel to flow to impact the lump position, and ensuring that the preflux is added according to the initial adding speed after the lump is completely melted;
when 50cm is smaller than the diameter of the lump, stopping adding the preflux, adjusting the ladle, and ensuring that molten steel flows to impact the position of the lump until tapping is finished.
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