CN117625882A - Production method for reducing surface quality defects of cast pig iron white and shrinkage pit iron beans - Google Patents
Production method for reducing surface quality defects of cast pig iron white and shrinkage pit iron beans Download PDFInfo
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- CN117625882A CN117625882A CN202311669348.5A CN202311669348A CN117625882A CN 117625882 A CN117625882 A CN 117625882A CN 202311669348 A CN202311669348 A CN 202311669348A CN 117625882 A CN117625882 A CN 117625882A
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 428
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 214
- 235000010627 Phaseolus vulgaris Nutrition 0.000 title claims abstract description 37
- 244000046052 Phaseolus vulgaris Species 0.000 title claims abstract description 37
- 230000007547 defect Effects 0.000 title claims abstract description 33
- 229910000805 Pig iron Inorganic materials 0.000 title claims abstract description 31
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 15
- 238000011081 inoculation Methods 0.000 claims abstract description 60
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 45
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 45
- 239000011777 magnesium Substances 0.000 claims abstract description 45
- 238000005266 casting Methods 0.000 claims abstract description 42
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 37
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 37
- 229910010271 silicon carbide Inorganic materials 0.000 claims abstract description 37
- 239000002893 slag Substances 0.000 claims abstract description 36
- 238000005507 spraying Methods 0.000 claims abstract description 33
- 238000003756 stirring Methods 0.000 claims abstract description 32
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 29
- 239000010703 silicon Substances 0.000 claims abstract description 29
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 19
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 18
- 230000023556 desulfurization Effects 0.000 claims abstract description 18
- 238000010079 rubber tapping Methods 0.000 claims abstract description 10
- 229910052751 metal Inorganic materials 0.000 claims description 41
- 239000002184 metal Substances 0.000 claims description 41
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 36
- 238000000034 method Methods 0.000 claims description 20
- 229910052757 nitrogen Inorganic materials 0.000 claims description 18
- 229910002804 graphite Inorganic materials 0.000 claims description 17
- 239000010439 graphite Substances 0.000 claims description 17
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 16
- 229910052717 sulfur Inorganic materials 0.000 claims description 16
- 239000011593 sulfur Substances 0.000 claims description 16
- 239000011856 silicon-based particle Substances 0.000 claims description 11
- 239000007921 spray Substances 0.000 claims description 11
- 229910001018 Cast iron Inorganic materials 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 8
- 238000007664 blowing Methods 0.000 claims description 4
- 239000013078 crystal Substances 0.000 claims description 4
- 230000003137 locomotive effect Effects 0.000 claims description 4
- 230000006911 nucleation Effects 0.000 claims description 4
- 238000010899 nucleation Methods 0.000 claims description 4
- 238000002161 passivation Methods 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- 238000005070 sampling Methods 0.000 claims description 4
- 238000004781 supercooling Methods 0.000 claims description 4
- 238000012360 testing method Methods 0.000 claims description 4
- 238000004364 calculation method Methods 0.000 claims description 3
- 238000005516 engineering process Methods 0.000 abstract description 4
- 230000001934 delay Effects 0.000 abstract description 2
- 238000003723 Smelting Methods 0.000 description 5
- 239000008187 granular material Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- 230000003111 delayed effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000012217 deletion Methods 0.000 description 1
- 230000037430 deletion Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000002068 genetic effect Effects 0.000 description 1
- XWHPIFXRKKHEKR-UHFFFAOYSA-N iron silicon Chemical compound [Si].[Fe] XWHPIFXRKKHEKR-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000012797 qualification Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 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
- C21C7/0068—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by introducing material into a current of streaming metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
-
- 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
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—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
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Multimedia (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
The production method for reducing the surface quality defects of cast pig iron white and condensed pit iron beans adopts the technology of primary silicon-adding inoculation during tapping, external desulfurization and secondary inoculation of silicon carbide during stirring of molten iron under the condition that a blast furnace does not adopt high silicon operation, properly improves the carbon equivalent of the molten iron, delays the inoculation decay of the molten iron, reduces the generation of the white and condensed pit iron bean defects in the casting process of the cast molten iron, and improves the appearance surface quality of iron blocks, and comprises the following steps: step 1, carrying out primary silicon-adding inoculation on molten iron output from a blast furnace into a molten iron tank; step 2, spraying magnesium in the molten iron tank for desulfurization after primary silicon-adding inoculation; step 3, stirring the molten iron subjected to magnesium spraying and desulfurization in a molten iron tank, and carrying out secondary inoculation on silicon carbide; step 4, slag skimming is carried out on molten iron in the molten iron tank outside the furnace; and 5, carrying out molten iron casting on the molten iron after slag skimming outside the furnace to obtain the iron block with reduced surface quality defects of cast pig iron white and shrinkage pit iron beans.
Description
Technical Field
The invention relates to the technical field of cast pig iron, in particular to a production method for reducing surface quality defects of white and shrinkage pit iron beans of cast pig iron.
Background
The cast pig iron is produced by direct smelting of a blast furnace, and when the blast furnace adopts a low-silicon smelting technology, the cast pig iron produced is generally low in silicon (Si is less than or equal to 0.4 percent), high in sulfur (S is more than 0.025 percent), low in physical heat of molten iron, low in carbon content in the molten iron, easy to generate surface quality defects such as shrinkage pit iron beans, white mouths and the like in the casting process, easy to generate genetic effect due to the white mouths and the like generated in the casting, and has adverse effect on the quality of castings using the iron block product.
The main reason for producing white and shrinkage pit iron beans in the casting process of cast pig iron is that the carbon equivalent of molten iron is low or the casting temperature is low, and the carbon of graphite precipitated in the casting process reduces carbide increase; in order to reduce the proportion of the surface quality defects of the iron blocks with white mouths and the shrinkage pit iron beans, the physical and thermal operations of high silicon, low sulfur and high molten iron are adopted in the general cast pig iron smelting process, but the corresponding production cost is increased more; or high silicon operation is not adopted, stream inoculation measures are adopted during casting, so that the generation of white mouths is avoided, slag inclusion defects can be generated on the iron block after the stream inoculation amount is increased, and the improvement of the surface quality is seriously influenced.
Disclosure of Invention
Aiming at the defects or shortcomings in the prior art, the invention provides a production method for reducing the surface quality defects of cast pig iron white and condensed pit iron beans, under the condition that a blast furnace does not adopt high silicon operation, the technology of primary silicon-increasing inoculation during tapping, external desulfurization and secondary inoculation of silicon carbide during molten iron stirring is adopted, the carbon equivalent of molten iron is properly improved, the inoculation decay of molten iron is delayed, the generation of the white and condensed pit iron bean defects in the casting process of cast molten iron is reduced, and the appearance surface quality of iron blocks is improved.
The technical scheme of the invention is as follows:
the production method for reducing the surface quality defects of cast pig iron white and condensed iron beans is characterized by comprising the steps of carrying out primary silicon-adding inoculation when a blast furnace is used for tapping, adding silicon carbide secondary inoculation in the process of stirring molten iron so as to reduce the defects of cast molten iron white and condensed iron beans in the casting process by improving the carbon equivalent of the molten iron and delaying the inoculation decay of the molten iron, thereby improving the appearance surface quality of iron blocks, and simultaneously avoiding supercooling tissues of the molten iron after the secondary inoculation of the silicon carbide in the casting process, so that the form of graphite in the cast iron is mainly tiny and uniformly distributed A-type graphite, and the mechanical property of the cast iron is improved.
The method comprises the following steps:
step 1, carrying out primary silicon-adding inoculation on molten iron output from a blast furnace into a molten iron tank;
step 2, spraying magnesium in the molten iron tank for desulfurization after primary silicon-adding inoculation;
step 3, stirring the molten iron subjected to magnesium spraying and desulfurization in a molten iron tank, and carrying out secondary inoculation on silicon carbide;
step 4, slag skimming is carried out on molten iron in the molten iron tank outside the furnace;
and 5, carrying out molten iron casting on the molten iron after slag skimming outside the furnace to obtain the iron block with reduced surface quality defects of cast pig iron white and shrinkage pit iron beans.
The step 1 includes: sampling and testing the silicon content of molten iron; 75 silicon particles in a 75 silicon particle bin are sequentially thrown into molten iron in a molten iron tank through a first blanking pipeline and a molten iron tank sliding nozzle, the adding amount of the 75 silicon particles is 0.4-0.8 wt% of the molten iron, and the silicon content of the molten iron after silicon addition is 0.7-1.0 wt%.
The step 2 includes: the locomotive is utilized to carry the molten iron tank after primary silicon-adding inoculation to a magnesium spraying tank position, a magnesium spraying gun is inserted into the molten iron tank, the magnesium spraying gun is 200-300 mm away from the bottom of the molten iron tank, passivation magnesium particles are sprayed into the molten iron tank by utilizing nitrogen to assist blowing, magnesium spraying desulfurization is realized, the sulfur content of molten iron is controlled to be S=0.011-0.019 wt% according to the calculation that the sulfur consumption of 0.001wt% of iron per ton is 0.020-0.030 kg, so that carbide generation and graphite carbon precipitation during molten iron casting are reduced, and the phenomenon of white mouth generation in molten iron casting caused by overlarge magnesium spraying consumption is avoided by controlling the sulfur content of the molten iron not to be less than 0.011 wt%.
The step 3 includes: the spray gun with high-pressure nitrogen is inserted into the position 200-300 mm away from the bottom of the hot metal ladle, the high-pressure nitrogen is utilized to stir the hot metal to ensure that the components of the hot metal are uniform, in the process of stirring the hot metal by using the nitrogen, silicon carbide is added into the hot metal ladle through a blanking conduit, the granularity of the silicon carbide is controlled to be 0.2-1.0 mm, the adding amount of the silicon carbide is 0.2-0.5 wt% of the molten iron, the secondary inoculation is realized, and the carbon equivalent is properly improved, so that the quantity of crystal nuclei in the hot metal is increased, the nucleation of graphite is promoted, and the tendency of shrinkage of white mouths and iron beans is reduced.
The step 4 includes: and (3) hauling the stirred and secondarily inoculated hot metal ladle to a slag removing tank position, and carrying out slag removing operation on the hot metal ladle by utilizing slag removing equipment, wherein the area ratio of the dross on the surface of the hot metal ladle after slag removing is over 20 percent.
The step 5 includes: and controlling the molten iron to be poured time after slag skimming outside the furnace to be within 20 minutes.
And in the step 3, the total stirring time is controlled to be 15-20 minutes, wherein the stirring time is not less than 10 minutes after the silicon carbide is fully added into the hot-metal ladle.
The physical heat of molten iron in the step 1 is 1472 ℃, and the casting temperature of casting by using an pig machine in the step 5 is 1282 ℃.
The invention relates to a production method for reducing the surface quality defect of cast pig iron white and shrinkage pit iron beans, which has the following technical effects compared with the prior art:
1. the qualification rate of the surface quality of the blast furnace smelting cast pig iron, especially the low-titanium cast pig iron, is improved.
2. The primary silicon-increasing inoculation is carried out when the blast furnace is tapped, and the secondary inoculation of silicon carbide is added in the stirring process of molten iron, so that the inoculation decay of the silicon carbide is delayed, the inoculation effect is improved, the stream inoculation in the casting process is banned, meanwhile, the molten iron after the silicon carbide inoculation avoids supercooling tissues in the casting process, and the graphite form in cast iron is mainly tiny and uniformly distributed A-type graphite, so that the mechanical property of cast iron is improved.
3. The blast furnace can realize low-silicon smelting operation in production, the fuel ratio is reduced, the production cost is saved, and the carbon emission is reduced.
Drawings
FIG. 1 is a process schematic diagram of a production method for reducing surface quality defects of cast pig iron white and shrinkage pit beans according to the invention. FIG. 1 includes step 1, a silicon-adding inoculation 13; step 2, spraying magnesium to desulfurize 14; step 3, stirring and secondary inoculation 15; step 4, slag skimming 16 outside the furnace; and 5, casting 17 of molten iron. In fig. 1, a 75 silicon granule bin 9 (75 silicon granules refer to granules containing 74-80 wt% of silicon and the balance of iron) sequentially inputs the 75 silicon granules into molten iron of a hot metal ladle 6 through a first blanking pipeline 1 and a ladle nozzle 2 to perform one-time silicon increasing inoculation. In the magnesium spraying desulfurization, a magnesium particle bin 10 sequentially passes through a third blanking pipeline 3 and a fourth spray gun 4 to throw magnesium particles into molten iron in a molten iron tank 6. Nitrogen N in stirring and secondary inoculation 2 The silicon carbide material bin 11 inputs silicon carbide into the molten iron of the molten iron tank 6 through the blanking conduit 5 by sequentially entering the molten iron of the molten iron tank 6 through the eighth blanking pipeline 8 and the seventh spray gun 7.
Detailed Description
The present invention will be described below with reference to examples and the accompanying drawings (fig. 1).
FIG. 1 is a process schematic diagram of a production method for reducing surface quality defects of cast pig iron white and shrinkage pit beans according to the invention. Referring to fig. 1, the production method for reducing the surface quality defects of cast pig iron white and condensed iron beans is characterized by comprising the steps of carrying out primary silicon-adding inoculation during tapping of a blast furnace, adding silicon carbide secondary inoculation during stirring of molten iron to reduce the defects of cast pig iron white and condensed iron beans during casting by improving the carbon equivalent of the molten iron and delaying the inoculation decay of the molten iron so as to improve the appearance surface quality of iron blocks, and simultaneously avoiding supercooling tissues of the molten iron after secondary inoculation of the silicon carbide during casting, so that the form of graphite in the cast iron is mainly tiny and uniformly distributed A-type graphite, thereby improving the mechanical property of the cast iron. The method comprises the following steps: step 1, carrying out primary silicon-adding inoculation on molten iron output from a blast furnace into a molten iron tank 6 in the molten iron tank 6; step 2, spraying magnesium in the molten iron tank 6 for desulfurization after primary silicon-adding inoculation; step 3, stirring the molten iron subjected to magnesium spraying and desulfurization in a molten iron tank 6, and carrying out secondary inoculation on silicon carbide; step 4, slag skimming is carried out on molten iron in the molten iron tank 6 outside the furnace; and 5, carrying out molten iron casting on the molten iron after slag skimming outside the furnace to obtain the iron block with reduced surface quality defects of cast pig iron white and shrinkage pit iron beans.
The step 1 includes: sampling and testing the silicon content of molten iron; 75 silicon particles in a 75 silicon particle bin 9 are sequentially thrown into molten iron in a molten iron tank 6 through a first blanking pipeline 1 and a molten iron tank spout 2, the adding amount of the 75 silicon particles is 0.4wt% -0.8wt% of the molten iron amount, and the silicon content of the molten iron after silicon increase is 0.7wt% -1.0wt%. The step 2 includes: the locomotive is utilized to drag the molten iron tank 6 after primary silicon-adding inoculation to the magnesium spraying tank position, a magnesium spraying gun (namely a fourth spray gun 4) is inserted into the molten iron tank 6, the magnesium spraying gun is 200-300 mm away from the bottom of the molten iron tank, passivation magnesium particles are sprayed into the molten iron tank 6 by utilizing nitrogen to assist blowing, magnesium spraying desulfurization is realized, the sulfur content of the molten iron is controlled to be S=0.011-0.019 wt% according to the calculation of 0.020kg-0.030kg of sulfur consumption magnesium of 0.001wt% of iron, carbide generation and graphite carbon precipitation increase during molten iron casting are reduced, and the phenomenon of excessive residual magnesium in molten iron caused by excessive magnesium spraying amount is prevented by controlling the sulfur content of the molten iron to be not less than 0.011wt%, so as to avoid the phenomenon of blushing in molten iron casting caused by excessive residual magnesium in the molten iron.
The step 3 includes: the spray gun (namely, the seventh spray gun 7) which is filled with high-pressure nitrogen is inserted into the position 200-300 mm away from the bottom of the hot metal ladle, the high-pressure nitrogen is utilized to stir the hot metal, so that the components of the hot metal are uniform, in the process of stirring the hot metal by using the nitrogen, silicon carbide is added into the hot metal ladle 6 through the blanking conduit 5, the granularity of the silicon carbide is controlled to be 0.2-1.0 mm, the adding amount of the silicon carbide is 0.2-0.5 wt% of the molten iron, the secondary inoculation is realized, the carbon equivalent is properly improved, the quantity of crystal nuclei in the hot metal is increased, the graphite nucleation is promoted, and the tendency of white mouth and iron bean shrinkage is reduced. The step 4 includes: and (3) hauling the stirred and secondarily inoculated hot metal ladle 6 to a slag removing tank position, and carrying out slag removing operation on the hot metal ladle 6 by using slag removing equipment, wherein the area ratio of the dross on the surface of the hot metal ladle 6 after slag removing is finished is not more than 20%. The step 5 includes: and controlling the molten iron to be poured time after slag skimming outside the furnace to be within 20 minutes. And in the step 3, the total stirring time is controlled to be 15-20 minutes, wherein the stirring time is not less than 10 minutes after the silicon carbide is fully added into the hot-metal ladle 6. The physical heat of molten iron in the step 1 is 1472 ℃, and the casting temperature of casting by using an pig machine in the step 5 is 1282 ℃.
Under the condition that the blast furnace does not adopt high silicon operation, the invention adopts the technology of primary silicon-increasing inoculation during tapping, external desulfurization and secondary inoculation of silicon carbide during stirring of molten iron, properly improves the carbon equivalent of the molten iron, delays the inoculation decay of the molten iron, reduces the generation of white and shrinkage pit iron bean defects in the casting process of the cast molten iron, and improves the appearance surface quality of the iron block. The method comprises the following steps:
1. tapping and one-time silicon increasing inoculation. After the blast furnace is opened to tap iron, taking iron samples in a molten iron runner after molten iron flows into a molten iron tank for about 3 minutes to test molten iron components, adding 75 silicon iron into the molten iron tank through a blast furnace tap runner nozzle according to the silicon (Si) content of the molten iron, wherein the adding amount is 0.4-0.8% of the molten iron, and the silicon (Si) content of the molten iron after silicon increase is in the range of 0.7-1.0%, so as to realize one-time silicon increase inoculation of the molten iron.
2. And desulfurizing outside the furnace. When the sulfur (S) content of the original molten iron in front of the furnace is not less than 0.020%, the locomotive drags the molten iron tank after primary silicon-adding inoculation to a magnesium spraying tank position in time, a magnesium spraying gun is inserted into the molten iron tank, the magnesium spraying gun is about 200mm-300mm away from the bottom of the molten iron tank, passivation particle magnesium is sprayed into the molten iron tank by utilizing nitrogen to assist blowing, the desulfurization outside the furnace is realized, the magnesium consumption for removing 0.001% sulfur according to ton iron is 0.020kg-0.030kg, the sulfur (S) content of the molten iron is controlled within the range of 0.011% -0.019%, the reduction of carbide generation during molten iron casting and the increase of graphite carbon precipitation are facilitated, if the sulfur (S) content of the molten iron after magnesium spraying desulfurization is less than 0.010%, the magnesium spraying consumption is too large, the residual magnesium content in the molten iron is too high, and a phenomenon of white mouth is easy to generate in casting.
3. Secondary inoculation is carried out when molten iron is stirred. The spray gun with high-pressure nitrogen is inserted into the position 200mm-300mm away from the bottom of the molten iron tank, the molten iron is stirred by utilizing the high-pressure nitrogen, so that the components of the molten iron are uniform, in the process of stirring the molten iron by utilizing the nitrogen, silicon carbide is added into the molten iron tank through a guide pipe for secondary inoculation, in order to ensure that silicon carbide particles are melted and decomposed in the molten iron, the absorptivity of the silicon carbide is improved, the granularity of the silicon carbide is controlled to be 0.2mm-1.0mm, the adding amount is 0.2% -0.5% of the molten iron, the secondary inoculation and proper improvement of carbon equivalent are realized, the quantity of crystal nuclei in the molten iron is increased, graphite nucleation is promoted, and the tendency of shrinkage of white mouths and iron beans is reduced; the total stirring time is controlled to be 15-20 minutes, wherein the stirring time is not less than 10 minutes after the silicon carbide is fully added into the hot-metal ladle.
4. And (5) slag skimming outside the furnace. And (3) hauling the stirred and secondarily inoculated hot metal ladle to a slag removing tank position, and carrying out slag removing operation on the hot metal ladle by utilizing slag removing equipment, so that slag on the surface of the hot metal ladle is completely removed as much as possible, and the area of the slag on the surface of the hot metal ladle after slag removing is completed is required to be not more than 20%.
5. And casting in time. And (3) controlling the time to be poured after slag skimming outside the furnace to be within 20min, casting in time, and delaying inoculation decay.
Examples:
1. after tapping of the casting blast furnace, sampling after molten iron enters an iron tank for 3min, wherein the physical heat of molten iron is 1472 ℃, and the molten iron of the blast furnace comprises the following components in percentage by weight:
| C％ | Si％ | Mn％ | Ti％ | P％ | S％ |
| 4.3 | 0.45 | 0.08 | 0.035 | 0.032 | 0.028 |
2. adding silicon into the hot metal ladle at one time during tapping, adding 75 silicon particles into the hot metal ladle according to 0.6% of the estimated weight of the hot metal ladle, wherein the estimated weight of the hot metal ladle is 65 tons, the actual added 75 silicon particles are 390kg, and the Si of the molten iron after silicon addition is 0.81%;
3. after tapping, transporting the hot metal ladle to a magnesium spraying tank position, spraying magnesium by a lower spray gun for desulfurization, wherein the consumption of magnesium is 30kg, and the sulfur content of the desulfurized molten iron is 0.017%;
4. after the magnesium spraying is finished, the spray gun continuously sprays nitrogen into the iron ladle and stirs, 200kg of silicon carbide particles are added into the iron ladle at the same time, secondary inoculation is carried out, the stirring time is 15 minutes after all silicon carbide is added, and the total stirring time is 20 minutes;
5. after stirring and secondary inoculation are finished, slag skimming is carried out, and the total time of slag skimming is 6 minutes;
6. when the slag is removed and reaches the pig machine, the time is 3 minutes, the casting temperature is 1282 ℃ in casting, the graphite carbon precipitated on the surface of the iron block is more in casting, the section of the iron block is grey, and the phenomenon of shrinkage pit of the iron bean is avoided.
7. The cast iron block comprises the following chemical components in percentage by weight:
| C％ | Si％ | Mn％ | Ti％ | P％ | S％ |
| 4.38 | 0.81 | 0.08 | 0.035 | 0.032 | 0.017 |
what is not described in detail in this specification is prior art known to those skilled in the art. It is noted that the above description is helpful for a person skilled in the art to understand the present invention, but does not limit the scope of the present invention. Any and all such equivalent substitutions, modifications and/or deletions as may be made without departing from the spirit and scope of the invention.
Claims (9)
1. The production method for reducing the surface quality defects of cast pig iron white and condensed iron beans is characterized by comprising the steps of carrying out primary silicon-adding inoculation when a blast furnace is used for tapping, adding silicon carbide secondary inoculation in the process of stirring molten iron so as to reduce the defects of cast molten iron white and condensed iron beans in the casting process by improving the carbon equivalent of the molten iron and delaying the inoculation decay of the molten iron, thereby improving the appearance surface quality of iron blocks, and simultaneously avoiding supercooling tissues of the molten iron after the secondary inoculation of the silicon carbide in the casting process, so that the form of graphite in the cast iron is mainly tiny and uniformly distributed A-type graphite, and the mechanical property of the cast iron is improved.
2. The production method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 1, comprising the steps of:
step 1, carrying out primary silicon-adding inoculation on molten iron output from a blast furnace into a molten iron tank;
step 2, spraying magnesium in the molten iron tank for desulfurization after primary silicon-adding inoculation;
step 3, stirring the molten iron subjected to magnesium spraying and desulfurization in a molten iron tank, and carrying out secondary inoculation on silicon carbide;
step 4, slag skimming is carried out on molten iron in the molten iron tank outside the furnace;
and 5, carrying out molten iron casting on the molten iron after slag skimming outside the furnace to obtain the iron block with reduced surface quality defects of cast pig iron white and shrinkage pit iron beans.
3. The method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 2, wherein the step 1 comprises: sampling and testing the silicon content of molten iron; 75 silicon particles in a 75 silicon particle bin are sequentially thrown into molten iron in a molten iron tank through a first blanking pipeline and a molten iron tank sliding nozzle, the adding amount of the 75 silicon particles is 0.4-0.8 wt% of the molten iron, and the silicon content of the molten iron after silicon addition is 0.7-1.0 wt%.
4. The method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 2, wherein the step 2 comprises: the locomotive is utilized to carry the molten iron tank after primary silicon-adding inoculation to a magnesium spraying tank position, a magnesium spraying gun is inserted into the molten iron tank, the magnesium spraying gun is 200-300 mm away from the bottom of the molten iron tank, passivation magnesium particles are sprayed into the molten iron tank by utilizing nitrogen to assist blowing, magnesium spraying desulfurization is realized, the sulfur content of molten iron is controlled to be S=0.011-0.019 wt% according to the calculation that the sulfur consumption of 0.001wt% of iron per ton is 0.020-0.030 kg, so that carbide generation and graphite carbon precipitation during molten iron casting are reduced, and the phenomenon of white mouth generation in molten iron casting caused by overlarge magnesium spraying consumption is avoided by controlling the sulfur content of the molten iron not to be less than 0.011 wt%.
5. The method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 2, wherein the step 3 comprises: the spray gun with high-pressure nitrogen is inserted into the position 200-300 mm away from the bottom of the hot metal ladle, the high-pressure nitrogen is utilized to stir the hot metal to ensure that the components of the hot metal are uniform, in the process of stirring the hot metal by using the nitrogen, silicon carbide is added into the hot metal ladle through a blanking conduit, the granularity of the silicon carbide is controlled to be 0.2-1.0 mm, the adding amount of the silicon carbide is 0.2-0.5 wt% of the molten iron, the secondary inoculation is realized, and the carbon equivalent is properly improved, so that the quantity of crystal nuclei in the hot metal is increased, the nucleation of graphite is promoted, and the tendency of shrinkage of white mouths and iron beans is reduced.
6. The method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 2, wherein the step 4 comprises: and (3) hauling the stirred and secondarily inoculated hot metal ladle to a slag removing tank position, and carrying out slag removing operation on the hot metal ladle by utilizing slag removing equipment, wherein the area ratio of the dross on the surface of the hot metal ladle after slag removing is over 20 percent.
7. The method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 2, wherein the step 5 comprises: and controlling the molten iron to be poured time after slag skimming outside the furnace to be within 20 minutes.
8. The method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 2, wherein the total stirring time in the step 3 is controlled to 15-20 minutes, wherein the stirring time is not less than 10 minutes after the silicon carbide is completely added into the hot-metal ladle.
9. The method for reducing surface quality defects of cast pig iron white and cratered beans according to claim 2, wherein the physical hot iron in the step 1 is 1472 ℃ and the casting temperature in the step 5 is 1282 ℃ by using an pig machine.
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