CN118109659A - Free-cutting alloy die steel and inclusion control method thereof - Google Patents
Free-cutting alloy die steel and inclusion control method thereof Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 238000005520 cutting process Methods 0.000 title claims abstract description 33
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 77
- 239000002893 slag Substances 0.000 claims abstract description 57
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 44
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 34
- 238000007664 blowing Methods 0.000 claims abstract description 30
- 229910052742 iron Inorganic materials 0.000 claims abstract description 30
- 238000009749 continuous casting Methods 0.000 claims abstract description 28
- 238000010079 rubber tapping Methods 0.000 claims abstract description 26
- 239000011593 sulfur Substances 0.000 claims abstract description 24
- 238000003723 Smelting Methods 0.000 claims abstract description 23
- 229910052786 argon Inorganic materials 0.000 claims abstract description 22
- 238000007670 refining Methods 0.000 claims abstract description 19
- 229910000604 Ferrochrome Inorganic materials 0.000 claims abstract description 16
- 229910001309 Ferromolybdenum Inorganic materials 0.000 claims abstract description 16
- 239000002245 particle Substances 0.000 claims abstract description 16
- 238000005275 alloying Methods 0.000 claims abstract description 13
- 238000010438 heat treatment Methods 0.000 claims abstract description 13
- 239000011449 brick Substances 0.000 claims abstract description 12
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims abstract description 10
- 235000011941 Tilia x europaea Nutrition 0.000 claims abstract description 10
- 238000005266 casting Methods 0.000 claims abstract description 10
- 239000004571 lime Substances 0.000 claims abstract description 10
- 239000000843 powder Substances 0.000 claims abstract description 9
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910010271 silicon carbide Inorganic materials 0.000 claims abstract description 9
- 238000005096 rolling process Methods 0.000 claims abstract description 7
- 238000005098 hot rolling Methods 0.000 claims abstract description 6
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims abstract description 6
- 238000002791 soaking Methods 0.000 claims abstract description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims description 20
- 239000010936 titanium Substances 0.000 claims description 19
- 229910052782 aluminium Inorganic materials 0.000 claims description 18
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 16
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 16
- 239000012535 impurity Substances 0.000 claims description 15
- 229910052719 titanium Inorganic materials 0.000 claims description 14
- 239000011572 manganese Substances 0.000 claims description 11
- 239000005997 Calcium carbide Substances 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 9
- 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 9
- 229910052748 manganese Inorganic materials 0.000 claims description 8
- 229910000914 Mn alloy Inorganic materials 0.000 claims description 7
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 7
- 229910052918 calcium silicate Inorganic materials 0.000 claims description 7
- 239000000378 calcium silicate Substances 0.000 claims description 7
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 6
- 238000006477 desulfuration reaction Methods 0.000 claims description 6
- 230000023556 desulfurization Effects 0.000 claims description 6
- 239000011819 refractory material Substances 0.000 claims description 5
- 229910000640 Fe alloy Inorganic materials 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 claims description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052593 corundum Inorganic materials 0.000 claims description 3
- 239000007789 gas Substances 0.000 claims description 3
- 238000009423 ventilation Methods 0.000 claims description 3
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 2
- 230000001276 controlling effect Effects 0.000 abstract description 10
- 230000001105 regulatory effect Effects 0.000 abstract description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 3
- 239000005864 Sulphur Substances 0.000 description 2
- 229910000323 aluminium silicate Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
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- 229910052751 metal Inorganic materials 0.000 description 2
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- 229910000838 Al alloy Inorganic materials 0.000 description 1
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- 229910000676 Si alloy Inorganic materials 0.000 description 1
- 229910000720 Silicomanganese Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000036280 sedation Effects 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
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- 150000004763 sulfides Chemical class 0.000 description 1
- 230000004222 uncontrolled growth Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Abstract
The invention discloses free-cutting alloy die steel and a method for controlling inclusions of the free-cutting alloy die steel, which comprises the following steps: smelting in a blast furnace: iron making is carried out on blast furnace slag by selecting high-sulfur iron ore, molten iron is obtained, and the discharged iron enters a ladle and is conveyed to a converter for smelting; smelting in a converter; tapping by a converter; LF refining: fully starting bottom blowing argon, electrifying and heating, and fully regulating the components and the temperature of molten steel to reach the standards by adding alloy manganese, ferrochrome and ferromolybdenum, wherein the argon flow of an air brick during charging and alloying is 300-400NL/min, the argon flow of the air brick during heating is 200-300NL/min, and the argon flow of the air brick during the rest time is 100-150NL/min; after the alloy components, the temperature and the slag components of the molten steel reach the standards, adding fine powder particles of lime and silicon carbide, controlling the alkalinity of ladle slag to be 1.5-2.0, and transporting the ladle slag to RH treatment; RH vacuum refining; continuous casting; and (3) hot rolling: and (3) delivering the casting blank obtained by continuous casting into a heating furnace, soaking at 950-1150 ℃ for more than or equal to 3 hours, and rolling to obtain a hot rolled plate with the thickness of more than 10 mm. The invention improves the cutting performance of alloy die steel.
Description
Technical Field
The invention relates to free-cutting alloy die steel and a inclusion control method thereof, belonging to the technical field of steelmaking.
Background
The free-cutting alloy die steel is mainly applied to various dies and die frames, is convenient for machining and cutting, reduces cutting resistance, prolongs the service life of a cutter, easily eliminates chips and improves the finish of a machined surface. The high-quality high-purity aluminum alloy material has extremely high requirements on the purity of a blank, the shape of a blank, the surface quality and the internal quality of the blank. In particular, the control of the internal inclusions has higher requirements, and too many small particle inclusions can cause uncontrolled growth of sulfide nucleation, thereby affecting cutting performance. The large particle inclusions or the external hard inclusions are unfavorable for controlling the cutting processability, and the loss of the cutter is increased.
The free-cutting alloy die steel is widely applied to various dies and die frames, is convenient for machining and cutting, and can prolong the service life of the cutter. The method has extremely high requirements on the shape control of sulfides, the purity of blanks, the blank shape of a casting blank, and the surface and internal quality of the casting blank due to extremely high processing performance and product quality. Therefore, in order to obtain high-quality free-cutting alloy die steel, the key is to control the S content stability, sulfide inclusion morphology, billet oxygen content, purity and casting blank quality in the steel. Based on the above, the present invention provides a free-cutting alloy die steel and a method for controlling inclusions in the same.
Disclosure of Invention
In order to solve the problems, the invention discloses free-cutting alloy die steel and an inclusion control method thereof, which have the following specific technical scheme:
A method for controlling free-cutting alloy die steel inclusions comprises the following steps:
Step 1: smelting in a blast furnace: the method comprises the steps of selecting high-sulfur iron ore to make iron in blast furnace slag, carrying out KR non-desulfurization treatment to obtain high-sulfur molten iron, delivering the iron into a ladle, and conveying the ladle to a converter for smelting, wherein the molten iron in the ladle comprises the following components in percentage by mass: c:4.05% -4.55%, S:0.025% -0.075% and the temperature is 1380-1450 ℃;
Step 2: smelting in a converter: the converter loading amount is 200+/-5 t, the scrap steel ratio is 15% -20%, sulfur-containing common scrap steel is selected for smelting, when the converter smelting is finished and the temperature of molten steel is more than 1600 ℃, the content of C is 0.020% -0.045%, the content of S is 0.020% -0.065%, blowing is stopped, slag is blocked by adopting a sliding plate, and then tapping is carried out;
Step 3: tapping by a converter: when 20-30% of converter tapping is performed, firstly adding 20-30% of aluminum-containing ferrosilicon alloy and 50-60% of aluminum-containing manganese alloy into a ladle for deoxidization alloying, then adding ferrochrome alloy, ferromolybdenum alloy and carbon powder for alloying, then adding low-alkalinity calcium silicate to synthesize slag for slagging after the ferrochrome alloy, the ferromolybdenum alloy and the carbon powder are added, controlling the bottom blowing flow rate of the slag alkalinity CaO/SiO 2 = 0.5-1.0 in the tapping process to be 400NL/min, and stirring for 2-4min and then conveying to an LF furnace for treatment;
step 4: LF refining: fully starting bottom blowing argon, electrifying and heating, wherein the alloy manganese, ferrochrome and ferromolybdenum fully regulate the components and the temperature of molten steel to reach the standards, the argon flow of an air brick during heating is 200-300NL/min, the argon flow of the air brick during alloy manganese, ferrochrome and ferromolybdenum alloying is 300-400NL/min, and the argon flow of the air brick during the other time is 100-150NL/min; after the alloy components, the temperature and the slag components of the molten steel reach the standards, adding fine powder particles of lime and silicon carbide, controlling the alkalinity of ladle slag to be 1.5-2.0, and transporting the ladle slag to RH treatment;
Step 5: RH vacuum refining: the RH station entering quick vacuumizing treatment is carried out, when the vacuum degree is below 20mbar, low-titanium low-aluminum ferrosilicon alloy is added to enable the low-titanium low-aluminum ferrosilicon alloy to reach target components, meanwhile, calcium carbide is added into a triangular area surrounded by two RH dip pipes and a steel ladle to carry out calcium carbide deoxidation, after the molten steel slag deoxidation alloying is finished, the lifting gas flow is changed to 150-200Nm 3/h, the ladle bottom blowing stirring is carried out, and the bottom blowing flow is 50-100NL/min; closing the ladle bottom blowing after the RH vacuum degree is reduced to below 2mbar, adding the ferrosulfur alloy, after the addition of the ferrosulfur alloy is finished, processing time is more than or equal to 15min, then RH clean circulation, breaking and tapping, soft stirring and calm treatment after tapping, and then transporting to continuous casting pouring;
Step 6: continuous casting: casting by adopting a slab continuous casting machine, wherein the thickness of a slab is 220mm or 320mm, the width is 1500-2300 mm, and the pulling speed is 0.8-1.1 m/min; the whole process of continuous casting is protected and poured, the argon blowing flow of the long nozzle is 150-250L/min, and the argon blowing flow of the stopper rod and the immersed nozzle is 3-5L/min;
Step 7: and (3) hot rolling: and (3) delivering the casting blank obtained by continuous casting into a heating furnace, soaking at 950-1150 ℃ for more than or equal to 3 hours, and rolling to obtain a hot rolled plate with the thickness of more than 10 mm.
Further, in the step 2, S is as follows: 0.010% -0.035%, and the balance of Fe and other conventional components.
Further, sulfur-containing slag is added in the later stage of the converter smelting in the step 2, the addition amount of the sulfur-containing slag is 5-10 kg/t, the S content in the sulfur-containing slag is 3.0% -5.0%, caO is more than or equal to 88%, and other unavoidable components.
Further, the ferrosilicon alloy used for converter tapping in the step 3 comprises the following components in percentage by mass: 73% -78% of Si, 3% -5% of Al, less than or equal to 0.013% of P, less than or equal to 0.002% of Ti, and the balance of Fe and other unavoidable components;
The manganese alloy mainly comprises the following components in percentage by mass: mn is more than or equal to 95%, al is 1-2%, P is less than or equal to 0.010%, ti is less than or equal to 0.0025%, and the balance is Fe and other unavoidable impurity components;
The ferrochrome comprises the following components in percentage by mass: cr:60% -65%, P is less than or equal to 0.012%, al is less than or equal to 0.0035%, ti is less than or equal to 0.002%, and the balance is Fe and other unavoidable impurity components;
the ferromolybdenum comprises the following components in percentage by mass: mo:45% -50%, P is less than or equal to 0.015%, al is less than or equal to 0.006%, ti is less than or equal to 0.004%, and the balance is Fe and other unavoidable impurity components;
The addition amount of the calcium silicate synthetic slag is 10-15 kg/t, and the components comprise the following components in percentage by mass: 35-45% of CaO, less than or equal to 2% of SiO 2 45%-55%、Al2O3%, 3-5% of MgO and other unavoidable components.
Further, the alloy manganese component used in the LF refining in the step 4 comprises more than or equal to 98% by mass of Mn, less than or equal to 0.010% by mass of P, less than or equal to 0.0030% by mass of Al, less than or equal to 0.0025% by mass of Ti, and the balance of Fe and other unavoidable impurity components;
The ferrochrome comprises the following components in percentage by mass: 60% -65%, P is less than or equal to 0.012%, al is less than or equal to 0.0035%, ti is less than or equal to 0.002%, and the balance is Fe and other unavoidable impurity components;
the ferromolybdenum alloy comprises the following components in percentage by mass: 45% -50%, P is less than or equal to 0.015%, al is less than or equal to 0.006%, ti is less than or equal to 0.004%, and the balance is Fe and other unavoidable impurity components;
the addition amount of lime in the fine powder particles is 3-5 kg/t, caO is more than or equal to 95 percent, and other unavoidable components, the particle size is 1-5 mm, the ratio is more than or equal to 90 percent, and the maximum particle size is not more than 10mm;
SiC in silicon carbide is more than or equal to 95 percent, and other unavoidable components.
Further, the low-titanium low-aluminum ferrosilicon component in the RH vacuum refining in the step 5 comprises the following components in percentage by mass: 70% -80%, P is less than or equal to 0.008%, S is less than or equal to 0.0035%, al is less than or equal to 0.0025%, ti is less than or equal to 0.0015%, and Fe and other unavoidable components;
The sulfur-iron alloy comprises the following components in percentage by mass: 30% -40% of iron and other unavoidable components;
the addition amount of the calcium carbide is 0.5-0.8 kg/t;
the bottom blowing ventilation of the two steel ladles is positioned below two triangular areas surrounded by the two dip pipes and the steel ladles.
Furthermore, the steel ladle, the continuous casting tundish, the continuous casting ladle long nozzle, the immersed nozzle and the refractory material of the stopper rod contacted with molten steel are all made of low alumina materials with the mass content of Al 2O3 being less than or equal to 5 percent.
Further, adopting a scanning electron microscope to count oxide inclusions in the molten steel of the continuous casting tundish in the step 6, wherein the counted area is 1000mm 2, the oxide inclusion size is 1-5 mu m, the inclusion proportion is more than 85%, the inclusion proportion is more than 10%, and the maximum size inclusion is not more than 25 mu m; the rolling ratio of the blank is more than or equal to 4, the aspect ratio of sulfide inclusions in the blank is more than or equal to 5, and the class A is more than or equal to 2.
The free-cutting alloy die steel prepared by the free-cutting alloy die steel inclusion control method.
Further, the steel chemical composition of the free-cutting alloy die comprises ：C：0.25%-0.55%、Si：0.20%-0.60%、Mn：1.25%-1.85%、Cr：1.7%-2.2%、Mo：0.10%-0.40%、S：0.05%-0.15%、Ni≤0.02%、Cu≤0.015%、P≤0.015%、T.O≤0.0015%、N≤0.0025%、H≤0.0002%、Alt≤0.0015%、Ti≤0.0008%, mass percent of Fe and other unavoidable components.
The invention has the technical principle and beneficial effects that:
KR is not desulfurized to obtain high-sulfur molten iron, and the high-sulfur molten iron and the common sulfur-containing scrap steel are added into a converter for smelting, so that the sulfur content in the initial raw materials is increased. And adding sulfur-containing slag in the later stage of converter smelting, increasing the sulfur content in the slag, promoting the sulfur increase of the slag into molten steel, or avoiding the desulfurization of the slag, and increasing the sulfur content of the molten steel during converter tapping. And then, no ferro-sulphur alloy is added in converter tapping and LF refining, and after all components are regulated to reach the standard in an RH vacuum furnace, the ferro-sulphur alloy is added, so that the sulfur content is regulated to reach the standard, and the desulfurization of molten steel in the refining process is avoided.
Part of aluminum-containing silicon and manganese alloy is firstly added for deoxidization in the tapping process of the converter, controllable metal Al, si and Mn carried by the alloy are utilized for forming composite deoxidization, oxygen in molten steel is removed completely, and aluminosilicate and silicate inclusions are formed. And adding low-alkalinity calcium silicate synthetic slag into converter tapping, simultaneously adding no lime and the like, and removing metal aluminum to a lower level by utilizing oxygen in molten steel and low-alkalinity acid slag.
The low-alkalinity slag system is adopted in the early stage of LF refining, the desulfurization is reduced, alloy manganese is adopted when components are regulated, the introduction of harmful components such as Al, ti and the like is avoided, after the components reach the standards, fine powder particle lime is added before refining tapping to quickly raise the alkalinity of slag, the desulfurization of slag is avoided, and the fine powder particle lime is added into low-alkalinity refining slag to quickly melt the slag. Under RH vacuum condition, firstly adding low-titanium low-aluminum ferrosilicon alloy, and simultaneously adding calcium carbide to the slag surface of the steel ladle to further remove oxygen in the slag, improve the alkalinity of the slag, and open the ladle bottom blowing of the RH vacuum furnace to promote the rapid progress of the deoxidization reaction of the slag, strengthen the floating removal of inclusions, avoid the secondary pollution of molten steel caused by oxidizing alloy elements in the molten steel in the continuous casting process, and further improve the cleanliness of the molten steel. After the RH vacuum furnace alloy adjustment and slag deoxidation are completed, adding the sulfur-iron alloy, so that the yield of sulfur element is improved.
Because the steel is the silicomanganese deoxidized steel, the inclusions are mainly silicate, the steel has certain corrosiveness, meanwhile, a ladle adopts a low-alkalinity slag system for a long time, and in order to prevent Al 2O3 inclusions generated by corrosion of refractory materials from entering molten steel, the refractory materials made of low-alumina materials are adopted, so that the stability of the inclusions is controlled. Then the mixture is subjected to heat preservation treatment in a heating furnace for a long time, so that sulfide is fully precipitated and grown, sulfide inclusions with excellent size and appearance are obtained, and the mixture is very beneficial to improving the cutting performance of alloy die steel.
Detailed Description
The invention is further elucidated below in connection with the specific embodiments. It should be understood that the following detailed description is merely illustrative of the invention and is not intended to limit the scope of the invention.
The free-cutting alloy die steel mainly comprises ：C：0.25%-0.55%、Si：0.20%-0.60%、Mn：1.25%-1.85%、Cr：1.7%-2.2%、Mo：0.10%-0.40%、S：0.05%-0.15%、Ni≤0.02%、Cu≤0.015%、P≤0.015%、T.O≤0.0015%、N≤0.0025%、H≤0.0002%、Alt≤0.0015%、Ti≤0.0008%, mass percent of Fe and other unavoidable components, and is produced according to the flow of blast furnace smelting-converter smelting-LF refining-RH vacuum treatment-continuous casting-hot rolling.
The oxide inclusion in the obtained tundish molten steel is mainly silicate and aluminosilicate inclusion, the inclusion is counted by adopting a scanning electron microscope, the counted area is 1000mm 2, the oxide inclusion size is 1-5 mu m, the inclusion proportion is more than 85%, the inclusion proportion is 5-15 mu m, the inclusion proportion is more than 10%, and the maximum size inclusion is not more than 25 mu m; the rolling ratio of the blank is more than or equal to 4, the aspect ratio of sulfide inclusions in the blank is more than or equal to 5, and the class A is more than or equal to 2.
Smelting in a blast furnace: iron making is carried out on high-sulfur iron ore in blast furnace slag to obtain molten iron, the discharged iron enters a ladle and is conveyed to a converter for smelting, and the molten iron in the ladle comprises the following components in percentage by mass: c:4.1% -4.5%, S: 0.03-0.08% and the temperature is 1380-1450 ℃.
The following is a description of specific examples of the application of the method, and the composition and temperature of the molten iron produced by the blast furnace are shown in Table 1.
TABLE 1
Smelting in a converter: the converter loading amount is 200+/-5 t, the scrap steel ratio is 15% -20%, clean scrap steel smelting is selected, the converter smelting is finished, when the temperature of molten steel is higher than 1600 ℃, the C content is 0.020% -0.045%, the S content is 0.020% -0.065%, blowing is stopped, a sliding plate is adopted to stop slag, and then tapping is carried out.
Cleaning waste steel, S:0.010% -0.035%, and the balance of Fe and other conventional components.
The following gives a specific example of the application of the method, and some parameters in the converter smelting process are shown in table 2.
TABLE 2
Tapping by a converter: when 20-30% of converter tapping is performed, firstly adding 20-30% of ferrosilicon alloy and 50-60% of manganese alloy into a ladle for deoxidization alloying, then adding all of ferrochromium alloy, ferromolybdenum alloy and carbon powder for alloying, then adding calcium silicate to synthesize slag for slagging after the alloy and the carbon powder are added, controlling the bottom blowing flow rate of slag to be 400-600NL/min, controlling the slag alkalinity CaO/SiO 2 to be 0.5-1.0, controlling the bottom blowing flow rate of slag to be 200-400NL/min when adding slag, stirring for 2-4min, and then conveying to an LF furnace for treatment.
73% -78% Of Si, 3% -5% of Al, less than or equal to 0.013% of P, less than or equal to 0.002% of Ti, and the balance of Fe and other unavoidable components; the main components of the manganese alloy comprise more than or equal to 95% of Mn, 1% -2% of Al, less than or equal to 0.010% of P, less than or equal to 0.0025% of Ti, and the balance of Fe and other unavoidable impurity components; ferrochrome Cr:60% -65%, P is less than or equal to 0.012%, al is less than or equal to 0.0035%, ti is less than or equal to 0.002%, and the balance is Fe and other unavoidable impurity components; ferromolybdenum Mo:45% -50%, P is less than or equal to 0.015%, al is less than or equal to 0.006%, ti is less than or equal to 0.004%, and the balance is Fe and other unavoidable impurity components; the addition amount of the calcium silicate synthetic slag is 10-15 kg/t, and the main components comprise 35-45% of CaO, less than or equal to 2% of SiO 2 45%-55%、Al2O3%, 3-5% of MgO and other unavoidable components.
The following gives a specific example of the application of the method, and the parameters of the converter tapping process are shown in table 3.
TABLE 3 Table 3
LF refining: fully starting bottom blowing argon, electrifying and heating, and fully regulating the components and the temperature of molten steel to reach the standards by adding alloy manganese, ferrochrome and ferromolybdenum, wherein the argon flow of an air brick during charging and alloying is 300-400NL/min, the argon flow of the air brick during heating is 200-300NL/min, and the argon flow of the air brick during the rest time is 100-150NL/min; after the alloy components, temperature and slag components of molten steel reach the standards, fine powder lime and silicon carbide are added, the alkalinity of ladle slag is controlled to be 1.5-2.0, and T.Fe+MnO is less than or equal to 2 percent, and the ladle slag is transported to RH treatment.
The addition amount of lime in the fine powder particles is 3-5 kg/t, caO is more than or equal to 95 percent, and other unavoidable components, the particle size is 1-5 mm, the ratio is more than or equal to 90 percent, and the maximum particle size is not more than 10mm; siC in silicon carbide is more than or equal to 95 percent, and other unavoidable components.
Specific examples of the application of the method are given below, and some of the parameters in the LF refining process are shown in table 4.
TABLE 4 Table 4
RH vacuum refining: and (3) performing quick vacuumizing treatment at an RH station, starting to add low-titanium low-aluminum ferrosilicon when the vacuum degree is below 20mbar, enabling the low-titanium low-aluminum ferrosilicon to reach target components (namely, adding calcium carbide deoxidization into a triangular area surrounded by two RH dip pipes and a steel ladle according to the mass percent ：C：0.25%-0.55%、Si：0.20%-0.60%、Mn：1.25%-1.85%、Cr：1.7%-2.2%、Mo：0.10%-0.40%、S：0.05%-0.15%、Ni≤0.02%、Cu≤0.015%、P≤0.015%、N≤0.0025%、H≤0.0002%、Alt≤0.0015%、Ti≤0.0008%）, at the same time, changing the lifting gas flow rate for molten steel slag deoxidization alloying to 150-200Nm 3/h, starting ladle bottom blowing stirring, and enabling the bottom blowing flow rate to be 50-100NL/min, closing ladle bottom blowing after the RH vacuum degree is below 2mbar, adding ferrosilicon alloy, enabling the processing time after the alloy addition is ended to be more than or equal to 15min, and then performing RH clean circulation, blank breaking tapping, soft stirring and sedation treatment after tapping, and then carrying out continuous casting pouring.
Low titanium low aluminum ferrosilicon Si:70% -80%, P is less than or equal to 0.008%, S is less than or equal to 0.0035%, al is less than or equal to 0.0025%, ti is less than or equal to 0.0015%, and Fe and other unavoidable components; S-Fe alloy: 30% -40% of iron and other unavoidable components; the addition amount of the calcium carbide is 0.5-0.8 kg/t; the bottom blowing ventilation of the two steel ladles is positioned below two triangular areas surrounded by the two dip pipes and the steel ladles.
Specific examples of the application of the method are given below, with some of the parameters during RH vacuum refining being shown in Table 5.
TABLE 5
Continuous casting: casting by adopting a slab continuous casting machine, wherein the thickness of the slab is 220 mm-320 mm, the width is 1500-2300 mm, and the pulling speed is 0.8-1.1 m/min; the whole process of continuous casting protects pouring, the argon blowing flow of the long nozzle is 150-250L/min, and the argon blowing flow of the stopper rod and the immersed nozzle is 3-5L/min.
The refractory materials of three parts (namely a continuous casting ladle long nozzle, a submerged nozzle and a stopper rod) of the ladle, the continuous casting tundish and the continuous casting, which are contacted with molten steel, are all made of low alumina materials, and the Al 2O3 content is less than or equal to 5 percent.
Specific examples of the application of the method are given below, and some of the parameters during continuous casting are shown in Table 6.
TABLE 6
And (3) hot rolling: and (3) delivering the casting blank obtained by continuous casting into a heating furnace, soaking at 950-1150 ℃ for more than or equal to 3 hours, and rolling to obtain a hot rolled plate with the thickness of more than 10 mm.
Specific examples of the application of the method are given below, and some of the parameters during hot rolling are shown in Table 7.
TABLE 7
The properties of the hot rolled sheet portions obtained in the above three examples are shown in Table 8 below.
TABLE 8
The technical means disclosed by the scheme of the invention is not limited to the technical means disclosed by the technical means, and also comprises the technical scheme formed by any combination of the technical features.
With the above-described preferred embodiments according to the present invention as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.
Claims (10)
1. The method for controlling the inclusion of the free-cutting alloy die steel is characterized by comprising the following steps of:
Step 1: smelting in a blast furnace: the method comprises the steps of selecting high-sulfur iron ore to make iron in blast furnace slag, carrying out KR non-desulfurization treatment to obtain high-sulfur molten iron, delivering the iron into a ladle, and conveying the ladle to a converter for smelting, wherein the molten iron in the ladle comprises the following components in percentage by mass: c:4.05% -4.55%, S:0.025% -0.075% and the temperature is 1380-1450 ℃;
Step 2: smelting in a converter: the converter loading amount is 200+/-5 t, the scrap steel ratio is 15% -20%, sulfur-containing common scrap steel is selected for smelting, when the converter smelting is finished and the temperature of molten steel is more than 1600 ℃, the content of C is 0.020% -0.045%, the content of S is 0.020% -0.065%, blowing is stopped, slag is blocked by adopting a sliding plate, and then tapping is carried out;
Step 3: tapping by a converter: when 20-30% of converter tapping is performed, firstly adding 20-30% of aluminum-containing ferrosilicon alloy and 50-60% of aluminum-containing manganese alloy into a ladle for deoxidization alloying, then adding ferrochrome alloy, ferromolybdenum alloy and carbon powder for alloying, then adding low-alkalinity calcium silicate to synthesize slag for slagging after the ferrochrome alloy, the ferromolybdenum alloy and the carbon powder are added, controlling the bottom blowing flow rate of the slag alkalinity CaO/SiO 2 = 0.5-1.0 in the tapping process to be 400NL/min, and stirring for 2-4min and then conveying to an LF furnace for treatment;
step 4: LF refining: fully starting bottom blowing argon, electrifying and heating, wherein the alloy manganese, ferrochrome and ferromolybdenum fully regulate the components and the temperature of molten steel to reach the standards, the argon flow of an air brick during heating is 200-300NL/min, the argon flow of the air brick during alloy manganese, ferrochrome and ferromolybdenum alloying is 300-400NL/min, and the argon flow of the air brick during the other time is 100-150NL/min; after the alloy components, the temperature and the slag components of the molten steel reach the standards, adding fine powder particles of lime and silicon carbide, controlling the alkalinity of ladle slag to be 1.5-2.0, and transporting the ladle slag to RH treatment;
Step 5: RH vacuum refining: the RH station entering quick vacuumizing treatment is carried out, when the vacuum degree is below 20mbar, low-titanium low-aluminum ferrosilicon alloy is added to enable the low-titanium low-aluminum ferrosilicon alloy to reach target components, meanwhile, calcium carbide is added into a triangular area surrounded by two RH dip pipes and a steel ladle to carry out calcium carbide deoxidation, after the molten steel slag deoxidation alloying is finished, the lifting gas flow is changed to 150-200Nm 3/h, the ladle bottom blowing stirring is carried out, and the bottom blowing flow is 50-100NL/min; closing the ladle bottom blowing after the RH vacuum degree is reduced to below 2mbar, adding the ferrosulfur alloy, after the addition of the ferrosulfur alloy is finished, processing time is more than or equal to 15min, then RH clean circulation, breaking and tapping, soft stirring and calm treatment after tapping, and then transporting to continuous casting pouring;
Step 6: continuous casting: casting by adopting a slab continuous casting machine, wherein the thickness of a slab is 220mm or 320mm, the width is 1500-2300 mm, and the pulling speed is 0.8-1.1 m/min; the whole process of continuous casting is protected and poured, the argon blowing flow of the long nozzle is 150-250L/min, and the argon blowing flow of the stopper rod and the immersed nozzle is 3-5L/min;
Step 7: and (3) hot rolling: and (3) delivering the casting blank obtained by continuous casting into a heating furnace, soaking at 950-1150 ℃ for more than or equal to 3 hours, and rolling to obtain a hot rolled plate with the thickness of more than 10 mm.
2. The method for controlling inclusions in free-cutting alloy die steel according to claim 1, wherein in the step 2, S:0.010% -0.035%, and the balance of Fe and other conventional components.
3. The method for controlling free-cutting alloy die steel inclusion according to claim 1, wherein sulfur-containing slag is added in the late stage of the converter smelting in the step 2, the addition amount of the sulfur-containing slag is 5-10 kg/t, the S content in the sulfur-containing slag is 3.0% -5.0%, caO is more than or equal to 88%, and other unavoidable components.
4. The method for controlling free-cutting alloy die steel inclusions according to claim 1, wherein the composition of the ferrosilicon alloy used for converter tapping in step 3 comprises, in mass percent: 73% -78% of Si, 3% -5% of Al, less than or equal to 0.013% of P, less than or equal to 0.002% of Ti, and the balance of Fe and other unavoidable components;
The manganese alloy mainly comprises the following components in percentage by mass: mn is more than or equal to 95%, al is 1-2%, P is less than or equal to 0.010%, ti is less than or equal to 0.0025%, and the balance is Fe and other unavoidable impurity components;
The ferrochrome comprises the following components in percentage by mass: cr:60% -65%, P is less than or equal to 0.012%, al is less than or equal to 0.0035%, ti is less than or equal to 0.002%, and the balance is Fe and other unavoidable impurity components;
the ferromolybdenum comprises the following components in percentage by mass: mo:45% -50%, P is less than or equal to 0.015%, al is less than or equal to 0.006%, ti is less than or equal to 0.004%, and the balance is Fe and other unavoidable impurity components;
The addition amount of the calcium silicate synthetic slag is 10-15 kg/t, and the components comprise the following components in percentage by mass: 35-45% of CaO, less than or equal to 2% of SiO 245%-55%、Al2O3%, 3-5% of MgO and other unavoidable components.
5. The method according to claim 1, wherein the alloy manganese component used in the LF refining in the step 4 comprises Mn not less than 98%, P not more than 0.010%, al not more than 0.0030%, ti not more than 0.0025%, and the balance Fe and other unavoidable impurity components in mass percent;
The ferrochrome comprises the following components in percentage by mass: 60% -65%, P is less than or equal to 0.012%, al is less than or equal to 0.0035%, ti is less than or equal to 0.002%, and the balance is Fe and other unavoidable impurity components;
the ferromolybdenum alloy comprises the following components in percentage by mass: 45% -50%, P is less than or equal to 0.015%, al is less than or equal to 0.006%, ti is less than or equal to 0.004%, and the balance is Fe and other unavoidable impurity components;
the addition amount of lime in the fine powder particles is 3-5 kg/t, caO is more than or equal to 95 percent, and other unavoidable components, the particle size is 1-5 mm, the ratio is more than or equal to 90 percent, and the maximum particle size is not more than 10mm;
SiC in silicon carbide is more than or equal to 95 percent, and other unavoidable components.
6. The method for controlling inclusions in free-cutting alloy die steel according to claim 1, wherein the low-titanium low-aluminum ferrosilicon composition in the RH vacuum refining in the step 5 includes, in mass%, si:70% -80%, P is less than or equal to 0.008%, S is less than or equal to 0.0035%, al is less than or equal to 0.0025%, ti is less than or equal to 0.0015%, and Fe and other unavoidable components;
The sulfur-iron alloy comprises the following components in percentage by mass: 30% -40% of iron and other unavoidable components;
the addition amount of the calcium carbide is 0.5-0.8 kg/t;
the bottom blowing ventilation of the two steel ladles is positioned below two triangular areas surrounded by the two dip pipes and the steel.
7. The method for controlling the inclusion of the free-cutting alloy die steel according to claim 1, wherein the steel ladle, the continuous casting tundish, the continuous casting ladle long nozzle, the immersed nozzle and the refractory material of which the stopper rod is in contact with the molten steel are all made of low alumina materials with the mass content of Al 2O3 percent or less.
8. The method for controlling the inclusion of the free-cutting alloy die steel according to claim 1, wherein scanning electron microscope is adopted to count oxide inclusions in the molten steel of the continuous casting tundish in the step 6, the counted area is 1000mm 2, the inclusion size of the oxide inclusions is 1-5 mu m, the inclusion proportion is more than 85%, the inclusion proportion is more than 10%, and the maximum size of the inclusion is not more than 25 mu m; the rolling ratio of the blank is more than or equal to 4, the aspect ratio of sulfide inclusions in the blank is more than or equal to 5, and the class A is more than or equal to 2.
9. A free-cutting alloy die steel produced by the free-cutting alloy die steel inclusion control method of claims 1-8.
10. The free-cutting alloy die steel of claim 9, wherein the free-cutting alloy die steel chemical composition comprises ：C：0.25%-0.55%、Si：0.20%-0.60%、Mn：1.25%-1.85%、Cr：1.7%-2.2%、Mo：0.10%-0.40%、S：0.05%-0.15%、Ni≤0.02%、Cu≤0.015%、P≤0.015%、T.O≤0.0015%、N≤0.0025%、H≤0.0002%、Alt≤0.0015%、Ti≤0.0008%, as well as Fe and other unavoidable components in mass percent.
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