CN112538589A - Preparation method of die-cast steel ingot - Google Patents
Preparation method of die-cast steel ingot Download PDFInfo
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- CN112538589A CN112538589A CN202011431792.XA CN202011431792A CN112538589A CN 112538589 A CN112538589 A CN 112538589A CN 202011431792 A CN202011431792 A CN 202011431792A CN 112538589 A CN112538589 A CN 112538589A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D7/00—Casting ingots, e.g. from ferrous metals
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
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- 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
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- 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
- C21C7/076—Use of slags or fluxes as treating agents
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- 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
Abstract
The invention provides a preparation method of a die-cast steel ingot, which comprises the following steps: smelting scrap steel and pig iron raw materials by adopting an electric arc furnace to obtain molten steel; refining the molten steel for the first time by adopting an LF ladle furnace to obtain alloy liquid; carrying out secondary refining on the alloy liquid by adopting a vacuum refining furnace to obtain refined liquid; and pouring the refining liquid to obtain a die-cast steel ingot. The method provided by the invention can effectively control the contents of hydrogen and nitrogen in the steel ingot of the plastic die steel to a lower level, is beneficial to improving and maintaining the comprehensive performance of the large module of the plastic die steel, and has good application prospect.
Description
Technical Field
The invention belongs to the technical field of die steel preparation, and particularly relates to a preparation method of a die-cast steel ingot.
Background
The high hydrogen content is the main reason causing the white point defect of the steel product, so that the product is scrapped; die steels with high nitrogen content will become brittle after long-term storage, and at the same time, the impact toughness, plasticity, formability, and weldability of the steel are significantly reduced. In medium carbon plastic die steel, the brittleness caused by high hydrogen and nitrogen contents in steel ingots is serious.
The medium-carbon chromium-containing plastic die steel contains alloy elements such as Cr, Ni, Mo and the like, and has high hardenability; moreover, because the steel contains alloy elements such as Ni, Cr and the like, the series of elements are intergrowth with hydrogen and nitrogen, and hydrogen and nitrogen are easy to absorb during production.
In the prior art, the control of chemical components is mainly emphasized when the conventional die-cast steel ingot is refined, and the control of hydrogen and nitrogen gases is in a weak link; at present, related researches on reducing the contents of hydrogen and nitrogen in the die steel and influencing the service life of the die steel through the interaction of chemical components are few in China.
Disclosure of Invention
In view of the above, the present invention provides a method for preparing a steel ingot of a mold steel, which can effectively control the contents of H and N in the steel ingot of the mold steel, so as to greatly improve the service life of the mold steel.
The invention provides a preparation method of a die-cast steel ingot, which comprises the following steps:
smelting the steel raw materials by adopting an electric arc furnace to obtain molten steel;
refining the molten steel for the first time by adopting an LF ladle furnace to obtain alloy liquid;
carrying out secondary refining on the alloy liquid by adopting a vacuum refining furnace to obtain refined liquid;
and pouring the refining liquid to obtain a die-cast steel ingot.
Preferably, the tapping temperature during the smelting is more than 1650 ℃.
Preferably, the mass content of H in the molten steel is less than or equal to 1.5 ppm; the mass content of N is less than or equal to 40 ppm.
Preferably, the mass content of H in the alloy liquid is 3.0-4.3 ppm; the mass content of N is 90-130 ppm.
Preferably, the time of the vacuum degree of < 67Pa in the secondary refining process is more than 15 min.
Preferably, the secondary refining comprises:
when the vacuum degree is reduced from one atmosphere to 67Pa, the flow rate of the argon is increased from 50Nl/min to 130 Nl/min;
and controlling the flow of the argon gas to be 130-200 Nl/min when the vacuum degree is less than or equal to 67 Pa.
Preferably, the secondary refining comprises:
and performing deoxidation treatment by using a Ca-Si wire.
Preferably, the method further comprises the following steps of:
argon gas was blown into the casting tube and the ingot mold used in the casting process.
Preferably, the mass content of H in the die-cast steel ingot is less than or equal to 1.2ppm, and the mass content of N in the die-cast steel ingot is less than or equal to 50 ppm.
Preferably, the casting method is a down-casting method.
The invention adopts the production process of electric furnace EBT + LF + VD + die casting, adopts the electric arc furnace with eccentric furnace bottom for primary smelting, and obtains molten steel with [ H ] less than or equal to 1.5ppm and [ N ] less than or equal to 30 ppm; refining in an LF ladle furnace: refining with large amount of slag, and reducing the nitrogen content in the molten steel to be below 100ppm by adding a pure aluminum wire in the later period; and (3) refining in a VD vacuum refining furnace: in the vacuum treatment process, ensuring that the time of the ultimate vacuum degree being less than 67pa is more than 15 minutes to ensure that [ H ] is less than or equal to 1.0ppm and [ N ] is less than or equal to 40ppm in the molten steel; when the die casting is carried out, 40t of commercial steel ingots made of special steel (plastic die steel) with [ H ] less than or equal to 1.2ppm and [ N ] less than or equal to 50ppm can be obtained by adopting a down-pouring method. The method provided by the invention provides high-quality steel ingots for large-scale mold production, and the adoption of the method provided by the invention realizes the localization of large-scale plastic molds in the plastic industry, can comprehensively meet the requirements of customers, and has good application and popularization prospects; can meet the urgent need of large moulds in the plastic industry and provide technical support for the development of the mould industry in China.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other examples, which may be modified or appreciated by those of ordinary skill in the art based on the examples given herein, are intended to be within the scope of the present invention. It should be understood that the embodiments of the present invention are only for illustrating the technical effects of the present invention, and are not intended to limit the scope of the present invention. In the examples, the methods used were all conventional methods unless otherwise specified.
The invention provides a preparation method of a die-cast steel ingot, which comprises the following steps:
smelting scrap steel and pig iron raw materials by adopting an electric arc furnace to obtain molten steel;
refining the molten steel for the first time by adopting an LF ladle furnace to obtain alloy liquid;
carrying out secondary refining on the alloy liquid by adopting a vacuum refining furnace to obtain refined liquid;
and pouring the refining liquid to obtain a die-cast steel ingot.
The method provided by the invention is suitable for manufacturing the plastic die steel ingot, in particular to the preparation of the plastic die steel ingot containing medium carbon and chromium, nickel and molybdenum.
In the present invention, the steel raw material preferably includes pig iron and scrap as an iron source, and the pig iron is preferably high-quality pig iron. In the invention, the pig iron and the scrap steel are preferably clean, dry and free of oil stains, and the requirements of the ingot for residual elements are completely met due to P, S and five-harmful elements in the alloy raw materials. In the invention, the addition amount of the alloy raw material is preferably more than 3200Kg, more preferably 3200 to 3600Kg, more preferably 3300 to 3500Kg, and most preferably 3400 Kg. In the invention, the mass ratio of the pig iron to the scrap steel is preferably (30-50): (50-70), more preferably (35-45): (55-65), most preferably 40: 60.
in the invention, the smelting process preferably further comprises adding alloy raw materials; the alloy feedstock preferably includes a Ni source, a Cr source, a Mn source, a V source, and a molybdenum source. In the present invention, the Ni source is preferably a Ni plate, the purity of which is preferably 99%; the Cr source is preferably a high Cr alloy, and the mass content of Cr in the high Cr alloy is preferably 50-60%, and more preferably 55.6%; the Mn source is preferably high-manganese alloy, and the mass content of Mn in the high-manganese alloy is preferably 68-72%, and more preferably 70%; the vanadium source is preferably a ferrovanadium alloy, and the mass content of vanadium in the ferrovanadium alloy is preferably 48-52%, and more preferably 50%; the molybdenum source is preferably a ferromolybdenum alloy, and the mass content of molybdenum in the ferromolybdenum alloy is preferably 58-62%, and more preferably 60%.
In the present invention, the electric arc furnace is preferably an eccentric hearth electric arc furnace. In the invention, the tapping temperature in the smelting process is preferably over 1650 ℃, more preferably 1650-1680 ℃, and most preferably 1660-1670 ℃; if the tapping temperature is lower than 1650 ℃, the refining time is very long, and the molten steel absorbs hydrogen and nitrogen seriously; the tapping temperature is higher than 1650 ℃, the refining time is greatly shortened, the nitrogen content in the molten steel is effectively controlled within 100ppm, the hydrogen content in the molten steel is effectively controlled between 3.0 ppm and 4.3ppm, and good conditions are created for secondary refining vacuum treatment.
In the invention, in the melting period in the melting process, high-power transmission is preferably adopted to melt the power, preferably 525-800 KW, more preferably 600-750 KW, and most preferably 650-700 KW; rapidly dephosphorizing by making aerobic slagging, ensuring that the oxidation temperature is higher than 1580 ℃, and ensuring a certain carbon content of the molten steel at the last stage of oxidation, wherein the carbon content of the molten steel is preferably 0.50-0.80% by mass, and more preferably 0.6-0.7% by mass; at the moment, the method of increasing the oxygen flow is adopted for quick decarburization, and hydrogen and nitrogen in the molten steel are removed as much as possible while decarburization is carried out (the hydrogen and the nitrogen in the molten steel are removed by a large amount of CO bubbles generated by C-O reaction at high temperature), so that the mass content of hydrogen in the molten steel at the end stage of smelting in an electric arc furnace is below 1.5ppm, and the mass content of nitrogen in the molten steel at the end stage of smelting in the electric arc furnace is below 30. In the invention, the mass content of H (hydrogen) in the molten steel is preferably less than or equal to 1.5ppm, and the mass content of N (nitrogen) in the molten steel is preferably less than or equal to 30 ppm.
In the present invention, the method for smelting preferably includes:
charging scrap steel and pig iron raw materials, feeding electricity for melting, making high-alkalinity silicate oxidizing slag, dephosphorizing at low temperature, oxidizing for decarbonizing, making foam slag, sampling and analyzing at the last stage of oxidation, and tapping.
In the invention, the alkalinity of the high-alkalinity silicate oxidation slag is preferably 4.8-6.0, and more preferably 5-5.5; the high-alkalinity silicate oxidation slag preferably comprises the following components:
55-60 wt% of CaO;
10 to 13 wt% of SiO2；
6-9 wt% FeO.
In the present invention, the CaO is present in a substantial amountThe content is preferably 56-59%, more preferably 57-58%, and most preferably 58%; the SiO2The mass content of (b) is preferably 11 to 12%, more preferably 11%; the mass content of the FeO is preferably 6.5%.
In the invention, the low-temperature dephosphorization temperature is preferably 1520-1550 ℃, more preferably 1530-1540 ℃ and most preferably 1535 ℃.
In the invention, the oxidation temperature in the oxidation decarbonization process is preferably more than 1580 ℃, more preferably 1580-1600 ℃, and most preferably 1590 ℃; the amount of decarburization is preferably not less than 0.30 wt%, more preferably 0.30 to 0.50 wt%, and most preferably 0.4 wt%. In the invention, the oxidation period in the oxidation and decarburization processes is preferably high-temperature oxidation and violent boiling, and the pure boiling time of the molten steel is preferably more than 10 minutes, so that the floating of gas and inclusions in the steel is facilitated.
In the present invention, the method for producing foamed slag preferably includes:
when the high alkalinity silicate oxidation slag is produced, carbon powder is sprayed on the slag surface.
In the invention, the spraying amount of the carbon powder is preferably 300-400 Kg, and more preferably 350 Kg.
The invention adopts foamed slag to prevent the molten steel from seriously absorbing hydrogen and nitrogen caused by air dissociation in an arc area.
In the invention, the sampling analysis of the quality content of H and N in the molten steel at the last stage of oxidation is preferred, and the quality content of H in the molten steel at the last stage of oxidation of the electric arc furnace is controlled to be less than or equal to 1.5ppm, and the quality content of N is controlled to be less than or equal to 30 ppm.
In the invention, a deoxidizer is preferably added into the molten steel in the tapping process, the deoxidizer is preferably Al, more preferably Al blocks, and the adding amount of the deoxidizer is preferably 2.5-3.5 Kg/t molten steel, more preferably 3Kg/t molten steel.
In the invention, an alloy is preferably added into molten steel in the tapping process, the alloy is preferably a low-chromium alloy, and the mass content of chromium in the low-chromium alloy is preferably 50-55%, and more preferably 52-53%; more preferably a red-baked alloy.
In the invention, slag charge is preferably added into molten steel in the tapping process, the slag charge preferably comprises lime and fluorite, and the mass ratio of the lime to the fluorite is preferably (1000-1500): 100, more preferably (1100 to 1400): 100, most preferably (1200 to 1300): 100, respectively; the slag is preferably a roasted red and powder-free slag. In the invention, the addition amount of the slag is preferably 45 to 55Kg/t of molten steel, more preferably 48 to 52Kg/t of molten steel, and most preferably 50Kg/t of molten steel.
In the invention, the primary refining is preferably large-slag refining, namely, a large amount of slag charge is added in the primary refining process; the slag preferably comprises lime and fluorite; the mass ratio of lime to fluorite is preferably (1000-1400): (100-300), more preferably (1100-1300): (150-250), most preferably 1200: 200 of a carrier; the preferable adding amount of the slag charge is 450 to 670Kg/t of molten steel, more preferably 500 to 600Kg/t of molten steel, and most preferably 550Kg/t of molten steel.
In the invention, molten steel is preferably selected in the primary refining process for alloying and temperature field control to obtain alloy liquid meeting the requirements; the alloying method preferably comprises:
and adding a Ni source, a Cr source, a Mn source, a V source and a molybdenum source into the molten steel.
In the present invention, the Ni source is preferably a Ni plate, the purity of which is preferably 99%; the Cr source is preferably a high Cr alloy, and the mass content of Cr in the high Cr alloy is preferably 50-60%, and more preferably 55.6%; the Mn source is preferably high-manganese alloy, and the mass content of Mn in the high-manganese alloy is preferably 68-72%, and more preferably 70%; the vanadium source is preferably a ferrovanadium alloy, and the mass content of vanadium in the ferrovanadium alloy is preferably 48-52%, and more preferably 50%; the molybdenum source is preferably a ferromolybdenum alloy, and the mass content of molybdenum in the ferromolybdenum alloy is preferably 58-62%, and more preferably 60%.
In the invention, the mass ratio of the Ni source, the Cr source, the Mn source, the V source and the molybdenum source is preferably (380-420): (1000-1400): (480-520): (55-65): (80-120), more preferably (390-410): (1100-1300): (490-510): (58-62): (90-110), most preferably 400: 1200: 500: 60: 100.
in the invention, the temperature field is preferably controlled to be 1670-1690 ℃ in the primary refining, more preferably 1675-1685 ℃ and most preferably 1680 ℃.
In the invention, after the molten steel enters the LF ladle refining furnace in the primary refining process, the flow of argon is preferably adjusted and power is supplied for refining, and the adjusted flow of argon is preferably 50-80 Nl/min, more preferably 60-70 Nl/min, and most preferably 65 Nl/min.
In the invention, in order to prevent nitrogen absorption caused by the fact that nitrogen in air enters molten steel during primary refining, large slag amount is preferably adopted and the temperature is rapidly raised during primary refining, the temperature raising speed is preferably 2-4 ℃/min, more preferably 3 ℃/min, mainly carbon powder is reduced, refined slag (slag charge CaO:500Kg and refined slag 400Kg) is rapidly manufactured, alloying is carried out, and the deoxidation and the desulfurization of the molten steel are ensured to be good, preferably, S is controlled to be less than or equal to 0.007 wt%, and S + P is controlled to be less than or equal to 0.018 wt%; controlling the nitrogen content in the molten steel to be reduced to below 100ppm preferably by feeding an aluminum wire according to the nitrogen content in the molten steel; preferably, the mass content of hydrogen in the molten steel is effectively controlled to be below 4.3ppm by greatly shortening the refining time; the refining time is preferably 40-60 min, more preferably 45-55 min, and most preferably 50 min.
In the invention, the whole process of the molten steel in the primary refining process belongs to the processes of increasing hydrogen and nitrogen, and the mass content of hydrogen in the obtained alloy liquid is preferably 3.0-4.3 ppm, more preferably 3.5-4.0 ppm; the mass content of nitrogen is preferably 80 to 110ppm, more preferably 90 to 100 ppm.
In the present invention, the primary refining method preferably includes:
molten steel is put into a tank, temperature is measured, and refined slag is produced.
In the present invention, the primary refining method more preferably includes:
adding lime and fluorite into molten steel, transmitting power to raise temperature, performing reduction refining by using carbon powder according to white slag operation, and performing sampling analysis, fine adjustment of components and sampling total analysis.
In the invention, the addition amount of the lime is preferably 400-600 Kg/t of molten steel, more preferably 450-550 Kg/t of molten steel, and most preferably 500Kg/t of molten steel; the adding amount of the fluorite is preferably 50-70 Kg/t of molten steel, more preferably 55-65 Kg/t of molten steel, and most preferably 60Kg/t of molten steel.
In the invention, the temperature of the power transmission and temperature rise is preferably 1670-1690 ℃, more preferably 1675-1685 ℃ and most preferably 1680 ℃.
In the present invention, the method of white slag operation preferably comprises:
adding slag CaO, refining slag and steel slag into the molten steel, wherein the refining slag is changed from light green to white.
The mass ratio of CaO, refining slag and steel slag is preferably (480-520): (380-420): (130-170), more preferably (490-510): (390-410): (140 to 160), most preferably 500: 400: 150.
in the invention, the holding time of the white slag in the white slag operation process is preferably not less than 15min, more preferably 15-30 min, and most preferably 20-25 min.
In the invention, the use amount of the carbon powder is preferably 2-3 Kg/t of molten steel, and more preferably 2.5Kg/t of molten steel.
In the invention, the sampling analysis is preferably carried out when the white slag fluidity and the molten steel deoxidation are good, the temperature is more than or equal to 1670 ℃, and the S is less than or equal to 0.008 wt%.
In the invention, the aluminum content in the molten steel is preferably controlled to be 0.05-0.07%, and more preferably 0.06% in the component fine-tuning process; the mass content of nitrogen is less than 100 ppm.
In the invention, the chemical composition of the alloy liquid preferably meets the requirements by sampling and total analysis.
In the present invention, it is preferable to perform secondary refining using a VD vacuum refining furnace.
In the present invention, in order to ensure the degassing effect of the VD vacuum refining furnace and the gas permeability and dehydrogenation and denitrification effects of the refining slag, it is preferable to reduce the amount of slag appropriately before the vacuum treatment of the alloy liquid to ensure good slag gas permeability during the vacuum treatment. In the present invention, before the vacuum treatment in the secondary refining process, it is preferable that: 40-60% of deslagging, more preferably 45-60%, and most preferably 60%.
In the invention, the thickness of the slag in the secondary refining process is preferably controlled to be less than or equal to 40mm, more preferably 30-40 mm, and most preferably 35 mm.
In the invention, the secondary refining process preferably carries out vacuum treatment at the temperature of not less than 1680 ℃ of molten steel, and more preferably carries out vacuum treatment at the temperature of 1680-1690 ℃.
In the present invention, it is preferable to reduce the oxygen content and inclusions in the molten alloy to as low levels as possible by vacuum treatment and deoxidation treatment with Ca-Si. The invention effectively controls the hydrogen content to be less than 1.0ppm and the nitrogen content to be less than 50ppm by vacuum treatment, and simultaneously reduces the nitrogen and hydrogen content in the alloy liquid as much as possible by VD vacuum treatment.
In the invention, the time of vacuum degree < 67Pa is preferably more than 15 minutes, the vacuum degree is preferably less than 50Pa, the time is preferably 16-22 minutes, the mass content of nitrogen in the refining liquid is preferably less than or equal to 40ppm, and the mass content of hydrogen in the refining liquid is preferably less than or equal to 1.0ppm during the vacuum treatment in the secondary refining process.
In the present invention, it is preferable that the flow rate of argon is reasonably adjusted in the secondary refining vacuum treatment process, and the method of adjusting the flow rate of argon preferably includes:
when one atmospheric pressure is reduced to 67Pa in the vacuum treatment process, the flow rate of argon is increased from 50Nl/min to 130 Nl/min; and when the vacuum degree is less than or equal to 67Pa, controlling the flow of argon to be 130-200 Nl/min.
In the invention, the argon flow is preferably controlled to be 140-190 Nl/min, more preferably 150-180 Nl/min, and most preferably 160-170 Nl/min.
The invention can make the dehydrogenation rate reach more than 70% and the denitrification rate reach more than 50% by controlling the argon flow.
In the present invention, the secondary refining process preferably includes:
and performing deoxidation treatment by using a Ca-Si wire.
In the present invention, the composition of the Ca — Si wire preferably includes:
20-30 wt% of Ca;
50 to 70 wt% of Si.
In the present invention, the mass content of Ca is preferably 25% Ca; the mass content of Si is preferably 55-65%, more preferably 60%.
In the invention, the addition amount of the Ca-Si wire is preferably 180-220 m.
In the present invention, the secondary refining is preferably performed so that the mass content of hydrogen in the alloy liquid is reduced from 4.0ppm before the secondary refining to 1.10 ppm; the mass content of nitrogen is reduced to 40ppm or less from 100ppm before secondary refining.
In the present invention, the betting method preferably includes:
the refining liquid flows into the ingot mould through the bottom hole of the mould after being injected into the middle injection pipe.
In the invention, before the pouring, argon is preferably blown into a casting pipe or an ingot mould in the pouring process to exhaust air, so that the suction of molten steel in the casting process is prevented, and the increase of hydrogen and nitrogen in the refining liquid in the pouring process is effectively prevented; the mass content of hydrogen in the obtained cast ingot is preferably less than or equal to 1.2ppm, and the mass content of N is preferably less than or equal to 50 ppm.
In the present invention, the composition of the plastic mold steel ingot preferably includes:
0.35 to 0.45 wt% carbon;
1.5-2.0 wt% of chromium;
1.0 to 1.2 wt% of nickel;
0.15 to 0.25 wt% molybdenum;
the mass content of H is less than or equal to 1.2 ppm;
the mass content of N is less than or equal to 50 ppm;
the mass content of O is less than or equal to 15 ppm;
the balance being iron.
In the invention, the mass content of the carbon is preferably 0.38-0.42%, and more preferably 0.4%; the mass content of the chromium is preferably 1.6-1.9%, and more preferably 1.7-1.8%; the mass content of the nickel is preferably 1.1%; the mass content of the molybdenum is preferably 0.18-0.22%, and most preferably 0.20%.
In the present invention, the mass of the cast steel slab is preferably 35 to 45 tons, more preferably 38 to 42 tons, and most preferably 40 tons.
The preparation method of the die-cast steel ingot provided by the invention has the advantages of simple process and convenience in control, and can effectively control the contents of hydrogen and nitrogen in the steel ingot of special steel (iron-based plastic die steel) to a lower level, so that the large plastic die in the plastic industry is made to realize localization, and the preparation method has a good application prospect.
Example 1
Preparing materials: high-quality pig iron and waste steel, Ni plates with the purity of 99 percent, high Cr alloy with the purity of 50.6 percent, high manganese alloy with the purity of 70 percent, ferrovanadium alloy with the purity of 50 percent and ferromolybdenum alloy with the purity of 60 percent are adopted for mixing, the mass content of the high-quality pig iron (C is more than or equal to 3.5 percent by weight, Mn is less than or equal to 0.50 percent by weight and P is less than or equal to 0.10 percent by weight) in the high-quality pig iron and the waste steel is 40 percent, and the mass content of the waste steel (C is less than or equal to 0.5 percent by weight, Mn is less than or equal to 0.50 percent by weight and.
Smelting in an electric arc furnace with an eccentric furnace bottom:
the process flow comprises the following steps: charging, electric power transmission melting, and making high alkalinity (R is 5.5) silicate oxidizing slag (the components include CaO 58 wt%, SiO211 wt% and FeO 6.5 wt%) to dephosphorize at low temperature (1530 ℃) below 0.006 wt% and to oxidize and decarbonize (oxidizing temperature 1590 ℃ and decarbonize 0.4 wt%); the oxidation period is required to realize high-temperature oxidation and violent boiling, and the pure boiling time of the molten steel is more than 10 minutes, so that the floating of gas and impurities in the steel is facilitated; foaming slag (350 Kg of carbon powder is sprayed on the slag surface when high alkalinity silicate oxidizing slag is produced) is produced, so that the serious hydrogen and nitrogen absorption of molten steel caused by the air dissociation in an arc region is prevented; analysis of samples taken at the end of Oxidation [ H]、[N]Content, controlling [ H ] in molten steel at last stage of oxidation in electric arc furnace]≤1.5ppm、[N]Tapping at the bottom of the eccentric furnace to a steel ladle at a concentration of less than or equal to 30ppm, and adding a deoxidizer into the steel ladle in the tapping process: 3Kg of Al block per t of molten steel; alloy: adding baked red low Cr alloy (Cr mass content is 52%) for 1.0 t; slag charging: baking red and no powdered lime 10Kg/t molten steel, fluorite 2.0Kg/t molten steel.
Refining in an LF ladle furnace:
the process flow comprises the following steps: putting into a tank, measuring temperature and refining slag, and specifically comprises the following steps: adding 13Kg/t molten steel of CaO of lime, 10Kg/t molten steel of refined slag and 4Kg/t molten steel of steel slag into the molten steel; feeding electricity and heating up to 1680 ℃, operating the LF ladle refining furnace according to white slag (the refined slag is changed from light green to white), and reducing and refining by using carbon powder, wherein the white slag is kept for 20min, and the using amount of the carbon powder is 2.5Kg/t molten steel; the white slag fluidity and the molten steel deoxidation are good, the temperature is more than or equal to 1670 ℃, and when the S is less than or equal to 0.008 wt%, sampling and total analysis are carried out; and (3) finely adjusting components, controlling the mass content of aluminum in the molten steel to be 0.06 wt%, controlling the mass content of nitrogen to be less than 100ppm, and completely analyzing sampling (including nitrogen content analysis) to ensure that chemical components completely meet the requirements of a protocol.
And (3) refining in a VD vacuum refining furnace:
performing vacuum treatment on the alloy liquid at the temperature of 1685 ℃ (considering deslagging and cooling before vacuum furnace treatment), wherein in the vacuum treatment process, in order to ensure the air permeability and dehydrogenation and denitrification effects of the refining slag, the vacuum operation can be performed when 50% of deslagging before vacuum treatment is performed, and the thickness of the slag is controlled to be 35 mm; the retention time is 20min when the ultimate vacuum degree is less than or equal to 50Pa, the argon flow is reasonably adjusted in the vacuum treatment process, and the specific adjustment steps are as follows: when the atmospheric pressure is reduced to 50Pa, the argon flow is gradually increased from 50Nl/min to 130 Nl/min; then, in the process of keeping the vacuum degree less than or equal to 67Pa, controlling the flow of argon gas at 170Nl/min, thus leading the dehydrogenation rate to reach more than 70 percent and the denitrification rate to reach more than 50 percent; in the vacuum treatment process, the hydrogen content in the alloy liquid is reduced to below 1.10ppm from 4.0ppm before vacuum refining, and the nitrogen content is reduced to below 40ppm from 100ppm before vacuum refining; high-quality refined molten steel can be obtained by vacuum treatment.
And (3) casting in a lower casting method:
during die casting, a downward pouring method is adopted (the refining molten steel is poured into an injection pipe and flows into an ingot mould through a mould bottom hole), argon is blown into the casting pipe and the ingot mould to discharge air before casting, so that hydrogen and nitrogen are effectively prevented from being added to the refining liquid in the casting process, and 40t sixteen-side large steel ingots with [ H ] less than or equal to 1.2ppm and [ N ] less than or equal to 50ppm can be obtained.
The steel ingot prepared in the embodiment 1 of the invention is subjected to component detection by adopting a direct-reading spectrometer, a carbon-sulfur analyzer, an oxygen-nitrogen analyzer and a hydrogen analyzer, and the detection result is as follows: 0.38 wt% of carbon, 1.6 wt% of chromium, 1.05 wt% of nickel, 0.20 wt% of molybdenum, 0.05 wt% of vanadium, 1.2ppm of hydrogen, 50ppm of nitrogen, 13ppm of oxygen and the balance of iron.
Example 2
Preparing materials: high-quality pig iron and waste steel, Ni plates with the purity of 99 percent, high Cr alloy with the purity of 50.6 percent, high manganese alloy with the purity of 70 percent, ferrovanadium alloy with the purity of 50 percent and ferromolybdenum alloy with the purity of 60 percent are adopted for mixing, the mass content of the high-quality pig iron (C is more than or equal to 3.5 percent by weight, Mn is less than or equal to 0.50 percent by weight and P is less than or equal to 0.10 percent by weight) in the high-quality pig iron and the waste steel is 45 percent, and the mass content of the waste steel (C is less than or equal to 0.5 percent by weight, Mn is less than or equal to 0.50 percent by weight and.
Smelting in an electric arc furnace with an eccentric furnace bottom:
the process flow comprises the following steps: charging, electric power transmission melting, and making high alkalinity (R is 4.8) silicate oxidizing slag (the components include CaO 56 wt%, SiO210 wt% of FeO 8 wt%) to dephosphorize at low temperature (1520 ℃) below 0.006 wt% and to oxidize and decarbonize (oxidizing temperature 1580 ℃, decarbonize amount 0.30 wt%); the oxidation period is required to realize high-temperature oxidation and violent boiling, and the pure boiling time of the molten steel is more than 10 minutes, so that the floating of gas and impurities in the steel is facilitated; foaming slag (350 Kg of carbon powder is sprayed on the slag surface when high alkalinity silicate oxidizing slag is produced) is produced, so that the serious hydrogen and nitrogen absorption of molten steel caused by the air dissociation in an arc region is prevented; analysis of samples taken at the end of Oxidation [ H]、[N]Content, controlling [ H ] in molten steel at last stage of oxidation in electric arc furnace]≤1.5ppm、[N]Tapping at the bottom of the eccentric furnace to a steel ladle at a concentration of less than or equal to 30ppm, and adding a deoxidizer into the steel ladle in the tapping process: 3Kg of Al block per t of molten steel; alloy: adding baked red low Cr alloy (Cr mass content is 52%) for 1.0 t; slag charging: roasted red, 11Kg/t molten steel without powdered lime and 1.8Kg/t fluorite.
Refining in an LF ladle furnace:
the process flow comprises the following steps: putting into a tank, measuring temperature and refining slag, and specifically comprises the following steps: adding 15Kg/t molten steel of CaO, 10Kg/t molten steel of refined slag and 3.8Kg/t molten steel of steel slag into the molten steel; transmitting power, heating to 1670 ℃, operating the LF ladle refining furnace according to white slag (the refined slag is changed from light green to white), and reducing and refining by using carbon powder, wherein the white slag is kept for 15min, and the using amount of the carbon powder is 2.5Kg/t molten steel; the white slag fluidity and the molten steel deoxidation are good, the temperature is more than or equal to 1670 ℃, and when the S is less than or equal to 0.008 wt%, sampling and total analysis are carried out; and (3) finely adjusting components, controlling the mass content of aluminum in the molten steel to be 0.06 wt%, controlling the mass content of nitrogen to be less than 100ppm, and completely analyzing sampling (including nitrogen content analysis) to ensure that chemical components completely meet the requirements of a protocol.
And (3) refining in a VD vacuum refining furnace:
performing vacuum treatment on the alloy liquid at the temperature of 1680 ℃ (considering deslagging and cooling before vacuum furnace treatment), and in the vacuum treatment process, in order to ensure the air permeability and dehydrogenation and denitrification effects of the refining slag, the vacuum operation is required to be performed when 50% of slag is removed before vacuum treatment, and the thickness of the slag is controlled to be 30 mm; the holding time is 16min when the ultimate vacuum degree is less than or equal to 67Pa, the argon flow is reasonably adjusted in the vacuum treatment process, and the specific adjustment steps are as follows: when the atmospheric pressure is reduced to 67Pa, the argon flow is gradually increased from 50Nl/min to 130 Nl/min; then, in the process of keeping the vacuum degree less than or equal to 67Pa, controlling the flow of argon gas at 120Nl/min, thus leading the dehydrogenation rate to reach more than 72 percent and the denitrification rate to reach more than 50 percent; in the vacuum treatment process, the hydrogen content in the alloy liquid is reduced to below 1.10ppm from 4.1ppm before vacuum refining, and the nitrogen content is reduced to below 40ppm from 90ppm before vacuum refining; high-quality refined molten steel can be obtained by vacuum treatment.
And (3) casting in a lower casting method:
during die casting, a downward pouring method is adopted (the refining molten steel is poured into an injection pipe and flows into an ingot mould through a mould bottom hole), argon is blown into the casting pipe and the ingot mould to discharge air before casting, so that hydrogen and nitrogen are effectively prevented from being added to the refining liquid in the casting process, and a twelve-side 39t large steel ingot with [ H ] less than or equal to 1.2ppm and [ N ] less than or equal to 50ppm can be obtained.
The steel ingot prepared in the embodiment 2 of the invention is subjected to component detection by adopting a direct-reading spectrometer, a carbon-sulfur analyzer, an oxygen-nitrogen analyzer and a hydrogen analyzer, and the detection result is as follows: 0.39 wt% of carbon, 1.63 wt% of chromium, 1.08 wt% of nickel, 0.21 wt% of molybdenum, 0.05 wt% of vanadium, 1.0ppm of hydrogen, 48ppm of nitrogen, 12ppm of oxygen and the balance of iron.
Example 3
Preparing materials: high-quality pig iron and waste steel, Ni plates with the purity of 99 percent, high Cr alloy with the purity of 50.6 percent, high manganese alloy with the purity of 70 percent, ferrovanadium alloy with the purity of 50 percent and ferromolybdenum alloy with the purity of 60 percent are adopted for mixing, the mass content of the high-quality pig iron (C is more than or equal to 3.5 percent by weight, Mn is less than or equal to 0.50 percent by weight and P is less than or equal to 0.10 percent by weight) in the high-quality pig iron and the waste steel is 50 percent, and the mass content of the waste steel (C is less than or equal to 0.5 percent by weight, Mn is less than or equal to 0.50 percent by.
Smelting in an electric arc furnace with an eccentric furnace bottom:
the process flow comprises the following steps: charging, electric power transmission melting, and making high alkalinity (R is 6.0) silicate oxidizing slag (the components include CaO 60 wt%, SiO212 wt% and FeO 6 wt%) to below 0.005 wt% and oxidation decarbonization (oxidation temperature 1600 deg.C, decarbonization amount 0.5 wt%); the oxidation period is required to realize high-temperature oxidation and violent boiling, and the pure boiling time of the molten steel is more than 10 minutes, so that the floating of gas and impurities in the steel is facilitated; foaming slag (when high alkalinity silicate oxidizing slag is produced, 400Kg of carbon powder is sprayed on the slag surface) to prevent the molten steel from seriously absorbing hydrogen and nitrogen caused by the air dissociation in an arc region; analysis of samples taken at the end of Oxidation [ H]、[N]Content, controlling [ H ] in molten steel at last stage of oxidation in electric arc furnace]≤1.5ppm、[N]Tapping at the bottom of the eccentric furnace to a steel ladle at a concentration of less than or equal to 30ppm, and adding a deoxidizer into the steel ladle in the tapping process: 3Kg of Al block per t of molten steel; alloy: adding baked red low Cr alloy (Cr mass content is 52%) for 1.2 t; slag charging: roasted red without powdered lime 11Kg/t molten steel and fluorite 1.5Kg/t molten steel.
Refining in an LF ladle furnace:
the process flow comprises the following steps: putting into a tank, measuring temperature and refining slag, and specifically comprises the following steps: adding 15Kg/t molten steel of CaO, 10Kg/t molten steel of refined slag and 5Kg/t molten steel of steel slag into the molten steel; transmitting electricity, heating to 1690 ℃, operating the LF ladle refining furnace according to white slag (the refined slag is changed from light green to white), and reducing and refining by using carbon powder, wherein the white slag is kept for 22min, and the using amount of the carbon powder is 2.5Kg/t molten steel; the white slag fluidity and the molten steel deoxidation are good, the temperature is more than or equal to 1670 ℃, and when the S is less than or equal to 0.008 wt%, sampling and total analysis are carried out; and (3) finely adjusting components, controlling the mass content of aluminum in the molten steel to be 0.05 wt%, controlling the mass content of nitrogen to be less than 90ppm, and completely analyzing sampling (including nitrogen content analysis) to ensure that chemical components completely meet the requirements of a protocol.
And (3) refining in a VD vacuum refining furnace:
performing vacuum treatment on the alloy liquid at the temperature of 1690 ℃ (considering deslagging and cooling before vacuum furnace treatment), wherein in the vacuum treatment process, in order to ensure the air permeability and dehydrogenation and denitrification effects of refining slag, vacuum operation can be performed when 50% of slag is removed before vacuum treatment, and the thickness of slag is controlled to be 40 mm; the retention time is 22min when the ultimate vacuum degree is less than or equal to 67Pa, the argon flow is reasonably adjusted in the vacuum treatment process, and the specific adjustment steps are as follows: when the atmospheric pressure is reduced to 67Pa, the argon flow is gradually increased from 50Nl/min to 130 Nl/min; then, in the process of keeping the vacuum degree less than or equal to 67Pa, controlling the flow of argon gas at 200Nl/min, thus leading the dehydrogenation rate to reach more than 70 percent and the denitrification rate to reach more than 52.8 percent; in the vacuum treatment process, the hydrogen content in the alloy liquid is reduced to below 1.03ppm from 4.0ppm before vacuum refining, and the nitrogen content is reduced to below 30ppm from 100ppm before vacuum refining; high-quality refined molten steel can be obtained by vacuum treatment.
And (3) casting in a lower casting method:
during die casting, a downward pouring method is adopted (the refining molten steel is poured into an injection pipe and flows into an ingot mould through a mould bottom hole), argon is blown into the casting pipe and the ingot mould to discharge air before casting, so that hydrogen and nitrogen are effectively prevented from being added to the refining liquid in the casting process, and 40t sixteen-side large steel ingots with [ H ] less than or equal to 1.2ppm and [ N ] less than or equal to 48ppm can be obtained.
The steel ingot prepared in the embodiment 3 of the invention is subjected to component detection by adopting a direct-reading spectrometer, a carbon-sulfur analyzer, an oxygen-nitrogen analyzer and a hydrogen analyzer, and the detection result is as follows: 0.37 wt% of carbon, 1.65 wt% of chromium, 1.06 wt% of nickel, 0.22 wt% of molybdenum, 0.05 wt% of vanadium, 1.03ppm of hydrogen, 49ppm of nitrogen, 10ppm of oxygen and the balance of iron.
The manufacturing method of the special steel (iron-based plastic die steel) die casting and pouring method 40-ton steel ingot provided by the embodiment of the invention has the advantages of simple process and strong practicability, can effectively control the contents of hydrogen, nitrogen and oxygen in the steel ingot of the plastic die steel to lower levels, is beneficial to realizing the localization of large plastic dies in the plastic industry, and has good application prospect; the steel ingot of the plastic die steel manufactured by the embodiment of the invention has the contents of [ H ] less than or equal to 1.2ppm, [ N ] less than or equal to 50ppm and [ O ] less than or equal to 15 ppm. The preparation method of the die-cast steel ingot provided by the invention has the advantages of simple process and convenience in control, and can effectively control the contents of hydrogen and nitrogen in the steel ingot of special steel (iron-based plastic die steel) to a lower level, so that the large plastic die in the plastic industry is made to realize localization, and the preparation method has a good application prospect.
Although the method of manufacturing a special steel (iron-based plastic mold steel) die cast 40-ton ingot of the present invention has been described above in connection with the exemplary embodiments, it will be apparent to those skilled in the art that various refinements and modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims. While only the preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (10)
1. A method for preparing a cast steel ingot comprises the following steps:
smelting the steel raw materials by adopting an electric arc furnace to obtain molten steel;
refining the molten steel for the first time by adopting an LF ladle furnace to obtain alloy liquid;
carrying out secondary refining on the alloy liquid by adopting a vacuum refining furnace to obtain refined liquid;
and pouring the refining liquid to obtain a die-cast steel ingot.
2. The method according to claim 1, characterized in that the tapping temperature during the smelting is > 1650 ℃.
3. The method according to claim 1, wherein the mass content of H in the molten steel is less than or equal to 1.5 ppm; the mass content of N is less than or equal to 40 ppm.
4. The method according to claim 1, wherein the mass content of H in the alloy liquid is 3.0 to 4.3 ppm; the mass content of N is 90-130 ppm.
5. The method according to claim 1, wherein the time of vacuum degree < 67Pa in the secondary refining process is > 15 min.
6. The method according to claim 1, wherein the secondary refining comprises:
when the vacuum degree is reduced from one atmosphere to 67Pa, the flow rate of the argon is increased from 50Nl/min to 130 Nl/min;
and controlling the flow of the argon gas to be 130-200 Nl/min when the vacuum degree is less than or equal to 67 Pa.
7. The method according to claim 1, wherein the secondary refining comprises:
and performing deoxidation treatment by using a Ca-Si wire.
8. The method of claim 1, further comprising, prior to said pouring:
argon gas was blown into the casting tube and the ingot mold used in the casting process.
9. A method according to claim 1, characterized in that the mass content of H in the ingot is equal to or less than 1.2ppm and the mass content of N is equal to or less than 50 ppm.
10. The method of claim 1, wherein the casting is performed by a down-cast method.
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