CN111850385B - Silicon-molybdenum turbocharger shell and preparation method thereof - Google Patents

Silicon-molybdenum turbocharger shell and preparation method thereof Download PDF

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CN111850385B
CN111850385B CN202010705187.0A CN202010705187A CN111850385B CN 111850385 B CN111850385 B CN 111850385B CN 202010705187 A CN202010705187 A CN 202010705187A CN 111850385 B CN111850385 B CN 111850385B
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silicon
iron
molten iron
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inoculant
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CN111850385A (en
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田政
田龙
田中青
王青松
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Xixia Zhongde Automobile Parts Co ltd
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Xixia Zhongde Automobile Parts Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/10—Cast-iron alloys containing aluminium or silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/08—Making cast-iron alloys
    • C22C33/10—Making cast-iron alloys including procedures for adding magnesium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/06—Cast-iron alloys containing chromium
    • C22C37/08—Cast-iron alloys containing chromium with nickel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
    • F01D25/005—Selecting particular materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
    • F01D25/24—Casings; Casing parts, e.g. diaphragms, casing fastenings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

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  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Abstract

The invention relates to the field of casting metallurgy, in particular to a silicon-molybdenum turbocharger shell, which comprises the following components in percentage by weight: 2.9-3.2% of C, 3.9-4.4% of Si, less than 0.30% of Mn, 0.012-0.020% of S, less than 0.05% of P, 0.5-0.7% of Mo, less than 0.50% of Cr, less than 0.50% of Cu, less than 0.60% of Ni, less than or equal to 0.20% of Ti and the balance of Fe.

Description

Silicon-molybdenum turbocharger shell and preparation method thereof
Technical Field
The invention relates to the field of casting metallurgy, in particular to a silicon-molybdenum turbocharger shell and a preparation method thereof.
Background
The vermicular graphite cast iron has the advantages of excellent casting heat conduction and shock absorption performance of gray cast iron and the advantages of wear resistance, high strength and high plasticity of the nodular cast iron, is widely applied to the production of automobile parts such as automobile exhaust pipes, turbocharger shells of engines, cylinder covers and cylinder liners, and has more and more strict requirements on automobile discharge capacity along with the attention of people on environmental protection in recent years, the requirements on the power of automobile engines are higher and higher, and the increase of the power of the automobile engines causes the working temperature to be higher and higher, and the thermal fatigue load and the mechanical load of the engines to be greatly increased.
According to the national standard, the vermicular cast iron has a vermicular rate of more than 50%, and is a cast iron between nodular cast iron and gray cast iron, if the vermicular rate is low, the performance of the vermicular cast iron is close to that of nodular cast iron, and if the vermicular rate is over 90%, the vermicular cast iron is close to that of gray cast iron, so that the performance of the vermicular cast iron is good when the vermicular rate is controlled to be 55-85%.
The conventional method for producing vermicular cast iron adopts a vermicular agent made of high rare earth low magnesium alloy for vermicular treatment, but because of the special use performance of the vermicular cast iron, the special solidification characteristic of the vermicular cast iron in an as-cast state is determined, and the vermicular cast iron is influenced by factors such as the vermicular graphite characteristic, the segregation distribution and cooling speed of carbon and alloy elements, the inherent structure of a casting, the wall thickness irregularity and the heat node change of the casting, and the like, the continuous shrinkage and expansion of the casting can be caused by the cold and hot alternation in the thermal fatigue process, the heat dissipation of the casting with high vermicular cast iron is good, otherwise, the stress concentration is easy to cause the cracking of the casting to fail in advance due to the inconsistent heat dissipation, the service life of the casting is greatly reduced, the conventional production method is difficult to obtain the vermicular cast iron with high and stable vermicular cast iron, or the vermicular cast iron with low vermicular rate of less than or the vermicular rate of 50 percent at the thin wall of the casting is qualified, however, gray iron graphite is formed at the thick wall and cannot be used, and the prior vermicular graphite cast iron production needs a two-step method for inoculation twice, so that the production efficiency is low.
Meanwhile, the failure analysis of the vermicular cast iron casting shows that the main reason of the casting cracking is that the difference of the vermicular rate of the thick wall and the thin wall is large, the sensitivity of the wall thickness is high, the vermicular rate of the thick wall is high, the vermicular rate of the thin wall is low, the difference of the vermicular rates causes uneven heat dissipation of the casting, the difference of expansion coefficients during thermal expansion is large, the thermal stress of the casting is uneven, the casting is broken and fails, and the problem of the sensitivity of the section is urgently needed to be solved at present.
Disclosure of Invention
The invention provides a silicon-molybdenum turbocharger shell and a preparation method thereof, aims to provide a turbocharger shell which is high in heat resistance, stable in creep rate, small in section creep rate difference and small in thermal sensitivity, solves the problems that an existing vermicular cast iron casting is unstable in creep rate, high in section thermal sensitivity and easy to break, and provides a preparation method which is simple and easy to operate.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the first object of the invention is to provide a silicon-molybdenum turbocharger housing, which comprises the following components in percentage by weight: 2.9 to 3.2 percent of C, 3.9 to 4.4 percent of Si, less than 0.30 percent of Mn, 0.012 to 0.020 percent of S, less than 0.05 percent of P, 0.5 to 0.7 percent of Mo, less than 0.50 percent of Cr, less than 0.50 percent of Cu, less than 0.60 percent of Ni, less than or equal to 0.20 percent of Ti, and the balance of iron.
Preferably, the following components are included in percentage by weight: 3.0-3.2% of C, 3.9-4.1% of Si, less than 0.2% of Mn, 0.012-0.020% of S, less than 0.029% of P, 0.5-0.7% of Mo, less than 0.45% of Cr, less than 0.40% of Cu, less than 0.60% of Ni, less than or equal to 0.12% of Ti, and the balance of iron.
The invention also aims to provide a preparation method of the silicon-molybdenum turbocharger shell, which comprises the following steps:
(1) melting the ingredients: sequentially adding 30-50 wt% of pig iron and 50-70 wt% of briquetting low-manganese scrap steel into a medium-frequency electric furnace for melting, and then adding 0.5-0.7 wt% of ferromolybdenum and a proper amount of ferrosilicon to obtain molten iron;
(2) analysis and control: controlling the temperature of the molten iron in the step (1) to be 1540-1560 ℃, powering off, standing for 3-5 minutes at 1540-1560 ℃, performing spectral analysis on a molten iron sample in the furnace, adjusting chemical components to obtain required chemical components of the molten iron, and detecting the sulfur content of the molten iron;
(3) primary creeping and inoculation treatment before furnace: controlling the tapping temperature of the base molten iron to be 1460-1500 ℃, sequentially adding a low-silicon spheroidizing alloy and an inoculant to the bottom of a pit ladle of a pouring treatment ladle, fully covering the inoculant on the low-silicon spheroidizing alloy, pouring the tapped molten iron into the pouring treatment ladle, and reacting the tapped molten iron with the low-silicon spheroidizing alloy and the inoculant to obtain vermicular molten iron;
(4) furnace-front rapid metallographic examination and spectral analysis: carrying out metallographic examination and chemical component analysis on the vermicular molten iron sample to determine the vermicular effect;
(5) slagging off: spreading a slag removing agent into the vermicular molten iron for slag removal;
(6) pouring: controlling the pouring temperature to 1370-1420 ℃ and the pouring time to be less than or equal to 14 min.
Preferably, the mass of the base iron is 600-800 kg.
Preferably, when the sulfur content in the raw molten iron is 0.012-0.015%, the amount of the low-silicon spheroidized alloy added is 0.65% of the amount of the raw molten iron, and when the sulfur content in the raw molten iron is 0.016-0.02%, the amount of the low-silicon spheroidized alloy added is 0.7% of the amount of the raw molten iron.
Preferably, the inoculant is added in an amount of 0.6% of the amount of the raw iron water.
Preferably, the low silicon spheroidized alloy comprises the following components in percentage by weight: 6.7-7.7% of magnesium, 2.2-3.2% of rare earth, 1.7-2.7% of calcium, 6-7% of silicon and the balance of iron.
Preferably, the particle size of the low-silicon spheroidized alloy is 14-16 mm.
Preferably, the rare earth comprises the following components in percentage by weight: 1.54-2.24% of cerium and 0.66-0.96% of lanthanum.
Preferably, the inoculant is a silicon-strontium inoculant comprising the following components in percentage by weight: 70-75% of silicon, 1.3-2.0% of strontium, less than or equal to 0.1% of calcium, less than or equal to 0.3% of aluminum and the balance of iron, wherein the grain size of the inoculant is 3-10 mm.
The invention provides a silicon-molybdenum turbocharger shell and a preparation method thereof, and compared with the prior art, the silicon-molybdenum turbocharger shell has the following beneficial effects:
(1) the silicon-molybdenum turbocharger shell obtained by the invention has excellent performance, the creep rate is 65-85%, and the silicon-molybdenum turbocharger shell is stable, Rm is more than or equal to 550mpa, A is more than or equal to 2.0%, Rp0.2 is more than or equal to 400mpa, and HB is 200-260 HBW.
(2) The creep rate difference of the shell structure of the silicon-molybdenum turbocharger is small, the section sensitivity is small, and because the matrix structure is mainly ferrite, the content is more than or equal to 90 percent, the phase change stress and the casting stress are small, the workpiece shows excellent fatigue performance under the service condition, the service life of the workpiece is greatly prolonged, the silicon-molybdenum turbocharger shell structure is suitable for being used under the complex working condition environment and can also be used for manufacturing the workpiece with a complex structure,
(3) in the preparation method of the silicon-molybdenum turbocharger shell, the silicon-molybdenum turbocharger shell can be poured only through one-time inoculation, the method is simple and easy to operate, and the excellent performance of the silicon-molybdenum turbocharger shell can be realized only by adding a low-silicon spheroidizing alloy in front of a furnace, so that the problems of low production efficiency caused by two-time inoculation of the conventional vermicular cast iron casting and the problems of unstable one-time inoculation vermicular rate and high sensitivity of the section are solved.
(4) In the preparation process, the low-silicon spheroidized alloy is adopted to replace a conventional vermiculizer, the rare earth content in the conventional vermiculizer is up to 12%, and the rare earth content in the low-silicon spheroidized alloy is only 2.2-3.2%, so that the use amount of rare earth is greatly reduced, the production cost is reduced, and the rare earth resource is saved.
Drawings
FIG. 1 is a cross-sectional view of a silicon molybdenum turbocharger housing.
Fig. 2 is a gold phase diagram at the tongue of a section of a silicon molybdenum turbocharger housing.
FIG. 3 is a gold phase diagram of the thick wall of the section of the silicon-molybdenum turbocharger shell.
FIG. 4 is a gold phase diagram of thin wall of the section of the silicon-molybdenum turbocharger shell.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments.
Silicon-molybdenum turbocharger shell
The first embodiment is as follows: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 2.9 percent of C, 3.9 percent of Si, 0.15 percent of Mn, 0.012 percent of S, 0.025 percent of P, 0.5 percent of Mo, 0.1 percent of Cr, 0.1 percent of Cu, 0.3 percent of Ni, 0.10 percent of Ti and the balance of iron.
Example two: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 3.2 percent of C, 4.3 percent of Si, 0.2 percent of Mn, 0.020 percent of S, 0.04 percent of P, 0.7 percent of Mo, 0.09 percent of Cr, 0.12 percent of Cu, 0.50 percent of Ni, 0.08 percent of Ti and the balance of iron.
Example three: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 3.0% of C, 4.5% of Si, 0.2% of Mn, 0.015% of S, 0.029% of P, 0.62% of Mo, 0.05% of Cr, 0.03% of Cu, 0.60% of Ni, 0.1% of Ti and the balance of iron.
Example four: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 3.1% of C, 4.6% of Si, 0.12% of Mn, 0.016% of S, 0.015% of P, 0.55% of Mo, 0.04% of Cr, 0.06% of Cu, 0.60% of Ni, 0.05% of Ti and the balance of iron.
Example five: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 3.1% of C, 4.7% of Si, 0.25% of Mn, 0.018% of S, 0.02% of P, 0.6% of Mo, 0.15% of Cr, 0.1% of Cu, 0.60% of Ni, 0.12% of Ti and the balance of iron.
Example six: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 3.0% of C, 4.3% of Si, 0.2% of Mn, 0.015% of S, 0.029% of P, 0.6% of Mo, 0.1% of Cr, 0.10% of Cu, 0.40% of Ni, 0.1% of Ti and the balance of iron.
Example seven: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 3.1% of C, 4.0% of Si, 0.12% of Mn, 0.016% of S, 0.015% of P, 0.55% of Mo, 0.04% of Cr, 0.06% of Cu, 0.50% of Ni, 0.05% of Ti and the balance of iron.
Example eight: a silicon-molybdenum turbocharger housing comprising the following chemical composition in weight percent: 3.1% of C, 4.0% of Si, 0.25% of Mn, 0.018% of S, 0.02% of P, 0.6% of Mo, 0.15% of Cr, 0.03% of Cu, 0.20% of Ni, 0.12% of Ti and the balance of iron.
Second, preparation method of silicon-molybdenum turbocharger shell
The preparation method of the silicon-molybdenum turbocharger shell comprises the following steps:
(1) melting the ingredients: sequentially adding 30-50 wt% of pig iron, 50-70 wt% of briquetting low-manganese scrap steel and a proper amount of ferrosilicon into a medium-frequency electric furnace for melting, and then adding 0.5-0.7 wt% of ferromolybdenum to obtain molten iron;
(2) analysis and control: controlling the temperature of the molten iron in the step (1) to be 1540-1560 ℃, powering off, standing for 3-5 minutes at 1540-1560 ℃, performing spectral analysis on a molten iron sample in the furnace, and adjusting chemical components to obtain required chemical components of the molten iron, wherein the chemical components of the molten iron are as follows by weight percent: 3.0-3.2% of C, 3.95-4.05% of Si, less than or equal to 0.30% of Mn, 0.012-0.0.18% of S, less than or equal to 0.05% of P, 0.5-0.7% of Mo, less than or equal to 0.5% of Cr, less than or equal to 0.5% of Cu, less than or equal to 0.6% of Ni and the balance of iron, and detecting the sulfur content of the base iron;
(3) furnace front creeping and inoculation treatment: controlling the tapping temperature of the base molten iron to be 1460-1500 ℃, sequentially adding a low-silicon spheroidizing alloy and an inoculant to the bottom of a pit ladle of a pouring treatment ladle, fully covering the inoculant on the low-silicon spheroidizing alloy, pouring the tapped molten iron into the pouring treatment ladle, and reacting the tapped molten iron with the low-silicon spheroidizing alloy and the inoculant to obtain vermicular molten iron;
(4) and (3) furnace-front rapid metallographic and spectral analysis and inspection: performing metallographic examination on the vermicular molten iron sample to determine the vermicular effect, and determining the chemical components of the vermicular molten iron by adopting a German Spiek spectrum analyzer, particularly determining the residual quantity of magnesium;
(5) slagging off: spreading a slag removing agent into the vermicular molten iron for slag removal;
(6) pouring: controlling the pouring temperature to 1370-1420 ℃, and the pouring time to be less than or equal to 14min, wherein the pouring time is the time interval from the completion of the vermicular reaction of the molten base iron poured into the pouring treatment bag to the completion of pouring.
The quality of the base iron is controlled to be 600-800 kg, when the sulfur content in the base iron is 0.012-0.015%, the amount of the low-silicon spheroidized alloy added is 0.65% of the amount of the base iron, and when the sulfur content in the base iron is 0.016-0.02%, the amount of the low-silicon spheroidized alloy added is 0.7% of the amount of the base iron.
The addition amount of the inoculant is 0.6 percent of the original iron water amount.
The low-silicon spheroidized alloy comprises the following components in percentage by weight: 6.7-7.7% of magnesium, 2.2-3.2% of rare earth, 1.7-2.7% of calcium and 6-7% of silicon, wherein the granularity of the low-silicon spheroidized alloy is 14-16 mm, and the rare earth comprises the following components in percentage by weight: 1.54-2.24% of cerium and 0.66-0.96% of lanthanum.
The inoculant is a silicon-strontium inoculant and comprises the following components in percentage by weight: 70-75% of silicon, 1.3-2.0% of strontium, less than or equal to 0.1% of calcium, less than or equal to 0.3% of aluminum, and the grain size of the inoculant is 3-10 mm.
Example nine: the preparation method of the silicon-molybdenum turbocharger shell comprises the following steps:
(1) melting the ingredients: sequentially adding 30 percent of pig iron and 50 percent of briquetting low-manganese scrap steel into a medium-frequency electric furnace for melting, and after the pig iron and the briquetting low-manganese scrap steel are completely melted, adding 0.5 percent of ferromolybdenum and a proper amount of ferrosilicon to obtain molten iron;
(2) analysis and control: adjusting the working temperature of the medium-frequency furnace, cutting off the power after the temperature of the molten iron reaches 1540 ℃, stopping the medium-frequency furnace and standing for 3 minutes, taking the molten iron in the furnace as a sample, performing spectral analysis by using a German Schpark spectrometer, detecting the chemical components of the molten iron, adjusting the chemical components of the molten iron, and obtaining the required chemical components of the molten iron, wherein the components are as follows by weight percent: 3.0% of C, 3.95% of Si, 0.30% of Mn, 0.012% of S, 0.05% of P, 0.5% of Mo, 0.5% of Cr, 0.09% of Cu and 0.6% of Ni, and the balance being iron, and simultaneously detecting the sulfur content of the base iron, determining the adding amount of the low-silicon spheroidized alloy according to the weight percentage of the sulfur element in the base iron, wherein the amount of the base iron is 600 kg;
(3) furnace front creeping and inoculation treatment: controlling the tapping temperature of the base iron to be 1460 ℃, sequentially adding a low-silicon spheroidizing alloy and an inoculant to the bottom of a pit ladle of a pouring treatment ladle, fully covering the inoculant on the low-silicon spheroidizing alloy, pouring the tapped iron water into the pouring treatment ladle, and reacting the tapped iron water with the low-silicon spheroidizing alloy and the inoculant to obtain vermicular iron, wherein the adding amount of the low-silicon spheroidizing alloy is 0.65% of the amount of the base iron water, and the adding amount of the inoculant is 0.6% of the amount of the base iron water;
(4) and (3) furnace-front rapid metallographic and spectral analysis and inspection: performing metallographic examination on the vermicular molten iron sample obtained in the step (3), determining the vermicular effect, determining chemical components of the vermicular molten iron by adopting a German Spiek spectrometer, particularly determining the residual quantity of magnesium, and indirectly judging the vermicular effect of the molten iron by detecting the content of the magnesium in the vermicular molten iron;
(5) slagging off: spreading a slag removing agent into the vermicular molten iron for removing slag, and removing floating slag, wherein the slag removing agent is perlite;
(6) pouring: controlling the pouring temperature to 1370 ℃ and the pouring time to 14min, wherein the pouring time is the time interval from the completion of the vermicularizing reaction of the base iron poured into the pouring treatment ladle to the completion of pouring.
In this embodiment, the low silicon spheroidized alloy includes the following components in weight percent: 6.7 percent of magnesium, 2.2 percent of rare earth, 1.7 percent of calcium and 6 percent of silicon, the granularity is 14mm, the rare earth comprises 1.54 percent of cerium and 0.66 percent of lanthanum by weight, and the inoculant is a silicon-strontium inoculant comprising 70 percent of silicon, 1.3 percent of strontium, 0.1 percent of calcium and 0.3 percent of aluminum by weight, and the granularity is 3 mm.
Example ten: the preparation method of the silicon-molybdenum turbocharger shell comprises the following steps: (1) melting the ingredients: sequentially adding 40 percent of pig iron and 60 percent of briquetting low-manganese scrap steel into a medium-frequency electric furnace for melting, and after the pig iron and the briquetting low-manganese scrap steel are completely melted, adding 0.6 percent of ferromolybdenum and a proper amount of ferrosilicon to obtain molten iron;
(2) analysis and control: adjusting the working temperature of the medium-frequency furnace, cutting off the power after the temperature of the molten iron reaches 1550 ℃, stopping the medium-frequency furnace and standing for 4 minutes, taking the molten iron in the furnace as a sample, performing spectral analysis by using a German Schpark spectrum analyzer, detecting the chemical components of the molten iron, adjusting the chemical components of the molten iron to obtain the required chemical components of the molten iron, wherein the components are as follows by weight percent: 3.1% of C, 4.0% of Si, 0.250% of Mn, 0.016% of S, 0.02% of P, 0.6% of Mo, 0.2% of Cr, 0.05% of Cu and 0.5% of Ni, and the balance being iron, and simultaneously detecting the sulfur content of the base iron, determining the adding amount of the low-silicon spheroidized alloy according to the weight percentage of the sulfur element in the base iron, wherein the amount of the base iron is 700 kg;
(3) furnace front creeping and inoculation treatment: controlling the tapping temperature of the base iron to be 1480 ℃, sequentially adding a low-silicon spheroidizing alloy and an inoculant at the bottom of a pit of a pouring treatment bag, fully covering the inoculant on the low-silicon spheroidizing alloy, pouring the tapped base iron into the pouring treatment bag, and reacting the tapped base iron with the low-silicon spheroidizing alloy and the inoculant to obtain vermicular base iron, wherein the adding amount of the low-silicon spheroidizing alloy is 0.70% of the amount of the base iron, and the adding amount of the inoculant is 0.6% of the amount of the base iron;
(4) and (3) furnace-front rapid metallographic and spectral analysis and inspection: performing metallographic examination on the vermicular molten iron sample obtained in the step (3), determining the vermicular effect, and determining the chemical components of the vermicular molten iron by using a German Spiek spectrometer, particularly determining the residual quantity of magnesium;
(5) slagging off: spreading a slag removing agent into the vermicular molten iron for removing slag, and removing floating slag, wherein the slag removing agent is perlite;
(6) pouring: controlling the pouring temperature to 1400 ℃ and the pouring time to 12min, wherein the pouring time is the time interval from the completion of the vermicular reaction of the base iron poured into the pouring treatment ladle to the completion of pouring.
In this embodiment, the low silicon spheroidized alloy includes the following components in weight percent: 7.0 percent of magnesium, 2.6 percent of rare earth, 2.2 percent of calcium and 6.5 percent of silicon, wherein the granularity is 15mm, the rare earth comprises 1.8 percent of cerium and 0.8 percent of lanthanum by weight, and the inoculant is a silicon-strontium inoculant comprising 72 percent of silicon, 1.65 percent of strontium, 0.05 percent of calcium and 0.2 percent of aluminum by weight, and the granularity is 5 mm.
Example eleven: the preparation method of the silicon-molybdenum turbocharger shell comprises the following steps:
(1) melting the ingredients: sequentially adding 50% of pig iron and 70% of briquetting low-manganese scrap steel by weight into a medium-frequency electric furnace for melting, and after the pig iron and the briquetting low-manganese scrap steel are completely melted, adding 0.7% of ferromolybdenum and a proper amount of ferrosilicon by weight to obtain molten iron;
(2) analysis and control: adjusting the working temperature of the medium-frequency furnace, cutting off the power after the temperature of the molten iron reaches 1560 ℃, stopping the medium-frequency furnace and standing for 5 minutes, taking the molten iron in the furnace as a sample, performing spectral analysis by using a German Schpark spectrometer, detecting the chemical components of the molten iron, adjusting the chemical components of the molten iron to obtain the required chemical components of the molten iron, wherein the components are as follows by weight percent: 3.2% of C, 4.05% of Si, 0.1% of Mn, 0.017% of S, 0.03% of P, 0.7% of Mo, 0.2% of Cr0.2%, 0.04% of Cu and 0.2% of Ni, and the balance being iron, and simultaneously detecting the sulfur content of the base iron, determining the adding amount of the low-silicon spheroidized alloy according to the weight percentage of the sulfur element in the base iron, wherein the amount of the base iron is 800 kg;
(3) furnace front creeping and inoculation treatment: controlling the tapping temperature of the base iron to be 1500 ℃, sequentially adding a low-silicon spheroidizing alloy and an inoculant at the bottom of a pit ladle of a pouring treatment ladle, fully covering the inoculant on the low-silicon spheroidizing alloy, pouring the tapped iron water into the pouring treatment ladle, and reacting the tapped iron water with the low-silicon spheroidizing alloy and the inoculant to obtain vermicular iron, wherein the adding amount of the low-silicon spheroidizing alloy is 0.70% of the amount of the base iron water, and the adding amount of the inoculant is 0.6% of the amount of the base iron water;
(4) and (3) furnace-front rapid metallographic and spectral analysis and inspection: performing metallographic examination on the vermicular molten iron sample obtained in the step (3), determining the vermicular effect, and determining the chemical components of the vermicular molten iron by using a German Spiek spectrometer, particularly determining the residual quantity of magnesium;
(5) slagging off: spreading a slag removing agent into the vermicular molten iron for removing slag, and removing floating slag, wherein the slag removing agent is perlite;
(6) pouring: controlling the pouring temperature to 1420 ℃ and the pouring time to 10min, wherein the pouring time is the time interval from the completion of the vermicular reaction of the base iron poured into the pouring treatment ladle to the completion of pouring.
In this embodiment, the low silicon spheroidized alloy includes the following components in weight percent: 7.7 percent of magnesium, 3.2 percent of rare earth, 2.7 percent of calcium and 7 percent of silicon, wherein the granularity is 16mm, the rare earth comprises 2.24 percent of cerium and 0.96 percent of lanthanum by weight, and the inoculant comprises 75 percent of silicon, 2.0 percent of strontium, 0.05 percent of calcium and 0.1 percent of aluminum by weight, and the granularity is 10 mm.
Through the preparation process, the vermicular cast iron casting, namely the silicon-molybdenum turbocharger shell, is obtained, the mechanical performance measurement, the ferrite content and the creep rate measurement are carried out on the silicon-molybdenum turbocharger shell, and the obtained tensile strength Rm is more than or equal to 550mpa, the elongation A is more than or equal to 2.0%, the yield strength Rp0.2 is more than or equal to 400mpa, the Brinell hardness HB is 200-260HBW, the matrix structure is that the ferrite content is more than or equal to 90%, the creep rate is 65-85%, and the creep rate is stable.
The creep ratios obtained by metallographic examination in the preparation step (4) of examples nine to eleven are shown in the following table 1, the metallographic image being obtained by microscopic magnification at 100:
TABLE 1
Rate of creep
Example nine 80.5％
Example ten 82.6％
EXAMPLE eleven 85.8
The results of the measurements of examples nine to eleven are given in table 2 below:
TABLE 2
Tensile strength Rm Elongation A Yield strength Rp0.2 Brinell hardness HB Ferrite content
Example nine 550mpa 2.0％ 400mpa 200HBW 90％
Example ten 572mpa 2.5％ 460mpa 230HBW 92％
EXAMPLE eleven 600mpa 3.2％ 485mpa 240HBW 95％
Cutting a silicon-molybdenum turbocharger shell, as shown in a schematic cross-sectional diagram obtained in figure 1, observing tongues, thin walls and thick walls of different parts of the shell, and performing metallographic examination on the tongues, the thin walls and the thick walls of the shell respectively, taking an eleventh example to obtain a metallographic diagram shown in figures 2-4, wherein figure 2 is the metallographic diagram of the tongues at the cross section of the shell, and the creep rate obtained by measurement is 86.82%, figure 3 is the metallographic diagram of the thick walls at the cross section of the shell, and the creep rate obtained by measurement is 81.80%, and figure 4 is the metallographic diagram of the thin walls at the cross section of the shell, and the creep rate obtained by measurement is 84.62%.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (5)

1. A preparation method of a silicon-molybdenum turbocharger shell is characterized by comprising the following steps: the method comprises the following steps:
(1) melting the ingredients: sequentially adding 30-50 wt% of pig iron and 50-70 wt% of briquetting low-manganese scrap steel into a medium-frequency electric furnace for melting, and then adding 0.5-0.7 wt% of ferromolybdenum and a proper amount of ferrosilicon to obtain molten iron;
(2) analysis and control: controlling the temperature of the molten iron in the step (1) to be 1540-1560 ℃, powering off, standing for 3-5 minutes at 1540-1560 ℃, performing spectral analysis on a molten iron sample in the furnace, and adjusting chemical components to obtain required chemical components of the molten iron, wherein the chemical components of the molten iron are as follows by weight percent: 3.0-3.2% of C, 3.95-4.05% of Si, less than or equal to 0.30% of Mn, 0.012-0.018% of S, less than or equal to 0.05% of P, 0.5-0.7% of Mo, less than or equal to 0.5% of Cr, less than or equal to 0.5% of Cu, less than or equal to 0.6% of Ni and the balance of iron, and detecting the sulfur content of the base iron;
(3) primary creeping and inoculation treatment before furnace: controlling the tapping temperature of the base molten iron to be 1460-1500 ℃, sequentially adding a low-silicon spheroidizing alloy and an inoculant to the bottom of a pit ladle of a pouring treatment ladle, fully covering the inoculant on the low-silicon spheroidizing alloy, pouring the tapped molten iron into the pouring treatment ladle, and reacting the tapped molten iron with the low-silicon spheroidizing alloy and the inoculant to obtain vermicular molten iron; wherein the low silicon spheroidized alloy comprises the following components in percentage by weight: 6.7-7.7% of magnesium, 2.2-3.2% of rare earth, 1.7-2.7% of calcium, 6-7% of silicon and the balance of iron, wherein the granularity of the low-silicon spheroidized alloy is 14-16 mm, the inoculant is a silicon-strontium inoculant, and the inoculant comprises the following components in percentage by weight: 70-75% of silicon, 1.3-2.0% of strontium, less than or equal to 0.1% of calcium, less than or equal to 0.3% of aluminum and the balance of iron, wherein the grain size of the inoculant is 3-10 mm;
(4) furnace-front rapid metallographic examination and spectral analysis: carrying out metallographic examination and chemical component analysis on the vermicular molten iron sample to determine the vermicular effect;
(5) slagging off: spreading a slag removing agent into the vermicular molten iron for slag removal;
(6) pouring: controlling the pouring temperature to 1370-1420 ℃ and the pouring time to be less than or equal to 14 min.
2. The method of claim 1, wherein the method comprises the steps of: the mass of the base iron is 600-800 kg.
3. A method of manufacturing a silicon molybdenum turbocharger housing as claimed in claim 2, wherein: when the sulfur content in the raw molten iron is 0.012-0.015%, the amount of the low-silicon spheroidized alloy added is 0.65% of the amount of the raw molten iron, and when the sulfur content in the raw molten iron is 0.016-0.018%, the amount of the low-silicon spheroidized alloy added is 0.7% of the amount of the raw molten iron.
4. A method of making a silicon molybdenum turbocharger housing as claimed in claim 3, wherein: the addition amount of the inoculant is 0.6 percent of the original iron water amount.
5. The method of claim 4, wherein the method comprises the steps of: the rare earth comprises the following components in percentage by weight: 1.54-2.24% of cerium and 0.66-0.96% of lanthanum.
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