阅读说明：本技术 一种硅钼涡轮增压器壳体及其制备方法 (Silicon-molybdenum turbocharger shell and preparation method thereof ) 是由 田政 田龙 田中青 王青松 于 2020-07-21 设计创作，主要内容包括：本发明涉及铸造冶金领域,具体涉及一种硅钼涡轮增压器壳体,包括以重量百分比计的以下成分：C 2.9～3.2％,Si 3.9～4.4％,Mn＜0.30％,S 0.012～0.020％,P＜0.05％,Mo 0.5～0.7％,Cr＜0.50％,Cu＜0.50％,Ni＜0.60％,Ti≤0.20％,余量为铁,还涉及其制备方法,包括配料熔化、分析控制、炉前一次蠕化孕育处理、炉前金相检验、光谱分析、扒渣、浇注,基体组织为以铁素体为主相变应力小,壳体各处蠕化率差别小、稳定,断面敏感性小,具备优良疲劳性能,制备时一次孕育即可浇注方法简单,炉前只加入一种低稀土含量的低硅球化合金代替常规蠕化剂,节约稀土资源。(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.)

1. A silicon molybdenum turbocharger housing, characterized by comprising the following components in weight percent: 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.

2. A silicon molybdenum turbocharger housing as claimed in claim 1, characterized by comprising the following composition in weight percent: 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 Mo0, 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.

3. A method of manufacturing a silicon molybdenum turbocharger housing as claimed in claim 1 or 2, characterized in that:

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, 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.

4. A method of making a silicon molybdenum turbocharger housing as claimed in claim 3, wherein: the mass of the base iron is 600-800 kg.

5. The method of claim 4, wherein the method comprises the steps of: 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.

6. The method of claim 4, wherein the method comprises the steps of: the addition amount of the inoculant is 0.6 percent of the original iron water amount.

7. The method for preparing a silicon-molybdenum turbocharger housing as claimed in any one of claims 4 to 6, 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.

8. The method of claim 7, wherein the method comprises the steps of: the granularity of the low-silicon spheroidized alloy is 14-16 mm.

9. The method of claim 7, 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.

10. The method of claim 9, wherein the inoculant is a silicon-strontium inoculant comprising, in weight percent: 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.

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, 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: 2.9-3.2% 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 Mo0, 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 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