CN1927505A - High nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe and casting method - Google Patents

Abstract

The invention relates to a high-nickel austenite nodular graphite cast iron vehicle discharge branch tube and relative casting method. Wherein, said casting method comprises core production, shaping, combining, smelting, irrigating, dropping sand and cleaning casting; while the core production uses low-nitrogen high-temperature cover sand; the inner sand core of discharge branch tube is internal flow sand core; the outer chamber sand core embeds cold iron at the clamp part between two tubes; and it uses side riser and uses the static compressor in irrigation supplied by wet mound sand; the smelting temperature is 1600-1700Deg. C; and it uses magnetite-silica alloy as nodulizer; and uses ferrosilicon and strontium inoculant to inoculate for two times; and it uses large flux and high temperature irrigation. The inventive branch tube has better corrosion-resistance, high-temperature resistance, and non radiation.

Description

High nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe and casting method

Technical field

The invention belongs to automobile exhaust Manifold technology field, be specifically related to high nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe and casting method.

Background technology

Development along with social and economic condition, continue to bring out middle and high shelves car on the market, its horsepower and discharge capacity require more and more higher to the condition of work of auto parts and components, as the operating temperature of traditional exhaust manifold above 900 ℃, especially under the condition of work of heat, cold alternation, the intensity and the plasticity of exhaust manifold are poor, cause distortion and cracking easily, cause engine operation pressure not enough, and influence the speed of car, cause engine operation malfunctioning when serious, can not satisfy developing of automobile industry, therefore material is selected to require to cut the garment according to the figure.

High-nickel austenite nodular cast iron is because there is its good corrosion-resistant, fire-resistant oxidation resistant, and is radiationless in the production operation, multiple advantage such as nonhazardous, and in the U.S., Germany, western developed countries such as Britain part apply to the production of vehicle key parts.Because high-nickel austenite nodular cast iron iron liquid surface tension is big, shrink tendency greatly, cooling is fast, the characteristics of mobile difference, use it for the automobile exhaust manifold and exist owing to the exhaust manifold wall is thin, complex structure, heat energy-saving position is many, foundry goods is prone to shrinkage cavity most, shrinkage porosite, misrun and cold shut defective.Therefore high-nickel austenite nodular cast iron is ripe not enough at home and abroad at the foundry engieering of automobile exhaust manifold, remains further to be developed.

Summary of the invention

For solving the problem that exists in the above-mentioned foundry engieering, the purpose of this invention is to provide a kind of high nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe and casting method thereof, the automobile exhaust manifold of casting with high-nickel austenite nodular cast iron has good anti-corrosion, hear resistance, resistance to sudden heating and high-temperature ductility.

For achieving the above object, the technical solution used in the present invention is: the automobile exhaust manifold that utilizes high-nickel austenite nodular cast iron to replace existing iron casting to become.

Its casting technique step is coremaking, moulding, mould assembly, smelting iron liquid, cast, unpack knockout and cleaning warehouse-in, wherein:

1, coremaking: adopt low N high-strength precoated sand, the intensity 〉=3.4Mpa of precoated sand, low getting angry≤14m/g; The interior core of exhaust manifold is interior circulation core, and the exocoel core is at position, two pipe clamp shelves places edge chill;

2, moulding: behind the film covered sand core combination forming, adopt macropore flow running gate system technology, utilize the side riser feeding, the hydrostatic head when providing cast by tide mould sand;

3, smelting iron liquid: 1600～1700 ℃ of smelting temperatures; Adopting mg-si master alloy is that nodulizer carries out spheroidising, and the addition of mg-si master alloy nodulizer is 0.9-1.2%; Breed once in bag with the ferrosilicon inovulant, the addition of ferrosilicon inovulant is 0.3-0.5%, instantaneously breeds once more pouring into a mould with silicon strontium inovulant, and the addition of silicon strontium inovulant is 0.13-0.16%; Tapping temperature is 1650 ℃～1690 ℃.

4, pouring technology

The technology that adopts big flow, high temperature to water is soon poured into a mould first oven temperature, degree≤1560 ℃, pours into a mould last oven temperature, degree 〉=1470 ℃.

Adopt the beneficial effect of technique scheme to be: high-nickel austenite nodular cast iron has good anti-corrosion, heat-resisting quantity, non-oxidizability, ductility, characteristic such as radiationless, apply to make on the automobile exhaust manifold, can make exhaust manifold have good anti-corrosion, hear resistance, resistance to sudden heating and high-temperature ductility can satisfy middle and high shelves its horsepower of car and the discharge capacity requirement more and more higher to the condition of work of auto parts and components.In the casting technique of high-nickel austenite nodular cast iron automobile exhaust pipe, the interior circulation core of blast pipe is adopted in coremaking, the condition of work exhaust performance is good, the exocoel core of blast pipe is provided with chill, reduce thermograde, the equalization temperature field is provided the hydrostatic head in when cast by tide mould sand in the moulding, increase the full ability of die cavity, thereby guarantee that foundry goods has enough pressure to obtain to perfect foundry goods at die cavity.Adopt the spheroidising of Si-Mg alloy nodulizer in the melting of iron liquid, breed twice when Bao Nei and cast, the nodularization rate has effectively formed the austenite metallographic structure all more than 85%, realizes metallographic structure: 90%VI6-8.The technology that adopts big flow, high temperature to water soon, the control pouring temperature has solved in the cast and has been prone to shrinkage defect, and what guaranteed austenite spheroidal iron fills type and poring rate.Adopt the index of the high nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe that above-mentioned casting technique makes to be compared as follows:

Every index all reaches or is higher than the requirement of DIN DIN1964, sees the following form:

	German standard din	Company's product index
			Tensile strength	≥370MPa	522.7MPa
Percentage elongation	≥10％	24％
			Hardness	130-170HB	159HB
Metallographic structure	90％VI6-8	90％VI 7
			Cold toughness	-196℃	-198℃

Description of drawings

Fig. 1 is a high nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe structural representation of the present invention

Fig. 2 is a preparation method flow chart of the present invention

The specific embodiment

High nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe as shown in Figure 1 is to be made by high-nickel austenite nodular cast iron, and each element wt percentage is in the metallic iron: C2.0～2.4; Si2.5～3.0; Mn≤0.8; P≤0.05; S≤0.01; Ni34.0～36.0; Cr1.5～2.5; Mo≤0.15; Cu≤0.5; Ce＜0.01; Ti≤0.03; Mg residual 0.06～0.11.The matrix of high-nickel austenite nodular cast iron is austenite+carbide, realizes metallographic structure: 90%VI6-8, has good anti-corrosion, heat-resisting quantity, non-oxidizability, ductility, characteristics such as radiationless.

Embodiment 1

The casting method of high nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe adopts coremaking, moulding, mould assembly, smelting iron liquid, cast, unpacking knockout and cleaning warehouse-in operation as shown in Figure 2.Wherein main improvement processing step is:

1, coremaking: adopt low nitrogen high temp degree precoated sand, the intensity of precoated sand is 3.4Mpa, and low getting angry is 14m/g; The interior core of exhaust manifold is interior circulation core, and the condition of work exhaust performance is good, and the exocoel core is at position, two pipe clamp shelves places edge chill or use internal densener, reduces thermograde, the equalization temperature field; Coremaking and formative technology can be carried out simultaneously.

2, moulding: behind the film covered sand core combination forming, adopt macropore flow running gate system technology, adopt side riser, the hydrostatic head when providing cast by tide mould sand; Mould assembly is stand-by after coremaking and the moulding.

3, smelting iron liquid: at first prepare the used raw material of smelting iron liquid, wherein to select for use be 1.5 to chromium element wt percentage; C is preferably 2.2; Si is preferably 2.8, adopts the medium-frequency induction furnace of 250Kg capacity to carry out melting then, and smelting temperature is 1600 ℃; The base iron composition is adjusted in check, makes in the metallic iron each element wt percentage in the scope of DIN DIN1694; Adopting mg-si master alloy is that nodulizer carries out spheroidising, and the addition of mg-si master alloy nodulizer is 0.9%; Breed once in bag with the ferrosilicon inovulant, the addition of ferrosilicon inovulant is 0.3%, instantaneously breeds once more pouring into a mould with silicon strontium inovulant, and the addition of silicon strontium inovulant is 0.13%; Tapping temperature is 1650 ℃, thereby has effectively stablized the metallographic quality.

4, pouring technology: the technology that adopts big flow, high temperature to water soon.Use the medium-frequency induction furnace of 250Kg capacity, the at full capacity big quick melting of electric current, short in more well from melting to pouring the fast more time more of operation; Casting mold is placed near the smelting furnace as far as possible, so that water soon; Reinforcement is bred; Pouring into a mould first oven temperature, degree is 1560 ℃, and pouring into a mould last oven temperature, degree is 1470 ℃.

5, unpacking knockout: the knockout of can unpacking after the iron liquid cooling but of cast is cast as high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe;

6, casting cleaning check warehouse-in: the foundry goods that casting is come out, through after the assay was approved, hang Shot Blasting, through clearing up, clean after the assay was approved, spray antirust oil warehouse-in.

Embodiment 2

Adopt coremaking, moulding, mould assembly, smelting iron liquid, cast, unpacking knockout and cleaning warehouse-in operation as its casting method of Fig. 2.Wherein main improvement processing step is:

1, coremaking: adopt low nitrogen high temp degree precoated sand, the intensity of precoated sand is 4Mpa, and low getting angry is 12m/g; The interior core of exhaust manifold is interior circulation core, and the condition of work exhaust performance is good, and the exocoel core is at position, two pipe clamp shelves places edge chill or use internal densener, reduces thermograde, the equalization temperature field; Formative technology can be carried out simultaneously with coremaking.

2, moulding: behind the film covered sand core combination forming, adopt macropore flow running gate system technology, adopt side riser, the hydrostatic head when providing cast by tide mould sand; Mould assembly is stand-by after coremaking and the moulding.

3, smelting iron liquid: at first prepare the used raw material of smelting iron liquid, wherein to select for use be 2.0 to chromium element wt percentage; C is preferably 2.4; Si is preferably 3.0, adopts the medium-frequency induction furnace of 250Kg capacity to carry out melting then, and smelting temperature is 1700 ℃; The base iron composition is adjusted in check, makes in the metallic iron each element wt percentage in the scope of DIN DIN1694; Adopting mg-si master alloy is that nodulizer carries out spheroidising, and the addition of mg-si master alloy nodulizer is 1.2%; Breed once in bag with the ferrosilicon inovulant, the addition of ferrosilicon inovulant is 0.5%, instantaneously breeds once more pouring into a mould with silicon strontium inovulant, and the addition of silicon strontium inovulant is 0.16%; Tapping temperature is 1690 ℃, thereby has effectively stablized the metallographic quality.

4, pouring technology: the technology that adopts big flow, high temperature to water soon, pouring into a mould first oven temperature, degree is 1550 ℃, pouring into a mould last oven temperature, degree is 1490 ℃.

5, unpacking knockout: the knockout of can unpacking after the iron liquid cooling but of cast is cast as high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe;

6, casting cleaning check warehouse-in: the foundry goods that casting is come out, through after the assay was approved, hang Shot Blasting, through clearing up, clean after the assay was approved, spray antirust oil warehouse-in.

Claims (2)

1, a kind of high nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe has exhaust manifold, it is characterized in that: described exhaust manifold is a high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe.

2, the casting method of high nickel austenite spheroidal graphite cast iron automobile exhaust branch pipe according to claim 1, its casting technique step are coremaking, moulding, mould assembly, smelting iron liquid, cast, unpack knockout and cleaning warehouse-in, it is characterized in that:

1), coremaking: adopt low nitrogen high temp degree precoated sand, the intensity 〉=3.4Mpa of precoated sand, low getting angry≤14m/g; The interior core of exhaust manifold is interior circulation core, and the exocoel core is at position, two pipe clamp shelves places edge chill;

2), moulding: behind the film covered sand core combination forming, adopt macropore flow running gate system technology, adopt side riser, the hydrostatic head when providing cast by tide mould sand;

3), smelting iron liquid: 1600～1700 ℃ of smelting temperatures; Adopting mg-si master alloy is that nodulizer carries out spheroidising, and the addition of mg-si master alloy nodulizer is 0.9-1.2%; Breed once in bag with the ferrosilicon inovulant, the addition of ferrosilicon inovulant is 0.3-0.5%, instantaneously breeds once more pouring into a mould with silicon strontium inovulant, and the addition of silicon strontium inovulant is 0.13-0.16%; Tapping temperature is 1650 ℃～1690 ℃;

4), pouring technology

The technology that adopts big flow, high temperature to water is soon poured into a mould first oven temperature, degree≤1560 ℃, pours into a mould last oven temperature, degree 〉=1470 ℃.