Summary of the invention
The object of the invention provides a kind of casting technique of high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe, the high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe of producing by this technology has strong thermal-shock resistance and heat resistanceheat resistant creep properties, good corrosion resistance and high-temperature oxidation resistance, and low thermal expansivity and good low-temperature impact toughness are arranged.
For achieving the above object, the designed casting technique step of the present invention is: coremaking → mulling → moulding → melting → cast → cleaning → heat treatment → Shot Blasting → inspection of blank → blank warehouse-in.
Wherein mainly improving processing step is:
1, melting:
The melting of high-nickel austenite nodular cast iron
A, furnace charge and proportioning
With pig iron content is that 50%-75% and steel scrap content are that 25%-50% is when being major ingredient, the content of trace harmful elements is in the furnace charge: Pb_≤0.002% As≤0.005% Ti≤0.045% or be that 2%-5% and steel scrap content are that 95%-98% is when being major ingredient with carburant content, fixedly phosphorus content≤98% of carburant, S 〉=0.03%, granularity is between 0.15-0.3mm, select fixed point for use, composition homogeneous, rustless, pure steel scrap; Ni adds with the electrolysis form, addition accounts for major ingredient mass percent 34-38%, and Cr adds with the ferrochrome that contains Cr60-65%, and addition accounts for major ingredient mass percent 1.6-2.2%, Si adds with 75% ferrosilicon form, and addition accounts for major ingredient mass percent 4.8-5.3%;
B, melting control
Once simultaneously with the pig iron with steel scrap is put into the electric furnace crucible or when being major ingredient with carburant and steel scrap, carburant once is added in the bottom of electric furnace crucible when being major ingredient, adds steel scrap according to carburant with the pig iron and steel scrap; When melting to molten iron reaches 1450 ℃-1550 ℃, add the nickel of electrolysis form; During cast iron melting to 1600 ℃-1680 ℃, add ferrochrome, the ductile Ni-resist cast iron tapping temperature is 1600 ℃-1680 ℃;
C, spheroidising
The spheroidising of ductile Ni-resist cast iron adopts easy pit to pour method, and nodulizer is selected nickel magnesium ferrosilicon nodulizer for use, and it is 0.80-1.20% that the addition of nickel magnesium ferrosilicon nodulizer accounts for the major ingredient mass percent;
D, inoculation
Employing contains the inovulant of strontium, and the amount that contains the strontium inovulant accounts for the major ingredient mass percent and is: 0.60%-1.20%; Or adopt and to contain the zirconium inovulant, the amount of zirconium inovulant accounts for the major ingredient mass percent and is: 0.10%-0.20%;
2, cast
In molten steel pouring course, keep molten iron to be full of cup all the time, pouring temperature is controlled at 1460 ℃-1530 ℃;
3, heat treatment
The high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe foundry goods is warming up to 870 ℃-1000 ℃, is incubated 3-6 hour, be chilled to 620 ℃ with stove and come out of the stove.
Adopt above-mentioned casting technique: as in furnace charge and proportioning process and melting control technology, the content of trace harmful elements Pb, As, TiO in the control furnace charge, content and adding mode and the sequencing of control important element Ni, Cr, Si, and control melts out furnace temperature, reduce the scaling loss of carbon, chromium, manganese alloy, effectively guaranteed to form high-nickel austenite nodular cast iron elemental composition and mass percent; Nodulizer is selected nickel magnesium ferrosilicon nodulizer for use, and inovulant adopts 75 ferrosilicon, by breeding the increase number of graphite ball, avoids containing the amount that the D-5S foundry goods of chromium more than 1.6% produces eutectic carbide and reduce the intergranular carbide; Foundry goods is through Overheating Treatment, and carbide is transformed into granularly in the tissue by strip and block, has improved the cutting ability of foundry goods.By the high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe that above-mentioned casting technique is produced, efficiently solve that existing casting manufacturability is poor, coarse the requirements height of cast(ing) surface, and this exhaust pipe fitting is little, wall is thin, the thickness difference is bigger, and is complex-shaped, the problem that existing casting technique can't guarantee.The matrix of the exhaust manifold that casts out is mainly austenite and a spot of carbide, this high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe is the ambient temperature mechanical properties height not only, fabulous thermal-shock resistance and heat resistanceheat resistant creep properties are arranged, fabulous corrosion resistance and high-temperature oxidation resistance, and low thermal expansivity and good low-temperature impact toughness are arranged.Performance can satisfy existing U.S. ASTM standard and Europe IV standard.
Its parameter such as following table:
Table 1 mechanical property (foundry goods body sampling)
Tensile strength/Mpa |
Yield strength/Mpa |
Percentage elongation (%) |
Hardness (10/3000HB) |
≥340 |
≥207 |
12 |
≤240 |
Table 2 metallographic structure (foundry goods body sampling)
Graphite form |
Graphite number (individual mm
2)
|
Matrix |
1+11≥90% |
?>100 |
Austenite+carbide |
Table 3 chemical analysis
Element |
Mass percent (%) |
Element |
Mass percent (%) |
C |
≤2.0 |
P |
≤0.08 |
Si |
4.8-5.3 |
S |
≤0.03 |
Ni |
34.0-36.0 |
RE |
≤0.01 |
Cr |
1.6-2.2 |
Other element |
≤0.2 |
Mn |
≤0.7 |
Total impurities |
≤2.0 |
Mg |
0.035-0.09 |
Fe |
Surplus |
Below in conjunction with accompanying drawing specific embodiments of the invention are described in further detail.
The specific embodiment
Embodiment 1
The casting technique of high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe as shown in Figure 1 has coremaking, mulling, moulding, melting, cast, cleaning, heat treatment, Shot Blasting, inspection of blank, blank warehouse-in.
Coremaking, mulling, moulding, cleaning, Shot Blasting, inspection of blank, blank warehouse-in are manufactured according to the exhaust manifold manufacturing process of routine.
Wherein mainly improving processing step is:
1, melting:
The melting of high-nickel austenite nodular cast iron
A, furnace charge and proportioning
With pig iron content be 50% and steel scrap content be 50% when being major ingredient, the content of trace harmful elements is in the furnace charge: Pb_≤0.002% As≤0.005% Ti≤0.045% or with carburant content be 2% and steel scrap content be 98% when being major ingredient, fixedly phosphorus content≤98% of carburant, S 〉=0.03%, granularity is between 0.15-0.3mm, select fixed point for use, composition homogeneous, rustless, pure steel scrap; Ni adds with the electrolysis form, and addition accounts for major ingredient mass percent 34%, and Cr adds with the ferrochrome that contains Cr60-65%, and addition accounts for major ingredient mass percent 1.6%, and Si adds with 75% ferrosilicon form, and addition accounts for major ingredient mass percent 4.8%;
B, melting control
Once simultaneously with the pig iron with steel scrap is put into the electric furnace crucible or when being major ingredient with carburant and steel scrap, carburant once is added in the bottom of electric furnace crucible when being major ingredient, adds steel scrap according to carburant with the pig iron and steel scrap; When melting to molten iron reaches 1450 ℃, add the nickel of electrolysis form; During cast iron melting to 1600 ℃, add ferrochrome, the ductile Ni-resist cast iron tapping temperature is 1600 ℃;
C, spheroidising
The spheroidising of ductile Ni-resist cast iron adopts easy pit to pour method.Nodulizer is selected nickel magnesium ferrosilicon nodulizer for use, and it is 0.80% that the addition of nickel magnesium ferrosilicon nodulizer accounts for the major ingredient mass percent;
D, inoculation
Employing contains the inovulant of strontium, and the amount that contains the strontium inovulant accounts for the major ingredient mass percent and is: 0.60%; Or adopt and to contain the zirconium inovulant, the amount of zirconium inovulant accounts for the major ingredient mass percent and is: 0.10%;
2, cast
In molten steel pouring course, keep molten iron to be full of cup all the time, pouring temperature is controlled at 1460 ℃;
3, heat treatment
The high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe foundry goods is warming up to 870 ℃, is incubated 6 hours, be chilled to 620 ℃ with stove and come out of the stove;
Embodiment 2
Wherein mainly improving processing step is:
1, melting:
The melting of high-nickel austenite nodular cast iron
A, furnace charge and proportioning
With pig iron content be 75% and steel scrap content be 25% when being major ingredient, the content of trace harmful elements is in the furnace charge: Pb_≤0.002%As≤0.005%Ti≤0.045% or with carburant content be 5% and steel scrap content be 95% when being major ingredient, fixedly phosphorus content≤98% of carburant, S 〉=0.03%, granularity is between 0.15-0.3mm, select fixed point for use, composition homogeneous, rustless, pure steel scrap; Ni adds with the electrolysis form, and addition accounts for major ingredient mass percent 38%, and Cr adds with the ferrochrome that contains Cr60-65%, and addition accounts for major ingredient mass percent 2.2%, and Si adds with 75% ferrosilicon form, and addition accounts for major ingredient mass percent 5.3%;
B, melting control
Once simultaneously with the pig iron with steel scrap is put into the electric furnace crucible or when being major ingredient with carburant and steel scrap, carburant once is added in the bottom of electric furnace crucible when being major ingredient, adds steel scrap according to carburant with the pig iron and steel scrap; Melting adds the nickel of electrolysis form when changing water and reach 1550 ℃; During cast iron melting to 1680 ℃, add ferrochrome, the ductile Ni-resist cast iron tapping temperature is 1680 ℃;
D, spheroidising
The spheroidising of ductile Ni-resist cast iron adopts easy pit to pour method.Nodulizer is selected nickel magnesium ferrosilicon nodulizer for use, and it is 1.20% that the addition of nickel magnesium ferrosilicon nodulizer accounts for the major ingredient mass percent;
D, inoculation
Employing contains the inovulant of strontium, and it is 1.20% that the amount that contains the strontium inovulant accounts for the major ingredient mass percent; Or adopt and to contain the zirconium inovulant, the amount of zirconium inovulant accounts for the major ingredient mass percent and is: 0.20%;
2, cast
In molten steel pouring course, keep molten iron to be full of cup all the time, pouring temperature is controlled at 1530 ℃;
3, heat treatment
The high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe foundry goods is warming up to 1000 ℃, is incubated 3 hours, be chilled to 620 ℃ with stove and come out of the stove;
When being major ingredient with the pig iron and steel scrap, the content of trace harmful elements is in the furnace charge: Pb≤0.002%As≤0.005%Ti≤0.045%;
When being major ingredient with carburant and steel scrap, fixedly phosphorus content≤98% of carburant, S 〉=0.03%, granularity is selected fixed point for use between 0.15-0.3mm, composition homogeneous, rustless, pure steel scrap;
Silicon: because the requirement of heat resistance, fixed very high of silicon content in the product, Si adds with 75% ferrosilicon form, and addition accounts for major ingredient mass percent 4.8-5.3%, the scope of preferred 4.8-4.9%, the flowability of ductile Ni-resist cast iron is also better in this scope;
Nickel: nickel is the basic element of austenite ductile cast iron, and D-5S is the highest a kind of of the content in the nickel spheroidal graphite cast-iron, reaches 34-38%, and Ni adds with the electrolysis form, and addition accounts for major ingredient mass percent 34-38%, and the nickel preferred amounts should be controlled at 34.5%-35%;
Chromium: chromium is the important element of ductile Ni-resist cast iron, small additions of chromium can be fused to austenitic matrix, help stable austenite, and obtain better heat-resisting and corrosion resistance because of the comprehensive function of Ni and Cr, but Cr is the strong carbide forming element, can influence cutting ability, should control to account for major ingredient mass percent 1.6-2.2%, preferred 1.6-1.9%, Cr adds with the ferrochrome that contains Cr60-65%;
Manganese: manganese is the element of generally selecting for use, owing to stipulate in the technical standard, generally lower limit can be avoided generating sclerotic tissue because of the segregation of Mn;
Phosphorus: phosphorus solubility in austenite is extremely low, and generally the form with iron phosphide eutectic is present in crystal boundary, degrade performance, then P<0.05;
Sulphur: sulphur is a kind of impurity in austenite ductile cast iron, requires base iron S≤0.02%.
Wherein melting control: adopt medium-frequency induction furnace to carry out melting, carburant once is added in the bottom of electric furnace crucible, and is different according to batchings such as steel scraps under the situation that guarantees the whole carbon amount of foundry goods≤2.0%, does corresponding the adjustment for the addition of carburant; The nickel of electrolysis form added in the melting later stage; Ferrochrome added in the overheated later stage of molten iron, and the ductile Ni-resist cast iron tapping temperature is 1600 ℃-1680 ℃.
Spheroidising: the spheroidising of ductile Ni-resist cast iron adopts easy pit to pour method.Nodulizer is selected nickel magnesium ferrosilicon nodulizer for use, and it is 0.80-1.20% that the addition of nickel magnesium ferrosilicon nodulizer accounts for the major ingredient mass percent;
Inoculation: inovulant adopts 75 ferrosilicon, and the amount of inovulant accounts for the major ingredient mass percent and is: 0.60%-1.0%; As preferably adopting the inovulant that contains strontium, the amount that contains the strontium inovulant accounts for the major ingredient mass percent and is: 0.10%-0.20%; Should be able to adopt to contain the zirconium inovulant, the amount of zirconium inovulant accounts for the major ingredient mass percent and is: 0.10%-0.20%; By breeding the globular graphite structure that can obtain rule, can eliminate spoken parts in traditional operas, increase number of graphite ball, avoid containing the amount that the D-5S foundry goods of chromium more than 1.6% produces eutectic carbide and reduce the intergranular carbide.
Iron liquid after the melting is poured into a mould, because ductile Ni-resist cast iron molten iron flowability is very fast with cavity filling process decline, should pours into a mould fast and fill type, helps feeding, and pouring temperature is controlled at 1460 ℃-1530 ℃.The high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe foundry goods has mechanical property and higher hardness preferably, by it is heat-treated, help postorder machining, the high nickel austenite spheroidal graphite cast-iron gas exhaust branch pipe foundry goods is warming up to 870 ℃-1000 ℃, be incubated 3-6 hour, be chilled to 620 ℃ with stove and come out of the stove.Foundry goods is through Overheating Treatment, and carbide is transformed into granularly in the tissue by strip and block, has improved the cutting ability of foundry goods.Add through machine after the heat treatment, remove burr and Shot Blasting, the check warehouse-in.