CN113106326A - Nodular cast iron for nail-free graphite of wind power equipment and preparation method thereof - Google Patents
Nodular cast iron for nail-free graphite of wind power equipment and preparation method thereof Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C37/00—Cast-iron alloys
- C22C37/04—Cast-iron alloys containing spheroidal graphite
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- C22C33/00—Making ferrous alloys
- C22C33/08—Making cast-iron alloys
- C22C33/10—Making cast-iron alloys including procedures for adding magnesium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C37/00—Cast-iron alloys
- C22C37/06—Cast-iron alloys containing chromium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C37/10—Cast-iron alloys containing aluminium or silicon
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Abstract
The invention belongs to the field of nodular cast iron casting, and relates to nodular cast iron for non-nail-shaped graphite of wind power equipment and a preparation method thereof. The invention reduces the intake of harmful elements by optimizing the component content of the nodular cast iron, strictly controls the carbon content in the eutectic period, accelerates the dissolution of carbon in hexagonal lattices after a large amount of silicon solid solution is formed, prevents a large amount of carbon from being separated out on crystal boundaries, prevents the anti-spheroidization segregation elements with higher content on the crystal boundaries, prevents the diffusion and accumulation of the carbon from different directions to the nucleation substances, leads the graphite to be spheroidized, and prevents the formation of spiky graphite. The pouring temperature, the mold filling speed and the heat preservation time are strictly controlled in the process of preparing the nodular cast iron, the segregation of the anti-spheroidization elements is reduced, the probability of forming the spiky graphite is reduced again, and the physical properties of the cast iron are ensured to a certain extent.
Description
Technical Field
The invention belongs to the field of nodular cast iron casting, and relates to nodular cast iron for non-nail-shaped graphite of wind power equipment and a preparation method thereof.
Background
The nodular cast iron is an important component part for national economic development and is mainly applied to wind power generation, nuclear power, automobile industries and the like. The wind power mainly uses ferrite nodular cast iron as main material, such as QT400-18AL, QT350-22AL, QT450-18AL, QT500-14, QT600-10, etc.; the nuclear power representing casting nuclear waste storage and transportation tank is mainly used for storing nuclear waste and represents the brand QT400-18 AL; in the automobile industry, small products are produced mostly, high-grade products such as QT600-3, QT700-2 and the like mainly represent that the castings have engine crankshafts. Whether the cast iron is low-grade or high-grade nodular cast iron, whether the cast iron is ferrite nodular iron or pearlite nodular iron, not only the indexes representing the mechanical properties of the casting but also the graphite form of the casting body need to be concerned; the core of the ductile iron smelting process control is to ensure good graphite form under the condition of randomly changing chemical components. However, in actual production, due to the change of the structural size of the casting, a large modulus and a large thermal node are generated locally on the casting, so that the local graphite form of the casting is deteriorated under the influence of the cooling speed and the solidification time. In the national standard GB/T1348-2009 nodular iron casting, 7.3 notes 1: the casting body performance values cannot be uniform, because the performance values depend on the complexity of the casting and the wall thickness variation of the casting.
The nail-shaped graphite is mostly present on the nodular iron casting, the QT400 mark is common, the nail-shaped graphite is also called as float grass-shaped graphite, the graphite is shaped like an iron nail which is randomly overlapped, the shape is like float grass, when the quantity of the nail-shaped graphite is large, the elongation of the body is rapidly deteriorated, the local mechanical property of the casting is deteriorated, when the casting is repeatedly stressed in the service stage, the fatigue strength of the casting is tested, the micro-cracks occur at the weak position of the surface quality of the casting, the cracks are continuously expanded along with time, when the cracks extend to the nail-shaped graphite area, the cracks are rapidly expanded, the macro-cracks are generated, even the casting is broken, and the economic loss is brought to the whole machine manufacturer.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides nodular cast iron with excellent mechanical property, high fatigue strength and fracture resistance for the nail-free graphite of wind power equipment and a preparation method thereof.
The purpose of the invention can be realized by the following technical scheme: the nodular cast iron for the nail-free graphite of the wind power equipment comprises the following components in percentage by mass: cr is less than or equal to 0.09 percent, Ti is less than or equal to 0.040 percent, Pb is less than or equal to 0.010 percent, Bi is less than or equal to 0.005 percent, Sb is less than or equal to 0.010 percent, Mn is less than or equal to 0.20 percent, Cu is less than or equal to 0.10 percent, Sn is less than or equal to 0.010 percent, C is 3.00-3.85 percent, Si: 1.80-3.85%, P is less than or equal to 0.030%, S is less than or equal to 0.015%, Re is less than or equal to 0.010%, Al is less than or equal to 0.02%, Mg: 0.035-0.045%, and the balance of Fe.
In the nodular cast iron for the nail-free graphite of the wind power equipment, the carbon equivalent of the graphite cast iron is 4.0-4.5%, and the carbon equivalent is the sum of the carbon content and one third of the silicon content.
Each graphite sphere has a core, the graphite core can be an inclusion or complex inclusion core, the shape of the core is different, and the size of the core is between 0.5 and 3 micrometers; carbon is piled up and grown on the core to finally form graphite nodules, and when the graphite nodule core is grown, the growth speed of the basal plane of the graphite branch is higher than that of the prism surface, so that the graphite balling is finally facilitated. For nail-shaped graphite like a pair of weeds or scattered nails, the interference of component segregation is mainly suffered from the graphite balling condition in the final solidification region of a casting, the diffusion movement of carbon atoms is blocked, the graphite cores cannot be normally stacked, the production speed of the edge surface is larger than that of a basal plane, a plurality of adjacent graphite cores rapidly grow along the edge surface, and finally the nail-shaped graphite is formed by interweaving the adjacent graphite cores after the carbon stacking is finished.
According to the invention, by optimizing the components of the nodular cast iron, harmful elements are prevented from being adsorbed on the interface growing along the graphite to change the normal growth mode of the graphite, so that spiky graphite is generated at the crystal boundary. The content of the spheroidizing elements of titanium, lead, bismuth, antimony, tin and the like in the cast iron is controlled, and the probability of nail-shaped graphite at the center of the casting is greatly reduced, because the content of antimony and bismuth in the ductile iron is too much, the antimony and bismuth have the function of neutralizing residual rare earth in molten iron, and the residual antimony and bismuth can cause the nail-shaped graphite to appear after the rare earth is neutralized; or the rare earth added into the cast iron is low, so that trace elements are excessive, and the spike formation can be caused.
The invention also provides a preparation method of the nodular cast iron for the non-nail-shaped graphite of the wind power equipment, which comprises the following steps:
s1, selecting furnace burden: 55-65 parts of high-purity pig iron, 15-25 parts of high-quality scrap steel, 15-25 parts of foundry returns, 0.5-2 parts of carburant and 0.5-4 parts of ferrosilicon;
s2, smelting: placing high-purity pig iron, high-quality scrap steel, foundry returns, a recarburizing agent and ferrosilicon into a smelting furnace for smelting, and controlling the tapping temperature of the molten iron to 1450-1480 ℃;
s3, spheroidizing inoculation: adding a nodulizer into the molten iron obtained in the step S2, then covering a ferrosilicon inoculant with the particle size of 2-10mm and the addition of 0.2-0.4% of the mass of the molten iron on the surface of the nodulizer, and carrying out spheroidization at 1450-1480 ℃;
s4, stream inoculation: after spheroidizing, pouring the molten iron into a connected test block casting mold, and adding a ferrosilicon inoculant with the grain diameter of 0.4-2mm and the addition amount of 0.1-0.2% of the mass of the molten iron along with the flow in the pouring process;
s5, casting and cooling: after the casting is finished, the temperature is preserved in the casting mould, then the casting mould is cooled to be below 350 ℃, and the casting is taken out of the casting mould.
In the preparation method of the nodular cast iron for the non-nail graphite of the wind power equipment, trace alloy element Sb is added before molten iron S2 is discharged from a furnace, and the addition amount is 0.001-0.005% of the mass of the molten iron.
Preferably, the high-purity pig iron comprises the following components in percentage by mass: c is more than or equal to 2.5 percent, and Si: less than 0.50 percent, less than or equal to 0.010 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.010 percent of Cr, less than or equal to 0.008 percent of Cu and less than or equal to 0.005 percent of Ti; v is less than or equal to 0.005 percent, Mo is less than or equal to 0.0001 percent, Pb is less than or equal to 0.0009 percent, B is less than or equal to 0.0009 percent, Sn is less than or equal to 0.0009 percent, Bi is less than or equal to 0.0008 percent, and the balance is Fe.
Preferably, the high-quality scrap steel comprises the following components in percentage by mass: less than or equal to 0.3 percent of C, less than or equal to 0.30 percent of Mn, less than or equal to 0.040 percent of Cr, less than or equal to 0.03 percent of S, and the balance of Fe.
Preferably, the ferrosilicon comprises the following components in percentage by mass: 72-80% of Si, less than or equal to 1.20% of Al, less than or equal to 0.50% of Mn, less than or equal to 0.50% of Cr and the balance of Fe.
Preferably, the carburant is a micro-sulfur carburant, wherein the sulfur content is less than or equal to 0.03 wt%, and the nitrogen content is less than or equal to 0.010 wt%.
In the preparation method of the nodular cast iron for the non-nail graphite of the wind power equipment, the grain diameter of the nodulizer in S3 is 4-30mm, and the adding amount of the nodulizer is 1.0-1.3% of the mass of molten iron.
In the preparation method of the nodular cast iron for the non-nail graphite of the wind power equipment, the nodulizer is one or two of a nodulizer A and a nodulizer B, and the nodulizer A comprises the following components: 5.7 to 6.3 percent of Mg, less than or equal to 2 percent of Al, 40 to 50 percent of Si, 1.0 to 2.0 percent of Ca, 0.5 to 1.0 percent of Re and the balance of Fe; the nodulizer B comprises the following components: 5.7 to 6.3 percent of Mg, less than or equal to 2 percent of Al, 40 to 50 percent of Si, 1.0 to 2.0 percent of Ca, less than or equal to 0.1 percent of Re and the balance of Fe.
When the used nodulizer is a mixture of the nodulizer A and the nodulizer B, the optimal mass ratio is 1: 1. The content of the rare earth added into the molten iron is controlled by matching two nodulizers, and under the same ingredients, the thicker the wall thickness is, the lower the content of the rare earth brought into the molten iron by the nodulizer is, and even the non-rare earth nodulizer can be used; the thin-wall part can be used with nodulizer with higher rare earth content and matched with pig iron with higher trace element content, so as to reduce the occurrence probability of spiky graphite, therefore, the invention can be flexibly matched with nodulizer according to actual requirements.
In the preparation method of the nodular cast iron for the nail-free graphite of the wind power equipment, the ferrosilicon fine grain inoculant comprises the following components: 70-80% of Si, less than or equal to 2.0% of Al, less than or equal to 0.5% of Mn, less than or equal to 0.5% of Cr, less than or equal to 0.040% of P, and the balance of Fe. The method is used for inoculating the molten iron twice, the graphite nucleation capability of the molten iron can be improved by twice inoculation, the addition amount is mainly the primary inoculation amount, the absorption effect of the instant inoculation along with the flow is poor, and the over-large inoculation amount is not suitable. And the particle size of the inoculant is controlled, so that the absorption effect of the components in the inoculant is greatly improved.
In the preparation method of the nodular cast iron for the nail-free graphite of the wind power equipment, the connected test block casting mold is a resin sand molding, and a bottom pouring type pouring channel is adopted for mold filling; the thickness of the casting mould wall is 10-600 mm.
In the preparation method of the nodular cast iron for the non-spike graphite of the wind power equipment, the time for pouring the molten iron S3 into the connected test block casting mold is 100-240S; the casting temperature is as follows: when the thickness of the casting mould wall is 10-60mm, the casting temperature is 1370-1380 ℃; when the wall thickness of the casting mold is 60-150mm, the casting temperature is 1350-; when the wall thickness of the casting mold is 150-300mm, the casting temperature is 1340-1350 ℃; when the wall thickness of the casting mold is 300-600mm, the pouring temperature is 1320-1330 ℃. The different pouring temperatures are adopted for the castings with different wall thicknesses because the solidification speeds of the cast iron molten irons with different wall thicknesses are different, the thicker the casting is, the longer the solidification time is, the lower the pouring temperature needs to be set, otherwise, graphite nodules are easy to distort; the casting with small wall thickness has high cooling speed and low pouring temperature and is easy to form cold shut defects.
In the preparation method of the nodular cast iron for the non-nail graphite of the wind power equipment, the heat preservation time of the S5 casting mold is as follows: when the wall thickness of the casting mould is 10-60mm, the heat preservation time is 48 h; when the wall thickness of the casting mould is 60-150mm, the heat preservation time is 96 h; when the wall thickness of the casting mold is 150-300mm, the heat preservation time is 168 h; when the thickness of the casting mold is 300-600mm, the heat preservation time is 240 h. The invention adopts different heat preservation time for the castings with different wall thicknesses because the castings are slowly cooled after being formed, austenite is transformed to ferrite and graphite when the heat preservation eutectoid transformation is carried out, if the box opening temperature is too early, the matrix structure of the castings is transformed to pearlite and cementite, the castings are hardened and embrittled, and the physical properties are greatly reduced.
When the wall thickness exceeds 150mm, the cast iron chill is arranged in the molding process, the chill wraps the casting, the thickness of the chill is 1.1-1.3 times of the wall thickness of the casting, the clearance between the chills is 15-20mm, and the chill has the function of forcibly chilling molten iron, so that the modulus of the casting is reduced, the solidification time is shortened, and the generation of spiky graphite is inhibited.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention reduces the intake of harmful elements by optimizing the component content of the nodular cast iron, strictly controls the carbon content in the eutectic period, accelerates the dissolution of carbon in hexagonal lattices after a large amount of silicon solid solution is formed, prevents a large amount of carbon from being separated out on crystal boundaries, prevents the anti-spheroidization segregation elements with higher content on the crystal boundaries, prevents the diffusion and accumulation of the carbon from different directions to the nucleation substances, leads the graphite to be spheroidized, and prevents the formation of spiky graphite.
2. The invention strictly controls the pouring temperature, the mold filling speed and the heat preservation time in the process of preparing the nodular cast iron, reduces the segregation of anti-spheroidization elements, reduces the formation probability of spiky graphite again, and ensures the physical properties of the cast iron to a certain extent.
3. The invention can increase the graphite nucleation capability of the molten iron by adopting the specific ferrosilicon inoculant in the two inoculation processes, and greatly improve the absorption effect of the components in the inoculant by controlling the addition amount and the particle size of the inoculant.
4. The wall thickness of the non-nail graphite nodular cast iron prepared by the invention can reach up to 600mm, and the non-nail graphite nodular cast iron still has excellent mechanical properties, high fatigue resistance and fracture resistance, and is completely suitable for wind power equipment.
Drawings
Fig. 1 is a metallographic picture of nodular cast iron of different wall thicknesses in example 1: a. the wall thickness is 25 mm; b. the wall thickness is 50 mm; c. the wall thickness is 95 mm; d. the wall thickness is 150 mm; e. the wall thickness is 400 mm; f. the wall thickness was 600 mm.
Fig. 2 is the metallographic images of nodular cast iron of example 2 with different wall thicknesses: a. the wall thickness is 95 mm; b. the wall thickness was 150 mm.
Fig. 3 is the metallographic images of nodular cast iron of comparative example 1 with different wall thicknesses: a. the wall thickness is 25 mm; b. the wall thickness is 50 mm; c. the wall thickness is 95 mm; d. the wall thickness was 150 mm.
Fig. 4 is the metallographic image of nodular cast iron of comparative example 2 with different wall thicknesses: a. the wall thickness is 95 mm; b. the wall thickness was 150 mm.
Fig. 5 is the metallographic images of nodular cast iron of comparative example 3 with different wall thicknesses: a. the wall thickness is 25 mm; b. the wall thickness is 50 mm; c. the wall thickness is 95 mm; d. the wall thickness was 150 mm.
Fig. 6 is the metallographic images of nodular cast iron of comparative example 4 with different wall thicknesses: a. the wall thickness is 25 mm; b. the wall thickness is 50 mm; c. the wall thickness is 95 mm; d. the wall thickness was 150 mm.
FIG. 7 is a scanning electron microscope image of the nail-shaped graphite.
Detailed Description
The following are specific examples of the present invention and further describe the technical solutions of the present invention, but the present invention is not limited to these examples.
Example 1
S1, selecting furnace burden: 60 parts of high-purity pig iron, 20 parts of high-quality scrap steel, 20 parts of a recasting material, 1 part of a carburant and 2 parts of ferrosilicon;
the high-purity pig iron comprises the following components in percentage by mass: c is more than or equal to 2.5 percent, and Si: less than 0.50 percent, less than or equal to 0.010 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.010 percent of Cr, less than or equal to 0.008 percent of Cu and less than or equal to 0.005 percent of Ti; v is less than or equal to 0.005 percent, Mo is less than or equal to 0.0001 percent, Pb is less than or equal to 0.0009 percent, B is less than or equal to 0.0009 percent, Sn is less than or equal to 0.0009 percent, Bi is less than or equal to 0.0008 percent, and the balance is Fe.
The high-quality scrap steel comprises the following components in percentage by mass: less than or equal to 0.3 wt% of C, less than or equal to 0.30 wt% of Mn, less than or equal to 0.040 wt% of Cr, less than or equal to 0.03 wt% of S, and the balance of Fe.
Carburant: the sulfur content is less than or equal to 0.03 weight percent, and the nitrogen content is less than or equal to 0.010 weight percent.
The ferrosilicon comprises the following components in percentage by mass: 72-80 wt% of Si, less than or equal to 1.20 wt% of Al, less than or equal to 0.50 wt% of Mn, less than or equal to 0.50 wt% of Cr and the balance of Fe.
S2, smelting: putting high-purity pig iron, high-quality scrap steel, foundry returns, a recarburizer and ferrosilicon into a smelting furnace for smelting, and controlling the tapping temperature of the molten iron to 1480 ℃; before the molten iron is discharged from the furnace, a trace alloy element Sb needs to be added, and the adding amount is 0.003 percent of the mass of the molten iron.
S3, spheroidizing inoculation: adding a nodulizer with the average particle size of 10mm and the addition amount of 1.1 percent of the mass of the molten iron into the molten iron obtained in the step S2, then covering the surface of the nodulizer with a ferrosilicon inoculant with the average particle size of 5mm and the addition amount of 0.3 percent of the mass of the molten iron, and carrying out nodulizing treatment at 1480 ℃; the nodulizer is a mixture of a nodulizer A and a nodulizer B in a mass ratio of 1:1, and the nodulizer A comprises the following components: 6.0 percent of Mg, less than or equal to 2 percent of Al, 45 percent of Si, 1.0 percent of Ca, 0.5 percent of Re and the balance of Fe; the nodulizer B comprises the following components: 5.8 percent of Mg, less than or equal to 2 percent of Al, 45 percent of Si, 1.0 percent of Ca, 0.05 percent of Re and the balance of Fe; the ferrosilicon inoculant comprises the following components: 70 percent of Si, less than or equal to 2.0 percent of Al, less than or equal to 0.5 percent of Mn, less than or equal to 0.5 percent of Cr, less than or equal to 0.040 percent of P, and the balance of Fe.
S4, stream inoculation: after spheroidizing, pouring the molten iron into a connected test block casting mold, and adding a ferrosilicon inoculant with the average grain diameter of 1mm and the addition amount of 0.1 percent of the mass of the molten iron along with the flow in the pouring process; the connected test block casting mold is a resin sand molding, and a bottom injection type pouring gate is used for filling; the thickness of the casting mould is 25mm, 50mm, 95mm, 150mm and 400 mm. The time for pouring the molten iron into the connected test block casting mold is 120 s; the casting temperature is as follows: when the wall thickness of the casting mold is 25mm and 50mm, the casting temperature is 1370 ℃; when the wall thickness of the casting mould is 95mm, the pouring temperature is 1360 ℃; when the wall thickness of the casting mold is 150mm, the casting temperature is 1350 ℃; when the mold wall thickness was 400mm, the casting temperature was 1325 ℃.
S5, casting and cooling: after the pouring is finished, preserving heat in the casting mold, then cooling to 200 ℃, and taking out the casting from the casting mold; the casting mold heat preservation time is as follows: when the wall thickness of the casting mould is 25mm and 50mm, the heat preservation time is 48 h; when the wall thickness of the casting mould is 95mm, the heat preservation time is 96 h; when the wall thickness of the casting mould is 150mm, the heat preservation time is 168 h; when the thickness of the casting mould wall is 400mm, the holding time is 240 h.
When the wall thickness exceeds 150mm, a cast iron chill is arranged in the molding process, the chill wraps the casting, the thickness of the chill is 1.2 times of the wall thickness of the casting, and the clearance of the chill is 15 mm.
The carbon equivalent of the final cast iron is 4.46, and the components and the mass percentage content thereof are as follows: 3.32% of C, 3.42% of Si, 0.07% of Mn, 0.022% of P, 0.009% of S, 0.0030% of Sb, 0.045% of Mg, 0.004% of Re, Cu: 0.009%, Cr 0.013%, Ti 0.014%, Sn 0.0011%, Pb 0.0007%, Bi 0.0005%, Al 0.011%, and the balance Fe.
Example 2:
the only difference from example 1 is that the casting temperature is: when the wall thickness of the casting mold is 25mm and 50mm, the casting temperature is 1430 ℃; when the wall thickness of the casting mold is 95mm, the casting temperature is 1425 ℃; when the wall thickness of the casting mould is 150mm, the casting temperature is 1420 ℃; when the mold wall thickness was 400mm, the casting temperature was 1415 ℃.
Comparative example 1:
the difference from the example 1 is only that the preparation process uses common pig iron, and the common pig iron comprises the following components in percentage by mass: c is more than or equal to 4.00 percent, and Si: 0.50-0.75%, Mn is less than or equal to 0.20%, P is less than or equal to 0.040%, Cr is less than or equal to 0.020%, Cu is less than or equal to 0.020%, and Ti is less than or equal to 0.040%; less than or equal to 0.020% of V, less than or equal to 0.010% of Mo, less than or equal to 0.010% of Pb, less than or equal to 0.0010% of B, less than or equal to 0.010% of Sn, less than or equal to 0.010% of Bi and the balance of Fe.
The carbon equivalent of the final cast iron is 4.43, and the components and the mass percentage content thereof are as follows: c: 3.30%, Si: 3.40%, Mn: 0.15%, P: 0.035%, S: 0.009%, Sb: 0.0060%, Mg: 0.045%, Re 0.003%, Cu: 0.017%, Cr: 0.020%, Ti 0.027%, Sn: 0.0042%, Pb 0.0033%, Bi 0.0025%, Al 0.012%, and the balance Fe.
Comparative example 2:
the difference from the example 1 is only that the carbon-silicon equivalent is increased to 4.65% in the preparation process, and the final cast iron components and the mass percentage content thereof are as follows: 3.50% of C, 3.46% of Si, 0.08% of Mn, 0.024% of P, 0.011% of S, 0.0035% of Sb, 0.048% of Mg, 0.005% of Re, 0.007% of Cu, 0.012% of Cr, 0.013% of Ti, 0.0012% of Sn, 0.0008% of Pb, 0.0003% of Bi and the balance of Fe.
Comparative example 3:
the difference from example 1 is only that the Sb content is increased during the preparation process, and the final cast iron composition and its mass percent content are: 3.44% of C, 3.40% of Si, 0.15% of Mn, 0.035% of P, 0.009% of S, 0.02% of Sb, 0.045% of Mg, 0.003% of Re, 0.017% of Cu, 0.020% of Cr, 0.027% of Ti, 0.0042% of Sn, 0.0033% of Pb, 0.0025% of Bi, 0.012% of Al and the balance of Fe.
Comparative example 4:
the difference from the embodiment 1 is only that the content of the whole spheroidizing elements of titanium, lead, bismuth, antimony and tin is improved in the preparation process, and the final cast iron comprises the following components in percentage by mass: 3.44 percent of C, 3.40 percent of Si, 0.15 percent of Mn, 0.035 percent of P, 0.009 percent of S, 0.02 percent of Sb0.02 percent of Mg, 0.045 percent of Re, 0.003 percent of Cu, 0.017 percent of Cr, 0.020 percent of Ti, 0.05 percent of Sn, 0.03 percent of Pb, 0.01 percent of Bi, 0.012 percent of Al and the balance of Fe.
Fig. 1 is a metallographic picture of nodular cast iron of different wall thicknesses in example 1: as can be seen from the figure: according to the manufacturing method of the embodiment 1, the production of spiky graphite can be effectively prevented even when the casting is formed within 600mm of the wall thickness.
Fig. 2 is the metallographic images of nodular cast iron of example 2 with different wall thicknesses: as can be seen from the figure: the higher the pouring temperature is, the higher the probability of nail-shaped graphite appears in the casting with the wall thickness of more than 95 mm.
Fig. 3 is the metallographic images of nodular cast iron of comparative example 1 with different wall thicknesses: as can be seen from the figure: ti, Pb, Bi, As, Sb, etc. in ordinary pig iron are taken into molten iron, and promote the formation of spiky graphite.
Fig. 4 is the metallographic image of nodular cast iron of comparative example 2 with different wall thicknesses: as can be seen from the figure: the carbon equivalent exceeds 4.5 percent, and the probability of spiky graphite of the casting with the wall thickness of more than 95mm is increased.
Fig. 5 is the metallographic images of nodular cast iron of comparative example 3 with different wall thicknesses: as can be seen from the figure: excess Sb is also a major cause of spiked graphite formation.
Fig. 6 is the metallographic images of nodular cast iron of comparative example 4 with different wall thicknesses: as can be seen from the figure: when the spheroidizing elements of titanium, lead, bismuth, antimony and tin are increased in large amounts, the possibility of formation of spiky graphite increases.
FIG. 7 is a metallographic electron microscope scan of spiked graphite: from the scanning results, it can be seen that the titanium content around the spiky graphite is very high, the titanium is also a forming factor of the spiky graphite, the titanium content needs to be controlled from the iron melt, and other trace elements cannot be detected by an electron microscope.
From the above results, it can be seen that the reason for the formation of the spike graphite of the present invention is as follows:
(1) when the contents of the anti-spheroidizing elements such as titanium, lead, bismuth, arsenic, antimony, tin and the like in molten iron are too high, nail-shaped graphite is easy to appear below the casting body by 30mm, the probability of appearing on high-grade ductile iron is higher, the high-grade ductile iron belongs to low-carbon high-silicon, and the nail-shaped graphite is easy to appear in the center of the casting due to the addition of alloy copper, tin, manganese, vanadium and molybdenum with improved strength and the production of ordinary iron and miscellaneous steel.
(2) The carbon content in the eutectic period is lower than the set value of the components, and after a large amount of silicon solid solution is formed, the solubility of carbon in hexagonal lattices is further reduced, a large amount of carbon is separated out on grain boundaries, and at the moment, anti-spheroidization elements with higher content exist on the grain boundaries, so that the diffusion and accumulation of carbon to nuclear substances from different directions are hindered, the graphite balling failure is caused, and the spiky graphite is formed.
(3) The casting temperature is too high and the mold filling speed is too fast, so that the solidification time of the casting is prolonged, and the segregation of the anti-spheroidization elements is serious.
(4) The content of antimony and bismuth in the nodular iron is excessive, the antimony and the bismuth have the function of neutralizing residual rare earth in molten iron, and after the rare earth is neutralized, the residual antimony and bismuth can cause nail-shaped graphite; or the rare earth added into the molten iron is low, so that trace elements are excessive, and the nail-shaped iron is formed.
(5) The casting has large modulus and low cooling speed, which causes serious element segregation and increases the probability of forming spiky graphite.
(6) Through scanning by an electron microscope, the spiky graphite is mainly distributed at a crystal boundary, harmful elements can be adsorbed at an interface growing along the graphite, and the normal growth mode of the graphite is changed. The content change of harmful elements in nanometer level can produce great effect without needing great amount, dozens or hundreds of PPM. Around the spiky graphite we have found that there is iron, and segregated harmful elements are generally distributed inside the graphite. The presence of Ti-containing compounds in the areas where spiky graphite is present, titanium agglomeration can exacerbate the adverse effects of other deleterious elements. The main harmful elements are Pb, Bi, As, Sb and the like. In thick-walled castings, segregation can strongly exacerbate this local area element clustering phenomenon. Through process experiments, the rare earth and cerium are found to play a role in neutralizing harmful elements; the segregation phenomenon can be reduced by accelerating the cooling effect of molten iron and increasing the density of graphite nodules. Optimizing control over raw materials, reducing the intake of harmful elements, and increasing the cooling rate are the most effective methods for controlling the production of spiked graphite.
Table 1: results of mechanical property test of nodular cast iron with wall thickness of 150mm in examples 1-2 and comparative examples 1-4
| Examples | Tensile strength (MPa) | Yield strength (MPa) | Elongation at Break (%) |
| Example 1 | 453 | 369 | 15.5 |
| Example 2 | 440 | 364 | 7.5 |
| Comparative example 1 | 446 | 362 | 9.7 |
| Comparative example 2 | 435 | 364 | 5.5 |
| Comparative example 3 | 438 | 358 | 8.5 |
| Comparative example 4 | 427 | 345 | 3.0 |
Table 2: results of mechanical property test of ductile cast iron with wall thickness of 600mm in examples 1-2 and comparative examples 1-4
| Examples | Tensile strength (MPa) | Yield strength (MPa) | Elongation at Break (%) |
| Example 1 | 433 | 355 | 15.0 |
| Example 2 | 429 | 348 | 8.5 |
| Comparative example 1 | 430 | 349 | 7.2 |
| Comparative example 2 | 418 | 340 | 4.3 |
| Comparative example 3 | 431 | 347 | 8.0 |
| Comparative example 4 | 420 | 327 | 3.5 |
In conclusion, the invention reduces the intake of harmful elements by optimizing the component content of nodular cast iron, strictly controls the carbon content in the eutectic period, accelerates the dissolution of carbon in hexagonal lattices after a large amount of silicon solid solution is formed, prevents a large amount of carbon from being separated out on crystal boundaries, and prevents high-content anti-spheroidization segregation elements from existing on the crystal boundaries at the moment, so that the diffusion and accumulation of carbon on nucleation substances from different directions are prevented, the graphite is pelletized, and the formation of spiky graphite is prevented; the casting temperature and the mold filling speed of the nodular cast iron are strictly controlled in the preparation process, the segregation of anti-spheroidization elements is reduced, the formation probability of spike-shaped graphite is reduced again, the nodular cast iron prepared by the method still has excellent mechanical property, high fatigue resistance and fracture resistance, is completely suitable for most wind power equipment, has a prominent effect of preventing spike-shaped graphite from being generated in the heat junctions and the thick and large section centers of wind power castings, improves the mechanical property of the nodular cast iron in a slow cooling region, enables the casting quality to be more superior, represents another innovation of a nodular cast iron smelting technology, and has far-reaching significance for the smelting technology development.
The technical scope of the invention claimed by the embodiments of the present application is not exhaustive, and new technical solutions formed by equivalent replacement of single or multiple technical features in the technical solutions of the embodiments are also within the scope of the invention claimed by the present application; in all the embodiments of the present invention, which are listed or not listed, each parameter in the same embodiment only represents an example (i.e., a feasible embodiment) of the technical solution, and there is no strict matching and limiting relationship between the parameters, wherein the parameters may be replaced with each other without departing from the axiom and the requirements of the present invention, unless otherwise specified.
The technical means disclosed by the scheme of the invention are not limited to the technical means disclosed by the technical means, and the technical scheme also comprises the technical scheme formed by any combination of the technical characteristics. While the foregoing is directed to embodiments of the present invention, it will be appreciated by those skilled in the art that various changes may be made in the embodiments without departing from the principles of the invention, and that such changes and modifications are intended to be included within the scope of the invention.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (10)
1. The nodular cast iron for the nail-free graphite of the wind power equipment is characterized by comprising the following components in percentage by mass: cr is less than or equal to 0.09 percent, Ti is less than or equal to 0.040 percent, Pb is less than or equal to 0.010 percent, Bi is less than or equal to 0.005 percent, Sb is less than or equal to 0.010 percent, Mn is less than or equal to 0.20 percent, Cu is less than or equal to 0.10 percent, Sn is less than or equal to 0.010 percent, C is 3.00-3.85 percent, Si: 1.80-3.85%, P is less than or equal to 0.030%, S is less than or equal to 0.015%, Re is less than or equal to 0.010%, Al is less than or equal to 0.02%, Mg: 0.035-0.045%, and the balance of Fe.
2. The nodular cast iron for studless graphite of wind power equipment according to claim 1, wherein the carbon equivalent of the graphite cast iron is 4.0-4.5%.
3. The method for preparing nodular cast iron for studless graphite of wind power plants as claimed in claim 1, wherein the method comprises the following steps:
s1, selecting furnace burden: 55-65 parts of high-purity pig iron, 15-25 parts of high-quality scrap steel, 15-25 parts of foundry returns, 0.5-2 parts of carburant and 0.5-4 parts of ferrosilicon;
s2, smelting: placing high-purity pig iron, high-quality scrap steel, foundry returns, a recarburizing agent and ferrosilicon into a smelting furnace for smelting, and controlling the tapping temperature of the molten iron to 1450-1480 ℃;
s3, spheroidizing inoculation: adding a nodulizer into the molten iron obtained in the step S2, then covering a ferrosilicon inoculant with the particle size of 2-10mm and the addition of 0.2-0.4% of the mass of the molten iron on the surface of the nodulizer, and carrying out spheroidization at 1450-1480 ℃;
s4, stream inoculation: after spheroidizing, pouring the molten iron into a connected test block casting mold, and adding a ferrosilicon inoculant with the grain diameter of 0.4-2mm and the addition amount of 0.1-0.2% of the mass of the molten iron along with the flow in the pouring process;
s5, casting and cooling: after the casting is finished, the temperature is preserved in the casting mould, then the casting mould is cooled to be below 350 ℃, and the casting is taken out of the casting mould.
4. The method for preparing the nodular cast iron for the non-nail graphite of the wind power equipment as claimed in claim 3, wherein trace alloying element Sb is added before molten iron S2 is discharged from the furnace, and the addition amount is 0.001-0.005% of the mass of the molten iron.
5. The method for preparing the nodular cast iron for the non-nail graphite of the wind power equipment as claimed in claim 3, wherein the grain size of the nodulizer in S3 is 4-30mm, and the addition amount is 1.0-1.3% of the mass of the molten iron.
6. The preparation method of nodular cast iron used in the non-spike graphite of wind power equipment as claimed in claim 3 or 5, wherein the nodulizer is one or two of nodulizer A and nodulizer B, and the nodulizer A comprises the following components: 5.7 to 6.3 percent of Mg, less than or equal to 2 percent of Al, 40 to 50 percent of Si, 1.0 to 2.0 percent of Ca, 0.5 to 1.0 percent of Re and the balance of Fe; the nodulizer B comprises the following components: 5.7 to 6.3 percent of Mg, less than or equal to 2 percent of Al, 40 to 50 percent of Si, 1.0 to 2.0 percent of Ca, less than or equal to 0.1 percent of Re and the balance of Fe.
7. The preparation method of the nodular cast iron for the nail-free graphite of the wind power equipment as claimed in claim 3, wherein the ferrosilicon inoculant comprises the following components: 78-80% of Si 70%, less than or equal to 2.0% of Al, less than or equal to 0.5% of Mn, less than or equal to 0.5% of Cr, less than or equal to 0.040% of P, and the balance of Fe.
8. The method for preparing the nodular cast iron for the nailless graphite of the wind power equipment as claimed in claim 3, wherein the connected test block mold is a resin sand mold, a bottom pouring type pouring gate is adopted for mold filling, and the wall thickness of the mold is 10-600 mm.
9. The method for preparing nodular cast iron used in non-spike graphite of wind power equipment as claimed in claim 8, wherein the time for pouring the molten iron of S4 into the connected test block mold is 100-240S; the casting temperature is as follows: when the thickness of the casting mould wall is 10-60mm, the casting temperature is 1370-1380 ℃; when the wall thickness of the casting mold is 60-150mm, the casting temperature is 1350-; when the wall thickness of the casting mold is 150-300mm, the casting temperature is 1340-1350 ℃; when the wall thickness of the casting mold is 300-600mm, the pouring temperature is 1320-1330 ℃.
10. The preparation method of the nodular cast iron for the nail-free graphite of the wind power equipment as claimed in claim 3, wherein the mold heat preservation time of S5 is as follows: when the wall thickness of the casting mould is 10-60mm, the heat preservation time is 45-50 h; when the wall thickness of the casting mould is 60-150mm, the heat preservation time is 90-100 h; when the wall thickness of the casting mold is 150-; when the thickness of the casting mold is 300-600mm, the heat preservation time is 230-250 h.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113736947A (en) * | 2021-09-07 | 2021-12-03 | 襄阳金耐特机械股份有限公司 | Preparation method of nodular cast iron |
| CN114411049A (en) * | 2021-12-29 | 2022-04-29 | 天润工业技术股份有限公司 | Low-cost and high-strength ferritic nodular cast iron and preparation method and application thereof |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63200504A (en) * | 1987-02-16 | 1988-08-18 | Mitsubishi Metal Corp | Fe alloy magnetic core materials for high frequency |
| CN1560308A (en) * | 2004-02-23 | 2005-01-05 | 王义波 | Nodular cast iron piston ring containing vanadium titanium alloy |
| CN105039839A (en) * | 2015-08-20 | 2015-11-11 | 合肥市田源精铸有限公司 | Manufacturing method for nodular cast iron used for crankshaft |
| CN106893930A (en) * | 2017-03-29 | 2017-06-27 | 江苏吉鑫风能科技股份有限公司 | A kind of big low-temperature ball spheroidal graphite cast iron of super thick and preparation method thereof |
| CN108085580A (en) * | 2017-12-31 | 2018-05-29 | 山东汇金股份有限公司 | A kind of high intensity, high tenacity cast condition ductile iron and its production method |
| CN108330383A (en) * | 2018-03-23 | 2018-07-27 | 江苏吉鑫风能科技股份有限公司 | A kind of casting method of large-scale wind electricity casting and casting by its casting |
| CN108441750A (en) * | 2018-03-12 | 2018-08-24 | 江苏吉鑫风能科技股份有限公司 | A kind of wind power equipment spheroidal graphite cast-iron and preparation method thereof |
| CN112048660A (en) * | 2020-09-07 | 2020-12-08 | 西峡县众德汽车部件有限公司 | Preparation method of nodular cast iron QT700-7 |
-
2021
- 2021-04-15 CN CN202110404209.4A patent/CN113106326B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63200504A (en) * | 1987-02-16 | 1988-08-18 | Mitsubishi Metal Corp | Fe alloy magnetic core materials for high frequency |
| CN1560308A (en) * | 2004-02-23 | 2005-01-05 | 王义波 | Nodular cast iron piston ring containing vanadium titanium alloy |
| CN105039839A (en) * | 2015-08-20 | 2015-11-11 | 合肥市田源精铸有限公司 | Manufacturing method for nodular cast iron used for crankshaft |
| CN106893930A (en) * | 2017-03-29 | 2017-06-27 | 江苏吉鑫风能科技股份有限公司 | A kind of big low-temperature ball spheroidal graphite cast iron of super thick and preparation method thereof |
| CN108085580A (en) * | 2017-12-31 | 2018-05-29 | 山东汇金股份有限公司 | A kind of high intensity, high tenacity cast condition ductile iron and its production method |
| CN108441750A (en) * | 2018-03-12 | 2018-08-24 | 江苏吉鑫风能科技股份有限公司 | A kind of wind power equipment spheroidal graphite cast-iron and preparation method thereof |
| CN108330383A (en) * | 2018-03-23 | 2018-07-27 | 江苏吉鑫风能科技股份有限公司 | A kind of casting method of large-scale wind electricity casting and casting by its casting |
| CN112048660A (en) * | 2020-09-07 | 2020-12-08 | 西峡县众德汽车部件有限公司 | Preparation method of nodular cast iron QT700-7 |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113736947A (en) * | 2021-09-07 | 2021-12-03 | 襄阳金耐特机械股份有限公司 | Preparation method of nodular cast iron |
| CN113736947B (en) * | 2021-09-07 | 2022-08-09 | 襄阳金耐特机械股份有限公司 | Preparation method of nodular cast iron |
| CN114411049A (en) * | 2021-12-29 | 2022-04-29 | 天润工业技术股份有限公司 | Low-cost and high-strength ferritic nodular cast iron and preparation method and application thereof |
| CN114411049B (en) * | 2021-12-29 | 2022-12-02 | 天润工业技术股份有限公司 | Low-cost and high-strength ferritic nodular cast iron and preparation method and application thereof |
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