Pouring instantaneous inoculant, spheroidizing inoculation method and nodular cast iron for wind power casting

Abstract

The invention relates to a pouring instantaneous inoculant, a spheroidizing inoculation method and nodular cast iron for a wind power casting, and belongs to the technical field of metal casting processing. The casting instantaneous inoculant comprises the following main chemical components in percentage by weight: 0.45 to 0.55 percent of Y, 2.0 to 3.0 percent of Ca, 3.0 to 5.0 percent of Ba, 1.5 to 2.5 percent of Bi, 55 to 65 percent of Si and the balance of Fe. According to the pouring instantaneous inoculant provided by the invention, the spheroidization decline resistance can be remarkably improved by adding yttrium, the bismuth can refine graphite and promote ferrite formation, and the rapid nucleation capacity of calcium cooperates with the long-acting inoculation capacity of barium, so that the stability of the graphite quantity is ensured, and the inoculation decline prevention effect is good; and the inoculation decay prevention effect of calcium and barium is cooperated with the graphitization capability of silicon, so that the long-acting inoculation is ensured, and the spheroidization rate and the elongation performance are improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal casting processing, and in particular to a pouring instantaneous inoculant, a spheroidizing inoculation method and ductile iron for wind power castings. Background Art

[0002] High-wind-power wind power castings are the need for wind turbines to develop in the direction of large-scale and lightweight. The strength and toughness indicators of ductile iron, the material, are required to be high. Research and application of silicon solid-solution ferrite ductile iron has become a trend, and its spheroidizing inoculation technology is one of the key technologies.

[0003] The existing spheroidizing inoculation casting flow inoculation adopts silicon barium inoculant.

[0004] However, when the above-mentioned existing spheroidizing inoculation is applied to ductile iron QT500-14 material, metallographic detection shows that the number of graphite nodules is small, the roundness of the graphite nodules is poor, the spheroidizing rate of the test block is 85%, and the elongation is low.

[0005] Moreover, there are currently few similar technologies targeting or involving the application of QT500-14 wind power castings.

[0006] Therefore, it is urgent to develop a method for pouring instantaneous inoculant and spheroidizing inoculation of ductile iron QT500-14 material to ensure high strength and further high elongation of the material to meet the requirements of high wind power wind turbine castings. Summary of the invention

[0007] In view of the above analysis, the present invention aims to provide a casting instantaneous inoculant, a spheroidizing inoculation method and ductile iron for wind power castings, so as to solve one of the problems that the existing ductile iron has low spheroidizing rate, strength and elongation and cannot meet the requirements of high wind power wind power castings.

[0008] On the one hand, the present invention provides a pouring instantaneous inoculant, wherein the main chemical components of the pouring instantaneous inoculant are, by weight percentage, Y: 0.45-0.55, Ca: 2.0-3.0, Ba: 3.0-5.0, Bi: 1.5-2.5, Si: 55-65, and the balance is Fe.

[0009] On the other hand, the present invention provides a spheroidization inoculation method, comprising: step 1: selecting at least one of a light rare earth spheroidizer and a heavy rare earth spheroidizer for spheroidization treatment; step 2: adopting a three-step combined inoculation method including long-term inoculation at the bottom of a ladle, inoculation with the flow of molten iron out of a furnace, and pouring instant inoculation for inoculation, wherein the pouring instant inoculation adopts the above-mentioned pouring instant inoculant.

[0010] Preferably, the step 2 comprises: S201: long-term inoculation at the bottom of the ladle; S202: inoculation with the flow of molten iron out of the furnace; S203: instantaneous inoculation during pouring.

[0011] Preferably, in step S203, an instantaneous inoculant having a mass ratio of 0.175-0.225% of the molten iron is uniformly added during pouring.

[0012] Preferably, step S201 uses a bottom inoculant, the main chemical components of which are, by weight percentage, Ca: 1.5-2.0, Ba: 4.0-6.0, Si: 67-72, and the remainder is Fe.

[0013] Preferably, in step S201, the bottom inoculant is spread on the spheroidizing agent, and the mass ratio of the bottom inoculant added to the molten iron is 0.75-0.85%.

[0014] Preferably, in step S202, when two-thirds of the molten iron flows out of the furnace and enters the ladle, the remaining one-third is added with 0.008%-0.010% by mass of metallic antimony into the molten iron.

[0015] Preferably, the main chemical components of the light rare earth spheroidizer are, by weight percentage, RE: 0.8-1.2, Mg: 6.0-7.0, Ca: 1.5-2.5, Ba: 1.0-3.0, Si: 42-46, and the balance is Fe; the main chemical components of the heavy rare earth spheroidizer are, by weight percentage, RE: 0.5-1.5, Mg: 5.5-6.5, Ca: 1.5-2.5, Ba: 1.0-3.0, Si: 44-48, and the balance is Fe.

[0016] In another aspect, the present invention provides a ductile iron, wherein the ductile iron is QT500-14 material and is produced by the above-mentioned spheroidizing inoculation method.

[0017] Preferably, the ductile iron is used for high wind power wind turbine castings.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0019] 1. The instantaneous inoculant for casting provided by the present invention can significantly improve the ability to resist spheroidization decay by adding yttrium, bismuth can refine graphite and promote the formation of ferrite, the rapid nucleation ability of calcium cooperates with the long-term inoculation ability of barium to ensure the stability of the amount of graphite and prevent good inoculation decay effect, the inoculation decay prevention effect of calcium and barium cooperates with the graphitization ability of silicon to ensure the long-term inoculation, and can further improve the elongation on the basis of ensuring high strength.

[0020] 2. The present invention realizes microalloying by adding antimony during inoculation after the furnace is discharged and adding bismuth and heavy rare earth yttrium during instantaneous inoculation during pouring, which can refine graphite, increase the number of graphite balls, and improve the roundness of graphite balls, thereby improving the spheroidization rate and elongation performance.

[0021] 3. The present invention preferably adopts a combination of light and / or heavy rare earth spheroidization and a triple inoculation method of bottom packaging, flow following the furnace, and instantaneous pouring to further improve the spheroidization rate, improve the graphite morphology and distribution, increase the number of graphite balls, refine the graphite, improve the roundness of the graphite balls, and significantly improve the ability of ductile iron to resist inoculation decay. It can increase the elongation while ensuring high strength, and meet the performance requirements of high strength and high elongation of ductile iron for high wind power wind power.

[0022] 4. The cast structure of the QT500-14 material obtained by the present invention is ferrite + graphite, the spheroidization rate is above 90%, the spheroidization level is above level 6, and its mechanical properties meet the grade requirements.

[0023] 5. The QT500-14 material obtained by the present invention is used for the hub test piece body: tensile strength>500MPa, yield strength>400MPa, elongation≥14%.

[0024] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0026] Figure 1 This is a metallographic diagram of the uncorroded ductile iron prepared in Example 3 provided by the present invention.

[0027] Figure 2 This is a metallographic diagram of the corroded state of the ductile iron prepared in Example 3 provided by the present invention. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0029] The invention provides a ductile iron pouring instantaneous inoculant, the main chemical components (%Wt) of which are: Y: 0.45-0.55, Ca: 2.0-3.0, Ba: 3.0-5.0, Bi: 1.5-2.5, Si: 55-65, and the balance is Fe.

[0030] The instantaneous inoculant provided by the present invention has the advantages that the addition of yttrium can significantly improve the ability to resist spheroidization decay, bismuth can refine graphite and promote the formation of ferrite, the rapid nucleation ability of calcium cooperates with the long-term inoculation ability of barium to ensure the stability of the amount of graphite and has a good effect in preventing inoculation decay, and the inoculation decay prevention effect of calcium and barium cooperates with the graphitization ability of silicon to ensure the long-term inoculation.

[0031] Specific description of the role and dosage of instantaneous inoculant components:

[0032] Y: The addition of a small amount of yttrium can significantly improve the ability to resist spheroidization decay. If the content of yttrium is too low, the ability to resist spheroidization decay will not be significantly improved, while if the content of yttrium is too high, it may cause an increase in shaped graphite. Therefore, the content of Y in the instantaneous inoculant of the present invention is controlled at 0.45-0.55%.

[0033] Ca: Calcium can effectively provide graphite nucleation cores, and has a good inoculation effect when used in combination with barium. The rapid nucleation ability of calcium cooperates with the long-term inoculation ability of barium to ensure the stability of the amount of graphite and prevent the inoculation decay. If the calcium content is too low, it cannot provide enough nucleation cores, and if it is too high, it can form slag that is not easy to remove, resulting in slag inclusions in castings. Therefore, the Ca content in the instantaneous inoculant of the present invention is controlled at 2.0%-3.0%.

[0034] Ba: Barium can effectively increase the amount of graphite and reduce the tendency of white cast, so as to play a long-term inoculation role. If the content of barium is too low, the number of nuclei provided is limited, and the long-term inoculation effect cannot be achieved. If the content of barium is too high, slag inclusion may occur. Therefore, the content of Ba in the instantaneous inoculant of the present invention is controlled at 3.0%-5.0%.

[0035] Bi: Bi can refine graphite and promote the formation of ferrite. If its content is too low, it will not refine graphite, and if it is too high, it may cause the deterioration of graphite morphology. Therefore, the content of Bi in the instantaneous inoculant of the present invention is controlled at 1.5%-2.5%.

[0036] Si: Silicon is a strong graphitizing element. The nucleation of calcium, barium, etc. requires silicon as a basis. The anti-inoculation decay effect of calcium and barium cooperates with the graphitization ability of silicon to ensure the inoculation effect. Too low silicon content leads to the inability to fully exert the nucleation inoculation effect of calcium and barium, while too high silicon content may cause graphite floating. Therefore, the content of Si in the instantaneous inoculant of the present invention is controlled at 55%-65%.

[0037] In addition, the present invention also provides a spheroidizing inoculation method for ductile iron, comprising:

[0038] Step 1: selecting at least one of a light rare earth spheroidizer and a heavy rare earth spheroidizer to perform spheroidization treatment;

[0039] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0040] It should be noted that the spheroidization inoculation method provided by the present invention adopts a triple inoculation method of light and / or heavy rare earth spheroidization and bottom packaging, furnace flow, and pouring instant, so as to improve the spheroidization rate, improve the morphology and distribution of graphite, increase the number of graphite balls, refine graphite, improve the roundness of graphite balls, and significantly improve the ability of ductile iron to resist inoculation decay. It can increase the elongation while ensuring high strength, and meet the performance requirements of high strength and high elongation of ductile iron for high wind power wind power.

[0041] For step 1:

[0042] Specifically, in step 1, 1.3-1.7% (the mass ratio of the molten iron) of light rare earth spheroidizer can be selected, and the spheroidization treatment is carried out by the bottom-injection method. As a preferred embodiment, 1.3-1.7% (the mass ratio of the molten iron) of heavy rare earth spheroidizer can also be selected, and the spheroidization treatment is carried out by the bottom-injection method. As another preferred embodiment, 0.6-0.8% (the mass ratio of the molten iron) of light rare earth spheroidizer and 0.7-0.9% (the mass ratio of the molten iron) of heavy rare earth spheroidizer can be selected as a composite spheroidizer, and the spheroidization treatment is carried out by the bottom-injection method.

[0043] Preferably, in step 1,

[0044] The main chemical composition (%Wt) of the light rare earth spheroidizer is: RE: 0.8-1.2, Mg: 6.0-7.0, Ca: 1.5-2.5, Ba: 1.0-3.0, Si: 42-46, and the balance is Fe;

[0045] The main chemical components (%Wt) of the heavy rare earth spheroidizer are: RE: 0.5-1.5, Mg: 5.5-6.5, Ca: 1.5-2.5, Ba: 1.0-3.0, Si: 44-48, and the balance is Fe.

[0046] When the light rare earth spheroidizer and the heavy rare earth spheroidizer are used in combination, the mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is (6-8):(7-9).

[0047] It should be noted that the light rare earth spheroidizer plays a basic spheroidizing role, and the heavy rare earth spheroidizer provides a long-lasting nucleation core. When the light rare earth spheroidizer and the heavy rare earth spheroidizer are used in combination, the synergistic effect ensures normal spheroidization and the amount and morphology of graphite, thereby improving the spheroidization rate and helping to improve the elongation performance.

[0048] Specifically, for light rare earth spheroidizer, it should be noted that:

[0049] RE is a light rare earth element, which can be selected from lanthanum and cerium. The main function of light rare earth is to form oxides and become an effective core for graphite nucleation. Too low a light rare earth content will result in poor spheroidization, while too high a light rare earth content will cause graphite morphology to deteriorate and graphite to deform. Therefore, the content of RE in the light rare earth nodulizer of the present invention is controlled at 0.8%-1.2%. In addition, the combined use of light rare earth and magnesium has a good effect. The light rare earth's role in purifying molten iron and providing a nucleation core cooperates with the spheroidization of magnesium, and the spheroidization effect is better.

[0050] Mg: The main function of magnesium is spheroidization reaction, and its oxides, sulfides and other reactants are the basic graphite nucleation core. If its content is too low, it is easy to cause poor spheroidization, and if it is too high, the residual magnesium content is high, causing problems such as slag inclusion, shrinkage, and subcutaneous pores. Therefore, the Mg content in the light rare earth spheroidizer of the present invention is controlled at 6.0%-7.0%.

[0051] Ca: The role of calcium is to provide nucleation cores, increase the number of graphite balls, and assist spheroidization. Too low a content cannot provide enough nucleation cores, and too high a content may cause slag inclusion and other problems. Therefore, the content of Ca in the light rare earth spheroidizer of the present invention is controlled at 1.5%-2.5%.

[0052] Ba: The role of barium is to form oxides and sulfides with oxygen and sulfur, becoming an effective nucleation core. If the content is too low, it will not play a long-term inoculation role, and if it is too high, it will form slag inclusions. Therefore, the content of Ba in the light rare earth spheroidizer of the present invention is controlled at 1.0%-3.0%.

[0053] Si: Silicon is a strong graphitizing element and is the basic element of the spheroidizer. Too low a content may cause poor spheroidization, and too high a content may cause graphite floating. Therefore, the content of Si in the light rare earth spheroidizer of the present invention is controlled at 42%-46%.

[0054] Specifically, for heavy rare earth spheroidizers, it should be noted that:

[0055] RE is a heavy rare earth element, which can be selected from yttrium. The addition of a small amount of heavy rare earth can significantly improve the ability to resist spheroidization decay, graphite distortion and interference elements. If its content is too low, it cannot play a role in improving the resistance to spheroidization decay, and if it is too high, it can cause graphite distortion. Therefore, the content of RE in the heavy rare earth spheroidizer of the present invention is controlled at 0.5%-1.5%. The ability of heavy rare earth to improve the resistance to spheroidization decay cooperates with the spheroidization ability of magnesium, and the spheroidization effect is good.

[0056] Mg: The main function of magnesium is spheroidization reaction. Its oxides, sulfides and other reactants are the basic graphite nucleation cores. If its content is too low, it is easy to cause poor spheroidization. If it is too high, the residual magnesium content is high, causing slag inclusion, shrinkage, subcutaneous pores and other problems. Therefore, the Mg content in the heavy rare earth spheroidizer of the present invention is controlled at 5.5%-6.5%.

[0057] Ca: The role of calcium is to provide nucleation cores, increase the number of graphite balls, and assist spheroidization. Too low a calcium content cannot provide enough nucleation cores, and too high a calcium content may cause problems such as slag inclusion. Therefore, the content of Ca in the heavy rare earth spheroidizer of the present invention is controlled at 1.5%-2.5%.

[0058] Ba: The role of barium is to form oxides and sulfides with oxygen and sulfur, becoming an effective nucleation core. If the content of barium is too low, it will not play a long-term inoculation role, and if it is too high, slag inclusions will be formed. Therefore, the content of Ba in the heavy rare earth spheroidizer of the present invention is controlled at 1.0%-3.0%.

[0059] Si: Silicon is a strong graphitizing element and is the basic element of the spheroidizer. Too low a silicon content may cause poor spheroidization, while too high a silicon content may cause graphite floating. Therefore, the content of Si in the heavy rare earth spheroidizer of the present invention is controlled at 44%-48%.

[0060] Specifically, in step 1, the size of the spheroidizing agent is 20-40 mm. It should be noted that if the size is too high, the spheroidizing agent cannot be fully absorbed, and if it is too low, the detonation time may be too short and the spheroidizing effect may be poor.

[0061] Specifically, in step 1, the spheroidizing agent dam is laid flat on the bottom of the ladle with a thickness of 200-300 mm. The light rare earth spheroidizing agent can be laid first and then the heavy rare earth spheroidizing agent. It should be noted that if the laying thickness is too high, the spheroidizing reaction is not sufficient, and if the laying thickness is too low, the molten iron may directly impact the spheroidizing agent, causing the spheroidizing reaction to detonate prematurely, affecting the spheroidizing effect or even failing to spheroidize.

[0062] Specifically, in step 1, before adding the spheroidizing agent, the spheroidizing agent may be fully preheated and dried, and the preheating temperature is preferably 200-300° C. It should be noted that if the preheating temperature is too high, the spheroidizing element will be lost, and if the preheating temperature is too low, the preheating effect cannot be achieved, resulting in a decrease in the spheroidizing effect with the same amount of spheroidizing agent added.

[0063] For step 2:

[0064] Specifically, step 2 may include:

[0065] S201: long-term incubation of the bottom of the package;

[0066] S202: molten iron is incubated as it comes out of the furnace;

[0067] S203: pouring instant incubation.

[0068] For step S201:

[0069] Specifically, in step S201, the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5-2.0, Ba: 4.0-6.0, Si: 67-72, and the balance is Fe.

[0070] The bottom inoculant provided by the present invention has the rapid nucleation ability of calcium and the long-term inoculation ability of barium to ensure the stability of the graphite quantity and prevent the inoculation decay effectively. The inoculation decay prevention effect of calcium and barium cooperates with the graphitization ability of silicon to ensure the long-term inoculation.

[0071] Specific description of the role and dosage of the bottom inoculant components:

[0072] Ca: Calcium can effectively provide graphite nucleation cores, and has a good inoculation effect when used in combination with barium. The rapid nucleation ability of calcium cooperates with the long-term inoculation ability of barium to ensure the stability of the amount of graphite and prevent the inoculation from decaying. If the calcium content is too low, the inoculation effect cannot be achieved, and if it is too high, slag inclusions may be formed. Therefore, the Ca content in the bottom inoculant of the present invention is controlled at 1.5%-2.0%.

[0073] Ba: Barium can effectively increase the amount of graphite and reduce the tendency of white cast iron, playing a role of long-term inoculation. If the barium content is too low, the long-term inoculation effect cannot be achieved, and if it is too high, the amount of slag will increase. Therefore, the content of Ba in the long-term inoculant of the bottom of the ladle of the present invention is controlled at 4.0%-6.0%.

[0074] Si: Silicon is a strong graphitizing element. The nucleation of calcium and barium requires silicon as a basis. The anti-inoculation decay effect of calcium and barium cooperates with the graphitization ability of silicon to ensure the long-term inoculation. Too low silicon content leads to the inability to fully exert the nucleation inoculation effect of calcium and barium, while too high silicon content may cause graphite floating. Therefore, the content of Si in the bottom long-term inoculant of the present invention is controlled at 67%-72%.

[0075] Specifically, in step S201, the bottom inoculant is spread on the spheroidizing agent, and after spheroidization, the bottom inoculant performs long-term bottom inoculation on the molten iron, and the thickness of the bottom inoculant is 100-200 mm. It should be noted that if the thickness of the bottom inoculant is too high, the spheroidization reaction may be initiated too late, resulting in poor spheroidization, and if it is too low, the inoculation effect is not good, which may cause the graphite morphology to deteriorate.

[0076] Specifically, in step S201, the mass ratio of the bottom inoculant added to the molten iron is 0.75-0.85%. It should be noted that too high an inoculant content will cause the final silicon content to exceed the standard, while too low an inoculant content will not achieve the effect of long-term inoculation. As a preferred embodiment, the mass ratio of the bottom inoculant added to the molten iron is 0.8%.

[0077] Specifically, in step S201, the particle size of the bottom inoculant is 3-8 mm. It should be noted that if the particle size is too high, it cannot be fully absorbed and the expected inoculation effect cannot be achieved, while if the particle size is too low, it may directly turn into scum and long-term inoculation cannot be achieved.

[0078] Specifically, in step S201, before adding the bottom inoculant, the bottom inoculant is preheated and dried, the preheating temperature is preferably 200-300°C, and the moisture is removed by drying.

[0079] For step S202:

[0080] Specifically, in step S202, when two-thirds of the molten iron flows out of the furnace and enters the ladle, 0.008%-0.010% (by mass of the molten iron) of metallic antimony is added to the remaining one-third.

[0081] It should be noted that antimony is very sensitive. Too high a content of metallic antimony will promote the formation of pearlite, while too low a content will not improve the roundness of graphite nodules. Therefore, the mass ratio of antimony to molten iron is controlled to be 0.008%-0.010%, preferably 0.009%.

[0082] Specifically, in step S202, the size of the metal antimony is 8-10 mm. It should be noted that antimony is easy to cut, and blocks that are too large or too small cannot form an effective graphite nucleation core.

[0083] Specifically, in step S202, before adding the metal antimony, the metal antimony is dried to remove moisture.

[0084] For step S203:

[0085] Specifically, in step S203, 0.175-0.225% (by mass of the molten iron) of instantaneous inoculant is uniformly added during pouring.

[0086] It should be noted that if the content of the instantaneous inoculant is too high, it cannot be fully absorbed and has no inoculation effect, and if it is too low, no inoculation effect can be achieved. Therefore, the mass ratio of the instantaneous inoculant to the molten iron is 0.175-0.225%, preferably 0.2%.

[0087] Specifically, in step S203, the particle size of the instantaneous inoculant is 1-3 mm. It should be noted that if the particle size is too high, it cannot be fully absorbed and the expected inoculation effect cannot be achieved. If the particle size is too low, the inoculant will directly turn into scum and cannot be absorbed, and instantaneous inoculation cannot be achieved.

[0088] Specifically, in step S203, before adding the instantaneous inoculant, the instantaneous inoculant is dried to remove moisture.

[0089] It should be noted that in step 2, the long-term inoculation at the bottom of the ladle provides sufficient long-term nucleation cores, the hot metal inoculation improves the roundness of the graphite balls, the pouring instant inoculation refines the graphite and prevents the inoculation decay. Under the synergistic effect of the triple inoculation, the graphite morphology is improved, the amount of graphite is effectively increased, and the strength index is guaranteed. The spheroidization rate is effectively improved and the elongation performance is improved. In addition, antimony is added during the inoculation after the furnace is taken out, and bismuth and heavy rare earth yttrium are added during the pouring instant inoculation to achieve micro-alloying, which can refine the graphite, increase the number of graphite balls, and improve the roundness of the graphite balls, thereby improving the spheroidization rate and elongation performance.

[0090] It should be noted that the light rare earth spheroidizer, heavy rare earth spheroidizer and inoculant provided by the present invention are prepared by conventional melt mixing method and crushed into granules.

[0091] In addition, it should be noted that the spheroidizing inoculation method provided by the present invention is to lay a spheroidizing agent on the bottom of the ladle, and lay the ladle bottom inoculant on the spheroidizing agent, so as to complete the spheroidizing of step 1 and the long-term inoculation of the ladle bottom in step 2 when the molten iron is added. When the molten iron is poured into the ladle, it first contacts with the inoculant, but the spheroidizing agent contains magnesium, and the melting point of magnesium is relatively low, so it first reacts with the spheroidizing agent and then performs the long-term inoculation of the ladle bottom.

[0092] In addition, as a preferred method, a covering agent can be set in the ladle to cover the spheroidizing agent and the inoculant tightly. The purpose is to isolate the molten iron and the spheroidizing agent for a short time after the molten iron is poured into the ladle, which plays a role in delaying detonation, avoiding violent reactions, and enhancing the spheroidizing effect.

[0093] The specific covering agent can be ductile iron chips, which can be preheated and dried before adding, and dried to remove moisture. The covering agent has a covering thickness of 15-20 mm. It should be noted that if the covering thickness is too thin, the effect of delayed detonation of the spheroidization reaction cannot be achieved, and if the covering thickness is too thick, poor spheroidization may occur.

[0094] Specifically, the size of ductile iron chips is 5-15 mm. It should be noted that if the size is too large or too small, the effect of delayed detonation of the spheroidization reaction cannot be achieved, thereby causing poor spheroidization or graphite floating.

[0095] The present invention also provides a ductile iron, which is a QT500-14 material and is prepared by the spheroidizing inoculation method. The ductile iron can be used for high-wind power wind power castings.

[0096] It should be noted that the casting performance index requirements of ductile iron QT500-14 material equivalent to 70mm test block are: tensile strength 480MPa, yield strength 380MPa, and elongation 12%.

[0097] The as-cast structure of the ductile iron QT500-14 material obtained by the invention is ferrite+graphite, the spheroidization rate is above 90%, the spheroidization level is above 6, and the mechanical properties thereof meet the requirements of the grade.

[0098] The ductile iron QT500-14 material obtained by the invention is used for the hub test piece body, with tensile strength greater than 500MPa, yield strength greater than 400MPa, and elongation greater than or equal to 14%.

[0099] The preferred embodiments of the present invention are described in detail below to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0100] Example 1

[0101] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: La: 0.8, Mg: 6.0, Ca: 1.5, Ba: 1.0, Si: 42, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 0.5, Mg: 5.5, Ca: 1.5, Ba: 1.0, Si: 44, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 8:7.

[0102] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5, Ba: 4.0, Si: 67, and the balance is Fe.

[0103] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.45, Ca: 2.0, Ba: 3.0, Bi: 1.5, Si: 55, and the balance is Fe.

[0104] A spheroidizing inoculation method for ductile iron, comprising:

[0105] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0106] Among them, 0.8% light rare earth spheroidizer and 0.7% heavy rare earth spheroidizer are selected as composite spheroidizers with a block size of 20 mm.

[0107] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0108] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0109] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0110] S201: long-term incubation of the bottom of the package;

[0111] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0112] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.75%, and the particle size is 3 mm.

[0113] S202: molten iron is incubated as it comes out of the furnace;

[0114] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.008% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0115] S203: pouring instant incubation.

[0116] Specifically, during pouring, 0.175% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0117] The structure of the ductile iron QT500-14 material prepared in this embodiment is ferrite+graphite, the spheroidization rate is 90%, and the spheroidization level is 6.

[0118] The ductile iron QT500-14 material prepared in this embodiment is used for the hub test piece body: the tensile strength is 508 MPa, the yield strength is 402 MPa, and the elongation is 18%, which meets the grade requirements.

[0119] Example 2

[0120] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: Ce: 1.2, Mg: 7.0, Ca: 2.5, Ba: 3.0, Si: 46, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 1.5, Mg: 6.5, Ca: 2.5, Ba: 3.0, Si: 48, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 7.5:7.5.

[0121] A bottom inoculant: The main chemical components (%Wt) of the bottom inoculant are: Ca: 2.0, Ba: 6.0, Si: 72, and the balance is Fe.

[0122] A pouring instantaneous inoculant: the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.55, Ca: 3.0, Ba: 5.0, Bi: 2.5, Si: 65, and the balance is Fe.

[0123] A spheroidizing inoculation method for ductile iron, comprising:

[0124] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0125] Among them, 0.75% light rare earth spheroidizer and 0.0.75% heavy rare earth spheroidizer are selected as the combined spheroidizer, and the block size of the light rare earth spheroidizer and the heavy rare earth spheroidizer is 30 mm.

[0126] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0127] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0128] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0129] S201: long-term incubation of the bottom of the package;

[0130] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0131] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.85%, and the particle size is 5 mm.

[0132] S202: molten iron is incubated as it comes out of the furnace;

[0133] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.010% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0134] S203: pouring instant incubation.

[0135] Specifically, during pouring, 0.225% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 2 mm.

[0136] The structure of the ductile iron QT500-14 material prepared in this embodiment is ferrite+graphite, the spheroidization rate is 90%, and the spheroidization level is 6.

[0137] The ductile iron QT500-14 material prepared in this embodiment is used for the hub test piece body: the tensile strength is 515 MPa, the yield strength is 409 MPa, and the elongation is 19%, which meets the grade requirements.

[0138] Example 3

[0139] A composite spheroidizer: The main chemical components (%Wt) of the light rare earth spheroidizer are: La: 1.0, Mg: 6.5, Ca: 2.0, Ba: 2.0, Si: 44, and the balance is Fe. The main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 1.0, Mg: 6.0, Ca: 2.1, Ba: 2.1, Si: 46, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 7:8.

[0140] A bottom inoculant: The main chemical components (%Wt) of the bottom inoculant are: Ca: 1.7, Ba: 5.0, Si: 70, and the balance is Fe.

[0141] A pouring instantaneous inoculant: the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.5, Ca: 2.5, Ba: 4.0, Bi: 2.0, Si: 60, and the balance is Fe.

[0142] A spheroidizing inoculation method for ductile iron, comprising:

[0143] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0144] Among them, 0.7% light rare earth spheroidizer and 0.8% heavy rare earth spheroidizer are selected as composite spheroidizer, and the block size of the light rare earth spheroidizer and the heavy rare earth spheroidizer is 40mm.

[0145] Among them, the spheroidization treatment is carried out by the bottom flushing method, specifically, the composite spheroidizer dam is spread flat on the bottom of the bag.

[0146] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0147] Step 2: adopting a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace, and instant inoculation during pouring to carry out inoculation;

[0148] S201: long-term incubation of the bottom of the package;

[0149] Specifically, the bottom long-acting inoculant is spread evenly on the spheroidizer and fully preheated and dried before adding.

[0150] Among them, the mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.8%, and the particle size is 8mm.

[0151] S202: molten iron is incubated as it comes out of the furnace;

[0152] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.009% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0153] S203: pouring instant incubation.

[0154] Specifically, during pouring, 0.2% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 3 mm.

[0155] The structure of the ductile iron QT500-14 material prepared in this embodiment is ferrite+graphite, the spheroidization rate is 95%, and the spheroidization level is 6.

[0156] The ductile iron QT500-14 material prepared in this embodiment is used for the hub test piece body: the tensile strength is 527 MPa, the yield strength is 418 MPa, and the elongation is 20%, which meets the grade requirements.

[0157] according to Figure 1 It can be seen that in the uncorroded state, the ductile iron prepared by the method provided in this embodiment has a high spheroidization rate and a good spheroidization effect. Figure 2 It can be seen that in the corroded state, the grain boundaries of the matrix structure are obvious and the matrix structure is ferrite.

[0158] Example 4

[0159] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: La: 0.9, Mg: 6.3, Ca: 1.8, Ba: 1.5, Si: 43, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 0.8, Mg: 5.8, Ca: 1.8, Ba: 1.5, Si: 45, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 6:9.

[0160] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.6, Ba: 4.5, Si: 69, and the balance is Fe.

[0161] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.49, Ca: 2.3, Ba: 3.5, Bi: 1.8, Si: 58, and the balance is Fe.

[0162] A spheroidizing inoculation method for ductile iron, comprising:

[0163] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0164] Among them, 0.6% light rare earth spheroidizer and 0.9% heavy rare earth spheroidizer are selected as composite spheroidizers with a block size of 40 mm.

[0165] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0166] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0167] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0168] S201: long-term incubation of the bottom of the package;

[0169] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0170] Among them, the mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.78%, and the particle size is 8mm.

[0171] S202: molten iron is incubated as it comes out of the furnace;

[0172] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.009% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0173] S203: pouring instant incubation.

[0174] Specifically, during pouring, 0.2% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0175] The structure of the ductile iron QT500-14 material prepared in this embodiment is ferrite+graphite, the spheroidization rate is 90, and the spheroidization level is 6.

[0176] The ductile iron QT500-14 material prepared in this embodiment is used for the hub test piece body: the tensile strength is 509 MPa, the yield strength is 403 MPa, and the elongation is 18%, which meets the grade requirements.

[0177] Example 5

[0178] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: Ce: 1.1, Mg: 6.8, Ca: 2.3, Ba: 2.5, Si: 45, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 1.3, Mg: 6.3, Ca: 2.3, Ba: 2.5, Si: 47, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 8:7.

[0179] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.8, Ba: 5.5, Si: 71, and the balance is Fe.

[0180] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.51, Ca: 2.8, Ba: 4.5, Bi: 2.3, Si: 63, and the balance is Fe.

[0181] A spheroidizing inoculation method for ductile iron, comprising:

[0182] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0183] Among them, 0.7% light rare earth spheroidizer and 0.8% heavy rare earth spheroidizer are selected as composite spheroidizers with a block size of 40 mm.

[0184] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0185] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0186] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0187] S201: long-term incubation of the bottom of the package;

[0188] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0189] Among them, the mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.83%, and the particle size is 8mm.

[0190] S202: molten iron is incubated as it comes out of the furnace;

[0191] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.009% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0192] S203: pouring instant incubation.

[0193] Specifically, during pouring, 0.2% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0194] The structure of the ductile iron QT500-14 material prepared in this embodiment is ferrite+graphite, the spheroidization rate is 90, and the spheroidization level is 6.

[0195] The ductile iron QT500-14 material prepared in this embodiment is used for the hub test piece body: the tensile strength is 510 MPa, the yield strength is 403 MPa, and the elongation is 18%, which meets the grade requirements.

[0196] Example 6

[0197] A light rare earth spheroidizer, the main chemical components (%Wt) are: La: 0.8, Mg: 6.0, Ca: 1.5, Ba: 1.0, Si: 42, and the balance is Fe.

[0198] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5, Ba: 4.0, Si: 67, and the balance is Fe.

[0199] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.45, Ca: 2.0, Ba: 3.0, Bi: 1.5, Si: 55, and the balance is Fe.

[0200] A spheroidizing inoculation method for ductile iron, comprising:

[0201] Step 1: Select light rare earth for spheroidization;

[0202] Among them, 1.5% light rare earth spheroidizer is selected, and the block size is 20mm.

[0203] Among them, the spheroidizing treatment is carried out by the bottom flushing method. Specifically, the spheroidizing agent is laid flat on the bottom of the bag.

[0204] Before adding the spheroidizing agent, the spheroidizing agent is fully preheated and dried.

[0205] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0206] S201: long-term incubation of the bottom of the package;

[0207] Specifically, the bottom long-acting inoculant is spread evenly on the spheroidizer and fully preheated and dried before adding.

[0208] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.75%, and the particle size is 3 mm.

[0209] S202: molten iron is incubated as it comes out of the furnace;

[0210] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.008% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0211] S203: pouring instant incubation.

[0212] Specifically, during pouring, 0.175% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0213] The structure of the ductile iron QT500-14 material prepared in this embodiment is ferrite+graphite, the spheroidization rate is 85%, and the spheroidization level is 5.

[0214] The ductile iron QT500-14 material prepared in this embodiment is used for the hub test piece body: the tensile strength is 525 MPa, the yield strength is 415 MPa, and the elongation is 12%, which meets the grade requirements.

[0215] Example 7

[0216] A heavy rare earth spheroidizer, the main chemical components (%Wt) are: Y: 0.5, Mg: 5.5, Ca: 1.5, Ba: 1.0, Si: 44, and the balance is Fe.

[0217] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5, Ba: 4.0, Si: 67, and the balance is Fe.

[0218] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.45, Ca: 2.0, Ba: 3.0, Bi: 1.5, Si: 55, and the balance is Fe.

[0219] A spheroidizing inoculation method for ductile iron, comprising:

[0220] Step 1: Select a heavy rare earth spheroidizer for spheroidization treatment;

[0221] Among them, 1.5% heavy rare earth spheroidizer is selected as the spheroidizer, and the block size is 20mm.

[0222] Among them, the spheroidizing treatment is carried out by the bottom flushing method. Specifically, the spheroidizing agent is laid flat on the bottom of the bag.

[0223] Before adding the spheroidizing agent, the spheroidizing agent is fully preheated and dried.

[0224] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0225] S201: long-term incubation of the bottom of the package;

[0226] Specifically, the bottom long-acting inoculant is spread evenly on the spheroidizer and fully preheated and dried before adding.

[0227] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.75%, and the particle size is 3 mm.

[0228] S202: molten iron is incubated as it comes out of the furnace;

[0229] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.008% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0230] S203: pouring instant incubation.

[0231] Specifically, during pouring, 0.175% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0232] The structure of the ductile iron QT500-14 material prepared in this embodiment is ferrite+graphite, the spheroidization rate is 80%, and the spheroidization level is 5.

[0233] The ductile iron QT500-14 material prepared in this embodiment is used for the hub test piece body: the tensile strength is 535 MPa, the yield strength is 423 MPa, and the elongation is 12%, which meets the grade requirements.

[0234] Comparative Example 1:

[0235] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: La: 0.8, Mg: 6.0, Ca: 1.5, Ba: 1.0, Si: 42, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 0.5, Mg: 5.5, Ca: 1.5, Ba: 1.0, Si: 44, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 8:7.

[0236] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5, Si: 75, and the balance is Fe.

[0237] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.45, Ca: 2.0, Ba: 3.0, Bi: 1.5, Si: 55, and the balance is Fe.

[0238] A ductile iron composite spheroidizing inoculation method, comprising:

[0239] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0240] Among them, 0.8% light rare earth spheroidizer and 0.7% heavy rare earth spheroidizer are selected as composite spheroidizers with a block size of 20 mm.

[0241] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0242] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0243] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0244] S201: long-term incubation of the bottom of the package;

[0245] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0246] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.75%, and the particle size is 3 mm.

[0247] S202: molten iron is incubated as it comes out of the furnace;

[0248] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.008% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0249] S203: pouring instant incubation.

[0250] Specifically, during pouring, 0.175% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0251] The structure of the ductile iron QT500-14 material prepared in this comparative example is ferrite+graphite, the spheroidization rate is 80%, and the spheroidization level is 5.

[0252] The ductile iron QT500-14 material prepared in this comparative example is used for the hub test piece body: the tensile strength is 518 MPa, the yield strength is 410 MPa, and the elongation is 10%, which does not meet the grade requirements.

[0253] Compared with Example 1, the bottom inoculant in this comparative example does not contain Ba, the spheroidization rate and spheroidization level are reduced, and the prepared ductile iron QT500-14 material does not meet the grade requirements.

[0254] Comparative Example 2

[0255] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: La: 0.8, Mg: 6.0, Ca: 1.5, Ba: 1.0, Si: 42, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 0.5, Mg: 5.5, Ca: 1.5, Ba: 1.0, Si: 44, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 8:7.

[0256] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5, Ba: 4.0, Si: 67, and the balance is Fe.

[0257] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.45, Ca: 2.0, Ba: 3.0, Bi: 1.5, Si: 55, and the balance is Fe.

[0258] A composite spheroidizing inoculation method for ductile iron, comprising:

[0259] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0260] Among them, 0.8% light rare earth spheroidizer and 0.7% heavy rare earth spheroidizer are selected as composite spheroidizers with a block size of 20 mm.

[0261] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0262] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0263] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0264] S201: long-term incubation of the bottom of the package;

[0265] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0266] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.75%, and the particle size is 3 mm.

[0267] S202: molten iron is incubated as it comes out of the furnace;

[0268] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.017% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0269] S203: pouring instant incubation.

[0270] Specifically, during pouring, 0.175% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0271] The structure of the ductile iron QT500-14 material prepared in this comparative example is ferrite+pearlite+graphite, the spheroidization rate is 85%, and the spheroidization level is 6.

[0272] The ductile iron QT500-14 material prepared in this comparative example is used for the hub test piece body: the tensile strength is 540 MPa, the yield strength is 420 MPa, and the elongation is 8%, which does not meet the grade requirements.

[0273] Compared with Example 1, the content of antimony inoculated in the comparative example is too high, resulting in the formation of pearlite, and the spheroidization rate and spheroidization level are reduced. The prepared ductile iron QT500-14 material does not meet the grade requirements.

[0274] Comparative Example 3

[0275] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: La: 0.8, Mg: 6.0, Ca: 1.5, Ba: 1.0, Si: 42, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 0.5, Mg: 5.5, Ca: 1.5, Ba: 1.0, Si: 44, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 8:7.

[0276] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5, Ba: 4.0, Si: 67, and the balance is Fe.

[0277] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) of: Ca: 2.0, Ba: 3.0, Si: 65, and the balance is Fe.

[0278] A composite spheroidizing inoculation method for ductile iron, comprising:

[0279] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0280] Among them, 0.8% light rare earth spheroidizer and 0.7% heavy rare earth spheroidizer are selected as composite spheroidizers with a block size of 20 mm.

[0281] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0282] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0283] Step 2: The inoculation is carried out by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace and instantaneous inoculation during pouring.

[0284] S201: long-term incubation of the bottom of the package;

[0285] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0286] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.75%, and the particle size is 3 mm.

[0287] S202: molten iron is incubated as it comes out of the furnace;

[0288] Specifically, when two-thirds of the molten iron is discharged from the furnace, 0.008% of metallic antimony is added to the remaining one-third, and the size of the metallic antimony block is 10 mm.

[0289] S203: pouring instant incubation.

[0290] Specifically, during pouring, 0.175% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0291] The structure of the ductile iron QT500-14 material prepared in this comparative example is ferrite+graphite, the spheroidization rate is 85%, and the spheroidization level is 6.

[0292] The ductile iron QT500-14 material prepared in this comparative example is used for the hub test piece body: the tensile strength is 510 MPa, the yield strength is 402 MPa, and the elongation is 12%, meeting the grade requirements.

[0293] Compared with Example 1, the instantaneous inoculant in this comparative example does not contain Y and Bi, the spheroidization rate and spheroidization level are reduced, and the prepared ductile iron QT500-14 material meets the grade requirements, but has a low elongation.

[0294] Comparative Example 4

[0295] A composite spheroidizer: the main chemical components (%Wt) of the light rare earth spheroidizer are: La: 0.8, Mg: 6.0, Ca: 1.5, Ba: 1.0, Si: 42, and the balance is Fe; the main chemical components (%Wt) of the heavy rare earth spheroidizer are: Y: 0.5, Mg: 5.5, Ca: 1.5, Ba: 1.0, Si: 44, and the balance is Fe. The mass ratio of the light rare earth spheroidizer to the heavy rare earth spheroidizer is 8:7.

[0296] A bottom inoculant: wherein the main chemical components (%Wt) of the bottom inoculant are: Ca: 1.5, Ba: 4.0, Si: 67, and the balance is Fe.

[0297] A pouring instantaneous inoculant: wherein the instantaneous inoculant has main chemical components (%Wt) as follows: Y: 0.45, Ca: 2.0, Ba: 3.0, Bi: 1.5, Si: 55, and the balance is Fe.

[0298] A ductile iron composite spheroidizing inoculation method, comprising:

[0299] Step 1: Select light rare earth and heavy rare earth spheroidizers for composite application and perform spheroidization treatment;

[0300] Among them, 0.8% light rare earth spheroidizer and 0.7% heavy rare earth spheroidizer are selected as composite spheroidizers with a block size of 20 mm.

[0301] The spheroidizing treatment is carried out by using the bottom flushing method. Specifically, the composite spheroidizing agent is laid flat on the bottom of the bag to build a dam.

[0302] Before adding the composite spheroidizing agent, the composite spheroidizing agent is fully preheated and dried.

[0303] Step 2: Inoculate by using a double combined inoculation method of long-term inoculation at the bottom of the ladle and instant inoculation by pouring.

[0304] S201: long-term incubation of the bottom of the package;

[0305] Specifically, the bottom long-acting inoculant is spread evenly on the composite spheroidizer and fully preheated and dried before adding.

[0306] The mass ratio of the ladle bottom long-acting inoculant added to the molten iron is 0.75%, and the particle size is 3 mm.

[0307] S202: pouring instant incubation.

[0308] Specifically, during pouring, 0.175% instantaneous inoculant is evenly added along the flow, and the material is fully preheated and dried before being added, and the particle size is 1 mm.

[0309] The structure of the ductile iron QT500-14 material prepared in this comparative example is ferrite+graphite, the spheroidization rate is 80%, and the spheroidization level is 5.

[0310] The ductile iron QT500-14 material prepared in this comparative example is used for the hub test piece body: the tensile strength is 508 MPa, the yield strength is 401 MPa, and the elongation is 8%, which does not meet the grade requirements.

[0311] Compared with Example 1, this comparative example does not include the step of inoculation after the furnace is discharged, the spheroidization rate and spheroidization level are reduced, and the prepared ductile iron QT500-14 material does not meet the grade requirements.

[0312] Comparative Example 5

[0313] This comparative example is basically the same as Example 1. The difference between this comparative example and Example 1 is that the main chemical components (%Wt) of the light rare earth spheroidizer in the composite spheroidizer are: La: 2.0, Mg: 6.0, Ca: 1.5, Ba: 1.0, Si: 42, and the balance is Fe.

[0314] The structure of the ductile iron QT500-14 material prepared in this comparative example is ferrite+pearlite+graphite, the spheroidization rate is 80%, and the spheroidization level is 5.

[0315] The ductile iron QT500-14 material prepared in this comparative example is used for the hub test piece body: the tensile strength is 490 MPa, the yield strength is 391 MPa, and the elongation is 6%, which does not meet the grade requirements.

[0316] Compared with Example 1, the content of light rare earth in the light rare earth spheroidizer of this comparative example exceeds the maximum value of the range of the present invention, which will lead to the production of a small amount of pearlite, reduce the spheroidization rate and spheroidization level, and the prepared ductile iron QT500-14 material does not meet the grade requirements.

[0317] Comparative Example 6

[0318] This comparative example is basically the same as Example 1, except that the main chemical components (%Wt) of the instantaneous inoculant are: Y: 1.0, Ca: 2.0, Ba: 3.0, Bi: 1.5, Si: 55, and the balance is Fe.

[0319] The structure of the ductile iron QT500-14 material prepared in this comparative example is ferrite+graphite, the spheroidization rate is 80%, and the spheroidization level is 5.

[0320] The ductile iron QT500-14 material prepared in this comparative example is used for the hub test piece body: the tensile strength is 498 MPa, the yield strength is 399 MPa, and the elongation is 7%, which does not meet the grade requirements.

[0321] Compared with Example 1, the content of Y in the instantaneous inoculant of this comparative example exceeds the maximum value of the range of the present invention, the spheroidization rate and spheroidization level are reduced, and the prepared ductile iron QT500-14 material does not meet the grade requirements.

[0322] Specifically, the QT500-14 material prepared by the methods in Examples 1-7 and Comparative Examples 1-6 was tested, as shown in Table 1 below.

[0323] Table 1 QT500-14 material properties obtained in Examples 1-7 and Comparative Examples 1-6

[0324]

[0325]

[0326] The QT500-14 material prepared by the methods of Examples 1-7 and Comparative Examples 1-6 was used to prepare a wheel hub test piece body, and the mechanical properties of the test piece body were tested, as shown in Table 2 below.

[0327] Table 2 Mechanical properties of QT500-14 materials obtained in Examples 1-7 and Comparative Examples 1-6

[0328] Tensile strength(MPa) Yield strength(MPa) Elongation(%) Example 1 508 402 18 Example 2 515 409 19 Example 3 527 418 20 Example 4 509 403 18 Example 5 510 403 18 Example 6 525 415 12 Example 7 535 423 12 Comparative Example 1 518 410 10 Comparative Example 2 540 420 8 Comparative Example 3 510 402 12 Comparative Example 4 508 401 8 Comparative Example 5 490 391 6 Comparative Example 6 498 399 7 Performance Indicators 480 380 12

[0329] Among them, the casting performance index requirements of the equivalent 70mm test block are: tensile strength 480MPa, yield strength 380MPa, and elongation 12%.

[0330] It can be seen that the spheroidizing inoculation method of the present invention is applied to ductile iron QT500-14 for wind power castings. Compared with the existing spheroidizing inoculation method, the spheroidizing rate and elongation indexes are improved, and the organizational properties can meet the technical requirements.

[0331] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A pouring instantaneous inoculant, characterized in that: The chemical composition of the pouring instantaneous inoculant is calculated by weight percentage as follows: Y: 0.45-0.55, Ca: 2.0-3.0, Ba: 3.0-5.0, Bi: 1.5-2.5, Si: 55-65, and the balance is Fe.

2. A spheroidization inoculation method, characterized in that: include: Step 1: selecting at least one of a light rare earth spheroidizer and a heavy rare earth spheroidizer to perform spheroidization treatment; Step 2: Inoculate by a triple combined inoculation method including long-term inoculation at the bottom of the ladle, inoculation with the flow of molten iron out of the furnace, and pouring instant inoculation, wherein the pouring instant inoculation adopts the pouring instant inoculant described in claim 1.

3. The method according to claim 2, characterized in that The step 2 comprises: S201: long-term incubation of the bottom of the package; S202: molten iron is incubated as it comes out of the furnace; S203: pouring instant incubation.

4. The method according to claim 3, characterized in that In step S203, during pouring, an instantaneous inoculant having a mass ratio of 0.175-0.225% of the molten iron is uniformly added along the flow.

5. The method according to claim 3, characterized in that: Step S201 uses a bottom inoculant, the main chemical components of which are, by weight percentage, Ca: 1.5-2.0, Ba: 4.0-6.0, Si: 67-72, and the remainder is Fe.

6. The method according to claim 3, characterized in that In step S201, a ladle bottom inoculant is spread on the spheroidizing agent, and the mass ratio of the ladle bottom inoculant added to the molten iron is 0.75-0.85%.

7. The method according to claim 3, characterized in that In step S202, when two-thirds of the molten iron flows out of the furnace and enters the ladle, the remaining one-third is added with 0.008%-0.010% of metal antimony by mass of the molten iron.

8. The method according to claim 2, characterized in that: The main chemical components of the light rare earth spheroidizer are, by weight percentage, RE: 0.8-1.2, Mg: 6.0-7.0, Ca: 1.5-2.5, Ba: 1.0-3.0, Si: 42-46, and the balance is Fe; The main chemical components of the heavy rare earth spheroidizer are, by weight percentage, RE: 0.5-1.5, Mg: 5.5-6.5, Ca: 1.5-2.5, Ba: 1.0-3.0, Si: 44-48, and the balance is Fe.

9. A ductile iron, characterized in that: The ductile iron is QT500-14 material, which is prepared by the spheroidizing inoculation method described in any one of claims 1 to 8.

10. The ductile iron according to claim 9, characterized in that: The ductile iron is used for high-wind power wind power castings.

Images