Production method of high-standard physicochemical index ductile iron 500-7 sintering pallet

Abstract

A production method of a high-standard physicochemical index ductile iron 500-7 sintering pallet comprises the steps that (1) an upper box is a plane, and a shaft head is arranged on the lower portion; (2) a refractory brick pipe with the diameter phi of 60-80 mm is adopted as a straight pouring gate, the size phi of an inner pouring gate is 30-40 mm, 18-24 inner pouring gates are evenly distributed, the left side and the right side of the vehicle body in the length direction are each provided with a trapezoid transverse pouring gate, and the tail ends of the transverse pouring gates extend by 50-100 mm; (3) after the temperature of the molten iron is 1450 DEG C or above, standing is conducted for 5 min or above, and the tapping temperature is 1450-1460 DEG C; 4) adding pure copper and pure tin along with the molten iron flow; (5) after the molten iron is discharged out of the furnace, spheroidizing treatment is conducted, specifically, a composite spheroidizing agent and a composite nucleating agent are adopted, the adding amount of the spheroidizing agent is 0.9%-1.1%, and the adding amount of the nucleating agent is 1.2%-1.3%; and 6) controlling the time from the beginning of tapping spheroidizing to the end of pouring to be less than 20 minutes. According to the invention, the proportion of chemical elements such as the spheroidization rate, the ductility and the spheroidization grade is accurately controlled, and corresponding smelting and pouring control methods are matched, so that the performance indexes of 90% of the spheroidization rate, the grade 2 of the spheroidization grade, 7%-15% of the ductility and the grade 6 of the graphite size of the product are obtained.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical manufacturing, and in particular to a production method of a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes. Background Art

[0002] my country is a strong country in casting, with more than 50 million tons of castings per year. Gray iron parts account for 41.9% of them, and ductile iron parts account for 29.5%. Due to the good toughness and high strength of ductile iron, its application proportion increases year by year. The production technology of ordinary ductile iron is relatively mature.

[0003] Commonly used sintering machine sintering trolleys in the market ( Figure 1 , Figure 2 ) is generally a ductile iron casting with a more complex structure. Its grade requires QT500-7, and generally requires R m >500MPa, elongation A>7, spheroidization rate 85%, spheroidization grade generally requires level 3, graphite size is level 5, HB150. After many years of domestic practice, through the selection of spheroidizing agent types, matching of addition amounts, reasonable use of inoculants, and requirements for residual magnesium and residual rare earth, this grade of ductile iron can meet the above performance index requirements during production.

[0004] However, facing fierce competition at home and abroad, users' requirements for long-life parts and high-quality parts, the current market users have begun to put forward strict requirements on the physical and chemical indicators of ductile iron QT500-7 to further improve the online service life of the sintering trolley, and its various indicators are far higher than the national standard level. Among them, the spheroidization rate is required to be 90%, the spheroidization level is level 2, the elongation is required to be precisely controlled at 7%-12%, and the graphite size is level 6. The above indicators require that the proportion of casting engineering is greater than 88%. Summary of the invention

[0005] The purpose of the present invention is to provide a production method of a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indicators, accurately control the chemical element ratio of spheroidization rate, elongation and spheroidization grade, and cooperate with corresponding smelting and pouring control methods to obtain the performance index requirements of product spheroidization rate of 90%, spheroidization grade 2, elongation accurately controlled 7%-15%, and graphite size 6.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A production method for a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes, specifically including two parts: molding and smelting treatment and pouring:

[0008] The first part of the modeling includes the following methods:

[0009] 1) The upper box is flat, which is convenient for casting production operation and high efficiency; the shaft head is at the bottom, which is conducive to shaft head shrinkage compensation to prevent shrinkage defects; the middle box is formed by sand core; the middle box is composed of 3 or 6 identical sand cores, which is easy to operate.

[0010] Self-hardening sand technology is adopted for molding. The raw sand of the middle box sand core is preferably 40-70 mesh scrubbed quartz sand. The raw sand particle size is the key to ensure the surface quality. The binder is furan resin sand. The binder addition amount is 0.8% to 1.2% of the weight of the raw sand. The curing agent addition amount accounts for 30% to 50% of the weight of the binder. It is mixed and molded in a continuous sand mixer.

[0011] 2) The sprue adopts Φ60~80mm high-quality refractory brick pipe, and a casting ceramic filter is placed at the connection between the sprue and the cross runner. The size of the inner runner is Φ30~40mm, and 18~24 runners are evenly distributed; there is a trapezoidal cross runner on each side of the length of the vehicle body, and the cross runner section size is upper bottom (100~90)mm*lower bottom (90~80)mm*height (70~80)mm, and the end of the cross runner is extended by 50~100mm to ensure the pouring speed and slag gathering effect.

[0012] The second part of smelting treatment and casting includes the following methods:

[0013] 1) After the temperature of the molten iron in the furnace reaches above 1450℃, it is left to stand for more than 5 minutes and then taken out of the furnace. The temperature out of the furnace is 1450-1460℃. The molten iron smelting adopts Q10 pig iron and low-carbon scrap steel as the ingredients, and the alloy is ordinary high-carbon ferromanganese and 75 ferrosilicon.

[0014] The chemical composition of smelting molten iron is calculated by mass percentage as follows: C 3.2%~3.8%, Si 1.3%~1.4%, Mn0.5%~0.8%, P≤0.04%, S≤0.02%, and the rest is Fe and unavoidable impurities.

[0015] 2) Add pure copper and pure tin into the molten iron after it comes out of the furnace and control the Cu content in the molten iron to be 0.15wt%-0.5wt% and the Sn content to be 0.002wt%-0.02wt%.

[0016] 3) Spheroidization treatment is carried out after the molten iron is taken out of the furnace: an isolation dam or spheroidization pit with a thickness of more than 200 mm is built in the middle part of the bottom of the molten iron ladle, and a "sandwich" treatment method is adopted, that is, spheroidizing agent is added first, then covered with inoculant, and finally covered with 10-20 mm thick iron filings. The slag is removed after spheroidization.

[0017] In order to increase the nucleation ability of molten iron and ensure high-level spheroidization effect of graphite, composite spheroidizer and composite inoculant are used. The addition amount of composite spheroidizer is 0.9% to 1.1% of molten iron by mass percentage, and the addition amount of composite inoculant is 1.2% to 1.3% of molten iron by mass percentage.

[0018] The chemical components contained in the composite spheroidizer include Si, Mg, and Re; the chemical components contained in the composite inoculant include Si, Ca, Ba, and Zr. It is beneficial to the formation and morphology of graphite, and is beneficial to the refinement and rounding of the structure.

[0019] 4) Strictly control the time from the start of spheroidization to the end of pouring to less than 20 minutes, and the optimal control time is within 15 minutes.

[0020] A production method for a ductile iron 500-7 sintering trolley with high-standard physical and chemical indicators. The chemical composition of the produced ductile iron 500-7 sintering trolley is as follows by mass percentage: C 3.2%-3.8%, Si 2.2%-2.6%, Mn 0.5%-0.8%, P≤0.04%, S≤0.02%, Cu 0.15%-0.5%, Sn 0.002%-0.02%; the rest is Fe and trace amounts of Mg, Re, Ca, Ba, Zr and inevitable impurities.

[0021] Preferably, the chemical composition of the ductile iron 500-7 sintering car is calculated by mass percentage as follows: C3.35%~3.55%, Si2.4%~2.55%, Mn0.6%~0.7%, P≤0.04%, S 0.008%~0.015%, Cu 0.2%~0.25%, Sn0.002%~0.02%; the rest is Fe and trace amounts of Mg, Re, Ca, Ba, Zr and unavoidable impurities.

[0022] The physical and chemical indicators of the ductile iron 500-7 sintering trolley are: spheroidization rate of more than 90%; spheroidization grade of more than 2 levels; graphite size of more than 6 levels; elongation of 7-15%.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention can improve the physical and chemical indicators of ductile iron 500-7 sintering trolley to 90% spheroidization rate, 2-grade spheroidization, 6-grade graphite size or above, and 7%-15% elongation. It effectively improves the service life of the sintering trolley. The above requirements are the first in China, and its product performance is at the leading level in the sintering machine sintering trolley industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a real picture of the sintering trolley body.

[0026] Figure 2 This is the front view of the sintering trolley parts diagram.

[0027] Figure 3 This is a top view of the sintering trolley parts drawing.

[0028] Figure 4 It is the front view of the trolley casting process diagram of the present invention.

[0029] Figure 5 It is a top view of the trolley casting process diagram of the present invention.

[0030] Figure 6 It is a partial enlarged view of the end portion of the parting surface of the trolley casting process of the present invention.

[0031] Figure 7 It is a partial enlarged view of the design of the sprue and the inner runner of the pouring system of the trolley casting process of the present invention.

[0032] In the figure: 1-upper box surface, 2-lower box surface, 3-1# sand core, 4-2# sand core, 5-inner runner, 6-sprue, 7-horizontal runner, 8-middle box, 9-axis head. DETAILED DESCRIPTION

[0033] The embodiments of the present invention are further described below in conjunction with the accompanying drawings:

[0034] See Figure 1-Figure 7 The present invention provides a production method for a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes, which specifically comprises:

[0035] 1) The upper box is flat, the shaft head 9 is at the bottom, and the middle box body 8 is formed by sand cores; the shaft heads 9 on both sides are formed by the end head 1# sand core 3 to ensure the accurate shape and position of the shaft head 9. The four shaft holes are formed by 2# sand core 4, all sand cores are completely positioned by core heads, and the wood mold is processed by the overall CNC machine tool according to the drawing to ensure the dimensional accuracy of each part.

[0036] 2) The sprue 6 is made of Φ60-80mm refractory brick tube, the inner runner 5 is Φ30-40mm in size, and is evenly distributed in 18-24 runs. There is a trapezoidal runner 7 on each side of the length direction of the vehicle body. The cross-sectional dimensions of the runner 7 are upper bottom (100-90)mm*lower bottom (90-80)mm*height (70-80)mm. The end of the runner 7 is extended by 50-100mm to ensure the pouring speed and slag gathering effect.

[0037] 3) After the temperature of the molten iron in the furnace reaches above 1450℃, let it stand for more than 5 minutes and then take it out of the furnace. The temperature out of the furnace is 1450-1460℃.

[0038] 4) Add pure copper and pure tin with the molten iron after it comes out of the furnace and control the Cu content in the molten iron to be 0.15wt%-0.5wt% and the Sn content to be 0.002wt%-0.02wt%.

[0039] 5) After the molten iron is taken out of the furnace, it is spheroidized: the "sandwich" treatment method is adopted, that is, the spheroidizing agent is added first, then the inoculant is covered, and finally the iron filings are covered with 10-20 mm thick. The slag is removed after the spheroidization.

[0040] A composite spheroidizer and a composite inoculant are used, wherein the addition amount of the composite spheroidizer is 0.9% to 1.1% of the molten iron by mass percentage, and the addition amount of the composite inoculant is 1.2% to 1.3% of the molten iron by mass percentage.

[0041] 6) Control the time from the start of spheroidization to the end of pouring to less than 20 minutes.

[0042] The middle box is composed of 3 or 6 identical sand cores.

[0043] The raw sand of the sand core of the middle box 8 is 40-70 mesh scrubbed quartz sand, the binder is furan resin sand, the binder addition amount is 0.8%-1.2% of the weight of the raw sand, and the curing agent addition amount accounts for 30%-50% of the weight of the binder.

[0044] The molten iron smelting uses pig iron and low-carbon scrap steel as ingredients, and the alloy is high-carbon ferromanganese and 75 ferrosilicon.

[0045] The chemical components contained in the composite spheroidizer include Si, Mg, and Re; the chemical components contained in the composite inoculant include Si, Ca, Ba, and Zr.

[0046] The time from the start of spheroidization to the end of pouring is controlled to be within 15 minutes.

[0047] The chemical composition of the smelting molten iron in step 3) is calculated by mass percentage as follows: C 3.2%-3.8%, Si 1.3%-1.4%, Mn 0.5%-0.8%, P≤0.04%, S≤0.02%, and the rest is Fe and unavoidable impurities.

[0048] A production method for a ductile iron 500-7 sintering trolley with high-standard physical and chemical indicators. The chemical composition of the produced ductile iron 500-7 sintering trolley is as follows by mass percentage: C 3.2%-3.8%, Si 2.2%-2.6%, Mn 0.5%-0.8%, P≤0.04%, S≤0.02%, Cu 0.15%-0.5%, Sn 0.002%-0.02%; the rest are Fe, Mg, Re, Ca, Ba, Zr and inevitable impurities.

[0049] The physical and chemical indicators of the ductile iron 500-7 sintering trolley are: spheroidization rate of more than 90%; spheroidization grade of more than 2 levels; graphite size of more than 6 levels; elongation of 7-15%.

[0050] Embodiment 1:

[0051] A production method for a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes, specifically including two parts: molding and smelting treatment and pouring:

[0052] The first part of the modeling includes the following methods:

[0053] 1) The upper box is flat, and the shaft head 9 is at the bottom, which is convenient for casting production operation and high efficiency, and is conducive to shaft head shrinkage compensation to prevent shrinkage defects; the middle box body 8 adopts a combination of 3 identical sand cores.

[0054] Self-hardening sand molding process is adopted. The raw sand of the middle box 8 sand core is preferably 40 mesh scrubbed quartz sand. The raw sand particle size is the key to ensure the surface quality. The binder is furan resin sand. The binder addition amount is 0.8% of the raw sand weight, and the curing agent addition amount accounts for 30% of the binder weight. It is mixed and molded in a continuous sand mixer.

[0055] 2) The sprue 6 is made of Φ60mm high-quality refractory brick pipe, the inner runner 5 is Φ30mm in size, and there are 24 runners evenly distributed. There is a trapezoidal cross runner 7 on each side of the length direction of the vehicle body. The cross-sectional dimensions of the cross runner 7 are upper bottom 90mm*lower bottom 80mm*height 80mm, and the end of the cross runner 7 is extended by 50mm to ensure the pouring speed and slag gathering effect.

[0056] The second part of smelting treatment and casting includes the following methods:

[0057] 1) After the molten iron in the furnace reaches a temperature of 1460°C and is left to stand for more than 5 minutes, the temperature out of the furnace is 1450°C; Q10 pig iron and low-carbon scrap steel are used as ingredients for molten iron smelting, and the alloy is ordinary high-carbon ferromanganese and 75 ferrosilicon.

[0058] The chemical composition of smelting molten iron is calculated by mass percentage as follows: C 3.35%, Si 1.3%, Mn 0.5%, P0.03%, S0.015%, and the rest is Fe and unavoidable impurities.

[0059] 2) Add pure copper and pure tin into the molten iron after it comes out of the furnace and control the Cu content in the molten iron to be 0.2wt% and the Sn content to be 0.003wt%.

[0060] 3) Spheroidization treatment is carried out after the molten iron is taken out of the furnace: an isolation dam or spheroidization pit with a thickness of more than 200 mm is built in the middle part of the bottom of the molten iron ladle, and a "sandwich" treatment method is adopted, that is, spheroidizing agent is added first, then covered with inoculant, and finally covered with 15 mm thick iron filings. The slag is removed after spheroidization.

[0061] In order to increase the nucleation ability of molten iron and ensure high-level spheroidization effect of graphite, composite spheroidizer and composite inoculant are used. The addition amount of composite spheroidizer is 1.1% of molten iron by mass percentage, and the addition amount of composite inoculant is 1.2% of molten iron by mass percentage.

[0062] The chemical components contained in the composite spheroidizer include Si, Mg, and Re; the chemical components contained in the composite inoculant include Si, Ca, Ba, and Zr.

[0063] 4) Strictly control the time from the start of spheroidization to the end of pouring to 14 minutes.

[0064] The chemical composition of the ductile iron 500-7 sintering trolley is as follows by mass percentage: C 3.35%, Si 2.5%, Mn 0.65%, P 0.03%, S 0.015%, Cu 0.2%, Sn 0.003%; the rest are Fe and trace amounts of Mg, Re, Ca, Ba, Zr and inevitable impurities.

[0065] The physical and chemical indicators of the ductile iron 500-7 sintering trolley of this embodiment are: spheroidization rate 90%; spheroidization grade 2; graphite size above grade 6; and elongation 15%.

[0066] Embodiment 2:

[0067] A production method for a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes, specifically including two parts: molding and smelting treatment and pouring:

[0068] The first part of the modeling includes the following methods:

[0069] 1) The upper box is flat, and the shaft head 9 is at the bottom; the middle box body 8 is composed of 6 identical sand cores.

[0070] Self-hardening sand molding process is adopted. The raw sand of the middle box 8 sand core is preferably 60-mesh scrubbed quartz sand. The raw sand particle size is the key to ensure the surface quality. The binder is furan resin sand. The binder addition amount is 1.0% of the raw sand weight, and the curing agent addition amount accounts for 40% of the binder weight. It is mixed and molded in a continuous sand mixer.

[0071] 2) The sprue 6 is made of Φ70mm refractory brick pipe, the inner runner 5 is Φ35mm in size, and there are 20 runners evenly distributed. There is a trapezoidal cross runner 7 on each side of the length direction of the vehicle body. The cross-sectional dimensions of the cross runner 7 are upper bottom 90mm*lower bottom 80mm*height 80mm. The end of the cross runner 7 is extended by 90mm to ensure the pouring speed and slag gathering effect.

[0072] The second part of smelting treatment and casting includes the following methods:

[0073] 1) After the temperature of the molten iron in the furnace reaches above 1460℃, it is left to stand for more than 5 minutes and then taken out of the furnace. The temperature out of the furnace is 1455℃. The molten iron is smelted with Q10 pig iron and low-carbon scrap steel as the ingredients, and the alloy is ordinary high-carbon ferromanganese and 75 ferrosilicon.

[0074] The chemical composition of smelting molten iron is calculated by mass percentage as follows: C 3.55%, Si 1.4%, Mn 0.6%, P 0.02%, S0.008%, and the rest is Fe and unavoidable impurities.

[0075] 2) Add pure copper and pure tin into the molten iron as it comes out of the furnace and control the Cu content in the molten iron to be 0.25wt% and the Sn content to be 0.006wt%.

[0076] 3) Spheroidization treatment is carried out after the molten iron is taken out of the furnace: an isolation dam or spheroidization pit with a thickness of more than 200 mm is built in the middle part of the bottom of the molten iron ladle, and a "sandwich" treatment method is adopted, that is, spheroidizing agent is added first, then covered with inoculant, and finally covered with 10-20 mm thick iron filings. The slag is removed after spheroidization.

[0077] In order to increase the nucleation ability of molten iron and ensure high-level spheroidization effect of graphite, composite spheroidizer and composite inoculant are used. The addition amount of composite spheroidizer is 1.0% by mass of molten iron, and the addition amount of composite inoculant is 1.3% by mass of molten iron.

[0078] The chemical components contained in the composite spheroidizer include Si, Mg, and Re; the chemical components contained in the composite inoculant include Si, Ca, Ba, and Zr.

[0079] 4) Strictly control the time from the start of spheroidization to the end of pouring to 15 minutes.

[0080] The chemical composition of the ductile iron 500-7 sintering trolley in this embodiment is as follows by mass percentage: C 3.55%, Si 2.4%, Mn 0.7%, P 0.02%, S 0.008%, Cu 0.25%, Sn 0.006%; the rest is Fe and trace amounts of Mg, Re, Ca, Ba, Zr and inevitable impurities.

[0081] The physical and chemical indicators of the ductile iron 500-7 sintering trolley of this embodiment are: spheroidization rate 92%; spheroidization grade 2; graphite size 6; elongation 14%.

[0082] Embodiment 3:

[0083] A production method for a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes, specifically including two parts: molding and smelting treatment and pouring:

[0084] The first part of the modeling includes the following methods:

[0085] 1) The upper box is flat, the shaft head 9 is at the bottom, and the middle box 8 is composed of 6 identical sand cores.

[0086] Self-hardening sand molding process is adopted. The raw sand of the middle box 8 sand core is preferably 50-mesh scrubbed quartz sand. The raw sand particle size is the key to ensure the surface quality. The binder is furan resin sand. The binder addition amount is 0.9% of the raw sand weight, and the curing agent addition amount accounts for 35% of the binder weight. It is mixed and molded in a continuous sand mixer.

[0087] 2) The sprue 6 is made of Φ65mm refractory brick tube, the inner runner 5 is Φ30mm in size, and there are 22 runners evenly distributed. There is a trapezoidal cross runner 7 on each side of the length direction of the vehicle body. The cross-sectional dimensions of the cross runner 7 are upper bottom 90mm*lower bottom 80mm*height 80mm. The end of the cross runner 7 is extended by 80mm to ensure the pouring speed and slag gathering effect.

[0088] The second part of smelting treatment and casting includes the following methods:

[0089] 1) The temperature of the molten iron in the furnace reaches 1460℃ and then it is left to stand for more than 5 minutes before being taken out of the furnace. The temperature of the molten iron is 1452℃. Q10 pig iron and low-carbon scrap steel are used as the ingredients for molten iron smelting, and the alloy is ordinary high-carbon ferromanganese and 75 ferrosilicon.

[0090] The chemical composition of smelting molten iron is calculated by mass percentage as follows: C 3.7%, Si 1.3%, Mn 0.7%, P 0.01%, S 0.01%, and the rest is Fe and unavoidable impurities.

[0091] 2) Add pure copper and pure tin into the molten iron as it comes out of the furnace and control the Cu content in the molten iron to be 0.3wt% and the Sn content to be 0.015wt%.

[0092] 3) Spheroidization treatment is carried out after the molten iron is taken out of the furnace: an isolation dam or spheroidization pit with a thickness of more than 200 mm is built in the middle part of the bottom of the molten iron ladle, and a "sandwich" treatment method is adopted, that is, spheroidizing agent is added first, then covered with inoculant, and finally covered with 10-20 mm thick iron filings. The slag is removed after spheroidization.

[0093] In order to increase the nucleation ability of molten iron and ensure high-level spheroidization effect of graphite, composite spheroidizer and composite inoculant are used. The addition amount of composite spheroidizer is 1.1% of molten iron by mass percentage, and the addition amount of composite inoculant is 1.2% of molten iron by mass percentage.

[0094] The chemical components contained in the composite spheroidizer include Si, Mg, and Re; the chemical components contained in the composite inoculant include Si, Ca, Ba, and Zr.

[0095] 4) Strictly control the time from the start of spheroidization to the end of pouring to 10 minutes.

[0096] The chemical composition of the ductile iron 500-7 sintering trolley in this embodiment is calculated by mass percentage as follows: C 3.7%, Si 2.3%, Mn 0.55%, P 0.01%, S 0.01%, Cu 0.3%, Sn 0.015%; the rest is Fe and trace amounts of Mg, Re, Ca, Ba, Zr and inevitable impurities.

[0097] The physical and chemical indicators of the sintering trolley of ductile iron 500-7 in the embodiment are: spheroidization rate 90%; spheroidization grade 2; graphite size 6; elongation 13%.

Claims

1. A production method for a 500-7 sintering trolley of high-standard physical and chemical index ductile iron, characterized in that: Specifically include: 1) The upper box is flat, the shaft head is at the bottom, and the middle box is formed by sand core; 2) The sprue adopts Φ60-80mm refractory brick tube, the inner pouring channel size is Φ30-40mm, and there are 18-24 channels evenly distributed. There is a trapezoidal cross runner on each side of the length direction of the vehicle body, and the end of the cross runner is extended by 50-100mm; 3) After the molten iron temperature in the furnace reaches above 1450°C, it is left to stand for more than 5 minutes before being taken out of the furnace. The temperature of the molten iron out of the furnace is 1450-1460°C; 4) adding pure copper and pure tin to the molten iron after it is discharged from the furnace and controlling the Cu content in the molten iron to be 0.15wt% to 0.5wt% and the Sn content to be 0.002wt% to 0.02wt%; 5) After the molten iron is taken out of the furnace, it is spheroidized: the "sandwich" treatment method is adopted, that is, the spheroidizer is added first, then the inoculant is covered, and finally the iron chips are covered with 10-20mm thickness; A composite spheroidizer and a composite inoculant are used, wherein the amount of the composite spheroidizer added is 0.9% to 1.1% by mass of the molten iron, and the amount of the composite inoculant added is 1.2% to 1.3% by mass of the molten iron; 6) Control the time from the start of spheroidization to the end of pouring to less than 20 minutes.

2. The method for producing a 500-7 sintering trolley for ductile iron with high physical and chemical indexes according to claim 1, characterized in that: The middle box is composed of 3 or 6 identical sand cores.

3. The production method of a high-standard physical and chemical index ductile iron 500-7 sintering trolley according to claim 1 or 2, characterized in that: The raw sand of the middle box sand core is 40-70 mesh scrubbed quartz sand, the binder is furan resin sand, the binder addition amount is 0.8%-1.2% of the raw sand weight, and the curing agent addition amount accounts for 30%-50% of the binder weight.

4. The method for producing a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes according to claim 1, characterized in that: The molten iron smelting uses pig iron and low-carbon scrap steel as ingredients, and the alloy is high-carbon ferromanganese and 75 ferrosilicon.

5. The method for producing a 500-7 sintering trolley for ductile iron with high physical and chemical indexes according to claim 1, characterized in that: The chemical components contained in the composite spheroidizer include Si, Mg, and Re; the chemical components contained in the composite inoculant include Si, Ca, Ba, and Zr.

6. The method for producing a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes according to claim 1, characterized in that: The time from the start of spheroidization to the end of pouring is controlled to be within 15 minutes.

7. The method for producing a 500-7 sintering trolley for ductile iron with high physical and chemical indexes according to claim 1, characterized in that: The chemical composition of the smelting molten iron in step 3) is calculated by mass percentage as follows: C 3.2%-3.8%, Si 1.3%-1.4%, Mn 0.5%-0.8%, P≤0.04%, S≤0.02%, and the rest is Fe and unavoidable impurities.

8. A sintering trolley of ductile iron 500-7 produced by the production method of a sintering trolley of ductile iron 500-7 with high-standard physical and chemical indexes as claimed in any one of claims 1 to 7, characterized in that: Its chemical composition by mass percentage is: C3.2%~3.8%, Si 2.2%~2.6%, Mn 0.5%~0.8%, P≤0.04%, S≤0.02%, Cu 0.15%~0.5%, Sn0.002%~0.02%; the rest are Fe, Mg, Re, Ca, Ba, Zr and inevitable impurities.

9. The ductile iron 500-7 sintering trolley produced by the production method of the ductile iron 500-7 sintering trolley with high physical and chemical indexes according to claim 8 is characterized in that: Its chemical composition by mass percentage is: C3.35%~3.55%, Si2.4%~2.55%, Mn0.6%~0.7%, P≤0.04%, S 0.008%~0.015%, Cu 0.2%~0.25%, Sn0.002%~0.02%; the rest are Fe, Mg, Re, Ca, Ba, Zr and inevitable impurities.

10. The ductile iron 500-7 sintering trolley produced by the production method of the ductile iron 500-7 sintering trolley with high-standard physical and chemical indexes according to claim 8 or 9 is characterized in that: The physical and chemical indicators of the ductile iron 500-7 sintering trolley are: spheroidization rate of more than 90%; spheroidization grade of more than 2 levels; graphite size of more than 6 levels; elongation of 7-15%.

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